:a^ i: ■im I ''Xm: •^m^m) ■;'-' '■ > '> 1 ■ ' nil n!-iV.'' yffl 'J^ ' ^. i*- ®l|e i. m. ItU Sitbrarg Nnrtb (Eaniltna i>talp (EollpaF QH366 P37 15SD3? This book may be kept out TWO WEEKS ONLY, and is subject to a fine of FIVE CENTS a day thereafter. It is due on the day indicated below: 23iua'6l^' 50M— May-54— Form 3 M A M M A L I A N D F. S ( ! E N T. By MM, ETHERIDGE and SEELEY, Part i., Handsome Clotli, Price i8s. A manuajL of geology. By JOHN PHILLIPS, M.A., LL.D., F.R.S., La^e Professor of Geology in the Unizfsrsiiy of Oxford. Re-written and Edited by R, Etiieridge, F.R. S., and H. G. Seelev, E.R.S. Part I. — Physical Geology, and Pal.^eontologv. By Prof. Seeley, F.R.S. With Illustrations and Frontispiece in Chromo-Lithography. i8s. By PROFESSORS LANDOIS and STIRLING. In Two Vols., Royal 8vo, Handsome Cloth. HUMAN PHYSIOLOGY (A TEXT-BOOK OF) Including Histology and Microscopical Anatomy. With Special Reference to Practical Medicine, By Dr. L. LANDOIS, PROF. OF PHYSIOLOGY, L-XIVERSITY OF GREIFSWALD. Translated from th.e Fourth German Edition By WM. STIRLING, M.D., D.Sc, REG. PROF. INSTS. OF !\IED., UNIVERSITY OF ABERDEEN. With very Nimtcrotis Illustrations. CHARLES GRH^TIN & COMPANY, LONDON. ON MAMMALIAN DESCENT: THE HUNTERIAN LECTURES FOE 1884. BEING NINE LECTURES DELIVERED IN THE THEATRE OF THE ROYAL COLLEGE OF SURGEONS DURING FEBRUARY, ISS4. BY W. KITCHEN PARKER, F.R.S., HUNTERIAN PROFESSOR, ROYAL COLLEGE OF SURGEONS OF ENGLAND. Wixil-) |li)t)Cttt)a ant) EUu^tration*;. LONDON: CHAELES GEIFFIN & COMPANY, EXETER STREET, STRAND. 1885. [All Rights Reserved.] TO MISS ARABELLA BUCKLEY {Mrs. Fisher) ZhxQ little Wlorft is 3nscrit)e^ AS A SLIGHT MARK OF REGARD AND ESTEEM BY HER FRIEND THE AUTHOE. 15S93 PREFACE. For many years past I liave been engaged in researches into the structure and development of the vertebrate skeleton, and the results of these investiga- tions have, from time to time, been published in the Transactions of various Scientific Societies — naturally, in technical language. The Hunterian Lectures also of former Sessions, which preceded the present course, were delivered in the terms of Biological Science, and were thus, of necessity, unintelligible to persons not familiar with studies of this kind. During the last year or two, however, many useful suggestions with regard to a more popular method of treating these matters have been made to me by my esteemed friend, best known to the reading world as Miss Arabella Buckley. To her I am indebted for tlie ] )lan of this last course. The following Lectures, therefore, I offer to my nun- VI PEEFACE. scientific friends as slips and cuttings from the Biological Tree, in the belief that the great and absorbing question with ^Yhicll they deal — the problem of " Man's place in Nature" — will be found to invest even minute details with a very real interest. And let me observe, in passing, that the doctrine of the gradual development of organic types, if it does not stand or fall with Embryology, yet must look for its greatest support from, or be contradicted by, that most important Science — the true root-stock of Biology. There is, however, no branch of human knowledge that is so difficult to j)nt into language which can be appre- ciated by those who are not familiar with its S23ecial methods, its facts, and its descriptive terms. One thing I cannot pass over without remark, and that is, the strong and almost insuperable a j^'i'iori objection in many minds to the deductions of modern Biology ; this must neither be lightly overlooked nor treated flij^pantly. To these opponents the biologist may say : — " It is a very light thing that I should be judged of you, or of man's judgment " ; — and yet he is pained at the thought of even seeming to Ije in oppo- sition to much that the greatest and best minds hold sacred. The biologist having given expression to this feeling on his part, it is certainly the duty of the non-biological opponent of his deductions to look these things fairly in PREFACE. VU the face ; the burden of disproof is now laid upon the objector. "- ■ In conclusion, I desire to take this opportunity of thanking very heartily those friends who have kindly helped me to see the work through the press. W. K. PARKEE. London, Novemher 1884. TABLE OF CONTENTS. LECTUEE I. Introductory, The New Things of Biology, Time, the Sexton, Duckbill and Echidna, Groups of the Mammalia, . Charles Darwin, The first Historical ]\Ian, , The Australian Region, The first Creature witli Xails, Primary Amphibia, . Protozoa and JVIetazoa, Low Ancestral Types, Family Arrangements, Page 1 2 3 4 5 6 7 8 9 10 11 12 Care of the Offspring, The Crown of Creation, Larviform Embryo of the Mole, Great Weights on Small Wires, Influence of Surroundings, Adaptation or Extinction, Metamorphosis of the Frog, Man's Ancestors all buried, Eastern Cosmogony, Hyperbolical Asiatics, A Buddhist Miracle, Antiquated Theories, Page 13 14 15 16 17 18 19 20 21 22 23 24 LECTUEE II. Prototheria (Monotremata). The Duck-billed Platypus, 25 Negative Evidence, . 26 The Ceratodus a Gift of Provi- dence, ..... 27 The Lancelet and Sea-squid, 28 The Axolotl, .... 29 Lower parts of the Earth, . 30 Mammalian Advance, 31 The Prototheria quasi-Reptilian, 32 Shoulder-bones of Duckbill, 33 Three Collar-bones in Mono- tremes, ..... 34 Extinct Birds, .... 35 Feeling the Way upwards, 36 The Duckbill's Skull, 37 Opening a new Scroll, 38 Hingeing of the Lower Jaw, 39 Surgery or Horticulture, . 40 Formation of the Lower Jaw, . 41 Compound Nature of the Lower Jaw, .... Bones forming the Ear-chain, New Elements of the Ear, The Egg-breaking Beak, . The Frog's Kindred, Ancestors of the Mammalia, Young Duckbills, All Animals come from Eofsrs, Evolution of a Hairy Creature, Relation of Mammals to Reptile.- Jacobson's Organs, . Old and New Structures, . A Country M'ithout Birds, Skeleton of the Prototheria, Primary Respiratory Organ, Respiration of a Soft-shelled Turtle, .... Oxygen consumed in Pharyngeal Respiration, . 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 COXTE^^TS. LECTUEE III. On the Marsupials, or Pouched Animals (Metatheria). A Supposed Common Root stock, .... Embryonic Membranes, Embryo of Opossum, New-born Kangaroo, Early Life of a Marsupial, Mighty Hunters, Feeding-Grounds, The Earth's Shaking Fits, Pouch-bearing Animals, An opposable Inner Toe, . The Skull in Marsupials, . Skull of Embryo Pig, Ear-drum of Marsupials, . Exit of the Optic Nerve, . Links in the Chain of Life, Page f I A Bye-path ]\readow, 59 j The hard palate, 60 A Semi-Marsupial Insectivore, 61 : Crocodile, Bird, and Opossum, 62 , The Turkish Saddle, 63 \ The Stirrup and Columella, 64 I The Arch of the Tongue, . 65 { Mimetic Types, 6Q ! "Works on the Marsupials, 67 I Fossil Marsupials, 68 I An Oak Tree, . 69 j The Australian Flora and Fauna 70 I Frogs and their Progeny, . 71 ! Newts and Frogs, 72 Nourishment of Early Germ, 73 : Development of the Germ, Page 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 LECTURE IV. Edentata. Distiibution of the Edentata, Specialisation of Low Types, Nature's dull Children, The Struggle for Life, Dwarf Edentata, The Extinct Glyptodon, . Hair turned into Armour, The Aard-Yark, A stunted Genealogical Ti'ce, Isolation of the Edentata, Variation of the number in the Neck-Joints, . Dying out of the Teeth, . When the Yertebrata had no Lungs, .... The Hard Palate, The Deep Things of Morphology Skull of Sloth and Ant-eater, Toothless Jaws, The Feeble-faced Pangolin, 90 ; 91 ' 92 ! 93 I 94 ! 95 I 96 I 97 1 98 : 99 100 i 101 I 102 I 103 i 104 ■ 105 I 106 ; 107 I Hinge for the Lower A new Jaw, Nature's Amputations, Structure, Habits, and Classifi cation of the Edentata, . Papers on the Edentata, . Ant-eaters and Pangolins, The Captive Pangolin, Strong Evidence for Darwinism Gigantic Sloths, Ant-eating Birds and Lizards, Food and Safety, Love of Ofispring, Mother Carey, ... An L^nclean Sacrifice, Southey as a Darwinian, . The Green Turtle and the Glyp todon, .... Plucking up Cedars, , The Grave of the Giant, 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 LECTURE V. Insectivora. Materials for AYork, . . .125 Edentata and Insectivora com- pared, ..... 126 The First Beast- namer, . . 127 Development of tlie Whale and the Bat, . . ... 128 Organic Root-stocks, . . 129 Wasted Types, .... Adaptive Changes, . Ungulate Lemurs and other Generalised Types, . 132, The Number Five in Digits, Plastic Types, .... Layers of the Skull, . 130 131 133 134 135 136 CONTENTS. XI The Hedgehog's Skull, . Skull of Cartilaginous Fishes, . Ear-dium of Hedgehog, Parts of the Palate and Ear in Hedgehog's Skull, Page 137 138 139 140 Arches of the Face, . Primitive Types of Maninialia, Bibliography, . Fossil Horses, . Extinct Mammals, . Page 141 142 143 144 145 LECTUEE YI. Insectivora — continued. The Mole very Archaic, Greediness of the Mole, Blind, but Quick of Hearing, Development of the Mole, Pecords of Lost Types, An Hereditary Agriculturist, The Formation of the Tissues oi the JMole, A Dry Skull, . Air-Galleries of the Ear, . Labyrinth of the Ear, . 146 Diet of the Mole, . 147 Ped Teeth of the Shrew, . . 148 Young of the Shrew, 149 Skull of Shrew, 150 Young of Shrew like Eocene . 151 Mammals, . . . . Distribution of tlie ShrcAvs, . 152 Browzing and Grazing, . 153 Improvement of Breeds, . . 154 Homo diliivii testis, . . 155 Signs of Transformation, . 156 157 158 159 160 161 162 163 164 165 LECTURE YII. Tnsectivora — concluded. Foreign Tnsectivora, . ^Mascarene Types, Skull of the Tenrec, . Nasal Labyrinth of the Tenrec, Lesser Kinds of the Centetidffl, Crested Skull of the Tenrec, Wallace's Line, A Complete Orbital Ring, The Young Colugo, A Puzzling Type, A Tertiary Bat, Comb-like Teeth of Colugo, . 166 . 167 . 168 169 . 170 . 171 . 172 . 173 . 174 . 175 . 176 . 177 The Colugo and the larger Bats, The Basi-Cranial Beam, Relations of Air - Breathing Types, .... Old Remnants in New Types, The Rhynchocyon, . A Proboscidean Insectivore, Marsupial Characters, Working out old Strains, . Bibliography of Insectivora, New Insectivora, , 178 . 179 T ? ISO 181 182 183 184 . 185 . 186 . 187 LECTURE VIIL The Remaining Orders of Mammalia, The Chiroptera, A Long-fingered Animal, , Evolution of a Flying Animal, An Unfolded Bat, The Rodentia, . Voyage of a Naturalist, Skull of a Guinea-Pig, Lemurs and Aye-aye, . 188 Zoological Position of Lemurs, 196 . 189 Diet of the Aye-aye, . 197 190 The Carnivoia, . IPS 191 Aquatic INIammals, . 199 192 The Quadrumana, 200 193 The Pig and the Ruminants, 201 194 195 Evolution of the Horse Type, . 202 Xll CONTEXTS. LECTURE IX. Conclusion. Page Page Metamorphosis of the Dragon - Searchers for Facts, . 216 fly, 203 Dry Light, . . . . 217 The Possibilities of Being, 204 A new Atlantis, 218 Soul and Body, 205 Quotations from Bacon, 219 Human Longings, 206 Second Causes, . . . . 220 Waves and Pulses, , 207 Gentle Modifications, 221 Arrested and Developed Types, 208 A Tithe-Farmer, 222 Our Forefathers, 209 Goethe on the Teleologists, 223 Astronomy, Geology, Biology, 210 The Seal, 224 The Links of Created Being, 211 Time-Marks, . . . . 225 Our Growing Knowledge, . 212 Plants and Animals, . 226 The Currents of Protoplasm, 213 How the Bones Grow, . 227 Embryological "Work, 214 Exogenus Growth, 228 Written on the Brain, 215 Expansion of Modern Thought, 229 MAMMALIAN DESCENT. LECTURE I. Inteoductory. Bpjef as is the title I have given to the present Course of Lectures, it contains enough, in two words, to give alarm to cautious and timid minds. I need hardly say that no harm is intended by it ; and I believe that no harm will happen to the mind of any one who will listen to me whilst I bring forward some of the " new things " of Biology. The Mammalia are important to the biologist beyond any other group whatever ; for they contain, within their circle, the highest known t}"pe of living creatures. A group which culminates in Man may well deserve our attention and study ; even the forms that make the nearest approach to the human race are, of necessity, full of interest to us. If in human society the toe of the peasant now and then galls the kibe of the courtier, so in this class the toe of the irrational beast treads, in some cases, very close upon the heel of rational man. A D. H. HILL LIBRARY North Carolina State College 2 MAMMALIAN DESCENT. [Lect. I. It is worthy of remark that this keeper of the mammals — himself a mammal — is, in size^ a good practical mean between the extremes. On one hand we have *' the smallest monstrous Mouse that creeps on floor," and on the other the unwieldy "Whale — large as an island. Taking the class as a whole, as to intelligence, we have " the extremity of both ends " — Man at one end, and the frog-witted Duckbill at the other. The mammalian class is, indeed, a most motley assemblage, whether we consider their form, their size, or their intelligence, for the wars of time have sadly thinned the ranks of regiment after regiment. Nor is the Darwinian in fault, if, when the roll-call is made, so few are found to respond to it. Let those who clamour for connecting-links lay this to heart : m}T:iads upon myriads of mammals have perished in the struggle of life ; time has buried them. "'Time, that old clock-setter, that bald sexton, time," has much to answer for ; he has not only thrown the mould over the links of the chain of types, but — to change the image — he has buried thousands of complete family trees, and the geological miner has only unearthed a broken twig here and there. He is in a low state of mental development who is unaware of the extreme antiquity of the planet on which we dwell ; and it is a far cry backwards, to the time when the young of four-footed beasts ^r,9^ tasted milK Lect. I.] DUCKBILL AND ECHIDNA. 3 The group, class, or family — as we may call it — wliicli acquired the peculiar faculty of giving of their very sub- stance to their offspring, is as ancient and as venerable as the group of the reptiles, out of which arose the feathered tribes. Not out of the stem, however, of the reptilian family tree, but out of its root-stock; and close to that fine sucker, there shot up this other branch, to become the new life-tree of the hairy creatures, that give their young ones suck. Two of the first twigs of that new shoot are still represented by the " Monotremes," namely, the Duck- hill and the Echidna; but, of course, as their line of ancestors must have existed during the formation of the outer half of the earth's ribs, they have had time enough for much specialisation in their structure. Therefore, the scientific imagination, after assuring itself that these living waifs do not lie at the root of mammalian being, bodies forth much lower and more generalised milch-kine than them. There are fossil remains, evidently mammalian, from the base of the Secondary rocks. Whether these small jaw-bones belonged to Monotremes that had teeth, or to the more ancient Marsupials,^ does not aff'ect our argu- ment. Mammalian remains will, I feel sure, turn up some day from older rocks : anyhow, in certain strata '' The Monotremes are so called because they have only one common outlet to their body, as in Reptiles and Birds ; Marsu'inals are so called because they possess a marsupium or pouch. 4 MAMMALIAN DESCEXT. [Lect. I. of the Secondary epoch we get various remains of tlie group above the Monotremes — the Marsupials. Professor Huxley's classification of the mammals is as follows : — 1. Frototheria, or the Monotremes : examples — Duck- hill and Echidna. These are the lowest mammals known ; they have udders, or milk-glands, but no teats, and in many things stand on the same level as the Sauropsida (reptiles and birds). - 2. Metatheria, or the MarsujDials : examples — Opos- sum, Fhalanger, Kangaroo. These have, besides the milk-glands, perfect teats, but their young are born so early that they derive no direct nourishment from the mother until they are placed on the teat. 2. Eutheria. — These forms are the highest, and their young do derive direct nourishment from the mother for a considerable time before birth — before they are nourished by milk. In this group we have Moles and Men, and all the forms that lie between these two extremes. I shall speak of the Mole as a low Eutherian, of Man and of his Horse as high Eutheria. There are at present three groups of labourers working at the Mammalia ; as, indeed at other t}^3es also ; these are : — 1. The Zoologists. These study the finished form, habits, and distribution of the various types, in the present state of the planet. Lect. L] CHARLES DAEWIK 5 2. The Palseontologists. These study the fossil re- mains of the extinct forms, and their ]Dast distribution. 3. The Embryologists. These men are working out the development of this or that type, following it through the various stages of the history of its life. These three divisions of the swarm of biological bees are rifling the treasures of this planet, ^' which pillage they with merry march bring home." They are all Darwinians, to a man ; and they scout the " lazy, yawn- ing drone " who eats of their honey, buzzing the while dissatisfaction at their work and their song. This seems, in the ears of many, to be a "new" song, but it is, indeed, the old song spoken of by that fine old eastern naturalist — the much-suffering Job. Who the morning stars of science were, we know not; the voice of one who lately spoke to us, in his wisdom, of living creatures, vegetable and animal, is, to our sorrow, now silent. There is a growing consensus, or harmony, amongst the three main divisions of the workers, who are now begin- ning to understand each other. This has taken time, for the harmony was not, at first, in the mind of the workers, but in Nature herself; they were working apart — each group apart, and each labourer apart ; but the zoological scouts, the earth-diggers, and the miners of the organisms, all these work well together now. I think that he who digs down, so as to see Nature, alone, at her work, in the (figuratively) lower parts of 6 MAMMALIAN DESCENT. [Lect. I. the earth, mil reap the richest reward, and have the highest honours. For, the pala3ontologist, in his luckiest finds, brings you up, at most, the framework, only, of a creature, and that, mostly, in its adult condition. Such shreds and patches of old organisms as he finds, although unspeak- ably precious, are difficult materials out of which to con- struct a history. But your embryologist has learned where to find little compendiums of the past history of the folks that did live here a long time ago. These, however, are written, so to speak, in shorthand, and are as difficult of interpretation as the old cuneiform characters ; that difficulty at once whets his ingenuity, and also makes him resolve to possess his soul in patience. You will see that I am weavino; this web of w^ords to catch your attention whilst I bring in my theory — not mine, but Darwin's, — and yet mine, notwithstanding. This theory seems to contradict the Sacred Records ; it does contradict the letter of certain passages — taken alone. Man was created perfect — that is, " calling the end from the beginning ;" and in the fulness of the times a Perfect Man did appear. We have His history. Having that, I, for one, care not a jot about any further history of the weak man who blots the historic j)age at its very beginning. Now let us leave Man, and go down among the beasts ; they are delightful creatures, — " what God Lect. L] the AUSTRALIAN EEGIOX. 7 liatli cleansed" [made pure and beautiful] "tliat call not thou common." Of tlie Prototlieria (first beasts), the lowest, teatless mammals, we have, now, only two types (genera) left. These are both limited, in their range, within the Australian region ; they are, the OrnithorJii/ncJms, and the Echidna. The former is the lower of the tw^o kinds ; but Professor Huxley's conception of the group in its early, and perhaps abundant, existence is, that it was composed of much less specialised forms than those now living. Are we to stand like men who cannot find their hands, because Nature and Time have buried nearly all the truly old families of the Mammalia ? If we are unable to frame convenient hypotheses, to be used as intellectual scafi'olding to our facts, we are out of our place in attemj^ting biological research. Let us, if such be the case, stand out of the sunshine of fitter and abler men. At present, I have only partially worked out the young of one of these kinds, — the Ornithorliyncliiis ; but although tolerably familiar with the structure of the Vertebrata generally, I am at a loss, even in this early stage of research, to see the meaning of many things in that type. Here is a beast — a primary kind of beast, a Proto- therian — whose general structure puts it somewhere on the same level as low reptiles, and old sorts of Ijirds ; but 8 MAMMALIAN DESCENT. [Lect. I. in which there are characters much more archaic than anything seen in SerjDents, Lizards, Tortoises, Crocodiles, or in Emeus. Therefore the existing reptiles and birds must stand aside as havino- nothino; to do with the family tree of the Monotremes, although in some things they are like these beasts, and many of their organs are formed on a similar pattern ; they are all equally below the morphological level of the nobler Mammalia. Although some of the mammalian characters are well marked out in the Monotremes, yet they only agree with the higher Mammalia to a very limited extent ; some things now seen in them are quite new to me. Most of the existing fishes have ceased, or nearly ceased, to begin life in a larval form, or one lower than that in which they spend the main part of their existence. Some degree of metamorjDhosis is seen in the Ganoids, and more in the Lamprey ; but T\dth the Amphibia (Newts and Salamanders, Frogs and Toads), it is in the larval, or gruh-stage, that we find the oldest things. One kind of frog, from the Cape, is the first creature that is possessed of nails to its toes and fingers ; it is termed Dactylethra. The tadpole of this frog has shown me some of the most archaic structures, and the lowest condition of the tissues themselves, that I have met with in the whole sub-kingdom of the Yertebrata. I speak of this for two reasons : — first, I find things in it which are quite like what are to be seen in the Lect. L] primary amphibia. 