^^l^BSH^ ©I|? i. 2^- l|tU ICihrarg Jfortlj (Carolina &tatf ffinllege QH366 W3Z y LIBRARIES S00588729 $ THIS BOOK IS DUE ON THE DATE INDICATED BELOW AND IS SUB- JECT TO AN OVERDUE FINE AS POSTED AT THE CIRCULATION DESK. Wp m \ mm 9 Wl f99fi APR 2 (^98 ^ 100M/7-89— 891646 THE WORLD OF LIFE THE WORLD OF LIFE A MANIFESTATION OF CREATIVE POWER, DIRECTIVE MIND AND ULTIMATE PURPOSE BY ALFRED RUSSEL WALLACE O.M., F.R.S., D.C.L., Etc. NEW YORK MOFFAT, YARD & COMPANY I 9 I I Copyright, 1910, 191 1, by Moffat, Yard and Company New York All Rights Reserved Published January, 191 1 PEEFACE In the present volume I have attempted to summarise and complete my half-century of thought and work on the Dar- winian theory of evolution. In several directions, I have extended the scope and application of the theory, and have shown that it is capable of explaining many of the phenomena of living things hitherto thought to be beyond its range. Among these are the detailed distribution of plants and animals, which I have discussed at some length. It occupies about one-fourth of the volume (Chapters II. to VI.)? and brings out certain facts and conclusions which I believe mil be of interest to all plant-lovers, and also be not without a certain value to botanists. 'Next in importance are three chapters (X., XL, and XII.) devoted to a general review of the Geological Eecord and a discussion of the various problems arising out of it. Some of the conclusions to which this examination leads us are, I believe, both important and of much general interest. In Chapter VIII. I have endeavoured to show natural selec- tion actually at work in the continually perfecting that won- derful co-adaptation of the most diverse forms of life which pervades all nature. Some little-known aspects of bird-migra- tion are here discussed, and proof is given of the enormous importance of mosquitoes for the very existence of considerable proportion of our birds, including most of our most favoured pets and songsters. This chapter will, I think, have a special interest for every bird-lover. 106920 yi THE WOKLD OF LIFE In Chapter IX. I deal with some little-known phenomena in that hitherto neglected field of enquiry which I have termed " Eecognition Marks." Besides the obvious uses implied by their name, I have shown that they are of great importance — perhaps absolutely essential — in the process of the evolution of new species. During the enquiry I have arrived at the somewhat startling conclusion that the exquisite variety and beauty of insect-coloration and marking have not been devel- oped through their ovni visual perceptions, but mainly — per- haps even exclusively — through those of higher animals. I show that brilliant butterflies do not, and almost certainly cannot, recognise each other by colour, and that they probably do not even perceive colour at all except as to a certain extent presenting visual differences. But besides the discussion of these and several other allied subjects, the most prominent feature of my book is that I enter into popular yet critical examination of those underlying funda- mental problems which Darwin purposely excluded from his "works as being beyond the scope of his enquiry. Such are the nature and causes of Life itself, and more especially of its most fundamental and mysterious powers — growi:h and repro- duction. I first endeavour to show (in Chapter XIV.) by a careful consideration of the structure of the bird's feather ; of the marvellous transformations of the higher insects ; and, more especially of the highly elaborated wing-scales of the Lepidop- tera (as easily accessible examples of what is going on in every part of the structure of every living thing), the absolute neces- sity for an organising and directive Life-Principle in order to account for the very possibility of these complex out-growths. PEEFACE Vll I argue that they necessarily imply first, a Creative Power, which so constituted matter as to render these marvels pos- sible; next, a directive Mind, which is demanded at every step of the process we term growth and often look upon as so simple and natural a process as to require no explanation; and, lastly, an ultimate Purpose, in the very existence of the whole vast life-world in all its long course of evolution through- out the eons of geological time. This Purpose, which alone throws light on many of the mysteries of its mode of evolu- tion, I hold to be the development of Man, the one crowning product of the whole cosmic process of life-development; the only being which can to some extent comprehend nature ; which can perceive and trace out her modes of action ; which can appreciate the hidden forces and motions everywhere at w^ork, and can deduce from them all a supreme and overruling mind as their necessary cause. If we accept some such view as I have now indicated, I show (in Chapters XV. and XVI.) how strongly it is sup- ported and enforced by a long series of facts and co-relations which we can hardly look upon as all purely accidental coin- cidences. Such are the infinitely varied products of living things which serve man's purposes and man's alone — not only by supplying his material wants, and by gratifying his higher tastes and emotions, but as rendering possible many of those advances in the arts and in science which we claim to be the highest proofs of his superiority to the brutes and of his advancing civilisation. From a consideration of these better-knoAvn facts I proceed (in Chapter XXII.) to an exposition of the mystery of cell- growth; to a consideration of the elements in their special relation to the earth itself and to the life-world ; while in the viii THE WORLD OE LIFE last chapter I endeavour to show the purpose of that law of diversity which seems to pervade the whole material Universe. As an '' excursus," I devote Chapter XIX. to a discussion of the nature, extent, and uses of Pain, as strictly deduced from the law of Evolution. Strangely enough, this has never, I believe, been done before ; and it enables us to answer the question — ^' Is Xature Cruel ? " with a decided negative. This outline of the varied contents and objects of my book, wdll, I hope, be useful to my readers, and especially to my reviewers, by directing their attention to those parts of the work in which they may be more especially interested. I also wish to point out that, however strange and heretical some of my beliefs and suggestions may appear to be, I claim that they have only been arrived at by a careful study of the facts and conditions of the problem. I mention this because numerous critics of my former work — Man's Place in the Universe (to which this may be considered supplementary) — ■ treated the conclusions there arrived at as if they were wholly matters of opinion or imagination, and founded (as were their own) on personal likes or dislikes, without any appeal to evi- dence or to reasoning. I have now only to express my thanks to the friends and strangers who have kindly assisted me with numerical and other data for various portions of my work ; as well as to those publishers and authors who have allowed me to use the en- gravings or photographs with which my book is illustrated. They are in, every case (I believe) acknowledged in the text, or on the various plates and figures. Broadstone, Wimborne, November 1910. CONTENTS CHAPTER I PAGE What is Life and Whence it Comes 1 CHAPTER II Species — their Numbers, Variety, and Distribution ... 12 CHAPTER III The Numerical Distribution of British Plants : Temperate Floras Compared 24 CHAPTER IV The Tropical Floras of the World • . . 43 CHAPTER V The Distribution of Animals 89 CHAPTER VI The Numerical Distribution of Species in Relation to Evolu- tion 100 CHAPTER VII Heredity, Variation, Increase 109 CHAPTER VIII Illustrative Cases of Natural Selection and Adaptation . . 134 ix X THE WORLD OF LIPE CHAPTEE IX ' PAGE The Importance of Eecognition-marks in Evolution . . .168 CHAPTEE X The Earth's Surface-changes the Motive Power of Evolution 187 CHAPTEE XI The Progressive Development of the Life-World as shown by the Geological Eecord 303 CHAPTEE XII Life of the Tertiary Period 235 CHAPTEE XIII Some Extensions of Darwin's Theory ....... 371 CHAPTEE XIY Birds and Insects as Proofs of an Organising and Directive Life-principle 309 CHAPTEE XV General Adaptation of Plants, Animals, and Man . . . .321) CHAPTEE XVI The Vegetable Kingdom in its special Eelation to Man . . 350 CHAPTEE XVII The Mystery of the Cell 361 CONTENTS xi CHAPTER XVIII PAGE The Elements and Water in Eelation to the Life-AYorld . . 383 CHAPTER XIX Is Nature Cruel? The Uses of Pain 398 CHAPTER XX Infinite Variety the Law of the Universe 415 LIST OF ILLUSTRATIONS FIG. PAGE 1. Forest in Kelantan, Malay Poninsula 48 2. Forest in Perak, Malay Peninsula 50 3. Campos of Lagoa Santa, Brazil GO 4. View of Campo Cerrado, Lagoa Santa 70 5. View at Lapa Vermelha Eocks, Lagoa Santa . . . 72 6. Casselia chamaedrifoUa 73 7. Andira laurifolia 74 8. A Forest Stream, West Java 80 9. Diagram of Curve of Stature IIG 10. Diagram of Variation 118 11. American Bison 124 12. The Lemming 129 13. Shooting Wild Cleese at the Arctic Circle .... 147 14. Geese Migrating 148 15. Mr. Seebohm's Mosquito Veil 149 16. Watching Grey Plover Among Mosquitoes .... 150 17. Ice Breaking up, Petchora Eiver 152 18. Midsummer on the Tundra 153 19. Sudden Arrival of Birds 154 20. Grey Plover, Xest and Young 156 21. The Higher Tundra 159 22. Migration Xight at Heligoland 162 23. Mimicry of Wasp by a Beetle 170 24. Tragelaphus speJcei 1<4 25. Boocercus euryceros 1<4 26. Gazella granii 1^4 27. Gazelli walleri l'^4 28. Strepsiceros Jciidu 1^" 29. Strepsiceros imherhis 1^6 30. Bubalis JacTcsonia 1'^^ 31. ^pyceros melampus 1*^6 • • • Xlll xiv THE WORLD OF LIFE riG. PAGE 32. Cohus leche 178 33. Cohus defossa 178 34. Cohus Maria 178 35. Oryx Gazella 178 36. (E dicnertius grallarius 176 37. (Edicnemus magnirostris 176 38. Great Indian Stone Curlew 177 39. Thelodus scoticus 208 40. Pteraspis rostrata 208 41. Cephalaspis murchisoiii 209 42. Protocercal Tail 209 43. Heterocercal Tail 209 44. Homocercal Tail 210 45. Pariasaurus Bainii 214 46. Skull of Dicynodon lacerticeps 214 47. Slvull of JEIusaurus felinus 215 48. Skull of Inostransevia 216 49. Eestoration of Dimetrodon 216 50. Skeleton of Iguanodon 218 51. Eestoration of Iguanodon 218 52. Skull of Iguanodon 218 53. Skeleton of Armoured Dinosaur 218 54. Skull of Horned Dinosaur 219 55. Eestoration of Stegosaurus 220 56. Sauropodous Dinosaur 221 57. Skeleton of Diplodocus carnegii 222 58. Skull of Sauropodous Dinosaur 222 59. Skull of a Theropodous Dinosaur 222 60. Outline and Skeleton of Plesiosaurus macro cephalus . 224 61. Outline and Skeleton of Ichthyosaurus communis . . 224 62. Bones and Paddles of Ichthyosaurus 224 63. Skeleton of Pterodactylus spectahilis 225 64. Eestoration of Rhymphorhynchus phyllurus .... 226 65. Toothless Pterodactyl 226 66. Skull of Peteranodon longiceps 227 67. Lower Jaw of Phasolothcrium huchlandi 228 68. Jaw and Teeth of Spalacotherium. tricuspidens . • • 228 LIST OF ILLUSTRxVTIONS xv FIG. . PAGE 69. Jaw of Triconodon mordax 228 70. Drawing of the Fossil Lizard-tailed Bird .... 230 71. Skull of Arcliccoptcryxsiemensi 231 72. Skeleton of Phenacodus primwvus 232 73. Skeleton of Uintatherium ingens 236 74. Skull of Uintatherium cornutum 237 75. Skeleton of Titanotherium rohustum 238 76. Skull of Arsinoitheriiim zitteli 240 77. Skeleton of a Creodont 242 78. Skeleton of Hyopotamus brachyrhynchus 243 79. Anoplotherium commune 244 80. Palwotheriiim magnum 244 81. Skull of Moeriilierium hjonsi 244 82. Skulls of Ancestral Elephants 246 83. Skeleton of Tetrahelodon angvstidens 246 84. Probable Appearance of Tetrahelodon augustidens . . 246 85. Skeleton of Mastodon americanus 247 ^Q. Skeleton of Mammoth Elephas promigenius .... 249 87. Skeleton of Toxodon platensis 250 S8. Skeleton of Glyptodon clavipeR 253 89. Probable Appearance of tlio Giant Ground-sloth . . 254 90. Mylodon rohustus 254 91. Skeleton of Scelidotlierium leptocephalum .... 255 92. Skull of an Extinct Marsupial 257 93. Skull of Thylacoleo carnifex 258 94. Sabre-toothed Tiger 284 95. Skeleton of Giant Deer 284 96. Conocoryphe sultzeri .» 287 97. Paradonides hohemiciis . ♦ 287 98. Acidaspis dufrenoyi 288 99. Ceratites nodosus 289 100. Trachyceras aon 28 J 101. Crioceras emerici 289 102. Heieroceras emerici 289 103. Macroscaphites ivanii . . o 290 104. Hamites rotundus -^"^^ 105. Ptychoceras emericiciniim '^•^^ xvi THE WORLD OF LIFE PAGE 106. Ancyloceroe matheronianiinis 390 107. Head of Babirusa 296 108. Perspective View of a Part of a Wing-feather . . .313 109. Oblique Section Showing how the Barbules hook To- gether 312 110. Diagram of Nuclear Division 3 TO THE WORLD OF LIFE CHAPTER I WHAT LIFE IS, AjI^D WHENCE IT COMES When primeval man first rose above the brutes from which he was developed ; when, by means of his superior intellect, he had acquired speech and the use of fire ; and more espe- cially when his reasoning and reflecting faculties caused him to ask those questions which every child now asks about the world around it — what is this ? and why is that ? — he would, for the first time, perceive and wonder at the great contrast between the living and the not-living things around him. He would first observe that the animals which he caught and killed for food, though so unlike himself outwardly, were yet very like his fellow-men in their internal structure. He would see that their bony framework was almost identical in shape and in substance with his own; that they possessed flesh and blood, that they had eyes, nose, and ears; that presumably they had senses like his own, sensations like his own ; that they lived by food and drink as he did, and yet were in many ways so different. Above all, he would soon notice how inferior they were to himself in intellect, inasmuch as they never made fires, never used any kind of tools or weapons ; and that, although many of them were much stronger than he was, yet his superiority in these things, and in making traps or pitfalls to capture them, showed that he was really their superior and their master. Gradually, probably very slowly, he would extend these observations to all the lower forms of life, even wdjen both 1 2 THE WORLD OF LIFE externally and internally he could find no resemblance what- ever to his own body; to crabs and winged insects, to land- shells and sea-shells, and ultimately to everything which by moving and feeding, by growdng and dying, showed that it was, like himself, alive. Here, probably, he would rest for awhile, and it might require several generations of incipient philosophers to extend the great generalisation of " life " to that omnipresent clothing of the earth's surface produced by the infinitely varied forms of vegetation. The more familiar any phenomenon is — the more it is absolutely essential to our life and well-being — the less attention we pay to it and the less it seems to need any special explanation. Trees, shrubs, and herbs, being outgrowths from the soil, being incapable of any bodily motion and usually exhibiting no indications of sensation, might w^ell have been looked upon as a necessary appendage of the earth, analogous to the hair of mammals or the feathers of birds. It was probably long before their end- less diversity attracted much notice, except in so far as the fruits or the roots were eatable, or the stems or foliage or bark useful for huts or clothing ; wdiile the idea that there is in them any essential feature connecting them wdth animals and en- titling them to be classed all together as members of the great ^vorld of life would only arise at a considerably later stage of development. It is, in fact, only in recent times that the very close resem- blance of plants and animals has been generally recognised. The basis of the structure of both is the almost indistinguish- able cell ; both grow from germs ; both have a varied life-period from a few" months to a maximum of a few" hundreds of vears : both in all their more highly organised forms, and in many of their lower types also, are bisexual ; both consist of an immense variety of distinct species, which can be classified in the same way into higher and higher groups; the laws of variation, heredity, and the struggle for existence apply equally to both, and their evolution under these laws has gone on in a parallel course from the earliest periods of the geological record. WHAT LIFE IS 3 The differences between plants and animals are, however, equally prominent and fundamental. The former are, with few exceptions, permanently attached to the soil ; they absorb nourishment in the liquid or gaseous state only, and their tissues are almost wholly built up from inorganic matter, while they give no clear indications of the possession of sensation or vol- untary motion. But notwithstanding these marked differences, both animals and plants are at once distinguished from all the other forms of matter that constitute the earth on which they live, by the crowning fact that they are alive; that they grow from minute germs into highly organised structures; that the functions of their several organs are definite and highly varied, and such as no dead matter does or can perform ; that they are in a state of constant internal flux, assimilating new material and throwing off that which has been used or is hurtful, so as to preserve an identity of form and structure amid constant change. This continuous rebuilding of an ever-changing highly complex structure, so as to preserve identity of type and at the same time a continuous individuality of each of many myriads of examples of that type, is a characteristic found nowhere in the inorganic world. So marvellous and so varied are the phenomena presented by living things, so completely do their powers transcend those of all other forms of matter subjected to mechanical, physical, or chemical laws, that biologists have vainly endeavoured to find out what is at the bottom of their strange manifestations, and to give precise definitions, in terms of physical science, of what "life'' really is. One authority (in Chambers's Ency- clopaedia) summed it up in three w^ords — "Continuity, Ehythm, and Freedom," — true, perhaps, but not explanatory ; while Herbert Spencer declared it to be — " the definite com- bination of heterogeneous changes, both simultaneous and suc- cessive, in correspondence with external co-existences and sequences." This is so technical and abstract as to be unin- telligible to ordinary readers. The following attempt at a tolerably complete definition 4 THE WORLD OF LIFE appears to sum up the main distinctive characters of living things : — Life is that 'power which, primarily from air and water and the substances dissolved therein, builds up organised and highly complex structures possessing definite forms and functions: these are preserved m a continuous state of decay and repair by internal circulation of fluids and gases; they reproduce their like, go through various phases of youth, maturity, and age, die, and quickly decompose into their constituent elements. They thus form continuous series of similar individuals; and, so long as external conditions render their existence possible, seem to possess a potential immortality. The characteristics here enumerated are those which apply to both plants and animals, and to no other forms of matter whatever. It is often stated that crystals exhibit the essential features of some of the lowest plants ; but it is evident that, with the exception of the one item of " definite form/^ they in no way resemble living organisms. There is no doubt, how- ever, that crystals do exhibit definite forms, built up by the atoms or molecules of various elements or compounds under special conditions. But this takes us a very small way towards the complex structure and organisation of living things. There are still people who vaguely believe that ^^ stones grow," or that '^ all matter is really alive," or that, in their lowest and simplest forms, the organic and the inorganic are indistinguishable. For these ideas, however, there is not a particle of scientific justification. But the belief that '^ life " is a product of matter acted upon by chemical, electrical, or other physical forces, is very widely accepted by men of science at the present day, perhaps by a majority. It is, in fact, held to be the only scientific view, under the name of ^' monism " ; while the belief that ^^ life " is sui generis, that it is due to other laws than those which act upon dead or unorganised matter, that it affords evidence of an indwelling power and guidance of a special nature, is held to be unscientific — to be, in fact, an indication of something akin to, if not actually WHAT LIFE IS 5 constituting, an old-fashioned superstition. That such a view is not uncommon may be shown by a few extracts from scien- tific writers of some eminence. The well-known German biologist Ernst Haeckel, in a recent work, makes the following statement : " The peculiar phenomenon of consciousness is not, as Du Bois- Eeymond and the dualistic school would have us believe, a com- pletely transcendental problem ; it is, as I showed thirty-three years ago, a physiological problem, and, as such, must be reduced to the phenomena of physics and chemistry " (The Eiddle of the Uni- verse, p. 65, translated by Joseph M'Cabe). Again he says : " The two fundamental forms of substance, ponderable matter and ether, are not dead, and only moved by extrinsic force, but they are endowed with sensation and will (although, naturally, of the lowest grade) ; they experience an inclination for condensation, a dislike of strain; they strive after the one and struggle against the other'' (p. 78). In these two passages we have a self-contradiction in mean- ing if not in actual words. In the first, he reduces conscious- ness to phenomena of physics and chemistry ; in the second he declares that both matter and ether possess sensation and will. But in another passage he says he conceives ^^ the ele- mentary psychic qualities of sensation and will which may be attributed to atoms to be unconscious" (p. 64). It is this quite unintelligible theory of matter and ether possessing sensation and will, being able to strive and struggle and yet be unconscious, which enables him to say: "We hold with Goethe that matter cannot exist and be oper- ative without spirit, nor spirit without matter. We adhere firmly to the pure, unequivocal monism of Spinoza : Matter, or infinitely extended substance, and Spirit (or Energy), or sensitive and think- ing substance, are the two fundamental attributes, or principal properties, of the all-embracing essence of the world, the universal substance" (p. 8). 6 THE WOELD OF LIFE Here we have yet another contradiction — that the tJiinking infinite substance is unconscious! This leads to his theory of the " cell-soul/' which is the origin of all consciousness, hut which is itself unconscious. This he reiterates emphatically. He tells us that at a certain grade of organisation '^ conscious- ness has been gradually evolved from the psychic reflex activity, and now conscious voluntary action appears" (p. 41). Along wdth these strange conceptions, "vvhich really explain nothing, he propounds his " Law of Substance " as the one great foun- dation of the universe. This is merely another name for " persistence of force " or ^' conservation of energ}^," yet at the end of the chapter expounding it he claims that, '' in a negative way, it rules out the three central dogmas of meta- physics — God, freedom, and immortality" (p. 83). A little further on he again states his position thus: " The development of the universe is a monistic mechanical process, in which we discover no aim or purpose whatever; what we call design in the organic world is a special result of biological agencies; neither in the evolution of the heavenly bodies, nor in that of the crust of the earth do we find any trace of a controlling purpose — all is the result of chance.^' Then, after discussing what is meant by chance, he con- cludes : " That, however, does not prevent us from recognising in each ' chance ' event, as we do in the evolution of the entire cosmos, the universal sovereignty of nature's supreme law, the taw of sub' stance'* (p. 97). Again, he defines his position still more frankly: *' Atheism affirms that there are no gods or goddesses, assuming that god means a personal, extra-mundane entity. This ^ godless world-system ' substantially agrees with the monism or pantheism of the modern scientist. It is only another expression for it, em- phasising its negative aspect, the non-existence of any supernatural deity" (p. 103). WHAT LIFE IS 7 These vague and often incomprehensible assertions are inter- spersed with others equally unprovable, and often worded so as to be very offensive to religious minds. After having put forth a host of assertions as to a possible future state, which exhibit a deplorable ignorance of the views of many advanced thinkers in all the Churches, he says: " Our own ^ human nature ' which exalted itself into an image of God in an anthropistic illusion, sinks to the level of a placental mammal, which has no more value for the universe at large than the ant, the fly of a summer's day, the microscopic infusorium, or the smallest bacillus. Humanity is but a transitory phase of the evolution of an eternal substance, a particular phenomenal form of matter and energy, the true proportion of which we soon perceive when we set it on the background of infinite space and eternal time" (p. 87). The writings of Haeckel, the extremely dogmatic and asser- tive character of which have been illustrated in the preceding quotations, have had an immense influence on many classes of readers, who, when a man becomes widely known as a great authority in any department of science, accept him as a safe guide in any other departments on which he expresses his opinions. But the fact is that he has gone altogether out of his own department of biological knowledge, and even beyond the whole range of physical science, when he attempts to deal with problems involving '' infinity " and ^' eternity." He de- clares that " matter," or the material universe, is infinite, as is the '' ether," and that together they fill infinite S2:)ace, and that both are ^^ eternal " and both '' alive." ^one of these things can possibly be hnown, yet he states them as positive facts. The whole teaching of astronomy by the greatest astronomers to-day is that the evidence now at our command points to the conclusion that our material universe is finite, and that we are rapidly approaching to a knowledge of its extent. Our yearly increasing acquaintance with the possibil- ities of nature leads us to the conclusion that in infinite space 8 THE WORLD OF LIFE there lyiay be other universes besides ours; but if so, they may l^ossibly be different from ours — not of matter and ether only. To assert the contrary, as Ilaeckel does so confidently, is surely not science, and very bad philosophy. He further implies, and even expressly states, that there is no spirit-world at all ; that if life exists in other worlds it must be material, physical life; and that, as all worlds move in cycles of development, maturity, and destruction, all life must go through the same phases — that this has gone on from all eternity past, and will go on for all eternity to come, with no past and no future possible, but the continual rise of life up to a certain limited grade, which life is always doomed to extinct tion. And it is claimed that this eternal succession of futile cycles of chance development and certain extinction is, as an interpretation of nature, to be preferred to any others ; and especially to those which recognise mind as superior to matter, which see in the development of the human intellect the prom- ise of a future life, and which have in our own day found a large mass of evidence justifying that belief. With Professor HaeckeFs dislike of the dogmas of theo- logians, and their claims to absolute knowledge of the nature and attributes of the inscrutable mind that is the power within and behind and around nature, many of us have the greatest sympathy ; but we have none with his unfounded dogmatism of combined negation and omniscience, and more especially when this assumption of superior knowledge seems to be put forward to conceal his real ignorance of the nature of life itself. He evades altogether any attempt to solve the various difficult problems of nutrition, assimilation, and growth, some of which, in the case of birds and insects, I shall endeavour to set forth as clearly as possible in the present volume. As Professor Weismann well puts it, the causes and mechanism by which it comes about that the infinitely varied materials of which organisms are built up ^' are always in the right place, and develop into cells at the right time," are never touched upon in the various theories of heredity that have been WHAT LIFE IS 9 put forward, and least of all in that of Haeckel, who comes before us with what he claims to be a solution of the Riddle of the Universe. Huxley on the Nature and Origin of Life Although our greatest philosophical biologist, the late Pro- fessor T. H. Huxley, opposed the theory of a '' vital force " as strongly as Haeckel himself, I am inclined to think that he did so because it is a mere verbal explanation instead of being a fundamental one. It conceals our real ignorance un- der a special term. In his Introduction to the Classification of Animals (1869), in his account of the Rhizopoda (the group including the Amoebse and Foraminifera), he says: "Nor is there any group in the animal kingdom which more admirably illustrates a very well-founded doctrine, and one which was often advocated by John Hunter, that life is the cause and not the consequence of organisation; for in these lowest forms of ani- mal life there is absolutely nothing worthy of the name of organi- sation to be discovered by the microscopist, though assisted by the beautiful instruments that are now constructed. . . . It is structureless and organless, and without definitely formed parts. Yet it possesses all the essential properties and characters of vitality. Nay, more, it can produce a shell; a structure, in many cases, of extraordinary complexity and most singular beauty. " That this particle of jelly is capable of guiding physical forces in such a manner as to give rise to those exquisite and almost mathematically-arranged structures — being itself structureless and without permanent distinction or separation of parts — is to my mind a fact of the profoundest significance'^ (p. 10). This was written only a year after the celebrated lecture on " The Physical Basis of Life," in which Huxley made statements which seem opposed to those above quoted, and which certainly appear to be less philosophical. For example, he says that when carbon, hydrogen, oxygen, and nitrogen are combined with some other elements, they produce carbonic acid, water, and nitrogenous salts. These compounds are all life- 10 THE WORLD OF LIFE less. " But wlien they are brought together under certain conditions they give rise to the still more complex body, proto- plasm, and this protoplasm exhibits the phenomena of life " (p. 52). Then follows an exposition of the well-known argu- ment as to water and crystals being produced by the " proper- ties " of their constituent elements, with this conclusion : " Is the case any way changed when carbonic acid, water, and nitrogenous salts disappear, and in their place, under the influence of pre-existing living protoplasm, an equivalent weight of the matter of life makes its appearance?" (p. 53). But here we have the words I have italicised introduced which were not in the previous staj:ement; and these are of fundamental importance considering the tremendous conclu- sion he goes on to draw from them — " that the thoughts to which I am now giving utterance are the exj)ression of molec- ular changes in that matter of life which is the source of our other vital phenomena." At the end of the lecture he says that " it is of little moment whether we express the phenomena of matter in terms of spirit, or the phenomena of spirit in terms of matter — each statement has a certain relative truth." But he thinks that in matters of science the materialistic ter- minology is in every way to be preferred. This is vague and unsatisfactory. It is not a mere question of terminology ; but his statement that " thought is the expres- sion of molecular change in protoplasm " is a mere begging of the whole question, both because it is absolutely unproved, and is also inconsistent with that later and clearer statement that " life is the cause of organisation " ; but, if so, life must be antecedent to organisation, and can only be conceived as indissolubly connected with spirit and with thought, and with the cause of the directive energy everyw^here manifested in the growth of living things. In the present volume I am endeavouring to arrive at a juster conception of the mystery of the Life- World than that of Professor Haeckel, and bv a verv different method. I shall WHAT LIFE IS 11 endeavour to give a kind of bird's-eye sketch of the great life- drama in many of its broader and less-known phases, showing how they all form parts of the grand system of evolution, through adaptation to continuous changes in the outer world. I shall also endeavour to penetrate into some of the less trodden paths of nature-study, in order to exhibit the many indications that exist of the preparation of the Earth for Man from the remotest eons of geological time. CHAPTER II SPECIES THEIK NUMBEKS, VAKIETY, AND DISTRIBUTION When we begin to inquire into the main features, the mode of development, the past history, and the probable origin of the great World of Life of which we form a part, which encloses us in its countless ramifications, and upon whose pres- ence in ample quantity we depend for our daily food and continued existence, we have perpetually to discuss and to deal with those entities technically kno^vn as species, but which are ordinarily referred to as soi'ts or kinds of plants and animals. When we ask how many hinds of deer or of thiTishes, of trout or of butterflies, inhabit Britain, w^e mean exactly the same thing as the biologist means by species, though we may not be able to define what we mean so precisely as he does. Many people imagine, however, that Darwin's theory proves that there are no such things as species ; but this is a complete misconception, though some biologists use language which seems to support it. To myself, and I believe to most natural- ists, species are quite as real and quite as important as when they were held to be special creations. They are even more important, because they constitute the only definite, easily rec- ogTiised, and easily defined entities which form the starting- point in all rational study of the vast complex of living things. They are now known to be not fixed and immutable as for- merly supposed; yet the great mass of them are stable within very narrow limits, w^hile their changes of form are so slow, that it is only now, after fifty years of continuous search by countless acute observers, that we have been able to discover a very few cases in which a real change — the actual produc- tion of new species — appears to be going on before our eyes. The reader may therefore rest assured that there is no mystery 1^ DISTRIBUTIO'N^ OF SPECIES 13 in the word species, but that he may take it as meaning the same as kind, in regard to animals and plants in a state of nature, and that he will have no difficulty in following the various discussions and expositions in which this term is nec- essarily so prominent. The reason why species is the better term is because hind is used in two distinct senses — that of species when we speak of kinds of deer, of squirrels, or of thrushes, but also that of a genus or a family when we speak of the deer, squirrel, or thrush kind, as meaning the whole group of these animals. If we used the word tribe instead of hind in this latter sense, all ambiguity would be avoided. Eew persons who have not studied some branch of natural history have any idea of the vast extent, the infinite variety, the omnipresence and the intermingling of the varied species of animals and plants, and still less of their wonderful co-adap- tation and interdependence. It is these very characteristics that are least dwelt upon in books on natural history, and they are largely overlooked even in works on evolution. Yet they form the very basis of the phenomena to be explained, and furnish examples of development through survival of the fittest, on a larger scale and often of easier comprehension than the special cases most frequently adduced. It is this ground-work of the whole subject that we will now proceed to consider. The Distribution of Local and ^yorld Species The first important group of facts which we have to con- sider is that which relates to the number of existing species of the tw^o great divisions of life, plants and animals, and their mode of distribution over the earth's surface. Every one who begins to study and collect any gToup of animals or plants is at once struck by the fact that certain fields, or woods, or hills are inhabited by species which he can find nowhere else ; and further, that, whereas some kinds are very common and are to be found almost everywliere, others are scarce and only occur in small numbers even in the places 14 THE WORLD OF LIFE where alone they are usually to be found. These peculiarities are most strongly marked in the case of plants, and in a less degree among insects and land-shells; and in the former group they are easily seen to depend mainly on such obvious peculiari- ties as soil and moisture, exposure to sun or wind, the pres- ence or absence of woods, streams, or mountains. But besides these inorganic causes — soil, climate, aspect, etc. — which seem primarily to determine the distribution of plants, and, through them, of many animals, there are other and often more powerful causes in the organic environment which acts in a variety of ways. Thus, it has been noticed that over fields or heaths where cattle and horses have free access seedling trees and shrubs are so constantly eaten down that none ever grow to maturity, even although there may be plenty of trees and woods around. But if a portion of this very same land is enclosed and all herbivorous quadrupeds excluded, it very quickly becomes covered with a dense vege- tation of trees and shrubs. Again, it has been noticed that on turfy banks constantly cropped by sheep a very large variety of dwarf plants are to be found. But if these animals are kept out and the vegetation allowed to grow* freely, many of the dwarfer and more delicate plants disappear owing to the rapid growth of grasses, sedges, or shrubby plants, which, by keeping off the sun and air and exhausting the soil, prevent the former kinds from producing seed, so that in a few years they die out and the vegetation becomes more uniform. A modified form of the same general law is seen when any ground is cleared of all vegetation, perhaps cultivated for a year or two, and then left fallow. A large crop of weeds then grows up (the seeds of which, must have beeoi brought by the wind or by birds, or have lain dormant in the ground) ; but in the second and third years these change their propor- tions, some disappear, while a few new ones arrive, and this change goes on till a stable form of vegetation is formed, often very different from that of the surrounding country. Such changes as these have been observed by local botanists on rail- DISTRIBUTION OF SPECIES 15 way banks, of which I have given several examples in my Island Life (p. 513, footnote). All these phenomena, and many others which will be referred to later, are manifestly due to that " struggle for existence " which is one of the great factors of evolution through " survival of the fittest." A Lincolnshire clergyman (Rev. E. Adrian Woodruff e-Pea- cock of Cadney) has long studied the distribution of plants in a very minute and interesting manner, more especially in his own parish, but very extensively over the whole county. His more exact method is to divide up a field into squares of about 16 feet each way with pegs, and then to note on special forms or note-books (1) a list of the species found in each square, and (2) the frequency (or proportion) of the occurrence of each species. From these the frequency over the whole field can be estimated, and the botanical peculiarities of various fields very accurately determined. By comparing the detailed flora of each field with its surface-geology, aspect, altitude, degree of moisture or aridity, etc., a very accurate conclusion as to the likes and dislikes of particular plants may be arrived at. As an example of the detailed treatment of a rather uncom- mon yet widely distributed plant, he has sent me a copy of his paper on the Black Horehound (Ballota nigra), sl species not uncommon over much of Central Europe, but scattered over Central and Southern Britain only in a few favourable locali- ties. In Lincolnshire it is found all over the county in suitable spots, but prefers a warm, open, and limy soil, as shown by 150 records giving notes of its occurrence. The general results of the inquiry are thus given: "AVhen the sheets of notes are analysed the following points come out. It is a hedge and ditch-side species, but it seems to prefer a bank to the flat in the proportion of 10 to 1 ; the sunny bank to the shady side of a road running east and west in nearly the same proportion. On sandy soils it seems to get away from the villages to a greater distance than on clays, but perhaps the rabbit may explain this. It extends from Cadney village along 16 THE WORLD OF LIFE hedge and ditch banks on roadsides as far as the Sandy Glacial Gravel extends in any direction. It is found in bushy ground, in old quarries and gravel pits, and on the decaying mud-capping of limestone walls. It is exterminated by stock in pasture, unless it is protected by the stinging-nettle or by the fouling of the ground by rabbits. It is apparently never found in meadows. It is even sometimes eaten by cows, when the much-loved Lamium album (the white dead-nettle) is left untouched; but it would seeem to be taken as a corrective or relish rather than as food. It is found so rarely in the open that it would almost appear to be a shade species of bushy ground. *' To sum up, Ballota nigra can only survive (in Lincolnshire) when unconsciously protected by man; for its natural require- ments, a bushy, open, limy, lightly stocked soil is practically not to be found.^' This careful study of a single species of plant gives us an excellent picture of the struggle for existence on the outer limit of the range of a species, where it first becomes rare, and, when the conditions become a little less favourable, ceases to exist. How this struggle affects the flora of limited areas under slightly different conditions is shown by the same writer's comparison of meadow and pasture. Tw^o fields of each were chosen in the same parish and with the same subsoil (Sandy Glacial Gravel) so as to afford fair examples of each. With the one exception of the mode of cultivation they were as alike as possible. Both had at some remote period been ploughed, as shown by faint ridges, but no one living or their immediate predecessors could remember them in any different condition from the present one. The four fields (29 acres together) contained in all 78 species of plants ; but only 46 of these were found in both pasture and meadow. The number of species in each was nearly the same — 60 in the meadows, 64 in the pastures ; 14 species being found only in the meadows and 18 in the pastures. Broadly speaking, therefore, one-fifth of all the species growing on these 29 acres became restricted to well-defined portions of them disteibutio:n^ of species 17 according as these portions were grazed by farm stock or reg- ularly mown for hay. Again, Mr. Woodruff e-Peacock states, that the assemblage of plants that form pasture-lands not only varies with every change of soil and climate, but also with any change of the animals that feed upon them ; so that any one experienced and observant can tell, by the presence of certain plants and the absence of others, whether horses, cattle, or sheep have been the exclusive or predominant animals that have grazed upon it. Another point of some importance is the greater stability in the flora of meadow as compared with that of pasture land. In the former only one plant was an accidental straggler, while in the latter there were 12, or two-thirds of the peculiar spe- cies. These are mostly rare, and are very often not truly Brit- ish plants, so that they cannot be considered as permanent pasture plants. The more stable meadow flora is no doubt largely due to the fact that few of the late-flowering plants are allowed to produce seed, and though seed may be often introduced by birds or the wind, many of these species soon die out. It thus appears that though pastures are actually richer in species than meadows, yet the latter have a more permanent character, as almost all those peculiar to pastures are comparatively rare and therefore very liable to disappear through very slight changes of conditions. These various facts, and many others which cannot be here given, serve to show us how very delicate are the mutual rela- tions and adjustments of plants to their total environment. In proportion as that environment is subject to change of any kind, some rare species die out, while others become diminished in numbers. And what takes place in single fields or other small areas, when closely studied, must certainly occur on a much grander scale over the whole earth, and especially in those countries and periods when great changes of climate or of physical geography are taking place. These detailed studies of " Meadow and Pasture Analysis " — as their author terms them — thus demonstrate on a very small scale that " struggle 18 THE WOELD OF LIFE for existence " which, as we shall see further on, is always present, acts in an almost infinite number of ways, and is one of the most important factors in the developmental changes of the World of Life. We will now proceed to give some of the numerical facts of plant distribution, in various areas small and large, as well as over the whole earth; but it will be ad- visable first to give a brief account of the way in which this is usually dealt with by botanists. Four years before the appearance of the Origin of Species the great Swiss botanist, Alphonse De Candolle, published one of the most remarkable and interesting botanical works in existence, his GeogTaphie botanique raisonnee, in two thick vol- umes. He not only brought together all the then available facts as to plant distribution in every part of the world, studied them from almost every point of view, and grouped them in relation to every known agency that might be supposed to influ- ence their distribution, but at every step he most carefully and ingeniously discussed the problems involved, often of a very intricate nature, with a view to arriving at a more or less complete explanation. It is impossible here to give any adequate notion of this great work, but a few of the chief subjects treated may be mentioned. The effects of temperature and of light upon the growth and vitality of plants are first examined, and some very interesting conclusions are reached, among others the great importance of the time during which any particular degree of heat continues. This discussion occupies the first three chapters. Sixteen long chapters then deal with " Botanical Geography," in which all the geographical conditions that affect the distribution of plants are elaborately discussed, such as alti- tude, latitude, aspect, humidity, geological and mineralogical causes, both in their direct and indirect action, and as apply- ing to cultivated as well as ^vild plants. The areas occupied by species, both as regards size and shape, are then discussed, and the causes that lead to their variations investigated. He then shows what are the actual areas in various parts of the DISTRIBUTION OF SPECIES 19 world, and under various geographical conditions, and thus arrives at the causes of great extension of certain species from Vilest to east in the north temperate zone, or along sea-shores or river-banks in the tropics ; while the normal area is consid- ered to be '^ massive " rather than elongated. Coming then to detailed facts, he shows that about 200 species (out of the total then known of about 120,000) have areas equal to one-third or more of the entire land surface of tlie globe. Further, in certain Families (usually called ^Nat- ural Orders) there are plants which range from the Arctic regions to the southern extremity of the great continents. Among the former are our common Marsh Marigold (Caltha palustris) and Common Sundew (Drosera rotund i folia), which are found in all Northern Europe, Asia, and America ; while our common Sowthistle (Sonchus oleraceus) is found scattered over the whole globe, tropical as well as temperate, and is per- haps the nearest of any known plant to being truly cosmopol- itan. By a laborious comparison the author arrives at the con- clusion that the average area occupied by the species of flower- ing plants is rroth part of the whole land surface of the globe. But the area varies enormously in different parts of the world. Thus, in the wdiole Russian Empire, species have a mean area of irVth the land surface, owing to the fact that so many range east and west over a large part of Europe and Xorth Asia ; while in South Africa the mean range is only W&oth of that surface, which expresses the fact of the extreme richness of the latter flora, many of the species composing w^hich have extremely restricted ranges. He also reaches the eonclusion that in passing from the pole to the equator the mean areas of the species become smaller. A few examples of very lim- ited areas are the following : — Several species of heaths are found only on Table Mountain, Cape of Good Hope; Cam- immda isopliylJa grows only on one promontory of the coast of Genoa; the beautiful Alpine Gromwell (Lithospermum Gastoni), on one cliff in the Pyrenees; Wulfenia Carintliiaca, 20 THE WORLD OF LIFE on one mountain slope in Carintliia ; Primula imperialis, on the summit of Mount Pangerago in Java, and many others. In order to compare the plants of different parts of the world in their various relations, De Candolle divides the whole land surface into fifty botanical regions, each distingTiished by the possession of a considerable proportion of peculiar species of plants. These regions are of greatly varying extent, from Xo. 18, comprising the whole of Xorthern Asia, to Xo. 10, limited to the small island of Tristan d'Acunha in the South Atlantic. The list is as follows : — A. De Candolle's Botaxical Regions 1. Arctic zone. 2. Europe, temperate. 3. Mediterranean. 4. Azores, Madeira, Canaries. 5. Sahara, Cape Verde Islands. 6. Guinea N., Soudan. 7. " S., Congo, Benguela. 8. Island of St. Helena. 0. South Africa. 10. Tristan d'Acunha. 11. Islands of Kerguelen, St. Paul, etc. 12. Madagascar, etc. 13. Mozambique, Zanzibar. 14. Abyssinia to Egypt. 15. Persia, Euphrates. 16. Caucasus, Armenia. 17. Tartary east of Caspian. 18. Siberia, Ural to Kamschatka, Lake Aral. 19. Asia Central. 20. Afghanistan to Indus. 21. Nepal to Bhutan. 22. China, Japan. 23. Philippines. 24. Siam, Cochin China. 25. Burma and Assam. 26. Bengal, Ganges. 27. Peninsular India, Ceylon. 28. Malacca, N. Ireland. 29. Australia, New Zealand. 30. Fiji to Marquesas. 31. Mariannes, Carolines. 32. Sandwich Islands. 33. N.W. America. 34. Canada and United States. 35. Texas, California, Mexico. 36. West India Islands. 37. Venezuela. 38. Colombia. 39. Peru. 40. Galapagos. 41. Bolivia and Andes. 42. Guayanas. 43. Amazonia. 44. Brazil N.E. 45. "" W., Paraguay. 46. " S.E. 47. Uruguay, La Plata. 48. Chile, Juan Fernandez. 49. Patagonia, Falkland Islands. 50. The Antarctic Archipelago. By an extensive comparison of floras all over the world it is found that less than Ave per cent, of the total of the kno^vn species are found in more than two of these regions. Fam- DISTRIBUTION OF SPECIES 21 ilies which have very few annual species show a still smaller percentage (three per cent) ; while those whose species are mostly trees or shrubs have less than two per cent which extend to more than two regions. He also finds that those with fleshy fruits have a wider dis- persal than those with dry fruits, and those with very small seeds, wider than those with larger seeds. Eighteen species only are found to be spread over half the land surface of the globe. There are no trees or shrubs among these; grasses are most abundant among them ; and composites — the daisy and aster family — the least ! This last conclusion seems very strange in view of the fact that this family has its seeds so frequently provided with special means of dispersal, either by the wind or by animals. But he also points out, what is now well known to botanists, that the species of Compositse are not usually very widely spread ; and also that several other natural orders in which the seeds are usually winged for wind-dispersal are not more widely distributed than those whose seeds are not winged. These facts certainly prove that the dispersal of seeds by wind or by birds has been brought about for the pur- pose of securing ample means of reproduction Avithin the area to which the whole plant has become specially adapted, not to facilitate its transmission to distant lands or islands which, only in a very few cases, would be suited for its growth and full development. Very extensive dispersal must, therefore, in most cases be looked upon as an adventitious result of gen- eral adaptation to the conditions in which a species exists. De Candolle's work also treats very fully the subject of the comparative preponderance of the various natural orders of plants in different regions or countries. This mode of study- ing plant-distribution was introduced by our greatest English botanist, Robert Brown, and it is that most generally used by modern botanical writers on distribution. It consists in the characterisation of the vegetation of each region or district by the proportionate abundance in species belonging to the dif- ferent natural orders. 22 THE WOKLD OF LIFE This is used in many different ways. In one the minimum number of orders whose species added together form one-half of the whole flora are given. Thus, it was found that in the Province of Bahia (Brazil) the 11 largest natural orders com- prise half the whole number of species. In British Guiana 12 orders are required, and in British India 17. Coming to temperate regions, in Japan there are 16, in Europe 10, in Sweden 9, in Iceland and in Central Spain 8. The general result seems to be that those regions which are very rich in their total number of plants require a larger number of their pre- ponderant orders to make up half the total flora ; which implies that they have a larger proportion of orders which are approxi- mately equal in number of species. Another mode of comparison is to give the names of the first three or four, or even ten or twelve, of the orders which have the greatest number of species. It is found, for example, that in equatorial regions LeguminossB usually come first, though sometimes Orchids are most abundant ; in temperate regions the Composites or the Grasses; and in the Arctic, Grasses, followed by Crucifera? and Saxifrages. A few of the tables constructed by De Candolle are given as examples. British Guiaxa ( Scliomburgh ) 3254 species Leguminosae 469 species Orchidese 214 " Rubiacege 176 " Melastomaceae 126 " The Andes of New Grenada (Humboldt) 1041 species Composite 86 species Leguminosae 65 " ' Rubiacese 49 " Graminese 42 " Orchidese .it,,. • 41 " DISTKIBUTION OF SPECIES 23 Australia and Tasmania (R. Brown) 4200 species Legiiminosse Euphorbiacese Compositae Orchidese Cyperaceae Giaminese Myrtaceaj Proteacese Iceland. 1. Cyperaceae 47 2. Graminese 45 3. Compositae 24 4. Caryophylleae 23 5. Cruciferae 21 6. Amentaceae 20 402 species 7. Saxifrageae 15 8. Rosaceae 15 9. Ericaceae 12 10. Juncaceae 12 11. Ranunculaceae 11 12. Polygoneae 11 As a short general conclusion De Candolle says: The Leguminosae The Composites , The Grasses . . . . dislike cold. , . dislike cold and wet. dislike drought. Other examples will be given when discussing the compara- tive relations of the various temperate and tropical floras of the world. CHAPTER III THE NUMEEICAL DISTRIBUTION OF BRITISH PLANTS I TEMPERATE FLORAS COMPARED Proceeding from the more to tlie less familiar regions we will be^rin witli a few of the facts as to the flora of our own country. Partly owing to its insular character, and also be- cause it has few lofty mountains or extensive forests, the num- ber of species of flowering plants is somewhat (but not much) below that of most continental countries of equal area. It con- tains about 1800 species, as a rough mean between the estimates of dift'erent botanists.^ It may seem curious that there should be any such difference of opinion, but one of the facts that have alwa^^s been adduced as showing that species are not fixed and immutable entities is the frequent occurrence of varieties, which are sometimes so peculiar and so apparently constant that they are treated by some botanists as distinct species, by others as sub-species, and by others again as forms or varieties only. These modifications of a species are usually confined to a more limited area than the species itself, and are occasionally connected with each other or with the parent species by inter- mediate forms. Again, when these varieties are cultivated, and esjDecially when a large number of plants are raised from their seeds, they are apt to revert partially or wholly to the parent form. Another source of difference of opinion among botanists is, as to the treatment of those plants, found usually near human habitations, which are supposed to have been orig- inally introduced, either purposely or accidentally, from foreign coimtrios. Such are the wild Larks])ur and Monkshood, the 1 In all the tables and comparisons of " Ploras " in this work, unless where ferns are specially noted, flowering plants only are intended, even when the term '* plants " is used. 24 TEMPERATE FLORAS 25 Red Valerian, the Balm, the Martagon Lily, and many others. This explanation is necessary in order to avoid any supposition of positive error when the figures here given do not agree with those of anv of the text-books or local floras. xJ The chief diiferences arise, however, from the increased study of certain difficult groups leading to the separation of large numbers of slightly differing forms, that hardly any one but an expert can distinguish, as distinct species. The most important of these are the Brambles (the genus Rubus) and the Ilawkweeds (the genus Hieracium). During the last thirty years the numbers of these have more than doubled, according to the standard authority for British botanists — The London Catalogue of British Plants. The numbers in an early and late edition are as follows : — Genus. 7th Ed., 1877. lOth Ed., 1908. Rubus 54 species 48 1 1 116 species 133 " Hieracium Euphrasia 15 Rhinanthus 8 " In the last two cases two well-known plants — the little " eyebright " of our turfy banks, and the '' yellow rattle " of peaty meadows, which have been each considered to form a single species from the time of Linnseus to that of Bentham and Hooker — are now subdivided into a number of distinct species, each claimed to be well recognisable and constant. With such rapid changes in the estimate of species in so well-known a flora as our own it may be thought that the number of species in foreign countries is even more uncertain. This, however, is by no means the case, as tlio great majority of the species of plants a^ well as of animals; offer little difficulty, and present few fixed varieties (though abundance of variation), so that for general comparisons the D. H. HILL LIBRARY 26 THE WORLD OF LIFE figures obtainable are very fair approximations, and give us interesting and valuable information. About one-third of the total numbe'r of our species of wild flowering plants belong to what the late Mr. H. C. Watson termed the British type ; that is, they are found in suitable places over the whole of Great Britain, and in most districts are so plentiful that they may be termed common plants — such are the Alder, Birch, and Hazel among trees and shrubs ; the Honeysuckle, Ivy, Heather or Ling, Daisy, Chickweed, !N^ettle, and a host of others. Another gi'oup is abundant in England, but absent from the Highlands or from Scotland generally, such as the Dwarf Gorse and Yellow Dead-Nettle. Several arctic or alpine plants are peculiar to the Highlands, a considerable number of species are found only in our eastern counties, while as many or more are characteristic of the west. More curious perhaps than all these are the cases of plants found only in one small area, or two or three isolated patches ; and of others which are limited to a single station, sometimes of a few acres or even a few yards in extent. Such are the Cotoneaster, found only on Great Orme's Head in ]^. Wales; the Yellow Whitlow-Grass, on Worms Head in S. Wales ; the pretty white-flowered Potentilla rupestres, on a single mountain-top in Montgomeryshire; the small liliaceous plant, Simetlius hicolor, in a single grove of pine trees near Bournemouth, now probably exterminated by the builder, and another plant of the same family, Lloydia serotina, limited to a few spots in the Snowdon range ; the beautiful alpine Gentiana verna, in upper Teesdale, Yorkshire, and others confined to single mountains in the Highlands. Between the extremes of widespread abundance and the greatest rarity, every intermediate condition is found ; and this is, so far as we know, a characteristic of every part of the world. This, again, affords a striking proof of that struggle for existence which has already been referred to, acting, as Darwin was the first to point out; first to limit the TEMPEEATE FLOKAS 27 range of a species, often so that it exists only in two more or less isolated areas, then to diminish the number of individuals in these areas, and finally to reduce them to a single group which ultimately succumbs to an increased stress of competi- tion or of adverse climatal changes, when a species which may have once been flourishing and widespread akogether ceases to exist. The rarity of a species may thus be considered as an indication of approaching extinction. Numerical Distribution of Plants hi Britain We will now give a few numerical statements as to the comparative abundance of the species of plants in large and small areas in various parts of the world, such facts having a special application to the theory of evolution. The 55 counties of England and Wales (counting the three Ridings of Yorkshire as counties) have usually areas from 500 to 2500 square miles; and a considerable number of them have had their plants enumerated in special catalogues or floras. The following are the approximate numbers of the flowering plants in a few of these : — Statistics of County Floras County. Area, Sq. Miles. No. of Species. Carnarvonshire 563 1357 980 1533 790 1612 840 636 1519 2638 233 2658 1056 Cornwall 1140 Dorsetshire 1010 Essex 1010 Glamorganshire 950 Hampshire 1150 Herefordshire 865 Hertfordshire 890 Kent 1120 Lincolnshire 1200 Middlesex 835 West Yorkshire 995 Mean of the 12 counties 1198 1026 Great Britain 87,500 1800 28 THE WOELD OF LIFE This table of the distribution of plants in our counties is very instructive, because it shows us the influence of diversity of soils on the number of species that can grow and maintain themselves naturally as wild plants. This is largely dependent on the extreme diversity of the geology of our island, almost every geological formation from the oldest to the most recent being rej^resented in it. This variety of soil seems to be much more important than diversity of sur- face due to altitude, so that our lowland counties are quite as rich as those which are hilly or mountainous. Again, we see that, within moderate limits, greater area has little in- fluence on richness of the flora, the largest. West Yorkshire, having only about one-fifth more species than the smallest, Middlesex, with only about one-twelfth the area. The preponderating importance of variety of soil and sur- face conditions affording good stations for plants, such as woods, hedgerows, streams, bogs, etc., is well shown by a few special comparisons that have been made by experienced botanists. The Parish of Cadney (Lincolnshire), a little over 3 square miles in area, has 720 species of flowering plants; the county nearly 900 times as large, having 1200. The Parish of Edmondsham (in Dorsetshire), covering less than 3 square miles, has 640 species ; the county, 340 times as large, having 1010 species. An equally remarkable instance was given by Mr. H. C. Watson fifty years ago, and no doubt from his own observa- tions, as he resided in the countv. Area, Sq. Miles. Species. Surrey 760 60 10 1 840 An area in Surrey of 660 600 " at Thames Ditton, Surrey. • - 400 TEMPEEATE FLOIUVS 29 Here we see that 10 square miles coutaiiied nearly as many species as 60, and nearly two-thirds the nmiibcr in TOO square miles ; while the single square mile produced nearly half the number in the whole county. Taking still smaller areas, Mr. Woodruffe-Peacock found fields in Lincolnshire and Leicestershire, of from 10 to 25 acres, to yield from 50 to 60 species of plants ; while a plot of 16 Vo feet square (or 1 perch) would usually have 20 to .')0 species. Old and long-disused stone-quarries are often very rich, one of about two acres producing sometimes as many species as the fields of eight or ten times the area. On a plot of turf 3 feet by 4, at Down in Kent, Mr. Danvin found 20 species of flowering plants growing. These facts of the distribution of plants in our own is- lands prove, that for moderately large areas in the same country possessing considerable diversity of soil and general conditions affecting plant-life, the majority of the species are, as a rule, so widely scattered over it that approximately similar areas produce a nearly equal number of species. Further, we find that areas of successively smaller and smaller sizes have a very much greater number of species relatively than larger ones ; so that, as we have seen, 10 square miles may show al- most as much variety in its plant-life as an adjacent area of 60 square miles, and that a single square mile may some- times contain half the number of species foimd in 700 square miles. This characteristic of many small areas being often much richer in proportion to area than larger ones of which they form a part, is a necessary result of the great differences in the areas occupied by the several species and the numbers of the individuals of each ; from those very common ones which occur abundantly over the whole country, to others which, al- though widespread, are thinly scattered in favourable situa- tions, down to those exceptional rarities which occur in a very few spots or in very small numbers. Those spots or small areas which present the most favourable conditions for plant- 30 THE WORLD OF LIFE life and are also most varied in soil, contour, water-supply, etc., will, when in a state of nature, be occupied by a large proportion of the common and widespread plants, together with so many of the less common or the rare species which find the requisite conditions in some part of its varied soil and aspects, as to produce that crowding together of species and luxuriance of growth which are such a joy to the botanist as well as to the less instructed lover of nature. All these peculiarities of vegetation are to be met with in every part of the world, and often in a more marked degree than with us. But this depends very much on diversities of climate and on the extent of land surface on which the entire flora has been developed. The total number of species de- pends mainly on these two factors, and especially on the former. The variety of species is small in arctic or sub-arctic lands, where the long and severe winter allows of only certain forms of vegetable and animal life; and it is equally if not more limited in those desert regions caused by the scarcity or almost complete absence of streams and of rain. It is most luxuriant and most varied in that portion of the tropics where the temperature is high and uniform and the supply of mois- ture large and constant, conditions which are found at their maximum in the Equatorial Zone within twelve or fifteen degrees on each side of the equator, but sometimes extend- ing to beyond the northern tropic, as on the flanks of the Himalavas in north-eastern India, where the monsoon winds carrv so much moisture from the heated Indian Ocean as to produce forests of tropical luxuriance in latitudes where most other parts of the world are more or less arid, and very often absolute deserts. Temperate Floras compared I will now endeavour to compare some of the chief floras of the Temperate Zone, both as regards the total number of species in fairly comparable areas, and the slight but clearly TEMPERATE FLOEAS oi marked increase of the number in more southern as compared with more northern latitudes. I will first show how this law applies even in the com- paratively slight difference of latitude and climate within our own country. Dividing Great Britain (without Wales) ^ into three nearly equal portions — Scotland north of the Forth and Clyde, Mid-Britain, and South Britain, including all the southern counties; with areas of 22,000, 26,000, and 31,000 square miles — the number of species (in 1870) was, respec- tively, 930, 1148, and 1230. At the same period the total of Great Britain was 1425 species. These figures are all ob- tained from Mr. H. C. Watson's Cybele Britannica, and must therefore be considered to be fairly comparable. We see here that the whole of the Scottish Highlands, with their rich alpine and sub-alpine flora, together with that of the sheltered valleys, lakes, and mountainous islands of the west coast, is yet de- cidedly less rich in species than Mid-Britain, while both are less rich than South Britain, with its more uniforai surface, but favoured with a more southern climate. The following table shows these facts more distinctly : — Area, Square Miles. No. of Species. North Britain 22,325 26,550 31,050 930 Mid-Britain, Lowlands south to Stafford -^ and Leicester J South Britain ( Wales excluded ) 1148 1230 The above figures have been kindly extracted from Wat- son's volume by my friend the late Mr. W. H. Beeby. Making a comparison of some countries of Europe we have similar results more clearly shown. 1 Wales is omitted in order to make the three divisions more equal, and contrasted in latitude only. 32 THE WOELD OE LIEE Floras of Europe, showing Influence of Latitude Countries. Europe Lapland Scandinavia and Denmark . . . . Sweden Britain Germany Switzerland . . . France Italy Sardinia Sicily Area. Square Miles. No. of Species. ;3,850,000 150,000 456,000 173,000 87,500 208,000 16,000 204,000 91,400 9,300 9,940 9500 500 1677 1165 1860 2547 2454 4260 4350 1770 2070 Nyman A. De Candolle (( Lend. Cat., 1895 Garehe, 1908 Schinz and Kellar, 1908 Coste, 1906 Beccari The above table shows us a continuous and well-marked increase as we go from north to south, the irregularities in this increase being well accounted for bj local conditions and by allowing something for differences of area. Sweden is so much poorer than Britain, owing to its having been completely ice-clad during the glacial epoch, while much of southern Brit- ain was free. Gennany is poorer than Erance, partly on account of its severer continental climate, but also owing to Erance possessing a greater variety of surface, owing to its including a portion of the loftiest Alps in the south-east, the isolated Pyrenees in the south, the Jura and Vosges mountains on the north-east, and its central volcanic ranges, together with its southern Mediterranean coast, and a very extensive west- ern and northern coast-line. It also has a more diversified soil, owing to far less of its surface being buried under glacial debris. Italy has still greater advantages of a similar kind, and its slight superiority to Erance, with less than half the area, is about what we should expect. It well illustrates the fact, already ascertained, that difference of area within moder- ate limits is of far less importance than comparatively slight advantages in soil and climate. TEMPERATE ELOEAS 33 Turning now to N'orth America, the following figures from the latest authorities have been supplied by my friend Mr. J. D. A. Cockerell : — state. Montana and Yellowstone Park Nebraska Colorado California Area, Square Miles. 150,000 118,000 104,000 158,000 No. of Species. 1934 1478 2872 2700 Remarks. Data in 1900 1898 1900 " recent Two subdivisions of the eastern United States show well the effects of latitude. Central and north-east ~ States — Michigan to L 736,000 32r98 Recent estimate Virginia, Kentucky South-east United States .... 630,000 6321 et (( The number of species in proportion to area and position is apparently less than in Europe, though the corresponding latitudes are farther south. Germany and Switzerland com- bined, with an area less than one-third of the north-eastern and central States, have about as many species ; while Erance, in about the same average latitude, but with less than one- third the area, has considerably more. The south-eastern States extending to 30° S. lat. have about the same number of species as Europe from the Alps and Carpathians south- ward, while the area of the latter is very much smaller and its latitude about eight degrees farther north. The whole Mediterranean flora was estimated bv Griesbach and Tchikatcheff, in 1875, to comprise 7000 species in an area of about 550,000 square miles ; so that the best comparisons that we can make between large European and American areas show a decided superiority in the former. This is no doubt partly due to the much severer winter climate in correspond- ing latitudes of !N'orth America ; and perhaps the long per- 84 THE WORLD OE LIFE sistence of siicli conditions before the glacial period may be the main cause of the whole phenomenon. It is, however, in temperate Asia that we find what seem to be the richest extra-tropical floras, at least in the north- ern hemisphere. The great work of Boissier, Elora Orientalis (1880), describes 11,876 species in the region of East Europe and South- West Asia, from Greece to Afghanistan inclusive, the area of which may be roughly estimated at 2,000,000 square miles. It is a region of mountains and deserts inter- mingled wdth luxuriant valleys and plains, and almost trop- ically warm in its southern portion. So much of it is diffi- cult of access, however, that the collections hitherto made must fall far short of being complete. Its extreme richness in certain groups of plants is showm by the fact that Boissier describes 757 species of Astragalus or Milk-vetch, a genus of dwarf plants spread over the w^hole northern hemisphere, but nowhere so abundant as in this region. Europe has 120 species. • The only other extensive area in temperate Asia the plants of which have been largely collected and recently catalogued (by Mr. W. B. Ilemsley of the Kew Herbarium) is China and Corea, occupying a little more than 1% million square miles. The enumeration, completed in 1905, shows 8200 species of flow^ering plants actually described. But as large portions of this area have never been visited by botanists, and as new species w^re still flowing in rapidly at the close of the enumeration, there can be little doubt that the total will reach, before many years have elapsed, 10,000 or per- haps 12,000 species. It is, moreover, an area that is es- pecially rich in trees and shrubs, and as these are less col- lected by the travelling botanist than the herbaceous plants, it becomes still less easy to speculate on the actual number of species this country really contains. Japan, which is prob- ably better known, has about 4000 species in less than one- tenth the area, and is thus a little richer than Erance. It TEMPERATE ELOEAS 35 agrees, however, very closely with the AVestern Himalayas as estimated by Sir J. D. Hooker. Coming to the southern hemisphere, we find several ex- amples of exceedingly rich floras. The first to be noticed is Chile, where, in an area of 250,000 square miles, 5200 species of flowering plants have been found. In Australia, Xew South Wales, with an approximately equal area, has 3105 species, while West Australia has 3242 species in what is probably not more than one-fourth the area, as so much of that Colony is absolute desert. But richer than either of these is extra-tropical South Africa, where, in about a million square miles, 13,000 species are known, and there are still probably many to be added. The richest portion of this area is the Cape Eegion, as de- fined by Mr. H. Bolus, where, in 30,000 square miles, there are about 4500 species of flowering plants. This area is the same as that of southern Britain, and about one-third that of West Australia excluding the tropical portions and the desert. All these rich areas in the southern hemisphere agree in one respect, they are limited inland hj mountains or deserts, and their coast-line is bordered by a considerable extent of sea less than 1000 fathoms deep, and another still larger extent under 2000 fathoms. There is thus a high prob- ability that in all these cases the flora was originally developed in a much larger and more varied area, and that it has been, in comparatively recent times, very greatly re- duced in extent, thus crowding the various species together. This has, no doubt, caused the extinction of some, while others show that they are on the road to extinction by their limitation to very narrow areas, as is especially the case with many of the orchids, the heaths, and other characteristic South African groups. Of course the mere submergence of a large amount of lowlands would not, of itself, enable any of its plants to invade the adjacent undisturbed land; but the subsidence would no doubt have been very slow, and 36 THE WOELD OE LIFE might have included the degradation of lofty mountains. It Avould also be accompanied by a lowering of some of the existing area. This would modify the climate in various ways, leading probably to a higher temperature and more moisture, thus giving more favourable conditions generally for a great variety of plants. For easy reference it may be well to give here a table showing the main facts as to these warm-temperate floras. Warm-Temperate Floras compared Northern Hemisphere Country. S.E. United States. Mediterranean Greece to -j Afghanistan j China and Corea. . . Japan Himalayas, West. . . Algeria Area, Square Miles. 