fi ^-^ ■': i t :r > ■ ^ I i-.'>. ■ ■.: K •- . . , y t ;•.- •■'•■•. r !>. :- ■,'• . ■ K r ^,-'' • ■ •■ • f= ,' f ■< • ■■ r i: ^;^:- ■ ■-■■ I ' L I* ■ <> f » / , • . / B (■ ' / ■■ - r • ' ' - • t, i' ^. ;:"-- ,' I. *:■ ' . ' / -,- * 'ii ','''■■, / ■ . ■ W. L. FOSTER Oltjp i. 1. Itll iCtbrarg ??urtb (Ear0ltna ^tatp (Eollpnp QH367 C66 N.C. STATE UNIVERSITY D.H, HILL LIBRARY S00258389 Z 14693 This book may be kept out TWO WEE ONLY, and is subject to a fine of Ml CENTS a day thereafter. It is due on day Indicated below: M% l<65 p; -sii? #^^ ^^^ cE)b \ THE ORIGIN OF THE FITTEST ESSAYS Olf EYOLUTIOjN" BY E. D. COPE, A. M., Ph. D. (Heidelberg) MEMBER OF THE UNITED STATES NATIONAL, ACADEMY OF SCIENCES ; CORRESPONDENT OP THE ROYAL BAVARIAN ACADEMY OF SCIENCES KKW YORK D. APPLETON AND COMPANY 1887 COPTKIGHT, 1S86, By D. APPLETON AND COMPANY. All rights reserved. TO MY FRIEND PROFESSOR ALPHEUS HYATT, OF BOSTON, MASS., WITH WHOSE STUDIES MY OWN HAVE LONG BEEN PARALLEL, AND WITH WHOSE CONCLUSIONS I HAVE LONG COINCIDED, THIS WORK IS DEDICATED BY THE AUTHOR. 146933 PEEFAOE. The tu^enty-one essays which constitute the present volume represent the reflections which have suggested themselves to the author while engaged in special zoological and paleontological studies. While the original work of the author has been nearly confined to the vertebrata, his studies have taken in a wider range. These have convinced him that the conclusions derived from the investigations of the vertebrata are applicable to inverte- brate animals and to plants. In reaching conclusions, the author has endeavored to avoid, as much as possible, any bias due to the influence of any opinions whatsoever on evolution and allied subjects which were already in the field. He therefore avoided, for a time, reading the works of the masters of the subject, apply- ing to them for confirmation or criticism only after the publication of his own results. It is therefore true that the generalizations contained in these essays have been worked out by the author from such material as has come under his own eyes, with little other aid. It has also followed that not a few of the conclusions he has reached were not new. On the other hand, some of the principles enunciated had not been clearly stated prior to the publication of these essays. In some cases the work accomplished has con- sisted in throwing well-known principles into accord with each other, as in the case of the laws of acceleration and retardation. The earlier essays are the more hypothetical, and the later present more numerous demonstrations. The latter have resulted chiefly from the author's researches in the field of vertebrate paleontology, which have thrown the greatest possible light on the fact and method of evolution. For the his- tory of this subject the reader is referred to the author's forthcoming *'• Manual of the Vertebrate Paleontology of North America ''' ; and, for the more detailed work, to the author's publications in the " Final Reports of the United States Geological Surveys," under "Wheeler and Hayden, and to the "Proceedings of the American Philosophical Society of Philadel- phia." The present essays are arranged (see table of contents) into four series, as follows : First, on General Evolution ; second, on the Structural Evidences of Evolution ; third, on Mechanical Evolution ; fourth, on Metaphysical Evo- lution. In the first series the author's earlier essays are arranged. The general principles are here laid down or foreshadowed. The essays of the vi PREFACE. succeeding sections are occupied with the demonstration of these and other generaUzations, so far as practicable. In each of the sections some essays will be found to be more, and others less, adapted to popular use. It is believed that the general reader can select a sufficient number of articles of minimum technicality to convey to his or her mind a sufficient idea of the views set forth. In Part I, articles first, fourth, and sixth are of this character. In Part II, the first, second, and third essays are the least technical. In Part III, the first article is the most popular, although tbe others are essential to an understanding of the doctrine of mechani- cal evolution. In Part IV, all are sufficiently popular for the reader who has some knowledge of mental science. A historical synopsis of the essays may be now given. The attempt is made to point out the aim of each, with an indication of what may have been new in its contents. They are taken up in the order of date of pub- lication ; II. The Origin of Geneea. From the "Proceedings of the Philadel- phia Academy of Natural Sciences " for October, 1868, and published sepa- rately by the author early in 1869. In this essay the following doctrines were taught : First, that development of new characters has been accomplished by an acceleration or retardation in the growth of the parts changed. This was demonstrated by reference to a class of facts, some of which were new, which gave ground for the establishment of the new doctrine. Second, that oi exact parallelism between the adult of one individual or set of individuals, and a transitional stage of one or more other individuals. This doctrine is distinct from that of inexact parallelism which had already been stated by von Baer. And that this law expresses the origin of gen- era and higher groups, because — Third, they can only be distinguished ly single characters when all their representatives come to be known. Fourth, that genera and various other groups have descended, not from a single generalized genus, etc., of the same group, but from corresponding genera of one or more other groups. This was called the doctrine of homologous groups. Fifth, the doctrine that these homologous groups belong to different geological periods, and. Sixth, to different geographical areas, which, therefore, in some in- stances, are. Seventh, related to each other in a successional way like the epochs of geological time. Of these doctrines it may be observed that the first and second are now the common property of evolutionists, and are recognized everywhere as matter of fact. The names which I selected to express them have, however, only come into partial use. The author believes that, although the doctrine was vaguely shadowed out in the minds of students prior to the publication of this essay, it had not previously been clearly expressed, nor been reduced PREFACE. ^i[ to a demonstration. Of the trnth of the doctrine the author is more than ever convinced, and he believes that paleontological discovery lias demonstrated it in many instances, and that other demonstrations will fol- low. The fourth proposition (that of homologous groups) is now held as a hypothesis explaining the phylogeny of various groups of animals. For the descent of one homologous group from another, the term poly- phyletic has been coined. It remains to be seen whether the doctrine is of universal application or not. That homologous groups belong to different geological horizons, as stated under the fifth head, has been frequently demonstrated since the publication of the essay. That the sixth proposition is true in a certain number of cases is well known, and it follows that the seventh proposition is alsd true in those cases. The latter hypothesis, which was originally advanced by Prof. Agassiz, is, how- ever, only partially true, and the advance of paleontological study has not demonstrated that it has had a very wide application in geological time. A proposition which was made prominent in this essay was, that the prevalence of non-adaptive characters, in animals, proves the inadequacy of hypotheses which ascribe the survival of types to their superior adaptation to their environment. Numerous facts of this kind undoubtedly indicate little or no activity of a selective agency in nature, and do point to the existence of an especial developmental force acting by a direct influence on growth. The action of this force is the acceleration and retardation ap- pealed to in this paper. The force itself was not distinguished until the publication of the essay entitled '' The Method of Creation " (No. V), where it was named growth-force, or bathmism. The energetic action of this force accounts for the origin of characters, whether adaptive or non-adaptive, the former differing from the latter in an intelligent direction, which adapts them to the environment. The numerous adaptive characters of animals had by that time engaged the attention of the author, and he found that they are even more numerous than the non-adaptive. Some of the latter were ac- counted for on the theory of the " complementary location of growth-force." IV. The Hypothesis of Evolution, Physical and Metaphysical. " Lippincott's Magazine," Philadelphia, 1870 ; reprinted by Charles C. Chat- field & Co. New Haven, 1870. This essay embraces a popular exposition of the principles maintained in the essay entitled the " Origin of Genera," with some conclusions derived from the general facts of anthropology. To this were added some facts in the evolution of human physiognomy and human character, which had not been previously thrown into harmony with the laws already set forth. Un- fortunately, the author attempted to correlate these again with the theories of some theologians, and, in some instances, without success. A few paragraphs have been stricken from this part of the essay, and others are allowed to remain as illustrations of far-reaching hypotheses resting on little information. V. The Method of Creation of Organic Types. From the "Pro- ceedings of the American Philosophical Society," December, 1871 ; repub- viii PREFACE. listed by McCalla & Stavely the same year. Read before the American Association for the Advancement of Science, at Detroit, August 27, 1871. Received the Walker prize of the Boston Society of Natural History. In this essay were added to the preceding, the following hypotheses: . 1. The law of repetitive addition, in which the structures of animals were shown to have originated from simple repetitions of identical ele- ments. 2. The existence of an especial force which exhibits itself in the growth of organic beings, which was called growth-force, or bathmism, 3. That development consists in the location of this energy at certain parts of the organism. 4. That this location was accomplished by use or effort, modifying and being modified by the environment; or the doctrine of kinetogenesis. 5. That the location of this energy at one point causes its abstraction from other points, producing "complementary diminution" of force at the latter. 6. That the location of this energy, so as to produce the progressive change called evolution, is due to an influence called " grade influence." 7. That inheritance is a transmission of this form of energy, which builds in precise accord with the sources from which it is derived. 8. That this " grade influence " is an expression of the intelligence of the animal, which adapts the possessor to the environment by an " intel- ligent selection." 9. An attempt to account for the origin" of " mimetic analogy " by "maternal impressions." On these propositions, the following comments may be made : First, the law of repetitive addition is much like the law of rhythm previously pro- posed by Herbert Spencer.* Second, the force of growth, or bathmism, had already been called constructive force by Carpenter, who, however, did not treat of its evolutionary or " grade " characteristics. That such force exists there can be no doubt at the present time, but it may be that its varied aspects should each be considered a separate species of force (i. e., energy). Third, the relations of the energetic and static conditions of this force were considered, but were not sufficiently followed out to be clear. It is hoped that greater clearness has been attained by the omission of a few paragraphs and the insertion of an explanatory foot-note. Fourth, that the location of this energy is due to the influence of use and effort. The doctrine of the development of parts of living beings by use, and their loss by disuse, is well known to have been put forth by Lamarck in 1809, who devotes one of the longest chapters (No. VII) of his " Philosophic Zoologique " to its discussion. He did not, however, include the element of efort, prior to the appearance of any rudiment of an organ, in his hypothesis, which was proposed, so far as I know, for the first time in the present essay. The doctrine of use and disuse has been sustained * « Principles of Biology.'* PREFACE. ix by Spencer in his " Principles of Biology " as respects the effect of motion on structure in general,* and in the particular case of the origin of verte- brsB.t Fifth, the complementary development of parts had also been pointed out by Herbert Spencer,! Seventh, tlie explanation of inheritance by the transmission of the type of growth-force possessed by one generation to another. This doctrine was subsequently announced by Haeckel, under the name of perigenesis,^ and is the only good hypothesis yet proposed for the explanation of this phenomenon. Eighth, the theory of "intelligent selection,"- or the agency of the intelligence of a living being in directing its movements, and there- fore its growth, although a plain and necessary consequence of the " law of use and effort," had not been, so far as I am aware, announced prior to the publication of this paper. This important theory at once opened the way for an investigation of the general relations of mind to evolution, which involved the question of the origin and development of mind itself. These questions were more fully discussed in the papers of Part IV, on " Metaphys- ical Evolution." Ninth, the origin of mimetic analogy. The explanation offered is almost necessary, if the doctrine of the influence of effort on struct- ural growth be true. I. Evolution and its Consequences, From the *' Penn Monthly Maga- zine," Philadelphia, for May, July, and August, 1872, This is a popular exposition, with elaboration, of the doctrines contained in the preceding essays. The evolution of mind is more fully stated, the hypothesis adopted being that proposed by Spencer in his " Principles of Psychology," published in 1855. VII. The Homologies and Origin of the Types of Molar Teeth OF THE Mammalia Edtjcabilia. From the " Journal of the Academy of Natural Sciences," Philadelphia, March 30, 1874. The object of this paper was to show that the various more or less com- plex types of molar "teeth displayed by the Ungulate Mammalia are referable to modifications of a primitive quadituberciilar type, from which they were supposed to have been descended. The histories and homologies of the carnivorous dentitioa were not included in this paper. In order to com- plete the subject, I have inserted brief notes of the conclusions I have since attained in this field : first, as to the type of inferior sectorial teeth, in 1875 ; and, second, as to the superior molars, in 1883. At the end of the paper a similar- comparison between the feet of the same type of mammals is made, and general conclusions reached in the fol- lowing language : " I trust that I have made it sufiiciently obvious that the primitive genera of this division of mammals [Mammalia Educabilia = Un- guiculata and Ungulata sensu lata] must have been bunodonts with penta- ■daetyl plantigrade feet." Vol. ii, p. 167. t Vol. ii, p. 195. X " Principles of Biology." * See Ryder, "American Naturalist," January, 1879. X PREFACE. The nearest approaches to a similar anticipation on the part of other naturalists, which I have been able to find, refer to the number of toes only, and are of restricted application. Thus Kowalevsky remarks (" Monographie der Gattung Anthracotherium, Palaeontographica," xxii, p. 1452) : "• So we can assume a tetradactyl foot as our point of departure, although it can not have the least effect on the result in case the original ungulate foot should have been pentadactyl. If I have set out with a tetradactyl foot it is simply because I wish to adhere so far as possible to facts." This was written August, 1873, but how soon thereafter it was printed I do not know. I did not meet with it until at least a year after the publication of my paper of March, 1874, cited. Secondly, Marsh, in writing on the genealogy of the horses ("American Journal of Science and Arts," March, 1874, p. 257), says : " A still older ancestor [of the horse], possibly in the Cretaceou?, doubtless had five toes on each foot, the typical number in mammals." My paper was published during the same month as the above; but I communi- cated the substance of the generalization in question to the Philadelphia Academy the day it was read, November 18, 1873, which was published in the "Proceedings of the Society," January 13, 1874, p. 2. XYIII. Consciousness in Evolution. From the " Penn Monthly Maga- zine," Philadelphia, July, 1875. In this paper the doctrine of intelligent selection is analyzed, and the problem reduced to its essential — the relations of consciousness to matter. The doctrine of the origin of reflex and automatic acts from conscious states, or archaesthetism, is here first proposed. From the characters of proto- plasm the inference is derived that that substance is not necessarily the only one capable of supporting consciousness. The author is not aware of any previous attempt to render these propositions probable. VIII. The Relation of Man to the Teetiaey Mammalia. From the " Penn Monthly Magazine," December, 1875. Read before the American Association for the Advancement of Science, at Detroit.' The fact that the hard tissues, and probably the digestive system, of man, are constructed on the type of the Mammalia of the early Eocene period is here pointed out for the first time. III. The Theoey of Evolution. Remarks made before the Academy of Natural Sciences of Philadelphia, February 22, 1876, and published in the "Proceedings of the Society," 1876, p. 15. These remarks exhibit the correspondence between the evolutionary systems of Haeckel and of the writer, and combine them into a symmetricid whole. XXI. The Oeigin of the Will. From the "Penn Monthly Magazine," Philadelphia, June, 1877. In this paper the attempt is made to render the existence of freedom of will probable by a process of argument, and also to demonstrate its exist- ence by another kind of argument. As is well known, there are two op- posed doctrines respecting this important question. One of these, which has by far the larger number of adherents, is that the human mind embraces PREFACE. xi among its powers a freedom of will, or spontaneity in action. The other view is, that there is no such power, but that the actions are merely the necessary result of the strongest pressure of the strongest inducement or motive. The doctrine of evolution is known to lend support to the latter doctrine. In the present paper the attempt is made to prove that free will is a new power which supervenes on the process of evolution. This is done by assuming the existence of a class of acts for which the term altruistic is retained, which, undoubtedly, would require freedom for their perform- ance. The only question here is, whether there be any such class of acts as are defined under the above name in this essay. If tliere be no such class of acts, the demonstration based on it falls to the ground ; and the author is xiot at present sure whether there be such a class of acts or not. The argument by which freedom of will is rendered probable is not open to any serious objection, and rests on the necessity for action which sometimes arises in cases where there is no experience or knowledge to serve as a determining motive or power. These cases are supposed to involve moral questions. The doctrine is then intermediate between the two oppos- ing ones which have long divided the world of thought,* It permits of the development of a free will in previously automatic beings, as a phenomenon superposed on mental evolution. The argument demonstrates nothing more tlian that freedom is possible; a conclusion which is, however, important, since it shows that the position of the determinists is not impregnable, XII. The Relation of Animal Motion to Animal Evolution. From " The American Naturalist," January, 1878. Read before the American Association for the Advancement of Science, at Nashville, August, 1877. The effects of the actions of animals on their structure are considered, as in previous papers, and especial attention is paid to the influence of ani- mals in the changes they produce in their environment.t XI Y. The Origin of the Specialized Teeth of the Carnivoea. From " The American Naturalist," March, 1879. The mechanical reasons for the changes in the dentition of carnivorous mammals during geologic time are pointed out for the first time. VI. A Review of the Modern Doctrine of Evolution. From "The American Naturalist," March and April, 1880. A lecture delivered before the California Academy of Sciences, October 27, 1879. It is a general synopsis of views presented in preceding papers. XY. On the Origin of the Foot-Structure of the Ungulates. From " The American Naturalist," April, 1881. This essay embraces an explanation of the cause of the diminution of the number of digits in the diplarthrous ungulate mammals ; of the reasons why some are even- and some odd-toed ; and of the origin of some of the * This view is adopted by President Xoah Porter in one of his latest metaphysi- cal works. f A synopsis of the relations of animals to their environment is given by Spen- cer, " Principles of Biology," vol. i, p. 466. xii PREFACE. articulations of the tarsus. These explanations, so far as based on paleonto- logical grounds, were new at the time. XVI. The Effect of Impact and Steains on the Feet of Mammalia. From " The American Naturalist," July, 1881. The origin of the structures of all the articulations of the limbs of all the Mammalia are explained as the effects of impacts and strains.- The demon- stration is based largely on paleontological evidence, and is new. XIX. On Aechaesthetism. From " The American Naturalist," June, 1882. This doctrine is discussed and illustrated on the basis laid down in the essay " Consciousness in Evolution," and a classification of theories of crea- tion is presented. IX. The Developmental Significance of Human Physiognomy. From "The American Naturalist," June, 1883. In this paper suggestions presented in Art. IV, entitled "The Hypothe- sis of Evolution, Physical and Metaphysical," are developed, and the physical significance of the form-characters of men in general are considered. Noth- ing except reference to a few leading points of the subject had been pub- lished prior to this paper, so far as the author has been able to discover. In connection with a paper on the "Evolutionary Significance of Human Char- acter," a foundation was laid for a scientific physiognomy. X. The Evidence foe Evolution in the Histoey of the Extinct Mammalia. A lecture delivered before the American Association for the Advancement of Science, at Minneapolis, August, 1883. In this paper are collected the evidences of descent displayed by the Mammalia (and in one instance by the Batrachia), as derived from the pale- ontological researches of the author. These had been in some points fore- shadowed in the author's memoir on the homologies and origin of the struct- ure of the molar teeth in the Mammalia Educabilia in 1874, which were here shown to have been realized by subsequent discovery, and a number of other evidences added. Restatements of the laws of kinetogenesis, and of the origin of morals, were made. XVII. The Evolutionaey Significance of Human Chaeactee. From the " American Naturalist," September, 1883, The characters of the adult mind are compared with those of the child, and with those of the lower animals, and the direction of their evolution pointed out. Most of the propositions contained in this paper were new at the time of its publication. XIII. The Teituberculae Type of Molae Teeth in the Mammalia. From the proceedings of the American Philosophical Society, 1883, page 324;* published in advance in the "Paleontological Bulletin," No. 37, January 2, 1884. The origin of the ungulate molar tooth had already been traced to a quadritubercular type in paper No. VII (March and January, 1874). The * Not published until 1884. PREFACE. xiii present paper shows that this type in the upper jaw is a derivative of a tri- tubercular type, while that of the lower jaw is a derivative of a quinquetu- bercular type, or a tritubercular type with a heel, which may support two additional tubercles. The tritubercular type was again traced to the sim- ple cone. This generalization was new at the time of publication. XX. Catagenesis. Vice-presidential address delivered before the bio- logical section of the American Association for the Advancement of Sci- ence, Philadelphia, September 4, 1884. The hypothesis of catagenesis which is put forth in this paper teaches that primitive energy was and is conscious, and that all unconscious forms of energy, whether "vital" or non-vital, have been derived from it by a process of retrograde metamorphosis. The first stage of this retrogression is the loss of consciousness, or cryptopnoy. Evidence for this kind of meta- morphosis is derived from every-day experience, and from the designed character of automatic acts. That a form of energy is conscious is inferred from the nature of designed conscious acts of animals. The author had not met with any scientific statement of this theory prior to the preparation of this lecture. XI. The Evolution of the Yeetebeata, Progeessive and Reteo- GEESsivE. From the "American Naturahst," February, March, and April, 1885. This paper sets forth the results of paleontological investigation of the Vertebrata, in a series of phylogenies. These are, first, the phylogeny' of the classes ; then the special phylogenies of their contents or of the orders. Here are introduced the newly-discovered relations of the Anti- archa and the Ichthyotomi to the fish-like vertebrates, and of the thero- morphous reptiles to the Mammalia. Also, the ancestral relation of the Theromorpha to most other reptiles, and of the Condylarthra to the placental Mammalia, and to man. Many of the other results set forth in this essay are derived from the paleontological researches of the author. Some of them, especially the lemurine (condylarthrous) ancestry of the placental Mammalia, had been anticipated on theoretical grounds by Haeckel in his- " History of Creation " (" Schopfungsgeschichte "). Haeckel was very general in his proposition, and did not anticipate the details of the demon- stration. My investigations enabled me to produce these, which bring out in a striking manner the sagacity of Prof, Haeckel. I consider further the question of degeneracy, and the significance of the phylogeny with refer- ence to this subject is pointed out. In conclusion, it may be said that the principal object which the author set before him, in the studies here recorded, has been the discovery of the laws of variation, or of the " Origin of the Fittest." These essays express the light which he has been able to obtain on this difficult question up to the present time. The results could be better and more briefly pre- sented in a systematic form, but the author reserves this for a future occa- sion. COH'TENTS. PART I.— GENERAL EVOLUTION. L — Evolution and its Consequences IL — The Origin of Genera in. — The Theory op Evolution IV. — The Hypothesis op Evolution, Physical and Metaphysical V. — The Method of Creation of Organic Forms . VI. — Review of the Modern Doctrine of Evolution PAGB 1 41 124 128 173 215 PART IL— STRUCTURAL EVIDENCE OF EVOLUTION. VII. — The Homologies and Origin of the Types op Molar Teeth of the Mammalia Educabilia 241 VIII. — The Relation of Man to the Tertiary Mammalia . . . 268 IX. — The Developmental Significance op Human Physiognomy . . 281 X. — The Evidence for Evolution in the History of the Extinct Mammalia 294 XI. — The Evolution of the Vertebrata, Progressive and Retrogres- sive 314 PART IIL— MECHANICAL EVOLUTION. XII. — The Relation of Animal Motion to Animal Evolution . . 350 XIII. — On the Trituberculate Tooth in the Mammalia .... 359 XIV. — The Origin of the Specialized Teeth of the Carnivora . . 363 XV. — The Origin of the Foot Structures of the Ungulates . . 368 XVI. — The Effect of Impacts and Strains on the Feet of Mammalia . 373 xvi COITTEN'TS. PART IV.— METAPHYSICAL EVOLUTION. PAGE XVII. — The Etolutionary Significance of Human Character . . 378 XVIIL — Consciousness in Evolution 390 XIX. — Arch>esthetism 405 XX. — Catagenesis 422 XXI.— The Origin of the Will 437 LIST OF ILLUSTEATIOI^S. Plates. PLATE PAGE I. Figures and Diagrams of the Circulatory Centers of Vertebrata. Copied from Gegenbaur and His, mostly enlarged 60 II and Ila. Figures of Lizards of the families Iguanidae and Agamidae compared 9*7 III and Illa. Mimetic analogy in the colors and patterns in snakes of dif- ferent genera and species 105 ly and V. Series of Crania of Different Families of Tailless Batrachia showing similar stages of development. Original . . . 220, 221 Explanation 222 VI. Succession of Modifications of Feet of Diplarthrous Ungulata. Original 271 VII. Succession of Dental Forms, mostly of LTngulata. From Gaudry, Wort- man, and Cope 275 VIII. Uintatherium eornutvm Cope, restored, one twenty-seventh natural size. From Cope, Marsh, and Osbom 277 IX. Anaptomorphus and Homo ; Cranium, Brain, and Teeth. Original, ex- cept Figs. 8 and 9 from Allen 279 X. Esequibo Indians. From photographs by Endlich .... 286 XI. The Wrestler. From the Vatican . . .... 289 XII. Venus of the Capitol 292 XIII. Phenacod^is primcevus Cope, Skeleton as found in matrix, one seventh natural size. Original ......... 300 XIV. Brains of Extinct Mammalia. Original, except Fig. 2 from Marsh . 308 XV. Diclonius mirabilis, Skull Profile. Original 338 XVI. Diclonius mirabilis, Skull from below, one half the mandible removed . 339 XVII. Phenacodus vortmani, Skeleton as found in Matrix, two ninths natural size. Original 345 XVIII. Hycenodon horridus Leidy, Skull one half natural size. From Lcidy . 364 Wood-Cuts. FIG. 1. Diagram illustrating acceleration and retardation 10 2. Diagram illustrating relations of genera of batrachia anura . . .80 3 to 6. Diagrams illustrating development of genera of batrachia anura . 81 7. Same as Fig. 1 . , 1*76 XVlll LIST OF ILLUSTRATIONS. FIG. 8. Sternum and adjacent parts of Scaphiopus Jiolbrooki .... 9. Sternum of Tadpole of Rana temporaria ...... 10. Sternum of adult Rana temporaria ....... 11. Metacarpus, carpus, and distal extremity of radius of Poehroiherium vihoni 12. The same, less radius, with first phalanges of Procamelus occidentalis 13. Skull of Protolahis transmontanus 14. Skull of Procamelus occidentalis . 15. Tooth of Globicephalus .... 16. Tooth of Jaculus hudsonicus 17. Tooth of Leploch(e7'us spectabilis. From Leidy 18. Tooth of Rhinocerus, milk superior molar . 19. Tooth of Achcenodon insolens 20. Tooth of Hippopotamus amphibius. From Cuvier 21. Tooth of Hyopotamu^ velaunus. From Blainville 2 1. Tooth of Hyopotamus americanus. From Leidy 23. Tooth of Procamelus robustus. From Leidy 24. Tooth of Merychyus major. From Leidy . 25. Tooth of Tapirus ..... 26. Tooth of Mastodon angustidois. From Cuvier 27. Tooth of Mastodon americanus. From Cuvier 28. Tooth of Dinotherium. From Cuvier 29. Tooth of Elephas indicus. From Cuvier . 30. Tooth of Microsyops elegans. From Leidy 31. Tooth of Hyopsodus paulus. From Leidy . 32. Tooth of Palceosyops kevidens. From Leidy 33. Tooth of Ancldppodus riparius. From Leidy 34. Tooth of Palceosyops vallidens. From Leidy 35. Tooth of Pcdceotherium. From Cuvier 36. Tooth of Hipposyus. From Leidy 37. Tooth of Hipposyus more worn. From Leidy 38. Tooth of Hypohippus. From Leidy . 39. Tooth of Equus, superior molar. From Leidy 40. Tooth of Equus, inferior molar. From Leidy 41. Tooth of Baihmodon radians 42. Tooth of Uintatherium robustum, superior molar. 43. Tooth of Uintatherium. robustum^ inferior molar. 44. Periptychus rhabdodon, part of posterior foot 45. Coryphodon elcphantopus, right fore foot, one third natural size 46. Coryphodon elephantopus^ right posterior foot . 47. Phenacodus primcevus, right anterior foot, one third natural size, 48. Phenacodm primcevus^ left posterior foot, one third natural size 49. Homo sapiens^ left anterior foot (hand), one third natural size . 50. Homo sapiens., left posterior foot, one third natural size 51. Phenacodus primcevus Cope, skull, one third natural size, from below 52. Simia satyrus, section of skull of adult ..... 52a. Simia satyrus, section of skull of young ...... 53. Homo sapiens, infant at term . . ..... From Leidy From Leidy PAGE . 217 . 217 . 217 . 219 . 219 . 223 . 223 . 243 . 243 . 243 . 244 . 253 . 254 . 254 . 254 . 254 . 255 . 255 . 256 . 256 . 256 . 256 . 257 . 257 . 257 . 257 . 257 . 258 . 258 . 258 . 258 . 259 . 259 . 260 . 260 . 260 . 268 . 269 . 269 . 270 . 270 . 272 . 272 . 273 . 283 . 283 . 284 LIST OF ILLUSTRATIONS. XIX PIG. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65.' 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. , PAGE Homo sapiens^ portrait of girl at five years . . . . . . 285 Homo sapiens^ portrait of same at seventeen years 285 Homo sapiens, portrait of Luchatze negro woman ..... 287 Homo sapiens, portrait of Luchatze negro woman 287 Homo sapiens, portrait of Satanta, chief of the Kiowa Indians of Xoith America 288 An Australian native 291 Eryops megacephabu, a batrachian of the Permian epoch of Texas ; vertebral column 804 Sleeve of coat, showing folds 305 Bothriolepis canadensis, from above ........ 323 Chelyosoma maclovianiim, a tunicate from Point Barrow, Alaska, from above S23 Stypolovhus whitice, skull and dentition, displaying the tritubercular type of molars ...... ' Deltatherium fundaminis, skull, profile Oxycena lupina, jaws and teeth . Procehcrtts julieni, skull. From Filhol Dinictis cyclops, skull Smilodon neoffceics, skull CorypJiodon elephantopus, hind foot above Aphelops megalodus, hind tarsus and metatarsus, from front and above Proiohippus sejunctus, posterior foot, front Po'ehrotherium labiatum, posterior foot, front Poebrotherium vilsoni, carpus, metacarpus, and end of radius, from^ front Amhlydonus sinosus, a creodont ; distal end of tibia Oxycena m,orsitans, a creodont ; distal end of tibia ArchcBlurus dehilis, an extinct cat ; distal end of tibia, Nimravus gomphodus, a cat ; femur . Procamelus occidentalis, part of fore foot Cosoryx furcatus, part of fore foot Poebi'oiherium vilsoni, part of fore foot with astragalus 360 362 365 366 306 367 369 369 370 370 371 375 375 375 375 376 376 376 PART I. GENERAL EYOLUTIOK I. EVOLUTION AND ITS CONSEQUENCES. The broad theory of evolution includes the theories of devel- opment of the solar system and its members, as expressed by the nebular hypothesis ; the theory of development of life by molecu- lar movements consequent upon certain combinations of non-living matter ; and, lastly, the theory of development of the species of animals and plants by descent, the later from the earlier, with accompanying change of form and character. It attempts noth- ing less than a history of the process of creation of the universe, so far as we can behold it ; and is, therefore, an attempt to formu- late the plans and thoughts of the Author of that universe. Hence, it is not surprising that it excites the interest of the best of men, especially as it is one of the results of the efforts of a class of these, crowning many centuries of labor and thought. The object of the present essay is to discuss familiarly the latter of these theories of evolution, viz., that respecting the si3ecies of animals and plants. As all are aware, this mode of accounting for the creation of organized beings has attained especial prominence at the present time, and possesses more of interest to most readers because of its explanation of our own origin. Moreover, it rests on more indubitable evidence than the two other theories. The constitution and arrangement of the members of the solar system point to their origin by derivation from primal masses of vaporous matter through the mutual opera- tion of the ordinary laws of attraction and motion. The position- ing is precisely as it should be had such process taken place, but the process itself, that is, the change from type to type of celes- tial body, has not been observed. I D. H. HILL LIBRARY North Carolina State Colteg« 2 GENERAL EVOLUTION. The case is far diCerent with the theory as regards organized or living beings. Not only are the mutual relations of animals and plants to each other such as should have resulted from a de- scent or development, but the changes from type to type have been actually observed, and in sufficient number to place the hypothesis on the basis of ascertained fact, as referring to a cer- tain range of objects — say, in the case of the animal kingdom, to individuals distinguished by structural characters within the range of each of the three to six great primary divisions or " branches." There are two totally distinct propositions involved in this question, which are confounded by the general public, and not unfrequently by students and writers on it. These are, first, the evidence which seems to prove that this evolution has taken place ; secondly, the evidence as to the nature of the laws of its progress. A want of constant distinction between these views of the case has greatly obscured it and injured the evidence on one side or the other. The evidence in favor of evolution is abundant, and is cited in fragments by various contemporary writers, foremost among whom, both in time and abundance of writings, comes Charles Darwin. Much less has been done in explanation of the laws of evo- lution. Darwin and his immediate followers have brought out the law of ^^ natural selection"; Spencer has endeavored to ex- press them in terms of force; while Hyatt, Cope, Packard, and others have advanced the law of "acceleration and retardation." In earlier days, when information was distributed slowly and books were few, it was long before any new truth or doctrine reached the majority of people, still less was adopted by the rul- ing classes. But the modern theory of evolution has been sjDread everywhere with unexamjoled rapidity, thanks to our means of printing and transportation. It has met with remarkably rapid acceptance by those best qualified to judge of its merits, viz., the zoologists and botanists, while probably a majority of the public, in this region at least, profess to reject it. This inconsistency is due to two principal causes. In the first place, Darwin's demon- stration contained in the " Origin of Species " extends little fur- ther than as stated in the title of his work. He proves little more than that species of the same genus or other restricted groups have had a common origin ; and, further, his theory of natural selection is to the plainest understanding incomplete as an ex- EVOLUTION" AND ITS CON-SEQUENCES. 3 planation of their ''origin/' as its author indeed freely allows. Besides, the unscientific world is particularly unreasonable on one point. Little knowing the slow steps and laborious effort by which any general truth is reached, they find in incompleteness ground of condemnation of the whole. Science is glad if she can prove that the earth stands on an elephant, and gladder if she can demonstrate that the elephant stands on a turtle ; but, if she can not show the support of the turtle, she is not discouraged, but labors patiently, trusting that the future of discovery will justify the experience of the past. If, then, some of the people find Mr. Darwin's argument in- complete, or in some points weak, it may be answered, so do the student classes, who, nevertheless, believe it. This is largely be- cause Darwin's facts and thoughts repeat a vast multiplicity of experiences of every student, which are of as much significance as those cited by him, and which only required a courageous officer to marshal them into line, a mighty host, conquering and to conquer. These will slowly find their way into print, some in one country and some in another. I. THE FACT OF EVOLUTION". As to the truth of the theory, the proof has been stated in more than one form. The first and simplest, and essentially the central argument of Darwin, is as follows : In every family or larger group of animals and plants there exists one or more genera in which the species present an aggre- gation of specific intensity of form ; that is, that species become more and more closely related, and finally varieties of single spe- cies have to be admitted for the sake of obtaining a systematic definition or '' diagnosis," which will apply to all the individuals. These varieties are frequently as well marked as the nearly-related species, so far as amount of difference is concerned, the distinc- tion between the two cases being that in the varieties there is a gradation from one to the other ; in the species, none. Neverthe- less, between some of the varieties transitions mav be of rare oc- currence, and in the case of the ''species" an intermediate indi- vidual or two may occasionally be found. Thus it is that differ- ences, called varietal and specific, are distinguished by degree only, and not in kind, and are, therefore, the results of the opera- tion of uniform laws. Yet, according to the old theory, the varie- ties have a common origin, and the species an independent one ! « 4 GENERAL EVOLUTION. To find examples of what is asserted, it is only necessary to refer to the diagnostic tables and keys of the best and most honest zoologists and botanists. It is true that these diagnoses are dry reading to the non-professional, yet they embrace nearly all that is of value in this part of biological science, and must be mastered in some department before the student is in possession of the means of forming an opinion. The neglect to do this explains why it is that, after all that has been written and said about protean spe- cies, etc., the subject should be so little understood. It is true that in but few of these cases have the varieties been seen to be bred from common parents, a circumstance entirely owing to the difficulties of observation. The reasoning derived from the relations of differences appears to be conclusive as to their common origin, unless we are prepared to adopt the oppo- site view, that the varieties have originated separately. As these avowedly grade into individual variations, we must at once be led to believe that individuals have been created independently — a manifest absurdity. But variations in the same brood have been found among wild animals ; for example, both the red and gray varieties of the little horned owl (Scops asio) have been taken from the same nest. As further examples of gradation between species and variety, found in nature, I only have to select those genera most numerous in species, and best studied. Among birds, Corvus, Emp)idonax, JButeo, Falco, etc. Eep tiles, Eutaeiiia, Anolis, Lyoodon, Naja, Caudisona^ Elaps, Oxyhrropus, etc. Batrachia, Rana, Hyla, Clioropliilus^ Borhorocoetes, AmUy stoma, Spelerpes, etc. Fishes, PtycliostomuSf Plecostomus, Amiurus, Sal mo , Pcrca, and many others. In all these groups of species, or '^genera," it is impossible in some cases to determine what is variety and what species. This is notoriously the case with the salmon and trout (Sahno), for one of the greatest opponents of close division of species. Dr. Giinther, of London, thought himself necessitated, a very few years ago, to name and describe half a dozen new species of trout from the lakes of the British Islands, and, from being a stanch supporter of the old view of distinct creations, was completely converted to evolutionism. Such is one of the views which has forced conviction on the minds of thoroughly honest men who were not only desirous of knowing the truth, but were in many cases brought over from a EVOLUTION AND ITS CONSEQUENCES. 5 position of strong opposition. But the earnest objector says, you have not after all shown me any real transitions from species to species ; until that is done your development is but a supposition. The all-sufficient answer to this statement is to be found in the imperfection of our system of classification. Thus, if we first assume, with the anti-developmentalist, that varieties have a com- mon parentage, and species distinct ones, when intermediate forms connecting so-called species are discovered, we must confess our- selves in error, and admit that the forms supposed to have had a different origin really had a common one. Such intermediate forms really establish the connection between species, but the question is begged at once by asserting unity of species, and, therefore, of origin, so soon as the intermediate form is found ; for, as before observed, it is not degree, but constancy of distinc- tion, which establishes the species of the zoological systems. Transitions between species are constantly discovered in existing animals ; when numerous in individuals, the more diverse forms are regarded as *^ aberrant"; when few, the extremes become *^ varieties," and it is only necessary to destroy the annectant forms altogether to leave two or more species. As the whole of a variable species generally has wide geographical range, the vari- eties coinciding with sub-areas, the submergence, or other change in the intervening surface, would destroy connecting forms, and naturally produce the isolated species. Formerly naturalists sometimes did this in their studies. A zoologist known to fame once pointed out to me some trouble- some specimens which set his attempts at definition of certain species at defiance. *' These," said he, ''are the kind that I throw out of the window." Naturalists having abandoned throw- ing puzzling forms out of the window, the result of more honest study is a belief in evolution by nine tenths of them. But, says the inquirer again, your variations and transitions are but a drop in the ocean of well-disting-uished species, classes, etc. The permanent distinction of species is matter of every-day observation ; your examples of changes are few and far between, and utterly insufficient for your purpose. It is true that the cases of transition, intermediate forms, or diversity in the brood, observed and cited by naturalists in proof of evolution, are few compared with the number of well-defined, iso- lated species, genera, etc., known ; though far more numerous than the book-student of natural history is apt to discover. But 6 GENERAL EVOLUTION although the origin of most species by descent has not been ob- served, every one knows the worthlessness of argument based on a negative. Unless these cases exhibit opposing evidence of a posi- tive character, they are absolutely silent witnesses. He who cites them against evolution commits the error of the native of the Green Isle who testified at a murder trial. '^ Al- though the i^rosecuting attorney brought three witnesses to swear positively that they saw the murder committed, I could produce thirty who swore they did not see it done ! " By the inductive process of reasoning we transfer the unknown to the known, for it is the key of knowledge. It rests upon the invariability of Nature's operations under identical circumstances, and for its application merely demands that analysis and com- parison shall fix that the nature of that of which something is unknown is identical with that of which the same thing is known. We then with certainty refer that which is known as an attribute of that object of which the same quality had been previously unknown. The following form exhibits its applica- tion to the question of evolution. As preliminary facts it may be assumed that : 1. Many species are composed of identical elemental parts which present minor differences. 2. Some of these differences have been seen to originate spon- taneously from parents which did not possess them, or, what is the same thing, are known to exist in individuals whose parentage is identical with others which do not possess them. 3. The gradation of differences of the same elemental parts is one of degree only, and not of kind. 4. Induction. — Therefore all such differences have originated by a modification in growth, or have made their appearance with- out transmission in descent. II. THE MAN'NER OE EYOLUTIOK. In discussing this point, new evidence in favor of develop- ment must be produced, and some statements of the history of the opinion made. The laws which are expressed by all that we find of structure in animals are four, viz. : 1. Homology. — This means that animals are composed of cor- responding parts ; that the variations of an original and fixed number of elements constitute their only differences. A part EVOLUTION AND ITS CONSEQUENCES. 7 large in one animal may be small in another, or vice versa ; or complex in one and simple in another. The analysis of animals with skeletons or vertebrata has yielded several hundred original elements, out of which the 28,000 included species are con- structed. Different this from the inorganic world, which can only claim about sixty- two elemental substances. The study of homologies is thus an extended one, and is far from complete at the present day. 2. Successional Relation. — This expresses the fact that species naturally arrange themselves into series in consequence of a mathe- matical order of excess and deficiency in some feature or features. Thus species with three toes naturally intervene between those with one and four toes. So with the number of chambers of the heart, of segments of the body, tlie skeleton, etc. There are greater series and lesser series, and mistakes are easily made by taking the one for the other. 3. Parallelism. — This states that while all animals in their embryonic and later growth pass through a number of stages and conditions, some traverse more and others traverse fewer stages ; and that, as the stages are nearly the same for both, those which accomplish less resemble or are parallel with the young of those which accomplish more. This is the broad statement, and is qualified by the details. 4. Teleology. — This is the law of adaptation so much dwelt upon by the old writers, and admired in its exhibitions by men gener- ally. It includes the many cases of fitness of a structure for its special use, and expresses broadly the general adaptations of an animal to its home and habits. Of course, these laws must be all laws of evolution, if evolution be true. And such they are ; but this is far from being perceived by some students, for some of them were in abeyance or neglect prior to the stimulus to thought caused by the appearance of the ** Origin of Species." Forty or fifty years ago Germany had been flooded with the writings of the ^^physiophilosophs." Oken and Goethe had ob- tained glimpses of the wonderful " unity in variety " expressed by the laws of homology. The latter saw vertebrae in the seg- ments of the skull, and leaves in the floral organs of plants. He had found the magic wand, and many were the harmonious visions that delighted the laborious toilers among old bones and dusty skins ; the patient haruspices saw omens in the intestines of birds 8 GENERAL EVOLUTION. and snakes, and he whose hours were spent over his lens ceased to be a mere wonder monger. But fashion is fashion, and always ends in absurdity and stagnation. The physiophilosophs became extravagant, and mistook superficial appearances for realities. They did not dream how misleading some of the resemblances between different elements, for example, of the skeleton may be, and for once German students did not analyze exhaustively. Cu- vier laughed at these seekers for beauty, and confounded the true and the untrue in one condemnation. But the best men labored forward ; errors began to be exposed, and soon a reaction set in. Another extreme followed, and the school of Miiller, at Berlin, denied the meaning of these resemblances and ceased to see any- thing but differences. Minute and thorough investigation flour- ished in their hands, and the modern school of German anatomists has seen no superiors. So the theory of evolution found Berlin. The disfavor in which physiophilosophy was held secured to evo- lution a cold welcome, and it has been for Jena and other univer- sities to give it its true impetus in Germany. So it has been with the law of parallelism. Some of the physiophilosophs declared it, stating that the inferior animals were merely the repressed conditions of the higher. This view was taught by some men in high position in France. Their state- ments were, however, too broad and uncritical. The father of embryology, von Baer, of Koenigsberg, declared there was ^'heine Rede^^ of such theory, and Lereboullet stated '* that it is founded on false and deceptive appearances." Even Professor Agassiz in our day has asserted that no embryonic animal is ever the same as the adult of another, though he also once informed the writer that the embryology of two nearly related species had never been studied and compared. This was subsequently done by Professor Hyatt, of Salem, for the nautilus and ammonite division of mollusks, and at about the same time by the writer, for many species of our na- tive frogs and salamanders, and the result has been a complete clearing up of the confusion about parallelism, and the clear estab- lishment of the law. The results attained are these : The smaller the number of structural characters which separate the two species when adult, the more nearly will the less complete of the series be identical with an incomplete stage of the higher species. As we compare species which are more and more different, the more necessarily must we confine the assertion of parallelism to single parts of the EVOLUTION AND ITS CONSEQUENCES. 9 animals, and less to the whole animal. When we reach species as far removed as man and a shark, which are separated by the ex- tent of the series of vertebrated animals, we can only say that the infant man is identical in its numerous origins of the arteries from the heart, and in the cartilaginous skeletal tissue, with the class of sharks, and in but few other respects. But the imjoortauce of this consideration must be seen from the fact that it is 07i single char- acters of this hind that the divisions of the zoologist depend. Hence we can say truly that one order is identical with an incom- plete stage of another order, though the species of the one may never at the present time bear the same relation in their entirety to the species of the other. Still more frequently can we say that such a genus is the same in character as a stage passed by the next higher genus ; but when we can say this of species, then their dis- tinction is almost gone. It will then depend on the opinion of the naturalist as to whether the repressed characters are perma- nent or not. Parallelism is then reduced to this definition : that each separate character of every kind, which we find in a species, represents a more or less complete stage of the fullest growth of which the character appears to be capable. In proportion as those characters in one species are contrasted with those of another by reason of their number, by so much must we confine our compari- son to the characters alone, and the divisions they represent ; but when the contrast is reduced by reason of the fewness of differing characters, so much the more truly can we say that the one species is really a suppressed or incomplete form of the other. The denial of this principle by the authorities cited has been in consequence of this relation having been assigned to orders and classes, when the statement should have been confined to single characters ; and divisions characterized by them. There seems, however, to have been a want of exercise of the classifying quality or power of *^ ab- straction " of the mind on the part of the objectors. This faculty seems to be by no means so common as one would expect, judging from the systematic ideas of many. To explain by a few examples selected at random : First, of species characters, I may cite the fact that all deer are spotted when young, and that some of the species of eastern and southern Asia retain the spotted coloration throughout life. All salaman- ders are uniform, often olive during a larval stage ; some species, and some individuals of other species, retain the color in maturity. To take a genus character : all the deer in the second year develop 10 GENERAL EVOLUTION. their first horn, which is unbranched and small, or a " spike." A genus of deer inhabiting South America never develops anything else. To take a character of higher grade : the exogenous plants usually present net- veined leaves, but the first pair, or those of the plumule, are of much simpler structure, being often parallel- veined ; for example, the cucumbers and squashes. Now, the en- dogens usually produce nothing else than parallel-veined leaves, and no case is known where a plant bearing this type of leaf exhibits the net-veined type as its earliest growth. But what do these facts mean ? As in growth the genus char- acters usually appear last, I will suppose a case where one genus represents truly, or is identical with, the incomj^lete stage of an- other one. In A we have four species whose growth attains a given point, a certain number of stages having been passed prior to its termi- nation, or maturity. In B we have an- A other series of four (the number a mat- ter of no importance), which, during the period of growth, can not be distin- guished by any common, i. e., generic character, from the individuals of group A, but whose growth has only attained to a point short of that reached by those of group A at maturity. Here we have a parallelism, but no true evidence of descent. But if we now find a set of individuals be- longing to one species (or, still better, the individuals of a single brood), and therefore held to have had a common origin or parent- age, which present differences among themselves of the character in question, we have gained a point. We know in this case that the individuals, a, have attained to the completeness of character presented by group A, while others, Z>, of the same parentage have only attained to the structure of those of group B. It is perfectly obvious that the individuals of the first part of the family have grown further, and, therefore, in one sense faster, than those of group b. If the parents were like the individuals of the more completely grown, then the offspring which did not attain that completeness may be said to have been retarded in their devel- opment. If, on the other hand, the parents were like those less fully grown, then the offspring which have added something have been accelerated in their development. I claim that a con- sideration of the uniformity of nature's processes, or inductive EVOLUTION AND ITS CONSEQUENCES. H reasouiug, requires me to believe that the groups of species, that is, groups A and B, are also derived from commou parents, and the more advanced have been accelerated or the less advanced re- tarded, as the case may have been with regard to the parents. This is not an imaginary case, but a true representation of many cases which have come under notice. I can not repeat them here, but refer to the original memoirs, where they may be found. * This is a simple statement of the law of '^ acceleration and re- tardation " of some American naturalists, which probably expresses better than any other the ^^ manner of evolution," the proposition with which we started. Hyatt thus defines it as seen in a group of ammonites which he studied : " The young of higher species are thus constantly accelerating their development, and reducing to a more and more embryonic condition the stages of growth corresponding to the adult periods of preceding or lower species." f This form of demonstration of evolution is of far wider appli- cation than that which I first brought forward. X Iii the latter case the induction may be limited to a certain range of variation, but the present law is as extensive as the organic world ; that is, the ^^positioning" essential to it is found everywhere, from the lowest to the highest, and in characters from the least to the greatest in import. Let an application be made to the origin of tlie human species. It is scarcely necessary to point out at the start the fact, univer- sally admitted by anatomists, that man and monkeys belong to the same order of Mammalia, and differ in those minor charac- ters, generally used to define a '* family" in zoology. Now, these differences are as follows : In man we have the large head with prominent forehead and short jaws ; short canine teeth without interruption behind (above) ; short arms, and thumb * See " Odgin of Genera, and Method of Creation," Naturalists' Agency, Salem, Massachusetts ; or McCalla & Stavely, 237 Dock Street, Philadelphia. f " On the Parallelism between Stages in the Individual and those in the Group of the Tetrabranchiata." " Boston Society of Natural History," 4to, 1866, p. 203. :j: It is quite misunderstood by Darwin, as will be sufficiently evident from the following quotation from the last edition of his " Origin of Species," 1872, p. 149: " There is another possible mode of transition, namely, through the acceleration or retardation of the period of reproduction. This has lately been insisted on by Prof. Cope and others in the United States." This has only been dwelt on as accounting for a very minor grade of differences seen in race and sex. 12 GENEEAL EVOLUTIOif. of hind foot not opposable. In monkeys we have the reverse of all these characters. But what do we see in young monkeys ? A head and brain as large relatively to the body as in man ; a facial angle quite as large as in many men, with jaws not more promi- nent than in some races ; the arms not longer than in the long-armed races of men, that is, a little beyond half way along the femur. These observations are made on a half-grown Cetus apella, from Brazil, a member of a group more remote from men than are the Old World apes, yet with an unusually large facial angle. At this age of the individual the distinctive characters are therefore those of homo, with the exception of the opposable thumb of the hind foot, and the longer canine tooth ; nevertheless, the canine tooth is shorter in the young than in the adult. Now, in the light of various cases observed, where members of the same sj^ecies or brood are found at adult age to differ in the number of immature characters they possess, we may conclude that man originated in the following way : that is, by a delay or retardation in growth of the body and fore limbs as compared with the head ; retardation of the jaws as compared with the brain case, and retardation in the protrusion of the canine teeth. The precise process as regards the hinder thumb remains obscure, but it is probably a very simple matter. The projDortions of the young Cehus apella enable it to walk on the hind limbs with great facility, and it does so much more frequently than an adult G. capiicinus with which it is confined.* The *' retardation" in the growth of the jaws still progresses. Some of our dentists have observed that the last (3d) molar teeth (wisdom teeth) are in natives of the United States very liable to imperfect growth or suppression, and to a degree entirely unknown among savage or even many civilized races. The same suppres- sion has been observed in the outer pair of superior incisors. This is not only owing to a reduction in the size of the arches of the jaws, but to successively prolonged delay in the appearance of the teeth. In the same way men, and the man-like apes, have fewer teeth than the lower monkeys, and these again fewer than the ordinary Mammalia, and this reduction has proceeded in rela- tion to an enlargement of the upper part of the head and of the brain. The cause of development may be next considered, and under * The same relations of man to the anthropoid apes have been dwelt upon by Prof. C. Yogt. EVOLUTION AND ITS CONSEQUENCES. 13 this head may be discussed the natural selection of Wallace and Darwin and other propositions of similar import. '^ Retardation " continued terminates in extinction. Examples of this result are common ; among the best known are those of the atrophy of the organs of sight in animals inhabiting caves. It is asserted that the young of both the blind crawfish {Orcoiiedes pellucidus) and the lesser blind fish [TyphlicMliys suhterraneus) of the Mammoth Cave possess eyes. If these statements be accu- rate, we have here an example of what is known to occur else- where, for instance, in the whalebone whales. In a foetal stage these animals i30ssess rudimental teeth like those of many other Cetacea when adult, which are subsequently absorbed. So also with the foetal ox ; the upper incisor teeth appear in a rudimental condition, but are very early removed. The disappearance of the eyes is regarded by Dr. Packard, with reason, as evidence of the descent of the blind forms from those with visual organs. I would suggest that the process of reduction illustrates the law of *^ re- tardation " accompanied by another phenomenon. Where charac- ters which appear latest in embryonic history are lost, we have simple retardation, that is, the animal in successive generations fails to grow up to the highest point of completion, falling farther and farther back, thus presenting an increasingly slower growth in the special direction in question. Where, as in the presence of eyes, we have a character early assumed in embryonic life, retarda- tion presents a somewliat different phase. Each successive genera- tion, it is true, fails to come up to the completeness of its prede- cessor at maturity, and thus exhibits ^^retardation," but this process of reduction of rate of growth is followed by its termina- tion in the part long before growth has ceased in other organs. This is an exaggeration of retardation, and means the early termi- nation of the process of force-conversion, which has been previ- ously diminishing steadily in activity. Thus the eyes of the Orconectes probably exhibited for a time at maturity the incomplete character now found in the young, a retarded growth continuing to adult age, before the termination of growth was withdrawn by degrees to earlier stages. With this early termination of growth came the phase of atrophy, the in- complete organ being removed and its materials transferred to other parts through the greater activity of '' growth-force." Thus, for the reduction of organs, we have ''retardation " ; but for their extinction, ''retardation and atrophy." 14 GENERAL EYOLUTIOK III. OIT THE CAUSES OF EYOLUTIOIS'. 1. Inductive Reasoning, In the present investigation we are endeavoring to discover new principles, not to apply old ones. The work is similar to that which occupied Newton in his investigation of the law of attraction or gravitation. The process by which we arrive at general truths rests on the consideration of a sufficient number of observed facts, and the determined qualities which are common to all we regard as a law. This process requires for its proper conduct a careful analysis and discrimination of the nature of the objects considered ; otherwise fallacy will result. As exact analy- sis is not always observed by the average mind, this inductive reasoning is not always successfully employed by it, nor under- stood when presented by others. In the deductive process it is more at home. With an ascertained principle given, as some- thing like a staff for the mind to lean on, its application is not so difficult ; but to such a mind induction presents an appearance of uncertainty and even of confusion, and these will certainly exist until order is evoked by the first step — classification. The theory of evolution has thus been charged with confusion, as though it asserted that which overtiirew the order of nature. But the confusion only exists in the mind of such critics. The order of the creation is one of the foundation facts, and thus enters the inductive argument as one of its elements. That conclu- sion which is consistent with this order can not be regarded as its enemy. - 2. On Natural Selection. In endeavoring to assign a cause for the existence of the pecul- iar structures which define the divisions among animals, Messrs. Wallace and Darwin have proposed the now well-known law of natural selection. This states, that, inasmuch as slight variations appear continually in all species, it is evident that some will be more beneficial to the animal than others, in its exertions to sup- ply itself with food, protect itself from enemies, the weather, etc. It then asserts that those whose peculiarities are beneficial will excel those less favored, in the successful use of their jDowers, and hence will live better, grow better, and increase more rapidly. That by the force of numbers, if not by direct conflict, they will ultimately supersede the weaker and destroy or drive them away. EVOLUTION AND ITS CONSEQUENCES. 15 Then, as there are many fields of action and possibilities of ob- taining support in the world, that the weaker will first be driven to adopt such of these as their peculiarities may adapt them for, or not exclude them from. Thus all the positions in the world's economy are filled and the surplus destroyed. This is styled by Spencer the ''^survival of the fittest" ; an expression both com- prehensive and exact. This doctrine is no doubt a true one, and has regulated the preservation of the variations of species, and assigned them their locations in the economy of nature. It was natural that this great law should have been brought out by such men as Darwin and "Wallace, who are by nature much more of observers of life in the field, or out-door physiologists, than they are (or were) anatomists and embryologists. Their writings in their chosen field of the mutual relations of living beings in their search and struggle for means of existence are admirable, and almost unique, especially some of those of Darwin. It is to be observed, however, that they both (especially Dar- win) start with the variations observed. This is assumed at the outset, and necessarily so, for ^^ selection" requires alternatives, and these are the product of variation. Great obscurity has arisen from the supposition that natural selection can originate anything, and the obscurity has not been lessened by the assertion often made that these variations are due to inheritance ! What is inheritance but repetition of characters possessed by some (no matter what) ancestor; and if so, where did that ancestor obtain the peculiarity? The origin of variation is thus only thrown upon an earlier period. Another reason why natural selection fails to account for the structures of many organic beings is the fact that in expressing " the survival of the fittest " it requires that the structures pre- served should be especially useful to their possessors. Now, per- haps half of all the peculiarities of the parts of animals (and probably of plants) are of no use to their possessors, or not more useful to them than many other existing structures would have been. It fails to account for many characters which express the relations of homology and parallelism, and is almost confined in its exhibitions to features which express teleology. This objection has been insisted on by Kolliker, the writer, and by Mivart ; and now Huxley, while defending Darwinism proper against the last- named author, says that *'what the hypothesis of evolution wants is a good theory of variation.^^ 16 GENERAL EVOLUTION". Plainly enough, tlien, nothing ever originated by natural se- lection, and as the present essay relates to the origin of types, lit- tle space can be given to its discussion ; for natural selection, important though it be, is but half the question, and indeed the lesser half. It is to the great causa,tive forces as are the gutters and channels which conduct the water in comi^arison with the pump and the man who pumps it. 3. On Teleology. Two classes of structures have been alluded to : those which are useful to an animal, and those which are not useful ; or the adaptive and non-adaptive. Nothing is better known than that animals are well adapted to their situations in the w^orld, and for their needs as to sujDplying themselves with food, etc. Some part of every species is so constructed as to enable it to live under con- ditions where most other kinds of animals would perish. Thus the sea-rangers, among birds, as the great albatross, etc., possess long and pointed wings ; while those that live in thickets or under cover have short, round ones, as grouse, woodcock, etc. Even our sparrows — those that love the bushes and swamps, as the song-sparrow {Melosjnza melodia) — have short, rounded wings, while those that haunt trees have them sharper and pointed, as the chipping and tree sparrow {Spizella socialis, pusilla, etc.). Water-frogs have their feet webbed ; land-frogs have small or no webs ; while tree-toads possess sucker-like expansions of the ends of the toes, which secrete a glutinous fluid, by which they adhere to the trunks and leaves of trees. Finally, frogs that burrow have one or more of the bones of the base of the hind foot {tarsus) modified into a projecting blade, like that of a shovel ; and, as they squat down, they literally sit into the ground, and are soon out of sight in the hole which they dig with these busy trowels. Cave insects have long and delicate antennae and limbs, ex- ceeding those of their out-door relations by much. Moreover, their usual lack of eyes is a clear case of the reverse of adaptation, i. e., the absence of an organ where not needed. Less attention has been directed to the non-adaptive charac- ters, yet they are as numerous as the adaptive. I do not include under this head useless organs or parts only, but also those which are useful, but whose peculiarities do not relate to that use as advantageous to it. Notable examples of this kind are to be found in the characters EVOLUTION" AND ITS CONSEQUENCES. 17 which distinguish all of the higher groups of animals and of plants among themselves. It is easier to ask than to answer what advan- tages the mammalian skeleton possesses over the reptilian that it should have superseded it. What end was served by aborting the coracoid bone, which in reptiles supports the shoulder-joint from behind, answering to the ischium of the pelvis ? I do not know how to answer this question on a teleological basis, although it involves one of the principal characters of the class of reptiles. What mechanical end was gained by withdrawing the rib-bones of two cranial segments into the cavity of the ear, to become the hammer, anvil, and stirrup of the organ of hearing ? * Was it to perfect the auditory faculty ? Scarcely ; for birds possess as re- fined and as musical an ear as any mammals, and appear to be superior to them in discriminating power, yet in them the ham- mer is the basal element of the lower jaw, and the anvil supports it, being entirely outside the cranial walls. See again one ground of distinction between reptiles and batrachians. The base of the brain-case in the former consists of an axis of bony segments de- veloped in the primordial cartilage, while in the batrachian it is a single bony plate, formed by deposit in the membrane which origi- nally bounded this cartilage. Who can assign any advantage of the one type above the other which can be looked upon as in any way related to the external needs of the animals of those classes ? Another example may be found in the ankle-joints of reptiles, birds, and mammals. In the first two the hinge is between the first and second series of tarsal bones ; in the mammals, between the bones of the lower leg and the first row of tarsal bones. Some- thing besides the superior mechanical advantages of the latter has given it predominance over the former. To turn to the nautilus and ammonite types of Mollusca, we observe beautiful illustrations of all the laws already stated. As is well known, these shells have their tubular cavity divided by transverse partitions. In the nautilus these unite with the outer wall by a plain angle, but in various genera which lead toward the ammonites this margin becomes complicated. This results from an excessive growth of the peripheral part of the partition or sep- tum, so that in order to confine it to the same space of contact it must be folded. This plication takes place in a symmetrical man- ner. The folded edge in Aturia forms a tongue-like loop on each * The homologies here expressed have been rendered improbable by late investi- gation. The argument is, however, not affected. 2 18 GENERAL EVOLUTION". side, on the outer surface. In Goniatites a fold is added on the back. In successive genera other main folds are added, the last appearing nearest the center of the coil. These then become complicated by subordinate undulations which in the more com- plex forms become the axes of a double row of new lobes and folds, the whole presenting symmetrical lobate outlines of much com- plexity and beauty. But another series of changes accompanies those of the septa, and are entirely independent of them. These relate to the yari- ous degrees of winding of the shell. The early form with simple septa (Orthoceras) was straight, but others which succeeded began to turn their shell-making round an axis, thus commencing a par- tial coil. In some the coil was very open ; in others it began close, and then ceased, the shell finishing straight. Others after such a course began to wind again, while some made a single turn near the middle. The most remote from -the starting-point [A^n- monites, sp.) made a tight and complete flat coil, while some, whose septa remained simple, did the same (JVautilus). The direct uses of these various forms of septum and coil are simply inexplicable, and that one of them was any *^ fitter" to *^ survive" than another, by virtue of its usefulness, is for me more than doubtful. I am tempted to continue this theme, for it might be pro- longed indefinitely by any one familiar with the details of ana- tomical structure, but I will only repeat that the illustrations would be drawn chiefly from the characters of the classes, orders, families, and other higher groups. It is not difficult to believe, in the case of the useful structures first cited, that the law of natural selection has had much, prob- ably everything, to do with the preservation of tbe animals pos- sessing them in the various localities to which they are adapted. But that it has had opportunity to direct the lines of progress in the second series is not likely. That it had nothing to do with the origin of either, is certain. 4. On Groivtli- Force. Every change by complication of structure is by addition; every simplification is by subtraction. Every addition is a matter of growth, which is carried on by a process of nutrition. The in- quiry respecting the origin of new forms centers itself at once on the history of growth and the influences affecting it. EVOLUTION AND ITS CONSEQUENCES. 19 If, as I suppose, these additions, either adaptive or non-adapt- ive, be produced by an acceleration * of growth, it is evident that the same immediate cause of that increase must be potent in both cases. That one of the *^ forces" is concerned in growth as well as in all the active animal and vegetable processes, is obvious to those who have carefully observed it. The fact that growth, like work, requires food for its progress and continuance, is reason enough for suspecting the existence of a force, and in some cases the relation between this force and other known forces may be measured. Prof. Henry pointed out these facts many years ago, and illustrated them by observations on the growth of the potato and of the Qgg. The starch of the former, a complex ''organic" chemical compound, weighs much more than the young shoot of cellulose, etc., into which it is converted by the process of growth, so that a portion of the substance of the tuber has evi- dently escaped in some other direction. This was found to be carbonic-acid gas and water, derived from the slow combustion of the starch, which, in thus ''running down " from the complex or- ganic state, to the more simple inorganic compounds, evolves an amount of force precisely equal in amount to the chemical force (chemism) requisite to bind together the elements in the new and complex substance cellulose, f It is well known that substances differ in their capacities for giving out different kinds of force. This, of course, means their capacity for converting one kind of force into another. Thus, if glass be rubbed with silk, the motion is converted into electricity, "while, if it be rubbed by the hand, heat is the principal result. In some cases chemical force, set free by decomposition, is con- verted into light ; in others, heat ; in others, to electricity, often- er to several at once. But one substance, so far as known, pos- sesses the power of converting this chemical force or heat into growth-activity, and that is the material out of which the living parts of animals and plants are composed. This is a protein, a compound of carbon, oxygen, and nitrogen in the order of rela- tive quantity, with a smaller proportion of hydrogen, the whole being often associated with still smaller quantities of sulphur * For the definition of this term see first article, in May number of '* Penn Monthly." (Antea, p. 11.) f "Agricultural Report of Patent Office," 185*7. 20 GENEKAL EYOLUTIOK and phosplionis. In its mechanical aspect, as the material out of which structures and tissues are made, it is called protoplasm. This substance exhibits two different phenomena of force- energy, viz., motion and growth. Motion is exhibited by con- traction and expansion, but which is the active state and which the passive state is matter of question. Some physiologists regard *^ contractility " as the energetic state. Kadcliffe believes that extension is the energetic condition, and contraction a rebound or discharge of the extending force. He finds dead protoplasm to be a dielectric, and believes that in life each muscular fibrilla acts like a Ley den jar. It has been demonstrated that the outer layer of the sheath of a muscular fibrilla is positively electrified in life, while the cut extremities are negative, and it is shown by Eadcliffe that the inner side of the sheath becomes negatively electrified by induction. The attraction of the opposite electrici- ties on opposite sides of the sheath compresses and elongates it, thus, according to his theory, producing muscular extension. The nervous cells and tubes he believes to act in the same way ; the difference being that the walls and sheaths are in a state which prevents compression and extension. The phenomena of mus- cular extension and nervous tension he believes to be terminated by a discharge of the force, such as takes place in electrical fishes, but in much smaller quantity. Thus motive force resides as a form of electricity in protoplasm, and in highly organized animals is specialized into neurism. As to growth-force, all its exhibitions may be reduced to cell- division, cell-nutrition, and cell-origin. Cell-division exhibits two prominent varieties. In both the cell nucleus first divides ; in the ordinary mode, the cell-wall contracts at opposite points, forming approaching plications, which, when they meet, divide the cell. In the other mode or proliferation, the divisions of the nuclei approach the cell-walls, which bulge opposite to them, forming diverticula, which isolate themselves by opposing con- tractions at the base, which meet as before. The nature of the force thus displayed is as yet only speculative, and its demonstra- tion will result largely from observation on cell-origin from homo- geneous protoplasm. Eadcliffe suggests an ingenious theory. He supposes that the protoplasm acquires an external layer differ- entiated from the internal mass by exposure to and contact with external substances, and that the electricity generated in the in- terior is distributed on the under surface of this stratum. That EVOLUTIOI:^ AND ITS CONSEQUENCES. 21 this induces opposite electricity on the external surface, which, as in the muscular cell, causes compression, and therefore extension of the stratum. This extends itself beyond its contents, which may be attenuated, filling the space, or contracting, forms the nucleus. This view will not, however, account for nucleus and cell- division, which are the subsequent and principal exhibitions of growth-force. Perhaps the following suggestions may throw some light on it. Should a polar tendency appear in the nucleus, were the protoplasm of the proper viscidity, the poles being of like electric name, would tend to separate by repulsion, thus forming the hour-glass shape so well known, and afterward division. This nucleus division would inevitably be followed by division of the cell-wall, if its inner face were electrified in opposition to the nucleus. For the wall being attracted toward it equally all round, the separation of the two nuclei would be followed by an incurvature of the walls opposite the interval between the nuclei, in order that each should maintain a position equidistant from its center. Further divergence would result in the completion of the cell-wall of each, apart from the other. This process would be supported by nutrition of the cell, which proceeds by the passage through the cell-wall to the nucleus, of additional protoplasm from the blood. Of course, the prime question is as to whether polarity can appear in the nucleus. That growth is first polar appears probable on consideration of the globular and discoidal forms of the lower animals, and that this principle lies at the basis of the growth of the higher is rendered equally probable by the phenomena of symmetry of different kinds, as bilateral, anteroposterior, etc. The electricity supplied to the outer sheaths of muscular fibrillae is, according to Dubois Eey- mond, positive. That covering the surface of the nucleus must be thought to be positive also, if it be effected in opposition to the inner wall of the cell-wall, which is known to be negative by ex- periment. But in that case it would be difficult to perceive why it should not fill the cell by attraction to the wall. If, on the other hand, it be a generator of negative electricity, it would re- tain its integrity and induce a temporary change in the wall. The transmission of protoplasm through the cell-wall to the nucleus would produce an accumulation of electricity to be dis- charged in extension, or a disturbance of equilibrium, to be fol- lowed by polarity and division ; but the conditions under which 22 GENERAL EVOLUTION". these results would appear are, of course, unknown. The me- chanical arrangement and condition of the parts would have much to do with it. We are, however, here in the arcana of life, and the forms of law which rise before the mental vision are but as the statues of Memnon that greet the toiler on the river of mysteries ; they loom upon its banks in twilight, and the w^hen, the how, and the where- fore remain unanswered. But the river of Africa is yielding her secrets, and, though the life that she nourishes may be the last she will give up, it is no less surely promised to the patient inquirer. A great advance toward an explanation of the operation of this growth-force was made in the demonstration of the fact that its highest exhibitions are confined to the multiplication of cells by division of pre-existent ones, by contraction of their nuclei and walls in lines which finally meet. The construction of additional parts consists solely of this cell- growth, but the character of the result is, of course, dependent on the position at which this addition takes place. It may be at the terminus of a limb to add another toe, or on the wall of an artery to add a valve. It may be in the brain to add a band of fibers, or on the edge of a muscle to extend its width. That tissues are made of cells of original or altered shape, sepa- rate or confluent (flown together) is well known. That the ar- rangement of tissues into organs is due to the direction of this multiplication is also true. Thus a gland is a collection of folli- cles, each of which is a bagging of a plane tissue. This bagging- is an exaggerated convexity, which is occasioned mechanically by excess of cell-growth at one spot on a uniform surface. Solid parts are all formed, in the first insta7ice, of simple segments. These are parts produced in a straight rod by excessive elongation or growth ; the process being as before, the division of cells and distribution of homogeneous protein between them. All this is derived from the study of homologies combined with embryology, and the result is wonderful, and simplifies at once our ideas of the action of the growth-force. It is mainly a repetition of cell-divis- ion, the result as to structure being entirely dependent on the influences which locate its activity and regulate its amount. Now, its amount will depend on the capacity of the existing organism to convert heat, etc., into it ; and the form, as to tissue, etc., in which it appears, depends no doubt on the complexity of the machines or organs of which the organism is composed. In EVOLUTION AND ITS CONSEQUENCES. 23 the case of the higher organisms we have muscle, converting the results of nutrition into muscle ; skin and nails making more skin, etc. ; brain making more brain ; bone making more bone. The prime question is the cause of the location of growth- force. Experiments on this point are greatly needed, and in their absence it will be necessary to take a wide survey of facts. A given animal Organism can only convert a given amount of force, and that capacity must remain uniform so long as the machine or structure remains the same. If, however, an addition to its work is developed in one quarter, a subtraction from some other region must take place if the whole amount remain the same. When, then, a useful organ is added, subtraction from some less important locality must result, and, as a consequence, the latter must become still less prominent in the general economy. Hence, the development of the useful class of organs already cited must always be accompanied by a corresponding disappearance of use- less ones. This would be by reduction or retardation. But, in the case of the complex folds of the margins of the septa in the ammonite, useless parts are added by acceleration. Here a gradual increase in the amount of growth-force must be believed in. The representation of simple growth-force, i. e., the result of bathmism, not specially located, is seen in general addition to size. In domestication careful feeding, associated with protection against all exhausting exposure or exertion, tends to this increase of size. This is well known to be the case in hogs and cattle and animals of quiet and easy life. The reverse conditions, as poor food, ex- posure, and disproportionate exertion, reduce the size ; witness the Maryland breed of cattle, and the semi-wild hogs of the Southern States. This matter is, however, nicely balanced with the pro- duction of motion, for if the latter be excessive, or the supply of material for consumption be insufiBcient, growth-force must be evolved in less amount. It will be necessary here to state that the supply for the con- version of all the forces of the body is derived from the nutriment as circulated in the blood. But the condition of plethora of growth-force is also the one highly favorable for the appearance of variations of structure, or the location of growth-force in new places. Domesticated animals are notorious for this variation, while the still more numerous ex- amples of *^ protean" species in nature are always predominant forms, abundant in individuals and widely spread. For example. 24 GENERAL EVOLUTION. the wolf, the red fox, the red-tailed hawk, the garter-snake, the tiger, salamander, etc. That the yariability depends on a peculiar condition of the ani- mals themselves, and not on domestication, excepting in so far as it produces these conditions, is plain, not only from the above facts, but from those observed in domestication. It is well known that while pigeons, fowls, cattle, dogs, etc., are variable, or '^ pro- tean," the peafowl (Pavo) has maintained its specific characters with great accuracy during a period of domestication as long as that of the other species named. The same may be said of the guinea {Numida) and the turkey {Meleagris). These facts show that domestication is only a remote cause of variability. 5. On the Location of Growth-Force. With the fact of increase of general growth-force before us, have we any others which can guide us in fixing on a cause for its special location ? It is plain that the useful additions which have constituted certain genera, families, orders, etc., what they are, must have been produced as a consequence of the existence of a need for them ; or, on the other hand, being created first, they must have sought for use, and found it. But what are the rela- tive chances of truth for these two propositions ? In the second case, admitting evolution as proved (see Part I), we perceive that an almost infinite chance exists against any usual amount of variation, as observed, producing a structure which shall be fit to survive in consequence of its superior adaptation to external cir- cumstances. It would be incredible that a blind or undirected variation should not fail in avast majority of instances to produce a single case of the beautiful adaptation to means and ends which we see so abundantly around us. The amount of attemjot, failure, and consequent destruction, would be preposterously large, and in no wise consistent with the facts of teleology as we behold them. What of the opposite view ? We have in its support the well- known facts of determination of nutritive fluid during use of parts, not only for supplying fuel for the motions of use, but also for growth-force and material for the increase in bulk of the part used. Who has not remarked the large size of the hands of the laborer, and of the nails of the working-woman ? Who can not remember some of the countless examj)les of certain modifications of form being associated with special excellence of use of the parts EVOLUTION" AND ITS CONSEQUENCES. 25 in different races of the same species of individuals of common parentage, showing that they must have grown with the history of those races ? Who does not know the short, wide jaws of the bull-dog, with their oblique teeth, produced by the expansion of the zygomata to accommodate the huge temporal muscles so neces- sary for maintaining a firm hold of its enemy. Then the long and full nose of the hound, and its more extended turbinate bones — how closely is this connected with its developed scent ; while the light muscular forms of the greyhound are undoubtedly necessary to its well-known speed. If it be said that these variations have not resulted in a single change of structure worthy of note by a systematist, we can point to the Japanese dog, where the excessive reduction of the jaws anteriorly has resulted in a total loss of some of the premolars and molars. The loss of molar and incisor teeth from shortening of the jaws, in the human species, has been al- ready noted. The number of such instances is very great, but, as space to enumerate them fails, it is only necessary to add that they are characters of high importance in a systematic sense. Their importance will be more readily conceded in remembering the proposition, already stated, that species are simply isolated varie- ties, and of similar origin. Confirmatory of this view are the facts already cited with ref- erence to the relation of motive to growth-force. The force in- volved in both being seen to be similar, perhaps identical, the former represents its energetic state as discharge and motion, the other energetic without discharge, in the growth of cells. And whatever determines this force to a given part of the body must then probably result in both of its exhibitions, dependent on the kind of cells which receive it. As above remarked, the conditions which determine the result are unknown, except that the two kinds of muscular cells are the only ones in which elongation is strongly marked. Another reason for believing in use as a cause of structural change is the manner in which the same useful structures have evidently appeared on totally distinct stems, as an evident adapta- tion to the same circumstances in which the different types have been equally placed. Thus the birds of prey possess the hooked, often toothed, beak, appropriate for tearing and destroying ani- mals. Their stock is the same as that of the cuckoos and parrots, and even of the pigeons. The butcher-birds are of the division of songsters, not widely removed from the thrushes, and far enough 26 GENERAL EVOLUTION. from the raptores, yet tlie same hook and dentate bill reappears in them, as adapted to flesh-eating habits. Among the reptiles, which were no doubt originally land ani- mals, and derived from batrachians, we haye a large number adapted to swimming in the ocean, and these not all of the same stock. Thus the Plesiosauri are crocodilian in relationship, while the Pythonomorpha of America were of the same that produced the snake and lizard. Again, the same modification appears in the Cetaceans, or whale, etc., among mammals which are primarily a terrestrial division. It is a nice point of phylogeny (or the science of genealogy) to ascertain whether adaptive or strictly ^'bathmic" (or embryonic grade) characters came first in a time in a given group. Among frogs we have four divisions. One has an embryonic mouth and embryonic breast-bones ; another, embryonic mouth and complete breast-bones ; the third, embryonic breast - bone but complete mouth; and the fourth, with both complete. The first is the lowest and probably the oldest in time ; agreeably to this supposition, it is distributed over the whole earth. The second is East Indian and African ; the third and most extensive is Australian and American ; while the fourth is confined to the Old World and JSTorth America. The second, third, and fourth divisions possess corresponding series of genera of different structure adapted to different modes of life. Some have shovels for burrowing, some webs for swimming, and some palettes for adhering to branches and leaves of trees. If these characters were first fixed, then those with the more perfect breast-bone and mouth are descendants of those with the less perfect ; if, on the other hand, the conditions of mouth and breast-bone were first fixed, then each division thus defined in its special region was modified into the subdivisions, each adapted to a special mode of life. I have called these parallel divisions "homologous groups," and probably the origin of the embryonic modifications has sometimes come first, and sometimes the adaptive structures have preceded. Nevertheless, the lowest or most embryonic division will often have developed its own adapt- ive divisions, and each of these will agree in 'producing descend- ants which have advanced in the embryonic scale, and so produce homologous groups. For these and other reasons it is concluded that the useful characters, defining natural divisions of animals, have been pro- duced by the special "location of growth-force" by use. Useless EVOLUTION AND ITS CONSEQUENCES. 27 ones have been produced by location of growth-force without the influence of use, or by its subtraction, due to a disturbance of equilibrium, consequent on the special location elsewhere. But we go back to the origin of the question in investigating the action of growth-force undisturbed by the interference of lo- cating influences. This is only to be ascertained by an examina- tion of lower organisms in connection with the higher. A point that first strikes the student of higher animals is, that after he has proved the law of Jiotnology to be true, as regards different animals when compared, he further finds that the parts of the same ani- mal are also homologous, that is, right hand and left, front and behind, bottom and top are also constructed on the same plan, so as to be reduced to the same elemental parts. This is described under the names of "anteroposterior" and ^* bilateral symmetry," etc.* These laws apply to all parts of the organism, and, though there appear to be exceptions, these are traceable to a common symmetrical type, the change wrought being one form of speciali- zation. It is not surprising then that the lower we descend in the scale of life the less marked is the departure from the entirely symmetrical disposition of parts as regards the common center. This is beautifully seen in the EacUata, etc., where the jelly-fish, the star-fish, and the sea-urchin are familiar examples. But these are complex compared with forms below them. The minute Polycystina construct shells of beautiful sculpture or tracery ; but, though they present many forms, they may be all referred as modifications, to the symmetrically-marked disk. Of cellular animals, Trichodiscus represents a discoidal aggregate, and Actinophrys a globular mass of cells. Monas and its allies consist of one or several cells in globular form. Lastly, in the first appearance of life in the most complex ani- mal we have first a cell, which, then '^ segmenting," divides itself so as to become a globular mass of identical cells, arranged about the center. From the cellular animal upward the operation of addition of parts is then one of repetition, and that centrifugally in the case of bodies which are developed in all planes, or peripherally in those which are in one plane. Thus the complication of the edges of the septa of the am- monites is accounted for. First, the growing animal was supplied See Prof. B. Wilder, in Proceed. Boston Society Nat. Hist. 28 GENERAL EVOLUTION. with an excess of growth-force. The type of the preceding gen- eration being strictly adhered to according to the laws of inherit- ance, the only opportunity for its exhibition was necessarily after the inherited parts were completed by acceleration. The results could only, therefore, be exhibited on the edges of the new septa and free margin of the outer wall. As the older growths me- chanically restrained the new septa from mere extension, folding or plication must have resulted from the crowding of additional surface into the small space. This folding would take the form of simple branching, and then "repetition" of the process by a refolding of the outlines of the first fold. The edge would thus have the digitate or pinnately branched appearance it is known to present. Another case of folding is that of the brains of the higher mammals, including man. This was occasioned by excess of growth-force distributed to the circumference (from an inherited central region), exceeding in amount that of the space (skull) in which it was inclosed. Folding was necessary for its accommoda- tion in the contracted space. This is a highly useful modification. Another case like that of the ammonite above cited, whose use is not so readily determined, but which illustrates excess of growth- force on some other account, is that of cotyledonary leaves in some plants. In these cases the growth of the leaf is accelerated, re- quiring plication for its accommodation. We therefore have the two laws regulating the " location of growth-force " irrespective of use, viz. : 1, the centripetal or po- lar tendency ; 2, the peripheral tendency ; both more or less de- termined by the inherited central or first grown parts. There is, however, another element which in animals disturbs the symmetrical direction of growth-force besides use, and which precedes use, i. e., effort. Use presupposes a part to use, and a simple part is sufficient for its influence, so that it be usable ; but the first beginnings of few structures are usable. As Mivart has objected to natural selection, that the first rudiments of organs could never be sufficiently important to an animal to give it a preference in the struggle for existence, so it might be urged against the theory of use that rudiments are generally useless, and could not have been originated by use. The effect of use is, howcA-er, twofold. The contact with ob- jects used has some effect in stimulating nutrition, as well as the exertion of the muscles necessary to use. But determination of EVOLUTION AND ITS CONSEQUENCES. 29 nutritive fluid is well known to be under the influence of nerve- force. How imagination stimulates secretion is seen in the famil- iar example of the flow of saliva in anticipation of food ; a very different example is the phenomenon of blushing under emotional stimulus. Nevertheless, it is not evident that growth can result with any such facility in a fully grown animal. It is thought that the effort becomes incorporated into the metaphysical acquisitions of the parent, and is inherited with other metaphysical qualities by the young, which during the period of growth is much more susceptible to modifying influences and is likely to exhibit struct- ural change in consequence. Certain it is that acceleration ceases with growth, and, as the young of animals are not in complete re- lation with the surrounding world, the influences controlling it must be inherited. This consideration renders it doubly probable that the results of effort on the part of the j)arent appear in change of structure in the offspring. Of course, immense numbers of cases of continued effort can be produced by the objector, in which no structural modification has resulted. There are various reasons why a modification should not take place. In the first place, the exertion of use must be great, habitual, and long-continued ; in the next place, abundant food must be at hand ; finally, growth-force must be to spare in the growing young, either from some less necessary part or by ex- cess. Now, cases are probably not rare where none can be spared from another part without injuring the efficiency or viability of the animal ; hence, all such changed individuals would perish through some form of natural selection or disease. Domesticated animals can be pointed out where effort and use have long been put forth in the service of man without changing structure. But such effort is not to be compared for a moment with that put forth by animals in a wild state, in seeking food or protection from enemies. The protection furnished by man, and consequent release from the struggle for existence, has reduced the chances for such variations greatly. Nevertheless, variations profitable to man have resulted ; witness the race-horse and carter. In cases where one side of the body is used in excess of the other, unsymmetrical development would be counteracted by the law of polar or centrifugal growth, all that might be acquired by the one side being inherited by both. Even this original sym- metry has, however, been overcome in some types, as in the flounders (in the jaws and teeth as used parts). This part of 30 GENERAL EVOLUTION. the subject is purely hypothetical, however probable, but the as- pect of the discussion will be materially brightened to the reader, if he have previously adopted, with the author, the principle that evolution has been the mode of origin of the present life-forms of the earth. Reverting now to those beings which are either in part or en- tirely destitute of the power of determining these movements, as plants, various causes present themselves as modifiers of the polar or centripetal activity of growth-force. In the case of a plant, the medium in which it grows modifies the result ; for example, the downward growing axis or root differs much from the upward aerial portion or stem. Aquatic plants, supported beneath or on the surface of the water, lack the strong stems and braces neces- sary to air-growing plants ; while of the latter, those with weak stems develop tendrils and other supports. In these cases physical laws have been the guides of growth-force. In the case of bright colors, which we know to be impossible in vegetation without sun- light, the influence is chemical. The first physical law is, that growth-force, uninfluenced by inherited peculiarity,* or any stronger influence locating a nutri- tive fluid, must develop extent in the direction of least resistance, and density on the side of greatest resistance, when not too great. The illustration of this statement would be that a globular mass of cells brought to the point of Junction of two media, as water and earth or air and earth, elongates in the direction of the medium pre- senting the least resistance, i. e., air. Thus a longitudinal develop- ment would originate from a centrifugal, and a repetition of the same process would produce branches. The reason why repetition should appear along the sides instead of as continued prolongation of the axis, arises probably from the difficulty of conveying fluid nutritive material far from the base as a source of supply, and the occurrence of various mechanical obstacles easy to be conceived. In low plants, where nutrition is absorbed by all parts of the axis, which branch, as the subterranean parts of fungi {myceliwn), dif- ference of local supply would produce an effect. In higher plants, where fluid nutriment is only introduced at one point (the root), and conveyed by special layers of cells or tubes, the difficulty of maintaining supply at a distance from its source would encourage lateral repetition or branching, f * This is supposed to be due to atomic peculiarity of cell-substance. f The great power exerted in a given direction by growth-force due to gradual EVOLUTION AND ITS CONSEQUENCES. 31 6. On the Origin of Intelligence, Leaving this part of the subject, we approach one of higher interest, viz., the effects of the metaphysical or mental acquire- ments of animals on their exertions in effort and use. The growth of the mind in animals has, no doubt, followed the same laws obeyed by that of man ; the difference being that the lower forms have remained permanently fixed in stages early passed by the lord of living beings. The foundation qualities from which all the phenomena of intellect may be derived are, the powers of re- tentiveness (memory) and of perceptions of resemblance and dif- ference. These traits are well known to be possessed by many animals, and perhaps in some degree by all. Their possession will be modified by the power of exercising attention, which, in its turn, will depend on the sensitiveness of the animal to impres- sions^n other words, the ease with which consciousness may be aroused. The origin of the disposition to take food will be the rudiment of all that appears as ivill in higher animals, and which, though supposed to guide, is the creature of so many stimuli. This ori- gin is supposed by metaphysicians to be the result of education of the '* spontaneous activity" of animals by their pleasures and pains. The brain of man and of other animals is an organ which re- ceives and retains pictures and impressions, both painful and pleasurable. The retention of these pictures is not a state of con- sciousness, but they may be brought into the consciousness accord- ing to the law of "contiguity," or association. That is, that the recurrence in the actual of some object or event, which was per- ceived on a former occasion, at or near the same time as another object or event not again repeated in the actual, will bring the latter before the consciousness. So, also, the revival of one such picture will bring within the mental vision others impressed on the mind at or near the same time as the first. These events may have been in the reality either painful or pleasurable. On the recurrence of circumstances which on a former occasion resulted in pain, the resuscitation of the mental picture, then impressed on acquisition and inheritance is illustrated by the plantain, Plantago majoy. Although without axis, it has been observed by James C. Cresson, in the Philadelphia Park, and Alfred Cope, on his drive, to force itself through a solid bed of hard vulcanite pavement, several inches in thickness. 32 GENERAL EVOLUTION". the memory, produces an anticipation of the pain, and the ani- mal at once flies from the source of danger. So, also, with pleasur- able objects, the resultant action being the reverse, or an attraction to the object. In both cases a previous experience of the relation between the object and the sensation of pleasure or pain must have been had. There is^ in addition, the power of determining differences and likenesses, by which contiguities or associations are originated in the mind, of a character different from that resulting from the relations of times of receipt of the impression. Such contiguities recall pictures to the consciousness in consequence of their resem- blances in essential qualities. On these two bases, together with the perceptive faculties, rest the complex phenomena of the animal and human minds. They are probably physiological functions of brain tissue, for the follow- ing reasons, among others : 1. Impressions are conveyed by physical means to the brain. The brain can only receive a given number at a time without ex- haustion, and is prepared to receive more after being nourished. Impressions long forgotten are revived in certain states of disease. Impressibility and memory are most marked during growth, and diminish with age. 2. If impressions are physically produced and preserved in the brain, those made at or near the same time would remain close together in the brain, and this material proximity would be the ^* contiguity " according to which they would come before the consciousness. 3. Classification or appreciation of resemblances takes place unconsciously in the mind (by '' unconscious cerebration "). Re- semblances not seen at the time of impression suddenly flash into the consciousness on a subsequent revival of it. The " contigu- ity " to like things thus established may be more or less lasting in the mind than the contiguity of circumstances under which the impression was made. 4. As ^^ contiguity" in time is believed to be revived by contiguity in location of impressions in the ^^i^erceptive" part of the brain, so *^ contiguity " of resemblance may be believed to depend on contiguity of location in the "reflective" part of the brain. The retention of the contiguities of time and of resemblance constitute the basis of education of an animal, and its intelligence EVOLUTION AND ITS CONSEQUENCES. 33 will be in proportion to the number and comj)lexitjof these ac- quisitions. The lowest exhibitions of contiguity, or association in time, do not require a nervous system for their display. The Protozoa, which are without nervous system, exhibit its results in their de- terminate seizure of some small objects as food and rejection of others. The sea anemones (Actinia) display some preferences as to the substances to which they attach themselves. All power of taking food implies the retention of the impression of pleasure on first accidentally coming in contact with it. This power is then present in protoplasmic beings of the simplest type. All the movements of animals have been shown to depend on a direction of this motive force, consequent on a necessity for avoiding pain and obtaining pleasure. It may be regarded, more- over, as a truth that heightened vitality or energetic conversion of force is always a state of pleasure, while depressed vitality is generally the cause (as well as a consequence) of pain. Hence the pleasurable nature of taking food, and the early education of an animal in the distinction between objects nutritive and non-nutri- tive. It is well known, however, that food may be taken, and many or all other functions and acts be performed automatically, or in a state of unconsciousness. This is as much the case with the highest powers of thought (as in unconscious cerebration) as with the humblest acts which satisfy bodily wants. The question then arises whether these acts may not arise in a state of unconscious- ness. So far as our own self-knowledge goes, we would reply in the negative. All intellectual functions are produced by educa- tion, and education involves consciousness at every step. Other habitual and automatic acts were originated consciously, but the contiguity of parts of the act becoming impressed on the brain, future repetitions of it are reflex or unconscious. We have seen that the development of the habits of animals is in strict obedi- ence to the preference for pleasure and avoidance of pain. Pleas- ures and pains of course express sensations which involve con- sciousness. It then appears to me that, in the lowest animal, con- sciousness must be present at the time of origin of every habit, but that it may have been soon lost in each case, and the habit become automatic. If this position be true, every subsequent addition to or change of habits must have been accompanied by a resuscitation of con- 3 34: GENERAL EVOLUTION. sciousness. But how is consciousness aroused in the cases which we can investigate — that is, in our own sjoecies ? In the common case of sleep, a mere sound is sufficient to cause its return. In syncope and other forms of loss of consciousness, a sudden shock, as of cold water thrown on the face, will often restore it. In ordinary states, comjiulsion or pressure will produce a more in- tense degree of consciousness. Indeed, in many j)ersons conscious- ness varies greatly under different influences ; thus a dreamy state naturally follows a lack of nutrition of the brain, as during a fast, but the mind is readily aroused from it by a strong or sudden im- pression made on the senses or by an effort of will. It is, hence, to be believed that in animals whose acts may be largely automatic consciousness is aroused by exceptional sights, sounds, hunger, and other sensible impressions, the more readily in proportion to the development of the sensory ganglia of the brain. In the low- est animals, consciousness will be aroused with much greater diffi- culty, and life must be in part a blank, and in part a dream, at rare intervals illumined by gleams of consciousness produced un- der the influence of strong external stimulus. At these times of awakening we must believe that new movements are instituted, which will become habitual in proportion to the extent to which they are repeated. From what is known of reflex actions, it is evident that move- ments may become habitual, and hence automatic, wherever cellu- lar or gray nerve-substance exists. Thus, movements instigated by the spinal nerves derive their automatism from the spinal medul- la. This axis no doubt derived the original nerve-force from the brain, but repetition of the act under the original stimulus con- fers the automatic power on the spinal cord or ganglionic center as certainly as on the brain. This must of necessity follow the complication of nervous structures by addition to the original center. Thus are explained the automatic movements of the frog's or centipede's legs in the well-known experiments, when separated from the brain or principal nervous center. Greater difficulties are experienced in accounting for the origin of the automatic movements of plants. It is evident, however, that many of these, perhaps all, are not due to the energy of mo- tive-force, but are phenomena of growth-force alone. Motion is produced by the change of direction imparted to growth-force by the influence of heat, light, contact, etc. This will largely follow as a consequence of the longer persistence of growth in plants EVOLUTION AND ITS CONSEQUENCES. 35 than in animals. In some of the yery lowest plants movement wonl'd seem to be similar to that seen in the lowest animals. The origin of intelligence is then to be found in the first traces of con- sciousness. But inquiry will go further in the search for truth. One school of physiologists believes consciousness to be due to cer- tain molecular changes of nerve (i. e., brain) substance. No doubt these are essential to consciousness ; yet it is, at least, utterly inconceivable that any molecular condition should be capable of recognizing either pleasure or pain. Here we find the first ap- pearance of the '^feelings," that part of the human mind which deserves to be called, par excellence, '*the soul," and which is the ^Mocator" of all the forces which go to build up the tis- sues, organs, and parts of the body ; and hence the organic type of the intellect and even of the will. For if we find growth-force to be a correlative of physical force, and subject to motive-force for its *Mocation," so, while we find that motive-force is in like manner but another equivalent of ordinary force, we find it also subordinate to this principle which "locates" it. 7. On Intelligent Selection. We will now retrace our steps along the line of causes and effects, and see, if possible, the nature and results of "intelligent selection." Protoplasm, homogeneous or cellular, discharges a force called "motive-force," or neurism, which it converts from surrounding forces by virtue of its molecular (chemical) or atomic constitu- tion. Its spontaneous exhibitions as movements bring it into contact with surrounding objects, when, if sufficiently sensitive to impressions, consciousness of a pleasurable or painful charac- ter is aroused. Then in proportion to its sensitiveness, and the strength of the impression, the protoplasm retains the latter in an unconscious way, and, on the subsequent recurrence of the ob- ject to the consciousness, the pleasurable or painful attribute is also revived by the law of "contiguity." The "vital principle" interfering restrains the motive-force from exercise toward it, if it be painful, or releases it for motion toward it, if it be pleasur- able. This quality of the vital principle is a power of choice, and, in so far as consciously exercised, is will* Nothing is better known than that acts originated consciously may, by repetition, * For further development of this subject see Part IV of this book. 36 GENERAL EVOLUTION. come to be exercised unconsciously, or as habits. The form these habits take, will depend on the opportunities and conditions offered, for instance, in the matter of food, by the surrounding order of things. Motive-force is, of course, only another name for effort and use ; the former being a putting forth by means of conducting material or organs, without executive apparatus ; the latter always requiring organs or parts by which to execute. If, as previously assumed, effort and use locate growth-force, cellular structure will appear in the directions indicated by the activity of motive-force. It is converted by protoplasm from heat and chemism, or one only of these. That it does not require dif- ferentiated *^ motive-force" as a source, is proved by the growth of plants, which have no motion proper. Growth-force, by its ^^ repetitive " action,* creates organs. These at first will be extremely simple, but, as machines, at once increase the power of the animal to produce motive-force by con- version, whether the machine be a digestive apparatus for the ap- propriation of the material, or a mechanical one for the exercise of the force, the former necessarily preceding the latter in time. With the increased power of assimilation (digestion) comes a larger amount of material for increased exhibition of growth-force, a part being burned or otherwise converted into the force, and a part remaining as the material from which the cells are construct- ed. In the latter 23art of the growth-period a considerable portion is usually consumed for motive-force. In the history of the material environment, various changes of condition succeeded each other. Changes of level took place ; waters were purified by precipitation of chemical compounds ; fresh waters were established ; the atmosphere deprived of various gases ; new mineral, and especially vegetable, products took their appropriate places. All these offer a vast variety of food-supply and opportunity for the pleasurable discharge of motive-force, and, under the laws pointed out, efforts of animals were directed in va- rious lines, as the conditions presented themselves. Thus execu- tive organs were produced of varied character. Some acquired limbs and others wings for transportation from place to place. What a vast addition to their impressions must have been acquired by the first animals which could thus leave the place of their birth ! How many new "contiguities" were established, and how * « See " Method of Creation," on the Law of Repetition. EVOLUTION AND ITS CONSEQUENCES. 37 many new habits originated ! Look again at the acquisition of teeth. From a soft uniform diet the animal no doubt gradually learned to appropriate hard substances, and what a world of ex- perience and consequent habit must have been at once placed in its way ! These acquisitions are of course mental, and include both kinds of contiguity, viz., that of succession in time, and that of association through resemblance. Animals choose between objects chiefly in accordance with the first mode, but are not lacking in the second quality. As an example of the latter, classification ac- cording to color is exhibited by some birds, which choose brightly colored objects and reject dull ones — the Australian bower-bird, for instance. As is well known to metaphysicians, these acquisitions lead to '^predication" and "forethought." Thus a hound becomes ac- quainted with the habit of a buck or rabbit in doubling, or in fol- lowing a given circuit. The recurrence of the chase recalls the habit in consequence of contiguity of the impression of the former pursuit of the animal and the course it took. The hound then supposes or " predicates " that the deer will repeat the course. We know that some do so from the fact that they have been observed to cut off the curves in the animal's track, or to station themselves at the point where the deer, for instance, will pass. In the sec- ond act forethought is also involved. The hound sacrifices the lesser pleasure of the chase for the greater one of securing the prey. In forethought, experience having taught which circum- stance results in greater and which in less pleasure, action is re- strained in the presence of the second for the sake of procuring the first. Thus in ants, immediate pleasure suggests a life of labor enough for present wants, and ease for the remaining time ; but the greater pleasure of existence during some time of scarcity has induced some of them to lay up a store, which has develoj^ed into the complete protection against winter they display in cold cli- mates. In the cases cited it is perfectly evident that the hound would never have learned to predicate had he not had limbs to bring him in contact (by pursuit) with the habits of the buck. Nor would the ant have learned to provide if it had not been furnished with the jaws necessary to the excavation of chambers and the carrying of food. And neither would have performed these mental acts had they not possessed nervous centers capable of sensation, reten- 38 GENEKAL EVOLUTIOi^. tion, and classification. But the development of these qualities depended on the possession of the executive organs. Thus intelligence of various degrees has resulted — first, from possession of executive organs ; secondly, establishment of con- tiguities by their use ; tliirdly, from classifications based on con- tiguities. There are two notable examples of the great advance in mental accomj)lishment inaugurated by the acquisition of an executive organ. The first is the acquisition of the hand by the monkey. Any one who has compared their manners with those of the si3e- cies of unguiculate (clawed) animals — as, for example, the dog — must be struck by the immense advantage possessed by the for- mer. To begin with, it renders the monkey an expert climber and catcher of moving objects. Then he greatly increases his habits of observation by the facility with which he brings objects before his eyes. The minuteness of his criticism is aided by his power of manipulating with his fingers. He learns the results of tlirowing. A cautious monkey, set on a strange animal or per- son, does not rush at them to bite like the dog, but takes the more refined method of throwing sticks and stones. In obtaining ob- jects, if they be out of reach, a monkey uses a stick to draw them in with. In a Cetus capucinus, in my possession, a leather strap was preferred, and was thrown with great dexterity, and the ob- ject always secured by drawing it nearer in loops of the strap. If the strap were sometimes thrown out of reach, the monkey would use a stick or poker in order to obtain it again. All this would have been quite imj^ossible without a hand. This facility has not been lost on the intelligence of the monkeys. Their curiosity is proverbial, and no animal can compare with them as successful thieves ; moving m bands, with watchers stationed, and taking pains to store their booty in their cheek-pouches while they have opportunity, and not wasting time in eating exclusively. Another instance is that of man. Here the acquisition con- sisted of vocal organs capable of speech. Any means of com- municating and recording thoughts had the stupendous conse- quence of rendering the acquisitions of one man or class of men the common property of all. Another consequence, equally im- portant, is the preservation of successive races of men from the necessity of passing through the experiences of those that pre- ceded them, and the enabling them to commence their intellectual life nearly where the others left off. So great would necessarily EVOLUTION AND ITS CONSEQUENCES. 