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 1653 East Main Streal 
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^ 
 
EDITED BY PKOEESiyQR KNIGHT 
 
 THE STUDY OF ANIMAL LIFE 
 
The Study 
 
 of 
 
 Animal Life 
 
 BY 
 
 J. ARTHUR THOMSON, M.A, F.R.S.E. 
 
 LECTURER ON ZOOLOGY, SCHOOL OF MEDICINE, EDINBURGH 
 
 JOINT-AUTHOR OF 'THE EVOLUTION OF SEX ' 
 
 AUTHOR OK 'outlines OF ZOOLOGY ' 
 
 THIRD EDITION 
 
 WITH JLLUSTNAT/OXS 
 
 TORONTO 
 G. N. MORANG & COMPANY LIMITED 
 
 LONDON 
 
 JOHN MURRAY 
 
 1902 
 
0L4 i^'^ 
 
 " Rut. for my part, wluch write the English story. 1 acknowledge 
 that no man must looke for that at my hands, which I have not 
 received from some other : .or I would bee unwilling to.write anythmg 
 untrue, or uncertaine out of mine own invention ; and truth on every 
 part is so deare unto me. that 1 will not lie to bring any man m love 
 and admiration with God and his works, for God needeth not the hes 
 
 "^ "'^'^- TOPSELL'S Apologia (1607). 
 
 J^ %' -^ ^ 5 
 
PREFACE 
 
 This book is intended to help those who would study 
 animal life. From different points of view I have made 
 a series of sketches. I hope that when these are united 
 in the mind of the reader, the picture will have some 
 truth and beauty. 
 
 My chief desire has been to give the student some 
 impulse to joyousncss of observation and freedom of 
 judgment, rather than to satisfy that thirst for knowledge 
 which leads many to intellectual r'nsobriety. In pursu- 
 ance of one of the aims of this series, I have also tried 
 to show how our knowledge of animal life has grown, 
 and how much room there is for it still to grow. 
 
 A glance at the table of contents will show the plan 
 of the book ; first, the everyday life of animals, next, their 
 internal activities, thirdly, their forms and structure, and 
 finally, the theory of animal life. This is a commonly 
 accepted mode of treatment, and it is one by which it is 
 possible in different parts of the book to appeal to students 
 of different tastes. For, in lecturing to those who attend 
 University Extension Courses, I find that seniors are 
 most interested in the general problems of evolution, 
 heredity, and environment ; that others care more about 
 the actual forms of life and their structure; that many 
 desire to have a clear understanding of the functions of 
 the animal body ; while most wish to study the ways of 
 living animals, their struggles and loves, their homes and 
 
 15914 
 
v! 
 
 Preface 
 
 societies. To each of these class s of students a quarter 
 of this volume is dedicated ; perhaps they will correct 
 their partiality by reading the whole. 
 
 As to the two Appendixes, I may explain that instead 
 of giving references at the end of each chapter, I have 
 combined these in a connected bibliut^aphy ; the other 
 Appendix on " Animal Life and Ours " may show how my 
 subject is related to some of the others usually discussed 
 in University Extension Courses. 
 
 My friend Mr. Norman Wyld has written the three 
 chapter, c. " The Powers of Life," pp. 1 2 5-1 66, and I am 
 also inu-^' jd to him for helpful suggestions in regard to 
 other parts of the book. I have to thank Mr. Murray, 
 Messrs. Chambers, and Mr. Walter Scott, for many of 
 the illustrations; while several original drawings have 
 been made for me by my friend Mr. William Smith. 
 
 Professor Knight and Mr. John Murray have given 
 me many useful hints while the book was passing through 
 the press, and Mr. Ricardo Stephens was good enough 
 to read the proof sheets. 
 
 J. A. T. 
 
 School of Medicine, 
 
 Edinburgh, May 1893 
 
CONTENTS 
 
 PART I 
 
 The Everyday Life of Animals 
 
 CHAPTER I 
 
 THE WEALTH OF LIFE 
 
 f Variety of life— ^. Haunts of life— :^. Wealth of form— ^ Wealth 
 of numbers— $. Wealth of beauty . . . Pages 1-17 
 
 CHAPTER II 
 
 THE WEB OF LIFE 
 
 I. Dependence upon surroundings -^a. /nter- relations <f plants and 
 animals— 2. Relation of animals to the earth— ^. Nutritive rela- 
 tions—^. More complex interactions . . , jg.^ 
 
 CHAPTER III 
 
 THE STRUGGLE OF LIFE 
 
 X. Nature and extent of the struggU—i. Armour and weapons— 
 3. Different forms of struggU-^. Cruelty of the struggle . 32-45 
 
VIU 
 
 Contents 
 
 PART 1 
 
 CHAPTER IV 
 
 SHIFTS FOR A LIVING 
 
 I. Insulation — 2. Concealment — 3. Parasitism — 4. General resem- 
 blance to surroundings— $. Variable colouring — 6. Rapid change 
 of colour — 7. Special protective resemblance — 8. Warning colours 
 — 9. Mimicry — 10. Masking— ii. Combination of advantageous 
 qualities — 12. Surrender of parts , . Pages 46-66 
 
 CHAPTER V 
 
 SOCIAL LIFE OF ANIMALS 
 
 Partnerships — 2. Co-operation and division of labour — 3. C7r«- 
 garious life and combined action — 4. Beavers — 5. Bees— 6. Ants 
 — 7. Termites — 8. Evolution of social life — 9. Advantages of 
 social life — 10. A note on "the social organism" — 11. Con- 
 clusions ....... 67-94 
 
 CHAPTER VI 
 
 THE DOMESTIC LIFE OF ANIMALS 
 t. The love of mates — 2. Love and care for offspring 
 
 9S-"6 
 
 CHAPTER VII 
 
 THE INDUSTRIES OF ANIMALS 
 
 I. Hunting — 2. Shepherding — 3. Storing — 4. Making of homes — 
 5. Movements ..... 117-134 
 
PAKT II 
 
 Contents 
 
 ix 
 
 PART II 
 The Powers of Life 
 
 CHAPTER VIII 
 
 VITALITY 
 
 I. The task of physiology — 2. The seat 0/ life — 3. 7 he energy 0/ lift — 
 4. Cells, the elements of life — 5. The machinery of life — 6. Proto- 
 plasm — 7. The chemical elements of lift — 8. Growth — 9. Origin 
 of life ...... Pages 125-142 
 
 CHAPTER IX 
 
 THE DIVIDED LABOURS OF THE BODY 
 
 I. Division of labour — 2. The functions of the body: Movement; 
 Nutrition; Digestion; Absorption; The work of the liwr and 
 the kidneys; Respiration; Circulation; The changes within the 
 cells ; The activities of the nervous system — 3. Sketch of 
 Psychology ...... 143.152 
 
 CHAPTER X 
 
 INSTINCT 
 
 I. Genetal usage of the term— 2. Cartful usage of the term— 3. 
 Examples of instinct— ^. The origin of instinct , 153-166 
 
i ! 
 ! t 
 
 X Contents part m 
 
 PART III 
 
 The Forms of Animal Life 
 
 CHAPTER XI 
 
 THE ELEMENTS OF STRUCTURE 
 
 I. The resemblances and contrasts between plants and animals— z. 
 
 The relaHon of the simplest animals to those which are more com- 
 
 plex—^ The parts of the animal body , , Pages 167-183 
 
 CHAPTER XII 
 
 THE LIFE-HISTORY OF ANIMALS 
 
 I. Modes of reproduction— 2. Divergent modes— 2. Historical—,^. The 
 egg-cell or ovum-*s. The male-cell or spermatozoon— 6. Matura- 
 tioncf the ovum— T. Fertilisation— Z. Segmentation and the ^rst 
 stages in development — <j. Some generalisations: the ovum 
 theory, the Gastraa theory, fact of recapitulation, organic con- 
 *■««»<>' 184-203 
 
 CHAPTER XIII 
 
 THE PAST HISTORY OF ANIMALS 
 
 I. The two records — 2. Imperfection of the geological record 3. 
 
 Palaontological series—^ Extinction of types — 5. Various diffi- 
 culties — 6. Relative antiquity of animals , . 204-209 
 
 CHAPTER XIV 
 
 THE SIMPLEST ANIMALS 
 
 The simplest forms of life— Q^. Surv^ of Protoaoa—^. The common 
 Amcaa—^. Structure of the Prototoa—i. Life cf Prototoa-d, 
 Psychical life of the Prototoa— J. History of the ProtoMoa—i. Rela- 
 lion to the earth— ^. Relation to other forms (f life— 10, Relation 
 t«man ...... 2io-a2X 
 
XI 
 
 PART IV Contents 
 
 CHAPTER XV 
 
 BACKBONELESS ANIMALS 
 
 T. Sponges — 3. Stinging - animals or Cailenteraia—^. "Worms" — 
 4. £cAinoderms—s. Arthropods — 6. Molluscs . Pages 932-347 
 
 CHAPTER XVI 
 
 BACKBONED ANIMALS 
 
 I. Balanoglossus—3. Tunicates—^. The LnnctUt—4. Round-mouths 
 or Cyclostomata — s. Fishes — 6. Amphibians — 7. Reptiles— 9. 
 Birds— g. Mammals ..... 248-272 
 
 PART IV 
 
 The Evolution of Animal Life 
 
 CHAPTER XVII 
 
 THE EVIDENCES OF EVOLUTION 
 
 I. The idea of evolutior—a. Arguments for evolution : Physiological, 
 Morphological, Historical— -i. Origin of life . . 273-281 
 
 CHAPTER XVIII 
 
 THE EVOLUTION OF EVOLUTION THEORIES 
 
 1. Greek philosophers— 3. AristotU—^. Lucretius— 4. Evolutionists 
 before Darwin-i. Three old masters : Bujfbn, Erasmus Darwin, 
 Lamarck— 6. Darwin— 7. Darwin's fellow -workers— i. The 
 present state of opinion .... 282.302 
 
 CHAPTER XIX 
 
 THE INFLUENCE OF HABITS AND SURROUNDINGS 
 
 I. The influence of funcHon—a. The influence of surroundings— 2. 
 Our own environment . .... 303.319 
 
xii 
 
 Contents 
 
 TAKT IV 
 
 CHAPTER XX 
 
 HEREDITY 
 
 X. The facts tf heredity— i. Theories of heredity, historical retrospect— 
 3. The modem theory of heredity— /^. The inheritance cf acquired 
 characters— $. Social and ethical aspects— 6. Social inheritance 
 
 Pages 330-339 
 
 APPENDIX I 
 
 ANIMAL LIFE AND OURS 
 
 A. Our relation to animals : 1. Affinities and differences between man 
 and monkeys— t. Descent cf man — 3. Various opinions about the 
 descent of man— /^. Ancestors of man—S- Possible factors in the 
 ascent of man. B. Our relation to Biology : 6. The utility of 
 science— 7. Practical justification of biology ~-Z. Intellectual 
 justification of biology ..... 340-35° 
 
 APPENDIX II 
 
 SOME OF THE BEST BOOKS ON ANIMAL LIFE 
 
 A. Books on " Zoology "^ti. Books on "Natural History" —C. Books 
 or "Biology" ..... 3S1-369 
 
 Index 
 
 37I-37S 
 
PART I 
 
 THE EVERYDAY LIFE OF ANIMALS 
 
 CHAPTER I 
 
 THE WEALTH OF LIFE 
 
 I. Variety of Life— 2. Haunts of Life~i. Wealth of f-^m— 
 4. Wealth of Numbers— s^. Wealth of Beaut;, 
 
 The first steps towards an appreciation of animal life must 
 be taken by the student himself, for no book-lore can take 
 the place of actual observation. The student must wash 
 the quartz and dig for the diamonds, though a book may 
 help him to find these, and thereafter to fashion them into 
 a treasure. 
 
 Happily, however, the raw material of observation is not 
 rare like gold or diamonds, but near to us as sunshine and 
 rain-drops. Within a few hours' walk of even the largest 
 of our towns the country is open and the animals are at 
 home. Though we may not be able to see "the buzzard 
 homing herself in the sky, the snake sliding through 
 creepers and logs, the elk taking to the inner passes of 
 the woods, or the razor-billed auk sailing far north to 
 Labrador," we can watch our own delightful birds building 
 their "homes without hands," we can study the frogs from 
 the time that they trumpet in the early spring till they or 
 their offspring seek winter quarters in the mud, we can 
 follow the bees and detect their adroit burglary of the 
 
 B 
 
I 
 
 ! i 
 
 ' i 
 
 : I 
 
 11 ! 
 
 ii: ! 
 
 3 TAe Study of Animal Life part i 
 
 flowers. And if we are discontented with our opportunities, 
 let us read Gilbert White's History of Selborne^ or how 
 Darwin watched earthworms for half a lifetime, or how 
 Richard Jefferies saw in the fields and hedgerows of Wilt- 
 shire a vision of nature, which seemed every year to grow 
 richer in beauty and marvel. It is thus that the study 
 of Natural History should begin, as it does naturally begin 
 in childhood, and as it began long before there was 
 any exact Zoology, — with the observation of animal life in 
 its familiar forms. The country schoolboy, who watches 
 the squirrels hide the beech nuts and pokes the hedgehog 
 into a living ball, who finds the nest of the lapwings, 
 though they decoy him away with prayerful cries, who 
 catches the speckled trout in spite of all their caution, and 
 laughs at the ants as they expend hours of labour on booty 
 not worth the having, is laying the foundation of a naturalist's 
 education, which, though he may never build upon it, is 
 certainly the surest. For it is in such studies that we get 
 close to life, that we may come to know nature as a friend, 
 that we may even hear the solemn beating of her heart. 
 
 The same truth has been vividly expressed by one 
 whose own life-work shows that thoroughness as a zoologist 
 is consistent with enthusiasm for open-air natural history. 
 Of the country lad Dr. C. T. Hudson says, in a Presi- 
 dential Address to the Royal Microscopical Society, that he 
 " wanders among fields and hedges, by moor and river, sea- 
 washed cliff and shore, learning zoology as he learnt his 
 native tongue, not in paradigms and rules, but from Mother 
 Nature's own lips. He knows the birds by their flight and 
 (still rarer accomplishment) by their cries. He has never 
 heard of (Edicnemus crepitans, the Charadrius pluvialis, or 
 the Squatarola cinerea, but he can find a plover's nest, and 
 has seen the young brown peewits peering at him from 
 behind their protecting clods. F -. has watched the cun- 
 ning flycatcher leaving her obvious and yet invisible young 
 in a hole in an old wall, while she carries off the pellets 
 that might betray their presence ; and has stood so still to 
 see the male redstart that a field-mouse has curled itself on 
 his warm foot and gone to sleep." 
 
 til 
 
 i ! 
 
 I i ! 
 
 t^jviSWiStX,^-. - 
 
CHAP. I 
 
 The Wealth of Life 
 
 But the student must also attempt more careful studies 
 of living animals, for it is easy to remain satisfied with 
 vague "general impressions." He should make for himself 
 — to be corrected afterwards by the labours of others — a 
 "Fauna" and "Flora" of the district, or a "Naturalist's 
 Year Book " of the flow and ebb of the living tide. He 
 should select some nook or pool for special study, seeking 
 a more and more intimate acquaintance with its tenants, 
 watching them first and using the eyes of other students 
 afterwards. Nor is there any difficulty in keeping at least 
 freshwater aquaria— simply glass globes with pond water 
 and weeds — in which, within small compass, much wealth 
 of life may be observed. Those students are specially 
 fortunate who have within reach such collections as the 
 Zoological Gardens and the British Museum in London ; 
 but this is no reason for failing to appreciate the life of the 
 sea-shore, the moor-^. id, and the woods, or for neglecting 
 to gain the confiden.e of fishermen and gamekeepers, or 
 of any whose knowledge of natural history has been gathered 
 from the experience of their daily life. 
 
 I. Variety of Life.— Between one form of life and another 
 there often seems nothing in common save that both are 
 alive. Thus life is characteristically asleep in plants, it is 
 generally more or less awake in animals. Yet among the 
 latter, does it not doze in the tortoise, does it not fever in 
 the hot-blooded bird.? Or contrast the phlegmatic am- 
 phibian and the lithe fish, the limpet on the ruck and the 
 energetic squid, the barnacle passively pendent on the float- 
 ing log and the frolicsome shrimp, the cochineal insect like 
 a gall upon the leaf and the busy bee, the sedentaiy corals 
 and the free-swimming jellyfish, the sponge on the rock 
 and the minute Night-Light Infusorians which make the 
 waves sparkle in the summer darkness. No genie of Oriental 
 <"incy was more protean than the reality behind the myth 
 — the activity of life. 
 
 2. Haunts of Life.— The variety of haunt and home 
 is not less striking. There is the great and wide sea with 
 swimmmg thmgs innumerable, our modem giants the whales 
 the seals and walruses and the sluggish sea-cows, the flipl 
 
 i 
 
 \\ 
 
4 The Study of Animal Life part \ 
 
 pered penguins and Mother Carey's chickens, the marine 
 turtles and swift poisonous sea-serpents, the true fishes in 
 prolific shoals, the cuttles and other pelagic molluscs; 
 besides hosts of armoured crustaceans, swiftly-gliding 
 worms, fleets of Portuguese Men-of-War and throbbing jelly- 
 fish, and minute forms of life as numerous in the waves as 
 motes in the sunlit air of a dusty town. 
 
 " But what an endless worke have I in hand, 
 To count the seris abundant progeny, 
 Whose fruitful seede farre passeth those on land, 
 And also those which wonne in th' azure sky ; 
 For much more eath to tell the starres on hy, 
 Albe thty endle e seem in estimation, 
 Then to recount ihe seas posterity ; 
 So fertile be the flouds in generation. 
 So huge their numbers, and so numberlcsse their nation." 
 
 Realise Walt Whitman's vivid picture : — 
 
 " The World below the brine. 
 
 Forests at the bottom of the sea the branches and leaves, 
 
 Sea-ktUice, vast lii liens, strange tluwers and seeds,— the thick 
 tang'e, the openings, and tlic pink turf. 
 
 Different colours, pale grey and green, purple, white, and gold— 
 the play of light through the water. 
 
 Dumb swimmers there among the rocks— coral, gluten, grass, 
 rushes— and the aliment of the swimmers. 
 
 Sluggish . sistcnccs grazing tlicre, suspended, or slowly crawling 
 close to tlie bottom : 
 
 The sperm whale nt the surface, blowing air and .piay, or dis- 
 porting with his flukes, 
 
 Tiie Icaden-eyed shaik, ilie walrus, tie turtle, tlie hairy sea- 
 leopard, and the sting r.iy. 
 
 I'assions there, wars, pursuits, tribes sight in those ocean depths 
 — breathing that thick breathing air, as so many do." 
 
 The sea appears to have been the cradle, if not the 
 birthplace, of the earliest forms of animal life, and some 
 have never wandered out of hearing of its lullaby. From 
 the sea, animals sceir to have migrated to the shore and 
 thence to the land, but also to the <,'cat depths. Of the 
 life of the depp sea wc have had certain knowledge only 
 
CHAP. I 
 
 The Wealth of Life 
 
 I 
 
 Fi.;. I. -Suggestion of ilccj,-..-.. llf,-. (|„ |,,„t fi.mi .i figure by W. Marshall.) 
 
 ■.TnK.7?3i«ia^srffi-. 
 
 rSBK.ra&^trznMHK'.Aut^'B^-iii^BEIRf^ii ::'S1. 
 

 TAe Study of Animal Life 
 
 PART I 
 
 within the last quarter of a century, since the Challenger 
 expedition (1872-76), under Sir Wyville Thomson's leader- 
 ship, following the suggestions gained during the laying of the 
 Atlantic cables and the tentative voyages of the Lightning 
 (1868) and the Porcupine (1870), revealed what was 
 virtually a new world. During 3^ years the Challenger 
 explorers cruised over 68,900 nautical miles, reached with 
 the long ann of the dredge to depths equal to reversed 
 Himalayas, raised sunken treasures of life from over 300 
 stations, and brought home spoils which for about twenty 
 years have kept the savants of Europe at work, the results 
 of which, under Dr. John Murray's editorship, form a 
 library of about forty huge volumes. The discovery of this 
 ucw world has not on'y yielded rich treasures of knowledge, 
 but has raised a wave of wider than national enthusiasm 
 which has not since died away. 
 
 We are at present mainly interested in the general 
 picture which the results of these deep -sea explorations 
 present, — of a thickly-peopled region far removed from 
 direct observation, sometimes three to five miles beneath 
 the surface — a world of darkness relieved only by the living 
 lamps of phosphorescence, of silent calm in which animals 
 grow into quaint forms of great unifoimity throughout wide 
 areas, and moreover a cold and plantless world in which 
 the animals have it all their own way, feeding, though 
 apparently without much struggle for existence, on their 
 numerous neighbours, a^d ultimately upon the small organ- 
 isms which in dying sink gently from the surface like snow- 
 flakes through the air. 
 
 Far otherwise is it on the shore — sunlight and freshening 
 waves, continual changes of time and tide, abundant plants, 
 crowds of animals, and a scrimmage for food. The shore 
 is one of the great battlefields of life on which, through 
 campaign after campaign, animals have sharpened one 
 another's wits. It has been for untold ages a great school. 
 
 Leaving the sea-shore, the student miglit naturally seek 
 to trace a migration of animals from sea to estuary, ond 
 from the brackish \/ater to river and lake. But this pa^'i, 
 though followed by some animals, does not seem to have 
 
 i 
 
 ■'CifA_ \-'<^.i^ 
 
 mmsmm 
 
 •yLfrmrssimasaiiaPitrg.^ ,1 c^Mdy 
 
 •kJ-Te 
 
 Tliir 
 
CHAP. I 
 
 The [Vealth of Life 
 
 been that which led to the establishment of the greater part 
 of our freshwater fauna. Professor Sollas has shown with 
 much conclusiveness that the conversion of comparatively 
 shallow continental seas into freshwater lakes has taken 
 place on a large scale several times in the history of the 
 earth. This has been in all likelihood accompanied by the 
 transformation of marine into freshwater species. It is 
 thus, we believe, that our lakes and rivers were first peopled. 
 Many freshwater forms differ from their marine relatives in 
 having suppressed the obviously hazardous free-swimming 
 juvenile stages, in bearing young which are sedentary or in 
 some way saved from being washed away by river currents. 
 Minute and lowly, but marvellously entrancing, are 
 .merous Rotifers, of which we know much through the 
 labours of Hudson and Gosse. These minute forms are 
 among the most abundant tenants of fresh water, and their 
 eggs are carried from one watershed to another on the 
 wings of the wind and on the feet of birds, so that the same 
 kinds may be found in widely separate waters. Let us 
 see them in the halo of Hudson's eulogy : "To ^e into 
 that wonderful world which lies in a drop of water, crossed 
 by some atoms of green weed ; to see transparent living 
 mechanism at work, and to gain some idea of its modes of 
 action ; to watch a tiny speck that can sail through the 
 prick of a needle's point ; to see its crystal armour flashing 
 with ever-varying tints, its head glorious with the halo of its 
 quivering cilia ; to see it gliding through the emerald 
 stems, hunting for its food, i^natching at Us prey, fleeing 
 from its enemy, chasing its mate (th lercest of our 
 passions blazing in an invisib'e speck) ; to see it whirling 
 in a mad dance to the sound of its own music — the music of 
 its happiness, the exquisite happiness of living, — can any 
 one who has once enjoyed th's siglit, ever turn from it to 
 mere books and drawings, without the sense that he has 
 left all fairyland behind him?" Not less lively than the 
 Rotifers are crowds of minute crust.iceans or water-fleas 
 which row swiftly through the clear water, and are eaten in 
 hundreds by the fishes. Hut there are higher forms still : 
 crayfish, and the larvjc of mayflies and dragonflies, mussels 
 
 ift.vjR:-«p.»« 
 
 _ jL A .1! ^SJ^- :iKttllWiJ«v-iSiLi *.K? 
 
 '>3is'-''-fcje»a.'.r!.," 
 
s 
 
 The Study of Animal Life 
 
 PART I 
 
 and water-snails, fishes and newts, the dipper and the king- 
 fisher, the otter and the vole. 
 
 As we review the series of animals from the simplest 
 upwards, we find a gradual increase in the number of 
 those which Hve on land. The lowest animals are mostly 
 aquatic — the sponges and stinging-animals wholly so; 
 worm-like forms which are truly terrestrial are few com- 
 pared with those in water ; the members of the starfish 
 group are wholly marine ; among crustaceans, the wood- 
 lice, the land-crabs, and a few dwellers on the land, are 
 in a small minority ; among centipedes, insects, and spiders 
 the aquatic forms are quite exceptional ; and while the great 
 majority of mollusrs live in water, the terrestrial snails and 
 slugs are legion. In the series of backboned animals, 
 again, the lowest forms are wholly aquatic ; an occasional 
 fish like the climbing- perch is able to live for a tim- 
 ashore ; the mud-fish, which can survive being brought fronj 
 Africa to Europe within its dry " nest " of mud, has learned 
 to breathe in air as well as in water ; the amphibians really 
 mark the transition from water to dry land, and usually 
 rehearse the story in each individual life as they grow from 
 fish-like tadpoles into frog- or newt-like adults. Among 
 reptiles, however, begins that possession of ihe earth, which 
 in mammals is established and secure. As insects among 
 the backboneless, so birds among the backboned, possess the 
 air, achieving in perfection what flying fish, swooping tree- 
 frogs and lizards, and above all the ancient and extinct 
 flying reptiles, have reached towards. Interesting, too, are 
 the exceptions — ostriches and penguins, whales and bats, the 
 various animals which have become burrowers, the dwellers 
 in caves, and the thievish parasites. 
 
 But it is enough to empnasise ^he fact of a general ascent 
 from sea to shore, from shore to dry land, and eventually 
 into the air, and the fact that the haunts and homes of animals 
 are not less varied than the pitch of their life. 
 
 3- Wealth f Form. — As our observations accumjJate, 
 the desire for order asserts itself, and we should at first 
 classify for ourselves, like the savage before us, allowing 
 similar impressions to drav/ together into groups, such as 
 
CHAP. I 
 
 The Wealth of Life 
 
 birds and beasts, fishes and worms. At first sight the types 
 of architecture seem confusingly numerous, but gradually 
 certain great samenesses are discerned. Thus we distin- 
 guish as higher animals those which have a supporting rod 
 along the back, and a nerve cord lying above this ; while 
 the Imver animals have no such supporting rod, and have 
 their nerve-cord (when present) on the under, not on the 
 upper side of the body. The higher or backboned seiies 
 has its double climax in the Birds and the furred Mammals. 
 Indissolubly linked to the Birds are the Reptiles, — lizards 
 and snakes, tortoises and crocodiles — the survivors of a 
 great series of ancient forms, from among which Birds, and 
 perhaps Mammals also, long ago arose. Simpler in many 
 ways, as in bones and brains, are Amphibians and Fishes in 
 close structural alliance, with the strange double-breathing, 
 gill- and lung-possessing mud-fishes as links between them. 
 Far more old-fashioned than Fishes, though popularly in- 
 cluded along with them, are the Round-mouths— the half- 
 parasitic hag-fish, and the palatable lampreys, with quaint 
 young sometimes called "nine-eyes." Near the ba^e of 
 this series is the lancelet, a small, almost translucent 
 animal living in the sea-sand at considerable depths. 
 It may be regarded as a far-off prophecy of a fish. 
 Ju't at the threshold of the higher school of life, the 
 sea-squirts or Tunicates have for the most part stumbled ; 
 for though the active younj^ forms have been acknowledged 
 for many years as reputable Vertebrates, almost all the 
 adults fall from this estate, and become so degenerate that 
 no zoologist ignorant of their life-history would recognise 
 their true position. Below this come certain claimants for 
 Vertebrate distinction, notably one Balattoglossus, a worm- 
 like animal, idolised by modern zoology as a connecting link 
 between the backboned and backboneless series, and 
 reminding us that exact boundary-lines are very rare in 
 nature. For our present purpose it is immaterial whether 
 this strange animal be a worm -like vertebrate or a 
 vertebrate-like worm. 
 
 Across the line, among the backboneless animals, it 
 is more difficult to distinguish successive grades of higher 
 
xo 
 
 The Study of Animal Life 
 
 PART I 
 
 !l 
 
 .i 
 
 i 
 
 !l 
 
 and lower, for the various classes have progressed in very 
 different directions. We may liken the series to a school 
 in which graded standards have given place to classes which 
 have " specialised " in diverse studies ; or to a tree whose 
 branches, though originating at different levels, are all strong 
 and perfect. Of the shelled animals or Molluscs there 
 are three great sub -classes, (a) the cuttlefishes and the 
 pearly nautilus, {b) the snails and slugs, both terrestrial and 
 aquatic, and {c) the bivalves, such as cockle and mussel, 
 oyster and clam. Simpler than all these are a few forms 
 which link molluscs to worms. 
 
