i, i tea en a hahah i ALBERT R. MANN LIBRARY AT CORNELL UNIVERSITY Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924002872376 MAMMALIAN DESCENT. By MM. ETHERIDGE and SEELEY. Part I., Handsome Cloth, Price 18s. A MANUAL OF GEOLOGY. By JOHN PHILLIPS, M.A., LL.D., F.R.S., Late Professor of Geology in the University of Oxford. Re-written and Edited by R. ETHERIDGE, F.R.S., and H. G, SEELEY, F.R.5. Part I.—PuysIcat GEOLoGy, and PaL.ZonTroLocy. By Prof. SEELEY, F.R.Ss. With Illustrations and Frontispiece in Chromo-Lithography. 18s. 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 Dractical Medicine. By Dr. L. LANDOIS, PROF. OF PHYSIOLOGY, UNIVERSITY OF GREIFSWALD. Translated from the Fourth German Edition By WM. STIRLING, M.:D., D.Sc., REG. PROF. INSTS. OF MED., UNIVERSITY OF ABERDEEN. With very Numerous Illustrations. CHARLES GRIFFIN & COMPANY, LONDON. ON MAMMALIAN DESCENT: THE HUNTERIAN LECTURES FOR 1884. BEING NINE LECTURES DELIVERED IN THE THEATRE OF THE ROYAL COLLEGE OF SURGEONS DURING FEBRUARY, 1884. BY W. KITCHEN PARKER, F.R.S., HUNTERIAN PROFESSOR, ROYAL COLLEGE OF SURGEONS OF ENGLAND. With Addenda and Ellustrations, LONDON: CHARLES GRIFFIN & COMPANY, EXETER STREET, STRAND. 1885. [All Rights Reserved.] fe CORN ELL UNIVERSITY: LIBRARY , TO MISS ARABELLA BUCKLEY (Mrs, FisHer) This little Work is J$nscribed AS A SLIGHT MARK OF REGARD AND ESTEEM BY HER FRIEND THE AUTHOR. PREFACE. For many years past I have 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 the plan of this last course. The following Lectures, therefore, I offer to my non- val PREFACE. scientific friends as slips and cuttings from the Biological Tree, in the belief that the great and absorbing question with which 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 dificult to put into language which can be appre- ciated by those who are not familiar with its special methods, its facts, and its descriptive terms. One thing I cannot pass over without remark, and that is, the strong and almost insuperable a priori objection in many minds to the deductions of modern Biology; this must neither be lightly overlooked nor treated flippantly. 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 be 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. vii 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. PARKER. Lonvon, November 1884. TABLE OF CONTENTS. The New Things of Hioleey, Time, the Sexton, Duckbill and Echidua, Groups of the Mammalia, . Charles Darwin, : % The first Historical Man, . The Australian Region, , The first Creature with Nails, . Primary Amphibia, . Protozoa and Metazoa, Low Ancestral Types, Family Arrangements, LECTURE 1 INTRODUCTORY. Page 1 | Care of the Offspring, 2 | The Crown of Creation, 3 | Larviform Embryo of the Mole, 4 | Great Weights on Sinall Wires, 5 | Influence of Surroundings, 6 | Adaptation or Extinction, 7 | Metamorphosis of the Frog, 8 | Man’s Ancestors all buried, 9 | Eastern Cosmogony, 10 | Hyperbolical Asiatics, 11 | A Buddhist Miracle, 12 | Antiquated Theories, LECTURE II. ProToTHERIA (MoNOTREMATA). The Duck-billed Platypus, Negative Evidence, . The Ceratodus a Gift of Provi- dence, . , The Lancelet and Sea- squid, The Axolotl, . Lower parts “of the Earth, . Mammalian Advance, ‘ The Prototheria quasi- -Reptilian, Shoulder-bones of Duckbill, Three Collar-bones in Mono- tremes, . . . : Extinct Birds, ; b Feeling the Way upwards, The Duckbill’s Skull, Opening a new Scroll, Hingeing of the Lower J aw, Surgery or Horticulture, _. Revaindon of the Lower Jaw, 25 26 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 Eggs, Evolution of a Hairy Creature, . Relation of Mammals to Reptiles, Jacobson’s Organs, Old and New Structures, . A Country without Birds, Skeleton of the Prototheria, Primary Respiratory Organ, . Respiration of a Soft-shelled Turtle, . Oxygen consumed in Phar yngeal Respiration, . CONTENTS. LECTURE III. ON THE MaRsurIALs, OR PoucHED ANIMALS (METATHERIA). A Supposed Common 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, Root- Page A Bye-path Meadow, The hard alate, A Semi-Marsupial Insectivore, . 3 Crocodile, Bird, and Opossum, . The Turkish Saddle, 2 The Stirrup and Columella, The Arch of the Tongue, . Mimetic Types, Works on the Marsupials, Fossil Marsupials, An Oak Tree, . The Australian Flora ‘and Fauna, Frogs and their Progeny, . ‘i Newts and Frogs, Nourishment of Early Germ, Development of the Germ, LECTURE IV. Distribution of the Edentata, Specialisation of Low Types, Nature’s dull Children, The Struggle for Life, Dwarf Edentata, The Extinct Glyptodon, Hair turned into Armow, The Aard-Vark, A stunted Genealogical Tree, Isolation of the Edentata, Variation of the number in the Neck-Joints, . é m ‘ Dying out of the Teeth, . When the Vertebrata’ had no Lungs, . i The Hard Palate, ‘ The Deep Things of Mor phology, Skull of Sloth and Ant- -eater, Toothless Jaws, The Feeble-faced Pangolin, EDENTATA, 90 | A new Hinge for the Lower 91 Jaw, . 92 | Nature’s Amputations, : 93 | Structure, Habits, and Classifi- 94 cation of the Edentata, . 95 | Papers on the Edentata, . 96 | Ant-eaters and Pangolins, 97 | The Captive Pangolin, ‘ 98 | Strong Evidence ‘for Darwinism, 99 | Gigantic Sloths, Ant-eating Birds and Lizards, 100 | Food and ‘Safety, 101 | Love of Offspring, Mother Carey, . ‘ 102, An Unclean Sacrifice, 103 | Southey as a Darwinian, . 104 | The Green Turtle and the @lyp- 105 todon, . 1066 Plucking up Cedars, . 107 | The Grave of the Giant, LECTURE V. Materials for Work, Edentata and Insectivora com- pared, . . . The First Beast- namer, 7 Development of the Whale and the Bat, : Organic Root-stocks, INSECTIVORA, 125 | Wasted Types, . | Adaptive Changes, 126 | Ungulate Lemurs and ‘other 127 Generalised T 'ypes, The Number Five in Digits, 128 | Plastic Types, . 129 | Layers of the Skull, . 132, 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 130 131 133 134 135 136 The Hedgehog’s Skull, Skull of Cartilaginous "Fishes, Ear-drum of Hedgehog, . ' Parts of the Palate and Ear in Hedgehog’s Skull, ; ; CONTENTS. Page 137 138 139 140 Arches of the Face, ss Primitive Types of Mammalia, a Bibliography, . - Fossil Horses, . . Extinct Mammals, LECTURE VI. INsEcTIVORA—continued. The Mole very Archaic, Greediness of the Mole, Blind, but Quick of Hearing, Development of the Mole, Records of Lost Types, . An Hereditary A greuiturist, The Formation of the Tissues of the Mole, A Dry Skull, . ‘Air-Galleries of the Ear, Labyrinth of the Ear, 146 147 148 149 150 151 152 153 154 155 Diet of the Mole, . : Red Teeth of the Shrew, . Young of the Shrew, Skull of Shrew, a Young of Shrew like Eocene Mammals, . Distribution of the Shrew. 