39 De the location of activity in the brain, that its stages of growth would be the principal changes of structure to be witnessed in human history, together with those which should result from loss of growth-force in other regions by abstraction. To return to the material aspect of the case. The discrimina- tion between pleasure and pain locates motive-force, which is derived from without. Motion or use locates growth-force, also derived from without, and thus produces organs out of material derived from without. These organs diversify the directions of motion. From new movements arise new pleasures and pains, and motion is again '* located" in its exhibitions in some particu- lar directions, and restrained in others. These directions depend on external circumstances at the first. The determination of motion to certain lines locates growth-force in those lines, and new parts are produced, which are further executive organs and types of structure. We now repeat the circuit. New executive organs introduce new contiguities, the number depending on the general complication of the animal in connection with that of the organ, and new pleasures and pains result. The pleasures again determine activity, and, under the circumstances already men- tioned, growth-force is again located. In these facts lies the explanation of the principle of direction or location of executive structures about the head, termed by Prof. Dana ^^cephalization." The increasing demands of in- telligence locate growth-force round its organ, the brain, etc., while such location reacts by furnishing means of increased ac- tivity of mind. These conjunctions of growth with executive capacity, consti- tute a class of *^ expression points"; points attained without leaps, and abandoned without abruptness, but constituting great steps of progress, pregnant with future results. The part played by ^Mntelligent selection" remains to be considered. I have heretofore spoken only of variation of types, and not dwelt on their persistence. This is a most important consideration, for most men see a great deal more of the latter than the former. Species present their characters intact for long periods, and many structural peculiarities have had great range in time. I recur to the origin of the "location of growth-force," i. e., the direction of motive-force. This is located by the appreciation of pleasure and pain. Now, every one knows that different ani- 40 GENERAL EVOLUTION. mals of the same species yary exceedingly in their sensitiveness to exterior influences ; that is, they differ in the degree in which the same object affects their consciousness. That which excites one is unnoticed by another ; what fills one with alarm scarcely rouses the attention of another. It is well known also that differ- ences in the power of retention are to be found in the same spe- cies of animals. The variations in persistence of memory are very great. While, therefore, one individual of a species will ac- quire a store of '^ contiguities," another of the same will possess but few. In other words, the degree with which objects are impressed on the consciousness, and the degree with which they are returned to the consciousness, vary greatly in the same spe- cies. Here we have the basis for the origin of totally different unconscious habits and reflex actions, and consequent divergences in the "location of growth-force." Those in which these impressibilities are most highly devel- oped will accumulate mental acquisitions most rapidly ; in other words, they will be the most intelligent of their species. While others follow the old routine of once acquired and then inherited habits, those in whom consciousness most frequently recognizes events will originate new acts and new habits. Intelligence is a conservative princijole, and always will direct effort and use into lines which will be beneficial to its possessor. Here we have the source of the fittest — i. e., addition of parts by increase and location of growth-force, directed by the influence of various kinds of compulsion in the lower, and intelligent option among higher animals. Thus, intelligent choice, taking advantage of the successive evolution of physical conditions, may be regarded as the originator of the fittest, while natural selection is the tribunal to which all the results of accelerated growth are submitted. This preserves or destroys them, and determines the new points of departure on which accelerated growth shall build. If the above positions be true, we have here also the theory of the develoi3ment of intelligence and of other metaphysical traits. In accordance with it, each trait appropriates from the material world the means of perpetuating its exhibitions by constructing its instruments. These react by furnishing increased means of exer- cise of these qualities, which have thus grown to their full expres- sion in man. 11. ON THE OEIGm OF GENERA. Introduction. — The present fragmentary essay is a portion of what other occupation has prevented the author from completing. It does not, therefore, amount to a complete demonstration of the points in question, but it is hoped that it may aid some in a classi- fication of facts with a reference to their signification. When all the vast array of facts in possession of the many more learned than the writer are so arranged, a demonstration of the origin of species may be looked for somewhere in the direction here at- tempted to be followed. Conclusions of any kind will scarcely be reached, either by anatomists who neglect specific and generic characters, or, secondly, by systematists who in like manner neglect internal structure. Such will never perceive the system of nature.* ANALYSIS OF THE SUBJECT. I. Relations of allied genera. First : in adult age. Second : in relation to their development. a. On exact parallelism. /8. On inexact or remote parallelism. y. On parallelism in higher groups. 8. On the extent of parallelisms. II. Of retardation and acceleration in generic characters. First : metamorphoses in adult age. a. The developmental relations of generic and specific char- acters. * It might seem incredible that either class should systematize with confidence, yet a justly esteemed author writes even at the present day, " However, there is scarcely a systematist of the present day who does not pay m.ore or less attention to anatomical characters, in establishing the higher groups!" (The italics are our own.) As though a system were of any value which is not based on the whole struct- ure^ and as though loxcer groups were only visible in external characters ; in a word, as though external (muco-dermal, dental, etc.) characters were not " anatomical " ! 42 GENERAL EVOLUTION. y8. Probable cases of transition. y. Ascertained cases of transition. Second : earlier metamorphoses. 8. The origin of inexact parallelisms. III. Eelations of higher groups. a. Of homologous groups. p. Of heterology. y. Of mimetic analogy. IV. Of natural selection. a. As affecting class and ordinal characters. p. As affecting family characters. y. As affecting generic characters. 8. As affecting specific characters. c. On metaphysical species. V. Of epochal relations. The laws which have regulated the successive creation of or- ganic beings will be found to be of two kinds, as it appears to the writer. The first, that which has impelled matter to produce numberless ultimate types from common origins ; second, that which expresses the mode or manner in which this first law has executed its course, from its commencement to its determined end, in the many cases before us. That a descent, with modifications, has progressed from the beginning of the creation, is exceedingly probable. The best enumerations of facts and arguments in its favor are those of Darwin, as given in his various important works, *'The Origin of Species," etc. There are, however, some views respecting the laws of development on which he does not dwell, and which it is proi^osed here to point out. In the first place, it is an undoubted fact that the origin of genera is a more distinct subject from the origin of species than has been supposed. A descent with modification involves continuous series of or- ganic types through one or many geologic ages, and the co-exist- ence of such parts of such various series at one time as the law of mutual adaptation may permit. These series, as now found, are of two kinds : the uninter- rupted line of specific, and the same uninterrupted line of generic characters. These are independent of each other, and have not, it appears to the writer, been developed pari passu. As a general ON THE ORIGIN OF GENERA. 43 law, it is proposed to render highly probable that the same specific form has existed through a succession of genera, and perhaps in different epochs of geologic time. With regard to the first law of development, as above proposed, no one has found means of discovering it, and perhaps no one ever will. It would answer such questions as this : What necessary- coincidence of forces has resulted in the terminus of the series of fishes in the perches as its most specialized extreme ; or, of the Batrachia, in the fresh- water frogs as its ultimum ; or, of the thrushes, among birds, as their highest extreme : in a word, what necessity resulted in man as the crown of the mammalian series, instead of some other organic type ? Our only answer and law for these questions must be, the will of the Creator. The second law, of modes and means, has been represented to be that of natural selection, by Darwin. This is, in brief, that a disposition to a general variation on the part of species has been met by the greater or less adaptation of the results of such varia- tion to the varying necessities of their respective situations. That the result of such conflict has been the extinction of those types that are not adapted to their immediate or changed conditions, and the preservation of those that are. In determining those characters of plants and animals which constitute them what they are, we have, among others of higher import, those which constitute them species and those which con- stitute them genera. What we propose is : that, of the latter, comparatively very few in the whole range of animals and plants are adaptations to external needs or forces, and of the former a large proportion are of the same kind. How, then, could they owe their existence to a process regulated by adaptation ? Darwin is aware of these facts to some degree, but, as already said, he does not dwell on them. Where he does, he does not at- tempt to account for them on the principle of natural selection. There are, it appears to us, two laws of means and modes of development : I. The law of acceleration and retardation. II. The law of natural selection. It is my purpose to show that these propositions are distinct, and not one a part of the other : in brief, that, while natural selec- tion operates by the ^'preservation of the fittest," retardation and acceleration act without any reference to '^ fitness" at all; that, instead of being controlled by fitness, it is the controller of fitness. Perhaps all the characteristics supposed to mark generalized groups 44 GENERAL EVOLUTION. from genera up (exceiDting, perhaps, families) have been evolved under the first mode, combined with some intervention of the sec- ond, and that specific characters or species have been evolved by a combination of a lesser degree of the first with a greater degree of the second mode. I propose to bring forward some facts and propositions in the present essay illustrative of the first mode. I. OJT THE KELATIOXS OF NEAKLY ALLIED GENERA. First. The writer's views of the relations of genera have al- ready been given at the close of an *' Essay on the Cyprinoid Fishes of Pennsylvania."* It is easy enough to define isolated genera which have few immediate afiines ; but among extensive series of related forms the case is different. One principle, how- ever, pervades the conception and practice of all zoologists and botanists, which few take pains to analyze or explain. It is simply that they observe a successional relation of groups, by which they pass from one type of structure to one or several other types, and the presence or absence of the steps in this succession they regard as definitions of the genera. It is true that the reader will often find introduced into diag- noses of genera characters which indicate nothing of this sort. It is often necessary, indeed, to introduce characters which are not peculiar to the genus characterized, for the sake of distinguishing it from similar ones of other series, but this only in an imperfect state of the record. Moreover, the ability of the writer to distin- guish genera being thus tested, he too often fails by introducing family and specific characters, or by indulging in an unnecessary redundancy. In general, it may be said that adjacent genera of the same series differ from each other by but a single character ; and, generally, that the more remote differ by characters as numer- ous as the stages of their remove. It is precisely as, among the inorganic elements, we pass from the electro-negative, non-oxidizing extreme of the halogens, with fluorine as the extreme, to the electro-positive, violently oxidizing extreme of the alkaline metals, whose extreme is potassium, by steps whose relative position is measured or determined first by these tests ; and as these steps have each their included series of * "Trans. Amer. Philos. Soc," 1866, from "Proc. Acad. Nat. Sci.," Phil., 1859, p. 332. ox THE ORIGm OF GENERA. 45 bodies, characterized by tlieir successive relations on the lower level of a subordinate range of characters. This principle is dis- tinctly admitted by many zoologists,* those who deny it generally failing to perceive it because they attempt to gauge a major scale by characters which are really the test of one or all of the subordi- nate or included scales. It holds true of most of the groups of organic beings ; thus the class is a scale of orders, the order of tribes. I will not now say that the tribe is a scale of families, as the case is here much modified ; but what is chiefly to be consid- ered in this essay is, that the family is composed of one or several scales of genera. Second. Now, the more nearly allied genera are, the more surely will these generic steps be found to fall into the direct line of the steps of the development of the highest, or that with the longest scale, the former being truly identical with the latter in generic characters. Less allied genera will offer an inexact or in- complete imitation of such identity — some additional character being present to disturb it. Such genus belongs to another series, characterized by the disturbing feature, whose members, however, l)ear to each other the relation claimed above for such. The relation of genera, which are simply steps in one and the same line of development, may be called exact parallelism ^ while that of those where one or more characters intervene in the maturity of either the lower or higher genus, to destroy identity, may be called incomplete parallelism. The latter relation has been dwelt on by von Baer, Agassiz, and other writers, but none have accepted the existence of exact paral- lelism, or seen its important relation to the origin of genera. Third. That the lowest or most generalized terms or genera of a number of allied series will stand to each other in a relation of exact parallelism. That is, if we trace each series of a number, up to its lowest or most generalized genus, the latter together will form a series, similar in kind to each of the sub-series ; i. e., each genus will be identical with the undeveloped conditions of that which progresses the farthest, in respect, of course, to the char- acters which define it as a series. Those characters of the skeleton which we are accustomed to call embryonic are only so because they relate to the develop- * Prof. Bronn, in his " Classen u. Ordnungen des Thierreiches," has everywhere a chapter on " Die aufsteigende Rcihe" ("the ascending scale"). 46 GENERAL EVOLUTION. mental succession witnessed in animals at the present time. Characters not so called now were probably as much so at one period now passed. Hence embryonic characters of the bony system do not, as I have often had occasion to observe, charac- terize the types of the highest rank, but only subordinate divis- ions of them. Thus the elasmobranchs are i:)robably rejoressed forms of groups of a really higher grade than the bony fishes, or teleostei, which may be known to us. In their early presence in the geologic series we have evidence of the first beginning of a higher type. In the same manner it has been discovered that the molecular aggregation of the elementary substances does not characterize their highest or most distinct series, but rather the substances themselves within the group or family to which they belong. The gaseous, liquid, and solid molecular conditions, being charac- ters distinguishing otherwise allied substances in the same way morphologically (we can not say yet developmen tally), as the car- tilaginous, osseous, and exostosed or dermosseous characters dis- tinguish otherwise nearly allied genera. The *^family" group embraces one or many of such series. If we trace the series in scA^eral families to their simplest or most generalized terms or genera, and compare them, we will not find the relation to be one of exact j)arallelism in the series of the ** order," so far as our present knowledge extends, but, in a devel- oj)mental sense, one of divergence from the commencement. If we could know the simplest known terms or family charac- ters of a number of groups of families, or *^ orders," we would probably find them to represent a series of exact parallelism, though to find such simplest terms we must go far into past periods, since the higher the group the more extensive the range of its character, and the less likely to be found unmixed with ad- ditions and extensions, in modern times. Finally, the series of classes is in the relation of the essential characters of the same, as expressed in their now extinct, most generalized and simple representatives, also one of " exact paral- lelism.'' a. Examples of Exact Parallelism,^ 1. As an example we may take the genus Trachycephalus {Batrachia anurd). Nearly allied to it is the genus Osteo- * In generic series. ON THE ORIGIN OF GENERA. 47 cephalus, wliicli differs in the normal exostosis of the cranium not involving the derm, as in the former. Close to this is Scytopis, where the fully ossified cranium is not covered by an exostosis. Next below Scytopis is Hyla, where the upper surface of the cranium is not ossified at all, but is a membranous roof over a great fontanelle. Still more imperfect is Hylella,* which differs from Hyla in the absence of vomerine teeth. Now, the genus Trachycephalus, after losing its tail and branchiae, pos- sesses all the characters possessed by the genera Hylella and Hyla, either at or just before the mature state of the latter, as the ethmoid bone is not always ossified in advance of the parietals. It soon, however, becomes a Scytopis, next an Osteocephalus, and finally a Trachycephalus. It belongs successively to these genera, for an exhaustive anatomical examination has failed to reveal any characters by which, during these stages, it could be distinguished from these genera. Now, it would be a false comparison to say that the young of Trachycephalus was identical with the genus Agalychnis, which in truth it resembles, because that genus is furnished with one other character — the presence of a vertical pupil — and belongs to another series in consequence, which is represented as yet, with our present imperfect knowledge — or perhaps imperfect fauna — by three genera only. 2. The lowest type of the near allies of our common fresh- water frogs is the genus Eanula, where the prefrontal bones are narrow strips on each side the ethmoid cartilage ; the ethmoid cartilage itself entirely unossified above, and the vomerine teeth very few and on a small elevation. There are two species, R. affinis and R. palmipes.\ The other species have the ethmoid cartilage ossified above, at least beneath the extremities of the frontoparietals. Those of the latter most like Eanula possess the same type of narrow prefrontals, separated by a broad area of cartilaginous ethmoid, and fasciculi of teeth. Of this type is Rana delalandii, and probably R. porosissima, Steind., of the South Ethiopian region. Other species of the same type extend their vomerine patches into lines ; such are R. mascariensis, R. fasciata, R. oxyrhynchus, R. grayi, and other South African species. * I refer to H. carnea m., not having Reinhardt and Liitken's type of this genus, f These species are now believed to be identical, but three others have been dis- covered (1886). 48 GENERAL EYOLUTION". The prefrontals are subtriangular, and approacli eacli other more or less in the numerous species of North America and of the Regio Paleearctica, while generally the vomerine teeth are in fascicles or yery short series. In the -Ethiopian Rana fuscigula the prefrontals unite on the median line, roofing over the ethmoid cartilage and reducing it, while the vomerine teeth are in very short lines. In the species of the Palaeotropical region, Rana tigrina, R. vittigera, R. cyanophlyctisy R. grimniens, R. liexadactyla, R. corrugata, R. ehrenhergii, R» gracilis, and the Ethiopian R. occi- pitalis, the prefrontals not only unite solidly (the suture remain- ing on the median line), but extend and closely fit to the fronto- parietals. The vomerine patches have lengthened out into series. Now, the young of the latter type of Eana (I take as an ex- ample the R. tigrina, one of the most abundant and largest of Indian frogs) presents the subtriangular prefrontals neither in contact with each other or with the frontoparietals, and the vomerine series is much reduced ; in fact, it belongs in all respects to the Palsearctic grouj). I have not examined younger specimens, but have no doubt they are like those of the Palse- arctic ; which are, in their young stage, precisely of the type of the Ethiopian Rana, with fasciculate teeth like the young of those of the same region with teeth in series, since the prefrontals are still more reduced, becoming linear. Finally, the first stage of the Nearctic Rana, after losing the larval tail, is the genus Ranula, having linear prefrontals, minute vomerine teeth, and the ethmoid ring cartilaginous above. These points of structure are of generic quality, but I have not regarded any group as sufficiently defined to be so regarded, except Ranula, as the adults of some species appear not to be con- stant in possessing them. Thus a very large Rana catesleyana sometimes exhibits prefrontals in contact on the median line, while it is difficult to say whether R. areolata of North America is of the Nearctic type so much as of the Ethiopian. Neverthe- less, the groups are generally quite geographically restricted. 3. A similar relation exists between the genera Hyperolius, Staurois, and Heteroglossa in respect to the prefrontal bones and the separation of the outer metatarsi, and — 4. Between Ixalus, Rhacophorus, and Polypedates also, in reference to vomerine teeth, bifurcation of last phalange, and dermoossification of the cranium. ON THE ORIGm OF GENERA. 49 5. When the larvae of certain salamanders (Spelerpes) possess branchiae, they also lack one digit of the hind foot, also the max- illary, nasal, and prefrontal bones, and exhibit a broad continuous palatopterygoid arch, in close contact with the parasphenoid. The prootic is separated from the exoccipital by a membranous space, and the exoccipitals themselves are not yet united above the foramen magnum. There is at the same time a series of splenial teeth. Both ceratohyals are confluent, the posterior is present, and there are but three superior hyoid arches. After they lose the branchiae, the hinder foot, which has four toes only for a time, gradually adds another at first rudimental digit, in the Mexican species ; in most North American species the fifth digit appears at an early larval stage. Five digits are finally present in all Spelerpes. We have thus four combinations of the above characters, at different periods of the life history of certain (but not of all) of the species of Spelerpes. There exist four permanent series of species or genera, equivalent to these stages. The well-known ^^perennibranchiate" J^ecturus is nearly identical with the first, Batrachoseps with the second, the half-toed Spelerpes with the third, and the typical Spelerpes is the last. In one character of generic value only do I find that Necturus differs from the early larval Spelerpes. It closes the premaxillary fontanelle with which it commences, by an approximation of the premaxillary spines, but not by a sutural union, as takes place in Amblystoma. It thus, in this one point, advances a stage beyond the condition to which Spelerpes attains, though it may be a question whether such a closure without union should not be classed among the specific characters by which iV. maculatus dif- fers from the young of the various Spelerpes, as they do from each other. Characters of the latter kind are the following : in N. maculatus the frontals are more deeply emarginate behind ; it has little or no ala on the inferior keel of the caudal vertebrae, which is prominent in Spelerpes larvae. It may be that the parallelism in the case of Spelerpes is inex- act by one character, and that a strictly developmental one ; or it may be regarded otherwise.* 6. It is well known that the Cervidae of the Old World devel- * Necturus differs from these larvas by another and more important character, viz., the presence of the os intercalare. 4 50 GENERAL EYOLUTIOK op a basal snag of the antler (see Cuvier, " Ossem. Fossiles"; Gray, " Catal. Brit. Mus.") at the third year ; a majority of those of the 'New World (genera Cariaciis, Subulo) never develop it except in ^'abnormal" cases in the most vigorous maturity of the most northern Cariacus (C. virginianus) ; while the South Ameri- can Subulo retains to adult age the simple horn of the second year of Cervus. Among the higher Cervidae, Rusa and Axis never assume char- acters beyond an equivalent of the fourth year of Cervus. In Dama the characters are on the other hand assumed more rapidly than in Cervus, its third year corresponding to the fourth of the latter, and the development in after years of a broad plate of bone, with points, being substituted for the addition of the corre- sponding snags, thus commencing another series. Returning to the American deer, we have Blastocerus, whose antlers are identical with those of the fourth j^ear of Cariacus. Now, individuals of the genus Cervus of the second year do not belong to Subulo, because they have not as yet their mature dentition. Rusa, however, is identical with those Cervi whose dentition is complete before they gain the antlers of the fifth year. When the first trace of a snag appears on one beam of Cariacus virginianus, the dentition includes the full number, but there remain - milk molars much worn and ready to be shed. Perhaps the snag is developed before these are displaced. If so, the Cariacus is never a Subulo, but there can be little doubt that the young Blastocerus belongs to that genus before its adult char- acters appear. 7. Leidy states * that certain Perissodactyl remains, contain- ing a foot of a horse, contained the teeth of a genus, Protohippus, which has the permanent teeth of Equus, and the deciduous dentition of Anchitherium. He observes : *^The deciduous and permanent dentitions of both these genera are alike ; therefore the new genus is in early life an Anchitherium, and later in life a true horse." This is therefore a case of exact parallelism, always providing that the Protohippus has not added to its immature equine characters others in other parts of the body, which in- validate the identity. In the latter case it will still be an inter- esting example of the *^ inexact parallelism." \ * "Proceed. Acad. Xat. Sci," 1858, p. 7. f This is not a proper example of parallelism if, as some zoologists believe, the ON THE ORIGIN OF GENERA. 51 8. It is well known that the Cephalopoda form a number of series of remarkable regularity, the advance being, in the first place, in the complication of the folds of the external margins of the septa, and, in the second place, in the degree of involution of one or both extremities of the shell to the spiral ; third, in the position of the siphon. Alpheus Hyatt, in an important essay on this subject,* points out that the less complex forms are in many cases iden- tical with the undeveloped conditions of the more complex. He says : ^^ There is a direct connection between the position of a shell, in the completed cycle of the life of this order, and its own development. Those shells occujoying the extremes of the cycle" (in time), ^Hhe polar forms, being more embryonic than the intermediate forms, f The first epoch of the order is especially the era of rounded, and, in the majority of the spe- cies, of unornamented shells with simple septa ; the second is the era of ornamentation, and the septa are steadily complicat- ing ; in the third the complication of the septa, the ornamen- tation, and the number of species, about twice that of any other epoch, all combine to make it the zenith of development in the order ; the fourth is distinguishable from all the preced- ing as the era of retrogression in the form, and partially in the septa. ** The four periods of the individual are similarly arranged, and have comparable characteristics. As has been previously stated, the first is rounded and smooth, with simple septa ; the second tuberculated, and the septa more complicated ; the third was the only one in which the septa, form, and ornamentation simultaneously attained the climax of individual complication ; deciduous or temporary dentition is not a remnant of the primitive dentition, but is a later product of mammalian evolution. If it be a case of parallelism, it is inexact, because the genus Protohippus was discovered by the writer to have three toes, while Equus has but one. * " Memoirs Boston Soc. Nat. Hist.," 1866, p. 193. f He adds here : " Although in regard to geological sequence and structural po- sition one of the extremes must be of higher geological rank." The " highest " ex- treme will be of higher geological rank, according to the complexity of structure and length of developmental scale, whether it come at the middle or end of the history of the class in time. If, as has been the case, so far as known, a decline has termi- nated the history of a class, its later forms are zoologically loicer than its older ones. Hence the adjective high is only appropriate to types of the latter kind^ when used as synonymous with extreme. 52 . GENERAL EVOLUTION. the fourth, when amounting to anything more important than the loss of a few ornaments, was marked by a retrogression of the whorl to a more tabular aspect, and by the partial degradation of the septa." I will here quote an entirely antagonistic statement of Bronn's,* as follows : ** In the development of lamellibranchiate mollusks it is not possible to estimate the successional changes of one genus by those of another, though nearly related ; so diverse are the most significant relations in the manner of progress among nearest allies. Therefore, embryologic indications are throughout useless in classification, and it is necessary to keep carefully se^oa- rate the statements of observations on development of a given species, and not transfer such facts to the history of another spe- cies for the purjDose of completing it. We can not even range these histories in conformity with family groups." For us this statement, though no doubt largely true, is an indication of im- perfection — first, of knowledge of true affinities of recent, but esi^ecially of extinct adults, and, second, of imperfection of knowl- edge of development. The position api^ears to be based on nega- tive evidence, while the opposing can and does stand on nothing but positive. /?. Examples of the Inexact Parallelism. 1. The genera of the batrachian family Scaphiopodidae form a series of steps differing a little more than as repressions or joer- manent primary conditions in the development of the highest, f Thus two of the genera, which are North American, maintain their tubae eustachii and tympanum through life, while three European lose them at an early period. J; The three European genera also advance beyond the larval character of the Ameri- can in the ossification of the basis of the xiphisternum into a broad style. Thus we have two series established, which differ only in the two characters named. Each shows its develop- mental steps in a similar manner, the European series extending further ; thus : * " Classen u. Ordnungen des Thierreichs," iii, p. 445. f See "Journal Academy," Philadelphia, 1866, on Areifera. X According to Bruch and Tschudi, in Pelobates. I have found traces of the eustachian diverticula, in a tailed Pelobates fuscus, whose body measured 1 in. 4 lin., from Mus. Peabody Institute, Salem, Mass. ON THE ORIGIN OF GENERA. 53 European, North American, 1. Temporal fossa over arched. Oultripes. * * Temporal roof not ossified. 2. Fronto-parietal bones ossified, involving derm. Pelobates. Scapliiopns. 3. Fronto-parietals ossified, distinct from derm. * * (Unknown.) * * 4. Fronto-parietals not ossified, distinct from derm. Didocus. Spea. In this case Didocus can not be said to be identical as a genus with an undeveloped stage of Oultripes, since, while the cranium of the latter is in the condition of Didocus, it bears a long tail, and the limbs are but little developed. Nor is Didocus identical with the undeveloped condition of Pelobates, since both cranium and limbs of the latter are developed before the tail is absorbed. Nor is Pelobates identical with the undeveloped condition of Oul- tripes, since, while the cranium of the latter is that of the former, the limbs and tail are still larval. The same relations exist be- tween the other members of the family; The genus Scaphiopus is not an undeveloped form of Pelobates as to its auditory organs, for, when the latter is identical with the former in this respect, it bears otherwise entirely larval characters. Nor is Spea an arrested Scaphiopus, the relation being here precisely that between Dido- cus and Pelobates. Spea approaches more closely ah arrested Didocus in all respects, but that when the latter possesses the au- ditory apparatus * of the former, it is a larva in limbs and tail, and that it loses this apparatus before reaching the other charac- ters of Spea. The relations of these genera, as compared with those of the Trachycephalus, Oystignathidse, and Bufo series, may be represented as follows : the lines represent the developmental scale of each. This is an example of the simplest case of inexact parallelism, as distinguished from the exact parallelism or identity. As the fauna of the present period is but a fragment, so the simple inex- * The possession of eavum tympani and tuba Eustachii in the undeveloped con- dition of this genus is only assumed from its close relation to Pelobates. 54 GENERAL EVOLUTION". Relations between the terms of the different series, Heterol- ogy or Remote Parallel sm. 1 « o m i N 02 V a .2 "3 03 ft 4^ jN. I N; ^^ ^ > N, i ^^^^'^ >^ CD a> \ C 5 N^ 3 ^^^^ ^^ 02 3 ^ 1^^*^ h-( -«^ O 6 <0^^^ OD • ^ 02 ^ <-4 oS P a ^ "3 : m ?< ^ • 02 >> &.2 .a o o * c3 u 02 -IJ es ft c3 -12 >, • ">> ti 02 o -^j Eh O m : W ^ 1 k1 1 H 1 'a : CO ^ 02 02' 'c a •?; '- O -kJ S 0) _-"^ O o ■i-J o •«-d a: 02 O p. Q} 02 OQ -u 1 3 'tJ tT O 9* li 02 02 a 2 3 02 a m 02 o o 3 .—4 c 1— 1 6 6 act is a more frequent relation than the exact, while the more complex inexact relation is still more common. The greater the inexactitude, the more fre- quently do such parallels occur till we have those of the most remote character, as, for instance, the parallelism between the different stages of the development of the mammal, in the structure of the heart and origins of the aorta, and the existing classes of vertebrates. The re- lation of these facts to the origin of genera will be noted hereafter. It will be borne in mind that in the Scaphiopodidae the generic types are identical for a long portion of their developmental history. (See figures on plate iv for the representation of these facts. ) 2. In both Perissodactylous and Ar- tiodactylous Mammalia, certain types develop their family character of ca- nines at the earliest appearance of den- tition, others not till a comparatively late period of life (Equus), and the ex- treme individuals never produce them. 3. Among cetaceans the genus Orca maintains a powerful and permanent series of teeth, which is an important generic character. In Beluga the se- ries is shed in old age, in Globiocepha- lus, or the Caing whales, they are shed at middle age, while in the Balsenidse, of which the absence of teeth is an es- sential character, these organs are de- veloped and absorbed during fcetal life (Eschricht). Though the condition of the teeth is not of systematic value in the two named intermediate genera, it is the important feature in the his- tory of progress to such value. OE" THE ORIGIN OF GENERA. 55 4. Among the tortoises, the Testudinidae rapidly extend the ribs into a carapace, which fits closely the marginal bones, while equally early in life the elements of the sternum unite together. This is also the case with most Emydidee ; among whose genera, however, we find the transitional scale. In Dermatemys and Batagur the carapace is very late in attaining its complete ossifi- cation, while the plastron is early finished. In Chelydra, on the other hand, while the carapace is even more slowly developed, the plastron is never free from its larval fontanelles. In the marine turtles neither plastron nor carapace is ever completed, while in the Trionychidag the marginal bones are also entirely unde- veloped. In order that this last illustration be a true one for the theory in question, as applied to ihQ families, these developmental char- acters should be the true distinctive features of these families re- spectively. This, as is well known, they are not. The Chelo- niidse are characterized by the form of their anterior limbs, which is in an adaptive structure, while the Testudinidae similarly are distinguished by an extreme opposite modification of foot-struct- ure, adapted to an extreme difference of habit. Here there is an example of the co-working of both laws. Nevertheless, we only claim at present to show the developmental relation of genera of the same family and the same series. This we see among the Emydidae. 5. In the important character of the sciitellation of the tarsi among the Passerine birds, the ^^boot" appears early in life in the highest Oscines, later in the lower, and does not ai:)pear at all in the majority. In respect to the still more important feature of the long posterior plates which appear very early in most Oscines, in the Myiadestes type * they appear late, the squamse remaining long, while the Clamatores never develop the plates, not advancing beyond the infantile squamous stage. 6. It has been shown by Falconer that the genera of great Proboscidians form a remarkably regular and graded series, dis- tinguished by their dentition. These are Dinotherium Kaup, Trilophodon Falc, Mastodon Cuv., Pentalophodon Falc, Stego- don Falc, Loxodon F. Cuv., and Elephas Linn. In the first there are but two cross crests on the third molars, and a pair of permanent mandibular tusks ; in the second, three cross crests * Baird, " Review of Birds of North America." 56 GENERAL EVOLUTION. and mandibular tusks permanent in some males ; in the third, four cross crests and the mandibular tusks variable ; in the fourth, five cross crests on the third molar ; tusks unknown. In Stego- don the mandibular tusks cease to appear, the crests of the third molar become more numerous, and embrace between them, in the bottoms of the valleys, a strong deposit of cementum. In Loxo- don the crests have the whole interspaces filled with cementum, while the same thing holds in Elephas, with a greatly increased number of cross crests, which become vertical laminae. The lami- nar character has become ap2)arent from its rudimental condition in Stegodon. 'Now, these are stages of development, though not in a con- tinuous, single line. The shedding of the inferior tusks takes place earlier and earlier in the genera from Dinotherium, till they never appear in Stegodon. The molar teeth, it is well known, present, as they succeed each other from back to front, a regularly increasing number of transverse crests in the same species. Thus, in Trilophodon oliioticus the first molar presents but two, while the last presents six. The last molars of other genera present a very much increased number. What is it, then, but that the increased number of crests in the third molar, definitive of these genera, is an acceleration of growth ; the fourth in Trilophodon is structurally third in Mastodon, and the fourth of Mastodon being third in Pentalophodon ; the fourth of Pentalophodon becoming third in Stegodon, and so to the end ? This is confirmed from the proved fact of the disap- pearance of the premolars. They are fewer in Trilophodon than in Dinotherium, and are soon shed ; they are also early shed in Mastodon and Stegodon {insig7iis Falc. Caut.), and are not known to exist in the succeeding types ; the acceleration of succession of teeth has caused them to be entirely omitted. The young tooth of Elephas, moreover, is represented by a series of independent parallel laminae at first, which, when they unite, form a series of crests similar to the type of the genus Mastodon and others of the beginning of the series. The deposit of cemen- tum takes place later, till the valleys are entirely filled up. Thus the relations of this part of the tooth-structure in the series are also those of the successional growth of those of Elephas, the ex- treme of the series. It would be only necessary to show that two distinct condi- tions, in any of these respects, occurred among the different indi- ox THE ORIGm OF GENERA. 57 viduals of the same species of any of tliese genera, to render a hypothesis of evolution a demonstrated fact.* It must be here observed that great size indicates little or nothing as to zoological rank. The greatest species are often not far removed in affinity from the least ; thus there can be but little doubt that elephants are not far removed from the rodents, and the rhinoceros is near the cony. Indeed, in the same genus the most extraordinary diversity prevails, for we have a very small elephant of Malta, and in the Miocene of Maryland a fin-back whale not so large as the new-born young of the fin-backs now living. Hence the objection to the developmental hypothesis, based on the great size of the primal Selachians and Ganoids, has but little weight. 7. Eathke has shown . that the arteria ophthalmica of the higher Ophidians is originally a branch of the arteria cerebralis anterior, and that it later forms a connection with the arteria facialis. This connection increases in strength, while the other diminishes, until finally its supply of blood is derived from the facialis instead of the cerebralis. Eathke has also shown that the cerebral origin of this artery is continued through life in the three lowest suborders of the ser- pents, the'Scolecophidia, Catodonta, and Tortricina ; also in the next succeeding group, the Peropoda. 8. In most serpents the left lung is never developed ; in such the pulmonary artery, instead of being totally wanting, remains as a posterior aorta bow, connected with the aorta by a ductus bo- talli ; serpents without left lung being therefore identical in this respect with the embryonic type of those in which that lung exists. 9. Dr. Lespes states that the optic region of the brain of blind cave Coleoptera, examined by him is similar in structure to that in the blind larvae of Coleoptera, whose imagos j^ossess visual organs. 10. t Those Saurians (Uromastix, etc.), in which the pre- maxillary region is produced into a uniform cutting edge, are furnished during early stages with a series of premaxillary teeth, which become gradually fused and confluent with the alveolar margin. Hence other Acrodonts are equivalent, in this respect, * This variability has since been shown to exist in species of the M. angmtidens type (1886). \ See under section on Acceleration and Retardation. 58 GENERAL EYOLUTIOX. to the young of Uromastix, etc. The same tiling occurs among the Scaroid and Labroid fishes. In this most natural family we find the majority of generic forms provided with a normal com- plete dentition ; in others (Chaerops, Xiphochilus, Pseudodax, etc.) the lateral teeth are gradually and normally replaced by a more or less cutting edge of the mandible ; and finally, in the Scarina and Odacina, the entire mass of teeth and jaws are coa- lesced, forming a beak with sharp cutting edges, the single teeth being still visible in the true Scarus, while they have entirely dis- appeared in adult Pseudoscarus and Odax.* Thus, in dentition, the adult Scarus is identical with not fully developed Odax ; Chaerops, with the teeth less confluent, equals a still younger stage of Odax, while those with distinct teeth are tiie same in this point as the embryos of the highest — Odax, etc. I venture to predict that here will be found a long series of exact parallelism, in which the different genera, resting exclusively on these dental characters, will be found to be identical generically with the various stages of the successively most advanced. 11. Prof. Agassiz states that the absence of ventral fins is char- acteristic of an embryonic condition of the Cyprinodont fishes. The genus Orestias does not progress beyond this stage in this one point. Probably the genus will be found which will only differ from Orestias in the presence of ventral fins. If so, Orestias will be identical with an imperfect stage of that genus, if, as will prob- ably be the case, the fins appear in the latter, after other struct- ures are fully completed. yy. Parallelism in Higher Groups. It is not to be anticipated that the series of genera exhibiting exact parallelism can embrace many such terms, since compara- tively few stages in the developmental condition of the same part, in the highest, would bring us back to a larval condition, which, as far as we yet know, has no exact parallel among existing genera. But it is to be believed that the lowest terms of a number of the most nearly allied of such series do of themselves form another series of exact parallelisms. Thus exact parallelism between existing genera of mammals ceases, with all characters which are larval or foetal, only prior to * Giinther on Hatteria, "Philosophical Transactions," 186Y, ii. I had already noticed the peculiar development in Uromastix, but not published it. ox THE ORIGIN OF GENERA. 59 the assumption of the adult dentition, since among the higher Mammalia at least we know of no genus which, however similar to undevelo^Ded stages of the higher, never loses the milk dentition. It is nevertheless an important fact that among smooth-brained mammals, or many of them, but one tooth of the second series appears ; and inasmuch as smooth-brained forms of the higher orders have become extinct, it is not too much to anticipate that a type of permanent milk dentition will be found among the ex- tinct forms of the same high orders. As an example of exact parallelisms in series of series, I select the following : 1. In the batrachian family Cystignathidae there are six groups or sets of genera. In the highest of these we have an ossified cra- nium and xiphisternum — i. e., in the Cystignathi ; in the Pleuro- demae the cranium is not ossified, thus representing the Cystigna- thi while incomplete ; in the Crini^ the xiphisternum is cartilagi- nous, as well as the fronto-parietal region, being an equivalent of a still lower stage of the Cystignathi. From this simplest type we can find a rising series by a different combination of characters ; thus the Ceratophydes add an osseous cranium to the incomplete xiphisternum, while two succeeding groups diverge from each other at the start, the Pseudes loosening the outer metatarsus in their development to maturity, while the Hylodes add by degrees a cross-limb to the last phalange. The Ceratophrydes and Criniae are stages in the development of these ; but neither one of them is a step in the development of the other. They are measured by adaptive characters purely. 2. The whole suborder 'of the Anurous Batrachia, to which the above family belongs, the Arcifera, differs from the suborder Eaniformia by a character which distinguishes a primary stage of growth of the latter from its fully developed form. That is, the Eaniformia present, at one period of their development, a pair of parallel or over-lapping curved cartilages, connecting the procora- coid and coracoid bones, which subsequently unite and become a single, slender median, scarcely visible rod, while the bones named expand and meet. The first condition is the permanent and sole systematic character of the Arcifera.* Ohjection. — It may be objected, by those who have observed * This may be readily understood by comparing my monograph of the Arcifera, "Jour. Ac. Nat. Sci.," Phil, 1866, with Duges's work, or Gegenbaur and Parker's memoir on the Shoulder-Girdle. 60 GENERAL EVOLUTION. some of these developmental relations, that they are exhibited by certain single structures only, and not by whole organisms. These objectors must not forget that the distinctions of those groujis, which alone we have in one geological period in a relation of near affinity, exists in single characters only ; and that it is therefore infinitely probable that the higher groups, when we come to know their rejDresentatives with the same completeness, will prove to be separated by single characters of difference also. 3. The following table (pages 63 to 73) is introduced to illus- trate the relations of groups higher than the preceding. This is largely measured by the circulatory system, not only as to the class relations, but also as regards orders. In its less central por- tions it is, however, definitive of families at times.* (See also Plate!) If the reader will comjoare the history of the development of vertebrates of any class or order, as those of Teleosts and the lizard by Lereboullet, of the snake and tortoise by Kathke and Agassiz, and of the bird and mammal by von Baer, he will find the most complete examples of the inexact paraTlelism of the lower types with the embryonic stages of the higher. A few points are selected as examples, from the histories included in a few of the columns of the table, and given at its end. Similar parallels may be found to exist in the most beautiful manner between the adult anatomv and structure of the uroo^eni- */ CI? tal aj)paratus within each class of the series taken separately, as indicating ordinal relationship. This department is, however, omitted for the present. As an example of the homologies derivable from the circula- tory system, and of the use of the following table, I give the fol- lowing relations between the types of the origins of the aorta, f The single ventricle of Teleostei is no doubt homologous with that of Lepidosteus, and that of Lepidosiren. The arteria vesiccB * This sketch is not nearly complete, but is published in hopes of its being use- ful to students. It is compiled from the works of Meckel, Rathke, Barkow, Miiller, Ilyrtl, Briicke, Stannius, and others, in connection with numerous dissections. f Prof. Agassiz (" Contrib. Nat. Hist. U. S.," i, p. 285) states that the ven- tricle of the Testudinata " is not any more identical with the one ventricle of fishes than with the two ventricles of warm-blooded vertebrata ; for in fishes we find only one vessel, the aorta, arising from it, while in turtles both the ao7'ta and arteria pulmonalis start to'^ether from it." We think this statement, which, if true, is destructive to the asserted homologies of the circulatory system, can not be sub- stantiated, for the reasons above given. occ cul 5 m ao Central Circulatory System. ao— Figs. 1, 2, fish. Figs. 3, 4, batracliian. Fig. 5, reptile. Fig. 6, bird. Figs. 7, 8, human foetus. PLATE I. Figures and Diagrams of the circulatory centers of Vertebrata. Copied from Gegenbaur and His, mostly enlarged. Fig. 1. Diagram of the arterial arches of a Fish (species not given). Fig. 2. Head of an embryonic Teleostean, with the rudiments of the vascular system (diagrammatic). Fig. 3. Heart and arterial trunks of a larva of a Salamander. Fig. 4. Arterial system of the Frog. Fig. 5 Heart and arteries of an Ophidian (Boa). Fig. 6. Diagram of the arterial system of the adult Fowl. Fig. 7. Central circulatory system of Man ; foetus of the second month ; front view. Fig. 8. Same as Fig. 7, left side. V, ventricle of heart. «, auricle of heart. s V, sinus venosus of heart. b a, bulbus arteriosus of heart. a 6, aorta branchialis. 1, 2, 3, 4, 5, arteriae branchiales. V 1, 2, 3, venae branchiales. ao, aorta. ad, aorta dextra (right). a 5, aorta sinistra (left). p, arteria pulmonalis. db, ductus botalli. ca, arteria carotis. cca, common carotid. Jisc, Isc, right and left subclavian arteries. i?m,^m, right and left innominatearteries. cut, arteria cuticularis. occ, arteria occipitalis. V c, vena cardinal! s. V c7, right vena cava. V s, left vena cava. vi, inferior (posterior) vena cava. ces, (esophageal artery. wi, mesenteric artery. s, spiracular or branchial fissure. «, nostril. dc, ductus cuvieri. I, lingual artery. ON THE ORIGIN OF GENERA. (Ji natatoricB, wliicli is the homologue of the A. pulmonalis of air- breathers, issues in Lepidosteus from the last vena IrancMcdis, thus receiving aerated blood from the gills. In Lepidosiren it issues from the point of junction of two gill-less and two gill-bear- ing venoR hrancMales, thus receiving mixed blue and red blood, or blue blood altogether, Avhen the branchiae are not in functional activity. In Proteus it issues from the last vena branchialis, where it receives the ductus hotalli of the preceding vein, which, when the gill is inactive, becomes a gill-less aorta-bow, which brings it only carbonized blood, which it readily aerates in the swim- bladder, now become a lung. The ventricle is homologous with the preceding. In salamanders, where the substitution of the accessory gill arches by the ductus hotalli, converts the arterice and vencB hrancMales into ^^ aorta-bows," the A. pulmonalis is given off from the posterior bow, and receives henceforth mixed blood. In the Anura the origin is the same, but nearer the heart. In CaeciliidaB it approaches the heart so far as to issue from the extremity of the hulhus arteriosus, which is now divided by an incomplete septum, one half conveying blood to the aorta-roots, and the other to the A. pulmonalis. This septum was already preceded by a longitudinal valve with free margin in the Anura ! As if to meet the coming event, a trace of ventricular septum ap- pears at the apex within. There can now be no question of the homology of the ventricles of the gar, and of the Cascilia. But we have next the true Eeptilia. The hulhus arteriosus is split externally, as it already was internally, but it is first represented in most tortoises by an adherent portion, one half being the now, to this point, independent arteria pulmonalis and the other the nearly sjjlit aorta-roots. There can, I think, be little question of the exactitude of the homology throughout. It is no less certain that the salamander * fulfills in its devel- opment the different stages to its permanent one, and is identical in each stage, in respect to this point, with the orders it represents at the time. This is true even of the long period during which it bears the long branchial appendages and contained arteries and veins which are not found in fishes ; it is then like the Protop- terus, which has hyoid venous arches and appendages of those arches at the same time. The tortoise f and Troj^idonotus I are also identical in their successive stages with the types already * Amblystoma. f Agassiz. X Rathke. 62 GENERAL EVOLUTION". eniiinerated, the external or appendicular branchial vessels being omitted, as belonging to the special serial deyelopment of the line of air-breathing Anallantoidans. The division of the bulbus arte- riosus into three instead of two may indicate a case of inexact parallelism ; but, on the other hand, it may be that the pulmonary partition is completed a little before the aorta-root partition, thus passing through the batrachian permanent type. For explana- tions of inexactitude see under Part II. No doubt the batrachian type of hulhus arteriosus is passed by many serpents less extreme and specialized than the Tropidonotus. The aortic and pulmonary divisions of the bulbus in the Cae- cilia are not laterally placed, but one is dorsal and the other ven- tral, the one passing a little spirally to the right of the other. So the pulmonary division of the bulbus turns over to the right in the Anura. When the septum of the true reptiles appear, it rises on the anterior wall of the ventricle till it is seen, in Eunectes, to meet the partition between the arteria pulmo7ialis and aorta-roots^ and we have at once the right and left ventricles of the bird and mammal structurally and functionally. Thus are the two ven- tricles of man the same as the one ventricle of the fish, merely divided by a septum.* In the fissure of the aortic bulbus, in the reptiles, a spiral turn is again given, and in Testudo the one aorta-root issues behind the other. In the crocodile the turn is still greater, and the right aorta-root issues to the left of the left root, and vice versa. In the birds we have lost the left root, and parallelism ceases with this change. In the Mammalia the right root turns to the left, so that in the comparison of these classes the rule of von Baer above quoted is true ; no mammal at present known is identical in a foetal stage with any fully grown bird, but with a foetus of the same, up to a certain point. But for both classes the joaral- lelism of those below them holds true. But it is with the exact parallelism or identity of genera that we have to do in the present essay. That being established, the inexact parallelism between the modern representatives of higher groups follows by a process of reduction. * Agassiz, I. c , denies the homology of the ventricles of the turtle and mammal; but it appears to me erroneously. He says : " The fact that the great blood-vessels {aorta and art. puhnonalis) start together from the cavum venosum seems to prove that the two cavities in the heart of turtles, which are by no means very marked, do not correspond to the two ventricles in Mammalia and birds." 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O • £iS S -*^ > cS ft a :".- ,r3 53 ; o «3 •'£ a i: = a O bj tc 3 a S ^ CO OT3 . ^ O fteS^ « ^ «-a -- «3 O a ft -Sft ££P4 6 6Q GENERAL EYOLUTION". 8 K ^ ''^ 2 11 00 s; a, <*^ ie^ o 5.1 g: CO *^* <<> s » iS, , « ii (5^ > a o O S o a . So C O .5 3 o5g o cj 1=: ^ . - .r^ ax: . C 1h . £«§ ,5 03 S3 t< ej t- Si > * 5^ O c -(J OQ O - CO 8 1 u o 5 2 5 ' ti s-i l; g t, c o .2 ei tc s o «J3 a a c3 C =o £ 11^ o o •7- »G OJ »-i O t< c =* • o 5> ^ o OQ CS c3 O 13 .2 a 0/ e3 c3 u CO a a -S 3 3S a 0) o «^ A c . 02 S M c o 05 bCcS is 4^ U &«^ O bJDoj p ^ fi=3 2=| C o o e3 ."3 C3 o o u o 03 HI o cc O it Si 00 •— «- -c !> v^ O rH x> a t ^ c-2 o o o C3 o O ^" o a a o C3 3 a-^ o-^ a " ^ "^ *j «.a,o as w c3 a Is o a o >. ti > 53 J3 oa a "C o o . ^^ O 03 S^ c: > • « =3 O Sill a cs^^ S-^ § « 3 « t- a 3"^ 02 £ C3 £tr tp fe ^; • <^^ o u P3 O CM a> ,a •»^ > o a a s o 03 6 o o f-t o 03 a o oa >. .a o C3 H e3 (-< a> 'd o 03 0) Eh 03 « o 03 (1 a a a o O a a a o be c3 03 i.2 =3 03 a a.-a :3 o o o u O m > cS a a ON THE ORIGIN OF GENERA. 67 CO «0 o S3 O O a eS O t-i m a o a a o U, 'S ajlls' :-• t- ^ « o 5 S =3.- C .. S C! > - U O > c3 3 o V o ^ V e -< § o fl 03 hi ,o o a> P. o 03 O c3 O -§-50 «^ - — p,— '^ . "o . tn QD ;-i :-i o c C3 Si ,o O p. -a o c c3 o be ;-i P c3 O Si c3 si o o t-l a u <1> o3^M 03 oi:e a ■M O a ilS5 .2 « ^ *^ ^ C S a^iS « aj ^ c— ' "«• p a 3 ll 3 O) O g "5) o tl e3 ? o ^• c3 ^ 2 3 « ?. p ^ .P P Si w <*-i t- ^ ri t- *^-p .2 5 5 c/j a; j3 O -wtS Cu"P i3 .-== p .2a^ a^^c^o p s a^.-« age .0^30 o 5.P o a-§ o . 00 *J p. a °6 p c3 P 4) 3 ^ «■ • ci =0 c3 P ^as p-E-^ Si .^ c3 Pi « P "P o Si 0;2 . P -P 't-'.Pc^. i- Si r/J •3XJ O ^- aL.=3 «>^'§ p --^= p i GO ia o Si w r -* >J2 CO < o; 03 u o <0 X! -« 00 . 03 .P =3 a|-^ P S o +J . o O > P Si S3 c3 «i_j Si « O-P tJ b o -M S3 P P^Wto C ti0<1 o Si 03 u OQ O P< Si OJ p I3 o Si o 03 Si « a o 03 QQ S3 o o ^ so « .a§ o " Si n" ^" =3 a g« a-^45 O p p 2 « 3 £|« ^03^ O o ^ Si tl p e3 a o 8s=^ ^ s-a (U o g ^ P o £xi 2 03 -^^j ^p •■ 0) & p ^a QJ 05 <<-i tl O ODu_i ^ P U P ® -" a . .• n P «2 a O O (c « ■ tl .*i ' *^ _» C3 C 2 ■^ t. P o^a to O ,P P Si o • • d IP'S OJ -^ o a •§§"W 23 p o 3 P < 63 p O O P a >> Pi O 68 GENERAL EVOLUTIOK ■ OQ « a TS 2 ;-. .^ ==3 § r-.B ^ 5^ L?^ i^uS s t-i r; o *-> "d f^^ . o t- g •>: >^ ^- .2 • fc! >H S l~ o t; cJ o c3 O *- C o t-r « c3 S s O oo « O 00 si *- >1 o c3 a o Of 63 c a; •HI >< X! 5 e3 OQ to S e KJ it :^ " C ^ C iO 5;, -.2 "-S _ J3 tH y a ^ ii C «i-i ^ t-. i, S O O -i-i 03 CO c3 c a a o " y OK p to 08 £f p a fi •"'"'"' c . a «_. . tc o ^ ts ,: -r; Eh o a a-^ rt C3 3 o O W 32 -M •r a ^ 2 - w^ o o s OJ o y a » *j a ii X c3 c> W 5J -a o •is ^ a „ .«<-. o o o si i33 o « g O .^ . g gj- pa '55 H, S.ti § a c3 c3 a . o o c3 t4 03 03 a " P. a O O 02 ^3 tj o « ^ OS J* 5S * • • Ci~i S^ac ° ^ ° i: - o a a a oo 2 - ^- = a s '-' 53 a-^ 115 !j"a « ^3«" a 5 a-= 5^ a. So a-2c-wt«c3 t-l o 53 to o a a a a o o a c .S «3 .22 a fl 05 a a c3 O -a "o PQ'O. 00 o o aSo^S. c3^ O.'^ c3 u o o t4 o o a § " C3 CM a-Y rt r o rt a A fc a is aE:-ls a^a-s^" g S 5 - a a- " o o . ^< o- «p 00 ^^ a f" a ., ■^a --: 2 c3 ■^ a cc .S tl— -» a ^ a 32 ::i' O a: •4^ • a o cS O HC3 o o «<« a CO .^d a g a at; o — "a a- I! e a "^ a K a o a •^ a s o c3 -fe a o ad a a a," =s — "S JS on, . Or-i .tj a aa £a§ u c es O ^ . o •^ a o a a-d c3 , fc, , — ,— ^ OQ C3 a o a a 63 a o a a o c 03 o c3 O u .2 "'3 o cS o3 cj aai O C^ (U go.— a a « O o I-} a p c3 !> 5 c3 a .a a m o o o o O 00 Ci W S3 y I III a M CI t>5 rt VI S-i •• CO ■"i3 S£ o to y ss c-:: a ti =3 ^ ■g -a - 3 aT 6 ;2i ON THE ORIGIN OF GENERA. 69 a o < CO ^ o3 CO -a^b =* a 2 ^ n 9 ** o o c . 'C o > lo 2,0 ^ C « .s- o «-^ ^ -*J o u -<^ |i r cS 4^ ^ « i: -a 'a 13 3 a=3 ^1s « •' u .■— CD <1 .S GQ <1 O 1/) O :3 5 Hi C « > S o '-' y .2 CS O 0* 5=^ -°Z- II «3 -^ O O Q O (^ II -s o <«3 a o s a o t-l a a o — o 00 <5 o O P-. sa o . OQ CD JS 3 -tJ ■S8 as -t-> 0) 5 « O c; e3 ^■■£ •^ O . c3 as S3 o <-• ^' 9 eS O « .^ « c3 C -" O O cS o S3 X a o a a o 3 = s .a S-3 3d 03 O a Si -« a .£f 2 a o u a Pi a 3 .3 e3 o a o a 3 to a 3SB Sag C «£ c a .^a o ^ ^"'3 . 3 00- a a 303 a^a o " o 3*^ 3 a o 3 3 O f-i >-'"3 03 g si o " 03 3 u 3 +^ 3 ii (- o bJO ^ OE 00- 3 c3 3 o o 03 a a «a . o o a c3 o . ^^ O cj pq o CO CJC II g P 3 a; c3 ^§ 3^ 3 3 3 0, 03 O 03 a o 3 3 03 a a . ^3 '■-=: S o o 2 .S « o u CS 3 c3 CU 3 jjr- (3 fl O O -H h^H e3 at^S ^ ^a 3 o 3 a> u 03 I— I c3 p— « O IK o pO o Pi >^ « *i (rt « r-t 03 rr) -t^ ^ u < PU TO GENERAL EVOLUTION". «> ^ GO.S- ,2 ao a a ^ C 4* O 00 O fn ■D* tS] • ^ 00 S=SOO h-; c o « CD C O O ^1 * * 01 1=1 N s c3 (U l=i o .E (E O) p'5 8 ^ 5^ > u .-« -S 2 i= ^ p. oWt^ O t. . c3 Q ■ ~ w S5 ■^ "O ._• "> _, o — • u ^ d — ':2 O y 3 s "^ £h^ =0 to S n o o O) o e3 GQ 0) ;3 01 cc V (-1 s o a,- P-. v i; » e ■si o 0) CQ O Pi a m a e3 O P4 Ol -IJ e3 c o> CD 0) o 03 O I— I 03 o 0)X5 fO 03 a 3 a C 00 tH ±5 « 03 c a 03 o> a o tc a; Si— I g c3 o O o « O J2 03 03 ;h 03 Oh 0) OQ o3 « . •E 03 an ^ . a - O u C o a. O) s c3 00 03 O c a — t) ^ 01 I a y 0.2 "« 03 O, P. 03 O O f-> it O O) o C 03 o a 03 a o .2§ 03 GQ 03 Ol "u S3 « P-t a, O 03 EH CS to o o Ol Ol CO o .^ Si go to o 03 !2 o3'3 2^ •- c3 a^ « H O 03 OJ >^ ON THE ORIGIN OF GENERA. 71 a> .Ho go >, ■rH ft fl03 wa ^8 f>> C a _• o a • QD « c C3 M^ <5 ■d 1— ih:; a o i'- ;3 HH IK a rt (U O eS .t^« . o -e a d . 0) ach rteb en 03 ^ . ^ c Cl 3 hH c3 4J >% c3 s; > O a « r • « 03 C > ,_; cc 01'" 83 3 a< o" « a =3 >0J 3- inal nite t. qual ; right 3 OB a> S o -a su a fl ^ r4 «M 2ro gig C3'.2 03 -S Eh a s . « QJ t> - <" ..^ CO o^rg 1— ( B^c^ C3 3 S' . >i1^- hH O Kh- 1 o 03 •'^ CD O •S.2 .S a -S o —■ G "■' C C QJ e3 O--: rr- S-l ?^ 5 '^ >^v c ?► o 03 o - - s^g cc 3 3 03 c3 o fexi . 3 ej *r-! > 3 03 5 2 «■ =* =»■ O 3 >>3 3 ^ a) 00 o • 3 •Sis 3 03 03 5 ,3 o 03 3 03 OQ 03 V a 03 as "S 'S a o « 3 m Ph 3 0) oa c3 as 03 03 3 u 03 3 S aj a t-i cc *j a; ^^ a 3 OJ s- »- +j y « 03 03 "•=3 . <» ftoo 03'=^ SB - c3 <» 2 .2o ^ 03 J a 03 >;. 3—' O) "3 O rf" °3 03 G >> 3 ^.2 a fccS^ 0} 3^ .2.3 O o ,3 03 ^ .3 00 03 6D CO 3} ^ *-* e.a o .S 3 , 3 3iS =0 (^» o 00 03 50 O '. o ^o . P. 03 O 03 70, t^2 03 02 ,^03 • a trts 03 a> 00 03 ^-i S3 • 03 B 3 OJ 03 o 3 o 3 vfLja OJ e3 o rt O rQ 3 03 03 03 . . ^ 3 = o 03 p. o DO • 3 • t- 3 • 03 : O a 03 BO aj ^03 O <1l-J EH c3 o o o t-l CD O) > o 5-03 03 a a .2 Is .i-H 3 a> o 03 a 03 o3 o3 a'5 =3 §.2-.::: o -^ *^ 3 £ !3 c 3 g 03 ^i3 .4.3 ^ ^ s-" 3 a> rd o 04 a P-.2 Z 8 o 03' 3 Eh .3 P.C3 u 0~B > a a> (E O O O 03 2 03 O 3 '=i ^ S aj ^ ow5 03 <-> P- o (1 ,3 O CD '^ « Or-i • §o-H^ io X +j H O-i p. t^ 11^ tors "^ •2 ^ < > o a. So :=■ »>< ri ^ ij^ IT c «fi « 2 •u " TS o O r-' "O rt i-H oi C a2 1 e i a c 1 1 P « a D c 1 s i — H to . • to • X « : ra e «"* « « > t< ex: s o 5 « ..o . ^ QE to tn S « !^ O 1 .3 'S . S| c O ^ X 11 .■S°.2 1 u o o H-1 P o a p o o p > a o o a a t-i o : F ^ CD S o o "E es O on ^ -J 1 § o •II c o O > o e o P < /c3 o c 2 08 • |-g| e3 o3 § X3 C aa "1 ON THE ORIGIN" OF GENERA. 73 =9 o a ft? s ct '3 o^irt. PI . OS o O =3 a H ^ C3 o -a o -23 5 cc p W cS C3 > -t-s CO sS *I C3-W-2 g . O CO <(-i'3 a o C rt 54-1 4> - iss^'i^dli > > aS >z: .-= a e3 u o B C S S d CO bJO^ ill it =3 a eS o a a C3 5 • ^ > o a t/DT p — ' 02 ^ •-■ ^ " S s ^ "-C "f^ -" OQ O 5/ gtfa C O Sh a . •^H ..^ es >> oc m o§ « > > Is CO 3 ^ ^ c3 fl a to 3 a ia a "a «2 a a s CO i^^ 32 H §3 SI C3 o :ia O «-" — ^*j r< ^ «> a 0.'ja a ^ "J2 C3 fcC • OQ ^^ a^ a f-l=(-l 33 ft) c3 • c- _ S3 t^ C « > o O (1 tiC jd be • a >» ^0 CO a a o GQ a 2a .H«; ^ K a c3 O c8 c3 j^ --? a to c3 ,0 « O § Si C-03 o ^ a ^ /u< '-I a c c- o a 4) Eh a 3 1— > . ... 3Q a 3 go O-a-e o c3 Xi 33 3 cs OS o a o M a a, t>. ,a a o != 2 C3 ft So O— ' a « OD 33 S3 > S3 O a o o Xi to o a S3 03 -H :3 ft O 2 "a fta> 03 a 3 -»j to o E-t T3 O o o 00 o3 a^ 5 . c3 >, *j;a.a i^ S i3ti.2 P1O 5 . S3 sss g 53;:^ g a = •- "2 n y « 3 S 74 GENERAL EVOLUTION. 6. TJie Extent of Parallelism. Prof, de Serres and others have stated it as their belief that the lower ^* branches" of the animal kingdom are identical with the undeveloped forms of the higher ; i. e., that the mollusk and articulate are not merely parallel with, but the same as the lower conditions of, the vertebrate. The works of various embryologists, as von Baer and Lereboullet, have shown this statement to be erroneous, *^and founded on false and deceptive appearances." The embryos of the four great branches of the animal kingdom appear to be distinct in essential characters from their first appearance. But Lereboullet, who, in his prize essay, has compared with care the development of the trout, pike, and perch of the Teleosts, with that of a Lacerta among reptiles, has failed to point out characters by which the embryos of the two vertebrate classes essentially differ, for a considerable period. It is true that, as each and all of the species belong to widely differ- ent generic series, parallelism is of the kind to be called inexact or remote. But enough is known of embryology and paleontol- ogy to render it extremely probable that the historic predecessors, of the types whose embryology Lereboullet studied, formed a se- ries of parallels of the kind termed in this essay exact. Lereboullet states that a certain difference exists between the eggs of the fishes and those of the Lacerta. This is for us merely stating that the parents of the embryos differ, a fact which no one will contest. The same may be said of the elevated or depressed character of the surface of the vitellus on which the embryo re- poses. Secondly, after the appearance of the embryo the Lacerta is furnished with the amnios and allantois ; the Teleost not. This is certainly neither a generic, ordinal, nor class character of the adult, for it is but temporary ; therefore, in generic, ordinal, and class characters the embryos of the Teleost and Eeptile are still identical. It is a physiological character, and not morphological, and therefore far the less likely to be a permanent one, even in embryos, under changed circumstances. The female of one of the species of Trachycephalus inverts the skin of the back at one season of the year to receive her eggs, because she can not lay them in the water ; the other species of the genus do not. The next genus in direct morj)hological line possesses a single species whose female does the same for the same reason ; but the rela- ON THE ORIGIN OF GENERA. 75 tions of these species and genera are zoologically the same as though this modification did not occur. Many such instances will occur to many naturalists. It is not pretended that they are as important as the presence of the allantois ; but they constitute a character, no doubt, similar in kind, and entirely at the service of the needs of the great system of morphological succession. The same may be said of the vascular area of the Reptile. Lereboullet concludes his summary of the differences between the Teleost and Reptile, up to the period of completion of the heart, by saying, *^ It is easy to perceive that all these differences, however imj)ortant they may appear, are constituted by the acces- sory organs of the embryo, and do not modify the development of the latter, which progresses in reality exactly as in the fishes." He says the same previously, as to the relation of the same to the bird and mammal. We have, then, in the embryos of the lower vertebrates at a certain time in the history of each, an ''exact parallelism''^ or identity with the embryonic condition of the type which pro- gresses to the next degree beyond it, and of all the other types which progress successively to more distant extremes. We have, however, so far, every reason to suppose that the embryos of the other branches of animals never present an exact parallelism with those of the Vertebrata.* The embryo of the fish and that of the reptile and mammal may be said to be generically, if not specifically, identical up to the point where preparation for the aerial respiration of the latter appears. They each take different lines at this point. The fish diverges from the course of the reptile, and proceeds to a different goal ; the shark does the same, but proceeds a shorter distance ; while the Dermopter scarcely leaves the point of departure. No doubt, there have been types which never left this point and tvliose plan of circulatory system is identical with that of the embryo reptile and mammal. Such a type was only generically different from the reptile or mammal ivhich had only taken the succeeding step, provided other structures were not superadded. By comparing the development of types of different classes in * At about the time this was written the important papers of Haeckel on his admirable Gastraea theory were published, but had not reached the author. Haeckel shows the approximate identity of all the types of embryonic development. (Note, 1886.) 76 GENERAL EVOLUTION. certain features whicli are only ordinal or generic in meaning, yery erroneous conclusions may be reached by the inexact student as to the want of parallelism of classes to each other. Thus Rathke says of the development of the eye of the snake Tropidonotus, at a certain period, that it is far in advance of that of the mammal at the same stage. Here, says the objector, is a case where their parallelisms do not coincide ; the mammal is really similar to a younger stage of the reptile. But, in fact, the size of the eye is but a generic or family char- acter ; if the development of the lemur had been compared with the snake, the mammal would have been found to be in advance ; of the mole, much farther behind. If the snake selected were the purblind Atractaspis, almost any mammal would have been in advance ; if, on the other hand, the great-eyed Dii3sas, but few Mammalia would have been parallel to it. In a word, to find exact parallelism it is necessary to examine the closest allies. It is also of first importance to distinguish between the exist- ence of generic or higher characters, and their condition under various circumstances of individual life. If a foetal or larval character be conserved through the adult life of a type, it will be of course adapted to the functions of mature age. Thus the un- developed character of the horns of the genus of deer, Rusa, are not accompanied with the marks of individual youth of the cor- responding stage of Cervus ; its individuals are fully grown and functionally perfect. The species of Hyla are not small and in- capable of self-preservation and reproduction, as is the corre- sponding stage of Trachycephalus ; they are functionally devel- oped. The student need not be surprised, then, if, when identity or exact parallelism is asserted, he finds some differences depend- ent on age and adaptation, for if he be an anatomist he need not be informed that a morphological relation constitutes types what they are, not a physiological. II. OF KETARDATIOK AI^D ACCELEEATIOK 11^ GENERIC CHAE- ACTEES. First. Of adult metamorphosis : The question has necessarily arisen, Have these remarkable relations between genera resulted from an arrangement of distinct generations according to a permanent scale of harmony, or have the same genetic series of individuals been made to assume the ON THE ORIGIN OF GENERA. 77 different positions at tlie same or different periods of the earth's history.* Prof. Marcel de Serres proposed the theory of repressions of develojDment to account for the existence of the lower groups of animals as 7iow existing^ an error easily exposed, as has been done by Lereboullet in his yarious important embryological writings. But little obseryation is sufficient to prove that a mammal is not a shark where it has five gill-arches or aorta-bows, nor a batrachian where it has three, or a reptile where it has the two aorta-roots. This has been already sufficiently pointed out by von Baer, who says there is " keine Eede " of such a theory as was afterward proposed by de Serres. Thus are true the rules propounded by this author, f 3. ^^Each embryo of a given animal type, instead of passing through the other given animal found, diverges still more from it." 4. ^^ In the basis, therefore, the embryo of a higher animal type is never identical with an inferior type, but with the embryo only of the latter." I think that I have already made some progress in proving that the near or true generic relationship is one of absolute devel- opmental repression or advance. Paleontology shows that fami- lies and orders, as now existing, were preceded in time by groups which are synthetic or comprehensive, combining the common characters of modern generic series. This process of synthesis must, it is obvious, if continued, result in the near approximation of the single representatives of the now numerous and diverse groups. There is every reason to believe that a backward view through time will show this to have prevailed throughout the * Some naturalists seem to imagine that the demonstration of the existence of intermediate types is only necessary to establish a developmental hypothesis. Thus Dr. Dohrn (" Ann. Magaz. N. Hist.," 1868), writing of his discovery of that most interesting genus, Eugereon, which combines characters of Neuroptera with those of Hemiptera, does not hesitate to say that it proves the truth of Darwin's theory. Now, it appears to me that a demonstration of the existence of a regularly graduated succession of types, from the monad to man, would be only the minor of a syllogism without its major, in evidence for development, so long as the proof of transition of one step into another is wanting ; and the idea that such a discovery could estab- lish a developmental theory is entirely unfounded. Indeed, the reasoning in which some indulge— if we dare so call the spurious article— based on this premise alone, is unworthy of science. The successional relation of types, though a most important element in our argument, has been long known to many who give no sanction to the idea of development. f " Entwickclungsgeschichte," p. 224. 78 GENERAL EVOLUTION. Vertebrata and other brandies, as we already can in part prove. And I have no doubt that the synthetic types, which represent modern orders, have existed in a generic relationship subordinate to the plan of the synthetic class, and that the latter have existed as genera only, of the type of the great branch. This is not ideal. We only have to look to our extinct ganoids^ Archegosaurs, Laby- rinthodonts, Compsognathus, Archseopteryx, Ornithorhynchus, etc., to realize these facts. The first genera then formed a scale of which tlie members were identical with the undeveloped stages of the highest, and each to each according to their position. Such a series of antitypic groups having been thus established, our present knowledge will only permit us to suppose that the resulting and now existing kingdoms and classes of animals and plants were conceived by the Creator according to a plan of his own, according to his pleasure. That directions or lines of development toward these ends were ordained, and certain laws applied for their realization. That these laws are the before-mentioned law of re- tardation AND ACCELERATION ; and law of NATURAL SELECTION. The first consists in a continual crowding backward of the successive steps of individual development, so that the j^eriod of reproduction, while occurring periodically with the change of the year, falls later and later in the life history of the species, confer- ring upon its offspring features in advance of those possessed by its predecessors, in the line already laid down partly by a prior suppression on a higher platform, and partl}^, as above supposed, by the special creative plan. This progressive crowding back of stages is not, however, supposed to have progressed regularly. On the contrary, in the development of all animals there are well- known periods when the most important transitions are accom- plished in an incredibly short space of time (as the passage of man through the stages of the aorta-bows, and the production of limbs in Batrachia anura) ; while other transitions occupy long periods, and apparently little progress is made. The rapid change is called metamorphosis ; the intervening stages may be called larval or pupal. The most familiar examples are those which come latest in life, and hence are most easily ob- served, as in the insects and frogs. "When, during the substationary period, the species reproduces, a constancy of type is the result ; when the metamorphosis only appears at the period of reproduc- tion, a protean type is the result ; when the metamorphosis is crowd- ox THE ORIGIN OF GENERA. 79 ed back to an earlier period of life, then we have another persistent type, but a new genus of a higher grade than its predecessor. In reviewing many examples everywhere coming under the eye of the naturalist, it is easy to perceive what would constitute a plastic and what a conserved condition of generic, or even of spe- cific form. As one or more periods in the life of every species is character- ized by a greater rapidity of development (or metamorphosis) than the remainder, so in j^roportion to the approximation of such a period to the epoch of maturity or reproduction, is the offspring liable to variation. During the periods corresponding to those be- tween the rapid metamorphoses the characters of the genus would be preserved unaltered, though the period of change would be ever approaching. Hence the transformation of genera may have been rapid and abrupt, and the intervening periods of persistency very long ; for it is ever true that the macrocosm is a parallel or repetition of the microcosm in matter and mind. As the develoj^ment of the in- dividual, so the development of the genus. We may add : so the development of the whole of organized beings. These metamorphoses may be fitly compared to those in the molecular constitution of matter. The force of cohesion between the atoms of a vapor steadily increases with descending tempera- ture, and in a regular ratio, till a given point is reached, when a sudden metamorphosis to a denser or liquid condition takes place. Nor have we reason to believe, with regard to many substances, that there is any parallel relation between the temperature and the molecular constitution before or after the metamorphosis takes place. So, the temperature continuing to descend, the molecular character of the liquid remains unchanged until, the vis conserva- trix suddenly giving way at the ordained point, a soild is the re- sult. Thus, while the change is really progressing, the external features remain unchanged at other than those points, which may be called expression-points. Now, the expression-point of a new generic type is reached when its appearance in the adult falls so far prior to the period of reproduction as to transmit it to the offspring and to their de- scendants, until another expression-point of progress be reached. Thus a developmental succession does not so obliterate the lines drawn around Nature's types as to render our system ineffectual as an exDression of them. 80 GENERAL EVOLUTION. The successional acceleration or retardation in metamorphosis may be best illustrated in certain tailless batrachians, by the fol- lowing tables. These are taken, it will be remembered, from the Bufonidse and Hylidse as examples of '^ exact parallelism " ; three are now added from the Eanidae and Discoglossidae. The case of ^' inexact parallelism " is that of the Scaphiopodidae. Whether they are cases of acceleration or retardation can only be determined by reference to the paleontology of the respective groups, or a careful comparison of times of metamorphosis. In the case of the Discoglossidae I suspect it to be retardation, as the highest genus is extinct. The others I shall arrange with them for temporary conyenieuce. Were I dealing with a group of Ga- noids, I should imagine the process to be retardation, as this group is going out of existence. On the other hand, were they higher Oscine birds, we might imagine the case to be reversed. Assumed, 140th gen. 120th gen. 100th gen. 80th gen. 60th gen. 40th gen. 20th gen. 1st gen. Series No. 1. No. 2. Bombinator. . .Hyla Alytes * No. 3. .Epidalea. e : Discoglossus Scy topis e Pf : F e Pf F : . . Buf o sp. Osteocephalus. . . e. Pf F Ex : . ,Bufo sp. Pf : F Ex t Latonia Trachycephalus. Pf ?F : Ex t . .Peltaphryne . ? : : p >-s 5 c> rj «i 2 « >-^ 3 g. O .°° g" P' £S r^ — CO H 3 t:- CO a of o O ffi „ P-S.S IX ^ ■ ^ o CO o W s o ■-1 SS -I o o O CO ►c P •s "*• C 3- P- 3 o o Fig. 3. T T T F T F Ex T F Ex o ^ f <1 ^ "-J O rt- t-t- c "■» o P t='2.'C 2; 00 • 3 3-0 OD ft P 3 Pi ft y< P 00 p 22. Q CD p o orq ft 1-1 o & 3 ft ft Ixalus. i Rhacophorus, Polypedates. No vera, teeth. Sometimes " Always " ^ 2 §1 P ft Points not attained. Fig. 4. * A parotoid gland of small size is added here, but is not generic as compared with Bom- binator, as the latter has collections of crypts on the same region and over the body. ON THE ORIGIN OF GENERA. 81 u a OB % Pi O OS EC be o CD a, / * * / / u * 1 Death. Eeprodiic- tion. Tail lost (re- tard.). Temp, roof (ace). Ossif. front (ace). Hatching. 6 M PR \ \ \ \ Reproduce. Prefrontals unit. Ethmoid oss. Tail lost. Frontak 0B8i£ p. o e a Hatched. In the preceding diagrams each horizontal cohimn represents the life history of the individuals of each genus. The line of dots, stars, etc., represents the same developmental stage of each, as it appears earlier or later in the life of the individuals. The point of crossing the breeding period is that at which the charac- ter is rendered permanent. When the change falls on this period the character is not generic, as in Ixalus, Fig. 4. The period of losing the tail, like that of breeding, is represented as occurring at nearly the same time in the history of every genus, as it is gener- 6 82 GENERAL EVOLUTIOK ally seasonal. Yet this is not always so, and, like the other char- acters, has most likely had its period of shifting. Compare differ- ence of time of development, for instance, of the frontal and pre- frontal bones in Figs. 3 and 6. The comparison of the adult stages of the less developed genera, at the tops of the columns, with the larval conditions of those more fully developed, may be traced in the absence of characters which appear in the latter. I have convinced myself of the accuracy of the above relations by the examination of many skeletons and wet preparations of adults and larvae. The diagrams* are representations of nature, and not ideal sketches. It is to be noted as remarkable that the advance throughout so many diverse groups is in the same direction, viz., to complete or excessive ossification of the cranium ; and this identity of progress might be readily shown hy adding other char- acters, were it not that the tables would become too complex for convenience. Has, any, such transition from genus to genus ever heen seen to occur 9 It must of course take place during the life of the individuals of a species, and probably at different times during the lives of different individuals, dependent on their relative vigor. In our view, ordinary metamorphosis is such a change, and we have stated its bearing in this form, that ^' every character distinguish- ing suborders, families, and genera is to be found among the indi- viduals of some species, living or extinct, to mark new varieties or stages of growth." a. The Developmental Relation of Generic to Specific Characters. For the relation of the law of retardation and acceleration to specific characters we will look to development again. While the * Notes on the diagrams : Fig. 4. Polypedates is here restricted to P. maeulatus and P. quadrilineatus. The other species are referred to Rhacophorus, which has not hitherto rested on any proper basis ; the asserted character — the palmation of the hands — being one quite graduated from species to species among Hylas. Chiromantis, Peters, is referred to the same, as its character is not strongly marked and is visible in other species. For similar reasons Lcptomantis is referred to Ixalus. Fig. 6. In each of series ii and iii, two series are mingled for the sake of com- paring the structures of the prefontal bones. Thus Heteroglossa, Staurois, Hylo- rana and Trypheropsis are one series, and Hyperolius and Hylambates members of another. ON THE ORIGIN OF GENERA. §3 young of Trachycephalus are successively different genera, they preserve most of their specifle characters so as not to be mistaken. Agassiz says of the development of the North American turtles,* " I do not know a turtle which does not exhibit marked specific peculiarities long before its generic characters are fully devel- oped." The same thing can be said of the characters of our sala- manders, whose specific marks appear before their generic or even family characters. I suspect that this will be found to be a uni- versal law. It also follows, if a developmental process, as proposed, has existed, that at times the change of generic type has tahen place more rapidly than that of specific,] and that one and the same species {if origin he the definition) has, in the natural succession, existed in more than one genus. Apart from any question of origin, so soon as a species should assume a new generic character it ceases, of course, to be specific- ally the same as other individuals which have not assumed it. If supposed distinctness of origin be, however, a test of specific difference, we shall then have to contend with the paradox of the same species belonging to two different genera at one and the same time. It follows, therefore, in our interpretation of nature, that groups defined by coloration alone are not to be regarded as genera, as is done by some ornithologists and entomologists. They are simply groups of species in which distinctive generic characters had not appeared up to the period of reproduction. Inasmuch as in development certain specific characters appear first, among them part or all of the coloration pattern, it is obvious that the latter do not belong to the generic category. The employment of such characters, then, in this sense, is only to commence reversing the terms generic and specific, and to inaugurate the process of regarding each species as type of a separate genus. p. Of ProbaUe Cases of Transition. Thus the transition between the toothed and edentulous con- ditions in Cetacea takes place in the ordinary growth of the indi- viduals of the genus Globiocephalus, and the transition between * Gontrib. " N. Hist. United States," i, p. 391. Note. f See " Proceedings Academy," Philadelphia, 1867, p. 86, where I observe that genei'ic characters are probably less inherent than specific. 84 GENERAL EVOLUTION. the ossified and non-ossified types of Chelonia occurs during the life of the individuals of the genus Dermatemys. But, in attempting to demonstrate this proposition, we must bring forward facts of another kind. The anti-developmentalists are accustomed to put such changes aside, as part of the necessary history of established types ; hence we will not aj^peal to such. 1. The frog Ranula qffinis, of South America, was described by Peters as probably a climatal variety of European Bana te7npo- raria. In this he is supported by the fact that the specific char- acters do not differ more than would characterize it as a local variety, were it an inhabitant of Europe. But I have found that it differs generically in the non-ossification of the ethmoid bone, as has been confirmed by Steindachner, and represents an embry- onic condition of the same bone in Eana. It is in fact an unde- veloped Eana. That this is a true genus is confirmed by many specimens, by additional species, and by the fact that the allied genus Trypheropsis, embracing three species in the same region, differs in the same way from the otherwise identical genus of the Old World, Hylorana. 2. The South African Saurians, ChamcBsaura anguina and Ma7icus macrolepis, are very closely allied in specific characters in all respects, though distinct. They have one important ground of generic distinction : the latter has one pair of limbs less than the former. They are rudimental in Oham£esaura, and tlie disap- pearance in Mancus is but another step in the same direction. The difference in specific characters is of mucli less degree. 3. In the genus Oelestus there are numerous species, which range from a slender snake-like form with weak limbs, to stouter, strong-limbed forms with a more saurian build. Among these the Haytian O. plioxinus is well distinguished by form and color- ation. An allied genus from the same region is Panolopus, which in specific characters approaches the C. plioxinus very closely, much more so than any Oelestus (one species possibly excepted). But in generic characters it is distinguished by the loss of all its toes and the non-separation of nine plates on the end of the muz- zle. The genus Diploglossus, on the other hand, occupying a superior place on account of the division of the fronto-nasal into three, is, in specific characters (of B. 7no7iotropis) much closer to the stout Celesti than the species of the latter genus are among themselves. 4. The Gronim nigrilahris is a Silurid, which in specific char- OJT THE ORIGIN OF GENERA. §5 acters more nearly resembles the Amiurus lynx, than the latter does the A. albidus and many other species of the genus. The A. lynx is found in the same streams. The important generic character, the absence of eyes, is, however, its constant feature (in three specimens known to naturalists, others to fishermen). 5. The Cinclidium maximum, a large tree-toad of Brazil, re- sembles in all its characters the Gentrotelma geograpMcum. The specific differences between them amount to almost nothing, but both sexes of the former grow larger and are furnished with a generic peculiarity in the addition of some phalanges to the thumb. 6. The Oporornis agilis, Baird, a North American bird of the Tanager family, resembles very closely, in form, color, and habits, the adjacent species of the adjacent genus Geothlypis. While its specific characters are thus very close to Geothlypis teplirocotis, it differs in the generic feature of a longer wing. By this it is associated, and properly so, with another species 0. formosus, which has the general color and habits of species of Myiodioctes (if. canadensis), the next related genus. 7. The following fact I give on the authority of Prof. Leicly, who will publish it in his forthcoming work on the extinct Mam- malia of Nebraska, etc. Three species of Oreodon occur in the Miocene strata ; they are a larger, a medium, and a small sized species. In the Plio- cene beds above them they are represented by three species of Merychyus, which are in all respects known, identical specific- ally with the three preceding. Each one may thus be said to be more nearly allied to the species of the other genus than to its fellow of the same genus, in specific characters. But each, on the other hand, differs from each in generic characters. The teeth of Merychyus are more prismatic, have longer crowns and shorter roots, approaching the sheep, as Oreodon does the deer.* * This phenomenon suggests an explanation on the score of adaptation, which the other cases do not. The existence during the later period of a tougher material of diet would increase the rapidity of wearing of the crown of the tooth, and require a longer crown and greater rapidity of protrusion. This necessitates a dimi- nution of the basal shoulder and shortening of the roots, producing the prismatic form aforesaid. The deer browse on forest foliage, which is more tender, while the Cavicornia graze the grasses, which contain, as is known, a greater amount of silex ; hence the more rapid attrition of the tooth. This may have been the case with the two extinct genera ; the different periods QQ GENERAL EVOLUTION. 8. The Coreopsis discoidea T. and (r., var. anomala, Gray, is, according to Mr. Aubrey Smith, much more nearly allied to Bid- ens fro7idosa than to other species of its own genus, and the latter is nearer to it than to other species of Bidens. It differs chiefly, if not altogether, in the generic character : the barbs of the ache- nia are directed upward ; those of the Bidens downward. From these and many other such instances it may be derived : That the nearest species of adjacent genera are more nearly allied in specific characters than the most diverse species of the same genus. 9. While Taxodium distichum and Glyptostrolus europcens, conifers of North America and of Eastern Asia, respectively, are readily distinguished by generic peculiarities of their cones, in specific characters they appear to be identical.* Confirmatory of this proposition is the statement of Parker : f *^In tracing out the almost infinite varieties of the modifications of any one specific type of shelled Rhizojood, my friend Prof. Rupert Jones and I found that like varieties of distinct species are much nearer in shape and appearance than unlike varieties of the same essential species." (It is not unlikely that species should here be read genus and variety species, though the latter may not fulfill the requirements in regard to distinctiveness observed among higher animals. In types like the Rhizopod, forms of this grade may not be really differentiated. Their enormous geo- graphical range would suggest this, if nothing else. ) Objection. — A class of objectors to the preceding explanation of the relations in question will ascribe them to hybridization. They have already done so to considerable extent among the Teleosts (see the writings of von Siebold, Steindachner, and Giinther). That hybrids exist in nature will be denied by none, but that they are usual or abundant is not a probable condition of a creation regulated by such order as ours is. The tendency to modify in given lines of generic series, if admitted, will account for many of the cases regarded as hybrids by the above authors, for it is to be remarked in many cases how the generic characters during which they lived may have seen a change from forest to praii'ie. (It is not intended to suggest that the species of the two genera arc necessarily of the same or any given number.) * See Meehan, " Proc. Amer. Ass. Adv. Sci.," 1868. Newberry, " Ann. Lye," N. Y., 1868. f " Transac. Zool. Soc.,'' London, 1864, p. 151. ON THE ORIGIN OF GENERA. 37 are strikingly affected, and are chiefly used in guessing at tlie parentage. This is among Cyprinidae so much the case that there is scarcely an example of a hybrid between two species of the same genus brought forward, but often between species of different genera. y. Ascertained Cases of Transition. This naturally suggests that, in accordance with the theory of acceleration and retardation, a transition can take place in the life history of species. Have we any means of proving this sus- picion ? 1. The genus Ameiva (Saurians of South America) has been composed of species of moderate size furnished with acutely tri- cuspid teeth. Teius, on the other hand, embraces very large spe- cies with the molars obtusely rounded and of the grinding type. These genera are generally held to be well founded at present. I find, however, that in Ameiva pleii, which is the largest species of the genus, in adults the greater part of the maxillary and mandib- ular teeth lose their cusps, become rounded, then obtuse, and finally like those of Teius. While young, they are true AmeivaB. Strangely enough the A. pleii, from Porto Rico, acquires but three such obtuse teeth when of the size of the other (St. Croix) forms. In youth the teeth of all are as in other Ameivse. Here is a case of transition from one genus to another in the same species. 2. In the important characters of the possession of branchiae, of maxillary bones, and of ossified vertebrae, the tailed Batrachia presents a series of a rising scale, measured by their successively earlier assumption. Thus Salamandra atra^ produces living young, w^hich have already lost the branchiae ; S. maculosa living young with branchiae ; Plethodon f produces young from eggs which bear branchiae but a short time, and do not use them func- tionally ; Desmogantlms nigra uses them during a very short aquatic life ; D, fusca and other Salamanders maintain them longer ; while Spelerpes preserves them till full length is nearly reached. Finally, species of Amblystoma reproduce while carry- ing branchiae, thus transmitting this feature to their young as an adult character. And it is a very significant fact that Spelerpes, which bears branchiae longest, next to Amblystoma, is associated * See Scbreiber's " Isis," 1833, p. 527; Koeliker, "Zeitschr. f. wissensch. Zoolo- gie," ix, p. 464. f Baird, " Iconographic Encyclopaedia " ; Wyman, Cope. 88 GENERAL EVOLUTION. in the same zoological region with a genus (N'ecturus) which dif- fers from its four-toed form (Batrachoseps*) in nothing more than the possession of the osseous and branchial characters of its larva, in a permanent and rej^roducing condition. That this is a genus, to be one day converted into Batrachoseps by an accelera- tion of its metamorphosis, or that has been derived from it by the reverse process, I am much inclined to believe, f In supj^ort of this I quote the following examination into the time of change of the species of Amblystoma from my essay on that genus : J *^ The great difference between the different species, and be- tween individual species in this respect, may be illustrated by the following comparison between the size of the animals at the time of losing the branchiae, so far as known, and that to which they ultimately attain. Species. Size at loss of branchi^. In. Lines. A. jeffersonianum, 1 S'YS A. punctatum, 1 10 A. conspersum, 1 10"5 A. opacum, 2 2 A. texense, 2 1 A. microstomum, 2 3'5 A. talpoideum, 3 (perhaps too large). A. paroticum, 3 7*5 (not smallest). .... { S 1 to A. tigrinum, j ^ ^ A ^' i 3 9-5 to 8 9 A. mavortium, ■] s A. mexicanum, ? branchias persistent. 8 " The last species, though not uncommon in collections, is not known to pass through its metamorphoses in its native country, but reproduces as a larva, and is therefore tj^DC of the genus Sire- don of Wagler, Cuvier, Owen, and others. The larva of A. ?na- vortium in like manner reproduces, but their offspring have in the Jardin des Plantes and at Yale College undergone an early metamorphosis.* ERAG] E FULL SIZE. In. Lines. 6 6-1 6 2 7-5 3 9-5 9 4 3 9-5 7-2 2-5 8 to 10 * See Cope, *' Jour. Ac. Nat. Sci.," Phila., 1866. f Necturus differs from all true Salamanders in the possession of the os interca- lare of the skull; the parallelism is therefore inexact. (Note, 1886.) X " Proceed. Academy," Phila., 1867. * Through the kindness of Prof. Dumeril I have received both larvae and adult of the species here noted, and observed by him. The larva is, as he states, Siredon lichenoides of Baird, while the adult is his Amhlyntoma mavortium^ not A. tigriyium { = luridum), as also supposed by Dumeril. (Note, 1886. I now believe these forms to belong to one species.) . ON THE ORIGIN OF GENERA. §9 Here is a case where all the species but two change their generic characters ; one changes them or not, according to cir- cnmstances, and one does not change them at all. What are the probabilities respecting the change in the first set of species ? As we know from the experiments of Hogg, Dumeril, and others that metamorphosis is greatly hastened or delayed by the conditions of temperature and light, what would not be the effect on such a protean species of a change of topographical situation, such as the elevation or depression of the land ? And I liaye no hesitation in saying that if the peculiarities of series of individuals of A. tigrinum and A. mavortmm, in the respects above enumer- ated, were permanent, they would characterize those series as spe- cies, as completely as any that zoologists are accustomed to recog- nize. For the evidences on this head, see the discussions of those species in my monograph. The experimxcnts of Hogg, above alluded to, are as follows, as given by him in the "Annals and Magazine of Natural History." He placed a number of impregnated ova of frogs in vessels arranged at regular distances from the light, in a cave. The les- sening degrees of light were of course accompanied by a corre- sponding but much less rapid decline in temperature. The result- ing effects on the metamorphosis may be tabulated as follows : 310. day. 60° 56° 53° 51° 3 11 Ecrg. Egg. Egg. 20 Larva free, * ^ * 25 * Larva free, * « 31 * * Larva free, Larva free. 4 10 Larva very large, * * * 22 Metam. complete. Larva large, Larva large. Larva small. 8 11 Metam. complete, * * 28 Metam. complt. ■se- 10 31 Metam. comp. 3. The reproduction of some sj^ecies of insects before they complete their metamorphosis is a well-known fact, and it is par- ticularly to the point that, in many of them, some individuals do attain to their full development, while the many do not. West- wood says,* "Two British species of this family (the Reduviidae), Prostemma guttula and Cor anus siibapterus, are interesting on account of their being generally found in an undeveloped state, the latter being either entirely apterous or with the fore-wings rudimental, although occasionally met with having the fore-wings * Uhler informs me that Amyot's asserted color characters are not reliable. 90 GENERAL EVOLUTIOK completely developed." ''I think," says Spinola, "that the pres- ence of wings and their development depends on the climate" ; and, in speaking of Oncocephalus griseus, he says, " The influence of the northern climate appears to have arrested the development of the organs of flight. It will be seen that I have referred else- where that I have noticed that it is especially in hot seasons that certain species acquire wings, while the circumstance noticed re- specting the ordinary occurrence of winged specimens of Micro- coelia in the West Indies is confirmatory of the same opinion." 4. It is now known that certain Orthoptera do not get through their metamorphosis in time for the period of reproduction, and hence never, or in rare instances only, develop more than a short distance beyond the pupa state. 5. My friend P. R. Uhler tells me of an example among Hemiptera of the genus Velia. The species V. rivulorum, Fab., and V. curreiis,^ of Europe, are only distinguished by the devel- opmental feature of the presence of wings in one, and their ab- sence in the other. Another species of the tropical region of the West Indies, Halobates americanus, Uhler, is furnished with wings, while its individuals, which occur abundantly in North America, have been generally supposed to lack them. Individuals, however, no doubt occur whose development is so far accelerated as to permit them to acquire wings before the period of rej^roduc- tion, since one such has been found by Uhler. These wing characters are in many cases generic, it aj^pears to the writer ; and the fact that they differ, without corresponding specific differences, is important evidence as to the origin of the genera. 6. The females of the Lepidopterous genus Thyridopteryx never develop beyond the pupa state, according to the same au- thority, before reproduction ; they are reproducing pupae, so far as the external characters concerned in metamorphosis go. In other words, the latter have been retarded, while the reproductive system and others have progressed. Now, generic characters are seen in the first, not in the last. The influence of the males is sufficient to prevent more than a part of the offspring from being retarded in the same manner. I have selected a few of this class of facts which have come before my mind during the present writing, as drawn mainly from * On " Insects," ii, p. 493, ON" THE ORIGIN OF GENERA. 91 my own experience. How many more of the same purport could be found by search through the great literature of science, or in the field of nature, may be readily imagined. I have no doubt that the field of entomology especially will furnish a great number of evidences of the theory of acceleration and retardation, espe- cially among the insects with active pupa3. Finally, having already stated the law according to which these processes naturally take place, I quote the following significant language of Hyatt in the above quoted essay on the Cephalopoda, as approaching nearer to the ^Maw of acceleration and retarda- tion " than anything I have found written. He says : '^'^In other words, there is an increasing concentration of the adult characteristics of lower species, in the young of higher sjoe- cies, and a consequent displacement of other embryonic features, which had themselves, also, previously belonged to the adult peri- ods of still lower forms." The preceding propositions have been formulated as follows, a few additions being now made : I. That genera form series indicated by successional differences of structural character, so that one extreme of such series is very different from the other, by the regular addition or subtraction of characters, step by step.* II. That one extreme of such series is a more generalized type, nearly approaching in characters the corresponding extreme of other series. III. That the other extreme of such series is excessively modi- fied and specialized, and so diverging from all other forms as to admit of no type of form beyond it. f IV. That the peculiarities presented by such extremes are either only in part or not at all of the nature of adaptations to the external life of the type. J; V. That rudimental organs are undeveloped or degraded con- ditions of the respective characters developed or obliterated in the extreme of the series. VI. That the differences between genera of the same natural series are only in the single modifications of those characters which characterize the extreme of that series. * St. Hilaire, Owen, Agassiz, Dumeril. f Dana on " Cephalization " ; Leconte. X Owen on " Cetacea," " Trans. Zool. Soc," London, 1866, p. 44. Leconte on " Carabidae," " Trans. Amer. Philos. Soc.," 1853, p. 364. 92 GENEEAL EYOLUTIOK VII. That the relations of the genera of a primary series are those of the different steps in the development of the individuals of the extreme genus ab ovo {von Baer^ Agassiz) (with sometimes the addition of special adaptive features ?). VIII. That the presence, rudimental condition, or absence of a given generic character can be accounted for on the hypothesis of a greater rapidity of development in the individuals of the spe- cies of the extreme type, such stimulus being more and more vig- orous in the individuals of the types as we advance toward the same, or by a reversed imj^ulse of development, where the extreme is characterized by absence or "mutilation" of characters. IX. And that, as the character of the genus at the period of reproduction of its species is that which is per^^etuated ; - X. So the character of the genus has been first inferior, then protean, and then advanced, as the metamorphosis has been by a retrograde movement in time, posterior to, at, or anterior to the period of reproduction. XI. That it therefore results that there is one primary struct- ural type involved in such a series of species, which is made to present, at any given j)eriod in its geologic history, that appearance of succession of genera ordained by Creative Power. d. On the Origin of Inexact Parallelism. The hypothesis can only be demonstrated in case of exact par- allelism. If proved in these, it readily accounts for the cases of inexact parallelism, which are of course in any single period vastly in the majority. First take the case of simple inexact parallel- ism. A series of individ uals of the genus Didocus undergo the metamorphosis of the cranial structure earlier and earlier in life, commencing by completing the ossification of the membrane of the fronto-parietal region in full age, until at last it becomes com- 13leted as early as the period of reproduction. Heretofore the adult offspring have appeared during a long period, invariably characterized by the larval cranium ; but like now producing like, this development springs into new power, and the offspring ossify the cranial bones far earlier than their immediate predecessors ; in a word, the genus Pelobates has been created ! At this state of progress Didocus is an undeveloped Pelobates. Let us, however, suppose the '^acceleration " of development of the cranial bones still to progress. The character appears now soon after the ordinary metamorphosis has been passed, and now ON" THE ORIGIN OF GENERA. 93 a little before. The identity of Diclocus with the undeveloped Pelobates is thereupon lost ! So may have been the relations between Pelobates and Cul- tripes. Pelobates was probably once identical with the undevel- oped Cultripes ; but the same acceleration has concentrated the characters more rapidly than the other larval stages, leaving Pelo- bates behind. This I conceive to be the explanation of this relation : when the parallelism is inexact by two steps, as in Spea to Didocus, by the obliterated ear and ossified xiphisternum. The continued concentration of characters has been carried to earlier stages till the identity exists in the adult state of neither one, but at a pe- riod of larval life of botli, shortly preceding the adult period of the lower. The relations between the Amblystomidae and Pletho- dontidaB, which I have elsewhere * pointed out, have probably had their origin in this way. If we attempt to ]3rove the identity of the modern Mammalian foetal circulation with that of the modern adult fish, we may find nearly an exact parallel in this respect, as it is the basis of class distinction ; but in other respects the identity will not exist, ren- dering the parallel inexact or remote. The structure of the ori- gins of the aorta is at one time identical with that of the shark, with one exception : in the former but four aorta-bows appear to- gether ; in the latter five. In the former the first disappears as the fifth comes into being. This is simply a continuation of ac- celeration. The first generalized representative of the Mammalia lost the first aorta-bow toward the latter part of its growth, and became the next genus in advance of the selachian. The fact that these bows do not appear exactly simultaneously, but rather successively, renders it necessary that in a regularly shortening period of possession of transitory characters, one such, as the ex- istence of the first aorta-root, should vanish before the appearance of a permanent, the fifth, in the more specialized types, where acceleration reaches its maximum. This is indicated by the fact that in the Batrachia, where the acceleration has not attained so high a degree, the first and fifth aorta-bows co-exist for some time, though the first and second disappear before maturity. So also with the splitting of the bulbus arteriosus. As in the Batrachia, the pulmonary ductus communis only is to be sepa- * "Jour. Ac. Nat. Sci.," Phil., 1866, p. 100. 94: GENERAL EVOLUTION. rated ; the remaining bulbus is divided by a long valve or incom- plete septum, tracing the division of the aorta-roots. In the ser- pent (Rathke) this division is so accelerated as to appear at nearly the same time as the septum of the pulmonary duct. In the mammal, on the other hand, while the division of the aorta-root takes place as soon as in the last, the pulmonary seiDtum is accel- erated so as to appear long before the first named. Hence, in the septa in the serpent, the singular anomaly seems to present of the mammal passing through the Batrachian stage, while the ser- pent, a nearer relative, does not.* If, however, we take the less typical serpent, we will find the aortic septum to appear a little later, thus giving the Batrachian type, and if we reverse the order of time, so that the succession becomes one of retardations, we wdll find the same known ratio will bring us to an identity under all circumstances. This, then, is the explanation of the divergence and want of ** exact parallelism," which is observed in comparing the develop- mental histories of all tjipes not 7nost closely allied. It has not, according to our theory, always been a divergence, but was at a prior epoch in each case a relation of "exact parallelism," the lower type a rej^ressed higher ; the former identical with one of the stages of the latter. But the process which has produced this relation, continued, has of necessity destroyed it, so that the ex- act parallelism has always been a temporary relation, and one shifting over the face of the system. III. OF HIGHER GROUPS. First. Comparison of the contemporary. Having now admitted a developmental succession of genera, and, second, that this has progressed more rapidly at certain times in the earth's history than any modification of specific forms, the hypothesis already broached naturally comes up : Has such trans- formation of types, generic or higher, tahen place in any degree simultaneously, throughout a great number of species 9 An af- firmative answer to such a proposition is absolutely necessary to its acceptance as expressing the phenomena exhibited by geolog- ical succession of types. Let us try to answer the question put in a closer form. Have the same species been transferred from one * This is the way indeed in which it is stated by Rathke, " Entwickelungsge- schichte der Natter," p. 164. ON THE ORIGm OF GENERA. 95 geologic epoch to another by a change of generic form ; and has not the genus been transferred from one epoch to another under change of ordinal type, and as a consequence the same species ? As a reply I propose to render the affirmative of the first of these questions highly probable. Paleontology only will be able to answer this question conclu- sively, though, as we have abundant evidence that the relations of species to genera and other higher groups were the same then as now, we may look to the present status as furnishing important evidence on the subject. We are turned at once to the probable history of development in the separate zoological areas of the earth's surface. The question may be asked, Are the present zo- ological regions on an equal plane as to the geologic relations of their faunae, or are they related as the different subdivisions of a geologic period in time ? I have on a former occasion asserted that the latter of these propositions was true.* a. Of Homologous Groups. Naturally following the admission of a developmental succes- sion of organic beings is the question of its relation to the differ- ent surfaces of land and water on the earth. The following con- siderations bear on this subject. Among the higher groups of animals can be detected series ^* homologous " on the same principle as the alcohols (? com- pound radicals) and their derivatives ; and the component types of each can be, and have been in many instances, shown to be ''heterologous," as are the ethers, mercaptans, aldehydes, acids, etc. Among Mammalia two partly homologous series have been pointed out, Implacentialia and Placentialia ; possibly such are the types Altrices and Prgecoces among Aves ; of a lesser grade in this class are the parallel series of Pullastrae and Gallinae, of Clamatores and Oscines. Among tortoises I have alluded to the Pleurodira as compared with the remainder of the order, already parallelized by Wagler ; and, of lesser grades, the series among Lacertilia of Acrodonta and Iguania, parallelized by Dumeril and Bibron, and of Teidae and Lacertidae, compared by Wiegmann. I have discovered a full parallelism between the Raniform and Arcif- erous Anura. It is carried out between the Characini and a group of remaining Physostomous Fishes, perhaps not yet well defined ; it ^ On " Arciferous Anura," " Journ. Ac. Nat. Sci.," 1866, p. 108. 96 GENERAL EVOLUTION. is exhibited between tlie orders Diptera and Ilymenoptera among insects. None of these comparisons can be allowed, of course, without the most searching anatomical and embryological analysis. This heterology i^ what Swainson and others called ''^analogy" as distinguished from affinity. It generally relates genera of dif- ferent zoological regions. Mimetic analogy, on the contrary, re- lates genera of the same region ; it is a superficial imitation which has occurred to critical biologists, and is of much interest, though as yet but little investigated. It has as yet been observed in ex- ternal characters only, but occurs in internal also ; it has been accounted for in the first case by the supposed immunity from enemies arising from resemblance to wxll-defeuded types. No such explanation will, however, answer in the latter case. I be- lieve such coincidences express merely the developmental type common to many heterologous series of a given zoological ** re- gion " ; this will be alluded to a few pages later. We naturally inquire. Is there anything in the food, the vege- tation, or the temiDcrature to account for this aj^parent diversity in the different regions ? Are there not carnivora, herbivora, seed-eaters, insectivores, and tree-climbers, where game and grass, seeds and insects and forests grow the world over ? We answer undoubtedly there are, and these adaptations to food and climate are indeed as nothing in the general plan of creation, for every type of every age has performed these functions successively. 3. Of Heterology.^ This relation will be exhibited by a few examples from groups known to the writer, commencing with the Batrachia anura. Raniformes. Arciferi. External metatarsal free. Aquatic. Rana. Pseudis. Metatars. shovel, Hoplobatrachus. Mixophyes. External metatarsal attached. Feet webbed. Metatars. shovel. Pyxicephalus. Tomopterna. * Some of the cases below cited as heteroloiry I believe to be trulv of this char- acter ; but some others are probably not such, but are merely series of genera pre- senting similar structural peculiarities as consequences of the operation of identical laws. I would place under this head, and withdraw from the homologous class, the families of Lacertilia Leptoglossa, Diploglossa^ and Typhlophthalmi^ those of the Old and New "World Quadrumana and those of Cephalopoda. These distinct modes of origin of corresponding forms have been recently termed, by Lancaster, homogeny in the ease of homologous groups, and homoplassy when the imitative types are on distinct lines. (Ed. 1886.) PLATE n. 1 ^ PLATE II a r'^^'^^ "^H^ PLATE II. Figures of Lizards of the family Iguatiidfe to be compared with a homologous series of Agamidae represented in Plate Ila. The species are : Fig. 1. Basiliscus phimifrons Cope, Costa Rica. From Cope. Fig. 2. Iguana tuhercidata Linn., South America. From the " Standard Xatural History." Fig. 3. Crotaphytus wislizeni B. G., Sonoran Region of North America. From Baird. Fig. 4. Phy maiurus pallumaGTSLV., ChWi. From Bell. Fig. 5. Fhrynosoma cornutum Harl., Texas. From " Standard Natural History." PLATE Ila. Figures of Lizards of the family Agamidae which form a homologous series with the Iguanidse represented on Plate 11. Fig. 1. Lophura arnboinetisis Schloss., Amboina. From "Wagler. Fig. 2. Physignathus mentager Giinther, Siam. From Giinther. Fig. 3. Liolepis hellii Gray, China. From Dumeril and Bibron. Fig. 4. Uromasiix spinipes Cuv., Arabia. From Guerin. Fig. 5. Moloch horridus Gray, Austi-alia. From " Standard Natural History." ON THE OKIGIN^ OF GENERA. 97 Raniformes. Arciferi. Arboreal ; vom. teeth. Subarboreal. Leptopelis. Hyperolius. Hylambates, Hvla. Hylella. Nototrema. Terrestrial. " spurred, Feet not webbed. Cassina. Hemimantis. Cystignathus. Gomphobates. Comparmg the genera in a general physiological sense, we may parallelize further. Aquatic, with digital dilatations. Heteroglossa, Arboreal : cranium hy- ) -r, , , ^ perostosed. \ ^oljved^tes. " cranium free. Rhacophorus. Acris. Trachycephalus. j Hyla. ( Agalychnis. The same kind of parallels exists between the primary groups of the Testudinata, as follows : Crtptodira. Plefrodira. Five complete pairs of bones across the plastron. Pleurosternidae. Stemothseridae. Four pairs of bones across plastron ; not more than two phalanges on all toes. Testudinidae. Pelomedusidae. Three phalanges on most digits ; Zygomatic arch ; no parieto-mastoid. Eraydidae. Podocneraididae, Temporal fossa over-roofed hj parietal. Macrochelys. Podocnemis. No zygoma ; a parieto-mastoid arch. Hydraspididae. * * * If we compare the peculiarities of generic structure merely with reference to their adaptation to the animals' habits, we will see the following : Cryptodira. Feet reduced for terrestrial progress. Testudinidae. Feet normal. Anterior lobe of sternum movable. Cistudo. Cinosternum. Anterior lobe fixed. Neck very elongate. Trionychidae. Neck shorter ; aquatic. Temporal fossa open. Emydidae in gen. Temporal fossa over-roofed. Cheloniidae. Pleurodira. Pelomedusidae. Sternothaerus. Chelodina. Hydraspididae. Podocnemis. The parallels between the genera of the American Iguanidae and the Old World Agamidae are similarly quite close. They are shown on Plates II and II a. 1 98 GENERAL EVOLUTION. Abdominal ribs. Iguanidje. Polvchrus. AGAMIDiE. No abdominal ribs. llibs greatly prolonged into a lateral wing. * * Draco. Ribs not prolonged. Arboreal types, generally compressed. A dorsal and caudal fin supported by bony rays. Basiliscus (no lem. pores). Lophura (pores). No vertebral fin. No femora] pores. Form slender, scales in Calotes. equal series. Bronchocc Form elongate ; eyebrows Gonyocephalus. cela. ) Lasmanctus. elevated, tail compressed. Form stouter, scales less regular. Hypsibates. Femoral pores. Brachylophus. Ophryoessa. Tiaris. Diporophora. Pliysignathus. * * Low crested; small hyoid disk. High crested; large hyoid disk. Iguana. Tail with spinous whorls. Cyelura. Terrestrial types of flattened form. Femoral pores. Tail with whorls of spiny scales. Hoplocercus. Uromastix. Tail long, simple; scales small. Crotaphytus. Liolepis. Tail simple, scales large. Sceloporus. * * No femoral pores ; preanal pores. Tail with whorls of spines. * * Stellio. Tail simple, not elongate, ear open. Proctotretus. Agama. Neither femoral nor anal pores. Much flattened, tail short, scales irregular. Ear exposed. Phrynosoma. Moloch. Ear concealed. (Doliosaurus, s. g.) j Segd'Sus!'"'' A similar parallel may be drawn between the American Teidas, and the Old World Lacertidae, and in fact between all the families of the Lacertilia Leptoglossa. I have added to these for compari- son two families of the Typhlophthalmi. Each family embraces one or more series, and these exhibit a remarkable similarity in the relative development of the limbs and digits ; among the higher groups the parallelisms lie in the arrangement — as greater or less separation — of the head shields. The Scincidae are cosmopo- lite ; the Gymnophthalmidae, which have the eyelids of their foe- tus, are Australian ; the Sepsidas, either larval or senile in head shields, are mostly Ethiopian. ON THE ORIGIN" OF GENERA. 99 ^ a. §i ■ 'til 03 .2 03 a ■i— « Ilerpetosaura. Acontias. Typhlosaurus. P'eylinia. Anelytropsia. S3 <1 1 CO at to . 03 « 00 XI 02 <: 03 B . .■73 1 — 1 1 > ■3 g « 5 ! > \ > •5 ^-^ • A > ( 03 a 5 P. B ! OD o a 100 GENERAL EVOLUTION. The first comparison of these groups was made by Wiegmann (Herpetologia Mexicana), who employed, however, only the Scin- cidse and Lacertidae, and could not include the many types made known since his day. From the class Aves I have selected only the homologous series of the Clanatorial and Oscine Passeres. Naturalists more fully acquainted with the genera could probably increase the examples of heterology largely. Each group furnishes us with carnivo- rous, insectivorous, and frugivorous forms ; each with walkers, climbers, and sedentary genera ; each with butcher-birds, thrushes, warblers (not in song !), wrens, and fly-catchers. Each and all of these types are teleologically necessary to any country complete in the wealth of nature, and to each geological period. Clamatores. Oscines. I. Tree-climbers, with long hind toe and tail feathers stiffened and acute. Dendrocolaptidce. Certliiidce. II. Terrestrial in part, with the tertials as long as the primary quills. Geobatidce. ITotacillidce. III. Tree-perchcrs with hooked bill, graduating from powerful to medium and slender. JPbrmicariidce Turdidce. Thamnophilus. Bill strongest, hooked. Lnnius. Formicarius. " moderate. Turdus. Formicivora. " weak. iSylvia. Rhamphoccemus. " slender (wrens). Troglodytes. IV. Fly-catchers with flat bill and weak legs ; wait for their prey and take it on the wing. Tyrannidve. Muscicapa et aff. V. Flat-billed berry and fruit eaters. Cotingidce. Bomhycillidce. From the Mammalia the well-known series of the Marsupialia and Placentialia may be chosen. Placentialia. Marsupialia. I. Toes unguiculate, in normal number ; sectorial teeth ; i. e., one or more molars with one or no internal tubercles ; canines strong : Carnivora. Sarcophaga. I. Digitigrade. Toes 5 — 1. True molars § (upper incisors more numerous in some). Amphicyon. Thylacinus. II. Plantigrade ; molars tubercular. a. Posterior molars f . * * Dasyuridae. aa. Posterior molars |. Ursidffi. * * II, Toes unguiculate ; molars with more than one row of pointed tubercles ; canines weak or none ; incisors large. ON TEE ORIGIN OF GEKERA. 101 Insedivora. Gymnura. Cladobates. a. Tubercular molars |, toes 4 — 5. Tail naked. Tail hairy. Entomophaga. Didelpbys. Myoietis rV. Molars with transverse crests, no canines ; tusk-like incisors ; pairs of limbs of similar proportions. Froboscidia. Diprotodontidfe. Two inferior incisors ; molars with two cross-crests ; size huge. a. Two rudimental lateral incisors above. * * Diprotodon. aa. ? One pair of incisors only above ; a trunk. Dinotherium. Y. No canines ; two pairs of cutting incisors. «. Three true molars. Rodentia. * * aa. Four true molars. * * Rkizophaga. The parallels are in this case very imperfect in details, and but few worthy of the name can be made. They are, however, illus- trative of a remote heterology, sufficiently remarkable to have claimed the notice of naturalists for many years. "^ I also have little doubt but that future paleontological discoveries will in- crease the number of parallels, f and bring to light truly heterolo- gous generic terms of the Marsupial series. Predictions of this kind have been on many occasions fulfilled (e. g., some of D'Or- bigny's among the Cephalopoda), and I look with confidence to the ultimate demonstration of that heterology here which has been already seen in the Batrachia and Reptilia. The homologous groups of the Catarrhine and Platyrrhine Quadrumana are measured as follows : CatarrJiini. Platyrrhini. Tailless. Andropithecus. * Simla. * Hylobates. * Tail short. Cynocephalus. * Macacus. Brachyurus. Long tail. Thumb developed. Cercopithecus. Lagothrix. Mycetes. Thumb rudimental. Semnopithecus. Brachyteles. Thumb none. Colobus. Ateles. * We owe very many observations on the Marsupials to Owen. f The extinct carnivorous family of the Nimravidae which forms a homologous series with the cats (Felidae) was discovered by the writer some years after this was written. (Ed. 1886.) 