9 Duchhill, but wliicli I have in vain sought for in any other type. My second reason is this, namely, that the extremely wide range of structure taken by each individual of that species, and indeed, of all its kindred, from the time of hatching to the time when the permanent adult form has been reached, is such as to suggest almost limitless possibilities in the development of the Yertebrata, so that my thoughts run almost unconsciously parallel with the suggestions so ably put by Professor Huxley, in his paper. I can, and do ' imagine a group below the Prototheria, their root-stock, which may well be called " Hypotheria," or creatures under the beasts. That these were akin, closely akin, to the ^9?"M?ia7^;^ Amphibia, there is every reason to believe. If they were metamorphic, and that I think is very probable, they lived in their infancy in the water, and their respiration was aquatic. Our present work, however, is not to stand peering down into those dark depths, but to see whether the stages of the existing Prototheria will not show us many instructive facts. Yet even here we are almost as poor in embryos of these types, as we are in their fossils ; and the present destruction of these invaluable types, for the sake of mere museum exhibition, painfully suggests their probable early extinction. The Eoyal Society, however, has lately, with great liberality, furnished certain scientific Knights with means 10 MAMMALIAN DESCENT. [Lect. I. for following tliis quest — that of finding the embryos of the Monotremes. If they succeed, and we can get the early stages of the existing Prototheria, I have no doubt but that we shall be able to see much further into "that dark backward and abysm of time," when the Huxley an Hypotheria did duty for the existing. Mammalia. I shall show in these lectures that some of the lower kinds of Eutheria (placental mammals) undergo, in their pre-natal state, and also during their infancy and youth, most remarkable transformations. I use the word transformation in a popular sense, as the term "metamorphosis" has a very limited and absolute meaning m science. All the animals above the Protozoa (first creatures) are called " Metazoa," because they undergo remarkable changes of form, heyond their first stage or state* When these various stages are gone through in the active condition — the partially developed animal leading for some time a free and out-of-door life — it is said to undergo metamorphosis. If these changes are not utilised, if they are _29r6-?ia^a^, and the new-born active creature is practically the same as the adult, the more familiar word transformation is employed for the unused early changes. A Snake undergoes remarkable transforniation whilst in the egg ; a Frog is marvellously metaniorjjJiosed during its active life. Lect. I.] LOW ANCESTEAL TYPES. 11 The early transformations of those types wliicli have no larval stage I look upon as the unused equivalents of the metamorphic steps of types, which, like insects, have an active larval stage, or stages. These transi- tory, unused stages are, manifestly, of an historical import ; they suggest to the Darwinian lower and still lower types of ancestral animals — the Fauna of a bygone time. And this view of the matter is well borne out by what we already know of the structure of the Prototheria, or Monotremes, and of the Meta- theria, or Marsupials. It is also borne out by every- thing I have seen, as yet, in the structure and de- velopment of the other groups of the Yertebrata, as they rise one above the other in the order of morpho- logical excellence. The perfection of every organ for its special use in the adult makes it the more noteworthy that there are so many things to be found, during growth, that are not only useless, but, as a rule, transient — some of them, however, are permanent. The doctrine of Final Pur- pose, on its old platform, and taken as if it were the conclusion of the matter, wholly fails to explain these rudiments, or remnants — these useless odds and ends of i forgotten organs. Whether transitory, or permanent, they are the opprobrium of the teleologist who has not studied the growth of the embryo, but they are goads and spurs to him who devotes himself to the study of Development. Yet the doctrine of Final Causes is not 1 1 2 MAMMALIAN DESCENT. [Lect. I. affected by this deeper kind of research — it is merely placed on a higher platform. Looking upon these facts as having an historical meaning, we shall find some light thrown upon many unexplained problems in the structure and development of our own. frame. If it be a fact that these unused and useless things were once useful, and did their work as part of the machinery of a living and active, but low form, and that in conformity with new conditions this loiu, larval life became abbreviated, then some light is shed upon these dark problems. Let this once be well settled upon sure foundations, or as a strong nail in the wall of science, and then we shall be able to harmonise our old faith with our new knowledge. The study of the lower forms is ever giving us fresh and fresh evidence of the infinite fertility of nature's expedients in adapting living forms to varying condi- tions — to new surroundings. And this is seen more especially with regard to the Family Arrangements of the various types, in the matter oi paternity, maternity, and time. The surrounding's are often cruel and destructive : yet nature does not temjDer the weather to the lamb — she clothes the lamb so that it can brave the weather. All through nature we see that the most marvellous care is taken so that the Children shall have their chance ; mostly the care is on the maternal side, in Lect. I.] CARE OF THE OFFSPRING. 1 3 some cases, nature teaches even tlie stupid husband to do his part in wrapping wp the children, and in keeping the home safe. But the most wonderful part of the family arrange- ments takes place before the period of hatching, or of birth, the parents being unconscious agents. In many cases the parents are workers together with nature in preserving the germ ; albeit the casket of this treasure is wholly unlike, as an egg, the infant that is to be here- after in their own image and their own likeness. It is not in the human kind, but among the cattle, that the young one is made to do most of its development in the dark, so that at birth it is strong and in good liking. This is the very culmination of reproductive adaptation ; the furthest from the careless, thoughtless state of things seen in low, fish life, where, as in the cod-fish, millions of germs are sown broadcast upon the waters by one mother, who is hardened against her young ones, as though they were not hers. But the growing care of the germ by the proper living mother, she hiding it longer and longer in her bosom be- fore she commits it to the waters, is well seen in certain sharks, that do, in the most striking manner anticipate the last and most perfect specialisation of this kind. The family, as such, both in birds and mammals, is not seen in its perfection among those creatures whose young are ripest at the time of birth. Birds are divided by some ornithologists into ^'Prsecoces" and "Altrices ;" 14 MAMMALIAN DESCENT. [Lect. I. it is among the latter, wliose young are feeble at the time of hatching, that the most tender care is taken of the family. The same holds good amongst mammals, as we all know ; yet the young one, when born in a tender state, has fairly the form of its parents ; it does not shock them by its larval ugliness ; and the first human mother on record, seeing her first-born son, exclaims — " I have gotten a 3fan from the Lord." All these things are so familiar to us that I fear you will wonder why I speak of them ; but if you reflect upon the ivay in which they came about, and the time they took to get perfected, you will see what I am aiming at. Mentally, in imagination, I have been tarrying Nature's leisure, whilst, during untold ages, she has wrouoiit all these wonders. If anyone will consider the great uniformity, both in size and shape, of all mammalian embryos and germs, he will see that the marvel of evolution is always going on in a thousand types, here, in the highest class, at the very top and crown of creation. That which is now, is like that which has been ; the mere shortness or length of time during which the various processes of growth and development take place is a non-essential matter. The embryo of a mammal at the stage which represents a gill- bearing vertebrate, in all cases that I have examined, ranges from one-third of an inch to an inch in length ; the former size belongs to the smaller kinds, the latter to the larger. Lect. I.] LAEVIFOEM EMBRYO OF THE MOLE. 15 Know one, know all ; one diagram would represent all, one description serve for all. Such a stage, moreover, gives us a form extremely like that of any other gill-less type — bird or reptile ; while to make it into a semblance of the lower aquatic types, more '^visceral arches," with more and more gaping clefts, are all that would have to be added. In all we have the curved, larviform creature, with its TT'^C Fig. 1. — Embryo of Mole {Talpa europwa, 1st stage), magnified 12 diameters. large brain-lobes bent under, in front ; its tail-end bent under, behind; its solid front folds, its rudimentary gill- openings, and its paddle-sha^Dcd limb-buds. But the characters derived from its more immediate ancestry soon show themselves. By the time the gaps in the throat are filled up, and the embryo has doubled its <. 16 MAMMALIAN DESCENT. [Lect. I, lengtli, the special cliaracters of the type to which it belongs begin to be seen. Nevertheless, in the embryo of a medium-sized mammal — e.g., the Hyomoschus, a generalised ruminant — nearly an inch long round the curve, I find nothing that suggests its proper place in nature : it might belong to a Lion, or to a Gorilla, as far as its outer form is concerned. And yet an embryo of this kind — a sort of temj)orary, sleeping, dependent larva — becomes, in one case, a Eear- mouse with leathern wings, and in another a Whale, whose skin and blubber are as thick as a house-wall. Lord Bacon gravely remarks that — " God hangs the greatest matters on the smallest wires." He might have been an embryologist ; certainly, neither a Darwin nor a Huxley could have put such an aphorism into a better form. AVhale's eggs are no larger than '^ fern seed ;" and yet the protoplasm in any one of them has the power, when planted where it can get due nourishment, to develop an embryo wdiich, whilst as yet it is unborn, is as large as a good-sized cow. This phenomenon of development, wdiicli is always repeating itself in all mammals, only not to so huge a bulk as in the instance just given, is as great a "sign" or "wonder," or "miracle," as anything suggested by the most thorough-going Darwinian as part of the process of secular evolution. All this differentiation, all this development of com- plex, correlated organs, in one single organism, worketh Lect. I.] INFLUENCE OF SUEROUNDIXGS. 17 that one and tlie self-same force, bringing forth severally, according to the ancestry of each, modified and fashioned into various types during untold ages of the past, the various Mammalia that tenant the waters, flit in the air, or trample the paths of the forest. In each of these the force is manifestly the same, essentially ; but the sur- roundings of the organism in which this force has been enshrined have been the same during no two successive moments of time, during all the ages in which the earth has brought forth living creatures. The sensitiveness of a livino- creature to outward impressions is excellently put by our great poet. lie says that you cannot press your hand with a rush, but it will JDear a visible mark or cicatrix, and that the eyes do shut their cow^ard gates on atomies. The infinite number of delicate and o-entle modifica- tions in the human form, all S23eak eloquently of the influence of '•' surroundings." All the races of this t3rpe are evidently varieties of one common S23ecies ; a species whose existence upon this planet, according to Usher, has been barely six thousand years. As the wind pipes, so the creatures dance ; and the wind and the sun are ever renewing their old contest as to who can make the traveller pull off his cloak first. For a long while the eager, nipping wind of Siberia tried this on with the Mammoth : he merely had his cloak made warmer and thicker. The wind ultimately killed the beast, but never got him to take his garment B 1 8 MAMMALIAN DESCENT. [Lect. L oj0f. On tlie other liand, in tlie tropics of the Old World, to this day, the brothers of the old Mammoth have been living in harmony with the Sun ; but they have thrown away their cloaks, and bask, naked, in his beams. But, during great, sudden changes in the home or feeding-ground of animals, the dilemma has again and again been adaptation or extinction', in many cases nothing short of metamoiyhosis has saved them from death, and kept them alive in famine. Speaking of- metamorj)hosis, I am brought to that which is, evidently, the key to the intricate wards of this long-locked-up problem — I mean the descent of organic t}^3es. The metamorphosis of insects — a marvel always fresh and wonderful both to the man of years and to the child — reveals to us the practically infinite jDOSsibilities of the modifications that may take place in the lifetime of a single worm-like creature. If we were not thoroughly familiar, from our childhood, with the astounding phenomena of insect-transformation, if we only knew the Grub, the Pupa, and the perfect, winged Imago, separately, any assertion of such a possi- bility by some far-seeing biologist, would be treated with contempt, and the brand of heresy would be set upon liim. Such a developmentalist would fare as Bruce, the traveller, fared, when lie related his adventures, telling of the sights his eyes had seen — " All he gets for his harangue is — ' Well ! ^Miat monstrous lies some travellers tell.' " Lect. I.] METAMOEPHOSIS OF THE FROG. 19 How does all this bear on mammalian descent ? Mammalia are not insects. My answer to this curt but pertinent question is — that insects show us what is possible as to metamorphosis in a very high group of the Metazoa, or creatures that change their form during their development. Now, as I have spent the spring and summer, and some part of the grey autumn of my life in observing the phenomena of metamorphosis in the Yertebrata, you will, I hope, of your clemency, listen to my words. Before Darwin's Origin of Species had for any length of time been printed and discussed, I had seen such things in the metamorphosis of the common Frog as seemed to me like the writing in a newly-opened scroll of science. Starting as one of the lowest and most generalised kinds of fish, this creature does not end his strange, eventful history until he has given us the tj^Q and promise of almost everything in the structure of a high mammal (or Eutherian), even of Man himself, who lifts himself up above his mammalian fellows. Long before our era a gifted captive Jew saw, among the celestial hierarchies that appeared to him in vision, " the likeness as the appearance of a man." To us it is given to see man's image down among the living creatures that crowd around the foot of Jacob's ladder. Bacon remarks that — "Light doth stream down more clearly and divinely into the mind of a young than of an old man, for it is written — ' Your old men shall dream dreams,* 20 MAMMALIAN DESCENT. [Lect. I. but ' your young men, sliall see visions.' " Now, if one of the briglit young soldiers in our rapidly increasing army were permitted to see tlie whole web (woof and warp) of organic life, he would everyw^here see glimpses of the human face divine ; the features of the latest creature would be traceable in the face of the earliest. Yet these t}qDes and foreshadowings of the great Eeasoner, to be develoj)ed in the parturient fulness of time, only reached their own little Pisgahs ; they looked over towards the human territory, but they entered not in. As for the direct ancestors of man, time has buried them, and no man knoweth of their sepulchre to this day. ADDEXDUM TO LECTUEE I. That which is biological in the foregoing Lecture will be con- sidered and treated of from time to time in the succeedmg Lectures, and also in the Addenda attached to them. But there is one thing that may be brought in here, namely, the conceptions that the Ancients held with regard to the Origin of the Universe, and especially of living creatures. Amongst these the Jewish Bards stand first, far in front, indeed, and moreover their poems have been worthily ren- dered into what Swinburne truly calls "Divine English." I am, of course, well aware that Moses, and Job, and David were not the only great and wise and good men who in ancient times sang — "How the Earth rose out of Chaos." Whilst composing these Lectures, a friend kindly put into my hands two invaluable works that have yielded me great pleasure and profit. The first of these is A Manual of Buddhism,'^ by R. Spence Hardy; ^ 2iid edition. London : Williams & Norgate, 1880. Lect. I.] EASTERX COSMOGONY. 21 the second is Religious Tlioughts and Life in Lidia,^ hy Professor Monier Williams, M.A., CLE. Part I., Vedism, Bralimanism, and Hinduism. Some of the venerable hymns given in the latter work are sub- lime, and certainly come very near the Hebrew writings. I have only space for a specimen or two, but trust that the reader will be led to avail himself of Professor Williams's invaluable labours : — " In the begimiing there was neither nought nor aught ; Then there was neither sky nor atmosphere above. What then enshrouded all this teeming universe 1 In the receptacle of what was it contained ? Was it enveloped in the gulf profound of water ? Then was there neither death nor immortality ; Then was there neither day, nor night, nor light, nor darkness. Only the Existent One breathed calmly, self-contained. i^ought else but he there was — nought else above, beyond. Then first came darkness hid in darkness, gloom in gloom ; IsText all was water, all a chaos indiscrete, In which the One lay void, shrouded in nothingness. Then turning inwards, he by self-developed force Of inner fervour and intense abstraction, grew. First in his mind was formed Desire, the primal germ Productive, which the wise, profoundly searching, say Is the first subtle bond, connecting Entity And miUity."— Page 13. *' From glowing heat sprang all existing things. Yea, all the order of this universe {Bit a). Thence also Night and heaving Ocean sprang ; And next to heaving Ocean rose the l^ear. Dividing day from night. All mortal men Who close the eyelid are his subjects ; he The great Disposer, made in due succession Sun, moon, and sky, earth, middle air, and heaven." — Pngc 404. ^ London : John ^Murray. 1SS3. 22 MAMMALIAN DESCEXT. [Lect. I. I also give a few quotations from Mr Hardy's very important work, but these are to illustrate what is to me most remarkable, namely, the manner in which these Asiatic people threw the reins on the neck of their imagination. I cannot but think that modern scientific thinkers, here, in the Far West, are much more removed, in mind, from those cognate races, ^ than from the Semitic people that gave us our own Bible. These latter poets exaggerate no more than any one of us (supposing that he were a poet and not a scientific worker and registrar of hard, dry facts) would do. But the Buddhist is nothing if not hyperbolical, and when he does magnify, he magnities with a vengeance ; take one example : — " The Asurs, who reside under Maha Meru, are of immense size. Rahu is 76,800 miles high; 19,200 miles broad across the shoulders; his head is 14,500 miles round; his forehead is 4800 miles broad; from eye-brow to eye-brow measures 800 miles; his mouth is 3200 miles in size, and 4800 miles deep; the palm of his hand is 5600 miles m size ; the joints of his fingers, 800 miles ; the sole of his foot, 12,000 miles ; from his elboAv to the tip of his finger is 19,200 miles ; and with one finger he can cover the sun or moon, so as to obscure their light." — Page 59. And another, as follows : — " In the forest of Himala are lions, tigers, elephants, horses, bulls, buffaloes, yaks, bears, panthers, deer, hansas, peafowl, kokilas, kin- duras, golden eagles, and many other kmds of animals and birds ; but the lions and kokilas are the most abundant. There are four different species or castes of lions, called trina, kala, pandu, and kesara. The first is dove-coloured, and eats grass. The third is like a brown bull, and eats flesh. The kesara lion, wliich also eats flesh, has its mouth, tail, and the soles of its feet of a red colour, like a waggon laden with red dye. From the top of the head proceed three Imes, two of which turn towards the sides, and the third runs along the centre of the back and tail. The neck is covered with a mane, like a rough mantle worth a thousand jDieces of gold. The rest of the body is white, like a jDiece of pure lime. A\^ien he issues forth from his golden cave, and ascends a rock, he places his paws towards the ^ Of course, I refer to tlicse Aryans who adopted the Buddhist tenets. Lect. I.] A BUDDHIST MIRACLE. 23 east, breathes tliroiigli his nostrils with a noise Uke the thunder, shakes himself like a young calf at its gamljols, that lie may free his body from the dust, and then roars out amain. His voice may be heard for the space of three yojanas around. All the sentient beings that hear it, whether they be apods, bipeds, or quadrupeds, become alarmed, and hasten to their separate places of retreat. He can leap upwards in a straight line, 4 or 8 isubus, each of 140 cul)its ; ujwn level ground he can leap 15 or 20 isubus, from a rock 60 or 80. When the kokila begins to sing all the beasts of the forest are beside themselves. The deer does not finish the portion of grass it has taken into its mouth, but remains listening. The tiger that is pursuing the deer remains at once perfectly still, like a painted statue, its uplifted foot not put down, and the foot on the ground not uplifted. The deer thus pursued forgets its terror. The Aving of the flying bird remains ex- panded in the air, and the fin of fish becomes motionless." — Page 17. Among the Legends of Gcjtama Buddha, there is one which has interested me very much, for it exactly corresponds with the popular ideas of the sudden, miraculous creation of living forms : — " After eating the fruit, the sage gave the stone to Gandamba, and directed him to set it in the ground near the same spot ; and in like manner, after washing his mouth, he told Ananda to throw the water upon the kernel that had just been set. In a moment the earth clove, a sprout appeared, and a tree arose, with five principal stems and many thousand smaller branches, overshadowing the city. It was 300 cubits in circumference, was laden with blossoms and the richest fruit, and, because set by Gandamba, was called by his name." — Manual of Buddhism, p. 306. This creation-feat is scarcely greater than the one supposed to take place in the case of the first creation of every tree and every animal, by those Avho are unversed in Biology and who interpret, literally, the account of the Creation given in the first chapter of Genesis. But some of those who have a little knowledge, even of Biology, have very misty notions of the origin of living creatures. One such suddenly startled the writer by a hurried utterance of his cherished creed, which was as follows : — " I believe that God created Wellin'jtonia gigantea, 400 feet high, in a moment." 