630,000 550,000 2,000,000 1,500,000 150,000 150,000 150,000 No. of Species. 6,321 7,000 11,876 8,200 4,000 4,000 2,930 T. D. A. Coekerell Tchikateheff Boissier, Flora talis, 1880 Hemsley, 1905 Havati, 1908 Hooker, 1906 Matthews, 1880 { Orien- Chile Souther 250,000 310,700 ? 90,000 88,000 26,380 103,650 1,000,000 30,000 n Eemiepheri 5,200 3,105 3,242 1,830 965 1,474 13,000 4,500 ? • N.S. Wales W. Australia Victoria Miiller r " (tropics and \ deserts omitted ) Miiller Tasmania ii New Zealand South Africa The Cape Region . . Cheeseman, 1906 Thomer's Census H. Bolus, 1886 Temperate Floras of Smaller Areas compared We will now deal with a series of smaller areas (com- parable to our counties) which I have been able to collect from various parts of the world ; and I propose to arrange them in order of latitude, from north to south, so as to show still more distinctly the influence of climate. Each main TEMPERATE ELOEAS 37 division of the globe will be considered separately for convenience of reference, and we begin with Europe, for wbicli materials are the most accessible, though still far from abun- dant. The recent publication of a flora of Harjedal, a province of central Sweden, with a mountainous surface and abundant forests, shows how poor is a sub-arctic area which has recently been buried under an ice-sheet. The real wonder is that it should have acquired so rich a flora by the natural means of dispersal from more southern lands. Temperate Floras of Small Areas in Europe Locality. I C < a, Harjedal (Sweden), lat. 61°-64' Malvern Hills Hertford (near) Strasburg, lat. 48 J ° Schaflniiausen Thurgau Basel Zurich St. Gallen r Schwyz, Uri, Underwalden , < Glarus I Uri r Grisons , ^ Valais, 464° tTicino, 46J° Ofengebietes, Grisons Vallee de Joiix, Jura , Bergunerstocke, Engadine Poschiavo, S. of Bernina Pass ... Euganean Hills, Padua Susa, Piedmont (Beccari) Ferrara, Valley of Po (Beccari) Mytilene (Lesbos) (Candargy) . . Area, Sq. Miles. No. of Species. 5375 606 120 802 80 810 120 960 114 1220 381 1006 163 1117 666 1151 779 1295 950 1352 267 1100 415 1160 2773 1550 2027 1752 1088 1504 86 797 100 823 47 873 92 1200 795 1400 540 2203 1012 794 675 1249 Remarks. Birger. 1908 De Candolle (( a H. H. Field (( it it it it it it a Lat. 46°40' Lat. 46°40' Lat. 46°30' 46°20' 45°30' 45° 10' 44°50' 39°00' (I am indebted to Mr. Herbert H. Field for all the data in this table, except where otherwise stated. They are from 38 THE WOELD OF LIFE the original authorities, and he has kindly brought them up to date as far as possible, so that they may be fairly com- parable.) Although very unequal in extent, the various Swiss cantons, which form the bulk of this table, are remarkably similar in their botanical riches, the smallest, most northerly, and least alpine (Schaffhausen) having more than two-thirds the number of species of the Valais, the most southerly, nearly the largest, and the most alpine, the main chain of the Alps for nearly 100 miles forming its southern boundary, and the Bernese Alps its northern, But Schaffhausen geo- graphically connects eastern France wdth western Germany, and partakes of the rich flora of both countries. This table of the Swiss cantons is also very interesting in showing us that alpine floras are really no richer in species than those of the lowlands, if we compare approximately equal areas. A remarkable illustration of this is the comparison of the Ofengebietes, a district including snowy peaks, forests, and lowland meadows, having almost exactly the same number of species as an equal area near Strasburg, or one around the town of ITertford ! Switzerland, thouirh so verv unlike Great Britain in situation, climate, and physical conditions generally, yet reproduces in its cantons that curious uni- formity in species-production that we found to be the case in our counties. But as Switzerland, though only one-fifth of our area, has a gTeater number of species by one-third, that superiority is, as a rule, reproduced in its subdivisions. Susa, in Piedmont, wdth its fertile valleys and snowy Alps, has by far the richest flora of the whole series, due to its w^arm climate, variety of surface, and complete shelter from the north. Mytilene, the farthest south, has doubtless been impoverished botanically by its large population and extensive fruit culture. It is, I think, clear that, other things being equal, an alpine flora is not at all richer than a lowland one ; but, as we shall see further on, there are indications that the high TEMPERATE FLORAS 39 alpine flora really partakes of that poverty wliicli appertains to liigii latitudes. It is the novelty and beauty of alpine plants that are so attractive to the botanist and so entrancing to the lover of nature, that give an impression of abundance which is to some extent deceptive, and this is increased by the fact that Avhole groups of plants which are more or less rare in the lowlands are plentiful at higher altitudes. Two other circumstances add to this impression of abundance — alpine flowers are mostly very dwarf, and being all at the same level, attract the eye more than when distributed over various heights from that of the creeping herb to the summit of lofty trees ; and, in addition to this, the shortness of the season of growth leads to a much larger proportion of the species flowering together than on the lowlands at the same latitude. Extra-European Temperate Floras The number of floras which are available for comparison with those of Europe are few in number and yqxj widely scattered ; but they serve to illustrate the fact already dwelt upon, that the dift'erences of species-j^opulation in fairly com- parable areas approach to a general uniformity all over the world. Boulder County is probably one of the most favourably situated areas in the United States. It is onlv a little west of the centre of the country; it comprises warm valleys and one of the highest of the Rocky Mountain summits. Long's Peak, and being in the latitude of southern Italy and Greece, has abundant sunshine and a warm summer temperature. It thus agrees in physical conditions with some of the alpine cantons of Switzerland, and the number of its flowering plants is almost identical with the average of Zurich, St. Gall, Schwyz, etc., which have almost the same mean area. Washington, D.C., with an undulating surface just above the sea-level, and a fair amount of forest and river-swamp, agrees very well with the mean of Strasburg and Schaff- 40 THE WOKLD OF LIFE Extra-European Temperate Floras. Small Areas. Lat. 40°N. 39°N. 37°N. 37°N. 35 °S. 35*S. 34°S. 32rs. 27rS. 27J°N. Country. North America. Boulder Co., Colorado. . . Washington, D.C Japan. Mount Nikko Mount Fujiyama South Africa. Cape Peninsula Aust7nlia. Illawarra, N.S.W Cumberland Co., N.S.W. . Mudgee (Wellington Co.) Brisbane, Q North India. Temperate Sikhim Area Sq. Miles. 751 108 360 520 197 200 1400 600 800 1800 No. of Species. 1200 922 800 730 1750 829 1213 631 1283 2000 Remarks. Cockerell Ward Hayati Bolus A. G. Hamilton W. Woolls A. G. Hamilton Jas. Wedd Hooker liausen, somewhat similarly situated, but at a higher latitude. The two mountain areas in Japan, which Mr. Hajati informs me have been well explored, show an unexpected poverty in species, being much below any of the Swiss cantons of equal area. This is the more remarkable as Japan itself is equal to the most favoured countries in Europe — France and Italy; and this again indicates the combined effect of altitude and insularity in diminishing species-production, the lower parts of these Japan mountains being highly cultivated. In the southern hemisphere we come first to the Cape Peninsula, as limited by Mr. Bolus, and often thought to be the richest area of its size in the world. There are 80 species of heaths and nearly 100 species of orchises in this small tract only a little larger than the Isle of Wight. 'No other similar area in the temperate zone approaches it, though it is possible that an equally rich area of the same extent might be found in temperate Sikhim, where several TEMPEEATE ELOEAS 41 distinct floras meet and intermingle. But as the Valais is nearly as rich as Sikhim, and Susa with one-fourth the area is still richer^ it is quite possible that smaller areas may be found as rich as that of the Cape Peninsula. The best third of the Susa district would probably approach closely if it did not quite equal it. Temperate Australia is another country which has obtained a high reputation for its floral riches, for much the same reason as the Cape of Good Hope. In 1810 Robert Brown made known the extreme interest of the Australian flora, both from its numerous hitherto un- known types of vegetation and the variety and beauty of its flowering shrubs. It was therefore supposed that the country was not only botanically rich in new species and genera, but actually so in the number of its species in proportion to area, and this may really be the case with limited portions of West Australia (for which I have been able to obtain no detailed information), but is certainly not the case for Xew South Wales, Victoria, or Tasmania. Cumberland County, which contains Sydney and the celebrated Botany Bay, is only a little richer than our counties of about the same area, while the celebrated district of Illawarra only produces about the same number of plants as does Middlesex, which has, ex- clusive of London, a less area. Many parts of Europe in a similar latitude are much more productive. There is, however, one world-wide group of plants in which, as regards small areas, eastern temperate Australia seems to be pre-eminent — that of terrestrial Orchids. Mr. H. Bolus, in his work on the Orchids of the Cape Peninsula, states that there are 102 species in an area of 197 square miles ; and he quotes Mr. Eitzgerald, the authority on the Orchids of Australia, that " within the radius of a mile '' he remarks, " certainly no such concentration would be found on the Cape Peninsula." I think it probable that the " radius of a mile '' is meant a mile bevond the citv and suburbs of Svdnev, in which case it mio'ht bo an area of from 10 to 20 square miles. Or it might mean a picked 42 THE WORLD OF LIFE area of about 4 square miles of uncultivated land some miles away. That this latter is quite possible is shown by my friend Mr. Henry Deane, who has for many years studied the flora of 20 square miles of country around Hunter's Hill, on the Paramatta Kiver, to the north-west of Sydney, and he here obtained 59 species of Orchids out of a total of 618 flowering plants. The sequence of the first eight orders in number of species is as follows : — 1. Orchidese 51) 2. Myrtaceae 5.5 3. Leguminosse 53 4. Pioteacese 35 5. Compositae 32 6. Graminese 31 7. Cyperacese 30 8. Epacridese 25 In XcAv South Wales, as a Avhole, Leguminosse are first and Orchids fifth in order. There is probably no other purely temperate flora in which Orchids so distinctly take the first place as in the vicinity of Sydney. The contrast in the numbers of species, in approximately comparable areas, between these two groups of waiTQ-temperate floras is fairly well marked throughout, there being, with few exceptions, a decided preponderance in the southern hemis- phere. South Africa is undoubtedly richer than China, though its area is less ; and perhaps than the oriental region of Bois- sier; Avhile Chili compares favourably with Japan or the West- ern Himalayas. Still, the differences are not very pronounced, and are such as appear due to their past history rather than to any existing conditions. Those in the northern hemisphere (except perhaps in the case of the Mediterranean coasts) have probably been for a considerable period stationary or expand- ing; while those in the south have almost certainly been far more extensive, and in later geological time have been contrac- ting, and thus crowding many species together, as already ex- plained. CHAPTER IV TJIE TEOPICAL FLORAS OF THE WORLD Although the idea of the tropics is always associated with that of a grand develojiment of luxuriant vegetation, yet this characteristic by no means applies to the whole of it, and the inter-tropical zone presents almost as much diversity in this respect as the temperate or even the frigid zones. This diversity is due almost wholly to the unequal and even er- ratic distribution of rainfall, and this again is dependent on the winds, the ocean currents, and the distribution and ele- vation of the great land masses of the earth. Once a year at each tropic the sun at noon is vertical for a longer period continuously tlian in any other latitude, and this, combined with the more complex causes above referred to, seems to have produced that more or less continuous belt of deserts that occurs all round the globe in the vicinity of those two lines, but often extending as far into the tropics as into the temperate zone. In a few cases similar conditions occur so near the equator as to be very difficult of explanation. It will be instructive to review briefly these arid regions, since they must have had considerable influence in determining the character of the tropical vegetation in their vicinity. Beginning with the Sahara, pre-eminently the great desert of our globe, if we take it with its extension across Arabia, we find that it occupies an area nearly equal to the whole of Europe, and that the African portion extends as far to the south as to the north of tlie tropic of Cancer. It thus eats away, as it were, a great slice of what in other continents is covered with tropical vegetation, and forms a vast barrier separating the tropical and temperate floras, such as exists 43 44 THE WORLD OF LIFE in no other part of the world. Passing eastward, the desert regions of Baluchistan, Tibet, and Mongolia are situated farther and farther north ; while abundant rainfalls and a truly tropical vegetation extend far beyond the tropic into what is geographically the temperate zone. This is especially the case along the southern slopes of the Himalayas and their extension into Burma and southern China. In the western hemisphere we have the desert regions of Utah, Arizona, and parts of northern Mexico all in the tem- perate zone. In the southern hemisphere the desert interior of central and western Australia reproduces the Sahara on a smaller scale. In Africa there is the Kalahari desert, mostly south of the tropic, but on the west coast extending to about 15° from the equator. In South America an arid belt of almost complete desert extends along the coast from near the equator to Coquimbo in Chili, whence crossing the Andes it stretches south-eastward into Patagonia. Even more extraordinary is the fact that in north-eastern Brazil, in the provinces of Ceara, Pernambuco, and Bahia, are considerable areas which have such small and uncertain rainfall as to be almost des- erts, and are practically uninhabitable. And this occurs only a few hundred miles beyond the great Amazonian forests of Maranham in 3° S. latitude. With the exception of these areas of very deficient rain- fall, it will, I believe, be found that the intertropical regions of the globe are the most productive in species of plants, and, further, that as we approach the equator, where the temperature becomes more uniform throughout the whole year and the amount of rain and of atmospheric moisture is also more evenly distributed, the variety of the species reaches a maximum. There is some evidence to show that this is the case not only in the region of the great forests, but also in those less humid portions which are more or less open country with a vegetation of scattered trees and shrubs, to- gether with herbaceous and bulbous plants which cover the i TEOPICAL FLORAS 45 ground only during the season of periodical rains, as will be shown later on. Tropical Floras — Large Areas Country. British India The Indian Peninsula Burma Indo-China Malay Peninsula Ceylon Java Philippines New Guinea Queensland Tropical Africa south of-* Sahara / Madagascar and Mascarenes. Central America and Mexico. Nicaragua to Panama Brazil Trinidad , Jamaica Area, Square Miles. No. of Species. 1,300,000 500,000 172,000 225,000 35,000 25,000 50,000 115,000 310,000 668,000 6,500,000 229,000 910,000 80,000 3,200,000 1,750 4,200 17,000 4,500 6,000 7,000 5,100 2,800 4,000? 4,656 6,000 4,454 18,300 5,950 12,000 3,000 22,800 1,967 2,720 Authority. Sir J. D. Hooker Hooker Gagnepain Gamble Hooker Koorders Merrill Lauterbach Bailey Thonner's Census Thonner Hemsley Martius Harti Brittan The Tropical Flora of Asia As no part of the Asiatic continent (except the Malay Peninsula) approaches within eight degrees of the equator, its tropical area is very limited, barely reaching one and a quarter million square miles; and even if we add to it the whole of the Malay Archipelago, the Philippines, ^ew Guinea, and tropical Australia, it will not much exceed two millions. Yet these countries are in general so richly clothed with a tropical vegetation, that the actual number of their species will almost 1 Mr. W, E. Broadway, who has collected in the island, informs me that some hundreds of species remain to be discovered in Trinidad. 16 THE WORLD OF LIFE certainly surpass those of Africa, with three times their tropical area, and may approach, though I do not think they will equal, those of tropical America, or even of tropical South America only. Portions of this area have been well explored, especially the great peninsulas forming India proper, Burma, and Indo-China ; but the two latter are only sufficiently known to show their extreme richness botanically, and the same may be said of the numerous large islands of ^ the Malay Archipelago. We may, I think, be certain that what is known of these two sub-regions is less than what re- mains to be made known. Sir Joseph Hooker estimates the whole flora of British. India at 17,000 species, including the desert flora of the Indus valley and the rich temperate and alpine floras of the Himalayas above an elevation of 6500 feet in the east and above 4000 or 5000 in the west. But as I am here dealing with tropical floras, it is only necessary for me to give such figures as are available for the specially tropical portions of it. The Indian Peninsula, bounded on the north by a curving line of hills and mountains which run not far from the line of the geographical tropic, is somewhat poor when compared with the aboundino: riches of Burma and Indo-China; vet it possesses areas, especially in the Western Ghats and the Xiigiris, of great botanical richness and beauty, much of which is still inadequately explored. Arid conditions prevail over much of its surface, both in the north and in the central plains, but these are interspersed w'ith deep moist valleys containing a vegetation allied to that of Assam. As a result of this greater aridity than that of the countries farther east, the peninsula is much poorer in Orchids, having only 200 species against 700 in Burma ; but it has a great excess in Grasses, L^mbellifer?e, Labiatj:Te, and Boragine?e, and a cor- responding poverty in Melastomaceo?, Gesneracege, Myrtacese, Palms, and other more peculiarly tropical orders. Ceylon, though so closely connected with the peninsula, has TKOPICAL FLORAS 47 a distinct flora, nearly 800 of its species and 23 of its genera being '^ endemic/' that is, wholly peculiar to it. It has much stronger affinities with the ]\ialayan flora, due in part, no doubt, to its moister and more uniform insular climate, but also to some features of its past history. The figures given in the table of the chief tropical floras of the world (p. 45) indicate, so far as possible, the actual numbers of the species now existing in collections, and, for purposes of comparison, require certain allowances to be made. Burma and Tndo-China are much less known than Penin- sular India, vet in a smaller area each has a considerably laro;er number of species ; while the Malay Peninsula, which is more completely forest-clad, is in proportion to its area still richer, due mainly to its more equable equatorial climate. The fol- lowinc: table of the chief natural orders is taken from Mr. Ilemsley's Introduction to the Flora of Mexico and Central America : — British Ixdia (17,000 species) 1. Orchidere 1060 2. I^giiiiiinosiE 831 3. Glramineoe 800 4. Robiacese 611 5. Euphoibiacese 624 6. Acanthaceae 503 7. Compositae 598 8. Cypeiaceaj 385 0. Labiatae 331 10. Urticaceae 305 11. Asclepiadeae 249 12. Rosaceae 218 The sequence of the orders is taken from Sir J. Hooker's Sketch of the Flora of British India, a most interesting and instructive pamphlet published in 1906, but the numbers of species are inserted from Mr. Hemsley's work dated 1888. Since then the total numbers have increased from 13,647 to 17,000, about one-fourth, so that the above figures will have to be increased in that proportion ; but they will have increased unequally, as shown by the fact that the orchids are estimated by Sir. T. Hooker at 1600. There is apparently no other extensive region as varied in soil and climate as British India, in which Orchids occu]\v the first place in the sequence of the orders. This is due to 48 THE WORLD OF LIFE their great numbers in Burma, but even more to the fact that in the whole range of the Himalayas epiphytic Orchids extend far into the temperate zone, while in the more eastern ranges they are pre-eminently abundant. This is well shown by the well-explored district of Sikhim, in which Orchids take the first place, not only in the tropical lowlands, but in the temperate zone from 6500 to 11,500 feet above the sea-level. It is possible that in some parts of the temperate Andes, wdiere Orchids are known to be extremely plentiful, the same pro- portion may exist ; but no such district appears to have been yet sufficiently explored by botanists. Before going further it will be as well to give the sequence of the orders in the districts already referred to. Tropical Sikhim (up to 6500 feet) (2000 species) 1. Orchideae (1) 2. Leguminosae (2) 3. Gramineae (3) 4. Urticacese (8) 5. Euphorbiaceae (5) 6. Cyperaceae (7) 7. Rubiacese (4) 8. Compositae (9) 9. Aselepiadeae 10. Acanthaceae (6) The numbers enclosed in brackets give the sequence in Burma, Avhich is very similar, except that Scitaminese (the Gingerworts) is the tenth order, while Asclepiadese is ex- cluded. The Malay Peninsula differs still more from the flora of north-eastern India, in being more exclusively equatorial and typical Malayan, and in this case I am able, through the kind assistance of Mr. J. T. Gamble, to give the number of species for the first twelve orders, which will be interesting for com- parison with others to be given further on. Malay Peninsula (5138 species) 1. Orchidaceae 540 2. Rubiaceae 312 3. Leguminosae 266 4. Euphorbiaceae 255 5. Anonaceae 178 6. Palmae 163 Ferns 7. Lauraceae 153 8. Gramineae 144 9. Zingiberaceae (Scitamineae) 137 10. Gesneraceae 131 11. Acanthaceae 128 12. Cyperaceae 127 368 species. Fig. 1. — Forest in Kelantan, jNIalay Peninsula. TROPICAL FLORAS 49 This may be considered a typical Malayan flora of the low- lands, the mountains not being sufficiently extensive or lofty to favour the abundance of Composita' found in Sikhini and Burma; while the Anonacese (custard apples); the Lauracege (true laurels), producing cinnamon, cassia, and many other sj^ecies and odoriferous nuts, barks, and fruits, and, above all, the noble order of Palms, which have alwavs been con- sidered the most characteristic of the vegetable productions of the tropics, all take a higher place than in any part of India. Sir Joseph Hooker estimates the known, palms of Burma at 68, so that it is hardly probable that any future additions will bring them to an equality with the much smaller Malay Peninsula. This affords another illustration of the increase in the number of species of Palms as we approach the equator, and renders them, with the Rubiacese, the Euphorbiacese, and the Orchids, the most typical of equatorial orders of plants. Through the kindness of Professor R. H. Yapp I am able to give here two beautiful photographs taken by himself in the Malayan forests, which give an excellent idea of the general character of the vegetation, though unfortunately not many of the trees or other plants shown can be identified; but a few remarks may be made as to their general charao- ter. Very prominent on the large trunk in the foreground is the bird's-nest fern (Asplenium nidus), very common in the forests and also in our hot-houses. Above it is a climbing fern (AcrosticJium scandens). On the left is a light-coloured slender tree with knobs or spines, and having many climbers about it. This may be a palm. Among the tangled vegetation in every direction are slender lines, upright, oblique, or beautifully curved; these are the lianas or forest-ropes, many being rattans (palms), but others belong to various dicotyledonous plants of many natural or- ders; and these form one of the most constant and charac- teristic features of the damp equatorial forests both in the eastern and western hemispheres. The slender shrub to the 50 THE WOELD OF LIFE left, with a spray of foliage showing light against the dark trunk, may be an Ixora. On the left, crossing the spined trunk, is one of the climbing palms or rotangs (commonly called ^'rattan'' in England), while the dense mass of vege- tation to the right is largely composed of slender bamboos. The other view (Fig. 2) is more characteristic of the dense Malayan forest, where trees of all sizes, climbers of many kinds, and tangled undergrowth, of dwarf palms, shrubs, and herbs, fill up every spot on which plants can obtain a foot- ing. The large twisted climber in the foreground is perhaps a Bauhinia (Leguminosse), thougli it may belong to any of a variety of genera, and even orders, which form such ropes. The distinct ribbed leaf showing to the left of the most tw^isted part is probably one of the Melastomacege. The dwarf palms in the foreground are also very characteristic. Just above where the twisted climber goes out of sight is a climb- ing fern (Acrostichum scandens), and it seems to grow on a knobbed or spined trunk like the one in the other picture. A close examination will show that the five or six trunks of tall trees visible have each peculiarities of growth or of bark which prove tbem to belong to quite distinct species. The very straight one to the left of the rope-climber is a palm. The abundance of climbers is shown by the numerous very fine wdiite or black lines here and there crossing the picture, especially in the lower portion, each representing a liana or forest-cord striving to work its way upward to the light. In the original photograph the tangled mass of foliage in the foreground is seen to consist of a great variety of plants. The fern with very narrow fronds at the base of the rope is NepJu'oIejns cordifolia, while the large closely pinnate leaves in the foreground, as well as the smaller ones, truncate at the ends, are various species of palms. The prints, unfor- tunately, do not show all the details in the original photo- graphs. Professor O. Beccari, in the interesting volume on his ex- plorations in Borneo, tells us that when building a house Fig 2. — Forest in Perak. ^fal.iv Pcniiisiiln. TKOPICAL FLORAS 51 on tlie Mattang inuunUiiii in Sarawak, three straight trees, each about 9 inches diameter, were found growing at such a distance and position as to be exactly suitable for three of the corner posts of the house in which he afterwards resided during some months' collecting there. When the tops were cut off, and he could examine them, he found them to be- long to three different genera of two natural orders, and also that they were all new species probably peculiar to Borneo. Another illustration he gives of the great productiveness of these forests in species of trees is, that in the two months he lived in his forest home he obtained fifty species of Dipterocarps (an order in which he was much, interested) in two months' collecting and within a mile of his house. This order of plants consists entirely of large forest-trees, and is especially characteristic of the true Malay flora from the Peninsula to Java, Celebes, and the Philippines. It is prob- ably at its maximum in Borneo, as Professor Beccari gives it as the twelfth in the sequence of orders as regards number of species: (1) Rubiace^e; (2) Orchidace^, 200 species; (3) Euphorbiaceee ; (4) Leguminosse; (5) Anonace^e; (6) Melas- tomacene; (7) Palmse, 130 species; (8) Urticacese; (9) Myrtacese; (10) Aracese; (11) Guttiferse; (12) Diptero- carpe?e, 60 species. This list, it must be remembered, refers to the '^ primeval forests " alone, taking no account of the widespread tropical flora found in old clearings and in the vicinity of towns and villages. Before leaving the Asiatic continent I must say a few words as to the figures given in the table for the plants of Indo- China, comprising the whole territory between Buraia aud China, which has been at least as w^ell explored by French botanists as have Burma and the Malay Peninsula by our- selves. Having been unable to obtain any statistical infor- mation on this area from English botanists, I applied to ]\r. Gagnepain, of the botanical department of the ^N^atural His- tory Museum of Paris, who hns kindly furnished me witli the following facts. They have at the Museum very large 62 ' THE WORLD OF LIFE collections of 2)laiits from all parts of tliis territory, collected from 1862 onwards, but great numbers of the species are still undescribed. Only small portions of the Hora have been actually described in works still in process of publication ; but, from his knowledge of this extensive herbarium, he believes that the flora of Indo-China, as actually collected, comprises about 7000 species. Flora of the Malay Islands The great archipelago (usually termed the Malayan, or ^' Malaisia "), which extends from Sumatra to Xew Guinea, a distance of nearly 4000 miles, and from the Philippines to Timor, more than 1000 miles, comprises an actual land area of 1,175,000 square miles, which is fully equal to that of all tropical Asia, even if we include the lower slopes of the Eastern Himalayas. Tliis great land-area has the advan- tage over the continent of being mainly situated within ten degrees on each side of the equator, and having all its coasts bathed and interpenetrated by the heated waters of the Indian and Pacific Oceans. These conditions have led to its being almost wholly forest-clad, and to its possessing a flora com- parable in luxuriance and beauty with that of the great Amazonian plain, situated almost exactly at its antipodes. The western half of this archipelago has undoubtedly been united with the continent at a comparatively recent geological epoch, and this portion of it, both in its animal and vegetable life, is nearly related to that of the Malay Peninsula and Siam ; but the three chief islands, Sumatra, Borneo, and Java, are of such great extent, and have such, differences, both of geological structure and of climate, as to give to each of them a distinct individuality, combined with, in all probability, a Avealth of species fully equal to that of the adjacent continent.^ The remainder of the Archi- 1 The Director of Kew Gardens informs me that, in 1850, the flora of the ( " Netherlands India," extending from Sumatra to New Guinea but exclud- ing the Philippines, was estimated by the Dutch botanists to possess 0118 TEOPICAL FLORAS 53 pelago has bad, however, a different origin, and has been much longer isolated. Celebes and the Philippines have cer- tain features in common, indicating a remote but partial union with, or approximation to, the Asiatic continent, and probably subsequent submergence to an extent that has greatly impov- erished their mammalian fauna. Xew Guinea, however, stands alone, not only as the largest island in the world (ex- cluding Australia), but as, in some respects, the most remark- able, both by its extraordinary length of about 1500 miles, and its possession of a range of snow-capped and glaciated mountains. Biologically it is unique by having produced the wonderful paradise-birds, numbering about 50 species ; while its true land-birds already known amount to about 800 species, a number very far beyond tliat of any other island — Borneo, with its almost continental fauna, having about 450, and the great island-continent of Australia about 500. But, as regards plant-life, this vast archipelago is much less known than that of inter-tropical Asia, though it will, I believe, ultimately prove to be even richer. Of the two larger w-estern islands, Sumatra and Borneo, I can obtain no estimate of the botanical riches, and the same is the case with the whole of the Moluccas. Java is better known, but still inadequately. There remains for consideration the Philippines, Celebes, and ^ew Guinea, as to which we have recent information of con- siderable interest. Since the Americans have established themselves in the Philippines they have done much to make known its natural products; and Mr. E. D. Merrill, botanist to the Bureau of Science at Manilla, has greatly increased our former scanty knowledge of its very interesting flora. He has been so kind as to send me several of his published papers, as well as a complete MS. list of the families and genera of vascular plants, with the number of species known to inhabit the islands up to species of flowering plants then known. As such large portions of all the islands are almost unknown botanically, it seems not improbable that the actual numbers may be three times as many. 54 THE WORLD OF LIFE August 1909. This shows the large total of 4656 indigenous flowering plants already collected, though extensive areas in all the islands, and more especially in the great southern island Mindanao, are altogether unexplored. Besides these, there are no less than 791 ferns and their allies, a number which is probably not surpassed in any other country of equal extent and as imperfectly explored. The Malay Peninsula has rather more flowering plants, but its ferns are only 368, as given in ]\rr. Eidley's list, issued in 1908. The following is the sequence for the first twelve orders (excluding introduced plants) from Mr. Merrill's lists: — Philippixes (4G56 species) 1. Orchideffi 372 2. Eubiacese 267 3. Leguminosae 258 4. Euphorbiacese 227 5. Urticaceae, with ]\Ioraceae . . 221 G. Graminese 215 7. Cyperaceae 137' 8. Myrtaceae 105 9. Palmse 100 10. Asclepiadeae 94 11. Melastomaceae 86 12. Compositae 83 Ferns 791 species. Comparing this with the Malay Peninsula (jd. 18), we find the first four orders in similar places of the sequence, while Anonacese, ScitamineiT, and Melastomacese give way to Myr- tacese, Palma^, and Asclepiadeae. The Philippine flora has a large proportion of its species peculiar to it. In some families, such as the Ericaceae, Ges- neracese, Pandanacese, etc., almost all are so. Among species of limited range some interesting facts have been ascertained by Mr. Merrill. Of identical or closely allied species in sur- rounding countries, 39 have been found to extend to northern India, 38 to China, and 21 to Formosa, while only 9 have been noted in the nearer islands of Borneo, Java, and Sumatra. But the most decided similarity is found between the Philip- pines and Celebes, 76 species having been found either identical or represented by allied species ; and, considering how very imperfectly the Celebesian flora is known, the amount of simi- larity may be expected to be really very much greater. A sim- TEOPICAL PLOKAS 55 ilar relation of the mammals, birds, and insects of the two island groups have been pointed out in my Island Life, and leads to the conclusion that the islands have, at some distant period, been almost or quite united. The Flora of Celebes Very little was known of the flora of this extremely inter- esting island till 1898, wdien Dr. S. H. Koorders published a large quarto volume of nearly 750 pages, giving the results of his own collections during four months in the north-east pen- insula (Minahasa) together with all that had been made known by the few botanists who had previously visited the islands. Dr. Koorders himself collected or examined 1571 species, of which nearly 700 were trees ; and he has given lists of 468 species w-hich had been collected in various parts of the island by other botanists, making a total of 2039 species of flowering plants. The great peculiarity of the flora is indicated by the fact that nineteen of the genera of trees are not kno^\Ti in Java ; wdiile the affinities are, on the whole, more Asiatic than Australian, as is the case with the animals. The closest affin- ity is W'ith the Philippines, as with the birds and mammals, as indicated by a new genus of trees (W allacesdendron celehi- cwn), allied species having been since found in the adjacent group. Dr. Koorders also remarks that some of the plants have very peculiar forms, almost comparable with those I have pointed out m its butterflies. One of these is no doubt the new^ fig-tree (Ficus minaliassa) , a drawing of which forms the frontispiece of this volume. It is about 40 feet high, the fruits hanging thickly from the branches in strings 3 or 4 feet long, giving it a very remarkable appearance. His general result is, that the flora is very rich in peculiar species, but rather poor in peculiar genera. As this work is wholly in Dutch, I cannot give further details, but having counted tlie species in each natural order I will add a list of the ten largest orders for comparison with others here given : — 56 THE WOELD OF LIFE \ 1. Urticaeese 158 2. Legviminosse 105 3. Rubiacese 103 4. Euphorbiaceae 100 5. Orchideae 81 6. Palmaeeae 78 7. Gramineae 71 8. Compositse 63 9. :\Iyrtaeea». 58 10. Meliaceae 58 I will add a few words on a point of special interest to myself. Having fonnd that tlie birds and mammals of the eastern half of the Archipelago Avere almost wholly different from those in the western half, and that the change occurred abrnptly on passing from Bali to Lombok, and from Borneo to Celebes (as explained in chapter xiv. of my Malay Archi- pelago), the late Professor Huxley proposed that the straits between them should be called '' Wallace's Line," as it forms the boundary between the Oriental and Australian regions. But later, as stated in my Island Life, I came to the conclu- sion that Celebes was really an outlier of the Asiatic continent but separated at a much earlier date, and that therefore Wal- lace's Line must be dra^vn east of Celebes and the Philippines. The Flora of New Guinea Early botanical explorers in Kew Guinea were disappointed by finding the flora to be rather poor and monotonous. This was the case with Prof. O. Beccari, who collected on the north- w^est coast; and Mr. H. O. Forbes, of the Liverpool Museum, informs me that he formed the same opinion so long as he had collected on the lowlands near the coast, but that on reaching a height of near 1000 feet a much richer and quite novel flora was found. Prof. Beccari, who is at this time studying the palms from various recent Dutch, British, and German collec- tions, now thinks that the number of species in Xew Guinea is probably as gTeat, in equal areas, as in Borneo or the Malay Peninsula, but that the species are not so distinctly marked as in those countries. Thev are what he terms second-ffrade species as compared with the first-grade species of the latter. But he forms this opinion chiefly from the palms, of which he makes a special study. TKOPICAL riOKAS 57. Dr. Lauterbach, who is engaged in describing the new plant- collections recently obtained, is evidently much impressed by them. He states that down to 1905 there were known from German Xew Guinea 2048 species of flowering plants, while about 1000 additional species had been found in other parts of the island. But the last Dutch expedition, from the por- tions of the collections he has examined, will probably add another 1000 species. Again he says that from collections recently made by Schlechter in German Xew Guinea, and through letters from him, an ^' immense increase in the number of species is in prospect.'^ A few^ more years of such energetic collecting will disclose more of the treasures of this the largest of the great tropical islands, while its grand central chain of mountains may be expected to produce a large amount of nov- elty and beauty. Dr. Lauterbach's conclusion, in a letter to Prof. Beccari, is as follows : " I believe, indeed, that one would not estimate it too highly if one reckoned the sum total of the Papuan Phanerogams at a round number of 10,000." Con- sidering that ^ew Guinea has more than double the area of the Philippines (which Mr. Merrill also estimates may con- tain 10,000 species) ; that it is nine times the area of the Malay Peninsula, which has already more than 5000 species described; that it has the enormous length of 1500 miles, all between 0° and 11° of S. latitude; that it has an extremely varied outline ; that it possesses abundant diversity of hill and valley, and a central range of mountains which have now been proved to rise far above the line of perpetual snow ; and finally, that it is almost everywhere clad with the most luxuriant for- ests, and enjoys that moist and equable equatorial climate which is proved to be most favourable to vegetable as well as to insect life, it seems to me probable that it may ultimately prove to be among the richest areas on the earth's surface. In bird-life it seems likely to surpass any other equal area, and it may do so in plants also, but In the luxuriance of insect-life I am inclined to think that it will not equal the richest por- tions of equatorial America. 68 THE WORLD OF LIFE The only other tropical flora in the eastern hemisphere in- cluded in my table is that of Queensland, which is mostly within the tropics, but a large part of the interior consists of elevated plains with a rather arid climate where little of the luxuriance of tropical vegetation is to be met with. Probably not more than one-fourth of the area is clothed with a typical tropical vegetation, but this has as yet been very partially explored botanically. The number of species compares best with that of the Indian peninsula, with wdiich it agrees nearest in area ; and both these countries, though very rich in certain districts, cannot be considered to present examples of the full luxuriance of tropical vegetation. Floras of Tropical Africa and America The floras of the remainder of the tropics are, for various reasons, of less interest for the purposes of this work than those of the eastern hemisphere, and a very brief reference to them wdll be here given. Although Africa has a tropical area nearly equalling those of Asia and America combined, it has a flora of less extent and of less botanical interest than that of either of them. Its area of luxuriant tropical forest is comparatively of small extent, and much of it is yet unex- plored, so that the number of species in the latest enumeration is perhaps more than might have been expected. The islands belonging to Africa — ■ Madagascar, Mauritius, Bourbon, and the Seychelles — are, however, of extreme interest, on account of the remarkable character, as well as the extreme speciality, both of their plants and animals. As, however, these pecul- iarities have been rather fully discussed in chapter xix. of my Island Life, it is not necessary to repeat them here. I may state, however, that in Mauritius there are about 40 peculiar genera, nearly all of shrubs or trees, while no less than 5 peculiar genera of palms are found in the Seychelle Islands. The following table of tlie sequence of orders in Madagascar may be of interest for comparison with those of other large floras. TROPICAL FLOEAS 59 Madagascar (5000 species) 1. Leguminosae 346 2. Compositae 281 3. Euphorbiaceae 228 4. Orchideae 170 Ferns 5. Cyperaceae 160 6. Rubiaceaj 147 7. Acantluiceae 131 8. Giamineae 130 318 species. The above table was made when the whole flora consisted of 3740 known species. As it is now increased to nearly 5000, the figures given will have to be increased by one-third on the average. But as this increase may be very unequal, they have been left as sriven. Flora of Tropical America We have seen reason to believe that the temj^erate flora of ^orth America is somewhat poorer than that of Europe and northern Asia, though the south temperate zone as represented by Chili is exceptionally rich. But there can be little doubt that its whole tropical flora is extremely rich ; and it may not improbably be found to contain nearly as many species of plants as all the rest of the tropical world. This may per- haps be indicated by the fact that it has fourteen or fifteen natural orders quite peculiar to it, wdiile the remainder of the globe has about the same number ; but, taking account of three other orders that are almost exclusively American, Mr. Hemsley is of opinion that the balance is on the side of America. America has the great advantage of possessing the largest continuous or almost continuous extent of tropical forest on the globe. The vast Amazonian plain forms its central mass of about two millions of square miles of almost continuous forest. From this there are northward extensions over the Guianas and parts of Venezuela, along the north-east branch of the Andes to Trinidad, and thence through Panama and Honduras to the lowlands of eastern and western Mexico. Southward it sends out numerous branches along the great river valleys into central and western Brazil, and thence along 60 THE WORLD OF LIFE the eastern slopes of the Andes to beyond tlie southern tropic; while all along the Atlantic coast there is a belt of equal lux- uriance, spreading out again in the extreme south of Brazil and Paraguay to about 30° of south latitude. We could thus travel continuously for about five thousand miles from Mexico to northern Argentina in an almost unbroken tropical forest, or about the same distance down the Amazon valley to Par- anahyba in northern Brazil, and then, after a break of a few hundred miles, along the east coast forests for about two thou- sand miles more. This probably equals, if it does not surpass, the tropical forest area of the rest of the globe. We must also take into account the fact that, as a rule, tropical forests differ from those of the temperate zone in the s^^ecies not being gregarious, but so intermingled that adjacent trees are generally of distinct species, while individuals of the same species are more or less widely scattered. When, from some commanding elevation, we can look over a great extent of such a forest, we can usually see, at considerable intervals, a few, perhaps a dozen or more, small patches of identical colour, each indicating a single tree of some particular species which is then in flow^er. A few^ days later we see a different colour, also thinly scattered; but in the region of the most luxuriant tropical forests we never see miles of country thickly dotted with one colour, as would often be the case if our Euro- pean oaks or beeches, birches or pines, produced bright-col- oured flowers. This fact would alone indicate that the tropical forests are wonderfully productive in species of trees and woody climbers, and hardly less so in shrubs of moderate size, which either live under the shade of the loftier trees or line the banks of every river, stream, or brooklet, or other opening to which the sun can penetrate. In those latter positions there is also no lack of herbaceous plants, so that the whole flora is exceed- ingly rich, and the species composing it rapidly change in response to the slightest change of conditions. The difficulty of collecting and preserving plants in these forest-clad areas is so great, and the number of resident bot- TEOPICAL FLORAS 61 anists who alone could adequately cope with the work is com- paratively so small, that it is not surprising to find thai the great forest region of tropical America is still very imperfectly known. Only tw^o considerable areas have been systematically collected and studied — in ^orth America the entire tropical portion from South Mexico to Panama commonly known as '" Central America " ; and in South America the vast areas of Brazil, itself comprising more than half of tropical South America. The comparatively easy access to this latter country, the attraction of its gold and diamond mines, its extensive trade with England and with other civilised countries, have all led to its being explored by a long series of botanists and travellers, the result of whose labours have been incorporated in a moniimental work, the Flora Brasiliensis of Martins, re- cently completed after more than half a century of continuous labour. The number of species described in this work is 22,800, an enormous figure considering that its area is less than half that of tropical Africa, and that probably two-thirds of its surface has never been thoroughly examined by a botanist. The Cen- tral American flora, as described by Mr. Hemsley,^ in less than one-third of the area of Brazil has about 12,000 species, and this is no doubt a much nearer approach to its actual num- bers than in the case of Brazil. As regards the additions that may yet be made to that flora, and especially to the great forest region of adjacent countries, I will quote the opinion of a very competent authority, the late Dr. Bichard Spruce, who assiduously studied the flora of the Amazon valley and the Andes for fourteen years, and himself collected about 8000 species of flowering plants, a large pro- portion of which were forest-trees. In a letter to Mr. Bentham from Ambato (Ecuador), dated 22nd June 1858, he writes: " I have lately been calculating the number of species that yet remain to be discovered in the great Amazonian forest from 1 See Biologia Centrali Americana, by Messrs. Godman and Salveri; Botany, 4 vols., 1888. 62 THE WORLD OF LIFE the cataracts of the Orinoco to the mountaius of Matto Grosso. Taking the fact that by moving away a degree of latitude or longitude I found about half the plants different as a basis, and considering what very narrow strips have up to this day been actually explored, and that often very inadequately, by Humboldt, Martins, myself, and others, there should still remain some 50,000 or even 80,000 species undiscovered. To any one but me and yourself, this estimation will appear most extravagant, for even Martins (if I recollect rightly) emits an opinion that the forests of the Amazon contain but few species. But allowing even a greater repetition of species than I have ever encountered, there cannot remain less than at least half the above number of species undiscovered." ^ Spruce was one of the most careful and thoughtful of writers, and would never have made such a statement without full con- sideration and after weighing all the probabilities. In the same letter he describes how, when leaving the Uaupes River after nine months of assiduous collecting there in a very lim- ited area, a sunny day after continuous rains brought out' numerous flowers, so that as he floated down the stream he saw numbers of species quite new to him, till the sight became so painful that he closed his eyes to avoid seeing the floral treasures he was obliged to leave ungathered ! At Tarapoto he observed that some flowers opened after sunset and dropped off at daAvn, so that they would be overlooked by most collectors, while of many the flowering season was very limited, sometimes to a single day. Join to this the scarcity of individuals of many species scattered through a trackless forest, and it is evi- dent that the true floral riches of these countries will not be fully appreciated till numerous resident botanists are spread over the entire area. From the facts of distribution given by Mr. Hemsley we learn that about one-twelfth of the species of Central America 1 See Spruce's Xotes of a Botanist on the Amazon and Andes, vol. ii. p. 208. TEOPICAL FLORAS 63 are found also in South America, and that about TOO are found in the eastern portion from Venezuela to Brazil, so that prob- ably not more than 500 reach the latter country. The com- bined floras of Brazil and Central America, even as now imperfectly loiown, will therefore reach about 34,300 species. N^ow, considering how very rich the eastern slopes of the Andes are known to be, and that the average width of the forest zone between Brazil and the Andes is from 400 to 500 miles, while the plateaux and western slopes also have a rich and distinct flora and fauna, I think it will be admitted, that whatever the combined floras of Brazil and Central America may amount to, that number will be nearly or quite doubled when the entire floras of Venezuela, the Guianas, Colombia, Ecuador, and Peru are thoroughly explored. As, roughly speaking, Brazil con- tains about half the great tropical forests of South America, and allowing that its portion is the best kno^vn, we may fairly add one-third of Spruce's lower estimate (25,000) to its present numbers, Avhich will bring the whole to very nearly 40,000 sjDecies. By doubling this, we shall reach 80,000 as the probable number of species existing in tropical South America. As this number is considerably more than half the latest estimate of the number of flowering plants yet known in the whole world (136,000 species),^ more than half of which number will be absorbed by the comparatively well-known tem- perate floras, it will be apparent that we have at present a very inadequate idea of the riches of the tropical regions in vege- table life. This result will be further enforced by additional facts to be adduced later. I will here give a table of the few known statistics for trop- ical America, which, though very fragmentary, will serve to show the basis on which the preceding estimate of probable numbers rests. 1 This number has been given me by Mr. W. B. Hemsley, Keeper of the Kew Herbarium, as being that of Dr. Tlionner in 1008. 64 THE WORLD Or LIFE Floras of Tropical America Country. Area, Sq. Miles. De scribed Species. Remarks. Mexico (8.) and Cen- 1 tral America J Brazil 910,000 3,200,000 79,000 4,200 1,750 2,400 12,000 22,800 3,000 2,722 1,967 445 Hemsley, 1888 Martins Nicaragua to Panama .... Jamaica Hemsley L. N. Brittan, 1909 Trinidad J. H. Hart, 1908 CralaDasros (1902) Note. — The number of Trinidad plants is from a Herbarium List by Mr. J. H. Hart, F.L.S., Superintendent of the Botanical Gardens, published in 1908. He states, however, that "a large amount of material has not been arranged under natural orders " and that "the later added specimens have not been arranged for several years past." But he adds, " As it now stands, there is a good representation of the Trinidad flora." Mr. W. B. Broadway of Tobago, who has lived several years in Trinidad and has studied its flora, informs me that from his own observation he believes that many hundreds of additional species remain to be collected; and this is what we should expect, as the island is a continental one ; while Jamaica, though larger, is almost oceanic in character, and is therefore almost certain to have a less complete representation of the tropical American flora than the former island. The great work on the flora of Mexico and Central America deals, unfortunately for my present purpose, with an area in which temperate and tropical, arid and humid conditions are intermingled to a greater extent even than in the case of British India already referred to. Mexico itself comprises about four-fifths of the whole area, and nearly half its surface is north of the tropic and is largely composed of lofty plateaux and mountains. It thus supports a vegetation of a generally warm-temperate but rather arid type; and these same condi- tions with a similar flora, also prevail over the great plateau of southern Mexico. This type of vegetation extends even TEOPICAL FLORAS 65 farther south into the uphuuls of (liiateinala, so that we only get a wholly tropical flora in the small southern section of the area from Kicaragua to Panama. The following table of the twelve largest orders in the whole flora Avill be of interest to compare with that of British India; Mexico and Central America (11,688 species) 1. Compositse 1518 2. Leguminosae 944 3. Orchidese 938 4. Gramineae 520 5. Cactaceae 500 6. Rubiaceae 385 7. Eiiphorbiacese 368 8. Labiata? 250 9. Solanaceae 230 10. Cyperaceae 218 1 1. Piperaeese 214 12. Malvaceae 182 Ferns 545 The most remarkable feature in this table is the great pre- ponderance of Compositse characteristic of all the temperate and alpine floras of America, and the presence of Cactaceae, Solanaceae, Piperaeese, and Malvaceae among the 12 predomi- nant orders, the first of the four being confined to America. It may be noted that of the 12 most abundant orders 8 are the same in these two very widely separated parts of the earth. But even this table greatly exaggerates the actual difference between the two very distinct floras. There are 175 natural orders in British India, and of these only 20 are absent from the Mexican region. Of these 20 orders 18 have less than 10 species (5 of them having only 1 species), so that, judging from the great types of plants, the difference is wonderfully small. We can therefore understand Sir Joseph Hooker's view, that there are only two primary geographical divisions of the vegetable kingdom, a tropical and a temperate region. It must be remembered, however, that even when the series of orders in two remote areas are nearlv identical, there mav be a very marked difference between their floras. Orders that are very abundant in one area may be very scarce in the other ; and even when several orders are almost equally abundant in both, the tribes and genera may be so distinct in form and structure as to give a very marked character to the flora in 66 THE WORLD OF LIFE which they abound. Thus the Urticacese include not only nettles, hops, and allied plants, but mulberries, figs, and bread- fruit trees. Even Avith so much identity in the natural orders, there is often a striking dissimilarity in the plants of distinct or remote areas, owing to the fact that the genera are very largely different, and that these often have a very distinct facies in leaf and flower. Thus, though the Myrtacese are found in hot or warm countries all over the world, the Euca- lypti, so abundant in Australia, give to its vegetation a highly peculiar character. So the Onagracese are found in all the temperate regions, yet the Fuchsias of South-temperate America are strikinoly different from the Willow-herbs of CD «- Europe or the CEnotheras of ^^Torth America ; and there are thousands of equally characteristic genera in all parts of the world. In Mr. Hemsley's elaborate table of the General Distribution of Vascular Plants, he gives, in Central America, the number of species of each order in Nicaragua, Costa Rica, and Panama respectively, these three states constituting the tropical section of the whole area, and the same for six subdivisions of the rest of the area. But the numbers added together will give more than the actual number of species in the combined flora, be- cause an unlvnown portion of the species will be found in two or three of these divisions. But he gives the total numbers for these three states and also for the remainder of the nine areas. He also gives the numbers which are '^ endemic " in these two groups of areas separately and in the whole flora ; I have therefore been able to ascertain the proportion which the endemic bear to the total in Mexico and Guatemala, which I find to be as 3 to 4 verv^ nearly, so that by deducting one-fourth of the sum of the species in these areas I obtain the number existing in the combined area. But as it is known that in the tropics species have a less range than in the temperate zone, I deduct one-fifth in the case of the three tropical areas, which will, I believe, approach very nearly to the actual number of species in the combined floras as given in the following table. TEOPICAL FLOEAS 67 Nicaragua, Costa Kica, and Panama (3000 species) 1. Orchidcai 280 2. Conipositu? 107 o. LegLiiniiiQsaj 17(3 4. Riibiaeete 14(5 5. Uraminetp iH) 6. Eiiphoibiacese 72 7. Gesneraceaj GO 8. Cyperawa? 08 0. Alelastomacea^ 07 10. Urticacoai 58 11. Aioideie 5-t 12. Palraai 50 Ferns 252 This table brings out clearly the extra-tropical character of Mexico as compared with these tro|)ical sections of Central America. Xo less than five orders of the former twelve have to be omitted (Cactacea?, Labiates, Solanacese, Piperaceas, and Mal- vaceae), which are replaced by the more exclusively tropical Ges- neracea?, Melastomacese, Urticacese, xVroideae, and Palmte. Here, in two adjacent areas differing about 12° in mean lati- tude, there is a more pronounced difference in the prevalent orders of plants than exists between two great regions on oppo- site sides of the globe. Another characteristic tropical feature is seen in the large number of ferns, which are nearly one- half those of the whole number found in Mexico and Central America, which has an area nine times as great. Of the other tropical American floras little need be said. Jamaica and Trinidad are the onlv West Indian islands of the larger group for which I have been able to get recent figures. Mr. L. ]^. Brittan, of the ]^ew York Botanical Gar- dens, who has collected in the former island, estimates the species at 2722, which, for a sub-oceanic island, is a large amount. Trinidad, which is almost a part of the continent, should be much richer, and its existing collections, not quite reaching 2000, are certainly much below its actual number of species. The Galapagos, now probably fairly well known, but possessing only 445 species, show us how scanty may be the flora of a group of islands of considerable size and situated on the equator, when the conditions are not favourable for plant-immigration or for the gTowth of plants at or near the sea-level, as has been pointed out in my Island Life. Q8 THE WOKLD OF LIFE The Flora of Lagoa Santa There is, however, one small area in the Campos of Brazil in about 20° S. lat. and 2700 feet above the sea-level, which has been thoroughly explored botanically bv a Danish botanist, Professor Eug. Warming, who lived there for three years with his fellow-countrvman Dr. Lnnd, who first studied the fossil vertebrates in the caves of the district. This was in 1SG3-66; and after studying his collections for twenty-five years with the assistance of many other botanists he published in 1892 a quarto volume giving a most careful account of the vegetation in all its aspects, with numerous very characteristic illustra- tions, both of individual plants and of scenery, forming one of the most interesting botanical works I have met with. Un- fortunately it is printed in Danish, but a good abstract (about thirty pages) in French renders it accessible to a much larger body of readers. This flora is strictly limited to an area of sixty-six square miles, so that every part of it could be easily explored on foot, and again and again visited as different species came into flower or ripened their fruit. The surface is undulating and in parts hilly, with a lake, a river, some low rocky hills, marshes, and numerous deeply eroded ravines and valleys, often with perpendicular rocky sides, where there is perpetual mois- ture and a rich forest-vegetation. But everywhere else is for half the year arid and sun-baked, covered with scattered decid- uous trees and shrubs, and during the rains producing a fairly rich herbaceous vegetation. It is, in fact, a good example of the campos that occupy such a large portion of the interior of Brazil, though perhaps above the average in productiveness. An open country such as this is, of course, much easier to examine thoroughly than a continuous forest, which, though actually richer, calls for a much longer period of exploration before all its riches can be discovered. But though the coun- try is so open, with trees and shrubs spread over it in a park- like manner, Mr. Warming tells us that trees of the same spe- TROPICAL FLORAS 69 cies are so widely scattered that it is sometimes difficult to find two of the same kind. Another interesting fact is, that the number of species of all kinds — trees, shrubs, and herbs — ei (JJ CO 00 c3 O fcD bD d (VI Q •*-> to ^ 2 B o CO ^*^ 6 ^ M is twice as great in the patches of forest as in the open campos, while the two are so distinct that he believes them to have hardly a species in common. TO THE WORLD OF LIFE Through the kindness of Professor "Warming I am able to reproduce here a few of his characteristic drawings and photo- graphs, with descriptions furnished by himself. These offer a striking contrast to the photographs of typical Malayan vege- tation at pp. 48 and 50. As shewn in the view on p. 69 (Fig. 3) the vegetation cov- ering the hills is w^hat is termed ^^ cam2:)os limpos," consisting Fig. 4. — The Campo Cerrado; Lapa Vermelha Rocks to the Right. of grasses and herbs with small shrubs, but with few trees scattered in the grass-land. These trees are low, the stems and branches tortnons or twisted. In the valleys where the soil is richer in hnmus and always moist, there is thick forest. TEOPICAL FLOKAS 71 The soil in all the campos is red clay. In the distance is seen the smoke of fires on the campos. In the foreground is a '' campo cerrado," i.e. a campo with many trees, but never so close that the sun does not shine on the dense carpet of high grasses and herbs under the trees ; which latter belong mostly to the Leguminosge, Ternstromiacese, Vochysiacese, Anonacese, Bignoniacese, etc. Fig. 4 is a view taken in the " Campo cerrado," showing the stunted form of the trees which characterise it. In the back- ground are calcareous cliffs, in which are the fossil-producing caves. At the foot of the cliffs the trees are closer and higher ; and on the top is a more open and dry forest, each kind of forest having its peculiar species of trees. Fig. 5 (facing p. 72) is a view taken close to the rocks. The upper branches of Mimosas and other trees are shown, which grow at the foot of the cliffs, one of them being a tree of the custard-apple family, whose branches are fruit-laden. Numerous tall cactuses (Cereus ccerulescens) are seen growing up from the rock itself, and several stinging and thorny plants. Other genera growing on the rocks are Opuntia, Pereskia, Peperomia, Epidendrum, Tradescantia, Gloxinia, Amaryllis, Bomarea, Griffinia, and many others, so that we have here a curious mixture of forest trees and climbers with moisture- loving plants and those characteristic of arid conditions, all growing close together if not actually intermingled. Before describing a few of the special peculiarities of the campo vegetation of Lagoa Santa, I will here give some numer- ical data of interest to botanical readers. The sequence of the orders in this very interesting flora is as follows : — Lagoa Santa (2490 species) 1. Compositae 26G 2. Leguminosae 235 3. Gramineae 158 4. Orchidaceae 120 5. Euphorbiaceae 100 6. Myrtacese 100 7. Rubiaceae 94 8. Cyperaceae 77 0. Malpighiaceap 04 10. INIelastomaceae 62 1 1. Labiatae 49 12. AsclepiadeiB 48 Ferns and allies 106 species. 72 THE WORLD OF LIFE The chief feature which distinguishes this flora from that of Nicaragua and Costa Rica is the presence in some abundance of the highly characteristic South ximerican order Malpighia- cese, the high position of Myrtacese, with Labiates and Ascle- piads in place of Aroids and Palms. Of the rather numerous Orchids about 70 are terrestrial, 50 epiphytes. There are over 40 genera, of which Spiranthes has 16 species, Habenaria 12, while 22 have only 1 species each. The very large American genus Oncidium has only 5 species, while the grand genus Cattleya, so abundant in many parts of Brazil, seems to be entirely absent. Adaptations to Brought The plant figured on the next page, like many others of the campos, has its roots swollen and woody, forming a store of water and food to enable it to withstand the effects of drought and of the campo-fires. The old stems show where they have been burnt off, and the figures of many other plants with woody roots or tubers, figured by Mr. Warming, show similar effects of burning. Still more remarkable is the tree figured on p. 74 (Fig. 7), which is adapted to the same conditions in a quite different way, as are many other quite unrelated species.-^ The group of plants is really an underground tree, and not merely dwarf shrubs as they at first appear to be. What look like surface- roots are really the branches of a tree the trunk of which, and often a large part of the limbs and branches, are buried in the earth. The stems shown are the root-like branches, which are 4—5 inches diameter, w^hile the growing shoots are from 2 to 3 feet high. The whole plan (or tree) is from 30 to 40 feet diameter. As the branches approach the centre they de- 1 The following species have a similar mode of gro\vth : Anacardium Jiumile, Hortia Brasiliensis (Riitacese), Cochlospermum insigne (Cistaceae), Simaha Warniingiana (Simariibaeese) , Erythroxylon campestre (Erythroxy- laceae), Plumiera Warmingii ( Apocynaceae ) , Palicourea rigida (Cincho- naceae ) , etc. r. a o O) > fie o c3 fcX) P- fcJO o o c o ir^ TROPICAL FLOEAS 73 Fig. 6. — Casselia Chamcedrifolia, nat. size (Verbenacefie) . scend into the earth and form a central trunk. A French botanist, M. Emm. Liais, says of this species: " If we dig we 74 THE WORLD OF LIFE find liow all these small shrubs, apparently distinct, are joined together underground and form the extremities of the branches of a large subterranean tree which at length unite to form a single trunk. M. Eenault of Barbacena told me that he had Fig. 7. — Andira Laurifolia (Papilionacese). dug about 20 feet deep to obtain one of these trunks." The large subterranean trees with a trunk hidden in the soil form one of the most singular features of the flora of these campos of Central Brazil. The above facts are from Mr. Warming's book, supplemented by some details in a letter. They are certainly very remark- able ; and it is difficult to understand how this mode of growth has been acquired, or how the seeds get so deep into the ground as to form a subterranean trunk. But perhaps the cracks in the dry season explain this. A large part of these campos is burnt every year at the end of the dry season, but as the vegetation is scanty the fires pass TKOPICAL FLORAS T5 quickly onwards and do not appear to kill or injure the trees or even the small herbaceous plants. In fact, numbers of these plants as soon as the rains come produce foliage earlier than Avhere there has been no fire, and often produce flowers when unburnt trees or shrubs of the same species remain flowerless. Mr. Warming and otlier botanists believe that the practice of firing the campos was a native one long before the European occupation, and that many of the plants have become adapted to this annual burning so as to benefit by it. It is interesting to note here the opinions of two eminent botanists, only thirty years ago, as to the comparative riches of certain tropical and temperate countries. In his great work on The Vegetation of the Globe, Griesbach thus refers to the Brazilian flora : ^^ The results of the explorations of Martins, Burchell, and Gardiner, cannot be compared with those fur- nished by the Cape. The number of endemic species may per- haps reach 10,000, but the area is twenty times greater than that of Cape Colony, and we may conclude that, as regards its botanical riches, the Brazilian flora is very far from rivalling that of the extremity of South Africa." Gardiner, however, after spending three years in collecting over a large portion of the interior of Brazil, though chiefly in the campos and mountain ranges, concludes his account of his travels with these w^ords : " The countrv is beautiful, and richer than anv other in the world in plants." This general statement may not be strictly true, but it seems clear that the facts already adduced are sufficient to show that, as regards the comparison of tem- perate with tropical floras, there can be no doubt as to the superiority of the latter. This point will, I think, l)e made still clearer in the following discussion of some almost unno- ticed facts. In the case of Brazil and Cape Colony, however, it is clear that Griesbach was creatlv in error. Tlie wliole area of extra-tropical South Africa has probably been as well explored botanically as Brazil, the richest portions of which have been only as it were sampled. Yet wo find less than 14,000 species in the former against 22,S00 in the latter. It 76 THE WOELD OF LIFE will be now shown that when smaller and better known areas are compared the superiority of the tropics is more clearly apparent. The Floras of Small Areas and their Teachings The conclusions already reached by the examination of the chief floras of the world, whether in areas of continental extent, or in those more approaching to the average of our counties, that, other things being equal or approximately so, the tropics are far more prolific in species, will receive further confirma- tion, and I think demonstration, from data I have collected as to the botanical richness of much smaller areas, which having been more thoroughly explored afford more reliable evidence. They also afford very suggestive facts as to the best mode of future exploration which may enable us to arrive at a fair approximation as to the total world-population of flowering plants. For the convenience of readers I give here two tables I have prepared of the floras of small areas in tropical and tem- perate zones, each arranged in the order of their area in square miles for convenience of reference and comparison. I will now briefly discuss the various interesting questions raised by a consideration of these tables. It is, I believe, still a very common opinion among botanists that the wonderfully diversified flora of the Cape Region of South Africa is the richest in the whole world in so limited an area. This is partly owing to the fact that such a large proportion are beautiful garden plants, which for sixty years, from 1775 to 1835, j^oured in a continued stream into Europe and seemed almost inexhaustible. The wonderful group of heaths, of which there are about 350 species, all beautiful and many among the most exquisite of flowers ; the almost equally numerous pelargoniums, the brilliant ixias, gladioli and allies, the gorgeous proteas, the w^onderful silver-tree, the splendid lilies and curious orchises, the endless variety of leguminous shrubs, and the composites including the everlasting flowers. TEOPICAL FLORAS 77 Tropical Floras — Small Areas Place. 1 2 3 4 5 6 Malacca Singapore Penang Lagoa Santa, Brazil Mount Pangerango, Java Kambangan Island, Java Area. Species. 