 Clad in armour of a very different type from the shells 
 of most Molluscs are the jointed-footed animals or Arthro- 
 pods, including on the one hand the almost exclusively 
 aquatic crustaceans, crabs and lobsters, barnacles and 
 " water-fleas," and on the other hand the almost exclusively 
 aerial or terrestrial spiders and scorpions, insects and centi- 
 pedes, besides quaint allies like the '« king-crab," the last of 
 a strong race. Again a connecting link demands special 
 notice, Peripatus by name, a caterpillar- or worm- like 
 Arthropod, breathing with the air- tubes of an insect or 
 centipede, getting rid of its waste-products with the kidneys 
 of a worm. It seems indeed like «'a surviving descendant 
 of the literal father of flies," and suggests forcibly that 
 insects rose on wings from an ancestry of worms much as 
 birds did from the reptile stock. 
 
 Very different from all these are the starfishes, brittle- 
 stars, feather-stars, sea-urchins, and sea-cucumbers, animals 
 mostly sluggish and calcareous, deserving their title of 
 thorny-skinned or Echinodermata. Here again, moreover, 
 the sea-cucumbers or Holothurians exhibit features which 
 suggest that this class also originated from among 
 " worms." 
 
 But " Worms " form a vast heterogeneous «' mob," heart- 
 breaking to those who love order. No zoologist ever speaks 
 of them now as a "class" ; the title includes many classes, 
 bristly sea- worms and the familiar earthworms, smooth 
 suctorial leeches, ribbon-worms or i emerteans, round hair- 
 worms or Nematodes, flat tapeworms and flukes, and many 
 
 
 l< 
 
CHAP. I 
 
 The Wealth of Life 
 
 II 
 
 others with hardly any characters in common. To us these 
 many kinds of " worms " are full of interest, because in the 
 past they must have been rich in progress, and zoologists 
 find among them the bases of the other great branches — 
 Vertebrates, Molluscs, Arthropods, and Echinoderms. 
 "Worms" lie in a central (and still muddy) pool, from 
 which flow many streams. 
 
 Lower still, and in marked contrast to the rest, are the 
 Stinging-animals, such as jellyfish throbbing in the tide, 
 zoophytes clustering like plants on the rocks, sea-anemones 
 like bright flowers, corals half-smothered with lime. In the 
 Sponges the type of architecture is often very hard to find. 
 They form a branch of the tree of life which has many 
 beautiful leaves, but has never risen far. 
 
 Beyond this our unaided eyes will hardly lead us, yet 
 the pond-water held between us and the light shows vague 
 specks like living motes, the firstlings of life, the simplest 
 animals or Protozoa, almost all of which have remained mere 
 unit specks of living matter. 
 
 It is easy to write this catalogue of the chief forms of 
 life, and yet easier to read it : to have the tree of life as a 
 living picture is an achievement. It is worth while to 
 think and dream over a bird's-eye view of the animal king- 
 dom — to secure representative specimens, to arrange them 
 in a suitably shelver' cupboard, so that the outlines of the 
 picture may become clear in the mind. The arrangement 
 of animals on a genealogical or pedigree tree, which 
 Haeckel first suggested, may be readily abused, but it has 
 its value in presenting a vivid image of the organic unity 
 of the animal kingdom. 
 
 If the catalogue be thus realised, if the foliage come to 
 represent animals actually known, and if an attempt be 
 made to learn the exact nature, limits, and meaning of the 
 several branches, the student has made one of the most 
 important steps in the study of animal life. Much will 
 remain indeed — to connect the living twigs with those wliv>se 
 leaves fell off ages ago, to understand the continual renewal 
 of the foliage by the birth of new leaves, and finally to 
 understand how the entire tree of life grew to be what it is. 
 
12 
 
 fl 
 
 
 The Study of Animal Life part i 
 
 11 
 
 letters 
 Sphenex 
 
 Fig. 2 —Genealogical Ti.-,- 
 
 .e Mn.,11 tranche, in tl.e centre indicate the ..lasses of "norms- ,1„ 
 
 I 
 
CHAP. I 
 
 The Wealth of Life 
 
 13 
 
 There is of course no doubt as to the fact that some forms 
 of life are more complex than others. It requires no faith 
 to allow that the firstlings or Protozoa are simpler than 
 all the rest ; that sponges, which are more or less loose 
 colonies of unit masses imperfectly compacted together, are 
 in that sense simpler than jellyfish, and so on. The animals 
 most like ourselves are more intricate and more perfectly 
 controlled organisms than those which are obviously more 
 remote, and associated with this perfecting of structure there 
 is an increasing fulness and freedom of life. 
 
 We may arrange all the classes in series from low to high, 
 from simple to complex, but this will express only our most 
 generalised conceptions. For within each class there is 
 great variety, each has its own masterpieces. Thus the 
 simplest animals are often cased in shells of .lint or lime 
 whose crystalline architecture has great complexity. The 
 simplest sponge is little more than a double-walled sack 
 riddled by pores through which the water is lashed, but 
 the Venus' Flower-Basket {Euplcctella\ one of the flinty 
 sponges, has a complex system of water canals and a 
 skeleton of flinty threads built up into a framework of 
 marvellous intricacy and grace. The lowest insect is not 
 much more intricate, centralised, or controlled than many 
 a womi of the sea-shore, but the ant or the bee is a very 
 complex self-controlled organism. More exact, therefore, 
 than any linear series, is the image of a tree with branches 
 springing from different levels, each branch again bearing 
 twigs some of which rise higher than the base of the branch 
 above. A perfect scheme of this sort might not only express 
 the facts of structure, it might also express our notions of 
 the blood-relationships of animals and the way in which we 
 believe that different forms have arisen. 
 
 But the wealth of form is less varied ihan at first sight 
 appears. There is great wealth, but the coinage is very 
 uniform. Our first impression is one of manifold variety ; 
 but that gives place to one of marvellous plasticity when 
 we see how structures apparently quite different are redu- 
 cible to the same general plan. Thus, as the poet Goethe 
 first clearly showed, the seed-leaves, root-leaves, stem-leaves, 
 
14 
 
 The Study of Animal Life 
 
 VKKt I 
 
 and even he parts of the flower-sepals, petals, stamens, 
 and carpels are m reality all leaves or appendages more 
 or less modified for diverse work. The mouth-plrts Ta 
 lobster are masticating legs, and a bird's wing is a modified 
 
 fh^V 7 r c "^^"'■^^'^^^ ^^^'•e so far right in insisting on 
 the fact of a few great types. Nature, Lamarck said, is 
 never ^usque ; nor is she inventive so much as adaptive 
 
 4. Wealth of Numbers— Large numbers are so unthink- 
 n..^ f^.^'-^'^'^^y \ census-taking is so difficult, that we 
 need say little as to the number of different animals. The 
 census includes far over a million living species_a total so 
 rf. ^''^f° i ^%°"r power of realising it is concerned, 
 It IS hardly affected when we admit that more than half 
 are insects. To these recorded myriads, moreover, many 
 newly-discovered forms are added every year-now by the 
 individual workers who with fresh eye or improved micro- 
 scope find m wayside pond or shore pool some new thine 
 or again by great enterprises like the Challenger expedition / 
 Exploring naturalists like Wallace and Semptr return from / 
 tropical countries enriched with new animals from the dense 
 forests or warm seas. Zoological Stations, notably that Si 
 , Naples, are "register-houses" for the fauna of the neX 
 bpuring sea, not merely as to number and form, 2t in 
 many cases taking account of life and history as wdl Nor 
 can we forget the stupendous roll of the extinct, to' which 
 the zoological historians continue to add as they disentomb 
 primitive mammals, toothed birds, giant reptiles, huge 
 amphibians armoured fishes, gigantic cuttles, and a vast 
 multitude of strange forms, the like of which ho longer 
 • . Tf" °^ '^" Zoological Record, in which the 
 
 literature and discoveries of each year are chronicled, the 
 portentous size of a volume which professes to discuss with 
 some completeness even a single sub-class, the number of 
 special departments into which the science of zoology is 
 divided, suggest the vast wealth of numbers at first sight so 
 bewildering. More than two thousand years ago Aristotle 
 recorded a total of about 500 forms, but more newfpedes may 
 be described in a single volume of the Challenger Reports 
 We speak about the number of the stars, yet more than one 
 
CHAP. I 
 
 The Wealth of Life 
 
 15 
 
 family of insects is credited with including as many different 
 species as there are stars to count on a clear night. But far 
 better than any literary attempt to estimate the numerical 
 wealth of life is some practical observation, some attempted 
 enumeration of the inmates of your aquarium, of the tenants 
 of some pool, or of the visitors to some meadow. The 
 naturalist as well as the poet spoke when Goethe celebrated 
 Nature's wealth : " In floods of life, in a storm of activity, 
 she moves and works above and beneath, working and 
 weaving, an endless motion, birth and death, an infinite 
 ocean, a changeful web, a glowing life ; she plies at the 
 roaring loom of time and weaves a living garment for God." 
 
 5. Wealth of Beauty. — To many, however, animal life 
 is impressive not 'o much because of its amazing variety 
 and numerical greatness, nor because of its intellectual 
 suggestiveness and practical utility, but chiefly on account 
 of its beauty. This is to be seen and felt rather than 
 described or talked about. 
 
 The beauty of animals, in which we all delight, is usually 
 in form, or in colour, or in movement. Especially in the 
 simplest animals, the beauty of form is often comparable to 
 that of crystals ; witness the marvellous architecture in flint 
 and lime exhibited by the marine Protozoa, whose empty 
 shells form the ooze of the great depths. In higher animals 
 also an almost crystalline exactness of symmetry is often 
 apparent, but we find more frequent illustration of graceful 
 curves in form and feature, resulting in part from strenuous 
 and healthful exercise, which moulds the body into beauty. 
 
 Not a little of the colour of animals is due to the 
 physical nature of the skin, which is often iridescent ; 
 much, on the other hand, is due to the possession of pig- 
 ments, which may either be of the nature of reserve-products, 
 and then equivalent, let us say, to jewels, or of the nature of 
 waste-products, and thus a literal "beauty for ashes." It 
 is often supposed that plants excel animals in colour, but 
 alike in the number and variety of pigments the reverse is 
 true. Then as to movement, how much there is to admire ; 
 the birds soaring, hovering, gliding, and diving; the monkey's 
 gymnastics ; the bat's arbitrary evolutions ; the grace of the 
 
x6 
 
 The Study of Animal Life part i 
 
 fleet stag ; the dolphin gamboling in the waves ; the lithe 
 lizards which flash across the path and are gone, and the 
 snake flowing like a silver river : the buoyant swimming of 
 fishes and all manner of aquatic animals ; the lobster darting 
 backwards with a powerful tail-stroke across the pool ; the 
 butterflies fliuing like sunbeams among the flowers. But 
 
 Fig. 3.— Humming-birils {Floristiga 'iiellivora) visiting flowers. (From Belt.) 
 
 are not all the delights of form and colour and movement 
 expressed in the songs of the birds in spring ? 
 
 I am quite willing to allow that this beauty is in one 
 sense a relative quality, varying with the surroundings 
 and education, and even ancestral history, of those who 
 appreciate it. A flower which seems beautiful to a bee 
 may be unattractive to a bird, a bird may choose her mate 
 for qualities by no means winsome to human eyes, and a 
 
CHAP. I 
 
 The Wealth of Life 
 
 17 
 
 dog may howl painfully at our sweet music. We call the 
 apple - blossom and the butterfly's wings beautiful, partly 
 because the rays of light, borne frcm them to our eyes, 
 cause a pleasantly harmonious activity in our brains, partly 
 because this awakens reminiscences of past pleasant experi- 
 ences, partly for subtler reasons. Still, all heaWiy organisms 
 are harmonious in form, and seldom if ever are their colours 
 out of tone with their surroundings or with each other, — a 
 fact v/hich suggests the truth of the Platonic conception that 
 a living creature is harmonious because it is possessed by 
 a single soul, the realisation of a single idea. 
 
 The plants which seem to many eyes to have least 
 beauty are those which have been deformed or discoloured 
 by cultivation, or taken altogether out of their natural set- 
 ting ; the only ugly animals are the products of domestica- 
 tion and human interference on the one hand, or of disease 
 on the other ; and the ugliest things are what may be called 
 the excretions of civilisation, which are certainly not beauty 
 for ashes, but productions by which the hues and colours of 
 nature have been destroyed or smothered, where the natural 
 harmony has been forcibly put out of tune — in short, where 
 a vicious taste has insisted on becoming inventive. 
 
 '■\ \ 
 
CHAPTER II 
 
 THE WEB OF LIFE 
 
 Dependence upon Surroundings — 2. Inter-relations of Plants and 
 Animals — 3. Relation of Animals to the Earth — 4. NutHti', e 
 Relations — 5. Afore Complex Interactions 
 
 In the filmy web of the spider, threads delicate but firm 
 bind part to part, so that the whole system is made one. 
 The quivering fiy entangled in a comer betrays itself 
 throughout the web ; often it is felt rather than seen Vy the 
 lurking spinner. So in the substantial fabric of the world 
 part is bound to part. In wind and weather, or in the 
 business of our life, we are daily made aware of results 
 whose first conditions are remote, and chains of influence 
 not difficult to demonstrate link man to beast, and flower to 
 insect. The more we know of our surroundings, the more 
 we realise the fact that nature is a vast system of linkages, 
 that isolation is impossible. 
 
 I . Dependence upon SorroandinffS. — Every living body 
 is built up of various arrangements of at least twelve 
 "elements," viz. Oxygen, Hydrogen, Carbon, Nitrogen, 
 Chlorine, Phosphorus, Sulphur, Magnesium, Calcium, Pot- 
 assium, Sodium, and lion. All these elements are spread 
 throughout the whole world. By the magic touch of life 
 they ai-e built up into substances of great complexity and 
 instability, substances very sensitive to impulses from, or 
 changes in, their surroundings It may be that living matter 
 diflfers from dead matter in no other way than thi; Th- 
 
 I 
 
CHAP. II 
 
 The Web of Life 
 
 19 
 
 varied forms of life crystallise out of their amorphous 
 beginnings in a manner that we conceive to be analogous to 
 the growth of a crystal within its solution. Further, we do 
 not believe in a "vital force." The movements of living 
 things are, like the moveme-i* o*" all matter, the expression 
 of the world's energy, an I iilusu.tte the same laws; But 
 to these matters we shall efrn in anoti.er chapter. 
 
 Interesting, because of • s larply dc nned ?nd far-reaching 
 significance, and because ihc p^^c'^tiai mass is so nearly 
 infinitesimal, is the part played by iron in the story of life. For 
 food-supply we are dependent upon animals and plants, and 
 ultimately upon plants. But these cannot produce their 
 valuable food-stuffs without the green colouring-matter in 
 their leaves, by help of which they are able to utilise the 
 energy of sunshine and the carbonic acid gas of the air. 
 But this important green pigment (though itself perhaps 
 free from any iron) cannot be fonned in the plant unless 
 there be, as there almost always is, some iron in the soil. 
 Thus our whole life is baseu on iron. And all our supplies 
 of energy, our powers of doing work either with our own 
 hands and brains, or by the use of animals, or through the 
 application of steam, are traceable — if we follow them far 
 enough — to the sun, which is thus the source of the energy 
 in all creatures. 
 
 2. Inter-relations of Plants and Animals.— We often 
 hear of the " balance of nature," a phrase of wide appli- 
 cation, but very generally used to describe the mutual 
 dependence of plants and animals. Every one will allow 
 that most animals are more active than most plants, 
 that the life of the former is on an average more intense 
 and rapid than that of the latter. For all typical plants 
 the materials and conditions of nutrition are found in water 
 and salts absoibed by the roots, in carbonic acid gas 
 absorbed by the leaves from the air, and in the energy of 
 tlic sunlight which shines on the living matter through a 
 screen of green pigment. Plants feed on very simple sub- 
 stances, at a low chemical level, and their most char- 
 acteristic transformation of energy is that by which the 
 kinetic energy of the sunlight is changed into the potential 
 
I 
 
 r 
 
 f 
 
 ao 
 
 The Study of Animal Life 
 
 PAST t 
 
 energy of the complex stuffs which animals eat or which 
 we use as fuel. But animals feed on plants or on creatures 
 like themselves, and are thus saved the expense of build- 
 ing up food -stuffs from crude materials. Their most 
 characteristic transformation of energy is that by which the 
 power of complex chemical substances is used in locomotion 
 and work. In so working, and eventually in dying, they 
 form waste-products— water and carbonic acid, ammonia 
 and nitrates, and so on — which may be again utilised by 
 plants. 
 
 How often is the inaccurate statement repeated "that 
 animals take in oxygen and give out carbonic acid, 
 whereas plants take in carbonic acid and give out oxygen " ! 
 This is most misleading. It contrasts two entirely dis- 
 tinct processes — a breathing process in the animal with 
 a feeding process in the plant. The edge is at once 
 taken off the con rast when the student realises that plants 
 and animals being both (though not equally) ahve, must 
 alike breathe. As they live the living matter of both is oxi- 
 dised, like the fat of a burning candle ; in plant, in animal, 
 in candle, oxygen passes in, as a condition of li'"e or com- 
 bustion, and carbonic acid gas p sses out as a waste-pro- 
 duct. Herein there is no difference except in degree between 
 plant and animal. Each lives, and n>ust therefore breathe. 
 But the living of plants is less intense, therefore the breath- 
 ing process is less marked. Moreover, in sunlight the 
 
 respiration is disguised by an exactly reverse process 
 
 peculiar to plants— the feeding already noticed, by which 
 carbonic acid gas is absorbed, its carbon retained, and part 
 of its oxygen liberated. 
 
 There is an old-fashioned experiment which illustrates 
 the "balance of nature." In a glass globe, half-filled 
 with water, are placed some minute water-plants and water- 
 animals. The vessel is then sealed. As both the plants 
 and the animals are absorbing oxygen and liberating car- 
 bonic acid gas, it seems as if the little living world enclosed 
 in the globe would soon end in death. But, as we have seen, 
 the plants are able in sunlight to absorb carbonic acid and 
 liberate oxygen, and if present in sufficient numbers will 
 
33F* 
 
 ^ 
 
 (.>:' 
 
 CHAP. II 
 
 TAg WehofLife 
 
 ai 
 
 I.; 
 
 compensate both *or their own breathing and for that of 
 animals. Thus ti e result within the globe need not be 
 suffocation, but harmonious prosperity. If the minute 
 animals ate up all the plants, they would themselves die 
 for lack of oxygen before they had eaten up one another, 
 while if the plants smothered all the animals they would 
 also in turn die away. Some such contingency is apt to 
 spoil the experiment, the end of which may be a vessel of 
 putrid water tenanted fcr a long time by the very simple 
 colourless plants known as Bacteria, and at last not even 
 by them. Nevertheless the " vivarium " experinient is both 
 theoretically and practically possible. Now in nature th^re 
 is, indeed, no closed vivarium, for there is no isolation and 
 there is open air, and it is an exaggeration to talk as if our 
 life were dependent on there being u proportionate number 
 of plants and animals in the neighbourhood. Yet the 
 " balance of nature " is a general fact of much importance, 
 though the economical relations of part to part over a wide 
 area are neither rigid nor precise. 
 
 We have just mentioned the very simple plants call'-d 
 Bacteria. Like moulds or fungi, they depend upon other 
 organisms for their food, being without the green colouring 
 stuff so important in the life of most plants. These very 
 minute Bacteria are almost omnipresent ; in weakly animals 
 — and sometimes in strong ones too — they thrive and 
 multiply and cause death. They are our deadliest foes, but 
 we should get rid of them more easily if we had greater love 
 of sunlight, for this is thcT most potent, as well as most 
 economical antagonist. But it is not to point out the 
 obvious fact that a Bacterium may kill a king that we have 
 here spoken of this class of plants ; it is to acknowledge 
 their beneficence. They are the great cleansers of the 
 world. Animals die, and Bacteria convert their corpses 
 into simple substances, restoring to the soil what the plants, 
 on which the animals fed, originally absorbed through 
 their roots. Bacteria thus complete a wide circle ; th»;y 
 unite dead animal and living plant. For though many a 
 plant thrives quite independently of animals on the raw 
 materials of earth and air, others are demonstrably raisin^j 
 
 H 
 
 ■|«j 
 
33 
 
 The Study of Animal Life 
 
 PART 
 
 r': 
 
 the ashes of animals into a new life. A strange pat 
 ship between Bacteria on the one hand and leguminous .md 
 cereal plants on the other has recently been discovered. 
 There seems much likelihood that with some plants of 
 the orders just named Bacteria live in normal partner- 
 ship. The legumes and cereals in question do not thrive 
 well without their guests," nay more, it seems as if the 
 Bacteria are able to make the free nitrogen of the air 
 available for their hosts. 
 
 3. Relation of Animals to the Earth.— Bacteria are 
 extremely minute organisms, however, and stories of 
 their industry are apt to sound unreal. But this cannot 
 be said of earthworms. For these can be readily seen 
 and watched, and their trails across the damp footpath, 
 or their castings on the grass of lawn and meadow, are 
 familiar to us all. They are distributed, in some form or 
 other, over most regions of the globe ; and an idea of their 
 abundance may be gained by making a nocturnal expedition 
 with a lantern to any convenient green plot, where they 
 may be seen in great numbers, some crawling about, others, 
 with their tails in their holes, making slow circuits in search 
 of leaves and vegetable ddbris. Darwin estimated that there 
 are on an average 53,000 earthworms in an acre of garden 
 ground, that 10 tons of soil per acre pass annually through 
 their bodies, and that they bring up mould to the surface at 
 the rate of 3 inches thickness in fifteen years. Hensen found 
 in his garden 64 large worm-holes in I4| square feet, and 
 estimated the weight of the daily castings at about 2 
 cwts. in two and a half acres. In the open fields, how- 
 ever, it seems to be only about half as much. But whether 
 we take Darwin's estimate that the earthworms of England 
 pass annually through their bodies about 320,000,000 tons 
 of earth, or the more moderate calculations of Hensen, or 
 our own observations in the garden, we must allow that the 
 soil-making and soil-improving work of these animals is 
 momentous. 
 
 In Yorubaland, on the West African coast, earthworms 
 {Siphonogaster) somewhat different from the common Lum- 
 bricus are exceedingly numerous. From two separate square 
 
 % U r 
 
 ;i>,«f .iiifi^. S2^' , *tjafcsik26>-:= m-i 
 
cha;. II 
 
 The Web of Life 
 
 23 
 
 feet of land chosen at random, Mr. Alvan Millson collected 
 the worm-casts of a season and found that they weighed 
 when dry io| lbs. At this rate about 62,233 tons of sub- 
 soil would be brought in a year to the surface of each 
 square mile, and it is also calculated that every particle of 
 earth to the depth of two feet is brought to the surface once 
 in 27 years. We do not wonder that the district is fertile 
 and healthy. 
 
 Devouring the earth as they make their holes, which are 
 often 4 or even 6 feet deep ; bruising the particles in their 
 gizzards, and thus liberating the minute elements of the soil ; 
 burying leaves and devouring them at leisure ; preparing the 
 way by their burrowing for plant roots and rain-drops, and 
 gradually covering the surface with their castings, worms have, 
 in th3 history of the habitable earth, been most important 
 factors in progress. Ploughers before the plough, they 
 have made the earth fruitful. It is fair, however, to 
 acknowledge that vegetable mould sometimes forms inde- 
 pendently of earthworms, that some other animals which 
 burrow or which devour dead plants must also help in the 
 process, and that the constant rain of atmospheric dust, as 
 Richthofen has especially noted, must not be overlooked. 
 
 In 1777, Gilbert White wrote thus of the earthworms — 
 
 "The most insignificant insects and reptiles are of much more 
 consequence and have much more influence in the economy of 
 nature than the incurious are aware of. . . . Earthworms, though in 
 appearance a small and despicable link in the chain of Nature, yet, 
 if lost, would make a lamentable chasm. . . . Worms seem to be 
 the great promoters of vegetation, which would proceed but lamely 
 without them, by boring, perforatiny;. and loosening the soil, and 
 rendering it pervious to rains and the litres of plants ; by drawing 
 straws and stalks of leaves and twij^s into it ; and, most of all, by 
 throwint; up such infinite numbers of lumps of earth called worm- 
 casts, which, being their excrement, is a fine manure for grain and 
 grass. Worms probably provide new soil for hills and slopes where 
 the rain washes the earth away ; and they affect slopes piobably to 
 avoid being flooded. . . . The earth without worms would soon 
 l)ecome cold, hard-bound, and void of fermentation, and con- 
 sequently sterile. . . . These hints we think proper to throw out, in 
 order to set the inquisitive and discerning to work. A good mono- 
 
 n 
 
 .^tii 
 
 r^ 
 
 
 .fn- 
 
 ^^•IdSRiSw'^^ 
 
24 
 
 The Study of Animal Life 
 
 PART 1 
 
 graph of worms would afford much entertainment and information 
 hLJoryT" '""'' '"' "°"'' "P^" ^ '^^^^ ^"^ "- fieldTn natural 
 
 After a while the discerning did go to work, and Hensen 
 pubhshed an important memoir in 1877, while Darwin^ 
 "good monograph" on the formation of vegetable mould 
 appeared after about thirty years' observation in 1881 • and 
 now we all say with him, - It may be doubted whether 'there 
 
 prrtTnTh^h'r "V"f "''f' '^^" P'^y^^ - important a 
 cStures." "^ """"^^ "' ^"'*^ '^''' lowly-organised 
 
 Prof Drummond, while admitting the supreme imoort 
 ance of the work of earthworms, eloquently ple'lds the Ss' 
 
 Tn, ? Tul °',^^'^'^' "^"^ ^' ^" agricultural agent. TWs 
 insect, which dwelt upon the earth long before thf true ant 
 •s abunoant in many countries, and notably in Tropical 
 Atrica. It ravages dead wood with great rapidity "If 
 a man lay down to sleep with a wooden leg. it would be a 
 heap of sawdust in the morning," while houses and decaying 
 forest trees, furniture and fences, fall under the jaws of hf 
 hungry Termites. These fell workers are blind and 1 ve 
 underground ; for fear of their enemies they dare not show 
 fac:e. and yet without coming out of their ground they cannm 
 
 along" it! them'' TL" "'' ''""'l^'' ^ ^'^^J' '^'^^ '^'^ 8-""^ out 
 earthworms, keep the soil circulating. The earth tu£ cr,Vn 
 
 lief s;t:?^;::;nii^?d^ ' ^^^^^^"^ 
 
 alluvium of a distZit vall'J/' " '°°''"'^ grains to swell the 
 
 i:i 
 
 T.*apjMBiirwi vrft ifc 
 
CHAP. II 
 
 The Web of Life 
 
 *l 
 
 The influences of plants and animals on the earth are 
 manifold. The sea- weeds cHng around the shores and 
 lessen the shock of the breakers. The lichens eat slowly 
 into the stones, sending their fine threads beneath the sur- 
 face as thickly sometimes " as grass-roots in a meadow-land," 
 so that the skin of the rock is gradually weathered away. 
 On the moor the mosses form huge sponges, which mitigate 
 floods and keep the streams flowing in days of drought. 
 Many little plants smooth away the wrinkles on the earth's 
 face, and adorn her with jewels ; others have caught and 
 stored the sunshine, hidden its power in strange guise in 
 the earth, and our hearths with their smouldering peat or 
 glowing coal are warmed by the sunlight of ancient summers. 
 The grass which began to grow in comparatively modern 
 {i.e. Tertiary) times has made the earth a fit home for flocks 
 and herds, and protects it like a garment ; the forests affect 
 the rainfall and temper the climate, besides sheltering multi- 
 tudes of living things, to some of whom every blow of the 
 axe is a death-knell. Indeed, no plant from Bacterium to 
 oak tree either lives or dies to itself, or is without its 
 influence on earth and beast and man. 
 
 There are many animals besides worms which influence 
 the earth by no means slightly. Thus, to take the minus 
 side of the account first, we see the crayfish and their 
 enemies the water-vohs burrowing by the river banks and 
 doing no little damage to the land, assisting in that process 
 by which the surface of continents tends gradually to 
 diminish. So along the shores in the .arder substance 
 of the rocks there are numerous borers, like the Pholad 
 bivalves, whose work of disintegration is individually slight, 
 but in sum-total great. More conspicuous, however, is the 
 work of the beavers, who, by cutting down trees, building 
 dams, digging canals, have cleared away forests, flooded 
 low grounds, and changed the aspect of even large tracts 
 of country. Then, as every one knows, there are injuri- 
 ous insects innumerable, whose influence on vegetation, on 
 other animals, and on the prosperity of nations, is often 
 disastrously great. 
 
 But, on the other hand, animals cease not to pay their 
 
 "■*«< "/a««aBsw!WKA • '-'^-<».rij^?^-'%it:i 
 
- 1 
 
 26 
 
 The Study of Animal Life 
 
 PART I 
 
 filial debts to mother earth. We see life rising like a mist 
 in the sea, lowly creatures living in shells that are like 
 mosques of lime and flint, dying in due season, and sinking 
 gently to find a grave in the ooze. We see the submarine 
 volcano top, which did not reach the surface of the ocean, 
 slowly raised by the rainfall of countless small shells. Inch 
 by inch for myriads of years, the snow-drift of dead shells 
 fonns a patient preparation for the coral island. The 
 tiniest, hardly bigger than the wind-blown dust, form when 
 added together the strongest foundation in the world. The 
 vast whale skeleton falls, but melts away till only the ear- 
 bones are left. Of the ruthless gristly shark nothing stays 
 but teeth. The sea-butterflies (Pteropods), with their frail 
 shells, are mightier than these, and perhaps the microscopic 
 atomies are strongest of all. The pile slowly rises, and the 
 exquisite fragments are cemented into a stable foundation 
 for the future city of corals. 
 