24 MAMMALIAN DESCENT. [Lect. I. This sjoeaker, whose power of mental deghitition was so great, was one of onr own calling, and, therefore, had undergone a biological training ; surely we may hoj)e that better days are in store for us, when no educated man will be in danger of falling into such a deep pit of belief as this. But Man, the only reasoning being we know anything of, can be as unreasonable in his unbelief as in his belief. In Mr MaUock's charming little Lucretius,^ there are many things a Darwinian longs to quote, but one verse, with the translator's prefatory remarks, may be given : — " The chance to which our world owes itself, needed infinite atoms for its production, infinite trials, and infinite failures, before the j)resent combination of things arose. " ' For blindly, blmdly, and without design. Did these first atoms their first meetings try ; No ordering thought w^as there, no will divine To guide them ; but through infinite times gone by. Tossed and tormented they essayed to join. And clashed through the Void space tempestuously. Until at last that certain whirl began, "\"\T.iich slowly formed the earth and heaven, and man.' " —Page 93. The reader is also requested to look at the curious, abortive, imreasonable Darwinism of the chapter " On the Origin of Life and Species." — Section iv., pp. 45-50. Those who care for defunct theories of Creation may find one as good as the rest, but more amusing, in The Birds of Aristo2^1ianes.'^ I can only find space for the beginning of this part of the Drama : — " Before the creation of Ether and Light, Chaos and Night together were plight. In the dungeon of Erebus foully bedight, Nor Ocean, or Air, or Substance was there. Or solid, or rare, or figure, or form. But horrilDle Tartarus ruled in the storm." — Page 30. 1 William Blackwood & Sons, Edinburgh and London, 1878. - Sir John Hookham Frere's Translation. Cambridge, 18S3. Lect. II.] THE DUCKBILLED PLATYPUS. 25 LECTUKE II. Peototheeia (Monoteemata). The lowest, or teatless mammals, still linger in the Australian region, in tlie form of tlie spiny Ant-eater, or Echidna, and tlie great Water-Mole {Platypus, or Ornithorliynchus). A few fossils have been found in this same region, and described by Sir Kichard Owen as y faith as well as by sight. Imagine some low, ancient, simple form of fish, that did, by metamorphosis, become a creature as hidi as the Ceratodus. And that you may be able to see this hypothetical fish ascend, during its 28 MAMMALIAN DESCENT. [Lect. II. active lifetime, very far above its first condition, put l3e- fore your eyes the actual transformation of tlie Common Frog, with the metamorphosis of which every one is familiar. Having performed this mental feat, you will have brought up from the "vasty deep" a type that, in its larval state, would, probably, be intermediate be- tween the Lancelet (Amphioxus), and the Tadpole, or larva of the Frog. Now the Lancelet has no brain, no skull, slight dimensions, and scarcely any sense-organs ; it is, in reality, a sort of half-way creature between a larval Sea-squid (Ascidian), and the lowest of the Yerte- brata. But the Tadpole, or larval Frog, represents a low ancient kind of sucking fish (a sort of Lamprey) ; it has a brain, a skull, two sorts of gills, and soon shoots up into a musical, agile, air-breathing Frog. Once more let your imaginary forces work, and feign one of these ancient double-breathing fish [Dipnoi)^ formed by transformation from that supposed low type, and you have a stock which will grow you further suckers for your life-tree. Such a form or t}^3e, richly charged vdih. morphological force, might transform again and again — undergo, under ih^ stimulus of necessity, further metamorphoses. For havino: both outer and inner oiUs, and a sacculated air- bladder, acting as a rudimentary lung, it might, under the compelling force of threatening surroundings, suddenly blossom out into one of the root-t}^3es of the higher orsjanic forms. Lect. IL] the AXOLOTL. -J'J I am purposely forgetting, for the time, the slow accre- tion of minute variations, taking place through countless ages of time, and am considering sudden, per mhiim, transformations. Whenever and wherever it Ijecamc necessary that higher tracts of the drying surface of the earth should be peopled with semi-terrestrial and terres- trial forms, then I suppose these leaps of life to liave taken place. The morphological force — the indwellin<-»* spirit of protoplasm — actually did perform these wonders ; thus we have still living in abundance, reptiles tliat crawl upon the earth, mammals that march or gallop over it, and fowls that fly in the open firmament of heaven. I do not, of course, forget that the few existing Dipnoi — the Ceratodus and his companions — are settled in their low estate, at their own height, on their own morphological platform, and that there is little likeli- hood of their undergoing any further metamorphosis, now^ Still, with the AocolotV staring me in the flice, I cannot suppose even that to be imj^ossible. But when I imagine double-breathing: fishes undero-oino* metamor- pilosis in the olden times, I am thinking of more simple and archaic Dipnoi than even the Ceratodus or the Protopterus of the present day. Every biologist knows that some types have persisted in a low^ estate with little modification, others in a low estate with much specialisation ; whilst other ty^ds have 1 That large Mexican Salamander generally continues in a low larval state tlirono-hout life, but now and then it becomes transformed, loses its gills, and becomes a member of a higher family. 30 MAMMALIAN DESCEXT. [Lect. II. risen altogether far above the level or platform of their ancestors. With regard to the Prototheria (or first beasts) I am of o|)inion, that if the silent rocks of the Carboni- ferous epoch — the huge masses of Mountain Limestone — could speak, they would tell us of an abundance of teatless mammals (such as are now seen in the Ornitho- rhyncJnis) both on the dry land, and in the brooks and streams of water that then drained the land. It is the business of the palaeontologist to dig and bore the solid earth, and from thence extract a register from which he will probably learn that Duckbills and Echidnas swarmed in the ages of the Calamites and Lepidodendron. But there is a poetical use of the words '' lower parts of the earth," as well as a literal ; in these living strata (in stage below stage of types in their pre-natal life), hidden from the sun, it is my work to dig. These things are an allegory, and yet they are true ; between the embryologist and the palseontologist there is a mavellous harmony — they have one heart and one way — cor unum, via una. If my valued fellow-labourer, with his huge ungainly instruments, the hammer and the pick-axe, is slow in bringing up his facts, I shall not wait for him, but, with my small needle and shears, I shall go on laying bare and spreading out the strata of the organism — a real microcosm, a world in a nutshell. Many years ago the common Mole 3^ielded me results Xect. IL] MAMMALIAN ADVANCE. 31 tliat suggested a greater nearness of tins little delver to the great Water-Mole, the Ormthorhynchus of Australia, than had been imamned. Proof is not wantinsr, now, that some of the lower Eutheria, or high beasts, rose rapidly from the Prototheria, without utilising the Meta- therian or intermediate condition. They did not wait to become Marsupials, but ran up on to the top platform before they attained the adult condition. The Meta- theria — the pouch-bearers — did, and do still, utilize an intermediate morphological stage of development, but some of the Insectivora may have shot past them, and groAvn into the root-stocks of the existing noble beasts. The Primary Edentata also may have shot up in a similar manner ; but their culmination is very low, at its highest, as compared with the culmination of the Insectivora ; yet I imagine them to have had abbreviated stages in their pre-natal transformation. The ree^isters we have extracted from the orowinsr microcosm have enabled us to make these deductions. These writings may be likened to Palimpsests, written in many texts, one over the other ; the writing, however, was not made by fallible scribes, but by infallil)le morphological law. This witness is true : and truth so attested may be followed by anyone, little fearing where it will lead him. I have spoken of the common Mole ; I must speak of him again, in one of my lectures on the Insectivora. I will now speak of the Ornithorhynckus itself — the great Water-Mole. 32 MAMMALIAN DESCENT. [Lect. II. The structure and developmeiit of this type is both Eeptilian and Avian. Yet this is but a clumsy way of expressing it. The three groups — Reptiles, Birds, and low (Prototherian) Mammals — correspond in many im- portant points, so much so, as to suggest a common root for all these three branches. In some things which are common to all three, in the number and relation of parts, these low mammals are more archaic than the exist- ing reptiles, and very much more than the existing birds — not excluding the flat-breasted Ostrich and Emeu. But in the higher, winged birds, the parts that are distinct and simple in the Ornithorhynchus and Lizard, are found to be confluent and compound, and to undergo a jDractical metamorphosis into excjuisite new structures for new functions. The primitiveness of this low mammal is well seen in its shoulder-girdle ; its skull, as yet only partially worked out b}^ me, shows characters of the same sort, much more remarkably. The name given to this low order — Monotremes — suggests in one word, that which is most striking in these types, namely, that their renal and reproductive organs are constructed in a similar manner to those of a reptile or bird. In this resjDect, even the common Mole is a high and noble creature in comparison Avith the OrnitJiorhynchus, or the Echidna. The limbs of the Monotremes are normally pentadac- tyle (or five-toed), but excessively specialised, in each case, in relation to the habits of the creature. The hi])- Xect. it.] SHOULDER-BOXES OF DUCKBILL. 33 .girdle carries a pair of ejn-puhic (or so-called Marsupial) bones as in the Marsupials, in which they lie above or within the pouch, so that their use is not very apparent, for the "pocket" swings outside them. But their mor- phology is evident, for the pelvis of the Salamander, in.sc ---.^.6f '^?4.« Fig. 3. — Shoiilder-girtUe and sternum (breast-bone) of Omithorhynchns jmradoxxUf two-tliii'ds natural size, s.sc, supra-scapular region of scapula (shoulder-blade, sc) ; m.sc, middle scapular region ; cl, clavicle ; i.cl, inter-clavicle, cr, coracoid bone ; e.cr, epicoracoid ; gl, glenoid cavity, the head of upjier ann-bone (hunierua) ; mh.s, manubrium (top or handle) of sternum ; st, sternum ; x.s, .xiphoid end of sternum ; v.r, lower part of vertebral rib ; i.r, intermediate rib (as in Lixanh) ; s.r, sternal rib. and also, indeed, that of the Skate, shows similar out- growths of the pubic region of the girdle. But it is in the front cincture, or shouldor-giriUo, iliat we see the most remarkable siccus of ancientuess in tlic Prototheria. The scapula in them does not give off a c 34 MAMMALIAN DESCENT. [Lect. II. small coracoidal snag or beak (or imperfect coracoid), as in Man and most mammals, but the lower or ventral part of the girdle is continued downwards to articulate with the sternum (or breast-l3one) as a large and perfect coracoid. Here we have a condition like that which is seen in Amphibia and Sauroj)sida (Rej^tiles and Birds) ; on the other hand, the abortive development of the coracoid, and the freedom of the shoulder-girdle from the sternum, is a true diagnostic of a high Mammalian. The scapula (or blade-bone) in the Prototheria is very primitive in its form, being falcate, or scythe-shaped, and having a very low spine ; the coracoid is continued from it to the sternum as a large flat bone, and the fore part of the crescentic base of the whole plate is ossified as a separate epicoracoid, a part well seen in the Frog and Lizard. Such a term as "epicoracoid" for the more or less distinct broad part of a coracoid is not needed in mammals generally, for in them the lower part of the arch is absent, although it reappears in the native Bat and Shrew. In birds the whole of the main coracoid bar is ossified from one bony centre. Here, again, the Monotremes have to be compared with types below the bird class. Now it is well known that one diagnostic of the mammal is that it has only a pair of clavicles, or collar- bones, and that these are not simple parostoses or splints, but compound bones, composed of cartilage above and below, and of ossified fibrous tissue in the middle. But I^ECT. II.] EXTINCT BIRDS. 35 these low beasts, or Prototheria, have a large iiRMliaii clavicle (interclavicle) besides, and all the three Ijoues are simple, being merely ossified membranous tracts. So also are they in the Lizard trilje, and so were they in those huge whale-like Lizards of the Secondary epofji — the Ichthyosauri — whose triple clavicular structure is much like that of the Monotremes. Birds, as a rule, fuse these three bones together to make their merry- thought or furcula, but in these there is a rudimentary pro-coracoid cartilage, fused with the tops of the forks of the merrythought, similar to the ordinary cartilaginous nodule on the upper end of the mammalian chivicle. The old tooth-bearing birds of the Chalk had their clavicles distinct, as in the Emeu, and in embryo ].)irds generally. Here, again, to get at the root of the Monotremes, we must dig below the bird, and if we are safe in drawing any deductions whatever from our morphological observations, we are safe in saying that of a certainty the stock from which these l)easts were derived lay as low down as that from which the earliest birds grew. Moreover, there is a sort of solid primitiveness a])out the clavicles of the Monotremes, unlike what we see in the existing Lizard, in which they are very slender and graceful ; they show that the best t}^:)e for comparison is not the small modern Lizard, but the ancient reptilian giant — the Ichthyosaurus. The Prototheria have the sternum (or breast-bone) 36 MAMMALIAN DESCENT. [Lect. IL divided into segments corresponding with the costal cinctures, or arches of the chest ; this is diagnostic of the mammal, yet it begins in certain Lizards, e.g., the Chameleon. That which makes the vertebra of a mammal differ from that of the higher oviparous t3rpes is the development of the flat epiphyses or separate bony plates on its body or centrum. Now these are nearly absent in the Prototheria. Albrecht and Huxley, however, have found them in the vertebrae of the tail in OrnitJiorhynchus. This fact, again, is very instructive — the Monotreme is feeling its way upwards to the higher platform on which we stand. With regard to the skull, there is much of the deepest interest to the evolutionist, even in our present partial knowledge of its development. The Ornithorhynclnis is ])y far the most primitive type ; the Echidna has a huge brain for so foolish a creature, and it comes very near the Ant-eaters, proper, in many of its cranial characters. When I come to the Edentata, the group which contains the Ant-eaters, I shall refer to this fact again. At present I shall confine myself to the DuchhiU. That Avhich strikes the eye at once is the very amphibian look of the whole structure of the skull ; it is like that of some strange Dipnoan or Salamandrian just under- going transformation. We, like our fellow- vertebrates, have at first a carti- lagfinous cranium that forms the foundation of the finished ivory casket which, in the adult, so safely holds Lect. II.] THE duckbill's SKULL. 37 our brain and sense capsules. But in us, as soon as it is formed into proper cartilage, it is a mere hasin ; in many types it is a box, just open above, having there a small membranous " fontanelle," as this weak part was called by old anatomists. This chondro-craniiim, or cartilaginous skull, is very massive in the Duckbill, and much of the sides and roof formed by this primitive cartilage ossifies, and forms part of the permanent skull, inside the familiar invest- ing bones — frontal, parietal, temporal, &c. This is in the hinder half, but the fore part, or beak, is still more remarkable as to its cartilaginous foundations. The general form of the hind skull, or cranium proper, is intermediate between that of an Amphibian and a high mammal ; the paired occipital condyles, or convex cartilaginous tracts, for articulation with the first joint of the neck, are large, vertical, and very much like those of a Frog. But the nerves of the skull, and their passages, are arranged as in the higher or gill-less types, and the hypoglosssal or motor nerve of the tongue is a cranial, and not a spinal nerve, as in the Frog. The arched structures of the ventral aspect of the head — the parts of the face and throat— are of great interest. The best morphologists difi'er in the interpretation of some of the details ; whilst anatomists generally, those, namely, Avho have not been trained in Embryology, contrive to make the most absurd misinterpretations of these parts. Here, if I fail, I shall miss both the mark and the <^ A 38 MAMMALIAN DESCENT. [Lect. IL 'prize of the work of my life — tlie interpretation of the form of Man and of his vertebrated kindred. For, in reading off the characters of the Ovnitliorliyncliiis, and comparing them with those of the Amphibia, below, and of the Eutherian or high mammals, above, we are, so to speak, breaking the seals of a new scroll, on every line of which we can spell out the letters that go to form that great name — Man. That which strikes the morphologist as the most remarkable of all specialisations is the manner in which the mobile jaws of the lower type are exchanged for the fixed countenance of Man and the other mammals. In the more generalised fishes there is but little mobility of the lower jaw ; but that part is carried furthest from the face in such forms as the Sturgeon among the ganoids, and in the osseous fishes generally, where the lower jaw is not close to the head, as in a Skate, but swings upon a large compound pier, that intervenes between the jaw and the skull. But in reptiles and birds, the hinder part of the cartilaginous upper jaw — the rest being in a great measure suppressed — forms a hinge-piece or pier to the inverted arch of the lower jaw. In birds, generally, the whole upper jaw being mobile — or flexibly attached to the frontal region of the skull — the levator muscle, at the angle of the jaw, at once dejDresses the lower, and lifts the uj^per, jaw, and this is why these creatures are such skilled fly-catchers. Sir Charles Bell, in his charming work on the human hand, Lect. IL] HINGING OF THE LOWER JAW. 39 shows liow tills Is done, and why the feat of fly-catching is so difficult in the dog trying to sleep in the sun, but kept awake by teasing flies. In the Duchhill, as in mammals generally, the pier or hinge-piece is gone, and the maxilla inferior (or af- '-^ HJ Fig. 4a. Fig. 4. Fig. 4. — Skull of Common Fowl {Gcdlm domesticus) o\x&-'hsM larger than specimen. px, premaxillary; mx, maxillary; v, vomer; n, nasal; cth, ethmoid; /, lacrymal ; pe, perpendicular ethmoid ; x>^j presphenoid ; I, olfactory nerve ; io.s, interorbital space ; os, orbitosphenoid ; /, frontal ; pf, post-frontal ; p, parietal ; sq, squamosal ; s.o, superoccipital ; j.p, jugal x>rocess of squamosal ; co, exocciptal, V, 5th nerve ; 11, optic nerve ; ty.c, tympanic cavity ; 5^, basi-temporal ; q, quadrate ; pg, ptery- goid ; pa, palatum ; j, jugal ; qj, quadrate-jugal ; p.ap, posterior angular process ; icLp, internal angular process ; ar, articular ; ag, angular ; sa.g, supra-angular ; cl, dentary. Fig. 4a. — Auditory Columella of Fowl, magnified 6 diameters, and sho"\\Ti from the inside and end. mandible) is hinged directly to the temporal bone, a solid part of the strong skull- wall. What has become of the '' OS qiiadratum,'' as the bird's jaw-pier is called? The answer is, that in the mammal there takes place a 40 MAMMALIAN DESCENT. [Lect. II. process equivalent to amputation. It is done, however, not by a chirurgeon, for it is cut out without hands. Indeed, this is a kind of horticultural process, for the hinder third of the proper original lower jaw is slowly pinched off, and that hinder piece and its growing pier or quadrate cartilage are more than half starved, whilst the front two-thirds of the mandible are forced, so to speak, as if grown in a hot-bed. The starved pier or quadrate becomes the little incus or anvil bone of the ml q\9»c- Fig. 5. — Auditory Chain of Bones from the Middle Ear of a New-born Pig {Sus scTofa), magnified 5 diametei's. ml, malleus (hammer) ; pgr, processus gracilis of malleus ; iiib, manubrium (handle) of malleus ; spm, short process of malleus ; i, incus (anvil) ; sc.i, short process (crus) of incus ; lei, long process of incus ; st, stapes (stirrup) ; stm, stapedius muscle ; ihy, interhyal. ear-drum, while the hind part of the lower jaw itself, the mandible, also starved, becomes the malleus, or hammer ; and these two ossicles are now, for the first time, added to the structures that convey the vibrations of air from the ear-drum to the labyrinth. All at once, when we look at the forcing process, whereby that which was superficial and secondary becomes the arch of the lower jaw, we see that something has been brought in for Lect. II.] FORMATION OF THE LOWER JAW. 41 grafting purposes — a mass of cartilage wliicli we are not familiar with in the reptile or the bird. Looking for a slab of true hyaline cartilage large enough for Nature's purposes in these mammalian types, we travel down through Birds, Eeptiles, Amphibia, Osseous Fishes, Ganoids, Skates, and ordinary Sharks, and not until we come to the extraordinary Sharks or Chimseroids do we find anything large enough. There we stop. In these waifs of an old fish fauna we do light upon what is wanted. In these fishes there is, outside Fia. 6. — Mandible (Lower Jaw) of an Embryo Pig, 3 inches long, magnified Si- diameters ; inner view. mk, Meckel's cartilage ; d, dentary bone ; cr, coronoid process ; ar, articular process (condyle) ; ag, angular process ; ml, malleus ; inb, manubrium. the true mandible, a large slab of cartilage equal to it in size. This is a superficial (subcutaneous) band of solidified tissue, but it has no supporting bone on it. Such a supporting bone, however, is seen clearly enough in the foremost of the splints of the lower jaw (the dentary) in all fishes, except the cartilaginous kinds, and in all types above the fishes. Besides this, on the inside of the fore part of the lower jaw, in the o\dparous types, there is a second splint, the splenial, and Ijchind 42 MAMMALIAN DESCENT. [Lect. II. it a third, tlie coronoid. These can also be traced in the jaw of a young OrnithorhynchuSj but they are only semi-distinct. Then the fore part — about two-thirds of the primary cartilaginous jaw — called '' Meckel's " cartilage, is ossified whilst the pinching off is taking place. Here then let there be an end to all talk about the simplicity of the lower jaw in the Mammalia. After Nature has removed the hinder part, which in reptiles and birds is itself composed of three external and one internal bony centre, there still remain in the inferior maxilla, or lower jaw, of a mammal, the following elements, namely, (l) the dentary bone, with rudi- ments of the splenial and coronoid ; (2) a large super- ficial cartilage, or "inferior labial;" and (3) the distal two-thirds of the primary lower jaw, or Meckel's carti- lage. Now, as to its suspension to the skull, this of course is in front of the old swinging point of the non- segmented jaw of the ovipara. In them the quadrate, or huge prototype of the "incus," or anvil honey is attached to the skull over the tympanic cavity, and that is also the j^l^ce where the incus is always found in the mammal. In them also (the ovipara) the squamous element, or temporal scale-bone, has no cartilage on its under sur- face. In the bird, for instance, the " zygomatic process " is a mere snao^ for muscular attachment, for it has no Lect. II.] BONES FORMING THE EAR-CHAIN. 