660 2000 206 1740 107 1813 66 2488 n 1750 n 2400 Authoritj'. Gamble. Ridley. Curtis. Warming. Koorders. Koorders. Temperate Floras — Smalt. Areas 1 2 3 4 5 6 7 8 9 10 Place. Mount Nikko, Japan .... Cape Peninsula Schaffhausen Washington, D.C Hertford ( near ) Paramatta River, Sydney Capri, Italy Edmondsham, Dorset Cadney, Lines Tliames Ditton Area. Species. 360 800 180 1750 114 1020 108 922 80 810 20 620 4 719 3 640 3 720 1 400 Authority, Havati. Bolus. A. de Candolle. Ward. A. de Candolle. H. Deane. Beguinot. Rev. E. F. Linton. Rev. Woodruffe-Peacock. H. C. Watson. together with hundreds of other delicate and beautiful little greenhouse plants, — formed an assemblage which no other country could approach. Rich as it is, however, there is now reason to believe that West Australia — Swan River Colony in its original restricted sense — is quite as productive in spe- cies, while evidence is slowly accumulating that many parts of the tropics are really still more productive. The first to be noticed of these rich tropical areas of small extent is the island of Penang in the Straits of Malacca, which, though only 106 square miles in area, contains 1813 species. Sir Joseph D. Hooker, in his Sketch of the Flora of British India (1906), terms this " an astonishing number of species," and remarks on the large proportion which are arboreous, and of the altitude of the island being only 2750 feet. TTere, there- 78 THE WOKLD OF LIFE fore, in an area considerably less than that of the Cape Pen- insula, the species are actually more numerous, and this was evidently a new and astonishing fact to one of the greatest of our living botanists. But the somewhat larger island of Singapore shows us that this amount of productiveness is quite normal; for though it is 206 square miles in extent, it is almost flat, the greatest eleva- tion being only a few hundred feet. A large part of the sur- face is occupied by the town and suburbs, while the original forest that covered it has been almost all destroved. Yet Mr. Ridley finds it to have recently contained 1740 species, and when the town was founded and the forest untouched, it almost certainly had 2000 or even more. We have seen also that Lagoa Santa in South Brazil, 2700 feet above sea-level, with a much smaller area than Penang, and a much less favourable climate, has one-third more species, mainly collected by one enthusiastic botanist during three years' work in this limited district. Here are no mountains, the whole country being an undulating plateau, while for six months there is so little rain that the trees almost all lose their leaves. The aridity causes the trees to be mostly stunted and unshapely; the leaves are clothed on one or both surfaces with felt or dense hairs; and the stems of herbaceous plants are often swollen into thick tubers either underground or just above it. There is thus a mani- fest struggle for existence ajrainst the summer drought with intense sun-heat, and it would hardly be imagined that under such conditions the number of species would equal or exceed that of some of the most luxuriant parts of the tropics. I will now pass on to a consideration of the two last items in the table of small tropical floras, which are more instructive and even amazing than any I have met with in the course of this inquiry. "\^^ien I was in Java about fifty years ago I ascended the celebrated mountains Gede and Pangerango, the former an active, and the latter, much the higher, an extinct volcano. The two, however, form one TROPICAL FLORAS T9 mountain with two summits. During the ascent I was much impressed by the extreme hixuriance of the forest-growth, and especially of the undergrowth of ferns and herbaceous plants. I was told by the gardener in charge of the nursery of cinchonas and other plants, that 300 species of ferns had been found on this mountain, and I think 500 orchids. I was therefore anxious to learn if any figures for the plants of the whole mountain could be obtained, and was advised by the Director of Kew Gardens to apply to Dr. S. Koorders of the Reijks Museum, Leiden. In reply to my inquiries, Dr. Koorders wrote me as follows : — "The botanical mountain-reserve on the Gede (Pangerango) is indeed very interesting and very rich, but I know other parts of Java with a much larger number of phanerogams, e. g., the small island of Xoesa Kambangan near Tjilatjap. On that island I collected on an area of about 3 square kilometres (= 1% square mile) 600 of arborescent species of phanerogams, and about 1800 species of not-arborescent species. This island is about — 50 m. altitude (=164 feet).'' " On Mount Pangerango, between 5350 feet and the top, 10,000 feet, the number of forest-trees is about 350 species on the same area, and about 1400 species of not-arborescent phanerogams." On reading the above, I thought at first that Dr. Koorders must have made a mistake, and have meant to write 30 in- stead of 3 square kilometres. So I wrote to him again ask- ing for some further information, and pointing out that Kambangan Island was many times larger than the area he had given. To this he replied that he " only explored a small part methodically," and that the number of species he gave me '^ were found in that part only." ^ It thus became clear 1 It may seem to some readers, as it did at first to myself, that it is im- possible to have over two thousand species of flowering plants growing naturally on about a square mile. But a little consideration will show that it is by no means so extraordinary as it seems. Let us suppose that the average distance apart of trees in an equatorial forest is ten yards, which I think is much more than the average; then in a square mile there will be 176 X 170 = 30,976 trees. But in Kambangan Island there are 600 80 THE WORLD OF LIFE that no mistake had been made. I was further satisfied of this bj referring to a small volume by M. Jean Massart, en- titled Un Botaniste en Malaisie. He there describes the ^' mountain reserA'e " on Pangerango as being 300 hectares of virgin forest, extending from the limits of cultivation to near the summit. As '' 300 hectares " is the same area as '' 3 square kilometres/' there can be no doubt as to the figures given. M. Massart also states that Dr. Koorders was head of the " forest-fiora " department of the Buitenzorg Botanical Gardens, and that he had established eighteen other reserves in various regions of Java. Each of these reserves is under a native superintendent, who allows no tree to be cut down without orders, and watches for the flowering and fruiting of every species of tree. One specimen at least of all the species is numbered, and paths made and kept in order, so that they can be easily visited, and the flowers or fruit gathered for the herbarium. Dr. Koorders has now obtained specimens of about 1200 trees indigenous to Java, while 3500 specimens have been numbered in the reserves. This number is without counting either shrubs or climbers. I give here a reproduction of a charming little photo- graph taken in West Java more than fifty years ago by my friend, the late Walter Woodbury, and I believe in the south- ern country not very far from the island which Dr. Koorders found so rich (Fig. 8). The intermingling of dwarf palms and ferns, with the varied foliage of shrubs and herbaceous plants, and the abundance of lianas hanging everywhere from the trees overhead, give an impression of tropical luxuriance beyond even that of the Malayan photographs pp. 48 and 49. The system of small forest reserves in tropical or other im- species of trees in IJ square mile, so that each species would be represented on the average by 60 individuals. But, as some are comparatively common, others rare, there would in some cases be only 3 or 4 specimens, while many, having from 50 to 100, would be really abundant, but, if fairly scattered over the whole area, even these might require searching for to find two or three specimens; which accords with the facts as testified by all botanical travellers. !> *-' z o — o I ^ ^ u W. *» % ^ o >> E=< ■= hides and froghoppers on our roses and other shrubs or flowers, and grubs which attack our apples, our carrots, and most other crops; and all these the gardener usually re- gards under the general term " blight," as a serious blot on the face of nature, and wonders why such harmful creatures were permitted to exist. Most professional gardeners would be rather surprised to hear that all these insect-pests are an essential part of the world of life ; that their destruction would be disastrous ; and that without them some of the most beautiful and enjoyable of the living things around us would be either seriously diminished in numbers or totally destroyed. He might also be informed that he himself is a chief cause of the very evil he complains of, because, by growing the plants the insect-pests feed upon in large quantities, he provides for them a superabundance of food, and enables them to increase much more rapidly than they would do under natural conditions. Let us now consider what happens over our whole country in each recurring spring. At that delightful season our gar- dens and hedgerows, our orchards, woods, and copses are thronged with feathered songsters, resident and migratory, en- gaged every hour of the day in building their nests, hatching their eggs, or feeding and guarding their helpless offspring. A considerable proportion of these — thrushes, warblers, tits, finches, and many others — are so prolific that they have two or three, sometimes even more, families every year, so that the young birds reared annually by each pair varies from four or five up to ten or twenty, or even more. Now, when we consider that the parents of these, to the number of perhaps fifty species or more, are all common birds, which exist in our islands in numbers amounting to many CASES OF ADAPTATION 143 raillions each, we can partially realise the enormous quantity of insect-food, required to rear perhaps five or ten times that number of young birds from the egg up to full growth. Al- most all of the young of the smaller birds, even when their parents are seed-eaters, absolutely require soft insect-food, such as caterpillars and grubs of various sorts, small worms, or such perfect insects as small spiders, gnats, flies, etc., which alone supjoly sufficient nourishment in a condensed and easily digest- ible form. Many enthusiastic observers, by means of hiding-places near the nests or by the use of field-glasses, have closely watched the whole process of feeding young birds, for hours or even for w^hole davs, and the results are extremelv instructive. The chiff-chaff, for example, feeds its young on small grubs ex- tracted from buds, small caterpillars, aphides, gnats, and small flies of various kinds ; in a nest with five young, the hen-bird fed them almost all day from early morning to sunset, bringing mouthfuls of food at an average four times in five minutes. This may no doubt be taken as typical of a number of the smaller warblers and allied birds. Blue tits, with a larger family, worked continuously for sixteen hours a day at midsummer, bringing about two thou- sand caterpillars to the ravenous young birds, who, taking the average at 10 (and they sometimes have 16) would swallow 200 each in the day. A pair of marsh tits were observed to feed their young entirely with small green caterpillars, and in one case made 475 journeys with food in seventeen hours. A gold-crest with eight young brought them food 16 times in an hour for sixteen hours a day. A wren fed its young 278 times in a day. Even the common house-sparrow, itself a typical seed-eater, feeds its young on caterpillars or on small insects which it catches on the wins:. A flvcatcher was ob- served to sit on a dead branch of an ash tree near her nest, whence by short flights she cauglit small flies, etc., on the wing, bringing a mouthful to her young every two to five min- utes. 144 THE WORLD OF LIFE As every schoolboy knows, the number of nests is very great to those who know how to look for them, some being found in almost every wood, copse, or hedgerow. As examples, in a small copse in Herts, nine different species of birds had nests with young, all within 50 yards of each other. In another case, nests of a tit, a flycatcher, and a wood-wren were found within 10 to 15 yards of each other. In the case of many small birds the whole period, from hatching the eggs to that of the young leaving the nest is only two weeks, but swifts require from a month to six weeks. It must be remembered that the birds carefully clean out the nest after every meal, and in wet or very chilly weather carefully protect their young, and as they must also procure food for themselves, it is evident that their labours at this time are really prodigious. And this vast destruction of in- sect-life goes on unchecked for several months together, and the supply never seems to fail. When the parent birds leave the nest in search of food for their young, they may be seen to fly to some adjacent bush or branch of a tree, hop rapidly about it, and then perhaps fly off to another, having apparently decided that the first one had already been nearly exhausted. But in the few minutes of their absence they are always able to fill their mouths with small caterpillars, flics, grubs, etc., and return to the nest, not only from morning to night on one day, but the same day after day, for at least a fortnight and often much longer, till their first brood is fully fledged and able to provide for themselves. But unless the numbers of insects and their larvse were enormous, and were increased day by day by fresh hatchings from the egg as fast as they were devoured, hosts of these young birds would perish of hunger and cold. For if the parents had to range far away from their nests, and could not find the necessary supply so quickly as they do, the young birds would be subject to attack from some of their numerous enemies, would suffer from cold or wet, and as they grew older would often, in their frantic CASES OF ADAPTATIOX 145 struggles with each other, fall out of the nest and quickly perish. What wonderful perfection of the senses must there be in these various parent birds; what acuteness of vision or of hearing; what rapidity of motion, and what powerful instinct of jDarental love, enabling them to keep up this high-pressure search for food, and of watchfulness of their nests and j^oung, on the continuance of which, and its unfailing success, the very existence of those young and the continuance of the race depends. But all this perfect adaptation in the parent birds would be of no avail unless the insect tribes, on which alone most of them are obliged to depend, were as varied, as abun- dant, and as omnipresent as they actually are ; and also imless vegetation were so luxuriant and abundant in its growth and so varied in its character, that it can always supply ample food for the insects without suffering any great or permanent injury to the individual plants, much less to any of the species. By such considerations as these we learn that what we call insect-pests, when they are a little more abundant than usual in our gardens and orchards, do not exist for themselves alone as an apparently superfluous and otherwise useless part of the great world of life, but are, and must always have been through- out long past geological ages, absolutely essential for the origina- tion and subsequent development of the most wonderful, delightful, and beautiful of all the living things around us — our garden friends and household pets, and sweet singers of the woods and fields. Without the myriad swarms of insects everywhere devouring a portion of the new and luxuriant vege- tation, the nightingale and the lark, the wren, the redbreast, and the fairy-like tits and goldcrests might never have come into existence, and if the supply failed would now disappear for ever! The Uses of Mosquitoes If now we go beyond our OAvn country and see how birds fare in distant lands, we find the key to many of the secrets 146 THE WORLD OF LIFE of bird-life in the greater or less abundance of insects which supply them with food at the critical season of their lives when they have to supply daily and hourly food to their newly- hatched broods. Amid all the infinite variety of the insect world there is probably no one order which supplies such an enormous quantity of food to birds and other creatures as the two-winged flies (Diptera) whose larvx are the maggots which quickly devour all kinds of dead beasts and birds, as well as all kinds of putrefying animal matter ; but in the perfect state these insects abound in such swarms as also to supply food to whole groups of fly-catching birds. And among these no well- marked and very restricted group is at once so hateful to mankind and so delightful to birds as the mosquitoes. It is commonly supposed that these particular insect-pests are more especially tropical; but though they are no doubt very abun- dant in many parts of the tropics, yet their fullest develop- ment is to be found in the icy plains of the Far Xorth, espe- cially within the Arctic circle both in the Eastern and Western hemispheres. Sir William Butler in his w^orks — The Wild Lone Land, and others on Arctic and sub-Arctic Xorth America — de- scribes them as often swarming in such abundance as to com- pletely obscure the sun like a dense thundercloud ; and they furnish abundant material for the wildly exaggerated stories in which Americans delight — such as the serious statement that they can pierce through the thickest cow-hide boots, and that an Irishman, seeking protection from them by covering his head with a copper kettle, they pierced it in such countless numbers that their combined strength enabled them to fly away with it! Our best and most instructive writer on the wonderful bird- migrations to the Arctic regions is the late Mr. Henry See- bohm, who spent two seasons there, one in the north-east of Russia, at Ust-Zylma, and at the mouth of the Petchora River, far within the Arctic circle; and another in [N'orthern Siberia, at the mouth of the Yenesay River. He tells us, that — CASES OF xiDAPTxiTIOX 147 " Birds go to the Arctic regions to breed^ not by thousands but by millions. The cause of this migration is to be found in the lavish prodigality with which Nature has provided food. Seed or Fig. 13.— Sh oo t ing Wild Geese on the Pet- chora River at Ust- Zylma (May 14 , 18 75). fruit-eating birds find an immediate and abundant supply of cran- berries^ crowberries, and other ground fruit, which have remained frozen during the long winter, and are accessible the moment the snow has melted, while insect-eating birds have only to open their mouths to fill them with mosquitoes/' ^ Among the larger birds that come early to "these regions to breed are two species of wild swans and the bean goose. So early as 10th May they began to arrive, passing over Ust- Zylma (Lat. G6^ N.) in flocks, where, by constiiicting a shelter, Mr. Seebohm was able to shoot one. Even these large birds find ample food on the tundra to breed there ; for just before leaving the country, wdien near the mouth of the Petchora 1 Siberia in Europe, p. 296. 148 THE WORLD OF LIFE Eiver, he saw them returning southward with their young. He writes : " I had not gone more than a mile when I heard the cackle of geese ; a bend of the river's bed gave me an opportunity of stalking them, and when I came within sight I beheld an extraordinary and interesting scene. One hundred, at least, old geese, and quite as Fig. 14. — Geese Moulting as they migrate South over the Tundra (July and August ) . many young ones, perhaps twice or even thrice that number, were marching like a regiment of soldiers. The vanguard, consisting of old birds, was half-way across the stream, the rear, composed principally of goslings, was running down the steep bank towards the water's edge as fast as their young legs could carry them. Both banks of the river where the geese had doubtless been feeding, were strewn with feathers, and in five minutes I picked up a handful of quills. The flock was evidently migrating to the interior of the tundra, moulting as it went along." This species retires southwards before the winter, and visits us every year in September or October being especially abun- CASES OF ADAPTATIO:^ 149 dant in Ireland, where it is said to be found in every bog and marsh. On the Siberian tundra it no doubt feeds largely on the abundant berries, but also, of course, on the food it finds in swamps and river-mar- gms. Coming back to our more special subject of the mosquitoes, Mr. See- bohm writes as follows. After describing some of his early excursions after birds or their nests he adds: Fig. 15. — Mr. Seebohm in his Mosquito Veil. " That day (June 2nd) I recorded in my journal, with many groans, the arrival of the mosquitoes. Horrid-looking beasts, with bodies a third of an inch long, monsters, the Culex damnabilis of Eae, with proboscis infernali veneno inunita. I foresaw that we should have opportunities enough to study the natural history of these blood-thirsty creatures to our heart's discontent." About a month later he writes when searching for eggs, properly identified : " Doubtless the proper thing to have done would have been to lie down and watch the birds on to their nests; but to become tlie nucleus of a vast nebula of mosquitoes is so tormenting to the nerves, that we soon came to the conclusion that the birds had not begun to breed, and that it was no use martyrising ourselves to find their eggs. The mosquitoes were simply a plague. Our hats were covered with them; they swarmed upon our veils; they lined with a fringe the branches of the dwarf birches and willows; they cov- ered the tundra with a mist." 150 THE WORLD OF LIFE But this was quite at the beginning of the season, and he adds: " We were told that this pest of mosquitoes was nothing as yet to what it would become later. ' Wait a while/ said our Job's comforter, ' and you will not be able to see each other at twenty "^mmi Fig. 16. — Messrs. Seebohm and Harvie-Brown watching Grey Plover through a Cloud of Mosquitoes. paces distance; you will not be able to aim with your gun, for the moment you raise your barrel half-a-dozen regiments of mosquitoes will rise between you and the sight.' '' And Mr. Seebohm described how he Avas protected by india- rabber boots and cavalrv 2:auntlets, and a carefully constructed cage over his head, without which he never dare go out on the tundra (see Fig. 15). Xow this Arctic country, beyond the limit of forests and stretching to the polar ocean, ^vhich is buried for eight or nine months under six feet thick of snow^, is yet, during its short summer, a very paradise for birds of all kinds, which flock to it from all over Europe and Central Asia in order to breed and to rear their young; and it is very largely, and for many species almost exclusively, this very abundance of mosquitoes and their larvae that is the chief attraction. In Mr. Seebohm's works, already quoted, and in his fine volume on the Geo- CASES OF ADAPTATiOxX 151 graphical Distribution of the Plovers and allied birds, he gives a most graphic account of this country and of the birds flock- ing to it, which is worth quoting, as few people have any ade- quate idea of what the greater part of the iirctic regions really are in summer. After describing its extent and boundaries, he says: " I have called this district a paradise, and so it is for two or three months of the year. Nowhere else in the whole world can you find such an abundance of animal and vegetable life, brilliant flowers, birds both of gay plumage and melodious of song, where perpetual day smiles on sea and river and lake. For eight months or more (according to the latitude) every trace of vegetable life is completely hidden under a thick blanket which absolutely covers every plant and bush. Far as the eye can reach, in every direction nothing is to be seen but an interminable, undulating plain of white snow." Then after describing the few animals that live there even during the wunter, and the strange phenomenon in May of continuous day and almost perpetual sunshine, at midday hot enough to blister the skin, yet still apparently in mid-winter so far as the snow is concerned, he goes on to describe what there takes place: " The disc of snow surrounding the North Pole at the end of May extends for about two thousand miles in every direction where land exists, and is melting away on its circumference at the rate of about four miles an hour, and as it takes a week or more to melt, it is in process of being melted for a belt of several hundred miles wide round the circumference. This belt is crowded with migratoiv birds eager to push forwards to their breeding grounds — hurrying on over the melting snow so long as the south wind makes bare places soft enough to feed on, but perpetually being driven back by the north wind, which locks up their food in its ice-chest. . . . In watching the sudden arrival of summer on the Arctic circle, both in the valley of the Petchora, in East Eussia, and in the valley of the Yenesay, in Central Siberia, I was impressed with the fact that the influence of the sun was nearly nothing, while 152 THE WOKLD OF LIFE that of the south wind was almost everything. The great annual battle between summer and winter in these regions is the one event of the year: it only lasts a fortnight, during which a cold winter is transformed into a hot sunmier." He then gives a most interesting account of the breaking up of the ice on the great north-flowing rivers till they become roaring floods of muddy water, crowded with lumps of melted ice of all shapes and sizes. On the 20th May he had just crossed the Petchora to Ust-Zylma, over ice which was already cracking. " It was past midnight, and at any moment the crash might come. Cracks running for miles, with a noise like distant thunder, Fig. 17. — loe Breaking up on the Petchora River. warned us that a mighty power was all but upon us, a force which seemed to impress the mind with a greater sense of power than even the crushing weight of water at Niagara, a force which breaks up the ice more than a mile wide, at least tliree feet thick, and weighted with another three feet of snow, at tlie rate of a hundred CASES OF ADAPTATIO]^ 153 miles in twenty-four hours. . . . We slept for a couple of hours, when, looking out of the window, we found that the crash had come; the mighty river, Petchora, was a field of pack-ice and ice-floes marching past towards the sea at the rate of six miles an hour. We ran out on to the banks to find half the inliabitants of Ust-Zylma watching the impressive scene.'' A week later he writes : " Winter is finally vanquished for the year, and the fragments of his beaten army are compelled to retreat to the triumphant music Fig. 18. — Midsummer on the Tundra, at the Mouth of the Petchora River. of thousands of song-birds, amidst the waving of green leaves and the illumination of gay flowers of every hue. The transformation is perfect. In a fortnight the endless waves of monotonous white snow have vanished, and between the northern limit of forest growtli and the shores of the Polar basin smiles a fairy-land, full of the most delightful little lakes and tarns, where phalaropes swim about amongst ducks and geese and swans, and upon whose margins stints and sandpipers trip over the moss and the stranded pond-weeds, feeding upon the larvae of mosquitoes, or on the fermenting frozen fruit of last year's autumn. 154 THE WORLD OF LIFE " It is incredible how rapidly the transformation is completed. Twelve hours after the snow had melted the wood-anemone was in flower, and twenty-four hours after the yellow flowers of the marsh- marigold opened. In a short time the country looked like an English garden run wild. On the Arctic Circle wild onions, wild rhubarb, pansies, Jacob's ladder, purple anemones, dwarf roses, and a hundred other flowers made the country quite gay ; whilst on the tundras wild-fruits of various kinds — crowberry, cranberry, cloud- berry, arctic strawberry — were blended with reindeer-moss and Fig. 19. — Sudden Arrival of Birds in the Arctic Regions at the End of May. other lichens, together with the most characteristic flowers of an Alpine flora — gentians, saxifrages, forget-me-nots, pinks, monks- hoods (both blue and yellow), and sheets of the Silene acauUs, with its deep-red flowers. The Alpine rhododendron was replaced by a somewhat similar shrub. Ledum palustre; but the flora, on the whole, was like that of the Engadine brought down to the level of the sea. " Although the first rush of migratory birds across the Arctic Circle was almost bewildering, every piece of open water and every patch of bare ground swarming with them, a new species on an average arriving every two hours for several days, the period of CASES OF ADAPTATION 155 migration lasted more than a month. A^ery little migration was observable till the last week in May, but during the next fortnight the migration was prodigious. In additions to enormous numbers of passerine birds, countless flocks of geese, swans, and ducks ar- rived, together with a great many gulls, terns, and birds of prey. During the next fortnight, from the 5th to the 19th of June, fresh species of passerine birds continued to arrive, and the main migra- tion of the great plover family took place." One of the objects of Mr. Seebohm's journey to the Arctic regions was to obtain authentic eggs and nests of the grey plover. He found several, after long search. They were all situated in depressions on a slight ridge among black bog-lakes, and each had three or four eggs. The charming little i)icture on the next page shows both nest, eggs, and young birds. In order to ascertain approximately how many species of birds visit the Arctic regions in the summer breeding season, I have made rough lists of all those enumerated by Mr. Seebohm in his two books, Siberia in Europe and Siberia in Asia, and find that they amount to 160 species. This is very nearly equal to the whole number of resident and migratory birds which breed in our own country (about ISO) ; but they cannot be more than a portion of the species that actually migrate to the Arctic lands, as they were the result of two visits only of about a couple of months each, and only two very limited areas were explored. My friend, Mr. II. E. Dresser, who also knows these regions personally and has made a special study of their birds, has been so good as to make an enumera- tion of all the birds known to breed in the Arctic regions of Europe and Asia, and he finds it to be land birds 81) species, waders and aquatics 84 species, equal to 173 in alL Consider- ing how vast is the extent of the country, and how few ornithol- ogists visit it, we may put the total number at at least ISO, and possibly even 200 species. The great accumulation of bird-life is, however, vividly pic- tured by Mr. Seebohm, and it is clear from all that he says — as well as bv what he does not sav — that the vast hordes of 156 THE WORLD OF LIFE mosquitoes must be the chief support of the innumerable mil- lions of young birds which have to be fed here, both passerine and Avading birds. Of the former more than eighty species are named, including seven buntings, four tits, two grosbeaks, Fig. 20. — Grey Plover's Nest and Young {8quatarola helvetica). six pipits, eleven warblers, five wagtails, two sparrows, three woodpeckers, the beautiful Avaxwing, and a host of others, many of which are among our common birds. What a delight to them all must be this mish northward into a land of per- petual daylight, swarming with the most nutritious food, fruits and berries for the parents, inexhaustible clouds of mosquitoes CASES OF ADAPTATION 157 — which Mr. Seebohm tells us are an especially large kind with bodies a third of an inch long — and the equal myriads of their larvse in every little pond or water-hole, as well as quantities of larger worms and larva'. The extreme discom- forts as well as the cost of a journey to these far northern lands are so great that very few bird- or insect-collectors vi>ir them, and it is not easy to obtain direct and accurate obser- vations as to the actual part played by the myriad swarms of mosquitoes in attracting birds from almost every part of tlio northern hemisphere to go and breed there. Mr. H. 3^]. Dresser, who has made a special study of Palnearctic birds and their eggs, has, however, obtained for me some very interesting information. He writes: " Colonel Feilden tells me that the young of the knot are fed chiefly on the larvae of mosquitoes." He has also sent me a copy of the following interesting letter from an American ornithological correspondent, Mr. E. T. Seton : — " In reply to your recent favour I beg to say, that, in my forthcoming book on a canoe journey of 2000 miles which I made to the Arctic regions in 1907, I am setting forth at great length the numbers, virulence, and distribution of the mosquitoes, together with observations on those creatures which are immune from their attacks. ... I should say that the night-hawk (Chordeiles virginianus) is the most active enemy of this insect, feeding on it during the whole season. On one occasion T took over 100 mosquitoes from the throat of one of these night-hawks, that was carrying them home to feed its young. Many similar observations have been recorded. Next in importance would come the broad- billed flycatchers of the American group Tyrannidae, and the more abundant though smaller species of the Mniotiltidse. All of these I have seen feeding on the adult mosquitoes. Doubtless all of our thrushes do the same, although I do not recall any positive records. We are very safe, I take it, in cataloguing all of our small birds as enemies of the mosquitoes in the adult form. The various small wading birds, and the small ducks and grebes, are believed 158 THE WORLD OF LIFE to prey on the larval mosquitoes ; but doubtless it is the insects and small fish that are to be credited with the principal destruction in this stage." From his personal observations Mr. Dresser says: " I believe that most of the waders feed their young on them (mosquitoes) in the high north. In north Finland and Lapland I found the small birds (warblers, swallows, etc.) feeding on mosquitoes, and the snow bunting fed its young on them." There is, therefore, a concensus of evidence as to the pre- eminent attraction afforded by these insects to almost all birds which breed in the Arctic regions. The beautiful view on the opposite page gives us an idea of the appearance of the upland tundra along the shores of the Arctic Ocean. Here the southern slopes of the low hills are the first to be free from snow, and afford an abundant supply of last year's berries to the earliest migrants, as well as a variety of animal food for aquatic birds on the adjacent sea-shores in favourable situations. The combined physical and emotional enjoyment in this birds' paradise, during the whole of the Arctic summer, for so large a number of species of birds and in such enormous multitudes, is probably unequalled in any other part of the world; and we have the satisfaction of knowing that it is perhaps the only example of Nature's short-lived but annual pleasure-gardens which will not be destroyed or rendered hideous by the destructiveness and greed of civilised man. When much of the beauty and luxuriance of nature has been banished from milder regions, these inhospitable Arctic lands will long remain in their wild luxuriance of summer beauty, where those who trulv love nature wdll be able to witness one of the most wonderful illustrations of the mvriad forms and complex ada23tations which the world of life presents to us. It is a significant feature of this adaptation, that of all the higgler forms of life birds are the most completely pro- tected from the blood-sucking and iiTitation of mosquitoes. CASES OF ADAPTATIO]S[ 159 Every imrt of the body is protected either with a dense mass of phimage, or by a homy integument on the bill and feet, so that they are probably quite undisturbed while enjoying the super-abundant feast nature has spread for them in those remote and usually repellent lands. We may conclude, there- fore, that it is to the two special features of these Arctic Fig. 21.— The Higher Tundra. Stanavialachta at mouth of the Petchora River (N. Lat. 69°), tundras — their abundant berries preserved during the winter in a natural ice-house, and the myriad clouds of mosquitoes and their larvge — that we owe the very existence of a consid- erable proportion of the bird-life in the northern hemisphere. The Origin of Bird-migration These vast Arctic plains even in Tertiary times when climates were milder, would, owing to the long winter nights, have always been snow-covered during several months in winter although its melting might have been earlier and the sunnner somewhat longer ; there can be little doubt that the short sum- 160 THE WORLD OF LIFE mer with its perpetual sunshine was equally favourable to the production of a super-abundance of vegetable and insect food very similar to what now exists there, and in this fact, we find a very complete explanation of how bird-migration came about. Abundance of food suitable for both parents and young at the season of breeding, would inevitably attract birds of all kinds from more southern lands, especially as the whole area would necessarily have no permanent residents or very few, but would, each recurring season, be an altogether new and unoccupied but most fertile country, to be reached, from any part of the north temperate lands, by merely following up the melting snow. And as, a few months later, the myriads of young birds in addition to their parents were driven south by the oncoming of the cold and darkness, they would find it necessary to travel farther and farther southward, and would again find their way north when the proper season arrived. There would always be a considerable niunber of the old and experienced birds to show the way; and as, with increasing severity of the seasons, the area of the snow-covered plains would extend, and their capacity for feeding both old and young would be increased ; there would at last be brought about that marv^ellous rush of the migrating flocks which Mr. Seebohm has so vividly described. Before quitting the subject of migration, on which Mr. Seebohm's observations throw so much light, I will shortly describe the most wonderful exhibition of migration-phenom- ena in the world — that of the small island of Heligoland, 40 miles off the mouth of the Elbe in about the same lati- tude as Scarborough. Most of the migratory birds from Scandinavia and xlrtic Europe pass along the coasts of the German Ocean, and the lighthouse on Heligoland serves as a guide, and the island itself as a resting-place during bad weather. Mr. Seebohm's account of what he witnessed in the island, during nearly a month spent there in September to October 1875 (in chapter xx. of his Siberia in Euroj)e) is most interesting; and I refer to it here chiefly for the OASES OF ADAPTATION 161 sake of iDointing out a very important error as to the cause of a very singular fact recorded there, by Herr Gatke, who for fifty years, observed and registered the migrations both in spring and autumn, with great accuracy, and formed a collection of birds there, perhaps more extensive than could be made at any other station in Europe. The fact observed was, that, during the autumn migration, as regards many of the most abundant species, the young birds of the year, that is, those that had been hatched in the far north in the preceding June or July, and who w^ere, therefore, only about three or four months old, arrived in Heligoland earliest and alone, the parent birds appearing a week or two later. This is the fact. It has been observed on Heligoland for half a century; every resident on the island knows it, and ]\Ir. Seebohm declares that there can be no doubt whatever about it. The inference from this fact (dravni by Herr Gatke and all the Heligolanders, and apparently accepted by almost all European ornithologists) is, that these young birds start on their migration alone, and before their parents, and this not rarely or accidentally but every year — and they believe also that this is a fact, one of the most mysterious of the facts of migration. Neither Mr. Seebohm nor Professor Lloyd Morgan (in his Habit and Instinct) express any doubts about the inference any more than about the fact. Yet the two things are totally distinct ; and while I also admit the fact observed, I totally reject the inference (assumed to be also a fact) as being absolutely without any direct evidence sup- porting it. I do not think any English observer has stated that the young of our summer migrants all gather together in autumn and leave the country before the old birds ; the American observers state that their migrating birds do not do so; while many facts observed at Heligoland show that no such inference is required to explain the admitted fact. Let us see what these additional facts are. The enormous rushes of mic^ratorv birds which rest at Heligoland always occur at night, and are very intermittent. 162 THE WORLD OF LIFE They usuallj take place on dark nights, sometimes in mil- lions; at other times, a week will sometimes pass with only a few stragglers. Of one such pitch-dark night Mr. Seebohm writes : Fig. 22.— The Light- house at Heligoland on a Migration Night. " Arrived at the lighthouse, an intensely interesting scene pre- sented itself. The whole of the zone of light within range of the mirrors was alive with the birds coming and going. Nothing else was visible in the darkness of the night, but the lanthorn of the lighthouse vignetted in a drifting sea of birds. From the darkness in the east, clouds of birds were continually emerging in an unin- terrupted stream ; a few swerved from their course, fluttered for a moment as if dazzled by the light, and then gradually vanished with the rest in the western gloom. ... I should be afraid to hazard a guess as to the hundreds of thousands that must have passed in a couple of hours ; but the stray birds that the lighthouse- man succeeded in capturing amounted to nearly 300." He also tells us that 15,000 sky-larks have been caught on Helifi^oland in one nio-ht ; and all aiiTee that the count- CASES OF ADAPTATIOjST 163 less myriads that are seen passing over Heligoland are but a minute fraction of those that really pass, high up and quite out of sight. This is shown by the fact, that if, on a dark night, it suddenly clears and the moon comes out, the swarms of birds immediately cease. Another fact is, that, on what the islanders call '' good nights,'^ the birds that come to rest seem to drop down suddenly out of the sky. One other fact is mentioned by Mr. Seebohm. It is that every year the reg- ular migration season is preceded by a week or two, during which a few stragglers appear ; and these are all old birds and many of them slightly crippled, or partially moulted, or without some of their toes, or onlv half a tail, or some other defect. These are supposed to be mostly unmated birds or those whose young have been destroyed. It is also supposed that, during favourable weather (for the birds) migration goes on continuously during the season of about six weeks, though for the most part invisible at Heligoland, but often audible when quite invisible. Xow, the fact of the young birds only appearing on Heligo- land for the first week or so of the season of each species is easily explicable. Rem.embering that the autumnal migration includes most of the parent birds and such of their broods as have sur^dved, it is probable that the latter will form at least half or, more often, two-thirds of each migrating flock. But the young birds, not having yet acquired the full strength of the adults, and having had little, if any experience, in long and continuous flights, a considerable proportion of them on the occasion of their first long flight over the sea, on see- ing the lighthouse and knowing already that lights imply land and food-crops below them, and being also much fatigued, will simply drop down to rest just as they are described as do- ing. The old birds and the stronger young ones, however, pass high over head, till they reach the north coast of Hol- land, or, in some cases, pass over to our eastern coasts. We must also remember that the loncrer the birds are in mak- ing the journey overland, the more young birds are lost by 164 THE WORLD OF LIFE the attacks of birds-of-prey and other enemies. Hence the earliest flocks will have a larger proportion of young birds than the later ones. The earlier flocks also, being less pressed for time will be able to choose fine weather for the crossing, and thus it will be only the young and quickly-fatigued birds that will probably fly low and come dow^n to rest. Later on every recurrence of bad weather will drive down old and young alike for temporary shelter and rest. Thus all the facts are ex- plained without having recourse to the wildly improbable hypothesis of flocks of immature birds migrating over land and sea quite alone, and a week in advance of their parents or guides. What this World-wide Adaptation teaches us This co-adaptation of two of the highest and most marvel- lous developments of the vast world of life — birds and in- sects — an adaptation which in various forms pervades all their manifestations upon the earth, from the snow^-wastes of the tundra to the glorious equatorial forests; and the further co-adaptation of both, with the vegetation amid w'hich they have developed, suggest some very important considerations. As we might expect, both birds and insects are comparatively rare in a fossil state, but there are suflicient indications that the latter were first developed. A considerable number have been found in the Coal Measures, especially numerous cock- roaches. Ancestral forms of ^N^europtera and Hemiptera allied to our may-flies and dragon-flies, bugs and aphides, are found in Devonian and Carboniferous rocks. The more his^hlv organised insects with a complete metamorphosis, come later; beetles, dragon-flies, and bugs (Hemiptera) are rather common in Lias beds, and here, for the first time, we meet with a true ancestral bird with perfectly developed wings and feathers, and with toothed jaw^s, the celebrated Archseopteryx. Diptera (flies) are also found here, as ^vell as a wasp, some- what doubtfully identified ; while the most highly developed of all insects in structure and metamorphosis, as well as in CASES OF ADAPTATION" 16^ o size and beauty, the Lepidoptera, are first in Tertiary beds, at a time when birds allied to living forms also first appeared. This general parallelism of development seems clearly to indicate that birds, in the full and varied perfection in which we now find them, are dependent on a correspondingly wide- spread development of insects ; and more especially of those higher orders of insects, whose exceedingly diverse stages of larva, pupa, and perfect insect, afforded the special food for immature and full-grown birds respectively. We can see how the omnipresence of insects adapted to feed on every kind of vegetable food, as well as on all kinds of animal refuse, has afforded sustenance to the various kinds of small mammalia, reptiles, and birds, which have successively become specialised to capture and feed on them. The early birds with toothed jaws were able to feed upon the cockroaches and ancestral iVTeuroptera and beetles of the same period. As these early, birds became more numerous, so they became successively specialised to feed upon particular kinds of insects or their larvae, however completely these might seem to be concealed or protected. Thus were gradually formed the true fly- catchers (Muscicapidge) and the totally distinct American fly- catchers or tyrant birds (Tyrannidse), which capture all kinds of insects on the wing; the swallows, and the very distinct swifts, so specialised as almost to live in the air, and to feed on this kind of food exclusively; the goatsuckers, which capture night-flying insects; the curious little nuthatches and creepers which hunt over trees for small beetles concealed in crevices of the bark; while the marvellously specialised wood- peckers discover the larger grubs or caterpillars which burrow deeply into the wood of trees, and dig down to them with their wonderfully constructed hammer-and-chisel-like head and bill, and then pull them out on the tip of their extensile barbed tongue. In the tropics many distinct families of birds have been developed to grapple with the larger and more varied insect forms of those countries, so that it mav be safely concluded that no group of the vast assemblage of in- 166 THE WORLD OF LIFE sects but what has its more or less dangerous enemies among the birds. Even the great rapacious birds, the hawks, buz- zards, and owls, when their special food, the smaller mammals and birds, fails them, will capture almost every kind of ground-feeding insects; while the enormous tribes which feed largely on frnits and seeds often make up for its deficiency by capturing such insects as are available. One of the clearest deductions from these facts is, that the great variety of the smaller birds — warblers, stonechats, tits, w^agtails, pipits, wrens, and larks — owes its origin to the continuous specialisation throughout the ages of new forms of birds adapted to take advantage of every fresh development of the insect tribes as they successively came into existence. As Darwin repeatedly impresses upon us, excessive powers of multiplication with ever-present variations, lead to the almost instant occupation of every vacant place in the economy of nature, by some creature best fitted to take advantage of it. Every slight difference in the shape or size of bill, feet, toes, wing, or tail, or of colour of the various parts, or of supe- rior acuteness in anv of the senses, such as we can see in the different allied species of these birds, has been sufficient to secure the possession of some one of these vacant places ; and when this first partial adaptation has been rendered more and more perfect by the survival in each successive generation of those individuals best fitted for the exact conditions of the new environment, a position is reached which becomes at any future time a secure starting-point for further modification, either in the same or in any slightly diverging line, so as to be again fitted to occupy some other vacant place which may have arisen through the slightest changes either in the inor- ganic or the organic environment. So long as we limit ourselves to a consideration of the mode in which any existing species has been produced, by the adaptive modification of some other pre-existing closely allied species, by means of the known facts of universal variation and of the constant survival of the best adapted, there is no CASES OF ADAPTATION 167 difficulty whatever in accepting the " origin of species " from other species as a demonstrated fact ; and this alone was the hitherto insoluble problem Avhich Darwin first succeeded in solving. It is only in the extension of the process to isolated groups such as the whales, the elephants, the serpents, or the mammalia; or by enquiring how special organs, such as horns, teeth, ears, or eyes, could have begun their process of develop- ment, that difficulties appear, many of which seem, to some biologists, to be insuperable. But many of these difficult problems have been solved by more complete knowledge ; while others have been rendered easy by the discovery of inter- mediate stages either through the investigations of embryolo- gists, or of palaeontologists, so that many of the greatest diffi- culties of Darwin's early opponents have quite disappeared. Some of these recent explanations have been referred to al- ready, and many others are briefly described in my Darwin- ism. In that work also I have given so many illustrations of the way in which natural selection has worked, that it will be needless for me to go into further details here. I will, therefore, now proceed to an exposition of some problems of a more general nature, which involve difficulties and sugges- tions beyond the scope of Dar^vin's work, and which, I think, have not been sufficiently considered by later writers on evolu- tion. CHAPTER IX THE IMPORTANCE OF EECOGNITION-MAKKS FOR EVOLUTION The great problem of the exact causes of the infinitely varied colours and markings of the different species of the higher animals, is now gradually receiving an adequate amount of attention, and in consequence an almost complete solution. In the Origin of Species Darwin dealt with only one branch, of the subject — coloration for concealment, and that only in- cidentally ; but he at once accepted, and with enthusiasm, Bates's explanation of the beautiful phenomena of mimicry among insects, and also that of warning colours in the in- edible caterpillars, first suggested by myself. The whole subject, especially that of mimicry, is now so largely developed as to require many volumes for its adequate exposition ; and I have myself given a summary of the more interesting facts in my Darwinism: I shall therefore deal very briefly with it here, with the one exception of that form of it which I have named " recognition marks." These, though the last to be generally accepted have received the least at- . tent ion ; but, after many years' consideration of the whole problem of evolution I have come to the conclusion that, of all the causes of distinctive marking (among the higher ani- mals at all events), the need for easy recognition under the varied conditions of their existence is for most animals the most important. It is, however, on account of their being in most cases absolutely essential as a factor in the evolution of new species that I here devote the larger part of this chapter to their consideration. 168 KECOGA^ITIO^^ -MARKS 169 Coloration for Concealment and for Visibility Colour and markings for concealment pervade all nature. The hare on its form, the snipe in its covert, the vast major- ity of birds while sitting on their nests, the sand-coloured des- ert animals, and the prevalence of green colours in the in- habitants of tropical forests, are a few of the best-known ex- amples. The uses of such colours in order to protect the Herbivora from enemies, or to conceal those which devour other animals from their prey was at once acknowledged, and it was seen how, with variability of colour as a constant fact, survival of the fittest might soon bring about the beautiful harmony of coloration we everywhere find to prevail. But it was also undeniable that there were almost equal numbers of animals of all classes and sizes, in which colours and mark- ings occurred which could not by any possibility be interpreted as protective, because they seemed to render the creature glaringly conspicuous. Some of these, which w^ere most prev- alent among insects, were soon explained as " warning colours,' ' because they were exhibited by species which were either so nauseous as to be inedible by most insect-eaters ; or were armed wdth stings which might cause great pain or even loss of life to an enemy which attacked them. When it was found that many other groups of insects which did not pos- sess these protective qualities, yet acquired the same colours and often the same form ; and when my fellow-traveller on the Amazon, II. W. Bates, showed how this peculiar kind of ^^ mimicry " was beautifully explained on the Danvinian hypothesis, not only w^as the theory itself greatly strengthened but a whole host of curious and beautiful colour-phenomena in Xature, hitherto unnoticed, were seen to come under some form of the same general principle. As one rather extreme ex- ample of mimicry I give the figures of a black wasp with white- banded wings, which is closely imitated by a heteromcrous beetle. These I captured myself in the forests of Borneo, fly- ing together near the ground. They are of nearly the same 170 THE WOKLD OF LIFE size. The wing-coverts (elytra) of the beetle are reduced to pointed scales, allowing the true wings to be always extended. This is most unusual in beetles, as is the white band across the wings in this order of insects (Fig. 23). This strange and most unusual modification of an inoffensive insect, so as closely to resemble one of another order which is protected by a dangerous sting, can be explained in no other way than through the advantage derived by the harmless beetle by be- ing mistaken for the wasp. Of course, this change is the result of a very long series of slight modifications of the beetle, each bringing it a little nearer to the wasp, a series extend- ing probably through thousands or even millions of genera- tions.^ Becogniiion-Marlcs But though the subject of '^ mimicry " involves problems of extreme complexity and interest, and has therefore at- tracted the attention of numerous students, yet it is almost entirely confined to the insect world, and, taken as a whole, is not nearly so important a factor in the development of the great Avorld of life as the class of " recognition "-colours of which I will now give a short account. My attention was first directed to this subject during my visit to south Celebes in 1856-57, where, during about six months' collecting, I obtained the unusual number of fifteen different birds of prey, of which the majority were of the hawk sub-family. While skinning and preserving these birds, and after my return home, wdiile determining the species, I could not help observing in many of them the varied and 1 Other cases are given in my Darwinism ; but those who wish to under- stand the whole problem and what an important part it plays in nature should read Professor Poulton's elaborate papers in the Transactions of the Entomological Society of London for the years 1902 and 1908, together with those of Dr. F. A. Dixey and other writers. There is also a very good article by Mr. E,. Shelford, on mimetic insects from Borneo, and as these are illusttated by coloured plates and deal with cases of the same nature as the one here given, they are very instructive. (See Proceedings of the Zoological Society of London, Nov. 4, 1902.) beetle. i.MYCNIMIA AVICULUS. 2.C0L0B0RH0MBUS FASCIATIPENNIS, Fig. 23. — Mimicry of Wasp by a Beetle. EECOGNITION-MAEKS 171 beautiful markings of the tail-feathers, by means of white spots or bands on all the feathers except the middle pair. The result was that when the tail was expanded during flight, it was seen to be marked very conspicuously by white bands, sometimes across the middle of the tail, sometimes at the end, sometimes with one band, sometimes with two or even three, so that the species were easily distinguished by this one character. But the chief peculiarity to be noticed was, that these bands w^ere only seen during flight, the white markings being quite invisible when the birds were at rest. The impor- tance of this fact I did not see till many years later, when, in connection with other similar facts, it gave a clue to their meaning and purpose. Xow that we have learnt how rapid are the powers of in- crease of all animals, and the extreme severity of the process by which the population is kept down to a nearly fixed amount by the annual destruction of all the less adapted ; and further, when we know how all the higher animals roam about in search of their daily food, we are able to understand how vitally important it is for all such animals to be able to recog- nise their own species from all others without fail and at con- siderable distances. This is essential for several reasons. The young and half-grown, if they have strayed away from the flock or herd, need to rejoin them as soon as possible ; the two sexes of the same species require to know each other in the same way by unfailing marks whether they are approach- ing from behind or from the front; while the separate por- tions of flocks divided by the sudden attack of some enemy need to come together again as soon as possible. But there is a still more important use of these distinctive markings, since they are almost if not quite essential to the production of neiv species by adaptation to change of conditions, as will be shown later on. I first gave a somewhat full account of this class of mark- ings, with several characteristic illustrations, in my Darwin- ism, in 1889; but I had briefly treated the subject in my 172r THE WOELD OF LIFE lecture on the Colours of Animals given at many places in the United States and Canada in 1886-87, and in England in 1888. No doubt some of the facts had been noted by other writers, but I thinlv I was the first to claim for it a high place among the factors concerned in animal evolution. The clear- est and most picturesque illustration of the subject 1 have seen is in a very short article by Mr. E. Seton Thompson in the American periodical " The Auk " for October 1897, from which I will quote the most important passage : " The common jack-rabbit ^ when squatting under a sage-bush is simply a sage-gray lump without distinctive colour or form. Its colour in particular is wholly protective, and it is usually accident rather than sharpness of vision which betrays the creature as it squats. But the moment it springs it is wholly changed. It is diflScult to realise that this is the same animal. It bounds away with erect ears showing the black and white markings on their back and underside. The black nape is exposed. The tail is carried straight down, exposing its black upper part surrounded by a region of snowy white ; its legs and belly show clear white, and everything that sees it is clearly notified that this is a jach-rabhit. The coyote, the fox, the wolf, the badger, etc., realise that it is useless to follow ; the cotton-tail, the jumping rat, the fawn, the prairie dog, etc., that it is needless to flee; the young jack-rabbit that this is its near relative, and the next jack-rabbit that this may be its mate. And thus, though incidentally useful to other species at times, the sum total of all this clear labelling is vastly serviceable to the jack-rab- bit, and saves it much pains to escape from real or imaginary dangers. As soon as it squats again all the directive marks disap- pear, and the protective gray alone is seen. In the bird-world the same general rule applies. When sitting, birds are protectively coloured; when flying, directivelyf i The African antelopes offer very striking examples of " recognition "-marks, especially those that inhabit Central and South Africa, where such indications are most needed. The land is generally open, often quite bare, but usually with scat- 1 This appears to be the common grey hare {Lepiis a^nericanus) . KECOGNITION-MAEKS 173 tered trees and bushes ; and as these animals roam over a great extent of country in search of food or water, and are also liable to the attacks of many dangerous beasts of prey, their safety depends largely on their keeping together in small or large herds. There are nearly a hundred different kinds of antelopes known to inhabit Africa, the larger part of them being found in Central and South Africa. Almost all of these have very distinctive markings on a general ground-colour harmonising with the tint of the soil or rock. These mark- ings are usually confined to white patches on the head and face, and on the hinder parts, so as to be visible in the two directions that are most serviceable.-^ I have also come to the conclusion that the horns of these animals, though pri- marily developed as weapons of defence — for even the lion is occasionally killed by the horns of the gemsbuck — have been so changed in each species as to serve another purpose, as is so often the case in nature. Their curious modifica- tions of form in closely allied species, and their extreme diversity in the whole group, leads me to conclude that their actual shapes have been produced quite as much for purposes of recognition as for attack or defence. While moving among high grass or bushes, or when at rest and '^ ruminating," the horns would often be the only part visible at a distance ; and this, in a district inhabited by perhaps a dozen different species of these animals, would be of the greatest importance in guid- ing a wanderer back to his own herd, and for other purposes. To illustrate this I here give views of the horns or heads of twelve different species of antelopes all found in Central or South Africa, and thus often meeting in the same valley or veldt. To these I call the reader's special attention (Figs. 24- 35). The first group of four shows two of the larger antelopes 1 The beautiful gazelle figured in my Darwinism (p. 219) shows both these kinds of markings very strongly; while an examination of the numer- ous figures of antelopes in Wood's Natural History (or in any of the more recent illustrated works) aff'ords numerous examples of them. 174 THE WORLD OF LIFE on the left, which, with a general likeness of form, possess individuality both in face-marks and in the curvature of the horns ; while the two gazelles on the right are still more distinct. The next group consists of three species of the genus Cobus, in w^hich the horns are each so distinct in size and curvature as to be easily recognisable at considerable dis- tances ; the fourth figure shows the horns of the gemsbuck, a very distinct species, not only in the body markings, but also in the almost perfectly straight and very long horns. The third group shows, at the top, the two species of kudu, the horns of which, though exactly alike in spiral curvature, are yet placed at such a different angle on the head as to be easily distinguishable. The two lower figures are of animals not closely allied, but, as one inhabits East and the other South Africa, their ranges probably overlap each other, or once did so. Here there is a somewhat similar bend in the horns, but their thickness and direction render them absolutely distinct from every point of view. ^Now, as the antelopes are very closely allied to each other, both in structure and external form, it seems improbable that all the diversities in the horns (which are sometimes very great in closely allied species) should have been acquired for the sole purpose of fighting with each other or with an enemy. But as these animals all possess markings on the head and body which can only be interpreted as recognition-marks es- pecially serviceable while in motion, it seems quite natural that the horns should have been modified to serve the same pur- pose while the animals are at rest, or when their bodies are wholly and their faces partially concealed by the grasses or bushes around them. The essential character of directive or recognition-marks is strikingly shown by one of the best known of the African antelopes — the springbok — which in the early days of the Cape Colony swarmed over the whole of South Africa, even in the vicinity of Cape Town. Its chief feature is thus de- scribed in Chambers's Encyclopaedia : Fig. 24. TrageJayhus spekei. Fig. 25. Boocercus euryceros. Fig. 26. Fig. 27. Gazella granti. Gazella ualleri. Recognition-Marks in African Antelopes. KECOGNITION-MAEKS 175 " Two curious folds of skin ascend from the root of the tail to near the middle of the back; they are closed when the animal is at rest, but when leaping or running they open out and disclose a large white patch, which is otherwise concealed." We have here a structural peculiarity leading to the pro- duction of a distinctive white patch on a prominent part of the body, which patch is concealed Avhen not required and when it might be dangerous, and only exhibited in the pres- ence of some real or imaginary danger, for the sj^ringbok is said to be one of the most timid and cautious of all animals. This curious feature is more remarkable, and more clearly a proof of a mark designed to he seen, than even our rabbit's upturned tail wdien running, wdiich has been termed the *^ signal Hag of danger," and in moonlight or evening twilight serves, on the approach of an enemy, to guide the young, or those farthest from home, towards the family burrow. Recognition-Marks in Birds A large number of birds also possess these two kinds of recognition-markings, the one to be seen when resting or feed- ing, the other only during flight. As good examples of these I give figures of the head and wings of three allied species of stone-curlews, inhabiting Eastern Australia, the Malay Archipelago, and India, respectively, whose ranges sometimes overlap, and which are no doubt descended from a common ancestor. The head of each exhibits different markiuirs, bv which they can be easily distingTiished while feeding on the ground ; while the bolder markings on the wings enable them to keep together during their wanderings or migrations (Figs. 36, 37, and 38). Markings of this character, though varied almost infinitely, occur in all classes of the hioher animals, and very mucli in proportion as their mode of life requires them. When con- cealment is of more importance, then the recognition is made effective by differences of shape or of motions and attitudes, 176 THE WORLD OF LIFE or hy special cries, as in the cuckoo. Among the birds of the tropical forests, while the ground colour is often protec- tive, as in the green of parrots, the smaller fruit-pigeons of Fig. 36. — (Edicnemus grallarius (East Australian Stone-Curlew). This species is found all over Eastern Australia and the coasts of the Gulf of Carpentaria. It is distinguished from its allies by the better defined whit© spot on the wing and its more conspicuous markings on the breast. Fig. 37. — (Edicnemus magnirostris (Austro-Malayan Stone-Curlew). This species ranges from the Andaman Islands to the Philippines and the north coast of Australia. The markings of the face are almost intermediate be- tween those of the other two species. the Malay Archipelago, many of the barbets, and hosts of other birds, yet the different species will be almost always charac- Fig. 28. Strepsiceros kudu. FIG. 29. Strejisiceros im herb is. FIG. 30. Buhalis jacksoni. Fig. 31. JEpyceros melampus. Recognition-Marks in African Antelopes. RECOG^^ITION-MARKS >-^7 177 terised bj spots or bands, or caps of brilliant or contrasted colours. But as these usually break up the green body into irregular portions, and as flowers of equally varied hues are common on trees, or on the orchids and other epiphytes that Fig. 38. — (Edicnemus recurvirostris (Great Indian Stone-Curlew). This species is found all over India, and also in Ceylon and Burma. This species is clearly defined by the upturned bill and the compact black mark around the eye. grow upon their branches, the general effect is by no means con- spicuous. ]^ow, without this principle of the necessity for external differences for purposes of recognition of each species by their own kind, and especially of the sexes by each other, this end- less diversity of colour and marking, when not protective, seems difficult to explain. The Duke of Argyll, in his interesting work, The Reign of Law, published six years after the Origin of Species, expressed this objection very forcibly. After de- scribing many of the wonderful forms and ornaments of the humming-birds, he says : " Mere ornament and variety of form, and these for their own sake, is the only principle or rule with reference to which Creative Power seems to have worked in these wonderful and beautiful birds. ... A crest of topaz is no better in the struggle for existence than a crest of sapphire. A frill ending in spangles of 178 THE WORLD OF LIFE the emerald is no better in the battle of life than a frill ending in spangles of the ruby. A tail is not affected for the purpose of flight, whether its marginal or its central feathers are decorated with white. . . . Mere beauty and mere variety, for their own sake, are objects w^hich we ourselves seek when we can make the forces of nature subordinate to the attainment of them. There seems to be no conceivable reason why we should doubt or question that these are ends and aims also in the forms given to living or- ganisms." In a criticism of the Duke's book (written in 1867) I adduced sexual preference by the female bird as sufficiently explaining these varieties of plumage and colour, but I have since come to doubt the validity of this, except so far as the plumes are an indication of sexual maturity; while I see in the need for outward marking, whether for purposes of recog- nition or as preventing intercrossing between incipient species, a sufficient cause for all such conspicuous indications of specific diversity as are found perv^ading the whole vast world of life. It now only remains to point out how these mark- ings have been produced, even under conditions which some writers have considered must render their production for this purpose impossible, and therefore as constituting a valid ob- jection to the whole theory of recognition-marks. An Objection to Recognition-Marhs answered In a book on Darwinism and Lamarckism, the late Captain Hutton, a well-known Kew Zealand naturalist, objected to the validity of recognition-marks as a cause for the development of specific characters, that there are, all over the Pacific, numerous cases of small fruit-pigeons of the genus Ptilopus, which each have distinctive markings, and are almost always confined to one island or a small group of islands. In most of these cases there is no other pigeon or other bird on the same island for which they could possibly be mistaken. He then says : ^ fr ^ Fto. 32. Cohiis leche. Fig. 33. Col) us defdssd. FIG. 34. Cohus maria Fig. 35. Oryx (lazclUi. RECOG.MTIO.N M \HKS IX Afuua.n AXTKI.orKS. EECOGXITIOX-MAEKS 179 ^^ Consequently it appears certain that most of these species were developed singly, each in its own island. If this he the case, the colours which now distinguish tlic dilferent species cannot be recognition-marks, because there is no other species in each island with which they could be confounded." Shortly afterwards the late Dr. St. George Mivart made the same objection as regards the very numerous species of beautifully coloured, lories Avhich are found in all the islands around Xew Guinea and in the Western Pacific. He urijed that the various peculiarities of colour cannot be useful as recognition-marks, because the colour and markings of each of the 2,'enera of these birds is so very distinct from that of all other birds inhabiting the same island, and there is usually only one species in each island. This argument, looked at superficially, seems very strong, but it is not difficult to show^ that it is a complete fallacy, if we follow out in detail what must have occurred in each case. It is clear, admitting evolution (as both these writers did admit it), that each of the species of pigeon or lory noW' peculiar to an island must have originated from some parent species in the same or some other island; and there are only tw^o possible suppositions — either the species originated in is- land A by modification of the present form, and then migrated to island B, afterwards becoming extinct in A ; or it migrated from A to B and became modified into its present form in B. The latter case is by far the more probable, and as it is clearly that which the critics contemplated, let us see exactly what must have happened. We know as a fact that, when any species reaches an is- land or other new habitat for the first time, if the conditions are favourable, it increases with marvellous rapidity, till the island is fully stocked, and the supply of food at some time of the year begins to fail, or till some enemy — a rapacious bird, for instance — finds out the rich banquet, and is soon followed by others. The rabbit in Xew Zealand and Porto Santo, the sparrow in the United States, and many others, 180 THE WORLD OF LIFE are examples of such rapid increase. But as soon as the is- land is fully stocked, a number equal, or nearly so, to the annual increase must die off every year, and these will inevi- tably be the least fitted to survive. Hence natural selection at once begins to act, and as the conditions, even in two adjacent islands, are never quite the same, and as with such a large population slight variations in many directions will be very numerous, some modification to a more perfectly adapted form will necessarily follow. Here comes the point which both critics failed to notice, that the modification of the species into a better-adapted one must have occurred in the island ; and as it is universally admitted that intercrossing between the incipient species and the parent stock would be a serious check to adaptation ; and further, that varieties of the higher animals prefer to mate with their like, then any varia- tion of colour in those better adapted will be advantageous, will lead to more rapid change, and will thus come to charac- terise the new form as distinguished from that of the less- adapted parental form. It is clear, therefore, that species which are now peculiar to some island or other restricted locality, even when thev are quite unlike anything else now living around them, must have become differentiated from some parent stock just in the same way as all other species have become differentiated. During all the initial stages, w^hich may have occupied scores or hundreds of generations, some outward sign of the struc- tural change that was taking place was an essential part of the process, as a means of checking interbreeding with the less- modified parental form, which might linger on till the process was almost completed. Now, the distinctive recognition-mark seems to us to have no use ; but as the original form from the adjacent island A may still occasionally visit or be driven to the island B, it would now be treated as a stranger, and thus prevent the better-adapted form being deteriorated by inter- breeding with the less-adapted immigTant. EECOGXITIOX-MAEKS 181 Recognition hy Butterflies This case shows how easy it is to make mistakes or arrive at wrong conchisions, imless we take account of all the de- tails of a problem, and endeavour to follow out the exact proc- esses of nature by the help of facts known to us. I can say this with more confidence, because I find that I have myself come to a hasty conclusion, which I now see to be er- roneous, on one aspect of this very question ; and as it in- volves a problem of some importance I will here state what it is. I find that in all my writings on this subject I have as- sumed, without going into details, that the theory of ^^ recog- nition-marks," which so well accounts for a very widespread type of marking and coloration in birds and mammals, is also applicable to a large portion of the markings of insects, es- pecially in the case of butterflies. But a little consideration shows that there is no resemblance between the two cases. Young mammals and birds grow up with their parents, and get to know their appearance in every detail. They also have usually brothers and sisters growing up with them, so that by the time they go out into the w^orld to care for them- selves they are thoroughly acquainted with the difference be- tween themselves and other species, even those nearly allied to them. This complete knowledge is increased by the fact that they are able, through the mobility of the head and neck, to see almost every part of their own bodies, and thus know that they themselves do resemble their parents. But with the butterflies, and most other insects, everything is different. The caterpillar never knows its parent, and when the butterfly emerges from the pupa and takes flight, it seems quite impossible that, among the numerous butterflies of all sizes, shapes, and colours that it may immediately encounter, it can possibly know, h^j sight, which are of its own race. Tt must be remembered that from tlie position nf its eyes if cannot see itself except at so oblique an angle as to be al- most useless; and when we consider the extreme diversity of 7 t/ 182 THE WORLD OE LIEE the sexes in many butterflies this adds to the difficulty of supposing vision to be the 'primary means of recognition. But it may be a secondary means. It is well known that in some moths the females attract males by scores at night, and this can only be by scent, or something analogous to it. It is also known that the males of manv butterflies emit a strong perfume which has been traced to certain peculiarly formed scales on the wings. Scales, apparently of a similar nature, have been found in several distinct families of butterflies and moths, and it seems probable that the function of these is in all cases to produce a perfume agreeable to the other sex, though only in a few cases is such perfume perceptible to us. It seems probable, therefore, that the sexes of Lepidoptera are mutually attracted by a perfume agreeable to each other, but disagreeable or neutral to others of the same sex or to other species. Each time this attractive odour was perceived and the source of it traced, the visual image of the insect would be connected with the smell, and thus only would the colour and markings of the species become known and be distinguished from that of other species. This being the case, we see that the complete scaly covering of so many of these insects serves a double purpose. It affords the means of using an extended surface for the highly important scent- glands, which, by serving to bring together the sexes of each species and to prevent intercrossing, would facilitate differ- entiation and lead to that wonderful diversity of colour and marking accompanying comparatively slight differences of structure for which this order is so remarkable, and which are absolutely unequalled in the whole animal kingdom. This variety of colour, rendered possible by the large wing-surface covered with small but exquisitely organised scales, is util- ised for securing the safety of the perfect insect to a sufficient extent to provide for the continuance of the race, thus keep- ing up that endless variety of form and colour which is, per- haps, one purpose of their existence. KECOGNITIOX-MAliXS 183 The first great adaptation here, as throughout nature, is to secure conceahnent from their most dangerous enemies, and this is effected by various kinds of protective, deceptive, or -warning coloration which in some form or other pervades the whole order, and forms a most fascinating subject of study. The protective coloration is mostly on the under sides of the wings of butterflies, and on the upper sides of the upper wings of moths, the parts respectively exposed to view when the in- sect is at rest. Great numbers are also deceptively coloured by eye-marks (ocelli), which resemble the eyes of mammals in such a way as to be very striking in the mingled light and gloom of the forest and in the general surroundings of each species. Large groups in all the tropical regions possess warn- ing colours, either very bright and well contrasted, or of sober browns and yellows, and accompanied by such elongated wings, bodies, and antennae, that the facies of the whole group as well as of the individual species soon become known to in- sect-eating creatures. Those which are protectively or deceptively coloui-ed on the exposed portions of their wings often exhibit the most brilliant or gaudily contrasted colours elsew^here; but in these cases the flight is very rapid or jerky, and the insects are so continually hidden among the lights and shadows of the forest, that few enemies can capture them. The - great exj)anse of the wings is itself an additional protection by diverting at- tention from the body ; and it has thus become possible, with- out endangering the continuance of the species, to allow the development of that marvellous display of colour, the charm of which can only be fully appreciated by those who have for long periods sought it out in the forest regions of the Amazon, of the Eastern Himalayas, or of the Moluccas and Xew Guinea — the three most productive regions in the world for butterflies (ajiS also for birds) of resplendent hues and in endless variety. 