 At length, when the height at which they can live is 
 reached, coral germs moor themselves to the sides of the 
 raised mound, and begin a new life on the shoulders of death. 
 They spread in brightly coloured festoons, and have often 
 been likened to flowers. The waste salts of their living 
 perhaps unite with the gvpsum of the sea-water, at any rate 
 in some way the originahy soft young corals acquire strong 
 shells of carbonate of lime. Sluggish creatures they, living 
 in calcareous castles of indolence ! In silence they spread, 
 and crowd and smother one another in a struggle for stand 
 ing-room. The dead forms, partly dissolved and cemented, 
 become a broad and solid base for higher and higher growth. 
 At a certain height the action of the breakers begins, great 
 severed masses are piled up or roll down the sloping sides. 
 Clear daylight at last is reached, the mound rises above the 
 water. The foundations are ever broadened, as vigorously 
 out-growing masses succumb to the brunt of the waves and 
 tumble downwards. Within the surface -circle weathering 
 makes a soil, and birds resting there with weary wings, or 
 perhaps dying, leave many seeds of plants — the begin- 
 nings of another life. The waves cast up forms of 
 dormant life which have floated from afar, and a ter- 
 
 ■" " "' ^Ei 
 
 mm 
 
CHAP. 11 
 
 The Web of Life 
 
 27 
 
 restrial fauna and flora begin. It is a strange and beautiful 
 story, dead shells of the tenderest beauty on th^ rugged 
 shoulders of the volcano ; corals like meadow flowers 
 on the graveyard of the ooze ; at last plants and trees, 
 the hum of insects and the song of birds, over the coral 
 
 island. 
 
 4. Nutritive Relations.— What we may call " nutritive 
 chains " connect many forms of life — higher animals feed- 
 ing upon lower through long series, the records of which 
 sound like the stoty of «' The House that Jack built." On 
 land and on the shore these series are usually short, for 
 plants are abundant, and the carnivores feed on the 
 vegetarians. In the open sea, where there is less vegeta- 
 tion, and in the great depths, where there is none, carni- 
 vore preys upon carnivore throughout long series — fish feeds 
 upon fish, fish upon crustacean, crustacean upon worm, 
 worm on debris. Disease or disaster in one link affects 
 the whole chain. A parasitic insect, we are told, has killed 
 off the wild horses and cattle in Paraguay, thereby influencing 
 the vegetation, thereby the insects, thereby the birds. Birds 
 of prey and small mammals — so-called "vermin" — are killed 
 off in order to preserve the grouse, yet this interference seems 
 in part to defeat itself by making the survival of weak and 
 diseased birds unnaturally easy, and epidemics of grouse- 
 disease on this account the more prevalent. A craze of vanity 
 or gluttony leads men to slaughter small insect-eating birds, 
 but the punishment falls unluckily on the wrong shoulders 
 — when the insects which the birds would have kept down 
 increase in unchecked numbers, and destroy the crops of 
 grain and fruit. In a fuel-famine men have sometimes 
 been forced to cut down the woods which clothe the sides 
 of a valley, an action repented of when the rain-storms wash 
 the hills to skeletons, when the valley .i flooded and the 
 local climate altered, and when the birdi robbed of their 
 shelter leave the district to be ravaged by caterpillar and 
 fly. American entomologists have proved that the ravages 
 of destructive insects may be checked by importing and 
 fostering their natural enemies, and on the other hand, the 
 sparrows which have established themselves in the States 
 
 i- 1 ■ 
 
 ?^^s^ 
 
38 
 
 The Study of Animal Life 
 
 PART I 
 
 have in some districts driven away the titmice and thus 
 tavoured the survival of injurious caterpillars. 
 
 b. More Complex Interactions.— The flowering plants 
 and the higher insects have grown up throughout lone 
 ages together, in alternate influence and mutual per- 
 fectmg. They now exhibit a notable degree of mutual 
 dependence; the insects are adaoted for sipping the 
 nectar from the blossoms; the flov >rs are fitted for 
 givmg or receiving the fertilising golden dust or pollen 
 which their visitors, often quite unconsciously, carry from 
 plant to plant. The mouth organs of the insects have 
 to be interpreted in relation to the flowers which thev 
 visit; while the latter show structures which may be 
 spoken of as the "footprints " of the insects. So exact is 
 the mutual adaptation that Darwin ventured to prophesy 
 from the existence of a Madagascar orchid with a nectar- 
 spur 1 1 inches long, that a butterfly would be found in the 
 same locality with a suctorial proboscis long enough to 
 dram the cup ; and Forbes confirmed the prediction bv 
 discovering the insert. 
 
 As informatioii on the relations of flowers and insects is 
 readily attainable, and as the subject will be discussed in 
 the volume on Botany, it is sufficient here to notice that so 
 far as we can infer from the history half hidden in the 
 rocks, the floral wond must have received a marked impulse 
 when bees and other flower-visiting insects appeared ; that 
 for the successful propagation of flowering plants it is 
 advantageous that pollen should be carried from one indi- 
 vidual to another, in other words, that cross -fertilisation 
 should be effected; and that, for the great majority of 
 flowering plants, this is done through the agency of insects 
 How plants became bright in colour, fragrant in scent, rich 
 m nectar, we cannot here discuss ; the fact that they are so 
 is evident, while it is also certain that insects are attracted 
 by the colour, the scent, and the sweets. Nor can there be 
 any hesitation in drawing the inference that the flowers 
 which attracted insects with most success, and insects which 
 got most out of the flowers, would, ipso facto, succeed better 
 in life. 
 
CHAP. II 
 
 The Web of Life 
 
 29 
 
 No illustration of the web of life can be better than the 
 most familiar one, in which Darwin traced the links of 
 influence between cats and clover. If the possible seeds in 
 ihe flowers of the purple clover are to become real seeds, 
 they must be fertilised by the golden dust or pollen from 
 some adjacent clover plants. But as this pollen is uncon- 
 sciously carried from flower to flower by the humble-bees, 
 the propositi r 1 must be granted that the more humble-bees, 
 the better next year's clover crop. The humble-bees, how- 
 ever, have their enemies in the field-mice, which lose no 
 opportunity of destroying the combs ; so that the fewer 
 field-mice, the more humble-bees, and the better next year's 
 clover crop. In the neighbourhood of villages, however, it 
 is well known that the cats make as efiective war on the 
 field-mice as the latter do on the bees. So that next year's 
 crop of purple clover is influenced by the number of humble- 
 bees, which varies with the number of field-mice, that is to 
 say, with the abundance of cats ; or, to go a step farther, 
 with the number of lonely ladies in the village. It should 
 be noted, however, that according to Mr. James Sime there 
 were abundant fertile clover crops in New Zealand before there 
 were any humble-bees in that island. Indeed, many think 
 that the necessity of cross-fertilisation has been exaggerated. 
 
 Not all insects, however, are welcome visitors to plants ; 
 there are unbidden guests who do harm. To their visits, 
 however, there are often obstacles. Stiff hairs, impassably 
 slippery or viscid stems, moats in which the intruders 
 drown, and other structural peculiarities, whose origin may 
 have had no reference to insects, often justify themselves 
 by saving the plant. Even more interesting, however, is 
 the preservation of some acacias and other shrubs by a 
 bodyguard of ants, which, innocent themselves, ward off 
 the attacks of the deadly leaf-cutters. In some cases the 
 bodyguard has become almost hereditarily accustomed to 
 the plants, and the plants to them, for they are found in 
 constant companionship, and the plants exhibit structures 
 which look almost as if they had been made as shelters 
 for the ants. On some of our European trees similar 
 little homes or domatia constantly occur, and shelter small 
 
 f1 
 
 I: -y^ 
 
30 
 
 The Study of Animal Life 
 
 f 
 
 I'ART I 
 
 insects which do no harm to the trees, but cleanse them 
 from mjurious fungi. 
 
 In many ways plants are saved from the appetite of 
 
 animals. The nettle 
 has poisonous hairs ; 
 thistles, furze, and holly 
 are covered with spines; 
 the hawthorn has its 
 thorns and the rose 
 its prickles ; some have 
 repulsive odours ; others 
 contain oils, acids, fer- 
 ments, and poisons 
 .vhich many animals 
 dislike ; the cuckoo-pint 
 {Arum) is full of little 
 crystals which make our 
 lips smart if we nibble 
 a leaf. In our studies 
 of plants we endeavour 
 to find out what these 
 qualities primarily mean 
 to their possessors ; here 
 we think rather of their 
 secondary significance 
 as protections against 
 animals. For though 
 snails ravage all the 
 plants in a district ex- 
 cept those which are 
 repulsive, the snails are 
 at most only the second- 
 
 "^J^ ^'t t^'^^ft^'t^, -y ^f »-^in the evolu- 
 (After Schimper.) tion of the repulsive 
 
 T,, . qualities, 
 
 are atif Mhf^ >nter-relations between plants and animals 
 are agam .llustrated by the carnivorous, generally insecti- 
 vorous plants. It is not our busine;s%o discu s the 
 ongmal or primary import of the pitchers of pitcher-plants, 
 
CHAP. 11 
 
 The Web of Life 
 
 3> 
 
 or of the mobile and sensitive leaves of Venus' \ ly-Trap ; 
 nowadays, at any rate, insects are attracted to them, 
 captured by them, and used. Let us take only one case, 
 that of the common Bladderwort {Utricularid). Many of 
 the leaflets of this plant, which floats in summer in the 
 marsh ponJ, are modified into little bladders, so fashioned 
 that minute " water-fleas " — which swarm in every comer of 
 the pool — can readily enter them, but can in no wise get out 
 again. The small entrance is guarded by a valve or door, 
 which opens inwar-^s, but allows no egress. The little crusta- 
 ceans are attracted by some mucilage made by the leaves, or 
 sometimes perhaps by sheer curiosity ; they enter and cannot 
 return ; they die, and their debris is absorbed by the leaf. 
 
 Again, in regard to distribution, there are numerous 
 relations between organisms. Spiny fruits like those of 
 Jack-run-the-hedge adhere to animals, and are borne from 
 place to place ; and minute water-plants and animals are 
 carried from one watercourse to another on the muddy 
 feet of birds. Darwin removed a ball of mud from the 
 leg of a bird, and from it fourscore seeds germinated. Not 
 a bird can fall to the ground and die without sending a 
 throb through a wide circle. 
 
 A conception of these chains or circles of influence 
 is important, not only for the sake of knowledge, but also as 
 a guide in action. Thus, to take only one instance among 
 a hundred, it may seem a far cry from a lady's toilet-table 
 to the African slave-trade, but when we remember the ivoiy 
 backs of the brushes, and how the slaves are mainly used for 
 transporting the tusks of elephants — a doomed race — from 
 the interior to the coast, the riddle is read, and the respon- 
 sibility is obvious. Over a ploughed field in the summer* 
 morning we see the spider-webs in thousands glistening 
 with mist-drops, and this is an emblem of the intricacy of 
 the threads in the web of life — to be seen more and more 
 as our eyes grow c'ear. Or, is not the face of nature like 
 the surface of a gentle stream, where hundreds of dimpling 
 circles touch and influence one another in an infinite com- 
 plexity of action and reaction beyond the ken of the wisest ? 
 
 A 
 
 ■% 
 
 ''4| 
 
CHAPTER III 
 
 THE STRUGGLE OF LIFE 
 
 I. Nature and Extent of tkeStruggl,-2. Armcur and Weaiom- 
 3. Different Forms of Struggle -4. Cruelty of the Stru^le 
 
 I. Nature and Extent of the Struggle.— If we realise 
 what IS meant by the "web of life," the recognition of 
 the "struggle for existence" cannot be difficult Animals 
 do not live m isolation, neither do they always pursue 
 paths of peace. Nature is not iike a menagerie where 
 beast IS separated from beast by iron bars, neither is it 
 a mfilde such as would result if the bars of all the cages 
 were at once removed. It is not a continuous Waterloo, 
 nor yet an amiable compromise between weaklings The 
 truth lies between these extremes. In most places where 
 animals abound there is struggle. This may be silent and 
 yet decisive, real without being very cruel, or it may be 
 full of both noise and bloodshed. 
 
 This struggle is very old ; it is older than the conflicts 
 ^f men, older than the ravin of tooth and claw, it U as old 
 as life. The struggle is often very keen— often for life or 
 death. But though few animals escape experience of the 
 battlefield— and for some there seems no discharge from 
 this war— we must not misinterpret nature as "a continual 
 free-fight." One naturalist says that all nature breathes a 
 hymn of love, but he is an optimist under sunny southern 
 •kies ; another compares nature to a huge gladiatorial 
 show with a plethora of fighters, but he speaks as a pes- 
 
CHAP. lit 
 
 The Struggle of Life 
 
 simist from amid the din of individualistic competition. 
 Nature is full of struggle and fear, but the struggle is 
 sometimes outdone by sacrifice, and the fear is sometimes 
 cast out by love. We must be careful to remember 
 Darwin's proviso that he used the phrase "struggle for 
 existence " " in a large and metaphorical sense, including the 
 dependence of one being on another, and including (which 
 is more important) not only the life of the individual, but 
 success in leaving progeny." He also acknowledged the 
 importance of mutual aid, sociability, and sympathy among 
 animals, though he did not carefully estimate the relative 
 importance of competition on the one hand and sociability 
 on the other. Discussing sympathy, Darwin wrote, " In 
 however complex a manner this feeling may have originated, 
 as it is one of high importance to all those animals which 
 aid and defend one another, it will have been increased 
 through natural selection ; for those communities which 
 included the greatest number of the most sympathetic 
 members would flourish best, and rear the greatest number 
 of offspring." I should be sorry to misrepresent the 
 opinions of any man, but after considerable study of 
 modern Darwinian literature, I feel bound to join in the 
 protest which others have raised against a tendency to 
 narrow Darwin's conception of "the struggle for existence," 
 by exaggerating the occurrence of internecine competitive 
 struggle. Thus Huxley says, " Life was a continuous free- 
 fight, and beyond the limited and temporary relations of 
 the family, the Hobbesian war of each against all was the 
 normal state of existence." Against which Kropotkine 
 maintains that this "view of natt z has as little claim to 
 be taken as a scientific deduction as the opposite view of 
 Rousseau, who saw in nature but love, peace, and harmony 
 destroyed by the accession of man." ..." Rousseau has 
 committed the error of excluding the beak-and-claw fight 
 from his thoughts, and Huxley is committing the opposite 
 error; but neither Rousseau's optimism nor Huxley's pessi- 
 mism can be accepted as an impartial interpretation of 
 nature." 
 
 a. Armour and Weapons.— If you doubt the reality 
 
 o 
 
34 
 
 TJie Study of Animal Life part i 
 
 of the struggle, take a survey of the different classes of 
 animals. Ever)rwhere they brandish weapons or are forti- 
 fied with armour. "The world," Diderot said, "is the 
 abode of the strong." Even some of the simplest 
 animals have offensive threads, prophetic of the poison- 
 ous lassoes with which jellyfish and sea-anemones are 
 equipped. Many worms have horny jaws; crustaceans 
 have strong pincers; many insects have stings, not to 
 speak of mouth organs like surgical instruments ; spiders 
 give poisonous bites ; snails have burglars' files ; the cuttle- 
 fish have strangling suckers and parrots' beaks. Among 
 backboned animals we recall the teeth of the shark and the 
 sword of the swordfish, the venomous fangs of serpents, the 
 jaws of crocodiles, the beaks and talons of birds, the horns 
 and hoofs and canines of mammals. Now we do not say 
 that these and a hundred other weapons were from their 
 first appearance weapons, indeed we know that most of 
 them were aot. But they are weapons now, and just as we 
 would conclude that there was considerable struggle in a 
 community where every man bore a revolver, we must 
 draw a similar inference from the offensive equipment of 
 animals. 
 
 As to armoured beasts, we remember that shells of lime 
 or flint occur in many of the simplest animals, that most 
 sponges are so rich in spicules that they are too gritty to 
 be pleasant eating, that corals are polypes within shells 
 of lime, that many wonns live in tubes, that the members 
 of the starfish class are in varying degrees lime-clad, that 
 crustaceans and insects are emphatically armoured animals, 
 and that the majority of moiiuscs live in shells. So among 
 backboned animals, how thoroi'^hly bucklered were the 
 fishes of the old red sandstone aJ,^^inst hardly less effect- 
 ive teeth, how the scales of modem fishes glitter, how 
 securely the sturgeon swims with its coat of bony 'mail ! 
 -Amphibians arc mostly weaponless and armourless, but 
 reptiles are scaly animals par exxcllence, and the tortoise, 
 for instance, lives in an almost impregnable citadel. Birds 
 soar above pursuit, and mammals are swift and strong, 
 but among the latter the armadillos liave bony shields of 
 
CHAP, in The Struggle of Life 35 
 
 marvellous strength, and hedgehog and porcupine have 
 their hair hardened into spines and quills. Now we do not 
 say that all these structures were from the first of the 
 nature of armour, indeed they admit of other explanah'ons, 
 but that they serve as armour now there can be no doubt. 
 And just as we conclude that a man would not wear 
 a chain shirt without due reason, so we argue from the 
 prevalence of animal armour to the reality of struggle. 
 
 For a moment let me delay to explain the two saving- 
 clauses which I have inserted. The pincers of a crab are 
 modified legs, the sting of a bee has probably the same 
 origin, and it is likely that most weapons originally served 
 some ether than offensive purpose. We hear of spears 
 becoming pruning-hooks ; the reverse has sometimes been 
 true alike of animals and of men. By sheer use a structure 
 not originally a weapon became strong to slay ; for there 
 is a profound biological truth in the French proN jrb : " A 
 force de forger on devient forgeron" 
 
 And again as to armour, it is, or was, well known that a 
 boy's hand often smitten by the " tawse " became callous as 
 
 to its epidermis. Now that callousness was not a device 
 
 providential or otherwise— to save the youth from the pains 
 of chastisement, and yet it had that effect. Hy bearing 
 blows one naturally and necessarily becomes thick-skinned. 
 Moreover, the epidermic callousness referred to might be 
 acquired by work or play altogether apart from school 
 discipline, though it might also be the effect of the blows. 
 In the same way many structures which are most useful as 
 armour may be the "mechanical" or natural results of 
 what they afterwards help to obviate, or they may arise 
 quite apart from their future significance. 
 
 3- Different Porms of Struggle.— If you ask why 
 animals do not live at peace, I answer, more Scoitko, 
 Why do not we ? The desires of animals conflict with 
 those of their neighbours, hence the struggle for bread 
 ind the competition for mates. Hunger and love solve 
 the world's problems. Mouths have to be filled, but 
 population tends locally and temporarily to outrun the 
 means of subsistence, and the question "which mouths" 
 
r^w 
 
 ip^^?* 
 
CHAP. Ill 
 
 The Struggle of Life 
 
 37 
 
 has to be decided — sometimes by peaceful endeavour, as 
 in migration, sometimes with teeth clenched or ravenous. 
 Many animals are carnivorous, and must prey upon weaker 
 forms, which do their best to resist Mates also have to 
 be won, and lover may fight with lover till death is stronger 
 than both. But these struggles for food and for mates are 
 often strivings rather than strife, nor is a recognition of the 
 frequent keenness and fierceness of the competition incon- 
 sistent with the recognition of mutual aid, sociability, and 
 love. There is a third form of the struggle, — that between 
 an animal and its changeful surroundings. This also is a 
 struggle withoit strife. Fellow competitors strive for their 
 share of the limited means of subsistence ; between foes 
 there is incessant thrust and parry ; in the courtship of 
 mates tli« le are many disappointed and worsted suitors ; 
 over all are the shears of fate — a changeful physical 
 environment which has no mercy. 
 
 An analysis of the various forms of struggle may be 
 attempted as follows : 
 
 (a) Between animals of the same kind which 
 compete for similar food and other 
 necessaries of life — Struggle between 
 fellows. 
 
 {b) Between animals of diffefent kinds, the 
 one set striving to devour, the other set 
 endeavouring to escape their foes, e.g. 
 between carnivores and herbivores — 
 Struggle between foes. 
 
 (f) Between the rival suitors for desired 
 mates — Struggle between rivals in 
 love. 
 
 For 
 Food 
 
 For 
 Love 
 
 For 
 Foot- 
 hold 
 
 {(i) Between animals and changeful surround- 
 ings — Struggle with fate. 
 
 In most cases, besides the egoism or individualism, one 
 must recognise the existence of altruism, paren, love and 
 sacrifice, mutual aid, care for others, and sociality. 
 
38 
 
 The Study of Animal Life 
 
 PART I 
 
 Before we consider these different forms of struggle, let 
 us notice the rapid multiplication of individuals which 
 furnishes the material for what in "a wide and meta- 
 phorical sense " may be called a " battlefield." 
 
 A single Infusorian may be the ancestor of millions by 
 the end of a week. A female aphis, often producing one 
 offspring per hour for days together, might in a season be 
 the ancestor of a progeny of atomies which would weigh 
 down five hundred millions of stout men. " The roe of a 
 cod contains sometimes nearly ten million eg^s, and sup- 
 posing each of these produced a young fish which arrived 
 at maturity, the whole sea would immediately become a 
 solid mass of closely packed codfish." The unchecked 
 multiplication of a few mice or rabbits would soon leave no 
 standing-room on earth. 
 
 But fortunately, with the exception of the Infusorians, these 
 multiplications do not occur. We have to thank the 
 struggle in nature, and especially the physical environment 
 that they do not. The fable of Mirza's bridge is continually 
 true, — few get across. 
 
 (a) It is often said that the struggle between fellows of the 
 same kind and witli the same needs is keenest of all, but 
 this is rather an assumption than an induction from facts. 
 The widespread opinion is partly due to an a priori con- 
 sideration of the problem, partly to that anthropomorphism 
 which so easily besets us. We transfer to the animal 
 world our own experience of keen competition with fellows 
 of the same caste, and in so doing are probably unjust 
 Thus Mr. Grant Allen says — 
 
 " The baker does not fear the competition of the butcher in the 
 struggle for life ; it is the competition of the other bakers that 
 sometimes inexorably crushes him out of existence. ... In this 
 way the great enemies of the individual herbivores are not the 
 carnivores, but the other herbivores. ... It is not so much the 
 battle between the tiger and the antelope, between the wolf and 
 the bison, between the snake and the bird, that ultimately results 
 in natural selection or survival of the fittest, as the struggle between 
 tiger and tiger, between bison and bison, between snake and aiiakc 
 between antelope and antelope. . . . Homo komini lupus, says 
 the old proverb, and so, we may add, in a wider sense, lupus lupo 
 
CHAP. Ill 
 
 Ike Struggle of Life 
 
 39 
 
 lupus, also. . . . The struggle i.; fierce between allici. kinds, and 
 fiercest of all between individual members of the same species." 
 
 I have quoted these sentences because they are clearly and 
 cleverly expressed, after the manner of Grant Allen, but I 
 do not believe that they are true statements of facts. The 
 evidence is very unsatisfactory. In his paragraph sum- 
 marised as "struggle for life most severe between indi- 
 viduals and varieties of the same species ; often severe 
 between species of the same genus," Darwin gave five 
 illustrations : one species of swallow is said to have ousted 
 another in North America, the missel-thrush has increased 
 in Scotland at the expense of the song-thrush, the brown 
 rat displaces the black rat, the small Asiatic cockroach 
 drives its great congener before it, the hive-bee imported 
 to Australia is rapidly exterminating the small, stingless 
 native bee. But the cogency of these instances may be 
 disputed : thus what is said about the thrushes is denied by 
 Professor Newton. And on the other hand, we know that 
 reindeer, beavers, lemming, buffaloes and many other 
 animals migrate when the means of subsistence are unequal 
 to the demands of the population, and there are other 
 peaceful devices by which animals have discovered a way 
 out of a situation in which a life-and-death struggle might 
 seem inevitable. Very instructive is the fact that beavers, 
 when too numerous in one locality, divide into two parties 
 and migrate up and down stream. The old proverb which 
 Grant Allen quotes, Homo homini lupus, appears to me a 
 libellous inaccuracy ; the extension of the libel to the 
 animal world has certainly not been justified by careful 
 induction. For a discussion of the alleged competition 
 between fellows, I refer, and that with pleasure and grati- 
 tude, to Kropotkine's articles on '* Mutual Aid among 
 Animals," Nineieenth Century, September and November 
 1890. 
 
 {V) Of the struggle between foes difTering widely in kind 
 little need be said. It is very apparent, especially in wild 
 countries. Carnivores prey upon herbivores, which some- 
 times unite in successful resistance. Birds of prey devour 
 
 mnp 
 
40 
 
 "V 
 
 if 
 
 
 The Study of Animal Life 
 
 PART I 
 
 small mammals, and sometimes have to fight hard for their 
 booty. Reptiles also have their battles— witness the combats 
 between snake and mongoose. In many cases, however 
 carnivorous animals depend upon small fry; thus many 
 birds feed on fishes, insects, and worms, and many fishes 
 live on minute crustaceans. In such cases the term 
 
 Fig. 6. -Weasel attacking a grouse. (From St. John's mid Sports.) 
 
 Struggle must again be used " in a wide and metaphorical 
 
 i/Mihv- 
 
 sense 
 
 (r) In a great number of cases there is between rival males 
 a contest for the possession of the females,-a competition 
 m which beauty and winsomeness are sometimes as im- 
 portant as strength. Contrast the musical competition 
 between rival songsters with the fierce combats of the stags 
 
CHAP. Ill 
 
 The Struggle of Life 
 
 41 
 
 Many animals are not monogamous, and this causes strife ; 
 a male seal, for instance, guards his harem with ferocity. 
 
 (rf) Finally, physical nature is qui te careless of life. Changes 
 of medium, temperature, and moisture, continually occur, 
 and the animals flee for their lives, adapt themselves to 
 new conditions, or perish. Cataclysms are rare, but 
 changes are common, and especially in such schools of 
 experience as the sea-shore we may study how vicissitude 
 has its victims or its victors. 
 
 The struggle with Fate, that is to say, with changeful 
 surroundings, is more pleasant to contemplate than the 
 other kinds of struggle, for at the rigid mercilessness of 
 physical nature we shudder less than at the cruel competi- 
 tion between living things, and we are pleased with the 
 devices by which animals keep their foothold against wind 
 and weather, storm and tide, drought and cold. One illus- 
 tration must suffice : drought is common, pools are dried up, 
 the inhabitants are left to perish. But often the organism 
 draws itself together, sweats off a protective sheath, which 
 is not a shroud, and waits until the rain refreshes the pools. 
 Not the simplest animals only, but some of comparatively 
 high degree, are thus able to survive desiccation. The 
 simplest animals encyst, and may be blown about by the 
 wind, but they rest where moisture moors them, and are 
 soon as lively as ever. Leaping a long way upwards, we 
 find that the mud- fish {Protopterus) can be transported 
 from Africa to Northern Europe, dormant, yet alive, 
 within its ball of clay. We do not believe in toads appear- 
 ing out of marble mantelpieces, and a palaeontologist will 
 but smile if you tell him of a frog which emerged from an 
 intact piece of old red sandstone, but amphibians may 
 remain for a long time dormant either in the mud of their 
 native pools or in some out-of-the-way chink whither they 
 had wandered in their fearsome youth. 
 
 A shop which had once been used in the preparation 
 of bone-dust was after prolonged emptiness reinstated in a 
 new capacity. But it was soon fearfully infested with mites 
 {Glyciphagus\ which had been harboured in crevices in a 
 strange state of dry dormancy. Every mite had in a sense 
 
49 
 
 The Study of Animal Life 
 
 PART 
 
 ^ s' 
 
 died, but remnant cells in the body of each had clubbed 
 together in a life-preserving union so effective that a return 
 of prosperity was followed by a reconstitution of mites and 
 by a plague of them. Of course great caution must be 
 exercised with regard to all such stories, as well as in 
 regard to the toads within stones. Of common little 
 animals known as Rotifers, it is often said, and sometimes 
 rightly, that they can survive prolonged desiccation. In a 
 small pool on the top of a granite block, there flourished a 
 family of these Rotifers. Now this little pool was period- 
 ically swept dry by the wind, and in the hollow there 
 remained only a scum of dust. But when the rain returned 
 and filled the pool, there were the Rotifers as lively as 
 ever. What inference was more natural than that the 
 Rotifers survived the desiccation, and lay doi-mant till 
 moisture returned.? But Professor Zacharias thought he 
 would like to observe the actual revivification, and taking 
 some of the dusty scum home, placed it under his micro- 
 scope on a moist slide, and waited results. There were the 
 corpses of the Rotifers plain enough, but they did tiot revive 
 even in abundant moisture. What was the explanation ? 
 The eggs of these Rotifers survived, they developed rapidly, 
 they reinstated the family. And of course it is much easier 
 to understand how single cells, as eggs are, could survive 
 being dried up, while their much more complex parents 
 perished. I do not suggest that no Rotifers can survive 
 desiccation, it is certain that some do; but the story I 
 have told shows the need of caution. There is no doubt, 
 moreover, that certain simple "worms," known as "paste- 
 eels," « vinegar-eels," etc., from their frequent occurrence 
 in such substances, can survive desiccation for many years. 
 Repeated experiments have shown that they can lie dormant 
 for as long as, but not longer than, fourteen years ! and it 
 is interesting to notice that the more prolonged the period 
 of desiccation has been, the longer do these threadworms 
 take to revive after moisture has been supplied. It seems 
 as if the life retreated further and further, till at length it 
 may retreat beyond recall. In regard to plants there are 
 many similar facts, for though accounts of the germination 
 
CRAP. Ill 
 
 The Struggle of Life 
 
 43 
 
 of seeds from the mummies of the pyramids, or from the 
 graves of the Incas, are far from satisfactory, there is no 
 doubt that seeds of cereals and leguminous plants may 
 retain their life in a dormant state for years, or even for 
 tens of years. 
 