102 GENERAL EVOLUTION". I append two homologous series, represented by the Nautilea and the Ammonites of the Tetrabranchiate Cephalopoda, which are distinguished, the first by the simple septa and the siphon central or marginal ventral ; and the second by the complex and folded septa and siphon central or marginal dorsal. The parallel- isms have been noted by Barrande, Bronn, and many concholo- gisfcs, who can furnish a much more full table than the following, from the most recent sources : Nautili. Ammonites. A. The shell straight, unwound. Orthoceras. Baculites. B. The shell more or less curved or wound, c. Simply curved. Cyrtoceras, ) Toxoceras. Phragmoceras, ) aa. A more or less straight portion, folded on the remainder. j3. Folded poition in close contact with remainder. Ascoceras. Ptychoceras. /3/3. Folded portions not in contact. V ? Hamites. aaa. One extremity spirally wound, the volutions not in contact. /?. Extremity of the shell prolonged beyond the wound portion. Lituites. Ancyloceras. )8/3. Extremity not prolonged in a line. 7 The spiral flat. Gyroceras. Crioceras. yy. The spiral elevated (heliciform), Trochoeerus. Turrilites. aaaa. Spiral turns of the shell in contact. p. Er.tremity prolonged in line beyond the spiral. * * Scaphites. )S/3. Extremity not prolonged beyond spiral. Nautilus. Amrhonites. We may now consider the question of the origin of these higher groups. In the first place, we must lay down the proposition that the characters which constitute groups '' higher ''^ iii the compari- son of ranh (we do not of course mean higher in the same line, as we say higher genus in a family, or higher order in a class) are such solely from their bei7ig more comprehensivs, or i^esent throughout a greater range of species. What is true, therefore, in respect to characters of genera, is likely to be true in respect to characters of higher groups, such as we have been considering in the preceding pages. Believing, then, that a new genus has been established by the transition of a number of species of a preceding genus in-order, without neces- sary loss of specific characters, I think the same process may have established the suborders and orders in question. That is, that a large numiber of genera have near the same time, in past or pres- 01^ THE ORIGIN- OF GENERA. 103 cnt geological Idstory, passed into another suborder or order hii the assumption or loss of the character or characters of that to or from luhich they ivere transferred, and that without necessary loss of their generic characters. I will cite a probable case of this kind, the facts of which I have already adduced. It has been shown above that the genera of six of the fami- lies of the Batrachia anura form series characterized by the suc- cessive stages of ossification of the skull, terminating in a der- moossified condition, with over-roofed temporal fossae. That in nearly all the other families similar relations between genera exist, but are nowhere carried so far. The character attained by all the first series is now only generic ; but should all the genera of each of the six families assume this character in time, as is neces- sary in accordance with a development hypothesis, it would at once possess a new and higher importance, and would become or- dinal or otherwise superior. It would define a series homologous with all those types which had not attained it. This character of the over-roofing of the temporal fossae has actually attained a family significance among the Testudinata — e. g., as defining the marine turtles ; and similar characters are found by Owen to characterize the Labyrinthodontian order of Batrachia.* Agassiz has pointed out a similar and more extended case, in the lieterocercal and Homocercal ganoids. Had we not so many of the closest approximations between members of these groups, they would stand in the systems as two great homologous series, with their contained heterologous genera. As it is, these heter- ologous terms or genera are evidently so nearly allied that Agassiz, in the " Poissons Fossiles," has thought it best to arrange the latter together, thus instituting a system transverse, as it were, to the other. This may be necessary, since Kolliker points out transi- tional forms, and perhaps certain types may have begun to aban- don the heterocercal form near the period of reproduction, pro- ducing offspring somewhat protean in character, preparatory to an earlier appearance and consequent permanence of the homocer- cal type. This is to be derived from the history of the metamor- phosis of Amblystoma. In the same manner the development of the convolutions of the brain does not define groups of the highest rank, since it pro- * The roof here alluded to by Owen includes some two distinct bones not known in the arch of the Anura, and therefore different. 104 GENERAL EVOLUTION. gresses chiefly during the later periods of embryonic life, and is therefore a '^developmental character." Owen has endeavored to distinguish the primary divisions of Mammalia by the character of these convolutions, whereas they really define only the sub- groups of the orders. Eor we have Lissencej^halous (smooth- brained) monkeys — certain lemurs — and smooth-brained Eumi- nants — i. e., the extinct Brachyodon and Anoplotherium, accord- ing to Lartet and Gratiolet. The lowest types of the existing smooth-brained Mammalia, including es^^ecially those wdth no or rudimental corpus callosum, the Marsupials, are also distin- guished by the non-development of the deciduous teeth * (except- ing one premolar). If now, through some topographical change, the whole series of Mammalia between the smooth-brained and convolute-brained were lost to us, as by the elevation of a region, and the absence of favorable localities or bodies of water for the preservation of their remains, we would have to study two homol- ogous groups, with the heterologous terms of each corresponding with each other, as do now the genera of the Clamatores and Os- cines of the Arcifera and Eaniformia, etc. In the same way the characters defining Iraplacental Mam- malia will be found transitional in some type, and this great se- ries, homologous with the Placentals, will have to be placed in closer connection, in its genera, with the series of the latter, with genera of the same, perhaps, now extinct. y. Of Mimetic Analogy, It has been often remarked that the animals of the Equatorial Ethiopian region were very generally of smoky and black colors. This is remarkably the case, and the peculiarity of the genus Homo in this respect is shared by birds, reptiles, and fishes in a consider- able degree. This can not be traced to the effect of torrid climate, for the same latitudes in India and the Malaysian Archipelago, and in South America, do not produce such colors. The similarity in color of desert types has also been remarked. The gray sand-hue so well adapted for concealment is universal, with few variations, in the reptiles of the Tartar and Arabian * This I have alluded to as the non-development of the permanent series ; the homology of the dental system of Marsupials appears, however, to be with the latter and not with the milk series. See "Flower," "Trans. Roy. Soc," 1867. (Wortman now denies the correctness of Flower's view, and demonstrates that the milk series is primitive. See "Encyclopaedia of Dentistry," 1886. Ed. 1886.) Plate ni T. Sinclair. & Son, Phila MIMETIC ANALjOGY. Plate IIIc; T. Siriclait-. & Son.Fhiia MIMETIC ANALOGY. PLATE III. Fig. 1. Flaps dumerili Jan; New Gra- nada. Fig. 2. Elaps Icmniscatus L. ; Brazil. Fig. 8. Flaps semipartitus D. and B ; New Granada. Fig. 4. Flaps psyche Daud. ; Brazil. Fig. 5. Flaps corallinu^ Linn. ; Brazil, Central America. Fig. 6. Ophibohis doliatus Linn. ; South- ern United States to Central America. I PLATE III«. Fig. 1. Pliocercus elapoidcs Co\)Q ', Mex- ico. Fig. 2. Oxyrrliopus trigeminus Tt. and B.; Brazil. Fig. 3. PUocercus etiryzomcs Cope ; New Granada. Fig. 4. Frythrolamprus cscidapil L. ; Brazil. Fig. 5. Cemophora cocci7ica Blum. ; Southern United States. Fig. 6. Frythrolamprus vcnustissimus Neuw. ; Brazil, Ccntr'l America. The species placed opposite to each other present similar patterns of coloration. Figs. 3 and 4, Plate III, correspond with Fig. 3, Plate III«, and Fig. 6, Plate III, with Figs. 5 and 6, Plate Ilia. The species inhabit the same regions, more or less exactly, excepting the two Figs. 1. The Elapjs dumerili would have been better re- placed by a variety of the Elaps fidvlus of Mexico, which has the red spaces black bordered ; but a good colored plate was not accessible at the time the drawing was made. All the figures are copied from Jan's " Iconographie Generale des Ophi- diens " ; and the colors of such as I have not at hand for reference ( Ekqjs dumerili, Flaps semipartitus, and Flaps psyche) are derived from the " Erpetologie Generale," and from Jan's "Prodrome." The species of Elaps are poisonous; the others are harmless. ON THE ORIGIN OF GENERA. 105 deserts, the great Sahara and the sands of Arizona and California. There is also a tendency to produce spiny forms in such places • witness the Stellios and Uromastix and Cerastes of the Sahara, the Phrynosomas and horned rattlesnake of Southwestern Amer- ica. The vegetation of every order, we are also informed, is in these situations extremely liable to produce spines and thorns. The serpents of the Neotropical region furnisli remarkable illustrations of mimetic analogy. All the species of the genera Elaps, Pliocercus, Erythrolamprus, and many of those of Oxyr- rhopus, Ophibolus and Rhabdosoma are ornamented with black and yellow rings on a crimson ground. The species of all these genera are harmless, except in the case of Elaps, which is venom- ous. We may give for this genus, as the most varied, the follow- ing range of variation in coloration : Pairs of black rings ; Single black rings^far apart. Single black rings, very close. Oplieomorplius mimus. d Erythrolamprus venustissi- Elaps corrallinus. b nigrocinctus. c Pliocercus equalis. c Oxyrrhopus ? Erythrolamprus albostola- Elaps mipartitus, d Pliocercus euryzonus. d Oxyrrhopus petolarius. d Scolecophis zonatus. a mus. a tus. b Ophibolus polyzonus. a Xenodon bicinctus. b Leptognathus anthracops. a Single black rings loith faint laterals. Black rings in threes. Sifigle black rings about equal to intervals. Elaps fulvius. elegans. a Elaps lemniscatus. b Elaps. Pliocercus dimidiatus. a Pliocercus elapoides. a Procinura semula. a Oxyrrhopus trigeminus, b Pliocercus elapoides var. a Catostoma semidoliatum. a Oxyrrhopus sebae. d Ophibolus pyrrhomelas. h Chionactis occipitale. h Sonora semiannulata. h Contia isozona. h Chilomeniscus epliippicus. h Species a, from Mexico and Central America. (Two species are now added, 1886.) " b, " Brazil, Venezuela. " c, " Central America. " d, " western side of Andes. " h, " Arizona and Sonora. Many of the species in the same column are exceedingly simi- lar, and some have little (perhaps nothing) to distinguish them but generic characters. The most similar are almost always from the same sub-region.* These facts are illustrated in Plates III and III a. * Similar parallels exist between the Mexican species of Rhadinsea, Conophis, and Erythrolamprus ( = Coniophanes). (Note, 1886.) 106 GENERAL EVOLUTION. Similar analogies have been pointed out by Bates among the Lepidop'tera of Brazil, and by Wallace among those of Borneo and Celebes, etc. I call attention to these authors here without copying them, as they will repay perusal in the originals. A case of analogy which may belong to this class is that of the three genera Chelys among tortoises, Pipa among frogs, and As- predo among Siluroid fishes, species of which inhabit at the same time the rivers of Guiana. The crania of these genera are simi- larly excessively flattened and furnished with dermal aj^pendages, and their eyes are very minute. The singular similarity need only be mentioned to those familiar with these genera, to be recognized. The bearing of the mimetic analogy, on the question of transi- tion of types in the developmental hypothesis, is its demonstra- tion of the independence of generic and specific characters of each other, which may suggest the possibility of the former being modified without affecting the latter. These facts might have been introduced under Section II a, but they illustrate the general laws of the present section. IV. OF KATUKAL SELECTIO^h". a. As affecting Class and Ordinal Characters. The second law which may be supposed to have governed a descent with modification, in the production of existing genera, is the force which the environment exercises in permitting or for- bidding the existence or persistence of new forms. The forms which survive are supposed to have done so by virtue of their su- perior adaptation to their environment. This is the '' natural selection " of Darwin. That this law is subordinate to the one first propounded must, I think, be evident to any one who studies the assumed results of the workings of both, as seen in the characters of genera. It is sufficiently well known that the essential features of a majority of genera are not adaptive in their natures, and that those of many others are so slightly so, as to offer little ground for the supposi- tion that this necessity has preserved them. Both laws must be subordinate to that unknown force which determines the direction of the great series. If a series of sup- pressions of the nervous and circulatory systems of beings of com- mon birth produced the "synthetic " predecessors of the classes of Vertebrata, the direction toward which the highest advanced, ON THE ORIGIN OF GENERA. 107 or its ultimate type, can be only ascribed as yet to the divine fiat. So far as we can see, there is no reason or law to produce a prefer- ence for this direction above any other direction. If from these fixed bases descendants have attained to succes- sive stations on the same line of progress, in subordinate features of the nervous and circulatory systems, constituting the *^ syn- thetic " predecessors of the orders in each class, the type finally reached seems to rest on no other basis than the pleasure of the Almighty. (i. As affecting Family Characters. If from the single species generalizing a modern order we at- tempt to deduce synthetic predecessors of existing families, we find some difficulty, if we attempt to see in these stages a uniform succession of progress. A suppression of some features, and ad- vance in others, in one and the same individual up to the period of reproduction, would produce offspring divergent from the start, and represent the relationship of families as we find them. y. As affecting Generic Characters. If the extremes of our series of genera were characterized by structures particularly adapting them above all others to some contemporary necessity of existence, this second law, or Darwin's, might be regarded as primary. But the writer's experience of comparative anatomy has led him to believe that this is not the case, as expressed in Proposition IV, page 91. This view had not been overlooked by Darwin, who, however, treats of it very briefly, and appears to attach it to the theory of adaptations, or modifications for a physiological purpose. He says, ^^ Origin of Species," page 388 (Amer. edit., 1860) : "We may extend this view to whole families, or even classes. The fore-limbs, which served as legs in the parent species, may become, by a long course of modification, adapted in one descendant to act as hands, in another as paddles, in another as wings ; and on the above two principles— namely, of each successive modification supervening at a rather later age, and being inherited at a corre- spondingly late age— the fore-limbs in the embryos of the several descendants of the parent species will still resemble each other closely, for they will not have been modified. But in each indi- vidual new species the embryonic fore-limbs will differ greatly from the fore-limbs in the mature animal ; the limbs in the latter have undergone much modification at a rather late period of life, 108 GEi^ERAL EYOLUTION. and having thus been converted into hands, paddles, or wings." He then inclines to assign this change to the necessity of external circumstance. But such modification must be the same in kind as others, which the same hypothesis must explain, and of which the same author remarks (page 882) : '' We can not, for instance, suppose that in the embryos of the Vertebrata the peculiar loop- like course of the arteries near the branchial slits are related to similar conditions in the young mammal, which is nourished in the womb of its mother, in the egg of the bird which is hatched in a nest, and in the spawn of a frog under water. We have no more reason to believe in such a relation than we have to believe that the same bones in the hand of a man, wing of a bat, and fin of a porpoise, are related to similar conditions of life. 'No one will suppose that the stripes on the whelp of the lion, or the spots on the young blackbird, are of any use to these animals, or related to the conditions to which they are exposed." The law of natural selection, however, has no doubt been a very important agency in the production of organic types in dif- ferent periods of the world's history ; but the part it has played in the determination of generic features would appear to have been very small. In its first effect — that of producing a structure adapted for a particular purpose — it would seem to have acted differently to produce the same results, and hence not to have produced any of the more extended groups, as families, where hundreds of species are identical in a single feature. Witness the differences in di- verse types of the tree-frogs, each type adapting its possessor to an aboreal life : I. Claw-like, with globular base Hylid^. Leptopelis. II. Simple, obtuse-depressed at tip Ranid^. I aa and III a. III. With a terminal transverse limb Ranid^, Hylarana et aff. Callula. Brachymerus. Hi/lodes. IV. Bifurcate Bcitrachyla. Dendrohates. Polypedates. RhacopJioms. The short foot of the Testudinid?e, where one row of pha- langes is omitted, has been already alluded to. The gradual re- duction of this set of bones, accompanying general modification of form in the increased convexity of dorsal region, as Ave leave the more aquatic and progress toward the terrestrial tortoises, would ON THE ORIGIN OF GENERA. 109 seem to be intimately connected with difference of habit. The increased convexity of carapace is an increased defense from fall- ing objects — a danger to which land tortoises are far more subject than the aquatic. Another protection, not needed by water tor- toises so much as by terrestrial, is the faculty of closing one or both free lobes of the plastron, as seen in the Cistudo, Sternothse- rus, etc., or of portions of the carapace, as in Pixys, Cinixys, etc. This might really have been produced by excessive tension on the sternal and pelvic muscles while young, and while the sutures were not fully interlocked. This, continued for a long time, might have produced the result. Yet it is not easy to see what protection the aquatic Kinosterna need in this respect, above the Emydes of the same countries. The backs of these genera are also as convex as are many of the terrestrial genera or Testu- dinidse. I can not better express my views than by quoting the follow- ing from the pen of the late Dr. Falconer. It is extracted from one of his essays on the Elephantidae : * '^ Each instance, however different from another, can be shown to be a term of some series of continued fractions. When this is coupled with the geometrical law governing the evolution of form, so manifest in shells of the Mollusca, it is difficult to believe that there is not in nature a deeper-seated and innate princij^le, to the operation of which natural selection is merely an adjunct. ** The whole range of the Mammalia, fossil and recent, can not furnish a species which has had a wider geograjDhical distri- bution, and at the same time passed through a longer term of time, and through more extreme changes of climatal conditions than the mammoth. *'If species are so unstable and so susceptible of mutation through such influences, why does that extinct form stand out so signally a monument of stability ? By his admirable researches and earnest writings, Darwin has, beyond all his contemporaries, given an impulse to the philosophical investigation of the most backward and obscure branch of the biological sciences of the day ; he has laid the foundation of a great edifice ; but he need not be surprised if, in the progress of erection, the superstructure is altered by his successors, like the Duomo of Milan, from the Roman to a different style of architecture. * See writings of Hugh Falconer, vol. ii (ed. by Murchison). 110 GENERAL EVOLUTION. '' The inferences which I draw from these facts are not op- posed to one of the leading propositions of Darwin's theory. *^ With him I have no faith in the opinion that the mammoth and other extinct elephants made their appearance suddenly, after the type in which their fossil remains are pre:ented to us. The most rational view seems to be, that they are in some shape the modified descendants of earlier progenitors. Eut if the as- serted facts be correct, they seem clearly to indicate that the older elephants of Europe, such as U. meridionalis and E. antiqmis, were not the stocks from which the later species, E. primigenius and E. africanus sprung, and that we must look elsewhere for their origin. The nearest affinity, and that a very close one, of the European E. mericlio7ialis, is with the Miocene E. (Loxod.) planifrons of India, and of E. primige?iius with the existing In- dian species. *^ Another reflection is equally strong in my mind, that the [theories of the origin of] species by ^ natural selection,' or a pro- cess of variation from external influences, are inadequate to ac- count for the phenomena. The law of Phyllotaxis, which gov- erns the evolution of leaves around the axis of a plant, is nearly as constant in its manifestation as any of the physical laws con- nected with the material world." 6. Js affectiiig Specific Characters. As I have hitherto attempted to prove that the higher grade of groups, or, in other words, the higher grade of characters, could not have had their origin through natural selection alone, though admitting it as a conserving or restricting principle, I now come to ground where natural selection must be allowed full sway. The " origin of species " is not the object of this essay, as a greater has gone before me, and has done a great deal toward showing that a selective power, deiDcndent on adaptation and tele- ological relation, has favored or repressed, or even called into ex- istence, the varied peculiarities that characterize species and races. I will therefore only refer to his well-known works on the ^^ Origin of Species " and the ^' Modifications of Animals under Domestica- tion." I may add that it is within the range of possibility that that grade or kind of characters found to define i\iQ family group may be more or less the result of natural selection. Acceleration and retardation are also far from excluded from ON THE ORIGIN OF GENERA. m the probable causes of specific characters. The species of many genera do exhibit a proportion of characters which are the succes- sive stages of that one which progresses farthest, as the species of Amblystoma in the position of their teeth, nostrils, form of tail, and coloration ; of Hyla in form of vomerine teeth, etc. But the majority of specific characters are of divergent origin — are 'Amor- phic " as distinguished from developmental. e. On Metaphysical Species. One of the arguments employed against the developmental hypothesis, in any form, is that that inherent "potentiality," which causes that like shall always produce like, is a metaphysi- cal being, which can not be transformed, and which holds the structure which it vivifies as a material expression or stamp of it- self, and which therefore can not be changed. One expression of this inherent metaj^hysical specific individu- ality, if the term may be allowed, has been said to be the peculiar traits of the intelligence of species, their motions, voices, and in- stincts. But intelligence of all animals is susceptible of impres- sions, the lower the intelligence the less susceptible, and the more automatic. But, as we rise in the scale of animal being, this im- pressibility and capacity for education is undeniably exhibited by the dog, horse, and all the well-known domesticated companions of man. There can, in view of the capacities of Aves and Mam- malia in these respects, be little doubt that all animals are edu- cated by the *' logic of events," that their intelligence, impressed by changed circumstances, can accommodate itself more or less to them, and that there is nothing in this part of their being opposed to the principle of "descent with modification." There is another difficulty in the way of accepting metaphys- ical peculiarity or progenitiveness as isolating species. It is marked often strongly in races or varieties, which no one pre- tends to have had distinct origin. Here like produces like con- tinually, though not persistently, but sufficiently to show that it resides in varieties of common origin. The isolation of allied species in fact depends, I believe, solely on the supremacy of the automatic over the intelligent spirit. When the intelligent rises above the bounds of nature, or the automatic, the mixture or separation of allied species depends merely on circumstances of necessity, determined by that intelligence. But the metaphysical '' potentiality " loses all basis, if the law 112 GENERAL EVOLUTION. of acceleration and retardation be true, for in accordance with it, at certain times, like does not produce like, V. OF EPOCHAL EELATIOI^S, OR THOSE MEASURI2^G GEOLOGIC TIME. If it can be shown that groups haying the develo2)mental rela- tion above insisted on are contemporaries, and if it can be shown that this relation is identical in kind with that which we regard as measuring the successions of geologic time, we will be led to doubt the existence of any very great interruptions in the course of this succession throughout geologic time. And if we can show that faunae so related are more or less characteristic of distinct por- tions of the earth's surface, at the present time, we will be led to antici23ate that contemporaneous faunge in different regions, during geologic periods also, bore such a relation. If this proposition be true, we are led to the further conclusion, which is at variance with received canons, that identity of faunae proves successional relation in time, instead of synchronism.* That this will ulti- mately be demonstrated appears highly probable to the writer, though, as yet, the evidence is but fragmentary. If the relations expressed under the terms homology and het- erology, taken together with the observations on metamorphosis, render it j^robable that a number of genera have reached their ex- pression-points, or periods of metamorphosis, at near the same time in geologic history, an important point has been gained. If we can render it probable that a change in any organic charac- ter has been nearly simultaneous throughout a large extent of specific forms, the change becomes, on the latter account alone, of higher than generic value, but characteristic of such groups as Marsupialia, Clamatores, Acrodonta, Arcifera, Heterocerca, and the like. We have here, also, an important element in the estimation of the value of apj^arent interruptions in the geological history of the life of the globe. These interruptions, it is true, are greater than any such theory as the present can bridge over ; yet such a theory, if true, lessens their importance. They are in any case well accounted for on the theory of the existence of periods of elevation, during which the life of a given region is necessarily almost entirely lost to us, through lack of means of preservation of their remains. * This, view has been insisted on by Huxley. ON" THE ORIGIN OF GENERA. 113 We may also compare such extended metamorphoses with those of cosmical matter, such as when, in the course of ages, a primeval vapor has in a short time collapsed to the liquid form, or as when the vast of liquid in turn has shrunk to its solid con- dition ; both alike for ages approaching their change, yet sta- tionary in external relations till the moment of transition has arrived. The following are the zoological relations of the groups al- ready referred to : The most generalized group of fishes of the Regio Neotropica is that of Characins. Its type, in respect to fin-structure, which is common to all the Malacopterygians, is that of an undeveloped stage of the Acanthopterygians, the adipose fin being an undevel- oped cartilaginous fin, and the cartilaginous fin an undeveloped spinous fin.* It may be said to be the highest among Malacop- terygians, if we look to the conq^lete oviducts, opercula, jaws, etc.,t but it is the lowest as removed farthest from the extreme of Malacopterygian peculiarities, as being most generalized or em- bracing representatives of all the rest, and approaching nearest the types of the past — the Ganoids. Tor example, Butyrinus and Vastres may be compared with Amia. The family is distributed chiefly in the Southern Hemisphere. The genus Orestias, which Agassiz says is characterized by a feature which exists in the immature state of all other Oyprino- donts — the absence of ventral fins — is only found in the Neotrop- ical region. Of the yenomous serpents, the inferior group, the Proterogly- pha, belong to the Southern Hemisphere, and the Australian and Neotropical regions almost exclusively embrace by far the greater proportion. Australia contains none other. The Iguanian lizards are lower than the Acrodont, exhibiting a larval type of detention, and one characteristic of all lower Sau- ria and Batrachia. The only acrodont type of Ophiosaura (Trog- onophis) is Old World. The New World Teidas have not the extent of ossified tem- poral roof that their representatives, the Old World Lacertidae, have. So the chiefly Neotropical Anguidae haye the tongue part- * Kner, " Ueber den Bau der Flosscn." \ This is the correct view, for this family and the Siluroids are the most special- ized of the Malacopterygian fishes. (1886.) 8 114 GENERxiL EVOLUTIOK ly of papillose type of tlieir Old World representatives, the Zonu- ridae, and partly the smooth or scaly type of the cosmopolite Scin- cidse, which are inferior to them. The snake-like forms of the families of the Lacertilia Lepto- glossa greatly predominate in the Southern Hemisphere ; also those with undeveloped palj^ebrae. The Neotropical type of Testudinata is quite coincident with the family Characinidae in relations. It is, like it, largely dis- tributed over the Southern Hemisphere, and like it may be re- garded, in respect to its pelvic peculiarities, as higher than the remaining types, but in its generalized character and relationship to the past periods may be called lower. The Neotropical type of Batrachia anura, that is, the Arcifera, is lower in developmental characters than the opposed series, the Eaniformia ; such of the latter as are found in its limits partake in some way of larval incomjileteness. The Arcifera are chiefly distributed elsewhere in Australia, where no Eaniformia exist.* Those genera of Old World Eaniformia of the lowest or toothless group, which display the least development of the cranial bones, as Brachymerus and Breviceps, are of the Southern Hemisphere — South African. The Pullastrine birds are a generalized group, inferior to the group opposed to them — the Gallinae. Their typical forms, like the last, are distributed to the Neotropical and Australian regions : the outliers (pigeons) are not so numerously distributed in the other regions. The Struthious birds, the most synthetic of the class, belong exclusively to the Southern Hemisphere ; as is well known, they chiefly abound in Australia and its adjacent islands, with an abun- dant outlying type — the Tinamus — in South America. The penguins, which only of all birds display the metatarsus nearly divided, inhabit the Antarctic regions and Cape Horn. * The Eucnemis bicolor, Gray, would appear to be an exception, were its generic and subordinate affinities truly represented by its name. I have examined the type specimen through the kindness of Dr. Giinther, and can state that it is not an Ixa- lus {= Eucnemis), and does not even belong to the Eaniformia, but is an Arcifer of the family HyUdae. If it be not a young Calamita or Hyla, it will be a Hylella near the K carnea type. (Boulenger, in 1882, determined it to be a Hylella. Ed. 1886.) Giinther states that Hylorana erpthraea has been found at the extreme northern point — Cape York — of Australia. If so, the case is parallel to the occurrences of the Raniform Ranula in northern South America. ON THE ORIGIN OF GENERA. II5 The Clamatorial type of the Passeres exhibit larval characters in the non-development of the singing apparatus, and the scaled or nearly naked tarso-metatarsus. These are chiefly South Amer- ican. Of Mammalia, the placentals without enamel on their teeth, which, in this respect, never reach the full development of the class, whose dentition is also monophyodont, i. e., the Edentata, inhabit only the Southern Hemisphere, and almost altogether the Neotropical region. The implacental Mammalia, also (except in one tooth) monophyodont, which approach birds and reptiles in so many respects, are confined to the Southern Hemisphere, and chiefly, as all know, to Australia. Of the Quadrumana, the Platyrrhine group is known to be in- ferior to the Catarrhines : the former presents an entirely embry- onic condition of the os tympa7iicum, which is passed by the latter in early age ; * it contains also the only clawed genus of the true monkeys. It is confined to the Neotropical realm. To Madagascar, also of the Southern Hemisphere, and nearest in many ways to the Neotropical, pertain the lowest families of the Quadrumana, the Lemuridae and Chiromyidas ; the former presenting brains without convolutions, and approaching in many ways the Insec- tivora ; the last imitating, at least, a Eodent. There are also other reasons for the inferiority of South Amer- ica. Its deer, which are few, include those which never produce more than the ^^dague," or the first horn of the northern Cervus, and also those which never get beyond the fourth step in the de- velopment of the lower group of R. Nearctica. The Loricariidae, of South America, I am informed by Prof. Agassiz, possess the foetal pupil of the vertebrate type. If we glance at Coleoptera we find the great predominance of the groups with undeveloped tarsus, the three- and four-jointed Trimera and Tetramera, and of the lower group with undeveloped sternum, f the Rynchophora, in the Neotropical region. Among Lepidoptera it is known that the most gigantic of the species of the Neotropical region are Noctuidae (Erebus, etc. ), and that in that region this low type of the order reaches its greatest development. The largest forms of the Regio Nearctica, as well as Pal^arctica, are representatives of the higher type of the Satur- * See Dr. H. Allen, "Proceed. A. N. S.," Phila., 186Y. \ Leconte, American Association, 1867. 116 GENERAL EVOLUTION. niidse (Atticus, Telea, etc.), while the largest and most powerful of this order in the Palaeo tropical (Indian) region are the Papilio- nid forms of Ornithoptera, etc., the generally admitted crown and head of all. Of course other types, both higher and lower, are largely developed in each and all of these regions, and the signifi- cance of the aboye facts is perhaps only to be seen when taken in connection with a large number of others pointing in the same direction. Two or three comparisons of different faunae may be brought forward finally. First, returning to the birds, a survey of some of the differences between the birds of Panama, Pennsylvania, and Palestine may be made.* Tristram noticed three hundred and twenty-two species of birds within the range of the ancient territory of Palestine. Of these two hundred and thirty were land and ninety-two water birds, i. e., Natatores and the wading Cursores. Of the two hun- dred and thirty, seventy-nine are common to the British Islands, and thirty-six of them are found in China, but a small j^roportion extending their range to both these extremes. Of the water birds, which are always more widely distributed, fifty-five of the ninety- two are British and fifty-seven Chinese. Twenty-seven appear to be confined to Palestine, and to the immediately adjacent country ; the largest of these is a crow. Taking the two hundred and thirty land birds at a glance, we find the utter absence of so many of the well-known forms that enliven our grounds and forests. The absence of Tanagridse (including Sylvicolidae) and Icteridse, changes the aspect of the bird-fauna at once. What have we here, then, of nine-quilled Oscines to enliven the meadows like our swarms of blackbirds, or fill the tree-tops and thickets with flutter like our wood-warblers ? Nothing ; for the twenty-four species of finches, Fringillidae, will but balance our own, though the genera are all different but four, and they the most weakly represented by species. We must look to the higher series, the ten- quilled song-birds, for the missing rank and file. While a much larger extent of the Eastern United States possesses fifty species of these types, the little Palestine has already furnished a list of one hundred and twenty-eight. First, of the crows, which verge nearest Icteridae hj the star- lings, we have thirteen species against five in our district of the * From the "American Naturalist," 1868, by the author. ON" THE ORIGIN OF GENERA. ^^^ United States, and not less than seven of the typo genus Corvus to our one common and two rare. Of these two are of the laro-er species, the ravens. If we turn to the cheerful larks, we find the proportion again the same ; fifteen species for Palestine and one for the whole United States. One congener of our species occurs there ; the other genera call to mind the African deserts and Rus- sian steppes. Motacillidse, again, ten to one against our fauna. We have two Tanagridae to imitate them, besides the one true relative. In swallows we are about equal, and in the forest-haunting Parid^ — titmice and wrens — we exceed a little ; but the comparison of Sylviidse and Turdidas is most striking. These highest of the bird series, especially made to gladden man's haunts with song, exceed in number all the other ten-quilled Oscines together inhabiting Palestine, amounting to seventy-five species. In our correspond- ing region of the United States nineteen species is the quantum. It is true no mocking-bird or wood-robin is known away from our shores, but Palestine has the nightingale, the black-cap, and the true warblers or sylvias, which, while they glean from shrub and tree their smallest insect enemies, as do our equally numerous small Tanagridse, have much louder and sweeter voices. Our solitary bluebird represents the long-winged Turdidae ; in the Holy Land there are twenty species corresponding, though none are of our genus. There are, indeed, but three genera of these two families common to both countries. One of these, La- nius, the butcher-bird, occurs here in one species, in Palestine in six. Turning now to a lower series, we look in vain for Clamatorial perchers ; that series which gives us the fierce king-bird and queru- lous pewee, and which peoples South America with thrush and warbler, and shrike and tree-creeper. In taking a hasty glance over the lower groups, where the carot- id arteries begin to be double, as the Syndactyli, we find Palestine too far from the tropics to present us with much array ; but in the related zygodactyles our forest-crowned continent must claim great pre-eminence. It has but a solitary Picus, while we have eight in the immediate neighborhood of lat. 40°, in our Eastern States. I will close with the birds of prey. Four swamp-hawks, eleven species of falcons, four kites, and eight native eagles, form a list unequaled in the annals of nobility by any land. There are to- gether thirty-one species of Falconidae, and of Vultures four. The 118 GENEKAL EVOLUTION. eagles appear to be all common, among them the most magnificent birds of prey, the imperial and golden species of these creatures. To the ornithologist, acquainted with the fauna of North America, it will thus be readily perceived that, in comparison, the ornis just examined, possesses more numerous representatives of the higher groups of the birds, and among lower groups possesses chiefly those of superior grade, or lacks them altogether. Let us, however, compare it with that of Central America, where varied surface and temperature offer even greater opportunity for variety, within quite as restricted an area. The bird fauna has been found by Messrs. Sclater and Salvia to embrace about three hundred and eighty-five species, which is sixty-three more than were mentioned to occur in Palestine, which is open on three sides to the great continent. Eighty of three hundred and forty-eight land birds are characteristic of Central America ; and those which find their kin limited to the Isthmus and adjoining regions of New Grenada and Equador amount to about seventy-five more. Twenty-seven is the number not known to extend beyond the boundaries of Palestine ; as to the Middle States of our Union, not one species has been shown to be restricted within such narrow limits. A single species occurs in Europe ; this is the fish-hawk, an animal which combines the cosmopolite habit of the sea-bird with the powerful flight of the bird of prey. This is also the only sj^e- cies common to the Panama and Palestine catalogues. The birds of prey are numerous — twenty-nine species. Among these there is no true eagle or falcon, and of the nineteen genera but four belong to the fauna of the Holy Land. There is but one species to represent the great grouse family, but, instead, three families of their South American imitators, the Pullastrse, instead of the one — that of the Pigeons — slimly represented in Palestine, and in North America as well. Coming to the closer test of superiority, the Passeres — those delicate creatures, apparently so dependent on those laws which govern increase and provision, and so affected by the changes that man works in the face of Nature — what do we find ? We count one hundred and six distinct species. There are none in Pales- tine. Of songsters, the Oscines, ninety-six species, await man's conquest of the wilderness, to increase in numbers and to display their gifts, while Palestine rejoices in a whole army of them. But the contrast is more remarkable if we analyze these forms. Of the ON THE GRIGIN OF GENERA. 119 Isthmian Oscines, seventeen only hold the first rank, by virtue of their additional, the tenth primary quill, while this feature marks one hundred and twenty-eight species of Palestine. As we rapidly follow the line to the point where its extreme is manifested, in the family of the Thrushes or Turdidae, Panama is left but two soli- tary pioneers of these songsters of the North, while seventy-five species represent the family in Palestine. The comparison between different faunae exhibits an apparent gradation in some other groups equally curious. Thus, the true Cyprinidae in the Palaearctic region reach a great development, and produce the highest number of teeth on their pharyngeal jaws known, as well as attains the greatest bulk and importance. The number of these teeth is usually seven to five in the inner row ; only two or three genera exhibit only four on both. In the Ne- arctic region the number of teeth is almost always 4 — 4, more rarely 4 — 5, and very seldom as high as 5 — 5. The species of the family are excessively numerous, but are, with scarcely any excep- tion, of small size and weak organism. These statements apply to those of the eastern district of the region between the Rocky Mountains and the Atlantic. Similar types occur in the northern region of the Neotropical — Mexico, but in no great numbers. Farther south the family disappears, its place being sujoplied by the generalized family of Characinidae. I have already alluded to the great variety of the highest or pentamerous carnivorous beetles in the Palaearctic region. They are extremely abundant in the Nearctic, while the intermediate territory, the Sonoran and Mexican sub-districts, are the head- quarters of the next lower form, the Tenebrionidae, which have the tarsal joints 4 — 5. These give place in the Neotropical to the multitudes of the still lower series — those with the joints 4 — 4 and 3 — 3 — Tetramera and Trimera. The preceding comparisons indicate that an inherent difference between the types of a continent exists at the present time, tliough the difference is subordinated to a universal distribution of the higher groups throughout the earth. Has this state of things ex- isted for any long period, or is it a result of different progress in the same group since the human period ? This brings us neces- sarily to a consideration of the truths of paleontology, especially of the last periods, which have been already urged by Darwin. Thus the present fauna of Australia was preceded in the Post-Pli- ocene and Pliocene by forms possessing similar peculiarities, and 120 GENERAL EVOLUTION. belonging to the same classes. That is by herbivorous and car- nivorous marsupials and monotremes, and by Varanid Sauria, all of greater size than their predecessors. The same fact is well known of the Neotropical region, its present peculiar Edentata having been preceded by giants of the same type in the Post- Pliocene and Pliocene. In the Nearctic region peculiar existing genera, as Procyon, Alces, Castor, Bos, Sciurus, Arctomys, Lepus, Ovibos, Sorex, Me- phitis, Felis, Ursus, Menopoma, Aspidonectes, Orotalus, are rep- resented by Post-Pliocene fossils. The same occurs in the later Palsearctic formations, where Cer- vus. Bos, Canis, Mustelidse, Insectivora, Vipera, Alytes, Triton, etc., are allied predecessors of existing types. In the Palseotrop- ical area a wonderful development of Elephas and Gavialis preceded the same types of the present. Prior to these faunas another state of things has, however, ex- isted. North America has witnessed a withdrawal of a Neotrop- ical fauna, and the Palaearctic the retreat of an Ethiopian type. During the Post-Pliocene in North America, Neotropical genera were to Nearctic as 12 to 29, as the record now stands. In the Pliocene beds of Pikermi (Greece) antelopes, giraffes, rhinoceros, hippopotamus, huge manis,* monkeys, monitors, and other genera and species of African relationship are the prevailing forms. Still earlier, a strong mingling of Nearctic, and more of Neo- tropical types, abounded in the Palaearctic. The genera Chelydra, Andrias, Podocnemis,t Platemys, Caviiform, Psammoryctid and Hesperomys-like Eodentia, Opossums, and Raccoon-like Carnivora. We have, then, three important terms from which to derive a theory of the creation : 1, the existing six faunae bear in many of their parts developmental relations to one another ; 2, they were preceded immediately by faunae similar to them in each case, but more remotely by faunae like that now next lower. On the whole, there can be no doubt of the truth of the gen- eralization : That the Southern Hemisphere is a geologic stage hehind the Northern Hemisphere in progress, on account (1) of its perfection in types extinct in the Northern, and (2) inferiority in modern types prevalent in the Northern. In order, however, to demonstrate this jDoint more fully, let us * Ancylotherium, Macrotherium. f P. howcrbanJcii {Platemys^ Owen). P. Icevis {JEinys, Owen). ON THE ORIGIN OF GENERA. ;121 examine to what extent the higher types exist in the Southern and lower or ancient in the Northern. The Percoid fishes and their allies have Australian and South American representatives in their fresh waters, but they are as mere outliers of the great mass in the Northern Hemisphere. The higher type of venomous serpents (Solenoglypha) occur in both the Ethiopian and Neotropical regions, but they j^reponderate in the Northern Hemisphere. The higher group of the Saurians (the Acrodonta) abounds in the Ethiopian and Australian regions ; they are as abundant in the Indian and Palaearctic regions of the Northern Hemisphere. In the Southern, also, by Uromastix and the Rynchocephalia, they approach nearest the ancient types of the Dicynodontia and the Crocodilia. Lacertidae, and not Teidse, occur in the Ethiopian ; but they are but a proportion of the whole, which chiefly exists in the Nearctic. Eaniform, and not Arciferous Anura, populate South Africa ; they, however, form but a small proportion compared with the great series of the Nearctic, Palaearctic, and Palseotropical regions. It is, however, superior in Anura to the Nearctic, taken by itself. Rasorial birds, and not Pallastrae, are the food species of South Africa ; but they do not compare in abundance or size with those of the three regions just mentioned. Moreover, but few Clamatores exist in either Australia or Ethiopia. The Oscine types are abundant ; nevertheless, they can not be compared in relative abundance with those of the northern regions. It must also be remembered that the migratory capa- bilities of birds render them less expressive of the true nature of any fauna. The higher family of the Quadrumana, the Simiidae, replaces in Africa the Cebidae of the Neotropical ; they are, however, most abundant in the Palaeotropical region, in the other hemisphere. There are two ancient or inferior types of the Northern Hemi- sphere : First, its fishes, the Sturgeons of the Nearctic and Palse- arctic, and the Gars of the Nearctic* The latter only have rep- resentatives in the Southern Hemisphere, Polypterus and Cala- moichthys in Africa, and so may be said to be equally distributed ; but the former are confined to the north. We do not know, how- ever, whether they are of a modern or an ancient type, nor do we * Subsequent investigations have proved that Polypterus and Calamoichthys are of much more ancient type than gars and sturgeons. (Ed. 1886.) 122 GENERAL EVOLUTION. know of extinct sturgeons in the Southern Hemisphere. Indeed, the Ganoid series is not well defined or known as yet. If, as Agassiz states, the Siluroids pertain to it, it is cosmopolitan, though least represented in the Palasarctic. Second, the Tailed or Urodele Batrachia. This order, entirely characteristic of the Northern Hemisphere, is a group which com- bines characters of Anura with those of the ancient forms, and possesses in its Nearctic types many of low development. The Gymnophidia of the Southern HemisjDhere can not be considered inferior to them. In the possession of this group the Northern Hemisphere presents its first element of inferiority. The preceding comparisons indicate also the relations of the regions proper to each other. It is obvious enough that the Ethi- opian is much superior to the two others of the Southern Hemi- sphere. As to the Australian and Neotropical, the former must still be regarded as probably the most ancient, though possessing at the same time a much stronger admixture of northern forms. I liave already presented the relations, with the inferior forms of each, thus : * R. Australis. — Inferior in possessing Monotrematous and Marsu- pial Mammalia, Pullastriform and Struthious Birds, Serpent- iform Pleurodont Lacertilia, Arciferous Batrachia, Pleuro- dire Tortoises, its Elapid venomous snakes, and the whole Flora, according to linger. B, Neotropica. — Marsupial and Edentate Mammalia, Inferior Rodentia and Quadrumana, Pleurodire Tortoises, Pleurodont Lacertilia, Arciferous Batrachia, Clamatorial and Pullas- triform Birds, Characin and Erythrinid Malacopterigii. Conclusions, The following may be looked upon as conclusions which have been indicated in the preceding pages : I. Species have developed from pre-existent species by an in- herent tendency to variation, and have been preserved in given directions and repressed in others by the operation of the law of natural selection (Darwin). II. Genera have been produced by a system of retardation or acceleration in the development of individuals ; the former on pre-established, the latter on preconceived lines of direction. Or, «■ " Jour. Acad. Nat. Sci.," Philada., 1866, p. 109. ON THE ORIGIN OF GENERA. 123 in other words, that while nature's series have been projected in accordance with the hiw of acceleration and retardation, they have been limited, modified, and terminated by the law of natural se- lection, which may itself have operated in part by the same law. III. The processes of development of specific and generic, char- acters have not proceeded pari passu, transitions of the one kind not being synchronous with transitions of the other ; and that, therefore, species may be transferred from one genus to another without losing their specific characters, and genera from order to order without losing their generic characters. IV. And as the heterologous terms of the peculiar homologous groups present an ^^ inexact parallelism" with each other; and as types related by inexact parallelism are each among themselves exact parallels in separate series, whose earliest members present *^ exact parallelisms " with each other, it follows — Y. That the heterologous terms or genera in the later series are modified descendants of those of the earlier series ; in other words, that certain groups higher than genera are produced from others of similar high value by "descent with modification." YI. That the result of such successional metamorphoses will be expressed in geologic history by more or less abrupt transitions or expression-points, rather than by uniformly gradual succes- sions. Of course, under the conclusion stated in Proposition II, the genus Homo has been developed by the modification of some pre- existent genus. All his traits which are merely functional have, as a consequence, been produced during the process. Those traits which are not functional, but spiritual, are of course amenable to a different class of laws, which belong to the province of religion. III. ON THE THEOEY OF EVOLUTION". At a meeting of the Philadelphia Academy of Natural Sci- ences, held February 22, 1876, Prof. Cope gave a history of the progress of the doctrine of evolution of animal and vegetable types. While Darwin has been its prominent advocate within the last few years, it was first presented to the scientific world, in a rational form, by Lamarck, of Paris, at the commencement of the present century. Owing to the adverse influence of Cuvier, the doctrine remained dormant for half a century, and Darwin resuscitated it, making important additions at the same time. Thus Lamarck found the variations of species to be the primary evidence of evolution by descent. Darwin enunciated the law of *^ natural selection" as a result of the struggle for existence, in ■accordance with which "the fittest" only survive. This law, now generally accepted, is Darwin's principal contribution to the doctrine. It, however, has a secondary position in relation to the origin of variation, which Lamarck saw, but did not account for, and which Darwin has to assume in order to have materials from which a " natural selection " can be made. The relations exhibited by fully grown animals and plants with transitional or embryonic stages of other animals and plants, had attracted the attention of anatomists at the time of Lamarck. Some naturalists deduced from this now universally observed phenomenon that the lower types of animals were merely re- pressed conditions of the higher, or, in other words, were embry- onic stages become permanent. But the resemblances do not usually extend to the entire organism, and- the parallels are so incomplete that this view of the matter was clearly defective, and did not constitute an explanation. Some embryologists, as Lereboullet and Agassiz, asserted that no argument for a doctrine of descent could be drawn from such facts. The speaker, not adopting either view, made a full investiga- ON THE THEORY OF EVOLUTION. 125 tion into the later embryonic stages, chiefly of the skeleton of the Batrachia, in 1865, and Prof. Hyatt, of Salem, Mass., at the same time made similar studies in the development of the Ammo- nites and Nautili. The results as bearing on the doctrine of evo- lution were published in 1869 (in ^^The Origin of Genera"). It was there pointed out that the most nearly related forms of ani- mals do present a relation of repression and advance, or of perma- nent embryonic and adult type, leaving no doubt that the one is descended from the other. This relation was termed exact paral- lelism. It was also shown that, if the embryonic form were the parent, the advanced descendant was produced by an increased rate of growth, which phenomenon was called acceleration ; but that if the embryonic type were the offspring, then its failure to attain to the condition of the parent is due to the supervention of a slower rate of growth ; to this phenomenon the term retarda- tion was applied. It was then shown that the inexact parallelism was the result of U7iequal acceleration or retardation ; that is, ac- celeration affecting one organ or part more than another, thus disturbing the combination of characters which is necessary for the state of exact parallelism between the perfect stage of one animal and the transitional state of another. Moreover, accelera- tion implies constant addition to the parts of an animal, while re- tardation implies continual subtraction from its characters, or atrophy. He had also shown (''Method of Creation," 1871) that the additions either appeared as exact repetitions of pre-existent parts, or as modified repetitions, the former resulting in simple, the latter in more complex organisms. Prof. Haeckel, of Jena, has added the keystone to the doc- trine of evolution in his gastrsea theory. Prior to this generaliza- tion it had been impossible to determine the true relation existing between the four types of embryonic growth, or, to speak other- wise, than that they are inherently distinct from each other. But Haeckel has happily determined the existence of identical stages of growth in all of the types of eggs, the last of which is the gastrula ; and beyond which the identity ceases. Not that the four types of gastrula are without difference, but this differ- ence maybe accounted for, on plain principles. In 1874, Haeckel, in his "Anthropogenic," recognizes the importance of the irregu- larity of time of appearance of the different characters of animals, during the period of growth, as affecting their permanent struct- ure. While maintaining the view that the low forms represent 126 GENERAL EVOLUTION. the transitionaL stages of the higher, he proceeds to account for the want of exact correspondence exhibited by them at the present time, by reference to this principle. He believes that the rela- tion of parent and descendant has been concealed and changed by subsequent modifications of the order of appearance of charac- ters in growth. To the original, simple descent he applies the term palingenesis ; to the modified and later growth, coenogenesis. The causes of the change from palingenesis to coenogenesis he re- gards as three, viz., acceleration, retardation, and heterotopy. It is clear that the two types of growth distinguished by Prof. Haeckel are those which had been pointed out by Prof. Cope in "The Origin of Genera," as producing the relations of "exact" and "inexact parallelism"; and that his explanation of the origin of the latter relation by acceleration or retardation is the same as that of the latter essay. The importance which he at- taches to the subject was a source of gratification to the speaker, as it was a similar impression that led to the publication of " The Origin of Genera " in 1869. It remains to observe that the phenomena of exact parallelism or palingenesis are quite as necessarily accounted for on the prin- ciple of acceleration or retardation as are those of inexact paral- lelism or coenogenesis. Were all parts of the organism acceler- ated or retarded at a like rate, the relation of exact parallelism would never be disturbed ; while the inexactitude of the parallel- ism will depend on the number of variations in the rate of growth of different organs of the individual, with additions introduced from time to time. Hence it may be laid down that synchronous acceleration or retardation produces exact parallelism, and lietero- chronous acceleration or retardation produces inexact parallel- ism. In conclusion, it may be added that acceleration of the seg- mentation of the protoplasma or animal portion of the primordial Qgg, or retardation of segmentation of the deutoplasma or vegeta- tive half of the Qgg, or both, or the same relation between the growth of the circumference and center of the egg, has given rise to the four types which the segmentation now presents. An analysis of the laws of evolution may be tabulated as fol- lows : ON THE THEORY OF EVOLUTION. 127 -I:? 1 ^. ( Exact repetition .^ acceUrahon, \ Modified repetition I which proceeds by ] g^^^^^^^pyj - retardation^ j Exact atrophy ^ Avhich proceeds by ( Inexact atrophy (or senility r-' ^j. as o Si: P t< O Co s 2. Co i_l * * a, a O £1 t-b 05 * So called by Prof. Hyatt. IV. ON THE HYPOTHESIS OF EVOLUTION: PHYSICAL AND METAPHYSICAL. " Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God shall man live." There is apparently considerable repugnance in the minds of many excellent people to the acceptance, or eyen consideration, of the hypothesis of development, or that of the gradual creation by descent, with modifications from the simplest beginnings, of the different forms of the organic world. This objection probably results from two considerations : first, that the human sj^ecies is certainly involved, and man's descent from an ape asserted ; and, secondly, that the scheme in general seems to conflict with that presented by the Mosaic account of the Creation, which is regarded as communicated to its author by an infallible inspiration. As the truth of the hypothesis is held to be infinitely probable by a majority of the exponents of the natural sciences at the pres- ent day, and is held as absolutely demonstrated by another por- tion, it behooves those interested to restrain their condemnation, and on the other hand to examine its evidences, and look any con- sequent necessary modification of our metaphysical or theological views squarely in the face. The following pages state a few of the former ; if they suggest some of the latter, it is hoped that they may be such as any logical mind would deduce from the premises. That they will coincide with the spirit of the most advanced Christianity, I have no doubt ; and that they will add an appeal through the reason to that direct influence of the Divine Spirit which should control the motives of human action, seems an unavoidable conclusion. I. PHYSICAL EVOLUTIOK. It is well known that a species is usually represented by a great number of individuals, distinguished from all other similar associ- ON THE HYPOTHESIS OF EVOLUTION. 129 ations by more or less numerous points of structure, color, size, etc., and by habits and instincts also, to a certain extent; that the individuals of such associations reproduce their like, and can not be produced by individuals of associations or species v^^hich present differences of structure, color, etc., as defined by natural- ists ; that the individuals of any such series or species are incapa- ble of reproducing with those of any other species, with some exceptions ; and that in the latter cases the offspring are usually entirely infertile. The hypothesis of Cuvier assumes that each species was created by divine power as we now find it at some definite point of geo- logic time. The paleontologist holding this view sees, in accord- ance therewith, a succession of creations and destructions marking the history of life on our planet from its commencement. The development hypothesis states that all existing species have been derived from species of pre-existent geological periods, as offspring or by direct descent ; that there have been no total destructions of life in past time, but only a transfer of it from place to place, owing to changes of circumstance ; that the types of structure become simpler and more similar to each other as we trace them from later to earlier periods ; and that finally we reach the simplest forms consistent with one or several original parent types of the great divisions into which living beings naturally fall. It is evident, therefore, that the hypothesis does not include change of species by hybridization, nor allow the descent of living species from any other living species : both these propositions are errors of misapprehension or misrepresentation. In order to understand the history of creation of a complex being, it is necessary to analyze it and ascertain of what it con- sists. In analyzing the construction of an animal or plant we readily arrange its characters into those which it possesses in com- mon with other animals or plants, and tliose in which it resem- bles none other : the latter are its i7icUvidual characters, consti- tuting its individuality. Next, we find a large body of characters, generally of a very obvious kind, which it possesses in common with a generally large number of individuals, which, taken col- lectively, all men are accustomed to call a species ; these charac- ters we consequently name specific. Thirdly, we find characters, generally in parts of the body which are of importance in the ac- tivities of the animal, or which lie in near relation to its mechan- ical construction in details, which are shared by a still larger 9 130 GENERAL EVOLUTION. number of individuals than those which were similar in specific characters. In other words, it is common to a large number of species. This kind of character we call generic^ and the grouping it indicates is a genus. Farther analysis brings to light characters of organism which are common to a still greater number of individuals ; this we call Si family character. Those which are common to still more nu- merous individuals are the ordinal: they are usually found in parts of the structure which have the closest connection with the whole life-history of the being. Finally, the individuals compos- ing many orders will be found identical in some important char- acter of the systems by which ordinary life ic maintained, as in the nervous and circulatory : the divisions thus outlined are called classes. By this process of analysis we reach in our animal or j^lant those peculiarities which are common to the whole animal or vege- table kingdom, and then we have exhausted the structure so com- pletely that we have nothing remaining to take into account beyond the cell-structure or homogeneous protoplasm by which we know that it is organic, and not a mineral. The history of the origin of a type, as species, genus, order, etc., is simply the history of the origin of the structure or struct- ures which define those groups respectively. It is nothing more nor less than this, whether a man or an insect be the object of investigation. EVIDENCES OF DEEIVATION. a. Of Specific Characters. The evidences of derivation of species from species, within the limits of the genus, are abundant and conclusive. In the first place, the rule which naturalists observe in defining species is a clear consequence of such a state of things. It is not amount and degree of difference that determine the definition of species from species, but it is the permanency of the characters in all cases and under all circumstances. Many species of the systems include va- rieties and extremes of form, etc., which, were they at all times distinct, and not connected by intermediate forms, would be esti- mated as species by the same and other writers, as can be easily seen by reference to their works. Thus, species are either "restricted " or '^protean," the latter ON THE HYPOTHESIS OF EVOLUTION. 131 embracing many, the former few variations ; and the varieties in- cluded by the protean species are often as different from each other in their typical forms as are the ** restricted" species. As an ex- ample, the species Homo sapiens (man) will suffice. His primary varieties are as distinct as the species of many well-known genera, but can not be defined, owing to the existence of innumerable in- termediate forms between them. As to the common origin of such '^varieties" of the protean species, naturalists never had any doubt ; yet when it comes to the restricted ^'^ species," the anti-developmentalist denies it in toto. Thus the varieties of most of the domesticated animals are some of them known — others held with great probability to have had a common origin. Varieties of plumage in fowls and canaries are of every-day occurrence, and are produced under our eyes. The cart-horse and racer, the Shetland pony and the Norman, are without doubt derived from the same parentage. The varieties of pigeons and ducks are of the same kind, but not every one is aware of the extent and amount of such variations. The varieties in many characters seen in hogs and cattle, especially when exam- ples from distant countries are compared, are very striking, and are confessedly equal in degree to those found to define species in a state of nature : here, however, they are not definitive. It is easy to see that all that is necessary to produce in the mind of the anti-developmentalist the illusion of distinct origin by creation of many of these forms would be to destroy a number of the intermediate conditions of specific form and structure, and thus to leave remaining definable groups of individuals, and there- fore "species." That such destructions and extinctions have been going no ever since the existence of life on the globe is well known. That it should affect intermediate forms, such as bind together the types of a protean species as well as restricted species, is equally certain. That its result has been to produce definaUe species can not be denied, especially in consideration of the following facts : Protean species nearly always have a wide geographical distribu- tion. Thev exist under more varied circumstances than do indi- viduals of a more restricted species. The subordinate variations of the protean species are generally, like the restricted species, confined to distinct subdivisions of the geographical area which the whole occupies. As in geological time changes of level have separated areas once continuous by bodies of water or high mount- 132 GENERAL EVOLUTION. ain-ranges, so have vast numbers of individuals occupying sucli areas been destroyed. Important alterations of temperature, or great changes in abundance or character of vegetable life over given areas, would produce the same result. This part of the subject might be prolonged, were it necessary, but it has been ably discussed by Darwin. The rationale of the ^^ origin of species," as stated by him, may be examined a few pages farther on. p. Of the Characters of Higher Groups. a. Relations of Structures. — The evidences of derivative origin of the structures defining the groups called genera, and all those of higher grade, are of a very different character from those dis- cussed in relation to specific characters ; they are more diflScult of observation and explanation. First : It would appear to be supposed by many that the crea- tion of organic types was an irregular and capricious process, variously pursued by its Author as regards time and place, and without definite final aim ; and this notwithstanding the wonder- ful evidences we possess, in the facts of astronomy, chemistry, sound, etc., of his adhesion to harmonious and symmetrical sequences in his modes and plans. Such regularity of plan is found to exist in the relations of the great divisions of the animal and vegetable kingdoms as at present existing on the earth. Thus, with animals we have a great class of species which consists of nothing more than masses or cells of protoplasmic matter, without distinct organs ; or the Protozoa. We have then the Coelenterata (example, corals), where the organ- " ism is composed of many cells arranged in distinct parts, but where a single very simple system of organs, forming the only in- ternal cavity of the body, does the work of the many systems of the more complex animals. Next, the Echinodermata (such as star-fish) present us with a body containing distinct systems of organs inclosed in a visceral cavity, including a rudimental nerv- ous system in the form of a ring. In the Molluscs to this con- dition is added further complication, including extensions of the nervous system from the ring as a starting-point, and a special organ for a heart. In the Articulates (crabs, insects) we have like complications, and a long distinct nervous axis on the lower surface of the body. The last branch or division of ani- mals is considered to be higher, because all the systems of life ON" THE HYPOTHESIS OF EYOLUTIOX. 133 organs are most complex or specialized. The neryous rino- ig almost obliterated by a great enlargement of its nsual gano-lja, thus become a brain, which is succeeded by a long axis on the upper side of the body. This and other points define the Ver- tebrata. Plans of structure, independent of the simplicity or perfection of the special arrangement or structure of organs, also define these great groups. Thus the Protozoa present a spiral, the Coelenterata a radiate, the Echinodermata a bilateral radiate plan. The Articulates are a series of external rings, each in one or more respects repeating the others. The Molluscs are a sac, while a ring above a ring, joined together by a solid center-piece, repre- sents the plan of each of the many segments of the Vertebrates which give the members of that branch their form. These bulwarks of distinction of animal types are entered into here simply because they are the most inviolable and radical of those with which we have to deal, and to give the anti-develop- mentalist the best foothold for his position. I will only allude to the relations of their points of approach as these are affected by considerations afterward introduced. The Vertebrates approach the Molluscs closely at the lowest extreme of the former and higher of the latter. The lamprey eels of the one joossess several characters in common with the cuttle-fish or squids of the latter. The amj)hioxus is called the lowest Vertebrate, and, though it is nothing else, the definition of the division must be altered to receive it ; it has no brain ! The lowest forms of the Molluscs and Articulates are scarcely distinguishable from each other, so far as adhesion to the "plan " is concerned, and some of the latter division are very near certain Echinodermata. As we approach the boundary-lines of the two lowest divisions, the approaches become equally close. More instructive is the evidence of the relation of the subordi- nate classes of any one of these divisions. The conditions of those organs or parts which define classes exhibit a regular rela- tion, commencing with simplicity and ending with complication ; first associated with weak exhibitions of the highest functions of the nervous system — at the last displaying the most exalted traits found in the series. For example : In the classes of Vertebrates we find the lowest neryous system presents great simplicity — the brain can not be recognized ; next (in lampreys), the end of the nervous axis is 134 GENERAL EVOLUTION. subdivided, but scarcely according to the complex type that fol- lows. In fishes the cerebellum and cerebral hemispheres are minute, and the intermediate or optic lobes very large : in the reptiles the cerebral hemispheres exceed the optic lobes, while the cerebellum is smaller. In birds the cerebellum becomes complex and the cerebrum greatly increases. In mammals the cerebellum increases in complexity or number of parts, the o^^tic lobes diminish, while the cerebral hemispheres become wonderfully complex and enlarged, bringing us to the highest development, in man. The history of the circulatory system in the Vertebrates is the same. First, a heart with one chamber, then one with two divis- ions : three divisions belong to a large series, and the highest possess four. The origins of the great artery of the body, the aorta, are first five on each side : they lose one in the succeeding class in the ascending scale, and one in each succeeding class or order, till the Mammalia, including man, present us with but one on one side. From an infinitude of such considerations as the above, we derive the certainty that the general arrangement of the various grouj^s of the organic world is in scales, the subordinate within the more comprehensive divisions. The identification of all the 23arts in such a complexity of organism as the highest animals present is a matter requiring much care and attention, and con- stitutes the study of homologies. Its pursuit has resulted in the demonstration that every individual of every species of a given branch of the animal kingdom is composed of elements common to all, and that the differences which are so radical in the higher groups are but the modifications of the same elemental parts, representing completeness or incom^Dleteness, obliteration or sub- division. Of the former character are rudimental organs, of which almost every species possesses an example in some part of its structure. But we have other and still more satisfactory evidence of the meaning of these relations. By the study of embryology we can prove most indubitably that the simple and less complex are in- ferior to the more complex. Selecting the Vertebrates again as an example, the highest form of mammal — e. g., man — presents in his earliest stages of embryonic growth a skeleton of cartilage, like that of the lamprey ; he also possesses five origins of the aorta and five slits on the neck : both which characters belong to ox THE HYPOTHESIS OF EVOLUTION. 135 the lamprey and the shark. If the whole number of these parts does not co-exist in the embryonic man, we find in embryos of lower forms, more nearly related to the lamprey, that they do. Later in the life of the mammal but four aortic origins are found, which arrangement, with the heart now divided into two cham- bers, from a beginning as a simple tube, is characteristic of the class of Vertebrates next in order — the bony fishes. The optic lobes of the human brain have also at this time a great predomi- nance in size — a character above stated to be that of the same class. With advancing development the infant mammal follows the scale already pointed out. Three chambers of the heart and three aortic origins follow, presenting the condition permanent in the Batrachia ; and two origins, with enlarged cerebral hemi- spheres of the brain, resemble the reptilian condition. Four heart-chambers, and one aortic-root on each side, with slight development of the cerebellum, follow, all characters defining the crocodiles, and immediately precede the special conditions defin- ing the mammals. These are, the single aorta-root from one side, and the full development of the cerebellum ; later comes that of the cerebrum also in its higher mammalian and human traits. Thus we see the order already pointed out to be true, and to be an ascending one. This is the more evident as each type or class passes through the conditions of those below it, as did the mammal ; each scale being shorter as its highest terminus is lower. Thus the crocodile passes through the stage of the lam- prey, the fish, the batrachian, and the reptile proper. h. In Time, — We have thus a scale of relations of existing forms of animals and plants of a remarkable kind, and such as to stimulate greatly our inquiries as to its significance. When we turn to the remains of tlie past creation, preserved to us in the deposits continued throughout geologic time, we are not disappointed, for great light is at once thrown upon the sub- ject. We find, in brief, that the lowest division of the animal king- dom appeared first, and long before any type of a higher charac- ter was created. The Protozoon, Eozoon, is the earliest of animals in geologic time, and represents the lowest type of animal life now existing. We learn also that the highest branch appeared last. No remains of Vertebrates have been found below the lower Devonion period, or not until the Echinoderms and 136 GENERAL EVOLUTION. Molluscs had reached a great pre-emmeuce. It is difficult to be sure whether the Protozoa had a greater numerical extent in the earliest periods than now, but there can be no doubt that the Coelenterata (corals) and Echinoderms (crinoids) greatly exceeded their present bounds in Paleozoic time, so that those at present existing are but a feeble remnant. If we examine the sub- divisions known as classes, evidence of the nature of the succes- sion of creation is still more conclusive. The most poljp-like of the Molluscs (Brachiopoda) constituted the great mass of its repre- sentatives during Paleozoic time. Among Vertebrates the fishes appear first, and had their greatest development in size and num- bers during the earliest periods of the existence of the division. Batrachia were much the largest and most important of land ani- mals during the Carboniferous period, while the higher Verte- brates were unknown. The later Mesozoic j^eriods saw the reign of reptiles, whose position in structural develojoment has been already stated. Finally, the most perfect, the mammal, came upon the scene, and in his humblest rej^resentatives. In Tertiary times Mammalia supplanted the reptiles entirely. Thus the structural relations, the embryonic characters, and the successive appearance in time of animals coincide. The same is very probably true of plants. That the existing state of the geological record of organic types should be regarded as anything but a fragment is, from our standpoint, quite preposterous. And, more, it may be as- sumed with safety that when completed it will furnish us with a series of regular successions, with but slight and regular in- terruptions, if any, from the species which represented the sim- plest beginnings of life at the dawn of creation, to those which have displayed complication and power in later or in the present periods. For the labors of the paleontologist are daily bringing to light structures intermediate between those never before so connected, and thus creating lines of succession where before were only in- terruptions. Many such instances might be adduced : two might be selected as examiDles from American paleontology ; * i. e. , the * Prof. Huxley, in the last anniversary lecture before the Geological Society of London, recalls his opinion, enunciated in 1862, that "the positively-ascertained truths of Paleontology " negative " the doctrines of progressive modification, which suppose that modification to have taken place by a necessary progress from more to less embryonic forms, from more to less generalized types, within the limits of the ox THE HYPOTHESIS OF EVOLUTION. 137 near approach to birds made by the reptiles Laelaps and Megadac- tylus, and the combination of characters of the old genera Ich- thyosaurus and Plesiosaurus in the Polycotylus of Kansas. We had no more reason to look for intermediate or connectino- forms between such types as these than between any others of similar degree of remove from each other with which we are ac- period represented by the fossiliferous rocks ; that it shows no evidence of such modification ; and, as to the nature of that modification, it yields no evidence what- soever that the earlier members of any long-continued group were more generalized in structure than the later ones." Respecting this position, he says : " Thus far I have endeavored to expand and enforce by fresh arguments, but not to modify in any important respect, the ideas submitted to you on a former occasion. But when I come to the propositions re- specting progressive modification, it appears to me, with the help of the new light which has broken from various quarters, that there is much ground for softening the somewhat Brutus-like severity with which I have dealt with a doctrine for the truth of which I should have been glad enough to be able to find a good foundation in 1862. So far indeed as the Invertebrata and the lower Vertebrata are concerned, the facts and the conclusions which are to be drawn from them appear to me to re- main what they were. For anything that as yet appears to the contrary, the earliest known Marsupials may have been as highly organized as their living congeners ; the Permian lizards show no signs of inferiority to those of the present day ; the laby- rinthodonts can not be placed below the living salamander and triton ; the Devo- nian ganoids are closely related to polypterus and lepidosiren." To this it may be replied: 1. The scale of progression of the Vertebrata is measured by the condition of the circulatory system, and in some measure by the nervous, and not by the osseous : tested by this scale, there has been successional complication of structure among Vertebrata in time. 2. The .question with the evolutionist is, not what types have persisted to the present day, but the order in which types appeared in time. 3. The Marsupials, Permian saurians, labyrintho- donts, and Devonian ganoids are remarkably generalized groups, and predecessors of types widely separated in the present period. 4. Prof. Huxley adduces many such examples among the mammalian subdivisions in the remaining portion of his lect- ure. 5. Two alternatives ai*e yet open in the explanation of the process of evolu- tion : since generalized types, which combine the characters of higher and lower groups of later periods, must thus be superior to the lower, the lower must (first) be descended from such a generalized form by degradation ; or (second) not descended from it at all, but from some lower contemporaneous type by advance ; the higher only of the two being derived from the first-mentioned. The last I suspect to be a true explanation, as it is in accordance with the homologous groups. This law will shorten the demands of paleontologists for time, since, instead of deriving all Reptilia, Batrachia, etc., from common origins, it points to the derivation of higher Reptilia of a higher order from higher Reptilia of a lower order, lower Reptilia of the first from lower Reptilia of the second ; finally, the several groups of the lowest or most generalized order of Reptilia from a parallel series of the class below, or Batrachia. 138 GENEPwAL EYOLUTIOK quainted. And inasmucli as almost all groups, as genera, orders, etc., which are held to be distinct, but adjacent, present certain points of approximation to each other, the almost daily discovery of intermediate forms gives us confidence to believe that the pointings in other cases will also be realized. y. Of Transitions. The preceding statements were necessary to the comprehension of the supposed mode of metamorphosis or development of the various types of living beings, or, in other words, of the single structural features which define them. As it is evident that the groups of highest rank have had their origin in remote ages, cases of transition from one to the other by change of character can not be witnessed at the present day. We therefore look to the most nearly related divisions, or those of the lowest rank, for evidence of such change. It is necessary to premise that embryology teaches that all the species of a given branch of the animal kingdom (e. g., Verte- brate, Mollusc, etc.) are quite identical in structural character at their first appearance on the germinal layer of the yolk of the parent Qgg. It shows that the character of the respective groups of high rank api^ear first, then those of less grade, and last of all those structures which distinguish them as genera. But among the earliest characters which appear are those of the species, and some of those of the individual. We find the characters of different genera to bear the same re- lation to each other that we have already seen in the case of those definitive of orders, etc. In a natural assemblage of related genera we discover that some are defined by characters found only in the embryonic stages of others, while a second will present a perma- nent condition of its definitive part, which marks a more ad- vanced stage of that highest. In this manner many stages of the highest genus a2:)pear to be represented by permanent genera in all natural groups. Generally, however, this resmblance does not involve an entire identity, there being some other immaturities found in the highest genus at the time it presents the character preserved in permanency by the lower, which the lower loses. Thus (to use a very gross illustration) a frog at one stage of growth has four legs and a tail ; the salamander always preserves four legs and a tail, thus resembling the young frog. The latter is, however, not a salamander at that time, because, among other ON THE HYPOTHESIS OF EVOLUTION. 139 things, the skeleton is represented by cartilage only, and the sala- mander's is ossified. This relation is therefore an imitation only, and is called inexact ^parallelism. As we compare nearer and nearer relations — i. e., the genera which present fewest points of difference — we find the differences between undeveloped stages of the higher and permanent con- ditions of the lower to grow fewer and fewer, until we find numer- ous instances where the lower genus is exactly the same as the undeveloped stage of the higher. This relation is called that of exact parallelism. It must now be remembered that the permanence of a charac- ter is what gives it its value in defining genus, order, etc., in the eyes of the systematist. So long as the condition is permanent no transition can be seen ; there is therefore no development. If the condition is transitional, it defines nothing, and nothing is devel- oped ; at least, so says the anti-developmentalist. It is the old story of the settler and the Indian : ^^WiJl you take owl and I take turkey, or I take turkey and you owl ? " If we find a relation of exact parallelism to exist between two sets of species in the condition of a certain organ, and the differ- ence so expressed is the only one which distinguishes them as sets from each other — if that condition is always the same in each set — we call them two genera : if in any species the condition is va- riable at maturity, or sometimes the undeveloped condition of the part is persistent and sometimes transitory, the sets characterized by this difference must be united by the systematist, and the whole is called a single genus. We know numerous cases where different individuals of the same species present this relation of exact parallelism to each other ; and, as we ascribe common origin to the individuals of a species, we are assured that the condition of the inferior individual is, in this case, simply one of repressed growth, or a failure to ful- fill the course accomplished by the highest. Thus, certain species of the salamandrine genus Amblystoma undergo a metamorphosis involving several parts of the osseous and circulatory systems, etc., while half grown ; others delay it till fully grown ; one or two species remain indifferently unchanged or changed, and breed in either condition, while another species breeds unchanged, and has never been known to complete a metamorphosis. The nature of the relation of exact parallelism is thus explained to be that of checked or advanced growth of individuals having a 140 GENERAL EVOLUTION. common origin. The relation of inexact parallelism is readily ex- plained as follows : With a case of exact 2^arallelism in the mind, let the repression producing the character of form B parallelize the latter with a stage of form A in which a second part is not quite mature : we will have a slight want of correspondence be- tween the two. Form B will be immature in but one point, the incompleteness of A higher being seen in two points. If we suppose the immaturity to consist in a repression at a still earlier point in the history of the higher, the latter will be undeveloped in other points also : thus, the spike-horned deer of South Amer- ica have the horn of the second year of the North American genus. They would be generically identical with that stage of the latter, were it not that these still possess their milk dentition at two years of age. In the same way the nature of the parallelisms seen in higher groups, as orders, etc., may be a' counted for. The theory of homologous groups furnishes important evidence in favor of derivation. Many orders of animals (probably all, when we come to know them) are divisible into two or more sec- tions, which I have called homologous. These are series of genera or families, which differ from each other by some marked charac- ter, but whose contained genera or families differ from each other in the same points of detail, and in fact correspond exactly. So striking is this correspondence that were it not for the general and common character separating the homologous series, they would be regarded as the same, each to each. Now, it is remarkable that, where studied, the difference common to all the terms of two ho- mologous groups is found to be one of inexact parallelism, which has been shown above to be evidence of descent. Homologous groups always occupy different geographical areas on the earth's surface, and their relation is precisely that which holds between successive groups of life in the periods of geologic time.* In a word, we learn from this source that distinct geologic epochs co-exist at the same time on the earth. I have been forced to this conclusion f by a study of the structure of terrestrial life, and it has been remarkably confirmed by the results of recent deep-sea dredgings made by the United States Coast Survey in the Gulf Stream, and by the British naturalists in the North Atlantic. These have brought to light types of Tertiary life, and of even * The extinct family of the Nimravidas, which is homologous with the existing family of Felidae, has been discovered since this was written. (Ed. 1886.) f " Origin of Genera," pp. 70, 77, 79. ON THE HYPOTHESIS OF EYOLUTIOK 141 the still more ancient Cretaceous periods, living at the present day.* That this discovery invalidates in any wise the conclusions of geology respecting lapse of time is an unwarranted assumption that some are forward to make. If it changes the views of some respecting the parallelism or co-existence of faunas in different regions of the earth, it is only the anti-developmentalists whose position must be changed. For, if we find distinct geologic faunae, or epochs defined by faunae, co-existing during the present period, and fading or merg- ing into one another as they do at their geographical boundaries, it is proof positive that the geologic epochs and periods of past ages had in like manner no trenchant boundaries, but also passed the one into the other. The assumption that the apparent inter- ruptions are the result of transfer of life rather than destruction, or of want of opportunities of preservation, is no doubt the true one. 8. Rationale of Development. a. In Characters of Higher Groups. — It is evident in the case of the species in which there is an irregularity in the time of com- pletion of metamorphosis, that some individuals traverse a longer developmental line than those which remain more or less incom- plete. As both accomplish growth in the same length of time, it is obvious that it proceeds with greater rapidity in one sense in that which accomplishes most ; its growth is said to be accelerated. This phenomenon is especially common among insects, where the females of perfect males are sometimes larvae or nearly so, or pupae, or lack wings or some character of final development. Quite as frequently, some males assume characters in advance of others, sometimes in connection with a peculiar geographical range. In cases of exact parallelism we reasonably suppose the cause to be the same, since the conditions are identical, as has been shown ; that is, the higher conditions have been produced by a crowding back of the earlier characters and an acceleration of growth, so that a given succession in order of advance has extended over a longer range of growth than its predecessor in the same al- lotted time. That allotted time is the period before maturity and reproduction, and it is evident that as fast as modifications or characters should be assumed sufficiently in advance of that pe- riod, so certainly would they be conferred upon the offspring by * Most of the deep-sea forms are, however, degenerate forms of existing orders. (Ed. 1886.) 14:2 GENERAL EVOLUTION. reproduction. The acceleration in the assumption of a character, progressing more rapidly than the same in another character, must soon produce^ in a type whose stages were once the exact parallel of a permanent lower form, the condition of inexact parallelism. As all the more comprehensive groups present this relation to each other, we are compelled to believe that acceleration has been the principle of their successive evolution during the long ages of ge- ologic time. Each type has, however, its day of supremacy and perfection of organism, and a retrogression in these respects has succeeded. This has no doubt followed a law the reverse of acceleration, which has been called retardation. By the increasing slowness of the growth of the individuals of a genus, and later and later assump- tion of the characters of the latter, they would be successively lost. To what power shall we ascribe this acceleration, by which the first beginnings of structure have accumulated to themselves through the long geologic ages complication and power, till from the germ that was scarcely born into a sand-lance, a human being climbed the complete scale, and stood easily the chief of the whole ? In the cases of species, where some individuals develop farther than others, we say the former possess more growth-force, or *' vigor," than the latter. We may therefore say that higher types of structure possess more "vigor" than the lower. This, how- ever, we do not know to be true, nor can we readily find means to demonstrate it. The food which is taken by an adult animal is either assimi- lated, to be consumed in immediate activity of some kind, or stored for future use, and the excess is rejected from the body. We have no reason to suppose that the same kind of material could be made to subserve the production of force by any other means than that furnished by a living animal organism. The ma- terial from which this organism is constructed is derived first from the parent, and afterward from the food, etc., assimilated by the individual itself so long as growth continues. As it is the activity of assimilation directed to a special end during this latter period which we suppose to be increased in accelerated develojoment, the acceleration is evidently not brought about by increased facilities for obtaining the means of life which the same individual possesses as an adult. That it is not in consequence of such increased fa- cilities possessed by its parents over those of the type preceding it ON THE HYPOTHESIS OF EVOLUTION". 143 seems equally improbable when we consider that the characters in which the parent's advance has appeared are rarely of a nature to increase those facilities. The nearest approach to an explanation that can be offered appears to be somewhat in the following direction : There is every reason to believe that the character of the atmosphere has gradually changed during geologic time, and that various constituents of the mixture have been successively re- moved from it, and been stored in the solid material of the earth's crust in a state of combination. Geological chemistry has shown that the cooling of the earth has been accompanied by the j)recipitation of many substances only gaseous at high tempera- tures. Hydrochloric and sulphuric acids have been transferred to mineral deposits or aqueous solutions. The removal of carbonic- acid gas and the vapor of water has been a process of much slower progress, and after the expiration of all the ages a proportion of both yet remains. Evidence of the abundance of the former in the earliest periods is seen in the vast deposits of limestone rock ; later, in the prodigious quantities of shells which have been elaborated from the same in solution. Proof of its abundance in the atmosphere in later periods is seen in the extensive de- posits of coal of the Carboniferous, Triassic, and Jurassic periods. If the most luxuriant vegetation of the present day takes but fifty tons of carbon from the atmosphere in a century, per acre, thus producing a layer over that extent of less than a third of an inch in thickness, what amount of carbon must be abstracted in order to produce strata of thirty-five feet in depth ? No doubt it occu- pied a long period, but the atmosphere, thus deprived of a large proportion of carbonic acid, would in subsequent periods undoubt- edly possess an improved capacity for the support of animal life. The successively higher degree of oxidization of the blood in the organs designed for that function, whether performing it in water or air, would certainly accelerate the performances of all the vital functions, and among others that of growth. Thus it may be that acceleration can be accounted for, and the process of the development of the orders and sundry lesser groups of the Vertebrate kingdom indicated ; for, as already pointed out, the definitions of such are radically placed in the different structures of the organs which aerate the blood and distribute it to its various destinations. But the great question. What determined the direction of this 144 GENERAL EYOLUTIOK acceleration ? remains unanswered. One can not understand why more highly oxidized blood should hasten the growth of j)artition of the ventricle of the heart in the serpent, the more perfectly to separate the aerated from the impure fluid ; nor can we see why a more perfectly constructed circulatory system, sending purer blood to the brain, should direct accelerated growth to the cere- bellum or cerebral hemispheres in the crocodile. h. In Characters of the Specific Kind. — Some of the charac- ters usually placed in the specific category have been shown to be the same in kind as those of higher categories. The majority are, however, of a different kind, and have been discussed several pages back. The cause of the origin of these characters is shrouded in as much mystery as that of those which have occupied the pages im- mediately preceding. As in that case, we have to assume, as Darwin has done, a tendency in Nature to their production. This is what he terms ^^the principle of variation." Against an unlimited variation the great law of heredity or atavism has ever been opposed, as a conservator and multiplier of type. This principle is exemplified in the fact that like produces like — that children are like their parents, frequently even in minutiae. It may be compared to habit in metaphysical matters, or to that singular love of time or rhythm seen in man and lower animals, in both of which the tendency is to repeat in continual cycles a motion or state of the mind or sense. Further, only a proportion of the lines of variation is supposed to have been perpetuated, and the extinction of intermediate forms, as already stated, has left isolated groups or species. The effective cause of these extinctions is stated by Darwin to have been a "natural selection" — a proposition which distin- guishes his theory from other development hypotheses, and w^hich is stated in brief by the expression, "the survival of the fit- test." Its meaning is this : that those characters appearing as results of this spontaneous variation which are little adapted to the conflict for subsistence, with the nature of the supply, or with rivals in its pursuit, dwindle and are sooner or later ex- tirpated ; while those which are adapted to their surroundings, and favored in the struggle for means of life and increase, pre- dominate, and ultimately become the centers of new variation. "I am convinced," says Darwin, "that natural selection has been the main, but not exclusive, means of modification." ON THE HYPOTHESIS OF EVOLUTION. 145 That it has been to a large extent the means of preservation of those structures known as specific, must, I think, be admitted. They are related to their peculiar surroundings very closely, and are therefore more likely to exist under their influence. Thus, if a given genus extends its range over a continent, it is usually found to be represented by peculiar species — one in a maritime division, another in the desert, others in the forest, in the swamp or the elevated areas of the region. The wonderful interdepend- ence shown by Darwin to exist between insects and plants in the fertilization of the latter, or between animals and their food- plants, would almost induce one to believe that it were the true expression of the whole law of development. But the following are serious objections to its universal appli- cation : First : The characters of the higher groups, from genera up, are rarely of a character to fit their possessors especially for sur- rounding circumstances ; that is, the differences which separate genus from genus, order from order, etc., in the ascending scale of each, do not seem to present a superior adaptation to surround- ing circumstances in the higher genus to that seen in the lower genus, etc. Hence, superior adaptation could scarcely have caused their selection above other forms not existing. Or, in other words, the very differences in structure which indicate suc- cessional relation, or which measure the steps of progress, seem to be equally well fitted for their surroundings. Second : The higher groups, as orders, classes, etc., have been in each geologic period alike distributed over the whole earth, under all the varied circumstances offered by climate and food. Their characters do not seem to have been modified in reference to these. Species, and often genera, are, on the other hand, eminently restricted according to climate, and consequently vege- table and animal food. The law of development which we seek is indeed not that which preserves the higher forms and rejects the lower after their creation, but that which explains why higher forms were created at all. Why in the results of a creation we see any relation of higher and lower, and not rather a world of distinct types, each perfectly adapted to its situation, but none properly higher than another in an ascending scale, is the primary question. Given the principle of advance, then natural selection has no doubt modified the details; but in the successive advances we can 10 146 GENERAL EVOLUTION. scarcely believe such a principle to be influential. We look rather upon a progress as the result of the expenditure of some force fore-arranged for that end. It may become, then, a question whether in characters of high grade the habit or use is not rather the result of the acquisition of the structure than the structure the result of the encouragement offered to its assumed beginnings by use, or by liberal nutrition derived from the increasingly superior advantages it offers. €. The Physical Origin of Man. If the hypothesis here maintained be true, man is the de- scendant of some 2^re-existent generic type, the which, if it were now living, we would probably call an ape. Man and the chimpanzee were in Linnseus's system only two species of the same genus, but a truer anatomy places them in separate genera and distinct families. There is no doubt, how- ever, that Cuvier went much too far when he proposed to con- sider Homo as the representative of an order distinct from the Quadrumana, under the name of Bimana. The structural differ- ences will not bear any such inter23retation, and have not the same value as those distinguishing the orders of Mammalia ; as, for instance, between Carnivora and bats, or the cloven-footed ani- mals and the rodents, or rodents and edentates. The differences between man and the chimpanzee are, as Huxley well puts it, much less than those between the chimpanzee and lower Quadru- mana, as lemurs, etc. In fact, man is the type of a family, Hominidae, of the order Quadrumana, as indicated by the charac- ters of the dentition, extremities, brain, etc. The reader who may have any doubts on this score may read the dissections of Geoffroy St. Hilaire, made in 1856, before the issue of Darwin's '•'Origin of Species." He informs us that the brain of man is nearer in structure to that of the orang than the orang's is to that of the South American howler, and that the orang and howler are more nearly related in this regard than are the howler and the marmoset. The modifications presented by man have, then, resulted from an acceleration in development in some respects, and retardation perhaps in others. But nntil the combination now characteristic of the genus Homo was attained, the being could not properly be called man. And here it must be observed that as an organic type is char- ON THE HYPOTHESIS OF EVOLUTION. 147 acterized by the co-existence of a number of peculiarities which have been developed independently of each other, its distinctive features and striking functions are not exhibited until that co- existence is attained which is necessary for these ends. Hence, the characters of the human genus were probably de- veloped successively ; but few of the indications of human superi- ority appeared until the combination was accomplished. Let the opposable thumb be first perfected, but of what use would it be in human affairs without a mind to direct ? And of what use a mind without speech to unlock it ? xind speech could not be possible though all the muscles of the larynx but one were devel- oj^ed, or but a slight abnormal convexity in one pair of cartilages remained. It would be an objection of little weight could it be truly urged that there have as yet no remains of ape-like men been dis- covered, for we have frequently been called upon in the course of paleontological discovery to bridge greater gaps than this, and greater remain, which we expect to fill. But we have ape-like characters exhibited by more than one race of men yet existing. But the remains of that being which is supposed to have been the progenitor of man may have been discovered a short time since in the cave of Naulette, Belgium, with the bones of the extinct rhinoceros and elephant. We all admit the existence of higher and lower races, the latter being those which we now find to present greater or less approxi- mations to the apes. The peculiar structural characters that be- long to the negro in his most typical form are of that kind, how- ever great may be the distance of his remove therefrom. The flattening of the nose and prolongation of the jaws constitute such a resemblance ; so are the deficiency of the calf of the leg, and the obliquity of the pelvis, which approaches more the horizontal po- sition than it does in the Caucasian. The investigations made at Washington during the war with reference to the physical charac- teristics of the soldiers show that the arms of the negro are from one to two inches longer than those of the whites : another ap- proximation to the ape. In fact, this race is a species of the genus Homo, as distinct in character from the Caucasian as those we are accustomed to recognize in other departments of the ani- mal kingdom ; but he is not distinct by isolation, since intermedi- ate forms between him and the other species can be abundantly found. 148 GENERAL EVOLUTION. And here let it be particularly observed that two of the most prominent characters of the negro are those of immature stages of the Indo-European race in its characteristic types. The deficient calf is the character of infants at a very early stage ; but, what is more important, the flattened bridge of the nose and shortened nasal cartilages are universally immature conditions of the same parts in the Indo-European. Any one may convince himself of that by examining the physiognomies of infants. In some races — e. g., the Slavic — this undeveloped character persists later than in some others. The Greek nose, with its elevated bridge, coincides not only with assthetic beauty, but with developmental perfection. This is, however, only ^^ inexact parallelism," as the charac- ters of the hair, etc., can not be ex^^lained on this principle among existing races. The embryonic characters mentioned are probably a remnant of those characteristic of the primordial race or species. .But the man of Naulette, if he be not a monstrosity, is a still more distinct and ape-like species. The chin, that marked char- acter of other species of men, is totally wanting, and the dentition is quite approximate to the man-like apes, and different from that of modern men. The form is very massive, as in apes. That he was not abnormal is rendered probable by approximate characters seen in a jaw from the cave of Puy-sur-Aube, and less marked in the lowest races of Australia and New Caledonia. As to the single or multiple origin of man, science as yet fur- nishes no answer. It is very probable that, in many cases, the species of one genus have descended from corresponding species of another by change of generic characters only. It is a remarkable fact that the orang possesses the peculiarly developed malar bones and the copper color characteristic of the Mongolian inhabitants of the regions in which this animal is found, while the gorilla ex- hibits the prognathic jaws and black hue of the African races near whom he dwells. This kind of geographical imitation is very common in the animal kingdom. II. METAPHYSICAL EVOLUTIOIT. It is infinitely improbable that a being endowed with such ca- pacities for gradual progress, as man has exhibited, should have been full-fledged in accomplishments at the moment when he could first claim his high title, and abandon that of his simian ancestors. We are, therefore, required to admit the growth ot human intelligence from a primitive state of inactivity and abso- ON THE HYPOTHESIS OF EVOLUTION. 149 lute ignorance ; including the development of one important mode of its expression — speech ; as well as that of the moral qualities, and of man's social system — the form in which his ideas of moral- ity are first displayed. The expression '* evolution of morality" need not offend, for the question in regard to the laws of this evolution is the really important part of the discussion, and it is to the opposing views on this point that the most serious interest attaches. a. Development of Intelligence, If the brain is the organ of mind, we may be surprised to find that the brain of the intelligent man scarcely differs in structure from that of the ape. Whence, then, the difference of power? Though no one will now deny that many of the Mammalia are capable of reasoning upon observed facts, yet how greatly the re- sults of this capacity differ in number and importance from those achieved by human intelligence ! Like water at the temperatures of 50° and 53°, where we perceive no difference in essential char- acter, so between the brains of the lower and higher monkeys no difference of function or of intelligence is perceptible. But what a difference do the two degrees of temperature from 33° to 31° produce in water ! In like manner the difference between the brain of the higher ape and that of man is accompanied by a dif- ference in function and power, on which man's earthly destiny depends. In development, as with the water, so with the higher ape ; some Rubicon has been crossed, some floodgate has been opened, which marks one of Nature's great transitions, such as have been called ** expression-points" of progress. What point of progress in such a history would account for this accession of the powers of the human intelligence ? It has been answered, with considerable confidence — the power of speech. Let us picture man without speech. Each generation would learn nothing from its predecessors. Whatever originality or observa- tion might yield to a man would die with him. Each intellectual life would begin where every other life began, and would end at a point only differing with its original capacity. Concert of action, by which man's power over the material world is maintained, would not exceed, if it equaled, that which is seen among the bees ; and the material results of his labors would not extend be- yond securing the means of life and the employment of the sim- plest modes of defense and attack. 150 GENERAL EVOLUTION. The first men, therefore, are looked upon by tho develop- mentalists as extremely embryonic in all that characterizes hu- manity, and they appeal to the facts of history in support of this yiew. If they do not derive much assistance from written his- tory, evidence is found in the more enduring relics of human handiwork. The opposing view is, that the races which present or have presented this condition of inferiority or savagery have reached it by a process of degradation from a higher state — as some believe, through moral delinquency. This position may be true in certain cases, which represent perhaps a condition of senility, but in gen- eral we believe that savagery was the condition of the first man, which has in some races continued to the present day. /?. Evidence from ArchcBology. As the object of the present essay is not to examine fully into the evidences for the theories of evolution here stated, but rather to give a sketch of such theories and their connection, a few facts only will be noticed. Im'provement in the Use of Materials. — As is well known, the remains of human handiwork of the earliest periods consist of nothing but rude implements of stone and bone, useful only in procuring food and preparing it for use. Even when enterprise extended beyond the ordinary routine, it was restrained by the want of proper instruments. Knives and other cutting imple- ments of flint still attest the skill of the early races of men from Java to the Cape of Good Hope, from Egypt to Ireland, and through North and South America. Hatchets, spear-heads and ornaments of serpentine, granite, silex, clay slates, and all other suitable rock materials, are found to have been used by the first men, to the exclusion of metals, in most of the regions of the earth. Later, the probably accidental discovery of the superiority of some of the metals resulted in the substitution of them for stone as a material for cutting implements. Copper — the only metal which, while malleable, is hard enough to bear an imperfect edge — was used by succeeding races in the Old World and the New. Implements of this material are found scattered over extensive regions. So desirable, however, did the hardening of the material appear for the improvement of the cutting Q^ge, that combinations with other metals were sought for and discovered. The alloy with ON" THE HYPOTHESIS OF EVOLUTION. 151 tin, forming bronze and brass, was discovered and used in Enrojie, while that with silver appears to have been most readily produced in America, and was consequently used by the Peruvians and other nations. The discovery of the modes of reducing iron ores placed in the hands of man the best material for bringing to a shape convenient for his needs the raw material of the world. All im- provements in this direction made since that time have been in the quality of iron itself, and not through the introduction of any new metal. The prevalent phenomena of any given period are those which give it its character, and by which we distinguish it. But this fact does not exclude the co-existence of other phenomena belong- ing to prior or subsequent stages. Thus during the many stages of human progress there have been men more or less in advance of the general body, and their characteristics have given a pecul- iar stamp to the later and higher condition of the whole. It furnishes no objection to this view that we find, as might have been anticijoated, the stone, bronze, and iron periods overlapping one another, or men of an inferior culture supplanting in some cases a superior people. A case of this kind is seen in North America, where the existing *^ Indians," stone-men, have suc- ceeded the mound-builders, copper-men. The successional rela- tion of discoveries is all that it is necessary to prove, and this seems to be established. The period at which the use of metallic implements was intro- duced is unknown, but Whitney says that the language of the Aryans, the ancestors of all the modern Indo-Europeans, indicates an acquaintance with such implements, though it is not certain whether those of iron are to be included. The dispersion of the daughter races, the Hindoos, the Pelasgi, Teutons, Celts, etc., could not, it is thought, have taken j^lace later than 3000 b. c. — a date seven hundred years prior to that assigned by the old chro- nology to the Deluge. Those races co-existed with the Egyptian and Chinese nations, already civilized, and as distinct from each other in feature as they are now. Improvement in Architecture. — The earliest periods, then, were characterized by the utmost simplicity of invention and construc- tion. Later, the efforts for defense from enemies and for architect- ural display, which have always employed so much time and power, began to be made. The megalithic period has left traces 152 GENERAL EVOLUTION. over much of the earth. The great masses of stone piled on each other in the simplest form in Southern India, and the circles of stones planted on end in England at Stonehenge and Abury, and in Peru at Sillustani, are relics of that period. More complex are the great Himyaritic walls of Arabia, the works of the ances- tors of the Phoenicians in Asia Minor, and the titanic workmanship of the Pelasgi in Greece and Italy. In the iron age we find gra- nitic hills shaped or excavated into temples ; as, for example, everywhere in Southern India. Near Madura the circumference of an acropolis-like hill is cut into a series of statues in high re- lief, of sixty feet in elevation. Easter Island, composed of two volcanic cones, one thousand miles from the west coast of South America, in the bosom of the Pacific, possesses several colossi cut from the intrusive basalt, some in high relief on the face of the rock, others in detached blocks removed by human art from their original positions and brought nearer the sea-shore. Finally, at a more advanced stage, the more ornate and com- plex structures of Central America, of Cambodia, Nineveh and Egypt, represent the period of greatest display of architectural ex- penditure. The same amount of human force has perhaps never been expended in this direction since, though higher conceptions of beauty have been developed in architecture with increasing in- tellectuality. Man has passed through the block-and-brick building period of his boyhood, and should rise to higher conceptions of what is the true disposition of power for " him who builds for aye," and learn that *^ spectacle " is often the unwilling friend of j^rogress. No traces of metallic implements have ever been found in the salt-mines of Armenia, the turquoise-quarries in Arabia, the cities of Central America, or the excavations for mica in North Carolina, while the direct evidence points to the conclusion that in those places flint was exclusively used. The simplest occupations, as requiring the least exercise of mind, are the pursuit of the chase and the tending of flocks and herds. Accordingly, we find our first parents engaged in these occupations. Cain, we are told, was, in addition, a tiller of the ground. Agriculture in its simplest forms requires but little more intelligence than the pursuits just mentioned, though no employment is capable of higher development. If we look at the savage nations at present occupying nearly half the land surface of the earth, we shall find many examples of the former indus- ON THE HYPOTHESIS OF EVOLUTION. I53 trial condition of our race preserved to the present day. Many of them had no knowledge of the use of metals until they ob- tained it from civilized men who visited them, while their pur- suits were and are those of the chase, tending domestic animals, and rudimental agriculture. 7. Development of the Fine Arts. If we look at representation by drawing or sculpture, we find that the efforts of the earliest races of which we have any knowl- edge were quite similar to those which the untaught hand of in- fancy traces on its .slate or the savage depicts on the rocky faces of hills. The circle or triangle for the head and body, and straight lines for the limbs, have been preserved as the first at- tempts of the men of the stone period, as they are to this day tlie sole representations of the human form which the North American Indian places on his buffalo robe or mountain precipice. The stiff, barely outlined form of the deer, the turtle, etc., are liter- ally those of the infancy of civilized man. The first attempts at sculpture were marred by the influence of modism. Thus the idols of Cohan and Palenque, with human faces of some merit, are overloaded with absurd ornament, and deformed into frightful asymmetry, in compliance with the de- mand of some imperious mode. In later days we have the stiff, conventionalized figures of the palaces of Nineveh and the temples of Egypt, where the representation of form has somewhat improved, but is too often distorted by false fashion or imitation of some unnatural standard, real or artistic. This is distinsfuished as the day of archaic sculpture, which disappeared with the Etruscan nation. So the drawings of the child, when he abandons the simple lines, are stiff and awkward, and but a stage nearer true representation ; and how often does he repeat some peculiarity or absurdity of his own ! The introduction of the action and pose of life into sculpture was not known before the early days of Greece, and it was there that the art was brought to perfection. When art rose from its mediaeval slumber, much the same succession of development may be discovered. First, the stiff figures, with straightened limbs and cylindric drapery, found in the old Northern churches — then the forms of life that now adorn the porticoes and palaces of the cities of Germanv. 154 GENERAL EVOLUTION. d. Rationale of the Development of Intelligence. The history of material development shows that the transition from stage to stage of development, experienced by the most per- fect forms of animals and plants in their growth from the primor- dial cell, is similar to the succession of created beings which the geological epochs produced. It also shows that the slow assump- tion of main characters in the line of succession in early geological periods produced the condition of inferiority, while an increased rapidity of growth in later days has resulted in an attainment of superiority. It is not to be supposed that in ^^acceleration" the period of growth is shortened ; on the contrary, it continues the same. Of two beings whose characters are assumed at the same rate of succession, that with the quickest or shortest growth is necessarily inferior. ^^Acceleration" means a gradual increase of the rate of assumption of successive characters in the same period of time. A fixed rate of assumption of characters, with gradual increase in the length of the period of growth, would produce the same result — viz., a longer developmental scale and the attainment of an advanced position. The first is in part the relation of sexes of a species ; the last of genera, and of other types of creation. If from an observed relation of many facts we derive a law, we are permitted, when we see in another class of facts similar relations, to suspect that a similar law has operated, differing only in its ob- jects. We find a marked resemblance between the facts of struct- ural progress in matter and the phenomena of intellectual and spiritual progress. If the facts entering into the categories enumerated in the pre- ceding section bear us out, we conclude that in the beginning of human history the progress of the individual man was very slow, and that but little was attained to ; that, through the profitable direction of human energy, means were discovered from time to time by which the process of individual development in all meta- physical qualities has been accelerated ; and that up to the pres- ent time the consequent advance of the whole race has been at an increasing rate of progress. This is in accordance with the gen- eral principle, that high development in intellectual things is accomplished by rapidity in traversing the preliminary stages of inferiority common to all, while low develo^oment signifies slug- gishness in that progress, and a corresi^onding retention of in- feriority. ON THE HYPOTHESIS OF EVOLUTION. 