184 THE WOKLD OF LIFE A new Alignment against Female Choice Here again we find another, and I think a very conclusive argument against female choice having had any part in the production of beautiful and varied colours in the males of butterflies, or probably of any insects, since it is clear that the attraction is through another sense than that of sight, and all that vision can do in this direction is to enable the in- \ sect to recognise, perhaps at a greater distance, the individuals which are thus attractive. There is much evidence to support this view. H. Miiller, in his Fertilisation of Flowers, states that odour is pre-eminent in attracting insects to flowers, and, next to that, general conspicuousness rather than any special colour or form. And, by his detailed accounts of insects visiting flowers, we find that almost all the commoner butter- flies visit a great variety of honey-bearing flowers W'ithout much regard to colour. Thus Argynnis papliia visited flowers of four different natural orders, whose flowers w^ere white or pale red ; the large cabbage butterflies visited seven different orders, including red, white, purple, yellow, or blue flowers; the small tortoise-shell visited an even greater range of flowers and colours, so that we have no reason to impute to these in- sects anything more than the power to recognise, after experi- ence, any conspicuous flowers that produce pleasant odours and, usually, accessible honey. A consideration of the whole evidence as to the purpose served by the excessively varied and brilliant coloration of but- tei^ies leads us to the conclusion that its presence is due to general laws of colour-development — some of which will be discussed in later chapters — whose action is only checked when such development becomes injurious. In the case of butterflies, the comparatively short period that elapses between the emergence of the female from the chrysalis and the dep- osition of her eggs, and the still shorter period needed for the special functions of the more brilliantly coloured male to- gether wdth his power of irregular but rapid flight, render it EECOGNITIOX-MAEKS 185 possible for the colour-development to attain a degree of variety and beauty beyond that of all other living things. The larvae of Lepidoptera in their countless myriads un- doubtedly constitute an important factor in supporting the gloriously varied bird-life of the tropics, as we have seen that they so largely support that of our temperate ^nes. It is the comparatively small surplus that escapes which is yet ample for the development of the perfect insects in such abundance as to keep up an approximately equal supply of larva? for the next generation of birds. When this is done they themselves become the prey of birds, lizards, and other insect- eating animals. Some General Conclusions from Recognition-Marks We have thus been led by the study of colour as a means of recognition by birds and mammals to some very important general conclusions. The first is, that in both these groups, it has primarili/ a still more important function, that of facili- tating the formation of new species during the early stages of adaptation to changed conditions of life. Its secondary, but still very important use in many groups, is for easy identi- fication as alreadv described. That this is the true state of the case is rendered almost certain by the occurrence of a large number of species in which the markings for recognition are noiv unnecessary though they were of the highest impor- tance during the initial stages of evolution. Another and still more curious result of the study of this subject is the evidence it affords that the most varied in colour and markings ' of all insects — the butterflies — do not, pri- marily, recognise each other by sight, but by some sense analogous to that of smell. This seems now to be almost cer- tain, and it affords the explanation of what would otherwise be a great difficulty, how the males of polymorphic females, as in Papilio pammon in the East and Papilio apneas in the West, numerous American Pieridir and many other groups, in which the females are coloured as if with the purpose of being as un- 186 THE WOKLD OF LIFE like their mates as possible, are able to recognise each other. Intuitive knowledge or " instinct " is now given up by every thinker; but the proof now given that the only knoiun method of mutual recognition by Lepidoptera is by scent, explains the whole difficulty. The colours and markings of these insects have been produced in adaptive relation to their enemies al- most exclusively, and this explains the fact that the strangely diverse females above referred to are, probably in every case, either protectively coloured or mimics of distasteful forms in their own district. The fact that several of the Eastern Papilios have fully tailed females while they themselves are round-winged, is another indication that sight can have no part in leading to mutual recognition between the sexes. The almost universal presence of some form of recognition- marks in birds and mammals, no less than the proof now af- forded (and for the first time stated) of their entire absence in the Lepidoptera, affords, I think, ample justification for the importance I claim for them, and for the space I have devoted to them in the present volume. CHAPTER X THE EAETIl's SURFACE-CHANGES AS THE CONDITION AND MOTIVE-POWER OE ORGANIC EVOLUTION Having now sketched in outline the main factors on which organic evolution depends — heredity, variation, and rapid powers of increase — and having shown by a sufficient nuni- ber of examples that these factors are omnipresent features of organic life, only varying somewhat in the proportions of their occurrence in different species, we are now prepared to indi- cate the conditions under which they have acted in the produc- tion of those numerous changes of form and structure which we observe in the various forms of life. We have seen (in Chapter VI.) that so long as no consid- erable changes occur in the inorganic world, the effect pro- duced by the constant interaction between species and species, or between plants and animals, results in changes of local dis- tribution of the various species rather than in any important modification of the species themselves. And there really seems no reason why such changes should occur ; because when once complete or sufficiently complete adaptation to conditions is brought about, the whole of the organic world will bo in a state of stable equilibrium, with sufficient elasticity in all its parts to become adjusted to all minor periodical changes of climate, etc., by temporary changes in numbers, and by the local distribution of the sliffhtlv altered numbers. Once such an efpiilibrium is attained, there seems no reason why it should not be permanent. Xatural selection would keep up the suffi- cient adaptation of each species, but would not tend to change them. Geology proves that the inorganic environment — the 187 188 THE WORLD OF LIFE earth's surface — is not stable ; but that very considerable changes in climate, in the contour of the land surface, and even in the minor distribution of land and water, have con- tinually occurred during past ages; and that just in proportion to the evidence for such changes do we find that changes have occurred in the forms of life inhabiting every part of the earth. A short statement of the nature of these two groups of coincident and interdependent changes will therefore be useful here. The most general and most arresting facts of world-history, revealed by geology, are, that the superficial crust of the earth consists of various " rocks " (including in this term every kind of inorganic matter of which the crust is composed) deposited in more or less regular " strata " or layers, one above another ; that these strata are sometimes horizontal, more often inclined at various angles to the horizon, and even occasionally vertical; usually continuing at about the same angle or slope for many miles, but often curved or waved, or even crumpled up and contorted in remarkable ways. These various strata consist of many distinct kinds of rock — sandstones, limestones, clayey or slaty rocks, metamorphic or gneissic rocks ; and all of these give distinct evidence of having been deposited in water, both from mechanical texture and the arrangement of their com- ponent particles, and also by frequently having embedded in them the remains of various organisms, those that live in seas or lakes being by far the most abundant and varied. As an example of this abundance we may mention the Barton Cliffs on the Hampshire coast east of Christchurch, where, in a dis- tance of a few miles, over a thousand distinct species of the fossilised shells of molluscs, radiates, and other marine animals have been found. But the most suggestive fact from our present point of view is, that almost eveiy mountain-range on the earth presents us examples of such stratified rock-strata, often with abundant fossils of marine animals, at enormous heights above the sea- level. Such are found in the Alps at 8000 feet, in the Andes EARTH CHANGES AND EVOLUTION 189 at 14,000 feet, and in the Himalayas at 16,000 feet elevation. Innumerable cases of marine fossils at lesser heights are to be found in every part of the world, and in rocks of very various geological age. But the causes that have produced these great changes of level are still obscure. It is certain, however, that such changes have been exceedingly gradual in their operation, and have in all probability been of the same general nature as those going on at the present day — such as the earthquakes which, at irregular intervals, occur all over the world. There is one very instructive mode of ascertaining the rate of certain changes of the earth's surface which was first pointed out by Mr. Alfred Tylor more than half a century ago,^ and is generally accepted by geologists as of great value. The sur- plus water of the land is carried into the sea by rivers, each of which has a drainage area which contains a certain number of square miles. By careful measurements, it is possible to ascertain how much water flows away every year, and also how much solid matter is suspended in the water, how much is chemically dissolved in it, and how much is pushed along its bed at the mouth. The sum of these three quantities gives us the cubic yards or cubic miles of solid matter denuded from the surface of each river-basin in a year; and from this amount we can easily calculate how much the whole surface is lowered each year, while some corresponding area of the adjacent sea- bottom, on which it is deposited, must be proportionally raised. These measurements have been very carefully made for a num- ber of large and small rivers in various parts of the world, and the following results have been accepted as fairly accurate by Sir A. Geikie : — The Mississippi lowers its basin 1 foot in 6000 years. Ganges 2358 Hoang-Ho 1464 Rhone 1528 Danube 6848 Po 729 1 See Phil. Mag., April 1853. 190 THE WORLD OF LIFE We can easily see here that the rapidity of denudation is proportionate to the height and extent of the mountain-ranges in which the river has its sources, combined with the amount of the average rainfall, and the proportion of plains to uplands in its whole basin. The Ganges has a large proportion of low- land plain in its area; the Hoang-Ho has less, and therefore denudes more rapidly. The Danube and the Mississippi both drain an enormous area of lowlands where denudation is slight, and the rainfall of both is moderate; they therefore lower their basins slowly. The Po drains an enormous extent of snowy Alps in proportion to its whole basin, and in conse- quence lowers the land perhaps more rapidly than any impor- tant river on the globe. On the whole, we may take these rivers as fairly representative. Their mean rate of denuda- tion is very nearly one foot in three thousand years, and we may therefore, till more complete observations are made, take this as a measure of the average rate of denudation of most of the great continents. Of course, the rate of lowering will be extremely unequal, being at a maximum in the mountains and a minimum in the plains, where it may not only be nothing at all, but if they are flooded annually they may be raised instead of lowered. In the loftier mountains with numerous peaks and precipitous slopes the average lowering may often be ten times, and sometimes even a hundred times, the mean amount. In such districts w^e can even see and hear the process continually going on. Under every precipice there is a more or less ex- tensive mass of debris — the " screes " of our lake district ; and every winter, chiefly through the action of rain and frost, the rocks above are split off, and can be heard or seen to fall. Even on grassy hills after a few hours' downpour of rain, in- numerable trickles of muddy water course down in every di- rection ; while every streamlet or brook — though usually of water as clear as crystal — becomes a rapid torrent of mud- laden w^ater. It is by a consideration of these every-day phe- nomena in operation over every square yard of thousands of EAETH CHANGES AND EVOLUTIOiV 191 square miles of surface that we are able to understaucj ami appreciate the tremendous power of rain and rivers, greatly assisted by frost, in the disintegration of rocks, which lower the whole surface of the land at such a rate that, if we had means of accurate comparison with its condition a few thou- sand years ago, we should see that in many places the whole contour and appearance of the surface was changed. When this mode of estimating the rate of subaerial de- nudation was first applied to well-known regions, geologists themselves were surprised at the result. Eor 1 foot in three thousand years is 1000 feet in three million years, a period which has always been considered very small in the scale of time indicated by geological changes. When we consider that the mean height of all Europe (according to a careful esti- mate by Sir John Murray) is a little under 1000 feet, we find, to our astonishment, that, at the average rate of denudation, the whole would be reduced almost to sea-level in the very short period of three million years, while all the other great continents would be reduced to the condition of '^ pene-plains '' (as the American geologists term it) in about six or eight million years at the utmost. It is quite certain, therefore, that there must be some counteracting uplifting agency, either constantly or intermittently at work, to explain the often-re- peated elevations and depressions of the surface which the whole structure and mechanical texture of the vast series of distinct geological formations with their organic remains, prove to have taken place. The exact causes of these alternate elevations and depres- sions, sometimes on a small, sometimes on a gigantic scale, have not yet been satisfactorily explained either by geologists or physicists. Two of the suggested causes are undoubtedly real ones, and must be constantly acting; but it is alleged by mathematical physicists that they are not adequate to produce the whole of the observed effects. They are both, however, ex- ceedingly interesting, and must be briefly outlined here. We require first, however, to trace out what becomes of the de- 192 THE WORLD OF LIFE nuded matter that lowers the continental snrfaces at so rapid a rate, and is poured into the sea at various points around their coasts ; and this is the more necessary because recent re- searches on this matter have led to results as surprising as those of the measurement of the amount of denudation bv rivers. During the voyage of the Challenger round the world for the purpose of oceanic exploration, not only was the depth of the great oceans determined by numerous lines of soundings across them in various directions, but, by means of ingenious apparatus, samples of the sea-bottom w^ere brought up from all depths, and especially along lines at right angles to the shore at short distances from each other. The exact physical and chemical nature of all these samples was accurately determined, and some most curious results were brought to light. The earlier geologists had assumed, in the absence of direct evidence to the contrary, that the suspended matter poured into the sea by rivers was, sooner or later, by means of winds and waves and ocean currents, distributed over the whole of the ocean floors, and was gradually filling up or shallowing the oceans themselves. But the Challenger researches showed that this idea was almost as remote as possible from the truth. The actual facts are, that the wdiole of the land debris, with a few special and very minute exceptions, are being deposited on the sea-bottom very near the shore, comparatively speaking, and all but the very finest material quite close to it. Every- thing in the nature of gravel or sand, of which so much of the rocky strata consists, is laid down within a very few miles, only the finer muddy sediments being carried so far as from 20 to 50 miles from land; w^hile the very finest of all, under the most favourable conditions, rarely extends beyond 150 and never exceeds 300 miles from land into the deep ocean. Mr. A. Agassiz also, has found that the extremely fine mud of the Mississippi River is never carried to a greater distance than 100 miles from its mouth. If we take even so much as 50 miles for the average distance to which the denuded matter is carried, w^e find the whole area of deposit around South EAKTH CHANGES AND EVOLUTION 193 America to be 60,000 square miles. But the area of that con- tinent is about six million square miles, so that deposition goes on about a hundred times as fast as denudation ; while over considerable areas where the deposits are of a sand}^ rather than of a muddy or slaty nature, it may go on a thousand times as fast. This is a most important fact which does not appear to have been taken into full consideration by geologists even to-day. The correlative fact as to the ocean bed is, that over the whole of it, when more than the above-named distances from land, what are called " deep-sea oozes " are found. These are formed almost entirely by the calcareous or silicious skele- tons of minute organisms, together with small quantities of decomposed pumice and of meteoric or volcanic dust. Along with these in certain areas the remains of larger marine ani- mals are found, especially the otoliths (or ear bones) of whales and the teeth of sharks. And the extreme slowness of the deposit of these oozes is shown by the fact that it is often im- possible to bring up a dredging from the bottom that does not contain some of these bones or teeth. It seems as if much of the ocean bed were strewn with them ! Now, these oozes, so easily recognised by their component materials and their or- ganic remains, form no part of the upheaved crust of the earth on any of our continents. This is, of itself, a conclusive proof that oceans and continents have never changed places in the whole course of known geological time; for if they had done so (as is still maintained by many rather illogical writers) the epoch of submergence would be indicated by some fragments, at least, of the consolidated ocean ooze which must once have covered the whole continental area.^ 1 For a full discussion of this question, see my Darwinism, chap, xii.; Island Life, chaps, vi. and x.; and Studies Scientific and Social, vol. i. chap. ii. In this last work the whole argument is summarised and the numerous converging lines of evidence pointed out. 194 THE WORLD OF LIFE Thickness of the Earth's Crust We now have to consider a quite different set of phenomena which have a very important bearing on the causes which have produced the elevations and depressions which have occurred over much of the land surface of the globe. It is a universal fact that as we descend into the crust of the earth (in deep wells or mines) the temperature rises at a tolerably uniform rate, which is found to be on the average one degree Fahr. for eveiy 47% feet. This rate, if continued downwards, would reach the temperature of melted rock at a depth of about 20 miles. Hot springs in non-volcanic countries furnish an ad- ditional proof of the high temperature of the interior. Below the depth above indicated there would probably be some miles of rock in a plastic state, while irregularities w^ould result from the nature of the rock, some being more easily melted than others. ^ow, it has been ascertained that the various rocks of the crust are of less specific gravity in the solid state than when they are liquefied, so that the crust may be looked upon as actually floating upon the liquid interior, very much as the polar ice-sheets float upon the ocean. A curious confirmation of this has been given by measurements of the force of gravity, which show that near all great mountain masses gravity is di- minished, not only by the amount due to the mass of the moun- tain itself, but to about double that amount. This is so uni- versally the case that it has been concluded that the weight of the mountain mass is supported by a corresponding mass forced down into the fluid magma, and hence termed the ^^ roots of the mountains " ; just as every lofty iceberg must have a mass of submerged ice about nine times as great to sup- port it in the water. This, of course, proves that the crust is flexible, and that just as any portion of it is upheaved or made thicker by additions above, a corresponding increase in thick- ness must occur below to keep it in equilibrimn. Thus are explained the ver^^ frequent phenomena of hori- EARTH CHANGES AND EVOLUTION 195 o zontal strata occurring in similar beds for thousands of feet thick, while each successive bed must have been formed at or near the surface. Such are the deposits recently formed in the deltas of great rivers, in many of which borings have been made from 350 to 640 feet deep, with indications that each successive layer was formed near the surface, and that during the entire process of deposition the whole area must have been sinking at a very regular rate. This can best be explained by the weight of the matter deposited causing the slow sub- sidence. Exactly similar phenomena occur through the whole series of the geological formations to the most ancient ; in some cases strata eight miles in thicloiess showing proofs that the very lowest beds w^ere not deposited in a deep ocean, but in quite shallow w^ater near shore. ^ Now, as w-e have seen that, over many areas not far from shore, deposition may occur 100 or even 1000 times as fast as denudation, and that this same area is continuously lowered by the weight forcing the crust downwards, we have a real and efficient cause for continuous subsidence and the forma- tion of parallel strata of enormous thicknesses. It remains to account for the subsequent upheaval of these areas, their tilt- ing up at various angles, and in many cases their being frac- tured, curved, or contorted often to an enormous extent and in a most fantastic manner. Effects of a Cooling and Contracting Earth It is universally admitted that the earth is a cooling and therefore a contracting body. The cooling, however, does not take place by conduction from the heated interior through the solid crust, the temperature of which at and near the surface is due wholly to sun-heat, but by the escape of heated matter to the surface through innumerable hot or warm springs; by a continuous flow of heated gases from volcanic areas; and fre- quent outbursts of red-hot ashes or liquid lavas from vol- 1 In chapter iii. of vol. i. of my Studies Scientific and Social I have given details of these phenomena on the highest geological authority. 196 THE WORLD OF LIFE canoes. The springs bring up from great depths a quantity of matter in solution, and the whole of the above-mentioned agencies result not only in a very considerable loss of heat, but also in a very great outflow of solid matter, which, in the course of ages, must leave extensive cavities at various depths, and thus produce lines or areas of weakness which almost certainly determine the mode in which contraction will produce its chief effects. As the outer crust for a considerable depth has its tem- perature determined by solar heat, and also because the tem- perature at which the rocks become liquid is tolerably uni- form, the loss of heat, causing shrinkage of the globe as a whole, must occur in the liquid interior; and, as this becomes reduced in size, however slowly, it tends to shrink away from the crust. Hence the crust must readjust itself to the in- terior, and it can only do so by a process of crumpling up, owing to each successive concentric layer having a less area than that above it. This shrinkage has been compared with that of the rind of a drying-up apple. But the earth's crust having been for ages subject to ever-varying compressions and upheavals, and being formed of materials which are of un- equal strength and tenacity, the actual results will be exceed- ingly unequal, and the inequalities will be most manifested along or near to certain lines of weakness caused by earlier shrinkage due to the same cause. As the crust will be of greater extent than the contracted liquid core it has finally to rest upon, and as the chief effects of contraction are limited to certain directions and to com- paratively small areas, and if the less fractured and more rigid portions settle down almost undisturbed upon the contracted interior, then considerable areas along, or parallel to, the lines of weakness must be crumpled, fractured, and forced upward, and thus produce great elevations on the surface, though small in proportion to the whole dimensions of the earth. IN'ow, the ocean floors are enormous plains, except that they have, here and there, volcanic islands rising out of them. The water which EARTH CHANGES A:N'D EVOLUTION 197 covers them preserves uniform temperature, whicli, at the bot- tom, is not much above the freezing point of sea-water. We may conclude, therefore, that they are very nearly stable. Pen- dulum experiments show that the crust below these oceans is more dense than the subaerial crust, due, probably, to the uni- form pressure and temperature they have been subject to for geologic periods. We may assume, therefore, that they do not become crumpled or distorted by the contraction of the liquid earth beneath them. The great plains of Eussia, mostly of Triassic and Jurassic age, consist of nearly horizontal strata, while the Alps of Central Europe are greatly upheaved and contorted ; and the same difference between adjacent areas is found in the United States, and most probably in all the great continents. Mathematical physicists have calculated the possible up- heavals that could be produced by a shrinking crust at prob- able rates of contraction, and have declared them to be too small to account for the elevation of the existing land- masses above the ocean floors, that is, for the whole differences of height of the land surfaces. But if, as the Rev. O. Eisher suggests, the oceanic basins were formed at an early stage of the earth's consolidation, by the separation from it of the moon in the way described by Sir George Darwun and accepted by Sir Robert Ball ; and if the whole wrinkling effect of contrac- tion is concentrated on a few lines or areas of weakness, al- ways near existing mountains ; and further, if this cause of elevation be supplemented by the continual subsidence of large areas along the margins of all the continents by the weight of new deposits producing a pressure on the liquid interior, which must result in upward pressures elsewhere, then it seems pos- sible that a combination of these causes may be sufficient. Yet another cause of elevation has recently been demon- strated. After many unsuccessful attempts, the actual ex- istence of semi-diurnal lunar tides ivithin iJic earth's interior has been proved; and such tides must, it is said, generate a vast amount of heat, culminating at tlio bi-monthly periods of 198 THE WORLD OF LIFE maximum effect. The heat thus produced would be greatest where the under surface of the crust was most irregular, that is, under the land surfaces, and especially under the ^' roots of mountains " projecting below the general level. Their cumu- lative results would, therefore, add to the upward forces pro- duced by contraction along lines of weakness.^ But whether the various forces here suggested have been the only forces in operation or not, the fact of the repeated slow elevations and depressions of the earth's surface is un- doubted. The most general phenomenon seems to have been the very slow elevation of gTcat beds of strata, deposited one above another along the coasts of a continental mass, or some- times along the shores of inland seas; immediately followed by a process of denudation of this surface by rain and rivers, which, as the elevation continued, carved it out into a complex series of valleys and ridges till it ceased to rise farther. The denudation continuing, the whole mass became worn away into lowland plains and valleys. Then, after a long period of quiescence, subsidence began, and as the land sank beneath the water new deposits were laid down over it. Sometimes re- peated elevations and depressions of small extent occurred; while at very long intervals there was great and long-continued subsidence, and, while deeply buried under newer strata, the older masses were subjected to intense subterranean heat and compression, which altered their texture, and often crumpled and folded them up in the strangest manner conceivable. Then, perhaps, a long period of elevation brought them up and up, till they were many thousand feet above sea-level ; and, when the superficial covering of newer beds had been all re- moved by denudation, the folded strata were themselves ex- posed to further denudation, and all the strange peaks and ravines and rushing cataracts of alpine mountains became re- vealed to us. 1 This sketch of the internal structure of the earth, as affecting elevation and depression of its surface, is fully discussed in INIr. 0. Fisher's Physics of the Earth's Crust, a popular abstract of which is given in my Studies Scientific and Social, vol. i. chap. iii. EAKTH CHAKGES AND EVOLUTION I'JO ThuSj in alternate belts or more extended areas, our con- tinents have been, step by step, built up throughout the ages, ■with repeated alternations of sea and land, of mountain and valley, of upland plateaus and vast inland seas or lakes, the indications of which can be clearly traced throughout the ages. And, along with these purely terrestrial changes, there have been cosmic changes due to the varying eccentricity of the earth's orbit and the precession of the equinoxes, loading to alternations of hot, short summers with long, cold winters, and the reverse; culminating at very distant intervals in warm and equable climates over the whole land surface of the globe ; at other shorter and rarer periods in more or less severe " ice- ages," like that in which the whole north temperate zone was plunged during the Pleistocene period, long after the epoch when man had first appeared upon the earth. ^ Long Persistence of the Motive Power thus caused It is in tliis long series of physical modifications of the earth's surface, accompanied by changes of climate, partly due to astronomical revolutions, and partly to changes in aerial and oceanic currents dependent on terrestrial causes, that we find a great motive power for the work of organic evolution, the mode of operation of which we now have to consider. Before doing so, however, I would call attention to the fact of the very extraordinary complexity and delicacy of the physical forces that have continued to act almost uniformly, and with no serious break of continuity, during the whole vast periods of geological time. These forces have always been curiously balanced, and have been brought into action alter- nately in opposite directions, so as to maintain, over a large portion of the globe, land surfaces of infinitely varied forms, which, though in a state of continuous flux, yet never reached a stationary condition. Everywhere the land is being low- ered by denudation towards the sea-level, and part by part is 1 See my Island Life, chapters vii., viii., and ix., for a full discussion of the causes and effects of glacial periods. 200 THE WOKLD OE LIFE always sinking below it, yet ever being renewed by elevatory forces, whose nature and amount we can only partially deter- mine. Yet these obscure forces have always acted with so much regularity and certainty that the long, ever-branching lines of plant and animal development have never been com- pletely severed. If, on the other hand, the earth's surface had ever reached a condition of permanent stability, so that both degrading and elevating forces had come to a standstill, then the world of life itself would have reached its final stage, and, w^anting the motive power of environmental change, would have remained in a state of long-continued uniformity, of which the geological record affords us no indication whatever. Readers of my book on Man's Place in the Universe will remember how, in chapters xi, to xiv., I described the long series of mechanical, physical, and chemical adjustments of the earth as a planet, which were absolutely essential to the development of life upon its surface. The curious series of geological changes briefly outlined in the present chapter are truly supplementary to those traced out in my former work. The conclusion I drew from those numerous cosmic adapta- tions was that in no other planet of the solar system were the conditions such as to render the development of organic life possible upon them — not its existence merely, which is a vastly different matter. That conclusion seemed to many of my readers, including some astronomers, geologists, and physicists, to be incontestable. The addition of the present series of adaptations, whose continuance throughout the whole period of world-life history is necessary as furnishing the mo- tive power of organic development and adaptation, not only increases to an enormous extent the probability against the de- velopment of a similar ^^ world of life," culminating in man, in any other known or reasonably conjectured planet, but af- fords, in my opinion, an exceedingly powerful argument for an overruling Mind, which so ordered the forces at work in the material universe as to render the almost infinitely improbable EAKTH CHANGES AND EVOLUTION 20i sequence of events to which I have called attention an actual reality. Terrestrial Temperature Adjustments Among the many wonderful adjustments in the human body, and in that of all the higher vertebrates, none perhaps is more complex, more exact, and apparently more difficult of attainment than those which preserve all the circulating fluids and internal organs at one uniform temperature, vary- ing onlj^ four or five degrees Fahr., although it may be ex- posed to temperatures varying more than a hundred degrees. Hardly less wonderful are those cosmical and physical adjust- ments, which, during many millions of years, have preserved the earth's surface within those restricted ranges of temper- ature which are compatible with an ever-increasing develop- ment of animal and vegetable life. Equally remarkable, also, is that other set of adjustments leading to those perpetual surface-changes of our globe which I have shown to be the motive power in the development of the marvellously varied world of life; and which has done this without ever once leading to the complete subsidence of any of the great continents during the unceasing motions of ele- vation and depression which have been an essential part of that great cosmic scheme of life-development of which I am now attempting an imperfect exposition. That the temperature of the earth's surface should have been kept within such narrow limits as it has been kept during the enormous cycles of ages that have elapsed since the Cambrian period of geology, is the more amazing when we consider that it has always been losing heat by radiation into the intensely cold stellar spaces ; that it has always, and still is, losing heat by volcanoes and hot springs to an enormous extent; and that these losses are only counteracted bv solar radiation and the conservative effect of our moisture-laden atmosphere, which again depends for its chief conservative effect on the enormous 202 THE WORLD OF LIFE extent of our oceanic areas. That all these agencies should have continued to preserve such a uniformity of temperature that almost the whole land surface is, and has been for count- less ages, suitable for the continuous development of the world of life, is hardly to be explained without some Guiding Power over the cosmic forces which have brought about the result. 1 i i i CHAPTER XI THE PROGRESSIVE DEVELOPMEITT OF THE LIFE-WORLD^ AS SHOWN BY THE GEOLOGICAL RECORD In order to form any adequate conception of the world of life as a whole, of the agencies concerned in its development, and of its relation to man as its final outcome, we must en- deavour to learn something of its past history; and this can only be obtained by means of the fossilised remains preserved in the successive strata or layers of the earth's crust, briefly termed " the geological record." In the preceding chapter I have endeavoured to indicate the forces that have been at work in continually moulding and remoulding the earth's surface; and have argued that the frequent changes of the physical en- vironment thus produced have been the initial causes of the corresponding changes in the forms of organic life, owing to the need of adaptation to the permanently changed conditions; and also to the opening up of new places in the economy of nature, to be successively filled through that divergency of evolution which Darwin so strongly insisted upon as a neces- sary result of variation and the struggle for existence. But in order to appreciate the extent of the changes of the earth's surface during the successive periods of life-develop- ment, it is necessary to learn how vast, how strange, and yet how gradual were those changes ; how they consisted of alter- nate periods of not only elevation and depression, but also of alternations of movement and of quiescence, the latter often continuing for long periods, during which more and more complete adaptation was effected, and, perhaps in consequence a diminished preservation in the rocks, of the life of the period. Thus have occurred those numerous " breaks " in the geo- logical record which separate the great " eras " and " sys- 203 204 THE WORLD OY LIFE terns " of the geologist. These phenomena are admirably ex- plained in Professor James Geikie's attractive and well-illus- trated volume on '^ Earth Sculpture or the Origin of Land Forms," published in 1898. Here I can only attempt to sketch in outline the successive stages of life which are ex- hibited in the rocks, and point out some of their most striking features with the conclusions to which they lead us. During the latter part of the eighteenth century geologists were beginning to obtain some detailed knowledge of the earth's crust and its fossils, and arrived at a first rude di- vision into primitive, secondary, and tertiary formations. The first were supposed to represent the epoch before life ap- peared, and comprised such rocks as granite, basalt, and crystalline schists. 'Next above these came various strata of sandstones, limestones, and argillaceous rocks, evidently of aqueous origin and often containing abundant fossils of marine, fresh-water, or terrestrial animals and plants. The tertiary were clearly, of more recent origin, and contained shells and other remains often closely resembling those of liv- ing animals. It was soon found, however, that many of the rocks classed as " primitive " either themselves produced fossils, or were found overlying fossiliferous strata; and, by a more careful study of these during the early part of the nine- teenth century, the three divisions were more precisely limited — the first or '^ Primary,'' as containing the remains of Mol- lusca, Crustacea, and some strange fishes and amphibians; the '' Secondary," by the first appearance of reptiles of many strange forms ; and the ^' Tertiary," by abundance of Mam- malia of all the chief types now existing, with others of new and apparently primitive forms, or serving as connecting links w^ith living groups. It is a very remarkable fact, not sufiiciently dwelt upon in geological treatises, that this first grouping of the whole of the life-forms of the past into three great divisions, at a time when our knowledge of extinct animals and plants was ex- tremely scanty as compared with what it is now, should still THE GEOLOGICAL RECORD 205 be in universal use among the geologists of the world. The exact limits of each of these great divisions have been more ac- curately determined, but the abrupt change in the life-forms, and the world-wide unconformity in the stratification on pass- ing from one division to the other, are as great as ever. Tlie Primary or Palaeozoic period is still that of fishes and Am- phibia; the Secondary or Mesozoic, that of reptiles, in amazing abundance and variety; and the Tertiary or Caino- zoic, that of an almost equal abundance of Mammalia, and with a considerable variety of insects and birds. The exceptions to the generality of this classification are few, and are particularly interesting. Of the myriads of rep- tiles that characterise the Secondary era, only two of the nine orders into which they are subdivided have been found so far back as the Permian, the latest of the Palaeozoic formations. One of these most primitive reptiles has a near ally in the strange, lizard-like Hatteria still surviving in some small islands on the coast of l^ew Zealand ; while others which seem to form connecting links with the earliest mammals may be the ancestral form from which have descended the unique types of the lowest living Mammalia, the omithorhynchus and echidna of Australia. So with the highest type of vertebrates, the mammals. About the middle of the nineteenth century small mammalian jaws with teeth were discovered in w^hat was known as the dirt-bed of the Purbeck (Jurassic) formation at Swanage; others in the Stonesfield Slate of the same fomiation; and at a later period very similar remains were found in beds of the same age (and also in the Cretaceous) in Xorth America. These are supposed to be primitive insect-eating Marsupials or Insectivora, and were all about the size of a mole or a rat; and it is a striking example of the imperfection of the geo- logical record, that although they occur through the whole range of the Secondary period, from the Trias to the Cre- taceous, their remains are still exceedingly scanty, and they appear to have made hardly any structural progress in 206 THE WORLD OF LIFE that enormous lapse of time. Yet directly we pass from the Cretaceous to the Tertiary rocks, not only are Mammalia abundant and of fairly large size, but ancestral types of all the chief orders occur, and such highly specialised forms as bats, lemurs, and sea-cows (Sirenia) are found in its earliest division, the Eocene. Either there is no record of the missing links in the Sec- ondary formations, or, what is perhaps more probable, the break between the Secondary and Tertiary beds was of such enormous duration as to afford time for the simultaneous dvinsr out of numerous groups of gigantic reptiles and the develop- ment in all the large continents of much higher and more varied mammals. This seems to imply that a large portion of all our existing continents was dry land during this vast period of time ; the result being that the skeletons of very few of these unknown forms were fossilised; or if there were anv they have been subsequently destroyed by denudation during the depression and elevation of the land which we know to have occurred. We will now consider these great geological periods sep- arately, in order to form some conception of the changes in the world of life which characterised each of them. The Primary or Pdloeozoic Era The Palaeozoic differs from the two later eras of geology in having no known beginning. The earliest fossils are found in the Cambrian rocks ; they consist of a few obscure aquatic plants allied to our Charas and Algae, and some lowly marine animals allied to sponges, crinoids, and annelids. But there are also many forms of shell-bearing Mollusca, which had al- ready developed into the four great classes, lamellibranchs, pteropods, gasteropods, and cephalopods ; while some groups of the highly organised crustaceans were abundant, being rep- resented by water-fleas (ostracods) and numerous large and varied trilobites. Besides these, the curious Molluscoidea were fairly abundant, Terebratulae now first appear, and, as THE GEOLOGICAL EECORD 207 well as the genus Lingnla, have continued to persist through all the subsequent ages to the present time. Great masses of rocks stratified and imstratified exist below the Cambrian, but have mostly been metamorphosed by internal heat and pres- sure, and contain no recognisable organic remains. Geologists have been greatly impressed by this sudden ap- pearance of marine life in such varied forms and compara- tively high organisation, and have concluded that the strati- fied formations below the Cambrian must probably have equalled the whole series which we now know above it. Dr. Croll declared, that " whatever the present mean thickness of all the sedimentary rocks of our globe may be, it must be small in comparison with tlie mean thickness of all the sedi- mentary rocks which have been formed " ; while Darwin says, " Consequently, if the theory be true, it is indisputable that before the lowest Cambrian stratum was deposited long periods elapsed, as long as, probably longer than, the whole interval from the Cambrian age to the present day, and that during these vast periods the world swarmed with living creatures." ^ This view was supported by Sir Andrew Eamsay, Director- General of the Geological Survey, who possessed unrivalled knowledge of the facts as to the geological record. He says, speaking especially of the fossil fauna of the Cambrian age : " In this earliest known varied life we find no evidence of its having lived near the beginning of the zoological series. In a broad sense, compared with what must have gone before, both biologically and physically, all the phenomena connected with this old period seem, to my mind, to be of quite a recent description; and the climates of seas and lands were of the very same kind as those the world enjoys at the present day." - This consensus of opinion renders it highly probable that the existing geological record only carries us back to some- where about the middle of the whole period during which life has existed upon the earth. 1 Origin of Species, 6th ed. p. 286. 2proe. Roy. Soc., 1874, p. 834. 208 THE WOELD OF LIFE Passing through the long series of Lower Silurian strata, (now separated as Ordovician) we have fuller developments and more varied forms of the same classes found in the Cam- brian; but in the Upper Silurian we meet with remains of fishes, the first of the great series of the vertebrates to appear upon the earth. Thej are of strange forms and low type, mostly covered with a kind of plate-armour, and apparentlv without any lower jaw. Hence they form a separate class — Agnatha (^^ without jaws"). They also appear to have had no hard, bony skeleton, as the only parts fossilised are the outer skin with its more or less armoured covering. The illustra- tion (Fig. 39) shows one of the simpler forms, the whole sur- FiG. 39. — Thelodus scoticiis. From Upper Silurian, Lanarkshire. Half nat. size. (B.M. Guide.) face being covered with small quadrangular flattened tubercles. The tail is somewhat twisted to show the bi-forked character. The mouth must have been an aperture underneath the head. Good specimens of these are rarely preserv^ed. In another family, Pteraspidse (Fig. 40), the skin-tubercles Fig. 40, — Pteraspis rostrata. From Old Red Sandstone of Herefordshire. One-third nat. size. (B.M. Guide.) are united into plates and scales, while the head is covered with a dorsal shield, often terminating behind in a spine ; THE GEOLOGICAL RECORD 209 and there is often a smaller shield beneath. A separate piece forms a projecting snout. The shields of these fishes are often preserved, while the complete body is very rare. Another gi'oup (Fig. 41) has the head shield continuous Fig. 41. — Ceplalaspis murchisoni. From Old Red Sandstone of Herefordshire. About half nat. szie. (B.M. Guide.) or in two pieces, while the skin-tubercles are united into vertical plates on the sides of the body, as in the species here sho^vn, while others have two or three rows of plates. The highest group of these primitive fishes has the head and fore part of the body covered with large polygonal bony plates. As these died out in the Devonian epoch their place was taken by true fishes, having an ossified skeleton, a movable lower jaw, gill-covers, and pairs of pectoral and anal fins rep- resenting the four limbs of reptiles and mammals. The ear- liest of these were allied to our sharks ; and at each succeeding geological stage a nearer approach was made to the higher types of our modern fishes. Class — Pisces Fig. 42.— Protocercal Tail. The primitive type of true fishes, having a lower jaw and paired fins. (B.M. Guide.) Fig. 43. — Heterocercal (unequal-lobed) Tail. The middle type of true fishes. (B.M. Guide.) 210 THE WOKLD OF LIFE Fig. 44. — Homocercal (equal-lobed) Tail. Modern type of true fishes. The older types persist in some of the lower forms. (B.M. Guide.) This advance in development is well indicated by the gradual changes in the tail, as shown in the accompanying figures (42-44). The upper one is the oldest; but it soon became modified into the second, which in various modifica- tions prevailed throughout the Palaeozoic and most of the Sec- ondary periods; while the third perfectly symmetrical type did not appear till near the end of the latter, and only became predominant, as it is now, in the Tertiary period. Many of the earlier forms have tails which are quite symmetrical ex- ternally, but show a slight extension of the vertebrae towards the upper lobe. All three forms still exist, but the third is by far the most abundant. In the highest Silurian beds land-plants allied to ferns and lycopods first appear, and with them primitive scorpions. In the succeeding Devonian and Carboniferous strata an ex- tremely luxuriant land vegetation of a low type appeared and covered a large part of the existing lands. This supported a large variety of arthropods as well as true insects allied to mayflies and cockroaches, with a great number of Crustacea. Here, too, we come upon the next great step towards the higher land animals, in the appearance of strange Amphibia forming a distinct order — the Labyrinthodontia. They appear to have outwardly resembled crocodiles or lizards, and were rather abundant during the Carboniferous and Permian eras, dying out in the subsequent Triassic. That portion of the Palaeozoic series of strata from the Silurian to the Permian, during which a rich terrestrial vegetation of vascular cryptogams was developed, with numer- THE GEOLOGICAL RECORD 211 ous fonns of arthropods, insects, primeval fishes and am- phibians, comprises a thickness of stratified rocks somewhat greater than that of the whole of the Secondary and Tertiary strata combined. This thickness, which can ho measured with considerable approach to accuracy, is generally supposed to afford a fair 'proportionate indication of the lapse of time. There is a popular impression that in these remote ages the forces of nature were more violent, and their results more massive and more rapidly produced, than at the present time; but this is not the opinion of the best geological observers. The nature of the rocks, though often changed by pressure and heat, is in other cases not at all different from those of subse- quent ages. Many of the deposits have all the characters of having been laid down in shallow water, and in several cases footprints of Amphibia or reptiles have been preserved as well as impressions of raindrops, so exactly corresponding with those which may be seen to-day in suitable places, that we cannot suppose the operations of nature to have been more violent then than now. All our great coal deposits of PalaBOzoic age indicate long, and often repeated, but very slow depression of large areas of land, with intervening periods of almost perfect stability, during which dense forests had again time to grow, and to build up those vast thicknesses of vegetable matter which, when buried under successive rock-strata, became com- pressed into coal-seams, usually of several feet in tliickness. It is an extraordinary fact that in all the great continents, including even South America and Australia, coal-fields are more or less abundant at this period of the earth's history. This is proved by the identity or close similarity of the vege- tation and animal life, as well as by the position of the coal- beds, in regard to the strata above and beneath them. It is true that coal is also found in some Secondary and Tertiary strata, but these beds are much less extensive and the coal is rarely of such purity and tliickness ; while the later coal-fields are never of such world-wide distribution. Tt seems certain, therefore, that at this particular epoch there Avere some spe- 212 THE WOELD OF LIFE cially favourable conditions, affecting the whole earth, which rendered possible a rapid growth of dense vegetation in all situations which were suitable. Such situations appear to have been extensive marshy plains near the sea, probably the deltas or broad alluvial alleys of the chief great rivers ; and the special conditions were, probably, a high and uniform tem- perature, with abundance of atmospheric moisture, and a larger proportion of carbon-dioxide in the air than there has ever been since. We may, in fact, look upon this period as being the neces- sary precursor of the subsequent rapid development of terres- trial and aerial animal life. A dense and moisture-laden atmosphere, obscuring the direct rays of the sun, together wdth a superabundance of carbonic-acid gas and a corresponding scarcity of free oxygen, would probably have prevented the full development of terrestrial life with its magnificent culmi- nation in such examples of vital activity as we see manifested in the higher mammalia, and especially in the more perfectly organised birds and insects. In this first and most widespread of the coal-making epochs we see the results of a world-wide and even cosmical adaptation which influenced the whole future course of life-development; while the later and more limited periods of coal-formation have been due apparently to highly favourable local conditions, of which the production of our deeper peat beds are the latest example. If then, as I am endeavouring to show, all life development — all organic forces — are due to mind-action, w^e must postu- late not only forces but guidance; not only such self-acting agencies as are involved in natural selection and adaptation through survival of the fittest, but that far higher mentality which foresees all possible results of the constitution of our cosmos. That constitution, in all its complexity of structure and of duly co-ordinated forces acting continuously through eons of time, has culminated in the foreseen result. ISTo other view yet suggested affords any adequate explanation ; but this vast problem will be more fully discussed later on. THE GEOLOGICAL EECORD 213 This earliest, but, as some think, the most extended period of geological time, has been very cursorily touched upon, both because its known life-forms are more fragmentary and less generally familiar than those which succeeded them, and be- cause the object here is to show reasons for considering it as essentially 'preparatory for that wonderful and apparently sud- den burst of higher life-development of which we will now en- deavour to give some account. The Mesozoic or Secondary Formations When we pass from the Palaeozoic to the Mesozoic era we find a wonderful change in the forms of life and are trans- ported, as it were, into a new world. The archaic fishes wholly disappear, while the early Amphibia (Labyrinthodonts) linger on to the Trias, their place being taken by true reptiles, which rapidly develop into creatures of strange forms and often of huge dimensions, whose skeletons, to the uninstructed eye might easily be mistaken for those of Mammalia, as in fact some of them have been mistaken. The earliest of these new types, somewhat intermediate between Amphibia and reptiles, appear in the latest of the Palaeozoic strata — the Permian. These are the Theriomorpha (or "beast-shaped'' reptiles), which show some relationship to true mammals which so quickly followed them in the lowest of the Mesozoic strata. These early reptiles already show a large amount of speciali- sation. Some have greatly developed canine teeth, almost equalling those of the sabre-toothed tiger; others were adapted to feed on the luxuriant vegetation of the period, while their short, massive limbs made them almost as clumsy-looking as the hippopotamus. These strange creatures were first discov- ered in the Karoo formation of the Cape Colony, but have been found in a few places in India, Europe, and Xorth America, always either in the highest Primary (Permian) or lowest Secondary formation (Trias). Pemains of allied forms have been found in the north of England and in the Trias of Elgin, Scotland. Their nearest survivimr relatives arc supposed to 214: THE WOKLD OF LIFE be the monotremes (echidna and platypus) of Australia, jet in the whole series of stratified rocks of Secondary and Tertiary times no intermediate form has yet been discovered. A complete skeleton of one of the largest of these beast- shaped reptiles is represented here (Fig. 45). The body of this strange animal was nearly seven feet long, and its small teeth show it to have been a vegetable feeder. The total length of some specimens was nearly ten feet, and the immense limbs were apparently adapted for digging, so that in loose soil it mav have been of subterranean habits. In the same forma- tion other allied but much smaller species were found. Along with these w^ere many creatures of the same general type, but as clearly carnivorous as the others were herbivorous. About a dozen distinct genera have been characterised, and as each probably comprised several species, and as these have as yet been all obtained from a few very limited areas, it is quite possible that the land animals of the Cape Colony at that early period may have been almost as numerous, as varied, and as conspicuous as they are to-day. The two skulls here figured (Figs. 46 and 47) are of very different forms, and must have belonged to animals about the Fig. 46. — Dicynodon lacerticeps (Order — Anomodontia). From Karoo formation (Trias), South Africa. One-third nat. size. (B.M. Guide.) size of wolves; but there were many others of various shapes and sizes, some even equalling that of a large crocodile. But at the same epoch, apparently, Europe and North Amer- ica were equally well supplied w^ith these strange reptiles, Ira, •iiopouBn.§i aq; jo aouB.iBaddv 9iqi?qo.ij — -jc -oij (•9pinjc) 'H'a) "auids i^uoiB laaj 08 •q^Sueq; •uiniS[aa; Jo uapiBa^i eq; mox^ • ( siaudj. -jivasnudfi uopounn^i) .iuusouiq snopocToq^ui.iQ jo iio;e[9>^s — -qo -oij THE GEOLOGliCAL KECOiilJ lM:. Europe till recently only a few isolated bones or fragments of skulls bad been discovered, but about five or six years ago a rich deposit was found on the banks of the river Dwina in ^N^orthern Kussia. Tn a large fissure of the rocks quantities Fig. 47. — J^lusaurus felinus (Order — Anomodontia). From Trias (South Africa). Two-thirds nat. size. (B.M. Guide.) of nodules of very hard rock had been found, and being easy to obtain, were broken up for mending roads; till Professor Amalitzky from Warsaw, visiting the spot, found that each of these nodules contained well-preserved fossils of extinct ani- mals, which proved to be reptiles of the very same group as those of South Africa. Some of these nodules contained a skull; others contained the whole skeleton, these being some- times eight feet long, and of strange forms corresponding to the crushed or distorted body of the animal. Thenceforth Professor Amalitzky devoted himself to the work of explora- tion by the aid of a grant from the Imperial Academy of St. Petersburg. The nodules are taken to Warsaw, where ihey are carefully opened, and the fossilised bones extracted, cleaned, and put together. Some of these are found to be almost identical with those of South Africa; others, quite distinct, though allied. Fig. 48 represents the skull of a huge carnivorous reptile, which must have been about the same size as the herbivorous Pariasauri fabundantly preserved in tho nodules), upon which it doubtless preyed. As the skull is two 216 THE WOKLD OF LIEE feet long, and the whole head and body about nine feet, it must have far exceeded in size the largest lion or tiger, and prob- ably that of any carnivorous land mammal that has ever lived. In I^orth America these reptiles were also present in consid- erable abundance. Some, forming the sub-order Theriodontia, were allied to the Pariasauri, and were probably herbivorous; while the Pariotrichida? were carnivores, as were also a very distinct family, the Clepsydropidse. Of this latter group one 1 genus, Dimetrodon, is here figured as restored by Sir Ray Lankester (Fig. 49). This is supposed to be allied to the liv- ing Hatteria of New Zealand. These strange carnivorous rep- tiles of this early period may have preyed upon numerous herbivores which have not been preserved, as well as upon the primitive insects and land Crustacea, which at this period were probably abundant. The remarkable thing is, that some hundreds of species of varied form and size, herbivorous and carnivorous, should have been gradually developed, arrived at maturity, and completely died out, during the comparatively short periods of the Permian and Trias, or the interval between them. It is probable, however, that these transition periods really occupied a very great length of time, since all known reptiles seem to have originated during this era, though owing to unfa- vourable circumstances the connecting links have rarely been preserved. The singular Chelonia (turtles and tortoises) ap- pear fully formed at the end of the Trias or in the earliest Jurassic beds, as do the crocodiles, the aquatic Plesiosaurians and Ichthyosaurians, the flying Pterodactyls, and the huge Dinosaurs. All these have more or less obscure interrelations, and their common ancestors cannot well be older than the Permian, since the preceding Carboniferous offered highly favourable conditions for the preservation of the remains of such land animals had they existed. To bring about the modi- fication of some primitive reptile or amphibian into all these varied forms, and especially to bring about such radical changes of structure as to develop truly aerial and truly oceanic rep- -^^wy^jrw — *-« »~ ~i fUi Fig. 48. — Skull of the gigantic Theriomorpli Carnivorous Reptile Inostransevia. From Northern Russia. (Length of skull, 2 feet.) Permian or Triassic age. This animal was probably as large as a rhinoceros. (From Sir Ray Lankester's Extinct Animals.) Fig. 49. — Probable Appearance of the Therioniorj)!! KcitliU' Dinietroilon. From the Permian of Texas. It was the size of a large dog. (From Sir Kay Lan- kester's Extinct Animals.) THE GEOLOGICAL RECORD 217 tiles, must, with smy reasonable speed of change, have required an enormous lapse of time, yet all these had their origin seem- ingly during the same period. Some account of the strange animals whose abundance and variety so especially character- ised the Secondary period will now be given. Order — Dinosauria Some of the best known of these reptiles have been found in our own country, and we will therefore begin with the Iguanodon, of which teeth and bones were found near Maid- stone (Kent) by Dr. Mantell in the early part of the last century, but no complete skeletons have been found. A closely allied species from Belgium of the same age (the Wealden) is here figured (Fig. 50). It was about thirty foot long, and is believed to have walked chiefly on its hind feet, and to have fed upon the foliage or fruits of good-sized trees. As shown in the restoration of the animal in its supposed usual attitude when alive (Fig. 51), it would stand about fourteen feet high. The fore-limbs are comparatively small, termi- nating in a hand of five fingers, the thumb being represented by a bony claw. The much longer hind legs, however, have feet with only three toes, much resembling those of running birds, and numerous impressions of such feet have been found in rocks of the same age, hence the group to which it belongs has been named Ornithopoda or '^ bird-footed.'' From the character of these it seems probable that the animal would walk on all fours and leap with its hind legs in the manner of a kangaroo. The skull as shown by Fig. 52 is three and a half feet long, and the numerous close-set serrated teeth seem well adapted for grinding up large quantities of vegetable matter. The deep compressed tail indicates that it may have been used for swimming, and that the animal frequented lakes or marshes, and perhaps escaped its enemies by taking to the water. It appears to have had no protective armour. Another group was named Stegosauria, " plated lizards," 218 THE WORLD OF LIFE from tlieir protective armour, a skeleton of whicli Is figured (Fig. 53). It has long bony spines on the shoulders, which, if bearing a horny covering, would have been an effective pro- tection against beasts of prey; and this is followed by a row Fig. 52. — Skull of I guanodon bernissartensis. From the Wealden of Belgium. Three and a half feet long. (B.M. Guide.) Fig. 53. — Skeleton of Armoured Dinosaur {Scelidosaurus harrisoni). From the Lower Lias of Charmouth, Dorset. Length along spine, about 13 feet; height as drawn, 7 feet, (B.M. Giiide.) I— I p a' Co Co O 3 o a- o p P O O ^ ' P GO o p w O (h THE GEOLOGICAL RECORD 219 of bony knobs on the sides, which also probably carried spines protecting the vital organs. A row of similar bones along each side of the powerful tail may also indicate spines, which would have rendered this an effective weapon against an encmv from the rear. In another allied species, of which the skull is hero shown (Eig. 54), there were two enormous horns above the eyes and a smaller one upon the nose; while the margin of Fig. 54. — Skull of Horned Dinosaur (Sterrolophus flabellatus). From the Upper Cretaceous of Wyoming, U.S.A. (B.M. Guide.) the bony expansion behind seems to have borne a row of spiny plates. As an illustration of how these huge but ratlior w(>ak vege- table feeders ^vere protected, the above restoratiou uiny bo use- ful, especially w^hen we remember that the species above tigured was as bulky as a rhinoceros or elephant. It was found in the Upper Jurassic strata of Xorth America. We now come to some of the largest laud-auiiual> which ever lived upon the enrth — the Snuropodn, or liznrd-footed Dinosaur — and these were more or less amphibious. One of 220 THE WORLD OF LIFE the most singular of these is the Brontosaunis, the skeleton of which is here represented. It is said to have the smallest head in proportion to the body of any vertebrate animal. Pro- fessor O. C. Marsh, who discovered it, states that the entire skull is less in diameter or weight than the fourth or fifth neck vertebra, while the brain-cavity is excessively small. He says : '^ The very small head and brain indicate a stupid slow- moving reptile. The beast was wholly without defensive or offensive weapons or dermal armour. In habits it was more or less amphibious, and its remains are usually found in local- ities w'here the animals had evidently become mired." A creature nearly as large was the Cetiosaurus leedsi, from the Oxford clay near Peterborough, of which the left hind limb and the larger part of the tail are mounted in the British Museum. It measures 10 feet 6 inches high at the hip, and must have been nearly 60 feet long. Still larger was the Amer- ican Atlantosaurus immanis, of w^hich only fragmentary por- tions have been obtained; but a complete thigh-bone, 6 feet 2 inches long, is the largest yet discovered. It was found in the Upper Jurassic strata of Colorado, U.S.A. The largest complete skeleton is that of the Diplodocus car- negii, now w-ell known to all who have recently visited the British ^Natural History Museum, where a model of it is mounted, as shown in the photographic picture of it here repro- duced. It is SO feet in length, both neck and tail being enor- mously long in proportion to the body. It is supposed that it would have been unable to walk on land except very slowly, and that it inust have lived chiefly in the water on juicy water- weeds, which its very weak teeth, as shown in the above figure of the skull, would alone have been such as it could graze on. The very long neck would have enabled it to gather such food from moderately deep water. The brain occupied the small space between and behind the eyes (Fig. 58). These huge reptilian herbivora, feeding in marshes, lakes, or shallow seas, w^ere preyed upon by the numerous crocodiles which lived throughout the same j)criods and are everywhere Fig. od. — Probable Appearance of the Jurassic Dinosaur Stegosaurus. The hind leg alone is twice the height of a well-grown man. (From Sir Ray Lankester's Extinct Animals.) 1 1 THE GEOLOGICAL RECORD 221 found in the same strata. They were of varied forms and sizes, but as they did not differ much in appearance from the various crocodiles and alligators now living in the tropics they V !H "3 o 1^ M ^^ • --^ ^' CO Ul ■•*» s 2 ^•w C3 !