 But desiccation is only one illustration out of a score 
 of the mariner in which animals keep their foothold against 
 fate. I need hardly say that they are often unsuccessful ; 
 the individual has often fearful odds against it. How many 
 winged seeds out of a thousand reach a fit resting-place 
 where they may germinate ? Professor Mobius says that 
 out of a million oyster embryos only one individual grows 
 up, a mortality due to untoward currents and surroundings, 
 as well as to hungry mouths. Yet the average number of 
 thistles and oysters tends to continue, " So careful of the 
 type she seems, so careless of the single life." Yet though 
 the average usually remains constant, there is no use trying 
 to ignore, what Richard Jefferies sometimes exaggerated, 
 that the physical fates are cruel to life. But how much 
 wisdom have they drilled into us ? 
 
 " For life is not as idle ore, 
 
 But iron dug from central gloom, 
 And heated hot with burning fears. 
 And dipt in baths of hissing tears, 
 
 And battered by the shocks of doom 
 
 To shape and use." 
 
 4. Ornelty of the Struggle. — Opinions differ much as 
 to the cruelty of the " struggle for existence," and the 
 question is one of interest and importance. Alfred Russel 
 Wallace and others try to persuade us that our ccnception 
 of the "cruelty of nature" is an anthropomorphism; that, 
 like Balbus, animals do not fear death ; that the rabbit 
 rather enjoys a run before the fox ; that thrilling pain soon 
 brings its own anaesthetic ; that violent death has its 
 pleasures, and starvatioii its excitement. Mr. Wallace, 
 who speaks with the authority of long and wide ex- 
 perience, enters a vigorous protest against Professor 
 Huxley's description of the myriads of generations of 
 
»^ 
 
 44 
 
 '' '"''^iwWIipWWMIiiii'.tii'yiiii 11 /I'm 
 
 The Study of Animal Life 
 
 PART I 
 
 herbivorous animals "which have been tormented and 
 devoured by carnivores " ; of both alike " subject to all the 
 
 tTr"'' f"S^'?"' '° °'^ "«"' ^•^^^^' ^"d over-multiplica 
 tion ; of the "more or less enduring suffering" which is 
 the meed of both vanquished and victor; of the whole 
 creation groaning in pain. "There is good reason to 
 believe." says Mr. Wallace, " that the supposed to ments 
 and niisenes of animals have little real existence, but are 
 the reflection of the imagined sensations of cultivated men 
 and women in similar circumstances, and that the amount 
 
 aL'n?«t r"\ '^""'f ""' '''' ^^^"^^"'^ ^°r existence 
 among animals ,s altogether insignificant." " Animals are 
 spared from the pain of anticipating death ; violent deaths, 
 f not too prolonged, are painless and easy; neither do 
 those which die of cold or hunger suffer much the popula 
 Idea of the struggle for existence entailing misery and paL 
 on the animal worid is the very reverse of the tmth " ^He 
 concludes by quoting the conclusion of Darwin's chapter on 
 the struggle for existence: "When we reflect on this 
 struggle, we may console ourselves with the full belief that 
 the war of nature is not incessant, that no fear is felt ha 
 
 healthy, and the happy survive and multiply." Yet i was 
 Darwin who confessed that he found in the world "oo 
 much misery." ^"° 
 
 We have so little security in appreciating the real life- 
 the mental and physical pain or happiness-of anima^hat 
 there is apt to be exaggeratio. on both sides, according a 
 a pessimistic or an optimistic mood predominates. I there 
 fore leave It to be settled by your own observation whether' 
 hunted and captured, dying and starving, maimed aS half 
 frozen animals have to endure "an altogether insignificant 
 
 "TuM° vT' '"''""^ '" ^^^ =^-^^'« ^- existen";?" 
 whi^ M w n *^ """'' ''"^'"'' '^^' ^^^'^ is much truth in 
 what Mr. Wallace urges. Moreover, the term cruelty can 
 hardly be used with accuracy when the involved infliction 
 
 less'f'ruel-rth?- • I" ""^ ^^"^ ^^^ camivoresTr 
 IL " 1,.'° ?"L"^ '!?^ *^- - -« to our domesti- 
 
 .... — - "•«" wc arc lo OU 
 
 cated animals. We must also remember that the 
 
 struggle 
 
 <Tl9?«veW4f«. 
 
 isMaas&''iS!S'^-if. °r^!wiiii'''$^r:viF^E2fia?ssBSHE&> 
 
CHAP. Ill 
 
 The Struggle of Life 
 
 45 
 
 for existence " is often applicable only in its '* wide and 
 metaphorical sense." And it is fair to balance the happiness 
 and mutual helpfulness of animals against the pain and 
 deathful competition which undoubtedly exist. 
 
 What we must protest against is that one-sided inter- 
 pretation according to which individualistic competition is 
 nature's sole method of progress. We are told that animals 
 have got on by their struggle for individual ends ; that they 
 have made progress on the corpses of their fellows, by a 
 " blood and iron " competition in which each looks ov^ for 
 himself, and extinction besets the hindmost. To those who 
 accept this interpretation the means employed seem justified 
 by the results attained. But it is only in after-dinner talk 
 that we can slur over whatever there is of pain and cruelty, 
 overcrowding and starvation, hate and individualism, by 
 saying complacently that they are justified in us their 
 children; that we can rest satisfied that what has been 
 called "a scheme of salvation for the elect by the damnation 
 of the vast majority " is a true statement of the facts ; that 
 we can seriously accept a one-sided account of nature's 
 regime as a justification of our own ethical and economic 
 practice. 
 
 The conclusions, which I shall afterwards seek to 
 substantiate, are, that the struggle for existence, with its 
 associated natural selection, often involves cruelty, but 
 certainly does not always do so ; that joy and happiness, 
 helpfulness and co-operation, love and sacrifice, are also 
 facts of nature, that they also are justified by natural 
 selection ; that the precise nature of the means employed 
 and ends attained must be carefully considered when 
 we seek from the records of animal evolution support 
 or justification for human conduct ; and that the tragic 
 chapters in the history of animals (and of men) must be 
 philosophically considered In such light as we can gather 
 from what we know of the whole book. 
 
 ^^^'^^ESWa^v-:. 
 
CHAPTER IV 
 
 :•' 
 
 SHIFTS FOR A LIVING 
 
 I. Insulation -2. ConccahncH-i. Parasitism-^. General Re- 
 semblance to Surroundings -i. Variable Colouring~6. Rat^id 
 Chanse of Colour —t. Special Protective Resemblance -%. 
 IVarnmg Colours -q. Mimicry— lo. Afasiimr-ii. Com- 
 bmatton of Advantageous Qualities— 12. Surrender of Parts 
 
 Granting the struggle with fellows, foes, and fate, we are 
 led by force of sympathy as well as of logic to think of the 
 shifts for a living which tend to be evolved in such con- 
 ditions, and also of some other ways by which animals 
 escape from the intensity of the struggle. 
 
 I. InBUlation.— Some animals have got out of the 
 struggle through no merit of their own, but as the result 
 of geological changes which have insulated them from 
 their enemies. Thus, in Cretaceous times probably ihe 
 marsupials which inhabited the Australasian region were 
 insulated. In that region they were then the only re- 
 presentatives of Mammalia, and so, excepting the "native 
 dog, some rodents and bats, and more modern imports, 
 they still continue to be. By their insulation they were 
 saved from that contest with stronger mammals in which 
 all the marsupials left on the other continents were 
 exterminated, with the exception of the opossums, which 
 hide in American forests. A similar geological insulation 
 accounts for the large number of lemurs in the Island of 
 Madagascar. 
 
CHAP. IV 
 
 Shifts for a Living 
 
 47 
 
 2. Ooncealment. — A change of habitat and mode of life 
 is often as significant for animals as it is for men. It is 
 easy to understand how mammals which passed from 
 terrestrial to more or less aquatic life, for instance beaver 
 and pwlar bear, seals, and perhaps whales, would enjoy 
 a period of relative immunity after the awkward time 
 of transition was over. So, too, many must have passed 
 from the battlefield of the sea -shore to reLitive peace 
 on land or in the deep-sea. In a change from open air 
 to underground life, illustrated for instance in the mole, 
 many animals have sought and found safety, and the 
 change seems even now in progress, as in the New 
 Zealand parrot S/ri/tgops, which, having lost the power 
 of flight, has taken to burrowing. Similarly the power 
 of flight must have helped insects, some ancient saurians, 
 and birds out of many a scrape, though it cannot be 
 doubted th^t this transition, and also that from diurnal to 
 nocturnal habits, oft. brought only a temporary relief. 
 
 3. Parasitism. — i-rom the simple Protozoa up to the 
 beginning of the backboned sei s, we find illustrations of 
 animals which have taken to a thievish existence as unbidden 
 guests in or on other organisms. Flukes, tapeworms, and 
 some other " worms," many crustaceans, insects, and mites, 
 are the most notable. Few animals are free from some kind 
 of parasite. There are various grades of parasitism ; there 
 arc temporr-ry and permanent, external and internal, very 
 degenerate, and very slightly affected parasites. Some- 
 times the adults are parasitic while the young are free-liv- 
 ing, sometimes the reverse is true ; sometimes the parasite 
 completes its life in one host, often it reaches maturity only 
 after the host in which its youth has been passed is de- 
 voured by another. In many cases the habit was probably 
 l)cgun by the females, which seek shelter during the period 
 of egg -laying; in not a few crustaceans and insects the 
 females alone are parasitic. Most often, in all probability, 
 liun;;er and the search for shelter led to the estabUshment 
 of the thievish haLit. Now, the advantages gained by a 
 thoroughgoing parasite are great— safety, warmth, abund- 
 ant food, in short, "complete material well-being." But 
 
48 
 
 The Study of Animal Life 
 
 PART I 
 
 there is another aspect of the case. Parasitism tends to be 
 followed by degeneration — of appendages, food -canal, 
 sense-organs, nervous system, and other structures, the 
 possession and use of which make life worth living. More- 
 over, though the reproductive system never degenerates, 
 the odds are often many against an embryo reaching a fit 
 host or attaining maturity. Thus Leuckart calculates that 
 a tapeworm embryo has only about i chance in 83,000,000 
 of becoming a tapeworm, and one cannot be sorry that 
 its chance is not greater. In illustration of the degenera- 
 tion which is often associated with parasitism, and varies 
 as the habit is more or less predominant, take the case of 
 Sacculina—^ crustacean usually ranked along with bar- 
 nacles and acorn-shells. It begins its life as a minute free 
 " nauplius," with three pairs of appendages, a short food- 
 canal, an eye, a small brain, and some other structures 
 characteristic of many young crustaceans. In spite of this 
 promiseful beginning, the young Sacculina becomes a para- 
 site, first within the body, and finally under the tail, of a 
 crab. Attached by absorptive suckers to its host, and 
 often doing no slight damage, it degenerates into an oval 
 sac, almost without trace of its former structure, with 
 reproductive system alone well developed. Yet the 
 degeneration is seldom so great as this, and it is fair to 
 state that many parasites, especially those which remain as 
 external hangers-on, seem to be but slightly afTccted by their 
 laiy thievish habit ; nor can it be denied that most are well 
 adapted to the conditions of their life. But on the whole 
 the parasitic life tends to degeneration, and is unprogress- 
 ive. Meredith writes of Nature's sifting 
 
 " Behold the life of ease, it drifts. 
 The sharpened life commands its course 1 
 She winnows, winnows roughly, sifts, 
 To dip her chosen in her source. 
 Contention is the vital force 
 Whence pluck they brain, her pri«e of gifts." 
 
 4« Ckntnd Reiemblance to Snrroimdinfi. Many 
 
 transparent and translucent blue animals are hardly 
 
CHAP. IV 
 
 Shifts for a Living 
 
 49 
 
 visible in the sea; white animals, such as the polar bear, 
 the arctic fox, and the ptarmigan in its winter plumage 
 are inconspicuous upon the snow; green animals, such 
 as insects, tree-frogs, lizards, and snakes, hide among the 
 leaves and herbage ; tawny animals harmonise with sandy 
 soil ; and the hare escapes detection among the clods. So 
 do spotted animals such as snakes and leopards live unseen 
 in the interrupted light of the forest, and the striped tiger 
 is lost in the jungle. Even the eggs of birds are often well 
 suited to the surroundings in which they are laid. There 
 can be no doubt that this resemblance between the colour 
 of an animal and that of its surroundings is sometimes of 
 protective and also aggressive value in the struggle for 
 existence, and where this is the case, natural selection 
 would foster it, favouring with success those variations 
 which were best adapted, and eliminating those which were 
 conspicuous. 
 
 But there are many instances of resemblance to sur- 
 roundings which are hard to explain. Thus Dr. A. Seitz 
 describes a restricted area of woodland in South Brazil, where 
 the great majority of the insects were blue, although but 
 a few m"!(^ off a red colour was dominant. He maintains 
 that the facts cannot in this case be explained as due either 
 to general protective resemblance or to mimicry. 
 
 I have reduced what I had written in illustration of 
 advantageous colouring of various kinds, because this 
 exceedingly interesting subject has been treated in a readily 
 available volume by one who has devoted much time and 
 skill to its elucidation. Mr. E. B. Poulton's Colours of 
 Animals (International Science Series, London, 1890) is a 
 fascinating volume, for which all interested in these aspects 
 of natural history n»ust be gra' ful. With this a forth- 
 coming work {Animal Coloration, London, 1892) by Mr. 
 F, E. Beddard should be compared. 
 
 5- Variable Colouring.— Some animals, such as the 
 ptarmigan and the mountain-hare, become white in winter, 
 and are thereby safer and warmer. In some cases it 
 H certain that the pigmented feathers and hairs become 
 white, in other cases the old feathers and hairs drop 
 
 , TV^QJg' 
 
 ■"wic^MnwB^imT-'riraTW.Tniiiju .w.^:'* 
 
so 
 
 The Study of Animal Life 
 
 PART I 
 
 oflf and are replaced by white ones ; sometimes the 
 whiteness is the result of both these processes. It is 
 directly due to the formation of gas bubbles inside 
 the hairs or feathers in sufficient quantity to antagonise 
 the effect of .my pigment that may be present, but in 
 the case of new growths it is not likely that any pig- 
 ment is formed. In sc ue cases, e.g. Ross's lemming and 
 the American hare {Lepus americanus), it has been clearly 
 shown that the change is due to the cold. It is likely that 
 this acts somewhat indirectly upon the skin through the 
 nervous system. We may therefore regard the change as 
 a variation due to the environment, and it is at least 
 possible that the permanent whiteness of some northern 
 animals, e.g. the polar bear, is an acquired character of 
 similar origin. There are many objections to the theory 
 that the winter whiteness of arctic animals arose by the 
 accumulation of small variations in individuals which, being 
 slightly whiter than their neighbours, became dominant by 
 natural selection, though there can be no doubt that the 
 whiteness, however it arose, would be conserved like other 
 advantageous variations. 
 
 To several naturalists, but above all to Mr. Poulton, we 
 are indebted for much precise information in regard to the 
 variable colouring of many caterpillars and chrysalides. 
 These adjust their colours to those of the surroundmgs, and 
 even the cocoons are sometimes harmoniously coloured. 
 There is no doubt that the variable colouring often has 
 protective value. Mr. Poulton experimented with the 
 caterpillars of the peacock butterfly {Vanessa to), small 
 tortoise-shell (Vanessa urtica\ garden whites {Pieris 
 brassica and Pieris rapa\ and many others. Caterpillars 
 of the small tortoise-shell in black surroundings tend to be- 
 come darker as pupae ; in a white environment the pupx 
 are lighter ; in gilded boxes they tend to become golden. 
 The surrounding colour seems to influence the caterpillar 
 " during the twenty hours immediately preceding the last 
 twelve hours of the larval statr," "and this is probably the 
 true meaning of the hours during which the caterpillar 
 rests motionless on the surface upon which it will pupate. ' 
 
CHAP. IV 
 
 Shifts for a Living 
 
 5> 
 
 " It appears to be certain that it is the skin of the larva 
 which is influenced by surroundinjj colours during the 
 sensitive period, and it is probable that the cfifects are 
 wrought through the medium of the nervous system." 
 
 Accepting the facts that caterpillars are subtly affected 
 by surrounding colours, so that the quiescent pupie har- 
 monise with their environment, and that the adjustment has 
 often protective value, we are led to inquire into the origin 
 of this sensitiveness. That the change of colour is 
 not a direct result of external influence is certain, but 
 of the physiological nature of the changes we know little 
 more than that it must be complex. It may be main- 
 tained, that " the existing colours and markings are at any 
 rate in part due to the accumulation through heredity 
 of the indirect influence of the environment, working 
 by means of the nervous system ; " " to which it may 
 be replied," Poulton continues, «« that the whole use and 
 meaning of the power of adjustment depends upon its 
 freedom during the life of the individual ; any hereditary 
 bias towards the colours of ancestors would at once destroy 
 the utility of the power, which is essentially an adaptation 
 to the fact that different individuals will probably meet with 
 different environments. As long ago as 1873 Professor 
 Meldola argued that this power of adjustment is adaptive, 
 and to be explained by the operation of natural selection." 
 Foulton's opinion seems to be, that the power of producing 
 variable colouring arose as a constitutional variation apart 
 from the influence of the environment, that the power was 
 fostered in the course of natural selection, and that its 
 limits \\ere in the same way more or less defined in adapta- 
 tion to the most frequent habitat of the larvae before 
 and during pupation. The other theory is that the power 
 arose as the result of environmental influence, was accumu- 
 ated by mheritance throughout generations, and was fostered 
 like other profitable variations by natural selection. The 
 question is whether the power arose in direct relation 
 to environmental influence or not, whether external influence 
 was or was not a primary factor in evolving the power of 
 adapting colour, and in defining it within certain limits. 
 
f 
 
 5a The Study of Animal Life part i 
 
 6. Bapid Ohange of Oolonr. — For ages the chamaeleon 
 has been famous for its rapid and sometimes striking 
 changes of colour. The members of the Old World 
 genus Chamceleo quickly change from green to brown 
 or other tints, but rather in response to physical irrita- 
 tion and varying moods than in relation to change of 
 situation and surrounding colours. So the American 
 " chamaeleons " {Anolis) change, for instance, from emerald 
 to bronze under the influence of excitement and various 
 kinds of light. Their sensitiveness is exquisite ; " a pass- 
 ing cloud may cause the bright emerald to fade." Some- 
 times they may be thus protected, for " when on the broad 
 green leaves of the palmetto, they are with difficulty per- 
 ceived, so exactly is the colour of the leaf counterfeited. 
 But their dark shadow is very distinct from beneath." Most 
 of the lizards have more or less of this colour-changing 
 power, which depends on the contraction and expansion 
 of the pigmented living matter of cells which lie in layers 
 in the under-skin, and are controlled by nerves. 
 
 In a widely different set of animals — the cuttle-fishes— 
 the power of rapid colour-change is well illustrated. When 
 a cuttle-fish in a tank is provoked, or when one almost 
 stranded on the beach struggles to free itself, or, most 
 beautifully, when a number swim together in strange unison, 
 flushes of colour spread over the body. The sight suggests 
 the blushing of higher animals, in which nervous excitement 
 passing from the centre along the peripheral nerves influ- 
 ences the blood-supply in the skin ; but in colour-change the 
 nervous thrills affect the pigment-containing cells or chroma- 
 tophores, the living matter of which contracts or expands 
 in response to stimulus. It must be allowed that the colour- 
 change of cuttle-fish is oftenest an expression of nervous 
 excitement, but in some cases it helps to conceal the 
 animals. 
 
 More interesting to us at present are those cases of 
 colour- change in which animals respond to the hues of 
 their surroundings. This has been observed in some 
 Amphibians, such as tree-frogs ; in many fishes, such as 
 plaice, stickleback, minnow, trout, Goinus ruthtnsparri. 
 
 . BWIWP'Jft '-<■•*?• A-iVt»SThJ» 
 
CHAP. !▼ 
 
 Shifts for a Living 
 
 53 
 
 Serranus ; and in not a few crustaceans. The researches 
 of Briicke, Lister, and Pouchet have thrown much light on 
 the subject. Thus we know that the colour of surround- 
 ings affects the animals through the eyes, for blind plaice, 
 trout, and frogs do not change their tint. The nervous' 
 thrill passes from eye to brain, and thence extends, not down 
 the main path of impulse— the spinal cord— but down the 
 sympathetic chain. If this be cut, the colour-change does 
 not take place. The sympathetic" system is connected with 
 nerves passing from the spinal cord to the skin, and it is 
 along these that the impulse is further transmitted. The 
 result is the contraction or expansion of the pigment in the 
 skin-cells. Though the path by which the nervous influence 
 passes from the eye to the skin is somewhat circuitous, the 
 change is often very rapid. As the resulting resemblance 
 to surroundings is often precise, there can be no doubt that 
 the peculiarity sometimes profits its possessors. 
 
 7. Special Protective Resemblance. — The likeness 
 between animals and their surroundings is often very precise, 
 and includes form as well as colour. Thus some bright butter- 
 flies, <r.^. Kallima, are conspicuous in flight, but become 
 precisely like brown withered leaves when they settle upon 
 a branch and expose the under sides of their rai-ed wings ; 
 the leaf-insects {Phyllium) have leaf-like wings and legs ;' 
 the "walking-sticks" {Phasmid(f\ with legs thrown out at 
 all angles, resemble irregular twigs ; many caterpillars (of 
 Geometra moths especially) sit motionless on a branch, 
 supported in a strained attitude by a thin thread of silk, and 
 exactly resemble twigs ; others are like bark, moss, or 
 li "len. Among caterpillars protective resemblance is very 
 common, and Mr. Poulton associates its frequent occurrence 
 with the peculiarly defenceless condition of these young 
 animals. •• The body is a tube which contains fluid under 
 pressure ; a slight wound entails great loss of blood, while 
 a moderate injury must prove fatal." •• Hence larvai are so 
 coloured as to avoid detection or to warn of some unplea- 
 sant attribute, the object in both cases being the same— to 
 leave the larva untouched, a touch being practically fatal." 
 Among backboned animals we do not expect to find many 
 
 ■^ryS- ,-&. 
 
54 
 
 The Study of Animal Life 
 
 PART I 
 
 examples of precise resemblance to surrounding objects ; 
 but one of the sea-horses {Phyllopteryx eques) is said to be 
 exceedingly like the seaweed among which it lives. It is 
 very difficult at present to venture suggestions as to the 
 constitutional tendencies which may have resulted in 
 " walking-leaves " and " walking-sticks," but forms related 
 to these tend to resemble leaves or sticks sufficiently to deter 
 
 Fu;. 7.— r.taf-in-ccl -cata.l on a bran, h (From Heit.) 
 
 one from postulating a mere sport as the origin of the 
 p('( iili.'uity which distinguishes riiyllium or riuuituu On 
 the other hand, some of the strangely precise minute 
 resemblances n1^■^' be the fostered results of slight indefinite 
 sports. It is aiso possible that some of the cleverer 
 animals, such as spiders, learn to hide among the lichens 
 and on the bark which they most resemble. But in every 
 case, and especially where there are many risks, as among 
 
 ^U 
 
CHAP. IV 
 
 Shifts for a Living 
 
 55 
 
 caterpillars, the protective resemblance would be '"ostered 
 in the course of natural selection. 
 
 Fig. 8.— Moss insect. (From Belt.) 
 
 8. Warning Colours. — While many animals are con- 
 cealed by their colouring, others are made the more 
 conspicuous. But, as the latter arc often unpalatable or 
 dangerous, Wallace suggested that the colours were 
 warnings, which, as Poulton says, "assist the education 
 of enemies, enabling them to easily learn and remember 
 the animals which arc to be avoided.' Expressing 
 the same idea. Belt says, " the skunk goes leisurely along, 
 holding up his white tail as a danger-flag for none to come 
 within range of his nauseous artillery," So, the brightness 
 of the venomous coral-snake {Elafis) is a warning; the 
 rattlesnake, excitedly shaking its rattle, "warns an intruder 
 of its presence"'; the cobra " endeavours to terrify its enemy 
 by the startling appearance of its expanded hood and con- 
 spicuous eye-like marks." The language in which conspicu- 
 ous colours are described by many naturalists tends to 
 exaggerate the subtlety of animals, for the intentional 
 warning of possible molesters involves rather complex ideas. 
 Belt's description of the skunk, for instance, recalls a more 
 familiar sight — a cat showing fight to a dog — in regard to 
 \\\\\d\ Mantegazza gravely tells us that the cat " bristles up 
 her fur, and inflates herself to appear larger, and to frighten 
 the dog who threatens her " ! In our desire to be fair to the 
 subdety of animals, it is indeed difficult to avoid being 
 credulous. 
 
 ' llJUijlJl'J 
 
56 
 
 The Study of Animal Life 
 
 PART I 
 
 Perhaps the best illustration which Belt gives is that of 
 a certain gaily-coloured frog : — 
 
 " In the woods around Santo Domingo there are many frogs. 
 Some are green or brown, and imitate green or dead leaves, and 
 live amongst foliage. Others are dull earth-coloured, and hide in 
 holes and under logs. All these come out only at night to feed, and 
 they are all preyed upon by snakes and birds. In contrast to these 
 obscurely-coloured species, another little frog hops about in the 
 daytime dressed in a bright livery of red and blue. He cannot be 
 mistaken for any other, and his flaming vest and blue stockings 
 show that he does not court concealment. He is very abundant 
 in the damp wood, and I was convinced that he was uneatable 
 so soon as I had made his acquaintance, and saw the happy sense 
 of security with which he hopped about. I took a few specimens 
 home with me, and tried my fowls and ducks with them, but none 
 of them would touch them. At last, by throwing down pieces of 
 meat, for which there was a great competition amongst them, 1 
 managed to entice a young duck into snatching up one of the 
 little frogs. Instead of swallowinjj it, however, it instantly threw 
 it out of its mouth, and went alinut jerking its head, as if trying to 
 throw off some unpleasant taste.' 
 
 Admirable, also, are the illustrations given by Mr. Poulton 
 in regard to many caterpillars, such as the larva of the 
 currant or magpie moth (^Abraxas grossulariata), which is 
 conspicuous with orange and black markings on a cream 
 ground, and is refused altogether, or rejected with disgust, 
 by the hungry enemies of other caterpillars. Professor 
 Herdman and Mr. Garstang have also shown that the 
 Eolid Nudibranchs (naked sea-slugs), with brightly-coloured 
 and stinging dorsal papillae, are rarely eaten by fishes ; and 
 the same is true of some other conspicuous and unpalat- 
 able marine animals. 
 
 The general conclusion seems fairly certain that the 
 conspicuousness of many unpalatable or noxious animals is 
 imprinted on the memory of their enemies, who, after pay- 
 ing some premiums to experience, learn to leave animals 
 with "warning colours" alone. It will be interesting 
 to discover how far the bright colour, the nauseous taste, 
 the poisonous properties, the distasteful odour, sometimes 
 found associated, are physiologically related to one another, 
 but to answer these questions we are still unprepared. 
 
CHAP. IV 
 
 Shifts for a Living 
 
 57 
 
 9. Mimicry. — Mr. Poulton has carefully traced the transi- 
 t.vjn from warning to mimetic appearance, and it is evident 
 that if hungry animals have been so much impressed with 
 the frequent association of unpalatableness and conspicuous 
 colours that they do not molest certain bright and nauseous 
 forms, then there is a ch;uice that palatable forms may 
 also escape if they are sufficient y like those which are 
 passed by. The term mimicry is restricted to those cases 
 
 Fig. 9.— Hornet {Priocnemis) above, .nnd mimetic bug {Spinigcr) beneath. 
 
 (From Belt.) 
 
 " in which a group of animals in the same habitat, character- 
 ibed by a certain type of colour and pattern, are in part 
 specially protected to an eminent degree (the mimicked), and 
 in part entirely without special protection (the mimickers) ; so 
 that the latter live entirely upon the reputation of the former." 
 Tlie fact was " discovered by Bates in Tropical America 
 (1862), then by Wallace in Tropical Asia and Malaya 
 ( 1 866), and by Trimen in South Africa (1870)"; while Kirby, 
 in 18 1 5, referred to the advantage of a certain fly being 
 like a bee, and of a certain spider resembling an ant 
 
58 
 
 The Study of Animal Life 
 
 PART I 
 
 
 r 
 
 The constant conditions of mimicry are clearly and tersely 
 summed up by Wallace. They are : — 
 
 1. That the imitative species occur in the same area, 
 and occupy the very same station, as the imitated. 
 
 2. That the imitators are always the more defenceless. 
 
 }'. ^^^^ ^^^ imitators ire always less numerous in 
 individuals. 
 