155 How mucli meaning may we not see, from this standpoint, in the history of the intelligence of our little ones ! First they crawl, they walk on all-fours ; when they first assume the erect position they are generally speechless, and utter only inarticulate sounds. When they run about, stones and dirt, the objects that first meet the eye, are the delight of their awakening powers ; but these are all cast aside when the boy obtains his first jackknife. Soon, however, reading and writing open a new world to him ; and, finally, as a mature man he seizes the forces of Nature, and steam and electricity do his bidding in the active pursuit of power for still better and higher ends. So with the history of the species : first, the quadrumane ; then the speaking man, whose humble industry was, however, confined to the objects that came first to hand, this being the ** stone age" of i^re-historic time. When the use of metals was discovered, the range of industries expanded wonderfully, and the *^iron age " saw many striking efforts of human power. With the introduction of letters it became possible to record events and ex- periences, and the spread of knowledge was thereby greatly in- creased, and the delays and mistakes of ignorance correspondingly diminished in the fields of the world's activity. From the first we see in history a slow advance as knowledge gained by the accumulation of tradition and by improvements in habit based on experience ; but how slow was this advance while the use of the metals was still unknown ! The iron age brought with it not only new conveniences, but increased means of future progress ; and here we have an acceleration in the rate of advance. With the introduction of letters this rate was increased manifold, and in the application of steam we have a change equal in utility to any that has preceded it, and adding to the possibilities of fu- ture advance in many directions. By it power, knowledge, and means of happiness were to be distributed among the many. The uses to which human intelligence has successively applied the materials furnished by Nature have been — first, subsistence and defense ; second, the accumulation of power in the shape of a representative of that labor which the use of matter involves — in other words, the accumulation of wealth. The possession of this power involves new possibilities, for opportunity is offered for the special pursuits of knowledge and the assistance of the weak or undeveloped part of mankind in its struggles. Thus, while the first men possessed the power of speech, and 156 GENERAL EVOLUTION. could advance a little in knowledge through the accumulation of the experiences of their predecessors, they possessed no means of accumulating the power of labor, no control over the activity of numbers — in other words, no wealth. But the accumulation of knowledge finally brought this ad- vance about. The extraction and utilization of the metals, espe- cially iron, formed the most important step, since labor was thus facilitated and its productiveness increased in an incalculable de- gree. We have little evidence of the existence of a medium of ex- change during the first or stone period, and no doubt barter was the only form of trade. Before the use of metals, shells and other objects were used ; remains of money of baked clay have been found in Mexico. Finally, though in still ancient times, the pos- session of wealth in money gradually became possible and more common, and from that day to this avenues for reaching this stage in social progress have ever been opening. But wealth merely indicates a stage of progress, since it is but a comparative term. All men could not become rich, for in that case all would be equally poor. But labor has a still higher goal ; for, thirdly, as capital, it constructs and employs machinery, which does the work of many hands, and thus cheapens products, which is equivalent in effect to an accumulation of wealth to the consumer. And this increase of power may be used for the intel- lectual and spiritual advance of men, or, otherwise, at the will of the men thus favored. Machinery places man in the position of a creator, operating on Mature through an increased number of *' secondary causes." Development of intelligence is seen, then, in the following directions : First, in the knowledge of facts, including science ; second, in language ; and, as consequences of these, the accumula- tion of power by development — first, of means of subsistence ; and, second, of mechanical invention ; and, third, in the apprehension of beauty. Thus, we have two terms to start with in estimating the be- ginning of human development in knowledge and power : first, the primary capacities of the human mind itself ; second, a mate- rial world, whose infinitely varied components are so arranged as to yield results to the energies of that mind. For example, the transition-points of vaporization and liquefaction are so placed as to be within the reach of man's agents ; their weights are so fixed as to accord with the muscular or other forces which he is able to ON THE HYPOTHESIS OF EVOLUTION. 157 exert ; and other living organizations are subject to his conven- ience and rule, and not, as in previous geological periods, entirely beyond his control. These two terms being given, it is maintained that the present situation of the most civilized men has been at- tained through the operation of a law of mutual action and reac- tion — a law whose results, seen at the present time, have depended on the acceleration or retardation of its rate of action ; which rate has been regulated, according to the degree in which a third great term, viz., the law of moral or (what is the same thing) true re- ligious development, has been combined in the plan. What it is necessary to establish in order to prove the above hypothesis is — I. That in each of the particulars above enumerated the devel- opment of the human species is similar to that of the individual from infancy to maturity. II. That from a condition of subserviency to the laws of mat- ter, man's intelligence enables him, by an accumulation of power, to become in a sense independent of those laws, and to pursue a course of intellectual and spiritual progress. III. That failure to accomplish a moral or spiritual develop- ment will again reduce him to a subserviency to the laws of matter. This brings us to the subject of moral development. And here I may be allowed to suggest that the weight of the evidence is opposed to the philosophy, ^' falsely so called," of necessitarianism, which asserts that the first two terms alone were sufficient to work out man's salvation in this world and the next ; and, on the other hand, to that anti-philosophy which asserts that all things in hu- man progress, intellectual and moral, are regulated by immediate divine interposition instead of through instrumentalities. Hence, the subject divides itself at once into two great departments — viz., that of the development of mind or intelligence, and that of the development of morality. That these laws are distinct there can be no doubt, since in the individual man one of them may produce results without the aid of the other. Yet it can be shown that each is the most in- valuable aid and stimulant to the other, and most favorable to the rapid advance of the mind in either direction. III. SPIRITUAL OR MORAL DEVELOPMENT. In examining this subject, we first inquire (Section a) whether there is any connection between physical and moral or religious 158 GENERAL EVOLUTION. development ; then (/3), what indications of moral development may be derived from history. Finally (y), a correlation of the results of these inquiries, with the nature of the religious develop- ment in the individual, is attempted. Of course in so stupendous an inquiry but a few leading points can be presented here. If it be true that the period of human existence on the earth has seen a gradually increasing predominance of higher motives over lower ones among the mass of mankind, and if any parts of our metaphysical being have been derived by inheritance from pre-existent beings, we are incited to the inquiry whether any of the moral qualities are included among the latter ; and whether there be any resemblance between moral and intellectual develop- ment. Thus, if there have been a physical derivation from a pre- existent genus, and an embryonic condition of those physical characters which distinguish Homo — if there has been also an embryonic or infantile stage in intellectual qualities — we are led to inquire whether the development of the individual in moral nature will furnish us with a standard of estimation of the suc- cessive conditions or present relations of the human species in this aspect also. a. Belations of Physical and Moral Nature. Although, cmteris paribus, men are much alike in the deeper qualities of their nature, there is a range of variation which is best understood by a consideration of the extremes of such varia- tion as seen in men of different latitudes, and women and chil- dren. {a) In Children. — Youth is distinguished by a peculiarity, which no doubt depends upon an immature condition of the nerv- ous center concerned, which might be called nervous impressi- bility. It is exhibited in a greater tendency to tearfulness, in timidity, less mental endurance, a greater facility in acquiring knowledge, and more ready susceptibility to the influence of sights, sounds, and sensations. In both sexes the emotional nature predominates over the intelligence and judgment. In those years the character is said to be in embryo, and theologians, in using the phrase, '* reaching years of religious understanding," mean that in early years the religious capacities undergo develop- ment coincidentally with those of the body. {h) In Women. — If we examine the metaphysical characteris- ON THE HYPOTHESIS OF EVOLUTION. 159 tics of women, we observe two classes of traits— namely, those which are also found in men, and those which are absent or but weakly developed in men. Those of the first class are very similar in essential nature to those which men exhibit at an early stage of development. This may be in some way related to the fact that physical maturity occurs earlier in women. The gentler sex is characterized by a greater impressibility, often seen in the influence exercised by a stronger character, as well as by music, color, or spectacle generally ; warmth of emo- tion, submission to its influence rather than that of logic ; ti- midity and irregularity of action in the outer world. All these qualities belong to the male sex, as a general rule, at some period of life, though different individuals lose them at very various periods. Euggedness and sternness may rarely be developed in infancy, yet at some still prior time they certainly do not exist in any. Probably most men can recollect some early period of their lives when the emotional nature predominated — a time when emotion at the sight of suffering was more easily stirred than in maturer years. I do not now allude to the benevolence inspired, kept alive, or developed by the influence of the Christian religion on the heart, but rather to that which belongs to the natural man. Perhaps all men can recall a period of youth when they were hero-worshipers — when they felt the need of a stronger arm, and loved to look up to the powerful friend who could sympathize with and aid them. This is the ^* woman stage " of character : in a large number of cases it is early passed ; in some it lasts longer ; while in a very few men it persists through life. Severe disciiDline and labor are unfavorable to its persistence. Luxury preserves its bad qualities without its good, while Christianity j)reserves its good elements without its bad. It is not designed to say that woman in her emotional nature does not differ from the undeveloped man. On the contrary, though she does not differ in kind, she differs greatly in degree, for her qualities grow with her growth, and exceed m poiver many fold those exhibited by her companion at the original point of departure. Hence, since it might be said that man is the unde- veloped woman, a word of explanation will be useful. Embryonic types abound in the fields of nature, but they are not therefore immature in the usual sense. Maintaining the lower essential quality, they yet exhibit the usual results of growth in individual 160 GENERAL EVOLUTION. characters ; that is, increase of strength, powers of support and protection, size and beauty. In order to maintain that the mas- culine character coincides with that of the undeveloped woman, it would be necessary to show that the latter during her infancy possesses the male characters predominating — that is, unimpressi- bility, judgment, physical courage, and the like. If we look at the second class of female characters — nameh', those which are imperfectly developed or absent in men, and in respect to which man may be called undeveloped woman — we note three prominent points : facility in language, tact or finesse, and the love of children. The first two appear to me to be alto- gether developed results of ^^impressibility," already considered as an indication of immaturity. Imagination is also a quality of impressibility, and, associated with finesse, is apt to degenerate into duplicity and untruthfulness — a i^eculiarity more natural to women than men. The third quality is different. It generally appears at a very early period of life. Who does not know how soon the little girl selects the doll, and the boy the toy-horse or machine ? Here man truly never gets beyond undeveloped woman. Nevertheless, ^^impressibility" seems to have a great deal to do with this quality also. Thus the metaphysical relation of the sexes would appear to be one of inexact parallelism, as defined in Section I. That the physical relation is a remote one of the same kind, several charac- ters seem to point out. The case of the vocal organs will suffice. Their structure is identical in both sexes in early youth, and botii produce nearly similar sounds. They remain in this condition in the woman, while they undergo a metamorjohosis and change both in structure and vocal power in the man. In the same way, in many of the lower creation, the females possess a majority of em- bryonic features, though not invariably. A common example is to be found in the plumage of birds, where the females and young males are often undistinguishable.* But there are a few points in * Meehan states that the upper limbs and stronc^ laterals in Coniferge and other trees produce female flowers and cones, and the lower and more interior branches the male flowers. He calls the former condition one of greater " vigor," and the latter one of *' weakness," and argues that the vigorous condition of growth pro- duces females, and the weaker males. What he points out, however, is in harmony with the position here maintained — namely, that the female characters include more of those which are embryonic in the males than the male characters include of those ON THE HYPOTHESIS OF EVOLUTION. id the physical structure of man also in which the male condition is the immature one. In regard to structure, the point at which the relation between the sexes is that of exact parallelism, or where the mature condition of the one sex accords with the unde- veloped condition of the other, is when reproduction is no longer accomplished by budding or gemmation, but requires distinct organs. Metaphysically, this relation is to be found where dis- tinct individuality of the sexes first appears ; that is, where we pass from the hermaphrodite to the bisexual condition. But let us put the whole interpretation on this partial unde- velopment of woman. The types or conditions of organic life which have been the most prominent in the world's history— the Ganoids of the first, the Dinosaurs of the second, and the Mammoths of the third period— have generally died with their day. The line of succes- sion has not been from them. The law of anatom.y and paleon- tology is, that we must seek the point of departure of the type which is to predominate in the future, at lower stages on the line, in less decided forms, or in what, in scientific parlance, are called generalized types. In the same way, though the adults of the tailless apes are in a physical sense more highly developed than their young, yet the latter far more closely resemble the human species in their large facial angle and shortened jaws. How much significance, then, is added to the law uttered by Christ ! — ^'Except ye become as little children, ye can not enter the kingdom of heaven.'^ Submission of will, loving trust, con- fiding faith — these belong to the child : how strange they appear to the executing, commanding, reasoning man ! Are they so strange to the woman ? We all know the answer. Woman is nearer to the point of departure of that development which out- lives time and j^eoples heaven ; and if man would find it, he must retrace his steps, regain something he lost in youth, and join to which are embryonic in the female : the female flowers are the product of the younger and more growing portions of the tree — that is, those last produced (the upper limbs and new branches) — while the male flowers are produced by the older or more mature portions — that is, lower limbs or more axial regions. Further, we are not accustomed to regard the condition of rapid growth as that of great vigor in animals, but rather ascribe that quality to maturity, after such growth has ceased. Meehan's observations coincide with those of Thury and others on the origin of sexes in animals and plants, which it appears to me admit of a similar explana- tion. 11 102 GENERAL EVOLUTIOI^. the powers and energies of his character the suhmission, love and faith which the new birth alone can give. Thus the summing up of the metaphj'sical qualities of woman would be thus expressed : In the emotional world, man's superior ; in the moral world, his equal ; in the laboring world, his inferior. There are, however, vast differences in women in respect to the number of masculine traits they may have assumed before be- ing determined into their own special development. Woman also, under the influence of necessity, in later years of life, may add more or less to those qualities in her which are fully developed in the man. The relation of these facts to the principles stated as the two opposing laws of development is, it apjDcars to me, to be exjolained thus : First, that woman's most inherent peculiarities are not the result of the external circumstances with which she has been j)laced in contact, as the conflict theory would indicate. Such circumstances are said to be her involuntary subserviency to the physically more powerful man, and the effect of a compulsory mode of life in preventing her from attaining a position of equali- ty in the activities of the world. Second, that they are the result of the different distributions of qualities as already indicated by the harmonic theory of development ; that is, of the unequal posses- sion of features which belong to different periods in the develop- mental succession of the highest. There is then another beauti- ful harmony which will ever remain, let the development of each sex be extended as far as it may. (c) In Men. — If we look at the male sex, we shall find various exceptional approximations to the female in mental constitution. Further, there can be little doubt that in the Indo-European race maturity in some respects appears earlier in tropical than in northern regions ; and though subject to many exceptions, this is sufficiently general to be looked upon as a rule. Accordingly, we find in that race — at least in the warmer regions of Europe and America — a larger proportion of certain qualities which are more universal in women ; as greater activity of the emotional nature when compared with the judgment ; an impressibility of the nerv- ous center, which, cmteris paribus, appreciates quickly the har- monies of sound, form, and color ; answers most quickly to the friendly greeting or the hostile menace ; is more careless of conse- quences in the material expression of generosity or hatred, and more indifferent to truth under the influence of personal relations. ON THE HYPOTHESIS OF EVOLUTION. 1^3 The movements of the body and expressions of the countenance answer to the temperament. More of grace and elegance in the bearing marks the Greek, the Italian, and the Creole, than the German, the Englishman, or the Green Mountain man. More of vivacity and fire, for better or for worse, is displayed in the coun- tenance. Perhaps the more northern type left all that behind in its youth. The rugged, angular character which appreciates force better than harmony, the strong intellect which delights in fore- thought and calculation, the less impressibility, reaching stolidity in the uneducated, are its well-known traits. If there be in such a character less generosity and but little chivalry, there is persist- ency and unwavering fidelity, not readily obscured by the light- ning of passion or the surmises of an active imagination. All these peculiarities appear to result, first, from different de- grees of quickness and depth in appreciating impressions from without ; and, seco7id, from differing degrees of attention to the intelligent judgment in consequent action. (I leave conscience out, as not belonging to the category of inherited qualities.) The above observations have been confined to the Indo-Euro- pean race. It may be objected to the theory that savagery means immaturity in the senses above described, as dependent largely on "impressibility," while savages in general display the least '* im- pressibility," as that word is generally understood. This can not be asserted of the Africans, who, so far as we know them, possess this peculiarity in a high degree. Moreover, it must be remem- bered that the state of indifference which precedes that of impress- ibility in the individual may characterize many savages ; while their varied peculiarities may be largely accounted for by recol- lecting that many combinations of different species of emotion and kinds of intelligence go to make up the complete result in each case. (d) Conclusions. — Three types of religion may be selected from the developmental conditions of man : first, an absence of sensibility (early infancy) ; second, an emotional stage more pro- ductive of faith than of works ; thirdly, an intellectual type, more favorable to works than faith. Though in regard to responsibility these states may be equal, there is absolutely no gain to laboring humanity from the first type, and a serious loss in actual results from the second, taken alone, as compared with the third. These, then, are the physical vehicles of religion— \i the phrase 164 GENERAL EVOLUTION. may be allowed — which give character and tone to the deeper spiritual life, as the color of the transparent vessel is communi- cated to the light which radiates from within. But if evolution has taken place, there is evidently a provision for the progress from the lower to the higher states, either in the education of circumstances (^^ conflict ") or in the power of an in- terior spiritual influence {'' harmony "), or both. p. Evidence derived from History. We trace the development of Morality in — first, the family, or social order ; second, the civil order, or government. Whatever may have been the extent of moral ignorance before the Deluge, it does not appear that the earth was yet prepared for the permanent habitation of the human race. All nations preserve traditions of the drowning of the early peoples by floods, such as have occurred frequently during geologic time. At the close of each period of dry land, a period of submergence has set in, and the depression of the level of the earth, and consequent overflow by the sea, has caused the death and subsequent preservation of the remains of the fauna and flora living upon it, while the eleva- tion of the same has produced that interruption in the process of deposit in the same region which marks the intervals between ge- ologic periods. Changes in these respects do not occur to any very material extent at the present time in the regions inhabited by the most highly developed portions of the human race ; and as the last which occurred seems to have been expressly designed for the preparation of the earth's surface for the occupation of organized human society, it may be doubted whether many such changes are to be looked for in the future. The last great flooding was that which stratified the drift materials of the north, and carried the finer portions far over the south, determining the minor topogra- phy of the surface and supplying it with soils. The existence of floods which drowned many races of men may be considered as established. The men destroyed by the one re- corded by Moses are described by him as exceedingly wicked, so that ^'i\\Q earth was filled with violence." In his ej-es the Flood was designed for their extermination. That their condition was evil must be fully believed if they were condemned by the executive of the Jewish law. This law, it will be remembered, permitted polygamy, slavery, revenge, ag- gressive war. The Jews were expected to rob their neighbors, the ON THE HYPOTHESIS OF EVOLUTION. 165 Egyptians, of jewels, and they were allowed *' an eye for an eye and a tooth for a tooth." They were expected to butcher other nations, with their women and children, their flocks and their herds. If we look at the lives of men recorded in the Old Testa- ment as examples of distinguished excellence, we find that their standard, however superior to that of the people around them, would ill accord with the morality of the present day. They were all polygamists, slaveholders, and warriors. Abraham treated Ha- gar and Ishmael with inhumanity. Jacob, with his mother's aid, deceived Isaac, and received thereby a blessing which extended to the whole Jewish nation. David, a man whom Paul tells us the Lord found to be after his own heart, slew the messenger who brought tidings of the death of Saul, and committed other acts which would stain the reputation of a Christian beyond redemp- tion. It is scarcely necessary to turn to other nations if this be true of the chosen men of a chosen people. History, indeed, pre- sents us with no people prior to, or contemporary with, the Jews who were not morally their inferiors.* If we turn to more modern periods, an examination of the mo- rality of Greece and Rome reveals a curious intermixture of lower and higher moral conditions. "While each of these nations pro- duced excellent moralists, the influence of their teachings was not sufficient to elevate the masses above what would now be regarded as a very low standard. The popularity of those scenes of cruelty, the gladiatorial shows and the combats with wild beasts, sufficiently attests this. The Roman virtue of patriotism, while productive of many noble deeds, is in itself far from being a disinterested one, but partakes rather of the nature of partisanship and selfish- ness. If the Greeks were superior to the Romans in humanity, they were apparently their inferiors in the social virtues, and were much below the standard of Christian nations in both resj^ects. Ancient history points to a state of chronic war, in which tlie social relations were in confusion, and the develoi3ment of the useful arts was almost impossible. Savage races, which continue to this day in a similar moral condition, are, we may easily be- lieve, most unhappy. They are generally divided into tribes, which are mutually hostile, or friendly only with the view of in- juring some other tribe. Might is their law, and robbery, rapine. * The evidence on this point being very imperfect, judgment may be properly suspended. (Ed. 1886.) 166 GENERAL EYOLUTIOK and murder express their mutual relations. This is the history of the lowest grade of barbarism, and the history of primeval man so far as it has come down to us in sacred and profane records. Man as a species first appears in history as a sinful being. Then a race maintaining a contest with tlie prevailing corruption and exhibit- ing a higher moral idea is presented to us in Jewish history. Fi- nally, early Christian society exhibits a greatly superior condition of things. In it polygamy scarcely existed, and slavery and war were condemned. But jorogress did not end here, for our Lord said, *^I have yet many things to say unto you, but ye can not bear them now. Howbeit, when he, the sj)irit of truth, is come, he will guide you into all truth." The progress revealed to us by history is truly great, and if a similar difference existed between the first of the human sj^ecies and the first of whose condition we have information, we can con- ceive how low the oi'igin must have been. History begins with a considerable progress in civilization, and from this we must infer a long preceding period of human existence, such as a gradual evolution would require. y. Rationale of Moral Development, I. Of the Species. — Let us now look at the moral condition of the infant man of the present time. We know his small account- ability, his trust, his innocence. We know that he is free from the law that when he *^ would do good, evil is present with him," for good and evil are alike unknown. We know that until growth has progressed to a certain degree he fully deserves the praise pro- nounced by our Saviour, that "of such is the kingdom of heaven." Growth, however, generally sees a change. We know that the buddings of evil appear but too soon ; the lapse of a few months sees exhibitions of anger, disobedience, malice, falsehood, and their attendants — the fruit of a corruption within not manifested before. In early youth it may be said that moral susceptibility is often in inverse ratio to physical vigor. But with growth the more physically vigorous are often sooner taught the lessons of life, for their energy brings them into earlier conflict with the antagonisms and contradictions of the world. Here is a beautiful example of the benevolent principle of compensation. 1. Innocence and the Fall. — If physical evolution be a reality, we have reason to believe that the infantile stage of human mor- ON THE HYPOTHESIS OF EVOLUTION. 157 als, as well as of human intellect, was much prolonged in the his- tory of our first parents. This constitutes the period of human purity, when we are told by Moses that the first pair dwelt in Eden. But the growth to maturity saw the development of all the qualities inherited from the irresponsible denizen of the forest. Man inherits from his predecessors in the creation the buddino-s of reason — he inherits passions, propensities, and appetites. His cor- ruption is that of his animal progenitors, and his sin is the low and bestial instinct of the brute creation. Thus only is the origin of sin made clear — a problem which the pride of man would have explained in any other way had it been possible. But how startling the exhibition of evil by this new being as compared with the scenes of the countless ages already past ! Then the right of the strongest was God's law, and rapine and destruc- tion were the history of life. But into man had been ^''breathed the breath of life," and he had "■ become a Jiving soul." The law of right, the Divine Spirit, was planted within him, and the laws of the beast were in antagonism to that law. The natural devel- opment of his inherited qualities necessarily brought him into col- lision with that higher standard planted within him, and that war was commenced which shall never cease "till he hath put all things under his feet." The first act of man's disobedience con- stituted the Fall, and with it would come the first intellectual "knowledge of good and of evil" — an apprehension up to that time derived exclusively from the divinity within, or conscience.* 2. Free Agency. — Heretofore development had been that of physical types, but the Lord had rested on the seventh day, for man closed the line of the physical creation. Now a new develop- ment was to begin — the development of mind, of morality, and of grace. On the previous days of Creation all had progressed in accord- ance with inevitable law apart from its objects. Now, two lines * In our present translation of Genesis, the Fall is ascribed to the influence of Satan assuming the form of the serpent, and this animal was cursed in consequence, and compelled to assume a prone position. This rendering may well be revised, since serpents, prone like others, existed in both America and Europe during the Eocene epoch, five times as great a period before Adam as has elapsed since his day. Clark states, with great probability, that "serpent" should be translated monkey or ape — a conclusion, it will be observed, exactly comciding with our inductions on the basis of evolution. The instigation to evil by an ape merely states inheritance in another form. His curse, then, refers to the retention of the horizontal position re- tained by all other quadrumana, as we find it at the present day. 168 GENERAL EVOLUTION. of development were at the disposal of this being, between which his free will was to choose. Did he choose the courses dictated by the spirit of the brute, he was to be subject to the old law of the brute creation — the right of the strongest and spiritual death. Did he choose the guidance of the Divine Guest in his heart, he became subject to the laws which are to guide — 1, tlie human spe- cies to an ultimate ]3erfection, so far as consistent with this world ; and, 3, the individual man to a higher life, where a new existence awaits him as a spiritual being, freed from the laws of terrestrial matter. The charge brought against the theory of development, that it implies a necessary progress of man to all perfection without his co-operation — or necessitarianism, as it is called — is unfounded. The free will of man remains 'the source alike of his j^i'ogress and his relapse. But the choice once made, the laws of spiritual development are apparently as inevitable as those of matter. Thus men whose religious capacities are increased by attention to the Divine Monitor within are in the advance of progress — progress coinciding with that which in material things is called the har- monic. On the other hand, those whose motives are of the lower origin fall under the working of the law of conjlict. The lesson derivable from the preceding considerations would seem to be *^ necessitarian " as respects the whole human race, con- sidered by itself ; and. I believe it is to be truly so interpreted. That is, the Creator of 'all things has set agencies at work which will slowly develop a perfect humanity out of his lower creation, and nothing can thwart the jDrocess or alter the result. '' My word shall not return unto me void, but it shall accomplish that which I please, and it shall prosper in the thing whereto I sent it.^' This is our great encouragement, our noblest hope — second only to that which looks to a blessed inheritance in anotlier world. It is this thought that should inspire the farmer, who, as he toils, wonders, " Why all this labor ? The Good Father could have made me like the lilies, who, though they toil not, neither spin, are yet clothed in glory ; and why should I, a nobler being, be subject to the dust and the sweat of labor ? " This thought should enlighten every artisan of the thousands that people the factories and guide their whirling machinery in our modern cities. Every revolution of a wheel is moving the car of progress, and the timed stroke of the crank and the rhythmic throw of the shuttle are but the music the spheres have sung since time began. A new significance then OiT THE HYPOTHESIS OF EVOLUTION. 169 appears in the prayer of David : '^ Let the beauty of the Lord our God be upon us, and establish thou the work of our hands upon us : the work of our hands, Lord, establish thou it." But, be- ware of the catastrophe, for '* He will sit as a refiner"; ''The wheat shall be gathered into barns, but the chaff shall be burned with unquenchable fire." If this be true, let us look for — 3. The Extinction of Evil. — How is necessitarianism to be reconciled with free will ? It appears to me, thus : When a being whose safety depends on the perfection of a system of laws aban- dons the system by which he lives, he becomes subject to that lower grade of laws which govern lower intelligences. Man, falling from the laws of right, comes under the dominion of the laws of brute force ; as said our Saviour, " Salt is good, but if the salt have lost his savor, it is thenceforth good for nothing but to be cast forth and trodden under foot of men." In estimating the practical results to man of the actions prompted by the lower i^ortion of our nature, it is only necessary to carry out to its full development each of those animal qualities which may in certain states of society be restrained by the social system. In human history those qualities have repeatedly had this development, and the battle of progress is fought to decide whether they shall overthrow the system that restrains them, or be overthrown by it. Entire obedience to the lower instincts of our nature insures destruction to the weaker, and generally to the stronger also. A most marked case of this kind is seen where the developed vices of civilization are introduced among a savage peo2:)le — as, for exam- ple, the Korth American Indians. These seem in consequence to be hastening to extinction. But a system or a circuit of existence has been allotted to the civil associations of the animal species man, independently of his moral development. It may be briefly stated thus : Eaces begin as poor offshoots or emigrants from a parent stock. The law of labor develops their powers, and increases their wealth and num- bers. These will be diminished by their various vices ; but, on the whole, in proportion as the intellectual and economical ele- ments prevail, wealth will increase — that is, they accumulate power. When this has been accomplished, and before activity has slackened its speed, the nation has reached the culminating point, and then it enters upon the period of decline. The re- straints imposed by economy and active occupation being removed. 170 GENERAL EVOLUTION. the beastly traits find in accumulated power only increased means of gratification, and industry and prosperity sink together. Power is squandered, little is accumulated, and the nation goes down to its extinction amid scenes of internal strife and vice. Its cycle is soon fulfilled, and other nations, fresh from scenes of labor, as- sault it, absorb its fragments, and it dies. This has been the world's history, and it remains to be seen whether the virtues of the nations now existing will be suflQcient to save them from a like fate. Thus the history of the animal man in nations is wonderfully like that of the type or families of the animal and vegetable king- doms during geologic ages. They rise, they increase, and reach a period of multiplication and power. The force allotted to them becoming exhausted, they diminish and sink and die. II. Of the Individual. — In discussing physical development, we are as yet compelled to restrict ourselves to the evidence of its existence and some laws observed in the operation of its causative force. What that force is, or what are its primary laws, we know- not. So, in the progress of moral development, we endeavor to prove its existence and the mode of its operation, but why that mode should exist, rather than some other mode, we can not explain. The moral j)rogress of the species depends, of course, on the moral progress of the individuals embraced in it. Eeligion is the sum of those influences which determine the motives of men's actions into harmony with the divine perfection and the divine will. Obedience to these influences constitutes the practice of religion, while the statement of the growth and operation of these influences constitutes the theory of religion, or doctrine. The Divine Spirit j^lanted in man shows him that which is in harmony with the Divine Mind, and it remains for his free will to conform to it or reject it. This harmony is man's highest ideal of happiness, and in seeking it, as well as in desiring to flee from dissonance or pain, he but obeys the disposition common to all conscious beings. If, however, he attemj)ts to conform to it, he will find the law of evil present, and frequently obtaining the mastery. If now he be in any degree observing, he will find that the laws of morality and right are the only ones by which human society exists in a condition superior to that of the lower animals, and in which the capacities of man for happiness can approach a ON THE HYPOTHESIS OF EVOLUTION. 171 state of satisfaction. He may be then said to be ^'awakened" to the importance of religion. If he carry on the struggle to attain to the high goal presented to his spiritual vision, he will be deeply grieved and humbled at his failures ; then he is said to be '' con- victed." Under these circumstances the necessity of a deliverance becomes clear, and is willingly accepted in the only way in which it has pleased the Author of all to present it, which has been epito- mized by Paul as " the washing of regeneration and renewal of the Holy Spirit through Jesus Christ." Thus a life of advanced and ever-advancing moral excellence becomes possible, and the man makes nearer approaches to the *' image of God." Thus is opened a new era in spiritual development, which we are led to believe leads to an ultimate condition in which the na- ture inherited from our origin is entirely overcome, and an exist- ence of moral perfection entered on. Thus, in the book of Mark the simile occurs : ^^ First the blade, then the ear, after that the full corn in the ear" ; and Solomon says that the development of righteousness "shines more and more unto the perfect day." 8. Summary. If it be true that general development in morality proceeds in spite of the original predominance of evil in the world, through the self-destructive nature of the latter, it is only necessary to ex- amine the reasons why the excellence of the good may have been subject also to progress, and how the remainder of the race may have been influenced thereby. The development of morality is then probably to be understood in the following sense : Since the Divine Spirit, as the prime force in human progress, can not in itself be supposed to have been in any way under the influence of natural laws, its capacities were no doubt as eternal and unerring in the first man as in the last. But the facts and probabilities discussed above point to development of religious sensiUlity, or capacity to appreciate moral good, or to receive impressions from the source of good. The evidence of this is supposed to be seen m— first, improve- ment in man's views of his duty to his neighbor ; and, second, the substitution of spiritual for symbolic religions : in other words, improvement in the capacity for receiving spiritual impressions. What the primary cause of this supposed development of re- ligious sensibility may have been, is a question we reverently leave untouched. Tliat it is intimately connected in some way with, 172 GENERAL EVOLUTION. and in part dejoendent on, the evolution of tlie intelligence, appears very probable ; for this evolution is seen — 'first, in a better under- standing of the consequences of action, and of good and of evil in many things ; and, second, in the production of means for the spread of the special instrumentalities of good. The following may be enumerated as such instrumentalities : 1. Furnishing literary means of record and distribution of the truths of religion, morality, and science. 2. Creating and increasing modes of transportation of teachers and literary means of disseminating truth. 3. Facilitating the migration and the spread of nations holding the highest position in the scale of morality. 4. The increase of wealth, which multiplies the extent of the preceding means. And now, let no man attempt to set bounds to this develop- ment. Let no man say even that morality accomplished is all that is required of mankind, since that is not necessarily the evidence of a spiritual development. If a man possess the capacity for prog- ress beyond the condition in which he finds liimself, in refusing to enter upon it he declines to conform to the divine law. For *'from those to whom little is given, little is required, but from those to whom much is given, much shall be required." V. THE METHOD OF CREATION OF ORGANIC FORMS. Chapter I — Ox the Law of Acceleration and Retardation. — !N"ature of law of Natural Selection. Two kinds of evidence. Illustration. Examples from Cervidae, HelicidaB, insects and men. Chapter II — The Law of Repetitive Addition. — Segment and cell- repetition. Illustration from limbs and vertebral column. A, On seg- ment addition ; definitions. On repetition in bilateral and antero-pos- terior symmetry ; in structure of compound teeth ; in segments of Articulata; limbs of Reptilia ; brain of lain prey. B, On cell-repetition ; simple segment a repetition of cells; simple diverticulum the same. The cell theory ; the nucleated cell. C, Synthesis of repetition. From unicellular to multicellular animals; simple repetition to compound repetition ; Actinia, Lepidosiren, Ichthyosaurus, Plesiosaurus, Toenia ; the heart; mammalian teeth. D, On growth-force; relation to other forces; definition. E, Direction of repetition, its location, centrifugal and longitudinal ; movements longitudinal. Inheritance ; its relation to growth-force. Chapter III — The Law of Use and Effort. — Points to be investigated. A, On the location of growth-force. Relation of efi'ort to use. Rudi- mental characters. Examples of growth under influence of physical laws ; Examples of colors under influence of light. Use and disuse of gills. Rattlesnake ; horned animals. Teeth of ruminants. B, Change in amount of growth-force. Local increase of growth-force. Convo- luted structures; brain, teeth, cotyledons. Absolute loss of growth- force. Teeth and toes of Ruminants ; incisors of Rodents. Chapter IY — On Grade Influence. — A, On the nature of Grade In- fluence or Bathmism. Definitions. In plants; in animals. Increase in time of Bathmism and growth-force. Vital forces and vital in- fluences. Thought-force. Origin of Bathmism in time. B, Physio- logical origin of Bathmism. Function of nervous system in force- conversion. Automatic and habitual movements. Eflfect on nervous system. Chapter V — Intelligent Selection.— Development of intelligence. Stim- uli to use. Compulsion, Choice ; Bees, Food, Rattlesnake ; Change of color; Mimetic analogy ; Examples. Development of character. In the present state of biological science, essays like the pres- ent can only be tentative in so far as they treat of the laws of evo- 174 GENERAL EVOLUTION". lution. Nevertheless the present time is pre-eminently one of generalization in this field, and properly so. Facts have been ac- cumulating for a long period, and are now sufficiently numerous to yield important results, under proper classification and induc- tion. Darwin led the way in this work, and the development hypothesis is regarded as demonstrated by most biologists. The discussion of the laws of its progress involves a multitude of subordinate hypotheses. In the following essay, these are ar- ranged under five prominent heads, viz. : 1. The law of Accelera- tion and Eetardation; 2. The law of Repetitive Addition; 3. The law of Use and Effort; 4. The law of Grade Influence; 5. The law of Intelligent Selection. Of these, the first and second are regarded by the author as demonstrated, the third and fourth as only reduced to a partial demonstration, while the fifth is a con- sequence of the third, and stands or falls with it. The discussion of this subject divides itself into two parts, viz. : a consideration of the proof that evolution of organic types or descent with modification has taken place ; and, secondly, the investigation of the laws in accordance with which this develop- ment has progressed. As the latter involves the use of the evi- dence included in the former, I will not devote a special chapter to the proof for evolution. The influences and forces which have operated to produce the type structures of the animal kingdom have been plainly of two kinds : 1. Originative ; 2. Directive. The prime importance of the former is obvious ; that the latter is only secondary in the order of time or succession is evident from the fact that it con- trols the preservation or destruction of the results or creations of the first, and thus furnishes the bases of the exhibitions of the originative forces in the production of the successive generations of living beings. Wallace and Darwin have propounded as the cause of modifi- cation in descent their law of natural selection. This law has been epitomized by Spencer as the ''survival of the fittest." This neat expression no doubt covers the case, but it leaves the origin of the fittest entirely untouched. Darwin assumes a ''tendency to variation" in nature, and it is plainly necessary to do this, in order that materials for the exercise of a selection should exist. Darwin and Wallace's law is, then, only restrictive, directive, conservative, or destructive of something already created. I propose then to seek for the originative laws by which these sub- THE METHOD OF CREATION OF ORGANIC FORMS. 175 jects are furnished — in other words, for the causes of the origin of the fittest. It has seemed to the author so clear from the first as to re- quire no demonstration, that natural selection includes no ac- tively progressive principle whatever ; that it must first wait for the development of variation, and then, after securing the survival of the best, wait again for the best to project its owm variations for selection. In the question as to whether the latter are any better or worse than the characters of the parent, natural selec- tion m no wise concerns itself. I. ON THE LAW OF ACCELEKATION" A:N"D RETAEDATIO]!^-. There are two modes of demonstration of evolution, both de- pending on direct observation. One of these has been success- fully presented by Darwin. He has observed the origin of varieties in animals and plants, either in the domesticated or wild states, and has shown, what had been known to many, the lack of distinction in the grades of difference which separate varieties and species. But he has also pointed out that species (such, so far, as distinctness goes) have been derived from other species among domesticated animals, and he infers by induction that other species, wiiose origin has not been observed, have also descended from common parents. So far I believe his induction to be justified ; but when from this basis evolution of divisions defined by important structural characters, as genera, orders, classes, etc., is inferred, I believe that we do not know enough of the uniformity of Nature's processes in the premises to enable us to regard this kind of proof as conclusive. I therefore appeal to another mode of proving it, and one which covers the case of all the more really structural features of animals and plants. It is well known that in both kingdoms, in a general way, the young stages of the more perfect types are represented or imi- tated with more or less exactitude by the adults of inferior ones. But a true identity of these adults with the various stages of the higher has, comparatively, rarely been observed. Let such a case be supposed. In A we have four species whose growth attains a given point, a certain number of stages having been passed prior to its termination or maturity. In B we have another series of four (the number a matter of no importance), which, during the period 176 GENERAL EVOLUTION". of growth, can not be distinguished by any common, i. e., generic character, from the individuals of group A, but whose growth has only attained to a point short of that reached by those of group A at maturity. Here we have a parallelism, but no true evidence of descent. But if we now find a set of individuals be- longing to one species, or, still better, the individuals of a single brood, and therefore held to have had a common origin or parent- age, which present differences among themselves of the character in question, we have gained a point. -~ A We know in this case that the individ- uals, a, have attained to the complete- ness of character presented by group A, while others, b, of the same parentage have only attained to the structure of those of group B. It is perfectly obvious that the individuals of the first part of the family have grown further, and, therefore, in one sense faster, than those of group b. If the parents were like the individuals of the more completely grown, then the offspring which did not attain that completeness may be said to have been retarded in their development. If, on the other hand, the parents were like those less fully grown, then the offspring which have added some- thing have been accelerated in their development. I claim that a consideration of the uniformity of Nature's processes, or inductive reasoning, requires me (however it may affect the minds of others) to believe that the groups of species, whose individuals I have never found to vary, but which differ in the same point as those in which I have observed the above varia- tions, are also derived from common parents, and the more ad- vanced have been accelerated or the less advanced retarded, as the case may have been with regard to the parents. This is not an imaginary case, but a true representation of many which have come under observation. The developmental resemblances mentioned are universal in the animal, and probably in the vegetable kingdoms, approaching the exactitude above de- picted in proportion to the near structural similarity of the spe- cies considered. Example 1. — It is well known that the Cervidm of the Old World develop a basal snag of the antler (see Cuvier, '' Ossemens Fossiles," and Gray, " Oat. British Museum ") at the third year ; a majority of those of the New World (genera Subulo, Cariacus) THE METHOD OF CREATION OF ORGANIC FORMS. I77 never develop it except in abnormal cases in the most vio-orous maturity of the most northern Cariacus [C. viryinianus), while the South American Subulo retains to adult age the simple horn or spike of the second year of all Cervidce» Among the higher Gervidce^ Eusa and Axis never assume char- acters beyond an equivalent of the fourth year of Cervus. In Dama the characters are, on the other hand, assumed more rapidly than in Cervus, its third year corresponding to the fourth of the latter, and the development in after years of a broad plate of bone, with points being substituted for the addition of the correspond- ing snags, thus commencing another series which terminates in the great fossil elk, Megacerus. Returning to the American deer, we have Blastocerus, whose antlers are identical with the fourth year of Cariacus. Corre- sponding with the Dama-Megacerus type of the Old TVorld, we have the moose (Alces) developing the same palmate horn- on the basis of Cariacus (i. e., without eye-snag). Example 2. — I select the following series, embracing the ma- jority of the genera of the Korth American Helicidse.* 1. Turns of spire very few ; wide umbilicus ; shell thin, with thin W^s. . Binneya. 2. Turns few, but more ; rest as above Vitrina. 3. Turns still more numerous ; rest as above Hyalina. 4. As No. 3, but lip thickened inside Hygromia. 5. Coiled ; umbilicus closed ; lip thickened inside and out. . Tachea and Pomatia. 6. Same, with a parietal tootl^ Mesodon. 7. Same, with parietal and two interior lip teeth Isognomostoma. * * Recommencing at Xo. 4. A.\\ ^iih. open umbilicus. 5. As No. 4, but lip thickened in and out Arionta. 6. Same as No. 5, but with parietal tooth Polymita . T. Same, with both parietal and lip teeth Triodopsis. The successional relation of these genera may be represented in such a diagram as this : Umbilicus open. Umbilicus closed. Y * * 6 * * 5 * * 4 * 3 * 2 * 1 * * See Tryon, *' Terrestrial Mollusca of the United States." Probably other (e. g., dental) characters distinguish some of these genera, but the above furnishes the history of one set of characters. 12 178 GENERAL EYOLUTIOK 111 the history of the growth of the genera Isognomostoma and Triodopsis, the extreme forms of the two series, it is well known tliat at first the coils of the shell are extremely few, as in Binneya ; and that, like it, it is very thin and with a delicately thin edge ; that the turns increase successively in number, as in Vitrina and Hyalina ; and that, finally, the lip thickens, as in Hygromia. Then the umbilicus may close, as in Tachea, or (in Triodopsis) remain open, as in Arionta. In either case a tooth is soon added on the body-whorl (Polymita, Mesodon), and, finally, the full maturity of the shell is seen in the added teeth of the inside of the lip-mar- gin. How many of the stages of the genera Triodopsis and Meso- don are identical with the genera of the series which represent them, I leave to more thorough conchologists, but that some now exhibit and all have once presented illustrations of the relation of exact parallelism, I can not doubt. Example 1. — An abundant race of the American deer, Caria- cus virgiJiianus, exists in the Adirondack region of New York, in which the development of the antlers never progresses beyond the spike stage of the second year. Therefore, some individuals of this species belong to Cariacus and some to Subulo. * Example 2. — A large part of the individuals of the common snail, Mesodon alhokibris, never develop the tooth of the body- whorl, characteristic of the genus whose definition has to be modi- fied to retain them. Example 3. — Many individuals of Triodopsis tridentata from eastern North Carolina occur withotit the lip-teeth, characteristic of the genus Triodopsis. Hence these specimens, though of com- mon origin with others of the species, must be referred to another genus. Example 4. — Structural characters are known in many, if not all, species which are said to be *^ inconstant," being present or absent indifferently, thus being useless for definition. They may be rudimental when present or considerably developed. The pres- ence or absence of wings in some species of insects may be cited ; also the presence of generic characters in the male sex of many Coleoptera and their absence in the females. The characters of * Since the above was written the facts as stated have been denied. But the author has seen specimens of Cariacus virgmianus and C. maa'oiis in which the horns had assumed the characters of the genus Alces, throwing these individuals into that genus. See "American Naturalist," 1883-'84. (Ed. 1886.) THE METHOD OF CREATION OF ORGANIC FORMS. I79 males, females, workers and soldiers in bees and ants may be added. All these facts belong to the same category as those cited among deer and mollusks, and have a similar explanation. Example 5. — It does not seem to be the law in '^retardation " that parallelisms exhibited by the series in its rise to its highest point of development should retrace the steps by which it attained it, and that *' exact parallelisms " should be exhibited in a reversed order. Parallelisms, it is true, are exhibited ; but so far as I have observed always 'Mnexact," often in a high degree. A marked case of retardation occurs in the dental development of a number of persons who have come under my observation in the neighbor- hood of Philadelphia. It is not very uncommon to find persons in whom the third molars in both jaws are incomplete as to number, one, two, three, or all, being deficient. It is still more common for them to be incompletely covered by the enamel layer, and to become in consequence so worthless as to require early removal. I am acquainted with two families in which the absence of the ex- terior upper incisor on each side is common. In one of these the second and third generation have inherited it from the mother's side, and it now characterizes many of the children. The signifi- cance of this modification will be best understood by examining the dental structures of the Qiiadrumana in general. Commencing with the highest family and its abnormal dentition, w^e have : Incisors. Canines. Premolars. Molars. rr ■ '1 ( Abnormal. i i" f a — 2 ( >iiormal. f 1 t t Simiidce f \ I 3 Cebidce .... f "i- 3 f LemuridcB f \ I — 3 3 Mammalia^ Normal | \ 4 I In this table we see a decline in the number of teeth of the higher groups. Thus, the premolars are one less than the normal number in the whole order, and they lose one in each jaw in tlie Old World apes, and man. The molars maintain the normal num- ber throughout, but the third in both jaws is in the SimiidcB reduced by the loss of a fifth or odd tubercle, thus becoming four- lobed. In the upper jaw, this is first lost in the Semnopithecus ; in the lower, in the next highest genus Cercopithecus. In Homo its appearance is "retarded," the interval between that event and the protrusion of the second molar— six to ten years— being rela- tively greater than in any genus of Qiiadrumana. Its absence is 180 GENEPwAL EVOLUTION then the result of continued retardation, not of a new and adaptive suppression, and is of direct systematic zoological value. In the incisors a reduction is also plainly visible, as we pass from the most completely furnished mammals to the genus Homo. One from the upper jaw is first lost, then, in the Cebidce, one from the lower also. The number remains the same through the SimiidcB and normal Hommidce, but, in the abnormal cases cited, the process of reduction is continued and another incisor from each side disap- pears. That this also is truly *^ retardation" is evident from the fact, that the exterior incisor is the last developed, being delayed in ordinary growth a year later than those of the inner pair. The same retardation is seen in the quadrumane Cheiromys (the aye- aye), and the whole order Rodentia. In the latter, the rare pres- ence of the reduced second incisors, as in Lejjus, shows a less degree of this modification. This retardation is also of systematic impor- tance, and, should either of the characters described be constant in any of the species of the genus Homo, would at once entitle it to new generic rank. The very frequent absence of the posterior molars (wisdom teeth) has been recently found to characterize a race in India. Should this peculiarity prove constant, this race would with propriety be referred to as a new genus of Hominidm, as we have many cases of very similar species being referred to different genera. It is altogether probable that such will, at some future time, be the condition of some race or races of men.* I am now disposed to regard the above as the method of produc- tion, not only of generic but of all other, including specific char- acters. It would appear that, by excessive acceleration or retarda- tion, some of the characters of a series may be skipped; but observa- tions are not conclusive on this point, since very close examination is necessary for the appreciation of very transitory embryonic con- ditions. II. OK THE LAW OF REPETITIVE ADDITION. The origin of new structures, which distinguish one generation from those which have preceded it, I have stated to take place under the law of acceleration. As growth (creation) of parts usu- ally ceases with maturity, it is entirely plain that the process of acceleration is limited to the period of infancy and youth in all animals. It is also plain that the question of growth is one of * The preceding section is merely an abbreviation, with new illustrations, of the propositions brought forward in the writer's " Origin of Genera," 1868, where a con- siderable extension of the subject will be found. THE METHOD OF CREATION OF ORGANIC FORMS. 181 nutrition, or of the construction of organs and tissues out of pro- toplasm. The construction of the animal types may be referred to two kinds of increase— the addition of identical segments and the addi- tion of identical cells. The first is probably to be referred to the last, but the laws which give rise to it can not now be explained. Certain it is that segmentation is not only produced by addition of identical parts, but also by subdivision of a homogeneous part. In reducing the vertebrate or most complex animal to its simplest expression, we find that all its specialized parts are but modifica- tions of the segment, either simply or as sub-segments of compound but identical segments. Gegenbaur has pointed out that the most complex limb with hand or foot is constructed, first, of a single longitudinal series of identical segments, from each of which a similar segment diverges, the whole forming parallel series, not only in the oblique transverse, but generally in the longitudinal sense. Thus, the limb of the Lepidosiren represents the simple type, that of the Ichthyosaurus a modification. In the latter, the first seg- ment only (femur or humerus) is specialized, the other pieces being undistinguishable. In the Plesiosaurian paddle the separate parts are distinguished, the ulna and radius well marked, the carj^al pieces hexagonal, the phalanges defined, etc. As regards the whole skeleton, the same position may be safely assumed. Though Huxley may reject Owen's theory of the verte- brate character of the segments of the brain-case, because they are so very different from the segments in other parts of the column, the question rests entirely on the definition of a vertebra. If a vertebra be a segment of the skeleton, of course the brain-case is composed of vertebrae ; if not, then the cranium may be said to be formed of ^'sclerotomes," or some other name mav be used. Cer- tain it is, however, that the parts of the segments of the cranium may be now more or less completely parallelized or homologized with each other, and that, as we descend the scale of vertebrated animals, the resemblance of these segments to vertebrae increases, and the constituent segments of each become more similar. In the types, as Amphioxus, etc., where the greatest resemblance is seen, segmentation of either is incomplete, for they retain the original non-osseous basis. Other animals which present cavities or parts of a solid support are still more easily reduced to a simple basis of segments, arranged either longitudinally (worm) or centrifugally (star-fish, etc.). 182 GENERAL EVOLUTION. DEFINITIONS. a. The succession of construction of parts of a complex, was originally a succession of identical repetitions ; and grade influ- ence merely determined the number and location of such repeti- tions. (i. Acceleration signifies addition to the number of those repeti- tions during the period preceding maturity, as compared with the preceding generation, and retardation signifies a reduction of the numbers of such repetitions during the same time. y. The successive additions now characterizing the growth of the highest animals are not exact repetitions of segments at this time, because of influences brought to bear on cell-nutrition during long periods. The nature of these influences is made the subject of another section. In the endeavor to prove these positions, I will produce evi- dence, first, that some simpler animals grow according to the prin- ciple of modified repetitive addition, and that traces of it are to be observed in the most complex ; second, that every addition to structure which has resulted in the complexity of the higher ani- mals was originally a repetition of a pre-existent structure. Detailed explanations of the law of repetitive addition are at- tempted in the following pages, under two heads — segment-repeti- tion, and cell-repetition. A. On Segment- Repetition. This is everywhere seen in the construction of animals and plants. Double bilateral symmetry may serve as one example of repetition in growth. a. Bilateral symmetry. Anatomists have little diSiculty in de- termining the bilateral symmetry in most animals — that is, the homologies of the parts on opposite sides of the median line. It might be almost asserted that it was a necessity of organization ; but, when we observe the growth of many plants, we are unde- ceived. And though bilateral symmetry in the Ccelenterata and many Articulata is perfect, yet in higher animals it is more or less departed from. In the Vertebrata the Amphioxus is almost com- pletely bilaterally symmetrical. In the fishes, the digestive system is the only one which does not conform to it ; while in the birds the reproductive system is atrophied on one side. In the ser- pents the respiratory and part of the circulatory are similarly THE METHOD OF CREATION OF ORGANIC FORMS. 183 modified ; and in the Mammalia the digestive and circulatory systems have both become unsymmetrical ; and the cranium, even in the Cetacea. If evolution be true, the unsymmetrical forms have descended from the symmetrical, and the asymmetry being thus not inherited, is the result of laws which have interfered with the original tend- ency to bilateral repetition. Many cases of bilaterally symmetrical diseases have been enu- merated by physiologists, and I will select as an example one which has come under my observation. They were those of two boys who had had that disease involving the muco-dermal system called vari- cella, while the crowns of the successional incisor teeth were still inclosed in the mucous capsules of the alveolar walls. The deposit of phosphate of lime forming their surfaces was interrupted by the disease of the tissue, and the result was a surface pitted, or sculpt- ured intaglio fashion. The sculpture of the two incisors of the right side was precisely imitated by those of the left in reversed order, even in minute details, which were numerous, thus produc- ing a result not displeasing to the eye. This has been observed on two distinct occasions some years apart. Another interesting example of bilaterally symmetrical disease is recorded in a paper on ^^ A Case of Universal Hyperostosis, etc.," by Drs. Mears, Keen, Allen, and Pepper.* They describe the skele- ton of a boy of fourteen which displayed an extraordinarily exos- tosed condition, the bones themselves remaining in the condition known as osteoporosis. They describe the uniform repetition of the abnormal growths of one side on the other in the following language (p. 22) : '^ Comparing the two sides externally, not only is there no dif- ference in the extent and character of the disease, but there is the most remarkable symmetry of the corresponding diseased bones, which may be traced even into details. The disease begins and ends on both sides at corresponding points, it changes in character from simple porosity to the growth of osteophytes at corres])onding points ; if, on one side, the posterior part of the bone is most dis- eased, the same is true of the other side ; if the osteophyte growth is continuous or interrupted on one bone (fibula, Fig. 18), it is so on the opposite one ; if one is unusually diseased at a tendinous or aponeurotic insertion, so is its mate ; if a groove or a variation in * See "Proceed. Amer. Philos. Soc," 1810, p. 19. 184 GENERAL EVOLUTION. color exist on the one side, the same will be found on the other side ; even of single marked spiculae of bone the same may be said, so that a description of one side will answer for both, minute dif- ferences being noted as they occnr." h. Anteroposterior symmetry. That this is an absolute law of creation will be less readily ad- mitted than in the case of double bilateral symmetry, since the ex- ceptions appear to be so universal. Nevertheless, I believe it to be as much a part of the law of repetitive nutrition as the other. The anteroposterior homologies even of the human skeleton have been largely demonstrated, bitt, as usual, we must appeal to the lower forms for a clear view of it. In the rudimental skeletal axis we find such symmetry almost perfect in the AmjoMoxus, but in no other vertebrate. In limbs we have it clearly indicated in the Eeptilian order Ichthyopterygia, and in the Piscine order Dipnoi, where the anterior and posterior are scarcely or not at all distin- guishable. In the scapular and pelvic arches we find it also ap- proximated in the first-named orders. In the nervous system it also exists approximately in the Am- pMoxus. It is not seen in any vertebrate, and in but few other animals, in the digestive system, but it appears to exist in some lower Articulata in both the respiratory and circulatory systems. c. As illustrations of exact repetition involving large portions of the organism the higher Polyps may be cited, which differ from the lower chiefly by the addition of similar septa and similar ten- tacles. Examples of repetition of nearly the whole organism may be found in many Entozoa, as Tmnia, where the cephalic segment only differs from the others, the remainder or proglottides being alike. The most entire repetition of structure is seen in Vibrio, where the segments are all alike, there being none representing a head. d. As an example in special details of structure, the pelvic arch of Ichthyosaurus, when first created, was a repetition of the scapu- lar, and the hind limb, of the fore limb. The segments of the limbs of the Dipnoi are mere repetitions, the later created of the earlier. The special parts of the pes and manus of Ichthyosaurus are simply repetitive efforts of growth-force joined with a dimin- ishing amount. The addition of a digit, often distinguishing one genus of Salamanders or Saurians from another, is evidence of a similar repetitive effort. The low mammal Ornithorhynchus pos- sesses but a single tooth in each jaw ; the simple teeth of armadil- THE METHOD OF CEEATION OF ORGANTC FORMS. 185 los and cetaceans, increasing as they have done from a simpler commencement, present examples of repetitiye acceleration of growth-force. e. Complication of a single element of repetition is accomplished apparently by a double repetition. This is best understood by the consideration of the transition from simple to complex teeth. In the cetaceans this occurs in the Squalodonts ; the cylindric incisors are followed by flattened ones, then by others grooved on the fang, and then by two-rooted, but never double-crowned teeth. This is the result of anteroposterior repetitive acceleration of the simple cylindric dental type of the ordinary toothed cetacean. Another mode of dental complication is by lateral repetition. Thus, the heel of the sectorial tooth of a Carnivore is supported by a fang alongside of the usual posterior support of a premolar, and is the result of a repetitive effort of growth-force in a transverse direction. More complex teeth, as the tubercular molars, merely exhibit an additional lateral repetition, and sometimes additional longitudinal ones. As is well known, the four tubercles of the human molar commence as similar separate knobs on the dental papilla. The above are cited as examples to explain the meaning of the proposition. When fuller demonstration is desired, a greater num- ber might be given. • B. On Cell-Repetition. That each additional act of creation in growth was originally identical with one which preceded it, and therefore an exact repe- tition in its character and results, is proved by the following con- siderations. It has been already determined by the study of homologies that all organs and parts of an organism can be referred to an original simple archetype. The question then remains as to whether the first element, or lowest term, of a given organized part is essentially a new struct- ure, or whether it be a repetition of some previously existing one. It may be asserted that the simplest expressions which shall cover all organs are the solid segment, and the hollow sack, and tube. For example, we have already noted that the ultimate element of the limb is the first segment of the single ray of Lepidosiren. Is this short cartilaginous cylinder (which probably represents the fore limb of some undiscovered member of the Dipnoi) a result of 186 GENEKAL EVOLUTION. the repetition of a pre-existent structural element ? This is no doubt the case, for, as will be shown beyond, cartilage, though the least cellular of all the tissues, is formed originally by cell repetition or division. Again, the ultimate lobules of the most complex gland are but repetitions of the diverticula of the simply branched, and each of the latter repetitions of the simple cul-de-sac, which has its origin in a convexity of an originally plane surface. This con- vexity is again the result of repetition of cells or cell-division, whereby their number is increased and the surface rendered convex. We are thus, in both the solid segment and hollow sack, brought down to cell-repetition. Thus it is with organs, as with entire animals, in which, following the line of simplification, we reach at last forms composed of cells only {Act'mojjhrys, e. g.) and then the unicellular (Amceba). It this be the origin of organs, the question whether repetitive growth has constructed tissues remains for consideration. In growth, each segment — and this term includes the parts of a complex whole or parts always undivided (as the jaw of a whale or the sac-body of a mollusk) — is constructed, as is well known, by cell-division. In the growing foetus the first cell divides its nucleus and then its whole outline, and this process, repeated millions of times, produces, according to the cell theory, all the tissues of the animal organism or their bases, from first to last. That the ulti- mate or histological elements of all organs are produced originally by repetitive growth of simj^le nucleated cells, with various modifi- cations of exactitude of repetition in the more complex, is taught by the cell theory. The formation of some of the tissues is as fol- lows : First Change. — Formation of simple nucleated cells from ho- mogeneous i^rotoplasm or the cytoblastema. Second. — Formation of new cells by division of nucleus and body of the old. Third. — Formation of tissues by multiplication of cells with or without addition of intercellular cytoblastema. A. In connective tissue, by slight alteration of cells and addi- tion of cytoblastema. B. In blood, by addition of fluid cytoblastema (fibrin) to free cells (lymph-corpuscles), which in higher animals (vertebrates) de- velop into blood-corpuscles by loss of membrane, and by cell-devel- opment of nucleus. THE METHOD OF CREATION OF ORGANIC FORMS. 187 C. In muscles, by simple confluence of cells end to end, and mingling of contents (Kolliker). D. Of cartilage, by formation of cells in cytoblast which break up, their contents being added to cytoblast ; this occurring seyeral times, the result being an extensive cytoblast with few and small cells (Vogt). The process is here an attempt at development with only partial success, the result being a tissue of small vitality. Even in repair-nutrition, recourse is had to the nucleated cell. For Cohnhcim first showed that if the cornea of a frog's eye be scarified, repair is immediately set on foot by the transportation thither of white or lymph or nucleated corj^uscles from the neigh- boring lymph-heart. This he ascertained by introducing aniline dye into the latter. Repeated experiments have shown that this is the history in great part of the construction of new tissues in the adult man. Now, it is well known that the circulating fluid of the foetus contains for a period only these nucleated cells as corpuscles, and that the lower vertebrates have a greater proportion of these corpus- cles than the higher, whence probably the greater facility for repair or reconstruction of lost limbs or parts enjoyed by them. The in- vertebrates possess only nucleated blood-corpuscles. C. Synthesis of Repetition. That growth-force is capable of exhibiting great complexity of movement with increase in amount, will now be shown. That this quality of comiolication is one of its distinguishing features will appear plain. The simplest forms of life, as stated by Haeckel, are simply ho- mogeneous drops of protoplasm {Protamoeha). These only grow by ordinary accretion, and display a form of self division or repro- duction which is the simplest possible — i. e., the bisection of the mass by contraction at opposite points. The next grade of animal type is represented by the nucleated cell. This is simple in Amoeha, complex in Actinophrys, etc. With such forms as the latter, cell-growth begins, and its develop- ment is accomplished, by cell-division. This is simple repetition of ultimate parts. In the growth of all higher types we have nothing more than this, but following a law of complex repetition. Thus in the growth of the parts of an archetypal vertebral column or an archetypal limb, we have the repetition of cell-growth till the first segment is formed, when it ceases at that point, and re- 188 GENERAL EVOLUTION. peats the process again, forming another segment like the first ; repetition within repetition. So with the construction of muscu- lar tissue ; first, the nucleated cell repeated in a series, whose adjacent walls disappear, and whose cell-contents flow together, thus forming a fibrilla ; then a repetition of the same process, forming a second fibrilla ; and so on to the completion of thou- sands of them in fasciculi. Let us then trace the series of repetitions and duplicated and still more complex repetitions, seen in following up animal forms from their archetypes. In the simplest rejDetition of cell-growth in a longitudinal direction we have Vibrio ; in the centrifugal, Actinophrys. The former may be represented by a line of simple dots, thus : Fig. 1. A.^... _.. ^ S.y" *V ' J Ci ao to aQOoa ^. ooQOococ3cCf cO ^3 O f" o cjqOoc5 ^rs O oodODCD£i:n c:i> o ^^O, \ In a complex repetition we rarely have the same degree of com- plication in each repeated part. We have it centrifugally almost perfect in a Coelenterate {Actinia), and linearly in some of the lower vermes. An archetype of the latter kind might be repre- sented thus : Fig. 2. In a more complex form, as of the pro- glottides of TcBnia, thus : Fig. 3. The same might represent an archetypal vertebrate. If now we attempt to express the complication of an organ by modified repetition of once identical parts, the history of extremi- ties will serve us. Thus the limb of Lepidosiren, which is com- posed of identical segments, may be thus represented : Fig. 2. Each longitudinal segment of the limb of Ichthyosaurus may be similarly represented with a modification, in size only, of the proximal or humerus ; thus : Fig. 4. But in Plesiosatirus an important series of changes of shape (but not in complexity) ap- pears, which may be represented thus : Fig. 5 ; the first being THE METHOD OF CREATION OF ORGANIC FORMS.. 189 humerus, second ulna, third and fourth carpals (tarsals), the last phalanges, which are first specialized in this genus. By far the most usual modification is, however, complication bv duplicated and triplicated and still more highly multiplied repeti- tion in some segments of the archetype, and its omission in other segments. Thus in the Tcenia, the cejihalic segments are much modified, and the nature of the repetition might be thus ex- pressed : Fig. 6 ; the simpler segments representing the body segment, the two complex representing those of the head. In each, it will be observed, the complication is represented by loops of similar form, and each loop of dots which represent the cells in the first linear (Fig. 1) arrangement. A somewhat similar figure might represent the nature of the complication in the Myriapod. In the insect the additional com- plications of the thoracic segments would alter the diagram near the middle. In the vertebrate cranium a somewhat similar diagram might be used, except that the modification of the segments or vertebrae, as compared with the segments of the vertebral column, is not by rciDctition with modification of the parts of each segment, but rather by modification of the forms of the parts of the segments. The basicranial segments thus compare with the dorsal vertebrae as the segments of the limb of Plesiosaurus do with those of Ich- thyosaurus. The above considerations have reference to repetition of parts in a linear direction. Centrifugal repetition is seen in the addi- tion of chambers to the heart, by the subdivision in the earliest stages into auricle and ventricle in the linear direction, con- sidered in connection with the earlier division of each in the transverse direction by the growth of partitions. This mode of repetitive addition is not readily represented by diagram. A good example of repetitive addition, in both linear and transverse direction, may be found in the successive complication of tooth structure seen in Mammalia. In the dolphin, the dental series may be represented thus : Fig. 7 ; in the squalodon thus : Fig. 8 ; in the cat : Fig. 9 ; in the dog : Fig. 10 : in man : Fig. 11 ; in some Insectivora : Fig. 12. The circles represented here are each a simple cusp. In conclusion, the directions of repetitive growth may be tabulated as follows : The types to the left represent the original ; to the right, the derivative : 190 GENERAL EVOLUTION. Centrifugal. ' More bilaterally { n ^ ^.'^ ^. ^ symmetrical. '] Only bilateral. Longitudinal antero-pos- -< terior and bilateral. More antero-pos- j Only antero- teriorly. ( posterior. ( In plane. Centrifugal. •< ( In globe. D. On Growtli-Force. From such examples as those that precede, but more especially from the last, it seems necessary to believe that there resides in organized matter, and in its most unmodified representative, the nucleated cell, an affection which displays itself in repetition. This phenomenon reduced to its lowest terms, may mean cell-divis- ion only, but the proof is only clear in cases of gi'owth proper. This affection displays itself in very slow or more rapid repetitions — cell-division in growth occurring rapidly, while its recurrences at rutting seasons in the development of horns, feathers, etc., are separated by long intervals of time. In acceleration these repeti- tions occur with increased rapidity, i. e., in the adding of more structures during the same growth periods, while in low types its repetitions are few and therefore slow. What is the relation of cell-division to the forces of nature, and to which of them as a cause is it to be referred, if to any ? The animal organism transfers solar heat and the chemism of the food (protoplasm) to correlated amounts of heat, motion, electricity, light (phosphorescence), and nerve force. But cell-division is an affection of protoplasm distinct from any of these ; although addi- tion to homogeneous lumps or parts of protoplasm (as in that low- est animal, Protamceha of Hseckel) should prove to be an exhibi- tion of mere molecular force, or attraction, cell-division is certainly something distinct. It looks like an exhibition of another force, which may be called groiuth-force. It is correlated to the other forces, for its exhibitions cease unless the protoplasm exhibiting it be fed. Professor Henry i^ointed out many years ago that this must be the case, basing his belief on the observed phenomena of growth in the potato, and in the Qgg. The starch of the potato weighs much more than the young shoot of cellulose, etc., into which it has been converted by growth-activity, so that a portion of the substance of the tuber has evidently escaped in some other direction. This THE METHOD OF CREATION OF ORGANIC FORMS. 191 is shown to be carbonic acid gas and water, derived from the slow combustion of the starch, which in thus running down from the complex organic state to the more simple inorganic compounds, evolves an amount of force precisely equal in amount to the chemi- cal force (or chemism) requisite to bind together the elements in the more complex substance.* Carpenter also states that in his opinion the growth of the Funo-i is produced by a force liberated by the retrograde metamorpliosts of their food, which is of an organic character (i. e., humus). This metamorphosis consists, as in the tuber, in the production of carbonic acid gas and water, and a force equivalent to the chemism which had bound them in the former complex union, f But in higher forms of vegetable life, and in growth that follows germina- tion, the plant must appropriate carbon from the carbonic acid of the atmosphere. The decomposition of the binary compound (which sets free its oxygen) liberates the chemical force which luid previously maintained the compound (or an equivalent force), which Henry regards as furnishing the growth-force, which produces the plant. Carpenter derives but a portion of the force in this way, obtaining the greater part from the heat of the sun. To this source also he looks for the heat necessary to the construction of cold- blooded animals ; while in warm-blooded animals, the retrograde metamorphosis or running down of the material (protoplasm) of the food furnishes a requisite amount of heat. Growth-force we may then regard as potential in organized tis- sue, and as energetic during growth. J; Our present knowledge * "Agricultural Report of the Patent Office," ISSY. •(• " Correlation of Physical and Vital Forces," 1864 (" Quarterly Jour, of Science "). j: Bathmism or growth-force must be static or potential in each unit or plastid (cell) of a living organism, the type differing with each organic species. When it is in excess in a given locality it becomes energetic, and builds tissue in various forms. A portion of this energy is, in this process, developed as molar motion of nutritive material, and is accompanied in the completed structure by the ordinary cohesive energy, by which the newly-built material maintains its attachment as a whole and in its parts. If living tissue be constructed, a portion of the excess remains as the static energy of the plastids or cells of the new part, as it did of the old. The spermatozoid is highly endowed with static bathmism, and communicates it to the female ovum. The mingling of the two elements in the presence of nutritious ma- terial presents an excess, and form-building results. Its activity will regulate sub- sequent new growth, by giving the motion of nutritive material its proper direc- tion. When the tissue dies, this energy must leave behind a dynamic equivalent, but what this may be is as yet a mystery. (Ed. 1886.) 192 ^ GENERAL EVOLUTION". only permits us to believe that other force is only conA^erted into it under the influence of pre-existent life, but of the real cause of this conversion we are as ignorant as in the case of the physical forces. In the animal organism, different tissues display different de- grees of ^^ vitality." The most vital display cell-organization and its derivative forms, while the least so, approach nearer to homo- geneity. As organized tissue is the machine for converting vital forces, we may believe that less growth-force is potential as such in cartilage than in muscle, for it is formed by a retrograde process, by which cells once formed are mostly lost, and the contents form the intercellular, nearly structureless mass characteristic of this tissue. Growth-force must be here liberated in some other form, perhaps the mere cohesive force of the former or ^^ dead" inter- cellular substance. The higher vitality we may believe to result from the greater perfection of the more complex tnacliine as a force converter, as compared with the ineiSiciency of the more simple. E, On the Diredioii of Repetition, It has been already pointed out ihoi groiutli-force exhibits itself in cell or segment re^Dctition. The forms in which it thus displays itself may be briefly considered. The approximate cause is treated of in the next chapter ; but enough may be shown here to indicate that duplication and complex duplication is the law of growth-force, and that therefore this process must always follow an increase in a7nount in any given locality. The size of a part is then dependent on the amount of cell-divis- ion or growth-force, which has given it origin, and the number and shape of segments is due to the same cause. The whole ques- tion, then, of the creation of animal and vegetable types is reduced to one of the amount and location of groiuth-force. Repetition is of two kinds, centrifugal and longitudinal. As an example of the former, the genus Actinoplirys has been cited, where the animal is composed of cells arranged equidistally around a common center. The arrangement in this type may be dis- coidal or globular, providing no definite axis be discoverable. As an example of longitudi^ial repetition. Vibrio, and numerous cellular plants may be cited, where the arrangement is in a single line. In by far the greater number of animals these kinds of repeti- THE METHOD OF CREATION OF ORGANIC FORMS. I93 tive structure co-exist. The loyigitudinal is, however, predomi- nant in the Vertedrata, Mollusca, and Articulata, while the cen- trifugal is greatly developed in the Ooelenterata and Radiata. In none but the simplest forms are either of these modes to be found alone. The centrifugal repetition, or addition, more nearly resembles the mode of aggregation of atoms in inorganic or crystalline bodies, and hence may be regarded as the inferior manifestation. It implies that growth-force in this case conforms to a law of polarity in exhibiting itself at equal distances from a center — which is allied to ordinary molecular force, and independent of the localizing influences of which higher organisms seem capable. In centrifugal animals, then, the latter evidently plays an in- ferior part. In Coelenterates and Radiates, however, the body possesses a short longitudinal axis, in some (Asterias) very short, in others (Holothuria) more elongate. The amount of com- plication of centrifugal growth greatly exceeds the complication in a longitudinal direction in all of these animals except the Holothurida. It is now important to observe that great numbers of centrifu- gal animals are sedentary or sessile ; while the longitudinal are vagrant, moving from place to place. Many of the centrifugal animals which wander, do not do so in the direction of their axis, but sideways {Medusce). It is also proper to notice that not only the movements of the muscles but also the direction taken by the food is in the long axis. It is therefore to be concluded that in longitudinal animals growth-force has assumed a more truly animal type, and that this tendency has predominated over the polar or molecular tendency. In most longitudinal animals, however, certain lateral portions, limbs, etc., extend on each side of the axis ; and were the space marked by their extremities, and the extremities of the axis, filled, we would have the outline of a centrifugal animal. Before discussing the influences which have increased and lo- cated growth-force, it will be necessary to point out the mode in which these influences must necessarily have effected growth. Acceleration is only possible during the period of growth in ani- mals, and during that time most of them are removed from the influence of physical or biological causes, either through their hidden lives or incapacity for the energetic performance of life functions. These influences must, then, have operated on the 13 194 GENERAL EVOLUTION, parents, and become energetic in the growing foetus of the next generation. However little we may understand this mysterious process, it is nevertheless a fact. Says Murphy, '' There is no act which may not become habitual, and there is no habit that may not be inherited." Materialized, this maybe rendered — there is no act which does not direct growth-force, and therefore there is no determination of growth-force which may not become habitual ; there is, then, no habitual determination of growth-force which may not be inherited ; and, of course, in a growing foetus becomes at once energetic in the production of new structure in the direc- tion inherited, which is acceleration. But if the forces converted into growth-force are derived from without the animal organism, whence and what the agency by which the acceleration or retardation of the latter is inherited from the parent ? A few suggestions only on this head can be made in the fourth section. III. THE LAW OF USE AKD EFFORT. Up to this point we have followed paths more or less distinctly traced in the field of nature. The positions taken appear to me either to have been demonstrated or to have a great balance of probability in their favor. In the closing part of this paper I shall indulge in more of hypothesis than heretofore. Since repetitive addition only produces identical results in archetypes, and each effort produces results more and more unlike its predecessor as structure becomes specialized, it becomes im- portant to examine into the influences which have originally modified the repetitive efforts successively, producing structures more or less different in detail in the second generation from those of the parents, in acceleration, or the reverse, in retarda- tion. Going further back, the question arises, why a simple exhibi- tion of repetition (e. g., cell-division) should be converted into a complex or duplicated repetition (e. g., jointed ray). This, it has already been stated, is one consequence of increased amount of the growth-force. We then seek explanation of the main question, as to what de- termines the location of this additional or new growth-force. (Div. A.) Lastly, why the total amount of this force should change in a given individual or part of an individual. (Div. B.) THE METHOD OF CREATION OF ORGANIC FORMS. I95 A. On the Location of Groivth-Force. What are the influences locating growth-force ? The only efficient ones with which we are acquainted, are, first, physical and chemical causes ; second, use ; and I would add a third, viz. : effort. I leave the first, as not especiaUy prominent in the econo- my of type-growth among animals, and confine myself to the two following. The effects of use are well known. We can not use a muscle without increasing its bulk ; we can not long use the teeth in mastication without inducing a renewed deposit of den- tine within the pulp-cavity to meet the encroachments of attri- tion. The hands of the laborer are always larger than those of men of other pursuits. Pathology furnishes us with a host of hy- pertrophies, exostoses, etc., produced by excessive use, or neces- sity for increased means of performing excessive work. The tendency, then, induced by use in the parent, is to add segments or cells to the organ used. Use thus determines the locality of new repetitions of parts already existing, and determines an in- crease of growth-force at the same time, by the increase of food always accompanying increase of work done, in every animal. But supposing there be no part or organ to use. Such must have been the condition of every animal prior to the appearance of an additional digit or limb or other useful element. It ap- pears to me that the cause of the determination of grow^th -force is not merely the irritation of the part or organ used by contact with the objects of its use. This would seem to be the remote cause of the deposit of dentine in the used tooth ; in the thicken- ing epidermis of the hand of the laborer ; in the wandering of the lymph-cells to the scarified cornea of the frog in Cohnheim's experiment. You can not rub the sclerotica of the eye without producing an expansion of the capillary arteries and correspond- ing increase in the amount of nutritive fluid. But the case may be different in the muscles and other organs (as the pigment cells of reptiles and fishes) which are under the control of the volition of the animal. Here, and in many other instances which might be cited, it can not be asserted that the nutrition of use is not under the direct control of the will through the mediation of nerve force. Therefore I am disposed to believe that growth- force may be, through the motive, force of the animal, as readily determined to a locality where an executive organ does not exist, as to the first searment or cell of such an organ already com- 196 GENERAL EVOLUTION. menced, and that therefore effort is, in the order of time, the first factor in acceleration. Addition and subtraction of growth-force, in accordance with the modes pointed out below, account for the existence of many characters which are not adaptive in their nature. Acceleration under the influence of effort accounts for the ex- istence of rudiments of organs in process of develoj)ment, while rudiments of organs in process of extinction are results of retarda- tion, occasioned by absolute or complementary loss of growth-force. Many other characters will follow, at a distance, the modification resulting from the operation of these laws. Examples of the Influence of Physical Causes. — This is nowhere better seen than in the case of coloration, which requires the light of the sun for its production. The most striking examples of this are seen in the colorless surface of animals inhabiting the recesses of cayes, as the blind craw-fish and the AmUyopsis, etc. If evolu- tion be true, these have descended from more highly colored jDro- genitors. The flat fishes, also {Pleuronectidce), as is known, swim on one side in adult age, but many of them are hatched symmetrical fishes, or nearly so, one eye rotating from one side to the other by a twisting of the cranial bones. It is thus probable that they have descended from symmetrical fishes, which were similarly colored on both sides. Now the lower side is colorless, the upj^er retain- ing often brilliant hues. The influence of sunlight is thus as dis- tinctly discoverable among animals as among plants, where it has been generally accepted as a principle of vegetable physiology.* Examples of the Effects of Effort and Use. — a. The Respiratory and Circulatory System of Vei^tehrates. — It is well known that the succession of classes of Vertebrates is measured first by their adapta- tion to aeration in water, and then by their successive departures from this type in connection with the faculty of breathing air. The same succession of structure is traversed by the embryos of the vertebrates, the number of stages passed being measured by the final status of the adult. This transition takes place in the Batrachia later in development than in any other class. Now, it is well known that the transition or metamorphosis may be delayed * In this and similar cases, care must be taken not to misunderstand the writer by supposing him to mean that in each generation separately the peculiar coloration is the result of changed exposure to light. The evolutionist will understand that the effect of such influence increases with succeeding generations by the addition to in- herited character of the effect of immediate external cause. THE METHOD OF CREATION OF ORGANIC FORMS. 197 or encouraged by suppression of use of the branchial and encourage- ment of use of the pulmonary organs, or the reverse. The aquatic respiration of tadpoles may be indefinitely pro- longed by preventing their access to the surface, and it is known that in nature the size or age of the larva at time of metamorphosis may vary much in the same species. If perennibranchiates (Siren, e. g.) are deprived of their branchiae, they will aerate blood by the lungs exclusively, and there is no reason to doubt that by use of these, and disuse of the branchiae, aerial respiration might be- come the habit of the animal. It is also easy to perceive that geo- logic changes would bring about a necessity for precisely this change of habit. This occurred in the period of the coal measures, where large fresh-water areas were desiccated, and it was precisely at this period that many air-breathing Batrachians originated and had a great development. j3. The rattle of the Rattlesnake. — Nearly all the larger harm- less snakes which live on the ground have a habit of throwing the end of the tail into violent vibrations when alarmed or excited, with the view of alarming a supposed enemy. Among Coronelline snakes, Ophiholus triangulus possesses it ; among the water snakes, Tropidonotus sipedon. In the typical Colubrine group the black snake, Bascanium constrictor, is an example ; Pityophis sayi also shakes the tail violently. The copperhead {Ancistrodon contor- trix) and the moccasin {A. piscivorus) (fide Giinther) have the habit in a marked degree. Among the rattlesnakes it is a means of both warning and defense, in connection with the rattle which they carry. In the structure of the end of the tail of harmless snakes, we see a trace of the first button of the rattle in a horny cap that covers the terminal vertebrae. In the venomous genera, it is conspicuous in Lachesis especially, reaching a considerable length and having a lateral groove. In the plate-headed rattlesnakes (Crotalus) this corneous cap is inflated into a button with lateral groove, and in some of them possesses only one or two buttons or joints. In the perfected rattlesnakes {Gaudisona) not only are the segments nu- merous and inflated, but a number of the terminal caudal vertebra? are greatly enlarged vertically, and co-ossified into a mass.* This is important from the fact that the rattlesnakes are the most spe- * See good figures of this structure in *' Zeitschr. f. wissensch. Zoologic," viii, Tab. 12. 198 GENERAL EVOLUTION. cialized of all snakes, standing at the head of the order, and as such, on the principle of acceleratio7i, present the greatest amount of grade-nutrition. Now it appears to me that the constant habit of violent vibra- tion in a part tends to determine an increased amount of nutritive fluid to it, in other words to localize growth-nutrition, and when this has attained complex repetition or grade-nutrition, to result in new grade-structure. (The segments of the rattle being nearly all alike, it is a case of simple repetition.) This view appears to be as reasonable as that generally entertained with regard to the cause of spavin in the horse's leg. Here, owing to excessive use, exostoses appear on the bones surrounding the tibio-tarsal articula- tion. As to the reason of tbe structure in question not appearing in forms lower in the scale than the rattlesnake, it is explained below, if the law of accumulation of grade-nutrition be true. (See Sec. B.) This is, that repetition (or acceleration) is only possible where the animal has an excess of growth-force at its disposal, or can abstract it from some portion which is unused or useless. y. On horns. — The possession of horns on the posterior part of the cranium, as defenses against enemies, is a character found in many distinct types of animals. (Herbivora have no (dental) weapons and need horns.) It is seen in the Batracliia Stego- cephala in the extinct genus Ceraterpeton ; among ^?^^^r« it is approached by Triprion and Hemiplir actus. Among Reptilia it is well marked in PTirynosoma, a Lacertilian genus. In Mamma- lia the Artiodactyla Ruminantia are the horned animals of the order. We have opportunities of observing the habits of these representatives of the Frogs, the Lizards, and the Mammals. In the first case, any one who has kept ordinary toads and tree-toads in confinement, is aware that when attacked and unable to escape, they defend themselves by presenting the top of the head forward and using it as a shield. Now I have already pointed out * that in both toads, tree-toads, and frogs there are natural series of genera, measured by the degree of ossification of the superior cranial walls, the longest being that of the Hylidse, which embraces six terms, viz. : Hylella, Hyla, Scytopis, Osteo- ceplialus, Trachycephalus, and Triprion. The two last have the head thoroughly shielded, and Hemipliractus has projecting an- gles which appear in some South American forms, described bv M. * " Origin of Geaera," 1868, p. 14. This work, article L THE METHOD OF CREATION OF ORGANIC FORMS. 199 Espada, to be developed into short horns. That this excessive ossification is associated with the habit of protecting the whole body with the front seems likely. In the case of Phrynosoma we know that precisely the same habit is associated with the presence of the sharp horns ; and that some genera without horns possess it also. Phrynosoma is an ex- ceptionally sluggish genus in a family of most active forms, and must necessarily resort to this mode of defense more than they. In the case of Ruminants, we also know that defense is accom- plished by throwing the head down with the horns thrown for- ward. But this is not confined to this group. That generalized suborder, the Artiodactyla Omnivora, represented by the hog, which were no doubt the genetic predecessors of the Euminants in time, also throw the head down in defense in the same way, having thus a manner totally distinct from that seen in the Car- nivora. The latter show their teeth and often crouch prepara- tory to a leap. These cases present so constant an association between habit and use that, admitting evolution, we are compelled to believe that the structure has given rise to the habit or the habit to the structure. In the former case we have to suppose, with the au- thor of ^' Katural Selection," that among the many spontaneous variations rudimental horns occasionally appeared, and that their possessors, being thus favored in the struggle for existence, were preserved and multiplied ; while those not favored dwindled, and were ultimately nearly all extirpated or starved. The question of origin is here left to chance, and Alfred Bennett has made a mathematical estimate of the chances of any particular profitable variation occurring among the great number of possibilities of the case. This has shown the chance to be so excessively small as to amount in most cases to a great improbability. If we turn to the probabilities of such structure having arisen through the selection of that mode of defense by the animal, we find them greatly increased. The position occupied by the horns, in all the animals described, is that which is at once brought into contact with an enemy in conflict, and as sport among animals is a gentle imitation of conflict, the part would be constantly excited in sport as well. With an excess of growth-nutrition, our knowl- edge of the effects of friction on the epidermis, and of excessive ligamentous strain and inflammation on bone (e. g., spavin in horses), as well as of abnormal exostoses in general, would warrant 200 GENERAL EYOLUTION. US in the belief that the use of the angles of the parts in question in these animals would result in a normal exostosis, of a simple kind in the frogs, or as horn cores in the Euminantia.* As to the sheathing of the cores in the Bovidce, and nakedness in the Cer- vidcB, it is in curious relation to their habitat and to their habits. The epidermis and derm would of course share in the effects of friction. In the Bovidae which dwell in treeless plains, or feed on the grasses in great i:)art, the development of these coverings of the horn cores into a horny sheath would naturally meet with no interruption. In the case of the deer, which mostly live in forests or browse on trees, constant contact with the latter would prevent the healthy growth of the dermal covering, and it would be liable to injury or constant excoriation by the animals them- selves on the branches of trees, etc. This we know to be the pres- ent habit of the deer as regards the dermal covering of the horns. f I have elsewhere pointed out the similar connection between the dental structure and habitat among the oxen and the deer. The former, eating the harder grasses, are provided against the conse- quent rapid attrition of the tooth by a prismatic form, which allows of more prolonged growth and more rapid protrusion. The deer, in accordance with their foliage-eating habits, do not wear the crown of the tooth with such rapidity. Long-continned protrusion is not so necessary, hence the teeth are more distinctly rooted and have a prominence or shoulder, distinguishing the body of the crown. B. Change in Amount of Groioth- Force. 1. Absolute increase of Groiutli- Force. — As every type has had its period of greatest development in numbers, size, and complica- tion of structure, the present law indicates as an exjolanation, a culmination of the process of conversion of growth-force from its energetic to its potential state in tissue. The cause is primarily the increased exercise of effort and use, which, while effecting a conversion, increases the capacity of the organs by which further conversion is effected. * The now well-known fact that all cranial ossification was primitively dermal, is confirmatory of the idea that its appearance was due to moderate friction of the skin on resistant bodies. (Ed, 1886.) f Palaeontological studies go far to show that the origin of the shedding of the deer's horn was due to the loss of their dermal covering, and that this was caused by violent use. (1886.) THE METHOD OF CREATION OF ORGANIC FORMS. 201 2. Local increase of Growth-Force.— Bxam-phs of a local in- crease of this kind are probably to be seen in conyoluted organs ; as the convolutions of the brain in higher Mammalia ; the convo- lutions of the tooth-dentine of the Labyrinthodont Batrachia ; the same phenomenon in the cotyledons or plumule of some seeds. In these cases the superficial area of the parts is excessively developed, and the inclosing organs not being proportionately enlarged, a convolution necessary follows. In the first case, the skull ; in the second, the alveolus ; in the third case, the seed-envelope, restrain the expanse of the contained part, which would otherwise follow increase of growth-force. 3. Absolute loss of Growth-Force.— This will follow defective nutrition, produced by inability of the animal to obtain heat and food requisite to that end. This is supposed to be due, according to the view hereafter proposed, primarily to deficiency of intelli- gence, in failing to adapt habits to changed physical circumstances, and secondarily to the unfavorable influence of such changed cir- cumstances. The extinction of highly specialized types, which has closed so many lines of animal types, will be accounted for by their less degree of plasticity and want of capacity for change un- der such changed circumstances. Such changes consist of modified topography and temperature, with irruptions of many new forms of life by migration. The less developed forms would be most likely to experience modification of structure under a new order of things, and paleontology teaches that the predecessors of the characteristic types of one period were of the less specialized forms of that period which went before. Thus is explained the fact that, in following out the line of succession of animal forms, we have constantly to retrace our steps from specialized extremes (as osseous fishes, tailless Batrachia, song birds, etc.) to more generalized or simple forms, in order to advance beyond. 4. The complementary dimimitioii of growth-nutrition follows the excess of the same in a new locality or organ, of necessity, if the whole amount of which an animal is capable be, as I believe, fixed. In this way are explained the cases of retardation of char- acter seen in most higher types. The discovery of truly comple- mentary parts is a matter of nice observation and experiment. Perhaps the following cases may be correctly explained. A complementary loss of growth-force may be seen in absence of superior incisor teeth and digits in ruminating Mammalia, where 202 GENERAL EVOLUTION". excessive force is evidently expended in the development of horns, and complication of stomach and digestive organs. The excess devoted to the latter region may account for the lack of teeth at its anterior orifice, the mouth ; otherwise, there appears to be no reason why the ruminating animals should not have the superior incisors as well developed as in the odd-toed (Perissodactyl) Un- gulates, many of which graze and browse. The loss to the osseous system in the subtraction of digits may be made up in the develop- ment of horns and horn-cores, the horn sheath being perhaps the complement of the lost hoofs. It is not proposed to assert that similar parts or organs are necessarily and in all groups comple- mentary to each other. The horse has the bones of the feet still further reduced than the ox, and is nevertheless without horns. The expenditure of the complementary growth-force may be sought elsewhere in this animal. The lateral digits of the Equidce are successively retarded in their growth, their reduction being marked in Hiypotlierium, the last of the three-toed horses ; it is accom- panied by an almost coincident acceleration in the growth-nutri- tion of the middle toe, which thus ajipears to be complementary to them. The superior incisors of the Artiodadyla disa^Dpear coincident- ally with the appearance of horns, which always exist in the tooth- less division of the order, excej)t in some very small antelopes (Cephalophus, etc.) where the whole amount of growth-force is small. Possibly the superior incisors and horns are complementary here. The retardation in development of the teeth in the higher apes and men, as compared with the lower apes, is coincident with the increase of number of brain convolutions. That this is not necessarily coincident with reduction of teeth in other groups is plainly proved by the rodents and CMromys, where the loss of many teeth is complementary to the great size of the incisors of the mid- dle pair. But in man there is no complementary increase of other teeth, and the reduction is no doubt due to contraction of the jaws, which is complementary to increase in other parts of the cranium, in both apes and men. I am confident that the origin and loss of many structures may be accounted for in this way, and the correlation of parts to each other be measured accurately. Objection, — The first one which arises is that which the author of the ^^ Vestiges of Creation " made against Lamarck's theory of a similar kind, i. e., that by assuming that effort, use, and physical THE METHOD OF OREATIO]^ OF ORGANIC FORMS. 203 causes have originated modifications of structure, we give the adaptive principle too much to do. I have made the same objec- tion to the theory of natural selection. It is true that an ai^plica- tion to a purpose is involved in the present theory of the 'location of growth-force " ; but in point of fact, a large number of non- adaptive characters are accounted for by it. These are the rudi- mental and transitional ones which mark the successive steps pre- liminary to the completion of an adaptive structure ; second, those produced by deficiency of growth-force in less favored regions of the body ; and third and fourth, phenomena consequent on general deficiency and excess of growth-force. And it may be said in conclusion that if the three principles, or if use especially, should be found to be inadequate to the service here demanded of them, it may be at least said that they, or the last named, constitute the only controllers of growth-force to any degree at all with which we are acquainted. lY. 01^ GKADE-IKFLUE5^CE. The object of the present section is the attempt to discuss how the influence of effort and use on the parent is placed in a position to be inherited by the offspring. A. Of the Nature of Grade-Lifluence. In the first place, it is necessary to note the definition and char- acter of grade-influence. a. Growth- force uninfluenced by grade-influence simply adds tissue either {a) in enlarging size, or {b) in rejilacing waste. It does this by repeating the cell, by division, in localities which have already assumed their specific form. This form of growth-force may persist throughout life, but with diminished energy in age. (i. Grade-influence directs growth-force in building up the tis- sues into organs, and constructs the parts of the body successively to completion, the result expressing the type or grade of the ani- mal or plant. Its energy terminates with maturity, except in cases of periodical reproduction of sexual ornaments of the male (birds, deer), where it continues throughout life, appearing at regular intervals. But it has occurred in acceleration that instead of a simple repe- tition of the ultimate histological element of an organism, in add- ing to its amount, it adds a completely organized part of the struct- 204 GENERAL EVOLUTION. ure, as a tube, a phalange, a digit, a limb or an arch ; an ocellus or a tooth. For instance, in the genus Amhlystoma, one section possesses four phalanges on the longest digit ; another section exhibits but three. In the species A, mavortium, some individuals have the small number of phalanges, but the majority possess the larger number. As all are of common parentage, a whole phalange has been lost or added. The explanation of this phenomenon is essential to the comprehension of the origin of type structures. * In plants, growth-nutrition continues throughout life, but in the higher plants it is more active during the earlier years in peren- nial species, addition to size becoming less and less marked with increasing age. Grade-nutrition also persists throughout life, but is chiefly active during a short period only of every year, or during flowering and fruiting. Not only in the production of the repro- ductive organs, but also in the yearly additions to other tyj^ical parts of the plant, grade-nutrition is active. ** In animals, growth-nutrition is more active in the early stages of life, but is continued throughout in the lower divisions ; in the highest, it is also continued throughout life, but there is a greater contrast between its results during youth, when nearly the whole size is attained, and during age, where the additions are much less. Grade-nutrition is, on the other hand, entirely confined to in- fancy and youth, except in those low animals which produce their reproductive organs periodically (some Fntozoa, etc.), where it may be said to be in nearly the same condition as in plants. y. While the amount of simple growth-force, represented in adult living animals, has varied very irregularly throughout the animal kingdom, there being large and small in every division, it would seem to have accumulated, on the whole, with the rising scale of animal types. Thus the lower or Protozoa are the small- est ; Radiates are next in size ; Molluscs and Articulates reach nearly the same maximum, which exceeds that of the Radiates, and falls far below that of the Vertebrates. Among the last the Mammalia have attained as large if not larger size than any of the other orders (e. g., Cetaced). This is, however, not necessary to the history of evolution. That an increased amount of grade growth-force has been con- stantly rendered potential during the advance of time is clear, if the preceding inferences be true. It is also evident that some in- dividuals have accumulated it more rapidly than others. If all THE METHOD OF CREATION OF ORGANIC FORMS. 205 alike originated from the simplest forms known to us. Multi- tudes have remained in the earliest stages {Protozoa) of the whole series, or of their own special series {Lingula), forming *' persist- ent types " ; or taken directions which rendered them incapable of expansion beyond a certain point without exhaustion or death ; for example, complicated types, as Ammonitidcs. The quadruma- nous animal, which was the progenitor of man, may thus be be- lieved to have acquired a higher capacity of this accumulation than his contemporaries. Assuming the nucleated cell to be the ultimate element of or- ganic tissue, there are two types of hfe in which grade-influence has not appeared, viz. : unicellular animals and plants, and living forms composed of homogeneous protoplasm. In the latter neither grade-influence nor animal growth-force is potential ; in the for- mer, simple growth-force only. It is therefore apparent that grade- influence has been developed in the organism itself ; perhaps this may have been in the plant, through the modified influence of ex- ternal physical causes ; in the animal, if our inductions as to use and effort be true, under the influence of the activities of the par- ent, which determined a structural change either in itself or in its offspring. The possibilities of this origin are considered in the next section. 8. The Location of Growth-Force proceeds under the direction of what Prof. Henry calls "Vital Influence." With this author I discard the use of the term "Vital Force," what was originally understood by that term being a complex of distinct ideas. The Vital forces are (nerve-force) Neurism, (growth-force) Bathnism, and (thought-force) Plirenism.'^ All these are supposed to be correlated to the Physical Forces, but are under direction and control of the Vital principle which locates their action, etc., just as molecular or atomic constitution determines the locality and character of the physical forces. The laws of the vital principle and of atomic constitution also determine the nature of the con- version of one force into another. Now, since physical and vital forces are correlated and convertible, the close relationship of the two controlling principles becomes obvious and suggestive of their identity. * The objection of President Barnard to thought being an exhibition of a force, is that " thought can not be measured." This objection docs not take into consid- eration the two-fold nature of thought. The amount of thought can most assuredly be measured, the quality of the thought can not. 206 GENERAL EVOLUTION. Dr. Carpenter, in describing the correlation of j)hysical and vital forces, defines the difference of organic species to be similar to that prevailing between different chemical bodies (the latter depending on different molecular and atomic constitution), which leads them " to 'behave differently" from each other under simi- lar circumstances. This may be more fully expressed by saying that different species possess different capacities for the location of the conversion of the physical forces into growth-force. A " descent with modifications " contemplated by a process of evolu- tion, signifies a progressive change in this capacity. Acceleration means an increase in this capacity ; retardation a diminution of it. Grade-infiuence means the influence which produces this change of capacity. B, The Origin of Grade-Injiuence. Living protoplasm can convert heat and nutriment into growth-force without the agency of the nervous system. This is proved by the nutrition of the Protozoa and Ccelenterata, and from experiments on the muscles of frogs, etc. In the latter case, as is well known, the nerve may be divided, and the muscle retain its size if a current of electricity be passed through it, thus sus- taining the nutrition. As the presence and structure of the nerv- ous system is in relation to the specialization of animal struct- ure in other respects, it is very probable that the nervous system is in higher animals the agent of the location of growth -force. In the lowest it is not affected by any such means. As the nervous system is the instrument of the metaj^hysical peculiarities of the animal (emotions, choice, etc.), we may conclude that, in the lower animals, location of growth-force is influenced by necessity without choice ; in the higher by necessity with choice. The impulses derived from the nervous system, it is known, may be reflex or automatic in answer to stimuli from without. They may become so, also, after having been originated conscious- ly or by effort of will. In the case of habits, frequent exercise of choice has so impressed the nervous system as to result in its repetition of effort, often in opposition to changed choice. The influence of effort in muscular action, through the nervous system, appears to be, first, to enable it to convert heat to nerve- force, and, then, to conduct nerve-force to the involuntary mus- cles, or those controlling circulation, where it is converted into motion, which thus controls nutrition throuirh circulation. The THE METHOD OF CREATION OF ORGANIC FORMS. 207 nervous system, like others, develops in capacity with use, hence probably nerve-tissue converts heat * into nerve-force as muscular tissue converts heat into motion. In other words, by repetition, the capacity of the nervous system for this conversion of heat is known to increase. As the amount of heat converted is in pro- portion to the amount of appropriate nerve-tissue (see above), it is evident that use and effort increase the amount of nerve-tissue. The phenomena of thought render the same modification of structure j)robable. Effort in the direction of thought is supposed to convert heat into thought-force. Inasmuch as the more intelli- gent animals possess the highest development of cerebral hemi- spheres, it is highly probable that brain substance converts heat into growth-force also, which produces tissue of its own kind pre- cisely as muscle does. As different parts of the nervous centers subserve different purposes, the development of these parts must proceed approxi- mately under the influence of special kinds of effort and use. Where, as. in the adult, heat is converted into growth-force in the tissues to a very limited extent, if the above principles be true, the conversion of heat by the nervous system into nerve growth- force and tissue is, on the other hand, not terminated. Capacity for effecting conversion of force is regarded, as above pointed out, as dependent on molecular constitution. Hence we conclude that change in that capacity on the part of the nervous system involves a molecular change in its constitution. Now, we know physical and metaphysical peculiarities of parents to be inherited by offspring ; hence, no doubt, the nervous structure determinative of growth-force is inherited. This will then control the localities of special conversion of heat, etc. (from the mother), into growth-force, in accordance with the structure of the parent, and the more decidedly, as its own in- crease progresses. The result will be acceleration, or construction of tissues and organs in excess of those of the parent, if the effort or use de- voted to a nerve or organ be represented in the nerve-center of the parent by a greater amount of force-converting tissue than is * The supposition that this and other forms of vital energy are derived from metamorphosis of heat, was in accordance with views held at the time this essay was written (1871). The much more probable hypothesis is that such energy is derived from retrograde metamorphosis of nutritive material. (Ed. 1886.) 