5 Browzing and Grazing, Improvement of Breeds, Homo diluvii testis, Signs of Transformation, LECTURE VIL INSECTIVORA—concluded, Foreign Insectivora, . Mascarene Types, Skull of the Tenree, . p Nasal Labyrinth of "the Tenree, . Lesser Kinds of the Centetide, . Crested Skull of the ie, Wallace’s Line, A Complete Orbital Ring, | The Young Colugo, p A Puzzling Type, A Tertiary Rat, 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, ‘i 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, LECTURE VIII. Tue REMAINING ORDERS OF MAMMALIA. The Chironter By ‘ 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, 188 189 190 191 192 193 194 195 Zoological Position of Lemurs, . Diet of the Aye-aye, . The Carnivora, . Aquatic Mammals, The Quadrumana, The Pig and the Runinants, Evolution of the Horse Type, Xl Page 141 142 143 144 145 156 157 158 159 160 161 162 163 164 165 196 197 198 199 200 201 202 Xil CONTENTS. LECTURE IX. ConcLusIon, Page Metamorphosis of the Dragon- Searchers for Facts, . Yo . 203 | Dry Light, The Possibilities of Being, . 204 | Anew ‘Atlantis, Soul and Body, : . 205 | Quotations from Bacon, Human Longings, . 3 . 206 | Second Causes, . Waves and uses, ‘ 207 | Gentle Modifications, Arrested and Developed Types, 208 | A Tithe-Farmer, . Our Forefathers, . 209 | Goethe on the Teleologists Astronomy, Geology, Biology, . . 210 | The Seal, . ‘ The Links of Created Being, . 211 | Time- Marks, 5 Our Growing Knowledge, . . 212 | Plants and Animals,. The Currents of Protoplasm, . 213 | How the Bones Grow, Embryological Work, F . 214 | Exogenus Growth, . é Written on the Brain, =. . 215 Expansion of Modern Thought, : Page 216 217 218 219 220 221 aoe 223 224 22s 226 227 228 229 MAMMALIAN DESCENT. LECTURE IL INTRODUCTORY. Brier 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 type 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 2 MAMMALIAN DESCENT. [Lecr. 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: myriads 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 first tasted milk. Lect. I.] DUCKBILL AND ECHIDNA. 3 The group, class, or family—as we may call it—which 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- bell 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 affect our argu- ment. Mammalian remains will, I feel sure, turn up some day from older rocks: anyhow, in certain strata 1 The Monotremes are so called because they have only one common outlet to their body, as in Reptiles and Birds; Marsupials are so called because they possess a marsupium or pouch. : 4 MAMMALIAN DESCENT. [Lucr. I. of the Secondary epoch we get various remains of the group above the Monotremes—the Marsupials. Professor Huxley’s classification of the mammals is as follows :— 1. Prototheria, or the Monotremes : examples—Duck- bill 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 Marsupials: examples—Opos- sum, Phalanger, 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 types 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. Lxcr. I.] CHARLES DARWIN. 5 2. The Palzontologists. These study the fossil re- mains of the extinct forms, and their past 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. 1. the earth, will reap the richest reward, and have the highest honours. For, the paleontologist, 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 weaving this web of words 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 page at its very beginning. Now let us leave Man, and go down among the beasts; they are delightful creatures,—“what God Lect. I.] THE AUSTRALIAN REGION. 7 hath cleansed” [made pure and beautiful] “that call not thou common.” Of the Prototheria (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 Ornithorhynchus, and the Echidna. The former is the lower of the two 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 scaffolding to our facts, we are out of our place in attempting 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 Ornithorhynchus ; 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 birds; but 8 MAMMALIAN DESCENT. [Lecr. I. in which there are characters much more archaic than anything seen in Serpents, Lizards, Tortoises, Crocodiles, or in Emeus. Therefore the existing reptiles and birds must stand aside as having nothing 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 metamorphosis is seen in the Ganoids, and more in the Lamprey; but with the Amphibia (Newts and Salamanders, Frogs and Toads), it is in the larval, or grub-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 Vertebrata. I speak of this for two reasons :—first, I find things in it which are quite like what are to be seen in the Leocr, I.] PRIMARY AMPHIBIA. 9 Duckbill, but which 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 Vertebrata, 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 primary 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 Royal Society, however, has lately, with great liberality, furnished certain scientific Knights with means 10 MAMMALIAN DESCENT. [Lucr. 1. for following this 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 Huxleyan 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 in science. All the animals above the Protozoa (first creatures) are called “ Metazoa,” because they undergo remarkable changes of form, beyond 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 pre-natal, 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 transformation whilst in the egg ; a Frog is marvellously metamorphosed during its active life. Lect. I.] LOW ANCESTRAL TYPES. 11 The early transformations of those types which 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 Vertebrata, 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 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 12 MAMMALIAN DESCENT. [Lecr. 1. 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 low, 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 of paternity, maternity, and time. The surroundings are often cruel and destructive ; yet nature does not temper 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. 13 some cases, nature teaches even the stupid husband to do his part in wrapping up 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 “Preecoces” and “Altrices ;” 14 MAMMALIAN DESCENT. [Lxcr. I. it is among the latter, whose 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 Man from the Lorp.” 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 way 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 wrought 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. Lecr. I.] LARVIFORM 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. Tn all we have the curved, larviform creature, with its Fia. 1.—Embryo of Mole (Talpa europea, 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-shaped 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. ‘[Lecr. I. length, the special characters 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 toa Lion, or to a Gorilla, as far as its outer form is concerned. And yet an embryo of this kind—a sort of temporary, sleeping, dependent larva—becomes, in one case, a Rear- 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 tlie 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. Whale’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 which, whilst as yet it is unborn, is as large as a good-sized cow. This phenomenon of development, which 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, 1.] INFLUENCE OF SURROUNDINGS. 