 4. That the imitators differ from the bulk of their 
 allies. 
 
 Fig. la— Hunimin'-bird moth (Macroglossa titan), and humming-bird 
 (. >./>,\jmis GouUit), (From Bates.) 
 
 S. That the imitation, however minute, is external and 
 visible only, never extending to internal characters or to 
 such as do not aftect the external appearance. 
 
 Many inedible butterflies are mimicked by others quite 
 different. Many longicorn beetles exactly mimic wasps, 
 bees, or ants. The tiger- beetles are mimicked by more 
 harmless insects ; the common drone-fly {Eristalis) is like 
 a bee; spiders are sometimes ant-like. Mr. Bates relates 
 that he repeatedly shot humming-bird moths in mistake for 
 humming-birds. Among Vertebrates genuine mimicry is 
 rare, but it is well known that some harmless snakes mimic 
 
CHAP. IV 
 
 Shifts for a Living 
 
 59 
 
 lue swollen 
 
 poisonous species. Thus, the very poisonous coral-snakes 
 {Elaps), which have very characteristic markings, are 
 mimicked in din';i ;nt localities by several harmless forms. 
 Similarly in regard to birds, Mr. Wallace notices that the 
 powerful "friar-birds" {Tropidorhynckus) of Malaya are 
 mimicked by the weak and timid orioles. *' In each of the 
 great islands of the Austro-Malayan region t\ere is a dis- 
 tinct species of Tropidorhynchus, -md thpr. is al^^ays along 
 with it an oriole that exactly mimics it." 
 
 That there may be mimetic resembla uc I <. - • (_n d'£tii,«.\ 
 forms there can be no doubt, and tbt» v ii kj{ ii\^ -:».■- txw- 
 blance has been verified ; but there ?'~ -oir.r ,;m . u ;_i,d«' .rv 
 to weaken the case by citing instan.jt - ; j ,ii . t- = . liici 
 liave been insuflSciently criticised. flu.- f^ i,> ;? i ,. -dlv 
 justify us in saying that the larvae ot t'.r . .^^ lar*. tl^u.k 
 'Slolh {Chirrocatnpn) " terrify their en- r.ii . ' , r^> .ujij/o 
 tion of a cobra-like serpent ; " or that the 'ob . , nluch 
 spi'-es abrrii by the large eye-like 'specac 
 dilated h' od, offers an appropriate model foi 
 interior end of the caterpillar, with its terrifying markings." 
 
 Th°re is only on*; theory of mimicry, namely, that among 
 the min.icking animals varieties occurred which prospered 
 by bei.ig somewhat like the mimicked, and that in the 
 course of natural selection this resemblance was gradually 
 increased until it became domirant and, in many cases, 
 remarkably exact. 
 
 As to the primary factors giving rise to the variation, we 
 can only speculate. To begin with, indeed, there must 
 have been a general resemblance between the ancestors of 
 the mimicking animal and those of the mimicked, for cases 
 like the Humming-Bird and its Doppel-Ganger moth are very 
 rare. But this does not take us very far. The beginning 
 of the mimetic change is usually referred to ore of those 
 "indefinite," "fortuitous," "spontaneous" variations which 
 are believed to be common among animals. It is logically 
 possible that this may have been the case, and that there 
 was at the very beginning no relation between the variation 
 of the mimicker and the existence of the mimicked. But 
 as illustrations of mimicry accumulate — ar.d they are already 
 
 m 
 
 Mi 
 
 Hi 
 
6o 
 
 TJie Study of Animal Life 
 
 PART I 
 
 c 
 
 o 
 
 J £ 
 
 O 1. 
 
 X 'J 
 
 s ; 
 
 - I 
 
 S§i 
 
 '.--, iiiy-A r . 
 
CHAP. IV 
 
 Sh'"s for a Living 
 
 6i 
 
 very numerous — one ii tempted to ask whether there may 
 not be in many cases some explanation apart from the action 
 of natural selection upon casual changes. May not the 
 similar surroundings and habits of mimickers and mimicked 
 have sometimes something to do with their resemblance ; 
 may it not be that the presence of the n 'micked has had a 
 direct, but of course very subtle, influence on the mimickers ; 
 is it altogrether absurd to suppose that there may be an 
 element of consciousness in the resemblance between oriole 
 and friar-bird ? 
 
 10. *< Masking" is one of the most interesting ways 
 in which animals strengthen their hold on life. It is best 
 illustrated on the sea-shore, where there is no little struggle 
 for existence and much opportunity for device. There many 
 animals, such as crabs, are covered by adventitious dis- 
 guises, so that their real na«^ure is masked. Elsewhere, 
 however, the same may be seen ; the cases of the caddis- 
 worms — made of sand particles, small stones, minute shells, 
 or pieces of bark — serve at once for protection and conceal- 
 ment ; the cocoons of various caterpillars are often masked 
 by extrinsic fragments. The nests of birds are often well 
 disguised with moss and lichen. 
 
 But among marine animals masking is more frequent. 
 "Certain sea-urchins," Mr Poulton says, "cover themselves 
 so completely with pebbles, bits of rock and shell, that one 
 can see nothing but a little heap of stones ; and many marine 
 molluscs have the same habits, accumulating sand upon the 
 s'.'.rface of the shell, or allowing a dense growth of Algas to 
 cover them." 
 
 This masking is in many cases quite involuntar>'. Thus 
 the freshwater snails [LytttMcrus) may be so thickly covered 
 with Algae that they can hardly move, and some marine 
 forms are unable to favour or prevent the growth of other 
 orjjanisms upon their shells, but how far this is from be- 
 injj the whole story is well known to all who are ac([uain»'!(! 
 with our shore crabs. F"or though they also may be invol- 
 untarily masked, there is ample evi<ience that they some- 
 times disguise themselves. 
 
 The hermit-crabs are to some extent masked wiihin 
 
62 
 
 The Study of Animal Life part i 
 
 their stolen shells, especially if these be covered by I'no 
 Hydroid Hydractinia or other ortjanisms. Various other 
 crabs {Stenorhynchus^ Inachus^ Maitt, Drottiia, Pisa) arc 
 masked by the seaweeds, sponges, and zoophytes which 
 cover their carapace. Moreover, the interest of this mask- 
 ing is increased by the fact observed by Mr. Bateson at 
 Plymouth that the crabs sometimes fix the seaweeds for 
 
 Fig. la. -Sack-bearing caterpillar (.Vaff(>/Apra). (Ktani Mates.) 
 
 themselves. Mr. Hatesnn describes how the nah seizes a 
 piece of weed, tears off a piece, chews the end in his moufli. 
 and then nibs it firmly on his head and legs until it i- 
 raugh- by the turved hairs and fi.xed " Ihe whole pri 
 (ceding is most human and piirimseful. Many substance-, 
 as hydroids, spong« s I'oly/oa, and weetls of many kin<! 
 and colour?, arc thus used; but these various substaiu' 
 ate nearly always ..>minetrica!!y i>!attd on c orrt^ponduK; 
 
 M HA , 
 
CHAP. IV 
 
 Shifts for a Living 
 
 63 
 
 parts of the body, ar.d particularly long plume-like pieces 
 are fixed on the head." Thus, as Carus Sterne says, is the 
 story of " Bin am's walking wood " re-enacted on the sea- 
 shore. Furthermore, a Stenorhynchus which has been 
 cleaned will immediately begin to clothe itself again, with 
 the same care and precision as before. Mr. Robertson of 
 Millport often saw Stennrhynchus longirostris — a common 
 crab — picking about its limbs and conveying the produce 
 to its mouth. " If other observations confirm the view that 
 this animal is a true vegetarian, we shall have one example 
 at least of an independent agriculturist, who is not only 
 superior of his lands, but carries them with him when 
 he removes." I also have seen the crab doing what " tlie 
 naturalist of Cumbrae " observed. In further illustration 
 of masking we may cite Dromia vulgaris, often covered 
 with sponge ; Dromia excavata, with compound ascidians ; 
 the Amphipod Atylus, with seaweed ; while a species of 
 Dorippe is said to bear a bivalve shell, or even a leaf, as a 
 shield, and another crab cuts off the tunic of a sea-squirt 
 and hitches it on his own shoulders. 
 
 Sometimes this masking serves as a warning or deterrent ; 
 witness that hermit-crab {Pagurns cvamnsis) whose stolen 
 shell is surrounded by a bright orange sponge (Suberiles 
 domuncula). As this sponge is full of flinty needles, has a 
 strong odour and a disagreeable taste, we do not wonder 
 tint Mr. Garstang finds that fish dislike it intensely, noi 
 ran we doubt that the hennit-crab trades on the reputation of 
 its associate. In other cases the masking will aid in con- 
 icalment and favour attack. To the associations of crabs 
 and sea-anemones we shah afterwards refer. 
 
 II. OombinAtion of AdTantageoiw Qualities. — Mr 
 I'oulton describes, in illustration of the combination of 
 many methods of defence, the case of the larva of the 
 puss moth {Cerura vinula). It resembles the leaves of the 
 poplar and willow on which it lives. When disturbed it 
 assumes a terrifyinjj attitude, mimetic of a Vertebrate 
 appearance ! The effect is heightened by the protrusion of 
 two pink whips from the tenninal prongs of the body, an<l 
 tinally the (feature defemis itself hy squirting' formic acid. 
 
64 
 
 The Study of Animal Life 
 
 I'ART I 
 
 !-:i J 
 
 Yet in spite of all this power of defence, the laira often falls 
 a victim to ichneumon-flies. These manage to lay their egys 
 
 within the caterpillar, which 
 by and by succumbs to the 
 voracity of the hatched 
 ichneumon maggots. Mr. 
 I'oulton believes that the 
 puss moth larva " has been 
 saved from extennination 
 by the repeated acquisition 
 of new defensive measures. 
 But any improvement in 
 Fig. 13. -" Terrifying attitude" of the the means of defence ha^ 
 
 caterpillar of Crura vmuta (From ^^^^^ ,„et ^y j^e greater 
 Chambers s ^(•O'c/o'/. ; after Poultoii.) , ,1 
 
 mgenuity or boldness of 
 foes ; and so it has come about that many of the besl- 
 protected larv;e are often those which die in the largest 
 numbers from the attacks of enemies. The exceptional 
 standard of defence has been only reached through the 
 pressure of an exceptional need." 
 
 13. Surrender of Parts.— Among the strange life -pro- 
 serving powers which animals exhibit, we must also 
 include that of surrendering parts of the body in 'lu' 
 panic of capture or in the struggle to escape. A rat 
 will gnaw off a leg to free itself from a trap, and I ha\ r 
 heard of a stoat which did not refrain from amputatin* 
 more than one limb. But the cases to which we now refi r 
 are not deliberate amputations, but rctlex and unconsciou-^ 
 surrenders. Many lizards (such as our British " slowworm " ) 
 will readily leave their tails in their captor's grasp ; cnis- 
 tarcans, insects, and spiders part with their limbs and 
 scramljlc off maimed but safe ; starfishes, brittle-stars, and 
 feather-stars resign their arms, and the sea-cucumbers their 
 viscera. A large number of cases have been studied I'V 
 Kredericq and (liard. 
 
 Among Crustacea the habit is most perfectly developed 
 in the crabs, e.^. the common shore-rrab (('(/n///wj///(r«(/.»), 
 and in the spiny lobster {Pitlinitrus), but it is also exhibited 
 by the cra\ tish (As/uius), the common lobster (^llotnarus). 
 
CHAP. IV Shifts for a Living 5c 
 
 the shrimp (frangon\ and the prawn {Palamon). In crabs 
 and in the spiny lobster the surrender of a limb is effected 
 by the forcible contraction of the basal muscles, and the 
 line of rupture is through the second-lowest joint. FrtJde- 
 ricq's researches seem to prove conclusively that the sur- 
 render is a reflex and unconscious act, but its protective 
 value is not less great. The chances are in favour of the 
 crab escapmg, the residue of muscle prevents haemorrhage 
 from the stump, and in the course of time the lost limb is 
 replaced by a new growth. The crab does not know what 
 It IS doing, but It unconsciously illustrates that it is better 
 that one member should perish than that the whole life 
 should be lost. 
 
 Not a few insects readily surrender their legs, but these 
 are not replaced. Spiders arc captured if the legs are fixed 
 without irritating the nerves, for that is an essential con- 
 dition of the reflex amputation. In regard to lizards, also, 
 It has been shown that a reflex nervous excitement, and not 
 mere brittleness, is the condition of surrender. Here how- 
 ever, the lost tail may be replaced. Among Mollilsca a 
 surrender of parts has been recorded of Harpa veniricosa, 
 Dons cruenta, Stenopus, some species of Helix, the razor- 
 shell Solen ; while it is well known that male cuttle-fishes 
 sometimes part with one of their arms for special sexual 
 purposes. A great many « woms " break very easily, and 
 the severed parts are sometimes able to regrow the whole 
 organism. 
 
 Among the Echinoderms the tendency to disrupt is exhi- 
 bued to an extraordinary degree. Thus Professor Preyer has 
 ^liown that the seven-rayed ^l^x^^h {Asterias ienuisfiina) 
 urrenders its arms with great readiness, often giving off 
 three or four at a time. Hut each ray may reproduce an 
 entire starhsh. Professor Edward Forbes tells how a speci- 
 men of LuMa which lie had dredged, was disappearing 
 -r the side of the boat wlu.i he cau«ht it by one of its 
 ■«'n s; It surrendered the arm and escaped, giving "a wink 
 - ension " wi.b one of its eyes. Brittle-sta's (Ophiuroil) 
 >r many kinds are true to their popular name, and the 
 C rmoKis are not less disruptive. Not only are the arms 
 
66 The Study of Animal Life part i 
 
 readily given off, but these break into many fiagments. 
 There can be no doubt that this habit, combined with the 
 marvellous power of regrowth which these animals possess, 
 is of great protective value, while it is also probable in regard 
 to both Echinoderms and some worms, that the disruption 
 of parts may really increase the number of individuals. 
 
 There is no need to enumerate all the protective habits 
 and devices which animals exhibit. Some " feign " death, 
 by falling in panic into a state allied to hypnotic trance, 
 perhaps in some of the higher animals by conscious decep- 
 tion ; others roll themselves up into balls, as in forms so 
 different as myriapods and armadillos ; but, finally, I shall 
 cite from Dr. Hickson's Naturalist in North Celebes one 
 other device. '* I often saw advancing slowly over the 
 sea- ardens, in parties of from four to six, a group of 
 cutt -fish, swimming with an even backward movement, 
 the inges of their mantles and their arms trembling, 
 »»• ttei' colour gradually changing to what seemed to 
 n nost infinite variety of hues as they passed 
 jv. he rious beds of the sea -bottom. Then suddenly 
 ihe would be a commotion in what was previously a 
 cah md placid scene, the striped and speckled reef fishes 
 wo be sen darting away in all directions, and of the 
 cut ishef U that remained were four or five clouds of ink 
 in t,H clftfl Iter. They had thrown dust in the eyes of 
 some -OS* ark or voracious fish." 
 
 liu. should not like to suggest the ide.i that animals 
 are alw;» i careful and anxious, or forced to continual 
 struggle and shift. 
 
 •• They do not iweat and whine alwut their condition, 
 
 They do not lie awake in the dark and weep for their sins, 
 
 They do not make me sick discussing their duty to CJotl, 
 
 Not one is dissatisfied, not one is demented 
 
 With the mania of owning things ; 
 
 Not one kneels to another, nor to his kind that lived thous.^n(b 
 
 of years ago ; 
 Not one is respectable or unhappy over the whole earth." 
 
 Walt V.'iiitmak. 
 
CHAPTER V 
 
 SOCIAL LIFE OF ANIMALS 
 
 I. Partnerships— 2. Co-operation and Division of Labour— % Gre- 
 gartous Life and Combined Action—/^. Beai>ers—s Bees— 6 
 't"?"^; ^f':^'''"-^- Evolution of Social Life-^. Advanta^res 
 of Soaal Ltfe—io. A Note on the Social Organism — ii 
 Conditstons 
 
 The over- fed plant bears many leaves but its flowers 
 are few ; the animal which eats too much becomes fat • 
 and we know that within the living body one part may 
 K'row out of proportion to the others. It seems as if 
 organ competed with organ within the living engine, as 
 .f one tissue outgrew its neighbors in the living web, as 
 If there were some struggle for existence between the 
 individual units which form the city of cells in any of the 
 higher animals. This idea of internal competition has 
 been elaborated by a Gennan biologist, Roux, in a work 
 entitled 7-^^ Struggle of Parts within (he Organism, and 
 It IS full of suggestivencss. It can be verified from our 
 own experience ; but yet it seems strange. For we rightly 
 '»nk of an organism as a unity in which the parts are 
 Iranothef '" '""'"^' helpfulness, being members one 
 
 Now, just as a biologist would exaggerate greatly if he 
 maintained that the struggle of parts was tht most inv 
 Fitant fact about an organism, so would a naturalist if he 
 
t. 
 
 ill 
 
 i \ 
 
 I « 
 
 68 TAe Study of Animal Life pakt i 
 
 Coherence and harmony and mutual helpfulness of 
 parts— whether these be organs, tissues, or cells— are 
 certainly facts in the life of individuals ; we have now 
 to see how far the same is true of the larger life in 
 which the many are considered as one. 
 
 I. Partnersliips. —Animals often live together in strange 
 partnerships. The «« beef-eater" birds {Buphagus) perch 
 on cattle and extract grubs from the skin ; a kind of plover 
 {Pluvianus agyptius) removes leeches and other parasites 
 from the. back of the crocodile, and perhaps "picks his teeth," 
 as Herodotus alleged ; the shark is attended by the pilot-fish 
 {Naucrates ductor\ who is shielded by the shark's reputa- 
 tion, and seems to remove parasites from his skin. 
 
 Especially among marine animals, we find many almost 
 constant associations, the meaning of which is often obscure. 
 Two gasteropods Rhizochilus and Magilus grow along 
 with certain corals, some barnacles are common on whales, 
 some sponges and polypes are always found together, with- 
 out there being in any of these cases either parasitism or 
 partnership. But when we find a little fish living con- 
 tentedly inside a large sea -anemone, or the little pea-crab 
 (Pinnotheres) within the horse-mussel, the probable explana- 
 tion is that the fish and the crab are sheltered by their 
 hosts and share their food. They are not known to do 
 harm, while they derive much benefit. They illustrate one 
 kind of " commensalism," or of eating at the same table. 
 
 But the association between crabs and sea -anemones 
 
 affords a better illustration. One of the hermit-crabs of 
 
 our coast {Pagurus f»ideauxii) has its borrowed shell 
 
 always enveloped by a sea-anemone {Adamsia palliaia), 
 
 and Pagimis bernJumius may be similarly cnsheathed by 
 
 Adamsia rondeletii. Mobius describes two crabs from 
 
 Mauritius which bear a sea-anemone on each claw, and m 
 
 some other crab? a similar association occurs. It seems 
 
 that in some cases the crab deliberately chooses its ally and 
 
 plants it on its shell, and that it does not leave it behind at 
 
 the period of shell -chanKim Deprived of its polype c-Mn- 
 
 panion, one was seen to : restlessly ill at ease imtil 
 
 It obtained another of the same kind. The use of the sea- 
 
CHAP. V 
 
 Social Life of Animals 
 
 69 
 
 anemone as a mask to the crab — and also perhaps as 
 aid in attack or defence — is obvious ; on the other hand, 
 the sea-anemone is carried about by the crab and may 
 derive food from the crumbs of its bearer's repast. 
 
 Commensalism must be distinguished from parasitism, 
 in which the one orgapism feeds upon its host, though it is 
 quite possible that a commensal might degenerate into a 
 parasite. Quite distinct also is that intimate partnership 
 known as symbiosis, illustrated by the union of algoid and 
 fungoid elements to form a lichen, or by the occurrence of 
 minute Algae as constant internal associates and helpful 
 partners of Radiolarians and some Coelenterates. 
 
 2. Co-operation and Division of Labour.— The idea 
 of division of labour has been for a long time familiar to 
 men, but its biological importance was first satisfactorily 
 recognised by Milne-Edwards in 1827. 
 
 Among the Stinging-animals there are many animal 
 colonies, aggregates of individuals, with a common life. 
 These begin from a single individual and are formed by 
 prolific budding, as a hive is formed by the prolific egg- 
 laying of a queen-bee. The mode of reproduction is 
 asexual in the one case, sexual in the other ; the resulting 
 individuals are physically united in the one case, psychically 
 united in the other ; but these differences are not so great 
 as they may at first sight appear. Many masses of coral 
 are animal colonies, but among the members or " persons," 
 as they are technically called, division of labour is very raie ; 
 moreover, in the growth of coral the younger individuals 
 often smother the older. In colonial zoophytes the 
 arl)orescent mode of growth usually obviates crushing ; and 
 tliere is sometimes very marked division of labour. Thus 
 in the colony of Hydractittia polypes, which is often found 
 Kiowing on the shells tenanted by hermit-crabs, there may 
 be a hundred or more individuals all in organic connection. 
 Ihe polypes are minute tubular animals, connected at 
 their bases, and stretching out from the surface of the shell 
 into the still water of the pool in which the hermit-crab is 
 rciimif. But among the hundred individuals there are 
 three or four castes, the differences between which probably 
 
 ^SiSimX^. 
 
■ I 
 
 
 
 alii 
 
 1*. • I 
 
 70 
 
 T/t£ Study of Auimal Life 
 
 PAR r I 
 
 result from the fact that in such a large colony perfect 
 uniformity of nutritive and other conditions is impossible. 
 Individuals which are fundamentally and originally like one 
 another grow to be different, and perform different func- 
 tions according to the caste t > which they belong. 
 
 Many are nutritive in form like the little freshwater 
 Hydra— iv\m\7cc animals with an extensile body and with .1 
 terminal mouth wreathed round by mobile tentacles. On 
 
 these the whole nutrition of tlie 
 colony depends. Beside the>e 
 there are reproductive " per- 
 sons," which cannot feed, 
 being mouthless, but secure 
 the continuance of the species 
 and give rise to embryos which 
 start new colonies. Then there 
 are Ion,;, lank, sensitive mem- 
 bers, also mouthless, which 
 serve as the sense-organs of tlic 
 colony, and are of use in tlc- 
 tccting food or danger. Wht 11 
 danger threatens, the polypo 
 cower down, and there are IcU 
 projecting small hard spines, 
 which some regard as a fourtli 
 
 Fig. t4. -Colony of lfy.i,act!,.;<x class of individuals— star\c(l, 
 tchinata. a, luitritivo iiniividiiais ; abortive members like the 
 
 h, reproductive individiinl> ; c> ^, .^i i »i i _ i 
 
 abortive spines; and there are thoms On the hawthom hed^e. 
 
 .ilso louK mouthlps individii.-ils j^ rccognising their utility to 
 
 specialised m sensitiveness. (From ° ° ' 
 
 charnVjers's h'.ncyciop. ; .iftcr All- the colony as a whole we can 
 '"'"'>• hardly overlook the fact that 
 
 their life as individuals is prarticaliy nil. 
 
 trate the dark side of division of labour. 
 
 They well illus- 
 
 i! ■ I 
 
 Ilcriwrt .^pcnrer .nnd Krnst Ilacckel Imve cxiilnincl voiy rlc.TiIy 
 one l.tw of jir )j^rcss aiiionif those animals \v)iich form colonics. 
 'I'lio crmlo form nf a colciy is an ai,'::,'rij;aU of siniilat inilivi(hi.il^, 
 the perfected colony is an intcip-aie in wliich by division of lalimir 
 greater harmony of life li > resulted, and in which the whole colony 
 is more thoroughly compacted into a unity. Among the Stinging- 
 
 :i, 
 
CHAP. V Social Life of Animals 71 
 
 animals, we find some precise illustrations of such integrated colonies, 
 especially in the Siphonophora of which the Portuguese Man-of-War 
 i/'kysalia) is a good example. There is no doubt that these 
 beautiful organisms are colonies of individuals, which in structure 
 are all referable to a " medusoid " or jellyfish-like type. But the 
 division of labour is so harmonious, and the compacting or 
 oi^nisation of the colony is so thorough, that the whole moves and 
 lives as a single organism. 
 
 E. Perrier in his work entitled Les Colonies Animales (Paris, 
 1882), shows how organic association may lead from one grade of 
 organisation and individuality to another, and explains very clearly 
 how sedentary and passive life tends to develop mere aggregates, 
 while free and active life tends to integrate the colony. With this 
 may be compared A. Lang's interesting study on the influence of 
 sedentary life and its connection with asexual reproduction — Das 
 Einfluss des Festsitten (Jena, 1889). Haeckel, in his GmtrelU 
 MorpkologU (a vols,, Berlin, 1866), was one of the first to shed a 
 strong clear light on the difficult subject of organic individuality, 
 its grades and its progressive complexity. To Spencer, Principles 
 of Biology (2 vols., London, 1863-67), we owe in this connection 
 the elucidation of the transition from aggregates to integrates, and 
 of the lines of differentiation, i.e. the progressive complication of 
 structure which is associated with division of lalwur. 
 
 3- Gregarious Life and Combined Action.— Most 
 mammals are in some degree gregarious. The solitary 
 kinds are in a distinct minority. The isolated are ex- 
 posed to attack, the associated are saved by the wisdom 
 of their wisest members and by that strength which union 
 gives. Many hoofed animals, such as deer, antelopes, 
 goats, and elephants, live in herds, which are not mere 
 crowds, but organised bands, with definite conventions and 
 with a power of combined resistance which often enables 
 them to withstand the attacks of carnivores. Marmots and 
 prairie-dogs, whose " cities " may cover vast areas, live peace- 
 ful and prosperous lives. Monkeys furnish many illustra- 
 tions of successful gregarious life. As individuals most of 
 them are comparatively defenceless, and usually avoid com- 
 ing to close quarters with their adversaries ; yet in a body 
 tliey are formidable, and often help one another out of 
 scrapes. Brehm tells how he encountered a troop of baboons 
 which defied his dogs and retreated in good order up the 
 
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72 
 
 The Study of Animal Life 
 
 PART I 
 
 heights. A young one about six months old being left 
 behind called loudly for aid. *' One of the largest males, 
 a true hero, came down 3:sain from the mountain, slowly 
 went to the young one, co.xed him, and triumphantly led 
 him away — the dogs being too much astonished to make an 
 attack." 
 
 Fig. 15. — Chimpanzee (. ! hropopUhc. us or Troglodytts calvui). 
 (I .uiuDuChaillu.) 
 
 Many birds, such as rooks and swallows, nest together, 
 and the sociality is citen advantageous. Kropotkine cites 
 from Dr. Coucs an observation in regard to some little clirt"- 
 svvallows which nested in .1 colony quite near the home of a 
 prairie-falcon. "The little peaceful birds had no fear of 
 their rapacious neighbour ; they did not let it even approach 
 to their colony. They immediately surrounded it an<l 
 
■^Mwm 
 
 ) ' J a « y . t 
 
 CHAP. V 
 
 Social Life of Animals 
 
 73 
 
 chased it, so that it had to make oflF at once." Of the 
 cranes, Kropotkine notes that they are extremely "sociable 
 and hve m fnendly relations, not only with their congeners 
 but also with most aquatic birds." They post sentries, send 
 scouts, have many friends and few enemies, and are very 
 intelligent. So is it also with panots. «' The members of 
 each band remam faithfully attached to each other, and they 
 share m common good or bad luck." They feed together 
 fly together, rest together ; they send scouts and post sen- 
 tinels ; they find protection and pleasure in combination. 
 Like the cranes, they are very intelligent, and safe from 
 most enemies except man. 
 
 On the other hand, some of the most successful carni- 
 vores, e.g. wolves, hunt in packs, and not a few birds of 
 prey (some eagles, kites, vultures) unite to destroy their 
 quarry. Combination for defence has its counterpart in 
 combination for attack. In both cases the collective action 
 IS often associated with the custom of posting sentinels, who 
 warn the rest, or of sending scouts to reconnoitre. Pecu- 
 liarly mteresting are those cases in which the relatively 
 weak unite to attack the strong ; thus a few kites will rob an 
 eagle and wagtails will persecute a sparrow-hawk. Kropot- 
 kine has noticed how the aquatic birds which crowd on the 
 shores of lakes and seas often combine to drive off intrud- 
 ing birds of prey. « In the face of an exuberant life, the 
 Ideally armed robber has to be satisfied with the off-fall of 
 that life. 
 
 Among many animals there is co-operation in labour, as 
 well as combination for attack or defence. Brehm relates that 
 baboons and other monkeys act in thorough concert in 
 plundering expeditions, sending scouts, posting sentinels, and 
 even forming a long chain for the transport of the spoil. It 
 IS said that several Hamadryad baboons will unite to turn 
 over a large stone, sharing the booty found underneath. 
 When the Brazilian kite has seized a prey too large for it 
 to carry ,t summons its friends; and Kropotkine cites a re- 
 markable case in which an eagle called others to the car- 
 Lin'' I u'''.''^"%^'!' ^°^^'''^'" '" «^«t companies, forming a 
 wide half-circle facing the shore and catching the fish thus 
 
 k% 
 
 
 ! f i 
 
 S ■ .. 'A 
 
 
74 
 
 The Study of Animal Life 
 
 PART 1 
 
 If!!-. 
 
 enclosed. Burial beetles unite to buty the dead mouse or 
 bird in which the eggs are laid, and the dung-beetles help 
 one another in rolling balls of food. But of all cases of 
 combined activity the migration of birds is at once the most 
 familiir and the most beautiful — the gathering together, the 
 excitement before starting, the trial flights, the reliance 
 placed in the leaders. Migration is usually social, and 
 is sustained by tradition. 
 