208 GENERAL EVOLUTIOI^. necessary when inherited in the foetus for the construction (by conversion) of tissues and organs like those of the parent. ,y^ That this is a partial explanation of inheritance, is rendered probable from the fact that the types of structure presented by \ the nervous centers express the grade of the animals possessing them far more nearly than those of any other organ or set of or- gans. If the brain, like other organs, develops by intelligent use, it can not be doubted that this relation of its development to I grade is not accidental, but that grade-structure * is an expression of its capacities, physical and mental. V. o:n" intelligent selection. As neither nse nor effort can be ascribed to plants, and as we know that their life history is much more dependent on their sur- roundings than is that of animals, we naturally look to the physi- cal and chemical causes as having a prime influence in the origina- tion of their type-structures. Without greater familiarity with the subject, I will not attempt to say how far the various degrees of growth-force possessed by parent plants, located under the influ- ence of meteoric and other surroundings, and preserved, destroyed or restricted by natural selection, may account for the characters of their successors of the present period. But other agencies simi- lar to use, that is, automatic movements, may be also introduced as an element in the argument. The movements of tendrils seek- ing for support may be here considered, and, as Dr. Asa Gray has pointed out, have consequences similar to those of use in animals. When the tendril seizes a support, growth-force is located at the point of contact, for the tendril increases considerably in thick- ness. Among animals of the lowest grade, movement must be quite similar to those of plants, or automatic from the start, and not even at the beginning under the influence of will. Evidence of will is, however, soon seen in the determinate movements of many of the Protozoa in the seizing of food. With will necessarily ap- pears a power of choice, however limited in its lowest exhibitions, by the lack of suggestive metaphysical qualities, or the fewness of alternatives of action presented by surrounding circumstances, to animals of low and simple organism. We can, however, believe ^ Grade growth-force is not regarded here or elsewhere as a simple form of energy, but as a class of energies, which are the resultants of the interference of mind (i, e., consciousness) with simple growth-force. (Ed. 1886.) THE METHOD OF CREATION OF ORGANIC FORMS. 209 that the presence of greater or less number of external facilities for action characterize different situations on the earth's surface, as well as that greater and less metaphysical capacity for perceiv- ing and taking advantage of them must exist in diiferent indi- viduals of every species of animal, however low, which possesses consciousness and will. These qualities must, of course, influence eifort and use to the advantage of the animal, or the reverse. Effort and use have very various immediate stimuli to their exertion. Use of a part by an animal is either compulsory or optional. In either case, the use may be followed by an increase of nutrition under the influence of reflex action or of direct volition. A compulsory use would naturally occur in new situations which take place apart from the control of the animal, where no alternatives are presented. Such a case would arise in a submerg- ence of land where land-animals might be imprisoned on an island or in swamps surrounded by water, and compelled to assume a more or less aquatic life. Another case, which has also probably often occurred, would be when the enemies of a species should so increase as to compel a large number of the latter to combat who had previously escaped it. In these cases, the structure produced would be necessarily adaptive. But the effect would sometimes be to destroy or injure the animals (retard them) thus brought into new situations and compelled to an additional struggle for existence, as has, no doubt, been the case in geologic history. Direct compulsion would also exist where alternatives should be presented by nature, but of which the animal would not be sufficiently intelligent to take advantage. Most situations in the struggle for existence afford alterna- tives, and the most intelligent individuals of a species will take advantage of those most beneficial. Nevertheless, it is scarcely conceivable that any change or increase of effort, or use, could take place apart from compulsion derived from the relation of external circumstances, as a more or less remote cause. Preservation, with modifications, would most probably ensue when change of stimulus should occur gradually, though change of structure might occur abruptly, under the law of expression points. * * See " Origin of Genera," p. 3S. 14 210 GENERAL EYOLUTIOX. Choice is influence not only by intelligence, but by the imagi- nation and by the emotions. Intelligence is a conservative principle, and always will direct effort and use into lines which will be beneficial to its possessor. Here we have the source of the fittest — i. e., addition of parts by increase and location of growth-force, directed by the will — the will being under the influence of various kinds of compulsion in the lower, and intelligent option among higher animals. Thus, intelligent choice, taking advantage of the successive evolution of physical conditions, may be regarded as the originator of the fittest, while natural selection is the tribunal to which all the results of accelerated growth are submitted. This preserves or destroys them, and determines the new points of departure on which accelerated growth shall build. The influences locating growth -force may be tabulated as follows : DIVISION. INFLUENCE. Plants. Physical and ) chemical. ^ + 9 9 Plants with me- c h a n i c a 1 move- ments; animals with indeterminate movements. Animals with de- ^ terminate move- I ments or will,* but j no intelligence. J Animals with will and less intel- ligence. Animals with more intelligence. -h use « -f- effort under compulsion. (( (( (( (( (( (( -f choice. -I- intelligent choice. As examples of intelligent selection, the modified organisms of the varieties of bees and ants must be regarded as striking cases. Had all in the hive or hill been modified alike, all soldiers, neu- ters, etc., the origin of the structures might have been thought to be compulsory ; but varied and adapted as the different forms are to the wants of a community, the influence of intelligence is too obvious to be denied. The selection of food offers an opportunity for the exercise of * Will must be here regarded as the answer to stimulus, without any element of freedom. See Article XX, on the " Origin of the Will." (Ed. 1886.) THE METHOD OF CREATION OF ORGANIC FORMS. 211 intelligence, and the adoption of means for obtaining it still greater ones. It is here that intelligent selection proves its su- premacy as a guide of use, and consequently of structure, to all the other agencies here proposed. The preference for vegetable or for animal food determined by the choice of individual animals among the omnivores, which were, no doubt, according to the paleontological record, the predecessors of our herbivores, and per- haps of carnivores also, must have determined their course of life and thus all their parts, into these totally distinct directions. The choice of food under ground, on the ground, or in the trees would necessarily direct the uses of organs in the appropriate directions respectively. In the selection of means of defense a minor range of choice is presented. The choice must be limited to the highest capabilities of the animal, since in defense, these will, as a general thing, be put forth. This will, however, not be necessarily the case, but will depend in some measure on the intelligence of the animal, as we readily observe in the case of domesticated species. In the case of the rattlesnake, already cited, the habit of rapid vibration of the tail appears to me to be the result of choice, and not of compulsion. For the cobra of India, for the same pur- pose, expands the anterior ribs, forming a hood, which is a very different habit.* Here are two alternatives, from which choice might be made, and violent hissing is a third, which the species of the colubrine genus Pityopliis have adopted to some purpose. As to the benefit of the rattle, it no doubt protects the animal from all foes other than man ; but is rather a disadvantage as re- gards the latter, being by a beautiful turn of events a protection to the higher animal. On the principle of natural selection it might be supposed that the harmless snakes which imitate the Crotalus for the sake of defense were preserved ; but if the above explanation of the origin of the habit in the latter be true, the second explanation is not valid. (Since in time the harmless snakes preceded the rattle- snakes. Ed. 1886.) The power of metachrosis, or of changing the color at will, by the expansion under nerve-influence of special pigment cells, exists in most Reptilia, Batrachia, and fishes. It is then easy to believe that free choice should, under certain circumstances, so habitually * The North American Heterodons possess a similar habit. (Ed. 1S86.) 212 GENERAL EVOLUTION. avoid one or another color as to result finally in a loss of the power to produce it. Thus, it appears to be a fact that not only are species of fishes which dwell in the mud of darker hues than those that inhabit clear water, but that individuals of the same species differ in a simi- lar manner in relation to their habitats ; those that live in impure or muddy waters having darker tints than those of clear streams. Land animals present equally abundant and remarkable imita- tions of the objects or substances on which they live. This is well known in insects and spiders, which look like sticks or leaves, or the flowers on which they feed. It is seen in reptiles, which in very many cases can voluntarily assume the hue of leaf, stone, or bark, or have constantly the gray color of their native desert sands. These cases are largely selective or optional in their origin, for though metachrosis is also induced by some external stimulus, as an enemy or a food animal, yet other means of escaj)ing the one and procuring the other are generally open. These facts pave the way for a consideration of the phenome- non of mimetic analogy, which, though well known to naturalists, may be illustrated by the following new facts : On the plains of Kansas there is a species of Mutilla whose abdomen and thorax are colored ochraceous, or brown-yellow, above. A spider of the genus SaUicus is equally abundant, and is almost j)recisely similar in the color of the upper surfaces, so much so as to deceive any but a most careful observer. The Mutilla being a well-armed insect, and a severe stinger, there can be no doubt that the SaUicus derives considerable immunity from enemies from its resemblance. On the same plains, the Crotalus conjiuentus, or prairie rattle- snake, abounds. It is an olive gray, with a series of transverse brown dorsal spots, and two rows of smaller lateral ones. The head exhibits a number of brown and white bands. The prairie Heteroclon {H. nasicus) possesses not only the same tints but the same pattern of coloration, and at a short distance can not be dis- tinguished from it. In consequence, as one may justly say, this species is, with the rattlesnake, the most common serpent of the plains, as it shares, no doubt, in the protection which the armature of the Caudisona gives its possessor. This is in accordance with the views of Wal- lace and Bates. THE METHOD OF CREATION OF ORGANIC FORMS. 213 A curious case occurred to me in four species of fishes, which I took in a small tributary of the Yadkin River, in Roane County, N. 0, Among several others, there were varieties of the widely distributed species Chaenohryttus viridis, Hypsilepis analostanus, and Ptychostomus pidie7isis (each representing a different family), which differ from the typical form of each in the same manner, viz. : in having the back and upper part of the sides with longi- tudinal black lines, produced by a line along the middle of each scale. This peculiarity I have not observed in these species from any other locality. Until I had examined them I thought them new species. The only other species presenting such marking in the Yadkin River is the large perch, the Roccus lineatus. According to the theory of natural selection a resemblance to this well-armed species might be of advantage to the much weaker species in question ; yet the same species co-exist in other rivers without presenting the same mimicry. It is difficult not to urge the importance of the causes already regarded as efficient in the origination of structure in the present branch of the subject also. We are especially disposed to call in use and effort here, after noticing how much more distinctly change of color is under the control of the animal, than change of shape. It must, however, be borne in mind that similar resem- blances exist among plants ; though, as Professor Dyer shows, a large majority of these cases occur in species of different floral regions. Thus in this case, as in those of structure already cited, we appeal first to physical laws in the lowest beings, but with the increasing interference of use, effort, and intelligence, as we rise in the scale. Thus it is that, in the Vertebrates generally, the mi- metic resemblances are found in species of the same region, where only an intelligent or emotional agency could be illustrated. If among animals as low as butterflies the influence of intelligence be denied, that of admiration for the beauty, or fear of the armature, of the predominant species imitated, would appear to be sufficient to account for the result. Admiration and fear are possessed by animals of very low organization, and, with the instincts of hunger and reproduction, constitute the most intense metaphysical con- ditions of which they are capable. But our knowledge of this branch of the subject is less than it ought to be, for animals pos- sess many mental attributes for which they get little credit. It appears to be impossible to account for the highest il lustra- 214 GENERAL EVOLUTION. tions of mimetic analogy in any other way, the supposition of Wallace that such forms must be spontaneously produced, and then preserved by natural selection, being no explanation. It has been shown by Bennett that the chances of such modification aris- ing out of the many possibilities are exceedingly small. If the above positions be true, we have here also the theory of the development of intelligence and of other metaphysical traits. In accordance with it, each trait appropriates from the material world the means of perpetuating its exhibitions by constructing its instruments. These react by furnishing increased means of exer- cise of these qualities, which have thus grown to their full expres- sion in man. VI. A EEVIEW OF THE MODEEN DOCTRmE OF EVO- LUTION.* The doctrine of evolution of organic types is sometimes appro- priately called the doctrine of derivation, and its supporters, deriv- atists. This is because it teaches the derivation of species, genera, and other divisions, from pre-existent ones, by a process of modi- fication in ordinary descent by reproduction. The opposite or creativist doctrine teaches that these forms were created as we see them to-day, or nearly so ; and that the natural divisions and spe- cies of organic beings have never been capable of change, the one into the other. I. THE EVIDENCE FOR EVOLUTIOIS^ The reasons w^hich induce me to accept the derivatist doctrine, and to reject the creational, fall under the two heads of probabil- ities and conclusive evidence. The probabilities are cumulative in their pointings, and strengthen that part of the evidence which is, to my mind, conclusive. The reasons why derivation is prob- able are the successional relation of increment or decrement of structure, observed in : 1. Systematic relation (taxonomy) ; 2. Embryonic growth (embryology) ; 3. In geologic time (paleontology) ; 4. And in the coincidence in the successions seen in Nos. 1, 2, and 3. The fact that it is necessary to arrange animals in an order cor- responding with the phases of their embryonic history is remark- able ; but the further fact, shown by paleontology, that the same succession marked the ages of past time, at once brings evolution within the limits of strong probability. Nevertheless, all this might have been a mere system, without transitions between its * Abstract of a lecture delivered before the California Academy of Sciences, Oct. 27, 1879. 216 GENERAL EVOLUTION. members ; organic types miglit have been created unchangeable, but presenting the mutual relations in question. But if transi- tions among these members can be shown to take i^lace, then indeed the phenomena mentioned received a sufficient explanation. They are seen to be the necessary relations of the parts of a shift- ing scene of progression and retrogression ; they express combina- tions of structure, which, though often long enduring, are, never- theless, not perpetual, but give way to other combinations to be in their turn dissolved. Now, if there is anything well known in nature, it is that there are divisions of various ranks in the vege- table and animal kingdoms, whose contents present variations of structure which are confessedly additions to or subtractions from the characters of ancestors, which have appeared during ordinary descent. The j^rotean species, genera, etc., are well known to biologists, and every naturalist who admits varieties, sub-species, sub-genera, etc., admits derivation so far as they are concerned. The facts of variation, including ''^sporting," etc., are notorious, not only among domesticated, but also in wild animals and plants. The facts have led some persons to suggest that species have been produced by evolution from a single specific center, but that the genus and other comprehensive divisions are unchangeable. But I think I have shown, in a paper entitled " The Origin of Gen- era," * that the structural characters which define genera, and even higher divisions, are subjects of variation to as great an extent as are the less profound specific characters ; and, moreover, that the evidence of derivation which they present is singularly clear and conclusive. The changes of both genus and species character are always of the nature of additions to or subtractions from those of one generation displayed by their descendants. As such, they form the closing chapters of the embryonic or growth-history of the modified generation. In order to explain more fully the application of the above statements, I introduce a few examples selected from the subjects of my studies. Their number might be indefinitely extended. I first cite the genera of the tailless BatracMa Anura (frogs, toads, etc.), whose relations are very simple and clear, and show the parallelism between adult structure and embrj^onic succession. See above, 1 and 2. The greater number of BatracMa Anura fall into two divis- * Philadelphia, 1869. "Proceedings Academy Natural Sciences, 1868." REVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 217 Fig. 8. Fig. 9. ions, which differ only in the structure of the lower portion of their scapular arch, or shoulder-girdle. In the one the opposite halves are capable of movements which contract or expand the capacity of the thorax; in the other the opposite halves abut against each other so as to be incapable of movement, thus pre- serving the size of the thoracic cavity. But during the early stages, the frogs of this division have the movable shoulder-girdle which characterizes those of the other division, the consolidation con- stituting a modification superadded in attaining maturity. Further- more, young Amir a are toothless, and one section of the species with embryonic shoulder-girdle never ac- quire teeth. So here we have a group which is imperfect in two points instead of one. This is the tribe Bufoniformia; the tribe with teeth and embryonic shoulder-girdle is called the Arcifera, and that which is advanced in both these res- pects is the Raniformia. Now the frogs of each of these divisions pre- sent nearly similar scales of develop- ment of another part of the skeleton, viz., the bones of the top of the skull. We find some in which one of these bones (ethmoid) is represented by cartilage only, and the frontoparietals and nasals are represented by only a narrow strip of bone each. In the next type the ethmoid is ossified ; in the next, we have the frontoparietal completely ossified, and the nasals range from narrow strips to complete roofs ; in the fourth station on the line, these bones are rough, with a hyperostosis of their surfaces ; and in the next set of species this ossification fills the skin, which is thus no longer separable from the cranial bones ; in the sixth form the ossification is extended so as to roof in the temporal muscles and inclose the orbits behind, while in the rare seventh Fig. 10. SlIOULDEK-GIRDLES OF " AnURA." Fig. 8, of the Arciferous type (Scaphiopus holbroohi). Fig. 9, Rana temporaria^ tadpole -nith budding limbs. Fig. 10, do. adult. Figs. 9 and 10 from Parker. 218 GENERAL EVOLUTION. and last stage, the tympanum is also inclosed behind by bone. Now all of these types are not found in all of the families of the Anura, but the greater number of them are. Six principal fami- lies, four of which belong to the Arcifera, are named in the dia- gram below, and three or four others might have been added. I do not give the names of the genera which are defined as above described, referring to the explanation of the cuts for them, but indicate them by the numbers attached in the plate, which corres- pond to those of the definitions above given. A zero mark signi- fies the absence or non-discovery of a generic type. Sternum embryonic. Sternum complete. Bufoniformia. Bufonidae. Arcifera. Eaniformia. Scaphiopidse and Pelobatidae. Cystignathidse. Hylidae. Eanidae. 1— 1 1 1 2— 2 2 2 2 3— 3 3 3 3 4— 4 4 4 4 4 5— 5 5 5 5 6— 6 6 6 6 1— 7 It is evident, from what has preceded, that a perfecting of the shoulder-girdle in any of the species of the Bufoniform and Ar- ciferous columns would place it in the series of Eaniformia. An accession of teeth in a species of the division Bufonifor?ma would make it one of the Arcifera j while a small amount of change in the ossification of the bones of the skull would transfer a species from one to another of the generic stations represented by the numbers of the columns from one to seven. There are few groups where this law of parallelism is so readily observed among contemjoorary types as the Batracliia, but it is none the less universal. The kind of parallelism usually observed is that in which there is only a partial resemblance between adults of certain animals and the young of others. This has been termed *^ inexact parallelism," and the relation is presented by forms not very nearly phylogenetically related. The more remote the phylo- genetic lines of two types, the more *"' inexact " will their parallel- ism be. It was once a question whether any parallelism can be traced between the members of the five or six primary divisions of animals, and in my essay on the *^ Origin of Genera," I was com- pelled to state that there was then ^'no evidence of the community KEVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 219 of origin of these diyisions." Since that time, Haeckel has pub- lished his '^Gastraea Theory." This is a grand generalization from the facts of embryology, which shows the community in type of the early stages of all animals, and the similarity of the phases which they present during a part of their larval life. The exceptions to this law which have been observed will probably be explained, as have been those which have been urged against the law of homologies in anatomy. The paleontology of the Batracliia anura is largely unknown, so we must look elsewhere for proof of the truth of the fourth proposition, viz., that the suc- cessional relation in embryology corre- sponds with that shown by paleontology to have existed in geologic time. For this purpose I select one of the most complete series known to paleontology; that of the camels or CameUdcB, whose re- mains are found abund- antly in various parts of our country. The succession of the known genera is seen in the structure of the bones of the feet, and of the superior incisor and premolar teeth. The metatarsal and meta- carpal bones are or are not co-ossified into a cannon bone ; the first and second superior in- cisor teeth are present, rudimental or wanting, and the premolars num- ber from four to one. The relations which these conditions bear Fig. 11. Fig. 12. Fig. W.—Poebrotherium vilsoni carpus and meta- carpus with end of radius, three fifths natural size. Original ; from White Eiver Miocene of Colorado. Fig. 12.— Carpus and metacarpus of Procamelus occidentalism about two fifths natural size. Original ; from report of G. M. Wheeler, U. S. Expl. Surv. W. ot 100th Mer., vol. iv, pt. ii. From New Mexico. PLATE IV. Fig. 1. Fio. 33. Fig. 2. Fig. 3, wanting. FjG. 5. Fig. 6. Fig. 6. Fig. 7. BUFONID^. Fig. 7, wanting. SCAPHIOPIDJE AND PELOBATIDM. PLATE V. Fig. 1. Fig. 1. Fig. 2. Fig. 2. Fig. 3. Fig. 83. Fig. 32. Fig. 3 1. Fig. 3. Fig. 31. Fig. 32. Fig. 4. Fig. 33. Fig. 6. Fig. 6. CYSTIGNATHID^. Fig. 5. RANID^. 222 GENEKAL EVOLUTION. EXPLANATION OF CUTS OF CRANIA OF ANURA. The numbers in each column correspond with the types of ossification mentioned in the text, and are the same as those in the table of families given in the same con- nection. The power numbers attached to Fig. 3, represent the degree of ossification of the nasal bones, except the ~\ which signifies unossified ethmoid. Most of the cuts are original. BcFONiDJE. — Fig. 2, anterior part of skull of Chdydohairachas gouldi Gray, from Australia. Fig. 3, do. of Schismaderma carens Smith, S. Afi"ica. Fig. 6, top of head of Peltaphryne peltacephala D. and B., Cuba. Fig. 7, top of head of Otaspis empusa Cope, Cuba. SoAPHiopiD^ AND Pelobatid^. — Fig. 2, diagram of top of cranium of Didocus ccdcaratus Micahelles, Spain. Fig. 5, skull of Scaphiopm liolhroolci Harl., United States. Fig. 6, skull of Cultripes provincialis, from France, after Duges. llYLiDiE. — Fig. 1, Thoropa miliaris Spix., Brazil. Fig. 2, Hupsiboas doumerci D. and B., Surinam. Fig. 2\ Hypaihoas punctatus Schn., Brazil. Fig. 3^, Scytopis vemdosus Daudin, Brazil. Fig. 6, Trachycephalus geographicus D. and B., Brazil, after Steindachner. Cystignathid^. — Fig. 1, Eusophus nehuloaiis Gir., Chili. Fig. 2, Borhoroccetes tas- maniensis Gthr., Tasmania. Fig. 3, Elosia nasiis Licht., Brazil. Fig. 3^, Ify- lodes oxyrhyiichus D. and B., W. Indies. Fig. 4, Grypiscus umbrinus Cope, Brazil. Fig. 6, Calyptocephalus gayi D. and B., Chili. Ranid^. — Fig. 3~^ — Ranula chry&oprasina Cope, Costa Rica. Fig. 3, Rana oxy- rhyncha Sund., S. Africa. Fig. 3\ Rana clamata Daud., N. America. Fig. 3^, Rana agilis Thomas. Fig. 3'^, Rana hexadactyla Less., India. Fig. 4, PoJy- pedates quadrilineatus D. and B., Ceylon. to geologic time are displayed in the follo^^ng table, commencing with the lowest horizon : No cannon bono. Cannon bone present. Incisor teeth present. Incisors one and two wanting 4 premolars, 3 prem'rs. 2 prem's. 1 prem'r. r- Lower Miocene. -] Pochrotherium. { Protolahis. Upper Miocene. < Procamelus Pliocene and Recent. ( Pliauchenia. Camelus. Auchenia. This table shows that geological time has witnessed, in the his- tory of the CamelidcB, the consolidation of the bones of the feet and a great reduction in the numbers of the incisor and premolar teeth. The embryonic history of these parts is as follows : In the REVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 223 foetal state all the Ruminantia (to which the camels belong) have the cannon bones divided as in Poehr other ium ; they exhibit also incisor teeth, as in that genus and Protolabis. Very young recent Fig. 13. — Protolabis Iransmontanus Cope, skull, a, in profile ; 5, from below, one third (linear) natural size. Original; from vol. iv, Report U. S. Geol. Surv., under F. V. Hayden. Ticholeptus bed of Oregon. camels have the additional premolar of Pliauchenia. They shed this tooth at an early period, but very rarely a camel is found in which the tooth persists. The anterior premolar of the normal Fig. 14. — Procamelus occidentalis Leidy, profile of skull, about two sevenths natu- ral size. Original ; from report of Capt. G. M. Wheeler, IT. S. Geol. Geog. Surv. W. of 100th Mer. Vol. iv, pt. ii. From Loup Fork bed of New Mexico. Camelus is in like manner found in the young lama (Auchenia), but is shed long before the animal attains maturity. I may add that in some species of Procmnelus caducous scales of enamel 224: GENERAL EVOLUTIOIN". and dentine in shallow cavities represent the incisive dentition of Protolabis. It remains to show that characters of the kind above men- tioned are sometimes inconstant ; that they may or may not ap- pear in individuals of a species. Under such circumstances it is evident that their origin does not imply any break in the line of descent. First, as to a family character. It is well known that the deer differ from the giraffes in the presence of a burr or ring of osseous excrescences surrounding the base of the horn. Now, in the ex- tinct tertiary genus Cosoryx there are three species which possess or lack this burr indifferently. Why some individuals should, and others should not possess it, is not known.* Second, as to a generic character. The genus Canis (dog) is defined by the presence of two tubercular molars in the inferior series. The allied genus Tlious possesses three such teeth, while Idicyon has but one. Kow examples of Canis familiar is (domes- tic dog) with but one tubercular molar are not rare, while an in- dividual with three is occasionally found. To take another case. The normal dentition of Homo (man) is, on each side, incisors, 2 ; canine, 1 ; premolars, 2 ; molars, 3. It is very common to find in the higher races, individuals who have molars only two in one or both jaws ; and the absence of the external incisors of the upper jaw is almost as frequently met with. Here we have two new generic variations in one and the same species. In specific characters variations are most familiar. Thus, the young of deer are generally spotted, and the adults are nearly uniform in coloration. Some deer (as the Axis) retain the spotted coloration throughout life, while an occasional spotted individual of unicolor species is a violation of specific character by a failure to develop. The larvae of some salamanders are of uniform col- oration, and the adults spotted. The unicolor adults of the same species, not uncommonly met with, present examples of the same kind of variation. Any biologist can select hundreds of similar cases from his special department of study. * The explanation I have offered is that the horn was stripped of its integuments to the position of the burr by the animals in fighting. The condition of the speci- mens renders this hypothesis pi'obable. See "Report U. S. Expl. Surv. W. 100th Mer.," Capt. G. M. Wheeler, vol. iv, pt. ii. EEYIEW OF THE MODERN DOCTRmE OF EYOLUTIOIT. 225 II. THE LAWS OF EVOLUTIOIT. Having reviewed the reasons why the doctrine of evolution should be received as truth, I desire to give attention to the laws which may be made out by reference to its phenomena. Progress in this direction is difficult, owing to the natural impediments in the way of studying the history of the growth of living beings. We will, however, commence by examining more fully the phe- nomena with which we have to deal. It is well understood that the world of animal life is a nicely adjusted equilibrium, maintained between each individual and its environment. This environment exerts forces both purely physi- cal, and those exercised by other animals. Animals antagonize each other in procuring food, whether that food consist of vegeta- tion or of other animals, but in the latter case the conflict is more severe. A similar competition exists among male animals in the matter of reproduction. These exhibitions of energy constitute the struggle for existence, which is the daily business of the living world. It is well understood that in this struggle the individuals best provided with means of self-preservation necessarily survive, while the weak in resources must disappear from the scene. Hence those which survive must display some especial fitness for existence under the circumstances of their environment, whatever they may be. So the ^^ survival of the fittest" is believed to be a law of evolution, and the process by which it is brought about has been termed ** natural selection." The works of Darwin and others have satisfied biologists that this is a vera causa. Before the excellence of a machine can be tested, it must exist, and before man or nature selects the best, there must be at least two to choose from as alternatives. Furthermore, it is exceedingly improbable that the nicely adapted machinery of animals should have come into existence without the operation of causes leading directly to that end. The doctrines of **^ selection " and "sur- vival " plainly do not reach the kernel of evolution, which is, as I have long since pointed out, the question of "the origin of the fittest." The omission of this problem from the discussion of evolution, is to leave Hamlet out of the play to which he has given the name. The law by which structures originate is one thing ; those by which they are restricted, directed, or destroyed, is another thing. There are two kinds of evolution, progressive and retrogres- 15 226 GENERAL EVOLUTION. sive ; or, to use expressions more free from objection, by addition of parts, and by subtraction of parts. It is further evident that that animal which adds something to its structure which its par- ents did not possess, has grown more than they ; while that which does not attain to all the characteristics of its ancestors has grown less than they. To express the change in the growth-his- tory which constitutes the beginning of evolution, I have employed the terms *^ acceleration and retardation." Generally these ex- pressions are literally exact, i. e., there is an increased rate of growth in evolution by addition, and a decreased rate in evolution by subtraction ; but this is not always the case, for some divisions of animals have increased the length of their growth-period with- out reference to evolution in structure. The terms express the phenomena figuratively, where not exact in the sense of time, and I believe they are sufficiently clear. The origin of the fittest is then a result of either acceleration or retardation. It is easy to perceive that a character which makes its appearance in a j^arent before or near to the breedino^ season is likelv to be transmitted to its descendants ; so also a character which is lost near this time is likely to be wanting from the offspring. The causes of accelera- tion and retardation may next claim attention. It is well known that the decomposition of the nutritive fluids within living animals gives rise, in the appropriate tissues, to exhibitions of different kinds of forces. These are, motion in all classes ; heat in some only ; in a still smaller number, electricity and light ; in all. at certain times, growth-force or bathmism ; in many, phrenism or mental or thought-force. These are all derived from equivalent amounts of chemical force which are liberated by the dissolution of protoplasm. This organic substance, consisting of CHON, undergoes retrograde metamorphosis, being resolyed into the simpler CDs, HO, etc., and necessarily liberates force in the process. None of the functions of animal life can be main- tained without supplies of protoplasm. TVe have here to do with bathmism. It consists of the movement of material to, and its deposition in, certain definite portions of the growing egg, or foetus, as the case may be. It is different in its movements in every species, and its direction is probably the resultant of a num- ber of opposing strains. In the simplest animals its polar equili- brium is little disturbed, for these creatures consist of nearly globular masses of cells. As we ascend the scale a greater and more marked interference becomes apparent ; radiated animals REVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 227 display energy in a number of radiating lines rather than in the spaces between them ; and in longitudinal animals, a longitudinal axis exceeds all others in extent and importance. In the highest animals its results are much more evident at one extremity of the axis (head) than at the other, and the diyerging lines are reduced to four (the limbs). In each species the movements of this force are uniform and habitual, and it is evident that the habit is so deeply seated that only a very strong dynamic interference can modify or divert it. The interfering forces are probably all those transmissible through living tissue, and especially molar force. Thus every species has its own specific kind of bathmic force. The characters of living beings are either adaptive or non- adaptive ; they are either machines especially fitted to meet the peculiarities of their environment, or they are not. Among the latter may be ranged rudimental structures and also many others of no sufficient use. They are all due either to excess or defect of growth-force ; they are either consequences of a removal of nutri- tive material to other portions of the body ; or they are due to an excess of such material which renders an organ or part useless through disproportionate size. Of the former class may be cited the absence of the tail in some monkeys and birds ; also of the teeth in some Cetaceans ; of the latter kind are the enormous tusks of the mammoth and the recurved superior canines of the bab}Tussa. The change of destination of this material has been probably due to the construction of adaptive machines whose per- fection from time to time has required the use of larger and larger proportions of force and material. In considering the origin of adaptive structures, two alterna- tive propositions are presented to us. Did the occasion for its use follow the appearance of the structure, or did the need for the structure precede its appearance ? The following answer to the question has always been the most intelligible to me. Animals and plants are dependent for existence on their environment. It is an every-day experience that changes in environment occur without any preparation for them on the part of living things. If the changes are very great, death is the result. It is evident that the influence of environment is brought to bear on life as it is, or has been, and that special adaptations to it on their part must fol- low, not precede, changes of climate, topography, population, etc. We have another important consideration to add to this one, viz., the well-known influence of use, i. e., motion, on nutrition. Ex- 228 GENERAL EVOLUTION. ercise of an organ determines nutritive material to it, and the nervous or other influence which does this, equally determines nutritive material to localities in the body to which an effort to move is directed, whether an executive organ exist there or not. The habit of effort or use determining the nutritive habit must be inherited, and result in the growing young, in additional struct- ure. Change of structure, denied to the adult on account of its fixity, will be realized in the growing or plastic condition of foetal or infant life. The two considerations here brought forward lead me to think that the cause of acceleration, in many adaptive structures, is environment alone, or environment producing move- ments, which in turn modify structure. The character of the stimulus in the successive grades of life may be expressed by the following table, passing from the lowest to the highest : 1. Passive or motionless beings : by climate and food only. 2. Movable beings : by climate, food and motion. By motion either : a, unconscious, or * aa, conscious, which is, h, reflex, or M, directed by desire without ratiocination, or Mb, by desire directed by reason. The only general rules as to the direct influence of motion on structure which can be laid down at present are two, viz., That density of tissue is in direct ratio to pressure, up to a certain point ; t and that excess of growth-force, in a limited space, pro- duces complications of the surfaces stimulated. \ These and other laws, yet unknown, have probably led the changes expressed by evolution, while many others have followed the disturbance of equilibrium which they have produced. I here allude incidentally to the question of transmission or inheritance. It has been maintained above that the bathmic force of each species is different from that of all other sj^ecies. This force is characteristic of some unit of organization of living be- * Movements coming under this head are often called reflex, •f- See "Penn. Monthly," 1872; this work Art. L X " Method of Creation," Philadelphia, 1871. EEVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 229 ings ; and this probably consists of several molecules. This unit has been termed, by Haeckel, the plastidule. The transmission of the bathmic force of one generation to another would be effected by the transmission of one or more living plastidules ; and this is probably precisely what is accomplished in reproduction. The Dynamic Tlieory of reproduction I proposed in 1871,* and it has been since adopted by Haeckel under the name of perigenesis. I compared the transmission of bathmic force to that of the phe- nomenon of combustion, which is a force conversion transmitted from substance to substance by contact. The recent observations of Hertwig, Biitschli and others, confirm this view. The theory of pangenesis, devised to explain the phenomenon of rej^roduction, is to my mind quite inadequate. III. METAPHYSICS OF EVOLUTION". I enter here upon a wide field, over which I can only skim on an occasion like the present. The subject has been already intro- duced by reference to consciousness as modifying movement ; of course, then, if movement modify structure, the latter is influenced by consciousness. The word consciousness was then, and is now, used in its simplest sense, viz. : as synonymous with physical sensibility. Its lowest and most usual exhibition is the sense of touch ; the special senses, taste, sight, etc., are higher forms, while thoughts and desires are organized products of the same raw material. Consciousness can not be denied to many of the inferior animals ; indeed, if we grant it to any, we must admit that it is displayed at times by even the lowest Protozoon. That these humble creatures should possess it, is apparently quite as proba- ble as that the very similar bioplasts of the brain of man should be its seat. Consciousness alone is not a sufficient basis for the develop- ment of mind. For this, one more element is necessary, and that is, memory. Impressions made by the environment are registered, and soon cease to be present in consciousness. Under the influ- ence of association the impressions return to consciousness. Asso- ciations are those of place, of the order of time, and of similarity or difference in various qualities, as size, color, or any other physi- cal features. Experiences of these qualities are to all conscious beings either painful, indifferent, or pleasurable. When associa- * "Method of Creation," 18V1. 230 GENERAL EVOLUTION. tion requires, events, objects, or cliaracteristics, are returned to consciousness in the order in which they cohere most firmly in the mind, which may or may not be that in which they entered it. The liking for or dislike to the object, are equivalent to an attrac- tion to or repulsion from it. Thus experience is begotten : as its material increases, new combinations are formed, new relations observed, and in the highest tyipes of mind, laws are discovered. No one can deny memory to animals ; it is the medium of their education by man, and has been as well the means of their edu- cation by nature. Impressions cause a re-arrangement of cer- tain elements of structure which give the form to consciousness when it arises again. It is also probable that these arrangements are not the same as those which represent classifications and con- clusions, but that nevertheless the arrangement or organization of these is determined by the simpler arrangements caused by perceptive stimuli. Experience produces these combinations in the bioplastic aggregations of all animals, be they in the form of ganglia, brains, or less specialized forms. Nowhere in the human organism are the effects of effort and use so strikingly witnessed as in the increase of brain power ; and familiarity with the educa- tion of the lower animals shows that this is the case with them also, though in a lesser degree than in man. If, then, we grant the p^ropositions, first, that effort and use modify structure ; and second, that effort and use are determined by mind in direct ratio to its development, we are led to the con- clusion that evolution is an outgrowth of mind, and that mind is the parent of the forms of living nature. This is, however, to reverse a very usual evolutionary hypothesis, viz. : that mind is the product and highest development of the universe of matter and force. The contradiction is, however, not so absolute as at first appears. By mind, as the author of the organic world, I mean only the two elements, consciousness and memory. But it is the view of some thinkers that consciousness is a product ; that it is not only a correlative of force, but a kind of force. To the latter theory I can not subscribe ; when it becomes possible to metamorphose music into potatoes, mathematics into mountains, and natural history into brown paper, then we can identify consciousness with force. The nature of consciousness is such as to distinguish it from all other thinkable things, and it must be ranged with matter and force as the third element of the universe. EEVIEW OF THE MODERN" DOCTRINE OF EVOLUTION. 231 It is true that unconsciousness does not imply absence of life as generally understood. A majority of the processes of life are performed unconsciously by living creatures ; mind itself being no exception to this rule. There is another class of acts whose performance produces sensation, but consciousness is not con- cerned in. them as an immediate cause. Therefore, it is a com- mon endeavor to associate reflex and unconscious acts with the molecular movements of inorganic and non-living substances. But the one great difficulty in making this identification has never been surmounted. This is the different nature of the movements in the two cases. In non-living matter they are sim- ply polar, nothing more. In living beings they display design. Perhaps I use the word *^ design " in a new sense, but the expres- sion is nevertheless appropriate. What I mean is, that the move- ments of living things have direct reference to consciousness, to the satisfaction of pleasures, and to the avoidance of pains. The molecular movements within animals of the simplest class are the digestion of food and the elaboration of the materials of repro- duction. The molar movements of the simplest animals are to enable them to escape the pains of hunger and celibacy. More- over there is reason why the movements of living beings display design. We all know the nature of habits ; how they are per- formed unconsciously, and as automatically as digestion itself. But did any one ever know of a habit in an animal, whose origin he could trace, which has been formed in unconsciousness ? Ac- cording to our knowledge, habits are always the result of stimuli which are consciously felt, and which cause by repetition or through reminiscence a repetition of the resulting movement. After a sufficient number of rej^etitions such an act becomes a habit, i. e., is performed automatically, or without the interven- tion of effort, and frequently without consciousness. It thus be- comes a part of the character of the individual or species. This common phenomenon is explained by the hypothesis that an or- ganization of the centers controlling action is caused by the efforts of the animal under the stimulus, and that finally a machine is constructed which determines the nature of the force expended, without further mental exertion of the individual. Such a pro- cess is education, and the result is an addition to the stock of faculties already on hand. Thus is explained the vast number of automatic and unconscious activities displayed by animals ; to the same source, I believe, the common reflex acts may be traced ; it 232 GENERAL EVOLUTION. even appears to me probable that the organic functions in general have had the same origin.* While these latter have mostly long since passed beyond the control of the mind, portions of the uro- genital functions still linger within the confines of its jurisdiction. Thus have consciousness and mind endowed living nature with useful functions ; and this, which may be called the Theory of Endoiument, accounts for the element of design which is so puz- zling when seen in unconscious and reflex acts. As it has been maintained above, that structure is the effect of the control over matter exercised by mind, it is evident that the evolution of mind must be directly followed by corresponding de- velopment of organism. The science of paleontology substantiates this theory in a wonderful manner. But the animal mind being generally occupied with simple functions, its expressions in struct- ure are usually nothing more than the progressive creation of im- proved instruments for obtaining food, resisting climate, escaping enemies, and reproducing their kind. The struggles of animals have been seen on this j^latform, and mind has only been necessary to aid in accomplishing the ends above mentioned. AYonderfully effective machines for grinding, cutting, seizing, and digging ; for running, swimming, and flying have been produced. The develop- ment of mind proper must appear in the size and structure of the brain ; and though the history of the latter in past ages must always remain, in large part, hidden from us, it is known that in the former respect there has been great progress made in various lines of animals. Now the line which has carried brain to its pres- ent development in man, the Quadrumana, has been deficient in special mechanical excellencies of the kind enumerated above. Perhaps primitive inferiority in these many respects has kept the Quadrumana under greater mental tension, and compelled them to exercise caution in their acts, and give that opportunity to thought which was less demanded in the case of other animals. Furthermore, if they are less specialized in their mechanism than most other Mammalia, they are less restricted by it to peculiar modes of life. They are more versatile, and more capable of the adoption of new habits as a consequence. And here we have a glimpse of a most important principle in evolution, which is the keynote to its method ; this is what I have called the The Doctrine of the Unspecialized. * " Consciousness in Evolution." " Penn Monthly," 1875. REVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 233 Paleontology shows that the succession of living types has not been in a. single straight line. It has been in many divergent lines, and a large number of them have not continued to the present time. The history of life has been well compared to a tree with divergent branches, many of which do not reach the elevation of the summit. Furthermore, in the many cases in which we can trace the lower lines to the present period, it is evident -that in - their present condition they could not have given rise to the higher forms. Each line, in fact, has developed to an extreme of spe- cialization of structure, which it would seem is incapable of modifi- cation in any direction very divergent from that which it has al- ready taken. Much less have such specialized types been able to survive the environment for which they were designed ; with im- portant changes in that respect they have perished. A few exam- ples will serve to illustrate my meaning. The direction of develop- ment has been from fishes, through BatracMa and rei)tiles, to birds and mammals. But we can not derive any living type from the osseous fishes of the present or past ages {Teleostomi): to find the origin of BatracMa, we must pass below these to more generalized and older forms, the Dipnoi, a class whose position in the system was for years a controverted point. We can not obtain Mammalia from any of the existing types of reptiles, but we must go back to the Permian period, and trace their outlines in the Tlieromorplia of that day. In spite of the prophetic resemblance of these remarkable animals, they are inferior to later Eeptilia in the structure of their vertebral column, and display resemblance to some of their immature stages, as well as to those of the Mammalia. Among mammals we can not derive monkeys from Carnivora or Ungulata, nor the latter from each other, but can only trace their close approximation in the Bunotherian types of the Lower Eocene. So with the great divisions of Ungulata ; Prohoscidians, Hyrax, and the even- and odd-toed orders must all be traced to the un- specialized AmUijpoda, with small brains and five-toed plantigrade feet, as their ancestors.* It is easy to perceive that the generali- zation and plasticity of all these forms has furnished the ground of their ancestral relation. "We are now in a position to comprehend more clearly the general nature of evolution. The doctrine of the unspecialized * See the origin of types of Mammalia educabilia, " Journal Academy," Philadel- phia, 1874. 234: GENERAL EVOLUTION. teaches that the perfection produced by each successive age has not been the source or parent of future perfection. The types which have displayed the most specialized mechanism have either passed away, or, undergoing no change, have witnessed the prog- ress and ultimate supremacy of those which were once their infe- riors. This is largely true of animals which have attained great bulk. Like those with perfected weapons, they have ever been superior to the attacks of other animals in their day, and doubt- less led, so long as food abounded, lives of luxurious indolence. With change or diminution of food, such huge beasts would be the first to succumb, and it is a fact that no type of land animals has maintained great size through many geologic changes. It is true that all of the lines of ancestry of the existing higher Mam- malia, as the subdivisions of the Carnivora, Ungulata, and Quad- rumana, which we know in detail, commenced with types of small size and correspondingly little muscular power. Some important conclusions may be derived from what has preceded. It seems that evolution has witnessed a continual run- ning down of types to their great specialization or extinction. That many types have arisen in weak and small beginnings, but that the conflict with more powerful forms has developed some qualities in which they sooner or later excelled, and which formed the basis of their future superiority and persistence. That while this has probably been the true cause of the origin of the many admirable mechanical adaptations displayed by animals, it is pre- eminently true of the development of mind. That the reason why progress has reached its limit in the lines of greatest speciali- zation, has probably been the removal of the occasion of its origi- nal cause, i. e., active exercise in the struggle for existence. This explanation is suggested by the remarkable degradation which is witnessed in animals whose mode of life relieves them from the necessity of working for a livelihood, e. g., the parasites and ses- sile animals whose young are free. Some of these creatures, on assuming their parasitic life, lose the semblance of even the order to which their young belong. The primary stages of various plants move acti^^ely through the water like the lowest forms of animals, and their sessile adult condition must be looked upon as a degeneration. It is well known that the endeavor to relegate the lowest forms of life to the two kingdoms of animal and vege- table, has been generally abandoned. The great vegetable king- dom probably exhibits a life degraded from more animal-like be- KEVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 235 ginnings. Animal irritability and mobility have been lost, and their own consciousness must be entirely eliminated from the question of the origin of the many later and specialized types of plants. But I venture here the hypothesis that the consciousness of plant-using animals, as insects, has played a most important part in modifying the structure of the organs of fructification in the yegetable kingdom.* Certain it is that insects have been effective agents in the preservation of certain forms of plants. I would suggest whether the mutilations and strains they have for long periods inflicted on the flowering organs, may not, as in some similar cases in the animal kingdom, have originated peculiarities of structure. Evolution of living types is then a succession of elevations of l^latforms on which succeeding ones have built. The history of one horizon of life is, that its own completion but prej^ares the way of a higher one, furnishing the latter with conditions of a still further development. Thus the vegetable kingdom died, so to speak, that the animal kingdom might live ; having descended from an animal stage to subserve the function of food for animals. The successive types of animals have first stimulated the develop- ment of the most susceptible to the conflict of the struggle for existence, and afterward furnished them with food. Doubtless, in the occupation of the world's fields, the easiest and nearest at hand have been first occupied, and successively those which were more difficult. The digging animals are generally those which first abandoned the open field to more courageous or stronger rivals ; and they remain to this day generally of low type compared with others of their classes (e. g., Monotremata, Roden- Hay Insectivora). All occupations have been filled before that one which requires the greatest expenditure of energy, i. e., mental activity. But all other modes of life have fallen short of this one in giving the supremacy over nature. Automatism then represents a condition of ^'lapsed intelli- gence" and diminished life. The unconscious automatism of animals is a condition of still greater lapse. On the contrary, sensibility is the condition of development, and the susceptibility and impressibility which is the extreme reverse of automatism is the especial character of youth. Here the " doctrine of the un- specialized" finds justification again. * This opinion has also been expressed by Hermann Miillcr. 236 GENERAL EYOLUTIOK What the future has in store for us in the history of inorganic force and its results we can not now foresee, but I call attention in this connection to the important part played by life in the dis- tribution of minerals. It has long been known that the carbon of the earth's crust was once in a living state, and it is admitted that the limestone once circulated in the fluids of animals. We have recently been compelled to believe that siliceous rocks are com- posed of the consolidated shells of minute plants, which they have elaborated from the water of the ocean. Silver and gold are seg- regated and deposited by seaweeds. The principal rock material, whose relation to life has not been ascertained, is alumina. How far the processes which now characterize dead matter were once related to life is a problem for the future. IV. THE MORALS OF EVOLUTION?". The doctrines of the struggle for existence and survival of the fit in human life have a two-fold application. The relative pro- portions in which these applications are made will depend on the moral development of him who makes them. Moral density and intellectual stupidity (often nearly allied) will see in these two laws only the struggle for material power, and the survival of the strongest. They will hardly urge in these days, as they would infallibly have done had they lived a few centuries ago, that the strongest means the hardest hitter, or the most successful assassin, but they will probably believe that this pre-eminent ]oosition be- longs to the most wealthy. From a purely dynamical standpoint this position is correct, yet it might be a useful question for such advocates to consider why it is that physical oppression and assas- sination should be less successful avenues to power than they once were. There, are two reasons why man does not grant the first place in his esteem to physical force. The first principles of morals are acquired in the struggle for existence* The idea of meum and tuujYi was speedily developed so soon as men associated together ; and the habit of justice has doubtless been formed by the insist- ence of every man on his own rights, and by the power of combi- nations of men to control those who may from superior strength or other cause seek to violate the rights of property. Thus law originated, and from the earliest history of the race to the present day it has educated the barbarous and semi-barbarous to civiliza- tion. It is then easy to perceive that man gives the highest place EEVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 237 in his affections to the most just ; but there is yet another reason why this should be the case. The reproductive instinct in the lower animals has developed into social affections, and these form a part of the character of the higher animals and, in an especial degree, of man. The senti- ments of sympathy and benevolence are j^robably outgrowths of the same. While the rational faculties are concerned in the knowledge of right, these sentiments are a source of the love of right. This disposition is trusted by men as leading to ihQ prac- tice of right, in cases where the power to enforce it is not immedi- ately present. The struggle for existence then among men ranges all the way from a rivalry of physical force to a rivalry for the l")OSsession of human esteem and affection. The robber and assas- sin of the lowest human races are represented by the slanderer and defamer in the higher. The ultimate prosperity of the just, as- serted and foretold by prophets and poets, is but a forecast of the doctrine of the survival of the fittest. The unjust are sooner or later eliminated by men from their society, either by death, seclu- sion, or ostracism. But the organized moral qualities can not normally transcend in power, as motives of human action, those which secure man's physical preservation. Lines of men in whom the sympathetic and generous qualities predominate over the self-preservative, must inevitably become extinct. Evolution can produce no higher de- velopment of the race (whatever may sometimes appear in indi- viduals) than an equivalency in these two classes of forces. Be- yond this the organization of the social faculties of the brain must always be repressed in the race, so that we can only expect to attain an equilibrium between them and the more purely selfish ones, as the very highest result of unassisted evolution. In this position the judgment is suspended between the opposing classes of motives ; and it must ever remain doubtful in general as to whether resulting action will be just and right, or the reverse. I exclude from this question those generous acts which do not appear to the actor to conflict with self-interest. These may be termed sympathetic acts, and are quite distinct from the altruistic* The sympathetic actions are seen at times in most animals. The al- truistic acts, on the other hand, are those that express what is usu- ally called ''moral principles." Sach acts may often coincide * " On the Origin of the Will." " Penn Monthly," 1877. 238 GENERAL EVOLUTION. with the interest of the actor, but so long as they do not appear to him to do so, they are altruistic. It is part of the doctrine of evolution that habits will ultimately disappear on the removal of their stimulating cause. The moral nature originated, and has been maintained, through the pressure of the fear of consequences. The removal of this pressure, through the acquisition of power, would then ultimately result in the diminution or loss of the moral nature, through disuse. The abuses of power are well known. This appears to be all that evolution can do for us in the produc- tion of the moral nature. So it would appear that no organized faculty of self-sufficient altruistic justice can be derived by the process of mental evolution. The result is rather a continued struggle between justice and injustice. It is, then, evident that any power which shall cause the permanent predominance of the just over the selfish faculties must be derived from without. After we omit from customary religion, cosmogony, which be- longs to science, and theogony, which belongs to the imagination, we have left an art which has for its object the development and sustentation of good works or morals among men. If the teachers and professors of this art produce the results in this direction at which they aim, their great utility must be conceded by all. Their method has the advantage over that of the law, in being of the character of inducements supplied before action, instead of pains and penalties inflicted after action. They strive to originate good conduct, rather than to punish bad conduct. They are working on the side of the originative force in development, rather than the destructive ; the '^origin of the fittest y^' rather than the '^sur- vival of the fittest. ^^ Whether man possesses the spontaneous power called '*free will " or not, the work of supplying inducements for good conduct is most useful to society. But religion, as generally understood, pre-supposes free will ; and the definition of the word responsibility implies its existence. The question as to the pres- ence of such a faculty is an interesting one, and will now be briefly considered. The well-known doctrine of necessity leaves no j^lace for free will. All acts are the consequences of motives, and are the out- come of a balancing of interests. The heaviest side of the account determines action. Our physical necessities supply the motives for most of our activities ; our pursuit of food and clothing is of necessity, and no condition is free from it. Evolution supports and explains this doctrine, as can readily be perceived. It de- EEVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 239 rives our instincts from an ancestry whose daily occupation has been their gratification. But it has been shown above that this development does not supply the motives of an independent morality. * The direction of action under stimulus is determined by intel- ligence, which is, as has been above maintained, the product of experience. Intelligence is organized or classified knowledge, and directs the activities set on foot by the likes and dislikes, that is, the affections. When there is knowledge, there is no necessity for spontaneous action or free will, since action is determined by the organization of the mind. Even if the mind is conscious of insuf- ficient knowledge, an inducement to seek knowledge is supplied, and according to the result of investigation will be the direction of knowledge. But we are here brought to face the case where knowledge can not be or is not obtained. This is the condition of the two ques- tions of the practice of morals, and the nature of the future life. The evolution of mind consists of a continual advance from the known into the unknown, and a transfer of the unknown to the known. So long as there is any inducement to progress of this kind, and nature responds to inquiry, development will go on. Al- though it is true that it is only among men, and but few men at that, that the pursuit of knowledge is an occupation, most men add to their stock incidentally as they pursue other avocations. The knowledge of right and the inducements to its practice are learned in their every-day intercourse, so far as it can be acquired. But knowledge in these directions soon attains its limit, and ac- cordingly, development dependent on knowledge must cease. If any further progress in practical morals is to be made, some new force must intervene at this point. Here is the opportunity for the appearance of will or sponta- neity ; here it is at least needed. I am willing to believe that it may appear at this point, and that so long as we have to face the unknown in moral progress, so long it will remain. As a force it must be equivalent of other forces, but as a form of conscious- ness it is a new element of mind. As represented in new molecu- lar organization, it may always continue, even after much of the unknown may have been conquered, and a stationary period may have ensued. Such an accession to character would be a fitting * " On the Origin of the Will." " Penn Monthly," ISVY. 240 GENERAL EVOLUTION. crown of eyolution, and a justification of this labor of the ages. If a true factor in human development, it might be compared, in the creation of character, to the apical bud of a growing tree. As the part pre-eminently living, it leads the growth of the trunk and branches. They all follow of necessity the path it has marked out. Under its lead they are successively formed, become fixed, and finally decay. PART II. THE STEUOTUEAL EYIDEI^^CE OF EYOLUTIO]^. VII. ON THE HOMOLOGIES AND ORIGIN OF THE TYPES OF MOLAR TEETH OF THE MAMMALIA EDUCA- BILIA. I. THE TYPES OF MAMMALIAN MOLARS. It has been already stated * that the transition from simple to complex teeth is accomplished by repetition of the type of the former in different directions. ^^In the cetaceans this occurs in the Squalodonts ; the cylindric incisors are followed by flattened ones, then by others grooved in the fang, and then by two-rooted, but never by double-crowned teeth. This is the result of antero- posterior repetitive acceleration of the simple cylindric dental type of the ordinary toothed cetacean. Another mode of dental com- plication is by lateral repetition. Thus the internal heel of the superior sectorial tooth of a carnivore is supported by a fang alongside of the usual posterior support of a premolar, and is the result of a repetitive effort of growth-force in a transverse direc- tion. More complex teeth, as the tubercular molars, merely ex- hibit an additional lateral repetition, and sometimes additional longitudinal ones. As is well known, the four tubercles of the human molar commence as similar separated knobs on the [primi- tive] dental papilla." Accordingly, the simple tubercle may be regarded as the least specialized form of tooth. It may be low and obtuse, as in the Cliiromys, or the walrus ; more elevated and conic, as in the dol- * " Method of Creation," p. 10. Philadelphia, 1871. 16 242 THE STRUCTURAL EVIDEN'CE OF EVOLUTION. phins ; or truncate, as in sloths and some rodents. The form is complicated in two ways, viz., either by the folding of the sides, as in Glyptodon and many rodents, as Arvicola, Castor, Lepus, etc. ; or by the develoj^ment of tubercles on the crown, as in Mus, Dicotyles, Homo, etc. Upon this basis are constructed the more complex types of teeth exhibited by the various families of Ungu- lata and some Rodentia, as has been pointed out in the following language : '^ The genus Uintatlierium^ has been shown to be a Pro- boscidian, which combines some important features of the Peris- sodadyla with those of its own order. . . . The number of such characters was shown to be somewhat increased in Bathmodon, which therefore stands still nearer to the common point of de- parture of the two orders. This point is to be found in types still nearer the clawed orders {Unguiculata) in the number of their digits (4, 5), and in which the transverse and longitudinal crests of the molar teeth are broken up into tubercles more or less con- nected, either type of dentition [i. e., Proboscidian or Perissodac- tyle] being derived according as such tubercles are expanded in the transverse or longitudinal directions." f As is well known, the crowns of the superior molar teeth of the higher Mammalia are supported on three roots, two of which are external, and the third internal. The corresponding inferior molars are supported on two roots, and are therefore, in so far, less complex. But these two roots usually support four tubercles, two to each, while the roots of the superior molars support directly but one each. Hence, as Prof. Harrison Allen remarks, the crown of the inferior molar is more complex than that of the su- perior. \ In tracing the degrees of complication of the crowns of the superior molars of Mammalia from the simple cone of the Ceta- cean, the first step is seen in the Squalodon and teeth of similar character. In these there are two roots, antero-posteriorly related. In the Squalodont Portheodon gervaisii {Squalodon Auct.) the third root is present. In Mammalia with but three tubercles in the crown, e. g., Carnivora, the inner root has much the form of one of the external ones. In many of those with four tubercles of the crown, e. g., Qiiadrumana, the form of the internal root is * Eohasileus in the original. (Ed. 1886.) f " On tlie Primitive Types of Mammalia Educabilia," published by E. D. Cope, May 6, 1873. "Proceedings of the American Philosophical Society," 1873, p. 224. X "Dental Cosmos," December, 1874. MOLAK TEETH OF THE MAMMALIA EDUOABILIA. 243 not modified ; but in the Lophodont types it is materially altered. In Hyracodon, RMnocerus, Anchitherium, Oreodon, Cervus, and others, it is flattened, with the long diameter anteroposterior, and is grooved on the inner face, so as to assume the form, as it does the function, of two roots conjoined. In the temporary dentition of Bus, Merychyus, etc., the inner root is divided, so that the superior molar has four distinct roots. The proper homologizing of the various forms of dental struct- ure of the Ungulates with each other, and with the primitive types of tubercular teeth, is entirely essential to their intelligent classification, and therefore comprehension of their mode of origin. In order to lay a foundation for this work, I define the four types as follows, giving the subdivisions of the first two in brief, and discussing those of the third and fourth more fully afterward : Division I. Haplodont type ; the crown undivided or simple. a. Crown low, obtuse; Cetacea {Be- luga), Carnivora (Rosmarus). h. Crown elevated, acute ; Cetacea {Delplii7ius) ; canine teeth in general. c. Crown truncate ; Edentata {Bra- dy pits) ; Rodentia { Qeomys, Dipodomys). Division 11. Ptycliodont type ; the crown folded on the sides ; the folds frequently crossing the crown. a. Sides only folded ; Rodentia (Arvicola Castor) ; Edentata ^ {Glyptodon). h. Summit of crown also folded ; Rodentia {Lepus, Chinchilla). Division III. Bunodont type ; crown supporting tubercles. a. Tubercles few, opposite ; TJ71- gulata, Achcenodon, Dicotyles, Elotherium ; Carnivora, Pro- cyon ; Rodentia, Heliscomys. h. Tubercles few, alternate ; Hyop- -, Fio. 17. — LeptocJicerus. sodus. c. Tubercles numerous, irregular ; Mastodon, Phacochoerus. Division IV. Lophodont type ; the summit of the crowns thrown into folds of transverse or longitudinal direction. Higher Ungulates. Fig. 15. — Glohicephalus. Fig. 16. — Jaculus hudsonicus. 244 THE STRUCTURAL EVIDENCE OF EVOLUTION. This division embraces the many types observed in the Ungu- lates, some Rodents, and possibly Garni vora. Inasmuch as the teeth of the maxillary and dentary (mandibular) bones do not al- ways conform to the same type (e. g., Symborodo7i, Equus), it will be necessary to consider them separately. Besides the differ- ence in type, they differ in their rela- tive development in width in the more specialized forms ; thus, in Homo, Mus, Mastodon, and such genera, the molars of both jaws are identical ; in Palceotlierium, Eohasi- leus, Tcqnrus, etc., and most Car- nivora, the superior are the wider, the inferior narrower, appropriately to the greater slenderness of the mandibular bone. The latter, or anisognathous type, may then be regarded as the more specialized. The Bunodonts, except some Carnivora, are all of the former or isognathous type ; among Lophodonts the few Rodents, the Dino- theriidcB, and Elephas are isognathous, while all of the other Prohoseidia, the Perissodactyla, and Rumina7itia are anisogna- thous. Examples may be selected as follows : Isognatlious ; Bunodonts : Homo, Dicotyles, Sus, Mastodon, Elotlieriiim ; Lophodonts : Dmotheriidce, Eleplias ; Rodentia, JSciuridce. Anisognatlious ; Bunodonts : Macacus, Lemur oidea, Procyon ; Lophodonts : A7iopIotherium, Hyoj^otamus, Oreodon, Ruminantia, Perissodactyla, Batlimodon, TJintatlierium, Fig. 18. — BJiinocerus (temporary). II. THE subordi:n"ate types of bui^odojs^ts. 1. The Maxillary Teetli.^ » It is apparent that the type of superior molar tooth which pre- dominated during the Puerco epoch was triangular or tritubercu- lar ; that is, with two external and one internal tubercles, f Thus, of sixty-seven species of placental Mammalia of which the suj^erior molars are known, all but four have three tubercles of the crown, * This division is inserted from the " Proceedings of the American Philosophical Society," for December, 1883, for the sake of supplying an omission in the original memoir. (Ed. 1886.) f See "American Naturalist," April, 1883, p. 407. MOLAR TEETH OF THE MAMMALIA EDUOABILIA. 245 and of the remaining sixty-five, all are triangular, excepting those of three species of Periptychus, and three of Oonoryctes, which have a small supplementary lobe on each side of the median prin- cipal inner tubercle. This fact is important as indicating the mode of development of the various types of superior molar teeth, on which we have not heretofore had clear light. In the first place, this type of molar exists to-day only in the insectivorous and carnivorous Marsupi- alia ; in the Creodonta, and the tubercular molars of such Carnivo- ra as possess them (excepting the i^lantigrades). In the Ungu- lates its persistence is to be found in the molars of the Corypho- dontidse of the AYasatch, and Dinocerata of the Bridger Eocenes. In later epochs it is occasionally seen only in the last superior molar. It is also evident that the quadritubercular molar is derived from the tritubercular by the addition of a lobe of the inner part of a cingulum of the posterior base of the crown. Transitional states are seen in some of the Periptychidae {Anisonchus), and in the sectorials of the Procyonidae. 2. The Mandibular Teeth. The tritubercular or triangular superior molar is associated with a corresponding form of the anterior part of the inferior molar. This kind of inferior molar I have called the tubercular sectorial, and is very variable as to the degree of development of the sectorial cutting edge. The anterior triangle is formed by the connection by angle or crest, of the median and anterior internal crests with the anterior external. Its primitive form is seen in Didelphys, Pelycodus, Pantolambda and the Amblypoda gener- ally ; in Centetes and Talpa ; and in its sectorial form, in Stypo- lophus and Oxyaena, etc. The * tubercular molar of some ViverridcB, and among the ex- tinct forms especially the Didymictis protenus, Cope, present a similar structure to that just described. This furnishes a ready explanation of the tooth immediately in advance, which is the primitive form of sectorial tooth characteristic of primitive Car- nivora. The three anterior tubercles are largely developed, stand- * The remainder of this section (2) is taken from the writer's " Synopsis of the Vertebrata of the Eocene of New Mexico," p. 800. Publication of the U. S. G. G. Survey, W. 100th Meridian, 1875. (Ed. 1886.) 246 THE STRUCTUKAL EVIDENCE OF EVOLUTION. ing at opposite angles of a triangular space ; the outer and ante- rior cusps are the most elevated, and the ridge which connects them is now a cutting blade. The posterior portion of the tooth does not share in this elevation, and its two tubercles are in some genera obsolete, and in others replaced by an elevation of one mar- gin, which leans obliquely toward the middle of the crown. In Mesonyx this is represented by a median longitudinal crest. If the two tubercles of the posterior part oi this tooth (which may be termed a tubercular seciorial) are elevated and acute, we have the molar of many recent and extinct Insectivora ; if the same por- tion (now called a lieel) is much reduced, we have the type of Oxycena and Stypolo2)lius. In the Canidce the three anterior tu- bercles are much less elevated than in the genera above named ; the external is much the larger, and the anterior removed farther for- ward so as to give the blade a greater antero-posterior extent. The heel is large and without prominent tubercles. In the Muste- lidm the inner of the two median cusps is often reduced to a rudi- ment, or is entirely wanting, and the heel is large. The lower sectorial of the HycenidcB has no inner tubercle, and the heel is much reduced. In some of the saber-toothed tigers the heel re- mains as a mere rudiment, while in the true cats it has entirely disappeared, and the carnassial tooth remains perfected by sub- traction of parts, as a blade connecting two subequal cusps. The HycBnodontidcB, as is known, possess three carnassial teeth without inner tubercles. The history of this form is as yet uncertain, as it was evidently not derived from contemporary forms of the Eocene with tubercular sectorials. The development of the inferior carnassial dentition has thus been accomplished by the subtraction of the inner and posterior cusps, so that of the original four of the quinquetuberculate molar but a single one, i. e., the anterior external, remains. III. THE SUBORDIjq-ATE TYPES OF LOPHODOXTS. 1. The Maxillary Teeth, In the essay already quoted * the following remarks (page 7) explain the relation between the Bunodont genera and several of the Lophodont types of superior molar teeth : "In the superior * "Primitive Types of Mammalia Educabilia," May, 1873, and Hayden's "Re- port on Geological Survey of Montana, Wyoming, etc.," ISYS, p. 646. MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 247 molar series the flattening of the outer tubercles may proceed so far as to produce, on wearing, a confluence of the [resulting] cres- centoid surfaces. ... In both PalcBOsyops and Hyrachyus these tubercles of the upper molars are confluent into two Vs (more or less open when unworn). In the former the inner tubercles retain their primitive conic tubercular form, but in Palceotheriwn, EJii- nocerus, Lopliiodon^ Hyrachyus, and Tapirus they elongate trans- versely so as to meet the corresponding outer tubercles (now crests) forming the familiar cross-crests of those genera. If alternate, the oblique crests of Palceotheriuyn ; if opposite, the cross-crests of Tapirus. If, on the other hand, the inner tubercles flatten like the outer, we have, on wearing, the quadricrescentoid [Selenodont] type of the Ruminantia and Anoplotlierium: In the Quadruma- nous families, including man, the primitive quadrituberculate type of molars is preserved." Four types of Lophodont dentition are included in the above discussion, and three others may be added. They belong to two series, viz., those in which the crests represent the modification of opposite tubercles, and those where the tubercular elements of the crown are alternate. These series may be called the Ammho- dont (alternate), and Antiodont (opposite), and the component types are : Antiodoj5"ts. — Selenodont (Ruminants) ; Tapir odont {Tapir, Rhinoceriis) ; Trichecliodont (Manati, Elephant). Amcebodokts. — PalcBotheriodont (Palasotherium, etc.) ; Sym- lorodont (Palaeosyops Symborodon, etc.) ; Batlimodont (Bathmo- don, etc.) ; Loxolopliodont (Uintatherium, etc.). These types are defined as follows : 1. Antiodoxts. Sele7iodonts.—T\\Q tubercles separate or united at their angles, much elevated, narrow crescentic in section, separated by deep valleys. To this group belong the molars of the Euminants, the Tra- gulidce, the Oreodontidm, and Mery copotamido ; of Perissodac- tyles the EquidcB. Tapir odo7its.— The outer tubercles longitudinally compressed, subcrescentic in section ; the inner transversely compressed, con- tinued as transverse ridges to the end or middle of the correspond- ing exterior crests. RUnocerus, Tapirus, Hyrachyus, LopUodon, and Hyrax rep- 248 THE STRUCTURAL EVIDENCE OF EYOLUTIOX. resent this type ; the last molar of LopModon appears to be Attkb- lodont, Tricliecliodonts. — Tubercles confluent into two or more trans- verse crests. The Dinotherium represents this form, so does Eleplias, Tri- checus (the manati), and a number of the larger Marsupialia. 2. Amcebodonts. PalcBotheriodonts. — External tubercles longitudinal, subcres- centic in section ; the inner united with them by transverse oblique crests. Palceotherium and Ancliitlierium present this type, which only differs from the Tapirodont in the alternation of the opposing tubercles. Syniborodonts. — External tubercles longitudinally compressed and subcrescentic in section ; the inner indejDendeut and unal- tered, i. e., conic. To this group are to be referred the types of Palcsosyops, Me- nodus, and Symhorodon. They, of all Lopliodonts, approach near- est to the Bunodonts, Bathmodonts. — The posterior pair of tubercles approximated and connected, together compressed and subcrescentoid in section ; the anterior outer connected with the anterior inner by an oblique crest forming a V with the preceding. Bathmodon and Metalopliodon. — The homologies of the crests are difficult to make out ; the subcrescentic crest of the second molar may include only the posterior outer tubercle, and thus be entirely homologous with the posterior crescent of Palseosyops. In support of this view we have the structure of the premolars, where it becomes the only external crescent, while the anterior transverse crest turns round on its inner side, supporting the inner anterior tubercle of the tooth. [Note to this edition : The latter view is the correct one, as the posterior inner tubercle is wanting.] Loxolopliodonts — Anterior inner tubercle connected with the two external by oblique crests ; the posterior inner tubercle rudi- mental or wanting. Uintatherium and probably Tillotherium represent this group, both being like those of the last, extinct genera from the Eocene of Wyoming. MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 249 • 2. Tlie Mandibular Teeth, The types of structure are less numerous than those of the maxillary teeth, since I am only acquainted with six. Still more distinctly than those of the upper jaw do they represent the types of opposite or alternating tubercles, or the antiodont and amoebo- dont. The essential principles of modification are the same as in the maxillaries, and they correspond with them as to genera, as follows : Aktiodont. Inferior. Selenodont. Hyracodont. Trichecodont. Superior. Selenodont. Tapirodont pt. j Tapirodont pt. ( Trichecodont. Amcebodoxt. J Palaeotheriodont. ■ I Symborodont. Selenodont pt. j Bathmodont. ( Loxolophodont. The characteristics of these groups are as follows : A. Antiodonts. Symborodont. Hippodont. Loxolophodont. Selenodonts. — Constructed, typically, like the upper molars, Rummantia. Hyracodonts, — External tubercles compressed longitudinally and crescentic in section, continuous by a cross-crest with the cor- responding tubercle of the iuner side. The animals which possess this type of teeth are the Bliinoce- riiSj Hyracodon, and the Hyrax ; it is nearly approached by some of the Hyrachyi. It corresponds in structure with the true tapiro- dont arrangement of the maxillary teeth ; but many of the Ta^^iro- donts have the Trichecodont type of mandibular teeth. Trichecodonts. — Definition the same as for the maxillary teeth. Tapirus, LopModo7i, Hyracliyus, Dinotlierium, Eleplias, Tri- checus (the manati), and the Kangaroos and their extinct allies belong here. B. Amcebodonts. Hippodonts. — In the horses the maxillary molars are con- structed on an opposite crested basis, while the mandibulars repre- 250 THE STRUCTURAL EYIDEII^OE OF EVOLUTION". sent an alternate crested type. This is not constituted as in the next form, by a union of alternating tubercles, but as in the Sele- nodonts by the special deyelo^Dment of each crest into a crescent extended antero-posteriorly. As alternating, the inner crescents stand at the apices of the outer, and are connected with them. In Ancliitherium the inner are so reduced as to constitute a condi- tion intermediate between the Hippodont and Syiiiborodont types. Syniborodonts. — The alternating tubercles connecting by oblique ridges which form together two Vs. To this type is to be referred a great number of Perissodac- tyles, e. g., Anchitheiium, Palceotherium, Falmosyops, Menodus, Syiiiborodon, A ncMppodus. Loxolopliodonts. — Alternate cusps connected by two cross ridges from the outside forward and one from the inside forward ; from which result an oblique posterior cross ridge, and a V open- ing inward. Here are Eohasileus and Batlimodon- ; the last molar of the latter having the anterior ridge of the V quite low. S. Comparison of the Opposing Series. In review, the above types of molar dentition may be classified as follows, with reference to the amount or complication of the modification of the tubercular type. The orders of Ungulata with which they correspond, are also given. a. Both inner and outer tubercles crescentoid. JRuminantia. (Anoplotheintim, Oreodon, Hyopotamus). Perissodactyla (Equidce). 13. External tubercles only crescentoid ; the inner transverse or tubercular. Tapirodonts. j Palaeotheriodonts. >• Perissodactyla in gen. Symborodonts. ) y. Neither kind of tubercles crescentoid, but. united in pairs. Trichecodonts. Prohoscidia. It may be added that the groups arranged under y are the only ones in which the types of crests of the superior and inferior molars are fundamentally simple and alike. Thus in the group a, tubercles of both upper and lower series are modified indeiDcnd- ently to produce the type ; in group (3, the tubercles of the upper series are modified independently of each other, while those of the MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 251 inferior series unite, in order to produce the result ; in diyision y the tubercles of both jaws unite entirely across the crown, with- out any distinction between those of the outer and inner sides. Thus the molar type of dentition of the Proboscidians is the most generalized among the Lophodonts, resembling in this respect the type of construction of the feet. lY. THE ORIGIK OF THE MODER]S" TYPES OF BUKODOKT AKD L0PH0D02iT DENTITIOi^. The four types of molar dentition, the Haplodont, Ptycho- dont, Bunodont, and Lophodont, are by no means sharply de- fined, but pass into each other by insensible gradations at many points. The addition of cusps to the simple cone has been accomplished by the appearance of folds at the base of the crown, which have increased in size so as to resemble the primi- tive cusp to which they are attached. As already pointed out, the first additional cusp in the transverse direction appears on the inner side of the first, or anterior cusp. The last one was ap- parently the inner posterior. I first consider the carnassial mo- lars. 1. Tlie Carnassial Bunodo7its. In tracing the appearance of the different types of superior sectorial in time, the following facts are patent : In the Eo- cene genera Mesonyx, AmUyctonus, Oxymna, Stypolophus,* etc., the inner tubercle is much more largely developed than in any ex- isting Carnivora, with the exception of some of the Viverridce. In all, the sectorial crowns are less efficient as shear-like cutters than in Canidce, Mustelidce, Hycenidm, and Felidce, on account of the shortness of the posterior blade and the slight compression of the anterior cone. On the other hand, in all of them the number of teeth presenting the carnassial or three-tubercled type is greater than in existing genera, the posterior upper molars in the latter being either narrowly tubercular or wanting. The genus Hyceno- don, while agreeing with the others in this respect, differs from them in the great reduction of the inner cusp, which is obsolete even in the representative of the true carnassial tooth, although the inner root remains in all. Hence this type of dentition might be regarded as the most specialized of those of the Carnivora, * In the original, the synonym Prototomus is used here. 252 THE STRUCTURAL EVIDENCE OF EVOLUTION. but for the fact of the imperfection of the shear blades in all ex- cept the last. This is seen in the large and prominent anterior cusp and very short posterior blade. In all recent and most Miocene Carnivora, the sectorials are reduced to one in each jaw, the exception in the latter period being the genus Hycenodon, which did not continue later. The posterior carnassials of the Eocene forms disappear, and in the most specialized recent families HymnidcB^ Mustelidm, and Fe- lidcB have scarcely any representatives. The shortening of the series appears in the premolars as well, until we have the formula of the FelidcB, P. m. 2 ; M. 2. In the inferior dentition the same process may be observed in the successional modifications of the entire series. The Eocene forms of carnivora frequently display more numerous sectorial teeth (such as they are) than any of the existing families. The important change, which is clearly indicated, is the progressive extinction of the genera with numerous sectorial teeth, accom- panying the increasing specialization of the sectorial tooth in the genera which remain. In other words, the numerous types of digitigrade carnivora which have survived are those developing but one sectorial tooth (whose earliest rei^resentative is Didymic- Us). The increased perfection of the sectorial tooth has been as- sociated with a reduction in the number of other molars, first, posterior, then anterior to it, which reduction has been accom- panied by an increased relative size of the sectorial. By this pro- cess concentration of the carnassial function has been gained, and increased robustness of the jaws, by progressive shortening. The slender form of the rami of the Eocene genera and Hymnodon are much less efficient in functional use than the stout jaws of exist- ing MustelidcB, Hywnidce, and Felidce. 2. The Lopliodonts. Transitions between the Bunodonts and Lopliodonts are very obvious, so much so as to lead to the belief that the several sub- divisions of the Lopliodonts represent modifications of correspond- ing types of Bunodonts, and that the two are partially '^ homolo- gous groups." Both present corresponding Amoebodont and An- tiodont types ; as an example of the former kind of Bunodont, the mandibular molars of the genus Hyopsodus may be cited ; of the latter kind, the same of the genus AchcBnodon, both the ear- liest, or Eocene genera. It remains to indicate the intermediate MOLAE TEETH OF THE MAMMALIA EDUCABILIA. 253 forms, if any there be, which give color to the supposition that the various divisions of Lophodonts have descended from Buno- dont predecessors. Here, then, I mention a fact of prime impor- tance, i. e., that in America, at least, no Selenodonts are known from formations of older age than Miocene ; while the greatest development of Bunodonts is in the beds of the next older epoch, the Eocene. The special forms of Lophodonts may be separately considered as follows : First, as to the opposite and alternate types, or the Antiodont and Amoebodont. They pass into each other by many intermedi- ate conditions among the Bunodonts, as in Notharchis, Lim- notherium, etc., of the Wyoming Eocene. There is reason, also, to believe that this has been the case with some of the Lophodonts after they had left the bunodont stage behind. Thus Equus is an antiodont as to its upper molars, but has been probably derived from Palmotlieriodont ancestors, which are amoebodont ; this is rendered especially probable by the fact that the mandibular teeth are of the amoebodont division (hippodont). It is also highly probable that the antiodont genus Tapirus, though so near to PalcBotlierhim, was derived from an antiodont Bunodont. Hence, while the discrimination between opposite and alternate types is in some cases most radical, in others its importance is but slight. L Antiodonts: Bunodont type AcTicenodon (Fig. 19). 1. Selenodont type apjDroximated by the bunodont Hippopota- muSi where the tubercles are com^^ressed, thus : the intervening Fig, 19. — AcTicenodon insolens. valleys are deepened, and the cusps wear readily into separate crescents. Another intermediate form is seen in the genus An- tliracotherium, where the tubercles of the mandibular teeth are compressed, while they remain conic (Fig. 21) ; selenodont forms of Omnivora present us with near approaches to these Bunodont genera. Thus in Hyopotamiis and Anoplotheriiim, the crowns. 254 THE STRUCTURAL EVIDENCE OF EYOLUTIOIT. when unworn, present four principal tubercles, wliicli are openly V-shaped in section, and which are separated by open valleys. The latter are deeper than those of the truly Btmo- clont genera, but much shallower than those of the typical Selenodonts. In Oreodon the valleys are somewhat deepened and the crescents elevated, while in the deer the same infold- ing is carried still further. In the Cavicornia the type reaches its fullest expres- sion in the loss of the shoul- der at the base of the crown, the great elougation of the latter, and corresponding- ly deep infolding of the terminal valleys. Professor Lartet* states that the most ancient deer have very short - crowned molars, and the depressions on the surface are so shallow that the bottom is always visible, while in the CervidcB of the more recent Tertiary periods, and especially the Plistocene and living species, these same cavities are so deep that what- FiG. 20. — Hippopotamus. Fig. 21. — Hyopotamus velaumis. Fig. 22. — ITyopotamus americanus. Fig. 23. — Procamelns robust us. ever be the state of attrition, the bottom can not be seen. This, he says, is a perfectly reliable rule for distinguishing the ancient from the more modern forms of deer, and can be applied to other animals as well as the CervidaB. * u Comptes Rendus," 1868, p. 1119. MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 255 Fig. 24. — Merychyus major. The writer nearly contemporaneously * recalled the obserya- tions of Leidy that the teeth of the Oreodont ^' Merycliyus are more prismatic, have larger crowns atid shorter roots, approaching the sheep, as Oreodon does the deer." Now Oreodon is Miocene, and MerycJiyus Pliocene. It was then ob- seryed : *' This phenomenon suggests an ex- planation on the score of adajjtation which the other cases do not. The existence dur- ing the later period of a [hardjer material of diet would increase the rapidity of wear- ing of the crown of the tooth, and require a longer crown and greater rapidity of j)rotru- sion. This necessitates a diminution of the basal shoulder and shortening of the roots, producing the prismatic form aforesaid." These observations render it highly probable that the seleno- dont molar is produced by a modification of the antiodont buno- dont molar. Also, that the manner of the change has been by constant acceleration of growth of the folds of the tooth upward and i^erhaps downward in its long axis ; and an acceleration in the lengthening of the crown. 2. Tapir odonts. — This form is so nearly similar to the Palaeo- theriodont that any series annectant between the latter and the Bunodonts will render very probable such a connection for the Tapirodonts also. Indeed, it is clear that the same evidence will be sufficient in both cases, since the pre- molars and last molar of Lopliiodon are amoebodont, like Palceotherium. In point of fact, however, the tubercles of the molars of Achcenodon are partly united in transverse pairs, while there are intermediate tubercles connecting the opposite cones in some molars of Elotlierium. These structures foreshadow this group as well as the Trichechodont. 3. Trichecodonts. — The J[/«.«;^Of7o^5 and Elephants form a most complete series between this form and the Bunodonts, as has been pointed out by Falconer. In this series, the transverse rows or pairs of tubercles, as well as the crests, may be few or many. Thus Fig. 25. — Tapirus. *" Proceedings of the Academy of Natural Sciences of Philadelphia," 1868, p. 2Y4. " Origin of Genera," p. 44. 256 THE STRUCTURAL EVIDENCE OF EVOLUTION. in Elotlierium, HalWierium, and Tricliechus they are few ; in Trachytherium and Dinotlierium more numerous ; in Mastodon, Stegodon, and Elephas, most numerous. The tubercles are united into serrated cross- crests in Halitherium, the ex- tinct sea-cow ; in Tracliytlie- rium, another fossil ally of the Manati, the tubercles are not united. The succession from Mastodon to Elephas may be represented by the accompany- ing figures : Fig. 26 (from Cuvier) is a molar of M. an- FiG. 26. — Mastodon angusHdens. gustidens, where, beside the principal tubercles, numerous lesser ones appear. Fig. 27 represents Mastodon oMoticus, in which Fig. 27. — Mastodon oMoticus. Fig. 28. — Dinotherium giganteum. the opposite tubercles are nearly united into transverse crests. In Dinotlierium (Fig. 28) and Elephas (Fig. 29) the union is complete. The relation of these genera has been described as one of *' inexact parallelism" ; a condition supposed by the writer to de23end on modification in descent under the law of acceler- ation. The language used is :* ^* The young tooth of Elephas, moreover, is represented by a » . n T , TT 1 Fig, 29. — Elephas indicns. series of independent parallel ^ laminee at first, which, when they unite, form a series of crests * "Origin of Genera," p. 17. MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 257 similar to the type [i. e., pattern] of the genus Mastodon [Stego- don\ and others of the beginning of the series. The deposit of cementum takes place later, till the valleys are entirely filled up. Thus the relations of this part of the tooth structure in the series are also those of the cuccessional growth of Elephas or the extreme of the series." The transition from the Fig. 30. — Microsyops elegans. bunodont type to the lophodont in the mandibular dentition is seen in the Eocene genera Microsyops and Limnotlierium, where the opposite cones are connected by a low cross-crest. n. Amcebodonts; Bunodont type ^^o/^.so(iws.* 4. Symlorodonts. — In Hyopsodus the exterior cones are already somewhat excavated on the inner side, so that a section of each is somewhat triangular. It is obvious that but little more compres- sion and curvature are required to produce the type of FalceosyopSf Fia. 31. — Eyopsodus. Fig. 33. — AncMppodus. Fig. 32. — PalcEOsyops IcEvidens. Fig. 34. — Palceosyops. etc. (Fig. 32). The angles of the outer cones in Hyopsodus are also slightly produced as low ridges to the bases of the alternating tubercles of the opposite side : the elevation of these ridges is only * I oridnallv (" On the Priinitive Types of Mammalia Educabilia," p. 9 ; " Hay- den's Geolog. Survey Terr.," 1872, 1873, p. 648) selected Pliolophus ( Oligotomus Cope) for this position, but as it has a considerable diastema, it is better exchanged for Hyopsodus^ where the dental series is uninterrupted. 17 258 THE STRUCTURAL EVIDENCE OF EVOLUTION. iiG. 35. — Falcjcotherlum. Fig. 36. — HipposTjus. necessary to produce the two Vs of the mandibular dentition of PcdcBotherium, Palceosyops (Fig. 34), Symiorodon, Anchippodus (Fig. 33), and all their allies (Fig. 35, PalcB other ium). 5. PcdcBotlieriodont type.— Immediately following the form of the Pcdceosyojjs molar we have that of Hipposyus, where inter- mediate tubercles stand be- tween the inner subconic and the exterior longitudinal cres- centoid tubercles. They are compressed so as to be trans- verse, and only need more complete connection with the adjacent tubercles to give the oblique transverse ridges of A ncliitheriiwi, Palceotherium, and Hyracodon, Rlmiocerus, etc. Hipposyus was origin- ally compared with Anchitherium by Dr. Leidy, and the writer in ignorance of his language remarked :* "An interesting annectant form is seen in Lamhdotherium\ procyoiiinum, where the two inter- mediate tubercles which separate the inner cones from the outer Vs in Limnohyus are so developed as to constitute parts of an in- complete pair of transverse ridges wiiich disappear in front of the bases of the outer Vs. They represent the oblique crests of Pcdmo- therium and A^ichitherium, and thus the genus Lamb- dothermm furnishes a sta- tion on the line from Palce- osyops to the horses." Contemporaneously and quite independ- ently Prof. Marsh expressed similar views X as to its affinities. A greater longitudinal extent of these ridges or longitudinal expansion of the tubercles in the molars in both jaws, the oblique connections being still retained, gives the type of Equus (Fig. 39). The elevation of the tubercles and deepening of the valleys gives * Hayden's "Geol. Surv. Montana," etc., 1873, p. 647. f This species was in the original erroneously called Orohippus procyonirvus, (Ed. 1886.) X "Amer. Joum. Sci. A>ts," 1873, p. 407. Fig. 37. — Hipposyus. Fig. 38. — Ihjpoliippus. Fig. 39. MOLAR TEETH OF THE MAMMALIA EDUOABILIA. 259 us the Selenodont type of superior molars again in this genus • while the lower molars only differ from that type in haying the crescents alternate instead of opposite, forming the Hippodont pattern (Fig. 40). There can be little doubt that the line of the horses comes through Hipp osij us* from the Bunodonts, rather than through Palceotherium, as has been sug- gested by some writers. 6. Bathmoclont type. — I know of no ge- nus which by its intermediate structure connects this type of molar with the Amoe- bodont form of Bunodonts.f Such will doubtless be discovered, for it is impossible that the upper molar of Bathmodon could have been produced by the modification of any known PalsGotheriodont, the type which it most nearly resembles. The structure of the feet of the animal forbids any such sup- position. Such intermediate tyj^es would have, firstly, the (oblique) crests more nearly equal in length and similar in direction. A depression of the crests and indication of diagonal ridges connecting the tubercles in the opposite direction would produce an approach to a W, and the form of Hyopso- dus. That this was probably the history of this curious type is rendered probable by the form of the mandibular teeth, which exhibit two of the in- termediate stages above anticipated. Thus the last inferior molar exhibits two obliquely transverse crests of subequal length, with rudimental oblique or diagonal ridges connecting them. In the median lower molai's one of the latter is developed, giving a V, as in PalcBotherium, but the posterior one is undeveloped, leaving only the original oblique cross- crest. J 7. The Loxolophodonts. — Like the preceding group I know of no type connecting this form with the Bunodont, but antici- pate the discovery of a type with, a rudimental posterior V on the Superior molar of Equus, Fig. 40. — Inferior molar of Equus. * I have since shown that Hyracotherium and Pliolophus, which have very similar dentition, are the types which occupy this position. (Ed. 1886.) •f Such has since been discovered in the genus Pantolambda (Cope). (Ed. 1886). X See " Proceed. Amer. Philosophical Society," Sept., 1872, " On the Dentition of Metalophodony 260 THE STRUCTURAL EVIDENCE OF EVOLUTION. upper molars,* which shall connect it with the W-shaped type proposed above as the probable predecessor of Bathmodon. Or, a pair of oblique parallel crests with rudimental diagonals like the posterior lower molars of Bathmodon may intervene between this form and the Bunodont. This is, however, not probable in view Fig. 41. — Bathmodon. of the diagonal crest of the upper molars (Fig. 42, Uintatlierium robustum), and especially if the parallel with the type of the lower molars is kept up. These are like those of Bathmodon, ex- Figs. 42 and 43. — Uintatherium rohustum. cept that the type of the middle molars of the latter is continued to the posterior end of the series in Uintatherium (Fig. 43) ; that is, the last molar of the latter consists of a V and an oblique cross- crest. Y. RELATIOKS OF THE TYPES OF DEI^TITIOI^' TO TYPES OF FOOT STEUCTURE . I hope that I have succeeded in showing that the Bunodont and Lophodont types of dentition form two homologous series, * This has since been discovered in Pantolambda (Cope). (Ed. 1886.) MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 261 similar to those already indicated among BatracMa, Anura, CepJi- alopoda, etc.* That this relation indicates descent of the corre- sponding terms of the one series from those of the other has also been rendered highly probable. This conclusion has also been previously stated as a theorem, f as follows : ^' V* The heterologous terms or genera in the later series are modified descendants of those of the earlier series " ; in other words, that certain groups higher than genera are produced from others of a similar high value by *^ descent with modification." As already pointed out, the Bunodont primary genera belong to the older geologic epoch of the Eocene, while most of the deriva- tive ones belong to later periods. Some were contemporary with the primary forms, but doubtless have descended from pre-existent members of the same type as yet unknown to us. The genus Achmnoclon, Cope, is especially generalized in three respects : (1) the simplicity of the construction of its molars ; (2) the same simplicity of the premolars, which are without inner or posterior lobes ; (8) the absence of all diastemata and consequent continu- ity of the dental series. Hence it maybe regarded as more primi- tive than PalcBOchcerus, Cheer omor us, Dicotyles, or Elotlierium, in all which there are marked diastemata. The two series may then be arranged as follows : with the understanding that in some cases names of genera used represent rather family groups, in which the special generic lines have not yet been made out.| The following table has been already published in its essential features in the ^* Report on Geological Survey of the Territories," 1873, p. 648.* It remains now to ascertain whether the genealogical or taxo- nomic relations expressed by the teeth coincide with those derived from the other diagnostic regions of the body. First of these must be selected, as of chief importance, the limbs and feet. * See " Origin of Genera," p. 53. t Lo<^- ^«^- P- '^9. X Since the following table was published it has become probable that Achaeno- don is an unguiculate and a flesh-eater. It has also been discovered that the genus Phenacodus possesses the characters which give it the place as the ancestor of all the lines in the table. (Ed. 1886.) # It was previously published in a separate form in " On the Primitive Types of Mammalia Educabilia," May 6, 1SY3. An error occurs in this edition in the reversal by a lapsus calami of the positions of the types Omnivora and Anoplothcrium. It is also important to note, that in the " Report G. S.," p. 645, where it is stated that " during the Eocene they (the orders) were in process of difPerentiation," etc., Mam- malia Educabilia and not Zissencephala, are referred to. 262 THE STRUCTURAL EVIDENCE OF EVOLUTION. o o o CO r^_ 13:1 52: O Q O 8 o o •to ^ o o a. // s =0 O Loxolophodont Bathmodont =0 o — CO o - .1 .1 ^ Symborodont Palseotheriodont Selenodont pt. -8 _ P _ O ■5. to e OS O _ o 09 Trichechodont 8 •50 - o - t o 60 CO O I- Tapirodont — % — h — -o Selenodont 6 00 O -Y- o O o O o MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 263 We may look on the Artiodadyla — even-toed or cloven- footed mammals — as one of the most homogeneous groups in the class, not only in respect to the structure of the extremities, but also in that of the cranium, vertebrae, etc. But here we have both Buno- dont and Selenodont types of molars. The Perissodactyla, as de- fined by the feet, axis, palate, etc., present us with the Symhoro- dont, PcdcBotheriodont, Tapirodont, and Selenodont types of denti- tion in the superior series, and the Hippodont, Hyracodont, Pa- IcBotheriodont, and Trichecliodont types in the mandibular teeth. The pentadactyle, plantigrade type, for which I have used the name Proboscidia, presents us with the Trichecliodont, Bathmo- dont, and Loxolophodont types of molar structure. Among Siren- ians, as defined by the marked peculiarities of the entire skeleton, we have the great differences in dentition presented by Halicore and Trichecus, the former being Haplodont, the other TrichecJio- dont. Finally, the Marsupial group is unquestionably well defined, and here Pliascolomys is Ptycliodont ; Didelphys, Bunodont j Pe- taiirus between Bunodont and Selenodont, and the Kangaroos and their gigantic extinct allies the Diprotodontidce, Trichecliodont. It is thus evident that the molar types are everywhere subor- dinated to those which we call ordinal ; therefore in the case of the placental mammals, and especially those with complex folding of the cerebral hemispheres, to the types of construction of the feet. As to the modifications presented by the canine and incisor teeth, these exist within a still more narrow range of variation ; for instance, in the allied genera Equus, Rhinaster, and Symhoro- don ; Sus and Phacochwrus ; Bathmodon and Unitatherium, and others. It is thus probable that modifications in the three points of structure considered were introduced in the following order : First, Of the feet. Second, Of molar type.* Third, of the relations of canines and incisors. With regard to the significance of the tnree types of feet, Pro- hoscidian, Perissodactyle, and Artiodactyle, it has been already remarked: ^'It is to be observed that the lines of Ungulata, * In the case of the Marsupialia the relation of the dental and extremital types may be reversed. Thus we have pentadactyle plantigrade forms (Opossums) and (nearly) didactyle digitigrade forms {Macropus) in the same order. Also Hahnatu- rus and Diprotodon, both Trichechodonts, differ in the type of feet, as do the car- nivorous Didelphys and Thylacinus, both Bunodonts. 264 THE STRUCTUEAL EVIDENCE OF EVOLUTION. Quadrumana, and Carnivora originate in plantigrade types, a state of things quite predominant among the lower series or Lis- sencephala (smooth brains). It is universal in Edentata and very usual in Rode7itia and Insectivora. The lower forms of Marsu- pialia and all of the Monotremes present it. In the Marsupials, Rodents, Ungulates, and Carnivores, we have series whose highest expression is in the most highly digitigrade genera."* To this it may be added that the lower terrestrial vertebrates are plantigrade, with some exceptions. Thus in some Anurous BatracMa there is a partial digitigradism ; the only digitigrade Reptilia are some Dinosauria, especially such carnivorous forms as Lcelaps ; all birds are digitigrade. The digitigrade modification evidently has reference to speed in running, or projectile force in leaping. The connecting points between the different types of foot- structure among the Ma7nmalia Educahilia are as obvious as in the case of the types of molar structure. Examples may be ad- duced as follows : Carnivora. — In all of the genera of the Eocene Carnivora which I have had the opportunity of examining, excepting 3Iesonyx, namely, Amhlyctonus, Oxycena, Prototomus, Didymictis, the tibio- astragalar articulation is of a primitive character. The astragalus is flat, and the applied surfaces are nearly a plane, and without the pulley-shaped character seen in existing Carnivora ; as dogs, cats, and in a less degree in the bears and in other Mammalia with specialized extremities, as Perissodactyla, Artiodactyla, etc. The simplicity of structure resembles, on the other hand, that found in the opossum and various Insectivora, Rodentia, and Quadru- mana, and in the Proioscidia, most of which have the generalized type of feet. The structure indicates that the carnivorous genera named were plantigrade — a conclusion which is in conformity with the belief already expressed that the Mammalia of the Eocene exhibit much less marked ordinal distinction than do those of the Miocene or the recent periods. It is, indeed, questionable whether some of the genera here included in the Carnivora are not gigantic Insectivora, since the tibio-tarsal articulation in many, the separa- tion of the scaphoid and lunar bones in Mesonyx, the form of the molars, and the absence of incisor teeth in some, are all character- istic of the latter rather than the former order. Artiodactyla. — Approximations to the Perissodactyla are to be *" Mammalia Educabilia," p. 8; Hayden's "Geological Survey," 18Y3, p. 647. MOLAR TEETH OF THE MAMMALIA EDUOABILIA. 265 seen in Hippopotamus in the increase in development of the lat- eral or first and fourth digits, thus equaling the number in the fore-foot of Tapirus and Menodus, though preserving the equal- ity of the two median digits. But an inequality of these digits appears in the genera Anoplotherium and Cmnotlierium, as has been stated^ in the following language : '^In Anoplotherium se- cundarium the digit ii is developed in each foot, though not nearly so long as m, which is nearly symmetrical in itself. There is an approach to the same structure in the manus of Cmnotlie- rium.^^ The only approximation to the Proboscidian type is to be seen in the shortening of the metapodial bones in Hiiopopotamus, a point of very inconsiderable value. Perissodadyla. — Approximation to the preceding order is made in the anterior foot of Menodus, in which, according to Marsh, there are four toes of nearly equal size, f Apj^roximation to the Proboscidia X is seen in Symtorodon, where the cuboid facet of the astragalus is rather larger than in Rhinoceros, and devel- oped much as in Bathmodon ; the small third trochanter of the femur is also much like that in Bathmodon. The osseous horn- cores may be compared with those on the front of Loxolophodon. The knee was probably free from the integument of the abdomen, as in Proboscidians, In all other respects there is no approxima- tion to this order. Proboscidia. — The approximations to other orders in the structure of the feet are only to be seen in the Eocene genera Bathmodon and Eohasileus. The latter, or its ally JJiyitatherium, presents, according to Marsh, but four toes on the hind foot ; the anterior has five. In the former point we have a resemblance to Hippopotamus, but one of little significance, in view of the radical differences between the two in the form of the astragalus, cal- caneum, and cuboid bones. The former is essentially Proboscidian in all respects, with the addition of a cuboid facet alongside of and behind the navicular, as in Symhorodon ; thus constituting a Perissodactyle character, but leaning to the forms of that order which betray probably the closest, though slight, approach to the omnivorous division of the Artiodactyla. Thus, while the Uinta- theriidcB present the Proboscidian type of feet and molar dentition, * Huxley, "Anatomy of the Vertebrated Animals," p. 321. f "American Journal of Science and Arts," 1873, p. 486. i This should be Amblypoda, not separated from the Proboscidia at the time this was written. (Ed. 1886.) 266 THE STRUCTURAL EVIDENCE OF EVOLUTION. if they present any ordinal characters resembling those of the Artiodactyla, they are equally shared by certain extinct Perisso- dactyla. From the hints above furnished, we may regard the succession of modifications of foot-structure to be nearly as follows ; Ruminantia. Rhinocerus. Equus. Elephas. Omnivora. Palseotheriura. Hyracotherium.* \ / / \ / / Sjinborodoa. Palseosyops. Uintatherium. \ / / \ / / \ / / x/ / , * Bathmodon. \ / \v // \ / \ / \/ * VI. THE ANCESTRAL TYPE OF MAMMALIA EDUCABILIA. I trust that I have made it sufficiently obvious that the primi- tive genera of this division of mammals must have been Buno- donts with pentad actyle plantigrade feet. It therefore follows that Eleplias was not the descendant of Eoiasileus nor Bathmodon in a direct line, but from some common ancestor with tubercular teeth, through Mastodon. We may anticipate the discovery of such a genus, and believe that it will not be widely removed from the Eocene Hyopsodus, or perhaps Achcenodon. This will, then, be the primitive ungulate. But it will be more than this ; it can not be far removed from the primitive carnivore and the primitive quadrumane. The Car- nivora are all modified bunodonts, and the lower forms ( Ursus Procyon, e. g.) are pentadactyle and plantigrade. As to the Quadrumana, man himself is a pentadactyle plantigrade buno- dont. This view has been already expressed, as follows: '^^The type of Tomitlierium, already described, evidently stands between lemurine monkeys and such small allies of Palmotlieriidm with conic tubercular teeth {Oligotomus, OrotJierium,\ etc.), and which abound in the Eocenes of Wyoming. . . . The dentition of the two types is, indeed, but little different in the Quadrumanous and * This was called Hipposyus in the original essay — a name which really applies to a different type. (Ed. 1886.) t Both these are names for Pliolophus, a close allay of Ilyracotherium. (Ed. 1886.) MOLAR TEETH OF THE MAMMALIA EDUCABILIA. 267 Ungulate types respectively, being a continuous series of I. 1 or 2 ; C. 1 ; P. m. 3 — 4 ; M. 3 ; the canines but moderately devel- oped. "* Such a hypothetical type might be expressed by the name BunotlieriidcB, with the expectation that it will present sub- ordinate variations in premolar, canine, and incisor teeth. The premolars might be expected to differ in the degree of development of the internal lobes, the canine in its proportions, and the incisors in their number. In respect to the limbs proper, neither the Quadriimana nor Carnivora attain to the specialization seen in the Artiodactyla and Perissodadyla, for the ulna and fibula are never atrophied nor co-ossified with the radius and tibia, but are always distinct and free ; the only modification of structure in these points being the slight one involved in developing the rotary capacity seen in the higher monkeys. Thus the human series preserves in its feet, limbs, and den- tition, more of the characteristics of the primitive Bunotlieriwn than any other line of descent of the Mammalia EducaMlia. It even exhibits a retrogression, in the transition from the anisog- nathous Tomitherium to the genus Homo, where the teeth in the two jaws are exactly alike, as well as in the resumption of the continuity of the dental series after the diastema had prevailed among the higher monkeys. In one respect it has steadily ad- vanced, viz., in the number of convolutions and extent of the cerebral hemispheres and relative size of the brain as a whole. Note (Ed. 188fi). — As remarked in a previous note, the discovery of the general characters of the genus Phenacodus in 1881, more than six years after the publica- tion of this paper, demonstrated the truth of the hypothesis here proposed, viz. : that the ancestor of the Mammalia Educabilia was a pentadactyle plantigrade buno- dont. The numerous genera and species allied to Phenacodus have been placed in a suborder Condylarthra. See " American Naturalist," 1884, 790, for an illustrated article on this group. * Ilayden's " Geological Survey of Montana," etc., 1872, p. 645. VIII. THE EELATION OF MAN TO THE TERTIARY MAMMALIA.* Ii^" order to prove the affirmative of a doctrine of evolution by descent of the existing types of living beings, two propositions must be established. The first, that a relation of orderly succes- sion of structure exists, which corresponds with a succession in time. Second, that the terms (species, genus, etc.) of this suc- cession actually display transitions or connection by intermediate forms, whether observed to arise in descent, or to be of such vari- Fia. AA.-Periptychm rhabdodon part ^^^^ character aS to admit of nO of posterior foot, two thirds natural size ; • ^ i • • • b, astragalus from above, showing flat other explanation of their origin face; e, metatarsals, the first lost, show- than that of deSCCnt.. ing plantigrade foot. Original; from j^ ^|-^g g^i^j ^f paleontology it Puerco Epoch of New Mexico. . ., -i i j t 7 i IS quite possible to demonstrate the first of these propositions, while the proof of the second is necessarily restricted to the observation of variations and the dis- covery of connecting forms which destroy the supposed definitions of species, genera, etc. The conditions are more favorable for the investigation of animals of the higher types than of those of the lower. Their late origin insures to us the opportunity of discovery of their ancestry far more certainly than in the case of the lower, whose beginnings are lost in the remote past, and belong to periods whose deposits have undergone physical changes, or have been en- tirely removed and redeposited elsewhere, thus insuring the de- struction of the fossil remains once contained in them. The series of the tertiary Mammalia is becoming more complete through the * Read before the American Association for the Advancement of Science, at Detroit, 1875, under another title. EELATION" OF MAN TO THE TERTIARY MAMMALIA. 269 Fig. 45. — Caryphodon elepJiantopiLS^ anterior foot from above, one third natural size. From Lower Eocene of New Mexico. The cuneiform {Cu) is injured. (Original.) recent explorations in the West, and the results are embraced in the forthcoming quarto reports of the Hayden and z^^^fc^^'^K^S'c Wheeler U. S. Geological, Cu etc., surveys of the Terri- ^'n- tories. An abstract of some of these is given in the present essay. The primary forms of the Mammalia repose in great measure on the struc- ture of the feet. Those of the teeth are also very sig- nificant, but present a greater number of varia- tions among animals other- wise nearly related. The osteology of the feet of re- cent land mammals falls into several categories. These may be called the plantigrade, many-toed type ; the car- nivorous type ; the horse type, and the ruminant (e. g., ox) type. The lower vertebrates, as sala- manders, lizards, etc., dis- play the simplest form of feet, having usually five toes, with numerous sepa- rate bones of the palm and the sole, which they apply to the ground in progression. The many- toed or multidigitate type of mammalian foot most nearly resembles this condition, but dif- FiG. 46.— Posterior foot of CorypTiodon elephan- fers in the points of dif- topus. From Lower Eocene of New Mexico. (Orig- f p^'ence which are Com- mon to all Mammalia. In the hind foot a succession of forms leads from this general- 270 THE STRUCTURAL EVIDENCE OF EVOLUTIOK ized type to the extreme specializations observed in the horse and the ox. The modifications are as follows : The hind foot is composed of two rows of tarsal bones, of which the second is followed by the long metatarsal bones, from which the bones of the toes origi- nate. The second segment of the hind leg is composed of two boues, tibia and fibula, which in the salamander, etc., have a sub- equal union with the foot. In some multidigitates, as the genus Corypliodon, both these bones articulate with the two bones of the first row of the tarsus, and one (fibula) is the smaller of the two. In many higher forms they articulate with but one of these tar- sal bones, viz., the astragalus, with which they form a perfect hinge joint ; the other tarsal bone of the first row is the calcaneum or heel-bone. In Coryjjliodon the as- tragalus and the applied leg-bone (tibia) are near- ly flat, offering an ex- tremely imperfect hinge for the foot, and the heel-bone (calcaneum) is exceedingly short. The animal plainly walked on the entire sole of the foot, and must have had an awk- ward gait, from the Fig. 47.