43 -tD glenoidal cavity or cartilaginous facet ; there is no hinge — nothing is joined to it/ But in the mammal the large superficial cartilaginous tract, after serving as the matrix out of which most of the lower jaw is formed, becomes segmented into three parts at the hinge ; the lower part is the condyle, or head of the joint, the upper the glenodial facet, or shallow cup, attached to the temporal bone, and the intermediate part the meniscus, a sort of pad, the interarticular fibro-cartilage. I could not find, in my young specimen of the Duck- hill, splints on the large rough malleus corresponding to the " angulare" and " supra-angulare," two bones that strengthen the upper or articular portion of the jaw in birds and reptiles. But I find the " angulare " in several kinds of mammals, and in the Koala, a kind of Marsupial, both of these well-known splints of the com23ound jaw of the ovipara are found as small separate pieces. After long years of labour and much vacillation of mind on the matter, I am now quite satisfied that the stapes, or little stirrup-bone of the ear-drum, is the uppermost element of the second, or hyoid arch. Those who have studied human anatomy know that the three little bones which are fastened as a chain across the insiduC of the cavity of the ear-drum or " middle ear," ^re called malleus (hammer), incus (anvil), and stai^es (stirrup). The latter bone, by its base, stops up a small 1 The reader who is not familiar with the skull, is referred to my figures of those of the Fowl and the Pig in the Fhilosoj^hical Transactions of the Royal Society^ 1869, plate Ixxxvii. ; and ihicL, 1874, x^lates xxxiv.-xxxvii. 44 MAMMALIAN DESCENT. [Lect. II^ oval window [fenestra ovalis) tliat lies between the drum cavity and tlie vestibular part of the labyrinth of the ear. That bone (the stapes) exists in Birds and Keptiles, but the other two, as such, do not. Also, in them, it is not a stirrup, but a little column (columella). So it is in these low mammals. We have then, in this curious piece of morphology, no new structure, but a very new specialisation of an old one. Whatever parts grow out of, or are attached to^ the columella of the ovipara, are merely processes, or at most, segments, of the ^'pharyngo-hyal" element of the tongue-arch, or uppermost piece of the arch. Thus, in mammals, by a curious horticultural process^ so to speak, two new elements are added to the auditory chain, namely, the incus and malleus. These parts,, so modified, are diagnostic of a mammal. Why they should be correlated with mammary glands, and hair, I cannot say. I have yet to speak of the most remarkable part of the skull of the Duckbill; I refer to the composition of its beak. Much as it resembles the beak of a duck, its structure is widely different, yet the superficial bones are homologous, and not altogether dissimilar ; these are the premaxillaries in front, the maxillaries exter- nally, the nasals above, and the palatines and pterygoids below. All these bones are peculiarly thin and lathy in the young animal. They do not, as in the Duck, finish the Xect. II.] THE EGG-BEEAKING BEAK. 45 margins of the beak ; for in that bird, as in its con- geners, the bones of the upper face run close to the quick that secretes the bony sheath. But the duck- billed mammal is quite unique ; the whole outline of the great rostrum is formed by a large sheet of solid hyaline cartilage right and left. Over this, in front, the thin horny layer still shows the " neb " for breaking the egg-shell, quite like what is seen in Tortoises, Croco- diles, and Birds. The extraordinary growth of true cartilage in the extended upper lip is quite similar to the growth in the lower lip of mammals generally, namely, that slab of cartilage on which the dentary bone grafts itself to form the bulk of the solid niaxilla inferior, or lower jaw. We have to go down, as I have just stated, amongst the lower cartilaginous fishes for similar growths of superficial cartilage in the region of the mouth. But although I am quite familiar with superficial cartilaginous structures in these fishes, it is only in the Tadpoles of the Frog and Toad, and in the adult Lamprey, that I find anything equal to what is seen in the Orinthovhynchus. In those pouch-gilled (marsipobranch) types, however, these parts are all separate, neat, finished tracts of cartilage, each having its place and its function as an orderly element of the front face. But in this strange remnant of a lost race of archaic mammals, the growth of cartilage is a wild leafy tract, very unlike the well- 46 MAMMALIAN DESCENT. [Lect. IL finislied labials (lip-cartilages) of tlie types just referee! to. There is, however, just one waif from the Old World, which helps us here. Of the eight hundred known tail- less Amphibia, there are two Toads — one in Surinam, and one in the Cape region — that are tongueless, and these have their Eustachian tubes (or passages between the ear-drum and the throat) opening at the mid-line, as in a bird. The Cape Toad (Dactylethra), has nails on his fingers and on his toes, and he is the first of the gill-bearing creatures that has taken on this specialisation — a prophecy of those exquisite supports to the finger-pulps that we see in the daintiest and most elegant of all the Vertebrates. Now the children of this first claw-bearer are not like their parents, which themselves are the most modified of all the kindred of the Frog, but are very much like the most bizarre forms of the Ganoid fishes of the Old Eed Sandstone. So much is this the case, that it is difiicult to avoid the conclusion that we have in this larva, whose outline is like that of a half-opened fan, a descendant of one of those old fishes, but a meta- morphosed descendant, only retaining the old family features during the time of its minority.-^ Now this larva has a skull which difi'ers from that of the adult Toad, into wdiich it transforms itself, quite as 1 For the transformation of the skull in the Cape Toad, and for the figures of the larva, see my pax^er in the Philosojjliical Transactions of the Eoyal Society^ 1876, plates Ivi.-lix. Lect. II.] ANCESTORS OF THE MAMMALIA. 47 mucli as, or more than, the skull of the Ornitho- rhynchiis differs from that of a Man. We may suppose the ancestors of the original teatless mammals (Prototheria) to have been something like, and not much higher than, the larva of the nailed Toad, and that these underwent an amount of transformation, during an active out-of-door life, equal to that under- gone by the existing type. Afterwards, by little and little, such Prototheria may have improved themselves into higher and still higher ty]^)es ; they have had plenty of time for such changes. ADDENDUM TO LECTURE II. Bibliography: Eeferences to Works and Papers treating OF THE Ornitliorhynclius and Echidna. Armit, Captain William E., E.L.S., "Ilotes on the Presence of Tacliijglossus and Ornitliorhynclms in JSTorthern and J^ortli Eastern Queensland," Proceedings of the Linnean Society^ Zoology, vol. xiv., 1879, pp. 411-413. Bennett, Dr George, E.L.S., F.Z.S., &c,, Gatlierings of a Naturalist in Australia. London : John Van Voorst. 1860. Flower, Prof. W. H., LL.D., F.R.S., An Lifrodnction to the OsteoJogy of the Mammalia. London: Macmillan & Co. 1876. Article " Mammalia " in the Encyclojpcedia Britannica, 9th edit., vol. XV., pp. 377-378. Huxley, Prof. T. H., LL.D., Pres. K.S., A ManiiaJ of the Anatomy of the Vertehrated Animals, pp. 319-323. London: J. & A. Churchill. 1871. 48 MAMMALIAN DESCENT. [Lect. II. Huxley, Prof., " On the Application of the Laws of Evolution to the Arrangement of the Yertebrata, and more especially of the Mammalia," Proc. Zool. Soc, Dec. 14, 1880, pp. 649-662. LijTKEN, Dr Ch. W., " A Letter to the Secretary of the Zoological Society," Proc. ZooJ. Soc, March 4, 1884, pp. 150-152. MuRiE, Dr James, F.Z.S., &c., "Kemarks on the Skull of the Echidna from Queensland," Proc. Linn. Soc, vol. xiv., Zoology 1879, pp. 413-417. See also Captain Armit's "Notes," sujrra. Owen, Prof. Richard, F.R.S., L "On the Marsupial Pouches, Mammary Glands, and Mammary Poetus of the Echidna hystrix" Philo- 8oj)hical Transactions, 1865, plates xxxix.-xli., pp. 671-686. 11. " On the Ova of Echidna hystrix," Philoso2:>hical Transac- tions, 1880, plate xxxix., pp. 1051-1054. Parker, "W. K., P.R.S., " On the Shoidder-girdle and Sternum," Ray Society^s PuUicatimis, 1868, plate xviii., pp. 192-194. At present, data are wanting to enable us to form a thoroughly clear idea of what a primary mammal, an original, ancient " Proto- there," must have been like. For, at present, we are only very partially masters of what Nature has left for us to work out, namely, the structure and development of the two types that still linger on the planet. One thing we do see, however, and that is, that those two forms are far more unlike in their adult than in their embryonic (or early) condition (see Owen, I., plate xL, figs. 6-10). The beak, when undeveloped, does not differ in essentials in the two genera, namely, rnithorhyv^Mis and Echidna {TachyrjJossus and Acanthoglossiis). In the figure of the young Ornitliorhynchus given by Professor Owen, and in that made for me from a young specimen nearly as large as a man's fist (p. 25, fig. 2), two very important characters can be seen in the beak. 1. The first of these is that the fore part of the bill or beak arises out of a swollen basal or hind part, M'hich ensheaths the proximal part of the free beak, exactly as in the non-flying birds (Ostrich, Emeu, Cassowary), and their nearest relatives, the Tinamous of South America. — See Dr P. L. Sclater, M.A., F.R.S., "On Struthious Birds," Trans. Zool. Soc, vol. iv., plates Ixvii^.-lxxvii., pp. 353-364. Lect. II.] ALL ANIMALS COME FEOM EGGS. 49 2. The second character is the presence of the old familiar egg- breaker on the bend of the " neb " above, just like that seen in the chick of any bird, and in the embryos of the Turtles, Tortoises, Crocodiles, and Alligators. So that we may accuse the Duck-billed Platypus, and say — " You were hatched out of an egg and are not a proper mammal at all." But if he, like the Lamb, asserts his innocence, then we, like the "Wolf, will throw the accusation backwards, and say — " Your father (ancestor) was so produced, and you are, after all, merely an oviparous creature." Probably the highest dignity this creature will ever attain to in Biology will be to be classified as an Ovovivijparous type, a sort of compromise between a Keptile and a ^Mammal. That may be true, for all animals come from eggs, — oriine animal ex ouo, — and as Man is known to be an animal, he also once had all his potential excellences squeezed into the small space of an egg-shell — an egg which was small, indeed. We hope soon to get more light upon the development of the Prototheria. Some hunters belonging to the last and best kinds of the Eutheria are upon their track, and they must hide themselves either in the earth beneath, or in the water's under the earth, if they would escape them. It is, I think, more than probable that the original Prototherians possessed ieetli ; yet these may have been, and most probably were, of a still simpler type than those of Opossums and Kangaroos, from whose teeth we start in making an ascending survey of these organs in the ]\Iammalia. It is not unreasonable to think that the mammals which have ddjene- rate teeth, such as Sloths, Armadillos, the Aard-Yark, might serve to give us some idea of what this primitive Mammalian dentition Avas like. Anyhow, if they had a gooel mouthful of teeth, their upper and lower jaws did not resemble those of their highly modified descend- ants ; probably they were very mucli like M'liat we see in the least specialised of the living ]\Iarsupials, namely, in the Opossums of the Western World. As to their outer covering, of course they all were more or less clothed with a hairy garment, for this is correlated, always, with milk-glands; when, "in the end of the days," the last mammal ajipears, but appears shorn of that covering, it has to be borro'sved, again, from those types in which it had not been suppressed. "L'nto Adam also, and to his wife, did the Lord God make coats of skins, and clothed them." This has become, as everyone knows, a custom among D 50 MAMM^xLIAX DESGEXT. [Lect. IL the race of men, and shows, at present, no signs of becoming obsolete. Moreover, that first correlation, namely, the existence of milk-glands and a hairy covering, appears to have entered into the very soul of the creatures of this class, and to have become ]jsychical as well as ^physical, for in that type, which is only, for a icliile^ inferior to the angels, the fondness for this kind of outer covering is a strong and ineradicable passion. But it began, physically, as a sudden modifica- tion, with those Ai'chaic Prototheria ; yet in what forms did it appear ? Hardly, at first, one would suppose, in the form of wool, rather of coarse hair mixed with spines, as in the existing Echidna. I strongly suspect that it struggled for a good while with the old kinds of covering, namely, scales, both bony, in the skin proper, and horny, in the cuticle. If so, the existing Edentata, of which I shall speak anon, are a much more precious legacy of time and nature than they have hitherto seemed, even to the most enthusiastic biologists. In a purely technical paper on this group, lately read before the Royal Society,^ I have said that the fact that in the Armadillos the new husbandry, or growth of hair — the correlate of milk-glands — thrives badly on the old stony ground of Reptilian horn-covered (bony) scales, breaking out where it can among the clefts — is not more won- derful than that this same new growth of hair in the Pangolin should mat itself together, and imitate the scales of Reptiles and Fishes. If this be true of those placental descendants of the almost ovi- parous Monotremes, much more, one would suppose, must it be true when we are speaking of the very first evolution of a hairy creature. Indeed, if the first creature clothed by the Creator, to speak enigmati- cally — after the manner of men — with the hairy skin of a beast, did, ]per saltum, gain his hairy coat in one great metamorphic leap, it would be nothino' wonderful if some of his descendants sliould backslide a little, and, under degenerating influence, now and then show some mark or stigma of the old Reptilian nature. In the paper just quoted, speaking of the scale-covered Pangolins, I have remarked — " If the term Reptilian might be applied to characters seen in any placental mammal, it might to what I find in this. This creature has most remarkable correspondences with the Reptilian ^ See Proceedings of the Royal Society for June 1884, p. SO. Lect. II.] DELATION OF MAMMALS TO REPTILES. 5 1 group. Of course, the scaly covering is mimetic of the Lizard's scales, and is in reality made up of cemented hairs ; that may pass ; but not the structure of the sternum in some species, with its long 'xiphisternal horns,' as in the SteUioJiidce, and the cartilaginous abdominal ribs, as in the Chameleons, and some other kinds."^ In the poverty of the existing, but highly modified, Proto- theria, we are glad to get any addition to our materials for work, any knowledge that may help us in our deductions. As I shall soon show, the Edentata are only a sort of Eutheria, or high kind of mammal, quoad hoc, in this and that point in their organisa- tion ; in other respects they have kept in a low estate, having the slow temi^er of some races of men, who are haters of change, however beneficial, and of whom it may be said " as their fathers did, so do they." My task in writing of these types, after straining the eyes of my mind to see what sort of folk those mammalian forefathers were, is rendered more difficult through my being j^recluded the free use of technical terms. A rustic gymnast in a sack, with nothing but his homely features free, and yet having the necessity of jumping laid upon him, is not more an object of sympathy than a biologist, when robbed of his familiar terms — his special nomenclature. As the movements of the one are of necessity a series of jerks, so the thoughts of the other are too often put into language that to an easy-going, well-trained writer must seem to be spasmodic. Loosen- ing my bonds a little, however, and taking a few technical liberties with the reader, I will endeavour to give some of the remarkable evidences to be found in the quasi rej)tiUan nature of these prim- ordial beasts. In the mid-region of the Yertebrata, especially amongst the Serpents and Lizards, we come across some very remark- able structures in the fore part of the organs of smell ; these are called " Jacobson's organs." They were described by Kathke, in the Snake, under the term "nasal glands"; that term was adopted by mo in my papers on the Skull of the Snake and of the Lizard.^ In those papers the contained organ was not described, as not lacing in my plan, 1 See my memoir on the "Shoulder-Girdle and Sternum," Tmij Society Publications, 1868, plate xxii. fig. 13, ^ Philoso2)hiccd Transactions, 1878, plates xxvii.-xxxiii., and 1879, plates xxxvii.-xlv. 52 MAMMALIAN DESCENT. [Lect. IL but the bones and cartilages that encapsule it were carefully described, and coj^iously illustrated. In those tyj^es we have the culmination of these organs, which have some mysterious connection with the organ of smell ; the first or olfactory Jiei'ves give off fibres to them. If these organs have their height in these Eeptiles, they have their decline in Man, Avho, however, in an early stage, possesses them, as Professor A. Kolliker's invaluable researches show, both those })ub- lishedat Leipzig in 1877, and those much later, at AViirzburg in 1883. For an abstract of this last piece of research I am indebted to the excellent " Summary " in the Journal of the Royal Microscojncal Society, for April 1884, pp. 201-203. The concluding sentences of this abstract are as follows : — "From the rich possession of nerves l)y Jacobson's organ in an eight-week old embryo, and their dis- ap2)earance in older embryos, we may conclude that the organ is now in a rudimentary condition as compared with what it Avas in ancestral forms." Xow, on one hand, in Serpents, and Lizards, we have these organs and their related skeletal parts, both cartilaginous and bony, higiily developed and persistent, and on the other, in ]Man, these organs are soon aborted ; nor am I aware that the skeletal parts that should •support them are more than feebly developed. Although we are in a deplorably agnostic condition with regard to these organs, they may be used as a measure of the height of any mammal or order of mammals, in the scale of life. In my young specimens of Ornithorhynchus (the size of a moderate fist, with the hair appear- ing), these parts and their capsules are as large as in Serpents and Lizards. In the IMarsupials, Edentates, and Insectivores they are well developed in the embryo up to the time of birth, and for some time after, having considerable persistence in several at least of those kinds. They are present in all sorts of mammals, as far as research has gone, at least in the embryo ; and the bones and cartilages that support them are more persistent than the organs themselves. In the Reptiles, these organs are mostly invested by bone, in the Mannnals they are ^vell encapsuled by cartilages growing back- wards from the snout. In the Mammals only one 2^air of small bones assists in protecting the soft gland-like organ ; in the Reptiles it lies on oach side, as in a dish, formed by a bone, the so-called vomer (plough- sliare), and it is covered in by another bone which serves as an elegant Lect. II.] OLD AXD XEAV STRUCTUEEvS. 53 lid, not present in the mammal, the so-called " turbinal."