17 that one and the 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 swr- 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 sensitiyeness of a living creature to outward impressions is excellently put by our great poet. He says that you cannot press your hand with a rush, but it will bear a visible mark or cicatrix, and that the eyes do shut their coward gates on atomies. The infinite number of delicate and gentle modifica- tions in the human form, all speak eloquently of the influence of “surroundings.” All the races of this type are evidently varieties of one common species ; 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 18 MAMMALIAN DESCENT. (Lecr. I. off. On the other hand, in the 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 metamorphosis has saved them from death, and kept them alive in famine. Speaking of metamorphosis, 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 types. 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 possibilities 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 him. Such a developmentalist would fare as Bruce, the traveller, fared, when he related his adventures, telling of the sights his eyes had seen— “ All he gets for his harangue is—‘ Well! What monstrous lies some travellers tell.’ ” Lect. I.] METAMORPHOSIS 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 ina 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 Vertebrata, 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 type 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. [Lecr. I, but ‘ your young men, shall see visions.’” Now, if one of the bright young soldiers in our rapidly increasing army were permitted to see the whole web (woof and warp) of organic life, he would everywhere see glimpses of the human face divine; the features of the latest creature would be traceable in the face of the earliest. Yet these types and foreshadowings of the great Reasoner, to be developed 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. ADDENDUM TO LECTURE I. That which is biological in the foregoing Lecture will be con- sidered and treated of from time to time in the succeeding 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; 12nd edition. London: Williams & Norgate. 1880. Lecr, 1] EASTERN COSMOGONY. 21 the second is Religious Thoughts and Life in India,! by Professor Monier Williams, M.A., C.LE. Part I., Vedism, Brahmanism, 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 :— “Tn the beginning there was neither nought nor aught ; Then there was neither sky nor atmosphere above. What then enshrouded all this teeming universe ? 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. Nought else but he there was—nought else above, beyond. Then first came darkness hid in darkness, gloom in gloom ; Next 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 Nullity.”—Page 13. “Fyrom glowing heat sprang all existing things, Yea, all the order of this universe (Rita). Thence also Night and heaving Ocean sprang ; And next to heaving Ocean rose the Year, 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.”—Page 404. 1ZLondon: John Murray, 1883. 22 MAMMALIAN DESCENT. [Lecr. 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 magnifies with a vengeance ; take one example :— “The Asurs, who reside under Maha Méru, 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 in size; the joints of his fingers, 800 miles; the sole of his foot, 12,000 miles ; from his elbow 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 kinds 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 késara. The first is dove-coloured, and eats grass. The third is like a brown bull, and eats flesh. The késara lion, which 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 lines, 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 pieces of gold. The rest of the body is white, like a piece of pure lime. When he issues forth from his golden cave, and ascends a rock, he places his paws towards the 1 Of course, I refer to these Aryans who adopted the Buddhist tenets. Lecr. 1.] A BUDDHIST MIRACLE. 23 east, breathes through his nostrils with a noise like the thunder, shakes himself like a young calf at its gambols, that he 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 cubits 3 upon 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 wing of the flying bird remains ex- panded in the air, and the fin of fish becomes motionless.”—Page 17. Among the Legends of Gétama 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 who 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 Gop created Wellingtonia gigantea, 400 feet high, in a moment.” 24 MAMMALIAN DESCENT. (Lect. I. This speaker, whose power of mental deglutition was so great, was one of our own calling, and, therefore; had undergone a biological training; surely we may hope that better days are in store for us, when no educated man will be in danger of falling into such a deep pit of beldef 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 Mallock’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 present combination of things arose. “ «For blindly, blindly, and without design, Did these first atoms their first meetings try ; No ordering thought was 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, Which slowly formed the earth and heaven, and man.’ ” —Page 93. The reader is also requested to look at the curious, abortive, unreasonable 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 Aristophanes.? 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 horrible Tartarus ruled in the storm.”——Page 30. 1 William Blackwood & Sons, Edinburgh and London. 1878, ° Sir John Hookham Frere’s Translation. Cambridge, 1883. Lecr. IL] THE DUCKBILLED PLATYPUS. 25 LECTURE IL PRoTOTHERIA (MoNnoTREMATA). THE lowest, or teatless mammals, still linger in the Australian region, in the form of the spiny Ant-eater, or Echidna, and the great Water-Mole (Platypus, or Ornithorhynchus). A few fossils have been found in this same region, and described by Sir Richard Owen as MAE Fic. 2.—Young of Ornithorhynchus paradocxus, one half the natural size. belonging to a larger species of Echidna than any of the three known existing kinds. But in the northern world (Arctogwa) no remains of any kind of Monotreme—Duckbill, or Echidna—have rewarded the labour of the paleontologist. Yet fossil marsupials have long been known in this hemisphere ; although, as Professor O. C. Marsh suggests, Microlestes the oldest of these—the jaws of which are found at 26 MAMMALIAN DESCENT. (Lect. IT. the bottom of the Secondary rocks—may belong to some simple primordial mammal, and not to a proper Marsupial. If this be so, we may have in those most precious, but also most puzzling, remains, the evidence of the existence of Prototheria (first beasts) with true teeth. The living forms of these Prototheria are either tooth- less, as the Echidna, or have only peculiar horny plates, as a succedaneum to true teeth, as in the Ornithorhynchus. That, at present, we are in the dark as to the early existence of forms of such surpassing interest to the Darwinian, is no proof that they have not had their day, and their reign, or dynasty, in this part of the world, long before the higher, or even the Marsupial, mammals. appeared. For negative evidence is literally no evi- dence at all in matters of this kind. A few years ago we had no evidence of the existence, in the geological strata, of birds with true teeth, nor of birds with a long chain of caudal vertebra, and distinct metacarpals. Now, however, two new additional orders of the bird class are known to have existed in the Secondary epoch, one as far below the other as the higher of the two is. below ordinary flying birds; the newest of these kinds possessed teeth, and the lowest—the Archaeopteryx—had the metacarpals, or bones of the hand, distinct, and the joints of its tail developed and elongated, whereas in existing birds they are aborted. All attempts at keeping back the tide of modern biology are but imitations of the labours of Sisyphus ; Lect. Il.] THE CERATODUS A GIFT OF PROVIDENCE. 