/> , O <1 c •rH 02 fi ^ 05 3 bo o a 'T3 O e- o o f^ %^ >■ t^ »-» w^ rt •M m o 1 t> 1 • r^ 1 CO 09 es • o •-D e P< o. p a> .d ■** a o M Pm need only be mentioned. But besides these there were true Dinosaurs of similar shape to tlie Tguanodon, but of rather less massive form and with strong teeth curved backward, which 222 THE WORLD OF LIFE Avitli tliolr wicle-openlng jaws evidently adapted them to seize and prey ujDon the larger land-reptiles. These form the Sub- FiG. 58. — Skull of Sauropodous Dinosaur {Diplodocus) . From the Upper Jurassic of Colorado, U.S.A. One-sixth nat. size. (B.M. Guide.) Fig. 59. — Skull of a Theropodous Dinosaur {Ceratosaurus nasicornis). From the Upper .Jurassic of Colorado, U.S.A. One sixth nat. size. (B.:\r. Guide.) order Theropoda, or beast-footed Dinosaurs. The skull of one of these here shown (Fig. 59) is more than 2 feet long, but f. •+-5 'T. c I- 4 THE GEOLOGICAL EECORD 223 no complete skeleton has been jet discovered. The allied Megalosaurus was found by Dr. Bnckland in the Weahh'ii beds in such abundance that he was able to piece together enough of the skeleton to show its affinity to the Iguanodon. Order — Sauropterygia We now come to the group of aquatic lizards wdiich abounded in all the seas of the Mesozoic period from the Trias to the Chalk. They had lizard-like heads, powerful teeth, both fore and hind limbs converted into paddles, and often with a dilated swimming tail. They varied much in size, but were often very large. Plesiosaurus cramptoni, from the Upper Lias of Whitby, w^as 22 feet long, but some species from the Chalk formation were from 30 to 40 feet long. A skull and jaws of P. grandis, from the Kimmeridge clay, is 6 feet long, which, if the proportions were the same as those of the species here represented (Fig. 60), w-ould have belonged to an animal nearly 50 feet long. The whole group w^as extremely varied in form and structure, but all w^ere adapted for preying upon such aquatic or marsh-frequenting animals as abounded during the same period. Order — Ichthyopterygia All the members of the preceding order have the paddles supported by a complete bony foot or hand composed of five separate fingers and connecting wrist-bones. But in the pres- ent order the adaptation to marine life is more perfect, a dorsal fin and bi-forked tail having been developed (Fig. 61), while the bony skeleton of the four limbs often consists of seven or eight rows of polygonal bones closely fitted together as shown in the drawings here reproduced (Fig. 62 A, B). They were also remarkable for their verv larG:e and hiffhlv oro-anised eves, which, with the lengthened jaws and closely set sharp teeth, indi- cate a perfect adaptation for capturing the fishes which the seas of that age no doubt produced iu the same abundance and almost as great variety as our own. These creatures also varied uiuch 224 THE WOKLD OF LIFE B in size and shape, one from the Lower Lias of Warwickshire being 22 feet long, but detached vertebra? sometimes indicate a much larger size. In the older Triassic beds smaller species are found which were less completely aquatic ; and these seem to show an affinity to Am- 23hibia rather than to rep- tiles, indicating that the two aquatic orders may have had independent ori- gins. Still later, in the Cre- taceous formation, there were other aquatic reptiles quite distinct from all the preceding, and more al- lied to our living lizards, having well-formed swim- ming feet, but snake-like bodies. These serve to in- dicate how completely the ?'^-.?^-~?^S'H^,''''^ ^^^ and Hind (B) reptiles of the Secondary Paddles of Ichthyosaurus intermedius. ^ From Lower Lias of Lyme Regis. One-third CpOCh OCCUpicd the plaCC nat. size. (B.M. Guide.) n^^ ^ ^ ,^ T\r now nlled by the J\lam- malia, somewhat similar forms adapted for aquatic life being again and again developed, just as the Mammalia subsequently developed into otters, seals, manatees, porpoises, and whales. Order — Ornithosauria We come finally to one of the most remarkable developments of reptilian life, the bird-lizards, more commonly known as Pterodactyls, which accompanied all the other strange forms of reptilian life in the Mesozoic period. They are first found a little later than the earliest Dinosaurs, in the Lowc-r Lias of IC 0, o Oj • a ,- — ^ u C3 • p^ -d fcJD QJ ^ »— 1 0) "rt o >^v OS « }-^ Oi ««-< .S 2 '^ ^ ec • ri OJ W P W a t^ )-H §■ o w p. O S3 ^ — ' be O +» =c c o c ^ 1— t • ^^ r^i. _>> «M c -4J o -5S 0) "c 2 ?i. «t-i o <» ^ o 00 tS 0) o 1 m Oi ^ tr- > 3 p s CO g s ee :3 "5d ft ?►. CO 05 O S P5 r* Ph %» v ;i^. T ^^ ^ -♦^ CO fS: cS u a. ^ ^ CO ^ •— ' d M flH THE GEOLOGICAL RECORD Bavaria; but as they are, even then, fully developed, though small, there must have been a long series of intennediate forms which probably reached back to the Triassic if not to the Permian era. Fig. 63. — Skeleton of Pterodactylus spectahilis. From the Upper Jurassic of Bavaria. Nat. size. This early form has teeth and a very short tail, and the body was not larger than that of a sparrow. (B.M. Guide.) The illustration of the skeleton of one of these early forms on this page is of the natural size (Fig. 63), Tt shows the greatly elongated fifth finger to which the wing-membrane was attached. In this form there were small teeth in the jaws, and the tail was very short. OQfi THE WORLD OF LIFE Fig. 64. — Restoration of a Long- Tailed Pterodactyl {Rhamphorhynchus 'phyllurus ) . From the Upper Jurassic of Bavaria. (B.M. Guide.) Expanse of wings more than 2 feet. The long tail has a terminal web, shown in casts in fine lithographic stone. The above restoration (Fig. 64), shows a larger species from the Jurassic formation, at which period they were more varied. This had a very long tail with a dilated membrane at its tip. Allied species, with a long pointed tail, have been found in the Lias of Lyme Regis, and also at Whitby. Fig. 65. — Toothless Pterodactyl {Pteranodon occidentalis) . From the Upper Cretaceous of Kansas, U.S.A. (B.M. Guide.) It was not till the Cretaceous period that the Pterodactyls reached their greatest size, the species figured here having an expanse of eighteen feet ; and these large forms have a pow- erful but toothless beak (Fig. 65). Fragments of bone from the English Chalk indicate an THE GEOLOGICAL REC0RT3 227 equally large size. The backward prolongation of the head is supposed to show that the powerful muscles required for such immense wings were attached to the head. This is rendered more probable by the skull, nearly 4 feet long, of another still larger species, in which the occipital crest projects a foot back from the head, and which Professor ^Farsli believes had a spread of wdng of 20 or even 25 feet (Fig. 66). Fig. 66. — Lateral View of Skull of Pteranodon longiceps. From the Cretaceous of North America. One-twelfth nat. size. The jaws are en- tirely without teeth. There is an enormous occipital crest (c) projecting far behind the occiput, to which the mirscles for flight were probably attached; (a) the nares and pre-orbital cavity; (&) the orbit. This species had an expanse of wings of about 20 feet. (From Nicholson's Manual of Palaeontology.) We thus see that during the Secondary epoch the great class Reptilia, wdiich had originated apparently during the last stages of the Primary, became developed into many special types, adapted to the varied modes of life wdiich the higher warm-blooded vertebrates have attained in our own time. The purely terrestrial type had their herbivora and carnivora cor- responding to ours in structure and habits, but surpassing them in size; the amphibious or marsh species surpassed our largest existing crocodiles, while the true aquatics almost exactly an- ticipated the form and habits of our porpoises and smaller whales. The air, too, was peopled by the strange Pterodactyls which surpassed the bats in powers of flight, in which they almost rivalled the birds, while they exceeded both in the enor- mous size thev attained. Considering how rare must have been the circumstances which led to tlie preservation in the rocks of these aerial creatures, we may conclude, from the large number of species known to us, that they \u\\<\ have been extremely abundant in middle and late ^Icsozuic times, and that they 228 THE WORLD OF LIFE occupied almost as important a place in nature as do tlie birds now. Yet not one of the varied forms either of the terrestrial Dinosaurs, the aerial Pterodactyls, or the aquatic Sauroptery- gia and Ichthyopterygia — all abounding down to Cretaceous times — ever survived the chasm that intervened between the latest Secondary and the earliest Tertiary deposits yet discov- ered. This is perhaps the most striking of all the great geolog- ical mysteries. One more point may here be noticed. The early small- sized Pterodactyls arose just when highly organised winged insects began to appear, such as dragon-flies and locusts, soon followed by wasps, butterflies, and two-winged flies in Middle Jurassic times ; from which period all orders of insects were no doubt present in ever-increasing numbers and variety. It is interesting to note further, that at the very same epoch in which we find this great increase of insect life there ap- peared the first true flowering plants allied to the Cycads, with which they were till quite recently confounded. These also must have rapidly developed into a great variety of forms, since in the later Cretaceous formation in many parts of the world true flowering plants, allied to our magnolias, laurels, maples, oaks, walnuts, and proteaceous plants, appear in great abundance. These seem to have originated and developed very rapidly, since in the earliest deposits of the same formation none of them occur. Mesozoic Mammalia There is perhaps nothing more remarkable in the whole geological record than the fact of the existence of true mam- mals contemporaneous with the highly diversified and abundant reptile life throughout the period of their greatest development from the Trias to the Cretaceous. They were first discovered nearly a century ago in the Stonesfield Slate at the base of the Great Oolite in Oxfordshire, and were described under the names Amphitherium and Phascolotherium (Fig. 67). About forty years later a considerable number of similar remains Fig. 67. — Lower Jaw of Phascolotherium bucklundi. Prom the Stonesfield Slate (Lower Jurassic), Oxfordshire. Outline fig. nat. size. (B.M. Guide.) c? Fig. 68. — Lower Jaw and Teetli of IS i>* a o ~ ^ m o ^ c3 •^ ^ o o i> £ P ^3* »*<• "^ "5 o «,, ^ ■ ^H ^i^ ^ a §■ ^ C 0) > ~^_j K' •4—* O 1 k> 'u S p. « •^^ t> CO c o '>! K a I- ^ <» a) p— 1 o r 1— 1 a o THE GEOLOGICAL EECOKD 233 tion, with a variety of nourishing products, in foliage, fruit, and flower, never before available. Now here we have a tremendous series of special develop- ments of life-forms simultaneous in all parts of the earth, affecting both plants and animals, insects and vertebrates, whether living on land, in the water, or in the air, all contem- poraneous in a general sense, and all determining the transi- tion from a lower to a very much higher grade of organisation. Just as in the first such great step in advance from the '' age of fishes " to the '' age of reptiles " we see reason to connect it with the change from a more carbonised to a more oxygen- ated atmosphere, produced by the locking up of so much carbon in the great coal-fields of the world ; so, I think, the next groat advance was due to a continuation of the same process by a different agency. Geologists have often remarked on the pro- gressive increase in the proportion of limestone in the later than in the earlier formations. In our own country w^e see a remarkable abundance of limestone during the Secondary era, as shown in our Lias, Oolites, Portland stone, and Chalk rocks ; and somewhat similar conditions seem to have prevailed in Europe, and to a less extent in Xorth America. As limestone is generally a carbonate of lime, it locks up a considerable amount of carbon which might otherwise increase the quantity of carbonic acid in the atmosphere ; and as lime, or its metallic base, calcium, must have formed a considerable portion of the original matter of the earth, solid or gaseous, the continued formation of limestone through combination with the carbonic acid of the atmosphere must have led to the constant diminu- tion of that gas in the same way that the formation of coal reduced it. It seems probable that when the earth's surface was in a greatly heated condition, and no land vegetation existed, the atmosphere contained a much larger proportion of carb(m- dioxide than at present, and that a continuous reduction of the amount has been going on, mainly through the extraction 234 THE WOKLD OF LIFE of carbon from the air by plants and from the water by marine animals and by chemical action. The superabundance of this gas during the early stages of the life-world facilitated the process of clothing the land with vegetation soon after it ap- peared above the waters; while its absorption by water was equally useful in rendering possible the growth of the calcare- ous framework or solid covering of so many marine animals. With the progressive cooling of the earth and the increased area of land-surface, more and more of the atmospheric carbon became solidified and inactive, thus rendering both the air and the water better fitted for the purposes of the higher, warm- blooded, and more active forms of life. This process will, I think, enable us partially to understand the fundamental changes in life-development which characterised the three great geological areas; but it does not seem sufficient to explain tbe very sudden and complete changes that occurred, and, more especially, the almost total extinction of the lower or earlier types just when they appear to have reached their highest and most varied structure, their greatest size of body, and their almost world-wide distribution. Before attempting a solution of this difficult problem an outline must be given of the latest, and in some respects the most interesting, of the geological eras — the Tertiary, or, as more frequently termed by geolo- gists, the Cainozoic. CHAPTER XII LIFE OF THE TERTIARY PERIOD Directly we pass from the Cretaceous into the lowest of the Tertiary deposits — the Eocene — we seem to be in a new world of life. Xot only have the whole of the gigantic Dino- saurs and the accompanying swimming and flying reptiles totally disappeared, but they are replaced in every part (tf the world by Mammalia, which already exhibit indications of being the ancestors of hoofed animals, of Carnivora, and of Quadru- mana. Order — Ungulata In the Lower Eocene strata of ISTorth America and Europe, the sub-order Condylarthra is well represented. These were primitive, five-toed, hoofed animals which, Dr. A. Smith Wood- ward tells us, '" might serve well for the ancestors of all later Uiigulata." One of these, Phenacodus primcevus, was found in the Lower Eocene of Wyoming, U.S.A., and was about 4 feet long exclusive of the tail (see Eig. 72). Considering that this is one of the very earliest Tertiary mammals yet discov- ered, it is interesting to note its comparatively large size, its graceful form, its almost full series of teeth, and its large five- toed feet; affording the starting-point for diverging modifica- tion into several of the chief types of the higher mammalia. So perfectly organised an animal could only have been one of a lono^ series of forms brido:inc: over the 2:reat c'ulf between it and the small rat-like mammals of the ^lesozoic period. Another sub-order is the Amblypoda, of which the Corypho- don of Europe and Xorth Americn is one of the best known. This was about 6 feet long, and was first obtained from our 235 206 THE WORLD OF LIFE London Claj. It had a heavy body, five-toed stumpy feet, and a complete set of 22 teeth in each jaw adapted for a vege- table diet ; but no defensive tusks or horns. Other allied spe- cies were much smaller, and all were remarkable for a very small brain. But a little later, in the Middle Eocene of North America, they developed into the most wonderful monsters that have ever Fig. 73. — Uintatherium ingens. Eocene of Wyoming, U.S.A. One-thirtieth nat. size. (B.M. Guide.) lived upon the earth — the Dinocerata or '^ terrible-horned " beasts. These had greatly increased in size; they often had large tusks in the upper jaw ; and horns of varied forms and sizes were developed on their heads. The tusks were some- times protected by a bony flange projecting downwards from the lower jaw immediatelv behind it, as well sho^vn in the figure here given of Uintatherium ingens. This animal must have been about 11 feet long and nearly 7 feet high; and if the six protuberances of the skull carried horns like our rhinoceroses, it must, indeed, have been a '' terrible '' beast, LIFE OF TERTIARY PERIOD The imperfect skull of another species (Fig. 74) shows even larger the honj horn-cores presenting all tlie appearance of having carried some kind of horns. This seems the more probable, as many of the species had no tusks, and in that case mere rounded bony protuberances would have been of little Fig. 74. — Uintatherium cornutum. From the Middle Eocene of Wyoming, U.S.A. (Nicholson's Palaeontology.) protective use. Figure 75 (on p. 238) represents the skeleton of one of the largest species without tusks. From the scah^ given, it must have been 11 or 12 feet long and nearly 8 feet high. Professor Marsh informs us that these strange-homed ani- mals have been found onlv in one Eocene lake-basin, in Wyoming, U.S.A. He says: "These gigantic beasts, which nearly equalled the elephant in size, roamed in great numbers about the borders of the anciout 238 THE WOKLD OF LIFE tropical lake in which many of them were entombed. This lake- basin, now drained by the Green Eiver, the main tributary of the Colorado, slowly filled up with sediment, but remained a lake so long that the deposits formed in it during Eocene time reached a LIFE OF TERTIAEY PEETOD 239 vertical thickness of more than a mile. ... At the present time this ancient lake-basin, now 6000 to 8000 feet above the sea, shows evidence of a vast erosion, and probabl}^ more than one-half of the deposits once left in it have been washed away, mainly by the action of the Colorado River. What remains forms one of the most picturesque regions in the whole West, veritable mauvaises terres, or bad lands, where slow denudation has carved out cliffs, peaks, and columns of the most fantastic shapes and colours. This same action has brought to light the remains of many extinct animals, and the bones of the Dinocerata, from their great size, naturally first attract the attention of the explorer." As regards the mental powers of these strange animals, Pro- fessor Marsh saj's: " The brain-cavity of the Uintatherium is perhaps the most re- markable feature in this remarkable genus. It shows us that the brain was proportionately smaller than in any other known mam- mal, recent or fossil, and even less than in some reptiles. It is, in fact, the most reptilian brain in any known mammal. In U. mira- bile (one of the large- tusked, horned species) it could apparently have been drawn through the neural canal of all the presacral vertebrae." "^ It was, in fact, a small oval mass of about the same diameter as the spinal cord ! One other strange form which may belong to the earliest ungulates has been found in the Upper Eocene of Egypt, and forms a new suborder, Barjpoda. It is known from a very complete skull (Fig. 76), which is remarkable for the very regular set of teeth, as well as for the wonderful horn-cores, two small at the back and two enormous ones projecting in front. The skull is nearly 3 feet long, and the larger horn- cores about 2% feet ; and as these certainly carried true horns they probably surpassed any of the Dinocerata. Large quan- tities of detached bones have also been obtained, sufficient to show that the creature was an ungulate of elephantine dimen- sions and altogether unique in appearance. This creature hail a somewhat larsjer brain thnn the great American ungulates, 240 THE WORLD OF LIFE and has affinities with a curious little existing animal, the hyrax. Fig. 76. — Skull of Arsinoitherium zitteli. From the Upper Eocene of the Fayoum, Egypt. One-twelfth nat. size. (B.M. Guide.) Order — Camivora These can also be traced back to middle or late Eocene times both in l^orth America and Europe. They were mod- erate-sized animals, forming a distinct sub-order, Creodonta, the skeleton of one of which is shown in Fisr. 77. Thev had flesh-eating teeth, but more like those of the carnivorous mar- supials of Australia than of our living carnivores, with a type of skeleton showing considerable litrhtness and activity. Some of the species were as large as lions. LIFE OF TERTIAEY PERIOD 241 Some of the older remains in South America, called Sparas- sodonta, are believed to belong to the same or an allied sub- order. They occur in beds of Lower Miocene age in Pata- gonia ; and Mr. Lydekker holds them to be " undoubtedly marsupials," allied to the Dasyuridic of Australia. One of these has been named Prothylacinus, from the resemblance of its jaw to that of the Tasmanian wolf (Thylacinus australis). Other small species forming a distinct family, Microbiothe- ridie, he also thinks were probably " minute polyprodont mar- supials of Australian type." ^ In the later (upper) beds of the Eocene formation and the early or middle Miocene, ancestral forms of many of our Mam- malia have been found both in Europe and Xorth America ; but these are so numerous, and their affinities in some cases so obscure, that only a few of the prominent examples need be given. One of these, whose skeleton is figured on page 243, belongs to the family Anthracotheridae, which has affinities with the pigs and the hippopotami, of which it seems to be an ancestral form. The fossil remains of this group are found in deposits of middle Tertiary age all over the northern hemi- sphere. They have two, three, or four separate toes, and teeth much like those of swine. Another family, the Anoplotheridae, contains a variety of animals w^hich seem to be ancestral forms of the ruminants. The genus Anoplotherium (Fig. 79) was one of the most re- markable of these in having a full and continuous set of teeth without any gaps, like that of the Arsinoitherium already figured. 1 Geog. Hist, of Mammals, pp. 111-112. From these facts and otliers re- ferred to in my preceding chapter, Mr. Lydekker thinks that " it is difficnlt to come to any other conclusion than that the ancestors of the Santa Crucian polyprotodont marsupials reached the country either by way of the Antarc- tic continent or by a land-bridge in a more northern part of the Pacific." To avoid a break of connection in the present exposition, I have briefly stated some of the difTieuliies in the way of such a theory in an Ap- pendix to this chapter. Those who wish to see the whole subject of the " Permanence of Oceanic and Continental Areas " more fully discussed are referred to my volumes on Darwinism and Island Life. 242 THE WORLD OF LIFE An allied family, Oreodontidse, somewhat nearer to rumi- nants, but with four-toed feet, were very abundant in Xorth America in Miocene times. They were remotely allied to deer and camels, and were called by Dr. L-eidy " ruminating hogs." They seem to have occupied the place of all these LIFE OF TEKTIAEY PEEIOD 243 animals, six genera and over twenty species havlnp: lieen de- scribed, some of which survived till the earlv Pliocene. The family Pala^otheridnc was also abundant during tho 244 THE WORLD OF LIFE same period in Europe, and less so in !N"orth America. As shown in the restoration in Fig. 80, it somewhat resembled the tapir; but other genera are more like horses, and show a series of gradations in the feet towards those of the horse- tribe, as shown bj Hnxley's figures reproduced in my Dar^vin- ism. The Origin of Elephants Till quite recently one of the unsolved problems of palaeon- tology was how to explain the development of the Proboscidea or elephant tribe from other hoofed animals. Hitherto extinct species of these huge beasts had been found in a fossil state as far back as the Miocene (or middle Tertiary) in various parts of Europe, Asia, and Xorth America ; one species, the mammoth, being found ice-preserved in Arctic Siberia in great quantities. Some of these w^ere somewhat larger than existing elephants, and several had enormously large or strangely curved tusks; but, with the exception of Dinotherium, which had the lower jaw and tusks bent downwards, and Tetrabelodon, with elongated jaws and nearly straight tusks, none were very different from the living types and gave no clue to their line of descent. But less than ten years ago a number of fossils have been obtained from the middle and higher Eocene beds of the Fayoum district of Egypt, which give the long-hoped-for missing link connecting the elephants with other ungulates. The most primi- tive form now discov- ered was about the size of a very large dog, and its skull does not differ very strikin2:lv from those of other primitive ungulates. It has, Fig. 81. — Skull of Moeritherium lyonsi. however some slie'ht From the Middle Eocene cf the Fayoum, Egypt. One- , . '. . , ^ , seventh nat. size. (B.M. Guide.) peculiarities whlch Fig. 7!). — Anoplotherium commn/tie. Upper Eocene (Paris; also at Binstead, Isle of Wight.) From Nicholson's Palaeontology.) This animal was about the size of an ass, and was especially remarkable fur its continuous set of 44 teeth, there being no gap in the series. No livins mammal except man has this characteristic. It is supposed to have been a highly spe- cialized enrly type which has left no direct descendants. Fj(;. 80. — /'(ilaotherium ntogntini. from the Upper Eocene of Paris and the Isle of "Wight. (Nicholson's PahuDntology.) The numerous species of Pala?otlierium were three-toed animals bavins resembbmces to horses, tapirs, and llamas. The species here figured (as restored by Cuvier) was about the size of a horse, but it is now known that the neck was consid- erably longer than here shown. LIFE OF TEETIARY PERIOD 245 show a connection with the Proboscidea. These are that the nasal opening is near the end of the snout, indicating, prohably, the rudiment of a proboscis; the back of the skull is also thick- ened and contains small air-chambers, the first step towards the very large air-chambers of the elephant's skull, whose purpose is to afford sufficient surface for the powerful muscles which sup- port the weight of the tusks and trunk. The teeth show two short tusks in front in the upper jaw in the same position as the tusks of elephants, while the lower jaw or chin is lengthened out and has two incisor teeth projecting forward. The molar teeth show the beginning of the special characters which dis- tinguish the huge grinding teeth of the elephants. This crea- ture was named MoerWierium lyonsi; and its remains have been found in great abundance along with those of both land and sea animals, shoAving that they were deposited in what was then the estuary of the ISTile, though now far inland. Somewhat later, in the Upper Eocene, another group of animals, the Palseomastodons, have been found, showing a con- siderable advance (see Diagram, Fig. 82). They vary in size from a little larger than the preceding to that of a small ele- phant. The skull is very much modified in the direction of some of the later forms. After these come the Tetrabelodons from the Miocene beds of France and North America, and the Pliocene of Germany. These w^ere more like elephants in their general form, though their greatly elongated lower jaw, bearing incisor teeth, seem to be developing in another direc- tion. In Tetrahelodon longirostris, however, we see the lower jaw shortened and the incisor teeth greatly reduced in size; thus leading on to the true elephants, in which these teeth disappear. The skeleton of Tetrahelodon angustidens shows the lower tusks sliorter than the upper ones, but in the fine specimen moimted in the Paris Museum, and photographed in Sir Ray Lankester's Extinct Animals, both are of the same h^igth, and the upper pair curve slightly (hnvnwards on each side of the lower pair; and they are thus shown in the suggested 246 THE WOKLD OF LIFE Recenl Pleistocene ELE PHA3 ( short chinj Ufiper Pliocene Lower Pliocene Upjier Miocene TETRABELODON [LONGIROSTRrS STACE] (shortening chinj Middle Miocene TETRABELODON fANCUSTTDENS STAGE] lower Miocene (long chinj l/frper Oligocene Migration from Africa into EuTvp.e -Asia Imer Oligocene? Upfier Eocene MiddleBocene Lower Eocene PALAEOMASTODON ^lengthening chinj MOERlTHEKrUM (short chin) Fig. 82. — Diagrams showing Increase of Size and Alteration in Form of Skull and Teeth of the Proboscidea since Eocene Time. (B.M. Guide.) Fig. 83. — Skeleton of Tetrahelodon luigustidens. From the Middle Eocene of Sansaus, France. (B.M. Guide.) 4 4-i i A .;■ V •'*®*v,, '^^ ""^N, ■•>- --^j>- ■ ^-»- . »AX Fig. 84. — Probable Appearance of Tetrahelodon (HKjustidens. /From Sir Ray Lankester's Extinct Animals.) LIFE OF TERTIARY PERIOD 247 appearance of the living animal, here reproduced from his book. (Fig. 84.) The trunk could not therefore have hung down as in the modern elephants, and it seems hardly likely that with such tusks a trunk would have been developed. If a short one had been formed it would probably have been for the purpose of drinking and for pushing food into the mouth side- ways. It is most interesting to see how the difficulty was Fig. 85. — Skeleton of Mastodon Americanus. From the Pleistocene of Missouri, U.S.A. Length, 20 feet; height, 9% feet. (B.M. Guide.) overcome. In the next stage both pairs of tusks have become straightened out, the lower ones much reduced in length and the chin also somewhat shortened. That this process went on step by step is indicated by the ^lastodons, which are elephants with a simpler form of teeth, and a pair of tusks like all living and recently extinct elephants (see Fig. 85). But when very young the American Mastodon had a pair of short tusks in the lower jaw, which soon fell out. In the character of its teeth generally, the Mastodon agrees with Tetrabelodon (wliich was originally classed as a Mastodon) ; and there are Indian extinct 248 THE WORLD OF LIFE species which show other stages in the reduction of the lower jaw. We have here, therefore, a most remarkable and very rare phenomenon, in which we are able to see progressive evolution upon what seems to be a wrong track which, if carried further, might be disastrous. Usually, in such cases, the too much developed or injuriously developed form simply dies out, and its place is supplied by some lower or less modified species which can be more easily moulded in the right direction. But here (owing probably to some exceptionally favourable conditions), after first lengthening both lower jaw and lower tusks to keep pace with the upper ones, a reversal of the process occurs, reducing first the lower tusks, then the lower jaw, till these tusks completely disappeared and the lower jaw was reduced to the most useful dimensions in co-ordination with a greatly lengthened and more powerful trunk. Although in this case the gaps are still rather large, there can be no doubt that we have here obtained a view of the line of development of the most remarkable land mammals now living from a small gen- eralised ungulate mammal, as indisputable and as striking as that of the horses from the little five-toed Eohippus of the American Eocene. It may be here mentioned that the huge American Mas- todon has been found in the same deposits with stone arrow- heads, and was undoubtedly hunted by early man; as was also the huge mammoth whose beautifully curved tusks form its chief distinction from the living Indian elephant (Eig. 86). This species is abundant in the frozen mud at the mouths of the Siberian rivers; and in some cases the whole body is preserved entire, as in an ice-house, and the flesh has been sometimes roasted and eaten by the natives. Remains of skeletons have been found in our own country and over a large part of Northern Europe and Asia ; while its portrait has been drawn from life by prehistoric man, either upon the tusks themselves or upon the flat portions of the horns of reindeer which he hunted for food. LIFE OF TERTIAEY PERIOD 249 5 « Co 03 a. e ^ CD ^ w TO - <— I M a I a 00 o u o rT a 1—1 o EC4 Tertiary Mammals of South America and Australia ISTo part of the world has so many distinct groups of !Mam- malia peculiar to it as South America, among wliioh the most remarkable are the sloths and the armadillos; and all of tlicm are found fossil in the middle or late Tertiary or the Pleisto- cene, from Brazil to Patagonia, and are often represented by strange forms of gigantic size. Some account of these will now be given. DarAvin was one of the first collectors of these fossils on his voyage in the Beagle, and during the la:^t twenty 250 THE WOKLD OF LIFE ?> a> CO ^ ■^ ^ o ■p-i to s 1-" C5 l»*..i S- O g* Si 6 o »« S o Pk 05 si O Cj «4-l o ^ >. a> C , ^ 1-^ O" -fc^ ;3 OQ T3 I <4H p O ^ 1 • Ol t^ c > CO o -^ • rH • o 03 s a f^ O c3 1 a p4 p< or tliirty years niimerous travellers and residents, especially in Argentina, have more thoroughly explored the deposits of LIFE OF TERTIAKY PEFaOD 251 the pampas of various ages. Their great richness and im- portance may be indicated by the following enumeration of the chief orders of Mammalia represented in them. Of the Peimates (or monkeys) all the remains are of the peculiar American families Cebidas and Ilapalida:', with one extinct genus of the fonner. Bats (the order Chiroptera) are abundant, with several peculiar genera. The Insectivora arc very rare in South America, but a fossil has been found sup- posed to belong to the peculiar West Indian family Solenodon- tidge. The Carnivora are chiefly represented by fossils of the American family Procyonidse (comprising the racoons and coati-mundis), of which several extinct genera have been ol>- tained. The hoofed animals (Ungulata), which, from tlieir great abundance in a living state in every part of the world, and their habit of living together in great herds often of many thousands, have been most frequently preserved in a fossil state, are here represented not only by all the chief forms that still inhabit the country, but also by some which are now only found in other continents, as well as by many which arc altogether extinct. Among the former the most interesting are true horses of the genus Equus, as well as two peculiar genera of ancestral Equidge, distinct from those so abundant in I^orth America. There are also several ancestral forms of the Llama tribe, one of which, Macraiichenia patacJionica, was as large as a camel; and there are others so distinct as to form a separate family Proterotheriidse. Another sub-order, Astrapotheria, were more massive ani- mals, some of which equalled the rhinoceros in size. They consist of two distinct genera, only found in the Patagouian deposits of Mid-Tertiary age.-^ Still more remarkable is another group — the Toxodontia — sometimes exceeding the rhinoceros in bulk, but with teeth which approached those of the Rodentia; of these there are various forms, which are grouped in three distinct families. The skeleton of one of the most remarkable of this group is iLydekker's Geographical History of Mammals, p. 81. 252 THE WOELD OF LIFE shown in Fig. 87. Yet another distinct sub-order, Pyrotheria, which in its teeth somewhat resembled the extinct European Dinotherium, and which had a large pair of tusks in the lower jaw is found in the earlier Tertiary strata of Santa Cruz in Patagonia. The elephants also had a representative among these strange monsters in the form of a species of Mastodon, a genus also found in North America. The very numerous and peculiar South American rodents commonly called cavies, including the familiar gniinea-pig, are well represented among these fossils, and there are many ex- tinct forms. Most of these are of moderate size, but one, Megamys, said to be allied to the viscachas, is far larger than any living rodent, about equalling an ox in size. Perhaps more remarkable than any of the preceding are the extinct Edei^tata which abound in all these deposits. The entire order is peculiar to America, with the exception of the scaly ant-eater of Asia and the aard-vark of South Africa, and there is some doubt whether these last really belong to the same order. The living American edentates comprise three fam- ilies, generally known as sloths, ant-eaters, and armadillos, each forming a well-marked group and all with a fair number of distinct species. But besides these, two extinct families are known, the Glyptodontidse and the Megatheriidse, the former being giant armadillos, the latter equally gigantic ter- restrial sloths. Both of these lived from the Miocene period almost to our own time, and they are especially abundant in Pliocene and Pleistocene deposits. Some of the extinct forms of armadillo were very much larger than any now living; but it is among the Glyptodonts, which had a continuous shield over the whole body, that the largest species occurred, the shell being often 6 or 8 feet long. The skeleton of one of these is represented by Fig. 88. One of the most recent (Dsedicurus) was 12 feet long, of which 5 feet consisted of the massive armoured tail, which latter is believed to have borne a number of movable horns. The earlier fossil species were of much smaller size, and, though far more abundant in the south, a LIFE OF TEETIARY PERIOD few of them have been found in the Pliocene deposits of Texas. The extinct ground-sloths arc even more remarkable, since 254 THE WORLD OF LIFE they were intermediate in structure between the living sloths and the ant-eaters, but adapted for a different mode of life. Almost all are of large, and many of gigantic size. The Mega- therium, which was discovered more than a century ago, was one of the largest, the skeleton (represented by a cast in the British Museum) being 18 feet long. Their massive bones show enor- mous strength, and they no doubt were able to uproot trees, by standing erect on the huge spreading hind feet and grasping the stem with their powerful arms, in order, to feed upon the foliage, as shown in the illustration (Fig. 89). The jaw-bones are lengthened out, indicating extended lips and probably a prehensile tongue with which they could strip off the leaves. An allied genus, Mylodon, which is somewhat smaller, has been found also in Kentucky in beds of the same age, the Pleistocene. What renders these creatures so interesting is that they sur- vived till a very recent period, and that they were contemporary with man. Both human bones and stone implements have been found in such close association with the bones or skele- tons of these extinct sloths that they have been long held to have lived together. But a more complete proof of this was obtained in 1897. In a cavern in Patagonia, in a dry powdery deposit on the floor, many broken bones of a species of Mylodon were found ; and also several pieces of skin of the same animal showing marks of tools. Bpnes of many other extinct animals were found there, as well as implements of stone and bone, remains of fires, and bones of man himself. Among the other animal remains were those of an extinct ancestral horse, and on some of the bones there were found shrivelled remains of sinews and flesh. Allied forms are found in older deposits, as far back as the Miocene, but these are all of smaller size. They probably ranged all over South America, and the two genera Megathe- rium and Mylodon occur also in the most recent deposits of the southern United States. The numerous skeletons in the pampas of Argentina are usually found on the borders of old Fig. 89. — Probable Appearance of the (iiant Ground-Sloth ( Megatherium gigan icnui ) . As large as an elephant. Found in the Pleistocene gravels of South America (From Sir Ray Lankester's Extinct Animals, p. 172.) Vic. 'JU. — MyUxlon robust ufi. From the Pleistocene of South America. ( Nicholson s Palii'ontohtpy. ) J J LIFE OF TERTIARY PERIOD 255 lakes and rivers, in the positions in which they died. Thrv are supposed to have perished in the mud or quagmires whih- o 3 o ^ to 'y 05 o 2 ^ o til ^ o o O ja c a> .2 -S 3 c: 2 a S attempting to reach the water for drink during dry seasons, great droughts being prevalent in the district; but when these 256 THE WOKLD OF LIFE large animals lived there must have been much more woody vegetation than there is now. During the voyage of the Beagle, Darwin collected a large quantity of these interesting fossils, as described in his JSTaturalist's Voyage round the World (chap, v.). The skeleton and outline figure of a Mylodon shown in Fig. 90 was 11 feet in total length, but other species were larger. A remarkable extinct genus, Scelidotherium, of which the complete skeleton is shown in Fig. 91, was about 10 feet long, and has less massive limbs than the Megatherium or Mylodon, and more elongated jaws. In some respects it approached the ant-eaters, and was probably, like them, terrestrial in its habits. About twelve distinct genera of these ground-sloths are now known, comprising a large number of species. They ranged all over South America and into the warmer parts of North America, and before the immigration of the horse and the sabre-toothed tiger in Pleistocene times, they must have con- stituted the larger and more important portion of the mam- malian fauna of South America. Extinct Mammals of Australia The existing Australian mammals, although of varied form and structure, are almost all marsupials, the only exceptions being the aerial bats, and small rodents allied to rats, which latter might have entered the country by means of floating timber or trees from the nearest islands. These two orders are therefore of little importance geographically, although by counting the species it may be made to appear that the higher mammals (Placentalia) are nearly as numerous as the lower (Marsupialia). The wild dog, or dingo, is also appar- ently indigenous, but it may have been introduced by early man, as may some of the rodents. It is unfortunate that the deposits of Tertiary age in Australia seem to be very scanty, except recent gravels and alluvial muds, and none of these have produced fossils of Mammalia except in caves and dried- up lakes, which are all classed as of Pleistocene age. These, LIFE OF TERTIARY PERIOD 2:.7 however, are very productive in animal remains wliidi arc extremely interesting. They consist of many living species, but with them numljers of extinct forms, some of gigantic size, but all undoul)t(Mlly allied to those living in Australia to-day. Thus, bones of kangaroos are found ranging in size from that of the smallest living species np to that of a donkey, and sometimes of verv distinct forms and proportions. But with theso have been found a huge wombat, the size of a large rhinoceros, of which the skull is here represented (Fig. 92). The complete skele- FiG. 92. — Skull of an Extinct Marsupial, Diprotodon australis. From the Pleistocene of Queensland and South Australia. With a man's skull, to show comparative size. (B.M. Guide.) ton has been quite recently obtained from Lake Callabonna in South Australia. It is found to be 12 feet long measured along the vertebrae, and 6 feet 2% inches high. As it has been found in various parts of the continent, it was probably abun- dant. Another smaller animal of somewhat similar form was the Xototherium, which was found in Queensland, to- gether with the Diprotodon, about fifty years ago. A large phalanger was also found, which Professor Owen called the pouched lion {Tliylacoho carnifex), but it is doubtful whether 258 THE WORLD OF LIFE it was carnivorous (see Fig. 93). True carnivorous mar- supials allied to the ^' Tasmanian wolf" (Thylacinus) and the Tasmanian devil {Sarcopliilus) are also found. Fig. 93. — Skull of Thylacoleo carnifex. From the Pleistocene of Australia. One-fifth nat. size. (B.M. Guide.) How and when the marsupials first entered Australia has always been a puzzle to biologists, because the only non-Aus- tralian family, the opossums, are not closely allied to any of the Australian forms, and it is the opossums only which have been found in tlie European early Tertiaries. But recent dis- coveries in South America have at length thrown some light on the question, since the Santa Cruz beds of Patagonia (Mid- dle Tertiary) have produced several animals whose teeth so closely resemble those of the Tasmanian Thylacinus that Mr. Lydekker has no doubt about their being true marsupials allied to the Dasvurid^e. There is also, in the same beds, another distinct f amilv of small mammals — the Microbiotheridge of Dr. Ameghino — which, from a careful study of their denti- tion, are also considered by Mr. Lydekker to be " polypro- todont marsupials of an Australian type." ^ But even more important is the discovery of living mar- supials of the Australian rather than the American type in the very heart of the South American fauna. In 1863 a small mouse-like animal of doubtful affinities was captured in Ecua- lA Geographical Historj^ of Mammals, p. 109. LIFE OF TERTIARY PERIOD 259 dor. But in 1895 a larger species of the same genus was obtained from Bogota; and it was then seen that they be- longed to a group of which large numbers of fossil remains had been found in the Santa Cruz beds. By a comparison of these remains of various allied forms with the specimens of those now living, it seems no longer possible to doubt that marsupials of Australian type have existed in South America in Middle or Late Tertiary times, and tiiat some of them survive to-day in the equatorial Andes, where their small size has probably saved them from extinction. Of these latter, Mr. Lydekker says: "In the skeleton the lower jaw exhibits the usual inflexion of the angle ; and the pelvis carries marsupial bones. A small pouch is present in the female." These small marsupials have been named Csenolestes, while their fossil allies are so numerous and varied that they have to be classed in three families — Abderitidae, Epanorthidse, and Garzoniidae. This is only mentioned here to show the large quantity of materials upon which these conclusions are founded. Teachings of Pleistocene Mammalia For the purpose of the present work it is not necessary to go into further details as to the development of the higher forms of life, except to call attention to some other cases of the sudden dying out of great numbers of the more developed species or groups during the most recent geological period — the Pleistocene. It has already been shown how, in temperate South America, the huge sloths and armadillos, the giant llamas, the strange Toxodontia, and the early forms of horses all disappeared at a comparatively recent epoch. In Xorth America a similar phenomenon occurred. Two extinct lions; a number of racoons and allied forms, including several ex- tinct genera; six extinct species of horses; two tapirs; two genera of peccaries ; a llama and a camel ; several extinct bisons, sheep, and deer; two elephants and two mastodons, 260 THE WORLD OF LIFE and four genera of tlie wonderful terrestrial slotlis, ranged over the whole country as far north as Oregon and the Great Lakes in quite recent times; while four genera of the great ground-sloths have been found as far north as Pennsylvania. This remarkable assemblage of large Mammalia at a period so recent as to be coeval with that of man, is most extraor- dinary; while that the whole series should have disappeared before historical times is considered by most geologists to be almost mysterious. At an earlier period, especially during the Miocene (Middle Tertiary), Xorth America was also wonderfully rich in Mammalia, including not only the ancestors of existing types, but many now quite extinct. At this time there were several kinds of monkevs allied to South American forms; numerous extinct Carnivora, including the great sabre- toothed tiger, Machserodus; several ancestral horses, includ- ing the European Anchitherium ; several ancestral rhinoceroses, the huge horned Brontotheriidae, the Oreodontidse, and many ancestral swine. Almost all these became extinct at the end of the Miocene age. "^ In Europe we find very similar phenomena. During the Pleistocene age, the great Irish elk, the cave-lion and the sabre-toothed tiger, cave-bears and hyaenas, rhinoceroses, hippopotami and elephants, extinct species of deer, antelopes, sheep and cattle, were abundant over a large part of Europe (many even reaching our own country), and rapidly became extinct; and what renders this more difficult to explain is, that all of these and many others, with numerous ancestral forms, had inhabited Europe throughout the Pliocene and some even in Miocene times. These very interesting changes in the northern hemisphere are paralleled and completed in far-distant Australia. In caves and surface deposits of recent formation a whole series of fossil remains have been found, all of the marsupial order, and most of them of extinct species and even extinct genera. But what is more extraordinarv is, that several of them were larger than any now living, while some were as gigantic as LIFE OF TERTIARY PERIOD 201 the huge gi'ound-sloths and armadillos of the Pampas. There were numerous kangaroos, some much lar. Equally remarkable was the Tliylacoleo carnifex, nearly as large as a lion and with remarkable teeth (Fig. 03, p. 258). The very peculiar Xototherium, allied to the wombats, was nearly as large as a rhinoceros; and several others imperfectly known indicate that they were of larger size than their nearest living allies. A number of very similar facts are presented by recently extinct birds. The Moas of ^ew Zealand were of various sizes, but the largest was 8% feet high when standing natu- rally, but when raising its body and neck to the fullest extent it would have perhaps reached to a height of 12 feet. In Madagascar also there was a huge bird, the ^pyornis, which was probably larger than the largest of the Moas, and whose egg, frequently found in sand-hills, sometimes measures 3 feet by 2% feet in circumference, and will hold more than two gallons. It is almost certain that these huge birds were all coeval with early man, and in the case of the Moas this has been completely proved by finding their bones in ancient native cooking ovens. It is probable, therefore, that their final extinction was due to human agency. Probable Cause of Extinction of the Pleistocejie Mammalia The complete extinction of many of the largest Mammalia, which were abundant in almost all parts of the world in Pleistocene times, has not yet received a wholly satisfactory explanation. The fact that the phenomenon is so near to our own era renders it more striking than similar occurrences in remote ages. With the one exception of the glacial e]><^ch, there has been very little modification of tlie earth's surface since the close of the Tertiary era ; and in several cases species 262 THE WORLD OF LIFE which iindo"abtedly survived that event have since become ex- tinct. This great climatic catastrophe did nndoubtedly pro- duce extensive migration of Mammalia ; but, owing to the fact that the ice-sheet had very definite limits, and that numbers of large mammals were merely driven southward, it is not held to be a sufficient cause for so general a destruction of the larger forms of life. Another circumstance that puts the glacial epoch out of court as a sufficient explanation of the widespread extinction is that in two very remote parts of the earth, both enjoying a warm or even a sub-tropical climate — x\ustralia on the one hand, and Brazil to Argentina on the other, — exactly the same phenomena have occurred, and, so far as all the geo- logical evidence shows, within the same general limits of time. It is no doubt the case that at each of the dividing lines of the Tertiary era — that is, in passing from the Eocene to the Miocene, or from the latter to the Pliocene, and thence to the Pleistocene — many large Mammalia have also become extinct. But in these cases a much greater lapse of time can be assumed, as well as larger changes in the physical condi- tions, such as extension of land or water, climate, vegetation, etc., which, combined with the special disabilities of very large animals, are sufficient to account for the facts. It may be well here to state again the causes which lead to the ex- tinction of largo animals rather than small ones, as given in my Darwinism (p. 394) more than twenty years ago, and also in my Geographical Distribution of Animals, i. p. 157 (1876): " In the first place, animals of great bulk require a proportionate supply of food, and any adverse change of conditions would affect them more seriously than it would affect smaller animals. In the next place, the extreme specialisation of many of these large animals would render it less easy for them to become modified in any new direction required by the changed conditions. Still more impor- tant, perhaps, is the fact that very large animals always increase slowly as compared with small ones — the elephant producing a LIFE OF TERTIARY PERIOD 203 single young one every three years, while a rahbit may have a litter of seven or eight young two or three times a year. Now the prob- ability of useful variations will be in direct proportion to the popu- lation of the species, and, as the smaller animals are not only many hundred times more numerous than the largest, but also increase perhaps a hundred times as rapidly, they are able to become quickly modified by variation and natural selection, while the large and bulky species, being unable to vary quickly enough, are obliged to succumb in the struggle for existence/^ To these reasons we may add that very large animals arc less rapid in their motions, and thus less able to escape from enemies or from many kinds of danger. The late Professor O. Marsh, of Yale University, has well observed : " In every vigorous primitive type which was destined to survive many geological changes, there seems to have been a tendency to throw off lateral branches, which became highly specialised, and soon died out because they were unable to adapt themselves to new conditions. . . . The whole narrow path of the Suilline (hog) type, throughout the entire series of the American tertiaries, is strewn w4th the remains of such ambitious offshoots, manv of them attaining the size of a rhinoceros; while the typical pig, with an obstinacy never lost, has held on in spite of catastrophes and evolu- tion, and still lives in America to-day." We may also remember that it is still more widely spread over the Old World, under the various forms of the hojr-family (Suidse), than it is in America, under the closely allied peccary type (Dicotylida?). That this is a true cause of the more frequent passing away of the largest animal types in all geological epochs there can be no doubt, but it certainly will not alone explain the dying out of so many of the very largest ^Mammalia and birds dur- ing a period of such limited duration as is the Pleistocene (or Quaternary) age, and under conditions which were cer- tainly not very different from those under whicli they had been developed and had lived in many cases down to the historical period. 264 THE WORLD OF LIFE What we are seeking for is a cause which has been in action over the whole earth during the period in question, and which was adequate to produce the observed result. AVhen the problem is stated in this way the answer is very obvious. It is, moreover, a solution which has often been suggested, though generally to be rejected as inadequate. It has been so with myself, but why I can hardly say. In his Antiquity of Man (4th ed., 1873, p. 418) Sir Charles Lyell says: ^^ That the growing power of man may have lent its aid as the destroying cause of many Pleistocene species must, however, be granted; yet, before the introduction of fire-arms, or even the use of improved weapons of stone, it seems more wonderful that the aborigines were able to hold their own against the cave-lion, hyena, and wild bull, and to cope with such enemies, than that they failed to bring about their extinction.'' Looking at the whole subject again, with the much larger bodv of facts at our command, I am convinced that the above somewhat enigmatic passage really gives the clue to the whole problem, and that the rapidity of the extinction of so many large Mammalia is actually due to man's agency, acting in co-operation with those general causes w^hich at the culmina- tion of each geological era has led to the extinction of the larger, the most specialised, or the most strangely modified forms. The reason why this has not been seen to be a suffi- cient explanation of the phenomena is, I think, due to two circumstances. Even since the fact of the antiquity of man w^as first accepted by European geologists only half a century ago, each fresh discovery tending to extend that antiquity has been met with the same incredulity and opposition as did the first discovery of flint weapons by Boucher de Perthes in the gTavels near Amiens. It has been thought necessary to minimise each fresh item of evidence, or in many cases to re- ject it altogether, on the plea of imperfect observation. Thus the full weight of the ever-accumulating facts has never been LIFE OF TERTIAKY TERIOD 265 adequately recognised, because each new writer has Weu afraid to incur the stigma of credulity, and therefore usually limited himself to such facts as he had himself observed, or could quote from his best-known contemporaries. On the other hand, the old idea that man was the latest product of nature (or of evolution) still makes itself felt in the attempt to escape from any evidence proving man's coexistence with such extinct species as would imply greater antiquity. In the chapter on The Antiquity of Man in l^orth America (in my Xatural Selection and Tropical !N'ature) I have given numerous ex- amples of both these states of mind. And what makes them so specially unreasonable is, that all evolutionists are satis- fied that the common ancestor of man and the anthropoid apes must date back to the Miocene, if not to the Eocene period ; so that the real mystery is, not that the works or the remains of ancestral man are found throughout the Pleistocene period, but that they are not also found throughout the Pliocene, and also in some Miocene deposits. There is not, as often as- sumed, one " missing link " to be discovered, but at least a score such links, adequately to fill the gap between man and apes ; and their non-discovery is now^ one of the strongest proofs of the imperfection of the geological record. When we find, as we do, that, with the one exception of Australia, proofs of man's coexistence with all the great ex- tinct Pleistocene Mammalia are sufiiciently clear, while that the Australians are equally ancient is proved by their form- ing so well-marked and unique a race, the fact that man should every^vhere have helped to exterminate the various hugo quadrupeds, whose flesh would be a highly valued food, al- most becomes a certainty. The following passage from one of our best authorities, Mr. R. Lydekker, F.K.S., puts the w^hole case in a very clear light, though he does not definitely accept the conclusion whicli I hold to be now well established. He says: " From the northern half of the Old World have disappeared the mammoth, the elasmothere (a very peculiar, huge rhinoceros, whose 266 THE WORLD OP LIFE skull was more than three feet long), the woolly and other rhino- ceroses, the sabre-toothed tigers, etc.; North America has lost the megalonyx and the Ohio mastodon; from South America, the glyptodonts, mylodons, the megalothere, and the macrauchenia have been swept away; while Australia no longer possesses the diprotodon and various gigantic species of kangaroos and wombats. In the northern hemisphere this impoverishment of the fauna has been very generally attributed to the effects of the glacial period, but, although this may have been a partial cause, it can hardly be the only one. The mammoth, for instance, certainly lived during a considerable portion of the glacial epoch, and if it survived thus far, why should it disappear at the close? Moreover, all the Eu- ropean mastodons and the southern elephant {Elephas meridionalis) died out before the incoming of glacial conditions; and the same is true of all the extinct elephants and mastodons of Southern Asia. Further, a large number of English geologists believe the brick earths of the Thames valley, which contain remains of rhino- ceroses and elephants in abundance, to be of post-glacial age. As regards the southern hemisphere, it can hardly be contended that glacial conditions prevailed there at the same time as in the north- ern half of the world. " It is thus evident that, though a very great number of large mammals were exterminated (perhaps partly by the aid of human agency) at the close of the Pleistocene period, when the group had attained its maximum development as regards the bodily size of its members, yet other large forms had been steadily dying out in previous epochs. And it would seem that there must be some general, deep-seated cause affecting the life of a species with which we are at present unacquainted. Indeed, as there is a term to the life of an individual, what is more natural than that there should also be one to the existence of a species. It still remains indeed, to account for the fact that the larger Pleistocene mammals had no successors in the greater part of the world, but perhaps, is in some way connected with the advent of man." ^ It is sometimes thought that early man, with onlv the rudest weapons, would be powerless against large and often well- 1 A Geographical History of Mammals, R. Lydekker, B.A., F.R.S., V.P.G.S. etc., 1896, p. 18. LIFE OF TEKTIAEY PERIOD 267 armed mammals. But this, I think, is quite a mistake. Xo weapon is more effective for this purpose than a spear, of various kinds, when large numbers of hunters attack a single animal; and when made of tough wood, with the point hard- ened by fire and well sharpened, it is as effective as when metal heads are used. Bamboo, too, abundant in almost all warm countries, forms a very deadly spear when cut obliquely at the point. The way in which even a man-eating tiger is killed by this means in Java is described in my ^lalay Archipelago (p. 82). Such a method would doubtless have been adopted even by Palaeolithic man, and would have been effective against any of the larger animals of the Pleistocene age. It is therefore certain, that, so soon as man possessed weapons and the use of fire, his power of intelligent com- bination would have rendered him fully able to kill or cap- ture any animal that has ever lived upon the earth ; and as the flesh, bones, hair, horns, or skins would have been of use to him, he would certainly have done so even had he not the additional incentive that in many cases the animals were destructive to his crops or dangerous to his children or to himself. The numbers he would be able to destroy, es- pecially of the young, would be an important factor in the extermination of many of the larger species. There remains, however, the question, well put by Mr. Lydekker, whether there is not some general deep-seated cause affecting the life of species, and sending to explain, if only partially, the successive dying out of numbers of large ani- mals involving a complete change in the preponderant typos of organic life at certain epochs; and to this question and some others allied to it a separate chapter must be devoted. APPEXDIX THE THEORY OF COXTINEXTAL EXTEXSIOXS Most writers consider that the preceding facts (see p. 2-11) go to prove the existence of a land-connection l)otwecn Soiitli America 268 THE WORLD OF LIFE and Australia in Early or Middle Tertiary times. This, however, seems to me to be highly improbable for reasons given at full in my Island Life. Its supposed necessity depends on the assumption that the geological record is fairly complete, even as regards these small mammals, and that their not being yet discovered in the northern continents proves that they never existed there. But the extreme rarity of the small Secondary Mammalia, though they have been found scattered over the whole northern hemisphere, and the limited area in South America in which these Tertiary marsupials have been found, taken in connection with the enormous areas of geologically unexplored land in Asia and Australia, should make us very cautious in assuming such vast and physically improbable changes of land and sea at such a comparatively recent epoch. The theory of land-connection also introduces enormous difficulties of various kinds which it is well briefly to consider. If we suppose an absolute land-connection in order to allow the marsupial type to have entered Australia from temperate South America, we have to face the incredible fact, that of the whole varied mammalian fauna of the latter country this one group only was transmitted. In these same deposits there are found ancestral hoofed animals of small size (Pyrotherium) ; numerous rodents allied to cavies and porcupines; a host of Edentata allied to sloths, ant-eaters, and armadillos. These, taken altogether, are many times more numer- ous than the marsupials; they were more varied in structure and mode of life; and it is almost incredible that not one representa- tive of these somewhat higher forms sliould have reached the new country, or having reached it should have all died out, while the inferior group alone survived. Then, again, we know that birds and insects must have abounded in South America at the same period, while the whole 7000 miles of connecting land must have been well clothed with vegetation to support the varied life that must have existed upon it during the period of immigration. Yet no indication of a direct transference or interchange of these nu- merous forms of life in any adequate amount is found in either Australia or South Temperate America. We can hardly suppose such an enormous extent of land to have been raised above the ocean; that it should have become sufficiently stocked with life to serve as a bridge (7000 miles long!), and that a few very small marsupials only should have crossed it; that it then sank as rap- LIFE OF TERTIARY PERIOD 261) idly as it had been formed; with the one result of slocking Aus- tralia with marsupials, while its other forms of life — plants, birds, insects, molluscs — show an unmistakable derivation from the Asiatic continent and islands. A careful examination ol' a large globe or South Polar map, with a consideration of the diagram of the proportionate height of land and depth of ocean at p. .315 of my Darwinism, together with the argument founded upon it, will, I think, convince my readers that difficulties in geographical dis- tribution cannot be satisfactorily explained by such wildly im- probable hypotheses. If the facts are carefully examined, it will be found, as I have shown for the supposed " Atlantis " and " Lemuria," that such hypothetical changes of sea and land always create more serious difficulties than those which they are supposed to explain. People never seem to consider what such an explana- tion really means. They never follow out in imagination, step by step, the formation of any such enormous connecting lands between existing continents in accordance with what we know of the rate of elevation and depression of land, and the corresponding organic changes that must ensue. They seem to forget that such a vast and complete change of position of sea and land is not really known ever to have occurred. Let us consider for a moment what the supposed land-connection between South America and Australia really implies. The distance is more than half as much again as the whole length of the South American continent, and 1000 miles farther than from Southamj)- ton to the Cape. This alone should surely give us pause. P)ut unless we go as far south as the Antarctic circle, the depth of the intervening ocean is about two miles; and until we get near Xew Zealand there is not a single intervening island. There are here none of the indications we expect to find of any geologically recent depression of land on a vast scale. Of course we may suppose the connection to have been along a great circle within ten degrees of the South Pole, but that will not greatly shorten the distance, while we have not a particle of evidence for such a vast ehange of climate in Mid-Tertiary times as w(nild be required to render such a route possible. But the mere physical dilhculties are equally great. All land elevation or depression of which we have geo- logical evidence has been exceedingly gradual, very limited in extent, and always balanced by adjacent opposite movements. Such 270 THE WORLD OF LIFE movements appear to be slow creeping undulations passing over continental plateaus and their immediately adjacent submarine extensions. Sometimes the depressions seem to have taken the form of basins; but we cannot conceive of any elevation of conti- nental dimensions, or depression of oceanic character as to depth and area, without the complementary movement to complete the un- dulation. A continental extension between South America and Australia would almost necessarily imply a subsidence of one or both of those countries over an equal area and to an equal depth; and, so far as I am aware, no geological evidence has been ad- duced of any such vast changes having occurred at so recent a period in either continent. I believe it can now be truly said that no stratigraphical geologist accepts the theory of frequent inter- changes of continental and oceanic areas, which are so hastily claimed by palaeontologists and biologists to be necessary in order to overcome each apparent difficulty in the distribution of living or extinct organisms, and this notwithstanding the number of such difficulties which later discoveries have shown to be non-existent. CHAPTER XIII SOME EXTENSIONS OF DARWIn's THEORY During the fifty years that have elapsed since the Darwinian theory was first adequately, though not exhaustively, set fortli, it has been subject to more than the usual amount of ob- jection and misapprehension both by ignorant and learned critics, by old-fashioned field-naturalists, and by the newer schools of physiological specialists. Most of these objections have been shown to be fallacious by some of the most eminent students of evolution both here and on the Continent; but a few still remain as stumbling-blocks to many earnest readers, and, as they are continually adduced as being serious difii- culties to the acceptance of natural selection as a sufficient ex- planation of the origin of species, I propose to give a short statement of what seem to me the three objections that most require an answer at the present time. They are the follow- ing:— 1. How can the beginnings of new organs be explained ? 2. How can the exact co-ordination of variations, needed to produce any beneficial result, be effected with sufficient rapidity and certainty ? 