— Left anterior slio'ht power of flexins^ ^ooX.oi Phenacodus primal- foot of PTienacodusprimos,- the ankle-joint. From ""''^^"^- '^''- ^^"^^-^ t^^«, K nat. size. (Orig.) this point to the horse on one side, and to the ox on the other, we have a line of succession of intermediate forms. And before de- scribing them, I may state that the Corypliodon is one of the old- est known Mammalia, its remains having been found in the Lower Eocene Tertiary of New Mexico and Wyoming, while the ox and horse are extremely modern animals, their advent on the earth having preceded that of man by but one geological period. The most perfect ankle-joint is that of the ruminating animals. The astragalus presents a deeply grooved segment of a pulley ; an angulated pulley, face downward to the rest of the foot, and a Fig. 48. — Left posterior PLATE VI. 272 THE STRUCTURAL EVIDENCE OF EVOLUTION. smooth convexity to the hollow of the applied heel-bone behind. No such astragalus has ever been found in the Lower Eocene forma- tions of America ; animals bearing it in a less perfect stage appear in the next higher period, the Miocene ; but it is not until the Pliocene and modern times that they abound. In the Hipjwpota- mus foot, we have an example of the less perfect astragalus of this type of animals. The pulley surfaces are flatter and less deeply grooved. In the horse, the upper surface of the astragalus forms as perfect >7mrve /irfaulan POLLICIS Cfjrpi'S eJT. CARPI ULNAR IS pni»M RNoan nirER0NELIS1,0NCUS Oroox-t* for PONEUS BPEVIS 3liicn:/e/ororoyiit o^ AS: OIN. Die. Fig. 50. — Posterior foot of do. from above, one third natural size. From Allen's Anatomy. a joint as in ruminants, but the lower and hinder faces present the flattened surfaces which belong to the many-toed Mammalia. The lower face especially is mainly occupied by one large facet, in- stead of the two-faced pulley of the ruminants. In the rhinoceros a later facet is more distinct, while in the Miocene Menodus the second facet is larger, resembling, except in the still convex tibial articulation, the structure of that of the primitive Corypliodon. RELATION OF MAN" TO THE TERTIARY MAMMALIA. 273 In the heel-bone we have a succession from the short and flat form of Coryphodon to the long and slender one of the horse and ruminants ; the increase in length being associated with the elon- gation of the bones of the toes, and the assumption of the digiti- grade type from the planti- grade. The mammals of the Lower Eocene* exhibit a greater percentage of types that walk on the entire sole of the foot, while the suc- ceeding periods exhibit an increasing number of those that walk on the toes, while the hoofed animals and Car- nivora of recent times nearly all have the heel high in the air, the principal exceptions being the elephant and the bear families. A most noticeable succes- sion is seen in the diminu- tion of the number of toes. In the series leading to the horse, the ox, and the hyaena and cat, this reduction pro- ceeds by the loss of a toe from the one side or the other, until in the ruminants but two are left, and in the horse but one. The series ex- tending from the primitive Eocene types with five digits, to the existing reduced forms, is most complete, although Fig. b\.—Phenacodus primcevus skull, one a few of the New Mexican third natural si^e, from below, showing quadri- -c^ ,1 1 tubercular true molars. From specimen figured Eocene genera themselves , . r & ^ _ on plate. probably exhibit but four digits on one or both pairs of feet. The presence of the rudiments * All the Mammalia of the Puerco fauna (which was unknown at the time this lecture was delivered) are plantigrade. (Ed. 1886.) 18 274 THE STRUCTURAL EVIDENCE OF EVOLUTION. of the lost lateral digits is constantly observed, and when these disappear it is to be finally replaced by the rudiments of the ad- joining toes in i^rocess of similar reduction. The bones of the sec- ond row of the tarsus which are in connection with the toes are not reduced so rapidly as the toes themselves; hence, the bones of the toes, in order to maintain the fit of the i^arts, increase in width, and consequently in strength. As is well known, in the horse the single toe is as stout as several united toes of lower forms, and the two toes of the ruminants have their basal seg- ments (metatarsals) united into a stout solid mass, the cannon- bone. At the same time several of the small bones of the sec- ond tarsal row become coossified, so that we have, in the rumi- nants and horse, the greatest consolidation of structure, connected in the former with the most elegant mechanism. It is scarcely necessary to add that, in the various cases of coossification and consolidation described, the foetus displays the original elements separated. In the fore limb the same successional reduction in the number of toes may be traced as I have described in the hind foot ; but, as the bones of the palm differ from those of the sole, the succes- sional modification of these is also characteristic. The bones of the second row of the carpus are four in number, but as the toes are reduced, in the lines of the hoofed animals, the inner (tra- pezium) is soon dropped, and the second (trapezoides) becomes united with the third (magnum). In the carnivorous order, the trapezoides is always separate, but the inner pair of bones of the first row (scaphoid and the lunar) become consolidated into a single mass, although their original distinctness is easily determined by examination of the foetus. The two bones of the leg which articulate with the foot and hand, exhibit a succession of changes of relation in progress to- ward the more specialized types. In the Corypliodon and Umta- therium of the Eocene, each of these bones has considerable share in the articulation ; but as we rise in the series, the surface of at- tachment of the lesser bones, the fibula in the foot, and the ulna in the hand, becomes successively smaller, until in the ruminants the fibula is almost obliterated, its distal end remaining as a small tuberosity coossified to the side of the end of the tibia. In the same manner the articular end of the ulna in the fore leg is suc- cessively reduced, until this bone also becomes a thin strip coossi- fied to the lower side of the radius, with no distinct termination. PLATE VIL pec... Fia. 5. Fig. 7. acQ -ax Fig. 9. acc Fig. 2. Fig. 4. ktti' ai pi pi Pe ji Fig. 6. ai aV P} Fig. 8. ae y —-h ye Fig. 10. Fig. 1, Mioclaenus corrxigatus^ superior molars. Fisf. 2, Pantolambda hathmodon^ superior true molars. Fig. 3, Phenacodus primcevus, superior molar. Fig. 4, do. inferior molar. Fig. 5, Lambdotherium popoagicum^ superior molar. Fig. 6, do. inferior molar. Fig. 7, AncMtherium anrelianense, superior molar. Fig. 8, Hippotlieriu'm gracile^ infe- rior molar. Fig. 9, superior molar young crown of a Hippotherium. Fig. 10, superior molar of Equus. Figs. 1, 2, 5, 6, from Cope ; 3, 4, from Wortman ; the others from '"audry. G: 276 THE STRUCTURAL EVIDENCE OF EVOLUTION. in both the horse and the ox. In the foetus these bones are well distinguished. The dentition tells as clearly as possible the same story. Here, again, as I have pointed out in a paper on the ** Homologies and Origin of the Types of Dentition of the Mammalia Educahilia,^'' the most specialized forms of dental structure are presented by the horse, the ox, and the tiger. But they are all modifications of a single type of tooth, viz., an oval crown supporting four tubercles on the summit, in the lower jaw, and three or four in the upper jaw. In the lower cutting molar of the cat but one of these tu- bercles remains, forming with another in front of it a double shear blade, whose development may be traced from its earliest begin- nings in the genera of the Eocene. In the odd-toed forms (tapir, rhinoceros, etc.) the tubercles become connected transversely, forming cross-crests, and the outer ones are generally flattened on the outer side. In the horse the tubercles have a very complex form, and the spaces between them filled by a peculiar substance, the cementum. In the ruminants the tubercles come to have a crescent-shaped section and are drawn out to an enormous length, forming a prismatic tooth : here, also, the intervening deep valleys are filled with cementum. . In the third series, that of the ele- phant, the original tubercles (permanently separate in the masto- dons) are connected into cross-crests, which are drawn out to a great length, and as in the other series are supported by a deposit of hard cementum in the intervening valleys. The transitions be- tween these and the primitive four-tubercled molar are numerous and direct. There is not now opportunity to consider the question of tran- sition from type to type by descent, further than to indicate by a few examples the manner in which it has evidently occurred. This has been by unequal growth of parts during foetal life, ac- cording to the laws of acceleration and retardation. The union of the two basal bones of toes into a single one (the "cannon- bone ") in the ruminants, is accomplished by the more and more rapid completion of the process of ossification in the growth of those bones ; the confluence of the various carpal and tarsal bones in various orders has the same history. In many genera it has been observed that the milk dentition has resemblances to other and older dentitions, which entirely disappear in the permanent teeth. This is the case with Coryphodon and Equus ; while it may be observed in the kitten, whose sectorial milk-tooth has the PLATE VIII. 278 THE STRUCTURAL EVIDENCE OF EVOLUTION. heel belonging to all the lower and primitive Carnivora which is wanting from the sectorial of the adult cat. Moreover, in complex teeth, the different stages of wear represent primitive conditions of the same animal, elsewhere preserved to us in extinct adult genera and species. Forms which violate the definitions of the orders above given are also well known. Thus Mesonyx, with the skull and denti- tion of a carnivore, has the separate scaphoid and lunar bones and flat claws or hoofs of an ungulate. Calamodon has the molars of an ungulate, the incisors of a rodent, and claws resembling somewhat those of a carnivore. Uintatlierium has feet partly like an elephant, and teeth of a tapir. I have referred the Mammalia with five and four toes, the full number of distinct tarsal and carpal bones, which form interlock- ing series, and in which the tread is plantigrade, to a new order called the AmUyjJoda. These represent the primitive type of the higher Mammalia with convoluted brains, etc., but present much variation in the constitution of the teeth. From the latter have come off not only the three hoofed-orders represented by the ele- phant, the horse, and the ox, but the origin of the Carnivora and Quadrwnana is scarcely distinguishable from it, if at all ; while there is little doubt that the natatory Sireniaii order was derived from it by a process of degradation, chiefly of the extremities, in connection with the assumption of an aquatic life. The mana- tee, of which a fine example may now be seen in our zoological gardens, represents this division. The relation of man to this history is highly interesting. Thus in all general points his limbs are those of the primitive type so common in the Eocene. He is plantigrade, has five toes, separate carpals and tarsals ; short heel, rather flat astragalus, and neither hoofs nor claws, but something between the two. The bones of the forearm and leg are not so unequal as in the higher types, and remain entirely distinct from each other, and the ankle-joint is not so perfect as in many of them. In his teeth his character is thoroughly primitive. He possesses, in fact, the original quadri- tuberculate molar with but little modification. His structural superiority consists solely in the complexity and size of his brain. The forms of the quadrumanous order, while agreeing with each other in most respects, display the greatest range of brain struct- ure, and show that while they have made but little progress since the Eocene in perfection of organization of the skeleton, they PLATE IX. Fig. 7. Fig. 1. Fig. 4. C V ^ Fig. 5. Fig. 6. Fig. 8. COMPAEISOK BETWEEN THE DENTITION OF THE LEirtJE AnAPTOMORPHUS AND MaN. Fig. 1, skull of Anaptomovplixis Tiormmctdus^ natural size. Fig. 2, same, oblique view, displaying the large cerebral hemispheres ; compare Plate XIV for relatively small size in a contemporary (Fig. 3) or a successor in time (Fig. 2). Fig. 3, superior view of skull, natural size. Fig. 4, inferior view, 3/2 natural size. Figs. 5, 6, and 7, left branch of lower jaw of Anaptomorphus cemulus, twice natural size; 5, from left side; 6, inner Bide ; 7, from above. Fig. 8, superior dentition of Homo sapiens (from Alien), natural size. 280 THE STRUCTURAL EVIDENCE OF EVOLUTION. accom23lished a mucli greater work, the eyolution of tlie human brain and its functions. A very important lesson is derived from these and kindred facts. The monkeys were anticipated in the greater fields of the world's activity by more powerful rivals ; the ancestors of the ungulates held the fields and the swamps, and the Carnivora, driven by hun- ger, learned the arts and cruelty of the chase. The weaker an- cestors of the Quadrumana possessed neither speed nor weapons of offense and defense, and nothing but an arboreal life was left them, where they developed the prehensile powers of the feet. Their digestive system unspecialized, their food various, their life the price of ceaseless vigilance, no wonder that that quality of in- quisitiveness and wakefulness was stimulated and developed which is the condition of progressive intelligence. So *' the race has not been to the swift nor the battle to the strong" ; the *' survival of the fittest" has been the survival of the most intelligent, and natural selection proves to be, in its highest animal phase, intel- ligent selection. IX. THE DEVELOPMENTAL SIGNIFICANCE OF HUMAN PHYSIOGNOMY.* The ability to read character in the form of the human face and figure is a gift possessed by comparatively few persons, al- though most people interpret, more or less correctly, the salient points of human expression. The transient appearances of the face reveal temporary phases of feeling which are common to all men ; but the constant qualities of the mind should be expressed, if at all, in the permanent forms of the executive instrument of the mind, the body. To detect the peculiarities of the mind by external marks has been the aim of the physiognomist of all times ; but it is only in the light of modern evolutionary science that much progress in this direction can be made. The mind, as a function of part of the body, partakes of its perfections and its defects, and exhibits parallel types of development. Every pecu- liarity of the body has probably some corresponding significance in the mind, and the causes of the former are the remoter causes of the latter. Hence, before a true physiognomy can be attempted, the origin of the features of the face and general form must be known. Not that a perfect physiognomy will ever be possible. A mental constitution so complex as that of man can not be expected to exhibit more than its leading features in the body ; but these include, after all, most of what it is important for us to be able to read from a practical point of view. The present essay will consider the probable origin of the structural points which constitute the permanent expression. These may be divided into three heads, viz. : (1) Those of the general form or figure ; (2) those of the surface or integument of the body with its appendages ; and (3) those of the forms of the * Abstract of a lecture delivered before the Franklin Institute of Philadelphia, January 20, 1881, in exposition of principles laid down in "The Hypothesis of Evo- lution," New Haven, 1870, p. 31. 282 THE STRUCTURAL EVIDEN^OE OF EVOLUTION". head and face. The principal points to be considered under each of these heads are the following : 7. The General Form. 1. The size of the head. 2. The squareness or slope of the shoulders. 3. The length of the arms. 4. The constriction of the waist. 5. The width of the hips. 6. The length of the leg, principally of the thigh. 7. The sizes of the hands and feet. 8. The relatiye sizes of the muscles. //. The Surfaces. 9. The structure of the hair (whether curled or not). 10. The length and position of the hair. 11. The size and shape of the nails. 12. The smoothness of the skin. 13. The color of the skin, hair, and irides. III. The Head and Face. 14. The relative size of the cerebral to the facial regions. 15. The prominence of the forehead. 16. The prominence of the superciliary (eyebrow) ridges. 17. The prominence of the alveolar borders (jaws). 18. The prominence and width of the chin. 19. The relation of length to width of skull. 20. The prominence of the malar (cheek) bones. 21. The form of the nose. 22. The relative size of the orbits and eyes. 23. The size of the mouth and lips. The significance of these, as of the more important structural characters of man and the lower animals, must be considered from two standpoints, the paleontological and the embryological. The immediate paleontological history of man is unknown, but may be easily inferred from the characteristics displayed by his nearest relatives of the order Quadrumana. If we compare these animals with man, we find the following general differences. The num- bers correspond to those of the list above given. HUMAN PHYSIOGNOMY. 283 /. As to General Form, — (3) In the apes the arms are longer ; (8) the extensor muscles of the leg are smaller. //. As to Surface, — (9) The body is covered with hair which is not crisp or woolly ; (10) the hair of the head is short ; (13) the color of the skin, etc., is dark, ///. As to Head and Face. — (14) The facial region of the skull is large as compared with the cerebral ; (15) the forehead is Fig. 52. — Section of skull of adult orang-outang {Simla safyrus). «, section of skull of young orang, showing; relatively shorter jaws and more prominent cerebral region. not prominent, and is generally retreating ; (16) the superciliary ridges are more prominent ; (17) the edges of the jaws are more prominent ; (18) the chin is less prominent ; (20) the clieek-bones are more prominent ; (21) the nose is without bridge, and with short and flat cartilages ; (22) the orbits and eyes are smaller (except in Nyctipithecus) ; (24) the mouth is small and the lips are thin. It is evident that the possession of any one of the above char- acteristics by a man approximates him more to the monkeys, so 284: THE STRUCTURAL EVIDENCE OF EVOLUTION. far as it goes. He retains features wliicli have been obliterated in other persons in the process of evolution. In considering the ph3'siognomy of man from an embryological standpoint, we must consider the peculiarities of the infant at birth. The numbers of the following list correspond with those already used (Fig. 53). /. As to the General Form. — (1) The head of the infant is rel- atively much larger than in the adult ; (3) the arms are relatively longer; (4) there is no waist; (6) the legs, and especially the thighs, are much shorter, //. As to the Surfaces. — (10) The body is covered with fine hair, and that of the head is short. ///. The Head and Face. — (14) The cerebral part of the skull greatly j^redomi- nates over the facial ; (16) the superciliary ridges are not developed ; (17) the al- veolar borders are not prom- inent ; (20) the malar bones are not prominent ; (21) the nose is without bridge and the cartilages are flat and generally short ; (22) the eyes are larger. It is evident that per- sons who present any of the characters cited in the above list are more infantile or em- bryonic in those respects than are others ; and that those who lack them have left them behind in reaching maturity. We have now two sets of characters in which men may differ from each other. In the one set the characters are those of monk- eys, in the other they are those of infants. Let us see whether there be any identities in the two lists, i. e., whether there be any of the monkey-like characters which are also infantile. We find the following to be such : Fig. 53. — ^Figure of infant at birth; a, front of face. huma:n' physiognomy. 285 L As to General Form. — (3) The arms are longer. //. Surface. — (10) The hair of the head is short, and the hair on the body is more distributed. ///. As to Head and Face. — (21) The nose is without bridge, and the cartilages are short and flat. Three characters only out of twenty- three. On the other hand, the following characters of monkey-like significance are the oppo- sites of those included in the embryonic list : (14) The facial re- gion of the skull is large as compared with the cerebral ; (15) the forehead is not prominent ; (16) the superciliary ridges are more ¥iQ. 54. i'lG. 55. Fig. 54. — Portrait of a girl at five years of age. Fig. 55. — Portrait of the same at seventeen years, showing the elongation of the facial region, and less protuberance of the cerebral. prominent ; (17) the edges of the jaws are more prominent. Four characters, all of the face and head. It is thus evident that in at- taining maturity man resembles more and more the apes in some important parts of his facial expression. It must be noted here that the difference between the young and embryonic monkeys and the adults is quite the same as those just mentioned as distinguishing the young from the adult of man (Figs. 1-2). The change, however, in the case of the monkeys is greater than in the case of man. That is, in the monkeys the jaws and superciliary ridges become still more prominent than in PLATE X. Esequibo Indian women, showing the following peculiarities : deficient bridge of nose, prognathism, no waist, and deficiency of statm-e through short femur. From photographs by Endlich. HUMAN PHYSIOGNOMY. 287 man. As these characters result from a fuller course of growth, from the infant, it is evident that in these respects the apes are more fully developed than man. Man stops short in the develop- ment of the face, and is in so far more embryonic* The promi- nent forehead and reduced jaws of man are characters of " retar- dation." The characters of the prominent nose, with its elevated bridge, is a result of ^* acceleration," since it is a superaddition to the quadrumanous type from both the standpoints of paleontology and embryology. f The development of the bridge of the nose is no doubt directly connected with the development of the front of the cerebral j)art of the skull and ethmoid bone, which sooner or later carries the nasal bones with it. If we now examine the leading characters of the physiognomy of three of the principal human sub-sj)ecies, the Negro, the Mon- FiG. 56. Fig. 57. Fig. 56, — Profile of a Lucliatze negro woman, sbowin;? deficient bridge of nose and chin, and elongate facial region and prognathism. Fig. 57. — Face of another Luchatze, showing flat nose, less prognathism and larger cerebral region. From Serpa Pinto. golian, and the Indo-European, we can readily observe that it is in the two first named that there is a predominance of the quad- rumanous features which are retarded in man ; and that the em- bryonic characters which predominate, are those in which man is * Thi3 fact has been well stated by C. S. Minot, in the "Naturalist " for 1882, p. 511. f See Cope, " The Hypothesis of Evolution," New Haven, 1870, p. 31. 288 THE STRUCTURAL EVIDENCE OF EVOLUTION accelerated. In race description the prominence of the edges of the jaws is called prognathism, and its absence orthognathism. The significance of the two lower race characters, as compared with those of the Indo-European, is as follows : Negro. — Hair crisp (a special character), short (quadrnm. ac- cel.) ; prognathous (quadrum. accel.) ; nose flat, without bridge (quadrum. retard.) ;* malar bones prominent (quadrum. accel.) ; beard short (quadrum. retard.) ; arms longer (quadrum. accel.) ; extensor muscles of legs small (quadrum. retard.). Mongolian. — Hair straight, long (accel.) ; jaws prognathous (quadrum. accel.) ; nose flat or prominent, with or without bridge ; malar bones prominent (quadrum. accel.) ; beard none (embryonic) ; arms shorter (retard.) ; extensor muscles of leg (''calf") smaller (quad, retard.). Indo-European. — Hair long (accel.) ; jaws orthog- nathous (embryonic re- tard.) ; nose (generally) prominent with bridge (accel.) ; malar bones re- duced (retard.) ; beard long (accel.); arms shorter (retard.) ; extensor mus- cles of the leg large (accel.). The Indo - European race is then the highest by virtue of the acceleration of growth in the develop- ment of the muscles by which tiie body is main- tained in the erect position Fig. 58.— Portrait of Satauta, a late chief of the (extensorS of the leg), and Kiowas (from the Ked Eiver of Texas), from a j^ those important elc- pfiotoarraph. The predominance of the facial re- + -p v. i gion, and especially of the malar bones, and the ^^nts 01 beauty, a WCll- absence of beard, are noteworthy. developed nose and beard. * In the Bochimans, the flat nasal bones are coossified with the adjacent ele- ments as in the apes (Thulie). PLATE XL '■'V;;:;:Vi;:V;::;/;r'!'-. ^'S^\ii\^■'l■■r,l,,;■\^.v.i\\\t,';I'.'->a The Wrestler ; original in the Vatican. This figure displays the characters of the male Indo-European, except the beard. 19 290 THE STRUCTURAL EVIDENCE OF EYOLUTION. It is also superior in those points in which it is more embryonic than the other races, viz., the want of prominence of the jaws and cheek-bones, since these are associated with a greater predom- inance of the cerebral part of the skull, increased size of cerebral hemispheres, and greater intellectual power. A comparison between the two sexes of the Indo-Europeans expresses their physical and mental relations in a definite way. I select the sexes of the most civilized races, since it is in these, ac- cording to Broca and Topinard, that the sex characters are most pronounced. They may be contrasted as follows. The numbers are those of the list on page 282, already used. I first consider those which are used in the tables of embryonic, quadrumanous, and race characters : MALE. FEMALE. /. The General Form. 2. Shoulders square. Shoulders sloped. 4. Waist less constricted. Waist more constricted. 5. Hips narrower. Ilips wider. 6. Legs longer. Legs shorter (very frequently). 8. Muscles larger. Muscles smaller. II. The Integuments^ etc. 10. More hair on body, that of head Less hair on body, that of head longer ; shorter ; beard. no beard. 12. Skin rougher (generally). Skin smoother. III. TJie Head and Face. 16. Superciliary ridges more prominent. Superciliary ridges low, 22. Eyes often smaller. Eyes often larger. The characters in which the male is the most like the infant are two, viz., the narrow hips and short hair. Those in which the female is most embryonic are five, viz., the shorter legs, smaller muscles, absence of beard, low superciliary ridges, and frequently larger eyes. To these may be added two others not mentioned in the above lists ; these are (1) the high-pitched voice, which never falls an octave as does that of the male ; and (2) the structure of the generative organs, which in all Mammalia more nearly resem- ble the embryo and the lower Vertebrata, in the female than in the male. Nevertheless, as Bischoff has pointed out, one of the most important distinctions between man and the apes is to be found in the external reproductive organs of the female. From the preceding summary sketch the reader will be able to explain the meaning of most of the peculiarities of face and form HUMAIT PHYSIOGNOMY. 291 which he will meet with. Many persons possess at least one quad- rumanous or embryonic character. The strongly convex upper lip frequently seen among the lower classes of the Irish is a modified quadrumanous character. Many people, especially those of the Sclavic races, have more or less embryonic noses. A retreating chin is a marked monkey character. Shortness of stature is mostly Fig. 59, — Australian native (from Brough Smyth), showing small development oi muscles of legs, and prognathism. due to shortness of the femur, or thigh ; the inequalities of people sitting are much less than those of people standing. A short femur is embryonic ; so is a very large head. The faces of some people are partially embryonic, in having a short face and light lower jaw. Such faces are still more embryonic when the forehead and eyes are protuberant. Retardation of this kind is most frequently PLATE XIL The Venus of the Capitol (Rome). The form and face present the characteristic paculiarities of the female of the Indo-European race. HUMAN PHYSIOGNOMY. 293 seen in children, and more frequently in women than in men. The length of the arms would appear to have grown less in compar- atively recent times. Thus the humerus in most of the Greek statues, including the Apollo Belvidere, is longer than those of modern Europeans, according to a writer in the '^Bulletin de la Societe d' Anthropologic " of Paris, and resembles more nearly that of the modern Nubians than any other people. This is a quad- rumanous approximation. The miserably developed calves of many of the savages of Australia, Africa, and America, are well known. The fine swelling gastrocnemius and soleus muscles char- acterize the highest races, and are most remote from the slender shanks of the monkeys. The gluteus muscles developed in the lower races as well as in the higher, distinguish them well from the monkeys with their flat posterior outline. It must be borne in mind that the quadrumanous indications are found in the lower classes of the most developed races. The status of a race or family is determined by the percentage of its individuals who do and do not present the features in question. Some embryonic characters may also appear in individuals of any race, as a consequence of special circumstances. Such are, how- ever, as important to the physiognomist as the more normal vari- ations. Some of these features have a purely physical significance, but the majority of them are, as already remarked, intimately con- nected with the development of the mind, as an effect or necessary coincidence. I will examine these relations in a future article. X. THE EVIDENCE FOR EVOLUTION IN THE HIS- TORY OF THE EXTINCT MAMMALIA.* The subject to which I wish to call your attention this morn- ing requires neither preface nor apology, as it is one with the dis- cussion of which you are perfectly familiar. I bring it before the general session of the Association in view of the fact that you are all familiar with it in a general way, and that it probably in- terests the members of sections who do not pursue the sjoecial branch to which it refers, as well as those who do : also, since it has been brought before us in various public addresses for many years, during the meetings of this Association, I thought it might be well to introduce it at this meeting, in order that we might not omit to have all the sides of it presented. The interests which are involved in it are large : they are chiefly, however, of a mental and metaphysical character ; they do not refer so much to industrial and practical interests, nor do they inyolve questions of applied science. They involve, however, questions of opinion, questions of belief, questions which affect human happiness, I venture to say, even more than questions of applied science ; certainly, which affect the happiness of the higher grades of men and women more than food or clothing, be- cause they relate to the states of our mind, explaining as they do the reasons of our relations to our fellow beings, and to all other things by which we are surrounded, and the general system of the forces by which we are controlled. So it has always appeared to me : hence I have selected the department of biology for study, and have taken a great interest in this aspect of it. The doctrine of evolution, as taught by the biologists of to- day, has several stages or parts of its presentation. First, the foundation principle is this : that the species of animals and of * An address delivered before the American Association for the Advancement of Science, 1883. THE EXTINCT MAMMALIA. 295 plants, the species of organic beings, as well as the yarious natu- ral divisions into which these organic beings fall, have not always been as we see them to-day, but they have been produced by a process of change which has progressed from age to age through the influence of natural laws ; that, therefore, the species which now exist are the descendants of other species which have existed heretofore, by the ordinary processes of reproduction ; and that all the various structures of organic beings, which make them what they are, and which compel them to act as they now act, are the result of gradual or sudden modifications and changes during the periods of geologic time. That is the first phase or aspect which meets the naturalist or biologist. Another phase of the question relates to the origin of that life itself which is supposed to inhabit or possess organic beings. There is an hypothesis of evolution which derives this life from no-life, which derives vitality from non-vitality. This is another branch of the subject, to which I can not devote much attention to-day. There is still another department of the subject, which relates to the origin of mind, and which derives the mental organization of the higher animals, especially of man, from pre-existent types of mental organization. This gives us a genealogy of mind, a his- tory of the production or creation of mind, as it is now j^resented in its more complex aspects as a function of the human brain. This aspect of the subject is, of course, interesting ; and upon it I can touch with more confidence than upon the question of the origin of life. Coming now to the question of the origin of structures, we have by this time accumulated a vast number of facts which have been collated by laborious and faithful workers, in many countries and during many years ; so that we can speak with a good deal of confidence on this subject also. As to the phenomena which meet the student of zoology and botany at every turn, I would merely repeat what every one knows — and I beg pardon of my bio- logical friends for telling them a few well-known truths, for there may be those present who are not in the biological section — the phenomena which meet the student of biology come under two leading classes. The first is the remarkable fidelity of species in reproducing their like. *^ Like produces like," is the old theo- rem, and is true in a greiat many cases ; just as coins are struck from the die, just as castings are turned out from a common 296 THE STRUCTURAL EVIDEXCK OF EYOLUTIOi^. mold. It is one of the most wonderful phenomena of nature, that such complex organisms, consisting of so many parts, should be repeated from age to age, and from generation to generation, with such surprising fidelity and precision. This fact is the first that strikes the student of these sciences. The first impression of the ordinary person would be, that these things must continue unchanged. When I began to study zoology and botany, I was surprised to find there was a science of which I had no concep- tion, and that was this remarkable reproduction of types one after another in continued succession. After a man has had this idea thoroughly assimilated by his honest and conscien- tious studies, he will be again struck with another class of facts. He will find, not unfrequently, that this doctrine does not apply. He will find a series of facts which show that many individuals fail to coincide with their fellows precisely, the most remarkable variations and the most remarkable half-way atti- tudes and double-sided aspects occurring ; and he will come to the conclusion, sooner or later, that like does not produce like in some animals with the same precision and fidelity with which it is accomplished in other animals. So that we have these two classes of facts — the one relating to, and expressing, the law of heredity ; the other which expresses the law of variation. I should not like to say which class of facts is the most numerously presented to the student. In the present fauna we find many groups of species and varieties ; but exactly how many species we have, how many genera and families we have, we can not defi- nitely state. The more precise and exact a person is in his defini- tion and in his analysis, the more definite his science becomes, and the more precise and scientific his work. Biology is a science of analvsis of forms. What the scales are to the chemist and the physicist, the rule and measure are to the biologist. It is a ques- tion of dimension, a question of length and breath and thickness, a question of curves, a question of crooked shapes or simple shapes — rarely simple shapes, mostly crooked, generally bilateral. It requires that one should have a mechanical eye, and should have also something of an artistic eye, to appreciate these forms, to measure them, and to be able to compare and weigh them. Now, when we come to arrange our shapes and our measure- ments, we find, as I said before, a certain number of identities, and a certain number of variations. This question of variation is so common and so remarkable, that it becomes perfectly evi- THE EXTINCT MAMMALIA. 297 dent to the specialist in each department, that like does not at all times produce like. It is perfectly clear, and I will venture the assertion that nearly all the biologists in this room will bear me witness, that variability is practically unlimited in its range, and multiplied in the number of its examples. That is to say : species vary by adding or by failing to retain certain characteris- tics ; and generic and other characters are found to appear or disappear in accordance with some law to be discussed farther on. I believe that this is the simplest mode of stating and explain- ing the law of variation : that some forms acquire something which their parents did not possess ; and that those which ac- quire something additional have to pass through more numerous stages than their ancestors ; and those which lose something pass through fewer stages than their ancestors ; and these processes are expressed by the terms *' acceleration " and *^ retardation." Of course we are met with the opposite side of the case — the law of heredity. We are told that the facts there are not ac- counted for by any law of evolution ; that we can not pass from one class of facts to the other class of facts ; that the law of the one class is not that of the other. Here is a question of rational processes, of ordinary reason. If the rules of chemistry are true in America, I imagine they are true in Australia and Africa, al- though I have not been there to see. If the law of gravitation is effective here, I do not need to go to Australia or New Zealand to ascertain whether it be true there. So, if we find in a group of animals a law sufficient to account for their creation, it is not necessary to know that others of their relatives have gone through a similar process. I am willing to allow the ordinary practical law of induction, the practical law of inference, to carry me over these gaps, over these interruptions. And I state the case in this way, because it is Just here that some people differ from me, and it is Just here that I say the simple question of rationality comes in. I can not believe that Nature's laws are so dissimilar, so irregular, so inexact, that those which we can see and understand in one place are not true in another ; I also believe that the ques- tion of geological likelihood is similar to the question of geo- graphical likelihood. If a given process be true in one of the geological periods, it is true in another ; if it be true in one part of the world, it is true in another ; because I find interruptions in the series here, it does not follow that there need be interrup- tions clear through from age to age. The assumption is on the 298 THE STRUCTUPwAL EVIDENCE OF EVOLUTION. side of tlie man who asserts that transitions have not taken place between forms which are now distinct. We are told that we find no sort of evidence of that transition in past geological periods ; we are assured that such changes have not taken place ; we are even assured that no such sign of such transition from one species to another has ever been observed — a most astonishing assertion to make to a biologist, or hy a biolo- gist ; and such persons have even the temerity to cite such a special case as that between the wolf and the dog. Many of our domestic dogs are nothing but wolves, which have been modified by the hand of man to a very slight extent indeed. Many dogs, in fact nearly all dogs, are descendants of wild species of various countries, and are variously modified. To take the question of the definition of species. Supposing we have several species well defined, say four or five. In the process of investigation we obtain a larger number of individuals, many of which betray characters which invalidate the definitions. It becomes necessary to unite the four or five species into one. And so, then, because our system requires that we shall have ac- curate definitions (the whole basis of the system is definitions ; you know the very comprehension of the subject requires defini- tions), we throw them all together, because we can not define all the various special forms as we did before, until we have but one species. And the critic of the view of evolution tells us, ^^I told you so ! There is but one species, after all. There is no such thing as a connection between species : you never will find it." Now, how many discoveries of this kind will be necessary to con- vince the world that there are connections between species ? How long are we to go on finding connecting links, and putting them together, as we have to do for the sake of the definition, and then be told that we have, nevertheless, no intermediate forms between species ? The matter is too plain for further comment. We throw them together, simply because our definitions require it. If we knew all the known individuals which have lived, we should have no species, we should have no genera. That is all there is of it. It is simply a question of a universal accretion of material, and the collection of information. I do not believe that the well- defined groups will be found to run together, as we call it, in any one geological period, certainly in no one recent period. We recognize, however, in looking backward, tliat they converge to a wonderful extent : one group has diverged at one period, and THE EXTINCT MAMMALIA. 299 another one has become diversified in a different period ; and so each one has its history, some beginning farther back than others, some reaching far back beyond the very beginning of the time when fossils could be preserved. I call attention to this view be- cause it is a very easy matter for us to use words for the purpose of confusing the mind ; for, next to the power of language to ex- press clear ideas, is its power of expressing no ideas at all. As we all know, we can say many things which we can not tliink. It is a very easy thing to say twice two are equal to six, but it is im- possible to think it. I would cite what I mean by variations of species in one of its phases : I mention a genus of snakes, Ophibolus, which is found in the United States. If we take the species of this snake-genus as found in the Northern States, we have a good many species well defined. If we go to the Gulf States, and examine our material, we see we have certain other species well defined, and they are very nicely distinguished. If, now, we go to the Pacific coast, to Arizona and New Mexico, we shall find another set of species well defined indeed. If we take all these different types of our specimens of different localities together, our species, as the Ger- mans say, all tumble together : definitions disappear, and we have to recognize, out of the preliminary list of thirteen or fourteen, only four or five. That is simply a case of the kind of fact with which every biologist is perfectly familiar. When we come to the history of the extinct forms of life, it is perfectly true that we can not observe the process of descent in actual operation, because, forsooth, fossils are necessarily dead. We can not perceive any activities, because fossils have ceased to act. But, if this doctrine be true, we should get the series, if there be such a thing ; and we do, as a matter of fact, find longer or shorter series of structures, series of organisms proceeding from one form into another form, which are exactly as they ought to be if this process of development by descent had taken place. I am careful to say this ; because it is literally true, as we all must admit, that species must fall into some kind of order or other. You could not collect bottles, you could not collect old shoes, but you could make some kind of a serial order of them. There are, no doubt, characters by which such and such shoes could be distinguished from other shoes, these bottles from other bottles. But if serial order does not prove evolution, as is too often assumed, we have in recent forms of life in zoology and PLATE XIII. THE EXTINCT MAMMALIA. 30I botany, irrefragable proofs of the metamorphoses, and transfor- mations, and changes of the species, in accordance with the doc- trine with which we commenced. We now come to the second chapter of our subject. With the assumption, as I take it already satisfactorily proved, of species having changed into others, in considering this matter of geo- logical succession or biological succession, I bring you face to face with the nature and mode of the change ; and hence we may get a glance perhaps at its laws. I have on the board a sketch or table which represents the changes which took place in certain of the Mammalia. I give you a summary of the kind of thing which we find in one of the branches of paleontology. I have here two figures, one represent- ing a restoration, and the other an actual picture, of two extinct species that belong to the early Eocene periods. One represents the ancestor of the horse line, Hyracotherium, which has four toes on his anterior feet, and three behind ; and the other (Plate XIII) a type of animal, Phenacodus, which is antecedent to all the horse series, the elephant series, the hog, the rhinoceros, and all the other series of hoofed animals. It has five toes on all the feet. Each presents us with the primitive position in which their series first come to our knowledge in the history of geological time. I have also arranged here a series of some leading forms of the three, principal epochs of the Mesozoic times, and six of the lead- ing ones of the Tertiary time. I have added some dates to show you the time when the faunae which are entombed in those beds were discovered, in the course of our studies ; and you will easily see how unsafe it is to say that any given type of life has never ex- isted, or even to assert that such and such a form is unknown ; and it is still more unsafe, I think, to assert that any given form of life properly defined, or that a specific intermediate form of life, will not be found. I think it is much safer to assert that such and such intermediate forms will be found. I have frequently had the pleasure of realizing anticipations of this kind. I have asserted that certain types would be found, and they have been found. You will see that I attend to the matter of time because there have been a great many things discovered in the last ten or fifteen years in this department. With these forms I give the date of the dis- covery of the fauna in which they are embraced. Here we have the White River fauna discovered in 1856 ; then we skip a considerable period of time, and the next one was in 1869, 302 THE STRUCTURAL EVIDENCE OF EVOLUTION. when the Cretaceous series was found. Six or seven Cretaceous faunae have been discovered. Then we have the Bridger fauna in 1870, the Wasatch fauna in 1874. Next we have, in 1877, the Equus beds and the fauna which they embrace, part of which was also found in 1878. The Permian fauna, which is one of the last, in 1879 ; and the latest, the Puerco, which gives the oldest and ancestral types of the modern forms of Mammalia, was only found in 1881. When I first commenced the study of this subject, about 1860, there were perhaps two hundred and fifty species known. There are now somewhere above 1,000, and we are augmenting them all the time. I have found many myself : if they were dis- tributed through the days of the year, I think in some months I should have had several every day. You see then that the acces- sions to knowledge which are constantly being made make it un- safe to indulge in any prophecies ; as, for instance, that, because such and such things have not been found, therefore they can not be ; for we find such and such things really have been and really are discovered. The successive changes that we have in the Mammalia have taken place in the limbs, feet, teeth, and brain, and the vertebral column. The parts which present us with the greatest numbers of variations are those in which many parts are concerned, as in the limbs and feet. In the Lower Eocene (Puerco), the toes were 5-5. In the Loup Fork fauna, some possess toes but 1-1. Prior to this period no such reduction was known, although in the Loup Fork fauna a very few species remained 5-5. Through this en- tire series we have transitions steady and constant, from 5-5, to 4- 5, to 4-4, to 4-3, to 3-3, to 2-2, to 1-1. In the Puerco period there was not a single mammal of any kind which had a good ankle-joint ; which had an ankle-joint constructed as ankle-joints ought to be, with tongue and groove. The model ankle-joint is a tongue-and- groove arrangement. In this period they were nearly all perfectly flat. As time passes on we get them more and more grooved, un- til in the Loup Fork fauna and the White Eiver fauna they are near- ly all grooved. The soles of the feet, in the Puerco fauna, are all flat ; but in the Loup Fork fauna the soles of the feet are in the air, and the toes only are applied to the ground, with the excep- tion of the line of monkeys, in which the feet have not become erect on the toes, and the elephant, in which the feet are nearly flat also, and the line of bears, where they are also flat. As regards the angulation between the small bones of the palm and of the sole, THE EXTINCT MAMMALIA. 303 1 o o 1 DO aj a .a -u O fcT 0) J* • ::a £f £f i "5 ^a ^ ,5 03 QQ Q a to •^ OQ 00 C S3 to 5 DO ID OD a -H pq to £ ^ QJr^ s 4) OJ 0) Oi J3 OB a m W w K ^ 00 o . . lU 00 -s^ s i 0) G, O a 13 '^3 o a > ^ "o > .a 6>? 0^' t>> P W) Ua t*a p to ^ N o 3 C O S .S-3 ci s a fi'ai SP c»-. !»S KoQ S -^ 1 -4J -^I. -4-3 •s u v QQ OQ 00 a; 4-1 c "o a 2 2 01 o "^ -d 'd 'd o3 1 1 2.1 '3 v.-^ -^v. .a ^* .d 0) a> -1-3 +j ^ o -S S^ o o »^ •SO 'oo c3 la 52 I- 1— 1 C ;- o « o5 o P< c O ^ 1 • -^3 • 'd '6 13 cs m 4) (U 0) a> . o s- :j >o > > >0 1"^ §3 g 1 §3 -4^ o3 5 ^ ^ /— s • a; -d .1 -1^ +3 'Sd^ M i.£f se^ 5 oS es ES S II 1 1 Y III cc«^ 1 1 1 1 III 1 T-i'Tt eO-^j^ ©JC<3' dj ■* ji . ^-N O ) =3 P^ ^ t. 3 iJ^ b'M O t.-a t- t> &4 ai'ts. All animals are degenerate in some respect or another, as, for instance, the Mam- malia in the small size of the pineal gland and of the coracoid bone ; so that degeneracy, as a whole, can only be affirmed where the sum of the subtractions is greater than the sum of the addi- tions. Function of the parts must, however, be consulted in this matter. We naturally regard sensibility as the highest of animal functions, and mind as the highest form of sensibility. There- fore development of organs of sensibility and sense and mind, con- stitutes a better claim of progress than development of stomach or of skin. Since motion is under the direction of sensibility, EVOLrXION OF THE VERTEBRATA. 315 organs of movement have much to do with the question. When perfection in this respect conflicts with perfection of brain, in evidence of position, we naturally give the preference to the latter in deciding. Thus the ruminating mammals are much superior to man in the structure of their feet, teeth, and stomach, yet we properly assign the higher position to the Quadrumana and to man, on account of the superior complication of their brain- structure. Paleontology has proved,* what had been already surmised, that the development of animal organisms has been on lines of increasing specialization of parts. That is, in lines of increas- ingly perfect adaptations of structures to ends, or functions. In certain series of animals we witness steadily increasing perfection of mechanisms of the limbs for running ; in others for digging ; in others for flying. In the teeth we find increasing perfection of machines for grinding, for cutting, or for seizing. In the brain the specialization has evidently been toward increased acuteness of perception, increased energy of action, and increased intelli- gence. Specialization does not, however, necessarily imply pro- gressive development. Adaptation may be to a parasitic or a ses- sile mode of life. Such adaptation is often displayed in a very special modification of parts, as in the anterior limbs of some of the parasitic Crustacea ; in the mouth parts of some Arachnida ; in the feet of the sloth, and in the jaws of the ant-eaters. Embryology has furnished, and will furnish, many important hints and demonstrations as to the true meaning of the rudiment- ary condition or absence of parts, and thus indicate the phylo- genetic connections of animals. Thus the origin of the Tunicata from primitive vertebrate-like forms would probably never have been suspected but for embryological studies ; and the origin of the very peculiar order of Eotifera has been explained in like manner. But embryology has its limitations, for the transitional characters presented by embryos are only partially of the nature of a record of the structures which belonged to their ancestors in successive geological ages, and are frequently special adaptations to the necessities of their embryonic life. Such are the stato- blasts which are present in fresh-water sponges and Polyzoa, and wanting in the marine forms ; and the allantois and placenta of * Cfr. " On the Evidence for Evolution in the History of the Extinct Mam- malia," "Proc. Amer. Assoc. Adv. Sciences" for 1883. 316 THE STRUCTURAL EVIDENCE OF EVOLUTION. Vertebrata. In a number of groups the embrj^o seems to have been more susceptible to the influence of the environment than the adults.* It results that in many cases the phylogeny can only be determined by the discovery and investigation of the ancestors themselves, as they are preserved in the crust of the earth. In all cases this discovery confirms and establishes such definite conclusions as may be derived from embryology. It is also clear that on the discovery of phylogenetic series it becomes at once possible to determine the nature of defective types. It becomes possible to ascertain whether their rudimental parts represent the beginnings of organs, or whether they are the .result of a process of degeneration of organs once well develoj^ed. A great deal of light has been happily thrown on this question, as regards the Vertebrata, by the recent work done in North American paleontology. The lines of descent of many of the minor groups have been positively determined, and the phyloge- netic connections of most of the primary divisions or classes have been made out. The result of these investigations has been to * A remarkable instance of this state of things appears in the history of the evolution of the insects. It is quite impossible to understand this history without believing that the larval and pupal states of the highest insects are the results of a process of degeneracy which has affected the middle periods of growth but not the mature results. The earliest insects are the Orthoptera, which have active aggres- sive larvae and pupae, undergoing the least changes in their metamorphosis (Ameta- bola), and never getting beyond the primitive mandibulate condition at the end. The metamorphosis of the jawed Neuroptera is little more marked, and they are one of the oldest orders. The highest orders with jaws undergo a marked metamorphosis (Coleoptera, Hymenoptera), the Hymenoptera even requiring artificial intervention in some in- stances to make it successful. Finally, the most specialized orders, the suctorial Diptera and Lepidoptera, especially the latter, present us with very unprotected more or less parasitic stages, both active and inactive. These animals have evidently degenerated, but not so as to prevent their completing a metamorphosis necessary for purposes of reproduction. As is well known, many imagines (Satur- niidae, (Estridae) can perform no other function, and soon die, while in some Diptera the incomplete larvae themselves reproduce, so that the metamorphosis is never completed. This history is parallel to that proposed by Dohrn to account for the origin of the Amraocoetes larval stage of the Marsipobranchii. He supposes this form to be more degenerate than its probable ancestral type in the ancestral line of the Verte- brata, as it is inferior to its own adult. An inactive life in mud is supposed by Dohrn to have been the effective cause. An inactive life on the leaves of plants, or in dead carcases, has probably been the cause of the same phenomenon in the Lepidoptera and Diptera. EVOLUTION OF THE VERTEBRATA. 317 prove that the evolution of the Vertebrata has proceeded not only on lines of acceleration, but, to a much greater extent than has been heretofore suspected, on lines of retardation.* That is, that evolution has been not only progressive, but at times retrogressive. This is entirely in accord with the views derived by Dohrn from embryology,! who, however, wrote only of the origin of the Vertebrata as a whole and not of its divisions, excepting only the Leptocardii and Marsipobranchii, that is, of the sand-lance and the lampreys and hags. The demonstration of such relations for the higher Vertebrata is now done nearly for the first time. J Omitting from consideration the two classes above mentioned, whose remains have not yet been certainly found in a fossil state, there remain the following : the Pisces, Batrachia, Eeptilia, Aves, and Mammalia. The Mammalia have been traced to the theromorphous reptiles through the Monotremata. The birds, some of them at least, ap- pear to have been derived from the Dinosaurian reptiles. The rep- tiles, in their primary representative order, the Theromorpha, have been probably derived from the rhachitomous Batrachia.* The Batrachia have originated from the subclass of fishes, the Dipnoi, though not from any known form. I have shown that the true fishes or Teleostomi have descended from an order of sharks, || the Ichthyotomi, which possess characters of the Dipnoi also. The origin of the sharks remains entirely obscure, as does also that of the Pisces as a whole. Dohrn believes the Marsii^o- * See "Origin of Genera," E. D. Cope, Philadelphia, 1868, where these terms are introduced. f See "Der Ursprung der Wirbelthiere u. d. Princip des Functionwechsels," Leipsic, 18'75. ^ "On the Phylogeny of the Vertebrata," Cope, " Amer. Naturalist," Dec., 1884. I here remark that my researches have now, as I believe, disclosed the ancestry of the mammals, the birds, the reptiles, and the true fishes, or Teleostomi, including the special phylogenies of the Batrachia and Reptilia, and some of the Mammalia. See the following references: "American Naturalist," 1884, p. 1136 ; "Proceedings Academy Philadelphia," 186Y, p. 234; "Proceedings American Philosoph. Society," 1884, p. 585; "American Naturalist," 1884, p. 27; "Proceedings American Asso- ciation for the Advancement of Science," xix, ISTl, p. 233; "Proceedings Amer- ican Philosophical Society," 1882, p. 447; "American Naturalist," 1884, pp. 261 and 1121 ; "Report U. S. Geol. Survey W. of lOOth Mer.," G. M. Wheeler, 1877, iv, ii, p. 282. * Through the batrachian order Embolomeri. (Ed. 1886.) I "Proceedings Am. Phil. Soc," 1884, p. 585. 318 THE STRUCTURAL EVIDENCE OF EVOLUTIOi^. branchii to have acquired its present characters by a process of degeneration. The origin of the Vertebrata is as yet entirely un- known, Kowalevsky deriving them from the Ascidians, and Semper from the Annelida. The above results I have embodied in the following phylogenetic diagram : Aves Mammalia \ / \ / Reptilia / / [ Teleostomi* Batrachia I I ^ ■ Pisces \ Selachii Ichthjotorai Dipnoi Holocephali Leptocardii Marsipobranchi Accepting this phylogeny, it becomes possible to determine the course of development, first, of the whole series ; and, secondly, of the contents of each class taken by itself. I will first consider the direction of the evolution of the Vertebrata as a whole. IT. THE VERTEBRATE LINE. The Vertebrata exhibit the most unmistakable gradation in the characters of the circulatory system, f It has long been the custom to define the classes by means of these characters, taken in connection with those of the skeleton. Commencing in the Leptocardii with the simple tube, we have two chambers in the Marsipobranchii and fishes ; three in the Batrachia and Reptilia ; and four in the Aves and Mammalia. The aorta-roots commence as numerous pairs of branchial arteries in the Leptocardii ; we see seven in the Marsipobranchi, five in the fishes (with number reduced in some) ; four and three in Batrachia, where they gener- ally cease to perform branchial functions ; two and one on each side in Reptilia ; the right-hand one in birds, and the left-hand one in Mammalia. This order is clearly an ascending one through- out. It consists of, first, a transition from adaptation to an aquatic, to an aerial respiration ; and, second, an increase in the power to aerate and distribute a circulating fluid of increased quantity, * In the original I used the name Hyopomata for this division, but Owen's name Teleostomi is prior. (Ed. 1886.) + See *' Origin of Genera/' 1868, p. 20, for a table of the characters of the circu- latory system. EVOLUTION OF THE YERTEBRATA. 319 and of increased calorific capacity. In other words, the circula- tion passes from the cold to the hot blooded type coincidentally with the changes of structure above enumerated. The accession of a capacity to maintain a fixed temperature while that of the surrounding medium changes, is an important advance in animal economy. The brain and nervous system also display a general progress- ive ascent. Leaving the brainless Leptocardii, the Marsipo- branchs and fishes present us with small hemispheres, larger optic lobes, and well-developed cerebellum. The hemispheres are really larger than they appear to be, as Rabl Riickard has shown * that the supposed hemispheres are only corpora striata. But the superior walls are membranous, and sujoport on their in- ternal side only a layer of epithelial cells, as in the embryos of other Vertebrata, instead of the gray substance. So that, al- though we find that the cerebellum is really smaller in the Batrachia and most Eeptilia than in the fishes, the better de- velopment of the hemispheres in the former gives them the pre- eminence. The Elasmobranchii show themselves superior to many of the fishes in the large size of their corpora restiformia and cerebellum. The Eeptilia constitute an advance on the Ba- trachia. In the latter the optic thalami are, with some excep- tions, of greater diameter than the hemispheres, while the reverse is generally true of the reptiles. The crocodiles display much superiority over the other reptiles in the larger cerebellum, with rudimental lateral lobes. The great development of the hemi- spheres in birds is well known, while the general superiority of the brain of the living Mammalia over all other vertebrates is admitted. The consideration of the successive relations of the skeleton in the classes of vertebrates embraces, of course, only the characters which distinguish those classes. These are not numerous. They embrace the structure of the axis of the skull ; of the ear-bones ; of the suspensors of the lower jaw ; of the scapular arch and anterior limb, and of the pelvic arch and posterior limb. Other characters are numerous, but do not enter into consideration at this time. The persistence of the primitive cartilage in any part of the skeleton is, embryologically speaking, a mark of inferiority. * n Biologisches Centralblatt," 1884, p. 449. 320 THE STRUCTURAL EVIDENCE OF EVOLUTION. From a physiological or functional standpoint it has the same significance, since it is far less effective both for support and for movement than is the segmented osseous skeleton. That this is a prevalent condition of the lower Vertebrata is well known. The bony fishes and Batrachia have but little of the primitive cartilage remaining, and the quantity is still more reduced in the higher classes. Systematically, then, the vertebrate series is in this respect an ascending one. The Leptocardii are membra- nous ; the Marsipobranchii and most of the Elasmobranchii cartihiginous ; the other Pisces and the Batrachia have tlie basicranial axis cartilaginous, so that it is not until the Eeptilia are reached that we have osseous sphenoid and presphenoid bones, such as characterize the birds and mammals. The vertebral column follows more or less inexactly the history of the base of the skull, but its characters do not define the classes. As regards the suspensor of the lower jaw, the scale is in the main ascending. We witness a gradual change in the segmenta- tion of the mandibular visceral arch of the skull, which clearly has for its object such a concentration of the parts as will produce the greatest effectiveness of the biting function. This is accom- plished by reducing the number of the segments, so as to bring the resistance of the teeth nearer and nearer to the power, that is, the masse ter and related muscles, and their base of attachment, the brain-case. This is seen in bony Vertebrates in the reduction of the segments between the lower jaw proper and the skull, from four to none. In the fishes we have the hyomandibular, the sym- plectic, the inferior quadrate, and the articular. In the Ba- trachia, reptiles and birds, we have the quadrate and articular only, while in the Mammalia these elements also are wanting. The examination of the pectoral and pelvic arches reveals a successive modification of the adaptation of the parts to the me- chanical needs of the limbs. In this regard the air-breathing types display wide diversity from the gill-bearing types or fishes. In the latter, the lateral elements unite below without the inter- vention of a median element or sternum, while in the former the sternum, or parts of it, is generally present. Either arrange- ment is susceptible of much mechanical strength, as witness the Siluroid fishes on the one hand, and the mole on the other. The numerous segments of the fishes' pectoral arch must, however, be an element of weakness, so that from a mechanical standpoint it must take the lowest place. The presence of sternal elements, EVOLUTION OF THE VERTEBRATA. 321 with both clavicle, procoracoid, and coracoid bones on each side, gives the Reptilia the highest place for mechanical strength. The loss of the coracoid seen in the tailed Batrachia, and loss of cora- coid and procoracoid in the Mammalia, constitute an element of weakness. The line is not then one of uniform ascent in this re- spect. The absence of pelvis, or its extremely rudimental condition in fishes, places them at the foot of the line in this respect. The forward extension of the ilium in some Batrachia and in the Mam- malia, is to be compared with its backward direction in Reptilia, and its extension both ways in the birds. These conditions are all derived by descent from a strictly intermediate position in the Batrachia and Reptilia of the Permian epoch. The anterior di- rection must be regarded as having the mechanical advantage over the posterior direction, since it shortens the vertebral column and brings the posterior nearer to the anterior feet. The prev- alence of the latter condition in the Mammalia enables them to stand clear of the ground, while the Reptilia move with the abdo- men resting upon it. As regards the inferior arches of the pelvis, the Mammalia have the advantage again, in the strong bony me- dian symphysis connecting the ischium and pubis.* This char- acter, universal among the land Vertebrata of the Permian epoch, has been lost by the modern Reptilia, and birds, and is retained only by the Mammalia. So the lines, excepting the mammalian, have degenerated in every direction in the characters of the pelvis. The limbs of the Pisces are as well adapted to their environ- ment as are those of the land Vertebrata ; but, from an embryolog- ical standpoint, their structure is inferior. The primitive raj^s are less modified in the fin than in the limb ; and limbs them- selves display a constantly increasing differentiation of parts, com- mencing with the Batrachia and ending with the Mammalia. The details of these modifications belong to the history of the contents of the classes, however, rather than to the succession of the Vertebrata as a whole. In review, it may be said that a comparison of the characters which define the classes of the Vertebrates shows that this branch of the animal kingdom has made with the ages successive steps of progress from lower to higher conditions. This progress has not been without exception, since, as regards the construction of * This is an advantage as a protection during gestation. 21 322 THE STRUCTURAL EVIDENCE OF EVOLUTIOK the scapular arch, the Mammalia have retrograded from the rep- tilian standard as a Avhole. In subsequent pages I shall take up the lines of the classes separately. III. THE LliTE OF THE UKOCHOKDA. Embryological evidence leads us to anticipate that the primi- tive Vertebrata possessed nothing representative of the vertebrate skeleton beyond a chorda dorsalis. Above this axis should lie the nervous chord, and below it the nutritive and reproductive sys- tems and their appendages. Such a type we have in its simplest form in the Branchiostoma, the representative of the division of the Acrania. In the animals of this division the mouth and anus have the usual vertebrate jDosition, at opposite ends of the body- cavity. The Tunicata (formerly referred to the Mollusca) are now known to present a still more primitive type of Vertebrata, to which the name of Urochorda has been given. These curious, frequently sessile creatures, have a vertebrate structure during the larval stage, which they ultimately lose. They have the necessary chorda, and nervous axis with a brain, and a cerebral eye. They have at this time a tail> and are free-swimming ; a peculiarity which a few of them retain throughout life (Appendicularia).* They differ from the Acrania in the positions of the extremities of the alimentary canal. The mouth is on the top of the anterior end of the animal, and is supposed by some anatomists to repre- sent an open extremity of the pineal gland of other Vertebrata ; while the tract represented by this body, the third ventricle of the brain, and the pituitary body of the Craniata, are the remains of the primitive oesophagus of the Urochorda. The anus in the adult tunicates is either dorsal, or it opens into the body-cavity, as in the young larvas. In Appendicularia it is ventral (Gegenbaur). The history of the Tunicata can not be traced by paleontolo- gists as yet, owing to the absence of hard parts in their structure. The evidence of embryology has, however, convinced phylogenists that the ancestors of this class resembled their larvae, and that they have as a whole undergone a remarkable degeneracy. They have passed from an active, free life to a sessile one, and have lost the characters which pertain to the life of vertebrates generally. It was to have been anticipated, however, that all of these an- * See Lankester on "Degeneration," " Nature Series," 1880. EVOLUTION OF THE VERTEBRATA. 323 cestral Tunicata did not undergo this degenerative metamorphosis for it is to such types that we must look for the ancestors of the other Vertebrata, the Acrania and the Craniata. And here pale- ontology steps in and throws new light on the question. I have pointed out briefly, in the " American Naturalist/' * that a second order must be added to the Urochorda, viz., the Antiarcha, in which the anus presents the same position as in the Acrania, at the posterior end of the body, while an orifice of the upper surface represents the mouth of the Tunicata. To this order is to be re- ferred the family of the Pterichthyidag, of which the typical genus, Fig. 63. Fig. 62. Fig. 62. Bothriolepis canadensis Whiteaves, from above, half size of a small speci- men. The valve of the dorsal mouth, or notostome, is broken. Fig. 63. Chelyosoma maclomanum Brod. & Sow., Y3 natural size, from Point Barrow, Alaska. Pterichthys, is a well-known form of the Devonian period. This genus retained its tail, which was the cause, in connection with the i^resence of lateral fin-like appendages, of its having been sup- posed to be a fish, by Agassiz, Hugh Miller, and others. It is pos- sible that the American Bothriolepis canadensis lost its tail, as in the majority of Urochorda. The tunicate which approaches near- est to the Antiarcha is the Arctic Chelyosoma. From the Antiarcha to the Acrania and Craniata, then, the line is an ascending one. * March, 1885, p. 289. 324: THE STRUCTURAL EVIDENCE OF EVOLUTION. lY. THE LIl^E OF THE PISCES. The fishes form various series and subseries, and the tracing of all of them is not yet practicable, owing to the deficiency in our knowledge of the earliest or ancestral forms. Thus the ori- gins of the four subclasses, Holocephali, Dipnoi, Elasmobranchii, and Teleostomi, are lost in the obscurity of the early Palaeozoic ages. A comparison of the four subclasses just named shows that they are related in pairs. The Holocephali and Dipnoi haye no distinct suspensory segment for the lower jaw, while the Elasmo- branchii and Hyopomata have such a separate element. The lat- ter, therefore, present one step in the direction of complication be- yond the former ; but whether the one type is descended from the other, or whether both came from a common ancestor or not, is unknown. If one type be derived from the other, it is not certain which is ancestor, and whether the process has been one of advance or retrogression. The fauna of the Permian epoch throws some light on the relations of these subclasses in other respects. The order of the Ichthyotomi,* while belonging technically to the Elasmobranchi, presents characters of both the Dipnoi and the Teleostomi. It is so near to the Dipnoi in the characters of the skull that nothing save the presence of a free suspensor of the lower jaw prevents its entering that subclass. It indicates that the one of these divisions is descended from the other, or both from a common division which may well be the group Ichthyotomi itself. In case the Elasmobranchi have descended from the Ich- thyotomi, they have undergone degeneracy, as the Ichthyotomi have a higher degree of ossification and differentiation of the bones of the skull. If they descended from a purely cartilaginous type of Dipnoi, they have advanced, in the addition of the free hyo- mandibular. If the Dipnoi have descended from either division, they have retrograded, in the loss of the free hyomandibular. As regards the Teleostomi, we have a clear advance over the other subclasses in the presence of the maxillary arch and the opercular apparatus. Too little is known of the history of the subclasses, excepting the Teleostomi, for us to be able to say much of the direction of * See " Palseontological Bulletin," No. 38, E. D. Cope, 18S4, p. 512, on the genus Didvmodus. EVOLUTION OF THE VERTEBRATA. 325 the descent of their contained orders. On the sharks some light is shed by the discovery of tlie genus Chlamydoselachus Garman,* which is apparently nearly related to the Cladodonts of the Devo- nian seas. This genus has more numerous branchial slits than all but two of the genera of existing sharks, and it differs from all but these two in having a more perfect articulation between the tooth- bearing bones and the cranium. Of the Teleostomi a much clearer history is accessible. It has three primary divisions or tribes which differ solely in the structure of the supports of the fins. In the first division, the Crossopterygia, the anterior limbs have numerous basilar bones which are supported on a peduncle of axial bones. The posterior limbs are similar. In the second division, or Chron- drostei (the sturgeons, etc. ), the posterior limb remains the same, while the anterior limbs have undergone a great abbreviation in the loss of the axial bones and the reduction of the number and length of the basilar bones. In the third group, or Actinopteri,t both limbs have undergone reduction, the basilar bones in the pos- terior fin being almost all atrophied, while those of the fore limb are much reduced in number. The phylogeny of these tribes is not easy to make out at pres- ent. The descent has been, no doubt, in the order named in time, but the starting-point is yet uncertain. Thus the Chondrostei appear later in time than either of the other tribes, a history which probably only represents our ignorance. The characters of the genus Crossopholis Cope, from the American Eocene, strongly suggest that the existing forms have descended from scaled an- cestors. The Crossopterygian fore limb, with its arm-like axis, tells of the origin of the first limbed vertebrates, the Batrachia, whose skull-structure, however, only permits their derivation from the Dipnoi or Ilolocephali. As the former subclass has the Crossopterygian fin-structure, we can safely regard them as the ancestors of the Batrachia, while the Crossopterygia are a side- line from a similar type, probably the Ichthyotomi, because these have a free suspensor of the lower jaw. But of the structure of the fins of the Ichthyotomi unfortunately we know nothing. If this position be true, then the successive derivation of the Chon- drostei and the Teleostomi in one line is rendered probable. The modification of structure has consisted in the contraction of the * "Proceedings American Assoc. Adv. Sci.," 1884. f Partly agrees with the Teleostei of Miiller, but includes many of his Ganoidea. 326 THE STRUCTUKAL EVIDENCE OF EYOLUTION. supporting elements of the pectoral and ventral fins by the reduc- tion of their numbers and length. According to paleontological history, however, the tribe of Teleostomi with most contracted fins, Actinopteri, appeared in the Coal Measures (Paleoniscidse), or very soon after the Crossopterygia in the Devonian. The descent of the fishes in general has witnessed, then, a contraction of the limbs to a very small compass, and their sub- stitution by a system of accessory radii. This has been an ever- widening divergence from the type of the higher Vertebrata, and from this standpoint, and also a view of the ^Hoss of parts with- out complementary addition of other parts," may be regarded as a process of degradation. Taking up the great division of the Actinopteri, which em- braces most of the species of living fishes, we can trace the direc- tion of descent largely by reference to their systematic relations when we have no fossils to guide us. The three sub tribes adopted by Jordan represent three series of the true fishes which indicate lines of descent. The Holostei include the remainder of the old ganoids after the subtraction of the Crossopterygia and the Chondrostei. They resemble these forms in the muscular bulbus arteriosus of the heart and in the chiasm of the optic nerves. Both of these characters are com- plexities which the two other divisions do not possess, and which, as descendants coming later in time, must be regarded as inferior, and therefore to that extent degenerate. Of these divisions the Physostomi approach nearest the Holostei, and are indeed not distinctly definable without exceptions. The third division, or Physoclysti, shows a marked advance beyond the others in : (1) the obliteration of the primitive trachea, or ductus pneumaticus, which connects the swim-bladder and oesophagus ; (2) the advance of the ventral fins from the abdomen forward to the throat ; (3) the separation of the parietal bones by the supraoccipital ; (4) the presence of numerous spinous rays in the fins ; and (5) the roughening of the edges of the scales, forming the ctenoid type. There are more or less numerous exceptions to all of these char- acters. The changes are all further divergencies from the other vertebrate classes, or away from the general line of ascent of the vertebrate series taken as a whole. The end gained is specializa- tion ; but whether the series can be called either distinctively pro- gressive or retrogressive, is not so clear. The development of osseous spines, rough scales, and other weai)ons of defense, together EVOLUTION" OF THE YERTEBRATA. 327 with the generally superior energy and tone which prevail among the Physoclysti, characterize them as superior to the Physostomi, but their departure from the ascending line of the Vertebrata has another appearance. The descent of the Physoclystous fishes has probably been from Ilolostean ancestors, both with and without the intervention of Physostomous forms. This is indicated by increase in the number of basilar bones in the fins of families which have pec- toral ventral fins, as in the extinct genus Dorypterus.* The Physostomi display three or four distinct lines of descent. The simplest type is represented by the order Isospondyli, and paleontology indicates clearly that this order is also the oldest, as it dates from the Trias at least. In one line the anterior dor- sal vertebrae have become comjolicated, and form an interlocking mass which is intimately connected with the sense of hearing. This series commences with the Characinidae, passes through the Cyprinidae, and ends with the Siluridae. The arrangements for audition constitute a superadded complication, and to these are added in the Siluroids defensive spines and armor. Some of this order, however, are distinctly degenerate, as the soft pur- blind Ageniosus, and the parasitic Stegophilus and Vandellia, which are nearly blind, without weapons, and with greatly re- duced fins. The next line (the Haplomi, pike, etc.) loses the precoracoid arch and has the parietal bones separated, both characters of the Physoclysti. This group was apparently abundant during the Cretaceous period, and it may have given origin to many of the Physoclysti. Another line also loses the precoracoid, but in other respects diverges totally from the Physoclysti and all other Physostomi. This is the line of the eels. They next lose the connection be- tween the scapular arch and the skull, which is followed by the loss of the pectoral fin. The ventral fin disappeared sooner. The palatine bones and teeth disappear, and the suspensor of the lower jaw grows longer and loses its symplectic element. The opercu- lar bones grow smaller, and some of them disappear. The ossi- fication of most of the hyoid elements disappears, and some of their cartilaginous bases even vanish. These forms are the marine eels or Colocephali. The most extraordinary example of speciali- * See " Proceeds. Amer. Assoc. Adv. Science," 1 SVS, p. 297. 328 THE STRUCTURAL EVIDENCE OF EVOLUTION'. zation and degeneracy is seen in the abyssal eels of the family Eurypharyngidge. Here all the degenerate features above men- tioned are present in excess, and others are added, as the loss of ossification of a part of the skull, almost total obliteration of the hyoid and scapular arches, and the semi-Dotochordal condition of the vertebral column, etc. The Physoclysti nearest the Physostomi have abdominal ven- tral fins, and belong to several orders. It is such types as these that may be supposed to have been derived directly from Holos- tean ancestors. They appear in the Cretaceous period (Derceti- dae), along with the types that connect with the Physostomi (Haplomi). Intermediate forms between these and typical Phy- soclysti occur in the Eocene (Trichophanes, Erismatopterus), showing several lines of descent. The Dercetidse belong appar- ently to the order Hemibranchi, while the Eocene genera named belong apparently to the Aphododiridse, the immediate ancestor of the highest Physoclysti, the Percomorphi. The order Hemi- branchi is a series of much interest. Its members lose the mem- brane of their dorsal spinous fin (Gasterosteidse), and then the fin itself (Fistularia, Pegasus). The branchial apparatus has under- gone, as in the eels, successive deossification (by retardation), and this in direct relation to the degree with which the body comes to be protected by bony shields, reaching the greatest defect in the Amphisilidas. One more downward step is seen in the next succeeding order of the Lophobranchii. The branchial hyoid ap23aratus is reduced to a few cartilaginous pieces, and the bran- chial fringes are much reduced in size. In the Hippocampidae the caudal fin disappears and the tail becomes a prehensile organ by the aid of which the species lead a sedentary life. The mouth is much contracted and becomes the anterior orifice of a suctorial tube. This is a second line of unmistakable degeneracy among true fishes. The Physoclysti with pectoral ventral fins present us with per- haps ten important ordinal or subordinal divisions. Until the paleontology of this series is better known, we shall have diffi- culty in constructing phylogenies. Some of the lines may, how- ever, be made out. The accompanying diagram will assist in un- derstanding them. The Anacanthini present a general weakening of the organiza- tion in the less firmness of the osseous tissue and the frequent reduction in the size and character of the fins. The caudal ver- EVOLUTION OF THE VERTEBRATA. 329 tebrae are of the protocercal type. As tliis group does not appear early in geological time, and as it is largely represented now in the abyssal ocean fauna, there is every reason to regard it as a degenerate type.* The scyphobranch line presents a specialization of the su- perior pharyngeal bones, which is continued by the Haplodoci (Batrachid^e). This can not be called a degenerate line, although the fin-ravs are soft. The Heterosomata (flounders) found it convenient to lie on one side, a habit which would appear to result from a want of motive en- ergy. The fins are very inefficient organs of move- ment in them, and they are certainly no rivals for swift-swimming fishes in the struggle for existence, excepting as they conceal themselves. In order to see the better while un- S 'S § \^ 13 "S seen, the inferior eve has -^ S ^ '^ c .2 turned inward, i. e., up- | J ^ A' I 2 ^ ward, and finally has pen- ''^ "~^ etrated to the superior surface, so that both eyes are on one side. This pe- culiarity would be incred- ible if we did not know of its existence, and is an illustration of the extraordinary powers of accommodation pos- * The general characters of the deep-sea fish-fauna are those of degeneracy. (Ed. 1886.) f This order was proposed by Gill for the Eurypharyngidae, and is now added, (Ed. 1886.) 330 THE STRUCTURAL EVIDENCE OF EVOLUTION". sessed by nature. ThQ Heterosomata can only be considered a degenerate group. The double bony floor of the skull of the Distegous percomorph fishes is a complication which places them at the summit of the line of true fishes. At the summit of this division must be placed the Pharyngognathi, which fill an important role in the economy of the tropical seas, and the fresh waters of the Southern hemi- sphere. By means of their powerful grinding pharyngeal appara- tus they can reduce yege table and animal food inaccessible to other fishes. The result is seen in their multifarious species and innu- merable individuals decked in gorgeous colors, and often reaching considerable size. This is the royal order of fishes, and there is no reason why they should not continue to increase in importance in the present fauna. Very different is the line of the Plectognathi. The probable ancestors of this division, the Epilasmia (ChaetodontidaB, etc.), are also abundant in the tropical seas, and are among the most brill- iantly colored of fishes. One of their peculiarities is seen in a shortening of the brain-case and prolongation of the jaws down- ward and forward. The utility of this arrangement is probably to enable them to procure their food from the holes and cavities of the coral reefs among which they dwell. In some of the genera the muzzle has become tubular (Chelmo), and is actually used as a blow-gun by which insects are secured by shooting them with drops of water. This shortening of the basicranial axis has pro- duced a corresponding abbreviation of the hyoid apparatus. The superior piharyngeal bones are so crowded as to have become a series of vertical plates like the leaves of a book. These charac- ters are further developed in the Plectognathi. The brain-case is very small, the face is very elongate, and the mouth is much con- tracted. The bones surrounding it in each jaw are co-ossified. The axial elements (femora) of the posterior fins unite together, become very elongate, and lose the natatory portion. In one group (Orthagoriscidae) the posterior part of the vertebral column is lost and the caudal fin is a nearly useless rudiment. In the Ostracion- tidae (which may have had a different origin, as the pharyngeal bones are not contracted) the natatory powers are much reduced, and the body is inclosed in an osseous carapace so as to be capable of very little movement. The entire order is deficient in osseous tissue, the bones being thin and weak. It is a marked case of degeneracy. EVOLUTION OF THE VERTEBRATA. 331 There are several evident instances of sporadic degeneracy in other orders. One of these is the case of the family of the Icos- teidse, fishes from deep waters off the coast of California. Al- though members of the Percomorphi, the skeleton in the two gen- era Icosteus and Icichthys is unossified, and is perfectly flexible. Approximations to this state of things are seen in the parasitic genus Cyclopterus, and in the ribbon-fishes, Trachypteridee. Thus nearly all the main lines of the Physoclysti are degener- ate ; the exceptions are those that terminate in the Scombridse (mackerel), Serranidae, and Scaridae (Pharyngognathi). Y. THE LIKE OF THE BATRACHIA. We know Batrachia first in the Coal Measures. They reach a great development in the Permian epoch, and are represented by large species in the Triassic period. From that time they dimin- ish in numbers, and at the present day form an insignificant part of the vertebrate fauna of the earth. The history of their suc- cession is told by a table of classification such as I give below : I. Supraoccipital, intercalary and supratemporal bones present. Propodial bones distinct. Vertebral centra, including atlas, segmented, one set of segments together support- ing one arch Rhachitomi. Vertebrae segmented, the superior and inferior segments each complete, forming two centra to each arch EmbolomeH. Vertebral centra, including atlas, not segmented, one to each arch StegoccpJiali. II. Supraoccipital and supratemporal bones wanting. Frontal and propodial bones distinct. a. An OS intercalare, A palatine arch and separate caudal vertebrae Proteida. aa. No OS intercalare. A maxillary arch ; palatine arch imperfect ; nasals, premaxillaries and caudal verte- brae distinct Urodela* No maxillary or palatine arches ; nasals and premaxillary, also caudal vertebrae, dis- tinct Trachystomata, III. Supraoccipital, intercalare and supratemporal bones wanting. Frontals and parietals connate ; propodial bones and caudal vertebrae confluent. Premaxillaries distinct from nasals ; no palatine arch ; astragalus and calcaneum elongate, forming a distinct segment of the limb Anura. The probable phylogeny of these orders as imperfectly indi- cated by paleontology is as follows : * Probably includes the Gymnophiona. 332 THE STRUCTURAL EVIDENCE OF EVOLUTION". Anura Urodela Trachjstomata * I Proteida Stegocephali I. Embolomeri Rhachitomif Ganocephala J An examination of the above tables shows that there has been in the history of the Batrachian class a reduction in the number of the elements composing the skull, both by loss and by fusion with each other. It also shows that the vertebrae have passed from a notochordal state with segmented centra, to biconcave centra, and finally to ball-and-socket centra, with a great reduction of the caudal* series. It is also the fact that the earlier forms (those of the Permian epoch) show the most Mammalian characters of the tarsus and of the pelvis. The latter forms, the salamanders, show a more generalized form of carpus and tarsus and of pelvis also. In the latest forms, the Anura, the carpus and tarsus are reduced through loss of parts, except that the astragalus and cal- caneum are phenomenally elongate. We have then, in the Batra- chian series, a somewhat mixed kind of change ; but it princijDally consists of concentration and consolidation of parts. The ques- tion as to whether this process is one of progression or retrogres- sion may be answered as follows : If degeneracy consists in **the loss of parts without complementary addition of other parts," then the Batrachian line is a degenerate line. This is only partly true of the vertebral column, which presents the most primitive char- acters in the early, Permian, genera (Rhachitomi). If departure from the nearest approximation to the Mammalia is degeneracy, then the changes in this class come under that head. The carpus, tarsus, and scapular and pelvic arches of the Rachitomi are more Mammalian than are those of any of their successors. || * The Trachystomata probably came from the Urodela by a process of degener- acy. See "American Naturalist," Dec, 1 885. (Ed. 1886.) f Includes the Eryopidae. X Includes Trimcrorhachidae and Archegosauridae ; and is distinguished from the Rhachitomi only by the presence of a single and cotyloid articulation of the skull with the atlas. * This reduction extends to the dorsal series as well. (Ed. 1S8G.) 11 This should read, than their latest, or anurous successors. (Ed. 1886.) EVOLUTIOI!^ OF THE VERTEBRATA. 333 There are several groups which show special marks of degen- eracy. Such are the reduced maxillary bones and persistent gills of the Proteida; the absence of the maxillary bones and the presence of gills in the Trachystomata ; the loss of a pair of legs and feebleness of the remaining pair in the sirens ; and the ex- treme reduction of the limbs in Amphiuma. Such I must also regard, with Lankester, the persistent branchiae of the Siredons. I may add that in the brain of the Proteid Necturus the hemi- spheres are relatively larger than in the Anura, which are at the end of the line. It must be concluded, then, that in many respects the Ba- trachia have undergone degeneracy with the passage of time. VI. THE KEPTILIAl:^ LIKE. As in the case of the Batrachia, the easiest way of obtaining a general view of the history of this class is by throwing their prin- cipal structural characters into a tabular form. As in the case of that class, I commence with the oldest forms and end with the latest in the order of time, which, as usual, corresponds with the order of structure. I except from this the first order, the Ichthyopterygia, which we do not know prior to the Triassic period : * A. Extremities not differentiated in form beyond proximal segment. I. Os quadratum immovably articulated to squamosal, etc. Tubercular and capitular rib-articulations present and distinct. . .1. Ichthyopterygia. AA. Elements of extremities differentiated. II. Os quadratum immovably articulated ; capitular and tubercular rib-articula- tions distinct. Archosauria. Pubis and ischium united, and with little or no obturator foramen ; one posterior cranial arch ; limbs ambulatory ; a procoracoid 2. Theromorpha. Ischium and pubis distinct, the latter directed forward, backward, or downward ; two postei'ior cranial arches; limbs ambulatory; no procoracoid 3. Dinosawia.j- Ischium and pubis united ; two postcranial arches ; anterior limbs volant 4. Ornlthosauria. III. Os quadratum closely united to cranial arches ; but one rib-articulation. Synaptosauria. * Generally similar to the system published by me in " Proceedings Amer. Ass. Adv. Science," xix, p. 233. f This definition includes the Crocodilia in the Dinosauria, as it is absolutely connected with the typical Dinosaurs by the Opisthocoela (Sauropoda Marsh). 334 THE STPwUCTURAL EVIDENCE OF EVOLUTION. Distinct hyposternal and postabdominal bones ; ribs joining each two vertebrae, and generally forming a carapace ; one posterior cranial arch 5. Testudinata. Hyposternal and postabdominal bones not distinct ; two posterior cranial arches ; ribs attached to one vertebra ; a sternum ; ? no procoracoid 6. RhyncliocepJialia. Hyposternal and postabdominal bones not distinct ; two posterior cranial arches ; ribs attached to one centrum ; no sternum ; * a procoracoid . . Y. Sauropterygia. IV. Os quadratum attached only at the proximal extremity, and more or less movable; ribs with one head. Streptostylica.f Brain-case membranous in front of prootic bone ; trabecula not persistent 8. Lacertilia. Brain-case with osseous walls anterior to prootic ; a scapular arch and sternum 9. PythonomorpJia. Brain-case with osseous walls anterior to prootic ; no scapular arch nor sternum ; trabecular grooves of sphenoid and presphenoid bones 10. Ophidia. An inspection of the characters of these ten orders, and their consideration in connection with their geological history, will give a definite idea as to the character of their evolution. The history of the class, and therefore the discussion of the question, is limited in time to the period which has elapsed since the Permian epoch inclusive, for it is then that the Eeptilia enter the field of our knowledge. During this period but one order of reptiles in- habited the earth, so far as now known, that of the Theromorpha. The important character and role of this type may be inferred from the fact that they are structurally nearer to both the Ba- trachia and the Mammalia than any other, but present characters which render it probable that all the other reptiles, with possibly the exception of the Ichthyopterygia, derived their being from them. The phylogeny may be thus expressed : Dinosauria Testudinata Ehynchocephalia Lacertilia Ophidia ~ \ / Pythonomorpha J (Crocodilia) Pterosauria DinosauriaX Sauropterygia^ / / / Ichthyopterygia Theromorpha * Episternum present. f It is quite possible that the three divisions of this head form one natural order, the Streptostylica, or Squamata. X Some unknown type of this order will represent the ancestor of the Ophidia, while the Lacertilia may have come directly from the Theromorpha. (Ed. 1886.) EVOLUTION OF THE VERTEBRATA. 335 In the first jDlace, this line departs with lapse of time from the primitive and ancestral order, the Theromorpha, in two respects : First, in the loss of the capitular articulation of the ribs, and, sec- ond, in the gradual elongation and final freedom of the suspensory bone of the lower jaw (the os quadratum). In so departing from the Theromorpha, it also departs from the mammalian type. The ribs assume the less perfect kind of attachment which the mam- mals only exhibit in some of the whales, and the articulation of the lower jaw loses in strength, while it gains in extensibility, as is seen in the development of the line of the eels among fishes. The end of this series, the snakes, must therefore be said to be the result of a process of creation by degeneration, and their lack of scapular arch and fore limb and usual lack of pelvic arch and hind limb, are confirmatory evidence of the truth of this view of the case. Secondly, as regards the ossification of the anterior part of the brain-case. This is deficient in some of the Theromorpha, the an- cestral order, which resemble in this, as in many other things, the contemporary Batrachia. Some of them, however (Diadecti- dae), have the brain comjDletely inclosed in front. The late orders mostly have the anterior walls membranous, but, in the strepto- stylicate series at the end, the skull in the snakes becomes en- tirely closed in front. In this respect, then^ the latter may be said to be the highest or most perfect order. As regards the scapular arch, including the sternum, no order l^ossesses as many elements as thoroughly articulated for the use of the anterior leg as the Permian Theromorpha, though the cor- acoid is of reduced size. In all the orders there is loss of parts, excepting only in the Ornithosauria and the Lacertilia. In the former the adaptation is to flying. The latter retain nearly the Theromorph type, enlarging the coracoid. An especial side de- velopment is the modification of abdominal bones into two pecul- iar elements to be united with the scapular arch into a plastron, seen in the Testudinata. In this part of the skeleton the orders are generally degenerate, the last one, the Ophidia, especially so. The pelvic arch has a more simple history. Again, in the Theromorpha we have the nearest approach to the Mammalia. The only other order which displays similar characters is the Ornithosauria (Dimorphodon, according to Seeley). In the Dino- sauria we have a side modification which is an adaptation to the erect or bipedal mode of progression, the inferior bones being 336 THE STRUCTURAL EVIDENCE OF EVOLUTION. thrown backward so as to support the viscera in a more posterior position. This is an obvious necessity to a bipedal animal where the vertebral column is not perpendicular, as in birds. And it is from the Dinosauria that the birds are supposed to have arisen. (Plates XV and XVI.) The main line of the Eeptilia, however, departs from both the mammalian and the avian type and loses in strength as compared with the former. In the latest orders, the Phythonomorpha and Ophidia, the pelvis is rudimental or absent. As regards the limbs, the degeneracy is well marked. No reptilian order of later ages apj^roaches so near to the Mammalia in these parts as do the Permian Theromorpha. This approxi- mation is seen in the internal epicondylar foramen and well-devel- oped condyles of the humerus, and in the well-differentiated seven bones of the tarsus. The epicondylar foramen is only re- tained in later reptiles in the Ehynchocephalian Hatteria (Dollo) ; and the condyles of the Dinosauria and all of the other orders, excepting the Ornithosauria and some Lacertilia, are greatly wanting in the strong characterization seen in the Theromorpha. The posterior foot seems to have stamped out the greater part of the tarsus in the huge Dinosauria, and it is reduced, though to a less degree, in all the other orders. In the paddled Sauroptery- gia, dwellers in the sea, the tarsus and carpus have lost all char- acterization, probably by a process of degeneracy, as in the mam- malian whales. This is to be inferred from the comparatively late period of their appearance in time. The still more unspecial- ized feet and limbs of the Ichthyosaurus (Ichthyopterygia) can not yet be ascribed to degeneracy, for their history is too little known. At the end of the line, the snakes present us with another evidence of degeneracy. But few have a pelvic arch (Stenostomi- dse Peters), while very few (Peropoda) have any trace of a poste- rior limb. The vertebrae are not introduced into the definitions of the orders, since they are not so exclusively distinctive as many other parts of the skeleton. They nevertheless must not be overlooked. As in the Batrachia, the Permian orders show inferioritv in the deficient ossification of the centrum. Many of the Theromorpha are notochordal, a character not found in any later order of reptiles excepting in a few Lacertilia (Gecconidaa). They thus differ from the Mammalia, whose characters are approached more nearly by some of the terrestrial Dinosauria in this respect. EVOLUTION OF THE VERTEBRATA. 337 Leaving this order, we soon reach the prevalent ball-and-socket type of the majority of Reptilia. This strong kind of articula- tion is a need which accompanies the more elongated column which itself results at first from the posterior direction of the ilium. In the order with the longest column, the Ophidia, a sec- ond articulation, the zygosphen, is introduced. The mechanical value of the later reptilian vertebral structure is obvious, and in this respect the class may be said to present a higher or more perfect condition than the Mammalia. In review it may be said of the reptilian line, that it exhibits marked degeneracy in its skeletal structure since the Permian epoch ; the exception to this statement being in the nature of the articulations of the vertebrae. And this specialization is an adap- tation to one of the conditions of degeneracy, viz., the weakening and final loss of the limbs and the arches to which they are at- tached. The history of the development of the brain in the Eeptilia presents some interesting facts. In the Diadectid family of the Permian Theromorpha it is smaller than in a Boa constrictor, but larger than in some of the Jurassic Dinosauria. Marsh has shown that some of the latter possess brains of relatively very narrow hemispheres, so that in this organ those gigantic reptiles were degenerate, while the existing streptostylicate orders have advanced beyond their Permian ancestors. There are many remarkable cases of what may now be safely called degradation to be seen in the contents of the orders of reptiles.* Among tortoises may be cited the loss of the rib- heads and of one or two series of phalanges in the especially terrestrial family of the Testudinidae. The cases among the Lacertilia are the most remarkable. The entire families of the Pygopodidse, the Aniellidse, the Anelytropidae, and the Dibamidae are degraded from superior forms. In the Anguidae, Teidae, and Scincidae, we have series of forms whose steps are measured by the loss of a pair of limbs, or of from one to all the digits, and even to all the limbs. In some series the surangular bone is lost. In others the eye diminishes in size, loses its lids, loses the folds of the epidermis which distinguishes the cornea, and finally is en- tirely obscured by the closure of the ophthalmic orifice in the * Such forms in the Lacertilia have been regarded as degradational by Lan- !ou] 22 kester and Bouhmger, PLATE XV. o P o c cS o o o • r-H CS 02 o r— t o CS P CO o CO S o PLATE XVI. Diclonius mirabilis skull, one seventh natural size, from below. 340 THE STRUCTURAL EVIDEISrCE OF EVOLUTION. true skin. Among the snakes a similar degradation of the organs of sight has taken place in the order of the Scolecophidia, which live underground, and often in ants' nests. The Tortricidae and UropeltidsB are burro wing-snakes which display some of the earlier stages of this process. One genus of the true snakes even (accord- ing to Giinther) has the eyes obscured as completely as those of the inferior types above named (genus Typhlogeophis). YII. THE AVIAIiT LINE. The paleontology of the birds not being well known, our con- clusions respecting the character of their evolution must be very incomplete. A few lines of succession are, however, quite ob- vious, and some of them are clearly lines of progress, and others are lines of retrogression. The first bird we know at all com- pletely, is the celebrated Archeoj^teryx of the Solenhofen slates of the Jurassic period. In its elongate series of caudal vertebrae and the persistent digits of the anterior limbs we have a clear in- dication of the process of change which has produced the true birds, and we can see that it involves a specialization of a very pronounced sort. The later forms described by Seeley and Marsh from the Cretaceous beds of England and North America, some of which have biconcave vertebrae, and all probably, the American forms certainly, possessed teeth. This latter character was evi- dently speedily lost, and others more characteristic of the subclass became the field of developmental change. The parts which sub- sequently attained especial development are the wings and their appendages ; the feet and their envelopes, and the vocal organs. Taking all things into consideration, the greatest sum of progress has been made by the perching birds, whose feet have become effective organs for grasping, whose vocal organs are most perfect, and whose flight is generally good, and often very good. In these birds also the circulatory system is most modified, in the Ibss of one of the carotid arteries. The power of flight, the especially avian character, has been developed most irregularly, as it appears in all the orders in especial cases. This is apparent so early as in the Cretaceous toothed birds already mentioned. According to Marsh the Hes- peornithidae have rudimental wings, while these organs are well developed in the Ichthyornithidae. They are well developed among natatorial forms in the albatrosses and frigate pelicans, and in the skuas, gulls, and terns ; among rasorial types the EVOLUTION OF THE VERTEBRATA. 341 sand-grouse, and, among the adjacent forms, the pigeons. Then among the lower insessores, the humming-birds exceed all birds in their powers of flight, and the swifts and some of the Capri- mulgidae are highly developed in this respect. Among the higher or true song birds, the swallows form a notable example. With these high specializations occur some remarkable deficiencies. Such are the reduction of the feet in the Caprimulgidae, swifts, and swallows, and the foetal character of the bill in the same families. In the syndactyle families, represented by the king- fishers, the condition of the feet is evidently the result of a pro- cess of degeneration. A great many significant points may be observed in the developmental history of the epidermic structures, especially in the feathers. The scale of change in this respect is in general a rising one, though various kinds of exceptions and variations occur. In the development of the rectrices (tail-feathers) there are genera of the wading and rasorial types, and even in the in- sessorial series, where those feathers are greatly reduced or abso- lutely wanting. These are cases of degeneracy. There is no doubt that the avian series is in general an as- cending one. VIII. THE MAMMALIAN" LIXE. Discoveries in paleontology have so far invalidated the ac- cepted definitions of the orders of this class that it is difficult to give a clearly cut analysis, especially from the skeleton alone. The following scheme, therefore, while it expresses the natural groupings and affinities, is defective in that some of the defini- tions are not without exceptions : I. A large coracoid bone articulating with the sternum. Marsupial bones ; fibula articulating with proximal end of astragalus 1. Monotrcmata. II, Coracoid a small process co-ossified with the scapula. o. Marsupial bones ; palate with perforations (vagina double ; placenta and corpus callosum rudimental or wanting; cerebral hemispheres small and generally smooth). But one deciduous molar tooth 2. Marsupialia. aa. No marsupial bones; palate entire (one vagina; placenta and corpus callosum well developed). j8. Anterior limb reduced to more or less inflexible paddles, posterior limbs wanting (Mutilata). 342 THE STRUCTURAL EVIDENCE OF EVOLUTION. No elbow-joint ; carpals discoid, and with the digits separated by cartilage ; lower jaw without ascending ramus 3. Cetacea, An elbow-joint ; carpals and phalanges m ith normal articulations ; lower jaw with ascending ramus 4. Sirenia. j8^. Anterior limbs with flexible joints and distinct digits ; ungual pha- langes not compressed and acute at apex* (Ungulata f). y. Tarsal bones in linear series ; carpals generally in linear series. Limbs ambulatory ; teeth with enamel 5. Taxeojxxla.X 77. Tarsal series alternating; carpal series linear. Cuboid bone partly supporting navicular, not in contact with astragalus . 6. Prohoscidia. 777. Both tarsal and carpal series more or less alternating. Os magnum not supporting scaphoides ; cuboid supporting astragalus ; superior molars tritubercular 7. Arahlijpoda. Os magnum supporting scaphoides ; superior molars quadritubercular * 8. Diplarthra,\ /3/3j3. Anterior limbs with flexible joints. Ungual phalanges compressed and pointed-^ (Unguiculata). e. Teeth without enamel; no incisors. Limbs not volant; hemispheres small, smooth 9. Edentata. 66. Teeth with enamel ; incisors present. No postglenoid process ; mandibular condyle round ; limbs not volant ; hemispheres small, smooth 10. Rodentia. Limbs volant ; hemispheres small, smooth 11. Chiroptera. * Except the Ilapalidse. f Lamarck, "Zoologie Philosophique," 1809. X This order has the following suborders, whose association is now made for the first time : Carpal series linear ; no intermedium ; fibula not interlocking with astragalus ; no anapophyses ; incisors rooted ; hallux not opposable. Condylartha. Carpal series linear ; an intermedium ; fibula interlocking with astragalus ; hallux not opposable Hyracoidea. An intermedium ; fibula not interlocking ; anapophyses ; hallux opposable ; incisors growing from persistent pulps Dauhentonoidea. An intermedium ; fibula not interlocking ; anapophyses; hallux opposable ; incisors rooted ; carpus generally linear Qiiadt^mana. No intermedium ; * nor anapophyses ; carpal rows alternating ; incisors rooted A nthropoidea.\ The only difference between the Taxeopoda and the Bunotheria is in the unguli- form terminal phalanges of the former as compared with the clawed or unguiculate form in the latter. The marmosets among the former division are, however, fur- nished with typical claws. Some may prefer to use the term Primates in place of Taxeopoda, and such may be the better course. * Except Pantolestes. II This order includes the suborders Pcrissodactyla and Artiodactyla. It is the Ungulata of some authors. ^ Except Mesonyx. * Except in Sijnia and Hylobates. t Includes the Anthropoid apes and man. EYOLUTTON OF THE YERTEBRATA. 843 A postglenoid process; mandibular condyle transverse; limbs not volant; no scapholunar bone;* hemispheres small, smooth 12. BuiiotheriaA A postglenoid process ; limbs not volant, with a scapholunar bone ; hemispheres larger, convoluted 13. Carnivora. Paleontology has cleared up the phylogeny of most of these orders, but some of them remain as yet unexplained. This is the case with the Cetacea, the Sirenia, and the Taxeopoda. The last-named order and the Marsupialia can be supposed with much probability to have come oS from the Monotremata, but there is as yet no paleontological evidence to sustain the hypothesis. Xo progress has been made in unraveling the phylogeny of the Ceta- cea and Sirenia. The facts and hypotheses as to the phylogeny of the Mammalia may be representad in the following diagram : Diplarthra Hyracoidea Insectivora Rodentia Chiroptera Proboscidea Amblypoda Anthropoidea I Qaadrumana Edentata Carnivora Sirenia Cetacea Tillodonta Ta3niodonta [ Oreodonta Oondylartbra Marsupialia pt.J. Monotremata Marsupialia pt. It will be readily seen from the above diagram that the dis- covery of the Condylarthra was an important event in the history of our knowledge of this subject. This suborder of the Lower Eocene epoch stands to the placental Mammalia in the same rela- tion as the Theromorphous order does to the reptilian orders. It generalizes the characteristics of them all, and is apparently the parent stock of all, excepting, perhaps, the Cetacea. The dis- covery of the extinct Bunotherian suborders united together in- separably the clawed orders, excepting the bats ; while the extinct order Amblypoda is the ancestor of the most specialized of the Ungulates, the odd- and even-toed Diplarthra. The characters of the skeleton of the order Monotremata show that it is nearest of kin to the Reptilia, and many subordinate * Except Erinaceus. f With the suborders Insectivora, Oreodonta, Taeniodonta, and Tillodonta. X This was inadvertently omitted in the original. (Ed. 1886.) 34:4: THE STRUCTURAL EVIDENCE OF EYOLUTIOX. characters point to tlie Theromorplia as its ancestral source.* In the general characters the Marsupialia naturally follow in a rising scale, as proved by the increasing perfection of the reproductive system. The Monodelphia follow with improvements in the re- productive system and the brain, as indicated in the table already given. The oldest Monodelphia were, in respect to the structure of the brain, much like the Marsupialia, and some of the existing orders resemble them in some parts of their brain-structure. Such are the Condylarthra and Amblypoda of extinct groups, and the Bunotheria, Edentata, Rodentia, and Chiroptera, recent and extinct. The characters of the brains of Amblypoda and some Oreodonta are, in their superficial characters, even inferior to ex- isting marsupials. The divided uterus of the recent forms named, also gives them the position next to the Marsupialia. In the Car- nivora, Hyracoidea, and Proboscidia, a decided advance in both brain-structure and reproductive system is evident. The hemi- spheres increase in size, and they become convoluted. A uterus is formed, and the testes become external, etc. In the Quadru- mana the culmination in these parts of the structure is reached, excepting only that, in the lack of separation of the genital and urinary efferent ducts, the males are inferior to those of many of the Artiodactyla. This history displays a rising scale for the Mammalia. Looking at the skeleton, we observe the following successional modifications : f First, as to the feet, and (A) the digits. The Condylarthra have five digits on both feet, and they are plantigrade. This char- acter is retained in their descendants of the lines of Anthropoidea, Quadrumana, and Hyracoidea, also in the Bunotheria, Edentata, and most of the Rodentia. In the Amblypoda and Proboscidia the palm and heel are a little raised. In the Carnivora and Dip- larthra the heel is raised, often very high, above the ground, and the number of toes is diminished, as is well known, to two in the Artiodactyla and one in the Perissodactyla. (B) The tarsus and carpus. In the Condylarthra the bones of the two series in the carpus and tarsus are opposite each other, so as to form continuous and separate longitudinal series of bones. This continues to be * "Proceedings American Philosoph. Society," 18S4, p. 43. f See the evidence for evolution in the history of the extinct Mammalia. " Pro- ceeds. Araer. Assoc. Adv. Science," 1883. PLATE XVII. 346 THE STRUCTURAL EVIDENCE OF EVOLUTION". the case in the Hyracoidea and many of the Quadrumana, but in the anthropoid apes and man the second row is displaced inwards so as to alternate with the first row, thus interrupting the series in the longitudinal direction, and forming a stronger structure than that of the Condylarthra. In the Bunotherian Rodent and Eden- tate series, the tarsus continues to be without alternation, as in the Condylarthra, and is generally identical in the Carnivora. In the hoofed series proper it undergoes change. In the Proboscidia the carpus continues linear, while the tarsus alternates. In the Amblypoda the tarsus alternates in another fashion, and the car- pal bones are on the inner side linear, and on the outer side alter- nating. The complete interlocking by universal alternation of the two carpal series is only found in the Diplarthra. (C) As to the ankle-joint. In most of the Condylarthra it is a flat joint or not tongued or grooved. In most of the Carnivora, in a few Rodentia, and in all Diplarthra, it is deeply tongued and grooved, forming a more perfect and stronger joint than in the other orders, where the surfaces of the tibia and astragalus are flat. (D) In the high- est forms of the Rodentia and Diplarthra the fibula and ulna be- come more or less co-ossified with the tibia and radius, and their middle portions become attenuated or disappear. Secondly, as regards the vertebras. The mutual articulations (zygapophyses) in the Condylarthra have flat and nearly horizon- tal surfaces. In higher forms, especially of the ungulate series, they become curved, the posterior turning upward and outward, and the anterior embracing them on the external side. In the higher Diplartha this curvature is followed by another curvature of the postzygapophysis ujDward and outward, so that the vertical section of the face of this process is an S. Thus is formed a very close and secure joint, such as is nowhere seen in any other Vertebrata. Thirdly, as regards the dentition. Of the two tjipes of Mono- tremata, the Tachyglossidse and the Platypodid£e, the known gen- era of the former possess no teeth, and the known genus of the latter possesses only a single corneous epidermic grinder in each jaw. As the Theromorphous reptiles from which these are de- scended have well-developed teeth, their condition is evidently one of degeneration, and we can look for well-toothed forms of Mono- tremata in the beds of the Triassic and Jurassic periods. Perhaps some such are already known from jaws and teeth. In the mar- supial order we have a great range of dental structure, which almost EYOLUTIOISr OF THE VERTEBRATA. 347 epitomizes that of the Monodelph orders. The dentition of the carnivorous forms is creodont ; that of the kangaroos is perisso- dactyle, and that of the wombats is rodent. Other forms repeat the Insectivora. I therefore consider the phicental series espe- cially. I have already shown that the greater number of the types of this series have derived the characters of their molar teeth from the stages of the following succession. First, a simple cone or reptilian crown, alternating with that of the other jaw. Second, a cone with lateral denticles. Third, the denticles to the inner side of the crown forming a three-sided prism, with tritubercular apex, which alternates with that of the opposite jaw. Fourth, development of a heel projecting from the posterior base of the lower jaw, which meets the crown of the superior, forming a tubercular-sectorial inferior molar. From this stage the carnivo- rous and sectorial dentition is derived, the tritubercular type being retained. Fifth, the development of a posterior inner cusp in the superior molar, and the elevation of the heel in the inferior molar, with the loss of the anterior inner cusp. Thus the molars become quadritubercular, and opposite. This is the type of many of the Taxeopoda, including the Quadrumana and Insectivora as well as the inferior Diplarthra. The higher Taxeopoda (Hyracoidea) and Diplarthra add various complexities. Thus the tubercles become flattened and then concave, so as to form Vs in the section pro- duced by wearing ; or they are joined by cross- folds, forming vari- ous patterns. In the Proboscidia the latter become multii^lied so as to produce numerous cross-crests. The dentition of some of the Sirenia is like that of some of the Ungulata, especially of the suilline group, while in others the teeth consist of cvlinders. In the Cetacea the molars of the old- est (Eocene and Miocene) types are but two-rooted and com- pressed, having much the form of the premolars of other Mam- malia. In existing forms a few have simple conical teeth, while in a considerable number teeth are entirely wanting. A review of the characters of the existing Mammalia as com- pared with those of their extinct ancestors displays a great deal of improvement in many ways, and but few instances of retro- gression. The succession in time of the Monotremata, the Mar- supialia, and the Monodelphia, is a succession of advance in all the characters of the soft parts and of the skeleton which define them (see table of classification). As to the monotremes them- selves, it is more than probable that the order has degenerated in 348 THE STRUCTURAL EVIDENCE OF EVOLUTION. some res]3ects in producing the existing types. The history of the Marsupialia is not made out, but the earliest forms of which we know the skeleton, Polymastodon (Cope) of the Lower Eocene, is as specialized as the most specialized recent forms. The dentition of the Jurassic forms, Plagiaulax, etc., is quite specialized also, but not more so than that of the kangaroos. The premolars are more specialized, the true molars less specialized than in those animals. Coming to the Monodelphia, the increase in the size and com- plication of the brain, both of the cerebellum and the hemi- spheres, is a remarkable evidence of advance. But one retro- gressive line in this respect is known, viz., that of the order Amblypoda,* where the brain has become relatively smaller with the passage of time. The successive changes in the structure of the feet are all in one direction, viz., in the reduction of the number of the toes, the elevation of the heel, and the creation of tongue and groove joints where plain surfaces had previously ex- isted. The diminution in the number of toes might be regarded as a degeneracy, but the loss is accompanied by a proportional gain in the size of the toes that remain. In every respect the progressive change in the feet is an advance. In the carpus and tarsus we have a gradual rotation of the second row of bones on the first, to the inner side. In the highest and latest orders this process is most complete, and, as it results in a more perfect me- chanical arrangement, the change is clearly an advance. The same progressive improvement is seen in the development of dis- tinct facets in the cubito-carpal articulation, and of a tongue and groove (^* in tertrochlear crest ") in the elbow-joint. In the ver- tebrae the development of the interlocking zygapophysial articula- tions is a clear advance. Progress is generally noticeable in the dental structures ; for, unlike the marsupial line, the earliest dentitions are the most simple, and the later the more complex. Some of the types re- tain the primitive tritubercular molars, as the Centetidae, shrews and some lemurs, and many Carnivora, but the quadritubercular and its derivative forms are by far the most common type in the recent fauna. The forms that produced the complicated modifica- tions in the Proboscidia and Diplarthra appeared latest in time, and the most complex genera. Bos and Equus, the latest of all. The extreme sectorial modifications of the tritubercular type, as * See "Naturalist," Jan., 1885, p. 55. EVOLUTION OF THE YERTEBRATA. 349 seen in the Hyaenidge and the Felidae, are the latest of their line also. Some cases of degeneracy are, however, apparent in the mono- delphous Mammalia. The loss of pelvis and posterior limbs in the two mutilate orders is clearly a degenerate character, since there can be no doubt that they have descended from forms with those parts of the skeleton present. The reduction of flexi- bility seen in the limbs of the Sirenia and the loss of this char- acter in the fore limbs of the Cetacea are features of degeneracy for the same reason. The teeth in both orders have undergone degenerate evolution ; in the later and existing forms of the Ceta- cea even to extinction. The Edentata appear to have undergone degeneration. This is chiefly ajoparent in the teeth, which are deprived of enamel, and which are wanting from the premaxillary bone. A suborder of the Bunotheria, the Tgeniodonta of the Lower Eocene period, display a great reduction of enamel on the molar teeth, so that in much-worn examjoles it appears to be wanting. Its place is taken by an extensive coat of cementum, as is seen in Edentata, and the roots of the teeth are often un- divided as in that order. It is probable that the Edentata are the descendants of the Tseniodonta by a process of degeneracy. Local or sporadic cases of degenerate loss of parts are seen in various parts of the mammalian series, such as toothless jMamma- lia wherever they occur. Such are cases where the teeth become extremely simple, as in the honey-eating marsupial Tarsipes, the carnivore Proteles, the Pteropod bats, and the aye-aye. Also where teeth are lost from the series, as in the canine genus Dysodus, and in man. The loss of the hallux and pollex without corresponding gain in various genera, may be regarded in the same light. In conclusion, the progressive may be compared with the re- trogressive evolution of the Vertebrata, as follows : In the earlier periods and with the lower forms, retrogressive evolution pre- dominated. In the higher classes progressive evolution has pre- dominated. When we consider the history of the first class of vertebrates, the Tunicata, in this respect, and compare it with that of the last class, the Mammalia, the contrast is very great. PART III. MECHAIs^IOAL EYOLUTIOE". XII. THE EELATION OF ANIMAL MOTION TO ANIMAL EVOLUTION. To explain the origin of variation in animal structure is, par excellence, the object of the doctrine of evolution. There can be little doubt that the law of natural selection includes the cause of the preservation of certain modifications of pre-existent structure, in preference to others, after they have been brought into exist- ence. In what manner or by what process the growing tissues of young animals have been so affected as to produce some organ or part of an organ which the parent did or does not possess, must be explained by a different set of laws. These have been termed originative^ while those involved in natural selection are restrictive only. I. Of course we naturally look to something in the *^ surrounding circumstances" in which a plant or animal is placed, or its "en- vironment," as the most probable stimulant of change of its char- acter, because we know that such beings are totally dependent on cosmic and terrestrial forces for their sustenance and preservation. The difficulty has been to connect these forces with change of structure SLS originative ; to show their operation as multiplying, restricting or destroying organisms already in existence is compar- atively easy. This difficulty is partially due to the fact that such modifications must be realized during a limited portion of the life of an animal at least ; that is, during the period of growth, when it is not at all or but little subject to the influence of external en- vironment, but is usually protected or supported by the parent. That the environment and changes in it affect the movements RELATION OF ANIMAL MOTION TO ANIMAL EVOLUTION. 