27 people who do this vain thing are emulating the fame of the renowned Mrs Partington, endeavouring with her mop to keep back the Atlantic waves. Whatever the famous Triassic jaw of Microlestes may turn out to be, it must not be left unnoticed that its owner co-existed with a fish (Ceratodus), that still co- exists with Monotremes and Marsupials in the Australian region. The living Ceratodus is a waif or stray from a nearly lost order of fishes—the Dipnoi, or double- breathers—fishes that possess both gills and lungs, and thus enjoy both aquatic and aérial respiration. Now such fishes as this Australian Ceratodus, as the African Protopterus, and as the American Lepidosiren, may have co-existed with the Ganoids, or fishes with enamelled armour, through much of the Primary period. Could this be proved, we should have a capital generalised stock, existing long before the period of the Trias, from which to derive all the lung-breathing forms, whether of Am- phibia, Reptiles, Birds, or Mammalia. Indeed, Professor Huxley is very bold in this matter, and suggests that Ceratodus is a special gift of Providence, kept for these latter days, to rebuke and convince the gainsayers of the truth of Darwinism. I cannot go into details; we walk here by faith as well as by sight. Imagine some low, ancient, simple form of fish, that did, by metamorphosis, become a creature as high as the Ceratodus. And that you may be able to see this hypothetical fish ascend, during its 28 MAMMALIAN DESCENT. (Lecr. IT, active lifetime, very far above its first condition, put be- fore your eyes the actual transformation of the 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 Verte- 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 (Dzpnor), 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 type, richly charged with morphological force, might transform again and again—undergo, under the stimulus of necessity, further metamorphoses. For having both outer and inner gills, 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-types of the higher organic forms. Lect. IT.] THE AXOLOTL. 29 Iam purposely forgetting, for the time, the slow accre- tion of minute variations, taking place through countless ages of time, and am considering sudden, per saltwm, transformations. Whenever and wherever it became 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 have taken place. The morphological foree—the indwelling spirit of protoplasm—actually did perform these wonders ; thus we have still living in abundance, reptiles that 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 Awolotl’ staring me in the face, I cannot suppose even that to be impossible. But when I imagine double-breathing fishes undergoing metamor- phosis in the olden times, [ 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 types have 1That large Mexican Salamander generally continues in a low larval state throughout life, but pow and then it becomes transformed, loses its gills, and becomes a member of a higher family. 30 MAMMALIAN DESCENT. (Lecr. II. risen altogether far above the level or platform of their ancestors. With regard to the Prototheria (or first beasts) I am of opinion, 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- rhynchus) both on the dry land, and in the brooks and streams of water that then drained the land. It is the business of the paleontologist 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 paleontologist 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 yielded me results ‘Lect, IL] MAMMALIAN ADVANCE, 31 that suggested a greater nearness of this little delver to the great Water-Mole, the Ornithorhynchus of Australia, than had been imagined. Proof is not wanting, 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 grown 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 registers we have extracted from the growing 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 infallible morphological law. This witness is true: and truth so attested may be followed by anyone, little fearing where it will lead him. Ihave 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 Ornithorhynchus itself—the great Water-Mole. 32 MAMMALIAN DESCENT. (Laer. II. The structure and development of this type is both Reptilian 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 practical metamorphosis into exquisite 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 by 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 respect, even the common Mole is a high and noble creature in comparison with the Ornithorhynchus, 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 hip- Lect. II.] SHOULDER-BONES OF DUCKBILL. 33 girdle carries a pair of epi-pubic (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, NPs Fic. 8.—Shoulder-girdle and sternum (breast-bone) of Ornithorhynchus paradoxus, two-thirds natural size. s.sc, supra-scapular region of scapula (shoulder-blade, sc) ; m.sc, middle scapular region ; cl, clavicle; ¢.cl, inter-clavicle, cr, coracoid bone ; e.cr, epicoracoid; gl, glenoid cavity, the head of upper arm-bone (humerus) ; mb.s, manubrium (top or handle) of sternum ; sé, sternum; .s, xiphoid end of sternum ; v.7, lower part of vertebral rib; 4.7, intermediate rib (as in Lizards) ; 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 shoulder-girdle, that we see the most remarkable signs of ancientness in the Prototheria. The scapula in them does not give off a C 34 MAMMALIAN DESCENT. [Lxcr. 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-bone) as a large and perfect coracoid. Here we have a condition like that which is seen in Amphibia and Sauropsida (Reptiles 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 Lect. II.] EXTINCT BIRDS. 35 these low beasts, or Prototheria, have a large median clavicle (interclavicle) besides, and all the three bones are simple, being merely ossified membranous tracts. So also are they in the Lizard tribe, and so were they in those huge whale-like Lizards of the Secondary epoch —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 clavicle. The old tooth-bearing birds of the Chalk had their clavicles distinct, as in the Emeu, and in embryo birds 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 beasts were derived lay as low down as that from which the earliest birds grew. Moreover, there is a sort of solid primitiveness about 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 type 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. {Lecr. IT. 