 4. Beavers. — That the highly -socialised beavers have 
 been extenninated in many countries where they once 
 abounded is no argument against their sociaUty, for man 
 has ingenuity enough to baffle any organisation. A family 
 of about si . members inhabits one house, and in suitable 
 localities — secluded and rich in trees — many families con- 
 gregate in a village community. The young leave the par- 
 ental roof in the summer of their third year, finu mates for 
 themselves, and establish new homesteads. The community 
 becomes overcrowded, however, and migrations take place 
 up and down stream, the old lodges being sometimes left to 
 the young couples. It is said, moreover, ihat lazy or other- 
 wise objectionable members may be expelled from the society, 
 and condemned to live alone. Under constraint of fear or 
 human interference, and away from social impulse, beavers 
 may relapse into lazy and careless habits, and in many 
 cases each family lives its life apart; but in propitious 
 conditions their achievements are marvellous. Th*; burrow 
 may rise into a constructed home, and the members of 
 many families may combine in wood-cutting and log-rolling, 
 and yet more markedly in constructing dams and digging 
 canals. Make allowances for the exaggeration of enthusiastic 
 observers, but lead Mr. Lewis Morgan's stories of the evolu- 
 tion of a broken burrow into a comfortable lodge, varying 
 according to the local conditions ; of the adaptation of the 
 dams against the rush of floods ; of canals hundreds of feet 
 in length — labours without reward until they are finished ; 
 of the short-cut waterways across loops of the river ; an \ cf 
 " locks " where continuous canals are, from the nature of the 
 ground, impossible. The Indians have invested beavers 
 with immortality, but it is enough for us to recognise that 
 
CHAP. V 
 
 Social Life of Animals 
 
 75 
 
 they exhibit more sagacity than can be explained by heredi- 
 tary habit, for they often adapt their actions to novel condi- 
 tions in a manner which must be described as intelligent. 
 Especially when we remember that the beaver belongs to a 
 somewhat stupid rodent race, are we inclined to believe that 
 it is the cleverest of its kind because the most socialised. 
 
 5. Bees.— Many centuries have passed since men first 
 listened to the humming of the honey-bees, and found in the 
 hive a symbol of the strength of unity. From Aristotle's 
 time till now naturalists have 
 been studying the life of bees, 
 without exhausting either its 
 facts or its suggestions. The 
 society is very large and 
 complex, yet very stable and 
 successful. Its customs seem 
 now like those of children at 
 play, and now like the real- 
 ised dreams of social refor- 
 mers. The whole life gives 
 one the impression of an old- 
 established business in which 
 all contingencies have been 
 so often experienced that 
 they have ceased to cause 
 hesitation or friction. There 
 is indeed much mortality, 
 some apparent cruelty, and 
 the constantly recurring ad- 
 venture of migration ; but though hive may war against 
 hive, inter-civic competition has virtually ceased, and the 
 life proceeds smoothly with the hannony and effectiveness 
 of a perfected organisation. 
 
 The mother-bee, whom wc call a " queen " — though she 
 is without the wits and energy of a ruler — is to this extent 
 lic.ul of the community, that, by her prolific egg-laying, she 
 increases or restores the population. \'ery sluggish in 
 tlieir ordinary life are the numerous males or ♦• drones,' 
 one of whom, fleet and vigorous beyond his fellows, w ill pair 
 
 G. 16. — Honey-bee {A fits mellifica). 
 A,_ queen ; 1!, drone ; C, worker. 
 (From Chambers's Khij\/o/>.) 
 
 » 1 
 
 m 
 IP 
 
 ^m 
 
 
76 
 
 The Study of Animal Life 
 
 PART I 
 
 with a queen in her nuptial flight, himself to die soon after, 
 saved at least fiom the expulsion and massacre which await 
 all the sex when the supplies of honey run short in autumn. 
 The queen and drones are important only so far as multiplica- 
 tion is concerned. The sustained life of the hive is wholly in 
 the hands of the workers, who in brains, in activity, and 
 general equipment are greatly superior to their " queen." 
 " The queen has lost her domestic arts, which the worker pos- 
 sesses in a perfection never attained by the ancestral types ; 
 while the worker has lost her maternal functions, although 
 she still possesses the needed organs in a rudimentary state." 
 What a busy life is theirs, gathering nectar and pollen 
 unwearyingly, while the sunshine lasts, neatly slippinj into 
 the secrets of the flowers or stealing their treasures by 
 force, carrying their booty home in swift sweeping flight, 
 often over long distances unerringly, unloading the pollen 
 from their hind-legs and packing it into some cells of the 
 comb, emptying out the nectar from their crop or honey- 
 sac into store-cells, and then off again for more — s.ich is 
 their socialised mania for getting. But, besides these 
 •' foragers " — for the most part seniors — there are younger 
 stay-at-home " nurses," whose labours, if less energetic, are 
 not less essential. For it is their part to look after the 
 grubs in their cradles, to feed them at first with a " pap " of 
 digested nectar, and then to wean them to a diet of honey, 
 pollen, and water ; to attend the queen, guiding her move- 
 ments and feeding her while she lays many eggs, sometimes 
 2000 to 3000 eggs in a day. Mr. Cheshire, in his incom- 
 parably careful book on Bees and Beekeeping^ laughs at the 
 "many writers who have given the echo to a mediaeval 
 fancy by stating that the queen is ever surrounded by a 
 circle of dutiful subjects, reverently watching her move- 
 ments, and liable to instant banishment upon any neglect 
 of duty. These it was once the fashion to compare to the 
 twelve Apostles, and, to make the ridiculous suggestion 
 complete, their number was said to be invariably twelve ! ' 
 But Mr. Cheshire's own account of the nurses' work, and of 
 the whole life of the hive, is more marvellous than any 
 mediaeval fancy. 
 
 hi 
 
CHAP. V 
 
 Social Life of Animals 
 
 77 
 
 We have not outlined nearly all the labours of the 
 workers. There is the exhausting though passive labour of 
 forming the wax which oozes out on the under-surface of the 
 body, and then there is the marvellous comb-building, at 
 which the bees are very neat and clever workers, though they 
 do not deserve the reputation for mathematical insight once 
 granted them. "Their combs," Mr. Cheshire says, "are 
 rows of rooms unsurpassably suitable for feeding and nurtur- 
 ing the larvae, for giving safety and seclusion during the 
 mystic sleep of pupa-hood, for ensconcing the weary worker 
 seeking rest, and for safely warehousing the provisions ever 
 needed by the numerous family and by all during the 
 winter's siege. Corridors run between, giving sufficient 
 space for the more extensive quarters of the prospective 
 mother, and affording every facility to the busy throng 
 walking on the ladders the edges of their apartments supply ; 
 while the exactions of modern hygiene are fully met by air, 
 in its native purity, sweeping past the doorway of every 
 inhabitant of the insect city." 
 
 We shall not seek to penetrate into the more hidden 
 mysteries of the life of bees ; for instance, " how the drones 
 have a mother but no father," or how high feeding makes 
 the difference between a queen and a worker. An outline 
 of the yearly life is more appropriate. From the v/inter's 
 rest the surviving bees reawaken when the early-flowering 
 trees begin to blossom ; the workers engage in a *' spring 
 cleaning," and the queen restores the reduced population 
 by egg-laying. New supplies of food are brought in, new 
 bees are bom, and in early summer we see the busy life in 
 all its energy. The pressure of increased population makes 
 itself felt, and migration or " swarming " becomes impera- 
 tive. In due time and in fair weather " the old mother 
 departs with the superabundance of the population." 
 Meanwhile in the parent-hive drones have been born, and 
 several possible queens await liberation. The first to be 
 set free has to hold her own against newcomers, or it may be 
 to die before one of them. The successful new queen soon 
 becomes restless, issues forth in swift nuptial flight, is 
 fertilised by a drone, and returns to her home to begin 
 
 li 
 
 * 
 
 
78 
 
 The Study of AninuU Life 
 
 PART 1 
 
 prolific egg-laying, and perhaps after a time to lead off 
 another swarm. During the busy summer, when food is 
 abundant, the lazy males are tolerated ; but when their 
 function is fulfilled, and when the supplies become scarce, 
 they are ruthlessly put to death. " No sooner does income 
 fall below expenditure, than their nursing sisters turn 
 their executioners, usually by dragging them from the hive, 
 biting at the insertion of the wing. The drones, strong for 
 their especial work, are, after all, as tender as they are 
 defenceless, and but little exposure and abstinence is 
 required to terminate their being. So thorough is the war 
 of extermination, that no age is spared ; even drone eggs 
 are devoured, the larvae have their juices sucked and their 
 ' remains ' carried out — a fate in which the chrysalids are 
 made to take part, the maxim for the moment being, He 
 that will not work, neither shall he eat." This Lycurgan 
 tragedy over, the equilibrium of the hive is more secure, 
 and the winter comes. 
 
 The social life of hive-bees is of peculiar interest, 
 because it represents the climax of a series of stages. 
 Hermann Miiller has traced the plausible history of the 
 honey-bee from an insect like the sand -wasp, and has 
 shown in other kinds of bees the various steps by which 
 the pollen-gathering and nectar-collecting organs have been 
 developed. The habits of life gradually lead up to the 
 consummately social life of the hive. Thus Prosopis, which 
 lays its eggs in the pith of bramble-stems ; the wood-boring 
 Xylophaga ; and the leaf-cutting Megachile, which lines its 
 burrows with circles ct' om rose leaves, are solitary bees. 
 The various species of humble- or bumble-bee {Bombus), so 
 familiarly industrious ^rom the spring, when the willows 
 bear their catkins, till the autumn chill benumbs, are half 
 way to the hive-bees ; for they live in societies of mother, 
 drones, and workers during summer, while the sole surviv- 
 ing queens hibernate in solitude. From the humble-bee, 
 moreover, we gain this hint, thr.t the home is centred in 
 the cradle, for it is in a nest with honey and pollen stored 
 around the eggs that the hive seems to have begun. 
 
 6. Ants.— Even more suggestive of our own social organ- 
 
'*Me 
 
 CHAP. V Socta/ Li^e ^f Animals 
 
 79 
 
 isation is the LUiputian wor\,d of the ants, who, like micro- 
 scopic men, build bams and h^y ^p stores, divide their labour 
 and indulge m play, wage warig and make slaves. Like the 
 bee-hive, the ant-nest includes , three kinds of individuals- 
 a queen mother or more than c.^e, a number of short-lived 
 males, and a crowd of workers. ^ The queen is again pre- 
 eminently maternal, and if we , can trust the enthusiastic 
 observers, she is attended with k^y^i devotion, not without 
 some judicious control. Farren white describes how the 
 workers attend the queen m her. pe^mbulations : -They 
 formed round her when she rested ; s-^^e showed their regard 
 for her by gently waking over her, ot^^ers by patiently watch- 
 mg by her and cherishing her wito^ their antenL, and 
 in every way endeavouring to testifyl to their affectionate 
 attachment and generous submission « Qould ventures 
 further, alleging that «'m whatever \ apartment a queen 
 condescends to be present, she commands obedience and 
 respect, and a universal gladness spreacjs itself through the 
 who e cell, which is expressed by partici ,iar acts of joy and 
 exultation. They have a peculiar way ok cWinnmo- iAo«;«,r 
 and standing up on their Ld legs, a'nd ,;SwXhe 
 others. These frolics they make use of ^"oth'o^congratu- 
 late each other when they meet, and to shuw their rLard 
 for the queen." These are wonderful hG of assumed 
 emotions 1 Should an indispensable queei,, Up dp«:;rn„« f« 
 quit the nest, the workers do not hesitatt'! t ^3 l^d tn 
 keep her by force, and to tear off her wingCg to secure her 
 stay. It is certain at least that as the queens settle down 
 to the labour of maternity, their wings are lo^t—Derhans in 
 obedience to some physiological necessity. FLom th*» mnrh 
 greater number of the wingless workers, we zxL ^JtI fnm?t 
 that the males and mothers of the social ant^ are win/ed 
 insects ; but this fact becomes impressive if in > «„„ „nmm.r 
 weather we are fortunate enough to see therm alesTnd 
 young queens leaving the nest in the nuptial flight during 
 which fertilisation take place. Rising in th? 'j^ Xv 
 glitter like sparks, pale into curling smoke, an^ vanish 
 "Sometimes the swarms of a whole district hav.» y.' 
 noticed to unite their countless myriads, and, seen at' a dis- 
 
 if 
 
 
 if-. 
 
8o 
 
 The Study of Animal Life 
 
 I'AKT I 
 
 Si 
 
 ^\Vi. 
 
 tance, produce an effect resei^tibling the flashing of the 
 Aurora BoreaHs ; sometimes the effect is that of rainbow- 
 hues in the spray of laughing waterfalls ; sometimes that of 
 fire ; sometimes that of a smoke- wreath." *' Each column 
 looks like a kind of slender metwork, and has a tremulous 
 undulating motion. The poise emitted by myriads and 
 myriads of these creatures does not exceed the hum of 
 a single wasp. The sliightest zephyr disperses them."' 
 After this midsummer d^y's delight of love, death awaits 
 many, and sometimes mo/st. The males are at best short- 
 lived, but the surviving /queens, settling down, may begin 
 
 ^--^!^ 
 
 FiG. 17.— Sauba aiyts at work ; to the left below, an ordinary worker ; to the 
 right a large-headyd worker ; above, a subterranean worker. (From Hates.) 
 
 to form nests, jgathering a troop of workers, or sometimes 
 proceeding alojne to found a colony. 
 
 A caste o.f workers {i.e. normally non -reproductive 
 females) disti/nct from the males and queens, involves, nf 
 course, some J division of labour ; but there is more tliau 
 this. Worke/rs of different ages perform different tasks — 
 foraging or /lousekeeping, fighting or nursing, as the case 
 may be ; amd just as the various human occupations lea\ e 
 marks botln for good and ill in those who follow them, so 
 the divisybn of labour among ants is associated with differ- 
 ences ofif structure. Thus, in the Saiiba or Umbrella Ant of 
 ^rdizW JyCEcodof/ia ccpJialotcs\ so well described by Bates in 
 
 / 
 
 / 
 
CHAP. V 
 
 Social Lt/e of Aninuds 
 
 8i 
 
 \ix% Naturalist on the Amazons, there are three classes of 
 workers. All the destructive labour of cutting sixpence-like 
 disks froin the leaves of trees is done by individuals with 
 smal heads, while others wiifh enormously large heads 
 simply walk about looking on. These «« worker-majors " 
 are not soldiers, nor is there \any need for supervising 
 office.3. "I think," Bates say^/.<they serve, bsomf 
 sort, as passive instruments of < protection to the real 
 workers. Their enormously large, .hard, and indestructible 
 heads may be of use in protecting them against the 
 attacks of insectivorous animals. T>hey would be, on this 
 vievv, a kind ofpzkes de resistance, sf^rving as a foil against 
 onslaughts made on the main body of workers." The 
 third order of workers includes very .strange fellows, with 
 he same kind of head as the worker-majors have, but "the 
 ront IS clothed with hairs instead of b-eing polished, and 
 hey have in the middle of the forehead a^win simple 
 
 n' ; /.T^ °^ '^^ ^^^"'■^ P°^^^^s«- Among the 
 honey ants {Myrmecocystus mexicanus) .described by Dr 
 M'Cook from the "Garden of the Gods "tin Colorado, the 
 division of labour is almost like a joke*. The woiers 
 
 fn!r-??u^^" ^'T '''^^'" ^^"^' and discharge their 
 spoils mto the mouths of some of their stay-at-home fellows 
 These passive " honey-pots " store it up, till' the abdomen 
 becomes tense and round like a grape, but e^ventuaUy they 
 have even more tantalisingly to disgorge it foV other mem- 
 
 exhibited, as Forel has shown, by many sp^^cies of ants. 
 The hungry apply to the full for food, anld get it. A 
 reiusal is said to be sometimes punished by de;ath » 
 
 Marvellous in peace, the ants may also ^practise the 
 anti-social "art of war," sometimes against i^other com! 
 ™rbl^>TrP"'"' --times lith other kind" 
 and^^. H . ''^^'^y '^y^' "^^^^ ^"'^^ b^^" c-^lebrated; 
 fmnn ^^l °^.*^'"'' ^' '^ '* ^^'^ ^" event o{f the firs 
 mportance, has been formally recorded." ^neas x Sylvius 
 
 S TJS X^"^ circumstantial account of one contested 
 the tn^I obstinacy between a great and small species on 
 the tnmk of a pear tree, gravely states, "This actioA was 
 
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 83 TAe Study of /animal Life part i 
 
 fought in the pontificate of Eufenius IV., in the presence of 
 Nicholas Pistoriensis, an eminent lawyer, who related the 
 whole history of the battle w«th the greatest fidelity." In 
 the fray the combatants are thoroughly absorbed, yet at a 
 little distance other worker's are uninterruptedly Heading 
 their daily paths ; the mel^;e is intense, yet every ant seems 
 to know those of its own j/party ; the result of it all is often 
 nothing. We laugh at tK>e ants— the laugh comes back on 
 ourselves. / 
 
 In some cases an ex/pedition has the definite end of slave- 
 making, as is known ,^^0 be true of Formica sanguinea—s. 
 British species, and oi j°olyergus rufescens, found on the Con- 
 tinent. The former c/aptures the larvae of Formica fusca, 
 carries them home, /and owns them henceforth as well- 
 treated slaves ; whjfie the Amazon Ant {Polyergus) draws 
 its supply from t >oth F. fusca and F. cunicularia, and 
 seems to have be come almost dependent on its captives. 
 Indeed, Huber sa ys that he never knew the Amazons take 
 nourishment but / from the mouth of the negro captives ; 
 while Lubbock riotes that every transition exists between 
 bold and active b/)aron-like marauders and enervated masters, 
 who are virtuallly helpless parasites upon their slaves— a 
 suggestive illusjtration of laziness outwitting itself. 
 
 Slaves som-'ewhat painfully suggest domesticated animals, 
 and these ar e also to be found among ants. For what 
 Linnjeus said long ago, that the ants went up trees to " milk 
 their cows, th e Aphides," is true. The ants tickle these little 
 plant-lice wit' h their antennae, and lick the juice \vhich oozes 
 from them ; 'nay more, according to some, they inclose and 
 tend these , -milch kine, and even breed them at home. 
 Seed-harves 'ting and the like may be fairly called agricul- 
 tural, and d' o not the leaf-cutters grow mushrooms, or at 
 least feed 'on the fungi which 2^iow on the leaves, stored 
 some say '" with that end in view ? The driver ants, 
 "whose "dread is upon every living thing," when they 
 are on 'the stampede, remind us of the ancient troops 
 of non:Aad hunters, though some of them are blind. Thus 
 there/ are hunting, agricultural, and pastoral ants — three 
 type/vs, as Lubbock remarks, offering a strange analogy 
 
 / 
 
CHAF. V Social Life of Animais 
 
 H 
 
 to^the three great phases in the history of human develop- 
 Very quaint is another habit of thi. "little people, so 
 
 hZt" T-r'' ^^"' °?''P^"^ °^ ^°^^^^^'^^ guests in'the 
 home These are mostly little beetles, and have been 
 carefiilly studied by Dr. Weismann, who distinguishes trSe 
 guests {Atemeles, Lomechusa, Claviger) which are caredTor 
 and fed by the ants, from others {Dinarda, H^^terius 
 Form^oxenu^ wh.ch are tolerated, though not Ireated whh 
 special fnendlmess, and which feed on dead ants or vege 
 table debris ; while a third set are tolerated-like mice in 
 our houses-only because they cannot be readily tumTout 
 
 Z^l^ ^'""'f ^T'''' '^^ ''^'' ^"°^" '^ ^^^'«^^-^, a lively 
 an mal, constantly moving its feelers, and experimenting 
 with everything. If one be attacked by a hostile ant k 
 
 ut i/^htis?","' '-^ ^"^^^°"'^^ '^y -^--'y --S e 
 but If this IS hopeless it emits a strong odour, which seems 
 
 to narcotise the ant. These little^ familiarr are reX 
 
 dependent upon their hosts, who feed them and get 
 
 caresses in return. It is easy to understand the presence 
 
 are pets, taken away by the owners when there is a flitting 
 
 relations, since they can be shifted from one nest to 
 another, or even from spe-.ies to species. It seems hkev 
 ;rfre mo-^^"!? ^TT^ '""I ''^'^ semi-d;rsuS 
 
 I cannot Img.-r longer over the interestin? character 
 
 tu^e r^h'""'" V"""'" ''"' '" '^'^ of'theirS: 
 lecture, oi their roads, tunnels, bridges and rnv^r^H 
 
 r:Lh,ed''ofT-'°' "■' r??' -" --'^« -" f° 
 
 me aisabled, of their proverbial industry, and vet of th.ir 
 
 * tf r itr\°eTan'?z"ci';i:rj;^ trr r 
 
 C^tht? *^"^ ''^ "^'^ n.mi„n're"de«sf oraZ; 
 
 3i 
 
 > m 
 
84 The Study of Animal Life part i 
 
 about their power of recognising their fellow-citizens (even 
 when intoxicated), and of communicating definite impres- 
 sions to one another by a subtle language of touch and 
 gesture ; or about their instincts and intelligence, and the 
 limitations of these. But it will be better to read some of 
 the detailed observations, endeavouring, though necessarily 
 with slight success, to think into the nature of ants, — their 
 pertinacity, their indomitable "pluck," their tireless in- 
 dustry, their organic sociality. Surely all will agree with 
 Sir John Lubbock, to whose patient observations we ewe 
 so much, that, "when we see an ant-hill, tenanted by- 
 thousands of industrious inhabitants, excavating chambers, 
 forming tunnels, making roads, guarding their home, 
 gathering food, feeding the young, tending their domestic 
 animals, each one fulfilling its duties industriously and 
 without confusion, it is difficult altogether to deny them the 
 gift of reason," or, perhaps more accurately, intelligence, 
 for we cannot rscape the conviction •* that their mental 
 powers differ hum those of men not so much in kind as 
 in degree." 
 
 Kropotkine says that the work of ants is performed 
 "according to the principles of voluntary mutual aid." 
 " Mutual aid within the community, self-devotion grown into 
 a habit, and very often self-sacrifice for the common wel- 
 fare, are the rule." The marvels of their history are " the 
 natural outcome of the mutual aid which they practise at 
 every stage of their busy and laborious lives." To this 
 mode of life is also due " the immense development of indi- 
 vidual initiative." Ants are not well protected, but *' their 
 force is in mutual support and mutual confidence." " And 
 if the ant stands at the very top of the whole class of In- 
 sects for its intellectual capacities; if its courage is only 
 equalled by the most courageous Vertebrates, and if its 
 brain~to use Darwin's words— * is one of the most mar- 
 vellous atoms of matter in the world, perhaps more so tlian 
 the brain of man,' is it not due to the fact that mutual aid 
 has entirely taken the place of mutual struggle in the com- 
 munities of ants ? " 
 
 7. Ttrmites. — The true ants are so supremely interest- 
 
 iilit 
 
 ik^ 
 
CHAP. ▼ Social Life of Animals 85 
 
 ing, that the Termites or « white ants " (which are not ants at 
 all) are apt to receive scant justice. Perhaps inferior in intel- 
 ligence, they have the precedence of greater antiquity and 
 all the interest which attaches to an old-established society 
 Nor IS their importance less either to practical men or to 
 speculative biologists. In 1781 Smeathman gave some 
 account of their economy, noting that there were in everv 
 spec.es three castes, "first, the working insects, which, for 
 brevity, I shall generally call labourers-, next, the fighting 
 m^sox soldters, which do no kind of labour ; and, last of 
 all, the wmged ones, or perfect insects, which are male and 
 female, and capable of propagation " 
 
 The "workers," blind and wingless, and smallest in the 
 ant-hill, do all the work of foraging and mining, attending 
 the royal pair and nursing the young. The soldiers, also 
 blind and wingless, are much larger than the workers, but 
 diere are relatively only a few in each hill. « They stand " 
 Prof Drummond says, "or promenade about as sentries, it 
 the mouths of the tunnels. When danger threatens, in the 
 shape of true ants, the soldier termite advances to the fight " 
 With a few sweeps of its scythe-like jaws it clears the 
 
 thai 'work'"' A?/ ""^^^-j?- ^^ '^e fray, quietly Continue 
 
 vhnL 7 / "'"^', '" '^^ ^"^■^•"' ^'^"^ "P i" a chamber 
 whose door admits workers but is much too small for the 
 
 enants to pass out if they would, a fortunate investigator 
 
 ome times finds the royal pair. The male is sometimes 
 
 though by no means extraordinary. The queen-mother 
 
 oTxTcits' ;7 T"^^°^^^"•^"^• ''^•^ -easur's two 
 to SIX inches while the worker is only about a fifth of an 
 
 witr iS • ^"^^ \'' T'^ '''' ''''' '-^"^ ^^^ -- '-" 
 
 Drt of it K% ' ^'^"^ ^^''^ ^'■"PP^^ ^fl^- The hind 
 
 ^iLi ^ K^^ 's enormously distended with eggs, and 
 
 the head bears about the same proportion to the rest of 
 
 m n.5^ V. • ^" ^^' P^''''''^>' ^"'J " phenomenal cor- 
 
 -^'' h ' ' V T 1 ''''^'''''' -^-'^'*-^"»* of femaleness 
 a Iari,e. cylindrical package, in shape like a sausage, 
 
 j 1 1 J. 
 
 Wk 
 
 \ ' 
 
 iVj 
 
 
 M 
 
 
 Ml 
 
 ''1911 
 
86 
 
 The Study of Animal Life 
 
 PART I 
 
 and as white as a bolster." But have some admiration for 
 her: she sometimes lays 60 eggs per minute, or 80,000 
 in a day, and continues reproducing for months. As she 
 lays, she is assiduously fed by the nursing-workers, while the 
 eggs are carried off to be hatched in the nurseries. At the 
 breeding season, numerous winged males and females leave 
 
 Fig. 18.— Diagrammalic section of a termite's iie»t (after Houssay). In tin- walls 
 there are winiliiig passajjes (/) ; uppermost is a well-aired empty aliii' (D) 
 the next story (C) is a nursery where the young termites are hatclicil mi 
 shelves (r») and (*) ; the next is a hall (H) snpporte<l by pillars ; Ix-neaili iliis 
 is a royal chamber (>) in which the kinjj and queen are imprisoned ; aniuiul 
 this the chambers of workcr-tcrniites (v) and some store chambers (/'.); 
 excavated in the grnuiul arc holes (i) out of which the materi.d umcI in 
 making the termitary was dug. 'J'he whole structure is sometimes lu-is 
 feet in height. 
 
 the hill and its workers in swarms, most of them simply 10 
 die, others to mats with individuals from another hill and 
 to begin to form new colonics. 
 
 The plot of the story becomes more intricate, however, 
 when we notice Fritz Miiller's observations, that " besides 
 
CHAP. V 
 
 Social Life of Animals 
 
 87 
 
 the winged males and females which are produced in vast 
 numbers, and which, leaving the termitary in large swarms, 
 may intercross with those produced in other communities, 
 there are (in some if not all of the species) wingless 
 males and females which never leave the termitary where 
 they are born, and which replace the winged males or 
 females whenever a community does not find, in due time, a 
 true king or queen." There is no doubt as to the existence 
 of both winged and wingless royal pairs. According to 
 Grassi, the former fly away in spring, the others ascend the 
 throne in summer. The complementary kings or viceroys 
 die before winter ; their mates live on, widowed but still 
 maternal, till at least the next summer. 
 
 This replacement of royalty reminds us that hive bees, 
 bereft 0/ their queen, will rear one from the indifferent grub, 
 but the termites with which we are best acquainted seem 
 almost always to have a reserve of reproductive members. 
 This other difference between termites and ants or bees 
 should be noticed, that in the latter the "workers" are 
 highly-developed, though sterile females, while in the former 
 the workers seem to be arrested forms of both sexes. They 
 are children which do not grow up. 
 
 8. Evolution of Social Life.— To Professor Alfred 
 Espinas both naturalists and sociologists are greatly in 
 debted for his careful discussion of the social life of animals. 
 It may be useful, therefore, to give an outline of the mode 
 of treatment followed in his work — Des Sodith Animates : 
 Etude de Psychologic Compart'e (Paris, 1877) : 
 
 Co-operation, which is an essential characteristic of all society, 
 implies some degree of organic afT.nity. There are, indeed,' 
 occasional associations between unrelated forms—" mutualism," in 
 which both associates are benefited; "commensalism," in which 
 »he benefit is mainly one-sided ; parasitism, which is distinctly 
 anti-social, deteriorating the host and also the rank of the tempor- 
 arily benefited parasite. Of normal societies whose members are 
 mutually dependent, two kinds may be distinguished— (a) the 
 organically connected colonies of animals, in which there is a 
 common nutritive life ; {b) those associations which owe their origin 
 nnd meaning to reproduction. Of the latter, some do not become 
 more than domestic, and these are distinguished as conjugal (in 
 
 3.. 
 
 i 
 
 \M 
 
 
r! 
 