^ Tliose wlio are biologists, and care to go into this matter, will do well to refer to Wiedersheim's Lehrhuch der Vergleichenden Anafomie der Wirheltliiere, Jena, 1883. In my forthcoming paper on the Edentata there will be fonnd a Bibliographical List of varions IMemoirs and Papers on these organs. But the general reader will see that there is some big secret shut up here, and that, as far as it has been found to disclose itself, it is all unimpeachable evidence in favour of the gradual develoi:»ment of the higher, and even the highest, forms of animal life ; those curious parts of the nasal labyrinth that have had their rise and their decline in the various Yertebrata, now coming into morpho- logical and physiological importance, and then having a feeble and a fading growth — these facts must now be added to the enigmas of Biology. The structure of our body is full of old things as well as new ; the old things have had their day, but they are abrogated, and to us practically they are " beggarly elements." But the new things are not really new ; they are merely expansions and improvements, so to sj^eak, of things as old as the hills. It is just possible that in the Yertebrata of the Primary Kocks some rudiment or other existed of every structure that has now completed its evolution in the human body. But some one, — one whose mind carries no biological ballast, is always starting u}) and making the demand of a sudden creation of Man. Let him learn of the great Theologian, St Augustine, that the Creator of all things is patient, because eternal. This is exactly what modern Biology teaches : whatever the force is that worketh all in all, it is certain that it has had, practically, for all purposes of adaptive variation in organisms, unlimited time. There has been plenty of time, in the gradual accretion of gentle and almost insensil)le modification, for an almost unlimited amount of variation ; but per saltum changes have often occurred ; that is quite certain. These outbursts, so to speak, of morphological modification during the individual life of a creature — Butterfly or Prog, for instance — are amongst the most amazing of all pheno- ^ Both those paired bones were named as above by Cuvier, and both erroneously ; the Science of Embryology scarcely existed in his daj's, and many of these things can only be interpreted by an embryologist. 54 M A:\IMALIAX descent. [Lect. ii. mena. They remind one of tlie sudden and mysterious moral perfection of the antediluvian prophet Enoch, of whom it is said, that — " He being made perfect in a short time, fulfilled a long time." There is, however, another way in which the mysterious morpho- logical energy works, so as to force, as in a hothouse, the growth of the young of certain types. This is the case in the highest sorts of birds — the "Altrices," or high-lrailders — that have tender nestlings. These young, sweltering in their soft nest, and almost smothered by their feathered mother, Y\diose blood is nearly at fever heat, grow and develop at ten times the rate of the young of those birds that make poor nests on the ground ; for those chicks, hatched strong and lusty, grow slowly to perfection. Yet the temperature of the l^lood itself is apparently ecpial in both cases, and in both cases affects the teinjjer of the mother-bird. At that time the true maternal courage rages; at that time " a AYren will peck an Estridge ;" and a Hen, the gentlest of mothers when her brood is grown, is like one possessed whilst they are young. So we see that Nature fulfils herself in many ways ; her works have not fjone on from ao;e to a^e in tame and cold uniformity, but in the plenitude of her morphological energy she has at sundry times, and in divers manners, burst out into new developments — delivering herself in lier mighty energy of myriads of new and wondrous births. Let us imagine ourselves living in the time before the beginning of the reign of the Prototheria, and before the first feathered creature grew, when there were neither birds nor beasts, and to us it seems to be unenlivened gloom ; we have in idea depopulated the planet of almost all the living forms that make it laugh and sing. Tlie vision is like that of the prophet who — weeping over the desolations of that land which once flowed with milk and honey — says, "I beheld, and, lo, there was no man, and all the birds in the heavens were fled." Xow, if for the sake of BioJogy we should be glad to repeople the earth with the parents of the Prototheria, for the sake of Life we should indeed be sorry to peel away the newer Mammalian faunas until we got to that old core. To sum up these Prototherian matters, we may now look at some of the most remarkable characters in the Diickhill and Echidna that are manifestly reptilian, or quasi-rejMian : — 1. Jacobson's Organs are about equal in their development to Lect. II.] SKELETON OF THE PROTOTHERIA. 55 v,-]iat we find in Serpents and Lizards, wliere they have tlieir cuhnina- tion. 2. The sl<:ull itself lias a strong and thick foundation of cartilage, the ossification of which forms much of the permanent cranial box, whilst the superficial bones are flat and relatively small, as in such a reptile as the Lizard. 3. The fore face has a large vallance of solid cartilage, such as is not seen again, until we get down to the most archaic of the larvae seen in any metamorphosing type whatever — for example, in Dady- lethra caj)ensis, in whose larval skull a similar vallance of cartilage grows copiously. 4. The lower jaw is seen, even in the adult, to be the equivalent of the fore part of a Rei^tile's mandible, whilst the malleus (hammer- bone) is manifestly the hinder part of such a mandible, and has, cemented to it, a most rudimentary ear-drum bone. 5. The anvil-bone {incus) has not taken on the normal ^Mammalian form, but is a mere flat segment of ossified cartilage ; it is a very small "quadratum" or equivalent of the liinge-segment of the Reptilian mandible. 6. The stapes (stirrup-bone) is not normal, it is merely a Reptilian columella, or little column, with a dilated upper end. 7. The shoulder-girdle is perfect, both in its complete moieties of ossified cartilage, and in its superadded triple clavicular plates of simple ossified membrane. 8. The vertebrae of the spine, as a rule, are devoid of the normal IMammalian bony plates that are added, fore and aft, to the body of each vertebra, to take ofi" the shock in the quick movements of high and agile tyjoes. 9. The hip-girdle repeats the so-called "pre-pubic" bars seen in Salamanders and in some kinds of Skate. 10. The organs for the growth and maturation of the germs are, in essentials, cpiite like those of Reptiles and Birds, and there is, as in them, no difi'erentiation or subdivision of the terminal outlet. So that these creatures are just plucked oat of the Reptilian group by their skin^ with its hairy covering and its rudimentary milk- glands. Severely apply to them the rule ^^Cucullusnonfacit Monachum" and say — " The skin does not make the Tieast," and liack amongst the Reptiles they would have to be driver.. 56 MAMMALIAN DE.^CENT. [Lect. IT. After writing the above, I received from Professor Simon H. Gage, E.S., of Cornell University, Itliaca, N.Y., a most important com- munication on the respiration of certain fresh-water Tortoises. The information thus given covers just a page and a half, and yet it is of more value to the biologist than some bulky volumes that one could name. I shall insert it, bodily. Let the facts there disclosed be but fairly considered, and the difficulty of suj)posing a gradual melting down of the distinctions between the Amphiljia and Reptilia will be at an end. The lining of the pliarjjmr, or upper part of the gullet, is the l^roper normal respiratory organ of any creature possessed of a notocliord^ or primary spinal axis. All the various s^Dccialisations that may be found in Ascidians (Sea-squids), Ampliioxus (the Lancelet), and in all the Vertehrata, are of secondary importance to the embryologist. The peculiar structure and functions of the pharynx described l)y Professor Gage may be due to degradation or relapsp, but if so, it only proves that the aquatic ivas once the mode of respiration in the stock from which these Tortoises sprang. "Pharyngeal Respiration in the Soft-Shelled Turtle {Aspidonedes spinifer). By Simon H. Gage of Ithaca, X.Y. "During the last twenty-five years the mechanism of respiration in the Chelonia has been investigated with considerable thoroughness, both in this country and in Europe ; and at j^resent the Chelonian form of respiration is considered to be comparable Avith that of the mammal rather than with that of the frog, as formerly supposed. AVliile, however, the mechanism of respiration has been quite fully investigated, there has been, so far as I am aware, but one who has considered the organs of respiration in the different groups of turtles. " Professor Agassiz, in Part II. of the Contrilidions to North American Zoology (p. 284), states that the lung capacity of the soft-shelled turtle is far less in proportion to its body-weight than is that of the land turtles. He also states, in considering this fact, that the skin on tlie ventral side of the body, from its rich network Lect. IL] EESPIRATION OF A TURTLE. 57 of blood-vessels acts as a respiratory organ. He further states that in the pharynx are many fringe-like processes which reseml^le the inner gills of tadpoles, and probably have the same function^ although no mention is made as to the method of their use. "In 1878, while watching a soft-shelled turtle from Cayuga Lake, confined in a glass aquarium, it was observed that the throat and the floor of the mouth became alternately swollen and collapsed, while the turtle was completely immersed in the water. The appearance was very much like the respiratory movements of a frog in the air. As no air escaped from the turtle, the bulging of the throat and mouth must be caused by filling the mouth and pharynx with water, and expelling it, or the air must be forced into the mouth from the lungs and then forced back into the lungs, as is done sometimes by men when swimming under water. " In order to determine whether or not water was taken into the mouth and expelled, the bottom of the aquarium was covered with fine sea sand, and the observations were made when the animal was resting quietly on the sand. "At the beginning of the movement, the mouth would sliglitly open, and its floor would swell out, the swelling passing steadily onward to the throat. After a moment of quiet, the sv^^elling would disappear in the inverse order of its appearance. " During the disappearance of the swelling of the throat and mouth, the sand, for a considerable distance in front of the animal's head, would be swept aside as by a rapid stream. The movement of the sand, without the escape of air, seemed to prove conclusively that the mouth and throat were alternately filled with water and emptied. " These pharyngeal respirations, as they may be called, Avere very regular, occurring ten or fifteen times a minute. My observations were verified by Professor Wilder and several of our laboratory students. " While, therefore, the investigations of Agassiz showed that in the pharynx of the soft-shelled Turtle were organs apparently suitable for aquatic respiration, the observations here recorded of the rhythmical bathing of these organs with fresh water seem to make the evidence complete, that a true aquatic is combined with an aerial respiration. 58 MAMMALIAN DESCENT. [Lect. II. "It is hoped that durmg the coming year investigations may he completed which shall determine the exact amomit of oxygen consumed in this pharyngeal resjDiration, and the structure of this unusual respiratory organ in the soft-shelled Turtle." — From the Proceedings of the American Association for the Advaricement of Science, vol. xxxii., Mimieapolis Meeting, August, 1883. Xect. III.] EMBRYO OF THE MARSUPIALS. 59 LE CTUKE Hi. Ox THE Marsupials, or Pouched Aximals (Metatheria). In their structure generally, the Marsupials are inter- mediate between the Monotremes and the placental or nobler forms of mammals (Eutheria). AVith regard to the development of their embryo, these types are far l)elow the Eutheria, while they are most probably ^bove the Prototheria ; there, however, we are at a standstill for want of materials. In their early development these pouched mammals come very close to the higher oviparous animals (Reptiles and Birds), but we have good reasons for asserting that they are less specialised, or more archaic than the existing members of the great group of Sauropsida (Reptiles and Birds in one group). All these kinds — the Reptiles, Birds, and Marsupials — may have been on the same level once, — may have arisen from the same old Amphibian stock — but the embryo and its wrappings, in these mammals, is in some important respects less developed than in the other two groups. It is a very instructive fact that the tail-less Amphibia 60 MAMMALIAN DESCEXT. [Lect. IIL. — Frogs and Toads — sliould show a tendency to become members of the Amniota, the liigher gill-less t}q3es which develop an amnion and an allantois, two of the three meml^ranes that enclothe the embryo. No other explanation of the curious pouch developed in front of the lower jDart of the great intestine of the Frog, when it is passing into an air-breathing type, can be given, than that it is a rudiment of the allantois. Yet this is all ; there is no amnion corre- lated with it, and only in Eeptiles, Birds, and Mammals have we all three of the foetal membranes or bao:s — yolk-sac, amnion, and allantois. But there is every reason to suj)pose that other temporary gill-bearers, forms on a level with the existing Amphibia, did, during transformation, develop the rudiment of the amnion as well as of the allantois. Such Proto- amniota, under the quasi-magical influence of new surroundings, may, very probably, have grown into forms, of which some kinds had a huge development of all the three bags, while in others they all appeared, but were all arrested. In none of the Marsupials or of the higher mammals- is there more than a slight development of the yolk-sac ; none have any bulk of food-yolk, so that the embryos of both these groups are dependent upon some other source of food. In all cases the mother supplies this pabulum, but whilst in Birds and Eeptiles the food is prepared in the ovary and its duct, in the Metatheria or Lect. III.] EMBEYO OF OPOSSUM. 61 Marsupials that source of supply exists for a very short time, and then the mammary glands furnish the table. So also do they in the high types of mammals, but not until after a very long interval. In these the food- yolk is extremely small in quantity, yet the eml)ryo is not supplied with milk when that ceases, but receives its nourishment through the instrumentality of an enormous allantois, united with the highly vascular walls of the dilated oviduct. But even in the Eutheria there is a great variation ?v?4-® Fig. 7. — Uterine embryo of Virginian Opossum {Diddphys virginiana), magnitied 6 diameters. ■as to the time at which this last and newest mode of feeding an embryo comes into play, some kinds having tender, and others precocious, young. The observations of Professor Chapman of America show that these l3ags are all present in the Kangaroo, ]3ut that they are all small and arrested, so that neither the allantois, as in the higher mammals, nor the yolk- 62 MAMMALIAN DESCENT. [Lect. IIL sac, as in some Sharks, grow into more tlian a tem- porary union with the oviduct, or uterus, so as to derive nourishment from its walls. Hence the small size of the young of these creatures at birth, the food-yolk being so soon exhausted, and no other pre-natal supply being at hand. Two newly-l^orn young of the large Kangaroo- [Macropus major) sent to me by Dr Bennett of Sydney, were not so large as new-born Eats, i.e., they were, about an inch long. Yet these small Kangaroos, whose Fig. 8.--New-boru young from the poucli of Kangaroo {Macro23Us Major), magnified 2g diameters. parents are the size of Sheep, like the sedentary Oyster '^attend at ease moist nutriment," beino- attached to the teats, and there abiding. The embryo of the Marsupial is comparable in some degree to that of many fishes, in which the food-yolk is soon exhausted, [Lect. III. EAELY LIFE OF A MARSUPIAL. 63 and the embryo develops rapidly, the cartilage and bone ap]3earing very early. Such is the case in the Lejyidosteus, or Bony Garpike, and in the Sturgeon. In these young Kangaroos (an inch long) the ossifi- cation of the skull is much advanced, as I found to my sorrow when sections were made of them by the micro- tome; in young, three-fourths ripe, of the Virginian Opossum, the size of the larva of a Blue-fly (fig. 7, p. Gl), the development was also very advanced, and the cartilage quite solid. There is a considerable amount of contractile or muscular tissue in the teat of the mother, and the structure of the throat of the young is such that the syringing action of the walls of the duct does not choke it, the larynx passing up above the soft palate. There is thus, as in the Cetacea, a direct passage of air from the external nostrils to the glottis (or opening of the windpipe), and fluid can pass rio-ht and left of the breathino; tube, with no dano'er of choking. This temporary modification of the young Marsupial to conditions which, for a time, endanger its breathing apparatus, is well worthy of notice, albeit it is but one amid ten thousand instances of the ready response of the organism to the influences by which it is surrounded. Indeed, the earth and the inhabitants thereof, may in some sort he looked at, collectively, as a great, infinitely complex organism, and the working of the whole, as if 64 MAMMALIAX DESCENT. [Lect. III. it were one body witli many members, may justly be called earth -life. In this group — the Marsuj^ialia — the general intelli- gence is low, the brain has but few convolutions, and the great familiar jjridge, over which nerve-impressions travel right and left — the corpus callosum of our brain — is thin and feeble in these types. At first sight these Metatheria appear to be a very neat group, a peo23le quiet and secure, having no business with any other tribes, but living in their own zoological seclusion. But, as in all similar cases, this is only a23parent ; the hedge set about them, and all that they have, is as unsubstantial as a dream. Yet they are a feeble folk, and their structure, habits, and distribution in space and in time are all congruent to this view of the j^ouched tribes. The noble beasts, like the nobler tribes of men, are " mighty hunters," and they have driven the feebler MarsujDial tribes before them. Hence it is that in these days, " Wallace's line " bounds them on the north, in the Eastern world ; while in the Western continent, only one genus (Didelphys, or the Opossums) lingers amongst the Eutherian types, and one or two sj^ecies have found their way over that great western icorld-link, the Isthmus of Panama, yet the real home of that genus is in the southern, and not properly in the northern half of the American Continent at all. But the loss of so many of these low types, in this Lect. III.] FEEDING GROUNDS. G5 "conquest of tlie Canaanites" is only the partial working of a general law, in which Nature is always doing for every great fauna what the farmer does who seeks to improve the breed of his cattle. From year to year, as you may perhaps know, the sheej) are brought " under the hands of him that telleth them," and he, guiding his hand wittingly, judges with quick motion, which are fittest to be next year's mothers, and which are to be appointed for slaughter. His wisdom and intelligence are great, but how little, as compared with what his great Earth-mother — the farmer of farmers — has shown ever since the green earth was first stocked ! Of this huQ;e farm, with its o^reat un- enclosed tracts of pasturage, the forms least able to bear <3hanges of condition die out first. But there are various ways in which such changes necessarily affect living creatures, and one of these is caused by the frequent im- migrations made by the herbivorous tribes as the pastures become bare, and by the carnivorous tribes who follow them for plunder. Change of feeding-ground means also change of climate, more or less, to hotter or colder, to wetter or drier. Instinct, as we all know, is only an imperfect guide, and the animal tribes have to learn. Their tact is not always inborn, or always accurate ; as an instance, I will mention one familiar to me from childhood. When our u^^land sheej^ — used to close, qiiich fences — are removed to the fen-districts, where the fields are enclosed by straight canals, there arc E 66 MAMMALIAX DESCENT. [Lect. III. always some losses by drowning, until the sheep learn the meaning of those dark waters. The earth has often had her shakino; fits and her attacks of colic, and then the living creatures suffer with their mother ; those that escape are the strongest or the most cunning ; those that can " rough " it in new homes, or that are deftest in escaping from danger. Nature has, unconsciously, adopted this rough method of culling out her weaker tribes — appointing them for slauo'hter — and of saving; the best for the increase of the flock. These sugo'estions relate to the incomino; of the Eutheria, of wJiich I must treat soon ; if Nature had not dispossessed the Metatheria, and placed nobler beasts in their room, we ourselves — the Eutheria of the Eutheria, the noblest of the noble — should have had no existence. I now j)ass from that old occupation. Husbandry, to this new work. Embryology ; and if the reader will give me a little attention, I will show him reason for believing that the Marsupial group arose from similar low forms to those that o;ave orioin to us and the nobler beasts, some of which, indeed, may be transformed Mar- supials ; and that the line of demarcation between the nobler and less noble t}^3es does not form a perfect fence. In the study of nature, as every one knows, that seems to be the most bewitching ])avt in which each particular observer is working ; the skeletal frame- work takes the precedence T\ith most of us. There are many excellent diagnostic marks in the skeleton of the Lect. III.] POUCH-BEARI^'G AXIMALS. 