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, eg., the Chameleon. That which makes the vertebra of a mammal differ from that of the higher oviparous types 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 vertebree of the tail in Ornithorhynchus. 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 Ornithorhynchus is by 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 Duckbill. That which 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- laginous cranium that forms the foundation of the finished ivory casket which, in the adult, so safely holds Lect. II.] THE DUCKBILL’S SKULL. at our brain and sense capsules. But in us, as soon as it is formed into proper cartilage, it is a mere basin; 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-cranium, 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 differ in the interpretation of some of the details; whilst anatomists generally, those, namely, who 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 38 MAMMALIAN DESCENT. [Lecr. II. prize of the work of my life—the interpretation of the form of Man and of his vertebrated kindred. For, in reading off the characters of the Ornithorhynchus, 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—Mav. 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 depresses the lower, and lifts the upper, jaw, and this is why these creatures are such skilled fly-catchers. Sir Charles Bell, in his charming work on the human hand, Fig. 4a. Lxcr, II.] HINGING OF THE LOWER JAW. 39 shows how this 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 Duckbill, as in mammals generally, the pier or hinge-piece is gone, and the mazilla inferior (or Fig. 4. Fie. 4.—Skull of Common Fowl (Gallus domesticus) one-half larger than specimen, px, premaxillary ; mx, maxillary; v, vomer; ”, nasal; eth, ethmoid ; J, lacrymal ; pe, perpendicular ethmoid ; ws, presphenoid ; I, olfactory nerve ; 70.8, interorbital space ; 0s, orbitosphenoid ; /, frontal ; nf, post-frontal ; p, parietal ; sg, squamosal ; 8.0, superoccipital ; 7.0, jugal process of squamosal; eo, exocciptal, V, 5th nerve ; II, opticnerve ; ¢y.c, tympanic cavity ; b¢, basi-temporal ; g, quadrate ; pg, ptery- goid; pa, palatum ; 7, jugal; gj, quadrate-jugal ; ».ap, posterior angular process ; tap, internal angular process; avr, articular; ag, angular; sa.g, supra-angular ; d, dentary. Fic. 4a.—Auditory Columella of Fowl, magnified 6 diameters, and shown 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 quadratum,” as the bird’s jaw-pier is called? The answer is, that in the mammal there takes place a 40 MAMMALIAN DESCENT. [Lecr. 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 Fic. 5,—Auditory Chain of Bones from the Middle Ear of a New-born Pig (Sus scrofa), magnified 5 diameters. mi, malleus (hammer); pyr, processus gracilis of malleus ; mb, manubrium (handle) of malleus ; spm, short process of malleus ; i, incus (anvil); sc.z, short process (crus) of incus; Ici, long process of incus; st, stapes (stirrup) ; stm, stapedius muscle ; chy, 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. Al grafting purposes—a mass of cartilage which 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, Reptiles, Amphibia, Osseous Fishes, Ganoids, Skates, and ordinary Sharks, and not until we come to the extraordinary Sharks or Chimeroids 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 Fic. 6.—Mandible (Lower Jaw) of an Embryo Pig, 3 inches long, magnified 34 diameters ; inner view. mk, Meckel’s cartilage; d, dentary bone; cr, coronoid process ; ar, articular process (condyle); ag, angular process ; mZ, malleus ; mb, 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 oviparous types, there is a second splint, the splenial, and behind A2 MAMMALIAN DESCENT. [Lecr. IL. it a third, the coronoid. These can also be traced in the jaw of a young Ornithorhynchus, 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, (1) 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 bone, is attached to the skull over the tympanic cavity, and that ‘is also the place 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 snag for muscular attachment, for it has no Lecr. II.] BONES FORMING THE EAR-CHAIN. 43 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- bill, 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 compound jaw of the ovipara are found as small separate pieces. After long years of labour and much vacillation of mind on the matter, ] 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 inside of the cavity of the ear-drum or “ middle ear,” are called malleus (hammer), incus (anvil), and stapes (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 Philosophical Transactions of the Royal Society, 1869, plate lxxxvii. ; and 7éd., 1874, plates xxxiv.-XXXVii. 44 MAMMALIAN DESCENT. [Lect. IT. oval window (fenestra ovalis) that lies between the drum. cavity and the vestibular part of the labyrinth of the ear. That bone (the stapes) exists in Birds and Reptiles, 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 ‘Lect, IL] THE EGG-BREAKING 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 mamila 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 Iam 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 Ornithorhynchus. 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. [Lecr. II- finished labials (lip-cartilages) of the types just refered 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 Hustachian 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 Red Sandstone. So much is this the case, that it is difficult 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 differs from that of the adult Toad, into which 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 paper in the Philosophical Transactions of the Royal Society, 1876, plates lvi.-lix. Lecr. II.] ANCESTORS OF THE MAMMALIA. 47 much as, or more than, the skull of the Ornitho- rhynchus 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 types ; they have had plenty of time for such changes. ADDENDUM TO LECTURE II. BrpuioGRAPHY: REFERENCES TO WORKS AND PAPERS TREATING OF THE Ornithorhynchus anD Echidna. Armit, Captain Wittiam E., F.L.S., “Notes on the Presence of Tachyglossus and Ornithorhynchus in Northern and North Eastern Queensland,” Proceedings of the Linnean Society, Zoology, vol. xiv., 1879, pp. 411-413. Bewvyert, Dr Grores, F.L.S., F.Z.8., &c., Gatherings of a Naturalist in Australia. London: John Van Voorst. 1860. Fruowrr, Prof. W. H., LL.D., F.R.S., An Introduction to the Osteology of the Mammalia. London: Macmillan & Co. 1876. Article “Mammalia” in the Encyclopedia Britannica, 9th edit., vol. xv., pp. 377-378. Houxuey, Prof. T. H., LL.D., Pres. R.S., 4 Manual of the Anatomy of the Vertebrated Animals, pp. 319-323. London: J. & A. Churchill. 