3. How is it that excessive developments of bulk, weapons, ornaments, or colours, far beyond any utilitarian requirements, have been so frequently produced ? These three objections are of increasing degrees of impor- tance. The first is, in my opinion, wholly speculative and of no value, inasmuch as it applies to wliat happened in the earlier stages of evolution, of which we have a mininium of knowledge. The second is of somrwliat more importance: for, though in the great majority of cases of adaptation the ordinarv well-known facts of variation and survival would 271 272 THE WORLD OF LIFE amply suffice, yet there are conceivable cases in wbich they might be insufficient, and these cases are now explained by a very interesting combination of the effects of acquired modifications of the individual with the selection of congenital variations. The third is, I think, somewhat more important, as indicating a real deficiency in the theory, as originally stated, but which is now well supplied by an extension of that theory from the body itself to the reproductive germs from which its parts are developed. I will, therefore, en- deavour to explain in as simple a manner as possible how these three objections have been overcome. (1) The Beginnings of Organs The objection that the first slight beginnings of new organs would be useless, and that they could not be preserved and increased by natural selection, was one of the most frequent in the early stages of the discussion of the theory, and was answered by Darwin himself in the later editions of his book. But the objection still continues to be made, and owing to the great mass of controversial literature continually issued from the press many of the objectors do not see the replies made to them ; there is therefore still room for a somewhat more general answer, wdiich will apply not only to certain individual cases, but to all. The most general and therefore the best answ^er I have yet seen given is that of Professor E. B. Poulton in his recently published Essays on Evolution. He says: " Organs are rarely formed anew in an animal, but they are formed by the modification of pre-existing organs ; so that, instead of having one beginning for each organ, we have to push the be- ginning further and further back, and find that a single origin ac- counts for several successive organs, or at any rate several functions, instead of one." He then goes on to show that the four limbs of vertebrates have been again and again modified, for running, for climbing to? EXTEXSIOXS OF DARWINISM 273 for burrowing, for swimming, or for flying, and that their first appearance goes back to PalaBozoic times in the paired fins of early fishes, while their actual or'ujiii must have been much further back, in creatures whose skeleton was not suffi- ciently solidified to be preserved. There is, however, a more general explanation even than this, and one that applies to what has always been hehl to be the most difiicult of all — that of the origin of the organs of sense. The various sensations by which w^e come into relation with the external world — sight, hearing, smell, taste, and touch ■ — are really all specialisations of the last and most general, that of material contact. We hear by means of a certain range of air-waves acting on a specially constructed vibrating organ ; we smell by the contact of excessively minute particles, or actual molecules, given off by certain substances ; we taste by the action of soluble matter in food on the papilke of the tongue; and we see by the impact of ether-vibrations on the retina; and as other ether-vibrations produce sensations of cold or warmth, or, when in excess, acute pain, in every part of the body, the modern view, that matter and ether are funda- mentally connected if not identical, seems not unreasonable. Xow, as all our organs of sense, however complex, are built up from the protoplasm which constitutes the material of all living organisms, and as all animals, however simple, exhibit reactions which seem to imply that they have the rudiments of most, if not all of our senses, we may conclude that just in proportion as they have advanced in complexity of organi- sation, so have special parts of their bodies become adapted to receive, and their nervous system to respond to, tlio varinn? contacts with the outer world which produce what wo terra sensations. There is therefore, probably, no point in the whole enormous length of the cliain of being, fnnn ourselves back to the simple one-celled Amoeba, iu which the rudiments of our five senses did not exist, although no separnto organs may be detected. Just as its whole body sen'os alternately 274 THE WORLD OF LIFE as outside or inside, as skin or as stomach, as limbs or as lips, so may every part of it receive a slightly different sensa- tion from a touch outside or a touch inside, from an air- vibration or from an ether-vibration, from those emanations which effect us as noxious odours or disgusting tastes. But if this view is a sound one, as I think it will be admitted that it is, how absurd is it to ask, " How did the eye or the ear begin ? " They began in the potentiality of that marvel- lous substance, protoplasm, and they were rendered possible when that substance was endowed with the mysterious or- ganising power we term life. First the cell was produced; and, from the continued subdivision of the cell at each sub- division taking a slightly different form and function, numer- ous one-celled animals were formed; and a little later the union of many cells of diverse forms and functions led to the endless multicellular creatures, constituting the entire world of life. Thus every substance and every organ came into existence when required by the organism imder the law of perpetual variation and survival of the fittest, only limited by the potentialities of living protoplasm. And if the higher sense- organs were so produced, how much easier was the production of such superficial appendages as horns and tusks, scales and feathers, as they were required. Horns, for instance, are either dermal or osseous outgrowths or a combination of both. In the very earliest known vertebrates, the fishes of the Silurian formation, we find the skin more or less covered with tubercles, or plates, or spines. Here we have the rudiments of all those dermal or osseous outgrowths which continue in endless modifications through the countless ages that have elapsed down to our own times. They appear and disappear, as they are useful or useless, on various parts of the body, as that body changes in form and in structure, and modifi- cations of its external covering are needed. Hence the in- finite variety in nature — a variety which, were it not so familiar, would be beyond the wildest flights of imagination EXTENSIONS OF DARWINISM 275 to suggest as possible developments from an apparently simple protoplasmic cell. The idea, therefore, that there were, or could be, at any successive periods, anything of the nature of the abrupt beginning of completely new organs which had nothing analogous in preceding generations is quite unsup- ported by what is known of the progressive development of all structures through slight modification of those which pre- ceded them. The objection as to the heglmiings of new organs is a purely imaginary one, wdiich entirely falls to pieces in view of the wdiole known process of development from the simplest cell (though in reality no cell is simple) to ever higher and more complex aggregations of cells, till we come to Mammalia and to man. (2) The Co-ordination of Variations The next difficulty, one which Herbert Spencer laid much stress on, is, that every variation, to be of any use to a species, requires a number of concurrent variations, often in dilTerent parts of the body, and these, it is said, cannot be left to chance. Herbert Spencer discussed this poi';t at great length in his Factors of Organic Evolution ; and, as one of the illus- trative cases, he takes the giraffe, w^hose enormously long neck and fore-legs, he thinks, would have required so many con- current variations that we cannot suppose them to have oc- curred through ordinary variation. He therefore argues that the inherited effects of use and disuse are the onlv causes which could have brought it about; and Darwin himself ap- pears to have thought that such inheritance did actually occur. The points which Spencer mainly dwells upon are as fol- lows : The increased length and massiveness of the neck would require increased size and strength of the chest with its bones and muscles to bear the additional weight, and also great additions to the strength of the fore-legs to carry such a burthen. Again, as the hind-legs have remained short, the whole body is at a different angle from what it was before the change from the ordinary antelope-type, and this would 276 THE WORLD OE LIFE require a different shape in the articulating joints of the hips and some change in the muscles; and this would be the more important as the hind- and fore-legs now have unequal angular motions when galloping, involving changed co-ordination in all the connected parts, any failure in which would diminish speed and thus be fatal to the varying individuals. Even the blood-vessels and nerves of these various parts would re- quire modifioations exactly adapted to the change in the other parts ; and he urges that any individuals in Avhich all these necessary variations did not take place simultaneously, would be at a disadvantage and would not survive. To do his argu- ment justice, I will quote one of his most forcible paragraphs. " The immense change in the ratio of fore-quarters to hind- quarters would make requisite a corresponding change of ratio in the appliances carr3dng on the nutrition of the two. The entire vascular system, arterial and venous, would have to undergo succes- sive unbuildings and rebuildings to make its channels everywhere adequate to the local requirements, since any want of adjustment in the blood-supply to this or that set of muscles would entail in- capacity, failure of speed, and loss of life. Moreover, the nerves supplying the various sets of muscles would have to be appropriately changed, as well as the central nervous tracts from which they issued. Can we suppose that all these appropriate changes, too, would be, step by step, simultaneously made by fortunate spon- taneous variations occurring along with all the other fortunate spontaneous variations? Considering how immense must be the number of these required changes, added to the changes above enumerated, the chances against any adequate readjustments for- tuitously arising must be infinity to one." Xow, this seems very forcible, and has, no doubt, con- vinced many readers. Yet the argument is entirely fallacious, because it is founded on the tacit assumption that the number of the varying individuals is very small, and that the amount of coincident variation is also both small and rare. It is further founded on the assumption that the time allowed for the production of any sufficient change to be of use is also EXTEIsTSIONS OF DARWINISM 277 small. But I have shown in the early chapters of this book (and much more fully in my Darwinism) that all these as- sumptions are the very reverse of the known facts. The numbers of varying individuals in any dominant species (and it is only these which become modified into new species) is to be counted by millions ; and as the whole number can, as regards any needed modification, be divided into two lialves — those which possess the special quality required above or below the average — it may be said thali nearly half the total number vary favourably, and about one-fourth of the whole number in a very large degree. Again, it has been shown that the number of coincident variations are very great, since they are always present when only a dozen or twenty individ- uals are compared; bnt nature deals with thousands and mil- lions of individuals. Yet, again, we know that changes of the environment are always very slow as measured by years or generations, since not a single new species is known to have come into existence during the whole of the Pleistocene period ; and as fresh variations occur in every generation, almost any character, with all its co-ordinated structures, would be con- siderably modified in a hundred or a thousand generations, and ■we have no absolute knowledge that any great change would be required in less time than this.^ lA very familiar fact will, I think, show that a large amount of co- ordinated variability in different directions does actually occur. First-rate bowlers and wicket-keepers, as well as first-rate batters, are not common in proportion to the whole population of cricket-players. Each one of these requires a special set of co-ordinated faculties — good eyesight, accurate \ perception of distance and of time, with extremely rapid and accurate re- sponse of all the muscles concerned in the operations each has to perform. If all the special variations required to produce such individuals were sot forth by a good physiologist in the detailed and forcible manner of the passage quoted from Spencer about the giraffe, it would seem impossible that good cricketers should ever arise from the average family types. Yat they certainly do so arise. And just as cricketers are chosen, not by ex- ternal characters, but by the results of actual work, so nature selects, not by special characters or faculties, but by that combination of characters which gives the greatest chance of survival in the complex, fluctuating environment in which each creatures lives. The species thus lK»comes adapted, first to 278 THE WORLD OF LIFE Objectors always forget that a dominant species has become so because it is sufficiently adapted to its whole environment, not only at any one time or to any average of conditions, but to the most extreme adverse conditions Avhicli have oc- curred during the thousands or millions of years of its exist- ence as a species. This implies that, for all ordinary con- ditions and all such adverse changes as occur but once in a century of a millennium, the species has a surplus of adapt- ability which allows it to keep up its immense population in the midst of countless competitors and enemies. Examples of such thoroughly well-adapted species were the American bison and passenger pigeon, whose populations a century ago were to be counted by millions and thousands of inillions, which they w^ere fully able to maintain against all enemies and competitors then in existence. But civilised man has so modified and devastated the whole organic environment in a single century as to bring about an extermination which the slow changes of nature would almost certainly not have ef- fected in a thousand or even a million of centuries. This happened because the changes were different in kind, as well as in rapidity, 'from any of nature's changes during the whole period of the development of existing species. But although I feel confident that the known amount of variation would amply suffice for the adaptation of any domi- nant species to a nomially changing environment, I admit that there are conceivable cases in which changes may have been so great and so comparatively rapid as to endanger the exist- ence even of some of those species which had attained to a dominant position; such, for instance, as the opening of a land passage for very powerful new Carnivora into another con- resist one danger, then another; first to one aspect of the ever-changing environment, then to another; till during successive generations it becomes so perfectly adapted to a long series of more or less injurious conditions, that, under all ordinary conditions, it possesses a surplus of adaptation. And as this complete adaptation is as often exhibited in colour and marking as in structure, it is proved that the transmission of the effects of use and disuse are not essential to the most complex adaptations. EXTEXSIO.\S OF DAKWJMSM l>70 tinent or extensive area (as appears to have occurred with Africa in Tertiary times), in ^vllicll case it is quite possible that such an animal as the American bison mii^ht have been first reduced in numbers, and, for want of any suflicieutly rapid development of new means of protection, be ultimately destroyed. But a few years ago an idea occurred independently to three biologists, of a self-acting jorinciple in nature which would be of such assistance to any species in danger of extermination as, in some cases at all events, would enable it to become adapted to the new conditions. It would, in fact, increase the powers of natural selection, as above explainc(l, to a degree which might sometimes make all the difference between life and death to a certain number of species. It depends upon the w^ell-known fact that the use of any limb or organ strength- ens or increases the growth of that part or organ. On this fact depends all training for athletics or games; and it is alleged by some trainers that any one, however weak naturally, can have his strength very greatly increased by systematic but carefully graded exercise. If, therefore, the survival of any animal in presence of a new enemy or unaccustomed danger depends upon increased powers of running, or jumping, or tree-climbing, or swimming, then, during the process of eliminating those individuals who were the worst in these re- spects, all the remainder would have to exercise their powers to the utmost, and would, in the act of doing so, increase their power of escaping the danger. Thus a con-idrrable number would become capable of surviving, year after year, to a normal old age, and during this whole period would, year by year, have fresh descendants, and of these only the very best, the most gifted naturally, would survive. The in- creased adaptation during the life of the individual would not be transmitted, but the quality of being inijirovablc during life would be transmitted, and thus additional tim*^ and a consider- ablv increased ]K>])ulation would give more uuUcrials for natural selection to act upon. With this help the species 280 THE WOKLD OF LIFE might become so rapidly improved that the danger from the new environment would be overcome, and a new type might be produced which would continue to be a dominant one un- der the new conditions.^ N^ow, while it must be admitted, that under certain con- ditions, and with certain classes of adaptations, the normal effects of natural selection would be facilitated by the aid of individual adaptation through use of organs, yet its effect is greatly limited by the fact that it will not apply to several classes of adaptations which are quite unaffected by use or exercise. Such are the colours of innumerable species, which are in the highest degree adaptive, either as protecting them from enemies, as a warning of hidden danger (stings, etc.), as recognition-marks for young or for wanderers, or by mimi- cry of protected groups. Here the tise is simply being seen or not seen, neither of which can affect the colour of the object. Again, nothing is more vitally important to many animals than the form, size, and structure of the teeth, which 1 As many readers are ignorant of the extreme adaptability of many parts of the body, not only during an individual life, but in a much shorter period, I will here give an illustrative fact. A friend of mine was the resident physician of a large county lunatic asylum. During his rounds one morning, attended by one of his assistants and a warder, he stopped to converse with a male patient who was only insane on one point and whose conversation was very interesting. Suddenly the man sprang up and struck a violent blow at the doctor's neck with a large sharpened nail, and almost com- pletely severed the carotid artery. The warder seized the man, the assistant gave the alarm, while my friend sat down and pressed his finger on the proper spot to stop the violent flow of blood, which would otherwise have quickly produced coma and death. Other doctors soon applied proper pres- sure, and a competent surgeon was sent for, who, however, did not arrive for more than an hour. The artery was then tied up and the patient got to bed. He told me of this himself about two years afterwards, and, on my inquiry how the functions of the great artery had been renewed, he assured me that nothing but its permanent stoppage was possible, that numerous small anastomosing branches enlarged under the pressure and after a few months carried the whole current of blood that had before been carried by the great artery, without any pain, and that at the time of speak- ing he was quite as well as before the accident. Such a fact as this really answers almost the whole of Herbert Spencer's argument which I have quoted at p. 270. EXTEXSIONS OF DARWl.XLSM i'8l are wonderfully varied throughout the whole of th(^ VLricbrate sub-kingdom. Yet the more or less use of the teeth cannot be shown to have any tendency to change their fnnii or structure in the special ways in which they have been again and again changed, though it might possibly have induced growth and increased size. Yet again, the scales or plates of reptiles, the feathers of birds, and the hairy covering of mam- mal?, have never been shown to have their special textures, shape?, or density modified by the mere act of use. One common error is that cold produces length and density of hair, heat the reverse ; but the purely tropical monkey-tribe are, as a rule, quite as well clothed with dense fur as most of the temperate or arctic mammals, while no birds are more luxuriantly feather-clad than those of the tropics. XeitlnT is it certain that increased gazing improves the eyes, or loud noises the ears, or increased eating the stomach ; so that we must conclude that this aid to the powers of natural selection is very partial in its action, and that it has no claim to the important position sometimes given it. (3) Germinal Seleclion, an Important Eximfiion of the Theory of Natural Selection Although I was at first inclined to accept Darwin's view of the influence of female choice in determining the development of ornamental colour or appendages in the males, yet, when he had a(hhiced his wonderful array of facts bearing upon the question in the Descent of Man, the evidence for any such effective choice appeared so very scanty, and the ellects im- puted to it so amazingly improbable, that T felt certain that some other cause was at work. Tn my Tropical Nature (1878) and in my Darwinism (1889) I treated the subject at considerable length, adducing many facts to prove that, even in birds, the colours and ornamental })lunies of the males were not in themselves attractive, but served merely as signs of sexual maturity and vigour. Tn the case of insects, especially in butterflies, where the phenomena of colour, and to some 282 THE WOKLD OE LIEE extent of ornament, are strikingly similar to those of birds, the conception of a deliberate aesthetic choice, by the females, of the details of colour marking, and shape of wings, seemed almost unthinkable, and was supported by even less evidence than in the case of birds. After long consideration of the question in all its bearings, and taking account of the various suggestions that had been made by competent observers, I arrived at certain conclu- sions which I stated as follows : " The various causes of colour in the animal world are, molecular and chemical change of the substance of their integuments, or the action upon it of heat, light, or moisture. Colour is also produced by the interference of light in superposed transparent lamellae or by excessively fine surface striae. These elementary conditions for the production of colour are found everywhere in the surface-structures of animals, so that its presence must be looked upon as normal, its absence exceptional. " Colours are fixed or modified in animals by natural selection for various purposes : obscure or imitative colours for concealment ; gaudy colours as a warning; and special markings either for easy recognition by strayed individuals or by young, or to divert attack from a vital part, as in the large brilliantly marked wings of some butterflies and moths. " Colours are produced or intensified by processes of develop- ment, either where the integument or its appendages undergo great extension or change of form, or where there is a surplus of vital energy, as in male animals generally, more especially at the breed- ing season." ^ ISTow the idea here suggested, of all these strange and beau- tiful developments of plumage, of ornaments, or of colour being primarily due to surplus vitality and growth-power in dominant species, and especially in the males, seems a fairly adequate solution of the problem. For the individuals which possessed it in the highest degree would survive longest, would 1 Natural Selection and Tropical Nature (new ed., 1895), pp. 391-392. For full details see Darwinism, chap. x. (1901). EXTENSIONS OF DARWINISM 283 have most offspring who were equally or even more hijrhly gifted; and thus there would arise a continually increasing vitality whicli would be partly expended in the further develop- ment of those ornaments and plumes which are its result and outward manifestation. The varvine^ conditions of existence would determine the particular part of tlie body at which such accessory ornaments miglit arise, usually^ no doubt, directed by utility to the species. Thus the glorious train of the pea- cock might have begim in mere density of plumage covering a vital part and one specially subject to attack by birrls or beasts of prey, and, once started, these plumes would continue to increase in number and size, as being an outlet for vital energy, till at last they became so enormously lengthened as to become dangerous by their weight being a check to speed in running or agility in taking flight. This is already the case with the peacock, which has some difficulty in rising from the ground and flies very heavily. Its enemies in India are tigers and all the larger members of the cat-tribe, and when any of these approach its feeding-grounds it takes alarm and at once flies up to the low^er branches of large trees. In the ArgTis-pheasant it is the secondary wing-featliers that are ex- ceedingly long and broad, so as to be almost as much a liin- drance to strong or rapid flight as is the train of the pea- cock; and in both birds these ornamental plumes have evi- dently reached the utmost dimensions compatible with the safety of the species. There can also be little doubt that in manv of the birds- of-paradise and of the humming-birds, in the enormous crest of the umbrella-bird, in the huge beaks of the hornbiils and the toucans, in the lenc^thv neck and lec:s of the flaminc:os and the herons, these various oraamental or usefid appen(iag(\>< liave reached or even overpassed the maximum of utility. In an- other class of animals we have the same phenomenon. The expansion of the wings in butlerflies and motlis reaches a maximum in several distinct families — the Papilionidre, the Morphidffi, the Bond\vces, au'l the Xoctuje, in all <>f whirli it 2S4 THE WORLD OF LIFE is sometimes from nine to ten inches. Here, again, we seem to find a tendency to development in size, which has gone on from age to age, till limits have been reached to exceed which threatens the existence of the species. The progressive development of many groups of animals affords curious illustrations of this continuous increase in bulk, or in the size of particular organs, till they have actually over- passed the line of permanent safety, and under the first ad- verse conditions have led to extinction. Both reptiles and mammals originated in creatures of small size which gradually increased in bulk, in certain types, till they suddenly became exterminated. In the former class the increase was ap- parently rapid, till the hugest land-animals that ever lived appeared upon the earth — the Dinosauria of the Jurassic and Cretaceous periods, already described. Many of them also de- veloped strange horns and teeth; and these, too, when they reached their maximum, also suddenly disappeared. Flying reptiles — the Pterodactyles — also began as small animals and continually increased, till those of the period of our Chalk attained the greatest dimensions ever reached by a flying crea- ture, and then the whole group became extinct at a time when a higher type, the birds, w^ere rapidly developing. With mammals the case is even more striking, all the ear- liest forms of the Secondary age being quite small; while in the Tertiary period they began to increase in size and to de- velop into a great variety of types of structure ; till, in an age just previous to our own, such exceedingly diverse groups as the marsupials, the sloths, the elephants, the camels, and the deer, all reached their maximum of size and variety of strange forms, the most developed of which then became ex- tinct. Others of a lower and more generalised type, but equally bulky, had successively disappeared at the termina- tion of each subdivision of the Tertiary age. It is here that we can trace the specialisation and increase in size of the horse-tribe and of the deer; tlie latter passing from a horn- less state to one of simple horns, gradually increasing in size Fig. 94. — MacJurrodus neogwus ( Sabre-Toothed Ti<,n'r). From the Pleistocene of Buenos Ayres. One-eighth nat. size. (Nicholson's Palaeontology.) Fig. 95. — Skeleton of liiuiit Deer {Ccrrus : the extinct fonus are those in which they are developed to an unwieldy size, as in Elephas ganesa of Xorth-West India, whose slightly curved tusks, some- times nearly 10 feet long, must have put an enormous strain upon the neck, and the mammoth, whose greatly curved tusks were almost equally heavy. Excessive Development of Lower Animals before Extinction My friend Professor Judd has called my attention to the fact that many of the lower forms of life exhibited similar phenomena. The Trilobites (primitive crustaceans) which were extremely abundant in the Pala?ozoic rocks, in their last Fig. 96. — Conocoryphc sultzcri. Upper Cambrian. Fio. 97. — Paradonides bohcmicus. Upper Cambrian. 288 THE WORLD OF LIFE stages " developed strange knobs and spikes on their shells, so that thej seemed to be trying experiments in excessive vari- ation.'^ Figs. 96, 97^ show typical forms of Trilobites (so called from their three-lobed bodies) ; while at a later period, when the whole group was approaching extinction, it produced spined forms like that shown in Fig. 98. Excentric forms of Ammonites At a later period the wonderfully rich and varied Am- monites show still more curious changes. Beginning in the Devonian formation thev increased in varietv of form and structure all through the succeeding forma- tions, till they finally died out in the Cretaceous. The two species here figured from the Trias (Figs. 99, 100) may be taken as typical; but the variations in surface pat- tern are almost infinite. Visitors to Weymouth or Lyme Regis maj" find such in abundance under Lias cliffs, or in the former place along the shores of the backwater. As time went on Ammonites in- FiG. ^^ — Acidaspis dufrenoyi. creased in maximum size, till in Silurian (Bohemia). the Chalk formation specimens 2 or 3 feet diameter are not uncommon. One of the largest English specimens in the British Museiim (Xatural History) was found at Rottingdean, near Brighton, and is 3 feet 8 inches across; but the largest known is an allied species from the Upper Chalk of Westphalia, and has the enormous diameter of 6 feet 8 inches. It is an interesting fact that the very earliest Ammonites were straight, and gradually became closely coiled. This form was maintained almost constant throu2:hout the vast EXTENSIONS OF DARWINISM 289 periods of the Mesozoic age, till towards llie end, when the whole race was about to die out, they seemed to try to go back to their original form, which some almost reached (Fi^. Fig. 99. — Ceratites nodosus. Trias. Fig. 100. — Trachyceras aon. Trias. 105), while others, as Professor Judd remarks (in a letter), " before finally disappearing, twisted and untwisted them- selves, and as it were wriggled themselves into extraordinary Fig. 101. — Crioceras emerici. Cretaceous. Fig. 102. — Ileteroceras cmcrici. Cretaceous. shapes, in the last throes of dissolution.'- These strange forms (Figs. 90-106) are reproduced from Nicholson's PaUeontol- ogy, and there are many others. 290 THE WOKLD OF LIFE Fig. 103. — Macroscapliites ivanii. Cretaceous. ' Fig. 104. — Hamites rotundus. Cretaceous. Fig. 105. — Ptychoceras emericianum. Cretaceous. Fig. lOG. — Ancyloceras Matheronianum. Gault. Late Ammonites. (From Nicholson's Palaeontology.) Special Features in the Development of Vertehrates Another remarkable fact dwelt upon in Dr. Woodward's address is the remarkably small brains of those early types of vertebrates which were not destined to survive. The most EXTE:^rSIOXS of DARWIXISM 291 striking cases are those of the Mesozoic reptiles and the early Tertiary ungulate mammals, which both increased to such an enormous bulk, yet retained throughout an almost ludicrously small brain, as described in the last chapter. The same was the case to a somewhat less extent with the carnivorous mam- mals, the Creodonta and Sparassodonta of the early Tertiaries both of the eastern and western hemispheres. These were sometimes as large as lions or bears, and had equally well de- veloped canine teeth, but very small brains; and they all died out in Eocene or early Miocene times, giving way to small an- cestral forms of our modern carnivores, which then increased in size and developed larger brains, culminating in the highly intelligent fox and dog, cat and leopard, of our own day. Yet another singular feature of some of the more highly developed vertebrates is the partial or total loss of teeth. This is well shown in the camels, which have only a pair uf in- cisors in the upper jaw; while the whole vast family of the deer, cattle, and sheep have a completely toothless pad in the front of the upper jaws. This is apparently better adapted for rapid browsing of grass and low herbage — whieli is stored up in the 23aunch for rumination when at rest; and the ab- sence of teeth as a defence is compensated by the possession of horns in a great variety of form and structure. Even more remarkable is the total loss of teeth bv modern birds, although the early types of birds possessed them. The bill, however, is often a very effective piercing or tearing weapon ; and their strongly grasping claws and hooked bill render the birds of prey almost as powerful and d instructive as the smaller members of the cat-tribe. This partial or total disappearance of the teeth has no doubt been helped on l)y the same principle which led to the persistent increase of useless appendages till checked by natural selection or till it led to the extinction of the entire race. 292 THE WORLD OF LIFE Germinal Selection The numerous and varied phenomena which have been merely sketched in outline in the present chapter receive an approximate explanation by Professor Weismann's theory of germinal selection, which he first published in 1896. He appears to have been led to it by feeling the difficulty of ex- plaining many of these phenomena by the ^' natural selection " of Darwin; but to have laid more stress on those of Section 2 of the present chapter than those of Section 3. He had in 1892 published his elaborate volume on The Germ-Plasm a Theory of Heredity, to which this later theory is a logical sequel. During the last quarter of a century many striking discov- eries have been made in what may be termed the mechanism of growth and reproduction ; each successive advance in micro- scopic power and methods of observation have brought to light whole worlds of complex structure and purposive transfor- mations in w^hat was before looked upon as structureless cells or corpuscles. Some attempt will be made in a later chapter to discuss these primary life-phenomena; here it is only neces- sary to show briefly how Weismann's new theory helps us to understand the facts of life-development we have been dealing with. For this purpose I cannot do better than quote Pro- fessor Lloyd Morgan's very clear statement of the theory. He says : ^ " The additional factor which Dr. Weismann suggests is what he terms ^ germinal selection.' This, briefly stated, is as follows : — There is a competition for nutriment among those parts of the germ named determinants, from which the several organs or groups of organs are developed. In this competition the stronger deter- minants get the best of it, and are further developed at the expense of the weaker determinants, which are starved, and tend to dwin- dle and eventually disappear. The suggestion is interestingj but one well-nigh impossible to test by observation. If accepted as a 1 Habit and Instinct, p. 310. EXTEJN^SIO^^S OF DAKWINISM 293 factor, it would seiTe to account for the inordinate growth of cer- tain structures, such as the exuberance of some secondary sexual characters, and for the existence of determinate variations, that is to say, variations along special or particular lines of adaptation." It may be well to give here Weismann's own definition of what he means by " determinants," as quoted by Professor J. Arthur Thomson in his fine volume on Heredity (p. 435) : " ' I assume,' Weismann says, ^ that the germ-plasm consists of a large number of different parts, each of which stands in a definite relation to particular cells or kinds of cells in the organism to be developed — that is, tliey are * primary constituents' in the sense that their co-operation in the production of a particular part of the organism is indispensable, the part being determined both as to its existence and its nature by the predestined particles of the germ- plasm. I therefore call these Determinants, and the parts of the complete organism which they determine Determinates," ^ Professor Thomson continues thus: " But how many determinants are to be postulated in any given case? "Weismann supposes that every independently variable and independently heritable character is represented in the germ-plasm by a determinant. A lock of white hair among the dark may re- appear at the same place for several generations; it is difficult to interpret such facts of particular inheritance except on the theory that the germ -plasm is built up of a large number of different de- terminants. It may be pointed out that almost all biologists who have tried to form a conception of the ultimate structure of living matter have been led to the assumption — expressed in very varied phraseology — of ultimate protoplasmic units which have the power of growth and division. It is in no way peculiar to Weismann to imagine biophors and to credit them with the powers of growing and dividing.'' I quote these passages because Professor Thomson is thor- oughly acquainted, not only with all Weismann's work, having himself translated some of them, but also with that of other 1 The Evolution Theory, 1004. vol. i. p. 355. 294 THE WOELD OF LIFE European and American writers on this very difficult prob- lem; and he arrives at the conclusion, that Weismann's theory is the most carefully and logically worked out, and that some such conception is essential for a comprehension of the won- derfully complex phenomena of heredity. He also quite agrees with the conception that as these vital elements of the germ-plasm grow and multiply during the life of the organism, they must be nourished by fluids derived from it, and that there must be slight differences between them in size and vigour, and a struggle for existence in which the most vigorous survive. These more vigorous determinants will lead to more vigorous growth of the special part or organ they determine — hair, horns, ornaments, etc., — and wherever this increase is useful, or even not hurtful, to the species, it will go on in- creasing, generation after generation, by the survival of more and more vigorous determinants. There is therefore both an internal and an external strug- gle for existence affecting all the special parts — organs, or- naments, etc. — of ever}^ living thing. With regard to the more important sti-uctures, such as the limbs, the organs of vision and hearing, the teeth, stomach, heart, lungs, etc., on Avhich the very existence of the individual as well as of the species depends, survival of the fittest in due co-ordination with all other parts of the body will continually check any tendency to unbalanced development, and thus, generation by generation, suppress the tendency of the more vigorous de- terminants to increase the growth and vigour of its special determinates, by elimination of the individuals which exhibit such unbalanced gro^vth. But in the case of appendages, or- naments, or brilliant colours, which may begin as a mere out- let for superfluous vital energy in dominant races, and then be selected and utilised for purposes of recognition, warning, imitative concealment, or for combat among males, there w^ill not be the same danger to the ver)^ existence of the adult ani- mal. It will, however, often happen that the increase through germinal selection Avill continue beyond the point of absolute EXTENSlOiVS OF DxVK\VI.\i;SM 205 utility to tlie individual; between which and the jooint of ef- fective hurtfulness there may be a considerable margin. In this way w^e have a quite intelligible exi)lanation of the enor- mous development of feathers or decorative pi Limes in so many birds, enormous horns in deer and antelopes, huge tusks in elephants, and huge canine teeth in other quadrupeds. Tliis view is supported by the suggestive fact, that many of these appendages are retained only for a short period, during the breeding season, when vigour is greatest and food most abun- dant, and when therefore they are least injurious. Again, when acting in an opposite direction, the theory serves to explain the rapid dwindling and final disappearance of some useless organs, which mere disuse is hardly sufficient to explain; such are the lost hind limbs of whales, llie rudi- mentary wings of the Apteryx, the toothless beak of birds, ete. In such cases, after natural selection had reduced the part to a rudimental condition, any regrowth would be injurious, and thus determinants of increased vigour would be suppressed by the non-survival of the adult, leaving the weaker deter- minants to be crowded out by the competition of those of ad- jacent parts, the increased development of which was ad- vantageous. By this very ingenious, but, though speculative, highly probable hypothesis, extending the s]:)hero of c=m as a whole to some of its elementarv vital units, Professor Weis- mann has, I think, overcome the one real diHieulty in the in- terpretation of the external forms of living things, in all their marvellous details, in tenns of normal .variation and survival of the fittest. We have here that '^ mysterious impetus " to increase beyond the useful limit which Dr. Woodward has rt^ ferred to in his address already quoted, and which is also a cause of the extinction of species to which Mr. Lydekker referred us, as quoted towards the end of the preceding chap- ter. 296 THE WORLD OF LIFE Illustrative Cases of Extreme Development Two examples of this extreme development have not, I think, jet been noticed in this connection. The wonderful long and perfectly straight spirally twisted tusk of the strange Cetaceous mammal, the narw^hal, is formed by an extreme de- velopment, in the male only, of one of a pair of teeth in the upper jaw. All other teeth are rudimentary, as is the right tooth of the pair of which the left forms the tusk, often 7 or 8 feet long, and formed of a very fine heavy ivory. The use of this is completely unknown, for though two males have been seen playing together, apparently, with their tusks, they do not fight, and their food, being small Crustacea and other Fig. 107. — Head of Babirusa {Bahirusa alfurus). The tusks of this animal continue growing during life. Those of the upper jaw are directed upward from the base so that they do not enter the mouth, but pierc- ing the skin of the face, resemble horns rather than teeth, and curve backwards and downwards. (Flower, Study of Mammals.) marine animals, can have no relation to this weapon. We may, however, suppose that the tusk was originally developed as a defence against some enemy, when the narwhal itself was smaller, and had a wider range beyond the Arctic seas which it now inhabits; and when the enemv had become extinct this strange weapon went on increasing through the law of germinal selection, and has thus become useless to the existing animaL EXTEiS^SIOXS OF DAEWIXISM 297 The other case is that of the equally remarkable Babinisa of the islands of Celebes and Burn, in which the canines of the males are so developed as to be useless for fighting- (see Fig. 107). Here, too, there can be little doubt that the tusks were originally of the same type as in the wild boar, and were used for both attack and defence; but the ancestral form hav- ing been long isolated in a country where there were no ene- mies of importance, natural selection ceased to preser\'e thom in their original useful form, and the initial curvature became increased by germinal selection, while natural selection only checked such developments as would be injurious to the in- dividuals which exhibited them. A Wider Application of the Principle of Germ-Selection But it seems to me that the principle here suggested has a still higher importance, inasmuch as it has been the normal means of adding to and intensifying that endless varietv of form, that strange luxuriance of outgrowths, and that ex- quisite beauty of marking and brilliancy of colour, that ren- der the world of life an inexpressible delight to all who have been led to observe, to appreciate, or to study it. It is through the action of some such internal selecting agency that we owe much of what we must call the charming eccentricity of nature — of those exuberances of growth which cause the nature- lover to perpetually exclaim, " What can be the use of this ? '* In the birds-of-paradise we had long known of the tail- feathers, the breast-shields, the masses of plumage from under the wings, the crests, the neck-tippets, all in wonderful variety of shape and colour. Then, in the island of Batch iau 1 ob- tained a bird in which from the bend of the wing (correspond- ing to our wrist) there spring two slender and flexible white feathers on each side standine; out from the wine: durinc: ilii^ht, whence it has been termed the standard-winged bird-of-para- dise. Again, a few years ago, there was discovered in the mountains of German 'New Guinea another quite new type, in which, from the corner of each eye, a long plume arises more 208 THE WORLD OF LIFE than twice the length of the bird's body, and having, on one side only of the midrib, a series of leaf-shaped thin horny plates of a beautiful light-blue colour on the upper surface, contrasting in a striking manner with the purple black, ochre yellow, and rusty red of the rest of the plumage. In the comparatively small number of birds-of -paradise now known, we have a series of strange ornamental plumes w^hich in their shape, their size, their colours, and their point of origin on the bird, exhibit more varietv than is found in any other family of birds, or perhaps in all other known birds ; and we can now better explain this by the assistance of Weis- mann's law in a highly dominant group inhabiting a region which is strikin^'lv deficient in animals wdiich are inimical to bird-life in a densely forest-clad country. To this same principle we must, I think, impute that su- perfluity of dazzling colour in many birds, but more especially in many insects, in which it so often seems to go far beyond usefulness for purposes of recognition, or as a warning, or a distracting dazzle to an attacking enemy. Even in the vegetable kingdom this same law may have acted in the production of enoiTQOus masses of flowers or of fruits, far beyond the needful purpose of perpetuating the species ; and probably also of those examples of excessive bril- liancy of colour, as in the intense blues of many gentians, the vivid scarlet of the Cardinal lobelia, or the glistening yellow of many of our buttercups. It is quite possible, therefore, that to this principle of ^' germinal selection " we owe some of the most exquisite refinements of beauty amid the endless variety of form and colour both of the animal and the veg- etable world. We may also owe to it the superabundant production of sap which enabled the early colonists of America to make almost imlimited quantities of sugar from the '^ sugar maple." Each tree will yield about four pounds of sugar yearly from about thirty gallons of sap ; and it is stated by Lindley that a tree wull yield this quantity for forty years without being at EXTENSIONS OF DARWINISM 299 all injured; and large quantities of such sugar are still made for home consumption, the molasses produced from ii l)oing said to be superior in flavour to that from the sugar-cane. Here surely is a verv renuirkable case of an excessive sur- plus product which is of gTcat use to man, and, so far as we can see, to man only. The same phenomenon of a sur- plus product is presented by the Para rubber-trees (Sii)h«jnia, many species), from which, at the pro]ier season, larttc quan- tities of the precious sap can be withdrawn annually for very long periods, without injuring the trees, or producing a dimi- nution of the supply. There are also many other useful veg- etable products, among those referred to in our fifteenth chaj)- ter, to which the same remark will apply ; and it seems prrib- able that we owe the whole of these, and many others not yet discovered in the vast unexplored tropical forests, to this far- reaching principle of " germinal selection.'^ General Conclusions as to Life-Development Before quitting the subject of the course of development of the entire world of life as shown by the geological record, to which the present chapter is in a measure supplementary, it will be w^ell to say something as to its broader features from the point of view adopted in this work. This is, that beyond all the phenomena of nature and their immediate causes and laws there is Mind and Purpose; and that the ultimate pur- pose is (so far as we can discern) the development of mankind for an enduring spiritual existence. With this object in view- it would be important to supply all possible aids that a ma- terial world can give for the training and education of man's higlier intellectual, moral, and aesthetic nature. If this view is the true one, we may look upon our Universe, in all its parts and durinc; its whole existence, as slowlv ]>ut surelv marchiui:: onwards to a predestined end ; and this involves the further conception, that now that man /m.s^ boon dovolojiod, tliat lio is in full possession of this earth, and that upon his proper use of it his adequate preparation for the future life depends, then 300 THE WORLD OF LIFE a great responsibility is placed upon him for the way in which he deals with this his great heritage from all the ages, not only as regards himself and his fellows of the present generation, but towards the unknown multitude of future generations that are to succeed him. x\ll of us who are led to believe that there must be a being or beings high and powerful enough to have been the real cause of the material cosmos with its products life and mind, can hardly escape from the old and much-derided view, that this world of ours is the best of all possible worlds calculated to bring about this result. And if the best for its special pur- pose, then the whole course of life-development was the best; then also every step in that development and every outcome of it which we find in the living things which are our con- temporaries are also the best — are here for a purpose in some way connected with us; and if in our blind ignorance or prejudice we destroy them before we have earnestly endeav- oured to learn the lesson thev are intended to teach us, w^e and our successors will be the losers — morally, intellectually, and perhaps even physically. Already in the progress of this work I have dwelt upon the marvellous variety of the useful or beautiful products of the vegetable and animal kingdoms far beyond their o^^TL uses, as indicating a development for the ser^uce of man. This variety and beauty, even the strangeness, the ugliness, and the unex- pectedness we find everywhere in nature, are, and therefore were intended to be, an important factor in our mental de- velopment ; for they excite in us admiration, wonder, and curiosity — the three emotions which stimulate first our at- tention, then our determination to learn the how and the why, which are the basis of observation and experiment and there- fore of all science and all philosophy. These considerations should lead us to look upon all the works of nature, animate or inanimate, as invested with a certain sanctity, to be used by us but not abused, and never to be recklessly destroyed or de- faced. To pollute a spring or a river, to exterminate a bird EXTENSIONS OF DARWINISM 301 or beast, should be treated as moral offences and as social crimes; while all who profess religion or sincerely believe in the Deity — the designer and maker of this world and of every living thing — should, one would have thought, have placed this among the first of their forbidden sins, since to deface or destroy that which has been brought into existence for the use and enjoyment, the education and elevation of the human race, is a direct denial of the wisdom and goodness of the Creator, about which thej so loudly and persistently prate and preach. Yet during the past century, which has seen those great ad- vances in the Tcnowledge of Nature of which we are so proud, there has been no corresponding development of a love or rev- erence for her works ; so that never before has there been such widespread ravage of the earth's surface by destruction of native vegetation and with it of much animal life, and such wholesale defacement of the earth by mineral workings and by pouring into our streams and rivers the refuse of manufac- tories and of cities; and this has been done by all the greatest nations claiming the first place for civilisation and religion ! And what is Avorse, the greater part of this waste and devas- tation has been and is being carried on, not for any good or worthy purpose, but in the interest of personal greed and avarice; so that in every case, while wealth has increased in the hands of the few, millions are still living without the bare necessaries for a healthy or a decent life, thousands dying yearly of actual starvation, and other thousands being slowly or suddenly destroyed by hideous diseases or accidents, directly caused in this cruel race for wealth, and in ahuost everv case easily preventable. Yet they are not ])revented, solely be- cause to do so would somewhat diminish th(^ })rofits of the capitalists and legislators who are directly responsible for this almost world-wide defacement and destruction, and virtual massacre of the ignorant and defenceless workers. The nineteenth century saw the rise, the development, and the culmination of these crimes against God and man. Let 302 THE WORLD OF LIFE us hope that the twentieth century will see the rise of a truer religion, a purer Christianity; that the conscience of our rulers will no longer permit a single man, woman, or child to have its life shortened or destroyed by any preventable cause, however profitable the present system may be to their employ- ers; that no one shall be allowed to accumulate wealth by the labour of others unless and until every labourer shall have re- ceived sufficient, not only for a bare subsistence, but for all the reasonable comforts and enjoyments of life, including ample recreation and provision for a restful and happy old age. Briefly, the support of the labourers without any injury to health or shortening of life should be a first charge upon the products of labour. Every kind of labour that will not bear this charge is immoral and is unworthy of a civilised com- munity. The Teaching of the Geological Record But this is a digression. Let us now return to a consid- eration of the main features of the course of life-development. The first point to w^hich our attention may be directed is, that the necessary dependence of animal life upon vegetation is the cause of some of the most prominent and perhaps the most puzzling features of the early life-world as presented to us by the geological record. In the Palaeozoic age we already meet with a very abundant and very varied aquatic life, in which all the great classes of the animal kingdom — sponges, zoophytes, echinoderms, worms, Mollusca, and vertebrates — were already fully differentiated from each other as we now find them, and existed in considerable variety and in gi'eat numbers. It is quite possible that the seas and oceans of those remote ages were nearly as full of life as they are now, though the forms of life were less varied and generally of a lower type. But, at the same time, the animal life of the land was very scanty, the only vertebrates that occupied it being a few Am- phibia and archaic reptiles. There were, however, a consid- erable number of primitive centipedes, spiders, Crustacea, and EXTENSIONS OF DARWINISM ;J03 even true insects, the latter having already become specialised into several of our existing orders. All these occur either in the Coal formation of Europe or the Devonian rocks of North America, which seems to imply that when land-vegetation first began to cover the earth a very long period elapsed before any correspondingly abundant animal life was develo])ed ; and this W'as what we, should expect, because it would be necessary for the former to become thoroughly established and developed into a sufficient variety of forms well adapted to all the dif- ferent conditions of soil and climate, in order that they might be able to resist the attacks of the larger plant-feeding animals, as well as the myriads of insects when these appeared. So far as we can judge, the vegetable kingdom was left to develop freely during the enormous series of ages comprised in the Devonian, Carboniferous, and Permian formations, to which we must add the gap between the latter and the Triassic — the first of the Secondary formations. By that time the whole earth had probably become more or less forest-clad, but with vegetation of a Ioav type mostly allied to our ferns and horse- tails, with some of the earliest ancestral forms of pines and cycads. In the succeeding Secondary era the same general type of vegetation prevailed till near its close ; but it was then every- where subject to the attacks of large plant-devouring reptiles, and under this new environment it must necessarilv have started on new lines of evolution tending towards those higher flowering plants which, throughout the Tertiary period, be- came the dominant type of vegetation. It seems probable that throughout the ages animal and vegetable life acted and re- acted on each other. The earliest luxuriant land-vegetation, that which formed the great coal-fields of the earth, was probably adapted to the physical environment alone, almost uninfluenced by the scanty animal life. Then reptiles and mammals were differentiated ; but the former increased more rapidly, being perhaps better fitted to live upon the early vege- tation and to survive in the heavy carbonated atmosphere. This 304 THE WORLD OF LIFE in turn became more varied and better adapted to resist their attacks; and when the new type had become well established it quickly replaced the earlier forms ; and the highly specialised reptiles, unable to obtain sufficient nourishment from it, and being also subject to the attacks of Camivora of increasing power, and perhaps to some adverse climatic changes, quickly disappeared. Then came the turn of the Mammalia, the birds, and the more specialised insects, which, during this vast period, had been slowly developing into varied but always rather diminutive forms, the birds and mammals feeding probably on insects, roots, and seeds; but, in proportion as the reptiles disappeared, they were ready to branch out in various direc- tions, occupying the many places in nature left vacant by these animals, and thus initiated that wonderfully varied mam- malian life which throughout the whole Tertiary period occu- pied the earth's surface as completely, and almost as exclu- sively, as the reptiles had done during the middle ages of geo- logical time. The reactions of insects and flowers are universally ad- mitted, as are those between birds and fruits ; but the broader aspect of this reaction between animal and plant life as a whole has not, I think, received much attention. It does, however, seem to throw a glimmer of light on the very puz- zling facts of the vast development of Secondary reptilian life, the apparent arrest of development of mammals during the whole vast period, and the rapid and abundant outgrowths of the higher types both of plants and of Mammalia in the Tertiary age. The complete metamorphosis, broadly speaking, of both plant and animal life, on passing from the former to the lat- ter epoch, is most startling. Such a change was, however, ab- solutely essential, not only for the production of the higher Mammalia and intellectual man, but also to provide for the infinitely varied needs of man's material, moral, and aesthetic development. The immensely varied plant-group of phanero- gams has served to unlock for his service the myriad potenti- EXTENSIONS OF DARWINISM 305 alities which lay hidden in protoplasm — the mysterious physical basis of all life. To this vast series of herbs and shrubs and forest-trees he owes most of the charms, the deli- cacies, and the refinements of his existence — almost all his fruits, most of his scents and savours, together with a large part of the delight he experiences in mountain and valley, forest, copse, and flower-spangled meadow, whieli everywhere adorn his earthly dwelling-place. To this we must add the infinitely varied uses to man of domestic animals, all supplied by the higher Mammalia or birds, while no single reptile has ever occupied or seems able to occupy the same place. We can only speculate on the part these have played in man's full development, but it must have been a great and an important one. The caring for cattle and sheep, the use of milk, butter, and cheese, and the weaving of wool and preparation of leather, must have all tended to raise him from the status of a beast of prey to that of the civilised being to whom some animals at all events became helpers and friends. And this elevation was carried a step further when the horse and the dog became the companions of his daily life, while fowls, pigeons, and various singing- birds added new pleasures and occupations to his home. That such creatures should have been slowly evolved so as to reach their full development at the very time when lie became able to profit by them must surely be accepted as additional evi- dence of a foreseeing mind which, from the first dawn of life in the vegetable and animal cells, so directed and organised that life, in all its myriad forms, as, in the far-off future, to provide all that was most essential for the growth and develop- ment of man's spiritual nature. In furtherance of this subject it would be necessary to put a definite bar to the persistence of a lower type which might have prevented or seriously checked the development of the higher forms destined to succeed them ; and this seems to have been done in the case of the ]^^esozoic reptiles by endowing them with such a limited amount of intelligent vitalitv as 306 THE WORLD OF LIFE would not lead to its automatic increase under the stress of a long course of development, though accompanied by continual change of conditions and enormous increase in size. Hence the " ridiculously small brains " (as they have been termed) of these huge and varied animals. We may learn from this phenomenon, and the parallel case of the huge Dinocerata among the Tertiary mammals, that development of a varied form and structure through the struggle for existence does not necessarily lead to an increase in intelligence or in the size and complexity of its organ the brain, as has been generally as- sumed to be the case. If, as John Hunter, T. H. Huxley, and other eminent thinkers have declared, '' life is the cause, not the consequence, of organisation,'' so we may believe that mind is the cause, not the consequence, of brain development. The first implies that there is a cause of life independent of the organism through which it is manifested, and this cause must itself be persistent — eternal — life, any other supposition being es- sentially unthinkable. And if we must posit an eternal Life as the cause of life, we must equally posit an eternal Mind as the cause of mind. And once accept this as the irreducible minimum of a rational belief on these two great questions, then the whole of the argument in this volume falls into logical sequence. Life as a cause of organisation is as clearly manifested and as much a necessity in the plant as in the animal; but they are plainly different kinds (or degrees) of life. So there are undoubtedly different degrees and probably also dif- ferent kinds of mind in various grades of animal life. And as the life-giver must be supposed to cause the due amount and kind of life to flow or be dra^vn into each organism, from the universe of life in which it lives, so the mind-giver, in like manner, enables each class or order of animals to obtain the amount of mind requisite for its place in nature, and to or- ganise a brain such as is required for the manifestation of that limited amount of mind and no more. EXTEIsrSIO:N^S OF DARWINISM 307 Thus and thus only, as it seems to mo, can we under- stand the raison d' etre of these small-brained animals. They were outgi'owths of the great tree of life for a temporary pur- pose, to keep doA\Ti the coarser vegetation, to supply animal food for the larger Carnivora, and thus give time for higher forms to obtain a secure foothold and a sullicient amount of varied form and structure, from which they could, when bet- ter conditions prevailed, at once start on those wonderful di- verging lines of advance which have resulted in the perfected and glorious life-world in the midst of which we live, or ought to live. This view of the purport, the meaning, and the higher func- tion of the gTcat and varied life-world brings us by a differ- ent route to what many of our better thinkers and teachers have tried to impress upon us — • that our great cities are the " wens,'' the disease-products of humanity, and that until they are abolished there can be no approach to a true or rational civilisation. This was the teaching of that true and far-seeing child of nature, William Cobbett; it is the teaching of all our greatest sanitarians ; it is the teaching of Nature herself in the com- parative rural and urban death-rates. Yet we have no legis- lator, no minister, who will determinedly set himself to put an end to the continued growth of these " wens " ; which are wholly and absolutely evil. I will, therefore, take this oppor- tunity of showing how it can be done. There is much talk now of what will and must be the growth of London during the next twenty or fifty years ; and of the necessity of bringing water from Wales to su})])ly the increased pojjulation. But where is the necessity ? Why pro- vide for a population which need never have existed, and whose coming into existence will be an evil and of no pos- sible use to any human beings but the landowners and specu- lators, who will make money by the certain injury of their fellow-citizens. If the House of Commons and the l>ondt»n County Council are not the bond-slaves of the landowners and 308 THE WOELD OF LIFE speculators, they have only to refuse to allow any further water-supply to be provided for London except what now ex- ists, and London will cease to grow. Let every speculator have to provide water for and on his own estate, and the thing will be done — to the enormous benefit of humanity. The same thing can, I presume, be done by Parliament for any other growing town or city. It can justly say : '^ When you have not a gallon of polluted water in your town, and when its death-rate is brought down to the average standard of rural areas, we will reconsider the question of your further growth.'' By that time, probably, there will be no public de- mand for enlarging our " wens '' and a very strong and stem, one for their cure or their abolition. / CHAPTER XIV BIRDS AND INSECTS : AS PROOFS OF AN OKGANISING AND DIRECTIVE LIFE-PRINCIPLE If we strip a bird of its feathers so that we can see its bodj- structure as it really is, it appears as the most ungainly and misshapen of living creatures ; yet there is hardly a bird but in its natural garment is pleasing in its form and motions, while a large majority are among the most beautiful in shape and proportions, the most graceful in their activities, and often the most exquisite and fascinating of all the higher animals. The fact is, that the feathers are not merely a surface-clothing for the body and limbs, as is the hairy covering of most mam- mals, but in the wing and tail-feathers form an essential part of the structure of each species, without which it is not a com- plete individual, and could hardly maintain its existence for a single day. The whole internal structure has been gradually built up in strict relation to this covering, so that every part of the skeleton, every muscle, and the whole of the vascular system for blood-circulation and aeration have been slowly modified in such close adaptation to the whole of the plumage that a bird without its feathers is almost as helpless as a mam- mal which has lost its limbs, tail, and teeth. Although birds are so highly organised as to rival mam- ' mals in intelligence, while they surpass them in activity and in their high body -temperature, yet they owe this position to an extreme retrogressive specialisation resulting in the com- plete loss of the teeth, while the digits of the fore limb are re- duced to three, the bones of which are more or less united, and, though slightly movable, are almost entirely hidden under tho skin. The earliest fossil bird, the Arch^eopteryx, bad throe ap- 301) 310 THE WORLD OE LIFE parentlj free and movable digits on the fore limbs, each end- ing in a distinct claw ; while the two bones forming the fore- arm appear to have been also free and movable, so that the wing must have been much less compact and less effective for flight than in modern birds. This bird was about as large as a rook, but with a tail of twenty vertebra', each about half an inch long and bearing a pair of feathers, each four inches in length and half an inch broad, while the wing feathers were nearly twice as long. The almost complete disappearance of the unwieldy tail, with the fusing together of the wing-bones, must have gone on continuously from that epoch. In the Cretaceous period the long tail has disappeared, and the wing- bones are much more like those of living birds; but the jaws are still toothed. In the early Tertiary deposits bird-remains are more numerous, and some of the chief orders of modern birds seem to have existed, while a little later modern families and genera appear. The important point for our consideration here is that, in the very earliest of the birds yet discovered which still re- tained several reptilian characteristics, true feathers, both of wings and tail, are so clearly shown as to leave no doubt of their practical identity with those of living birds. It is therefore evident that birds with feathers began to be developed as early as (perhaps even earlier than) the mem- branous-winged reptiles (Pterodactyles), and that these two groups of flying vertebrates began on two opposite principles. The birds must have started on the principle of condensation and specialisation of the fore limb exclusively for flight by means of feathers ; the other by the extension of one reptilian digit to support a wing-membrane, while reserving the others probably for suspension, as in the case of the thumb of the bats. The Marvel and Mystery of Feathers Looking at it as a whole, the bird's wing seems to me to be, of all the mere mechanical organs of any living thing, PKOOIS OJ^^ OKGANiSi^'G Aili\D 311 that ^vhicli most clearly implies the working out of a j^recon- ceived design in a new and apparently most complex and dilli- cult manner, yet so as to produce a marvellously successful re- sult. The idea worked out was to reduce the jointed bony framework of the wings to a compact minimum of size and maximum of strength in proportion to the muscular power employed ; to enlarge the breastbone so as to give room for greatly increased power of pectoral muscles; and to construct that part of the wing used in flight in sucli a manner as to combine great strength with extreme lightness and the most perfect flexibility. In order to produce this more perfect in- strument for flight the plan of a continuous membrane, as in the flying reptiles (whose origin was probably contcm})ora- neous with that of the earliest birds) and flying mammals, to be developed at a much later period, was rejected, and its placo was taken by a series of broad overlapping oars or vanes, formed by a central rib of extreme strength, elasticity, and lightness, with a web on each side made up of myriads of parts or outgrowth so wonderfully attached and interlocked as to form a self-supporting, highly elastic structure of almost in- conceivable delicacy, very easily pierced or ruptured by the impact of solid substances, yet able to sustain almost any amount of air-pressure without injury. And even when any part of this delicate web is injured by separating the adjacent barbs from each other, they are so wonderfully constructed that the pressure and movement of other feathers over them causes them to unite together as firmly as before ; and this is done not by any process of gro^vth, or by any adhesive exudation, but by the mechanical structure of the delicate hooked lamelhn of which they are composed. The two illustrations here given (Figs. lOS, lOD) show two of the adjacent fibre-like parts (barbs) of which the web of a bird's feather is composed, and which are most clearly shown in the wing-feathers. Tlie slender barbs or ribs of which the web of the feather is made up can be best understood by strip- ping off a portion of the wel) and separating two of the barbs 312 THE WOELD OE LIEE from the rest. With a good lens the structure of the barbs, with their delicate hooked barbules interlocking with the bent- out upper margins of the barbules beneath them, can be seen, as shown in the view and section here given. The barbs (B, Magnified View of the Barbs and Barbules forming the Web of a Bird's Wing-Feathers (X 50). Fig. 108. — 'View of a portion of two adjacent Barbs (B, B), looking from the Shaft towards the edge of the Feather. bd, distal barbules; bp, proximal barbules. Fig. 109. — Oblique Section through the Proximal Barbules in a plane par- allel to the Distal Barbules of the upper Figure. Letters as above ; 1, 2, 3, barbicels and hamuli of the ventral side of the distal barbule; 4, barbicels of the dorsal side of the same, without hamuli. (From Newton's Dictionary of Birds.) B in the figures) are elastic, homj plates set close together on each side of the midrib of the feather, and pointing obliquely outwards; while the barbules are to the barbs what the barbs are to the feather — excessively delicate horny plates, which PKOors OF oega:xising mind 313 also grow obliquely outwards towards the tip of the barb. Laterally they touch each other with smooth, glossy surfaces, which are almost air-tight, yet allow whatever slight motions that may be required during use, while remaining interlocked with the barbules of the adjoining barb in the manner just de- scribed. They are the essential elements of the feather, on which its value both for flight and as a protective clothing depends. Even in the smallest wing- feathers they are probably a liundred thousand in number, since in the long wing-feather of a crane the number is stated by Dr. Hans Gadow to be more than a million. What are termed the " contour-feathers " are those that clothe the whole body and limbs of a bird with a garment of extreme lightness which is almost comj^letely impen-ious to either cold or heat. These feathers vary greatly in shape on different parts of the body, sometimes forming a dense velvety covering, as on the head and neck of many species, or de- veloped into endless variety of ornament. They fit and overlap each other so perfectly, and entangle so much air between them, that rarely do birds suffer from cold, except when un- able to obtain any shelter from violent storms or blizzards. Yet, as everv sino'le feather is movable and erectile, the whole bodv can be freely exposed to the air in times of oppressive heat, or to dry the feathers rapidly after bathing or after unusually heavy rain. A great deal has been written on the mechanics of a bird's flight, as dependent on the form and curvature of the feathers and of the entire wing, the powerful muscular arrangements, and especially the perfection of the adjustment by which dur- ing the rapid do^vn-stroke the combined feathers constitute a perfectly air-tight, exceedingly strong, yet highly elastic in- strument for flight ; while the moment the upward motion be- gins the feathers all turn upon their axes so that the air passes between them with hardly any resistance, and when they again begin the down-stroke close up nutomatically as air-tight as before. Thus the effective down-strokes follow each other so 314 THE WOKLD OE LIFE rapidly that, together with the support given by the hinder portion of the wings and tail, the onward motion is kept up, and the strongest flying birds exhibit hardly any undulation in the course they are pursuing. But very little is said about the minute structure of the feathers themselves, which are what renders perfect flight in almost every change of conditions a possibility and an actually achieved result. But there is a further difference between this instrument of flight and all others in nature. It is not, except during actual growth, a part of the living organism, but a mechanical instrument which the organism has built up, and which then ceases to form an integral portion of it — is, in fact, dead mat- ter. Hence, in no part of the fully grown feather is there any blood circulation or muscular attachment, except as re- gards the base, which is firmly held by the muscles and ten- dons of the rudimentary hand (fore limb) of the bird. This beautiful and delicate structure is therefore subject to wear and tear and to accidental injury, but probably more than any- thing else by the continuous attrition during flight of dust- laden air, which, by wearing away the more delicate parts of the barbules, renders them less able to fulfil the various purposes of flight, of body-clothing, and of concealment, as well as the preservation of all those colours and markings which are especially characteristic of each species, and generally of each sex separately, and which, having all been developed under the law of utility, are often as important as structural characters. Provision is therefore made for the annual renewal of every feather by the process called moulting. The important wing- feathers, on which the very existence of most birds depends, are discarded successively in pairs at such intervals as to allow the new growth to be Avell advanced before the next pair are thrown off, so that the bird never loses its power of flight, though this may be somewhat impaired during the process. The rest of the plumage is replaced somewhat more rapidly. This regrowth every year of so complex and important a part of a bird's structure, always reproducing in every feather PROOFS OF OEGAKISIKG MIIS'J) 315 the size and shape characteristic of the species, Avhile each of the often very diverse feathers grows in its right place, and re- produces the various tints and colours on certain parts of every feather which go to make up the characteristic colours, markings, or ornamental plumes of each species of bird, presents us with the most remarkable cases of heredity, and of ever-present ac- curately directed growth-power, to be found in the whole range of organic nature. The Nature of Growth The growth of every species of organism into a highly com- plex form, closely resembling one or other of its parents, is so universal a fact that, \vith most people, it ceases to excite won- der or curiosity. Yet it is to this day absolutely inexplicable. No doubt an immense deal has been discovered of the mech- anism of growth, but of the nature of the forces at work, or of the directive agencies that guide and regulate the forces, we have nothing but the vaguest hints and conjectures. All growth, animal or vegetable, has been long since ascertained to begin with the formation and division of cells. A cell is a minute mass of protoplasm, a substance held to be the physical basis of life. This is, chemically, the most complex substance known, for while it consists mainly of four elements — car- bon, hydrogen, nitrogen, and oxygen — it is now ascertained that eight other elements are always present in cells composed of it — sulphur, phosphorus, chlorine, potassium, sodium, magnesium, calcium, and iron. Besides these, six others are occasionally found, but are not essential constituents of pro- toplasm. These are silicon, fluorine, bromine, iodine, alumi- nium, and manganese.^ Protoplasm is so complex a substance, not only in the num- ber of the elements it contains, but also in the mode of their chemical combination, that it is quite beyond the reach of chemical analysis. It has been divided into throe groups of chemical substances — proteids, carbohydrates, and fats. The 1 Verworu's General Physiology, p. 100. 316 THE WOKLD OF LIFE first is always present in cells, and consists of five elements — carbon, hydrogen, sulphur, nitrogen, and oxygen. The two other groups of organic bodies, carbohydrates and fats, con- sist of three elements only — carbon, hydrogen, and oxygen, the carbohydrates forming a large proportion of vegetable products, the fats those of animals. These also are highly complex in their chemical structure, but being products rather than the essential substance of living things, they are more amenable to chemical research, and large numbers of them, including vegetable and animal acids, glycerin, grape sugar, indigo, caifeine, and many others, have been produced in the labora- tory, but always by the use of other organic products, not from the simple elements used by nature. The atomic structure of the proteids is, however, so wonder- fully complex as to be almost impossible of determination. As examples of recent results, haemoglobin, the red colouring matter of the blood, was found by Preyer in 1866 to be as follows — ^eoo-tlgeo-^ 154-'^ ^1^3^179? showing a total of 1894 atoms, while Zinoffsky in 1855 found the same substance from horse's blood to be — C'7i2-tiii3o-'^ 214^245!' 