 K 
 
 M 1 1 
 
 i 
 
 t 
 
 fi J 
 
 'I'l ijL 
 
 \\r,: 
 
 'ii;:; 
 
 r : 
 
 ii 
 
 
 '.1 
 
 I 
 
 I . 
 
 
 88 
 
 T/ie Study of Animal Life 
 
 PART 1 
 
 whi h the parents alone are concerned), maternal (in wliich the 
 mother is the head of the family), and paternal (in which the male 
 becomes prominent). But higher than the pair and the family is 
 what Espinas calls the "peuplade," what we usually call the 
 society, whose bonds are, for the most part, psychical. 
 
 But 'et us consider this problem of the evolution of 
 sociality. The body of every animal — whether sponge or 
 mammal — is a city of living units or cells. But there are 
 far simpler animals than sponges. The very simplest 
 animals, which we call firstlings or Protozoa, differ from all 
 the rest, in being themselves units. The simplest animals 
 are single cells ; each is comparable to one of the myriad 
 units which make up a sponge, a coral, a worm, a bird, a 
 man. 
 
 Here, therefore, there is an apparent gulf. The simplest 
 animals are units — single cells ; all other animals are com- 
 binations of units — cities of cells. How is this gulf to be 
 bridged ? It is strange that evolutionists have not thought 
 more about this, for on the transition from a unit to" a com- 
 bination of units the possibility of higher life depends. 
 
 Every higher animal begins its individual life as a single 
 cell, comparable to one of the firstlings. This single cell, 
 or egg-cell, divides ; so do most of the Protozoa. But when 
 a Protozoon divides, the results separate and live in- 
 dependent lives ; when an egg- cell divides, the results 
 of division cohere. Therefore, the whole life of higher 
 animals depends upon a coherence of units. 
 
 But how did this begin ? What of the gulf between 
 single-celled Protozoa and all the other animals which arc 
 many-celled .'' Fortunately we are not left to mere specula- 
 tion. The gu'*" has been bridged, else we should not exist ; 
 but, more than 'hat, the bridge, or part of it, is still left. 
 There are a few > ^ the simplest animals which form loose 
 colonies of units, wnich, when they divide, remain together. 
 Whether it was through weakness, as I am inclined to 
 believe, that the transition forms between Protozoa and 
 higher animals became strong, or for some hidden reason, 
 we do not know. Some speak of this coherence of 
 firstlings as a primal illustration of organic ;issociation, 
 
CHAP. V 
 
 Social Life of Animals 
 
 89 
 
 co-operation, surrender of individuality, of sociality at a low 
 level, but it is unwise to apply these words to creatures 
 so simple. All that we certainly knov/ is that some of the 
 simplest animals form loose colonies of units, that the gulf 
 between them and the higher animals is thus bridged, and 
 that the bridging depends on coherence. Our first con- 
 
 (.:>=a>^ 
 
 ".• !<>•— Siphonophore colony, showing the float (<i), tlie swimmiiiKbclls 
 I It nutntivo, reproductive, and other nieniljcrb of the colony Uiiealh (\ 
 the Hrolutio)! o/Scx ; after Haeckel.) 
 
 ,(/■); 
 
 (Ironi 
 
 elusion, therefore, is, that the possibility of there being any 
 lii^;her animals depends, primarily at least, not on competition 
 Itut on the coherence of units. 
 
 ')ur next step is this: When we study spong?s, or 
 zt'ophytes, or most corals,- or some t> pes usually classed as 
 
 "H% 
 
 % 
 
 ifsi 
 
90 The Study of Animal Life part i 
 
 «* worms," we see that the habit of forming colonies is 
 common. Every sponge is a simple sac to begin with, 
 but it buds off others like itself, and the result is a coherent 
 colony. A zoophyte is not one individual, but a connected 
 colony of individuals. Throughout the colony there is one 
 life ; all the individuals have a common origin, and all are 
 members one of another. In varying degrees of perfection 
 the life of the whole is unified. Moreover, the unity is 
 often increased, not diminished, by the fact that the indivi- 
 duals are not all alike. There is division of labour among 
 them; some may feed while others reproduce, some feel 
 much while others may be quite callous. Thus, as we 
 already mentioned, the Portuguese Man-of-War, a colony 
 of small jellyfish -like individuals, has much division of 
 labour, and yet there is much, though by no means perfect, 
 
 unity of life. 
 
 Our second conclusion is that among many animals- 
 beginning with sponges and ending with the searsquirts, 
 which are acknowledged to be animals of high degree— 
 the habit of forming colonies is common, and that these 
 colonies, though organically continuous, illustrate the essence 
 of society ; for in them many individuals of common descent 
 and nature are united in mutual dependence and help- 
 fulness. 
 
 The next step towards an understanding of the social 
 relations of animals is very different from that in which we 
 have recognised the habit of forming colonies. The factor 
 which we have now to acknowledge is the love of mates. 
 This also has its history, this also has its prophecies among 
 the firstlings, but we shall simply assume as a fact that 
 among crustaceans and insects first, in fishes and amphi- 
 bians afterwards, in reptiles too, but most conspicuously 
 among birds and mammals, the males are attracted to. the 
 females, and in varying degrees of perfection enter into 
 relations of mutual helpfulness. The relations and the 
 attractions may be crude enough to begin with, but perhaps 
 even we hardly know to what heights of devotion their 
 highest expressions may attain. To mere physical fondness 
 are added subtler attractions of sight and hearing, and 
 
CHAP. V 
 
 Social Life of Animals 
 
 9> 
 
 these are sublimed in birds and mammals to what we call 
 love. This love of mates broadens out ; it laps the family in 
 its folds ; it diffuses itself as a saturating influence through 
 the societies of animals and of men. ** Sociability," Espinas 
 says, " is based on the friendliness of mates." 
 
 The fourth step is the evolution of the family. From 
 monkeys and beavers and many kinds of birds, to ants and 
 bees and diverse insects, many animals illustrate family 
 life. There is no longer the physical continuity charac- 
 teristic of the colony, but there is a growing psychical 
 unity. It is natural that the first ties of family life should 
 be those between mother and young, and should be strong- 
 est when the number of offspring is not very large. But 
 even in some beetles, and more notably in certain fishes 
 and amphibians, the males exhibit parental care and affec- 
 tion ; while in higher animals, especially among birds, the 
 parents often divide the labours of the family. " Children," 
 Lucretius said, "children with their caresses broke down 
 the haughty temper of parents." 
 
 The fifth step is the combination of families into a 
 society, such as we find illustrated by monkeys and 
 beavers, cranes and parrots, and in great perfection by 
 ants. The members are less nearly related than in the 
 family, but there may be even more unity of spirit. 
 
 I do not say that it is easy to understand how coherence 
 of units led to the formation of a " body," how colonies 
 became integrated and the labours of life more and more 
 distributed, how love was evolved from apparently crude 
 attractions between the sexes, how the love of mates was 
 broadened into parental and filial affection, or how families 
 well knit together formed the sure foundations of society ; 
 but I believe that it is useful to recognise these steps in the 
 history. 
 
 We hardly know how to express ourselves in regard to 
 the origin of affection. But I cannot get beyond Aristotle's 
 fundamental principle of evolution, that there is nothing in 
 the end which was not also in the beginning. 
 
 Yet we may fairly say that the sociality and helpfulness 
 of animals are flowers whose roots are in kinship. Off- 
 
 m 
 
 ■ JS'i 
 13 
 
 r/; 
 
 :i3 
 
 lii 
 
; 
 
 9* 
 
 The Study of Animal Life 
 
 PART 1 
 
 spring are continuous in nature with their parents ; the 
 family has a unity though its members be discontinuous 
 and scattered ; "the race is one and the individual many." 
 
 9. Advantages of Social Life. — But animals are social, 
 not only because they love one another, but also because 
 sociahty is justified of her children. " The world is the 
 abode of the strong," but it is also the home of the loving ; 
 " contention is the vital force," but the struggle is modified 
 and ennobled by sociality. 
 
 (a) Darwin^s Position. — Darwin observed that "the 
 individuals which took the greatest pleasure in society 
 would best escape various dangers ; while those that 
 cared least for their comrades, and lived solitary, would 
 perish in greater numbers." He distinctly emphasised 
 that the phrase "the struggle for existence" was to be 
 used in a wide and metaphorical sense — to include all the 
 endeavours which animals make both selfishly and un- 
 selfishly to strengthen their foothold and that of their 
 offspring. But he was not always successful in retaining 
 this broad view, nor was he led to compute with sufficient 
 care to what extent mutual aid is a factor in evolution 
 counteractive of individualistic struggle. 
 
 Without losing sight of the reality of the struggle for 
 existence ; without disputing the importance of natural 
 selection as a condition of evolution — securing that the 
 relatively fittest changes succeed ; without ignoring what 
 seems almost a truism, that love and social sympathies have 
 also been fostered in the course of natural selection ; we 
 maintain— (i) that many of the greatest steps of progress 
 — such as those involved in the existence of many -celled 
 animals, loving mates, family life, mammalian motherhood, 
 and societies — were not made by the natural selection of 
 indefinite variations ; (2) that affection, co-operation, mutual 
 helpfulness, sociality, have modified the struggle for material 
 subsistence by lessening its intensity and by ennobling its 
 character. 
 
 (b) Kropotkitte's Posilion.—hgaSnst. Prof. Huxley's con- 
 clusion that " Life was a continual free- fight, and beyond 
 the limited and temporary relations of the family the 
 
 I 
 
CHAF. V 
 
 Social Life of Animals 
 
 93 
 
 Hobbesian war of each against all was the normal slate of 
 existence," let me place that of Kropotkine, to whose admir- 
 able discussion of mutual aid among animals I again 
 acknowledge my indebtedness. 
 
 " Life in societies is no exception in the animal world. 
 It is the rule, the law of nature, and it reaches its fullest 
 development with the higher Vertebrates. Those species 
 which live solitary, or in small families only, are relatively 
 few, and their numbers are limited. . . . Life in societies 
 enables the feeblest mammals to resist, or to protect them- 
 selves from, the most terrible birds and beasts of prey ; 
 it permits longevity ; it enables the species to rear its pro- 
 geny with the least waste of energy, and to maintain its 
 numbers, albeit with a very slow birth-rate ; it enables the 
 gregarious animals to migrate in search of new abodes. 
 Therefore, while fully admitting that force, swiftness, pro- 
 tective colours, cunning, and endurance of hunger and cold, 
 which are mentioned by Darwin and Wallace as so many 
 qualities making the individual or the species the fittest 
 under certain circumstances, we maintain that under any 
 circumstances sociability is the greatest advantage in the 
 struggle for life. . . The fittest are thus the most soci- 
 able animals, and sociability appears as the chief factor ot 
 evolution, both directly, by securing the well-being of the 
 species while diminishing the waste of energy, and indirectly 
 by favouring the growth of intelligence. . . . Therefore 
 combine — practise mutual aid ! That is the surest means 
 for giving to each and to all the greatest safety, the best 
 guarantee of existence and progress — bodily, intellectual, 
 and r.ioral. That is what nature teaches us." 
 
 lo. A Note on "The Social Organism." — It is com- 
 mon nowadays to speak of society as " the social organism," 
 and the metaphor is not only suggestive but convpnient 
 — suggestive because it is profitable to biologist and soci- 
 ologist alike to follow out the analogies between an organism 
 and society, convenient because there is among organisms 
 — in aggregates like sponges, in perfected integrates Ike 
 birds — a variety sufficient to meet all grades and views of 
 society, and because biologists differ almost as much in 
 
 1 4 
 
 m 
 
 
94 The Study of Animal Life part i 
 
 their conceptions of an " organism " as sociologists do in 
 regard to ** society." 
 
 It may be questioned, ho\ ever, whether we need any 
 other designation for society than the word society sup- 
 plies, and whether the biological metaphor, with physical 
 associations still clinging to it, is not more illusory than help- 
 ful. For the true analogy is not between society and an 
 individual organism, but between human society and those 
 incipient societies which were before man was. Human 
 society is, or ought to be, an integrate — a spiritual integrate 
 
 of organisms, of which the bee-hive and the ants' nest, 
 
 the community of beavers and the company of monkeys, 
 are like far-oflf prophecies. And in these, as in our own 
 societies, the modem conception of heredity leads us to 
 recognise that there is a very real unity even between 
 members physically discontinuous. 
 
 The peculiarity of human society, as distinguished from 
 animal societies, depends mainly on the fact that man is a 
 social person, and knows himself as such. Man is the realis- 
 ation of antecedent societies, and it is man's realisation of 
 himself as a social person which makes human society what 
 it is, and gives us a promise of what it will be. As bio- 
 logists, and perhaps as philosophers, we are led to conclude 
 that man is determined by that whole of which he is a 
 part, and yet that his life is social freedom ; that society is 
 the means of his development, and at the same time its 
 end ; that man has to some extent realised himself in society, 
 and that society has been to some extent realised in man. 
 
 But I am slow to suppose that we, who in our ignorance 
 and lack of coherence are like the humbler cells of a great 
 body, have any adequate conception of the social organism 
 of which we form part. 
 
 II. Conclusions. — I would in the main agree with 
 Kropotkine that " sociability is as much a law of nature as 
 mutual struggle " ; with Espinas that " Le milieu social est 
 la condition ndcessaire de la conservation et du renouvelle- 
 ment de la vie"; and with Rousseau that "man did ait 
 make society, but society made man." 
 
CHAPTER VI 
 
 THE DOMESTIC LIFE OF ANIMALS 
 
 I. The Love cf Mates — 2. Love and Care for Offspring 
 
 Winter in our northern climate sets a spell upon life. 
 The migrant birds escape from it, but most living things 
 have to remain spell-bound, some hiding with the supreme 
 patience of animals, others slumbering peacefully, others in 
 a state of " lat ife " stranger than death. But within 
 the hard rind of e trees, or lapped round by bud scales, 
 or imprisoned within the husks of buried see ' '^ life of 
 plants is ready to spring forth when the south wi. ' iws ; 
 beneath the snow lie the caterpillars of summer butterflies, 
 the frogs are waiting in the mud uf the pond, the hedgehog 
 curled up sleeps soundly, and everywhere, under the seeming 
 death, life rests until the spring. '* For the coming of 
 Ormuzd, the Light and Life Bringer, the leaf slept folded, 
 the butterfly was hidden, the germ concealed, while the sun 
 swept upwards towards Aries." 
 
 But when spring does come, heralded by r*- turning 
 migrants — swallows and cuckoos among the n- t — how 
 marvellous is the reawakening ! The buds swell a J burst, 
 the corn sends up its light green shoots, the primrose and 
 celandine are in blossom, the mother humble-bee conies 
 out from her hiding-place and booms towards the willow 
 catkins, the frogs croak and pair, none the worse of their 
 fast, the rooks caw noisily, and the cooing of the dove is 
 heard from the wood. Then, as the pale flowers are sue- 
 
96 
 
 The Study of Animal Life part i 
 
 ceeded by those of brighter tints, as the snowy hawthorn 
 gives place to the laburnum's " dropping wells of fire " and 
 the bloom of the lilac, the butterflies flit in the sunshine, the 
 chorus of birds grows stronger, and the lambs bleat in the 
 valley. Temperature rises, colours brighten, life becomes 
 strong and lusty, and the earth is filled with love. 
 
 I. The Love of Mates.— In human life one of the 
 most complex musical chords is the love of mates, in the 
 higher forms of which we distinguish three notes — 
 physical, emotional, and intellectual attraction. The love 
 of animals, however, we can only roughly gauge by 
 analogy; our knowledge is not sure enough to appreci- 
 ate it justly, though we know beyond any doubt that in 
 many the physical fondness of one sex for another is sub- 
 limed by the addition of subtler emotional syinpathies. 
 Among mammals, which frequently pair in spring, the 
 males are often transformed by passion, the " tirnid " I.. 
 becomes an excited combatant with his rivals, while in t' 
 beasts of prey love often proves itself stronger than hunger. 
 There is much ferocity in mammalian courtship— savage 
 jealousy of rivals, mortal struggles between them, and suc- 
 cess in wooing to the strongest. In many cases the love- 
 making is like a storm— violent but passing. The animals 
 pair and separate— the females to motherhood, the males to 
 their ordinary life. A few, like some small antelopes, seem 
 to remain as mates from year to year ; many monkeys are 
 said to be monogamous ; but this is not the way of the 
 
 majority. 
 
 Birds are more emotional than mammals, and their love- 
 making is more refined. The males are almost always 
 more decorative than their mates, and excel in the power of 
 song. They may sing, it is true, from sheer gladness of 
 heart, from a genuine joy of life, and their lay rises 
 "like the sap in the bough"; b.t the main motive of 
 their music is certainly love. It may not always be music 
 to us, but it is sweet to the ears for which it is meant— to 
 which in many tones the song says ever " Hither, my love ! 
 Here I am ! Here ! " Nor do the male birds woo by 
 singing alone, but by love dances and by fluttering displays 
 
 
 • i 
 
CHAP. VI The Domestic Life of Animals 
 
 \ h'M 
 
 
 97 
 
 -,!l.i. i.,1, 
 
 I^'SWA 
 
 I. 
 
 -t^ 
 
 
 ^t) 
 
 v( S 
 
 J 
 
 n 
 
 l« 
 
 E 
 
 I 
 
 ■9 
 2 
 
 ^^^Pi^^, 
 
 r,-«! wf.><>Jj^ 
 
 \' y\ 
 
 ™J\"W' 
 
 if) 
 
 /I 
 
 V 
 
 o 
 
 I 
 
 (3 
 
 H 
 
The Study of Animal Life 
 
 PART I 
 
 i >. 
 
 98 
 
 of their bright plumage ; with flowers, bright pods, and 
 I • i\hells the bower-birds decorate tents of love for 
 :S hUytool The mammals woo chiefly by force ; the 
 Wrds arToften moved to love by beauty, and mates often 
 hven prolonged partnership with mutual dehght and help- 
 fulness ^xty years before Darwin elaborated h.s theory of 
 exual selection'according to which males have grown more 
 auractive because the most captivating svutors were mos 
 sucSul in 'ove. the omitholorist Bechstem noted how the 
 female canary or finch would choose the best smger among 
 a^rowd oTsIitors ; and there seems some reason to beheve 
 ^ha^The female's Choice of the most --ca^ or tne .^^^^^^ 
 handsome has been a factor m progress. Wallace on he 
 contrar^ maintains that the females are plamly dressed 
 because of the fate which has befallen the conspicuous durmg 
 Sation and surely they must thus be handicapped. To 
 others it s;ems more natural to admit that there ts truth ,n 
 both Darwin's and Wallace's conclusions, bufto regard ,1 c 
 ml^es as stronger, handsomer, or more musical sinM;! 
 because hey are males, of more active constitutional hab.t 
 ?han their mates. To this view Mr Wallace himself mchnes, 
 clpard w th the lion', thundei, the elephant's trunv 
 oetS or the stag's resonant bass, and the might wn.ch 
 Tes beWnd tbese, or with the warble of the nightingale, 
 he caroUf the thrush, the lark's blithe lay, or the n.ocking- 
 Wrd? n!.cm,^e, and the en.utional wealth which these ex- 
 nress tne challenges and calls of love among jther classe 
 ranimaL are apt'to seem lacking in force or beauty^ 1 u 
 our human judgment affords no sure criterion. The f.ogs 
 Td newts which lead on an average a somewhat sluggish 
 Ufe wake up at pairing time, and croak according to .he,r 
 strength The males'are often furnished with two rcsoiv 
 at n/sacs at the back of the mouth, and how they can c k 
 TeUersb; marsh-land know ; the North American bu 
 frog bellows by himself, and the South American tree f.ogs 
 ViniH a rnncert in the branches. 
 
 '°'of the mJ^ing of fishes we know little, but there are ...ne 
 well known cases alike of display and o tournament T 
 stickleback fights with his rivals, leads h.s mate tc 
 
cH»p. VI The Domestic Life of Animals 99 
 
 the nest by captivating wiles, dances round lier in a frenzy, 
 
 ■1! 
 
 I^K' 
 
 
 vj^K't 
 
 
 
 '>! 
 
 •i* 
 
 !■ 
 
 Fi'i . I.— Male and female bird of paradise {P.ir.uiiua minor). (From ICvolu 
 tioH e/SiX ; after Catalogue of Dii.:,Jcn .Museum.) 
 
 ■ind .ifterwurds guards the eggs with jealous care. The 
 
 m 
 
 ^m 
 
The Study of Animal Life 
 
 PART I 
 
 XOO 
 
 male salmon, with their hooked lower jaws, fight with their 
 rivals sometimes to the death. ,• i . i :i.^ 
 
 5S.t,ht sr :f *e,n are ™f .. u.„g «, 
 Lrrl leas and wing-edges as mstruments. The crickets 
 S mem"fth« LL "sing," and the death-watch tap. 
 
 " t frslmer^lgh., when co.ours are put out by the 
 darlne* the"tow.woL 'shines brightly on the mossy bank^ 
 7 r. Rritifh soecies (Ijvnpyr nccHlucct) the wingKl 
 LV'»d the IgCfetiale Z. both luminous ; the latter 
 ^^.M Mcels n brightness, while her mate has larger eyes. 
 ^tv« Ae pho Jhorescence may mean to the const,tu.,o„ 
 Srh^«ct!i^ is certainly a love-slgnal between the sexc . 
 But U know most about the Italian glowworm (Luaoh, 
 te to^ of whose behaviour we have a lively picture-tha„b 
 « PmfessoT Emerys nocturnal observations u; the meadows 
 .Li Moena The females sit among the grass i the 
 Zl" s «y^Kn search of them. When a female catches 
 
 Skh«s::.^-e^^rrg^;t;n:H 
 S^rifn"ti::^irThV'^m:i^^^^^^^^^^^ 
 
 coquette s ?»<"«• ' ij^„,.,jj ^nd the intensity seems 
 ^mth th S;J t.^te >«« W the fem^e is .,we 
 restricted The most noteworthy difference »s that tw 
 Smrnous rhythm of the male is more rapid, with br,e^ 
 flaThes while that of the female is more prolonged ith 
 fonger inTervals, and more tremulous-iUummed symbols of 
 
 J^'U. we did not ignore that the courtship o au«t 
 mammals is somewhat rough So, ^«^J^J"'"f ,; ,^ 
 dances of many butterflies, the merry songs of the tra 
 
 ~'^m§^mK^mm*Js^:^sss^ 
 
2] 
 
 CHAP. VI The Domestic Life of Animals loi 
 
 hoppers, and the flashing signals of the glow-insects, it is 
 just that we should turn to the strange courtship of spiders, 
 which is less ideal. Of what we may be prepared to find 
 we get a hint from a common experience. Not long ago I 
 found in a gorge some spiders which I had never seen 
 before. Wishing to examine them at leisure, I captured a 
 male and a female, and, having only one box, put them, 
 with misgivings, together. When I came to examine 
 them, however, the male was represented by shreds. 
 Such unnatural conduct, though by no means universal 
 among spiders, is common. The tender mercies of spiders 
 are cruel. We have lately obtained an account of the 
 courtship of spiders from George W. and Elizabeth G. 
 Peckham, from whose careful observations I select the 
 following illustrations : 
 
 According to these observers, "there is no evidence that the 
 male spiders possess greater vital activity ; on the contrary, it is 
 the female that '<; the more ac*'ve and pugnacious of the two. 
 There is no rel- . in either sex between development of colour 
 and activity. 'Itie Lycosida, which are the most active of all 
 spiders, have the least colour-development, while the sedentary orb- 
 weavers show tlie most brilliant hues. In the numerous cases 
 where the male differs from the female by brighter colours and 
 ornamental appendages, these adornments are not only so placed 
 as to be in full view of the female during courtship, but the atti- 
 tudes and antics of the male spider at that time are actually such as 
 to display them to the fullest extent possible. The fact that in the 
 Altida the m.les vie with each other in making an elaborate dis- 
 play, ^ only of their grace and agility, but also of their beauty, 
 befor- t. females, and that the females, after attentively watching 
 the dances and tournaments which have been executed for their 
 Rraiification, select for their mates the males that they find most 
 pleasing, points strongly to the conclusion that the great differences 
 in colour and in ornament between these spiders are the result of 
 sexual selection." 
 
 These conclusions support Darwin's position that the female's 
 choice is a great factor in evolving at'ractiveness, and are against 
 Wallace's contention that bright colours express greater vitality, 
 and that the females are less brilliant because enemies eliminate 
 the conspicuous. It is quite likely that Darwin's view is true in 
 some cases (e.g. these spiders), and Wallace's conclusion true in 
 others (<^. birds and butterflies), m that both may be true in 
 
 ^M^ 
 
 ?:^Sft. 
 
 i^^§ffMi 
 
i' *^ -i 
 
 I02 
 
 Tlie Study of Animal Life 
 
 PART I 
 
 „„v c.^, »H.e ...fact ^^ tufS^l ^^ " '-\" 
 Xays more brilliant than t^^l'X'l^y of maleness, which 
 brSncy is wrapped «P^-lo"g ^ J ^^ superabundant vitality, or as 
 it is not sufficient to ^f^^^f^i^^ey towards a relative increase 
 greater activity, but rather as ^Jj^^^^^ges over those >.hich are 
 ^f destructive or d.srupUve ^^'^^^ ^^^ Wem is very complex, 
 constructive or ^^"^^f"^'':^' J't.^J^.^. We need to know 
 and dogmatic conclusions are prcm . ^^ to winch . 
 
 ?Je chemical nature and ^^^^°7,e ,n apprSmate balance-sheet 
 colour is due ; we "--'^., ° ^^^JheU s'^xes. Knough of th.s, 
 of the income and expenditure of the ^^^ ^^^^ romance- 
 
 however ; let us return to the pictures. 
 Su to these: patient observers: 
 
 G W und E. G. Peckham.) 
 
 e 1 tVint the males of Saiih 
 .. On reaching the country we found that ^ .^ ^^^^ ^.^^ 
 
 ;>„/.. were nuti.e and were waunjg f- hc^ej^ ^^^^ ,^ ,„niulc 
 Cilh both spiders and msccts. In U^is i ^^ ^^^^^^^ ^ 
 difference l^tween the sexes On May 4 ^^^ ^^^ ,, y 
 
 female and placed her m one of Ojc larg« ^ ^^ ^,^^ ^^^^, ,,,1 
 we put a male m wuh her. He sa ^^ ^^^.^^ 
 
 still, twelve =nches away. The glance .^^^^^^ f^,^„, ^et 
 
 he at once moved toward her. ^^^^y^^J^^.^Uable performances 
 he stood still, and then ^^^^^'^^ ^^dmnng female. She cyca 
 that an amorous male <^°»l^;^^ "^^^^.r time to time, so that h 
 him eagerly, changmg her f-'^ ^^^.;^\.„ ^.hde Ix^dy on one sj 
 might always be '" -^^-j J'*^' J owering it on the other by foW- 
 by straishtemng out th^ legs, aim 
 
CHAP. VI The Domestic Life of Animats 103 
 
 ing the first two pairs of legs up and under, leaned so far over as to 
 be in danger of losing his balance, which he only maintained by 
 sidling rapidly toward the lowered side. The palpus, too, on this 
 side was turned back to correspond to the direction of the legs 
 nearest it. He moved in a semicircle of about two inches, and 
 then instantly reveised the position of the legs and circled in the 
 opposite direction, gradually approachins; nearer and nearer to the 
 female. Now she das'^es toward him, while he, raising his first pair 
 of legs, extends them upward and forward as if to hold her off, but 
 withal slowly retreats. Again and again he circles from side to 
 side, she gazing toward him in a softer mood, evidently admiring 
 the grace of his antics. This is repeated until we have counted one 
 hundred and eleven circles made by the ardent little male. Now 
 he approaches nearer and nearer, and when almost within reach 
 whirls madly around and around her, she joining and whirling with 
 him in a giddy maze. Again he falls back, and resumes his semi- 
 circular motions with his body tilted over ; she, all excitement, 
 lowers her head and raises her body, so that it is almost vertical. 
 Both draw nearer, she moves slowly under him, he crawling over 
 her head, and the mating is accomplished." The males are quarrel- 
 some and fight with 
 one another ; but after 
 watching "hundreds 
 of seemingly terrible 
 battles " between the 
 males of twelve differ- 
 ent species, the obser- 
 vers were forced to the 
 conclusion that "they 
 are all sham affairs 
 gotten up for the pur- 
 pose of displaying be 
 fore the females, who 
 commonly stand by in- 
 terested spectators." 
 "It seemed cruel sirait 
 at first to put eight or 
 ton males (of Dendiy- 
 phaii/,s capitatiis) into 
 abox to see them fight. 
 