1871. 48 MAMMALIAN DESCENT. {Lzcr. II. Huxiey, Prof., “On the Application of the Laws of Evolution to the Arrangement of the Vertebrata, and more especially of the Mammalia,” Proc. Zool. Soc., Dec. 14, 1880, pp. 649-662. Liexen, Dr Ca. W., “A Letter to the Secretary of the Zoological Society,” Proc. Zool. Soc., March 4, 1884, pp. 150-152. Moris, Dr James, F.Z.8., &, “Remarks on the Skull of the Echidna from Queensland,” Proc. Linn. Soc. vol. xiv, Zoology 1879, pp. 413-417. See also Captain Armit’s “‘ Notes,” supra. Owen, Prof. Ricwanp, F.RB.S., I. “On the Marsupial Pouches, Mammary Glands, and Mammary Foetus of the Echidna hystrix,” Philo- sophical Transactions, 1865, plates xxxix.—xli., pp. 671-686. II. “On the Ova of Echidna hystrix,” Philosophical Transac- tions, 1880, plate xxxix., pp. 1051-1054. Parker, W. K., F.R.S., “On the Shoulder-girdle and Sternum,” Ray Society's Publications, 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, Ornithorhynchus and Echidna (Tachyglossus and Acanthoglossus). In the figure of the young Ornithorhynchus 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, which 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.RS. “On Struthious Birds,” Trans. Zool. Soc., vol. iv., plates Ixvii®.—lxxvii., pp. 853-364. Lect. IL] ALL ANIMALS COME FROM 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 Ovoviviparous type, a sort of compromise between a Reptile and a Mammal. That may be true, for all animals come from eggs,—ommne animal ex ovo,—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 waters under the earth, if they would escape them. It is, I think, more than probable that the original Prototherians possessed teeth ; yet these may have been, and most probably were, of a still siinpler type than those of Opossums and Kangaroos, from whose teeth we start in making an ascending survey of these organs in the Mammalia. It is not unreasonable to think that the mammals which have degene- vate teeth, such as Sloths, Armadillos, the Aard-Vark, might serve to give us some idea of what this primitive Mammalian dentition was like. Anyhow, if they had a good mouthful of teeth, their upper and lower jaws did not resemble those of their highly modified descend- ants ; probably they were very much like what we see in the least specialised of the living Marsupials, 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 appears, but appears shorn of that covering, it has to be borrowed, again, from those types in which it had not been suppressed. ‘‘Unto 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 MAMMALIAN DESCENT. (Lect. IT. 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 psychical as well as physical, for in that type, which is only, for a while, 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 Archaic 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 Hchidna. 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 nothing wonderful if some of his descendants should 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 —“Tf the term Reptélian 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 1 See Proceedings of the Royal Society for June 1884, p. 80, Lecr. II.] RELATION OF MAMMALS TO REPTILES. 51 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 (Stelléonide, 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, guoad hoc, in this and that point in their organisa- tion; in other respects they have kept in a low estate, having the slow temper 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 precluded 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 reptilian nature of these prim- ordial beasts. In the mid-region of the Vertebrata, 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 Rathke, in the Snake, under the term “nasal glands”; that term was adopted by me in my papers on the Skull of the Snake and of the Lizard.’ In those papers the contained organ was not described, as not being in my plan, 1 See my memoir on the ‘‘Shoulder-Girdle and Sternum,” Ray Society Publications, 1868, plate xxii. fig. 13. 2 Philosophical Transactions, 1878, ‘plates xxvii.-xxxiii., and 1879, plates Xxxvii.-xlv. 52 MAMMALIAN DESCENT. [Lecr. IT. but the bones and cartilages that encapsule it were carefully described, and copiously illustrated. In those types we have the culmination of these organs, which have some mysterious connection with the organ of smell; the jirst or olfactory nerves give off fibres to them. If these organs have their height in these Reptiles, they have their decline in Man, who, however, in an early stage, possesses them, as Professor A. Kélliker’s invaluable researches show, both those .pub- lished at Leipzig in 1877, and those much later, at Wiirzburg in 1883. For an abstract of this last piece of research I am indebted to the excellent “Summary” in the Journal of the Royal Microscopical Society, for April 1884, pp. 201-203. The concluding sentences. of this abstract are as follows :—‘“ From the rich possession of nerves by Jacobson’s organ in an eight-week old embryo, and their dis- appearance in older embryos, we may conclude that the organ is now in arudimentary condition as compared with what it was in ancestral forms.” Now, on one hand, in Serpents, and Lizards, we have these organs and their related skeletal parts, both cartilaginous and bony, highly 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 le 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 Marsupials, 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 Mammals they are well encapsuled by cartilages growing back- wards from the snout. In the Mammals only one pair of small bones assists in protecting the soft gland-like organ ; in the Reptiles it lies on each side, as in a dish, formed by a bone, the so-called vomer (plough- share), and it is covered in by another bone which serves as an elegant Lect. II.] OLD AND NEW STRUCTURES. 53 lid, not present in the mammal, the so-called “turbinal.”! Those who are biologists, and care to go into this matter, will do well to refer to Wiedersheim’s Lehrbuch dev Vergleichenden Anatomie der Wirbelthiere, Jena, 1883. In my forthcoming paper on the Edentata there will be found a Bibliographical List of various Memoirs 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 development 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 Vertebrata, 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 realy new ; they are merely expansions and improvements, so to speak, of things as old as the hills. It is just possible that in the Vertebrata of the Primary Rocks 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 up 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 insensible modification, for an almost unlimited amount of variation; but per saltwm 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 Frog, for instance—are amongst the most amazing of all pheno- 1 Both those paired bones were named as above by Cuvier, and both erroneously ; the Science of Embryology scarcely existed in his days, and many of these things can only be interpreted by an embryologist. 