6l^2> showing a total of 2301 atoms. Considering the very small number of atoms in inorganic compounds, and in the simpler vegetable and animal products, caffeine containing only 23 (C7H7(CH3)N402), the complexity of the proteids will be more appreciated. Professor Max Verworu, from whose gTeat work on General Physiology the preceding account is taken, is very strong in his repudiation of the idea that there is such a thing as a '' vital force." He maintains that all the powers of life reside in the cell, and therefore in the protoplasm of which the cell consists. But he recognises a great difference between the PEOOFS OF OKGANISING MIND 317 dead and the living cell, and admits that our knowledge of the latter is extremely imperfect. He enumerates many differ- ences between them, and declares that '' substances exist in liv- ing which are not to be found in dead cell-substance." He also recognises the constant internal motions of the living cell, the incessant waste and repair, while si ill preserving the highly complex cell in its integrity for indefinite periods; its resist- ance during life to destructive agencies, to which it is exposed the moment life ceases ; but still there is no '" vital force " — to postulate that would be unscientific. Yet in this highly elaborate volume of 600 closely printed pages, dealing with every aspect of cell-structure and physiol- ogy in all kinds of organisms, he gives no clue whatever to the existence of any directive and organising powers such as are absolutely essential to preserve even the unicellular organism alive, and which become more and more necessary as we pass to the higher animals and plants, with their vast complexity of organs, reproduced in every successive generation from single cells, which go through their almost infinitely elaborate processes of cell-division and recomposition, till the whole vast complex of the organic machinery ■ — the whole body, limbs, sense, and reproductive organs — are built up in all their per- fection of structure and co-ordination of parts, such as char- acterises every living thing ! Let us now recur to the subject that has led to this digres- sion — the feathers of a bird. We have seen that a full-gi'own wing-feather may consist of more than a million distinct parts — the barbules, which give the feather its essential character, whether as an organ of flight or a mere covering and heat-pre- server of the body. But these barbules are themselves highly specialised bodies with definite forms and surface-texture, attaching each one to its next lateral barbule, and, by a kind of loose hook-and-eye formation, to those of the succeeding barb. Each of these barbules must therefore be built up of many thousands of cells (probably many millions), differing considerably in form and powers of cohesion, in order to pro- 318 THE WORLD OE LIFE cluce the exact strength, elasticity, and continuity of the whole web. Now each feather " grows/' as we say, out of the skin, each one from a small group of cells, which must be formed and nourished by the blood, and is reproduced each year to replace that which falls away at moulting time. But the same blood supplies material for every other part of the body — builds up and renews the muscles, the bones, the viscera, the skin, the nerves, the brain. What, then, is the selective or directing power which extracts from the blood at every point where required the exact constituents to form here bone-cells, there muscle-cells, there again feather-cells, each of which possesses such totally distinct properties ? And when these cells, or rather, perhaps, the complex molecules of which each kind of cell is formed, are separated at its special point, w^hat is the constructive power wdiich welds them together, as it were, in one place into solid bone, in another into contractile muscle, in another into the extremely light, strong, elastic material of the feather — the most unique and marvellous product of life ? Yet again, wdiat is the nature of the power which deteiToines that every separate feather shall always " grow " into its exact shape ? For no two feathers of the twenty or more which form each wing, or those of the tail, or even of the thousands on the whole body, are exactly alike (except as regards the pairs on opposite sides of the body), and many of these are modified in the strangest way for special purposes. Again, what directive a2:encv determines the distribution of the col- ouring matter (also conveyed by the blood) so that each feather shall take its exact share in the production of the whole pattern and colouring of the bird, which is immensely varied, yet always symmetrical as a whole, and has always a purpose, either of concealment, or recognition, or sexual attraction in its proper time and place ? Xow, in none of the volumes on the physiology of animals that I have consulted can I find any attempt whatever to grapple Avith this fundamental question of the directive power PROOFS OF ORGANISING MIND 319 that, in every case, first secretes, or as it were creates, out of the protoplasm of the blood, special molecules adapted for the 2:>roductiou of each malcrial — bone, muscle, nerve, skin, hair, feather, etc. etc., — carries these molecules to the exact part of the body where and when they are required, and brings into play the complex forces that alone can 1)uild up with (ri-eat rapidity so strangely complex a structure as a feather adapted for flight. Of course the difficulties of conceiving how this has been and is being done before our eyes is nearly as great in the case of any other specialised part of the animal body; but the case of the feathers of the bird is unique in many ways, and has the advantage of being wdiolly external, and of being familiar to every one. It is also easily accessible for examina- tion either in the living bird or in the detached feather, which latter offers wonderful material for microscopic examination and study. To myself, not all that has been written about the properties of protoplasm or the innate forces of the cell, neither the physiological units of Herbert Spencer, the pan- genesis hypothesis of Darwin, nor the continuity of the germ- plasm of Weismann, throw the least glimmer of light on this great problem. Each of them, especially the last, help us to realise to a slight extent the nature and laws of heredity, but leave the great problem of the nature of the forces at work in growth and reproduction as mysterious as ever. IModern physiologists have given us a vast body of information on the structure of the cell, on the extreme complexity of the proc- esses which take place in the fertilised ovum, and on the exact nature of the successive changes up to the stage of maturity. But of the forces at work, and of the power which guides those forces in building up the whole organ, we find no enlighten- ment. They will not even admit that any such constructive guidance is required ! * A Physiological Allegory For an imaginary parallel to this state of tliinirs, let us suppose some race of intellia'cut beings wlio have tlie j)Ower 320 THE WORLD OF LIFE to visit the earth and see what is going on there. But their faculties are of such a nature that, though they have perfect perception of all inanimate matter and of plants, they are absolutely unable either to see, hear, or touch any animal living or dead. Such beings would see everywhere matter in motion, but no apparent cause of the motion. They would see dead trees on the ground, and living trees being eaten away near the base by axes or saws, which w^ould appear to move spon- taneously; they would see these trees gradually become logs by the loss of all their limbs and branches, then move about, travel along roads, float down rivers, come to curious machines by which they are split up into various shapes ; then move away to where some great structure seems to be growing up, where not only wood, but brick and stone and iron and glass in an infinite variety of shapes, also move about and ultimately seem to fix themselves in certain positions. Special students among these spirit-inquirers would then devote themselves to follow back each of these separate materials — the wood, the iron, the glass, the stone, the mortar, etc. — to their sep- arate sources; and, after years thus spent, would ultimately arrive at the great generalisation that all came primarily out of the earth. They would make themselves acquainted with all the physical and chemical forces, and would endeavour to explain all they saw by recondite actions of these forces. They would argue that what they saw was due to the forces they had traced in building up and modifying the crust of the earth ; and to those who pointed to the result of all this ^' mo- tion of matter " in the finished product — the church, the mansion, the bridge, the railway, the huge steamship or cotton factory or engineering works — as positive evidence of design, of directive power, of an unseen and unknown mind or minds, they would exclaim, " You are wholly unscientific ; we know the physical and chemical forces at work in this curious world, and if we study it long enough we shall find that known forces will explain it all." If we suppose that all the smaller objects, even if of the PEOOFS OF ORGANISING MIXD :]21 same size as ourselves, enn only he seen by microscopes, and that with improved instruments the various tools we use, as well as our articles of furniture, our food, and our tahlc-fit tings (knives and forks, dishes, glasses, etc., and even our watches, our needles and pins, etc.) become perceptible, as well as the food and drinks which are seen also to move about and dis- appear; and when all this is observed to recur at certain def- inite intervals every day, there woidd be great jubihition over the discovery, and it would be loudly proclaimed that with still better microscopes -all would be explained in terms of matter and motion ! That seems to me very like the position of modern physiol- ogy in regard to the processes of the growth and development of living things. Insects and their Metamorphosis We now have to consider that vast assemblage of small winged organisms constituting the class Insect a, or insects, which may be briefly defined as ringed or jointed (annuluse) animals, with complex mouth-organs, six legs, and one or two pairs of wings. They are more numerous in species, and perhaps also in individuals, than all other land-animals put together; and in either their larval or adult condition supi)ly so large and important a part of the food of birds, that the existence of the latter, in the variety and abundance we now behold, may be said to depend upon the former. The most highly developed and the most abundant of the insect tribes are those which possess a perfect metamorphosis, that is, which in their larval state are the most comi)letely unlike their perfect condition. They comprise the great orders Lepidoptera (butterflies and moths), Coleojitera (beetles), Hymenoptera (bees, ants, etc.), and Diptc^-a (two-winged flies), the first and last being those which are perha])s the most important as bird-food. In all these orders the eggs produce a minute aTub, maggot, or caterpillar, a- they are variously called, the first havino- a distinct head but no legs, the second 322 THE WORLD OF LIFE neither head nor legs, while the third have both head and legs, and are also variously coloured, and often possess spines, horns, hair-tufts, or other appendages. Every one knows that a caterpillar is almost as different from a butterfly or moth in all its external and most of its internal characters, as it is possible for any two animals of the same class to be. The former has six short feet with claws and ten fleshy claspers; the latter, six legs, five- jointed, and with subdivided tarsi; the foi-mer has simple eyes, biting jaws, and no sign of wings; the latter, large compound eyes, a spiral suctorial mouth, and usually four large and beauti- fully coloured wrings. Internally the whole muscular system is quite different in the two forms, as well as the digestive organs, while the reproductive parts are fully developed in the latter only. The transformation of the larva into the per- fect insect through an intervening quiescent pupa or chrysalis stage, lasting from a few days to several months or even years, is substantially the same process in all the orders of the higher insects, and it is certainly one of the most marvellous in the whole organic world. The untiring researches of modern ob- servers, aided by the most perfect microscopes and elaborate methods of preparation and observation, have revealed to us the successive stages of the entire metamorphosis, which has thus become more intelligible as to the method or succession of stages by which the transformation has been effected, though leaving the fundamental causes of the entire process as mys- terious as before. Years of continuous research have been devoted to the subject, and volumes have- been Avritten upon it. One of the most recent English writers is Mr. B. Thompson Lowne, F.E.C.S., who has devoted about a quarter of a cen- tury to the study of one insect — the common blow-fly — on the anatomy, physiology, and development of w^hich he has published an elaborate work in two volumes dealing with every part of the subject. He considers the two-winged flies to be the highest development of the insect-type ; and though they have not been so popular among entomologists as the Coleoptera PEOOFS OF ORGAXISLXG MLXl) and Lepidoptera, he believes them to be the most nnmenjus in species of all the orders of insects. 1 will now endeavour to state in the fewest words possible tbe general results of his studies, as well as those of the students of the other orders mentioned, which are all in substantial agreement. In those insects which have the least comi)lete metamorpho- sis — the cockroaches — the young emerge from the egg with the same general form as the adult, but with rudimentarv wings, the perfect wrings being acquired after a succession of moults. These seem to be the oldest of all insects, fossilised remains of a similar type being found in the Silurian forma- tion. Locusts and Hemiptera are a little more advanced, and are less ancient geologically. Between these and the four orders with complete metamorphosis there is a great gap, which is not yet bridged over by fossil forms. But from a minute study of the development of the egg, which has been examined almost hour by hour from the time of its fertilisation, the conclusion has been reached, that the great difference we now see between the larva and imago (or perfect insect) has been brought about by a double process, simultaneously going on, of progression and retrogression. Starting from a form some- what resembling the cockroach, but even lower in the scale of organisation, the earlier stages of life have become more sim- plified, and more adapted (in the case of Lepidoptera) for converting living tissues of plants into animal protoplasm, thus laying up a store of matter and energy for the development of the perfect insect ; wdiile the latter form has become so fully developed as to be almost independent of food-supply, by being ready to carry out the functions of reproduction within a few days or even hours of its emergence from the pupa case. At first this retrogression of the first stage of growth towards a simple feeding machine took place at the period of the suc- cessive moults, but it being more advantageous to hav(^ the larva stage wholly in the form best adaptcMl for the storing up of living protoplasm, the retrogressive variations became stop by step earlier, and at length occurred within the egg. At 324 THE WOELD OF LIFE this early period certain rudiments of wings and other organs are represented by small groups of minute cells termed by Weismann imaginal discs, which were determined by him to be the rudiments of the perfect insect. These persist un- changed through the whole of the active larval stage ; but as soon as the final rest occurs preliminary to the last moult, a most wonderful process commences. The whole of the internal organs of the larva — muscles, intestines, nerves, respiratory tubes, etc. — ■ are gradually dissolved into a creamy pulp ; and it has further been discovered that this is effected through the agency of white blood-corpuscles or phagocytes, which enter into the tissues, absorb them, and transform them into the creamy pulp referred to. This mass of nutritive pulp thence- forth serves to nourish the rapidly growing mature insect, with all its wonderful complication of organs adapted to an entirely new mode of life. There is, I believe, nothing like this complete decomposi- tion of one kind of animal structure and the regrowth out of this broken-down material — which has thus undergone decom- position of the cells, but not apparently of the protoplasmic molecules — to be found elsewhere in the whole course of organic evolution; and it introduced new and tremendous dif- ficulties into any mechanical or chemical theory of growth and of hereditary transmission. We are forced to suppose that the initial stages of every part of the perfect insects in all their wonderful complexity and diversity of structure are formed in the egg, and that during the subsequent raj^idly growing development of the larva they remain dormant ; then, that the whole structure of the fully grown larva is resolved into its constituent molecules of living protoplasm, still without the slightest disturbance of the rudimentary germs of the perfect insect, which at a special moment begin a rapid course of de- velopmental growth. This growth has been followed, step by step through all its complicated details, by ^Ir. Lowne and many other enthusiastic workers , but I will call attention here PEOOFS OF ORGANISING AilXD 325 only to the special case of the Lepidoptera, l)ocnu>c these are far more popuLarly known, and the special feature which dis- tinguishes them from most other insects is fauiiliar to every one, and can be examined by means of a good pocket lens or microscope of moderate power. I allude, of course, !<• the •wonderful scales Avhich clothe the wings of most buttcrllics and moths, and which produce the brilliant colours and in- finitely varied patterns with which they are adorned. (){' conrse, the still more extensive order of the C(deoptera (beetles) present a similar phenomenon in the cuh^urs and markings of their wing-cases or elytra, and what is said of the one order will apply broadly to the other. The wings of butterflies can be detected in very young caterpillars when they are only one-sixth of an inch long, as small out-foldings of the inner skin, which remain unchanged while the larva is growing; but at the chrysalis (or pupa) stage the wings ex^iand to about sixty times their former area, and the two layers of cells composing them then become visible. At this time they are as transparent as glass ; but two ur three weeks before emergence of the imago they become opaque white, and a little later dull yellow' or drab; twenty-four hours later the true colours begin to appear at the centre of each wing. It is during the transparent stage that the scales begin tf> Ix* formed as minute, bag-like sacks filled with protoplasm ; the succeeding whiteness is caused by the protoplasm being with- drawn and the sacks becoming filled with air. The pupal blood then enters them, and from this the colouring matter is secreted. The scales are formed in parallel lines along ridges of the corrugated wing membrane. The more bfilliani enloui-s seem to be produced from the dull yellow ]ugment by cheinical chanc'es Avhich occur within the scales. A few davs belore emergence the scales become fullv jxrown, as hii^hlv coniph.'X structures formed of parallel rows of minute cells, each -cale with a basal stem which enters a pocket of the skin or mem- brane, which pockets send out root^ wlii(^h seem to penetrate 326 THE WOKLD OF LIFE through the skin.^ Another complication is the fact that the wonderful metallic colours of so many butterflies are not caused by pigments, but are ^' interference colours " produced by fine striae on the surface of the scales. Of course, where eye-spots, fine lines, or delicate shadings adorn the wings, each scale must have its own special colour, something like each small block in a mosaic picture. As this almost overwhelming series of changing events passes before the imagination, we see, as it were, the gradual but perfectly orderly construction of a living machine, which at first appears to exist for the sole purpose of devouring leaves and building up its own wonderful and often beautiful body, thereby changing a lower into a higher form of protoplasm. Its limbs, its motions, its senses, its internal structure, are all adapted to this one end. Wlien fully grown it ceases to feed, prepares itself for the great change by various modes of con- cealment — in a cocoon, in the earth, by suspension against objects of similar colours, or which it becomes coloured to imitate — rests awhile, casts its final skin, and becomes a pupa. Then follows the great transformation scene, as in the blow-fly. All the internal organs which have so far enabled it to live and grow — in fact, the whole body it has built up, with the exception of a few microscopic groups of cells — be- come rapidly decomposed into its physiological elements, a structureless, creamy but still living protoplasm ; and when this is completed, usually in a few days, there begins at once the building up of a new, a perfectly different, and a much more highly organised creature both externally and internally — a creature comparable in organisation with the bird itself, for which, as we have seen, it appears to exist. And, in the case of the Lepidoptera, the wings, far simpler in construc- tion than those of the bird, but apparently quite as well adapted to its needs, develop a more or less complete covering of minute 1 This description is from Mr. A. G. Mayer's paper on the Development of the Wing Scales of Butterflies and Moths (Bull. Mus. Comp. Zool. Harv. Coll., June 1896), so far as I can give it in a verv condensed abstract. PEOOFS OF OKGA.XISIXG Ail.XD 327 scales, whose chief or only function aijpears tu be tu paint them with all the colours and all tlie glittering reflections of the animal, the vegetable, and the mineral kingdoms, to an equal if not a greater extent than in the case of the birds them- selves. The butterflies, or diurnal Le])idoi)tera alone, not only present us with a range of colour and pattern and of metallic brilliancy fully equal (probably superior), to that of l)irds, but they possess also in a few cases and in distinct families, changeable opalescent hues, in which a pure crimson, or blue, or yellow pigment, as the incidence of light varies, changes into an intense luminous opalescence, sometimes resembling a brilliant phosphorescence more than any metallic or mineral lustre, as described in the next chapter. And what renders the wealth of coloration thus produced the more remarkable is, that, unlike the feathers of birds, tlic special organs upon which these colours and patterns are dis- played are not functionally essential to the insect's existence. They have all the appearance of an added superstructure to the wing, because in this way a greater and more brilliant display of colour could be produced than even upon the ex- quisite plumage of birds. It is true that in some cases, these scales have been modified into scent-a'lands in the males of some butterflies, and perhaps in the females of some moths, but otherwise they are the vehicles of colour alone; and though the diversity of tint and pattern is undoubtedly useful in a variety of ways to the insects themselves, yet it is so almost wholly in relation to higher animals and not to their own kind, as I have already explained in Cluipter IX. It is generally admitted that insects with compound eyes possess imperfect vision, and their actions seem to show that they take little notice of distant objects, except of lights at night, and only perceive distinctly what is a few inches or a few feet from them; while there is no proof tliat they recognise what we term colour unless as a greater or less amount of light. But as regards the effect of the shading and coloration of insects upon the higher animals, who are ahuo^t always their 328 THE WOELD OF LIFE enemies, there is ample evidence. Almost all students of the subject admit that the markings and tints of insects often resemble their environment in a remarkable manner, and that this resemblance is protective. The eye-like markings, either on the upper or under surfaces, are often seen to be imitations of the eyes of vertebrates, when the insect is at rest, and this also is protective. The brilliant metallic or phosphorescent colours on the wings of butterflies may serve to distract ene- mies from attacking a vital part, or, in the smaller species may alarm the enemy by its sudden flash with change of posi- tion. But while the colours are undoubtedly useful, the mode of producing them seems unnecessarily elaborate, and adds a fresh complication in the way of any mechanical or chemical conception of their production. CHAPTER XV GENEBAL ADAPTATIONS OF PLANTS, ANIMAI.S, AND MAN The adaptations of plants and animals, more especially as regards the cross-fertilisation of flowers by insects, forms a very important part of Darwin's work, and has been fully and popularly elaborated since by Grant Allen, Sir John Lub- bock (now Lord Avebury), Hermann ^1 tiller, and many other writers. I have also myself given a general account of the whole subject both in my Tropical Xature, and my Darwin- ism; but as there are some points of importance which, 1 be- lieve, have not yet been discussed, and as the readers of this volume may not be acquainted with the vast extent of the evi- dence, I will here give a short outline of the facts before showing how it bears upon the main argument of the present work. Another reason why it is necessary to recapitulate the evi- dence is that those w^hose knowledge of this subject is derived from having read the Origin of Species only, can have no idea whatever of the vast mass of observations the author of that work had even then collected on the subject, but found it impossible to include in it. He there only made a few general, and often hypothetical, references both to the facts of insect- fertilisation, and to the purpose of cross-fertilisation. On the latter point he makes this general statement: " 1 have come to this conclusion (that flowers are coloured to attract insects) from finding it an invariable rule that when a flower is fertilised bv the wind it never has a ciailv-coloured ('or«)lla.'' Then a few lines farther on he advei'ts to beautifullv coloured fruits and says: "But the beauty servers merely as a guide to birds and beasts, in order tliat the fruit may be devoured and the matured seed disseminated: T infer that this is the case "■20 330 THE WORLD OF LIFE from having as yet found no exception to the rule that seeds are always thus disseminated when embedded within a fruit of any kind if it be coloured of any brilliant tint." ^ Such general statements as those here quoted do not make much impression. The astonishment and delight of botanists and plant-lovers can, therefore, be imagined when, a few years later, by his book on the Fertilisation of Orchids by Insects, and his papers on the Different Forms of Flowers in the prim- rose, flax, lythrum, and some others ; he opened up a vast new world of wonder and instruction which had hitherto remained almost unnoticed. These were followed up by his volumes on The Effects of Cross- and Self -Fertilisation (in 1876), and by that on Different Forms of Flowers on Plants of the same Species (in 1877) giving the result of hundreds of care- ful experiments made by himself during many years, serv'ing as the justification for the few general observations as regards flowers and insects, which form the only reference to the sub- ject in the Origin of Species. The facts now admitted to be established by these various researches are: (1) that crosses between different individuals of the same species, either constantly or occasionally, are ben- eficial to the species by increasing seed-production and vigour of growth; (2) that there are innumerable adaptations in flowers to secure or facilitate this cross-fertilisation; (3) that all irregular flowers — Papilionacese, Labiates, Schrophulari- acese, Orchidese, and others — have become thus shaped to facil- itate cross-fertilisation. Darwin's general conclusion, that " nature abhors perpetual self-fertilisation," has been much criticised, but chiefly by writers who have overlooked the term " perpetual." He has also shown how the wonderful variety in form and structure, and the beauty or conspicuousness of the colours of flowers, can all be readily explained, on this theory, through the agency of variation and natural selection, while by no other theory is any real and effective explanation possible. But besides these there are very numerous other 1 Origin of Species, 6th edition, p. 161. GEXEKAL ADAPTATIOXS 331 adaptations in flowers to secure them from injurious insects or from the effects of rain or wind in damaging the pollen or the stigmas, as beautifully shown in Kerncr's very inter- esting volume on Flowers and their Unhidden Guests — a book that forms an admirable sequel to Darwin's works, and is equally instructive and interesting. Of late years writers wdio are very imperfectly acquainted wdth the facts proclaim loudly that Darwin's views are dis- proved, on account of some apparent exceptions to the general conclusions he has reached. Two of these mav he here noticed as illustrative of the kind of opposition to which Darwinism is exposed. The bee-orchis of our chalky downs, though con- spicuously coloured and with a fully-developed labellum, like the majority of its allies wdiich are cross-fertilised by insects, yet fertilises itself and is never visited by insects. This has been held to show that Darwin's views must be erroneous, notwithstanding the enormous mass of evidence on which they are founded. But a further consideration of the facts shows that they are all in his favour. In the south of Europe, while the bee-orchis is self-fertilised as in England, several allied species are insect-fertilised, bnt they rarely produce so many seed-capsules as ours; but, strange to say, an allied species (OpJirys scolopax) is in one district fertilised by insects only, while in another it is self-fertilised. Again, in Portugal, w^here many species of Ophrys are found, very few of the flowers are fertilised and very few ripe seed-ca])snles are pro- duced. But owing to the great number of seeds in a eapsuU', and their easy dispersal by wind, the plants are ahnn(hint. These and many other facts show that tor some unknown cause, orchises which are exclusively insect-fertilised, are liable to remain unfertilised, and when that is the rase it becomes advantageous to the species to be able to f(M*tilise itself, and this has occurred, partially in many species, and (•(•mpletely in our bee-orchis. I may remark here llint lhe name " l>ee-orchis " Is mislead- ing, as the flower does nol resemble any of our bee-. But the 332 THE WORLD OE LIFE very closely allied '^ spider orchises " resemble spiders mucli more closely. It occurs to me, therefore, that the general resemblance to bee or spider may occasionally prevent the flowers being eaten off by sheep or lambs, to Avhom even spiders on their noses or lips would be disagreeable. Mr. Henry O. Forbes observed, in Sumatra, that many trop- ical orchids with show^y flowers, wdiich were perfectly adapted for insect-fertilisation, yet produced very few seed-capsules, and in many cases none. Yet the great abundance of seeds, as fine as dust, in a single capsule, together with the long life of most orchids, is quite sufficient, in most cases, to preserve the various species in considerable abundance. When, how- ever, there is any danger of extinction the great variability of orchids, which at first enabled them to become so highly spe- cialised for insect-fertilisation, also enables them (in some cases) to return to self-fertilisation as in our bee-orchis. Should this continuous self -fertilisation at length lead to a weak constitution, then, occasional variations serving to attract in- sects by nectar or in other ways, with minute alterations of structure may again lead to fertilisation by insects. The other popular objection recently made to Darwin's views on the origin of the flowers is, that the colours and shapes of flowers are often such as to deter herbivorous animals from eati-ng them, and that this is the main or the only reason why flowers are so conspicuous. The special case supposed to prove this is that some buttercups are not eaten by cattle because they are acrid or poisonous, and that the bright yellow colour is a warning of inedibility. Even if these statements were wdiolly correct they would not in the least affect the general proposition that all conspicuous flowers attract insects which do actually cross-fertilise them. But, in the first place, there is much difference of opinion as to the inedibility of buttercups by cattle; and, in the second, our three most common yellow buttercups (Banunculus acris, R. repens, and R. huJhosus) are so constructed that they can be cross-fertilised by a great variety of insects, and as a mat- GENERAL ADAPTATIONS O '> o ter of fact are so fertilised. IT. Miillcr grouped those lliroe species together, as the same insects visit them all, and lie found that thej were attractive to no less than sixty diilerent species, including 23 flies, 11 beetles, 2-1 bees, wasps, etc., and 5 butterflies. Any readers who are not satisfied with Darwin's own state- ments on this subject should examine :\Iiill(M''s Fcrtili-atinn of Elowers (translated by D'Arcy W. Thonii)son), in whirh details are given of the fertilisation of abuut 100 species of alpine plants by insects, while a General "Retrospect gives a most valuable summary of the conclusions and teadiings on the whole subject. As regards the general question of the u^^ and purposes of colour in nature the late Grant Allen's inter- esting and philosophical work on The Colour Sense >hnuld bo studied. Any one who does so will be satisfied of the general truth of Darwin's doctrines though there are a few errors in the details. As an example of the fascinatinjr stvle of the book I will quote the following paragraph comparing insect- agency with that of man in modifving and beautit'vinfr the face of nature. After describing the great alterations man has made, and the large areas he has modified for his own purposes, the author thus proceeds : "But all these alterations are mere surface scratches coniparod with the immense revolution wrought in the features of nature l\v the unobtrusive insect. Half the flora of tlie earth has taken the imprint of his likes and his necessities. While man has only tilK'd a few level plains, a few great river-valleys, a few peninsular moun- tain slopes, leaving the vast mass of earth unloudied hy liis hand, the insect has spread himself over every land in a thousand sliapes, and has made the whole flowering creation sul)servient to liis daily wants. His buttercup, his dandelion, and his meadow-sweet grow- thick in every English field. TTis thyme elothes the hill-side: his heather purples the bleak grey moorland. HiLrh up among the Alpine heights his gentian spreads itsi'lf in lakes of blue: amid the snows of the Himalayas his rhododendrons gleam with crimson light. The insect has thus turned the whole surface of the eartli 334 THE WORLD OF LIFE into a boundless flower-garden, which supplies him from year to year with pollen or honey, and itself in turn gains perpetuation by the baits it offers for his allurement." Although I wholly agree with my lamented friend in attrib- uting the origin and development of flowers to the visits of insects, and the consequent advantage of rendering many spe- cies of flowers conspicuous and unlike others flowering at the same time, thus avoiding the waste and injury of the frequent crossing of distinct species, yet I do not consider that the whole of the phenomena of colour in nature is thereby ex- plained. In my book on Tropical E'ature I devoted two chapters to the Colours of Animals and Plants, and I opened the discussion with the following remarks, which indicate my present views on the subject. I will, therefore, give a few passages here: " There is probably no one quality of natural objects from which we derive so much pure intellectual enjoyment as from their col- ours. The heavenly blue of the firmament, the glowing tints of sunset, the exquisite purity of the snowy mountains, and the end- less shades of green presented by the verdure-clad surface of the earth, are a never-failing source of pleasure to all who enjoy the inestimable gift of sight. Yet these constitute, as it were, but the frame and background of a marvellous and ever-changing picture. In contrast with these broad and soothing tints, we have presented to us, in the vegetable and animal worlds, an infinite variety of objects adorned with the most beautiful and the most varied hues. Flowers, insects, and birds are the organisms most generally orna- mented in this way; and their symmetry of form, their variety of structure, and the lavish abundance with which they clothe and enliven the earth, cause them to be objects of universal admiration. The relation of this wealth of colour to our mental and moral na- ture is indisputable. The child and the savage alike admire the gay tints of flower, bird, and insect; while to many of us their contemplation brings a solace and enjoyment which is wholly ben- eficial. It can then hardly excite surprise that this relation was long thought to afford a sufficient explanation of the phenomena GENERAL AD.U^TATIOXS 335 of colour in nature, and this received great support from the dilTi- culty of conceiving any other use or meaning in the colours with which so many natural objects are adorned. Why should the homely gorse be clothed in golden ruiiiiuiit, and the prickly cactus be adorned with crimson bells? Why sliould our fields be gay with buttercups, and the heather-clad mountains be clad in purple robes? Why should every land produce its own peculiar floral gems, and the alpine rocks glow with beauty, if not for the contemplation and enjoyment of man? What could be the use to the butterfly of its gaily-painted wings, or to the humming-bird of its jewelled breast, except to add the final touches to a world-picture calculated at once to please and to refine mankind? And even now, with all our recently acquired knowledge of this subject, who shall say that these old-world views were not intrinsically and fundamentally sound; and that although we now know that colour has * uses ' in nature that we little dreamt of, yet the relations of those colours — or rather of the various rays of light — to our senses and emo- tions may not be another, and more important use which they sub- serve in the great system of the universe ? " The above passage was written more than forty years ago, and I now feel more deeply than ever that the concluding paragraph expresses a great and fundamental truth. Although in the paragraph succeeding that which I have quoted from Grant Allen's book, he refers to my view (stated above) as being '' a strangely gratuitous hypothesis," I now propose to give a few additional reasons for thinking it to be subr^tantially correct. The first thing to be noticed is, that the insects whose per- ceptions have led to the production of variously coloured flowers are so very widely removed from all the higher animals (birds and mammals) in their entire organisation that we have no right to assume in them an identity, or even a similarity, of sensation with ourselves. That they see is certain, but that their sensation of sight is the sanio ns our own. or even at all closely resembling it, is highly improbable Still niorc improb- able is it that their perception of oolour i< the same as ours, their organ of sight and their whole nervous system being so 336 THE WORLD OF LIFE very different, and the exact nature of their senses being un- known. Even a considerable percentage of men and women are more or less colour-blind, yet some diversity of colour is perceived in most cases. The purpose of colour in relation to insects is that they should distinguish between the colours of flowers which are otherw^ise alike and which have no per- fume. It is not at all necessary that the colours we term blue, purple, red, yellow, etc., should be seen as we see them, or even that the sight of them should give them pleasure. Again, the use of colour to us is by no means of the same nature as it is to insects. It gives us, no doubt, a greater facility of differentiating certain objects, but that could have been obtained in many other ways — by texture of surface, by light and shade, by diversity of form, etc., and in some cases by greater acuteness of smell ; and there are very few uses of colour to us which seem to be of " survival value ''- — that is, in which a greater or less acuteness of the perception would make any vital difference to us or would lengthen our lives. But if so, the exquisite perception of colour we nor- mally possess could not have been developed in our ancestors through natural selection ; while what we call the '^ aesthetic sense,'' the sense of beauty, of harmony, of indescribable charm, which nature's forms and colouring so often gives us is still further removed from material uses. Another consideration is, that our ancestors, the Mammalia, derived whatever colour- sense they possess almost wholly from the attractive colours of ripe fruits, hardly at all from the far more brilliant and varied colours of flowers, insects, and birds. But the colours of wild fruits, which have been almost entirely developed for the purpose of attracting birds to devour them and thus to disperse their seeds, are usually neither very brilliant nor very varied, and are by no means constant indications to us of what is edible. It might have been anticipated, therefore, that our perception of colour would have been inferior to that of birds and mammals generally, not, as is almost certainly the case, very much superior, and so bound up Avith some of GENERAL ADAPTATIONS .» .1 T our higher intellectual achievements, tiial \Uv total absence of perception of colour would have checked, or pi rliaps wholly prevented, all those recent discoveries in spcctrosc^opy which now form so powerful a means of acquiring an extended knowl- edge of the almost illimitable universe. I venture to think, therefore, that we Jiave good reason to believe that our colour-perceptions have not been developed in us solely by their survival-value in the struggle for existenee ; which is all ^ve could have acquired if the views of such think- ers as Grant Allen and Professor Ilaeckel represent the wln.b* truth on this subject. They seem, on the other hand, to have been given us with our higher aesthetic and moral attributes, as a part of the needful equipment of a being whose spiritual nature is being developed, not merely to satisfy material needs, but to fit him for a higher and more enduring life of continued progress. Colours of Fruits: a Suggestion as to Nuts As flow^ers have been developed through insects, so have edible fruits been developed and coloured so that birds may assist in the dispersal of their seeds ; while inedible fruits have acquired endlessly varied hooks or sticky exudations in ord<'r that they may attach themselves to the fur of quadrupeds or the feathers of birds, and thus obtain extensive dissemination. All this was clearly seen and briefly stated by Darwin, and has been somewdiat fully developed by myself in the work already quoted: but there is one point on which I wish to mai:i* an additional suggestion. In my Tropical Nature I referred to Grant Allen's view (in his Physiological Esthetics) that nuts were '' not intended to be eaten"; and in my Darwinism (p. 305) I adopted this as being almost self-evident, because, though very largely edible, they are always protectively coloured, being green when unrijKi and brow^n when they fall u])ou the ground among the decay- ino" folia2:e. ^foreover, thoir outer-coverings arc often prickly, as in the sweet-chestnut, or bitter as in the walnut, while their 338 THE WORLD OF LIFE seed-boxes are often very hard, as in the hazel-nut, or intensely so_, as in the Brazil-nut and many other tropical species. But, on further consideration, 1 believe that this apparently obvious conclusion is not correct; and that nuts are, as a rule, intended to be eaten. I am not aware that this question has yet been discussed by botanists, and as it is one of much inter- est and exhibits one of the curious and indirect ways in which nature works for the preservation of species, both in the vege- table and animal world, I will briefly explain my views. The first point for our consideration is, that most nuts are edible to some animals, and a large number are favourite foods even to ourselves. Then they are all produced on large trees or shrubs of considerable longevity, and the fruits (nuts, acorns, etc.) are produced in enormous quantities. If now we consider that in all countries which are undisturbed by man, the balance between forest and open country, and be- tween one species and another, only changes very slowly as the country becomes modified by geographical or cosmical causes, we recognise that, as in the case of animals, the number of individuals of each species is approximately constant, and there is, broadly speaking, no room for another plant of any particular kind till a parent plant dies or is destroyed by fire or tempest. Imagine then the superfluity of production of seed in an oak, a beech, or a chestnut forest; or in the nut- groves that form their undergrowth in favourable situations. Countless millions of seeds are produced annually, and it is only at long intervals of time, when any of the various causes above referred to have left a space unoccupied, that a few seeds germinate, and the best fitted survives to grow into a tree which may replace its predecessor. But when every year ten thousand millions of seeds fall and cannot produce a tree that comes to maturity, any cause which favoured their wider dispersal would be advantageous, even though accompanied by very great destruction of seeds, and such a cause is found when they serve as food to herbiv- orous mammals. For most of these go in herds, such as swine, GENERAL AUAriATlOXS 339 peccaries, deer, cattle, horses, etc., and wlieu .such animals are startled while feeding and scamper away, two results, useful to the species whose fruit they are feedin-,^ upon, follow. As the acorns, chestnuts, etc., usually lie thickly un the ground, some will be driven or kicked along wiih the herd; an of the higlier insects, are absolutely unintelligible and unthinkable in the absence of such intelligence, we must go a stc}) further and assume, as in the highest degree proliable, a pur|)o>c which this ever-present, directing, and organising intelligence has had always in view. We cannot help seeing that we ourselves are the highest outcome of the developmental process on the earth ; that at the time of our first ajopearance, plants and animals in many diverging lines had approached their highest develop- ment; that all or almost all of these have furnished species "which seem peculiarly adapted to our purposes, whether as food, as providing materials for our clothing and our varied arts, as our humble servants and friends, or as gratifying our highest faculties by their beauty of form and colour : and as our occupation of the earth has already led to the extinction of many species, and seems likely ultimately to destroy many more except so far as we make special efforts to preserve them, we must, I think, assume that all these consequences of our development were foreseen, and that results which srrm to bo so carefully adapted to our wants during our growing civilisa- tion were really prepared for us. If this be so, it follows that the much-despised anthropomorphic view of the whole develop- ment of the earth and of organic nature was, after all, tho true one. But if the view now advocated is not so wholly unscientific, so utterly contemptible as it has hitherto been declared to bo by many of our great nuthnrities, it is certainly advisable to show how various facts in nature bear upon it and are ex- 342 .THE WOKLD OF LIFE plained by it. I will therefore now add a few more consid- erations to those I have hitherto set forth. On the question of the colour-sense I have already argued that though it may exist in birds and insects, it is hardly likely that it produces any such high aesthetic pleasure as it does in our own case. All that the evidence shows is, that thev do perceive what are to us broad differences of colour, but we have no means whatever of knowing n:]iai they really perceive. It is a suggestive fact that colour-blind persons, though they do not see red and green as strongly contrasted as do those with normal vision, yet do perceive a difference between them. It is therefore quite possible that birds may see differences be- tween one strongly marked colour and another without any sense of what we should term colour, and at all events without seeing '' colours " exactly as we see them. It is now generally admitted that birds arose out of primitive reptiles, and from their very origin have been quite distinct from mammals, which latter probably diverged a little later from a different stock and in a somewhat different direction. The eyes of both were developed from the already existing reptilian eye, and their type of binocular vision may be very similar. But at that early period there were, it is believed, no coloured flowers or edible coloured fruits, and it is probable that the perception of colour arose at a much later period. It is therefore unlikely that a faculty separately developed in two such fundamentally different groups of organisms should be identical in degree or even in nature unless its use and purpose were identical. But birds are much more extensive fruit-eaters than are mammals, the latter, as we have seen, being feeders on nuts which are protectively tinted rather than on fruits, while their largely developed sense of smell would render very accurate perception of colour needless. It is suggestive that the orang-utan of Borneo feeds on the large, green spiny Darian fruit ; and I have also seen them feeding on a green fruit which was re- pulsively bitter to myself. Our nearest relatives among exist- ing quadrupeds do not therefore seem to have any need of GExXEEAL ADAPTATiUAS 343 a refined colour-sense. AVliy then should ii have been so highly developed in us? It was one of the finKhmir^ntnl maxims of Darwin that natural selection couhl not prudiK-u absolute, but only relative perfection; and airain, that no species could acquire any faculty beyond its needs. The same ar^iments will apply even more strongly in the case of insects. They appear to recognise the colour-, the formSj and the scents of flowers, but we can only vagufly guess at the nature and quality of their actual sensations. Their whole line of descent is so very far removed from that of the birds that it is in the highest degree iinpnjbable that there is any identity even in their lower mental faculties with those of birds. For the colour-sense is mental, not })hysical ; it depends partly on the organ of vision, but more fundamentally on the nature of the nervous tissues which transform the etlects of light-vibrations into the visual impressions which irc rec- ognise as colour, and ultimately on some purely mental faculty. But the colour-sense in insects may be quite other than the bird's or than our own, and mav in most cases be combined with scent, and often with form to produce the recognition of certain objects, which is all they require. Yet insects, birds, and the flowers and fruits which attract them, all exhibit to our vision nearlv the same ranjje of the colour-scheme, and a verv similar intensitv, brilliancv, and purity of colour in particular cases; which is highly remark- able if their respective needs were the only etiicient causes in the production of these colours. Looking first at flow( rs, how very common and conspicuous are those of a yelh»w colour, yet far beyond the average are the rich orange petals of tlie Escholtzia and the glistening splendour of st^me of our butter- cups; red and purples are innumerable, yet in the Lobelia fulqens and some other flowers we r(\'ieh an intensity of huo which seem to us un^urpassahly b(\iutiful; blues of the type of the campanulas or the v.'irious blue lillaceir are all in tlieir way charming, but in the blue salvia (Salvia patens) the spring gentian {Geniiana vcrna), and a few others, we perceive U4: THE WOJRLD OF LIFE a depth and a purity of liue which seem to have reached the limits of the possible. We may surely ask ourselves whether these exquisite refinements of mere colour as well as the in- finity of graceful forms, and the indescribable delicacies of texture and of grouping, are all strictly utilitarian in regard to insect-visitors and to ourselves. To them the one thing needful seems to be a sufficient amount of difference of any kind to enable them to distinguish among species which grow in the same localitv and flower at the same time. Special Cases of Bird-colouration Coming now to birds, we find the colours with which they are decorated to be fully equal in variety and purity of tint to those of flowers, but extending still further in modifications of texture, and in occasionally rivalling minerals or gems in the brilliancy of their metallic lustre. The exquisite blues and vinous purples, reds and yellows of the chatterers and manakins, the glorious metallic sheen of the trogons, of many of the humming-birds, and of the long-tailed paradise-bird ; the glistening cinnabar-red of the king-bird of paradise, ap- pearing as if formed of spun-glass ; the silky orange of the cock-of-the-rock and the exquisite green of the Malayan crested gaper, are only a few^ out of thousands of the extreme refine- ments of colour with which birds are adorned. Add to these the marvellous ornaments with which the males are so frequently decorated, the crests varying from the feath- ery dome of the umbrella bird, to the large richly coloured crest of the roval flvcatcher of Brazil, and the marvellous blue plumes from the head of the fern-bearing bird of paradise (Pteridopliora Alherti), with a thousand others hardly in- ferior, and we shall more than ever feel the want of some general and fundamental cause of so much beauty. All this w'ealth of colour, delicacy of texture and exuber- ance of ornament, has been explained hitherto as being utili- tarian in two ways only: (1) that they are recognition-marks of use to each species, more especially during its differentiation GEXEKAL ADAI^TATIONS 345 as a species; and (2) as inllucncing female choice of the must ornamental males, and tlicrclure of use to each species in the struggle for existence. The former I have, I tliink, proved to be a true cause; the latter I reject for reasons given ii» my Darwinism. I there give an alternative solution of the prol>- lem which I still think to be fundnmontally correct and whicli has been arrived at by Weismann and others from theoretical considerations to whicli 1 may advert hiter on. C olouration of Insects Passing now to tlie order of insects wliich perhaps pxhil»its the greatest range of colour-display in the wh(de of the organic world — especially in the order Lepido])tera, we find the dif- ficulties in the way of a purely utilitarian solution still greater. Any one who is ac(iuainted with this order of insects in its fullest development in the equatorial zone of the great conti- nents, will recognise liow impossible it is to give any ade and horses, the sense of smell is so highly developed as for many purposes to take the place of vision. It is a very suggestive fact that tho tlioory of tlie develop- ment of the colour-sense through its utility, receives least s\ij>- port from those animals Avhich are nearest to us, and from which we have been corporeally developed — the niannnals; rather more support from those which have had a \vi(hdy dif- ferent origin — the birds ; and apparently most from tlioso farthest removed from us — the insects, for whom it has been claimed that we owe them all the floral beauty of the vege- table kingdom, through their refined perception of ditTerences of form and colour. This seems to me to be a kind of redudio ad dbsurdum, and to constitute a disproof of that whole argument as a final cause of the colour-sense. On the other hand, it gives the strongest support to the view that the refined perception and enjo\inent of colour ive possess has not, and could not have been developed in us by its survival- value in our early struggle for existence, but that these faculties are, as Huxley remarked in reirard to his eniovment of scenerv and of music, ^^ gratuitous gifts,'' and as such are powerful arsninients for ^' a benevolent Author of the Universe/' * iSee Darwinism (3rd ed. 1901), p. 478, Appendix. CHAPTEE XVI THE VEGETABLE KINGDOM IN ITS SPECIAL EELATION TO MAN It is obvious that, as animal life has from its very origin depended upon and been developed in relation to plant life, the entire organisation of the former would, by the continuous action of variation and survival of the fittest, become so harmoniously adapted to the latter, that it would inevitably have every appearance of the plant having been formed and preordained for the express purpose of sustaining and benefit- ing the animal. This harmonious co-adaptation cannot there- fore be adduced as, of itself, being any proof of design, but neither is it any proof against it. So with man himself, so far as his mere animal wants are concerned, his dependence on plants, either directly or indirectly, for his entire sus- tenance by food, and therefore for his very life, affords no grounds for supposing that either of the two kingdoms came into existence in order to render the earth a possible dwelling- place for him. But as regards those special qualities in which he rises so far above all other animals, and especially those on which the higher races found their claim to be " civilised," there seem to be ample grounds for such an argument, as I hope to be able to show. Taking first the innumerable different kinds of wood, whose qualities of strength, lightness, ease of cutting and planing, smoothness of surface, beauty, and durability, are so exactly suited to the needs of civilised man that it is almost doubtful if he could have reached civilisation without them. The con- siderable range in their hardness, in their durabilitv when ex- posed to the action of water or of the soil, in their weight and in their elasticity, render them serviceable to him in a 350 PLANTS IN RELATIOX TO MAX nr>i thousand ways which arc totally removed from any use made of them by the lower animals. Few of these qualities seem essential to themsclvos as vege- table growths. They might have been much smaller, which would have greatly reduced their uses; or so much harder as to be almost unworkable; or so liable to fracture as to ho dangerous; or subject to rapid decay by the action of air, or of water, or of sunshine, so as to be suitable for temjuirarv purposes only. With any of these defects they miirht have served the purposes of the animal world (piite as well as they do now; and their actual properties, all varyinir alxuit a mean value, which serves the infinitely varied purposes to which we daily and hourly apply them, may certainly be adduccni the ripened seed, consisting essentially of a single fertilised cell and a surrounding mass of nutritive material, a root is sent out into the soil and a shoot into the atmosphere, from which the whole plant with all its tissues and vessels arc formed, enabling it to rise up into the air so as to obtain exposure to light, to lift up tons weight of material in the form of limbs, branches, and foliage of forest trees, often to a hundred feet or more above the surface, by means of forces whose exact mode of operation is still a mysten.^ ; while by means of the very same tissues and vessels those recondite chemical processes are being carried on which result in the infinitely varied products already very brietly referred to. The living plant not only builds up its own man-ellous structure out of a few elements supplied to it either in a gaseous or liquid state, but it also manufactures all the aj> pliances — cells, vessels, fibres, etc. — needful for its complex laboratory work in producing the innumerable l)V(v})roducts possessing so many diverse properties useful to man, but which were mostly unneeded by the remainder of the animal world. Usually botanists as well as zoologists are satisfied to de- scribe the minute structure of the organs of j)lants or animals, and to trace out as far as possible the changes that occur dur- ing growth, without any reference to the unknown and un- intelligible forces at work. As Weismann has state animal nn.l vegetable kingdoms, 1 The Riddle of the L'niverse. p. 04. 3 CO THE WOKLD OF LIFE Avhich we alone can and do make use of, a preparation for ourselves, to assist in our mental development, and to fit us for a progressively higher state of existence as spiritual be- ings. CIlAl^TKK XV 11 THE MYSTERY OF THE CVAA. I HAVE already given a short aecount of the chemical composi- tion of protoplasm — the hii!;hly complex snhstance now ln-M to be the physical basis of life, and by one scIkjoI of biulorrists alleged to explain, as a resnlt of that complexity, all the won- drous phenomena of growth and development. 1 now propose to give a very brief sketch of the physical characteristics of the living cell, of its internal structure, and of the extraordinary internal changes it undergoes during the growth or reproduc- tion of all organisms. One of the lowest or most rudimentary forms of life is the Amoeba, a living cell, just visible to the unaided eye as a little speck of floating jelly. This creature, being one of the most common of living microscopic objects, will have been seen by most of my readers. At first, under a low microscopic power, it appears structureless, as it was for some time de- scribed to be, but with increasing power and perfection of the microscope it is found to consist of three parts — a central body of a nearly globular shape slightly darker and more granular in texture, the outer jelly-like mass, and a small more transparent globular portion, which looks like an air-bubble, and is seen to undergo a slow motion of contraction and ex- pansion; this is termed the "contractile vacuole,'' which, when it has reached its full size, p(Thaps a quarter «»r a fifth of the whole diameter, suddenly disappears, and after a little while reappears and gradually grows again to it< maximum size. The shape of the Amceba varies greatly. Sometimes it is globular and immovable, but most fr':^quently it is very ir- regTilar with arm-like processes jutting out in various direc- tions. By careful watching, these are seen t-. increase or []G1 362 THE WORLD OF LIFE diminish so as to change the whole shape in an hour ov two. But more curious is its power of absorbing any particles of organic matter that come in contact with it by gradually en- closing them in its substance, wdiere after a time they dis- appear. The Amoebae are found in stagnant water full of or- ganic matter, and if they are transferred to pure waiter they soon diminish in size, proving that they require food and can digest it. The '' contractile vacuole " is believed to have the function of expelling the carbonic acid gas and other waste products of assimilation. This Amoeba is one of the simplest forms of the lowest branch of the animal kingdom, the one-celled animals or Protozoa ; all other animals being classed as Metazoa, as they are entirely built up of separate cells, which in all the more complex forms are countless millions in number. Every part of our bodies, from blood to muscles and nerves, from bones to skin, hair, and nails, is alike constructed of variously modi- fied cells. It might be thought that animals consisting of single cells could not be very numerous or very differently organised. Yet they are grouped into five classes, the first, Rhizopoda, comprising not only many kinds of Amoeba?, but the beauti- ful Foraminifera, whose exquisite shells are such favourite microscopic objects. They are single amoeboid cells which yet have the power either of building up shells of small inorganic particles, or of secreting the more beautiful shells which seem to mimic the forms of those of the higher Mollusca. The fossils called Xummulites were Foraminifera with flat coiled shells, forming great masses of Eocene limestone. They are the largest of all, some equalling a half-crown in size. Radiolaria are rhizopods having a beautiful siliceous skele- ton, and often living in colonies. Another class, the Mastigo- phora, have extremely varied shapes, often like sea-weed or flowers, having long, slender, whip-like processes. These and hundreds of other strange forms are still essentially single cells, though often grouped together for a time, and they all MYSTERY OF THE CELL 3G3 increase either by division or by giving off buds, which ra[)i(lly grow into the perfect form. The remarkable thing in all these one-celled creatures is that they so much resemble higher animals without any of their organs. The writer of the article Cell iu Chambers's Encyclopaedia says: ''The absence of a circulating fluid, of digestive glands, nerves, sense-organs, lungs, kidneys, anounds, and 376 THE WOKLD OF LIFE which, in the freedom of the Eocky Mountains, may reach such a size that a man may walk without stooping through the archway made by setting up upon their points tlie shed antlers. In the eastern European forests the horns of the red deer reach a w^eight of 74 pounds, while in the recently extinct Irish elk the large, broadly palmated horns sometimes reached an expanse of 11 feet. These remarkable weapons were devel- I oped both for combats between the males and as a means of pro- \ tecting the females and young from enemies. As organic out- growths they are extremely simple when compared with the feathers of the bird or the scales of a butterfly's wing; yet as exemplifying the need for some guiding power, exerted upon the individual cells which carrv out the work with such won- derful precision every year, they are equally striking. The blood, we know, furnishes the materials for every tissue in the body; but here a large mass of bony matter, covered with a thin skin and dense hair, is rapidly built up, to a very definite form in each species; then the skin and hair cease growing and fall away, while the horns persist for nearly a year, when they, too, fall off and are again renewed. Concluding Remarks on the Cell-Prohlem The very short account I have now given of w^hat is known of the essential nature, the complex structure, and the alto- gether incomprehensible energies of these minute unit-masses of living matter, the cells — so far as possible in the very words of some of the most recent authorities — must, I think, con- vince the reader that the persistent attempts made by llaeckel and Yerw^oru to minimise their marvellous powers as mere re- sults of their complex chemical constitution, are w^holly un- availing. They are mere verbal assertions which prove noth- ing; w^hile they afford no enlightenment wdiatever as to the actual causes at work in the cells leading to nutrition, to growth, and to reproduction. Very few of the workers who have made known to us the MYSTEKY OF THE CELL 377 strange phenomena of cell-life in liie Protozoa, and of cell- division in the higher animals and plants, seem to think any- thing about the hidden causes and forces at work. They are so intensely interested in their discoveries, and in following out the various chani^es in all their ramitications, that tliev have no time and little inclination to do more than add con- tinually to their knowledge of the facts. And if one attempts to read through anv ffood text-book such as Parker and Has- well's Zoology, or J. Arthur Thomson's Heredity, it is easy to understand this. The complexities of the lower forms of life are so overwhelming and their life-histories so mysterious, and yet they have so much in common, and so many cross-affinities among the innumerable new or rare species continually being discovered, that life is not long enough to investigate the struc- ture of more than a very small number of the known forms. Hence very few of the writers of such books express any opin- ion on those fundamental problems which Haeckel and his fol- low^ers declare to have been solved by them. All questions of antecedent purpose, of design in the course of development, or of any organising, directive, or creative mind as the funda- mental cause of life and organisation, are altogether ignored, or, if referred to, are usually discussed as altogether imscien- tific and as showing a deplorable want of confidence in the powers of the human mind to solve all terrestrial problems. If, as I have attempted to do here, we take a broad and com- prehensive view of the vast world of life as it is spread out be- fore us, and also of that earlier world which goes back, and ever further back, into the dim past among the relics of pre- ceding forms of life, tracing all living things to more gen- eralised and usually smaller forms; still going back, till one after another of existing families, orders, and even classes, of animals and plants either cease to appear ur are represented only by rudimentary forms, often of types tpiite unknown to us; we meet with ever greater and greater ditiiculties in dis- pensing with a guiding purpose and an immanent creative powder. 