351 of plants and animals is clear enough. The potency of such changes may be read in the physical history of the earth. A long series of modifications preceded the advent of life upon it, and change, both gradual and sudden, has been exhibited in the con- figuration and climate of all portions of the surface of the globe since that period. Animals have again and again been called upon to face new conditions, and myriads of species have fallen victims to the inflexibility of their organization which has pre- vented adaptation to new surroundings. But it is evident that if change of environment has had any influence in the progress of evolution, it has not been alone destructive. It has preceded life as well as death, and has furnished the stimulus to beings capable of change, while it has destroyed those which were incapable of it. It is a truism that change of physical conditions has preceded all great faunal changes, and that the necessity for new mechanism on the part of animals has always preceded the appearance of new structure in geologic times. The embryology and paleontology of vertebrated animals show that the primary steps in the progress of this branch of the animal kingdom are marked by the successive changes in the structure of the circulatory system. First we have the various mechanical methods for the aeration of blood in a watery medium ; the result being a fluid whose metamorphosis in nutrition produces no heat. After the fishes followed Batrachia, the earliest air-breathers, whose long tarriance to-day in early aquatic stages is an epitome of the necessarily *' amphibious" character of air-breathing verte- brate life, when land and fresh water, in constantly changing areas, were rising and separating from the universal ocean. The successive disappearances of the traces of the fish type of circula- tion in Batrachia and reptiles, are familiar facts ; and the exclu- sion of the unaerated blood from the systemic circulation in the birds and mammals marks the increase of general temperature which gives those classes one of their claims to sui)eriority. The appearance of land of course furnished the opportunity for aquatic animals to assume a terrestrial life. Marine animals which had acquired the habit of gulping air from the surface, which some of them now possess, perhaps because its richness in oxygen produced an agreeable exaltation or intoxication, would not find visits to the land difficult. And this would naturally follow the necessity of escape from aquatic enemies, or the search for new supplies of food. 352 MECHANICAL EVOLUTION. In fine, it requires little argument to sliow that the enyiron- ment has had in the past, as in the present, a primary influence over the movements of animals. II. I will now endeavor to exhibit some reasons for believing that the movements of animals affect their structure directly. There are two alternative propositions expressive of the rela- tions of the structures of animals to their uses. Either the use or attempt to use preceded the adaptive structure, or else the structure preceded and gave origin to the use. The third alter- native, that use and structure came into being independently of each other, is too improbable for consideration in the present article. Many facts render the first of these propositions much the more probable of the two. A general ground for suspecting that movement affects struct- ure is the fact well known to systematic zoologists, that adaptive characters are the least reliable in systematic classification, i. e., are the most variable. What we call adaptive characters are those whose teleological significance we can most easily perceive ; those whose uses are at the present time most obvious. System- atists habitually fall back on characters which are apparently the least related to the ordinary necessities of the life of the animal, and this not from any theoretical considerations, but because such characters are found to be the most constant. This is a very sig- nificant fact, showing as it does that it is the adaptive structures which are undergoing modification to-day. And this truth can doubtless be discerned in all past ages, for many of the structures which are not now more related to the needs of an animal than many others might be, were at one time most essential to its well- being, or necessarily related to its environment. Such are the structural characters of the heart and arteries already enumerated. There seems to be no reason why all Vertehrata might not exist with equal comfort and success at the present if possessed of a uniform organization in this respect. But the successive modi- fications which they present were, in past ages, most intimately connected with the progressive changes of the medium in which they lived, as to the volume of oxygen su23plied for respiration, as compared with that of the vapor of water, carbonic acid gas, etc. But it must be here noted, in passing, that there are many structures in animals which have never been adaptive, but which RELATION OF ANIMAL MOTION TO ANIMAL EVOLUTION. 353 are simjoly due to excess or defect of nutrition following a redis- tribution of force.* The most direct evidence in support of the view that motion affects structure directly is to be found in the well-known phe- nomenon of the increase of the size and power of all organs by use. This increase is limited in the adult animal by the general fixity of all the organs, so that one of them cannot be developed beyond a certain point without injury to others, or without ex- hausting the source of supply of nutritive material or special force ' derived from other organs. The syncope of the gymnast is an illustration of the natural limitation to the development of the 1 muscular system which proceeds at the expense of the digestive and circulatory. But effort and exertion may become a habit of mind, which, even if limited in its executive means, is probably in- herited by offspring like all other mental traits. Such a quality possessed by an infant or child doubtless tells on the growth of \ its organs during their plastic stage, and produces structure by \ growth which is impossible to the mature body.f And no one knows as yet how far mental bias may affect the nutrition of the parts of the infant in utero. Certain it is, that if use modifies nutrition in the adult, it must have still greater influence in the young ; and it is in the young that tlie changes which constitute evolution necessarily appear. Change of structure during growth is accomplished either by addition of parts (^^acceleration") or by subtraction of parts ("retardation"). Acceleration is produced either by multiplication of parts (as cells or segments) already present (^Miomotopy "), or by the transfer of parts (cells) from one part of the organism to the other (*^heterotopy "). Homotopy or repetition is the usual and normal mode of acceleration ; it may proceed by an " exact repeti- tion " of the parts already existing, as in the simplest animals and plants ; or the new parts may differ from the old, as in higher animals, where the process is called "modified repetition." Where new forms traverse in their growth all the stages in which they previously existed, they necessarily present at each stage the char- acters of those forms which have remained stationary in them, and have not changed. This relation of " exact parallelism " is the * "Method of Creation," 1871, p. 23. f In raan these changes are chiefly produced in the brain. 23 354 MECHANICAL EVOLUTION. result of the simplest form of evolution or ^^palingenesis." When the history of growth of an advanced form does not show an identity between its stages and the various undeveloped or lower adult types, the relation is termed 'Mnexact parallelism," and the type of development '' coenogenesis. '' Change of structure is seen to take place in accordance with the mechanical effect of three forms of motion, viz.: hj friction, pressure and strain. Under the first two, epidermal tissues be- come both dense and thick, as is seen on the palms and soles of the hands and feet, and in corns. There is no doubt that strength of the teeth is intimately connected with the hardness of the food. Density of osseous tissue and the coossification of parts of the skeleton, are directly associated with the force and duration of muscular contraction. Pathology abounds in illustrations of the determination of nutrition to new localities to meet the exi- gencies and demands arising from new stimuli. It is only neces- sary for a structure-producing supply of nutritive material to be habitually determined to a new locality by oft-recurring stimulus, for the movement to become automatic and reflex ; and such a tendency would sooner or later be inherited, and produce struct- ure in the growing organism of the young to a degree far exceed- ing anything that is possible in the adult. In view of the above considerations, we can ascribe an exten- sive class of osseous projections at points of muscular insertion, to the strength and duration of muscular contractions. To the same cause may be ascribed various anchyloses, such, for instance, as is seen in the foot of the sloth. Transverse strains or their ab- sence may be looked upon respectively as the cause of the hinge- like or immovable articulations of the segments of the limbs of vertebrate animals. It is well knoAvn that in land animals, where easy flexibility of the limbs is essential to speed, these articula- tions are highly developed, while in marine animals, where the limbs are only used as paddles, they are almost or quite in- flexible, and the extremities of the bones are truncate. In the most highly organized land Mammalia, the tibio-tarsal and hu- mero-cubital articulations display an interlocking or tongue- and-groove character. The same thing is seen in the ulno- radial fixed articulation in the same types. These arrangements are especially adapted to prevent dislocation by side strains, and if the preceding explanations be true, this structure is a corrugation due to the lateral pressure of a more or less RELATION OF ANIMAL MOTION TO ANIMAL EVOLUTION. 355 convex surface, on a concave one which embraces it, and vice versa. In the circulatory system, pressure has doubtless played an im- portant part. Increased oxygenation of blood, the necessary con- sequence of the purification of the atmosphere, would stimulate the action of all the organs, including that of the heart. Greater pressure on its walls and septa w^ould increase their size and strength, and ultimately close such foramina as were not in the course of the blood current, as the foramen septi ventriculorum of reptiles, and the/, ovale. Increased force of the current would, on the other hand, soon cause the enlargement of one or other of the four or five pairs of primary aorta bows, and develop it at the expense of the others, until finally the pre-eminence of one chan- nel be secured and the aorta be the result. This part of the sub- ject might be prolonged to an unlimited extent, but the above illustrations must suffice to indicate the meaning of my proposi- tions. III. That movements change the environment of a plant or an ani- mal, or parts of them, is obvious enough. If we consider only the reflex class, to which all the movements of plants and many of those of animals belong, we perceive that but for them the or- dinary functions of assimilation, circulation, etc., could not be performed ; there would be no change in the contents of their tubes and cells, and the environment of these would be unaltered. But when we view the movements of the higher animals, w^e j)er- ceive the immense importance of the powers and organs of move- ment as a factor in evolution. It may be safely assumed that, without powers of designed or adaptive movement, life would never have advanced beyond the stage presented by the vegetable kingdom. The stimuli which are effective in animal consciousness are four, viz.: excessive temperature, hunger, danger from enemies, and the reproductive instinct. These prompt to the movements which we observe in animals in a wild state, and without which it is evident that the animals themselves would soon cease to exist. It can not be denied that organisms which are incapable of moving from place to place in search of food, or of migration to escape vicissitudes of temperature, are much more completely sub- 356 ' MECHANICAL EVOLUTION. ject to the influences of their environment than those that are ca- l)able cf such movement. Hence animals are much more inde- pendent of the supply of food and of temperature than are plants. Hence also, other things being equal, the greater the powers of motion, the greater the independence. Powers of movement then enable animals to avoid extremes of climate by migrations or by protective arts. They enable them to procure food by making journeys in search of it, and by all methods of capturing it. They furnish the agent of active defense against enemies, and of successfully reproducing their kind. When, through changes of level of the earth's surface, drought has overtaken a region, animals capable of the necessary migrations have escaped. When an irruption of destructive animal enemies has threatened an animal population with death, those members of it whose strength or speed insured them safety, were the sur- vivors. When land has been encroached upon by water to such a degree as to bring starvation on its animal inhabitants, those which could fly or swim have sought new localities. Since all food-supply, as well as the ability to obtain food, is dependent on temperature, those portions of the organism which furnish means of resistance to climatic vicissitudes have the deepest significance in the life-history of any division of ani- mals. The organs of circulation and motion are generally recognized as primary in the classification of Vertehrata. All situations where animal life is permitted by climate, support vegetable life also ; so each of the primary divisions of animals presents types adapted to the use of all kinds of food ; herbivorous, omnivorous, and carniv- orous. Accordingly, it has been found that dental and other structures connected with digestion define divisions of secondary value and minor extent. Paleontology shows that the origin of such divisions is of later date than that of the great classes first mentioned ; and each of the latter has in its day been modified in the subordinate directions indicated bv the teeth and beak. But here also organs of movement are of great importance ; so that the herbivorous and carnivorous types at least, have ever in land ani- mals (reptiles, birds and mammals) been characterized by the structure of their feet also. RELATION OF ANIMAL MOTION TO ANIMAL EVOLUTION, 357 IV. It has been maintained above, that environmeut governs the movements of animals, and that the movements of animals then alter their environment. It has also been maintained that the movements of animals have modified their structure so as to render them more or less independent of their environment. The history of animal life is in fact that of a succession of conquests over the restraints imposed by physical surroundings. Man has attained to a wonderful degree of emancipation from the iron bonds that confine the lower organisms. It becomes then all important to examine into the elements in- volved in animal movements. These are of the two classes, reflex and conscious. To the former belongs the accelerated activity of muscular action and circulation, inferred to have accompanied increase in the percent- age of oxygen in the atmosphere, during the periods of geological time. To the consciously performed acts belong all those due to states of pain or pleasure in animals ; such as are excited by the four classes of stimuli already mentioned. Doubtless physical changes in the surrounding medium have always produced new reflex movements in animals, and have been a first element in evolution. Such has been the immediate cause of change of structure m plants, and in animals so far as they are unconscious. But consciousness brings with it limitless possibili- ties, since it places an animal in contact with innumerable stimuli which leave unconscious beings unaffected. All the causes which 2)rovoke the movements of higher animals are appeals to conscious- ness, and the consequences due to movements of such beings have only been possible through consciousness. It is evident then that sensibility to impressions has been the prime essential to the acquisition of new movements, and hence of new structure, other things being equal. Another essential, not less important, has been memory ; because without this faculty, experience, and hence education and the acquisition of habits of movement, are not possible. The ascending development of the bodily structure in higher animals has thus been, m all probability, a concomitant of the evo- lution of mind, and the progress of the one has been dependent in an alternating way on the progress of the other. The develop- ment of mind has secured to animals the greatest degree of inde- 358 MECHANICAL EVOLUTION. pendence of their enyironment of whicli tbey are capable. The first important acquisition leading to this end was aerial respira- tion ; the second, rapid nutrition by hot blood. And as essential to tlie production and preservation of these, improvements in organs of movement have been superadded to every successive type of life. Consciousness remains as the unresolvable factor in the process ; as at once the measure of, and respondent to a large class of phe- nomena. XIIL ON THE TRITUBERCULATE TYPE OF MOLAR TOOTH m THE MAMMALIA. It is now apparent that the type of superior molar tooth which predominated during the Puerco epoch was triangular or trituber- cular ; that is, with two external and one internal tubercles.* Thus, of sixty-seven species of placental Mammalia of which the superior molars are known, all but four have three tubercles of the crown, and of the remaining sixty-five, all are triangular, except- ing those of three species of Periptychus, and three allied forms, which have a small supplementary lobe on each side of the median principal inner tubercle, f This fact is important as indicating the mode of development of the various types of superior molar teeth, on which we have not heretofore had clear light. In the first place, this type of molar exists to-day only in the insectivorous and carnivorous Marsupialia ; in the Creodonta, and the tubercular molars of such Carnivora as possess them (excepting the plantigrades). In the L^ngulates its persistence is to be found in the molars of the Coryphodontidae of the Wasatch, and Dinocerata of the Bridger Eocenes. In later epochs it is occasionally seen only in the last superior molar. It is also evident that the quadritubercular molar is derived from the tritubercular by the addition of a lobe of the inner part of a cingulum of the posterior base of the crown. Transitional states are seen in some of the Periptychidae {Anisonchiis), and in the sectorials of the Procyonidae. The tritubercular or triangular superior molar is associated with a corresponding form of the anterior part of the inferior molar. This kind of inferior molar X I have called the tubercular * See " American Naturalist," April, 1883, p. 407. f This type is tlierefore only an extension of the tritubercular. (Ed. 18S6.) X See Report G. M. Wheeler, D. Chief of Engineers on Explor. Surv. W. 100th Mer., vol. iv, pt. ii ; on the Creodonta, 360 MECHAII^ICAL EVOLUTION. sectorial, and is very variable as to the degree of development of the sectorial cutting edge. The anterior triangle is formed by the connection, by angle or crest, of the median and anterior in- ternal crests with the anterior external. Its primitive form is seen in Didelphys, Pelycodus, Pantolambda, and the Amblypoda generally ; in Centetes and Talpa ; and in its sectorial form, in Styi^olophus and Oxysena, etc. Fia, 64. — StypolopJim ivMtim Cope, sTcull two thirds natural size. A Creodont from the Wasatch Eocene, displaying well the tritubcrcular superior, and the tubercu- lar-sectorial inferior molars. The mechanical action of such teeth is as follows : Of course, it results from the form of the superior molars that the spaces be- tween them are wedge-shaped, the apex external, the base open- TRITUBERCULATE TYPE OF MOLAR TOOTH. 361 ing to the palate. The base of the triangular section of the an- terior part of the inferior molar is interior, and the apex exterior, and when the jaws are closed this triangular prism exactly fits the space between the superior molars. The lower heel of the in- ferior molar receives the impact of the crown of the superior molar. Thus the oblique edges of the inferior triangle shear on the edges of two adjacent superior molars. The anterior parts of the inferior molars, and the superior molars, form an alternate dental series as distinguished from the prevalent opposed denti- tion of most Mammalia. In so far it resembles the reptilian dentition. This primitive dentition has been modified in two directions, viz., to form the grinding and the sectorial dentitions. As already remarked, the superior molars gradually acquire a pos- terior internal lobe, which produces the quadrituberculate type. This, lobe, by opposing the anterior internal lobe of the next pos- terior inferior molar, precludes the entrance of the anterior trian- gle of the latter between the two superior molars. Hence we find in the types which possess quadri tubercular superior molars, that the anterior triangle of the inferior molar is not elevated, if pres- ent, as, for instance, in Rhinocerus. It is, however, more fre- quently atrophied, and disappears, contributing to form the in- ferior quadritubercular molar so well known. On the other hand, as I have pointed out,* the anterior internal cusp of the triangle of the inferior molar may be more developed antero-posteriorly, giving the antero-internal edge of the triangle much greater obliquity than the postero-internal. In correspondence with this modification, the superior triangular molar loses its equilateral character by the more anterior position of its internal angle, thus elongating the posterior internal side of the crown. The latter thus fits the corresponding form of the triangle of the inferior molar, forming with it the shear of the sectorial tooth. In a former article, ^^On the Homologies of the Molar Teeth," etc., I traced the modifications of the superior and many of the inferior molars of the ungulate mammals to a parent quadrituber- culate type. In a subsequent essay f I traced the origin of the * On the origin of the sectorial tooth of the Carnivora, " American Naturalist," 1875. f "Journal Academy Natural Sciences," Philadelphia, March, 18Y4. 362 MECHANICAL EVOLUTION. inferior sectorial to a primitive five-tubercled, or '^tubercular sectorial" type. Farther than this I did not go, and made no attempt to derive the few cases of triangular superior molars then known, nor the type of the superior sectorial. The revelations of the Puerco fauna show that the superior molars of both ungulate and unguiculate Mammalia have been derived from a tritubercular Fig. 65. — Deltatherium fnndaminis Cope, skull and ramus mandibuli, two thirds natural size, from the Puerco beds of New Mexico. Fitrs. a, i, c, from one individual. Fig, d^ from a second animal. Fig. a, right side of cranium ; J, palate from below ; c, mandible part, from above ; d^ left ramus, outer side. From the Eeport U. S. Geol. Surv. Terrs., vol. iii. Original. type ; and that the inferior true molars of both have been derived from a " tubercular sectorial " type. Shall we look for the origin of the latter in a tritubercular tooth also, i. e., tubercular sec- torial without heel ; and will the crowns of the true molars of the primitive mammals alternate with, instead of opjDose each other ? This is a probable result of future discovery. xiy. THE ORIGIN OF THE SPECIALIZED TEETH OF THE CARJSTIVORA. The specially developed teeth of the Carnivora are the canines and sectorials. The former are large in many orders of Mam- malia, and their origin is probably to be sought among the Thero- morphous reptilia,* as Clepsydrops and Deuterosaxirus, if not in still lower types. The successive modifications of form which have resulted in the existing sj)ecialized single lower sectorial tooth of the FelidcB have been already pointed out.f They were shown to consist in the gradual obliteration of the internal and posterior tubercles, and the enlargement of the external anterior tubercle in connection with an additional anterior tubercle. The modification in the character of the dentition, taken as a whole, was shown to consist in the reduction in the number of teeth, un- til in Felis, etc., we have almost the entire function of the molar series confined to a single large sectorial in each jaw. Observation on the movements of the jaws of Carnivora shows that they produce a shearing motion of the inferior on the su- perior teeth. This is quite distinct from the sub-horizontal movement of Ruminants, or the vertical motion of hogs and monkeys. Examination of the crowns of the sectorials shows that the inner side of the superior, and the external side of the inferior, are worn in the process of mastication. The attempt to cut the tough and stringy substances found in animal bodies is best accomplished by the shearing of the outer edge of the lower molar on the inner edge of the external tubercles of the superior molar, in an animal with simple tubercular teeth. The width of the mandible is too great to allow the inferior teeth to shear on the inner edge of the inner tubercles of the superior series. The * " American Naturalist," 1878, p. 829. f Cope, "Proceedings Academy Philada.," 1875, p. 22. PLATE XVIII. Hycenodon horridus Leidy, skull one half natural size. From the White River formation of Nebraska. From Leidy's " Extinct Mammalia of Dakota and Nebraska." ORIGIN OF SPECIALIZED TEETH OF THE CARNIVORA. 365 cusps of both superior and inferior teeth engaged in this process have developed in elevation, at the expense of those not engaged in it, viz. : the internal cusps of the same teetli. The atrophy of the latter can not have been due to friction, since the internal cusps of the inferior series, which have not been subjected to it, are reduced like those of the superior sectorial, which have. In- deed, it is possible that some of the Creodonta, the carnivores of Fig. 66. — Oxymna lupina Cope, jaws, one half natural size, from the Wasatch beds of New Mexico. Fig. a, maxillary bone with teeth, from below ; 6, last superior molar, from behind. Original ; from the Eeport U. S. G. G. Survey W. of 100th Mer., G. M. Wheeler. the Lower Eocene, may have been derived from ancestors without or with rudi mental inner cusps. In any case the effect of use in lengthening the external cusps appears to have operated in the Carnivora, as it has done to a greater degree in the Uiigidata ; and the lateral vertical wear would appear to have resulted in the blade-form, as transverse wear in the Ungulates has resulted in the plane grinding surface. The specialization of one tooth to the exclusion of others as a sectorial, appears to be due to the following causes. It is to be observed, in the first place, that when a carnivore devours a carcass, it cuts off masses with its sectorials, using them as shears. In so doing it brings the part to be divided to the angle or canthus of the soft walls of the mouth, which is at the front of the masseter muscle. At this point, the greatest amount of force is gained, since the weight is thus brought immediately to the power, which would not be the case were the sectorial situated much in front of the masseter. On the other hand the sectorial could not be situated farther back, since it would then be inac- cessible to a carcass or mass too large to be taken into the mouth. The position of the sectorial tooth being thus shown to be de- 366 MECHANICAL EVOLUTION", pendent on that of the masseter muscle, it remains to ascertain a probable cause for the relation of the latter to the dental series in modern Carnivora. Why, for instance, were not the last molars modified into sectorial teeth in these animals, as in the extinct Hycenodon, and various Creodontaf The an- swer obviously is to be found in the development of the pre- hensile character of the canine teeth. It is probable that the gape of the mouth in the Hyae- nodons was very wide, since the masseter was situated relative- ly far posteriorly. In such an animal the anterior parts of the jaws with the canines had little prehensile power, as their form and anterior direction also indicates. They doubtless snapped rather than lacerated their enemies. The same habit is seen in the existing dogs, whose long F G. 67. — rrooelurvs jalieni Filh., two thirds natural size. From tlic Phosphorites of France. From Filhol. Fig. 68. — Dinidis ajclops^ one half natural size. From John Day Miocene of Oregon. Mus. Cope. From vol. iii, U. S. Gcol. Surv. Terrs. jaws do not permit the lacerating power of the canines of the Felidce, though more effective in this respect than those of the Hycenodons. The usefulness of a lever of the third kind depends on the approximation of the power to the weight ; that is, in the ORIGIN OF SPECIALIZED TEETH OF THE CARNIYORA. 367 present case, the more anterior the position of the masseter muscle, the more effective the canine teeth. Hence it appears that the rela- tion of this muscle to the inferior dental series depended originally on the use of the canines as prehensile and lacerating organs, and that its insertion has advanced from behind forward in the history of carnivorous types. Thus it is that the only accessible molars, the fourth above and the fifth below, have become specialized as sectorials, while the fifth, sixth, and seventh have, firstly, remained tubercular as in the dogs, or, secondly, have been lost, as in hy- enas and cats. XV. ox THE ORIGIN OF THE FOOT STRUCTURES OF THE UNGULATES. The following considerations have been suggested by a study of the primitive types of the odd- and even-toed ungulates. I first, in 1874, recorded the opinion that the Mammalia with a reduced number of digits were derived from pentadactyle planti- grade types.* The ungulate order which fulfills this requirement is the Amhlypoda, and from them, I doubt not, both the Perisso- dactyla and Artiodactyla have arisen, although not from any of the genera now known. Both of these great orders display a regular diminution in the number of the digits ; in the former, by reduction and extinction on both sides of the third digit ; in the latter, by reduction and extinction on each side of the third and fourth digits. Mr. John A. Ryder f has pointed out that reduction in digits is probably directly related to strains and im- pacts. He reminds us that the anterior digits are reduced in Mammalia of unusual scansorial or fossorial powers ; while in forms which display powers of running, the reduction is seen first in the posterior feet, which j)ropel the* body much more than the fore feet. This view is well illustrated in the Perissodactyle families, the majority of which have the digital formula 4 — 3. No reason has ever been suggested, so far as I am aware, in explanation of the fact that one series of ungulates has retained two digits, and the other only one ; that is, why there should have been two kinds of digital reduction instead of one kind. In seeking for an explanation, we will remember that the tarsus in the odd or single-toed line is bound together by fixed articula- tions, while in the cloven-footed line it is interrupted by the hinge between the first (astragalus) and second rows of bones. The hinge-joint, being more liable to luxation than the fixed articula- * "Journal Academy Philadelphia," March, 1874. f "American Naturalist," October, ISY?. ORIGIN OF FOOT STRUCTURES OF THE UNGULATES. 369 tion, requires a wider basis of support, such as would be furnished by two divergent digits, rather than by a single central one. In the early types, w^here the median digits are slender, the mechanical advantage in favor of the bidigital over the undigital arrangement is much more obvious than in modern genera. Late in time, the horse developed the middle digit to such a width as to form almost as good a support as the bidigital structure. In the Eocene genera, the slender median digit could not have sus- tained the weight on a hinge, without great risk of dislocation. s Fig. 70. Fig. 71. Fig. 70. — Eight posterior foot of a species of Corypliodon from New Mexico, one half natural size. From Report Expl. W. of 100th Mer., G. M. Wheeler, iv, PI. ILx. Fig. 71. — Right posterior foot of the rhinoceros, ApJielops megalodus Cope, from Colorado, one half natural size. From Report U. S. Geol. Surv. Terrs. F. V. Hayden, iv, PI. cxxx. This explanation, it can be said, applies only to the posterior foot. The posterior foot has, however, led the way in the evolution of Ungulata, and the fore foot may have followed in accordance with the law of antero-posterior symmetry in growth. A curi- ously malformed deer from Mendocino County,' Cal., throws some light on this subject. It has apparently a single functional digit on each foot. Examination shows that the posterior foot is bi- digital, but that the phalanges are fused ; while the anterior foot 24 370 MECHANICAL EVOLUTION. is perissodactyle, all the digits but the third being rudimental ! Similar evidence is furnished by the genus Anoplotlierium * of the French Eocene. Its posterior foot is modified artiodactyle, while the anterior is modified perissodactyle. We may assume from Fig. 72. Fig. 73. Fig. 72. — Right posterior foot of ProtoTiippug sejunctus Cope, from Colorado, about one half natural size. From Eeport U. S. Geol. Surv. Terrs. F. V. Hayden, iv. Fig. 73. — Eight posterior foot of Foehrotherium labiatum Cope, from Colorado, three fifths natural size. From Hajden's Eeport, iv, PI. cxv. these facts, that the posterior foot is more subject to the influ- ences which tend to produce the bidigital structure than is the anterior limb. * Euryiherium Gerv. in the original, a name shown by Schlossev to apply to Anoplotherium. (Ed. 1886.) ORIGIN OF FOOT STRUCTURES OF THE UNGULATES. 37I I suspect that the production of a ginglymus in the middle of the tarsus has been due to the use of the posterior limb in soft swampy ground. In the absence of this condition, as in a life on harder ground than swamp, no ginglymus would be formed. The action of an ungulate in walking through deep mud is very suggestive. The posterior foot is bent on the leg, and the antero- posterior strain of the weight or propulsive force is transverse to its long axis. In progression on dry land, the impact is in the direction of the length or axis of the foot. The obvious effect of a cross strain is to produce by degrees greater and greater mobility of some articulation. The one which has yielded is that between the two tarsal rows. Another effect of walking in swampy ground is to spread the digits apart. As the first digit of both feet is always of reduced size, there are practically but four digits to be considered. The weight falling nearly medially on these, would tend to spread them equally, two on each side. Thus the same cause may have been effective in producing both the artiodactyle structures. The perissodactyle structure, so soon as the lateral digits are much reduced, ceases to be favorable for progression in soft ground, owing to the liability of the lateral digits to injury, in following the principal one into the yielding material, filled with sticks and other hard debris. The lowest existing forms of the Artiodac- tyJa, the Omnivora, are universally swamp lovers and livers. So, we are told, are the lower existing Perissodactyla, the tapirs and rhinoce- roses. The higher types of both orders are dwellers on plains and in forests. We do not know the habits of the Eocene Perissodactyla, Colorado, three fifths but I doubt their having inhabited muddy ^^a^urai size. From ground to the same extent as the hogs and hip- pf^^xT ^ ^^^° ' ^^' popotami, the lowest of the Artlodadyla. Now, in progression on dry land, any pre-existent inequality in the length of the digits would tend to become exaggerated. Such an inequality exists in the Amllypoda, the third, digit being a little the longer. In rapid movement on hard ground the longest toe receives the greatest part of the impact, even if its excess of Fig. 74.— Left fore foot with part of ra- dius of Poebrotheritim- mlso/ii Leidy, from 372 MECHAmCAL EVOLUTION". length is but little. The harder the ground, the larger the pro- portion of impact it will receive. The fact that the Perissodadyla did not develojo the solid un- gulate or equine foot until a late geological jDcriod, or, in other words, that the orders so long retained the digital formula 4 — 3, would indicate that it did not adopt a habitat wdiich required great speed as a condition of safety, so early as the Artioclactyla. XVI. ON" THE EFFECT OF IMPACTS AND STRAINS ON THE FEET OF MAMMALIA.* The principal specializations in the structure of the feet of the Mammalia may be summarized as follows : I. The reduction of the number of the toes to one in the Peris- sodadyla (horses, etc.), and two in the Artiodactyla (cloven feet). II. The second hinge-Joint in the tarsus of the Artiodactyla. III. The trochlear ridges and keels at the various movable articulations of the limbs. These are as follows : 1. Looking downward — a, Intertrochlear crests of the humerus. /?. On the carpal end of the radius. y. Metacarpals, distal ends. 6. Tibia distally. e. Metatarsals distally. 2. Looking upward — a. Radius distally. j9. Astragalus, edges. y. Astragalus distally {Artiodactyla). 6. Phalanges (very weak). The following observations may be made respecting the struct- ures included under Division III : The trochlear keels which look downward are much the most prominent and important. Those enumerated as looking upward are weak and insignificant, or of a different character from the down-looking ones. The latter are all projections from the middles of the ends of the respective ele- ments. The up-looking are generally projections of the edges of bones. Such are the lateral crests of the astragalus, and the ad- jacent edges of the cuboid and navicular bones which cause the distal emargination of the astragalus in the Artiodactyla. The * Read before the National Academy of Sciences, April, 1881, Abstract. Some of the points of this paper have already been discussed in the preceding article, but the present abstract contains additional matter. 374 MECHANICAL EVOLUTION. proximal ridges of the phalanges are very weak, and the concavities in the extremity of the radius can not be called trochlear, as they are adaptations to the carpal bones. I. The reduction in the number of toes is supposed to be due to the elongation of those which slightly exceeded the others in length, in consequence of the greater number of strains and im- pacts received by them in rapid progression, and the complement- ary loss of material available for the growth of the smaller ones. This is rendered probable from the fact that the types with re- duced digits are dwellers on dry land in both orders, and those that have more numerous digits are inhabitants of swamps and mud. In geological history it is supposed that the Perissodactyles (Figs. 72, 73) originated from the AmUypoda, or primitive Ungu- lata (Figs. 69, 70), which first assumed terrestrial habits, while the Artiodadyla (Fig. 74), originating from the same order, long continued as mud dwellers ; as witness the hippopotami and hogs of to-day. The mechanical effect of walking in the mud is to spread the toes equally on opposite sides of the middle line. This would encourage the equal development of the digits on each side of the middle line, as in the cloven-footed types. In progres- sion on hard ground, the longest toe (the third) will receive the greatest amount of shock from contact with the earth. There is every reason to believe that shocks, if not excessive, encourage gi'owth in the direction of the force applied. This is strongly suggested by the relations between the length of the legs and the rate of speed of animals ; and the lengths of the teeth and their long-continued use. Certain it is that the lengths of the bones of the feet of the Ungulate orders have a direct relation to the dry- ness of the ground they inhabit, and the possibility of speed which their habitat permits them, or necessarily imposes on them. II. The hinge between the first and second series of tarsal bones in the Artiodadyla may be accounted for by reference to the habits which are supposed to have caused the cloven-footed character. Observation on an animal of this order walking in mud, shows that there is a great strain antero-posteriorly trans- verse to the long axis of the foot, which would readily cause a gradual loosening of an articulation like that connecting the two series of tarsals in the extinct Amblypoda. Any one who has ex- amined this part of Corypliodon will see that a little additional mobility at this point w^ould soon resemble the second tarsal joint of the hogs. In the case of animals which progress on hard IMPACTS AND STRAINS ON TOE FEET OF MAMMALIA. 375 ground, no such cross-strain would be experienced, and the effect would be to consolidate by flattening the fixed articulation. III. The trochleae. These prominences, which form the tongues of the tongue and groove articulations, exhibit various degrees of development in the different Mammalia, Those of different parts of the skeleton coincide in their condition in any one type of ambulatory Mam- malia, and so may be all considered together. This fact suggests strongly that they are all due to a common cause. They are all imperfect in the Rodentia and Carnivora (Figs. 75-77) (except the Leporidce, which are especially characterized by their great speed). Among ungulates they are very imjDer- f ect in the Prohoscidea. The orders mentioned all have elastic pads on the under sides of their feet or toes. The same is true of the lowest types of both the Ar- tiodactyla and Perisso- dactyla, the hippopo- tami and rhinoceroses. In the Rumina7itia the trochleae are well de- veloped (Fig. 80) with one exception, and that is the distal metacar- pal and metatarsal keels of the Camelidm (Figs. 79, 81). These animals confirm the probability of the keels being the effect of long- continued shocks, for they are the only Euminants which have elastic pads on the in- ferior sides of their digits. That these processes may be displacements due to shocks long continued, is rendered probable by the structure of the bones themselves. (1) They project mostly in the direction of gravity. Fig. 75. Fig. 76. Fio. 78. Fig. 77. Fi^. 75, Distal extremity of tibia of Amhlyctonus sinosus Cope. Fig. 76, Distal extremity of tibia of Oxycena morsitans Cope. Both flesh-eaters, and two thirds natural size. From Eeport Expl. and Surv. W. of 100th Mer., G. M. Wheeler, iv, Pt. ii. Fig. 77, End of tibia and astragalus of Archcelurus debilis. Fig. 78^ Femnr of jyimravusffomphodus. Car- nivora ; one third natural size. Mus. Cope. 376 MECHAmCAL EVOLUTION". Constant jarring on the lower extremity of a hollow cylinder with soft (medullary) contents and flexible end walls, w^ould tend to a decurvature of both inferior and superior adjacent end walls. If the side walls are wide and resistant, the projection will be median, and will be prolonged in the direction of the flexure of the joint. The groove of the astraga- lus deepens coincidently with the increase of digitigradism, showing that, while it is primarily pro- duced by shocks, it is extended fore and aft by the repeated flex- ure of the ankle- joint. (2) They Fig. 7U. Fig. 80. Fig. 81. Fig. 79, Part of anterior foot of Procamelus occidentalis from New Mexico. Oiig- inal from Eeport of Capt. G. M. Wheeler, vol. iv, Pt. ii. Fig. 80, Metacar]~>als of Cosoryx furcatus from Nebraska, two thirds natural size, c, anterior face ; ft, posterior ; c, proximal end ; d^ distal end. Fig. 81, Left fore foot with part of radius of Poehrotherium tilsoni Leidy, from Colorado, tiiree fifths natural size. From Hajden's Eeport, iv. fit entering grooves of the proximal ends of corresponding bones. These will be the result of the same application of force and IMPACTS AND STRAINS OX THE FEET OF MAMMALIA. 377 displacement as the protrusion of tlie inferior, commencing with a concavity (Eleplias) ; becoming more concave (Fig. 77), and becoming finally a groove. (3) When the dense edge of a bone, as in the case of the lateral walls of the astragalus, is presented upward, a groove is produced in the down-looking bone ; e. g., the lateral grooves of the distal end of the tibia. (4) When the inferior bones are the denser, the superior articular face yields ; e. g., the distal end of the radius to the first row of carpals (Fig. 81). (5) The metapodial keels commence in the lower types on the posterior side of the distal extremity of the bone. This is j^artly due to the presence there of a pair of sesamoid bones which, with the tendons in which they are developed, sustain and press on the lateral parts of the extremities, and leave the middle line without support (Figs. 79-81). PART IV. METAPHYSICAL EYOLUTIOIsr. XVII. THE EVOLUTIONARY SIGNIFICANCE OF HUMAN CHARACTER.* The complicated constitution of the human mind is well im- pressed on the investigator as he seeks to understand the origin of any one of the many different types of character which come before him. The number of possible combinations of its numer- ous elements, each of which present developmental phases, is necessarily very great. The species of human minds, as one may properly term them, are probably as numerous as the species of animals, as defined by their physical structure. As in the case of anatomical species, however, analysis of the mind reduces its many details to a few leading departments. Although the classi- fication of the elements of the mind is a classification of func- tions, it is, if correct, a sure index of the classification of struct- ure also ; of the grosser and more minute structure of the brain, principally of the gray matter. The division of mental activities into three primary divisions is generally admitted. These are : the emotions, the intellect, and the will. The emotions include the likes and dislikes, or the tastes, and their strongest forms, the emotions and the passions. The intellect includes those powers which rearrange the experi- ences in an order different from that in which they enter the mind. This new order may have sole reference to questions of liking and disliking, and is then a product of the imagination ; * The present article is in continuation of the previous one on the Evolutionary Significance of Human Physiognomy, published in the "Naturalist" of June, 1883. EVOLUTIONARY SIGNIFICANCE OF HUMAN CHARACTER. 379 or it may be a result of experience of the laws of pure necessity, without regard to questions of taste ; then it is a process of rea- son. The will, properly so called, is the spontaneous power of the mind by which the other processes are originated, directed or restrained. The range of the will, and even its existence, are questions of dispute. Below and behind these mental activities lies seiisihility or consciousness, in its forms of general and special sensation ; that is, touch and hearing, taste, smell, sight, and the muscular sense, with many others, concomitants of both health and disease. It is well understood that these primitive mental qualities are more or less developed in animals in which the more purely mental func- tions are rudimental. The doctrine of evolution teaches that from this class the higher activities of the mind have been devel- oped, during long ages, through the agency of memory. The nature of the present essay only permits a casual reference to the astonishing character of memory, and the remark that its phe- nomena demonstrate most clearly, of all others, that mind is an attribute of some kind of matter. If we now consider these natural divisions of the mind as they present themselves in the combinations which we call human character, we shall observe a variety in the mode of their action which pervades all divisions alike. These variations fall under two heads, those of quantity and of quality. Thus as to quantity ; one human mind may present a greater amount of intellectual than emotional activity ; of imaginative than rational intellection ; of affectionate than irascible emotion ; of gastronomic than musical taste, etc., etc. The quantity here indicated is probably an index of the proportion of brain tissue devoted to the functions mentioned. The intensity or force of the action is a matter of quality. Of qualities the variety is much larger. They are often paral- lel to those of inorganic force, and suggest the same kind of modi- fications of the material bases as those which affect the latter. Two prominent qualities are fineness and coarseness. Fineness observes and uses detail in both rational and emotive acts, and is essential to the precision of finish. Coarseness neglects detail, but deals with the gross of things, and is sometimes accompanied by largeness of quantity. When it is not, the result is not good. Fineness is, on the other hand, often associated with smallness. It is a more feminine attribute, while coarseness is more masculine. 380 METAPHYSICAL EVOLUTIOK Another pair of antitlietic qualities are intensity of action and the reverse. This probably means that a given bulk of brain tissue produces (i. e. , converts) a greater amount of energy in a given time than an equal bulk of non-intense tissue. The speed or rate of action in time, and its opposite, slowness, are related to the last-named qualities, but are not identical with them. Thus growth of the mind always witnesses a diminution in the rate of action, but an increase in intensity. Tenacity of mental action is a very marked character, and of great importance. It signifies the persistence of mental action, or mental endurance, and may characterize the entire mind, or only a part of it. Its opposite, seen in changeability, desultori- ness or fickleness, may also characterize all or a part only of the mind. According as it characterizes the intellectual or emotional departments are its exhibitions most varied, though they probably have a common histological basis. Impressihility and stolidity express antitheses of character which are seen every day. The term impressibility is used as identical with irritability, and is preferred, because the latter has special physiological and popular meanings, some of which are only among its phases. These qualities are apt to pervade the entire mental organism, although, like others, they may char- acterize a part only. Impressibility is obviously a condition of tissue, since it varies greatly with physiological conditions in the same person. Its exhibitions in the department of the emotions may be confounded with strong development of the emotions themselves. A moment's thought, however, shows that easy ex- citation of emotion is a different thing from energy of emotion, and is often found apart from it. Impressibility of intellect shares with tenacity a leading position as an attribute of a first- class mind, and the combination of the two forms a partnership) of superior excellence. I may mention here a quality whose absence is pathological, and hence does not properly enter the field ; this is tonicity. In its normal condition, every organ should be supplied with suffi- cient nutriment or energy to insure the occupation of its entire mechanism. Anything short of this is followed by poor work. Debility of mental action in the emotional department is seen in abnormal irritability, such as peevishness or *^ spooning" ; and in the intelligence, in absence of mind and blundering; and in both, in general frivolity. EYOLUTIOXARY SIGNIFICANCE OF HUMAN CHARACTER. 381 Eeturning to the primary elements of mind, we may examine their divisions with reference to the question of growth. To be- gin with the perceptions, there are great diversities in the acute- ness of the general and special senses, and greater and less sus- ceptibilities to physical pleasure and pain. In the important representative faculty, memory, the ditferences between people are great. As perception as well as thinking involves a certain amount of structural change, it is evident that susceptibility or impressibility of the senses, which is the first stage of memory, signifies ready metamorphosis of tissue. Unimpressibility, which impedes memory, is a consequence of resistance on the part of tissue to the usual stimuli. Hence the effect of " sights, sounds, and sensations " is greatest in childhood, and the memory is most impressible, for at that time the nervous tissue is undergoing con- stant change, and nutrition, being in excess of waste, constantly \ presents new material to be organized. And I may here refer to the general truth, that consciousness of all kinds is the especial and distinguishing attribute of life as distinguished from death or no life.* Whatever other phenomena we may be accustomed to regard as "vital," are only distinguishable from inorganic motion or force, because they primitively took their form under the guidance of consciousness, and are hence, so to speak, its children. With the perfect working of most of the mechanism of the body, consciousness no longer concerns itself, although it may speedily do so in pathological conditions. This prerogative is now restricted to the nervous system, and to certain parts of it ; the one which is, histologically speaking, the most generalized of the systems. And it is quite consistent with the '^^ doctrine of the unspecialized," that nervous tissue in its unfinished state in childhood should be more impressible to stimuli than at later periods of life. But this statement requires this modification, that there is a stage of imperfection of mechanism which does not display high sensibility, as, for instance, in the earliest infancy. With age sensibility gradually diminishes. Next in order of appearance in growth are the emotions. It is true that some of these are not fully developed until long after the appearance of many or all of the intellectual faculties ; but it is also true that their full development precedes that of the intel- lect, in so far as they are developed at all. The primitive condi- * "The Origin of the Will," " Penn Monthly," 1877, p. 440. 382 METAPHYSICAL EVOLUTION. tion of the emotions is that of appetites. The first of these in the necessary physiological order, and hence in time, is the appe- tite of hunger. Second in order in the history of life, but not in the growth of individuals, is the instinct of reproduction, such as it is in animals that only multiply by fission. Very early in evo- lution the emotion of fear must have arisen, and it is probably the immediate successor of hunger in the young of most animals. Anger appears as early as the mind can appreciate resistance to its first desires, and no doubt followed as third or fourth in the history of evolution. The rudiments of parental feeling would follow the origin of reproduction at a considerable interval of time. One of the latest of the instincts to appear would be the love of power ; while later still would be the emotions of rela- tivity (Bain), because they are dependent on a degree of mental appreciation of objects. Such are admiration, surprise, and won- der. These, as well as all other consequences of inherited intel- lect, appear earlier in infancy than they did in evolution, as may be readily understood. Of these instincts and emotions, it is to be supposed that hun- ger remains much as it has ever been. The reproductive instinct ' has, on the other hand, undergone the greatest modifications. Sex instinct could not have existed prior to the origin of the male sex, which must be regarded in evolution as a derivative from the female. Hence it is probable that the parental instinct preceded the sexual in time. These two instincts being the only ones which involve interest in individuals other than self, furnish the sources of sympathy in all its benevolent aspects. Hence it has developed in man into the powerful passion of love ; into affection and charity in all their degrees and bearings. Fear be- ing, as Bain shows, largely dependent on weakness, has varied in development in all times, but must be most pronounced in ani- mals of high sensibility, other things being equal. Hence its power has, on the whole, increased until it probably reached its extreme in the monkeys or the lowest races of men. Increasing intelligence of the higher order diminishes the number of its occasions, so that it is the privilege of the highest types of men to possess but little of it. The earliest of the emotions of rela- tivity to appear in time has probably been the love of beauty ; how early it may have appeared it is difficult to imagine. Sur- prise and wonder, as distinct from fear, one can only conceive as following an advanced state of intelligence. EVOLUTIONARY SIGNIFICANCE OF HUMAN CHARACTER. 383 Thus in psychology as in physiognomy,* the palcontological order of development is somewhat different from the embryologi- cal. I might compare the two orders as follows : PAL EONTOLOGIC AL. EMDRYOLOGICAL. Hunger. Hunger. Reproduction. Fear. Fear. Anger. Anger. Beauty. Parental instinct. Wonder. Sex. Power. Power. Admiration. Beauty. Pity. Wonder. Sex. Parental instinct. The qualities enumerated in the first column follow each other directly in order from the simple to the complex. In the second column this order is disturbed by the earlier appearance of the derivative emotions, beauty, wonder, admiration, and pity, or be- nevolence, and the later appearance of the simple emotion of sex. Thus in psychological as in other evolution, some of the products of development appear earlier and earlier in life in accordance with the law of acceleration. The intelligence has already been considered under the two heads of the imagination and the reason. The action of the im- agination, unmixed with the exercise of reason, is chiefly to be seen in the creative fine arts, as distinguished from the imitative, the mechanic, and other arts. The musician, the painter, the sculptor, the poet, the novelist and the playwright, so far as they are not imitators, present the best illustrations of the work of the imagination. It is a faculty which must be very little developed in the animals below man. They occasionally make mistakes in the nature of objects, and suppose them to be other than what they are. Thus the Antilocapra supposes the Indian disguised with a skin and horns to be one of his own species, and suffers the penalty. But this is a most rudimental act of imagination, if it be not mere curiosity. The reason, properly so called, begins in its lowest grades with the simplest re-arrangement of the objects of sense and memory, in accordance with some principle of relation. As the principle or standard of relation varies, so does the intellectual process. If *" Naturalist," 1883, p. 618. 384 METAPHYSICAL EYOLUTION". the process be discovery, or the enlargement of knowledge, many experiences (or hypotheses) will be successiyely encountered and tested, and appropriate generalizations reached (inductions). If the process be to accomplish the practical ends of life by use of well-known means, the intellect uses the customary rules of action as standards, be they moral or mechanical, financial or political, and attains its deductions and applications. These two types of intellect are strikingly distinct, and produce the most diverse con- sequences. The inductive type is the most generalized, and hence callable of the largest growth and adaptability, and the widest range of thought. The deductive is the more specialized, the more ^^ practical," but less capable of growth or general thought. Its most remarkable exhibitions are seen in the skill with which some men conduct the game of chess, and corresponding enter- prises in real life. Also the ingenuity of mechanical invention, and the wonderful rapidity of calculation which some minds dis- play. In intellectual as in many other vital phenomena, the facil- ity once developed, the active process is often unaccompanied by consciousness in many or even all of its stages. Rapid and exact control of the muscles in obeying the direc- tions of the mind is essential to the practice of many arts, espe- cially to that of the musician. This accomplishment is acquired through the medium of the conscious mind, and may be regarded simply as the reflex of impressions made on the senses directed by some simple rule which has been impressed on the memory. The often surprising results involve the exercise of a very simj^le phase of intellection. The appearance of the rational faculties in time, may be esti- mated by their relative development in the existing divisions of animals whose period of origin is known or inferred. The ani- mal mind is capable of simple forms of induction and deduction, and sometimes acquires considerable artistic skill. Bees, ants and spiders display these in varying degrees, and their antiquity is probably co-extensive with that of the known sedimentary rocks. The supposed Ascidian ancestors of the Vertebrata, and even the lowest vertebrate (Branchiostoma), display far less intelligence than the articulates mentioned, which are really lower in the scale of organic types. From such unpromising sources did the noble verte- brate line descend. It is probable that the inductive act preceded by a little the deductive in time, as it does in logical order. But the elaboration of these powers was doubtless long delayed ; for EVOLUTIONARY SIGNIFICANCE OF HUMAN CIIxVRACTER. 385 untold ages they involved nothing more than the discovery and application of general principles of the simplest kind ; such as the customary sequence of natural phenomena, and the anticipation of their operations, as, for instance, in the laying up of winter provisions. Occasionally deductive application of an old rule to a new case would arise, as in that of the Mygale spider which was observed by Dr. McCook to substitute cotton for her own silk for the lining of her nest. The development of the rational faculty has been rather in quantity and quality, than in the nature of its constituent parts. I may remark, however, that the embryological order is here again different from the paleontological. Inherited aptitudes, as for music, calculation, etc., precede, in children, any considerable powers of thought, while the order of development of the race has been the reverse. As regards the appearance of the qualities of mind already mentioned, which depend on character of tissue, it is difficult to present an order which shall be generally true. Our ignorance of the subject is profound ; nevertheless observation of animals and men leads to the following conclusions : First, the primitive mind is negative, unimpressible, and little sensitive. In evolution, sensibility has been developed under stimuli, and diminished by disuse and repose. The energy of high-strung sensibility has prob- ably ever won for its possessors success in the struggle for existence, and more or less immunity from the pains which stimulate to ac tion.* It is true that the non-aggressive and ever-harassed Her- bivora have developed the higher brain structure. The inferiority of brain type of the Carnivora is a well-known fact of present and past time. The early ruminants were smaller than the contempo- rary flesh-eaters, and therefore subject to the greatest risks. The best-developed brains, those of the Quadrumana, have been devel- oped in still more defenseless animals, who in their arboreal life have been confronted by still more complex conditions.! Impressibility or sensitiveness has evidently been the means of acquisition of some of the other qualities mentioned. Thus inten- sity may have resulted from active use accompanied by vigorous nutrition, and the consequent construction of compact force-con- verting tissue. Rapidity without intensity must also result from * " The Relation of Man to the Tertiary Mammalia," "Penn Monthly," 1875. f Mr. C. Morris very reasonably regards the social life of these animals as the source of their development of intelligence. See "American Naturalist," June, 1886. (Ed. 1886.) 25 386 METAPHYSICAL EVOLUTION. exercise, with a less yigorous construction of tissue. Fineness and tenacity, on the other hand, can not be regarded as being so much produced by use as by very primitive conditions of tissue. Ee- straint under ]3ressure might produce fineness. Long-continued freedom from sudden changes, under pressure, might account for the origin of tenacious tissue. As to quantity, deficiency or diver- sion of nutritive energy or material must produce smallness, and the reverse condition, largeness. These qualities impress themselves on the external as well as the internal organization, and can be more or less successfully dis- cerned by the observer. I reserve the question of physiognomy to a later article, and here consider only the evolutionary bearings of character itself. As in physiognomy, we may arrange the facul- ties and their qualities under the two heads of ancestral and embry- onic, or that of the species and that of the individual. The order of succession is the same in both kinds of development. SPECIES. INDIVIDUAL. Indifference. . Indifference. Einotions. Emotions. Intellect. Intellect. a. Imagination. a. Imagination. b. Reason. b. Beaso7i. It is not practicable to go farther than this into the order of evolution of characteristics. There is probably little uniformity of sequence other than that I have already pointed out under the head of the emotions. As a complex outcome of the emotional and rational faculties must be now mentioned the moral sense, or the sense of justice. It consists of two elements, the emotion henevolence, and the ra- tional power of discrimination or judgment. The former fur- nishes the desire to do what is right to a fellow-being. Without the aid of reason, it is benevolence, not justice, and may often fail of its object. The rational element has acquired from experience a generalization, the law of right. It perceives what is most con- ducive to the best interest of the object of benevolence in his rela- tion to others or to society, or whether he be a proper object of benevolence at all. By itself, this quality is absolutely useless to mankind. When it guides the action of human symj^athy, it dis- plays itself as the most noble of human attributes. Many animals display sympathy and benevolence, but justice has not yet been observed in anv of them. Hence it has been said that it can not EVOLUTIONARY SIGNIFICANCE OF HUMAN CHARACTER. 387 be a derivative faculty, but is '^intuitive" in man. The objec- tion to this view is its great variability and occasional entire ab- sence in man, individually and racially. It is the last to appear in individual growth, as it has doubtless been in the order of evo- lution, of mind. I now devote a little space to the discussion of the distribution of these qualities in races and sexes. As regards the relative preponderance in action of the emotive and intellectual faculties, it is an axiom that in the great majority of mankind, apart from the necessities imposed by the simple physical instincts, it is a taste or an affection or an emotion that lies at the basis of their activities. Perhaps the most universal is the affection of sex. Given two types of rational beings who are objects of admiration and of pleasure to each other, each of whom desires to possess the other, and who therefore employs many de- vices to please and attract the other, and we have an effective agent of general development. Then the parental, and especially the maternal, affections arouse and direct many labors. Fear of suf- fering and death is at the basis of many others. The love of power or of possession, including ambition, is a well-known stimulus. The love of beauty is a strong motive in many persons. The pleasure derived from the exercise of the intelligence is a sufficient motive for a life-work in a comparatively small number of persons. These are the artists and the scientists ; but it is far from being an unmixed motive in many of them. Intellectual motives, however, enter into association with the affectional in many instances, as, for example, in the profession of teaching. But it is as guide and agent in the accomplishment of the main ends of life that the intellect, especially the reason, has its great field, and displays itself in an endless variety of ways. If we now survey men as we find them, it is a general truth that it is in the male sex that the greatest proportion of rational method is to be found, and in the female the greatest proportion of the affectional and emotional. As we descend the scale of humanity, the energy and amount of the rational element grows less and less, while the affectional elements change their propor- tions. The benevolent and sex elements diminish in force more rapidly than the other sentiments, but it is probable that all the emotions are less active in savages, excepting those of power and of fear. In the lowest races there is a general deficiency of the emotional qualities, excepting fear, a condition which resembles 388 METAPHYSICAL EVOLUTION. one of the stages of childhood of the most perfect humanity. To this must be added revenge, where hatred may be re-enforced by several other sentiments, with a feeble perception of equivalent suffering or punishment, which may or may not be just. The pleasure of muscular exercise is greatly developed in people of out- door habits. The order of the appearance of the intelligence is nearly de- pendent on the development of the powers of observation. In most savages these are very acute, and vary according to the na- ture of the environment which impresses them. The character of most civilizations tends to diminish the power of the ]3ercep- tive, while the higher departments of imagination and reason are enlarged. The imagination reached a high development before reason had attained much strength. With the exception of a few families, the intelligence of mankind has, up to within two or three centuries, expressed itself in works of the imagination. When exact knowledge first began to be cultivated, it was in the department of astronomy, where the least precision was attain- able, and where the greatest scope for the imagination is to be found.* Next in time metaphysics was the throne of learning, a field in which much may be said with the least possible reference to the facts of observation. With the modern cultivation of the natural and physical sciences, the perceptive faculties will be restored, it is to be hojoed, to their true place, and thus many avenues opened up for the higher thought-power of a developed race. Thus it is that in the order of human development there is to be a return to the primitive powers of observation, without loss of the later acquired and more noble capacities of the intellect. The relation of the qualities of impressibility, fineness, inten- sity, speed and tenacity, to our development in time, may have been as follows : Impressibility of mind is no doubt an embryonic character of ^' retardation," parallel to, and probably a consequence of, the retardation which is also expressed in the human skull and face. The preponderance of the osseous and nutritive elements over the nervous is the usual accompaniment of non-impressi- bility, and vice versa. Hence this quality is of late origin in the * The governments of antiquity required the knowledge of the Chaldean astrono- mers as important to the success of their undertakings, and the governments of Europe and America were, for a long period, more liberal in their support of as- tronomy than any other science. At present, however, geology shares in this aid, and to a less degree botany and zoology. EVOLUTION"ARY SIGNIFICANCE OF HUMAN CHARACTER. 389 history of the Vertebrata and of man, and is most developed in the young, and better developed in women than in men. Tenacity has an opposite significance, being an especial charac- teristic of maturity in the human mind. Hence it may have been more general in early ages than at present, but could have little value so long as the mind remained small in quantity. Curiously, it is a quality which may co-exist with a good deal of impressibility. Fineness can only be a quality of full development, and is totally independent of the other qualities. It is unknown among savages, and is developed apj)arently in a few animals. Of inten- sity it is difficult to say much definitely. The nervous operations of animals often display the highest degree of this quality, and it is not unlikely that its appearances differ as much in savages as in civilized people. Its importance in mental action depends of course on the kind and amount of mental function which exhibits it. The same may be said of speed. The faculties which exist are more or less affected by it. In the well -formed reason it is an important characteristic, and a special form of development. Having gone as far into the origin and developmental relation of mental functions and qualities as the nature of this sketch jier- mits, I refer briefly to the stimulus to their growth ; always re- membering that the percentage of inherited qualities is much larger in a given character than that of acquired ones. On this head one word expresses a good deal, and that word is use. No truth is better known than this one, that mental faculties develop with use more rapidly than those of any other organ of the human body. Brain and nerve are apparently the most plastic of all tis- sues ; the one which retains the properties of the primitive pro- toplasm, multiplied and intensified a thousand fold. It has al- ways been the seat of creation, throwing off its " formed matter " in useful directions. It is still doing so ; and in the human brain, ever creating itself, is in addition the seat of a new creation, which it executes through its instruments, the other organs of the body. Hence the greatest sin against the brain is idleness, or disuse. The brain activity of to-day is an indication of health and happiness beyond what the world has seen hitherto. The greatest stimulus to exercise of the brain is human soci- ety. Hence the greatest developments of mind have always been in the centers of population. Whatever may be the passive vir- tues of country life, it is the cities that furnish both the stimulus and the field for the triumphs of mind. y XVIIL CONSCIOUSNESS IN EVOLUTION.* I. PRELIMIKAKY. The evidence of what is termed ^^ design " in the structure of beings exhibiting life, is often appealed to by one class of think- ers, as proving the intervention of a personal Deity in the crea- tion of such ; and the same feature exhibited in the movements of living creatures is regarded by metaphysicians of a similar class as an indication of their possession of a power of choice, or " free agency," at least in the case of man. The opposing school, of whom Professor Bain may be selected as an example, believes that designed acts are without an element of freedom, but are simply performed in obedience to stimuli of various kinds, motion fol- lowing stimulus as inevitably as effect succeeds cause in the non- living world. The evolutionists attempt to explain design in structure through the operation of the Darwinian law of the *^ survival of the fittest," showing that only those beings whose organization displays that adaptation to use in relation to its sur- roundings, which is termed '^design," could possibly continue to exist. It is justly urged against this reasoning that it attempts no explanation of the origin of such structures. Another school of evolutionists have therefore maintained that such structures are due to the effect of effort, i. e., stimulus or use, exerted by the living being on its own body, and that the design thus displayed is an expression of the intelligence at some time possessed by itself. So long as there is any probability of the last explanation proving valid, it will be important to examine into the questions of metaphysics which it necessarily involves. The investigation is indeed but the necessary projection of those which have re- sulted in satisfying the great majority of biologists of the reality of evolution, or of the fact of the descent of existing living beings, * A lecture delivered before the Franklin Institute, Philadelphia, February, 1874. CONSCIOUSNESS IN" EVOLUTION. 391 species by species, order by order, and class by class, from others which have preceded them in time. Clearly, then, we enter the question by considering the nature of movements of plants and animals in relation to the stimuli which are supposed to call them forth. II. THE UNCONSCIOUS. A true study of metaphysics necessarily has for its objects plants, animals, idiots, and infants, as well as healthy men ; never- theless, necessity compels us, in discussing the question, to dwell on our own experiences as a sine qua non. Now experience, in a general sense, includes not only the memory of our conscious acts, but a knowledge of our unconscious ones, and to the latter espe- cial attention must be directed, since they are most readily over- looked. The marvelous character of memory can not be too much considered. Of the millions of impressions which the mind has received and registered, in the course of a lifetime, but one can be clearly present in consciousness at one time. The remain- ing millions are not lost ; they are stored, each in its apj^ropriate place, to be sprung into consciousness when the apj)ropriate suggestion presents. How much more vast, from this point of view, is the unconscious mind than the conscious ! But the phenomenon is not confined to memory. Who that has ever at- tempted the digestion of a subject which includes a mass of de- tails, is not acquainted with the unconscious activity of the mind in classification ? How frequently a question involving many parts, is, on the first reception of the constituent facts, all con- fusion ; but in time displays its symmetry clearly to the con- sciousness, every part in its proper place, and that with little or no further attention having been devoted to it. It is indeed proba- ble that the every-day process of inductive reasoning is conducted in unconsciousness on the part of the subject. Induction con- sists in the generalization of some quality as common to a great number of objects of memory ; a greater or smaller number of other qualities being neglected in the process. When this act is performed voluntarily, one or many qualities are successively passed in review before the mind — each one being in its turn im- pressed on the perceptive centers — so long as it is the object of inquiry, the others being excluded from consciousness for the time being. It is simply a process of classification, and when per- formed in consciousness, constitutes "experiment." But when 392 METAPHYSICAL EVOLUTION". no generality is anticipated, and its existence is unknown, it often hajjpens that sucli generalization becomes known or rises into con- sciousness, without the bestowal of effort in classification of the objects to which it refers. The impressions consciously received have been arranged out of consciousness, and when revived into consciousness display an order wliich was not previously known to exist. It is in the latter way that the '^23ractical man " "finds out " the rules by which, as by an instinct, he regulates his inter- course with the world. He often can not explain the reasons of their truth, nor does he know how he came by them, being gen- erally content to call them the results of ^' experience." In some persons they are so feebly expressed in consciousness as to be called *' feelings" ; and many experiences or repetitions are sometimes necessary to impress on us the importance of these mental prod- ucts before we are willing to follow them in action. '^ Strength of mind " is an expression applied to a high degree of this uncon- scious reasoning ; expressing the extent of ground the process covers continuously, as well as the exactitude of its results. The experimental investigator, on the other hand, performs this work deliberately, and is acquainted with the processes ; he is, there- fore, at first more confident of his results. And we observe here, in passing, that a rule once discovered is as readily retained in the cells of the unconscious as is the memory of a simple object or event. Another form of unconscious cerebration is seen in deductive reasoning, which employs rules already discovered in application to new cases. Calculating prodigies are a case in point. It is well known that those persons who have from time to time ap- peared possessed of the power of calculating with enormous num- bers with marvelous rapidity, have never been able to explain the process by which they reach their conclusion, nor are they con- scious of going through the steps involved in the calculation they perform ; and it has been said that great calculators have rarely been great mathematicians. The explanation of these phenomena is not far to seek. In simpler forms it is presented to us every day. Thus it is an easy matter to read with but little consciousness of the process, and no recollection of the subject-matter of what is read. Most manual operations can be performed while the consciousness is occupied with other objects. If these be facts of human experience, how much more likely CONSCIOUSNESS IN EVOLUTION. 393 are they to be true of animals ? If man be unconscious of the process during the performance of some of his most complex acts, how much more probable is it that animals are so while pursuing the narrower circle of their simpler ones ? Yet animals are not devoid of consciousness ; indeed, it is scarcely credible that any one should deny to them consciousness, after exjoerience in their education. But let these automatic acts be ever so simple or complex, it is here claimed that they could not have origmated out of conscious- ness. Whatever we call voluntary acts in ourselves undoubtedly have to be learned. The acquisition of the primary act of walking is accomplished by a slow and painful education ; while knitting and other manual exercises necessarily require preliminary train- ing, some of shorter, others of longer, duration. This is true of such voluntary acts as we perform most readily automaticall}^, and such as might be supposed to be most probably acquired by heredi- tary transmission, as for instance speaking. The case is the same with animals. All those services which are useful to us, or tricks which amuse us, are acquired at the expense of training, which involves a system of stimuli, consisting of rewards and punish- ments, as in our own species. Is there any reason to suppose that those habits which we observe them to possess in a state of nature have had a different origin ? It is incontrovertible that a regular succession of muscular movements may be committed to memory as certainly as a color or a shape, and that a change of brain substance, such as causes the retention of the simple impression, is also involved in the retention of the complex. When this machinery is completed, through the repetition of conscious stimulus, it works thenceforth without necessary intervention of consciousness. The conscious- ness may then be engaged in fresh acquisitions, accomplishing new organizations, thus accumulating a store of powers. Once organ- ized, these powers are at the disposal of their possessor, yet the organized machine will at some time undergo change, if not more or less frequently used. Without use it may indeed finally disap- pear, showing that the caj)acity for organization is identical with a facility of disorganization. III. THE ORIGII^ OF AUTOMATIC MOYEMEJ^TS. Is any habit originated in unconsciousness ? Those who affirm this proposition point to the movements of plants in the extension 394 METAPHYSICAL EVOLUTION. of their tendrils, and the closing of some sensitive leaves ; the timely expansion of the down of the Asclepias seed, and the in- sect-catchinof habits of Brosera and Dioncea. No one surely attributes consciousness to these. And there are many similar movements in animals which are as thoroughly unconsciously performed as are those of plants, from the first moment of the ani- mal's birth : as, for instance, the involuntary activities of the cir- culatory and digestive systems, etc. Did these originate in con- sciousness or unconsciousness ? The answer to this question constitutes the key to the mysteries of evolution, and around it the battle of the evolutionists of the coming years will be fought. It may be asserted at the outset that those habits whose origin we have had the opportunity of observing in ourselves and in other animals were certainly acquired in consciousness, and that we do not believe that they could have originated out of it. The stimuli to action are divided into the two general classes of pleasures and pains, and each stimulus is potent in proportion to the intensity with which it is consciously apprehended. If many and complex acts may be performed automatically, through the organization of special machinery in the gray matter of the brain, it is altogether reasonable that similar powers should be found to be conferred on gray nervous tissues in parts of the body which are no longer seats of consciousness. It is well known that the spinal cord of the head- less frog responds to stimuli, in the vigorous muscular contractions of the limbs which follow the application of acid to the skin. So the ganglionic centers of organic life respond to their appropriate excitants ; the various glands of the digestive system discharging their contents into the ingesta at the proper moment, conscious- ness having no share in the proceeding. These phenomena are more readily explained on the theory of endowment than on that of physical movements ; since by means of the former the evident design in the movements is accounted for, while the latter gives us no clew to this characteristic feature of these and all other vital processes. The lowest form of consciousness is common sensibility ; and, judging by the resemblance between our own experience and that of the higher animals, the lowest of animals also are not devoid of this quality. The structureless jelly of Rhizopods, such as Amoebas, Gromias, etc., evidently selects its food with regard to its nutritious qualities, in most instances preferring diatoms and desmids to sand and other innutritions substances. Its acquisi- CONSCIOUSNESS IN EVOLUTION. 395 'o tions in knowledge of articles of food can only be accounted for on the hypothesis of original, pleasurable or painful, conscious- ness of the effects of external and internal contact with these sub- stances, and retention of the impression in unconsciousness. The impression reviving on the recurring of a similar contact, the sub- stance is accepted or rejected as the former sensations were pleas- urable or painful. And this is not incredible, if, as the researches indicate, the structure of the protoplasm of these creatures is of the same type as that of the bioplastic bodies of the gray tissue of the brain. in accordance with this view, the automatic *^ involuntary " movements of the heart, intestines, reproductive systems, etc., were organized in successive states of consciousness, which con- ferred rhythmic movements, whose results varied with the ma- chinery already existing and the material at hand for use. It is not inconceivable that circulation may have been established by the suffering produced by an overloaded stomach demanding dis- tribution of its contents. The structure of the Coelenterata offers the structural conditions of such a process. A want of j^ropul- sion in a stomach or body sack occupied with its own functions would lead to a painful clogging of the flow of its products, and the *' voluntary" contractility of the body or tube-wall being thus stimulated, would at some point originate the pulsation necessary to relieve the tension. Thus might have originated the " con- tractile vesicle" of some protozoa, or contractile tube of some higher animals ; its ultimate product being the mammalian heart. So with reproduction. Perhaps an excess of assimilation in well- fed individuals of the first animals led to the discovery that self- division constituted a relief from the oppression of too great bulk. With the increasing specialization of form, this process would be- come necessarily localized in the body, and growth would repeat such resulting structure in descent, as readily as any of tlie other structural peculiarities. No function bears the mark of conscious origin more than this one, as consciousness is still one of the con- ditions of its performance. While less completely "voluntary" than muscular action, it is more dependent on stimulus for its initial movements, and does not in these display the unconscious automatism characteristic of the muscular acts of many other functions. Bearing in mind the property of protoplasm to organize ma- chinery which shall work automatically in the absence of con- 396 METAPHYSICAL EVOLUTION. sciousness, we can glance at the succession of vegetable forms. The active movements of the primary stages of the x^lgae are well known. After swimming actively through the water, they settle down, take root, and assume the role of plants. The Aethalium, swimming with the movements of a Rhizopod, has been known to take food before establishing itself on the damp piles of the tan- bark, where it speedily becomes a low form of fungus. The ap- proximation of the lower forms of plants to animals is notorious. The fungi, it is said, are the only terrestrial j)lants which live like animals on organic matter, appropriating the humus of their rich nidus in a state of solution. ISTow the paleontology of animals has absolutely established the fact that the predecessors of all charac- teristic or sioecialized ty|3es have been unspecialized or generalized types, '' neither one thing nor another." It may then be regarded as almost certain that the ancestors of the present higher types of plants were more animal-like than they ; that the forms dis- playing automatic movements were more numerous, and the diffi- culty of deciding on the vegetable or animal nature of a living organism greater than it is now. Hence it may be concluded that *^ animal" consciousness has from time to time organized its ma- chinery and then disappeared forever, leaving as result the per- manent form of life which we call vegetable. But it is not to be supposed that all changes of structure cease with the departure of consciousness. Given spontaneous movement (i. e., growth), and surrounding conditions, and the resultant product must be struct- ures adapted to their surroundings, just as the plastic clay is fitted to its mold. And this is essentially the distinguishing character of vegetable teleology as compared with animal. In the average plant we see adaptation to the conditions of unconscious nutrition ; in the animal, adaptation to conditions of conscious contact with the world under a great variety of conditions. IT. GROWTH-FORCE. The active processes of living beings are examples of conversion of physical forces, only differing from the conversions observed to take place in inorganic bodies, in the nature of the machinery which exhibits them. The construction of this machinerv, as in its use when finished, involves a conversion of force, the resultant consisting of the attraction of nutritious material in definite new directions. This determinate attraction has been regarded as a distinct force, to which the name of bathmic or growth force has CONSCIOUSNESS IN EVOLUTION. 397 been ap2)lied. It differs from all the physical forces in this, that while they are only exerted inversely as the square of the distance, this one is in addition most excessive where pleasure has been ex- perienced, and weakest where pain has left its deepest traces. In other words, its movements express design, the essential condition of which is consciousness. It is thus evident that it differs utterly from all other forces, although a retrograde metamorphosis of mat- ter is as necessary for its production as for that of any of the other forces. Now, although the evidences that stimulated consciousness, or if you choose, mind, can modify structure, are, as matter of observation, not very satisfactory ; yet, since the essential 2:)ecul- iarity of growth-force is its instant attendance on the needs of consciousness, it is a permissible hypothesis that its activity is immediately due to consciousness. This activity is located in bioplasts which do not exhibit consciousness ; whetlier it co-exists with consciousness in brain bioplasts is unknown. The successive exhibitions of this force, from the low^est to the highest of living beings, have ever been additions to the executive machinery of a more and more specialized consciousness. Thus it is that its re- sults in structure have ever become more and more complex, that is, composed of an ever-increasing number of parts in some region of the organism. Hence another point of distinction from other forces exists, which has been pointed out in a previous paper. It is quite evident that the higher forms of life are the result of con- tinued superaddition of one result of growth-force on another, some examples of subtraction or simplification of i^arts being gen- erally accompanied by a great preponderance of additions. This is evidence of the accumulation of the property of producing this kind of force, since each successive addition imposes on the grow- ing animals a great number of successive stages before the process reaches its termination, maturity. This involves the belief that the property of exhibiting frequent *' repetitions" of growth-ac- tivity exists in a higher degree in the reproductive bioplasm of the more complex animal than in that of the lower ones. This is in accordance with the fact of the regular increase in relative com- plexity and bulk of the nervous system, which accompanies com- plexity of structure in other respects in the ascending scale of ani- mals. Thus this force differs from all others, as remarked by Prof. Hartshorne, in that its expenditure ultimately increases the amount of its production, because it constructs machinery which feeds its especial organs more and more successfully. Although expended 398 METAPHYSICAL EVOLUTION. by becoming energetic, its energy produces the means of its own increase. Unlike the physical forces whose expenditure renders matter ever more inert, growth-force when expended adds mate- rial which, as a profitable addition, increases the power of the cen- tral machine from which the force emanates, by furnishing an in- creased supply of food.* Thus it is evident that growth-force is not concentric nor j)olar in its activity, as are the physical forces, and that its determina- tions are antagonistic to these. Its existence in the earth has been a succession of conquests over polar force, and, if preceding assumj^tions be true, the gradual progress presented by animals in abandoning the symmetrical forms exhibited by the lower types has doubtless been due to the constantly increasing amount of consciousness. V. THE DOCTRINE OF THE UXSPECIALIZED. It is, however, evident that the directing power of conscious- ness is limited by the nature of the matter with which it has to deal. There are certain fundamental necessities to which it must conform. No one supposes that any degree of power can make twice two equal to six, cause two solid substances to occupy the same space at the same time, or make an absolutely solid sub- stance out of incompressible atoms of different forms. These in- volve the absurdity that something can be made out of nothing, or nothing out of something. From the present conduct of the inorganic world, it would appear to possess properties which ren- der consciousness impossible to it. This is doubtless due to the relations existing between the atoms or molecules of which its various species consist. The movements it displays are polar. The colloid molecular state is, so far as this planet is concerned, the only one which we know to be capable of consciousness, and then only while in a state of active transformation. As we have seen, when protoplasm is once organized and working automati- cally, consciousness need not be present ; and when this is absent, the rate of transformation, that is, the amount of food consumed, is greatly lessened. The excess of expenditure during conscious * It is incorrect to say that growth-force is "potential" in highly organized- types, as it is undoubtedly expended in the movement of nutritive pabulum to a given locality. The maintenance of it in that locality is due to ordinary molecular cohesion, which can only be set free by greater molecular consolidation. CONSCIOUSNESS IN EVOLUTION. 399 activity over that necessary to unconscious activity is well known. It is thus evident that organization renders consciousness unne- cessary, GO long as external conditions are unchanged, and most probably a degree of fixity may be attained which renders con- sciousness impossible. The history of the evolution of animal types is apparently an illustration of this truth. The relations of the divisions of the animal kingdom are those of the limbs, branches, and trunk of a tree. Although the termini of the branches are successively nearer the root or starting-point as we proceed from the apex downward or backward, yet the connec- tion is not from end to end of these. To find this we pass down the limb to its junction with the trunk, and trace the branches from the axis outward. Thus with the branches of the animal kingdom. Although the divisions Vertebrata, Mollusca, Echino- dermata, etc., stand in an undoubted relation of succession to each other, there is no connection between the highest representa- tive of one and the lowest of another. It is the lower or less specialized forms of each which exhibit the relationship. Thus, among the articulates, the low group of the worms gives us con- nection with the Mollusca above by BracMopoda, and the echino- derms connect themselves with the Vermes by the less specialized Holothurida. It seems highly probable also that the point of con- tact of the Vertebrata with these is by one of the lowest divisions, formerly regarded as molluscan, viz.: the Ascidia. The same principle holds good within the great divisions. The most spe- cialized orders of Mammalia are the Artiodactyla, higher Perisso- dactrjla, the Carnivora, Quadrumana, and perhaps Cetacea ; but the higher of these have not been derived from the lower. Mod- ern investigations show that several of them have been derived from a common type of mammals of the Eocene period, wiiich is intimately connected with their lower forms, while wanting in the features which give them their special characters. These two illustrations serve to explain the universal law of zoological affin- ity, and therefore of evolution. The conclusion derived from a survey of this field is, that structure, like habit, when once established, is closely adhered to, and that the movement of growth-force once determined or or- ganized becomes automatic, i. e., independent of consciousness. Therefore a type which reproduces itself automatically becomes after a time so established as to be incapable of radical change, in consequence of a molecular fixity which precludes it. Neverthe- 400 METAPHYSICAL EVOLUTION". less susceptibility to influences of conscious stimuli may remain in some j)ortions of the organism, and thus subordinate modifica- tions of structure have their origin. When conditions of life change, as they often have done during geologic time, those changes of structure which are possible take place under the stimulus of roused consciousness. But if the changes be radical, affecting the foundation processes of vital economy, the specialized forms must undoubtedly perish, and the life of the succeeding time be derived from forms of less pronounced character. The adaptability of generalized types, as to habits, and the absence of mechanical peculiarities in their structure, explain fully the cause of their standing in ancestral relation to all the typical faunse of the earth. Nowhere is this truth more remarkably illustrated than in the case of man, the predominant mammal of the present period. From the generalized mammalian fauna of the Eocene, the Car- nivora developed a highly organized apparatus for the destruction of life and appropriation of living beings as food. The cloven- footed and odd- toed hoofed orders * are the result of constantly increasing growth of the mechanical apjDliances for rapid motion over the ground ; the former superadding exceptional powers of assimilation of innutritions food. The proboscidians developed huge bulk and an extraordinary prehensile organ. The Quadru- mana produced none of these things. In respect to speed of limb and powers of digestion, both in function and structure, they re- main nearly in the generalized condition from which the other orders of mammals have risen. The limbs and teeth of man re- tain the characters of the primitive type. Yet but two species of proboscidians remain ; the Perissodactyle multitudes are repre- sented by but a few vanishing species. The day of the Car- nivora has passed forever, and the remaining Artiodactyle herds exist but by the permission of their master, man. But past geo- logic time reveals no such abundance of true Quadrumana as the present period displays. These animals were evidently unable to compete with those of other types in seizing on the opjjortuni- ties of livino^. Thev were excluded from the chase bv the more sanguinary ancestors of the Carnivora, and from the field by the multiplying herds of the swifter or more resistant hoofed animals. They possessed neither bulk, nor speed, nor cruelty to serve them * Represented by the ox and the horse. CONSCIOUSNESS IN EVOLUTION. 40I in the struggle for existence. So they, were doubtless compelled to assume an arboreal life, which required little or no modifica- tion of the limbs for its maintenance, although the ultimate pro- duction of the grasping thumb from their primitive squirrel-like feet may be traced to this mode of life. The acquisition of a hand must be regarded as the first step in that marvelous acces- sion of experiences which is the condition of mental develoj)ment. And this latter growth has taken the place of all other means of conquering a position in the world of life, so that man has even retrograded in the efficiency of bodily powers. He has lost the prehensile quality of the hind feet, and the special usefulness of his canine teeth. But the competition among men continues to be such as to render it in the highest degree improbable that he will, as a species, lose the position gained, or suffer any prolonged diminution of the power of intelligence. Now it is obvious that the more restricted the conditions of the life of a given animal type, the more sensitive it will be to changes. Hence it is that the risks to the existence of Carnivora, Artiodac- tyla, Prohoscidia, etc., are much greater than to the omnivorous, all-adaptive order of Quadrwnana. The same is true of mind. The greater the proportion of unconscious automatism of habits, the less the power of adaptation ; and this must be the condition of all animals whose structure is so specialized as to place them beyond reach of competition, or to cut them off from a wide range of experiences. The greater the degree of consciousness of stim- ulus, the greater will be the degree of adaptability to new rela- tions, and to such constant rousing the unspecialized mind is always open. If, without strong natural weapons, vigilance is the price of existence ; if not confined by organization to a peculiar kind of food, ceaseless investigation is stimulated. And these are the mental peculiarities which distinguish the monkeys among all the Mammalia. The reverse of this picture may now be described, as has been done by Prof. Vogt. It is well known that the young of many parasitic animals are free and active, and discover during migra- tion the localities to which they afterward attach themselves for life. During the early stages they present the characteristic marks of their order and class, and in some instances the males, remain- ing free, continue to do so. Such are the Entoconclia miraMUs, the SaccidincB and the Trematoda ; the first a mollusk, the second a cirrhiped crustacean, the third a worm. On their becoming at- 26 402 METAPHYSICAL EVOLUTION". tached to their host a successive obliteration of their distinctive characters takes place, so that they become so simplified as to be no longer referable to their proper class, but susceptible, as Prof. Vogt remarks, of being united in a single division. A similar process is observed in the structural degeneration of the Lernean parasites, which are at first free, but afterward become parasitic on fishes. There is in this instance a coincidence between degen- eracy of structure and loss of compulsory activity : not only is every function of their sluggish lives automatically performed, but consciousness itself must experience little stimulus. From what has preceded, it is evident that automatism is at once the product and the antagonist of evolution, and that it is represented in structure by specialization. It appears also that consciousness is the condition of the inauguration of new habits, and this is only possible to structures which are not already too far specialized. This is doubtless true, whether osseous and mus- cular tissue be concerned in evolution, or whether it be nervous and brain tissue. Hence in the highest form of development, that of brain mechanism, automatism is the enemy, and con- sciousness the condition of progress. As a product of develop- ment, automatism is the condition of stationary existence, and constitutes its effective machinery, but every additional step re- quires the presence of consciousness. This may be expressed in the every-day language of human affairs, by saying that routine and progress are the opposite poles of social economy. YI. THE OKIGIiq" OF COKSCIOUSKESS. This question has not yet been touched upon, nor is it neces- sary to give it prolonged attention at present. Consciousness is in itself inscrutable to us, and the contrast which it presents to physical and vital forces is the great fact of life. It is obvious enough that certain molecular conditions are essential to its ap- pearance ; drugs intensify or obscure it ; concussions and lesions destroy it. It will doubtless become jDOssible to exhibit a parallel scale of relations between stimuli on the one hand, and the de- grees of consciousness on the other. Yet for all this it will be impossible to express self-knowledge in terms of force. The ques- tion as to whether the product of the force conversion involved is the consciousness itself, or only a condition of consciousness, may receive light from the following consideration. Nowhere does "the doctrine of the unspecialized" receive CONSCIOUSNESS IN EVOLUTION. 403 greater warrant than in the constitution of protoplasm. Modern chemistry refers compound substances to four classes, each of which is characterized by a special formula of combination. These are called the hydrochloric-acid type, the water-gas type, the ammonia type, and the marsh-gas type. These series are defined by the volumetric relations of their component simple substances : thus, in the first, a single volume unites with an equal volume of hydrogen ; in the second, two volumes of hydrogen unite with a single volume of another element ; in the third, three, and in the fourth, four vol- umes of hydrogen unite with the single volume of other elements. Hence the composition of these compounds is expressed by the fol- lowing formulas — chlorine, oxygen, nitrogen, and carbon being selected as typical of their respective classes : HCl, HjO, H3N, and H4O. Now it is an interesting fact that protoplasm is composed of definite proportions of four simple substances, each one repre- senting one of the classes above named, or, in other words, the ca- pacity for proportional molecular combination which characterizes them. The formula C24N8OH17 expresses the constitution of this remarkable substance. Now, although the significance of these combining numbers is unknown, there is a conceivable connection between the characteristic peculiarities of protoplasm and the na- ture of the substances which compose it. It is probable that these, when in combination with each other, exert a mutually antago- nistic control over each other's especial and powerful tendencies to form stable, and hence dead, compounds. It is therefore reason- able that the terms **unspecialized" or *^ undecided" should be applicable to the molecular condition of protoplasm, and in so far it is a suitable nidus for higher molecular organization, and a ca- pacity for higher forms of force-conversion than any other known substance. If also in inorganic types, as in the organic, the gen- eralized have preceded the specialized in the order of evolution, we are directed to a primitive condition of matter which presented the essentially unspecialized condition of protoplasm, without some of its physical features. We are not necessarily bound to the hypothesis that protoplasm is the only substance capable of supporting consciousness, but to the opposite view, that the proba- bilities are in favor of other and unspecialized, at present un- known, forms of matter possessing this capacity. Consciousness constitutes then the only apparently initial point of motion with which we are acquainted. If so, we are at liberty to search for the origin of the physical forces in consciousness, as 404 METAPHYSICAL EYOLUTIOlSr. well as the vital ; their present unconscious condition being possi- bly due, as in the case of the vital, to automatism : the automa- tism being the expression of the atomic type of the substance ex- hibiting it. And, doubtless, the simple quantitative relations of the lowest types of forces are related to correspondingly simple geometrical conditions of matter, both representing the simplest grade of automatic action and machinery. We may also suppose that all of these primary conditions were necessary to the produc- tion of protoplasm, the only form of matter known to us in which consciousness can persist. In conclusion, it is obvious that the metastatic condition of protoplasm necessary to the persistence of consciousness could not be supported without a constant source of supply by assimilation. Hence it would appear that the preliminary creation of dead and unconscious substances and organisms were a necessary antecedent to the accomplishment of this end ; at least under circumstances of temperature under which living beings or protoplasm exist on this planet. Without the unconscious inorganic and organic prod- ucts of nature, consciousness could not exist on the earth for a day. No animal can maintain consciousness without food ; and that food must be, in the main, protoplasm. Protoplasm is manu- factured from inorganic matter by the (sujoposed) unconscious protoplasm of the plant. What form of matter originally gave origin to protoplasm is yet unknown, but it is obvious that the ordinary physical forces must have existed as conditions of its creation, since now they are absolutely necessary to its persistence. Hence we may view the succession of automatic activities some- what in the light of the fagots used by the elephant to lift itself from the well into which it had fallen. One placed upon another finally raised the footing to an elevation which enabled the animal to obtain its freedom. Consciousness is the essential condition of personality ; so that in this view of the case we are led to a j)rimitive personality, al- though not to what we call life. And the reason why this person- ality is to us so obscure a conception is probably to be found in the fact that it, as well as ourselves, is conditioned in its rela- tions to matter by necessary laws of ^'^mathematical" truth. XIX. ON ARCHJESTHETISM. I. THE HYPOTHESIS OF USE AND EFFORT. The claims of the theory of Lamarck, that use modifies struct- ure in the animal kingdom, are being more carefully considered than heretofore, and are being admitted in quarters where they have been hitherto neglected or ignored. Eleven years ago I re- stated the question as follows : * ** The influences and forces which have operated to j^roduce the type-structures of the animal kingdom have been plainlv of two kinds : 1. Originative; 2. Directive. The prime importance of the former is obvious ; that the latter is only secondary in the order of time or succession, is evident from the fact that it con- trols the preservation or destruction of the results or creations of the first. *^ Wallace and Darwin have propounded as the cause of modi- fication in descent their law of natural selection. This law has been epitomized by Spencer as the ^survival of the fittest.' Tiiis neat expression no doubt covers the case, but it leaves the origin of the fittest entirely untouched, Darwin assumes a tendency to variation ' in nature, and it is plainly necessary to do this, in order that materials for the exercise of a selection should exist. Darwin and Wallace's law Is, then, only restrictive, directive, con- servative, or destructive of something already created. I propose then to seek for the originative laws by which these subjects are furnished — in other words, for the causes of the origin of the fittest. " It has seemed to the author so clear from the first as to re- quire no demonstration, that natural selection includes no actively progressive principle whatever ; that it must first wait for the de- * "The Method of Creation," 1871, pp. 2 and 18, Walker Prize Essay, Proceeds. Amer. Phllos. Soc, pp. 230-246. 406 METAPHYSICAL EVOLUTION. velopment of variation, and then, after securing the survival of the best, wait again for the best to i^roject its own variations for selection. In the question as to whether the latter are any better or worse than the characters of the parent, natural selection in no wise concerns itself." In seeking for the causes of the origin of variation, the follow- ing hypothesis was proposed : ^^ What are the influences locating growth -force ? The only efficient ones with which we are acquainted are, first, physical and chemical causes ; second, use ; and I would add a third, viz. : effort. I leave the first as not especially prominent in the econ- omy of type-growth among animals, and confine myself to the two following. The effects of use are well known. We can not use a muscle without increasing its bulk ; we can not long use the teeth in mastication without inducing a renewed deposit of dentine within the pulp-cavity to meet the encroachments of at- trition. The hands of a race of laborers are always larger than those of men of other pursuits. Pathology furnishes us with a host of hypertrophies, exostoses, etc., produced by excessive use, or necessity for increased means of performing excessive work. The tendency, then, induced by use in the parent, is to add segments or cells to the organ used. Use thus determines the locality of new repetitions of parts already existing, and deter- mines an increase of growth-force at the same time, by the in- crease of food always accompanying increase of work done, in every animal. ^ ^ But supposing there be no part or organ to use. Such must have been the condition of every animal prior to the appearance of an additional digit or limb or other useful element. It appears to me that the cause of the determination of growth-force is not merely the irritation of the part or organ used by contact with the objects of its use. This would seem to be the remote cause of the deposit of dentine in the used tooth ; in the thickening epidermis of the hand of the laborer ; in the wandering of the lymph-cells to the scarified cornea of the frog in Cohnheim's ex- periment. You can not rub the sclerotica of the eye without producing an expansion of the capillary arteries and correspond- ing increase in the amount of nutritive fluid. But the case may be different in the muscles and other organs (as the pigment cells of reptiles and fishes) which are under the control of the volition of the animal. Here, and in many other instances which might ON" ARCHiESTHETISM. 407 be cited, it can not be asserted that the nutrition of use is not under the direct control of the will through the mediation of nerve-force. Therefore I am disposed to believe that growth- force may be, through the motive force of the animal, as readily determined to a locality where an executive organ does not exist, as to the first segment or cell of such an organ already com- menced, and that therefore effort is, in the order of time, the first factor in acceleration." A difficulty in the way of this hypothesis is the frequently unyielding character of the structures of adult animals, and the difficulty of bringing sufficient pressure to bear on them without destroying life. But in fact the modifications must, in most in- stances, take place during the period of growth. It is well known that the mental characteristics of the father are trans- mitted through the spermatozooid, and that therefore the molec- ular movements which produce the mechanism of such mental characters must exist in the spermatozooid. But the material of the spermatozooid is combined with that of the ovum, and the embryo is composed of the united contents of both bodies. In a wonderful way the embryo develops into a being which resembles one or both parents in minute details. This result is evidently determined by the molecular and dynamic character of the origi- nal reproductive cells, which necessarily communicate their prop- erties to the embryo, which is produced by their subdivision. Rud. Hering has identified this property of the original cells with the faculty of memory. This is a brilliant thought, and, under restriction, probably correct. The sensations of persons who have suffered amputation shows that their sensorium retains a picture or map of the body so far as regards the location of all its sensitive regions. This simulacrum is invaded by consciousness whenever the proper stimulus is applied, and the locality of the stimulus is fixed by it. This picture probably resides in many of the cells, both sensory and motor, and it doubtless does so in the few cells of simple and low forms of life. The spermatozooid is such a cell, and, how or why we know not, also contains such an ar- rangement of its contents, and contains and communicates such a type of force. It is probable that in the brain-cell this is the condition of memory of locality. If now an intense and long- continued pressure of stimulus produces an unconscious picture of some organ of the body in the mind, there is reason to suppose that the energies communicated to the embryo by the spermato- 408 METAPHYSICAL EVOLUTION'. zooid and ovum will partake of tlie character of the memory thus created. The only reason why the oft-repeated stories of birth- marks are so often untrue is because the effect of temporary im- pressions on the mother is not strong enough to counterbalance the molecular structure established by impressions oftener re- peated throughout much longer periods of time. The demonstration of the truth or falsity of this position, so as to constitute it the true doctrine of evolution, could only be veri- fied from the prosecution of the science of paleontology. It is only in this field that the consecutive series of structures can be obtained which show the directions in which modification has taken place, and thus furnish evidence as to the causes of change. The most complete result of these investigations, up to the present time, has been the obtaining of sufficiently full series of the Mam- malia of the Tertiary period to show their lines of descent. In this way the series of modifications of their teeth and feet has been discovered, and the homologies of their parts been ascer- tained.* Perhaps the most important result of these investiga- tions is the following : The variations from which natural selec- tion has derived the persistent types of life have not been general or even very extensive. They have been in a limited number of directions, f and the most of these have been toward the increase in perfection of some machine. They bear the impress of the presence of an adequate originating cause, directed to a special end. Some of the lines struck out have been apparently inade- quate to cope with their environment, and have been discon- tinued. Others have been more successful, and have remained, and attained further modification. The reader can estimate the chance of the production of an especially adaptive mechanism in the absence of any pressure of force directing growth to that end. It appears to me that the probability of such variation appearing under such circumstances is very slight indeed, and its continuance through many geologic ages directed to the perfecting of one and the same machine still smaller. For this reason, attempts have been made to demon- strate a mechanical cause for the modifications of structure ob- * " Homologies and Origin of the Molar Teeth of the Mammalia educabilia." Journal Academy Nat. Sciences, Philadelphia, March, 1874. Proceedings Academy Nat. Sci., 1865, p. 22. f See Hyatt on this point, *' Tertiary Planorbis of Steinheim." Anniv. Mem. Bost. Soc. Nat. Hist., 1880, p. 20. ON APwCn^STHETISM. 409 served. For these I refer to papers by Messrs. Alpheus Hyatt, J. A. Ryder and myself : by Prof. Hyatt ..." Upon the Effects of Gravity on the Forms of Shells and Animals ; " * Mr. Ryder *'0n the Mechanical Genesis of Tooth Forms ;" f and '*0n the Laws of Digital Reduction ;" ]; by myself '' On the Origin of the Specialized Teeth of the Oarnivora ; " * " On the Origin of the Foot Structures of the Ungulates ; " || "On the Effect of Impacts and Strains on the Feet of Mammalia." ^ Now demonstration of the meclianical effects of the application of force to matter can only be obtained by observation of the process, and this can not be seen, of course, by the observation of fossils. The relation of the observed facts to the hypothesis is, however, shown by the above papers to be so precise that it only needs observation on the production of similar changes by similar causes in living types to give us a demonstration by induction, which will satisfy most minds. That such facts have been observed among the lower ani- mals is well known. The change of form of animals without hard parts, in adaptation to their environment, is an every-day occurrence. That these views are now shared by many naturalists is be- coming every day more evident. Prof. E. Dubois-Raymond ^ has recently delivered a lecture before the physicians of the German army, on exercise or use, in which he makes some important admissions. We give the following extract : " We should be, therefore, free to admit, with some appearance of reason, that the vigor of the muscles of wings and of digging feet ; the thick epidermis of the palm of the hand and of the sole of the foot ; the callosities of the tail and of the ischia of some monkeys ; the processes of bones for the insertion of muscles ; are the conse- quences of nutritive and formative excitation, transmitted by heredity." In this position Prof. Raymond is in strict accord with the Lamarckian school of evolutionists. But Prof. Raymond still clings to the obscurities of the Darwinians, though Darwin himself is not responsible for them, in the following sentences : " It is necessary to admit, along with development by use, develop- * "Proceeds. Amer. Assoc. Adv. Science," 1880, p. 527. f " Proceedings Academy Philadelphia," 1878, p. 45 ; 1879, 47. X Loe. cit.^ 1877, October. # " American Naturalist," March, 1879, p. 171. II Loc. cit, April, 1881, p. 269. ^ Loc. cit, July, 1881, p. 542. l "Revue Scientifique," Paris, Jan. 28, 1882. 410 METAPHYSICAL EYOLUTION. ment by natural selection, and that for three reasons. First, there are innumerable adaptations — I cite only those known as mimetic coloration — which appear to be only explicable by nat- ural selection and not by use. Second, plants which are, in their way, as well adapted to their environment as animals, are of course incapable of activity. Thirdly, we need the doctrine of natural selection to explain the origin of the capacity for exercise itself. Unless we admit that which it is imj^ossible to do from a scientific stand-point, that designed structures have a mechanical origin, it is necessary to conclude that in the struggle for exist- ence the victory has been secured by those living beings who in exercising their natural functions have increased by chance {^ par hasard^) their capacity for these functions more than others, and that the beings thus favored have transmitted their fortunate gifts to be still further developed by their descendants." To take up first the second and third of these propositions. Prof. Kaymond does not for the moment remember that move- ment (or use) is an attribute of all life in its simplest forms, and that the sessile types of life, both vegetable and animal, must, in view of the facts, be regarded as a condition of degeneration. It is scarcely to be doubted that the primordial types of vegetation were all free swimmers, and that their habit of building cellulose and starch is resjjonsible for their early-assumed stationary condi- tion. Their protoplasm is still in motion in the limited confines of their walls of cellulose. The movements of primitive plants have doubtless modified their structure to the extent of their dura- tion and scope, and probably laid slightly varied foundations, on which automatic nutrition has built widely diverse results. We may attribute the origi7i of the forms of the vegetable kingdom to three kinds of motion which have acted in conjunction with the physical environment ; first, their primordial free movements ; second, the intracellular movements of protoplasm ; third, the movements of insects, which have doubtless modified the structure of the floral organs. Of the forms thus produced, the fit have sur- vived and the unfit have been lost, and that is what natural selec- tion has had to do with it. The origin of mimetic coloration, like many other things, is yet unknown. An orthodox Darwinian attributes it to ^' natural selec- tion," which turns out, on analysis, to be '"liasard.'^^ The survival of useful coloration is no doubt the result of natural selection. But this can not be confounded with the question of origin. On ON AROH^STHETISM. 411 this point the Darwinian is on the same footing as the old-time Creationist. The latter says God made the variations, and the Darwinian says that they came by chance. Between these posi- tions science can perceive nothing to choose. I have attempted to explain the relation which non-adaptive structures bear to the theory of use and effort, in the following language : * *' The complementary diminution of growth-nutrition follows the excess of the same in a new locality or organ, of necessity, if the whole amount of which an animal is capable be, as I believe [for the time being], fixed. In this way are explained the cases of retardation of character seen in most higher types. The dis- covery of truly complementary parts is a matter of nice observation and experiment. Perhaps the following cases may be correctly ex- plained. '^ A complementary loss of growth-force may be seen in the ab- sence of superior incisor teeth and digits in ruminating Mammalia, where excessive force is evidently expended in the development of horns, and complication of stomach and digestive organs. The excess devoted to the latter region may account for the lack of teeth at its anterior orifice, the mouth ; otherwise, there appears to be no reason why the ruminating animals should not have the superior incisors as well developed as in the odd-toed (Perisso- dactyl) Ungulates, many of which graze and browse. The loss to the osseous system in the subtraction of digits may be made up in the development of horns and horn-cores, the horn sheath being perhaps the complement of the lost hoofs. It is not proposed to assert that similar parts or organs are necessarily and in all groups complementary to each other. The horse has the bones of the feet still further reduced than the ox, and is nevertheless without horns. The expenditure of the complementary growth-force may be sought elsewhere in this animal. The lateral digits of the EquidcB are successively retarded in their growth, their redaction being marked in Hippotlierium, the last of the three-toed horses ; it is accompanied by an almost coincident acceleration in the growth-nutrition of the middle toe, which thus appears to be com- plementary to them." * "Method of Creation," p. 23, ISTl. 412 METAPHYSICAL EYOLUTIOI^. II. THE OFFICE OF COKSCIOUSi^ESS. If the law of modification of structure by use and effort be true, it is evident that consciousness or sensibility must play an important part in evolution. This is because movements of ani- mals are plainly in part controlled by their conscious states. The question as to how many of the actions of animals are due to con- scious states at once arises. It is well known that most of the more strictly vital functions are unconsciously performed. Not only these, but many acts which have to be learned come to be performed in unconsciousness. Further, movements appropriate to needs which arise at the moment, and which are ordinarily termed voluntary, because they require the introduction of more or less of the rational faculty, are readily performed by verte- brated animals deprived of a brain, through the agency of the spinal cord alone.