54 MAMMALIAN DESCENT. [Lecr. IT. mena. They remind one of the 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-builders—that have tender nestlings. These young, sweltering in their soft nest, and almost smothered by their feathered mother, whose 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 blood itself is apparently equal in both cases, and in both cases affects the temper of the mother-bird. At that time the true maternal courage rages ; at that time ‘a Wren 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 gone on from age to age 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 her 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. The 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.” Now, if for the sake of Biology 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 Duckbill and Echidna that are manifestly reptilian, or quasi-reptilian -— 1. Jacobson’s Organs are about equal in their development to < Lect. IL] SKELETON OF THE PROTOTHERIA. 55 what we find in Serpents and Lizards, where they have their culmina- tion, 2. The skull itself has 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 larve seen in any metamorphosing type whatever—for example, in Dacty- lethra capensis, 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 Reptile’s mandible, whilst the madleus (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 (dncus) has not taken on the normal Mammalian form, but isa mere flat segment of ossified cartilage ; it isa very small “quadratum” or equivalent of the hinge-segment of the Reptilian mandible. 6. The stapes (stirrup-bone) is not normal, it is merely a Reptilian columelia, 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 vertebre of the spine, as a rule, are devoid of the normal Mammalian bony plates that are added, fore and aft, to the body of each vertebra, to take off the shock in the quick movements of high and agile types. 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, quite like those of Reptiles and Birds, and there is, as in them, no differentiation or subdivision of the terminal outlet. So that these creatures are just plucked out of the Reptilian group by their shin, with its hairy covering and its rudimentary milk-- glands. Severely apply to themthe rule “Cucullusnonfacit Mc onachum,” and say—‘ The skin does not make the beast,” and back amongst the Reptiles they would have to be driven. 56 MAMMALIAN DESCENT. [Lacr. IT. After writing the above, I received from Professor Simon H. Gage, B.S., of Cornell University, Ithaca, 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 supposing a gradual melting down of the distinctions between the Amphibia and Reptilia will be at an end. The lining of the pharynx, or upper part of the gullet, is the proper normal respiratory organ of any creature possessed of a notochord, or primary spinal acts. All the various specialisations that may be found in Asetdians (Sea-squids), Amphioxus (the Lancelet), and in all the Vertebrata, are of secondary importance to the embryologist. The peculiar structure and functions of the pharynx described by Professor Gage may be due to degradation or relapse, but if so, it only proves that the aquatic was once the mode of respiration in the stock from which these Tortoises sprang. “Pharyngeal Respiration in the Soft-Shelled Turtle (Aspidonectes spinifer). By Simon H. Gage of Ithaca, N.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 present the Chelonian form of respiration is considered to be comparable with that of the mammal rather than with that of the frog, as formerly supposed. While, 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 Contributions 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 the ventral side of the body, from its rich network Lecr. II.] RESPIRATION 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 resemble 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 4a 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. “Tn 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 slightly open, and its floor would swell out, the swelling passing steadily onward to the throat. After a moment of quiet, the swelling 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, were very regular, occurring ten or fifteen times a minute. My observations were verified by Professor Wilder and several of our laboratory students. 7 a “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 aérial respiration. 58 MAMMALIAN DESCENT. (Lect. I. “It is hoped that during the coming year investigations may be completed which shall determine the exact amount of oxygen consumed in this pharyngeal respiration, and the structure of this unusual respiratory organ in the soft-shelled Turtle.”—From the Proceedings of the American Association for the Advancement of Sedence, vol. xxxii., Minneapolis Meeting, August, 1883. Lucr, III.] EMBRYO OF THE MARSUPIALS. 59 LECTURE ITI. On THE Marsuprats, oR PoucHED ANIMALS (MzraTHERIA). In their structure generally, the Marsupials are inter- mediate between the Monotremes and the placental or nobler forms of mammals (Eutheria). With regard to the development of their embryo, these types are far below the Eutheria, while they are most probably above 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 DESCENT. [Lacr. III. —Frogs and Toads—should show a tendency to become members of the Amniota, the higher gill-less types which develop an amnion and an allantois, two of the three membranes that enclothe the embryo. No other explanation of the curious pouch -developed. in front of the lower part 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 Reptiles, Birds, and Mammals. have we all three of the foetal membranes or bags— yolk-sac, amnion, and allantois. But there is every reason to suppose 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 Reptiles the food is prepared in the ovary and its duct, in the Metatheria or Lect. IIL] EMBRYO 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 embryo 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 Fic. 7.—Uterine embryo of Virginian Opossum (Didelphys virginiana), magnified 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 bags are all present in the Kangaroo, but that they are all small and arrested, so that neither the allantois, as in the higher mammals, nor the yolk- 62 MAMMALIAN DESCENT. (Lect. III. sac, as in some Sharks, grow into more than 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-born young of the large Kangaroo (Macropus major) sent tome by Dr Bennett of Sydney, were not so large as new-born Rats, 1.e., they were, about an inch long. Yet these small Kangaroos, whose Fic. 8.--New-born young from the pouch of Kangaroo (Macropus Major), magnified 23 diameters. parents are the size of Sheep, like the sedentary Oyster “attend at ease moist nutriment,” being 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, [Lecr. III. EARLY LIFE OF A MARSUPIAL. 63 and the embryo develops rapidly, the cartilage and bone appearing very early. Such is the case in the Lepidosteus, 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. 