378 THE WOKLD OF LIFE For we are necessarily led back at last to the beginnings of life — to that almost infinitely remote epoch myriads of years before the earliest forms of life we are acquainted with had left their fragmentary remains in the rocks. Then, at some definite epoch, the rudiments of life must have appeared. But whenever it began, whenever the first vegetable cell began its course of division and variation ; and when, very soon after, the animal cell first appeared to feed upon it and be developed at its exj)ense, — from that remote epoch, through all the ages till our own day, a continuous, never-ceasing, ever-varying process has been at work in the two great kingdoms, vegetal and animal, side by side, and always in close and perfect adaptation to each other. Myriads of strange forms have appeared, have given birth to a variety of species, have reached a maximum of size, and have then dwindled and died out, giving way to higher and better-adapted creatures ; but never has there been a complete break, never a total destruction, even of terrestrial forms of life ; but ever and ever they became more numerous, more varied, more beautiful, and hetler adapted to tJie wants, the 'material 'progresSj, the higher enjoyments of mankind. The whole vast series of species of plants and animals, with all their diversities of form and structure, began at the very dawn of life upon the cooling earth with a single cell (or with myriads of cells) such as those whose structure and properties we have here been considering; and every single individual of the myriads of millions Avhich have ever lived upon the earth have each begun to be developed from a similar but not idm- tical cell ; and all the possibilities of all their organs, and structures, and secretions, and organic products have arisen out of such cells; and we are asked to believe that tliese cells and all their maiwellous outcome are the result of the fortuitous clash of atoms with the help of '^ an unconscious cell-soul of the most primitive and rudimentary kind ! " MYISTEKV OF THE CELL 3Tti The Fallacy of Eternity as an Explanation of Evolution It may perhaps not be out of place here to deal with what seems to me to be one of the common philosophical fallacies of the present day, the iilea that you can get over the difficulty of requiring any supreme mind, any author eeonie suns, the in- finite development had been at work and must liavc ])r(>diic(Ml gods of infinite degrees of powei-, any one of whom would pre- sumably be quite capable of starting such a solar system as ours, or one immensely larger and better, and of so determin- ing the material constitution of an " earth " as to initiate and guide a course of development which would have resulted in a far higher being than man. Once assume a mind-developing power from all eternity, and it must, noiu, and at all earlier periods of the past have resulted in beings of infinite power — what we should term — Gods ! It may, I think, be stated generally, that whatever has an inherent power of increase or decrease, of growth, develop- ment, or evolution, cannot possibly have existed from a past " eternity '' unless the law of its evolution is an ever-recurrent identical cycle, in which case, of course, it may, conceivably, have existed from eternity and continue through an eternity of future cycles, all identical; and, therefore, such cycles could never produce anything that had not been produced an in- finite number of times before. Is this a satisfactory outcome for an eternal self-existent universe ? Is this easier, simpler, more rational, more scientific, more philosophical, than to posit one supreme mind as self-existent and eternal, of which our universe and all universes are the manifestations I And yet the " infinity and eternity " men call themselves ^' monists,'^ and claim to be the only logical and scientific thinkers. With them matter, ether, life — (surely three absolutely distinct things) — with all the wonderful laws, and forces, and direc- tive agencies which they imply, and without which none of them could for a moment exist, all are to be accounted for and explained by the one illogical assumption, their eternity ; the one complete misnomer, monism ; the one alleged fundamental law which explains nothing, the " law of substance." It will be seen that this alleged explanation — the eternal material universe — does not touch the necessitv, becominc: 382 THE WORLD OF LIFE more clear every day, not for blind laws and forces, but for immanent directive and organising mind, acting on and in every living cell of every living organism, during every moment of its existence. I think 1 have sufficient! v shown that with- ont this, life, as we know it, is altogether unthinkable. Xo ^^ eternal " existence of matter will make this in the remotest defifree imaginable. It is this difficultv which the ^^ monists '' and the " eternalists " of the Llaeckel and Verworu type abso- lutely shirk, putting us off ^vith the wildest and most contra- dictory assertions as to what they have proved ! I venture to hope and to believe that such of my readers as have accompanied me so far through the present volume, and have had their memory refreshed as to the countless marvels of the world of life ; culminating in the two great mysteries — that of the human intellect wdth all its powers and capacities as its outcome, that of the organic cell with all its complexity of structure and of hidden powers as its earliest traceable origin — will not accept the loud assertion, that everything exists because it is eternal as a sufficient or a convincing explanation. A critical examination of the sub- ject demonstrates, as the greatest metaphysicians agree, that everything but the Absolute and Unconditioned must have had a beginning. CHAPTER XVIII THE ELEMENTS AND WATER, IN RELATION TO THE LIFE-WORLD I HAVE already (in Chapter XVI.) given the statements of two continental physiologists as to great chemical complexity of the proteid molecule, involving as it does, in certain cases already studied, a combination of about two thousand chemical atoms. A more recent authority (Mr. W. Bate Hardy) is of opinion that this molecule really contains about thirty thou- sand atoms, while the most complex molecule known to the organic chemist is said to contain less than a hundred. One of the results of this extreme complexity is that almost all the products of the vegetable and animal kingdoms are what are termed hydro-carbons, that is, they consist of compounds of carbon, with hydrogen, oxygen, or nitrogen, or any or all of them, combined in an almost infinite variety of ways. Yet the compounds of these four elements already known are more numerous than those produced by all the other elements, more than seventy in number. This abundance is largely due to the fact that the very same combination of carbon with the three gaseous constituents of the carbon-compounds often produces several substances very different in appearance and properties. Thus dextrine (or British gum), starch, and cellulose (the constituents of the fibres of plants) all consist of six atoms of carbon, ton of hydrogen, and five of oxygen ; yet they have very different properties, cellulose being insoluble in water, alcohol, or ether ; dextrine soluble in water but not in alcohol ; while starch is only soluble in Avarm water. These differences are supposed to be due to the different arrangement of the atoms, and to their being combined and recombinod in dift'orent ways; and as the more atoms are used, the possible complexity of these arrangements 383 384 THE WORLD OF LIFE becomes greater, and the vast numbers and marvellous diversity of the organic compounds becomes to some extent intelligible. Professor Kerner, referring to the three substances just men- tioned, gives the following suggestive illustration of their diverse properties, of which I have only mentioned a few. He says : " If six black, ten blue, and five red balls are placed close to- gether in a frame, they can be grouped in the most diverse ways into beautiful symmetrical figures. They are always the same balls, they always take up the same space, and yet the effect of the figures produced by the different arrangements is wholly distinct. It may be imagined, similarly, that the appearance of the whole mass of a carbon-compound becomes different in consequence of the arrangement of the atoms, and that not only the appearance but even the physical properties undergo striking alterations." Another and perhaps more interesting example, illustrated by a diagram, is given by Mr. W. Bate Hardy in his lecture already referred to. He says : " Here is a simple and startling case. The molecules of two chemical substances, benzonitrile and phenylisocyanide, are com- posed of seven atoms of carbon, five of hydrogen, and one of nitrogen : N C H— C I 1 C— H H— C I I C— H H— C I I C— H H— C I I C— H c c Benzonitrile. Phenylisocyanide. The only difference in the arrangement of the atoms is that those of nitrogen and carbon are reversed. But the properties of these two substances are as unlike as possible. The first is a harmless fluid with an aromatic smell of bitter almonds. The second is very poisonous, and its odour most offensive." THE ELEMENTS AXl) LIFE 385 Here only three elements are combined, and in identical pro- portions. We can imagine, therefore, what endless diversities arise when to these are added anv of nine other elements, and these in varying proportions, as Avell as being groii])ed in every possible manner. The fact of ^^ isomerism," or of different substances, often with very different properties, having the very same chemical composition, is now so familiar to chemists as to excite com- paratively little attention, yet it is really a marvel and a mys- tery almost equal to that of the organic cell itself. It is probably dependent upon the highly complex nature of the molecules of the elements, and also of the atoms of which these molecules are built up; while atoms themselves are now be- lieved to be complex systems of electrons, which are held to be the units of electricity and of matter. It is these electrons and their mysterious forces that give to matter all its mechan- ical, physical, and chemical properties, including those which, in the highly complex protoplasm, have rendered possible that whole world of life we have been considering in the present volume. Here, then, we find, as before, that the further back we go towards the innermost nature of matter, of life, or of mind, we meet with new complications, new forces, new agencies, all pointing in one direction towards the final outcome — the buikl- ing up of a living sentient form, which should be the means of development of the enduring spirit of man. Important and Unimportant Elements If we look at the long list of between seventy and eighty elements now known we shall see that a comparatively suuill number of these (less than one-fourth) seem to play any im- portant part either in the structure of the earth as a phinet, or in the constitution of the organised l)eings that have been developed upon it. The most important of the elements is oxygen, which is not only an essential in the structure of all living things, but forms a large part of the air and the water 386 THE WORLD OF LIFE which are essential to their contiiiTied existence. It is also a constituent of almost every mineral and rock, and is estimated to form about 47 per cent of the whole mass of the globe. The next most abundant elements are silicon, aluminium, and iron, which form 25, 8, and 7 per cent respectively of the earth- mass. Then follow calcium, magnesium, sodium, and potas- sium, contributing from about 4 to 2 per cent of the whole; while no other element forms so much as one per cent, and the majority probably not more than one-fiftieth or one-hundredth of one per cent. The gases, hydrogen and nitrogen, are, however, exceedingly important as forming with oxygen the atmosphere and the oceans of the globe, which by their purely physical action on climate, and in causing perpetual changes on the earth's sur- face, have rendered the development of the organic w^orld pos- sible. These ten elements appear to be all that were necessary to constitute the earth as a planet, and to bring about its varied surface of mountain and valley, rivers and seas, volcanoes and glaciers ; but in order to develop life, and thus clothe the earth with ever-growing richness of vegetation and ever-changing forms of animals to be sustained by that vegetation, four other elements were required — carbon, sulphur, phosphorus, and chlorine — but these being either gaseous or of very small spe- cific gravity, and thus existing (perhaps exclusively) near the earth's surface, comparatively little of them was needed. Elements in Protoplasm in Order of their Abundance {approximately). 1. Hydrogen 2. Carl) 011 3. Oxvgen 4. Nitrogen 5. Sulphur 6. Iron Phosphorus 8. Chlorine 9. Sodium 10. Potassium 11. Calcium 12. Magnesium List of the More Important Elements Elements in the Earth in Order of their Quantity {approximately). per cent. 1. Oxygen 47 2. Silicon 25 3. Aluminium 8 4. Iron 7 5. Calcium 4 6. Magnesium 3 7. Sodium 2.5 8. Potassium 2.5 9. Hydrogen (?) 0.1 10. Nitrogen (?) 0.1 All others (?) 0.8 100 THE ELEME:N^TS AXD life 387 The two elements in italics — iiilicoit and Alumijiiuni — altlioiii:li form- ing a large proportion of the earth's substance, are not ctmcndal constitu- ents of protophism, although occasionally forming part of it. In the list of the more important elements here given, I have arranged them in two series, the first showing the essential constituents of protoplasm ; the second showing the ten which are the most important constituents of the earth's mass as known to geologists and physicists. The four which are itali- cised in the first list do not appear in the second, and cannot, therefore, be considered as forming an essential portion of the rock-structure of the earth, although without them it seems fairly certain that the life-world could not have existed. The Elements in relation to Man So far as we can see, therefore, the fourteen elements in these two lists would have sufficed to brine: about all the essen- tial features of our earth as w^e now find it. All the others (more than sixty) seem to be surplusage, many exceedingly rare, and none forming more than a minute fraction of the mass of the earth or its atmosphere. All except seven of these are metals, including (with iron) the seven metals known to the ancients and even to some prehistoric races. The seven ancient metals are gold, silver, copper, iron, tin, lead, and mer- cury. All of these are widely distributed in the rocks. They are most of them found occasionally in a pure state, and are also obtained from their ores without much difficulty, which has led to their being utilised from very early times. But though these metals (except iron) appear to serve no important purpose either in the earth itself or in tlie vegetable or animal kingdoms, they have yet been of very gTcat importance in the history of man and the development of civilisation. From very remote times gold and silver have been prized for their extreme beauty and comparative rarity; the search after them has led to the intercourse between various races and peoples, and to the establishment of a world-wide conmierce ; wliile the facility W'ith wdiich they could be worked and polished called fortli the 388 THE WORLD OF LIFE highest powers of the artist and craftsman in the making of ornaments, coins, drinking-vessels, etc., many of which have come down to ns from early times, sometimes showing a beauty of design which has never been surpassed. Our own earliest rudiments of civilisation were probably acquired from the Phoenicians, who regularly came to Cornwall and our southern coasts to purchase tin. Each of the seven metals (and a few others now in com- mon use) has very special qualities which renders it useful for certain purposes, and these have so entered into our daily life that it is difficult to conceive how we should do without them. Without iron and copper an effective steam-engine could not have been constructed, our whole vast system of machinery could never have come into existence, and a totallv distinct form of civilisation would have developed — perhaps more on the lines of that of China and Japan. Is it, we may ask, a pure accident that these metals, with their special physical qualities which render them so useful to us, should have ex- isted on the earth for so many millions of years for no appar- ent or possible use ; but becoming so supremely useful when Man appeared and began to rise tow^ards civilisation ? But an even more striking case is that of the substances which in certain combinations produce glass. Sir Henry Ros- coe states that silicates of the alkali metals, sodium and potas- sium, are soluble in water and are non-crystalline ; those of the alkaline earths, calcium, etc., are soluble in acid and are crystalline; but by combining these silicates of sodium and calcium, or of potassium and calcium, the result is a substance which is noi soluble either in water or acids, and which, when fused forms glass, a perfectly transparent solid, not crystallised but easily cut and ]3olished, elastic within limits, and when softened by heat capable of being moulded or twisted into an endless variety of forms. It can also be coloured in an infinite variety of tints, while hardly diminishing its transparency. The value of cheap glass for windows in cold or changeable climates cannot be over-estimated. Without its use in bottles, THE ELEMENTS AXD LIEE 389 tubes, etc., chemistry could hardly exist ; while astronomy could not have advanced beyond the stage to which it had Itecn brought by Copernicus, Tycho Brahe, and Kepler. It rfu- dered possible the microscope, the telescope, and the si)ectro- scope, three instruments without which neither the starry heav- ens nor the myriads of life-forms would have had their inner mysteries laid open to us. One more example of a recent discovery of one of the rarest substances in nature — radium — and its extraordinarv effects, points in the same direction. So far as known at present, this substance may or may not be in any way important either to the earth as a planet or for the development of life upon it ; but the most obvious result of its discovery seems to bo the new light it throws on the nature of matter, on the con- stitution of the atom, and perhaps also on the mysterious ether. It has come at the close of a century of wonderful advance in our knowledge of matter and the mysteries of the atom. Many other rare elements or their compounds are now being found to be useful to man in the arts, in medicine, or by the light they throw on chemical, electrical, or ethereal forces.^ If now we take the occurrence of all these apparently use- less substances in the earth's crust ; the existence in tolerable abundance, or very widely spread, of the seven metals known to man during his early advances towards civilisation, and the many ways in which they helped to further that civilisation ; and, lastly, the existence of a few elements which, when spe- cially combined, produce a substance without which modern science in almost all its branches would have been impossible, w^e are broui2:ht face to face with a body of facts which are wholly unintelligible on any other theory than that the earth (and the universe of which it form> a part) was constituted 1 While this chapter is being written I see it announced that two of the rarest of the elements, lanthanium and noodyniuin. have l)ei'n found to pro- vide (through some of their comjiounds) light-lilters, which increase the efficiency of the spectroscope in <1h» study of the planetary atmospheres, and may thus be the menus of still furthoi- extending oiu* knowledge of the universe. 390 THE WOKLD OF LIFE as it is in order to supply us, when the proper time came, with * the means of exploring and studying the inner mechanism of the world in which we live — of enabling us to appreciate its overwhelming complexity, and thus to form a more ade- quate conception of its author, and of its ultimate cause and purpose. I have already shown that the postulate of a past eternal existence is no explanation, and leads to insuperable difficulties. A beginning in time for all finite things is thus demonstrable ^ but a beginning implies an antecedent cause, and it is impos- sible to conceive of that cause as other than an all-pervading mind. The Mystery of Carbon: the Basis of Organised Matter and of Life It is universally admitted that carbon is the one element which is essential to all terrestrial life. It will be interesting, therefore, to give a brief statement of what is known about this very important substance. Although it is so familiar to us in its solid form as charcoal, or in a more mineralised form as black-lead or graphite, it is doubtful whether it exists un- combined on the earth except as a product of vegetation. Though graphite (plumbago) is found in some of the earliest rocks, yet it is believed that some forms of vegetation existed much earlier. Graphite has also occurred (rarely) in mete- orites, but I am informed by my friend. Professor Meldola, that it cannot be decided whether this is derived from carbon- dioxide gas or from gaseous carbon. Sir William Huggins was also doubtful as to the state in Avhich it exists in the sun and comets, w^hether as carbon-vapour or a hydrocarbon. But the most interesting point for us is that it exists as a constitu- ent of our atmosphere, of which carbon-dioxide fonns about ^■g^ooth part, equal to about yoVo't^^ ^2iYi by weight of solid carbon ; and it is from this that the whole of the vegetable kingdom is built up. The leaves of plants contain a green substance named chlorophyll, which by the aid of sunlight can THE ELEMENTS AND JJFE 391 extract the carbon from the gas, and there is no other means known hj which this can be done at ordinary temperatures. The chemist has to use the electric spark, or very high tem- peratures, to perform what is done by the green leaves at the ordinary temperatures in which we live. The reverse operation of combining carbon with other ele- ments is equally difficult. In Chambers's Encyclopaedia we find the following statement: '^ At ordinary temperatures all the varieties of carbon are extremely unalterable ; so much so that it is customary to burn the ends of piles of wood whirh are to be driven into the ground, so that the coating of non- decaying carbon may preserve the inner wood. Wood-charcoal, however, burns very easily, animal charcoal less so ; then fol- low in order of difficulty of combustion coke, anthracite, black- lead, and the diamond." The two latter withstand all tem- peratures, except the very highest obtainable. These various states of carbon differ in other respects. Ordinary carbon is a good conductor of electricity; the diamond is a non-con- ductor. Carbon unites chemically with almost all the other elements, either directly or by the interv^ention of some of the gases. It also possesses, as Sir Henry Roscoe says : " A fundaiTiental and distinctive quality. This consists in the power which this ele- ment possesses, in a much higher degree than any of the others, of uniting with itself to form complicated compounds, contain- ing an aggregation of carbon-atoms united with either oxygen, hydrogen, nitrogen, or several of these, bound together to form a distinct chemical Avhole.'' Carbon is also the one element that is never absent from any part or product of the vegetable or animal kingdoms ; and its more special property is that, when combined with hydro- gen, nitrogen, and oxygen, together with a small quantity (about 1 per cent) of sulphur, it forms the whole group ^." — i< altoo;other beyond mv comprehension.^ 1 See The Riddle of the Universe, chap. xiii. (p. 87, col. 1). 404 THE WORLD OF LIFE The Evolution of Pain Taking it then as certain that the whole world-process is as it is, because it is the only method that could have succeeded, or that if there were alternative methods this was the best, let us ascertain what cojiclusions necessarily follow from it. And, first, we see that the whole cosmic process is based upon funda- mental existences, properties, and forces, the visible results of which we term the '' laws of nature,'' and that, in the organic world at all events, these laws bring about continuous develop- ment, on the whole progressive. One of the subsidiary results of this mode of development is, that no organ, no sensation, no faculty arises before it is needed, or in a greater degree than it is needed. This is the essence of Darwinism. Hence we may be sure that all the earlier forms of life possessed the minimum of sensation required for the purposes of their short existence ; that anything approaching to what we term '' pain " was imknown to them. Thev had certain functions to fulfil which they carried out almost automatically, though there was no doubt a difference of sensation just enough to cause them to act in one way rather than another. And as the whole purpose of their existence and rapid increase was that they should pro- vide food for other somewhat higher forms — in fact, to be eaten — there was no reason whatever whv that kind of death should have been painful to them. They could not avoid it, and were not intended to avoid it. It may even have been not only absolutely painless but slightly pleasurable — a sensation of warmth, a quiet loss of the little consciousness they had, and nothing more — " a sleep and a forgetting." People will not keep always in mind that pain exists in the world for a purpose, and a most beneficent purpose — that of aiding in the preservation of a sufficiency of the higher and more perfectly organised forms, till they have reproduced their hind. This being the case, it is almost as certain as anything not personally known can be, that all animals which breed very rapidly, which exist in vast numbers, and which are necessarily IS NATURE CRUEL? 405 kept down to their average population by the agency of those that feed upon them, have little sensitiveness, perhaps only a slight discomfort under the most severe injuries, and that they probably suffer nothing at all when being devoured. For why should they ? They exist to be dt.'voured ; their enormous pow- ers of increase are for this end; they are subject to no danger- ous bodily injury until the time comes to be devoured, and therefore they need no guarding against it through the agency of pain. In this category, of painless, or almost painless ani- mals, I think we may place almost all aquatic animals up to fishes, all the vast hordes of insects, probably all IMollusca and worms; thus reducing the sphere of pain to a minimum throughout all the earlier geological ages, and very largely even now. When we see the sharp rows of teeth in the earlier binU and flying reptiles, we immediately think of the pain suffered by their prey ; but the teeth were in all probability necessary for seizing the smooth-scaled fishes or smaller land-reptiles, which were swallowed a moment afterw^ards ; and as no useful purpose would be served by the devoured suffering pain in the process, there is no reason to believe that they did so suffer. The same reasoning will apply to most of the smaller birds and mammals. These are all so wonderfullv adjusted to their environments, that, in a state of nature, they can hardly suffer at all from what we teinn accidents. Birds, mice, squiiTcls, and the like, do not get limbs broken by falls, as we do. They leani so quickly and certainly not to go beyond their powers in climbing, jumping, or flying, that they are probahly never injured except by rare natural causes, such a^^ lightning, hail, forest-fires, etc., or by fichtino- amono' themselves; and those who are injured without being killed by thc-^e various causes form such a minute fraction of the whole as to be reasonably negligible. The wounds received in fighting seem to be rarely serious, and the rapiditv with whidi al in a state of nature shows that whatever pain exists is not long- continued. 406 THE WOKLD OF LIFE It is only the large, heavy, slow-moving mammals which can be subject to much accidental injury in a state of nature from such causes as rock-falls, avalanches, volcanic eruptions, or falling trees ; and in these cases by far the larger portion would either escape unhurt or would be killed outright, so that the amount of pain suffered would, in any circumstances, be small ; and as pain has been developed for the necessary purpose of safe-guarding the body from often-recurring dangers, not from those of rare occurrence, it need not be very acute. Perhaps self-mutilation, or fighting to the death, are the greatest dan- gers which most wild animals have to be guarded against ; and no very extreme amount of pain would be needed for this pur- pose, and therefore w^ould not have been produced. But it is undoubtedly not these lesser evils that have led to the outcry against the cruelty of nature, but almost wholly what is held to be the widespread existence of elaborate con- trivances for shedding blood or causing j^ain that are seen throughout nature — the vicious-looking teeth and claws of the cat-tribe, the hooked beak and prehensile talons of birds of prey, the poison fangs of serpents, the stings of wasps, and many others. The idea that all these w^eapons exist for the purpose of shedding blood or giving pain is wholly illusory. As a matter of fact, their effect is whollv beneficent even to the sufferers, inasmuch as they tend to the diminution of pain. Their actual purpose is always to prevent the escape of cap- tured food — of a w^ounded animal, which would then, indeed, suffer useless pain, since it would certainly very soon be cap- tured again and be devoured. The canine teeth and retractile claws hold the prey securely ; the serpent's fangs paralyse it ; and the w^asp's sting benumbs the living food stored up for its young, or serves as a protection against being devoured itself by insect-eating birds ; which latter, probably, only feel enough pain to warn them against such food in future. The evidence that animals which are devoured by lion or puma, by wolf or wdld cat, suffer very little, is, I think, conclusive. The sud- denness and violence of the seizure, the blow of the paw, the IS XATUKE CiWELi 407 simultaneous deep wounds by teeth and claws, either cause death at once, or so paralyse the nervous system that no pain is felt till death very rapidly follows. It must be remembered that in a state of nature the Carnivora hunt and kill to satisfy hunger, not for amusement; and all conclusions derived from the house-fed cat and mouse are fallacious. Even in the case of man, with his highly sensitive nervous system, which has been developed on account of his unprotected skin and excessive liability to accidental injury, seizure by a lion or tiger is hardly painful or mentally distressing, as testified by those who have been thus seized and have escaped.^ Our whole tendency to transfer our sensations of pain to all other animals is grossly misleading. The probability is, that there is as great a gap between man and the lower animals in sensitiveness to pain as there is in their intellectual and moral faculties; and as a concomitant of those higher faculties. We require to be more sensitive to pain because of our bare skin with no protective armour or thick pads of hair to ward off blows, or to guard against scratches and wounds from the many spiny or prickly plants that abound in every part of the world ; and especially on account of our long infancy and childhood. And here I think I see the solution of a problem which has long puzzled me — wJiy man lost his hairy covering, especially from his back, where it would be so useful in carrying off rain. He inaij have lost it, gradually, from the time when he first became Man — the spiritual being, the 'Miving soul" in a corporeal body, in order to render him 7nore se7isitivc. From that moment he was destined to the intellectual advance which we term civilisation. He was to be exposed to a thousand self- created dangers totally unknown to the rest of the animal world. His very earliest advance towards civilisation — the use of fire — became thenceforth a daily and liourlv danger to him, to be guarded against only by sudden and acute pain ; and as he advanced onwards and his life became more complex; as he surrounded himself with dwellings, and made clothing and 1 See a brief discussion «>f tliis snl»jc<'t in my Darwinism, i>]>. :^()-40. 408 THE WOKLD OF LIFE adopted cookery as a daily practice, he became more and more exposed to loss, to injury, and to death from fire, and thus would be subject to the law of selection by which those less sensitive to fire, and therefore more careless in the use of it, became eliminated. Ilia tools continually becoming more and more dangerous, and his weapons becoming more and more destructive, w^ere alike a danger to him. The scythe and the sickle caused acci- dental woimds, as did the needle and the knife. The club and the axe, the spear and the arrow, the sword and the dagger, caused wounds which, if not avoided, led quickly to death. Hence beneficent pain increased with him as a warning of dan- ger, impelling him to the avoidance of wounds by skill and dexterity, by the use of padded clothing or of flexible armour; w^hile nature's remedies were sought out to heal the less deadly injuries, and thus avoid long suffering or permanent disable- ment. And ever as civilisation went on, such dangers in- creased. Explosives caused a new kind of wound from musket or pistol, and later from bombs and mines. Boats and ships were built and the ocean traversed. Endless forms of machin- ery were invented, at first hand-worked, and not dangerous to the worker, but soon driven by steam with such force that if carelessly entangled in it the worker's limbs might be torn from his body. And all this went on increasing till at last a large proportion of the human race laboured daily in peril of life or limb, or of painful wounds, or worse diseases. Against this vast ever-present network of dangers, together with the ever- present danger of consuming fire, man is warned and protected by an ever-increasing sensibility to pain, a horror at the very sight of wounds and blood ; and it is this specially developed sen- sibility that we, most illogically, transfer to the animal-world in our wholly exaggerated and often quite mistaken views as to the crueltv of nature! As a proof of the increased sensibility of the civilised as compared with the more savage races, we have the well-known IS NATURE CRUEL ^ 409 facts of the natives of many parts of the world enduring what to us would be dreadful torments without exhibiting any signs of pain. Examples of this are to be found in almost every book of travels. I will here only mention one. Among most of the Australian tribes there is a regular scale of punishment for various offences. When a man entices awav another man's wife (or in some other offence of an allied nature) the allotted punishment is, that the complainant and his nearest relatives, often eight or ten in number or even more, are to be allowed to thrust a spear of a certain size into the offender's leg between ankle and knee. The criminal appears before the chiefs of the tribe, he holds out his leg, and one after another the members of the offended family walk up in turn, each sticks in his spear, draws it out, and retires. When all have done so, the leg is a mass of torn flesh and skin and blood ; the sufferer has stood still without shrinking during the whole operation. Tie then goes to his hut with his wife, lies down, and she covers the leg with dust — probably fine wood ashes. For a few days he is fed with a thin gruel only, then gets up, and is very soon as well as ever, except for a badly scarred leg. Of course we cannot tell what he actually suffered, but certainly the aver- age European could not have endured such pain unmoved. This, however, is only an illustration. It is not essential to the argument, which is founded wholly on the principles of Darwinian evolution. One of these principles, much in- sisted on by Darwin, is, that no organ, faculty, or sensation can have arisen in animals except through its utility to the species. The sensation of pain has been thus developed, and must therefore be proportionate in each species to its needs, not heyond those needs. In the lowest animals, whose numbers are enormous, whose powers of increase are excessive, whose individual lives are measured bv hours or davs, and which exist to be devoured, pain would bo almost or quite useless, and would therefore not exist. Only as the organism increased in complexity, in duratiou of life, nnrl in exposure to danger which no THE WORLD OF LIFE migtit possibly lead to its death before it could either leave offspring or serve as food to some higher form — only then could pain have any use or meaning. I have now endeavoured, very roughly, to follow out this principle to its logical results, which are, that only in the higher and larger members of the highest vertebrates — mammals and birds, do the conditions exist which render acute sensations of pain necessary, or even serviceable. Only in the most highly organised, such as dogs and horses, cattle, antelopes, and deer, does there appear to be any need for acute sensations of pain, and these are almost certainly, for reasons already given, very much less than ours. The logical conclusion is, therefore, that they only suffer a very moderate amount of pain from such bodily injuries as they are subject to in a state of nature. I have already shown that in most cases, even from our much higher standard, their death would be rapid and almost pain- less ; whence it follows, that the widespread idea of the cruelty of nature is almost wholly imaginary. It rests on the false assumption that the sensations of the lower animals are neces- sarily equal to our own, and takes no account whatever of these fundamental principles of evolution which almost all the critics profess to accept. There is, of course, a large body of facts which indicate that whole classes of animals, though very highly organised, suffer nothing which can be called pain, as in the insects ; and similar facts show us that even the highest warm-blooded animals suffer very much less than we do. But my argument here does not depend upon any such evidence, but on the universally accepted doctrine of evolution through adaptation. According to that theory, it is only life-preserving variations, qualities, or faculties that have survival value: pain is one of the most important of these for us, but it is by no means so important to any other animal, ^o other animal needs the pain-sensations that we need; it is therefore absolutely certain that no other possesses such sensations in more than a fractional degree of ours. What IS NATURE CRUEL? 411 that fraction is we can only roughly estimate by carefully con- sidering the circumstances of each case. These show that it is certainly almost infinitesimal in by far the larger part of the animal kingdom, very small in all invertebrates, moderately small in fishes and reptiles, as well as in all the smaller birds and mammals. In the larger of these two classes it is prob- ably considerable, but still far below that of even the lowest races of man. A Possible Misconception It may be said — I fear it will be said — that this idea of the lower animals suffering less pain than we suffer will Ix* taken as an argument in favour of vivisection. Xo doubt it will; but that docs not in the least affect the actual truth of the matter, which is, I believe, as I have stated. The moral argument against vivisection remains, whether the animals suf- fer as much as we do or only half as much. The bad effect on the operator and on the students and spectators remains; the undoubted fact that the practice tends to produce a callous- ness and a passion for experiment, which leads to unauthorised experiments in hospitals on unprotected patients, remains; the horrible callousness of binding the sufferers in the operating trough, so that they cannot express their pain by sound or motion, remains; their treatment, after the experiment, by careless attendants, brutalised by custom, remains ; the argu- ment of the uselessness of a large proportion of the experi- ments, repeated again and again on scores and hundreds of animals, to confirm or refute the work of other vivisectors, remains ; and, finally, the iniquity of its use to demonstrate already-established facts to physiological students in hundreds of colleges and schools all over the world, remains. T myself am thankful to be able to believe that even the hiijhest animals below ourselves do not feel so acutely as we do; but that fact does not in anv wav remove mv fundamental disgust at vivi- section as being brutalising and immoral. 412 THE WORLD OY LIFE A Recent Illustration of the Necessity of Pain Within the last few years we have had remarkable proofs of the beneficence of pain as a life-saver by the sad results of its absence. The recently discovered X-rays, so much used now for localising internal injuries, and of bullets or other foreign objects in any part of the body, have the property also of setting up a special internal disorganisation unaccompanied at the time by pain. The result has been loss of limbs or loss of life to some of the earlier investigators, and perhaps some in- jury even to the patients for whose benefit it has been applied. It seems probable, therefore, that if these rays had been asso- ciated in any perceptible degTce with the heat and light we re- ceive from the sun, either the course of evolution would have been very different from what it has been, or the development of life have been rendered impossible. Pain has not accompanied the incidence of these rays on the body, because living organ- isms have never hitherto been exposed to their injurious effects. Microbes and Parasites: their Purpose in the Life-World Much light is thrown on the analogous problem of those human diseases which are supposed to be caused by germs, microbes, or 2:)arasites, by the application of the more extended views of evolution I have advocated in the present volume. The medical profession aj^pear to hold the view that pathogenic or disease-producing microbes exist for the purpose of causing disease in otherwise healthy bodies to which they gain access — that they are, in fact, wholly evil. It is also claimed that the only safeguard against them is some kind of ^' anti-toxin " with which everv one must be inoculated to be saved from the danger of attack by some or all of the large number of such diseases which affect almost every organ and function of the body. This view seems to me to be fundamentally wrong, be- cause it does not show us any use for such microbes in the scheme of life, and also because it does not recognise that a condition nf health is the one and only protection we require IS NATURE CRUEL? 413 against all kinds of disease; and that to put any product of disease whatever into the blood of a really healthy person is to create a danger far greater than the disease itself. On the general principles of the present argunienr there can be nothing in nature which is not useful, and, in a broad sense, essential to the whole scheme of the life-wtudd. (Jn this principle the purpose and use of all parasitic diseases, including those caused by pathogenic germs, i?^ to seize upon the less adapted and less healthy individuals — those which are slowly dying and no longer of value in the preservation of the species, and therefore to a certain extent injurious to the race by recpiir- ing food and occupying space needed by the more fit. Tlicir life is thus shortened, and a lingering and unenjoyable exist- ence more speedily terminated. One recent writer seems to hold this view, as shown by the following passage: " Before it was perceived that disease is an undisputable battle- field of the true Darwinian struggle for existence, the tremendous part which it takes in ridding the earth of weaklings and causing the survival of health, was all credited to the environment and its dead physical forces." ^ Bnt in this interesting article the writer elsewhere uses lan- guage implying that even the healthy require rendering '' im- mune " against all zymotic diseases. It is tliat idea which I protest against as a libel on nature and on the Ruler of the Universe; and in its practice as constituting a crime of equal gravity Avith vivisection itself. It will be said that quite healthy persons die (^f thesi^ dis- eases, but that cannot be proved; and the absolutely universal fact that it is among those living under unhealthy conditions in our towns, and cities, and villages, that suft'er most from these diseases is strongly against the truth of the statement. No doubt savage races often suffer drearlfully from these diseases; but savages are no more universally healthy than the more civil- 1 Parasitism and Natural Sclrotioii. l)y R. O. Eccles, M.D., Brooklyn, N. Y., U. S. A. 414 THE WOELD OE LIFE ised, though it is usually a different kind of unhealthiness. The only doctrine on this matter worthy of an evolutionist, or of a believer in God, is that health of body and of mind are the only natural safeguards against disease; and that securing the conditions for such health for every individual is the one and only test of a true civilisation. A few words in conclusion on the main question of pain in the animal world. In my treatment of the subject I believe I have given imnecessary weight to those appearances by which alone we judge of pain in the lower animals. I feel sure that those appearances are often deceptive, and that the only true guide to the evolutionist is a full and careful consideration of the amount of necessity there exists in each group for pain- sensation to have been developed in order to preserve the young from common dangers to life and limb before they have reached full maturity. It is exactly the same argument as I have made use of in discussing the question of how mxuch colour-sense can have been developed in mammals or in butterflies. In both cases it depends fundamentally on utilities of life-saving value as required for the continuance of the race. Hitherto the prob- lem has never been considered from this point of view, the only one for the evolutionist to adopt. Hence the ludicrously exag- gerated view adopted by men of such eminence and usually of such calm judgment as Huxley — a view almost as far re- moved from fact or science as the purely imaginary and humanitarian dogma of the poet: The poor beetle, that we tread upon, In corporal sufferance feels a pang as great As when a giant dies. Whatever the giant may feel, if the theory of evolution is true, the '' poor beetle " certainly feels an almost irreducible minimum of pain, probably none at all. CHAPTER XX INFINITE VARIETY THE LAW OF THE UNIVERSE CONCLUSION Throughout the present work I have liad occasion to call attention to the endless diversity that characterises both organic and inorganic nature. In a previous work, Man's Place in the Universe, I was impressed by the diversity which the new astronomy had shown to exist throughout the stellar universe. Since that book was written such remarkable advance has been made in relation to the nature of matter itself, as to constitute almost a new science. It seems desirable, therefore, to say a few words here upon the whole question of the variety and complexity of every part of the material universe in its rela- tion to man as an intellectual and moral l:)eing, thus summaris- ing the whole aim and tendency of the present work. It will, I think, be most instructive to follow the same order as I have adopted in the present volume, of showing how each kind of variety and complexity that presents itself to us can be traced back as dependent upon a preceding complexity, usually less obvious and more recently brought to light. Thus, the most obvious of all the diversities in nature is that of the various forms (or kinds) of animals and plants ; whereas the diversities of inorganic nature — stones, rocks, etc., are far less obvious, and were discovered at a much later period. The Causes of the Diversity of Life-forms Modern research shows us that the immense diversitv of life- forms we now find upon the earth is due to two kinds of causes, the one immediate, the other remote. The iuimediate cause is (as I have endeavoured to show here), the slow but continu- ous changes of the earth's surface ns regards contour, altitude, climate, and distribution of land and water, which successively 415 416 THE WORLD OF LIFE open new and unoccupied places in nature, to fill which some previously existing forms become adapted through variation and natural selection. I have sufficiently shown how this proc- ess has worked throughout the geological ages, the world's sur- face ever becoming more complex through the action of the lowering and elevating causes on a crust which at each succes- sive epoch has itself become more complex. This has always resulted in a more varied and generally higher type of vegeta- tion, and through this a more varied and higher type of animal life. The remote but more fundamental cause, which has been comparatively little attended to, is the existence of a special group of elements possessing such exceptional and altogether extraordinary properties as to render possible the existence of vegetable and animal life-forms. These elements correspond roughly to the fuel, the iron, and the water which render a steam-engine possible; but the powers, the complexities, and the results are millions of times greater in the former, and we may presume that the Mind which first caused these elements to exist, and then built them up into such man^ellous living, moving, self-supporting, and self-reproducing structures, must be many millions times greater than those which conceived and executed the modem steam-engine. Variety of Inorganic Substances The recognised elements are now about eighty in number, and half of these have been discovered during the past century ; while twenty of them, or one-fourth of the whole, have been added during the last fifty years. These last are all very rare, but among those discovered in the preceding fifty years are such now familiar and important elements as aluminium, bromine, silicon, iodine, fluorine, and chlorine. So far as the elements are concerned, our earth has doubled in apparent com- plexity of structure during the last century. But if we take account of the advance of chemical science, the knowledge that has been obtained of the inner nature of the best-known older THE PURPOSE OF DIVEHSITY 417 elements, the wonderfully c'()ini)lr'x laws of tlioir combinations, and the immense variety of their known eompounds, our ever- increasing knowledge of the complexity of matter will he vory much greater. During the early part of the nineteenth century, tlie old idea of atoms as being indivisible, incompressible, and inde- structible particles, almost universally prevailed. They were usually supposed to be spherical in form, and 1<> 1m^ the scat of both attractive and repulsive forces, leading to cohesion and chemical combination. Those of the different elements were supposed to differ slightly in size, and energy, which led to their differences of weight and other properties. The whole conception, though we now see it to be totally inadequate, was comparatively simple, and with the help of the mysterious elec- tric and magnetic forces seemed capable of explaining much. But, decade after decade, fresh discoveries were made ; chem- ical theory became more and more complex; electricity, the more it was known the less intelligible it became ; while a host of new discoveries in the radiant forces of the ether seemed to show that this mysterious substance was really the seat of all the forces of the universe, and that the various basic forms of matter which we term elements were nothing more than the special manifestation of those forces. It thus became evident that all our progress in physical science rendered the world of matter far more wonderful, and at the same time less intel- ligible than it had ever seemed to us before.^ 1 The progress of modern chemistry well shows this increasing com- plexity with increasing knowledge. The fact of carbon existing in three distinct forms — charcoal, graphite, and diamond, each with its own special physical and chemical characters — has already been referred to. Hut it is found that many other elements have similar properties, especially sili- con, phosphorus, arsenic, antimony, sulphur, oxygen, and several others. This curious property is termed allotropy; and it seems somewhat analo- gous to that property of many compound substances termed isomerism, of which two striking examples were given at tlie beginning of the last chapter. Another modern braneh of chemistry is the stuily of the relation of crystallised substances to polarised light, which reveals nuiny new and strange properties of identical compounds, and is termed iStcrcochcmistry. 418 THE WORLD OF LIFE Eetuming now to the different forms under which matter exists in that portion of the earth which we can examine, we find them to be very limited as compared with those of the organic world. The crust of the earth, and presumably the interior also, consists mainly of what are called minerals, which is the term used for all chemical compounds of the elements which have been produced under natural laws and forces, and constitute the materials of the whole planet. They comprise, besides the elements themselves, the various salts, alkalis, earths, metallic ores, precious stones, and crystals, which have a def- inite chemical constitution, a permanent form, and definite characters ; forming what are termed mineral species. These, when disintegrated by natural forces, intermingled in various ways, and solidified in various degrees, make up the whole mass of rocks and surface material of the earth. The total number of mineral-species now known, almost the whole of which are to be found in the fine mineralogical gallery of the British Museum, is almost exactly a thousand. Many of these are very rare or local, the great bulk of the rocks being made up of a few score, or at most of a few hundreds of them. The generally accepted idea being that the whole earth was once a molten mass, the crust may be supposed to give a fair sample of the whole ; and the additional fact that, during all geological time, matter from the interior has been brought to These various properties of the atoms and molecules of matter have so complicated their relations, that the attempt to unravel them has led to a system of equations, of diagrams, and of formulae, which are almost as difficult for the general reader to follow in detail, as is the working out of some abstruse mathematical investigation. As an example of this complex- ity in chemical nomenclature I may refer to a recent paper by Sir William Crookes, on the rare metal scandium (discovered in 1879). Near the end of this paper (in the Proc. Roy. Soc, series A, vol. 84, p. 84), the author says : " By the kindness of Dr. Silberrad, I have had an oppor- tunity of experimenting with octamethyltetraminodihydroxyparadixunthyl- bezonetetracarboxilic acid." He then adds : " Previous experiments would lead one to expect the scandium salt of this acid to have the composition C44H4oOi4N4Se;. The only scandium salt I could form with this acid has the composition CssHjgOoaXsSCj. THE PURPOSE OF DIVEESITY 419 the surface by volcanoes and liot springs, renders it prol>:d)lo that very few either of the elements or compounds remain unknown. The skill of the chemist, however, has led to the production of a much greater number of stable chemical compounds than occur in nature. These are used in medicine or in the various arts, and their numbers are very great. They are usually divided into two classes, the inorganic and the (jrganic; the former being of the same nature as tliose of the great bulk of the mineral species, while the latter, called also carbon-com- pounds, resemble the products of living organisms of which carbon is an essential part. A recent estimate of the known inorganic compounds, natural and artificial, bv a French chemist is 8000 ; but ^Ir. L. Fletcher, of the British [Museum, informs me that this number must onlv be taken as an '' irreducible minimum.'' As to organic compounds, I am told by Professor II. E. Arm- strong, that they have recently been estimated at about 100, 000 ; but he states that the j^ossihilities of forming such com- pounds are infinite, that chemists can make them by thousand if required, and that they now limit themselves to those which have some special interest. The approximate figures for the various kinds of stable chemical compounds now known, will therefore form an easily remembered series : — Mineral species 1 ,000 Inorganic compounds (artificial) 10,000 Organic compounds (artificial) 100,000 Possible organic compounds Infinite! What a wonderful conception this affords us of the possi- bilities of the elements (or rather of about one-fifth of them) to produce the almost endless variety of natural products in the vegetable and animn! kinirdoms. Tliese possibilities must depend upon the "properties" of the elements; not only their actual properties as elements, but their latent pntperties through which they not only combine with each other in a great variety of ways, but, by each eombi nation create, as it 420 THE WOELD OP LIFE were, a new substance, possessing properties and powers dif- ferent from those of any other substances whatever. These almost infinitely various properties of chemical combinations, together with a host of other problems with which the organic chemist has to deal, have led some of them to almost exactly the same conclusion to which I have been led by a more super- ficial view of the marvels of '' growth " and cell-division in living organisms. In the Address already quoted, Sir H. E. Armstrong says, after referring to some of the complex and extraordinary chemical transformations produced by living plants : " The general impression produced by facts such as these is, that directive influences are the paramount influences at work in building up living tissues." And again more explicitly : " It would seem that control is exercised and stability secured in several ways; not only is the form laid down in advance but certain chosen materials are alone available, and the builders can only unite particular materials in particular ways." It is very satisfactory to find that both chemists and physiologists recognise the absolute need of some controlling and directive power in elaborating the special products or building up the complex tissues of plants and animals. The Cause and Purpose of this Variety The general conclusion to which the whole argument of this volume tends, is, that the infinite variety we see in nature can be traced back step by step to the almost infinite complexity of the cells by means of which they live and gi'ow; of the protoplasm which is the substance of the cells; of the elements of which protoplasm consists ; of the molecules of those elements ; and finally of the atoms whose combination forms the separate and totally distinct elementary molecules. And at each step farther back we are as far ofi^ as ever from com- THE PUliPOSE or DlVEruSITY 421 prehending how it is possible for such infinite diversity to be brought about. And now that we are led to believe that the atom itself is highly complex — that it is a system of re- volving electrons or coi-puscles, held together by tremon«lous forces — the mystery becomes deeper still, and we find it (piite hopeless to realise what is the nature of the controlling power and mind, Avhich out of such unimaginable entities lias built up the vast material universe of suns and systems of which our earth foimis a fractional part, together w^ith that even more complex world of life of which we ourselves are the out- come. The overwhelming complexity and divei'sity of this vast cosmos in its every part and detail, is the great fundamental characteristic which our highest science has brought promi- nently to our notice ; but neither science nor religion has given us the slightest clue as to why it should be so. Science says : " It is so. Ours not to reason why ; but only to find out what is.'' Religion says : " God made it so " ; and sometimes adds, " it was God's will ; it is impious to seek any other reason." In the present work I have endeavoured to suggest a reason which appeals to me as both a sufficient and an intelligible one: it is that this earth with its infinitude of life and beauty and mystery, and the universe in the midst of which we are placed, with its overwhelming immensities of suns and nebuho, of light and motion, are as they are, firstly, for the develop- ment of life culminating in man ; secondly, as a vast school- house for the higher education of the human race in pn^jia ra- tion for the enduring spiritual life to which it is destined. I have endeavoured to show that some portion at least of what seems a superfluity of elements in our earth-structure has ser\'ed the purpose of aiding the gi'adual progress of man from barbarism to material civilisation ; while another portion has furnished him with materials which have alone enabled him to penetrate into the two unkninvn worlds with which ho was encompassed — those of the nlniost infinitely great and of the almost infiuitelv little; but both alike attractive an^iila. 40: on orcliids of ('aj)e peninsula. 41 434 INDEX Borneo, rich forest flora of, 49; birds of, 51 Botanical, reserves, advantages of small, 82 BovERi's experiments on echini, 373 Brain-cavity of Dinocerata very small, 239 Brains of early vertebrates, small, 291 Brazil,, richness of flora of, 75 Britain, peculiar animals and plants of, 135 British India, flora of, 47; chief natural orders of, 48 British plants, numerical distribu- tion of, 24, 27; of limited range, 26 Brittan, Mr. L. K, on flora of Jamaica, 67 Brontosaurus excelsus, skeleton of, 221 Butler, Sir W., on mosquito- swarms, 146 Butterflies, recognition by, 181, 185 Butterexy, stages of development of, 325; scales on wings of, 325 Butterfly and caterpillar, diverse structure of, 321 Caltha palustris, wide range of, 19 Cambrian age, first known life of, 207 Campanula isofpTiylla, small range, 20 Cape Colony, flora of, 75 Cape peninsula, rich flora of, 40 Cape Region, rich flora of, 35, 77 Carbon, the mystery of, 390; prop- erties of, 391; in the ocean, 392 Carnlvora, early forms of, 240; ex- tinct South AmericaUj 249 Cavies, numerous extinct, 252 Celebes, flora of, 55, 85 Cell, the mystery of, 361; charac- teristics of, 363; implies an or- ganising mind, 364; described by Professor Lloyd-Morgan, 364 ; Weismann's description of a di- viding, 365; Weismann's state- ment of its powers, 369 Cell-problem, concluding remarks on, 376 Ceratites nodosus, 289 Ceratosaurus nasicornis, skull of, 222 Cetiosaurus leedsi from Oxford clav, 220 Challenger voyage defines area of deposition, 192 Chemical problems of water, 393; nomenclature, illustration of com- plexity of, 418 *u China and Coreaj flora of, 34 Christianity, gradual rise of a purer, 302 Cities, the "wens" of civilisation, 308 CoaLj wide distribution of palaeo- zoic, 212; prepared atmosphere for higher life, 213 Cobbett, William, on "wens," 308 Cockerell, on tropical species as compared with temperate, 104 Coleoptera, number of British, 90; number known, 91 Colour, for concealment, 169; ex- tremes of, 298; of flowers sup- posed to show inedibility, 332; purpose of in nature, 334; of plants and animals in relation to man, 340; our sensations of, an argument for design, 348, 349 Colour-sense not identical in birds, mammals, and man, 325, 342 Colours of butterflies, uses of, 183 Colours and ornaments of males, how caused, 282 Compounds, inorganic, number of, 418; number of organic (artifi- cial), 419 Condylarthra, 235 Conocoryphe sultzeri, 287 Continental extensions, appendix on, 268; great difficulties of, 269, 270 Continents, how built up, 196, 198 Coryphodon, an early ungulate, 235 Creators of matter and life not necessarily omnipotent, 422 Creodonta, early carnivores, 242 Crioceras emerici, 289 Crookes, Sir W., gives an example of complex chemical nomencla- ture, 418 Cruelty of nature, supposed, 398 Crustacea, early appearance of, 210 D^dicurus, giant extinct arma- dillo, 252 Darwin on flora of a very small area, 87; on increase of elephant, 123; on Porto Santo rabbits, 137; on the uses of colour to plants, 329; on cross-fertilisation of flowerSj 330; on war of nature. INDEX 435 399; on intelligent cause of the universe, 422 Darwinism, extensions of, 271 Deane, Mr. H., on flora of Sydney, New South Wales, 42 De Candolle, a., on botanical gco^j;- raphy, 18, 24; botanical regions of, 20 Definition of life, 3 Denudation, rate of, measured, 189 Deposition, area of, 191 Determinants, meaning of, 293 Development, reversal of, 245; cases of extreme, 29G Diagram of human stature, 116; of variation of rice-bird, 118; of nuclear division, 370; of isomer- ism, 384 Dicynodon lacerticeps, early reptile, 214 Dimetrodon, extinct reptile from Permian of Texas, 215 Dinocerata, " terrible horned beasts," 236 DiNOSAURIA, 217 DiPLODOCUS, skull of, 222 Diplodocus carnegii, skeleton of, 220 Diprotodon australis, skull of, 257 DiPTERocARPS, abundance of in Borneo, 56 Directive agency not explained by Darwin's *' pan-genesis " nor any other theory, 319, 358; indica- tions of, 354; at work, 373, 374 Distribution of species result of continuous adaptation, 103 Domestic animals, uses of, 305 Dresser, Mr. H. E., on birds breed- ing in Arctic regions^ 155; on mosquitoes as food for birds, 157 Drosera rotundifolia, wide range of, 18 Drought, adaptations of plants to, 72 DwiNA river, rich deposits with early reptiles, 214 Earth's surface changes a cause of evolution, 187 ; thickness of crust of, 194; crust floats on melted in- terior, 195; eff'ect of cooling ami contracting, 19G; surface-motions, long persistence of, 200 ; remlered habitable by water, 3!)6 Eccentricity in nature, 298 Eccles, Dr. R. G., on uses of par;i- sites, 413 Echinus microtuhcrculutus, egi^ of, 373 Edentata, extinct S. American, 252 Educational elTects. unlimited in tiie spirit-worlfl. 4'JM Elements in nlalion to tiie life- \\orI(l, 3S:{ : important and unim- portant, 385; list of important, 38(i ; in iclation to man, 387 Elephants, rate of increase of, 123; the origin of, 244 ; diagram of development of, 24(1 Elephas gatusa, enormous tusks of, 287; prim'ujcniuHy .skeleton of, 249 Eternity as explaining evolution fallacious, 37!> European floras in dilTerent lati- tudes, 32; compared, 36 Evolution, motive power of or- ganic, 187 Extensions of Darwinism, 271 Extinction of pleistocene mam- mals, cause of, 261 Feathers, marvel and mystery of, 309 Female choice, new argument against, 184 Ferns, extreme abundance of, in the Philippines, 54 Fishes, peculiar British, 135; the earliest known, 208; types of tails of, 209 Fletcher, Mr. L., on inorganic compounds, 419 Flight of birds and insects com- pared, 94 " Flora Orientalis," species in. 34 Flora of China, 34; of Chile, 35; of Cape region, 35; of tropical Asia, 46; of British India, 47; of ;Malay Peninsula, 47; of Borneo, 49; of Indo-Ciiina, 50; of Malay Islands, 50; of New C.uinea, 55; of Philij)pine8, 54; of CeleU's, 55, 85; of (.4)ueensland, 58; of trop- ical Africa, 59; of Madagascar, 59; of tropical America. 58, 59, ()5 ; of lirazil, 63; of Mexico luid Central America, 64; of Jamaica, 67; of Trinidaii, 67; of CJulapa- gos Islamls. 67; of I^igoa Santa. 67, 77; of Penang, 79; of Kain- bangan Islamls, 80; of Pange- ranifo. 81 ; of mountains in .la- pan. SCf. of very small areas. 87 I'l.ouAS of (liirercnt regions com- parctl. 11; of counties compared. 436 IKDEX 27 ; of some parishes, 28 ; of small areas, 28, 77 ; of temperate zones 30; cause of richness 35; warm temperate compared, 3G; of European small and 86; compared, of some. areas, o/ ; of mountains plains compared, 38, 40, extra-European temperate, 39 Flowering plants, peculiar British, 134 Flowers, al)undance of, within Arc- tic circle, 153 Food of young birds, 142 Forbes, Mr. H. 0., on self-fertilisa- tion of orchids, 332 Forest reserves, advantages of small botanical, 79 Fruits, colour of, 336 Galapagos, flora of, 67 Galton's law of heredity, 110 Gamble, Mr. J. T., on flora of Malay Peninsula, 47 Gardner, on flora of Brazil, 77; on supposed greater richness of mountain floras, 80 Gatke, Herr, on bird-migration at Heligoland, 161 Geese moulting in Arctic regions, 148 Gentiana verna, one locality in Britain, 26 Geological record, account of, 203; its three well-marked periods, 204; the teaching of. 300 Geology, as influencing evolution, 188 Germinal selection, 281, 292, 296 Glass essential for science, 338 (ilyptodon clavipes, skeleton of, 253 Glyptodontid.e, extinct armadillos, 252 Grant Allen on insects and colour of flowers, 333 Grey plover's nest in Arctic re- gions, 156 Griesbach, on Mediterranean flora. 34; on Brazilian flora, 76 Growth, the nature of, 315; by cell- division, 316; admitted to be in- explicable, 371; by cell-division, what it implies. Dr., on Gunther, 94 Haeckel human ether, 7, scions. 373 species of birds. on consciousness, o ; on nature, 6; matter and ,8; on soul-atom uncon- 358; his carbon-theoiv of life, 391 Hamites rotundity, 290 Hardy, Mr. W. B., on complexity of proteid molecule, 383 Hartert, Dr., on peculiar British birds, 135 Hayati, Mr., on floras of Japanese mountains, 39, 40 Heat, rate of increase in deep bor- ings, 194 Heligoland and migrating birds, 160 Hemsley, W. B., on flora of Central America, 61 Heredity a universal fact, 109; Galton's law of. 110 Heteroceras etnerici, 289 Hooker, Sir Joseph, on flora of British India, 47; on primary floras, 65; on rich flora of Pe- nang, 77; on floras of very small areas, 87 Horns as recognition-marks, 173 Horses, extinct South American, 250 Hudson, W. H., on field mice in Argentina, 132 Human character, diversity of. 426 Hutton, Capt., on recognition- marks, 178 Huxley, Professor, on nature and origin of life. 9; on matter and spirit, 10; on crueltv of nature, 400 Hycenodon cruentus, skeleton of, 242 Hyopotamns hrachyrhynchns, skele- ton of, 243 Ichthyopterygia, 223 Ichthyosaurus, paddles of, 224 Ichthyosaurus communis, skeleton of, 224 Iguanodon hemissartensis, of, 218; skull of, 219 Increase in plants and 121 Indo-China, estimate of flora of, 50 Inheritance of educational results would have checked diversity, 427 Inorganic substances, varietv of, 416 Inostransevia, huge carnivorous reptile, skull of, 2l6 Insect life of secondary period, 228 Insect pests, uses of, 142 Insects, known species of, 91; pe- culiar to Britain, 135; earliest known. 211; and their metamor- phosis, 321 skeleton animals, i:tTDEX 437 Insects and birds, co-adaptation of, 143 Irish deer, skeleton of, 287 Isomerism explained, 385 Jack-rabbit, E. S. Thompson on, 172 Jamaica, flora of, 67 Japan, mountain floras of, 40 Java, rich flora of, 80 JoRDAX, Dr. K., on phosphorescent colours in lepidoptera, 347 JuDD, Professor, on strange forms of ammonites, 87 Kambangan island, rich flora of, 80 Karoo formation, reptiles of, 213 Kearton on increase of rabbits, 122 Kerner, Dr. A., on power of in- crease of plants, 121 ; on the in- sect enemies of flowers, 331 ; on "vital force/' 356; on arrange- ment of atoms in the carbon- compounds, 384 KooRDERS, Dr., on the flora of Celebes, 55, 85; on rich floras of small areas in Java, 79 Lagoa Santa, flora of, 67, 75 Land-shells, peculiar British, 135 IjAtitude as influencing floras, 31 Lemming, periodical migrations of, 128-30 Lepidoptera, number of British, 89 ; number known, 91 ; peculiar British, 135; wealth of colour in, 345-47 Life, definition of, 3 ; Haeckel on, 4, 7 ; the cause of organisation, 8; reactions of animal and plant, 304 ; the sole cause of life, 306 ; a suggestion as to origin of, 422 Life-deveix)pment of mesozoic era, 231; conclusion on, 299 Life-forms, causes of diversity of, 415 Life-world, progressive development of, 203 Limestone, progressive increase of, 234 lAthospermiim gastoni, narrow range of, 19 Llamas, extinct S. American, 240 Lloyd-Moroan, statement of theory of germinal selection, 292; on rapid cell-growth, 375 Ltdekker, jSIr., on Patagonian mar- supials, 241; on affinities of American and Australian marsu- pials, 265 Lyell, Sir C, on causes of extinc- tion, 264 London, how to stop growth of, 308 LowNE, Mr. B. T., on development of blow-fly, 323 Machcerodus neogcpua, skull of, 286 Macrmichenia patachonica, 251 Macroscaphiies ivanii, 290 Madagascar, flora of, 59 M cerifherium lyonsi, skull of, 244 Malay Islands, flora of, 50; in- sects of, 92 Malay Peninsula, table of chief orders of plants, 47 ; character- istic plants of, 48 Mammalia, teachings of pleistocene, 265 Mammals, extinct Australian, 256 Man, the cause of extinction of pleistocene mammals, 268-70; the glory and distinction of, 402-06; the most sensitive of organisms, 409 Mantell, Dr., discovered extinct reptiles in Kent, 217 Marsh, Professor O. C, on Bronto- saurus, 220; on Dinocerata, 237; on small brains of early mam- mals, 239; causes of extinction of mammals, 263 Marsupials in Patagonian miocene, 240; of the Australian type still living in the Andes, 264 Martius's flora of Brazil, 63 Mastigophora, 362 Mastodon in S. America, 254 Mastodon americanus, skeleton of, 247 Mastodons, less developed ele- phants, 246 Max Verworu on chemistry of pro- toplasm, 316; on vital force, 317 Mediocrity, recession towards, 117 ^Mediterranean flora, species in, 34 Megatherium, extinct ground sloth, 252 Megatlierium giganteum, restoration of, 254 Mendelism and mutation inefficient as substitutes for Darwinian evo- lution, 133 ]\rKRRiLL, Mr. E. D., on flora of the Pliilii)pines, 54 Mesozoic era, 213; mammalia of, 228: insects of, 228; life-develop- ment of, 231 438 INDEX Metals, the seven ancient, 387; es- sential for civilisation, 388 Metamorphosis of insects, 321 Mexico and Central America, flora of, 64 Microbes, use of in nature, 412 Migration, origin of bird, 159; facts and inferences, 160-63 Mimicry, 169 Minahassa, N. Celebes, flora oF, 55, 85 Mind and purpose in life-develop- ment, 299 ; and life, different de- grees of, 307; produces brain, 307 Minerals, number of species of, 418 Mivart, St. George, on recognition- marks, 179 Morgan, Professor L., on germinal selection, 292; on rapid cell- growth, 375 Mosquitoes, uses of, 145; descrip- tion of Arctic, 146; food for most young birds, 151 Mosses and hepaticse, peculiar British, 135 Mountain floras, in Japan, 40; not richest, 97 MtJLLER on insect-fertilisation of flowers, 333 Mylodon, contemporary of man, 254 Mylodon rohii^tus, skeleton of, 254 Narwhal's tusk an extreme devel- opment, 296 Natural selection, illustrative cases of, 134; of sparrows at Ehode Island, 138; process of at Porto Santo, 138 Nature, the sanctity of, 301; our defacement of, 301; is it cruel? 398 New Guinea, biologically unique, 51 ; flora of, 55 : richness of its bird fauna, 96, 98 Newton, Professor A., on passenger pigeon, 128 North American floras in various latitudes, 34 Nototherium, extinct Australian wombat, 260 Nuclear division, diagram of, 370 Nucleus, importance of, 373 Nummulites, 363 Nuts, why intended to be eaten, 337 Ocean, carbon in, 392 Orchids, abundance of in Cape Peninsula and New South Wales, 41 ; in British India, 48 Okeodontid.e, early American rumi- nants, 242 Organising spirit the cause of life- production and control, 425 Organs, beginnings of new, 271 Ornithosaltiia, 224 Pain, its purpose and limitations, 398; a product of evolution, 404; beneficent purpose of, 412; where useless does not exist, 413; in na- ture, Huxley's exaggerated view of, 400, 414 Pal.eomastodons, early elephants, 244-45 Palceotherium magnum, restoration of, 244 Paleozoic era described, 206 Palms, abundance of in the Malay Peninsula, 47; in the Philippines, 54 Pangerango, Mount, rich flora of, 81 rarndoxides hohemicus, 287 Pariasaurus hainii, skeleton of, 214 Passenger pigeon now extinct, 125; enormous population of less than a century ago, 125 Penang, rich flora of, 79 Phascolotherium, 231 Phenacodiis primcBvus, early ungu- late, 235 Philippines, rich flora of, 54 Physiological allegory on growth, 319 Plant-cell, Kerner on, 371; iden- tity with animal cell, 372 Plants of wide distribution, 21; abundance of compared, 23; of very small areas, numbers of, 98 Pleistocene mammalia, teachings of, 259 Plesiosaurus macrocephalus, skeleton of, 222 PoE, extracts from supposed im- pressional poem by, 428 Porto Santo rabbits, newly formed species, 137 Potentilla rupestris, one locality in Britain, 27 PouLTON, Prof. E. B., on beginnings of new organs, 272 Primates, fossil species of South America, 249 i:n^dex 439 Primula imperialis, small range, 19 Proteid molecule, complexity of, 383 Prothylacinus, a Patagonian mar- supial, 240 Protoplasm, its chemical nature, 315 Pteranodon occidentalis, skeleton of, 226; longiceps, skull of, 227 Pterodactyl, restoration of long- tailed, 22G Pterodactylus spectahilis, skeleton of, 225 Ptychoceras emeridanum, 290 Purpose of our universe to produce variety of human character, 299, 421 Pyrothebia, 251 Queensland, flora of, 58 Rabbits, increase of in Australia, 123 Radiolaria, 362 Radium, its rarity and uses, 389 Ramsay, Sir A., on life of the Cam- brian age, 207 Recognition by butterflies, 181 Recognition-marks important for evolution, 168; explained, 170; objection to answered, 178; gen- eral conclusions on, 185 Religion, gradual rise of a true, 302 Reptiles, earliest, 214 Reptilian life of secondary period, 227 Retrogressive development in birds, 309 Rhizopoda, 362 Rice-bird, diagram of variation of, 118 Ridley, Mr., on flora of Singapore, 79 River-basins, rate of denudation of, 189 Roscoe, Sir H., on properties of carbon, 388; on water in relation to life, 391 Saleeby, Dr., on eternity as an ex- planation, 379 Sap, extreme production of, 299 Sauropterygia, 223 Scales on wings of buttciilics, .'l-i.") -. apparent purpose of, 327 Scelidosaurus harrisoni, skeleton of. 218 Sceloditherium leptocephalum, skel- eton of, 255 ScLATER, Dr. P. L., on species of birds, 94 Seeboiim, H., on food of birds in Arctic regions, 146 Seton-Tiiompson on recognition- marks, 172 SiiARPE, Dr. B., on species of birds, 94 Shipley, A. E., table of described animals, 99 Simethis bicolor, one locality of in Britain, 27 Singaporp:, flora of, 79; destruction of forest in, 85 Sisymbrium sophin, power of in- crease of, 121 Small-brained animals, purpose of, 306 South Africa, Cape Region, flora of, 79 South America, tertiary mammals of, 249 Spalacotherium, 229 Sparrows at Rhode Island, work of natural selection on, 138 Species defined, 12; distribution of, 13; uncertainty of limits of, 25; rarity of precedes extinction, 26; number of, in relation to evolu- tion, 100; variation of. 113; ex- tremely common, 114; to be seen everywhere, 115 Spencer, H., on co-ordination of variations, 275; reply to, 276, 277; his " unkno^^^l reality" more concretely expressed, 430 Spirit-life described (inspiration- ally) by Poe, 428 Springbok, curious recognition- mark on, 174 Spruce, Dr., on rich flora of Ama- zon, 61 Sterrolophus fJabeJIatus, skull of, 219 Stone-curlews, recognition marks of, 175 Sydnetx", extreme abundance of or- chids near, 41 Table of De Candolle's botanical regions, 20; of chief natural orders in various floras, 22; of number of species in large and small areas. 28; of numln^r of species in difTerent latitudes, 31: of floras of European oonntries according to latitude, 31; of 440 INDEX floras of XortH American areas, 32; of warm temperature floras, 36; of European floras of small areas, 37; of extra-European temperate floras, 39; of large tropical floras, 45; of chief orders of flora of British India, 47; of chief orders of tropical Sikkini. 48; of chief orders of Malay peninsula, 48; of chief orders of the Philippines, 54; of chief or- ders of Celebes, 56; of chief or- ders of Madagascar, 59; of chief orders in tropical American floras. 64 ; of chief orders of Mex- ico and Central America, 65; of chief orders of Nicaragua to Panama, 67; of chief orders of Lagoa Santa, 71; of number of species in tropical floras of small area, 77 ; of number of species in temperate floras of small area, 77; of distribution of lepidoptera in Britain, 89; of distribution of coleoptera, 90; of described species of orders of insects, 91; of species of birds in Europe, 95; of species of birds in zoological re- gions, 96; of described species of living animals, 99; of percentage of mean error of variation. 121 ; of peculiar sub-species of British birds, 136; of rate of lowering of river-basins, 189 Teeth, gradual loss of during de- velopment, 291 Temperate floras compared, 30, 36, 39; floras, small areas, 77 Temperature - adjustments of earth's surface. 202 Tertiary period, life of, 235 Tetrabelodon, restoration of, 245 Tetrahelodon angustidens, skeleton of, 246 Theriomorpha, beast-like reptiles of Karoo formation, S. Africa, 213 Thompson, E. Seton, on recogni- tion-marks, 172 Thomson, Prof. J. A., on deter- minants, 293; on mechanics of the germ-plasm, 370; on nature's stern methods, 399 Thought-transference the agent in life-production and guidance, 425 Thylacoleo carnifex, skull of, 258 Titanotherium rohustum, skeleton of, 238 Toxodon platensis, skeleton of, 250 TOXODONTIA, 251 Truchycerafiaon, 289 Tkicoxodon, 229 Tkilobites, early and late forms of, 287 Tkixiuad, flora of, 68 Thopical floras of the world, 43; of large areas compared, 45; small areas, 77 Tropical and temperate vegetation compared, 105 Thopical vegetation, causes of rich- ness of, 106 Tylor, a., on rate of denudation, 189 Uintatherium ingens, skeleton of, 236; cornutum, skull of, 237 Ungulata, early forms of, 235; extinct South American, 249 Universe, purpose of the stellar, 299 ' Upheaval produced by contraction, 197 Variation of mind as great as of body, 114; as shown in curve of stature. 116; of the various parts of a bird, 118 Variation of species, 113 Variations, co-ordination of, 275 Variety in nature, purpose of, 300; the law of the universe, 415; cause and purpose of, 420 Vegetable products in relation to man, 350 Vegetation, differences of tropical and temperate, 105; early, 210 VernoNj Dr. H. M., on variation, 119; on parts of human body varying independently, 120 Vertebrates, special features in development of, 291 Vital force. Max Verworu on, 316; Dr. A. Kerner on, 356 WARiiiNG, Professor Eug., on flora of Lagoa Santa, 67, 74 Water in relation to life, 394; com- plex problems of, 395; as prepar- ing earth for man. 397 Weismann's theorv of germinal se- lection, 292 Weymouth, abundance of ammon- ites at. 288 INDEX 441 Wilson, Alexander, on numbers of passenger pigeons, 125, 126 Winter transformed into summer, 153 Wood, various qualities of, 352 Woodrufffc-Peacock on detailed floras, 15; on meadow and pas- ture plants, 17 Woodward. Dr. A. S., on progress- ive developments of some charac- ters, 285; on small brains of early vertebrates, 270 Wulfenia carinthiaca, small range of, 19 X-RAYS prove use of pain, 411 Zoological regions, species of birds in, 96 i i