* The history of the origin of these movements must then be traced. The movements of living beings generally possess the pecul- iarity of design, in which they differ from the movements of non- living bodies. That is, their actions have some definite reference to their well-being or pleasure, or their preservation from injury or pain, and are varied with circumstances as they arise. This is not the case with non-living bodies, which move regardless of their integrity or of that of objects near them. This characteris- tic at once suggests that some element enters into them which is wanting to the movements of non-living masses. It has been suggested that the attraction of animals for their food and their repulsion from pain are derivatives from the attractions and repul- sions of inorganic bodies, supposed to be the exhibitions of the force called chemism. But this supposition does not explain the wide difference between the two classes of acts. The adaptation to the environment seen in organic acts is unknown to the inor- ganic world, while the invariable character of the motions of in- organic force is greatly modified in beings possessed of life. Whether consciously performed or not, the acts of organic beings resemble those of conscious beings actuated by instincts of hunger, reproduction, and defense. An explanation of these facts seems to be offered by a well- * Such expressions as " unconscious sensibility " and " unconscious will " are not used here, as being self -contradictory in terms and without meaning. ON" ARCH^STHETISM. 413 known phenomenon. We know that it is true of ourselves and of many other animals, that while all new movements have to be learned by repeated attempts, with each succeeding movement the act becomes easier, and that finally it can be performed with- out requiring any attention whatever. If continued, the move- ment becomes automatic, so that it may be or is performed in a state of unconsciousness. In the words of Spencer, nervous cur- rents move most readily along accustomed channels. Thus the " habits " of animals may be looked on as movements acquired in consciousness, and become automatic through frequent repeti- tion. Not only this, but the organization thus produced in the parent is transmitted to the succeeding generation, so that the movements of the latter are automatically and often unconsciously performed. This view may be even extended to the purely vital functions, with every probability of its being the true explanation of their origin and development. On a former occasion * I wrote : *^In accordance with this view, the automatic 'involuntary' movements of the heart, intestines, reproductive systems, etc., were organized in successive states of consciousness, which con- ferred rhythmic movements whose results varied with the ma- chinery already existing and the material at hand for use. It is not inconceivable that circulation may have been established by the suffering produced by an overloaded stomach demanding dis- tribution of its contents. The structure of the Coelenterata offers the structural conditions of such a process. A want of propulsive power in a stomach or body sac occupied with its own functions, would lead to a painful clogging of the flow of its i3roducts, and the * voluntary ' contractility of the body or tube wall being thus stimulated, would at some point originate the pulsation necessary to relieve the tension, Thus might have originated the ' con- tractile vesicle ' of some protozoa, or contractile tube of some higher animals ; its ultimate product being the mammalian heart. So with reproduction. Perhaps an excess of assimilation in wtII- fed individuals of the first animals led to the discoverv that self- division constituted a relief from the oppression of too great bulk. With the increasing specialization of form, this process would become necessarily localized in the body, and growth would repeat such resulting structure in descent as readily as any of the other structural peculiarities. No function bears the mark * " Consciousness iu Evolution." "Penn Monthly," August, 1875, p. 565. 414 METAPHYSICAL EYOLUTION". of conscious origin more than this one, as consciousness is still one of the conditions of its performance. While less completely * voluntary ' than muscular action, it is more dependent on stim- ulus for its initial movements, and does not in these display the unconscious automatism characteristic of the muscular acts of many other functions." It was not proposed in the preceding paragraph that the con- tractility of living protoplasm should be regarded as due to con- sciousness, but that the location in a particular place of a contrac- tility already existing might be due to that cause. The preceding hypotheses bring us to a general theory of the evolution of organic structures or species. It is that they are the result of movements long continued and inherited, and that the character of these movements was originally determined by con- sciousness or sensibility. It remains then to consider the nature of consciousness. It may be mentioned that it is here left open whether there be any form of force which may be especially designated as *^ vital." Many of the animal functions are known to be physical and chemical, and if there be any one which appears to be less expli- cable by reference to these forces than the others, it is that of nutrition. Probably in this instance force has been so metamor- phosed, through the influence of the originative or conscious force in evolution, that it is a distinct species in the category of forces. Assuming it to be such, I have given it the name of Bathmism ('^Method of Creation," 1871, p. 26). Perhaps the contractility generally regarded as an attribute of living protoplasm may be a mechanical phenomenon dependent of course on nutrition ; or it may be the exhibition of a force peculiar to living beings ; and hence one of the * vital ' group. III. ARCH^STHETISM. The doctrine of evolution derives the organs of special sense from those of simple sensibility or touch. In other words, their history has been that of other organs ; the complex have been derived from the general and simple. There are then generalized consciousness and specialized consciousness. A number of forms of consciousness multiplies its vividness, the one kind reenforcing the other by a slightly different appreciation of the same thing. In the case of persons deprived of the sense of touch, the sense of sight is not sufficient to convince them of their own existence, ON ARCHiESTHETISM. 415 as a matter of intellectual reflection. When there is no nervous system we must suppose sensibility to be generally distributed throughout the protoplasmic substance of the animal. The locali- zation of consciousness must depend on a localization of the kind and condition of protoplasm which sustains it ; while in other parts of the body the protoplasm is modified in other directions and for other purposes. If this be true, the nervous tissue of the higher animals should retain the characters of the lowest simple organisms. In point of fact this is the case, the nucleated cell being the essentially active element in the functions of brain and nerve, and being more numerous in that tissue than in any other. The remarkable evanescence of consciousness is one of its most marked characteristics. It is this peculiarity which has led many thinkers to deny its existence in the lower animals, and to induce others to believe that it can have had but little place among the causes of evolution. Partly for the same reason many biolo- gists attempt to derive it by metamorphosis from some form of force. But the nature of consciousness is such that it can not be de- rived from unconsciousness, any more than matter can be derived from no matter, or force from no force. The *' unthinkable dogma of creation " (Haeckel) can not be applied to consciousness more than to matter or force. It is a thing by itself, and with matter and force forms a trio of primitive things which have to be accepted as ultimate facts. This is perfectly consistent with the position that consciousness is an attribute of matter, and neither more nor less difficult to comprehend than the fact that force is an attribute of matter. This view is maintained in a fashion of his own by G. H. Lewes. Prof. Raymond* says in support of the same position : *^ More temperate heads betrayed the weakness of their dia- lectics in that they could not grasp the difference between the view which I opposed, that consciousness can be explained upon a mechanical basis, and the view which I did not question, but sup- ported with new arguments, that consciousness is bound to mate- rial antecedents." This position has been maintained by various writers, among them Prof. Allman f and the writer. But Prof. * Address on the celebration of the Birthday of Leibnitz. " Pop. Science Month- ly," Feb., 1882. f Address delivered before the British Association for the Advancement of Science. 416 METAPHYSICAL EYOLUTIOK Raymond has not found it to be acceptable to his nearest contem- poraries. He says : " The opposition which has been offered to my assertion of tiie incomprehensibility of consciousness on a me- chanical theory, shows how mistaken is the idea of the later phi- losophy, that that incomprehensibility is self-evident. It ap- pears, rather, that all philosophizing upon the mind must begin with the statement of this point." In stating this point some years ago we used the following language :* ^^It will doubtless become possible to exhibit a parallel scale of relations between stimuli on the one hand and the degrees of consciousness on the other. Yet for all this it will be impossible to express self-knowl- edge in terms of force." And again : f *'An unprejudiced scru- tiny of the nature of consciousness, no matter how limited that scrutiny necessarily is, shows that it is qualitatively comparable to nothing else. . . . From this stand-point it is looked upon as a state of matter which is coeternal with it, but not coextensive." It is probable then that consciousness is a condition of matter in some peculiar state, and that wherever that condition of mat- ter exists consciousness will be found, and that the absence of that state implies the absence of consciousness. What is that state ? It would be a monstrous assumption to suppose that conscious- ness and life are confined to the planet on which we dwell. I presume that no one would be willing to maintain such an hypoth- esis. Yet it is obvious that if there be beings possessed of these attributes in the planets Mercury and Saturn, they can not be composed of protoplasm, nor of any identical substance in the two. In the one planet protoplasm would be utterly disorganized and represented by its component gases ; in the other it would be a solid, suitable for the manufacture of sharp-edged tools. J; But as it is probable that j^rotoplasm is adapted for the phenomena of consciousness by a certain peculiarity of its constitution, it seems evident that other substances having a similar peculiarity may also be able to sustain it. I have elsewhere attempted to discover what this is, in the following language : * *^ Nowhere does ^the doctrine of the unspecialized ' receive greater warrant than in the constitution of protoplasm. Modern chemistry refers compound substances to four classes, each of * "Consciousness in Evolution." "Penn Monthly," July, 1875. f " The OrijTin of the Will." " Penn Monthly," 1877, p, 439. X Frazer in "American Naturalist," 1879, p. 420. * "Consciousness in Evolution," 1S75, p. 573. ON AECH^STHETISM. 4I7 which is characterized by a special formula of combination. These are called the hydrochloric-acid type, the water-gas type, the ammonia type, and the marsh-gas type. These series are de- fined by the volumetric relations of their component simple sub- stances : thus in the first, a single volume unites with an equal volume of hydrogen ; in the second, two volumes of hydrogen unite with a single volume of another element ; in the third, three, and in the fourth, four volumes of hydrogen unite with the single volume of other elements. Hence the composition of these com- pounds is expressed by the following formulas — chlorine, oxygen, nitrogen, and carbon being selected as typical of their respective classes : HCl, H2O, H3N", and H4C. Noav it is an interesting fact that protoplasm is composed of definite proportions of four simple substances, each one representing one of the classes above named, or, in other words, the capacity for proportional molecular com- bination which characterizes them. The formula C24N8OH1T ex- presses the constitution of this remarkable substance. Now, al- though the significance of these combining numbers is unknown, there is a conceivable connection between the characteristic pecul- iarities of protoplasm and the nature of the substances which compose it. It is probable that these, when in combination with each other, exert a mutually antagonistic control over each other's especial and powerful tendencies to form stable, and hence dead, compounds. It is therefore reasonable that the terms ' unspecial- ized' or -^undecided' should be applicable to the molecular con- dition of protoplasm, and in so far it is a suitable nidus for higher molecular organization, and a capacity for higher forms of force- conversion than any other known substance. If also in inorganic types, as in the organic, the generalized have preceded the spe- cialized in the order of evolution, we are directed to a primitive condition of matter which presented the essentially un specialized condition of protoplasm, without some of its physical features. We are not necessarily bound to the hypothesis that protoplasm is the only substance capable of supporting consciousness, but to the opposite view, that the probabilities are in favor of other and un- specialized, but unknown, forms of matter possessing this ca- pacity." The condition of living protoplasm was also referred to in the following language in a later publication : * * " The Origin of the Will." " Pouii Monthly," June, 1877, p. 439. 27 418 METAPHYSICAL EVOLUTION. ^^ The cause of tlie difference between conscious and uncon- scious force must be secondarily due to different conditions of matter as to its atomic constitution ; consciousness being only possible, so far as we can ascertain, to matter which has not fallen into fixed and automatic relations of its atoms." Protoplasm in the form of food is not conscious ; and tissue formed of protoplasm is not conscious, excepting certain cells where the forming process is in action. Nor is consciousness present in all cells where nutrition is active. From the increased consumption of energy, and the increased expenditure of energy (heat, Lombard) which takes place during conscious processes, we may well believe that the decomposition of protoj^lasm is more considerable in such processes than in other forms of nervous ac- tivity. We can imagine simple nutrition to be a condition of the elements of this substance in which the chemical force is simul- taneously combining and dissolving its combination, and that dur- ing the process there is a condition in which the chemism is for the time being unsatisfied, though present. The direction which this nutrition or metastasis takes, is due to the arrangement of the molecules already existing in the tissue, the new molecules taking the form of the old ones in replacement, so long as no extraneous force interferes. That they are rearranged under the influence of consciousness is apparent in the origin of variations of structure in accordance with the views of evolution already entertained. It is the arrangement of the molecules which constitutes the auto- matic machinery of nutrition as well as of other activities, so that consciousness necessarily only appears in that stage of nutrition while the matter is in a transition state, and unformed. Whether chemism must be regarded as suspended, or only unsatisfied, at this stage, can only be imagined. As non-satisfaction is probably the tem|)orary condition in all nutrition, it is not unlikely that sus- pension may be the condition of consciousness. Perhaps the character of the components of protoplasm is such that the movements of their atoms, i. e., their chemism, mutually interfere and destroy each other, as in the cases of the interference of the waves of light and sound. The colloid form of protoplasm is especially favorable to inter- nal movements which shall not destroy the integrity of the mass, perhaps more so than a gaseous state in a compound of similar con- stitution. It is, moreover, more favorable to the preservation of molarity than a gas could be, on account of the ease with which ON ARCIIiESTnETISM. 4I9 it adheres to solid substances, and transports and locates them as part of its external and internal supports. But it is not incon- ceivable that under other conditions of temperature, etc., the gaseous condition of matter jnight answer the same purpose. It must be borne in mind, however, that this is a subordinate ques- tion, and that the real characteristic of the "physical basis of life " is to be found rather in its generalized dynamic condition. We must then believe that wherever this generalized condition exists, consciousness will be present. As soon as mechanical or chemical force appears in the molecules of the sustaining sub- stance, consciousness disappears. The organism has taken the first step toward death, but is not dead, but is anmsthetized. Constant nutrition is essential to the performance of all life functions, in- cluding consciousness, and it is evident that this is necessary to the maintenance of the unspecialized condition in which the latter appears. Is the appearance of sensibility on the development of its sus- taining condition, evidence that the latter stands to the former in the relation of cause and effect ? If the view of the pre-existence of consciousness be true, there is no more relation of cause and effect than in the case of the opening of a door which admits a wind. The force expended in opening the door is not converted into the energy exerted by the wind as it enters the room. It simply releases it, or admits it to a new field. It is, however, true, that consciousness having once entered, a larger conversion of force is necessary to its ^persistence than is expended during its absence. Like combustion, which is only communicable under suitable con- ditions, consciousness having once been transmitted to a new cestJie- topliore* lives on it, and requires constant supplies of material for its sustenance. The hypothesis of the primitive and creative function of con- sciousness may be called Archmsthetism, IV. PAN^STHETISM. It has been the custom of men from the dawn of thought to attempt to construct for themselves cosmogonies and theologies. Science is yet far from supplying the facts necessary to the con- struction of a true system of the universe, and philosophy can only stretch out a little further into the unknown by the use of neces- * -^sthetophore, a substance which sustains consciousness. 420 METAPHYSICAL EVOLUTIOIN'. sary inference. In spite, however, of the insufficiency of the data, men still suggest new yiews or cling to old ones, and an occasional flight into this region of thought at least brings the thinker into sympathy with the thoughts of his fellow-men. The admission of the possibility of the existence of conscious- ness in other forms of matter than protoplasm, and in other regions than the Earth, lends countenance to a rational belief in the so- called ^^supernatural" (better called the supersensuous) so preva- lent among men in irrational forms. The question naturally arises. Is there any generalized form, of matter distributed through the universe which could sustain consciousness ? The presump- tion is that such a form of matter may well exist. Evolution or specialization has only worked up part of its raw material in the or- ganic world. Wherever primitive conditions remain, there primi- tive organisms abound. Protozoa are yet numerous on land, and the Protolatliyhius inhabits the depths of the sea. Highly spe- cialized forms of life are in fact numerically a minority of living beings. May not this be true also of inorganic beings ? It is thought that various celestial bodies reiDresent unfinished worlds. Is it not probable that the grand sources of matter not yet spe- cialized into the sixty odd substances known to us, may still sus- tain the primitive force not yet modified into its species, and that this combination of states may be the condition of persistent con- sciousness from which all lesser lights derive their brilliancy ? There is much to warrant such a view in the observed facts of life, taken in connection with the general course of evolution. More- over, that some form of matter connects the interstellar S2oaces, is thought to be proved by the transmission of light in some cases, and light and heat in others. That such a form of matter per- vades all spaces whatever, is the theory of some physicists. If it be so generalized as to be capable of sustaining consciousness, it becomes the source from which other substances derive it, so soon as they, through the energy of nutrition, which resists death, maintain the same primitive and unformed constitution capable of exhibiting it. Of course there is no evidence in our own memory of the ex- istence of our personality prior to our human experience. No one on awaking from unconsciousness remembers having been anywhere in particular during the interval. These facts may be harmonized with the theory here presented, on the supposition that memory is lost on a transfer of consciousness from one physi- ON ARCH^STHETISM. 421 cal basis to another. The arguments in favor of a transfer of consciousness do not sustain the idea of a transfer of memory. Memory requires an arrangement of molecules or atoms which when finished no longer exhibits consciousness. With proper stimulus, when the proper kind of force conversion is set up in them, consciousness extends into them, and, taking their form, produces reminiscence or conscious memory. The molecular arrangement would be probably lost on a transfer of conscious- ness to a new material basis. It might then be supposed that with every such transfer a new personality is established. Though the correct definition of personality includes memory as well as consciousness, when viewed as an objective concept, it may be questioned whether memory is necessary to the subjective belief in one's own personality. Those insane persons who believe that they have lost their personality, and think that they are some one else, nevertheless recognize the fact that what they now are has a continuity of existence with what they once were. The mate- rial limitations of consciousness are the authors of the kind of personality it presents. A limitation or an expansion of its range would not destroy the idea of personality, but would simply re- strict or extend it. The possible confluence of many personalities would not destroy them, but each one would regard the others as additions to himself, and himself, therefore, as so much the greater being. As a summary of the preceding conclusions, the following analysis of metaphysical systems may be given. It defines the place of the doctrine of archsesthetism, above proposed, as dis- tinguished from the opposing view of metsesthetism, which is held by many monists : I. Consciousness (" spirit ") is independent of mattei' Dualism. II. Consciousness is an attribute of matter Monism. o. Consciousness is primitive and a cause of evolution ArcJucsthetism. iS. Consciousness is a product of the evolution of matter and force. Metcesthdism. XX. ON CATAGENESIS.* I. THE EVOLUTIOJ^ OF ORGANISMS. The general proposition that life has preceded organization in the order of time, may be regarded as established. It follows ne- cessarily from the fact which has been derived from paleontological investigation, that the simple forms have, with few sporadic ex- ceptions, preceded the complex in the order of appearance on the earth. The history of the lowest and simplest animals will never be known, on account of their perishability ; but it is a safe infer- ence from what is known, that the earliest forms of life were the rhizopods, whose organization is not even cellular, and includes no organs whatever. Yet these creatures are alive, and authors familiar with them agree that they display, among their vital qualities, evidences of some degree of sensibility. The following propositions were laid down by Lamarck, as established by facts known to him, in 1809 : f I. '^In every animal which has not passed the term of its de- velopment, the frequent and sustained employment of an organ, gradually strengthening it, develops and enlarges it, and gives it power proportional to the duration of its use ; whilst the constant disuse of a like organ insensibly weakens it, deteriorates it, pro- gressively reduces its functions, and finally causes it to disappear. II. *^ All that nature acquires or loses in individuals, through the influence of circumstances to which the race has been exposed for a long time, either by the predominant use of an organ or by the disuse of such part, she preserves by generation among new * An address delivered before the Biological Section of the American Associa- tion for the Advancement of Science, at Philadelphia, September 4, 1884, by E. D. Cope, vice-president. f "Philosophic Zoologique," Pt. I, p. 235 (Edit. 1830). ON CATAGENESIS. 423 indiyiduals wliicli spring from it, j^rovidod the acquired changes be common to both sexes or to those which produce new indi- yiduals. '' The same ^proposition was previously enunciated by Lamarck in the following condensed form ('^Recherches sur les Corps vivans," p. 50) : ^^ It is not the organ, that is, the nature and form of the parts of the body, which have given origin to its habits and peculiar functions, but it is, on the contrary, its habits, its manner of life, and the circumstances in which individuals from which it came found themselves, which have, after a time, constituted the form of the body, the number and character of its organs, and the func- tions which it possesses." Several years ago, not having read Lamarck, I characterized the above hypothesis as the ^Haw of use and effort," * and I have subsequently formulated the modus operandi of this law into two propositions. The first of these is, that animal structures have been produced, directly or indirectly, by animal movements, or the doctrine of Icinetogenesis ; the second is, that as animal move- ments are primitively determined by sensibility, or consciousness, consciousness has been and is one of the primary factors in the evolution of animal forms. This is the doctrine of arclicBsfl^ci- ism. The doctrine of kinetogenesis is implied in the speculations of Lamarck in the following language ('* Philosophie Zoologique," ed. 1830, p. 239): *'With regard to the circumstances which [Nature] uses every day to vary that which she produces, one can say that they are inexhaustible. The principal arise from the influence of climates ; from diverse temperature of the atmos- phere and of the environment generally ; from diversity of loca- tion ; from habits, the most ordinary movements, and most fre- quent actions," etc. The influence of motion on development is involved in Spencer's theory of the origin of vertebrae by strains ; \ and I have maintained the view that the various agencies in pro- ducing change mentioned by Lamarck are, in the case of animals, simply stimuli to motion. \ The immediate mechanical effect of motion on animal structure has been discussed in papers by Eyder, * " Method of Creation," " Proceedings American Philosophical Society,'' 1871, p. 247. \ "Principles of Biology," II, p. 195. X " On the Relation of Animal Motion to Animal Evolution," "American Natural- ist," Jan., 1878. 424 METAPHYSICAL EVOLUTION". Hyatt, eleven ger, and myself, and I have cited the evidence of vertebrate paleontology as conclusively proving such an effect." * The object of the present paper is to pursue the question of the relation of sensibility to evolution, and to consider some of the consequences which it involves. It is scarcely necessary to observe that, in the early stage which the subject presents at the present time, I can only i^oint out the logical conclusions deriyable from facts well established rather than any exj^erimental discoA^eries not already known. And I will say here to those who object to the introduction of metaphysics into biology, that they can not logic- ally exclude the subject. As in one sense a function of nervous tissue, mind is one of the functions of the body. Its phenomena are everywhere present in the animal kingdom. Moreover, when studied in the inductive, a posteriori method, metaphysics is an exact science. As Bain observes, it is a good deal easier to fore- tell the actions of a man than those of the weather. It is only want of familiarity with the subject which can induce a biologist to exclude the science of mind from the field. For the benefit of those who are not familiar with the doctrine of archaesthetism, f I give an outline of its implications. In the first place, the hypothesis that consciousness had jolayed a leading part in evolution would seem to be negatived by the well-known facts of reflex action, automatism, etc., where acts are often un- consciously performed, and often performed in direct opposition to present stimuli. But while it is well understood that these phenomena are functions of organized structure, it is believed that the habits which they represent were inaugurated through the immediate agency of consciousness. It is not believed that a designed act can have been performed /or the first time X without consciousness on the part of the animal of the want which the act was designed to relieve or supply. This opinion accords with our knowledge of ourselves, and, by irresistible inference, with our belief regarding other animals. From such familiar observation we also know that so soon as a movement of body or mind has been acquired by repetition, consciousness need no longer accom- pany the act. The act is said to be automatic when performed * " The Evidence for Evolution in the History of the Extinct Mammalia," Am. Ass. Adv. 8ci., 1883, p. 32. f "American Naturalist," 1882, p. 454. X The same view is expressed by Ribot, " Diseases of the Will," p. 38 (Humboldt Libr.). ON CATAGENESIS. 425 witliout exertion, either consciously or unconsciously, and in those functions now removed from the influence of the unconscious mind such acts are called reflex. The origin of the acts is, how- ever, believed to have been in consciousness, not only for the rea- sons above stated, but also from facts of still wider application. The hypothesis of archsesthetism then maintains that conscious- ness as well as life preceded organism, and has been the jjrimum mobile in the creation of organic structure. This conclusion also flows from a due consideration of the nature of life. I think it possible to show that the true definition of life is, enei^gy directed hy sensihility, or ly a mechanism luliich has originated under the direction of sensiMUty. If this be true, the two statements that life has preceded organism, and that consciousness has preceded organism, are co-equal expressions. II. COls'SCIOUSIi^ESS, EITERGY, AN'D MATTER. Eegarding for the time being the phenomena of life as energy primitively determined by consciousness, let us look more closely into the characteristics of this remarkable attribute. That con- sciousness, and therefore mind, is a property of matter, is a neces- sary truth which to some minds seems difficult of acceptance. That it is not an attribute of all kinds of matter is clear enough, but to say that it is not an attribute of any kind of matter is to utter an -unthinkable proposition. To my mind the absence of tridimensional matter is synonymous with nothingness or abso- lute vacuity. To say that phenomena have a material basis, is for me only another way of saying that they exist. It being granted then that consciousness is an attribute of matter, or a certain behavior of matter, it remains to trace its relation to energy, which is here used in the sense of motion. Consciousness is clearly not one of the known so-called inorganic forces. Objects which are hot, or luminous, or sonorous, are not, as is well known, on that account conscious. Consciousness is not then a necessary condition of energy. On the other hand, in order to be conscious, bodies must possess a suitable temperature, and must be suitably nourished. So energy is a necessary condition of consciousness. For this reason some thinkers regard consciousness as a form or species of energy. For my own part, in classification, I prefer to keep very different things apart. To classify consciousness with heat, light, sound, etc., does violence to my sense of fitness and to all proper definitions. This is well shown by Prof. Clifford in 426 METAPHYSICAL EYOLUTIOX. the following passage : *^ It will be found excellent practice, in the mental operations required by this doctrine, to imagine a train the fore part of which is an engine and three carriages linked with iron couplings, and the hind part three other carriages linked with iron couplings ; the bond between the two parts being made out of the sentiments of amity subsisting between the stoker and the guard." * This satire, whether intentionally or not on thfe part of its learned author, expresses at once the distinctive char- acter of consciousness in esse and the imjDossibility of dissociating it from energy in posse. For it is sufficiently clear that while the conscious feelings of the stoker and the guard could hy tJie7nselves do nothing for the train, such a state is essential to the energy displayed by them when they are at work for its benefit. We all understand the absurdity of such expressions as the equivalency of force and matter, or the conversion of matter into force. They are not, however, more absurd than the corresponding proposition more frequently heard, that consciousness can be converted into energy, and vice versa. The energetic side of consciousness, however, may be readily perceived by a little attention to its operations. Acts j^erformed in consciousness involve a greater exjDenditure of energy than the same acts unconsciously performed. The difficulty of a given piece of labor is in direct proportion to its novelty ; that is, is in direct proportion to the amount of endeavor we use in its per- formance. This is another way of saying that the labor is direct- ly as the consciousness involved. Another evidence of the dynam- ic character of consciousness is its exclusive and therefore com- plementary character. Two opposite emotions can not occupy the mind at the same moment of time. An emotion excludes all high intellectual work, and vice versa. But there is no fact with which we are more familiar than that consciousness in some way determines the direction of the energy which it characterizes. The stimuli which affect the movements of animals at first only produce their results by transmission through the intermediation of consciousness. Without consciousness, edu- cation, habits, and designed movements would be impossible. So far as we know, the instinct of hunger, which is at the foundation of animal being, is a state of consciousness in all animals. This in- contestable fact is overlooked by the materialists properly so called. * " Scientific Basis of Morals," Humboldt Library Ed., p. 21. ON" CATAGENESIS. 427 On the other hand, as consciousness is an attribute of matter, it is of course subject to the laws of necessity to which matter and energy conform. For instance, it can not cause two solid bodies to occupy the same space at the same time, nor can it add one body to one body and thus make three bodies. No more can it make ten foot-pounds of energy out of five foot-j^ouuds of energy, and it can not abolish time more than it can annihilate space. These are fundamental truths which are overlooked by a majority of mankind. Moreover, nothing is more common than to hear life or mind spoken of as though it of itself is a "sub- stance," and not, as it should be, as an attribute or condition of substance or matter. What is, then, the immediate action of consciousness in direct- ing energy into one channel rather than another ? To take an illustration : Why, from a purely mechanical point of view, is the adductor muscle of the right side of the horse's tail contracted to brush away the stinging fly from the right side of the horse's body rather than the left adductor muscle ? Why was the con- traction-provoking energy deflected into the right interspinal motor nerves rather than into those of the left side ? Why is the ear of the horse turned forward to catch tlie sound in front of him and backward to gather the sound coming from behind ? The first crude thought is, that consciousness supplies another energy which turns aside the course of the energy required to produce the muscular contraction ; either as the man with the rein in his hand turns aside the horse's head, or as the shield he holds deflects a moving body. But consciousness jt?er 5e, that is, regarding it in its proper and distinctive definition, is not itself a force (= energy). How, then, can it exercise energy ? Certainly no more than the bare good-will of the train hands can pull the train. Such an explanation is to admit the possibility of making something out of nothing. III. THE RETROGRADE METAMORPHOSIS OF EifERGY. The key to many weighty and mysterious phenomena lies in the explanation of the so-called voluntary movements of animals. I sav "so-called," because true will is not at all involved in the question. I mean the acts directed by consciousness, the acts which would not take place at all if the animal were unconscious. That there are many such acts you well know. The explanation can only be found in a simple acceptance of the fact as it is, in 428 METAPHYSICAL EVOLUTION. the thesis, that energy can 'be conscious. If true, this is an ulti- mate fact, neither more nor less difficult to comprehend than the nature of energy or matter in their ultimate analyses. But how is such a hypothesis to be reconciled with the facts of nature, where consciousness plays a part so infinitesimally small ? The explanation lies close at hand, and has already been referred to. Energy become automatic is no longer conscious, or is about to be- come unconscious. That this is the case is matter of every-day observation on ourselves and on other animals. "What the molec- ular conditions of consciousness are, is one of the problems of the future, and for us a very interesting one. One thing is cer- tain, the organization of the mechanism of habits is its enemy. It is clear that in animals, energy, on the loss of consciousness, un- dergoes a retrograde metamorjohosis, as it does later in the history of organized beings on their death. This loss of consciousness is first succeeded by the so-called involuntary and automatic func- tions of animals. According to the law of catagenesis, the vege- tative and other vital functions of animals and plants are a later product of the retrograde metamorphosis of energy. With death, energy falls to the level of the polar tensions of chemism, and the regular and symmetrical movements of molecules in the crystalli- zation of its inorganic products. Let us now trace in more de- tail the energies displayed by animals and plants. It has been already advanced (see page 425) that the phenom- ena of growth-force, which are especially characteristic of living things, originated in the direction given to nutrition by conscious- ness and by the automatic movements derived from it. There remain, however, some other phenomena which do not yield so readily to this analysis. These are : first, the conversion by ani- mals of dead into living protoplasm ; second, the conversion of inorganic substances into protoplasm by plants ; and third, the manufacture of the so-called organic compounds from the inor- ganic by plants. To these points we may return again. It is also well known that living animal organisms act as producers, by conversion, of various kinds of inorganic eneregy, as heat, light, sound, electricity, motion, etc. It is the uses to which these forces are put by the animal organism, the evident design in the occasion of their production, that gives them the stamp of organic life. We recognize the specific ultility of the secretions of the glands, the appropriate distribution of the products of digestion, and adaptation of muscular motion to many uses. The increase ON CATAGENESIS. 4,29 of heat to protect against depression of temperature ; tlie liglit to direct the sexes to each other ; the electricity as a defense against enemies — display unmistakably the same utility. We must not only believe that these functions of animals were originally used by them under stimulus, for their benefit, but, if life preceded organism, that the molar mechanism which does the work has developed as the result of the animal's exertions under stimuli. This will especially apply to the mechanism for the production of motion and sound. Heat, light, chemism, and electricity doubt- less result from molecular aptitudes inherent in the constitution of protoplasm. But the first and last production of even these phenomena is dependent on the motions of the animal in obtain- ing and assimilating nutrition. For without nutrition all energy would speedily cease. Now the motion required for the obtain- ing of nutrition has its origin in the sensation of hunger. So, even for the first stej)s necessary to the production of inorganic forces in animals, we are brought back to a primitive conscious- ness. To regard consciousness as the primitive condition of energy, contemplates an order of evolution in large degree the reverse of the one which is ordinarily entertained. The usual view is, that life is a derivative from inorganic energies as a result of high or complex molecular organization, and that consciousness (= sen- sibility) is the ultimate outcome of the nervous or equivalent energy possessed by living bodies. The failure of the attempts to demonstrate spontaneous generation will prove, if continued, fatal to this theory. Nevertheless the order can not be absolutely reversed. Such a proceeding is negatived by the facts of the necessary dependence of the animal kingdom on the vegetable, and the vegetable on the inorganic, for nutrition, and consequently for existence. So the animal organism could not have existed prior to the vegetable, nor the vegetable prior to the mineral. The explanation is found in the wide application of the ^^ doctrine of the unspecialized," * so clearly demonstrated by paleontology. From this point of view creation consists in specialization, an ex- pression which describes the specific action of the general princi- ple described by Spencer as the conversion of the homogeneous into the heterogeneous. To be more explicit, it consists of the * The term specialized, introduced into biology by Prof. Dana, has been used in connection with energy in creation by the author, "Penn Monthly," 1875, p. 569. 430 METAPHYSICAL EVOLUTION. production of mechanism outof no mechanism, of different kinds of energy out of one kind of energy. The material basis of con- sciousness must then be a generalized substance which does not display the more automatic and the polar forms of energy. From a physical standpoint j^rotoplasm is such a substance. Its insta- bility indicates weakness of chemical energy also, which suggests that the complexity of its molecule may be due to some form of energy not properly chemical. The readiness with which it un- dergoes retrograde metamorphosis shows that it is not self-sustain- ing, and furnishes a good illustration of creation of specialized substances by a running down in the scale of being. Loew and Bokorny * suggest that 'Hhe cause of the living movements in protoplasm is to be sought for in the intense atomic movements, and therefore easy metamorphosis of its aldehyde groups of com- ponents " ; the molecular movements becoming molar, to use the language of Lester Ward. The position which I now present re- quires the reversal of the relations of these phenomena. General- ized matter must be supposed to be capable of more varied molecu- lar movements than specialized matter, and it is believed that the most intense of all such movements are those of brain tissue in mental action, which are furthest removed of all from molar move- ments. From this point of view, when molar movements are derived from molecular movements, it is by a process of running down of energy, not of elevation ; by an increase of the distance from mental energy, not an approximation to it. The fact that the physical basis of consciousness is composed of four substances, which are respectively a monad, a dyad, a triad, and a tetrad, doubtless has something to do, as I have sug- gested,! with its exhibition of this remarkable attribute. It might be supposed that the presence of carbon had the effect of restrain- ing the chemical and physical molecular tendencies of the three other substances. From this standing-ground we may imagine that other substances besides protoplasm might support conscious- ness and life. In other parts of the universe, other substances they would have to be, if consciousness exist there. The manner m which protoplasm is made at the present tinie is highly suggestive. It is manufactured by living plants out of * " Die chcmische Kraftquelle in Icbenden Protoplasma." von 0. Loew u. T. Bo- korny, Munich, 1882, L t "Penn Monthly," 1875, p. 574. ON CATAGENESIS. 43I inorganic matter, the hydrogen, carbon, nitrogen, and oxygen contained in the atmosphere and in the earth. As dead plants will not perform this function, this action is regarded as in some way due to the presence of life. The energy peculiar to living pro- toplasm, and derived primarily in part only from the sun's rays, directs energy so that the complex molecular aggregation proto- plasm is the result. This is the only known method of manufact- ure from inorganic matter of this substance. The first piece of protoplasm had, however, no paternal protoplasm from which to derive its being. The protoplasm-producing energy must, there- fore, have previously existed in some form of matter not proto- plasm. This is also suggested by the fact that it really antagonizes the chemical forces, and might be called, from this fact, anticliem" ism. The protoplasm-sustaining energy of animal protoplasm may be a less energetic derivative, or vice versa. In terms of the theory of catagenesis, the plant life is a derivative of the primi- tive life, and it has retained enough of the primitive quality of self-maintenance to prevent it from running down into forms of energy which are below the life level ; that is, such as are of the inorganic chemical type, or the crystalline physical type. A part of the energy does so run down, as can be seen in the few auto- matic movements of plants, and the phosphorescence of some. Also symmetrical crystals are made by some. But M. Pasteur has shown * that whenever the crystals are of the organic type, i. e., contain carbon, they are not symmetrical but are unilateral, or, as he terms them, dissymmetrical. This indicates that the presence of carbon has restrained a little the absolute symmet- rical automatism of the formative force. IV. ORIGIN" OF LIFE ON" THE EARTH. If, then, some form of matter other than protoplasm has been capable of sustaining the essential energy of life, it remains for future research to detect it, and to ascertain whether it has long existed as part of the earth's material substance or not. The heat of the earlier stages of our planet may have forbidden its presence, or it may not. If it were excluded from the earth in its first stages we may recognize the validity of Sir William Thomson's suggestion that the physical basis of life may have reached us from some other region of the cosmos by transporta- * "Revue Scientifique," 1884, Jan., p. 2. 432 METAPHYSICAL EYOLUTIOK tion on a meteorite. If protoplasm in any form were essential to the introduction of life on our planet, this hypothesis becomes a necessary truth. Here let me refer to the fact that hydrocar- bonaceous substances have been discoyered in meteorites. Here also the remarkable discovery of Huggins claims attention.* This veteran spectroscopist has detected the lines of some hydrocar- bon vapor in the spectra of interplanetary spaces. The signifi- cance of this discovery is at once perceived if we believe that hydrocarbons are only produced under the direction of life.f Granting the existence of living protoplasm on the earth, there is little doubt that we have some of its earliest forms still with us. From these simplest of living beings both vegetable and animal kingdoms have been derived. But how was the distinction be- tween the two lines of development, now so widely divergent, originally produced ? The process is not difficult to imagine. The original plastid dissolved the salts of the earth and appro- priated the gases of the atmosphere and built for itself more pro- toplasm. Its energy was sufficient to overcome the chemism that binds the molecules of nitrogen and hydrogen in ammonia, and of carbon and oxygen in carbonic dioxide. It apparently communi- cated to these molecules its own method of being, and raised the type of energy from the polar non-vital to tlje adaptive vital by the process. Thus it transformed the dead mineral world, j^er- haps by a process of invasion, as when a fire communicates itself from burning to not burning combustible material. Thus it has been doing ever since, but it has redeposited some of its gathered stores in various non-vital forms. Some of these are in organic forms, as cellulose ; others are crystals imprisoned in its cells ; while others are amorphous, as waxes, resins, and oils. But con- sciousness a]3parently early abandoned the vegetable line. Doubt- * See address of C. W. Siemens, Prest. British Ass. Adv. Science, 1882 ; " Nature/' 1882, p. 400. •}■ Says Mr. S. F. Peckham ("American Journal of Science and Arts," 1884, p. 105), on the origin of bitumens: "These chemical theories [of the origin of bitu- men] are supported by great names, and are based upon very elaborate researches, but they require the assumption of operations nowhere witnessed in nature or known to technology. . . . In the chemical processes of nature complex organic com- pounds pass to simpler forms, of which operation marsh gas, like asphaltum, is a resultant, and never the crude material upon which decomposing forces act." The fact that many organic compounds are now produced in the laboratory, does not prove that such substances can be produced without the exercise of a spe- cies of energy different from the inorganic types with which we are acquainted. OlSr CATAGENESIS. 433 less all the energies of vegetable protoplasm soon became automatic. The plants in general, in the persons of their protist ancestors, soon left a free-swimming life and became sessile. Their lives thus became parasitic, more automatic, and in one sense degen- erate. The animal line may have originated in this wise. Some indi- vidual protists, perhaps accidentally, devoured some of their fel- lows. The easy nutrition which ensued was probably pleasura- ble, and once enjoyed was repeated, and soon became a habit. The excess of energy thus saved from the laborious process of making j^rotoplasm was available as the vehicle of an extended consciousness. From that day to this, consciousness has aban- doned few if any members of the animal kingdom. In many of them it has specialized into more or less mind. Organization to subserve its needs has achieved a multifarious development. There is abundant evidence to show that the permanent and the successful forms have ever been those in which motion and sensi- bility have been preserved, and most highly developed. This review of the history of living organisms has been epito- mized in the following language: *^ Evolution of living types is then a succession of elevation of platforms, on which succeeding ones have built. The history of one horizon of life is that its own completion but prepares the way for a higher one, furnish- ing the latter with conditions of a still further development. Thus the vegetable kingdom died, so to speak, that the animal kingdom might live, having descended from an animal stage to subserve the function of food for animals. The successive types of animals first stimulated the development of the most susceptible to the conflict, in the struggle for existence, and afterward fur- nished them with food." V. CATAGEN"ESIS OF IXORGAIN'IC ENERGY. If the principles adopted in the preceding pages be true, it is highly probable that all forms of energy have originated in the process of running down or specialization from the primitive energy. In the department of physics I am not at home, and touch upon it merely to carry out to a necessary conclusion the hy- pothesis presented in the preceding pages. It may be that physi- cists and chemists may find value in the suggestions which come from the side of biology. A cursory perusal of the general hy- 28 434 METAPHYSICAL EVOLUTION. potheses current in these departments shows that the door is wide open to receive light from this quarter. What can be offered here is of the vaguest, yet it may suggest thought and research in some minds. In the first i^lace, it is highly probable that one of the problems to be solved by the physicists of the present and future is that of a true genealogy of the different kinds of energy. In this con- nection a leading question will be the determination of the essen- tial differences between the different forms of energy and the material conditions which cause the metamorphosis of one kind of energy into another. In constructing a genealogy of energies, it must be observed that we will probably obtain not a single line of succession, but several lines of varying lengths. It must also be remembered that, as in the forms of the material world, which are their expres- sion, a greater or less extensive exhibition of all the types remains to the present day. That the tendency of purely inorganic energy is to '*run down," in all excejot possibly some electric operations, is well known. Inorganic chemical activity constantly tends to make simpler compounds out of the more complex, and to end in a satisfaction of affinities which can not be further disturbed excej)t by access of additional energy. In chemical reaction the prefer- ence of energy is to create solid precipitates. In the field of the physical forces we are met by the same phenomenon of running down. All inorganic energies or modes of motion tend to be ulti- mately converted into heat, and heat is being steadily dissipated into space. Therefore the result has been and will be the creation of the mineral kingdom ; of the rocks and fluids that constitute the masses of the worlds. The process of creation by the retrograde metamorphosis of energy, or, what is the same thing, by the specialization of energy, may be called catagenesis. It may be denied, however, that this process results in a specialization of energy. The vital energies are often regarded as the most special, and the inorganic as the most simple. If we regard them, however, solely in the light of the essential nature of energy, i. e., power, we must see that the chemical and physical forces are most specialized. The range of each species is absolutely limited to one kind of effect, and their diversity from each other is total. How different this from the versatility of the vital energy ! It seems to dominate all forms of ON CATAGENESIS. 435 conversion of energy, by the mechanisms which it has, by evolu- tion, constructed. Thus, if the inorganic forces are the products of a primitive condition of energy which had the essential qhar- acteristics of vital energy, it has been by a process of specializa- tion. As we have seen, it is this specialization which is every- where inconsistent with life. With these preliminary remarks we may now consider very tentatively the relations of the different kinds of energy to each other and to consciousness. In practice it is sometimes difficult to draw the line between conscious and unconscious states of energy. One reason is that, although a given form of energy may be unconscious, consciousness may apprehend the action by perceiving its results. The distinction is rendered clearer by the reflection that we can perceive by sight or touch any action of the body of whatever character The energy of the conscious type is therefore altogether mental. The relations may be ex- pressed as follows : A. Designed (always molecular). Examples. I. Conscious. 1. Involving effort " Voluntary " acts. n -Ki ^ • ^ - tc ^ \ Passive perception. 2. Not involvmc^ effort „, ( Conscious automatism. II. Unconscious. 3. Involving mental process Unconscious automatic. 4. Not involving mental process Eefiex. B. Not designed. I. Molecular. 5. Electric, 6. Chemical, ) 7 Ph ' 1 \ Crystallific and non-crystallific. II. Molar. 8. Cosmic. The only strictly molar energies of the above list are the cos- mical movements of the heavenly bodies. The others are molec- ular, although they give rise to molar movements, as those of the muscles, of magnetism, etc. Some molar movements of organic beings are not, in their last phases, designed ; as those produced by nervous diseases. The transition between the organic and the inorganic energies may be possibly found in the electric group. Its influence on life, its production of contractions in protoplasm, and its resemblance to nerve force, are well known. It also compels chemical unions 436 METAPHYSICAL EVOLUTION. otherwise impracticable, thus resembling the energy of the pro- toplasm of plants, whose energy in actively resisting the disinte- grating inorganic forces of nature is so well known. Perhaps this type of force is an early-born of the primitive energy, one which has not descended so far in the scale as the chemism which holds so large a part of nature in the embrace of death. Vibration is inseparable from our ideas of motion or energy, not excluding conscious energy. There are reasons for supposing that in the latter type of activity the vibrations are the most rapid of all those characteristic of the forces. A center of such vibra- tions in generalized matter would radiate them in all directions. With radiant divergence the wave lengths would become longer, and their rate of movement slower. In the differing rates of vibra- tions we may trace not only the different forms of energy, but diverse results in material aggregations. Such may have been the origin of the specialization of energy and of matter v/hich we behold in nature. Such thoughts arise unbidden as a remote but still a legitimate induction from a study of the wonderful phenomenon of animal motion ; a phenomenon everywhere present, yet one which re- treats, as we pursue it, into the dimness of the origin of things. And when we follow it to its fountain head, we seem to have reached the origin of all energy, and it turns upon us, the king and master of the worlds. XXI. THE OEIGIN OF THE WILL. I. THE defikitio:n" of the will. Defikitioks of tlie term '"Will," as we find them in meta- physical writers, are not identical ; and much apparent difference of opinion depends, as usual, on this diversity of statement. Locke regards the concepts *^ will "and ** freedom "as entirely distinct in their nature, and not essentially related to each other. He says : *^ Freedom belongs as little to the will, as swiftness to sleep, or squareness to virtue. Freedom to do is one power, will to do is another : will, a power of the mind exerting dominion over some part of a man by employing it in or withholding it from any par- ticular action ; freedom, again, a power which a man has to do or to forbear doing any particular action." It appears that what Locke here denominates will is that common activity of the mind which expresses itself in action, which may be readily considered apart from the question of choice. This doubtless expressed some- thing to the metaphysicians of that time, but merely signifies to the physiologist of the present day the movement derived from the metamorphosis of nutritive material in the arterioles of the brain, which when consciously performed are called thoughts and feelings, and are the necessary precursors of a class of muscular acts. The question of will properly so called is not yet entered on at this point. Dr. Willis * elaborates Locke's position in the following language : *^ But there is, in fact, no one particular primitive faculty that wills in the human mind ; will is a general term, and belongs to and is expressive of the activity of each of the primitive faculties of our nature ; the benevolent faculty being active, causes us to will to do good and charitable offices ; the rev- erential faculty being active, to will to feel respectfully or rever- ently ; the musical faculty active, to will to sing or hear music, * "Benedict do Spinoza: his Life, Correspondence, and Ethics," 1S70, p. 145. 438 METAPHYSICAL EVOLUTION. etc. ; and the Vvilling here is necessary ; but whether we yield to the impulse of the benevolent, reverential, or musical faculty, and indulge therein their various willings, is not so ; here we are free, and can yield or abstain as we list." This passage renders it the more clear that the latter part of Locke's statement, in which he defines freedom, is that in which he really refers to the will as generally understood ; and Dr. Willis's assertion of the existence of our ability 'Ho yield or abstain as we list," grants all that the advocate of 'Hhe freedom of the will" could desire. The modern automatic school only avoid discarding the term will altogether by using it in the sense of Locke's definition. They make it merely the conscious mental activity that precedes the act ; the direction of that activity being necessary in its char- acter ; i. e., the result of impinging stimuli. In other words, on the automatic theory, the spontaneous activity of the body is directed or deflected by stimuli, whose ultimate form depends on the existing mental machinery through which they pass. There is avowedly no room for a self-determination in such a process, and its existence is therefore denied by this school. Inasmuch as a faculty of self-determination is what is here understood by the term will, and the question in the present article is whether there be or be not such a faculty, the inquiry to which we address our- S3lves is whether a human will exist or not. Says Dr. Carpenter : * '' The psychologist may throw himself into the deepest waters of speculative inquiry in regard to the relation between his mind and its bodily instrument, provided that he trusts to the inherent buoyancy of that great fact of consciousness that zue have within us a self'determiiiing poiuer which we call will, " The existence of such a faculty is in these words assumed by Dr. Carpenter, but I have looked in vain in his writings for a demonstration of the truth of this position. The same is true of the works of many other metaphysicians. Will may be considered in two aspects : first, as a control over the origin of mental or bodily movements ; and second, as a con- trol over the direction which those movements take. The latter case is the one chiefly considered here, as the one involved in cus- tomary definitions of human will. It need scarcely be added that the concept will is an abstrac- tion from supposed special exhibitions of it, and represents a sup- posed mental property. * " Mental Physiology," p. 28. THE ORIGIN" OF THE WILL. 439 II. THE iq^ATUEE OF ACTIONS. The discussion between the advocates of the freedom of the will on the one hand, and those of the doctrine of necessity on the other, has often been obstructed by a petitio principii, which yields the case to the latter side at the outset. This is the dictum which has often passed unchallenged by both parties, that "■ human action is the product of the strongest inducement," or, otherwise stated,. that "the will is the result of a balancing of opposing motives," or that "the will obeys the strongest motive." This is simply the statement, in reversed order, of what we might suppose without examination to be a general truth, viz. : that the motives which precede the acts which we observe are stronger than all others at the time. If this proposition be true without qualifica- tion, there is no further need of discussion, since it involves the negation of freedom, or of a power of choosing. But as such, it is an assumption in advance of a conclusion in the case under con- sideration ; a begging of the question in a clear sense. Such a position can only be adopted as a result of the fullest investigation into the phenomena ; it can not be accorded before examination into the facts. But the statement may be admitted with this important qualifi- cation, by which the argument is transferred to another stage of the subject, viz. : that we do not thereby explain why the induce- ments to act thus and so, do, in many obvious cases, overbalance all others in a given human mind. This inquiry is not fruitless, so long as we have before us every day examples of men acting differently under identical circumstances. If there be any " lib- erty," it is exercised at the point of permitting inducements or motives of one kind to occupy the mind to the exclusion of those of another kind ; and secondly, such occupation being granted, freedom might be exercised in removing restraint from the press- ure of the present motive, so that the act can take place. If there be no inherent power of controlling the attention, and none of restraining the pressure of motive, then there is no will in any proper sense of the word, and man is an irresponsible automaton. The proof or disproof of this proposition must, however, be the end, not the beginning, of the discussion. An inquiry into the origin of actions must be preceded by an examination into the nature of the acts themselves. The follow- ing classification is offered, as expressing as nearly as possible their 44:0 METAPHYSICAL EVOLUTIOK relations to the general developmental position of active beings, without any pre-suppositions as to their automatic or voluntary character. It is necessarily assumed that all acts are performed with reference to the acquisition of pleasure or the avoidance of pain ; in other words, that all acts are due to motive, and are the expression of design on the part of the actor. This is as true of the simplest as of the most complex actions of animals, whether consciously or unconsciously performed. The movement of the Amoeha in ingulfing a Diatom in its jelly, is as much designed as the diplomacy of the statesman, or the investigations of the stu- dent. And the motive may be the same in all three cases ; viz. : hunger. But as the unconscious acts have been probably derived from conscious ones by organization, a fundamental classification must first recognize their relations to the two necessary terms of consciousness, the subject and the object. All actions may then be divided into two classes ; those which are performed witli the design of securing the pleasure of the subject, and those whose motive is to secure pleasure for the object as distinct from, i. e., opposed to, that of the subject. The tendencies thus defined have been named, in other connections, the appetent and the altruistic, and these names may be preserved as equally appropriate for the present purpose. Actions of the appetent class difl'er according to the developmental grade of the animal displaying them, or the grade of the organ of the body to which they are proper. In their simplest form they are mechanical movements, following a stimu- lus without the intervention of any rational process ; the end being attained by movements, whose directions are determined by me- chanical or physical laws only. Such acts belong to the lowest type of animals, and are also seen in the organic functions of all animals ; they may be called the anoesthetic division. They may be performed consciously or unconscicasly. Acts of another order are those which, while due to stimuli, are directed by a process of ratiocination. They are higher than those of the previous order, because they successfully accomplish their object under changing circumstances, to which they adapt themselves as the others can not. Like them they may be performed in consciousness or in unconsciousness, or in a still higher state of the mind, that of self- consciousness. The last condition is only possible to animals of a high order of intelligence, since it not only demands an exercise of the rational faculty, with reference to objects, but also with reference to itself — the subject. These three groups form the TEE OPJGIX OF THE WILL. 441 rational order. The unconscious actions of both tlie anaesthetic and rational kinds are called '^ reflex ; " and all of them are ** auto- matic," in so far as they are performed without will ; terms more fully defined in the following pages. The process of intellection in unconsciousness is called unconscious cerebration. Actions of the second great class, the altruistic, demand for their performance the attributes necessary for the highest of the appetent class. They require intelligence enough for the percep- tion of what is the pleasure of the object, and self-consciousness, to know that that pleasure is inconsistent with its own, or subject- ive pleasure. The arrangement may be summarized as follows : L Appetent class. -.A J.1 i.- ( Unconscious (reflex). 1. Anaesthetic. 1 ^^ . ( Oonscious. ( Unconscious (reflex). 2. Eational. I Conscious. ( Self-conscious. II. Altruistic class ; rational and self-conscious. Under the definition of will above given, it can not be present in unconscious or reflex actions, and the inquiry is limited to the conscious groups exclusively. It may then be well to add a few words on the nature of consciousness. This faculty is here understood in its broadest sense, namely, subjective perception. The term consciousness expresses the knowledge by the subject of the effects of stimuli on itself, which ranges all the way from the mere sense of contact to, the sense of an idea. An unprejudiced scrutiny of the nature of conscious- ness, no matter how limited that scrutiny necessarily is, shows that it is qualitatively comparable to nothing else. The attempts to correlate it with the physical forces have so far been utter failures, although the vital forces, to which it gives direction, are evidently not excluded from the laws of quality and quantity. The com- mon hj^pothesis that consciousness is the product of evolution appears to the writer, in view of this primary fact, to be irra- tional ; while the converse, that evolution is a product of con- sciousness, is far more likely to receive ultimate demonstration. From this stand-point it is looked upon as a state of matter which is co-eternal with it, but not co-extensive. Itself in its totality a reservoir of force, it is the source of all physical and vital forces, with which it has therefore an equivalency of quanti- 442 METAPHYSICAL EVOLUTION. ties, but not of qualities. Tlie cause of the difference between conscious and unconscious force must be secondarily due to differ- ent conditions of matter as to its atomic constitution ; conscious- ness being only possible, so far as we can ascertain, to matter which has not fallen into fixed and automatic relations of its atoms. The condition appears to be one of tension, in which the automatic (crystalline) tendencies antagonize each other, the material being all the while in the metastatic condition of nutri- tion. This idea is parallel to that of Heraclitus, who held that the essence of all things lay in per|)etual modification, a universal becoming, an eternal emergence and disappearance. In accordance with the preceding views, the relations between consciousness and matter are thus depicted as of a mutually ne- cessary character, the movements of conscious force involving con- sequences to itself from which the properties of matter necessarily preclude its escape. If we trace the consciousness of animals to such an origin, it may be asked. Why have not such beings the powers and perfec- tions of their source, in quality if not in quantity ? The answer to this query, in view of the fact that they have not such qualities, is only to be found in an investigation of the nature of memory. The absence of memory of the past would be equivalent to igno- rance ; while a new material vehicle might render memory possi- ble for the future, and thus education, under new surroundings, create diverse beings from a primal common source. We must include in our estimation of the distributions of con- sciousness and forces not our planet alone, nor our system only, but the universe. Hence Sir William Thompson's idea, that con- sciousness ("life") was originally exotic to our earth, is an alto- gether permissible hypothesis. If there be such a state of consciousness as will, it must have appeared in course of the evolution of animals, at some point in the series of the stages of progress through which their mind has passed. Yet it is maintained by some thinkers that the doctrine of evolution necessarily excludes the idea of freedom from the nature of the minds thus produced. The case is, however, in- volved in that of consciousness, and the investigation of it must proceed in the same manner. If it has been shown that will does exist in connection with evolution, we must proceed to discover, if possible, the relation between the two facts. The proof of the existence of a freedom, power of choice, or THE ORIGIN OF THE WILL. 443 will, is found in the origin of the altruistic class of acts, which are probably only possible to the human species. These have been above defined as those in which the pleasure of the object, as dis- tinct from, and therefore opposed to, that of the subject, is the design of the act. This definition excludes acts for the benefit of others in which the actor is also gratified, since the motive may be in that case the pleasure of the subject. No doubt, many gen- erous acts are of this character, but they were not such the first time they were performed, since experience of their pleasurable character had not then been acquired, and the evidence of all past experience was of a diametrically opposite character. In other words, the motives already organized in the mind of the subject were all in favor of the subject. The laws of evolution render the introduction of a new element of character at this point absolutely necessary. It is well known that the development of mind, and through it of all the acts of the first or appetent class, has been due to the pursuit of pleasure and avoidance of pain on the part of the subject. The pursuit of an opposite course, by animals whose pleasures and pains are those of the successful ful- fillment of the necessary functions of life, or the reverse, would insure their speedy extinction. Their survival has been due to their prompt discrimination of favorable and unfavorable con- ditions through their sensibilities, and the human species, as the product of evolution, displays these sensibilities in their highest form. Under these circumstances it is obvious, since none but the inherited motives, with refinements due to more complex circumstances, can be found in his mind, that without the inter- vention of will, an altruistic act is impossible. It has also been pointed out that such can only be performed by a being capable of the highest state of consciousness, i. e., self- consciousness ; in other words, by a being capable of recognizing its own mental states. Under such circumstance only can it dis- tinguish the mental states of a being apart from itself, toward whom the altruistic act is directed. It being then conceded that will is exhibited in certain human actions, it becomes important to determine, if possible, the condi- tions under which it appeared in the course of the evolution of man. III. THE ELEMENTS OF MIND. Prior to considering the origin of states of mind, it is neces- sary to go over the well-trodden field of its original constitution. 444 METAPHYSICAL EVOLUTION. There are three primary conditions of consciousness^ which naturally grade into each other, viz.: pain, indifference, and pleasure. Consciousness is of one or the other of these types in all animals. The constant flow of activity, either in movements of the whole body or of particular 2:)arts of the body, has brought animals from their beginning into contact with other bodies, either at rest, or animated by active forces, as light and heat, which have varied their sensations, rendering them more positive in each of the three directions named. These sensations soon cease, leaving consciousness where it was, but not without marks of their former presence in the organism. They are recorded, and continue in unconsciousness so long as the organism remains unchanged. This is the first part of memory, i. e., retention. Under the influence of what is called cohesion, the impressions may be returned to consciousness in a less distinct form by the occurrence of new impressions which have some near relation with them as to time, place, or qualities of other kinds. This is the second part of memory, or reminiscence. The sum of the impressions which are necessar}' to memory constitutes experi- ence. It is evident that reminiscence is pleasurable or painful, as the experiences recalled were pleasurable or painful. Another quality is rendered possible by the two faculties of retention and cohesion, viz.: classification. This consists of a re-arrangement of retained impressions in accordance with different kinds of co- hesions, i. e., different kinds of likenesses. The products of classification may be brought into consciousness just as sensible impressions are revived ; but unlike these, they constitute in their totality a new experience of internal origin. When a cohesion between two circumstances is due to a repeated experience of the one as following the other, men entertain the idea that one is necessary to the other. From memory of the necessary results of our own activity, we have come to regard necessary sequences as the result of activity somewhere. If activity be discerned in the first of two coherent events, we regard it as a cause of the second : if the first be passive, the idea of cause does not arise in connection with it, but in some other active agent. Finally, all processes involving reminiscences are less distinct than the original impressions. Spencer calls the former /«m^, the loiter distinct ; the faint order are the processes of reason ; the distinct, of per- ception. Whether these processes are pleasurable, painful, or indifferent, THE ORIGIN OF THE WILL. 445 depends on the characteristics of the reminiscences wliich are their subjects. As the reminiscence is less distinct than the origi- nal impression, so there comes to be, as pointed out by Spencer, a faint order of pleasures and pains, which, with the indifferent class, form the material of the processes of reason. These mental states of pleasurable and painful consciousness constitute that primary diyision of the mind, the feelings or affections, as distinguished from the intellect. The feelings co-exist with intellectual operations of all grades of complication, since pleasures and pains are states which follow all kinds of activities, and therefore also reminiscences. To seek pleasure and to avoid pain constitutes the business of the lives of all conscious organisms ; and hence the feelings, as derived from exjDeriences, are the directive and often originative conditions of movements or actions. In animals with higher intellectual powers, the general classification of experiences of given objects or actions results in a higher order of the mental feelings, which are called likes and dislikes. When these forms of consciousness assume an intense condition due to stimuli, they become emotions or pas- sions. These details are entered into in order to show that the feel- ings in their various grades are the motives of action in all ani- mals, from the Amcela to man. In the former they are mere reminiscences ; in the latter they are so generalized as to become enduring principles of action, which put the intellect to every conceivable labor. And it is evident, from this foundation fact, how the intellect itself has been constructed. The activity stimu- lated by the feelings has resulted in new experiences, and the ac- cumulation and elaboration of these into new combinations of the faint type of consciousness, has been the law of their development. This we can observe in the education of one generation of living animals, and it has doubtless been the law of the generations of the past as well. We may then review the probable method of development of mind through the ages of past time. IV. THE DEYELOPMENT OF MIND. In the first place, it is evident that the evolution of mind has been due to the activity of animal life. Although not asserted, it is sometimes implied that '^ circumstances," in which the animal is passive, have been the efficient cause of mental development. That this could have been the case is inherently impossible, and 446 METAPHYSICAL EVOLUTION. since animals of the lowest types possess powers of movement, their activity has necessarily been an immediate cause, while sur- rounding circumstances have exercised a controlling influence. Animal activity must be traced to the generation of force or motion by a protoplasmic body which is constantly supplied with nutriment. This production of force is the basis of the acts of animals, up to and including man ; often, as remarked by Prof. Bain, displaying itself in aimless discharges or playful movements, as in lambs and boys. But we observe even in very simple organisms, as the Ammla, etc., that many movements are not aimless, nor without design. "We observe that these mere specks of jelly devour nutritious sub- stances, and reject the innutritions ; that they even distinguish between the Diatom which contains protoplasm within its shell, and the empty shell. Many facts of this kind lead us to believe in the consciousness of these pioneers of life, and seem to show that they have experiences of the pleasures of nutrition, and of the pains of retaining insoluble substances in the seats of assimi- lation. It would also appear that they rememler these sensations, so as to seek the pleasures and reject the pains, when in the course of their wanderings they again come into contact with the ma- terial objects which have caused thenl. Given these two terms, sensibility (consciousnsess) and memory, and we have the con- ditions by means of which the entire complex superstructure of the affectional and the intelligent acts has been elaborated out of mere movements. This has been accomplished by the well-known laws of organi- zation of habits, and heredity. The performance of an act under stimulus so modifies the structure of the bioplasts of the brain as to facilitate its repetition. With further repetition the organiza- tion is soon complete, and action follows the stimulus without direction, so long as no adverse influence affects the consciousness. Whether the act be one of the Rational or Anaesthetic orders, from this habitual stage it becomes automatic in the true sense, between which and the reflex act no line can be drawn. It is evident that the degree of consciousness present in animals will depend on the number of changes appearing in their surroundings, whether due to modifications of the external world, or movements of their own bodies. Inasmuch as the habits of the lower animals are few and simple, most of them must be automatically performed, the con- sciousness being only present at the commencements of the several THE ORIGIN OF TOE WILL. 447 processes. It is probable tliat the organization of mental functions was at the first identical with the so-called organic functions,* so far as they consist of mechanical movements ; and that the latter early became reflex and devoid of consciousness, developing sub- sequent forms through mechanical causes. The organization of mental functions, on the other hand, was by continued education, which requires the presence of consciousness at every step. The well-known fact of the inheritance of mental qualities shows that the evolution of mind has advanced by a continued process of accumulation as the product of animal experiences. The new generation has inherited the organization of the old, and all the reflex and automatic activities entailed by it, and has pro- ceeded in proportion to its activity to acquire new experiences, habits, and organization. V. THE BEGII^NIXGS OF DEVELOPMENT. (a) The Feeliiigs. The intellectual faculties of every animal thus belong to two classes : first, those which have been inherited ; and second, those which it has acquired by its own experiences. Of course 4:)rogress consists in accessions to the latter class, since inheritance without addition is mere repetition. If no acquisitions were made, or to be made, the mental, i. e., the cerebral organization inherited by animals would continually repeat the form of their actions as un- erringly as the nature of a machine gives the character to the movements propagated through its wheels and cranks. That much the larger proportion of animal acts are of this class, that is, are automatic, there can be no room to doubt. With an im- petus to movement given, the strongest liking or disliking selects the object or direction, and the reason furnishes the mode of ac- quisition or avoidance. The known past teaches of the unknown future, and the established circle of the functions of life is ful- filled. But without acquisitions, development is impossible. Acquisitions to experience are gained by movements of the body, and hence by the mental activity to which the latter are due. But it is evident that the primary movement has preced- ence in the order of time over the feeling which deflects it, or the experience which directs later actions. In the lowest animal * See " On Consciousness in Evolution, " "Pcnn Monthly," 1875, Aug., where this view' is held. 4^8 METAPHYSICAL EVOLUTION. the first movement was doubtless a mere discliarge of force ; but the first designed action, the appropriation of food, was due to a sense of want or hunger, which is a form of pain. This was fol- lowed by gratification, a pleasure, the memory of which consti- tuted a motive for a more evidently designed act, viz. : pursuit. These two mental states, the one painful, the other pleasurable, form the basis in the feelings of all appetent acts. The painful sense of want is the motive to the performance of the jDrimary class of actions, and the experience of pleasurable gratification fur- nishes the motive for a class which must be regarded as secondary. The primary organized feelings of animals are not numerous. In man, the most highly developed. Prof. Bain enumerates * only eleven types, and some of these he states may be further re- solved. From the stand-point of the evolutionist this is evidently necessary, and a corresponding reduction in number can be made. The develoiDment of the feelings has proceeded from the early be- ginnings above described, in subsequent ages, pari passu with that of the intellect. It is necessary in the nature of things that it should be so, since the finer and fuller the sensibility to pleasures and pains in all directions, the greater will be the complexity of experience, and hence of intelligence. It is not practicable to trace the history of the feelings here, but I allude briefly to one class of them — the social affections — as they have been treated by Herbert Spencer, whose contributions to this department of knowledge have been very important. This author maintains that the social affections are the product, in the department of mind, of the function of reproduction. They are the organized products of experiences of pleasures de- rived from fellow beings, just as other kinds of likes and dislikes are derived from experiences of the qualities of various objects. It is sufficiently evident that this faculty must survive, and the social instincts become more and more refined or specialized. It is a remarkable fact in the successional relations, and hence evo- lution, of the vertehrata, that the only system that has accompa- nied the nervous in its progress from generalization to specializa- tion and perfection, is the reproductive. Man, standing at the head of the series by his develojDcd brain, possesses also the most specialized reproductive system. He is inferior to many other Mammalia in his osseous and muscular type, and in his digestive * " The Emotions and the Will," p. 36. THE ORIGIN OF THE WILL. 449 organs, including dentition, etc., but the orders wliicli are his superiors in these respects yield to him the supremacy in the two systems mentioned. Functionally the two systems oppose each other, and that exercise of the one is at the exjoense of the other is a physiological law. Health of the individual, and persistence of the species, depend on the maintenance of the equilibrium between them. This is because success in obtaining food on the one hand depends on intelligence, and undue power can not be expended in other directions without starvation. Thus the law of evolution lends full support to the doctrine first formulated by Kant, of the dual nature of the human mind, in its division into the intellect and the affections. (b) In the Intelligence. The intellect includes a record of experiences of resemblances and differences, of causes and effects, arranged in orders of place, time, and of qualities of all kinds. The importance of an intellect depends on the number of experiences it contains ; on the clear- ness with which qualities can be brought into consciousness ; on the correctness with which the classification expresses the quali- ties ; on the relation which the qualities preferred bear to an ob- ject of pursuit ; and on the rapidity with which any or all of these functions may be performed. The triumph of reason is foresight or predication, in which it brings into consciousness the unknown, by reproducing its experiences of the known. This is the serv- ice rendered by education, by the acquisition either of experiences themselves, or of the experiences of others. Acquisitions then do not imply a predication of the unknown from the known, but an actual addition to the stock of the known. The automatic life above described includes no such process, but is a routine varying only in unimportant details, and changing in no great feature. Progress evidently depends on something be- sides knowledge, for in proportion to the degree of progress is the departure from the known, and in proportion to the novelty of a situation is experience worthless as a guide. Designed actions which are performed without a basis of knowl- edge which is sufficient for predication are not automatic. That is, while the activity may be physically spontaneous and comi)ul- 3ory, the direction it takes and the mode of its execution can not be automatic, unless the machinery which must give the direction, and which creates the mode, be already in existence. 29 450 METAPHYSICAL EVOLUTION. The field of the known is very limited, as compared with that of the unknown, in the experience of the Amcela. In its first movements, it has absolutely no basis on which to establish an anticipation of the future. Such is also the situation of the young of every animal. But the cases of the inferior and superior spe- cies present the important difference that in the former there exist few or no mental powers derived by inheritance, while in the latter such are present in proportion to the position of the species in the scale of intelligence. The facts of evolution teach that the habits of animals have been modified during past geological ages, under the influence of changes in their physical surroundings. While these changes may, perhaps, have furnished the stimuli to the adoption of new habits, the conditions have not often been so rigid as to define exactly what those habits should be, in some or all of their details. The animal has necessarily proceeded blindly in many instances ; in others, his mental darkness has been illumined by a low grade of imagination. This may be believed in view of the many attempts which animals often make before succeeding in attaining a desired end. Imagination plays an important part in the origin of mo- tives and of actions, and is related to predication. It is defined as the presentation or construction of images or representations from items of experience, which representations so far differ in the connection of their details from actual experience, or so far lack the qualities of experiences, as not to constitute a predica- tion of future events. Predication mav be defined as the certain knowledge of the unexperienced from the experienced ; while imagination includes the grades of probable, possible, and impos- sible concepts, constructed from the same material as predication. Whether this faculty exists in the animals which can not speak, is not readily ascertained ; but, inasmuch as many of them predi- cate, it is probable that they possess some degree of imagination also. But it is obviously a quality of the highest types of mind, since its development depends primarily on the furniture of mem- ory, derived from a long period of experience, whose amount de- pends on receptivity and retentiveness. YI. THE OEIGIi^ OF MOTIVES. It has been said that the operation ordinarily called choosing, in which the will is popularly supposed to be free, consists merely of a sum in addition and subtraction, where various inducements THE OPJGIX OF THE WILL. 451 are balanced, the resultant preponderance being expressed in the act. It will be easily seen that while this statement is true in re- gard to cases where the elements of the calculation are known, it is not true where any or all of them are unknown. The difference in the two cases is very great. All likes and dislikes are based upon experience or knowledge ; and when there is no knowledge, likes and dislikes can not be said to exist. Since likes and dis- likes constitute motives, where the former are wanting the latter are also wanting. Whatever inducements are presented from be- yond the field of knowledge are derived from the imagination, and are in self-conscious minds relatively weak as motives, or absolutely without weight. They might be regarded as motives in embryo, ready to become such on the acquisition of a corre- sponding experience. The imagination can prefigure one alterna- tive as well as another, in a direction wdiere experience is wanting, and might indeed be said under such circumstances to have no existence, and the expression, ^'1 can't imagine," be thought to have foundation in fact. The influence of such a guide is not imperative, and raises no obstacle to the origin of a new feature of consciousness by an act of choosing, when the pressure to act at all is sufficiently great. There is, perhaps, but one situation of the mind where the pressure of feeling is strong enough, and predication and imagina- tion sufficiently excluded, to develop a will which shall create motives rather than obey them. This is in the cases where self- interest is weighed in the balance against the interest or good of other people. Here the feelings are most severely ju-essed, and the future results to self most uncertain. Self-sacrifice may be beneficial to self, or it may not : one may be the gainer by the general prosperity, or he may be the loser. Morality may promise future good to the community, but why sacrifice self for the com- munity ? Gratitude for services rendered is an uncertain antici- pation. Man's most limited knowledge and greatest inability in predication is in the field of human motives and actions, and chiefly in respect to those which belong to his moral feelings. As already remarked, the complication in this direction is so great as to produce the effect of novelty : so that man, come into posses- sion of an intellect which is the product of ages of development, finds before him a new field of his own making, where his in- herited powers fail. This is the field where the most momentous decisions possible 452 METAPHYSICAL EVOLUTION". in human life are made. Since questions of right and wrong re- late to the happiness of men in their relations to each other, the social affections are the stronghold of the motives that bear on this result. It is evident that a thousand subordinate motives take their direction from the primary decisions between these two original alternatives of feeling. It is true that the predication of human actions, necessitated by bodily functions alone, is eas}^ even when' they come to be of a highly complex character, as in the mercantile transaction of a populous business center. But so soon as the ethical element enters into the calculation the difficulty is greatly increased, and with the majority of men predication ceases, and faith begins. This is illustrated in the many credit transactions, without which it is well known that trade on any but the most limited scale is impossible. So it must be admitted that many men practice faith in many affairs, and that this faith is chiefly reposed in the moral excellence of other men. Under these circumstances, that state of the affections arises in most men which is termed faith, and which is only present in the highest form of progressive action, whether the results of tliat action be beneficial or not. It is a condition of the affections, as imagination is a condition of the intellect. The lowest animal, when attempting a novel act in obedience to im- perative stimuli, doubtless moves blindly, and adopts one of two or more alternatives through pure accident. In animals of a higher grade of intelligence, new situations are known to be such, and fear or suspicion is the usual result. Generall}^, animals of the higher orders do not adopt new habits excepting under severe press- ure, and the majority of them have perished, in past geologic ages, on account of their inability to assume new modes of life. Never- theless, in so far as an animal or a man ventures into an unknown field of action, where he is without the guidance of a past ex- perience, he or it performs an act of trust in the broad meaning of the word. So far as this state of mind is known to the subject, the act is one of true faith in the restricted or proper sense of the word. Imaginations may and do assume to men the importance of truths, and in so far they are such to them. But in proportion as this is the case, faith in its proper sense is wanting, and the action following is automatic. The highest form of intellect is necessary to the highest form of faith, since it is only by a knowl- edge of the absence of knowledge that an act of faith is possible. In proportion to this knowledge of self is faith enlarged ; in pro- THE ORIGIN OF THE WILL. 453 portion to certainty, or supposed certainty, in affairs, is faith diminished in its scope. It is evident then that, abstractly speaking, occasions must arise in human experience where a decision between two alterna- tives is dependent on choice alone. That these occasions have arisen, and the choice been made, is shown by the existence of the altruistic class of actions. The number of these occasions may not be very great, but the consequences are ver}' important. In whatever direction these decisions are made, long series of auto- matic actions are organized. Although the existence of the altruistic class of acts affords the clearest proof of the origin of will, it is not denied that corre- sponding situations may not occur in other directions. It is also probable that will, once organized as a faculty of consciouness, can be exercised in many acts in opposition to habits, differing in accordance with the constitution of the individual ; and that it can be inherited like any other quality of mind. But I will show later, that the organization of altruistic habits has narrower limits than that of those of the appetent class, because self-preservation depends on the latter, and not on the former, so that the appe- tent qualities are more certain to be inherited and survive. The conclusion of this portion of the subject is, that that de- partment of mind called the feelings * is the primary source of action ; that they act automatically, with or without the aid of the reasoning powers, when dealing with the known ; but when deal- ing with the unknown may develop, in self-conscious beings, the state of faith and acts of will ; that this freedom is born of ten- sion of the affections and of inability of the intellect. Thus have the irregular and fortuitous decisions of animals been replaced by volition, as the highest quality of the mind, and therefore the crown of evolution. No new " physical '' force is here called into requisition. The determination of the direction of such forces already existing in or passing through the brain in executive action need not add to nor substract from them. Will is, under these circumstances, looked upon as developed consciousness. All this is, of course, opposed by the doctrine of the origin of moral excellence by development, on the basis of the utilitarian theory of morals. I therefore proceed to a brief examination of its claims in this direction. * Which appears to be identical with what Schopenhauer calls the will. 4:54: METAPHYSICAL EVOLUTION". Good is well defined as tlie greatest happiness of the greatest number ; and by a natural transfer, the term is applied to what- ever is conducive to that object. It therefore includes not only present pleasures, but also the influences which conduce to future pleasures, and which may be sown in the mind long before they bring forth fruit. As present pleasures are not always consistent with greater ones in the future, so present pleasure is not always good. Evil being the reverse or negation of good, or happiness, is avoided by all beings to whom it is consciously known ; but what they regard as evil will of course depend on their intelligence in determining or predicating the future effects of actions. But no matter what the degree of intelligence, no responsibility, as usu- ally understood, can be expected of beings which have no power of choosing, or will. The utilitarian theory of the evolution of morals asserts that the development of goodness is simply due to the discovery and enforcement of the law of self-jirotection and preservation. The selfish interests require the protection of person and property, without which a community is an impossibility. Law being thus established and enforced, moral habits are imposed ujDon men, which become incorporated into character and transmitted to suc- ceeding generations. This is all doubtless true, but whether it is a fundamental or secondary truth is the point requiring attention. The fundamental objection to this hypothesis is, that the al- truistic affections are not inherited or transmitted. This is be- cause the pains and penalties of wrong-doing as inflicted by law, can not (and ought not to) overcome the inherent instinct of self- preservation in man. It is true that moral character is inherited, and that changes in this department for better or worse are trans- mitted to offspring. The mental organization of a race may be improved by the weakening of the emotional or the strengthen- ing of the rational faculties. But since the affections are at the foundation of all activity whatsoever, of right-doing as well as of wrong-doing, it is obvious that no amount of legal restraint can render them innocuous. Their existence is necessary for self- preservation, and law only restrains their activities to certain di- rections. That intelligence tends to restrain wrong-doing is true ; but although intellect is inherited, the manner in which its teacli- ings are applied in practice is not. Each man must learn the merits of different courses of action in regard to morals for him- self ; his intelligence places before him the facts, and shows him THE ORIGIN OF TUE WILL. 455 how to execute his wishes, but the state of his affections deter- mines the direction of his acts. Moral amelioration has attended the progress of intelligence on the one hand, and moral abase- ment on the other. Intelligence is the condition of the perception of moral truth ; in other words, intelligence, as applied to moral questions, is the conscience. Consequences of acts are understood, and their relations to the pleasures and pains of men are weighed. Thus, no doubt, the world has advanced in the knowledge of good and evil, and of right and wrong. That it has improved in the practice of right has not been due to the inheritance of respect for law, but to the self-destructive nature of wrong. That con- tinued wrong sooner or later ends in the destruction of the wronc:- doer, either from within or without, must be generally admitted. Thus is the truth of the doctrine of '^ the survival of the fittest " vindicated in moral as in natural law. But it is also true that this law is restrictive onl}^, and that the school of Hume and Bentham has overlooked the deeper originative law in moral phi- losophy, as the school of Darwin has done in biological philosophy. It may still be urged that, if it be granted that experience of the pains of evil-doing be not transmitted as an intellectual ac- quisition from generation to generation, nevertheless such experi- ence is sufficient to educate each separate generation as it passes, without any other than automatic action on their part. It may be replied to this that the results thus obtained are not due to will, but simply follow compulsion, the motive thus created only varying in strength with the characters of the individuals. Its success is restricted to circumstances where the j^enalties are suffi- ciently certain to constitute counter-inducements to effect the necessary restraint. This can only be the case with the weaker members of society. Wherever there is sufficient power to escape penalties, wrong-doing has no restraint. Under such a system might and right are identical ; for the strongest needs no protec- tion of law. It is true that society can combine against a single malefactor, but it is also true that malefactors can combine. In fact, it is one of the usual phenomena of human society to find men becoming malefactors as soon as they attain to power ; or to find society governed by a few malefactors who have an army to enforce their pleasure. While then inheritance does not secure the performance of altruistic acts, appetent affections maybe so increased by accumu- lation in descent as to become uncontrollable, so that will either 456 METAPHYSICAL EVOLUTIOK does not come into existence, or is extinguished, so far as regards those affections. In such a situation there is no such equivalency between opposing motives as gives opportunity for the will, the experience of appetent pleasure being too strong to allow of hesi- tancy in the face of vague representations of imaginary conse- quences on the other side. Even in highly intelligent men, to whom consequences are best known, knowledge may be thrust from consciousness, by strong feeling in favor of one alternative at the moment of action. YII. COl^SEQUEIirCES. It is now w^ell to consider how far an automatic mind has any claim to personality or individuality, as generally understood. From the usual stand-point, a being without 'liberty," or will properly so called, is without character, and is in so far a nonen- tity. Even the character of the Deity can not escape this de- structive analysis ; for according to Spinoza, if He is good, but a single line of action, without alternatives, lies open to God, if He be at the same time omniscient. All this is changed if the ele- ment of spontaneity in character be presupposed. The existence of such a quality in man renders foresight of its decisions in some cases no more than a calculation of chances, and in other cases impossible ; thus offering the only conceivable limit to omnis- cience, and hence to omnipotence. And as we regard the good- ness of God as the anchor of the universe, if that goodness be in some respect inconsistent with omnipotence, we are strengthened if we discover that there is ground for correcting our traditional suppositions in regard to the latter. Can we not find this ground in a liberty or freedom which is the condition of what we suppose, in the absence of knowledge, to be the characteristic of the highest class of conscious existences ? Note. — Another explanation of this conclusion of Spinoza's, quite apart from the question of human freedom, is to be found in some of the necessary properties of matter. The old theologians expressed this point obscurely in their phrase, " the intractability of matter." (Ed. 1886.) Second Note. (Ed. 1886.) — The preceding essay was written several years prior to that on Catagenesis. In the latter article a mental quality was referred to as present in all animals, which constitutes " the will " of various writers, although it is not free. It is described in the following passage : " Why, from a purely me- chanical point of view, is the adductor muscle of the right side of the horse's tail con- tracted to brush away the stinging fly from the right side of the horse's body, rather than the left adductor muscle ? Why was the contraction-provoking energy deflected ON THE ORIGIN OF THE WILL. 457 into the right interspinal motor nerves rather than into those of the left side ? " The conclusion was that this phenomenon can not be explained on purely mechani- cal principles ; but that it required the assumption of the thesis that " energy can be conscious." {Supra, p. 427.) Further thought on this subject shows clearly that this conscious state of energy is self-directive in accordance with the lessons of experience, but without being necessarily free in the sense referred to in the preceding essay. In Mammalia the current of energy derived from stimulus, after reaching the cortical cells of the an- terior cerebral lobes, issues from them in a direction appropriate to the needs of the animal, having undergone a deflection or determination within them. This capacity for " design " is peculiar to beings which can be conscious, and constitutes the most important proof in evidence of a degree of control of mind over matter. The evidence strongly suggests that this control is greatest when the environment is simple or generalized, since motives are then relatively simple. Note to Catagenesis by the Author, 1886. On p. 434 reference is made to the fact that " in chemical reaction the preference of energy is to create solid pre- cipitates." This fact is but one illustration of the law of thermo-chemistry that *' in any reaction, those bodies, the formation of which gives rise to the greatest de- velopment of heat, are formed in preference to others." This is a retrograde meta- morphosis of energy, or catagenesis. IS"DEX. Acceleration, vi, 142, 182, 287, 383. Acceleration and retardation, 2, 11, 125, 127, 297. Acrania, 322, 323. Actinia, 33, Actinophrys, 27, 187, 192. Actinopteri, 325, 326. ^sthetophore, 419. Aethalium, 396. Agassiz,vii, 8, 45, 58, 60, 61, 62, 83, 91, 92, 103, 121, 124. Ageniosus, 327. Allen's "Anatomy," 272, 279. Allen, H., 115, 242. Allen, Keen, and Pepper on " Universal Hyperostosis," 183. Allman, Prof., 415, Altruism, xi, 237, 441, 453. Amhlydomis sinosus, 375. Amblyopsis, 196. Amblypoda, 278, 342, 343, 344, 346, 348, 360, 368, 371, 374, Amblystoma, 4. Amblijstoma mavortium^ 88. tigrhmm, 89. Ameiva pleii, 87. American Association for the Advance- ment of Science, x, xi, xii, xiii. "American Naturalist," ix, xi, xii, xiii, 244, 277, 359, 363, 383. Ametabola, 316. Aniiui'us, 4. Amiurus albidics, 85. lynx, 85. Ammocoetes, 316. Ammonites, 18. Amoeba, 440, 445, 446, 450. Amoebodonts, 247, 248, 257. Araphioxus, 182. Amphiuma, 333. Anaptomorphus cemiilus, 279. homnnculus^ 279. Ancestral types of mammalia cducabilia, 266. Anchitherium awclianense, 275. Ancisfrodon cordortrix, 197. piscivorus, 197. Anelytropidae, 337. Anguidae, 337. Aniellidae, 337. Anisonchus, 245, 359. Anolis, 4. Anoplotberium, 247, 265, 370. Anthracotherium, x. Anthropoidea, 342, 343. Antiarcha, 323. Antilocapra, 383. Antiodonts, 247. Anura, 331, 332, 333. Aphelops meffalodvs, 369. Aphododiridae, 328. Appendicularia, 322. Archcelu7'us dibilis, 375. Archaesthetism, xii, 406, 414, 419, 421. Arcliaeopteryx, 340. Arcifcrous anura, 95, 218. Artiodactyla, 344, 368, 371-374, 375, 399, 401. omnivora, 199. Ascertained cases of transition, 87. Ascidia, 399. Atrophy, 13, 127. 4:60 INDEX. Aturia, lY. Australian native, 291. Avian line, the, 340. Bain, Prof., 446, 448. Baird, S. R, 55, 85, 87. Barnard, 205. Bascanium constrictor, 197. Bathmism, 26, 205, 226, 414. Bathmodonts, 248, 259. Batrachia, 351. Batrachia anura, 46, 216, 332. Beginnings of development, the, 447. Bennett, Alfred, 199, 214. Bentham, 455. Bokorny, 430. Borborocoetes, 4. Bos, 348. Bothriolepis canadensis, 323. Boulanger, 337. Bibron, 95. Bidens frondosa, 86. BischofP, 290. Brachiopoda, 399. Branchiostoma, 322, 384. Bridger fauna, 302. Broca, 290. Bronn, Prof., 45, 51, 102. Bufoniformia, 217. Bunodont type, 243. Bunotheria, 343, 346, 349. Buteo, 4. Calamodon, 278. California Academy of Sciences, xi. Caraelidae, 375. Canidae, 246. Cams familia.i'is, 224. Caprimulgidae, 341. Cariacus virginianus, 50, 177-178, macrotis, 178. Carnassial bunodonts, the, 251. Carnivora, 264, 278, 344-346, 348, 399- .401. Carpenter, Dr., viii, 191, 206, 438. Casts of brain-chambers of extinct mam- malia, figures of, 308. Catagenesis, xiii, 422, 428, 434. Caudisona, 4. Causes of evolution, 14. Cebidae, 180. Cebus apella, 12. capucinus, 12, 38. Celestics pJioxinus, 84. Cell-repetition, on, 185. Centetes, 360. Centetidas, 348. Centrotelma geograpldcum, 85. Cephalizatiou, 39. Cervidae, 177. Cetacea, 26, 342, 343, 347, 349, 399. Chaenobryttus viridis, 213. ChEetodontidas, 330. Chamcesaura angiiina, 84. Change in amount of growth-force, 200. Characinidae, 327. Character of higher groups, of the, 132. Chelyosoma maclovianum, 323. Chiromys, 180, 202. Chiroptera, 342, 343, 344. Chorophilus, 4. Chrondrostei, 325, 326. Cinclidium maximum, 85. Cladodonts, 325. Clark, H. J., 167. Clepsydrops, 363. Clevenger, 424. Clifford, Prof., 425. Coelenterata, 182, 413. Coenogenesis, 126. Cohnheim, 195, 406. Coleoptera, 316. Colocephali, 327. Comparison of the opposing series, 250. Complementary diminution of growth force, viii. Condylarthra, xiii, 342-6. Consciousness, energy, and matter, 425. Consciousness in evolution, x, xii, 390. Coranus suhapterus, 89. Coreopsis discoidca, 86. Correlation of physical and vital forces, 191. Corvus, 4. Coryphodon, 270, 272, 273, 274, 276, 369, 374. INDEX. 4G1 Coryphodon elephantopiis^ 2G9. Coryphodontidae, 359. Cosoryx, 224, 271, 376. Crania of anura, 222. Craniata, 322, 323. Creodonta, 359, 365. Cretaceous fauna, 302. Crossopterygia, 325, 326. Crotalus conjluentus^ 212. Cuvier, 8, 88, 124, 129, 146, 176 Cyclopterus, 331. Cyprinidse, 327. Dana, J. D., 39, 429. Darwin, Charles, 2, 3, 11, 13, 15, 42, 106, 124, 174, 405, 409, 455. Daubentonioidea, 342. Deltatherium ftmdaminis, 362. De Serres, Prof., 74, 77. Desmognatlms jusca, 87. nigra, 87. Deuterosaurus, 363. Development of the fine arts, 153. of intelligence, 149. of mind, the, 445. Developmental relation of generic to specific characters, 82. Developmental significance of human physiognomy, 281. Diadectidae, 335. Dibamid^, 337. Didonius mirabilis, 338, 339. Didelphys, 360. Didymictis protemcs, 215. Dimorphodon, 335. Dinidis cydops, 366. Dinocerata, 359. Dinosauria, 333, 335, 336, 338. Dinotherium, 248. Diplarthra, 342, 343, 346, 347. Diploglossus monotropis, 84. Dipnoi, 184, 324. Diptera, 316. Direction of repetition, on the, 192. Doctrine of the unspecialized, the, 398. Dohrn, 316, 317. D'Orbigny, 101. Dorypterus, 327. Dualism, 421, Dubois-Raymond, Prof. E,, 409. Dumeril, 88, 89, 91, 95. Dyer, 213. Dysodus, 349. Edentata, 342, 343, 344, 349. Effect of impacts and strains on the feet of mammalia, on the, xii, 373. Effort, 195, 206-7, 426. Elaps, 4. Elasmobranchii, 319, 320, 324. Electric energy, 435. Elements of mind, the, 443. Elephas, 377. africanus, 110. antiqxius, 110. meridionalis, 110. planifrons, 110. primigenius, 110. Embolomeri, 331, 332. Embryology, 383. Emotions, 158, 163, 381, 447. Empidonax, 4. " Encyclopaedia of Dentistry," 104. Endlich, 286. Entocondm mirabilis, 401. " Entwickelungsgeschichte der Natter," 94. Eobasileus, 250. Epochal relations, 112. Epilasmia, 330. Equidae, 411. Equus, 276, 348. Eryops megacephalus, 304. Esequibo Indian women, 286. Eucnemis hicolor, 114. Eurypharyngida% 328, 329. Eurytherium, 370. Eutaenia, 4. Evidence from archaeology, 150. Evidences of derivation, 130, 215. Evidence for evolution in the history of extinct mammalia, xii, 294. Evolution and its consequences, ix, 1. Evolution of organisms, the, 422. Evolution of the vertcbrata, progressive and retrogressive, xiii, 314. 462 INDEX. Evolutionary significance of human char- acter, xii, 378. Exact parallelism, vi, 46, 76, 139. Extent of parallelism, 74. Extinction of evil, the, 169. " Extinct Mammalia of Dakota and Ne- braska," 384. Falco, 4, Falconer, 55, 109. Feelings, the, 447. Felidfe, 349, 363, 366. Felis, 363. " Final Reports of the U. S. Geological Surveys," v. Flower, W. H., 104. Ganocephala, 332. Garman, 325. Gastrsea theory, 219. Gaudry, A., 275. Gecconidge, 336. Gegenbaur, 322. General evolution, 1. " Geological Survey of Montana," 258, 267. Geothlypis teplirocotis, 85. Gill, T., 329. Goethe, 7. Goniatites, 18. Grade characteristics, viii. Grade influence, viii, 203-6. Gratiolet, 104. Gray, 86, 176. Gray, Asa, 208. Greatest resistance, 30. Gronias nigrilahris, 84. Growth-force, 18, 190, 396. GUnther, 58, 86, 340. Gymnophiona, 331. Glyptostrobus europcciis, 86. Haeckel, ix, x, xiii, 75, 125, 190, 219 229, 415. Halohates amcricanus, 90. Haplodont type, 243. Hartshorne, Prof., 397. Hayden, F. V., v, 246, 269, 369-71, 376. Hemibranchi, 328. Henry, Prof. Joseph, 19, 191. HesperornithidaB, 340. Hetcrodon nasicus, 212. Heterology, 96. Heterosomata, 328. Hippocampidae, 328. Hippodonts, 249. Hippopotamus, 272. Hippotherium, 202, 411. JIippothe7'ium gracile, 275. History of creation, xiii. Hogg, 89. Holoccphali, 324. Holothurida, 193, 399. Hominidae, 180. Homo sapiens, 272, 279. Homologies and origin of the types of molar teeth of the mammalia educa- bilia, 241. Homologous groups, vi, 26, 95. Homology, 6. Humboldt, 425. Hume, 455. Huxley, 15, 136, 146, 265. Hyaenidae, 246, 349. Hyaenodon, 366. Hycenodon horridus, 364. Hyaenodontidae, 246. Hyatt, A., 2, 8, 11, oi, 91, 125, 408-9, 424. Hyla, 4. Hylorana erythrcna, 114. Hyopomata, 318,324. Hypothesis of evolution, physical and metaphysical, vii, xii, 128, 167, 287. Hypothesis of use and effort, the, 403. Hypsilepis analostanus, 213. Hymenoptera, 316. Hyrachyus, 247. Hyracoidea, 342, 343, 344, 346, 347. Hyracodonts, 249. Hyracotherium, 301. Hyracotherium vcniicohon, 271. Hyrax, 233. Ichthyopterygia, 184, 333, 336. Ichthyornithidae, 340. INDEX. 4G3 Ichthyosaurus, 184, 336. Icichthys, 331. Icosteus, 331. Improvement in architecture, 151. Improvement in the use of materials, 150. Increase of growth-force, 200-1. Indo-European, 2SS. Induction, 6, 14. Inexact parallelism, 52, 139. Influence of physical causes, 196. Insectivora, 347. Intelligence, 449. Intelligent selection, viii, ix, 35, 208. Isospondyli, 327. Jena, 8. John Day river epoch, 366, Jones, Rupert, 86, Jordan, D. S., 326. Kant, 307, 449. Kiowa Indian, 288. Kner, R., 113. Kolliker, 15, 103. Kowalevsky, x, 318. Laccrtilia, 334, 335, 336. Lamarck, viii, 124, 342, 422, 405, 422- 423. Lambdoiherium popoafficum, 275. Lartet, 104, 254. Lankester, 96, 322, 333, 337, Laws -of evolution, the, 225. Least resistance, 30. Leconte, 115. Leibnitz, 415. Leidy, 50, 85, 258, 364, 371, 376. Lepidoptera, 316. Leporidse, 375. Leptocardii, 317, 318, 319, 320. Lereboullet, 8, 60, 74, 75, 77, 124, Lespes, 57. Lewes, G. H., 415. Line of the Batrachia, the, 331. Line of the Pisces, the, 324. Location of growth-force, on the, 24, 195, 205. Locke, 438. Loew, 0., 430. Lombard, 418. Lophiodon, 247. Lophodont type, 243. Loss of growth-force, 201. Loup Fork fauna, 302. Loxolophodonts, 248, 250, 259. Luchatze negro woman, 287. Lund, 367. Lvcodon, 4. Mammalia^ 278. Mammalia educabilia, ix, 241. Mammalian line, the, 341. Man, development of, 123, 146, 155, 267, 278. 3f uncus macrolipis, 84. Mandibular teeth, the, 245, 249. Manner of evolution, the, 6, 11. Marsh, 0. C, x, 258, 277, 308, 333, 340. Marsipobranchii, 316, 317, 318, 319, 320. Marsupialia, 341-344, 317-348, 359. Mastodon ohioticus, 56. Maternal impressions, viii, 213. Maxillary teeth, the, 244, 246, McCook, Dr., 385. Meehan, T., 160, 161. Mechanical evolution, 350. Meleagris, 24. " Memoirs Boston Society Natural His- tory," 51. 3fcnodus, 272. " Mental Physiology," 438. Mcsodon albolabris, 178. Mesonyx, 246, 278. Metachrosis, 211. Metaesthetism, 421. Metaphysical evolution, ix, 148, 378. Metaphysical species, on. 111. Metaphysics of evolution, 229. Method of creation of organic types, vii, 11, 173, 229, 241, 353. Mimetic analogy, viii, 104, 212. Mind, development of, 214, 385, 445. Minot, C. S., 287. Mioclacnus corruffatiis, 275, Mivart, 15, 28. 4:64: INDEX. Modifications of animals under domesti- cation, 110. Monas, 27. Mongolian, 288. Monism, 421. Monodelphia, 344, 347, 348. Monotremata, 341, 346, 347. Morals of evolution, the, 236, 311. Morris, C, 385. Miiller, 8, 325. Murphy, 194. MustelidaB, 246. Mutilla, 212. Mycelium, 30. Myiodioctes canadensis^ 85. Naja, 4. Natural selection, 2, 14, 43, 78, 106, 107, 174, 175. Nature of actions, the, 439. Nautilus, 18. Necturus, 333. Necturus maculatuii^ 49. Negro, 288. Neurism, 20, 205. Numida, 24. Neuroptera, 316. Newton, 14. Nimravus gomphodus^ 375, (Estridae, 316. Office of consciousness, 412. Oken, 7. Omnivora, 371. Oncocephalus griscus, 90. Ophiholus, 299. triangulus^ 197. Opbidia, 334, 335. Oporornis agilis, 85. formosus, 85. Orconeetes pcUucidus, 1 3 . Origin of automatic movements, the, 393. Origin of consciousness, 402. " Origin of the Fittest," xiii, 175, 225. Origin of the foot-structure of the un- gulates, xi, 368. "Origin of Genera," vi, vii, 11, 41, 125, 256. Origin of inexact parallelism, 92. Origin of intelligence, 31. Origin of the modern types of bunodont and lophodont dentition, 251. Origin of motives, 450. Origin of the specialized teeth of the carnivora, xi, 363. Origin of species, 2, 7, 42, 107. Origin of the will, x, 437. Ornithorhynchus, 184. Ornithosauria, 335, 336. Orthagoriscidse, 330. Orthoceras, 18. Osborn, H., 277. Ossemens fossiles, 49, 176, Osteocephalus, 46, 221. Ostraciontidas, 330. Owen, Sir K., 88, 91, lOS, 318. Oxyaena, 246, 360. Oxycena lupina^ 365. morsitans, 375. Oxyrrhopus, 4. Packard, A. S., 2, 13. Palaeosyops, 247. Palaeotheriodont, 258. Palaeotherium, 247, 248. Paleontological bulletins, xii. Paleontological evidence, 383. Palingenesis, 126. Pangesthetism, 419. Pantolambda, 360. Pantolambda hathmodon^ 275. Parallelism, 7. Parallelism in higher groups, 58. Parker, 86. Pasteur, 431. Pavo, 24. Pelycodus, 360. Perca, 4. Percomorphi, 328, 331. Perigenesis, ix. Periptychus, 359. Periptychus rhahdodon, 268, 308. Pcrissodactyla, 250, 265, 3^'8, 371-373, 375, 399. Permian fauna, 302. Peters, 336. INDEX. 465 Pharyngognathi, 330, 331. Phenacodus, 301. Phenacodus primoevus, 270, 273, 275, 300, 808. vortmani, 345. "Philosophie Zoologique," viii, 423. Phrenism, 205. Physical evolution, 128. Physical origin of man, the, 146. Physiophilosophs, 7. Physoclysti, 328. Physostomi, 328. Pityophis sayi, 197. Plagiaulax, 348. Platypodidse, 346. Plecostomus, 4. Plectognathi, 330. Plesiosaurus, 26, 188. Pleuronectidse, 196. Pliauchenia, 223. Poebrotherium, 223. Poebrotherium labiatum, 271, 370. vilsoni, 371, 376. Polycystina, 27. Polyphyletic descent, vii. Porter, Noah, xi. Pressure, effect of, 228. "Primitive Types of Mammalia Educa- bilia," 246. *' Principles of Biology," ix, xi, 423. " Principles of Psychology," ix. Procelurus julieni, 366. Probable cases of transition, 83. Proboscidia, 233, 265, 342-4, 346-8, 375, 401. Procamehis occidentalis, 308, 376. Procyonidee, 359. Prostemma gutiula^ 89. Protamoeba, 190. Proteida, 331-3. Proteles, 349. Protobathybius, 420. Protohippus sejundtis, 271, 370. Protolabis, 223. Protozoa, 33, 420. Ptychodont type, 243. Ptychostomus, 4. Ptychosiomus pidiensis, 213. 80 Puerco fauna, 302. Pygopodidae, 337. Pythonomorpha, 26, 334. Quadrumana, 179, 278, 280, 342-4, 347, 385, 899, 400, 401. Radcliffe, 20. Ptadiata, 27. Rana, 4. Rana affilis, 222. affijiis, 47, 84. areolata^ 48. catcsheiana, 48. clamata, 222. corrugata, 48. cyanopldydisy 48. delalandii, 47. ehrenhergii, 48. fasdata, 47. fuscigultty 48. gracilis^ 48. grayi, 47. grunniens, 48. hexadactyla, 48, 222. mascariensis, 47. occipitalis, 48. oxyrhyncJms, 47, 222. palmipes, 47. porosissima, 47. temporaria, 84. tigrina, 48. vittigera, 48. Raniformia, 217. Ranula chrysoprasina, 222. Rathke, 57, 61, 76, 93. Rationale of moral development, 166. Rattle of the rattlesnake, the, 197. Raymond, Dubois, 21, 409, 415. Relation of animal motion to animal evo- lution, xi, 266, 350. Rationale of the development of intelli- gence, 154. Relation of man to the tertiary mamma- lia, X, 268. Relations of nearly allied genera, on the, 44. Relations of physical and moral nature, 158. 466 INDEX. Eelations of the types of dentition to types of foot, 260. Repetitive addition, 180. "Report on Geological Survey of Mon- tana, Wyoming, etc.," 246. " Report United States Exploring Survey W. lOOth Meridian," 224. Reptilian line, the, 333, Respiratory and circulatory system of vertebrates. 196. Retardation, vi, 13, 142, 182, 281, 385. Retardation and acceleration, 11, 43, 15, 115, 226. Retrograde metamorphosis of energy, 427. " Review of Birds of North America," 55. Review of modern doctrine of evolution, xi, 215. Rhachitomi, 331, 332. Rhinocerus, 247. Rhynchocephalia, 334, 336. Riickhard, Rabl, 319. Roccus lineatus, 213. Rodentia, 180, 342-4, 346, 375, Rotifera, 315. Ruminantia, 223, 247, 375. Ryder, J. A., ix, 368, 409, 423. Sacculina, 401. Salamandra atra, 87. maculosa, 87. Salmo, 4. Salticus, 212. Saturniidae, 316. Sauropterygia, 334, 336. ScaridsD, 331. . Schlosser, 370. Schopenhauer, 453. Schopfungsgeschichte, xiii. Schreiber, 87. Scincidae, 337. Sclater and Salvin, 118. Scolecophidia, 340. Scombridge, 331. Scops asio, 4. Seeley, H. G., 335, 340. Segment-repetition, 182. fSelenodonts, 247. Serranidae, 331. Siluridae, 327. Simia satyrus, 283. Simiidae, 180. Siredon, 333. Sirenia, 342, 347, 349. Smilodoti neogceus, 367. Smith, Aubrey, 86. Smyth, Brough, 291. Spelerpes, 4. Spencer, Herbert, viii, ix, xi, 2, 15, 413, 444, 445, 448. Spinoza, 90, 456. Spiritual or moral development, 157. Spizclla pusilla, 16. socialis, 16. Stegocephali, 331, 332. Stegophilus, 327. Steindachner, 86. St.-Hilaire, 91, 146. Streptostylica, 334. Structural evidence of evolution, the, 241. Stypolophus, 246. whitice, 360. Subordinate types of bunodonts, the, 244. Subordinate types of lophodonts, the, 246. Successional relation, 7. Survival of the fittest, 15. Swainson, 96. Symborodonts, 248, 250, 257. Synopsis of the vertebrata of the eocene of New Mexico, 245. Synthesis of repetition, 187. Taenia, 184. Taeniodonta, 343, 349. Tachyglossidae, 346. Talpa, 360. Tapirodonts, 247, 255. Tapirus, 247. Taxeopoda, 342, 347. Taxodium distichum, 86. TeidaD, 337. Teleology, 7, 16. Teleostomi, 318, 324-326, INDEX. 467 "Tertiary Planorbis of Steiuhcira," 408. Testudinata, 334. Testudinidae, 33Y. Theory of evolution, x, 124. Theromorpha, 333, 335, 3oY. Thomson, Sir William, 431, 442. Thulie, 288. Tillodonta, 343. Tillotherium, 248. Topinard, 290. Tortricidae, 340. Trachystomata, 331, 332, 333. Trematoda, 401. Trichechodonts, 248, 255. Trichodiscus, 27. Triodopsis tridentata^ 178. Tritubercular type of molar teeth in the mammalia, xii, 359. Tropidonotits sipedon^ 197. Tryon, G. W., 177. Types of mammalian molars, the, 241. Typhlichthys subfei'raneiis, 1 3. Typhlogeophis, 340. Uhler, P. Ft., 90. Uintatherium, 248, 274, 278. Uintai/ierium cornuium, 277. mirabile, 277, 308. Unconscious, the, 391. Unconscious cerebration, 32. Ungulata, 347, 359, 365, 369, 374. Unity in variety, 7. Urochorda, 322, 323. Urodela, 331, 332. Use and effort, ix, 6, 194. Vegetable growth, force of, 31. Velia, 90. Venus of the Capitol, 292. Vermes, 399. Vertcbrata, 352, 356. 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