61), 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 right and left of the breathing tube, with no danger 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 be looked at, collectively, as a great, infinitely complex organism, and the working of the whole, as if 64 MAMMALIAN DESCENT. [Lecr. III. it were one body with many members, may justly be called earth-life. In this group—the Marsupialia—the general intelli- gence is low, the brain has but few convolutions, and the great familiar bridge, 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 people 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 apparent; 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 pouched tribes. The noble beasts, like the nobler tribes of men, are “mighty hunters,” and they have driven the feebler Marsupial 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 species have found their way over that great western world-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. 65 “conquest of the 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 sheep 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 huge farm, with its great un- enclosed tracts of pasturage, the forms least able to bear changes 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 upland sheep—used to close, quick fences—are removed to the fen-districts, where the fields are enclosed by straight canals, there are E 66 MAMMALIAN DESCENT. [Lecr, III. always some losses by drowning, until the sheep learn the meaning of those dark waters. The earth has often had her shaking 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. Pn nen. adopted this rough method ing out her weaker tribes—appointing them for slaughter—and of saving the best for the increase of the flock. These suggestions relate to the incoming of the Eutheria, of which 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 pass 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 gave origin 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 types does not form a perfect fence. In the study of nature, as every one knows, that seems to be the most bewitching part in which each particular observer is working; the skeletal frame- work takes the precedence with most of us. There are many excellent diagnostic marks in the skeleton of the Lect. III] POUCH-BEARING ANIMALS. 67 Marsupials, some well known, some less familiar to anatomists, but none of these are absolutely 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, which have the pouch rudimentary ; they also exist as pre-pubic 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 back. 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. (Lecr. IIT. process) is a mere spur, as in the Eutheria generally. So also the vertebrae, the ribs, and the sternum ; these are quite normal, having taken on the characters we are familiar with in the higher kinds. The limbs are very instructive. The front pair are very similar to what we find in Insectivora and Rodents, 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 pattern 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 Lzcr. ITI.) THE SKULL IN MARSUPIALS. 69 organs of the body. It has cost me but a moderate 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 suggestive 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 comparison 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 highest 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 types 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. [Lecr. III. the upper region of the mouth, and which is formed by a special ingrowth of bone from the maxillaries and palatines, is large and imperfect where the four plates Fic, 9.—Skull of an embryo Pig, 3 inches long, lower view, magnified 34 diameters. ala, ale nasi (snout cartilage); e.n, external nostrils; px., premaxillary; ma, maxillary ; d.g, dental groove (for tooth-pulps) ; pa, palatine; pg, pterygoid; », vomer ; é.pg, external pterygoid plate ; 0s, basi-;phenoid ; g.f, glenoid fossa (hinge cartilage for lower jaw); ¢y, tympanic bone; 0b, os-bulle (additional tympanic bone); 60, basi-occipital; y.oc, paroccipital process; oc.c, occipital condyle (hinge for first vertebra or atlas); eo, exoccipital; so, superoccipital; fim, foramen magnum (great opening); IX. X. XIL., holes for the exit of the 9th, 10th, and 12th cranial nerves. should meet. It is less imperfect in the embryo than afterwards, but the bone-cells are very thinly scattered Lect. III.] EAR-DRUM OF MARSUPIALS. 71 in the early state, and during growth become aggregated laterally, so as to leave large fenestrae, 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 hand, and the side-wings and petrous bones on the other, but burrows 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-bone of the middle ear, has a very large processus gracilis, which, be- 72 MAMMALIAN DESCENT. {Lecr. III. sides growing well forward into the Glaserian fissure, also sends a large sickle of bone in front of, and within, the bony tympanic ring; thus, that bone has two ancillary pieces, helping it to wall in the drum cavity. 7. The innermost bone of the middle-ear chain is not always stirrup-shaped, 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 hag 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 processes), 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. Lecr. 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 types (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- theria, nor their progress in types 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 DESCENT. [Luor. LIT. attain to its present height. 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, with a middle series, and a row, right and left, opposite the interspaces of the single row. Then, in the Amphibia, and in Snakes, Lizards, and Crocodiles amongst the Reptiles, 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 Lxcr. IIL] THE HARD PALATE. iD 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 bones in the lowest Ganoid Fishes. In the mammals, generally, during the embryo stage, there are 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 Rodents. 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 hollowness of the squamous part of the temporal bone, is very marked in the lower Eutheria, such as Edentates and Insectivora. In the tailed Amphibia there is no drum-cavity ; 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. [Lucr. ITT. 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 character in a mammal above the Marsupials, namely, in an Insectivore from Zanzibar (Rhynchocyon), a creature full of inconsist- encies, but a treasure to the Darwinian. To him who can wait, the whirligig of time brings its rewards as well as its revenges. That mixed type (of which Dr. Dobson was the kind donor) has come to me for the establishment of my faith in development. 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 Lecr. III.] = GROCODILE, BIRD, AND OPOSSUM. 77 region, which forms the rudiment of the excavated part that enlarges the drum cavity on its inner side, is