67 Marsupials, some well known, some less familiar to anatomists, but none of these are aljsolutely wanting in the forms above, nor are there any that cannot be traced to the forms below. Yet, fagoted together in the Metatheria, these diagnostics serve the purposes of the classifier, and are, indeed, in their combination, remarkably distinctive of the group. Firstly, those parts of the skeleton which are popularly supposed to be so important in relation to the pouch — the marsupial or pre-pubic bones — these are no new thing, but, as we have seen, are equally large in the Monotremes, Y/hich have the pouch rudimentary ; they also exist as pre-pu1jic cartilages in Salamandrians and Skates ; and they reappear, as rudiments, in the Eutheria. The pouch itself — a superficial structure, a mere apron or fold of the skin — reappears, as a rudiment, in the embryo of the Flying-cat of the Phillippines, a sort of primordial Bat, not quite out of the border of the Insectivora. Such a pouch holds the eggs of Pipe-fishes, but it is the male which possesses it ; and some Frogs have such a pouch, but it is on their Ijack. The shoulder-girdle of the Marsupials is quite like that of the highest kind of mammals, in which the clavicles are well developed ; there is no interclavicle between them, and they have a pro-coracoid rudiment at each end, a thin cartilaginous pad. The acromion (shoulder-point) is well-developed, and the coracoid (Crow's beak 68 MAMMALIAN DESCENT. [Lect. III. process) is a mere spur, as in the Eutheria generally. So also tlie vertebrae, the ribs, and the sternum ; these are quite normal, having taken on the characters we are familiar with in the hio-her kinds. The limbs are very instructive. The front pair are very similar to what we find in Insectivora and Eodents, and are not much modified, but the hind pair are very much specialised in those that can take long leaps — as the Kangaroos. The Opossums of America, and the Phalangers of Australia, have the hallux (great toe) short and opposable, as in the Dormouse, and in the Quadrumana (Apes and Monkeys), generally. From such a foot as that there is every transitional form to that of the Kangaroo, where the hallux or first toe is gone, the second and third extremely long and delicate and evidently useless, whilst the fourth is very large, and the fifth moderate. One peculiarity of these pouched animals is seen in their dentition. Several years ago. Professor Flower showed that only the third false grinder (pre-molar) has a predecessor. This milk tooth is like a true molar ; the tooth jiattern is simple, quite unlike that of the high Herbivora. The Rodents, which are lower, are extremely variable in this respect, and the dentition, in some of them, assumes a high condition, with extreme specialisation. As the metropolis of a country is the most instructive as well as the most important of its towns, so the skull takes to itself that which is best and noblest in the Lect. III.] THE SKULL IX MARSUPIALS. 69 organs of the body. It has cost me but a modei-ate amount of attention to this group (which I am now taking up in earnest) to find in the skull ten good diagnostic characters. These are easy to follow by anyone at all familiar with the skulls of the higher mammals. I must therefore beg the attention of the human anatomist, who will at once see how curious and suofo^estive these deviations are from what is normal in our own species, and indeed I may say also in most of the higher kinds. Nevertheless, these deviations are not confined to the Marsupials, but are to some extent seen in many of the lower kinds of Eutheria, and are in themselves nothing abnormal at all, but only so in relation to, and com23arison with, the standard we have set up, by making our own structure the measure of all others. Indeed, these peculiarities are so many stepping- stones between us and our hioiiest Mammalian relatives and the forms that lie below ; we are not so isolated as we have supposed ourselves to be. The things which strike the eye in the examination of the Marsupial t^rpes of skull are as follows: — 1. In the basal region of the nose there are several pairs of splint bones, belonging to the vomerine series, besides the large middle vomer or ploughshare bone, like that which sheaths the base of the partition of the nose-labyrinth in us. 2. That strong floor, the hard palate, which in us and our congeners divides the cavities of the nose from 70 MAMMALIAN DESCENT. [Lect. III. the upper region of the mouth, and which is formed by a special ingrowth of l:)one from the maxillaries and palatines, is large and imperfect where the four plates -^.o Fig. 9. — Skull of an embryo Pig, 3 inches long, lower view, magnified 3J diameters. al.n, aire nasi (snout cartilage); e.n, external nostrils ; ^ac, premaxillary ; mx, maxillary ; d.g, dental groove (for tootli -pulps) ; ^Jrt, palatine ; p(/, pterygoid ; v, vomer ; e.pc/, external pterygoid plate ; bs, basi-s plienoid ; g.f, glenoid fossa (hinge cartilage for lower jaw) ; ti/, tympanic bone ; ob, os-bullie (additional tympanic bone); bo, basi-occipital ; 2^-^(^j paroccipital process; oc.c, occipital condyle (hinge for first vertebra or atlas); eo, exoccipital ; so, superoccipital ; f.m, foramen magnum (great opening) ; IX. X. XII., holes for the exit of the 9th, 10th, and 12th cranial nerves. should meet. It is less imperfect in the einl)iyo than afterwards, but the l^one-cells are very thinly scattered Lect. III.] EAR-DRUM OF MARSUPIALS. 71 in the early state, and during growth become aggregated h-iterally, so as to leave large fenestras, or windows, towards the mid-line. 3. The temporal bone (squamosal) is hollow above the hinge of the lower jaw, and this large air-cell communicates with an extensive series of similar empty spaces that arise primarily in the mastoid region, or back part of the organ of hearing. 4. The bony ring of the ear passage (external auditory meatus and drum cavity), does not form all the cavity, but a hollow shell of bone from the hinder wing of the sphenoid (ala magna or alisphenoid) applies itself in front and within, so as to form what is called an " auditory bulla." Yet this bulla or bleb-like shell of bone, a part that we do not possess, does not corre- spond with that of the Cat, whose meatus-skeleton has a large shell-like inner tympanic bone added to the usual annulus, or ring-bone. 5. The internal carotid artery does not enter the skull, as in us, between the basal beam on one liand, and the side-wings and petrous bones on the other, but Inirrows through the basal beam, each branch appearing in the seat of the turkish saddle, '' sella turcica," instead of burrowing the "petrosal," and then passing through a " foramen lacerum," or ragged interspace between that bone and the lateral parts of the skull. 6. The malleus, or hammer-1)one of the middle ear, has a very large processus gracilis, which, be- 72 MAMMALIAN DESCENT. " [Lect. III. sides growing well forward into tlie Glaserian fissure, also sends a large sickle of bone in front of, and within, tlie bony tympanic ring ; thus, that bone has two ancillary pieces, helping it to wall in the drum ca^dty. 7. The innermost bone of the middle-ear chain is not always stirru23-sliaped, it is often a mere " columella," or rod, with an oval dilated plate above, where it fits into the oval window (fenestra ovalis), as in the Monotremes and Ovipara. 8. The angle of the lower jaw-bone is greatly incurved, and often has on its upper and inner face a hollow fossa. 9. The hyoid bone is not simply U-shaped, but is dilated into a wedge-shaped plate ; it has, however, the usual cornua (horns or jDrocesses), that are indeed the skeletal parts of the hyoid, or second arch, and of the rudimentary third, or first gill arch. 10. But the most interesting and instructive of all the characters is one which at first sight would seem to be a very small matter, but is indeed full of instruction, namely, that the optic or visual nerve does not pass from the brain to the eye through a special hole in that part of the skull, but through a large chink in the walls — the common outlet for all the nerves of the orbit. These are the ten good, useful, well-marked diag- nostic characters, which I promised to show^ in the skull of a Metatherian animal, or intermediate beast. Lect. III.] LINKS IN THE CHAIN OF LIFE. 73 It now has to be shown, in the interests of biology, that these are not present in the Marsupials as absolute characters, and that they are not formed here, either for the first or the last time. In other words, they are mere specialised modes of structure, quite familiar to the student of the oviparous t}^Des (either lower or higher), and they do not die out suddenly, but reappear in the Eutherian types that are far above them in zoological height. Every element of the skeleton of any of these classes, however inconspicuous, is a link in a very long chain, and often to the morphologist a golden link, very beautiful and valuable, suggesting to him origins and ends that would have been unintelligible but for some such small points of bone or nodules of cartilage. On the other hand, the proud conservative, who would isolate himself upon his human throne, must not think that we are removing biological landmarks, we are merely showing him that they never existed. I will now take these ten diagnostics one by one, and look at them in their rise and in their progress. But let me not be misunderstood ; their rise cannot be seen by us in any actual progenitors of these Meta- tlieria, nor their progress in t}^es that have arisen from them. That is absolutely impossible in the nature of the case. The lower types are mere survivals of races more or less on a level with the various supposed stages through which a Metatherian must have passed to 74 MAMMALIAN DESCEXT. [Lect. HI. attain to its present heigiit. And the types that have gone beyond the Metatheria are not the children or descendants of any existing Metatheria. The parents of the lowest Eutheria have been quietly inhumed for many an age, and there is indeed no reason to suppose that they all utilised the Metatherian or pouch-bearing stage at all ; but it is probable that they shot past the Marsupials in an embryonic stage. Many things seen in the Marsupials seem to suggest this ; they have formed for themselves a sort of '' bye-path meadow," far out of the line of the great highway of life. Letting imagination fold her wings for a while, we will now look at a very few dry anatomical facts. Character 1. — In Bony Fishes, but not in the more archaic Ganoids, there is a median vomer. In the lower Ganoids, e.g., the Sturgeon and Paddle-fish, there is a crop of such bones, with a tendency to a quincuncial arrangement, that is, Avith a middle series, and a row, right and left, opposite the inters23aces of the single row. Then, in the Amphibia, and in Snakes, Lizards, and Crocodiles amongst the Eeptiles, there is a pair of vomerine bones, but only in the Chelonians (Turtles, and Tortoises) is there a single median bone. In Birds also, certain groups show a single bone, as in rapacious Birds, Fowls, Geese, &c., in other kinds there are two, either for a time, as in Finches, or perma- nently as in Woodpeckers. But the vomer and the Lect. III.] THE HARD PALATE. 75 vomerine series of bones have behind them, under the main skull, another series, namely, the "para- ■sphenoid" and its divisions. This series, as I shall afterwards show, appears in the Mammalia, and the arrangement is always as one, two, or three — a recollec- tion, so to speak, of the primary pattern of median and sub-median l)ones in the lowest Ganoid Fishes. Tn the mammals, generally, during the embryo stage, there nre five vomers, but in Marsupials there may be ten. Character 2. — The bony palate is deficient in the Hedgehog and other low Eutheria, and is very limited in the lower Eodents. Such a specialisation of the cheek and palate bones is only rudimentary in the Amphibia, in Serpents, and in Lizards ; in the larger Chelonia (Turtles) it is very considerable, while in the Crocodile, as in some of the lowest Eutheria, e.g., Ant-eaters, it attains its utmost development. In birds, which, more than any other group, lie away from this line of descent, this structure is very slightly developed. Character 3. — This character, the hollo wness of the squamous part of the temporal bone, is very marked in the lower Eutheria, such as Edentates and Insectivora. In the tailed Amj^hibia there is no drum-ca^dty ; in the tail-less kind, where it is generally present, I never saw this cavity enlarged by extension of the air-cell into the neighbouring bones. Nor in Serpents or Lizards is there any excavation of the bones in this part ; the former have no drum cavity, most of the latter have. 76 MAMMALIAN DESCENT. [Lect. IIL But in the lesser Tortoises the tympanic cavity is made quite large by the hollowing out of both the quadrate and the squamosal, whilst in Crocodiles and Birds the whole hind skull, at any rate, is one system of air-galleries, all communicating with the cavity of the drum. In us, whatever kind of ear-drums our very first parents may have possessed, there are no cells of this- kind except in the "mastoid process," the thick mass- below the labyrinth, which we feel as a lump behind our ears. Character 4. — Whilst writing these notes, I have for the first time found this fourth charactei^ in a mammal above the Marsuj^ials, namely, in an Insectivore from Zanzibar [Rhyncliocyon), a creature full of inconsist- encies, but a treasure to the Darwinian. To him who- can wait, the whirlio^io- of time brins^s its rewards as well as its revenges. That mixed t5rpe (of which Dr. Dobson was the kind donor) has come to me for the establishment of my faith in develoj)ment. Another equally valued friend. Professor Burt Wilder,, of Cornell University, U.S., amongst other treasures,, sends me unborn embryos of the Virginian Opossum, and now, after years of patient longing, I can compare the development of this type of skull with that of the Crocodile and the Bird. The process of cartilage that grows out on each side of the second part of the skull-base, the hinder sphenoidal Xect. III.] CROCODILE, BIRD, AND OPOSSUM. 77 region, which forms the rudiment of the excavated part that enlarges the drum cavity on its inner side, is developed in the same manner in all the three types. There is much difference in detail, but the mode of growth, as well as the primordial condition, is alike in all these — Crocodile, Bird, and Opossum. Nature, who has framed strange fellows in her time, must have gone to the limits of her power in growing a Crocodile, a Nightingale, and an Opossum out of germs as like to each other as the right hand is to the left. These forms had, undoubtedly, an hereditary some- thing in them that determined each along its own diverging line. The angle of divergence is very acute, but ultimately the distance has become wide enough. Character 5. — This character, the entrance of the internal carotid artery through the substance of the basi-sphenoid, seems at first sight to l^e a very little matter. It is, however, a character correlated with a lesser brain and a lower intelligence than we find in the better sorts of the Eutheria. I see an approach to this state of things in the little Ant-eater, a very ancient kind of creature, of a very non-intelligent sort. No doubt, if anyone w^ould carefully give himself up to the investigation of the modes of arterial supply, he would find that there is a most orderly series of changes in the development and distribution of these vessels, and of all the arteries in the body. But the interest attached to those which go to form the " circle of AYillis " 78 MAMMALIAN DESCEN'T. . [Lect. IIL in Man is the greatest, as it is one of the principal means of supply of fresh blood to the l3rain. Anyhow, as the brain widens and grows, in the ascent of the types, these arteries get further from the mid- line at this their entrance into the skull. In Birds and Eeptiles the pituitary body drops into a hole, — does not lie on a saddle as in us, — and in them the internal carotids run up through the oj^en space, close beneath the pituitary bag. Thus, we see that the Marsupials are intermediate between the Sauropsida and the Eutheria ; they have an imperfect seat to their "sella turcica" (turkish saddle, as it is generally called in Man), and the internal carotids pass inwards, as in the oviparous types, but rather further apart Character 6. — The peculiar form of the malleu:^ (hammer) seen in many Marsupials. Its large size, and the sickle-shaped tympanic fork of the processus gracilis, is seen in low Eutheria, e.g., the Mole, for a time. The growth of j)eriosteal or superficial bone is an attemj^t to form the usual splints of an ordinary mandible in the ovipara. Sometimes the three plates — external articular, angular, and supra-angular — are quite distinct. These are formed just as the cartilaginous rod is being pinched in or starved off, so that the fore part of the jaw becomes segmented from the hind part, does all the mandibular functions, and leaves the hinder, or Lect. III.] THE STIERUP AXD COLUMELLA. 79 upper end, to partial starvation, in order tliat it may he small enough to form the special malleus. But the wrapping and binding of the cartilaginous lower jaw in bony splints — three on the fore part, and three on the hinder, proximal, or upper part — is as old as the Ganoid Fishes of the Old Eed Sandstone, who formed their mandibles in that way ; and the living Sauropsida — all known Birds and Reptiles — to this day form their mandibles in the same manner ; it is a neAv thing when the hinge-part of the lower jaw is starved, so that it may shrink into the little auditory malleus. Character 7. — This also is a Mammalian modification — a new specialisation of an old structure — when the innermost bone of the ear-chain otows so as to reseml)le a stirrup. It does so because of a peculiar branch of the " common carotid artery," which passes in the early embryo close to the opening (fenestra ovalis) of the vesti- bule, to press its way to, and unite with, the " inferior maxillary artery." In its passage it trespasses on the ground belonging to the topmost segment of the arch of the tongue (pharyngo-hyal), and a compromise is made by the cartilage hardening round the little artery. But in several of the Marsupials this does not take place; nor in several of the lower Eutheria, e.g., some of the Edentata. The Monotremes, also, the Saurop- sida, and the Amphibia, have this element imperforate, and thus it has received the name of the "auditory columella." 80 MAMMALIAN DESCEXT. [Lect. III. In tlie Skate this element is a large triangular cartilage, on which SAving both the first and second arches of the face ; hence it has been termed the " hyo-mandibular," for it carries the hyoid or tongue arch, and the mandible also. Character 8. — The incurved form of the lower jaw at its hind angle is not confined to the Marsupials ; it is also seen to a less degree in various kinds of lower Eutheria. In the types beneath, it simply represents the large development of the dentary bone ; in many of these it forms a " trough," and grows freely on the inner side of " Meckel's cartilage." Character 9. — The basi-hyal plate, or skeleton of the back of the tongue, is seen in the higher mammals, where this plate is enlarged in relation to the larynx. In Turtles and Crocodiles this plate is flat and wide ; in the Frog also it becomes a broad sheet, like an apron, the narrowed bands of the arch being the strings. But in fishes there is a chain of segments at this part, the basi-hyobranchial series of l^ey -stones of the series of giU-arches. It is thus short in the air-breathing types, because of the suppression, in them, of the gill-arches. Character 10. — This is a "small wire," but it will bear to have a large amount of induction hung upon it. I know of no case in the existing Yertebrata below mammals, where the optic or visual nerve is protected Iw a special bar behind it from the plate that forms the base of the skull at this part ('' orbito-sphenoid") Lect. III.] MIMETIC TYPES. 81 Above the Marsupials I have, as yet, only found, two cases, — the Common Shrew and the Rhynchocyon, — in which it is not thus protected, and. these small beasts are among the loAvest of the Eutheria. The teaching of all these details is manifestly a doctrine of development. Every new fact (and new facts are pouring in day by day) certainly makes the old theory of creation more and more untenable. The long time during which these pouched beasts have existed, their intermediate position between the Proto- theria and Eutheria, their present isolated position, and their distribution only in territories where archaic forms most abound — all these things look in the same direction, and tell us the same tale. There is something very remarkable in the manner in which this group, composed of forms so nearly related to each other, has been broken up into families, mimetic, or imitative, so to speak, of the Orders of the Eutheria. This appears like an attempt on their part to make the best of themselves on their low level. Nature says — " The Eutheria have I loved, but the Metatheria have I hated ; " and yet these latter, also, have attained to much increase, and to a rich variety of life. But their date is nearly out. Almost everywhere, in the Northern World, they are extinct ; and wherever the chosen people (the Eutheria) come, there these low- types will of necessity die out. The noble races show no mercy to the ignoble ; when Nature elected that 82 MAMMALIAN DESCEXT. [Lect. III. the Eiitlieria slioiild increase, and multiply, and fill the land, then she practically culled out, and appointed for slaughter, these poor silly pouch-bearers, the Metatheria/ adde:n^t)a to lecture hi. Tke numerous forms, still happily existing, of the Marsupials, have given rise to so large an amount of biological activity, that it is impossible here to mention more than one or two quarters where treasures of this kind are to be found. Of course, the late Mr Gould's valuable works are to be referred to, and also the inij^ortant papers, with illustrations, that from time to time appear in the publications of the Zoological Society. The reader interested in their anatomy may refer to the works, given in the first list, of Professors Huxley and Flower, and to my own pajDer on the " Shoulder-Girdle and Sternum," where those parts of the marsupial skeleton are described. An excellent and well- illustrated memoir on the muscles of the limbs and other parts of the anatomy of this group, by Dr. Cunningham, will be found in the CliaUenrier Mejwrts, vol. v. Remains of the huge extinct forms of those types of the Australian region long ago found their historian in Sir Richard Owen, and invaluable papers, freely illustrated, describing those huge creatures, will be found in the Philosophical Transactions ; for twenty-five years these have been gradually coming to the light. These are but a fraction or division of his work. The huge extinct relatives of the Goose, the Rail, and the Emeu — from another part of the Australian region, New Zealand — have also been revealed 1 From all that we can gather of the history of the "stocking" of the earth by mammals, the low-brained kinds have always given way to those with more developed brains. The utmost specialisation of peripheral parts cannot compensate for a small brain with low intelligence ; the cunning, and its twin- faculty invention, of dogs and foxes, give the dog-like Marsupial {Thylacinus) not the least chance ; and a few goats and ponies would soon drive out or starve whole herds of kangaroos. One man with a pocket-knife will do more than another with a whole chest of tools. Lect. III.] FOSSIL MARSUPIALS. 83 to us in a similar series of memoirs in the Zoological Transactions. These, and many others come flocking to my mind whilst I write. Having begun my own biological studies by the help of some of his earlier works, I take pleasure in making mention of these noble monuments of the labour of a long life. The great men who did so much for palaeontology half a century ago, of whom Owen is almost the only survivor, have now their rivals in the present generation of American geologists, who are daily giving us new and pleasant surprises. But, whilst one man will " cut Colossus out of a rock, another will carve a head in a cherry-stone." Great as is the value to be set upon the work of our palseontolo- gical fathers, the work of the rising biologists is of still greater value ; and that even with regard to the past history of these Metatherian types. Palaeontology is good, but Embryology is better, for if all Sir Richard Owen's giants could be made to live again — an exceeding great army — they would tell us less of the origin of the Marsupials than we should gain by the knowledge of the development of a single germ of any one living ty]3e. Mr J. J. Fletcher, B.A., B.Sc, has lately sent me two of his papers, the beginnings of his researches into the anatomy of the internal organs of the Australian Marsu23ials. These have been published in the Proceedings of the Linncean Society of New Sovfh Wales, Nov. 30, 1881, part i. (Introductory), pp. 796-811, and oS'ov. 31, 1883, part ii. pp. 6-11.^ There have also come across the Atlantic, lately, tAvo noteworthy memoirs; the first, "On the Embryo of the Kangaroo," is by Dr. H. C. Chapman (Proceedings of the Philadelphia Academy, 1881, part iii. p. 469), and the second. Observations upon the Fcetal Membranes of the Opossum and other Marsupials, is by Henry F. Osborn, Sc.D. The two papers just mentioned might, literally, be folded up and packed inside a nut-shell, and yet, if I am not greatly mistaken, they let in more light upon the incoming of both the Metatheria and the Eutheria than anything that has gone before. 1 On tlie same page (11) there is a paper by Mr C. W. de Vis, M.A., "On the Remains of an Extinct Marsupial, a new Type," called by him Sthenomerus char on. 84 MAMMALIAN DESCEXT. [Lect. Ill Of course, only the biological reader of such communications can value them properly, as he only can thoroughly understand their meaning and their bearings ; and yet the patient and thoughtful general reader may come at the gist of the matter. But first of all he must bind uj) all his old misconceptions into a bundle and burn them, and come into the Temple of IsTature with child-like simplicity of mind, and not like that "praying, synagogue-frequenting beau," who walked up to the Holy Place straight as a ram-rod — stiff with pride and prejudice. We know that in the oldest oak-tree living there has been no discontinuity of vital action since it first germinated, and that its germ, with the closely-packed cotyledons, were not created, but grew. These first, or larval, leaves, the cotyledons, had their day, and did their day's work like honest labourers, so also did the first crop of normal leaves, and the second crop, and so on, year after year, all doing the work of their generation. This increasing family of leaves T)udded and grew, and stopped in their growth and died ; but they all lielped to make that forest-king. As long as we think of the oak, merely, we can run back for some length of supposed time, along the line of our imagined oak-tree's an- cestors. But if we were to go some distance iDack — very far back, no doubt — we should find ourselves lost, for our oak would be the English kind no longer ; we should have reached the point where all the species of oak would meet in one generalised type. But the oak family has its relatives, and these would, far enough back, all become undis- tinguishable. Along such a descending road we should never find rest until we had reached the common, most generalised, protoplasmic mother-stufi", whose descendants, on our return journey, would turn out to be every green thing, every plant or herb or tree that the earth has borne, or is still bearing. This thrice-ancient mother of all the plants is the same as she who was the fruitful mother of all sentient creatures or animals. From her sprang the fishes of the sea, the fowls of heaven, and the beasts of the earth. If we could follow the pedigree of every living, moving creature, it would be traceable back to that common protoplasmic mass. " "Wisdom " saw tjie green corn, the rose, and the oak ; and also birds, and cattle, and jnen, in their first beginnings. Solomon says — and he, the wisest of the sons of men, should know — that She rejoiced in, and that her Lect. III.] THE AUSTRALIAN FLOEA AND FAUNA. 85 delights were with, those living creatures, whose evolution was, as yet, so far off. I think that Solomon, who rejoiced so greatly in the living crea- tures of his own country, would have been less enthusiastic over the lower and less beautiful types of Australia. The aboriginal human inhabitants of that strange country — Australia — the home of that grey, cheerless vegetation, and of thos(^ lowly unintelligent quadrupeds, have never shown any signs of mental evolution ; at their best they have risen but little above the dignity of a " connecting link." Palestine, most probably, and England, we know, did once possess a Flora and Fauna the counterpart of that now existing in Australia, but we have no evidence with regard to that human type, in its archaic state, which in the fulness of its evolution, long afterwards, took to Poetry and Biology. There is an unusually thick mist over that matter, a dark- ness that is felt, for its effect is very disappointing and distressing to the modern type of mind. There is no doubt that Darwin has roused our curiosity about these things to an almost morbid degree ; but let us look in the direction where the mist is lifting a little. Natun^ has set the Marsupials in the very midst of the higher tribes of the Yertebrata, and especially of the Mammalia : they are the mid-beasts. Sir R. Owen long ago got some light upon the peculiar position of the Marsupials, in relation to the truly vivijmrous jMammals ; Dr. Cliajj- man has lately helped the matter considerably, and Professor Osborn has thrown new and most welcome light upon it; and he will not rest until the j^roblem of the development of these types is fairly solved. One of those poetical emotional Easterns rises into the most joyous raptures over the early development of a man, of himself in- deed ; but he turns his thoughts all to poetical and devotional purposes. He had the stuff of a biologist in him, but lacked the proper train- ing. Let us look at the beginning of this mystery of development in a lower type. If we take a very low kind of fish, say the river Lam- prey, we shall find that it lays a countless number of small eggs that are hatched in the water, and the fry are like so many small black worms. Very little care is taken by the Lamprey, and by most of the common fishes, of their spawn and fry, but in some cases, as in the Pipe Eish {Si/7ir/7iat7ms), the eggs undergo their development in pockets or pouches in the abdominal region of the male. Some river fishes of 8G MAMMALIAN DESCENT. [Lect. III. the Silurus kind (Arius, &c.) lay a few large eggs — as large as a small cherry — and as these fishes have in them the beginnings of family affection, and yet are nomads, travelling about a good deal, up and down mountain streams, the male pockets those precious globes in his mouth, whilst he and his mate wander about, laying them down wdiilst they rest. The Amphibia (Xewts and Frogs and their kindred) lay small eggs, as in the Lamprey, with but little food-yolk, but a number of curious family arrangements are to be seen in these groups. The Common Frog lays multitudes of eggs, and each of these at first is covered with a tenacious jelly, which, SM'elling with the water, expands to the size, and has the appearance, of a white currant ; thus an egg-cup-full of eggs soon grows into a mass that would fill a quart measure, each white globe having a blackish egg inside, the size of a mustard-seed. The father and his wife hang about these, their future progeny, until they are hatched, but do not seem to under- stand the meaning of them, or that they are being eaten, by hundreds, by the Duck, whose voice might seem to indicate a Ranine descent. As for the Obstetric Frog, the male coils the slimy eggs round the thighs of the female, and she swims about with them attached to her, a family arrangement not unlike what we see in the Shrimp and her kindred. Lut these tail-less metamorphosing Amphibians, that in their transformation give us the promise, or anticijDation, of much that finds its culmination in our o^yn body, have also some very remark- able ways of showing their social and parental affection and care. This extremely ancient family holds its own, and keeps its place, in the presence of all the newer and nobler types of A'ertebrata. Their fecundity enables them to lose a large proportion of their progeny without diminution of their actual numbers, year by year, a considerable percentage slipping through the fingers, and out of the very mouth of fate. Moreover, we yearly see our common kinds taking hold of the forelock of time, and getting their water- bred brood out of the way before the drought can kill them. Some of the foreign races have very curious habits. " In NotodeJjyhis ovijiara the eggs are transported (by the male ?) into a peculiar dorsal pouch of the skin of the female, which has an anterior opening, but is continued backwards into a pair of diverticula. Lect. III.] NEWTS AND FROGS. 87 The eggs are very large, and in this pouch, which they enormously liism of the leaves of that beautiful tree admits ■of but one interpretation ; they each and all have responded to their surroundings, setting up their prickly backs, like Hedgehogs, in the lower parts of the tree, lest the ox that licketh up tlie grass .should lick them up also ; but above, in the steeple-like culmination of the tree, right under the eye of heaven, the defensive prickles are .suj)j)ressed, and each leaf glistens in the sunshine, unarmed and void of fear. Was each leaf separately created in spring-time? You answer — "No, no need for that ; the forces within the tree, working in exquisite harmony with the surroundings, sufficed to make all that difference in the form of the individual leaves." I rejoin — "Are you assured of that ? if so, good ! We now can imderstand each other." Of course every observer of nature is acquainted with a thousand instances of the same kind as that presented to us in the holly-tree; yet these familiar phenomena all speak one language; — that language is no longer barbarous; everj^one under- stands it now. That lies outside, but illustrates, our work ; every member of the animal tribes merely lives out the cycle of an individual life, which life is one continual struggle against drought and rain, heat and cold. Of ■course, each kind has the benefit of the whole accumulation of 'excellences developed in its own direct ancestry ; each oak tree and holly tree enjoys the rich 'inheritance, so also does the Armadillo, the Ant-bear, and the Man. I have no doubt of one thing, namely, that Armadillos, like Tortoises, are the descendants of types that were not cased in complete armour. I have, likewise, no doubt that Ant-eaters and Pangolins, like Tortoises and Birds, are the descendants of types that had a perfect series of teeth. The Ant- 122 MAMMALIAN DESCENT. [Lect. IV. Lear's head and tongue have lengthened through the ages ; in this he has gone on unto perfection. The Sloth, also, has cut olf, not his right hand, but all his unnecessary fingers, during the long secular period in which he has been slowly moving towards the mark of his particular type of excellence, and his face has gone on shortening, so that, although a long way below a IVIonkey, there is something monkey-like in his curious short muzzle. Time, that unwearied harvest-man, has almost finished his mowmgs in this held. Here and there, his two-handed engine has left a patch of poorer stuff, a narrow headland of weaker, and later- growth. The rest he has garnered and locked up safely, not, how- ever, without letting fall here and there, as if by accident, a handful or two, which the stranger from a far country has been too glad to glean. But if Time has been so much against the modern biologist, there was no reason why Xature (or "Wisdom, to use another image) should have been so anxious to hide these types from us ; nothing more perfect was ever developed by the morphological force. Here one can speak great words, and yet not be hyperbolical ; the little finger of the Megatherium was literally bigger than the sloth's loins, and all the existing Armadillos (one of each) might be packed in the body-case of a Glyptodon — the extinct Armadillo with sculptured teeth. The largest Green Turtle would look a j^oor, shrunken thing beside a living Glyptodon, a mean hero in a mean armour, not worth ten oxen, but the Glyptoclon's armour could not be bought for a hiuidrecl oxen. Yet that reptile-in-armour, in his own element, is like a swift ship; the Glyptodon had to carry his suj)erb body-house on stumpy legs; he must, in walking, have seemed like a huge bombard full of liquor, that was being carried off by his oaken tressles or undersetters. If the Megatherium, or his somewhat more modest-sized relation the Mylodon (another extinct Sloth), did find their supply of food in the way palaeontologists suggest, their mode of dining must have been a sight worth seeing. That delightful, typical English- man, the late Rev. Sidney Smith, once reviewed Waterton's Wanderings, and described the strange, grotesque, weird, unthought- of creatures of the New Tropics. Would that he held the pen here, now ! Let us, however, try to imagine a Megatherium waking up after Lect. IV.] PLUCKING UP CEDARS. 123 lazily dozing a month or two during the dry season, and then, hungry and "wet, in the heavy downpour of the beginning rainy season, setting to work to break his fast. As far as can be judged by the tools he had to work with — paws a yard, and claws a foot, in length — the first thing to be done was to throw out a few hundredweights of earth from the roots of some large tree. iN^ow he changes his tactics ; he has good collar-bones, and well-shaped arms for embracing ; so, bear-like, he hugs the tree npon which his desires are set, and, busily digging still, not now with his fore, but with his hind, paws, his great weight resting upon his haunches and his tail, he, with many groans, sways the big tree to and fro ; at last with a great crash it falls, not, however, without giving him some sense of its weight, for it was a tree worthy to grow in a forest trampled upon by this atlantean Sloth. That large crack in the outer table of his skull is of no consequence ; his small brain is a long way off, and there are many empty cavities to be found in a head like his; those broken tiles over the empty spaces of his head will soon be mended, and what M'ould be pain to us, is to him a pleasant sense of tickling. But Sloths live in trees, climljing from branch to l3ranch, supine, with strongly bent wrists and hooked fingers ! Yes, I admit, such Sloths as live in these degenerate days, but not the Sloth I am speaking of. Think, if you can, of a Sloth, half as thick again round ' the waist as an Elephant ; with a tail as bulky as a dray-horse's chest ; and feet as large as the many -knotted roots of the gum-tree ; thiiilc I say, of such a Sloth climbing trees. Xo, it is your poor little dwarfed modern Sloth who climbs — not the large j\Iega- therium. Our gigantic Prospero has plucked up his cedar by its spurs; his millstone-like teeth — he also is a Mylodon — and strong jaws will do the rest; he need not hurry and he Avill not. He has "blessed his maw '* to this good hour, and will now enjoy himself. The sorrow of it is that he is not to this day digging up, pulling down, and eating, the trees of the forest, for us to see the sight. For deatli has gnawed upon these huge beasts ; they are laid in the grave — their eternal dwelling. Speaking of such an one going down to the nether parts of the 124 MAMMALIAN DESCEXT. [Lect. IV. earth, we are reminded, by way of contrast, of the poet's account of the slow but suie fossil isaf ion of the rude forefathers of the hamlet — " Each in his narrow cell for ever laid." Seven feet of earth is enough for the biggest of these undeveloped, mute, inglorious Miltons of the little lone country place. When, however, the General Sexton gave the INIegatherium his seveji feet of earth, this was merely the measurement crosswise, for he was nearly that breadth across his loins with his flesh and his fell on ; his length was double that and more. If time had not failed me, I would have described his parts and his power, and his comely proportion. I might have dilated ujDon his feet, to the extent of filling a chapter ; the spoor Avhicli they made, being filled by timely rains, made a pond in which the Axolotl might have disported, and in which the largest of Frogs did, undoubtedly, take their j^astime. If the reader vrill visit the great Natural History Museum at South Kensington, and the Hunterian Museum in Lincoln's Inn Fields, and look at the remains of the fossil Sloths, he will make this discovery, namely, that the writer's attempt at the rejuvenescence of these beasts is dull and flat, and that not half the truth has been told him. Lect. v.] MATEKIALS FOR WORK. 125 LECTUKE y. Insectivora. The Edentata are very similar to the Inseetivora, but are arrested and modified largely on their own level. They are more related to the Monotremes than to the Marsupials, but the Inseetivora appear to be rather a development or outcome of the Marsupials. The works or papers that have been of most value to me in dealing with the Inseetivora are by Professors Huxley and Flower, and Dr Dobson ; we are rich, however, in the litera- ture of this Order. It has taken me many years to collect materials for my researches into the develop- ment of these animals. I published some of my results long ago — those which related to the shoulder- oirdle and sternum — but the accumulated matter on the skull, work doue during the last two years, has not yet seen the light. In working out the details of the development of the skull, I have followed my own bent, gladly accepting help from my fellow- workers in biology. But in arguing upon what has been seen and regis- tered in this special piece of research, I have been largely influenced by one whose aptitude for drawing 126 MAMMALIAN DESCENT. Lect. Y. clecluctions from facts, and for putting tliose deductions into sucli a form that other minds can receive and appreciate them, is far beyond anything I can boast of. The author I refer to is Professor Huxley, and the paper entitled " An Application of the Laws of Evolution to the Arrangement of the Yertebrata, and more particularly of the Mammalia," has been repeatedly referred to in these Lectures ; I have had much help from him, and from other fellow- workers. But I cannot pass unnoticed Dr Dobson's valuable work on the Anatomy of the Insectivora, nor Professor Flower's im- portant papers and works on the Mammalia generally. Although I shall refer merely to what can be seen in the skull and face, I have not been unmindful of the rest of the organisation of these creatures ; l)ut my views are mainly based on what can be seen in the head. Now the types treated of in my last lecture — the Edentata — as I showed, lead nowhere ; they end in themselves ; not so the Insectivora. Li them we evi- dently have the modified and dwarfed representatives of the original placental mammals, or Eutheria. These lowly forms, although small and inconspicuous, yet yield a rich harvest to the biologist, for they are the somewhat altered, living patterns, of the forms that did abound in the middle, and even in the early, Tertiary e230ch. In the Secondary rocks their exist- ence is doubtful, as the bony remains of the earliest Insectivora would be scarcely distinguishable from Xect. v.] THE FIRST BEAST-NAMEK. 127 those of the Metatheria or Marsupials. Once beyoud these lower forms, however, we soon find ourselves in the midst of types, which, if very unlike our modern Insectivora, are yet much more unlike the higher forms of beasts now existing. The four- or five-toed feet, the simple tooth-pattern, the generalised condition, indeed, of all the parts, and the very small brain cavity seen in their remains, show us that we are only just above the Metatheria. The commonly received 023inion of the multitude is, that the first-recorded beast-namer was contemporary with all these extinct forms, and also that they were his, and that he put either his brand, or his ear-mark, upon them all. All the evidence lies the other way. There is every reason to believe that that first zoologist was familiar with the beasts whose forms are so well known to us now — Lions, Bears, Horses, Cows, and Sheep. But such large and small cattle as he was, and as we are now, familiar with, were not to be seen in the days of the years of which we speak. In those days, no shepherds kept watch over their flocks by night — Sheep were not, and the paw of the Lion and the paw of the Bear had not been developed. It is evident that we must, in imagination, wait for a great time whilst the earth is jDreparing for these cul- minating types ; for some twelve thousand feet of fossili- ferous and other rocks have gradually been laid down since the first Eocene types of mammals appeared. The 128 MAMMALIAX DESCENT. [Lect. Y. mammalian forms of tliat time are more nearly related to our existing Insectivora than to any of the grouj^s that lie on a higher jDlatform or level. From some such common root-stock one great sucker or stolon after another arose : — Rodents, Bats, Hyracoids, Proljoscideans, Herbivora, Sirenia, Cetacea, Carnivora, and Primates. At first sight it might seem that the huge Whales were more worthy to have been brought upon the scene miraculously than the little Bats, but as both these sorts of beasts are continually developing, even now, from an almost infinitesimal pellet of j^rotoj^lasm, it seems to me that the large types came into being as easily as the small. Sjieaking of protoplasm, I may remark that the mind is overwhelmed when it at- tempts to follow the embr3"ology of one of the larger Cetacea ; however its feats are accomplished, it must be confessed that protoplasm has an amazing power of growth. Whatever may be the difficulty as to the gradual modification of a terrestrial form into one of these swimming islands, there can be no gainsay to the fact that each living Whale repeats its ancestral history in its own lifetime, more or less. Anyhow, in this present period, Whales exist, however we may account for their existence. Can the lowly. Insectivora throw any light upon the evolution of these huge types ? In attempting to answer my own question I shall sjDcak mainly of those diagnostic characters which are to be found in the head ; these will be looked at both from Lect. v.] ORGANIC EOOT-STOCKS. 129 below and from above, as tliey show ancient or modern relationship. The teeth, of course, are amongst the best of all characters for the use of the taxonomist ; if they do not dominate the creature, they are in harmony with all the rest of its organisation. But these superficial, and easily studied, parts are not the whole of the matter ; 1 should be relieved if they were, as my task would then be much easier. If morphology seems obscure, it should be remembered that it has to do Avith the obscure corners of nature. Now the Insectivora are so related to the various orders above them that they are for ever anticipating their diagnostic characters, and they are so related to the types below them that they are constantl}^ seen to retain the marks of those lower forms. They are an exceedingly variable group — promiscuous, so to speak — although in their external adaptive characters they are more uniform than might be supposed. 1 speak now both of the teeth and the limbs ; the teeth are of a simple type as compared with what is seen in the higher Eutheria, and the limbs are generally typical as to the number of the digits, which are seldom less than five. Also in the deep, or inner, part of the fore-limbs — the shoulder-girdle — the Insectivora are all typical except one, namely, Potamogale ; having well-developed clavicles ; thus they are capable of using the fore limbs for very various purposes ; the pelvis (liij)-girdle) is not unfrequently open below. 130 MAMMALIAN DESCENT. [Lect. V As to apparent uniformity, they are in contrast with the Marsupials, whose outward form and adaptive modification of teeth and limbs are much greater. But in that which lies deeper than teeth or limhs there is evidence, in the Insectivora, that they are a group whose organisation is full and fertile of the power of adaptive change. Now if we com^^are our present living Insectivora with the extinct Eutheria of the early Tertiary j)eriod, these two Faunae are manifestly similar ; they would indeed form one very uniform group if we could get back again all those t}^3es that nature has wasted and buried. If all those hidden treasures of the secret places of the earth, and all those that failed to leave their traces even there, could be restored to us, even, as it were, in "the valley of vision," then we should see that our living Insectivora are only the waifs and strays of countless groups of Pro-eutheria, of many a size and shape, but with very simple tooth-crowns ; with mostly pentadactyle feet ; with small brains ; and with a low intellig:ence. But as in the rude forefathers of the hamlet we have the quiet and unambitious progenitors of the men who, when their time comes, turn the world upside down, so in those Eocene and early Miocene quadrupeds — the equivalents of our little living Insectivora — we have the rough unhewn forms from which our noblest types have arisen. In those days the Mammalia, generally, had not only Lect. v.] adaptive changes. 131 a very simple form of tooth-pattern, much like that still seen in the Marsupials, but the teeth Avere in great number, and often with no interspaces. The digits gradually began to abort ; the innermost (the hallux and the poUex) going first ; but no sign was shown then of such feet as we see now in the even- and odd-toed tyjDes of our noble, existing, hoofed forms. The Cow, that parts the hoof, cleaving the foot into two equal por- tions, and the Horse, who brings his springy weight down upon a single digit on each foot — a digit that has drawn the life out of the others — such forms as these had no existence until near to the time when the ruler of the beasts appeared. In the olden time the term 2^'^'ohoscidean would have been applicable, not to an Order, but to certain Genera. Even now this elonsfation of the double nose-tube, and its seo;mentation into a rins^ed structure, is not confined to the Elephants, as I shall soon show. If there were any su23ra-mundane biologists watching the evolution of forms on our planet at this time they would see the first promise of defensive horns, and the gradual specialisation of certain teeth for ofi*ensive iind defensive purj^oses. If we suppose that such watchers of creation existed, and that they had joy at the sight of those strange beasts of an early age, then what must have been their feelings when they saw, at last, the forms with which we are all familiar — Antelopes, Oxen, Deer, Bears, Wolves and lions ? 132 MAMMALIAX DESCEXT. [Lect. V. Nature lias, undoubtedly, touched up the form of even tlie small conservative remnants of that old Fauna ; the Hedgehog, the Mole, and the Shrew ; the Colugo, the Tenrec, and the Tupaia ; each of these has its own style of beauty, and its own most perfect adaptation to its sur- roundings. That the old cpasi-insectivorous types were the root-stock out of which the higher Eutheria arose is made probable by a remarkable fact, namely, — to quote Professor Huxley, — that "numerous Lemurs, with marked uno'ulate characters, are being; discovered in the older Tertiaries of the United States, and else- where." Further, to continue my quotation — " No one can study the more ancient mammals with wdiich Ave are already acquainted, without being constantly struck with the insectivorous characters which they present. In fact, there is nothing in the dentition of either Primates, Carnivora, or Ungulates, which is not fore- shadowed in the Insectivora ; and I am not aware that there is any means of deciding whether a given fossil skeleton, A\ith skull, teeth, and limbs almost com23lete, ought to be ranged with the Lemurs, the Insectivora, the Carnivora, or the Ungulates " [Proc. Zool. Sqc, 1880, p. 651). In severe scientific research it is dangerous to take things upon trust, yet nothing could have been more opportune, to me, than the appearance of the paper I have now quoted, just as I was beginning to work Lect. v.] UNGULATE LEMURS. 133 at the development of the Insectivora, and the forms and types immediately Ijelow them. I confess that but for the enthusiasm with which that paper ha.s inspired me, I should have been afraid to draw such l)old conclusions as the author of that paper draws ; yet, in meditating upon the facts that are daily opening up to me in my own especial line of research, the truth of these deductions becomes more and more evident. Now, if these things are true, what is to be done with the old Systems ? Where is Linnaeus now ? and where Cuvier ? AVhere are your old hard and fast landmarks — your stony dykes that kept the types apart ? If there is any one whose happiness depends ujDon the safe preservation of these old things, to him I have nought to say ; for myself, that which is found to be false I should gladly see cast aside and forgotten. No Zoological System was revealed to the first man who named the cattle, yet, I repeat, his cattle were similar to ours, and were not the same as those of the early Tertiary period ; in his time there were Swine, Eumi- nants, and Single-hoofed types. Palaeontology has pre- ceded embryology in this field of biological research ; in embryology the harvest is great, but the labourers are few. The existing Insectivora lay their hands, so to speak, both on the low and on the ' high ; they are indeed tlie connectino^ links between the higher forms on the one hand, and the low marsupial, and low monotre- 134 MAMMALIAN DESCENT. [Lect. V. matoiis, types on tlie other. It is hard to say what their own diagnostic marks are, for they are evidently not hardened into a fixed zoological group, but are, as it were, a collection of plastic types ; low, as having the stigma of ancientness upon them, and yet full of the promise of all that is highest in the great mammalian Class. In all this group, only one type, the large aquatic otter- like Potamogale of West Africa, is devoid of clavicles ; also the presence of five fingers and five toes is very constant ; the pollex is deficient in Rhynchocijon and one species of Oryzorictes, and the hallux in MacrosceUdes tetradactylus. Five is evidently a sacred number to nature ; the Amphibians — Salamanders and Frogs — usher in this fixed number, fixed as against a greater number ; and man rejoices in its retention in his own hands and feet. That which often characterises a declining dynasty is the dwarfed condition of its members, as well as the loss of certain of its families ; in the past history of the types it is generally written down that "there were giants in those days." In minuteness, one of our native Shrews is the rival of that smallest Bat, the Pipistrelle, and that smallest of the Eodents, our beautiful scjuirrel-like Harvest Mouse. These three types of Mammalia show us how small a vessel of life will hold all that is essential to one of our own class ; these nursino- mothers are no lars^er than some of the insect tribes. Here we see that, as the lowly Lect. v.] PLASTIC TYPES. 135 lierbs of tlie field escape the violence of the storm, when the forest-king is hurled from his throne, so these exquisite little creatures inherit the earth because of their humility and meekness. It is a fact that they, and forms like them, have kept their ground during the ages that have witnessed the extinction of numbers without number of the strong burly-boned giants of the Class. Yet the small Shrew has numerous enemies ; the Cat mistakes it for a Mouse — a mistake common enouofh amongst us — but does not eat it ; that feathered cat, the Mousing Owl, swallows large numbers of both the land and water Shrew ; she has been my Falcon, for through her I have obtained my best specimens. Both the Shrew and the Hedgehog are considered uncanny by the country people ; have they an instinctive sense that these are ancient, and even degraded, types ? To the biologist there is no form in the group of greater interest than the common Hedgehog, which, specialised highly enough as to its outer skin, is found to be ver}' generalised when studied in its development. Taking the skeleton of the Hedgehog, merely, it is a good example of what is general, rather than special. Free from all violent modifications, it is very useful for comparison both with the old forms of the early Tertiaries, and the new forms of the present period. I have worked much at its skull. It serves as a kind of epitome for the rest ; when once you have mastered this you easily see the meaning of any other kind of 136 MAMMALIAN DESCENT. [Lect. V. eutherian skull ; hj it you can in some degree measure the various kinds and degrees of specialisation to be seen in the other and higher kinds. In the skull of the embryo Hedgehog we see several characters that are familiar to us in that of an embryo Reptile or Bird ; and some are like what are seen also in the Marsupials. As we ascend in the scale of the Orders these cjuasi-reptilian and marsupial (metatherian) characters die out, more or less. Beginning with the superficial bones that cover the inner or cartilaginous cranium — besides the flatness of their form, covering as they do, a flat skull with a small internal cavity — we see that the single jjlate, called '' interparietal," is very large. This addition to the occipital arch is peculiar to certain groups. In my former lectures I have frecpiently sjioken of the gradual specialisation of dermal scutes (or plates of the superficial armour) as we ascend in the scale of the Yerteljrata ; the internal skull — with its contained org^ans — dominating the outer ^^arts, making them answer to what is wanted for protection, both in numljer, in weight, and in measure. Now, in fish and in reptilian forms, besides the main frontal bones, we frecjuently find a series over the brows, the supra-orbital scales'; these linger even in the bird class. As yet, in no mammal except this, have I found more than one frontal bone, right and left ; but, for a while, in the Hedgehog, the orljital rim and jDlate are separate, as Lect. v.] THE HEDGEHOGS SKULL. 137 a single, distinct, lateral piece. Tliis might be con- sidered to be a very small tiling of itself, but many grains make a heap, and facts of this sort, as to exceptional characters, now accumulating, are be- coming very numerous indeed. Where the maxil- laries and palatines meet in the hard ]:)alate, there these bones are deficient to some extent, as in the Marsupials. Above these, toward the mid-line, the vomer and its companion bones are remarkably well developed in relation to the large Jacobson's organs, and so are the retral tracts of the alee nasi, or cartilages of the snout, that encapsule those remarkable organs. As in the Bird and Eej)tile, the pituitary space is open ; that is to say, the seat of the turkish saddle has a round hole through it. As a rule, the Mammalia agree with the cartilaginous Fishes and Frogs in having this part filled in with cartilage. The air- galleries into which the drum-cavities open in the Crocodile and the Bird are represented here by a large lateral recess, right and left, the basi-sphenoid giving off* a large, hollow wing, which takes the place of the distinct hiilla of the Cat. Amonsf the various modifi- cations found in the Insectivora this is one of the most constant, but it is not universal. In the embryo Hedge- hog, before any superficial bones are drawn towards the cartilaginous skull as its support (a state of things like that which is permanent in cartilaginous fishes), the deep cartilages forming the lower jaws are very solid for a 138 MAMMALIAN DESCENT. [Lect. V. mammal, and have superficial cartilages strapped to them. These superficial cartilages are largest in the Chimseroid fishes ; and the deep cartilages lessen in bulk as we ascend into the various culminations of the fishy, rejj- tilian, and avian types. Here, in the Hedgehog, we are much nearer the cartilaginous fishes in this respect than when amongst Reptiles and Birds ; in this, as in some other things, even the lower kinds of the Eutheria, or placental Mammalia, show a relationship to the lowest sorts of fishes known. But there are no fishes now living, low enough, or generalised enough, to be at all good living representatives of the stock out of which the highest and best sort of living Yertebrata must have arisen. We must, however, try and be con- tent with such things as we have, and by comjDaring the early stages of the mammal with even the j^erma- nent condition of some of the cartilaginous fishes, we do get some light upon this dark and difiicult subject. If you will put together what is familar to you in the parts of the human face, and recollect some of the many things I have from year to year reiterated about the face of Sharks and Skates, you will have a very good idea of the marvellous transformation the mammalian embryo undergoes during development. Meckel's carti- lages (the deep or inner lower jaws) are immense in the embryo of the Hedgehog ; they meet and unite in front, at the chin, and there form a single bar or basi- mandibular rod. Just behind this single, terminal, j^art Lect. v.] EAR-DEUM OF HEDGEHOG. 139 these cartilages become flattened and very solid, much more like their counterjjarts in the Shark than what is seen in the more specialised forms of fishes. I have followed the changes that take place in these parts, through about nine stages, for a lesser number would not have given me all I wanted in searching after the meaning of this transformation. Before this rod be- comes ossified, a thin superficial plate of bone, attached to, and grafting itself upon, a thick superficial slab of cartilage, appears above and outside the lower two- thirds of Meckel's cartilage. The bone is the well- known dentary of ganoid and bony fishes ; the slab of outer cartilage answers to the small lower labial of a common Shark, and to the huge massive lower labial of a Chimsera. I have repeatedly shown that the upper and lower jaw of those kinds of fishes is formed by the bending of the first internal gill-arch over the cavity of the mouth. The upper jaw, then, of a Shark, is, in technical language an "e23i-branchiar' element, the lower jaw is the " cerato-branchial" of the same first post-oral arch. Above the Sharks and Skates, the joints or seg- ments of the gill-arches become ossified, and each piece is further segmented into two, so that above the epi- branchial w^e have a " pharyngo-l)rancliial," and l)elow the cerato-branchial there is generally a "hypo])ran- chial." These further subdivisions we may forget for the present ; they are very inconstant in the first and second arches of the throat. 140 MAMMALIAN DESCEXT. [Lect. V. Very soon, whilst the su^jeriicial bone is forming hj transformation of the superficial cartilage, a thick, solid har of bone is formed in the front third of the Meckelian rod of the embryo Hedgehog. The upper part of the cerato-l)ranchial bar becomes detached after a time, but not until it has become ossified ; this ossification is arrested, to form the malleus (or hammer bone) of the middle ear. The huge epibranchial, or upper jaw of the Shark, is represented in the Hedgehog by two tracts of cartilao'e, one small and the other laro:e. The large cartilage is the hinge j^^i't — the hinder region of the upper jaw. The fore part, which in the Shark carries the upper teeth, is represented by an oval segment of solid hyaline cartilage, which becomes con- verted into the hamular process of the pterygoid bone ; the larger hind piece liecomes the incus, or anvil. The stapes is stirrup-shaped, and is, as I have l)efore stated, the phar^mgo-branchial element of the perfect hyoidean (or second arch). There is a ring, partly cartilaginous and partly bony, formed round the intersj^ace (cleft, or tympanic cavity) of these two arches. The inner part is bony, and forms the annulus, or osseous ring for the ear-drum ; the next is a partly segmented series of cartilaginous annuli or rings forming the coating of the meatus externus or ear-porch, which ends in the concha or projecting j^art of the ear. The wdiole of this latter structure is a specialisation of the familiar " spiracular ray" of the Shark — that small Lect. v.] arches of the fac;e. 1 4 1 cartilage wliicli supports the memljranoiis flap (operculum) of the blow-hole between the eye and the ear. There is nothing new in the main part of the skull containing the brain ; in the skeleton of the organs of special sense ; or in the superficial parts of the head — snout, lips, outer ears, and the like ; they are all de- velopments of old things, familiar to the anatomist in low, fishy forms. 142 MAMMALIAN DESCENT. [Lect. V. ADDENDUM TO LECTURE V. Here, again, I may remark that it does not enter into my plan to give an exhaustive bibliograjDhy, whether zoological, anatomical, or palseontological, but merely to set down the titles of such works as have been most useful to me in my special line of research, and which, therefore, may be of use to the reader. With regard to the fossil tyjDes that suggest so much as to the develoi^ment of the existing ]Mammalia, of which I have spoken in this fifth lecture, it seemed to me that it would be worth while to give a list of some of the papers, memoirs, and larger works that have come to hand during the last ten or a dozen years. The Catalogue of the Eossils in the Hunterian Museum belongs to an older period ; but it is very valuable, for it contains Professor Owen's description (with splendid plates) of the extinct Ghjxjtodon. BIBLIOGRAPHICAL LIST. Bettany, G. T. Esq., M.A., B.Sc, "On the Genus Meryochoerus (Family Oreodontidce)^ Avith Descriptions of Two Xew Species." Quart. Jour, of Geol. Soc, London, Aug. 1876, pp. 259-273, plates 17-18. Cope, Professor E. D., " On the Extinct Vertebrata of the Eocene of AVyoming, observed by the Expedition of 1872, with Notes on the Geology," U.S. Geol Survey, 1872, pp. 546-612. " On the Flat-clawed Carnivora of the Eocene of Wyoming." Read before the American Philosophical Society, April 4, 1873, pp. 1-12, plates i.-ii. " On the Short-footed Ungulata of the Eocene of AYyoming." Read before the American Philosophical Society, Feb. 21, 1873, pp. 1-37, plates i-iv. — "' On the Primitive Types of the Orders of Mammalia Educabilia." Read before the American Philosophical Society, April 18, 1873, pp. 1-8. Lect. v.] BIBLIOGRAPHY. 143 Cope, Professor E. D., "Report on the Stratigraphy and Pliocene Vertebrate Palaeontology of Northern Colorado," Bull. U. S. Geol. and Geog. S^irvey of the Territory , No. 1, pp. 1873, 9-28. " On the Homologies and Origin of the Types of IMolar Teeth of the Mammalia Ediicabilia," Philadelpliia, March, 1874. " Report on the Extinct Vertebrata obtained in New Mexico by Parties of the Expedition of 1874," U. S. Geol. Survey^ part ii., vol. iv., Palaeontology, 1877. " On the Brain of Coryphodon." Read before the American Philosophical Society, March 16, 1877, pp. 616-620, plates i.-ii. — "On the Brain of Procamelus occidentalis." Read before the American Philosophical Society, May 4, 1877, pp. 49-52, plate i. — " Second Contribution to a Knowledge of the Miocene Fauna of Oregon." Read before the American Philosophical Society, Dec. 5, 1879, pp. 1-7. — " The Relations of the Horizons of Extinct Vertebrata of Europe and North America," Bidl. U. S. Geol. Survey, vol. v., No. 7, pp. 33-54, 1879. -- - " Observations on the Faunae of the Miocene Tertiaries of Oregon," Ihid., vol. v. part i., pp. 55-69, 1879. — " The Genealogy of the American Rhinoceroses." Amer. Naturalist, October 1880, pjx 610, 611. — " On the Genera of the Creodonta." Read before the American Philosophical Society, July 16, 1880. — " On the Foramina Perforatino: the Posterior Part of the "o Squamosal Bone of the Mammalia." Read before the American Philosophical Society, Feb. 16, 1880. Flower, Professor W. H., F.R.S., " The Extinct Animals of North America," a Lecture delivered at the Royal Institution of Great Britain, Friday, March 10, 1876. art. "Mammalia," Encyc. Brit., vol. xv., 9th edit., 1883. IV., >> v.. J> VI., Key to the Questions in Arithmetic in 2 Parts, each 6d 9d. IS. od. IS. 6d. 2s. od. *^* Each Book of this Series contains within itself all that is necessary to fulfil the requirements of the Revised Code — viz., Reading, Spelling, and Dictation Lessons, together ^vith Exercises in Arithmetic for the whole year. The paper, type, and binding are all that can be desired. "The Books generally are very much what we should desire." — Times. 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