 Yxc, i — I'wo male spiders (Zygoballus btttini) 
 fighting. (After O. W. and E. G. Peckh.im.) 
 
 but it was soon apparent that they were very prudent little fellows, 
 and were fully conscious that 'he who fii;hts and runs away will 
 live t(. fight another d.ry.' In fact, after two weeks of hard fi hting 
 we were unable to discover one wounded warrior. . . . The 
 single female (of Phidippm morsitans) that we caught duung the 
 
164 
 
 The Study of Animal Life 
 
 PART I 
 
 I 
 
 FIG. .4.-Malc argus pheasant di>pbylng its plumage, tl'ron, l)arw»,.) 
 
 rrs:«:s^Lr^r;.=":="°------^^ 
 
 wmmm^^^^^%<w^~m 
 
CHAP. VI The Domestic Life of Animals 105 
 
 upon them and killed them." ''The female of Deudryphantes 
 tlegam is much larger than the male, and her loveliness is accom- 
 panied by an extreme irritability of temper, which the male seems 
 to r^ard as a constant menace to his safety ; but his eagerness 
 being great, and his manners devoted and tender, he gradually 
 overcomes her opposition. Her change of mood is only brought 
 about after much patient courting on his part." In other species 
 (Philaus militaris) the males take possession of young females and 
 keep guard over them until they become mature. We sometimes 
 hear of courtship by telephone. In the Epeiridse spiders " it seems 
 to be carried on, to some extent at least, by a vibration of web 
 lines," as M'Cook and Termeyer have also observed. 
 
 Surely it is a long gamut this, from a mammal's clamant 
 call and forcible wooing, or from the sweet persuasiveness 
 of our singing birds, and the fluttering displays of others, to 
 the trembling of a thread in the web of a spider. But, 
 however varied be the pitch of the song and the form of 
 the dance, all are expressions of love. 
 
 Mates are also attracted to one another by odours. 
 These are best known in mammals {e.g. beaver and civet) 
 and in reptiles ; they predominate in the males, and at the 
 breeding season. They usually proceed from skin glands ; 
 but we understand little about them. They serve as 
 incense or as stimulant, but perhaps this usefulness is 
 secondary. The zoologist Jaeger regards the odoriferous 
 substances in plants and animals as characteristic of and 
 essentially associated with each life ; but without going so 
 far we may recognise that in the general life of flowers 
 and animals alike odours are very important. We know, 
 too, that certain odours make much impression upon us ; 
 such as those of hawthorn and of the hay-field, of newly- 
 mown grass and of withered leaves, of violet and of 
 lavender; and furthermore, that in some mysterious way 
 some fragrances excite or soothe the system, and have 
 become associated with sexual and other emotions, 
 
 2. Love and Care for Offspring. — Gradual as the 
 incoming of spring has been the blossoming of parental 
 love among animals. We can: at tell in what forms it 
 first appeared in distinctness. We cannot say Lo here ! or 
 1.0 there ! for it is latent in them all 
 
 i ml 
 
 *ii-itf!»l 
 
 am!' 
 
!. 1 : 
 
 io6 TJie Study of Animal Life part j 
 
 In many of the lower animals the units which begin 
 new lives are readily separated from the parent ; but in 
 others, e.g. some of the simplest, or some by no means 
 simple "worms," and even some insects, the parent life 
 disappears in giving birth to the young. Reproduction or 
 the continuance of the species often involves a sacrifice of 
 
 the individual life. 
 
 It is strangely true, even in the highest forms, that 
 reproduction, though a blossoming of the whole life, is also 
 the beginning of death. It is costly, and brings death as 
 well as life in its train. This is tragically illustrated by 
 many insects, such as butterflies, who die soon after repro- 
 ducing, though often not before they have, in obedience to 
 instinctive impulse, cared most effectively for their eggs— 
 the results of which they do not live to see. Think also of 
 the mayflies, or Ephemeridae, who, after a prolonged aquatic 
 life as larva, become winged, dance in the sunlight for an 
 hc'ir, mate and reproduce, and die. ^ , , 
 
 Picture the long larval life in the water, and the short 
 aerial happiness lasting for an evening or two. Long life, 
 compared with the span of many other insects but short 
 love ; there may be years of patience, and but a day 
 of pleasure; great preparations, and the anli-climax 
 of death. The eggs lie half conscious m the water, 
 faintly stirred by the growing life within, lapped round 
 about by peace, — though the trout thin them sorely. 
 In the survivors the embryos become conscious, awaken 
 from their rocking, and turn themfelves in their cradles. 
 See the larvae creep forth, wash themselves gaily m 
 the water, and hungrily fall upon their prey, some 
 smaller insects. The little " water-wings " grow, and 
 the air soaks into the blood ; the larvae cast their skins 
 many times, and hide from the fishes. At length comes 
 the final moult, md the making oi the air-wings, of which 
 in the summer e ening you may see the first short flight as 
 the insects rise hke a living mist from the pool. But even 
 yet a thin veil, too truly suggestive of a shroud, encumbers 
 them ; and they rest wearily on the grass or on the 
 branches of the willow. Watch them writhe and jerk, as it 
 
CHAP. VI The Domestic Ltfe of Animals 107 
 
 impatient, till at length their last encumbrance — their 
 "ghost," as naturalists call it — is thrown off. Now the 
 other life, the life of love, begins. Merrily they dance up 
 and down, dimpling the smooth water into smiling with a 
 touch— chasing, embracing, separating. See the filmy fairy 
 wings, the large lustrous eyes of the males, the tail fila- 
 ments gracefully sweeping in the dance ! They never 
 pause to eat — they could not if they tried ; hunger is past, 
 love is present, and in the near future is death. The 
 evening shadows grow longer, — shadows of death to the 
 Ephemerides. The trout jump at them, a few rain-drops 
 thin the throng, the stream bears others away. The 
 mothers lay their eggs in the water, and wearily die forth- 
 with — cradle and tomb are side by side ; the males seem 
 to pass in a sigh from the climax of loving to the other 
 crisis of dying. But the eggs are in the water, and 
 the dance of love is more than a dance of death. 
 Turning homewards, we cannot but think sadly of other 
 Ephemerides, of patient larval life, of the gradual 
 revealing of the higher self, of shrouds thrown aside and 
 wedding robes put on, of hunger eaten up by love, of the 
 sacrifice of maternity, of cradle and tomb together. Yet 
 we remember the eggs in the water, the promise of the 
 future beneath the surface of the stream. Under the horse- 
 chestnut tree, too, the wind has blown the shed petals like 
 white foam, but the tree itself is strong like Ygdrasil, and 
 among the branches a bird sings in the twilight. 
 
 Returning in more matter-ot-fact mood to parental care, 
 we need not dwell upon those cases where the young 
 are simply sheltered for a while about the body of the 
 mother, hanging to a jellyfish, on some sea-urchins hidden 
 in tents of spines, in one or two sea-cucumbers half buried 
 in tht skin, adhering to the naked ventral surface of the 
 common little leech {Clepsine\ imprisoned in modified 
 tentacles in some marine worms, carried about in a dorsal 
 brood-chamber in many water-fleas, or under the curved 
 tail of higher crustaceans, retained within the gills of 
 bivalves^ and so on. Such adaptations are interesting, 
 they involve prolonged physical contact between mother 
 
I 
 
 1 1 
 
 io8 The Study of Animal Life parti 
 
 and offspring, but we are in search of cases where the 
 parent acts as if she cared for her young. 
 ^ But this care, as we said, begins very gradually. Thus, 
 in some lowly crustaceans the young may return to the 
 brood -chamber of the mother, even after hatchmg and 
 moulting; and young crayfish are said to jeturn to the 
 Tdter of the maternal tail after they have been se adnft. 
 Strange, too, are the males of some sea-spiders (Pycno- 
 gonidl) who carry about the ova on their legs. It is con- 
 Idently stated that the headless freshwater mussel keeps 
 the embryos imprisoned even after the norma period, 
 until some freshwater fish be present, to which they may 
 attach themselves ; while some cuttle-fishes are said to exert 
 themselves in keeping their egg-clusters dean an., safe 
 
 But it is among insects, with their full, free life that we 
 see the best examples of parental care in backboneless 
 animals. Some scoff at the « beetle-pricker » or the scara- 
 be!st.-and such genial laughter as that of the Profes^o:at 
 the Breakfast Table has a healthy resonance,-but those 
 who scoff have not read Kirb/s Utters, else they would 
 feel that the student of insects watches at a wdUhead o 
 romance and marvel inexhaustibly fresh. What, for 
 nsmce, shall we say of -e workerjees. who, though no 
 parents, tend and nurse the grubs with constant care ; or o 
 ^e likewise sexless worker-ants, whose first endeavou 
 when the nest is disturbed is to save, not themselves bu 
 the young ; or of the care that flies, moths, and other 
 insects wUl take to lay their eggs in ^"^stances and suua- 
 tions best fitted for the future young ? We must think back 
 nto the past history of climatic and other conditions if 
 rwould understand the frequently elaborate provision 
 which mother insects make for offspring which they neve 
 see • the ancestors had probably a longer life, and had the 
 gr^ ification of seeing the result of their labours, and no. 
 fhe inherited habit works on, perhaps with no vision of 
 the future. We must also allow that the offspnng mis- 
 takenly deposited by an imperfect maternal instinct would 
 most likely die, and thus leave the race more seleit. But 
 after thinking out these explanations, the facts remain mar- 
 
 iT-it--' 
 
CHAP. VI The Domestic Life of Animals 
 
 109 
 
 vellous. Thus W. Marshall saw an Ichneumon fly 
 {Polynema natans) remain twelve hours under water, 
 without special adaptations for such a life, swimming about 
 with her wings, and depositing her eggs within the larvae of 
 caddis-flies I 
 
 We are accustomed, the same naturalist says, to look 
 upon a hen which gathers her brood under her wings as a 
 picture of loving care, but we must recognise that the same 
 is true of earwigs, spiders, and scorpions. Many of us 
 have lifted a large stone on the dry bank, and seen the 
 hurry-scurry of small animals ; there are earwigs among 
 the rest, and the pale-yellowish young crowd quickly under 
 the shelter of their mothers, who stand guard with open 
 pincers. Female spiders, too, so fierce and impatient as 
 mates, are most "respectable mothers." Some make nests, 
 guard, feed, and even fight for the young ; others carry the 
 eggs about with them. " I have often," Marshall says, 
 "made fun of the little creatures, taking away their 
 precious egg-sac and removing it to a slight distance. It 
 was interesting to see how eagerly they sought, and how 
 joyously, one may even say, they sprang upon their * one 
 and all ' when they found it again. Sometimes I cheated 
 them with a little ball of wool of the size, form, and colour 
 of the egg-sac, which they quickly seized, and as rapidly 
 rejected." 
 
 Many fishes lay their eggs by hundreds in the water, 
 and thenceforth have .lothing more to do with them, but 
 even among these cold-blooded animals there are illustra- 
 tions of parental care. From a bridge over the river you 
 may be able to watch the female salmon ploughing a 
 furrow in the gravelly bed, and there laying her eggs, care- 
 ful not to disturb the places where others have already 
 spawned. In quiet by-pools you may find the gay male 
 stickleback guarding the nest which he has made of twined 
 fibres partly glued together with mucus. There the female 
 has laid eggs, but he has driven her forth : he will do all 
 the nursing himself. No approaching enemy is too large 
 for him to attack ; his courage equals his seeming pride. 
 When the youn^ are hatched, but not yet able to fend for 
 
 
no The Study of Animal Life part i 
 
 themselves, his cares are increased tenfold. It is hard to 
 keep the youngsters in the cradle. "No sooner has he 
 brought one bold truant back, than two others are out, and 
 so it goes on the whole day long." 
 
 We are not clever enough to understand why the males 
 among many fishes are so much more careful than the 
 females For the stickleback is not alone m his excellent 
 behavio'ir The male Chinese macropod {Polyacanthus) 
 makes .rothy nest of air and mucus, in which he places 
 his mates eggs. He, too, watches jealously over the brood, 
 and "has his hands— or rather his mouth— full to recover 
 the hasty throng when they stray, and to pack them again 
 into their cradle." Of all strange habits, perhaps that 
 is strangest which some male fish {e.g. Arius) have of 
 hatching the eggs in their mouths ; what external danger s 
 must have threatened them before this quaint brooding- 
 chamber was chosen ! Or is if not almost like a joke to see 
 
 the male sea-horse swelling up as 
 the eggs which he has stowed 
 away in an external pocket hatch 
 and mature, "till one day we 
 see emerging from the aperture a 
 number of small, almost transpar- 
 ent creatures, something like 
 marks of interrogation." Hut 
 . some female fishes also carry 
 
 S their eggs about, attached to the 
 ventral surface (in the Siluroid 
 fish, Aspredo), or stowed away in 
 a ventral pouch (in Solenostovui, 
 allied to pipe-fishes), arrange- 
 ments which recur among amphi- 
 FiG. as. — Sea-horse (Hippo- ^,;ans, but On the dorsal surface 
 
 campus guttulatus). (b rom , ^, ' , , 
 Evolution of Sex; after Atlas of the DOdy. 
 
 of Naples Station.) Amphibians, like fishes, to 
 
 which they are linked by many ties, are either quaint or 
 careless parents. Again, the males assume the responsi- 
 bilities of nurture. The obstetric frog {^lytes obstetnoim), 
 common in some parts of the Continent, takes the eggs from 
 
 
CHAP. VI The Domestic Life of Animals iii 
 
 his mate, winds them round his hind-legs, and retires into a 
 hole, whence, after a fortnight or so, he betakes himself to the 
 water, there to be relieved by the speedy hatching of his 
 precious burden. Even quainter is the habit of the male of 
 a Chilian irog{Rhinodenna darwinii), who keeps the eggs and 
 the young in a pouch near the larynx, turning a resonating 
 sac in a most inatter-of-fact way into a cradle. He is some- 
 what leaner after it is all over. It is interesting to notice 
 how similar forms and habits recur among animals of dif- 
 ferent kinds, like the theme in some musical compositions. 
 The spiral form of shell common in the simple, chalk-forming 
 Foraminilers recurs in the pearly nautilus ; the eye of a 
 fish is practically like that of many a cuttle, though the 
 two are made in quite different ways ; and an extraordinary 
 development of paternal care may signalise animals so 
 distinct as sea-spider, stickleback, and frog. 
 
 But we must not be unfair to the female amphibians. 
 Without doubt most of them are willing to be quickly rid 
 of their eggs or young, and as these are usually very 
 numerous, the mortality in the pools is of little moment. 
 In some cases, however, water-pools are less available 
 than in Britain, and then we find adaptations securing the 
 welfare of the young. The black salamander of the Alps, 
 living at elevations where pools are rare, retains her twin 
 oiibpring until more than half of the tadpole life is past. 
 They breathe and feed in a marvellous way within the 
 body of the mother, and are bom as lung-breathers. In 
 the case of the Surinam Toad {Pipa), the male places half 
 a hundred eggs on the back of the female, where they 
 become surrounded by small pockets of skiii, from which 
 the young toads writhe out fully formed. In two other 
 cases {Nototrema and Notodelphys\ the above somewhat 
 expensive adaptation, which involves a great destruction 
 of skin, is replaced by a dorsal pouch in which the eggs 
 hatch, an arrangement dimly suggestive of the pouch of 
 kangaroos and other marsupial mammals. 
 
 Fishes and amphibians are linked closely by their likeness 
 in structure, and, as we t,.ve seen, they are somewhat alike 
 in parental habits ; bui ixow great is the contrast between 
 
 Irti 
 
 
iia The Study of Animal Life fart i 
 
 the habits of birds and reptiles, in spite of their genuine 
 blood-relationship. Yet the python coiled round her eggs 
 is a prophecy of the brooding birds as in past ages the 
 flopping Saurians prophesied their sw.ft-wmged fl.gh . ^ The 
 sharpness of the contrast is also lessened by the fac* u,' <. 
 few birds, like the mound-builders, do not brood at a I , \vli.k 
 others, it must be confessed, are somewhat carde .. But, 
 exceptions and ciiminals apart, birds are so lav.sl, n, the. 
 love so constant i.i iheir carefulness, that it is difficuii t<. 
 speak of them without exaggeration. I am quite willing to 
 allow that they often act without thought (that is hall 
 the beauty of it) ; nor do I doubt that many spec.es 
 would have gone to the wall long since m the stioiggle of 
 life if the parents had not t„ken so much care of the young ; 
 but I would rather emphasise at present the reality that 
 they do sacrifice themselves for the sake of their young 
 to a most remarkable degree,.and spend themselves not for 
 individual ends, but for their offspring. .,,,.. 
 
 Before the time of egg-laying the birds build the.r nests, 
 eageily but without hurry, instinctively yet with some plas- 
 tidty, and often with much beauty. On the laid eggs, 
 whi-^h require warmth to develop, the mothers brood, 
 and though to rest after reproduction is natural, the brood- 
 ing is not without its literal patience. Among polygamous 
 birds the males are, as one would expect, more or less 
 carclc.s of their mates, but most of the monogamous males 
 are careful either in sharing the duty of brooding or m 
 supplying the females with food. After the eggs hatdi 
 the degree of care required vanes according to the 
 state of the young; for many are precociously energetic 
 and able to look after themselves, while others still requ.re 
 prolonged nurture. They need large quantities of food, 
 [o supply which all the energies of both parents seem 
 sometimes no more than adequate ; they may still require 
 o l2 brooded over, and certainly to be protected from 
 rain and enemies. After they are reared, they have o be 
 tr ht to fly, to catch food, to avoid danger, and a dozen 
 o a.ts. With what apparent love-willing and joyow 
 - s al' this done for them I 
 
MiiM 
 
 CHAP. VI The Domestic Life /Animals 113 
 
 Consider the cunning often displayed in leaving or 
 approaching the nest, in removing debris which would 
 betray the whereabouts of the young, or in distracting 
 attention to a safe distance ; remember, too, that some birds 
 
 
 Fii;. 26.— NcM of tail'ir-bird (prthotoinm heHettif). (AOer Firehni.) 
 
 Will shift cither eggs or yoiuig to a new resting-place when 
 extreme danger threatens ; estimate the energy spent in 
 feeding the brood, sometimes on a diet quite different 
 from that of adult life ; and acknowledge that the parental 
 instmrt is very deeply rooted, since fostering young not 
 their ouu may be practisc.l by orphaneil birds of both 
 i>tMs. Listen to the bird vvhi( h h is been bereaved, and tell 
 mc IS not the "lone singer wonderful, causing tears"? 
 
 riic female of the Indian and African hombill nests in 
 a hole in a tree, the entrance to which she plasters up so 
 that no room is left either for exit or entrance. The 
 
 1 
 
 i 11 
 
 .11 
 
 F ^ 
 
Tfu Study of Animal Life 
 
 PART I 
 
 114 
 
 Malays imagined that this was the work >f ,|^e J-l-s 
 male but it is the female's own domg. ^tie sus, 
 M^hTsays "securely hidden, safe from any carnivore 
 ^r m^Sievous ape or snake stealthily climbing, whde the 
 irfxlns him'self lovingly to bring h.s mate those 
 drfiehtfol things in which the tropical forest is nch-fruus 
 aW a 1, but occasionally a delicate mouse or juicy 
 C^ He flies with his booty to the tree and gives a 
 oTculiar knock, which his mate knows as his signal, and 
 ?h" "herbeak through the na-ow window welco^^^^g^^^^^^ 
 meal." At the end of the period of incubation. C. M Wood 
 forf says "the devoted husband is worn to a skeleton. 
 
 BSml. like men. have their vices, and birds, gener- 
 ally soTdeal i^ their behaviour, are sometimes criminal. 
 OmiAologists assure us that the degree of parental care 
 v^S^nofonly in neariv -related species, but also among 
 TrTberofthe same species. We need not ay muc 
 stress on the fact that a bird occasionally slips its egg 
 So a neighbour's nest, for when a partridge thus uses a 
 
 ^hLln^^'rough bed. or a V^^ ^^^^^ ^K^l^^^t^C^ 
 is likely enough that the mtruder had been disturbed 
 
 from her own resting-place when ^b«"% *° ^^^^ -^^J 
 approach something diflferent in the case of the American 
 SSrich (/?A.a). the female of which ^^^^^'^^^l^^^ 
 utilise a neighbour's burrow; nor does the owner seem 
 to oWect. for all the brooding is discharged by the mal 
 I^a^' t is no great art to be paUent and ^gn^--^ 
 
 know HS^'^Sibe7of females sometimes lay their eggs 
 
 ■" wra^s^glad to hear the cuckoo's call in spring that 
 we almost foi/et the wickedness of the voluble bird. Ih 
 ;:.rs have h?ped us. for they have generously .demised, n 
 fact idolised, the cuckoo, the "darhng f ^^V P^'^l;^ „ , 
 wandering voice babbling of sunshine ^^^f^^^'^^Xoo. 
 "sweet." nay more, a "blessed bird." But the cue k 
 harhoaxJ the p;>ets. for they are even worse than h.r 
 Tegwdary reputati^of being sparrow-hawks m d.sgu.se. 
 
CHAP. VI The Domestic Life of Animals 115 
 
 they are "greedy feeders," says Brehm, "discontented, ill- 
 conditioned, passionate fellows; in short, decidedly unamiable 
 birds." The truth must be told, the cuckoo is an immoral 
 vagabond, an Ishmaelite, an individualist, a keeper of game 
 "preserves." There are so many males that they have 
 perverted and thoroughly demoralised the females ; there is 
 no true pairing ; they are polyandrous. The birds are too 
 hungry for genuine love, though there is no lack of passion ; 
 while by voraciously devouring hairy caterpillars they have 
 acquired a gizzard-fretting feltwork in their stomachs, and 
 for all I know are cursed by dyspepsia as well as by a con- 
 stitutionally evil character. It is not quite correct to say 
 that the cuckoo-mother is immoral because she shirks the 
 duties of maternity; it is rather that she puts her young out 
 to nurse because she is immoral.^ The so-called " parasitic " 
 trick is an outcrop of an egoistic constitution which shows 
 Itself m many different ways. The young bird, "a dog in 
 the manger by birth," evicts the helpless rightful tenants 
 whether they are still passive in the eggs or more assertive 
 as nestlings, and as he grows up a spoilt child his foster 
 parents lead no easy life. But though the poet? have been 
 hoaxed, I do not believe that the nurses of the fledgling 
 are; it seems rather as if the naughtiness of their 
 changelmg had some charm. 
 
 Of course there is another way of looking at the cuckoo's 
 crime. It is advantageous, and there is much art m the 
 well-executed trick by which the mother foists her several 
 eggs, at intervals of several days, into the nests of various 
 birds, which are usually insectivorous and suited for the 
 upbnngmg of the intruder. I think there is at least some 
 deliberation m this so-called instinct. Nor should one forget 
 that the mother occasionally returns to the natural habit of 
 hatching her own eggs,--£i pleasant fact which several trust- 
 worthy observers have thoroughly established. Still, in 
 spite of the poets, the note of this " blessed bird » must be 
 regarded ^ suggestive of sin I 
 
 whkhil !I«.''TJ1 T*" "***'" '^** ^ *'*^«^ occasionally used word, 
 do „5.^ir^ !^*'"^ ***"*'*• * "-y '»»««'«« »*y definitely that I 
 «tS^^^!L*' "* ^^^^^ in crediting animals with morU 
 wihet , or. indoed, any conceptions. ^ 
 
 j^a*,:' 
 
 '*"j(L.t .-^,, 
 
^mMk 
 
 The Study of Animal Life 
 
 PART I 
 
 ii6 
 
 There IS much to be said about the domestic life of 
 animaU-their courtship, their helpful partnership, and the.r 
 parrtage-but perhaps I have said enough to jnduce you 
 fortSnk about these Things more carefully. Many of the 
 deep St problems of biology-the origin and evolution o 
 sex the delation of reproduction to the individual and to the 
 spec es-should be considered by those who feel themselves 
 naSly inclined to such inquiries ; moreover, m connection 
 "h our own lives, it is profitable to investigate among 
 ri mals the different grades of the love of "^^^^^./^^ the 
 Son between the rate of reproduction and the degree o 
 development. First, however, it were better that we should 
 waTchTe ways of animals and seek after some sympathy 
 wkh them, that we may respect their love, and salute hem 
 nf with stone or bullet, but with the praise of gladdened 
 
 ^^'Ruskin's translation of what Socrates said in regard to 
 the halcyon is suggestive of the mood in which we should 
 consider these things. 
 
 ^"^iiSr^ Not great ; but it has received great honour from the 
 all others in their calmness, though in the mids of °™; 
 
 Sir.r.ol.'r.hinr»aTt ho„ou? .ho„ h„. for i. r™ 
 
 ""S^'li.« " It is nghlly due imlMd, O Socralcs, for O.er. i. 
 . SZtlJl .hU.U for men »d women, rn .he, ..l- 
 
 '"l^^'r-Sh'Ilt « no. then ».«.. .he h.lc,on, .nd « go W 
 to the city by the sands, fo' »l « time ? 
 
 w^m^ 
 

 CHAPTER VII 
 
 it 
 
 THE INDUSTRIES OF ANIMALS 
 
 I. Hunting— 2. Shepherding— t,. Storing— a,. Making of Homei 
 
 5. Movements 
 
 It is likely that primitive man fed almost wholly upon fruits. 
 His early struggles with animals were defensive rather than 
 aggressive, though with growing strength he would become 
 able for more than parrying. We can fancy how a band of 
 men who had pursued and slain some ravaging wild beast 
 would satisfy at once hunger and rage by eating the warm 
 flesh. Somehow, we know, hunting became an habitual art. 
 We can also fancy how hunters who had slain a mother animal 
 kept her young alive and reared them. In this or in some 
 other way the custom of domesticating animals begar, and 
 men became shepherds. And as the hunter's pursuits'were 
 partially replaced by pastoral life, so the latter became in 
 some regions accessory to the labours of agriculture, with 
 the development of which we may reascnably associate the 
 foundation of stable homesteads. Around these primary 
 occupations arose the various human industries, with division 
 oflabour between mnn and woman, and between man and 
 man. 
 
 Thesft human industries suggest a convenient arrange- 
 ment for those practised by animals. For here again there 
 are hunters and fishers— beasts of prey of all kinds— pursuing 
 the chase with diverse degrees of art ; shepherds, too, for some 
 ants use the aphides as cows ; and farmers without doubt. 
 
 
1 18 TJie Study of Animal Life part i 
 
 if we use the word in a sense wide enough to include those 
 who collet, modify, and store the various fruUs of the 
 
 """t; illustrating these industries, I shall follow a charming 
 volume by Fr J^ric Houssay. Les Industries des Ammaux, 
 
 ^^t' a^W-Of this primary activity there are many 
 kinds The crocodile lies in wait by the ^^ucer's edge, 
 ^python hangs like a ^an fro^ t.e Uee, ^t^^^ 
 
 fSr -Se angler-fish ^Lophius piscatorius) is some- 
 what protectively coloured as he lies on the sand among 
 what Proiecuvc y filaments dangle, and 
 
 the seaweeds; on nis oacK uu.^ 
 
 nossiblv suggest worms to curious little fishes ^^nlc^, 
 vrturing nSr, areengulfed by the angler's horrid maw, 
 
 ^h^^zi :tr Ttr^ j^. 
 
 ,1- - Thmir of the Indian Toxctes, a nsn wnun 
 
 SS&,^e':^>nra%s^rcr^;tt 
 
 ^«1ref.sSe (i». J^Wor), which spite .ts v.cum 
 
 tions of the Amazon ants. AU sircngui «!•« 
 Thst^nding, ,h. *- J'jf- ^; "^nr.- <^«'« 
 
CHAP. VII The Industries of Animals 
 
 119 
 
 are often utilised, the weak combine against the strong, 
 and the victims of even the strong carnivores often show 
 fight valiantly. 
 
 2. Sbepherding. — Although the ants are the only animals 
 which show a pastoral habit in any perfection, and that 
 only in four or five species {e.g. Lasius niger and Lasius 
 brunneus), ! think that the fact is one about which we 
 may profitably exercise our minds. I shall follow Espinas's 
 admirable discussion of the subject. 
 
 We may begin with the simple association of ants and 
 aphides as commensals eating at the same bountiful table. 
 But as ants discovered that the aphides were overflowing 
 with sweetness, they formed the habit of licking them, the 
 aphides submitting with passive enjoyment. Moreover, as 
 the ants nesting near the foot of a tree covered with 
 aphides would resent that others should invade their pre- 
 serves, it is not surprising to find that they should continue 
 their earthen tunnels up the stem and branches, and should 
 eventually build an aerial stable for some of their cattle. 
 Thither also they transport some of their own larvae to be 
 sunned, and as they carried these back again when the 
 rain fell, they would surely not require the assistance of an 
 abstract idea to prompt them to take some aphides also 
 downstairs. Or perhaps it is enough to suppose that the 
 aphides, by no means objecting to the ants' attentions, 
 did not require any coaxing to descend the tunnels, and 
 eventually to live in the cellars of the nests, where they 
 feed comfortably on roots, and are sheltered from the bad 
 weather of autumn. In autumn the aphides lay eggs in 
 the cellars to which they have been brought by force or 
 coaxing or otherwise, and these eggs the ants take care of, 
 putting them in safe cradles, licking them as tenderly as 
 they do those of their own kind. Thus the domestication 
 of aphides by ants is completed. 
 
 Now what is the theory of this sljepherding ? (1) We 
 have no warrant for saying that the ants have deliberately 
 domesticated these aphides, as men have occasionally 
 added to the number of their domesticated animals. It 
 does not seem to me probable that even primitive man 
 
 •iff 
 
 1|i 
 
 m 
 
 
 •^1 
 
 !■#! 
 
 'W 
 
 lMP?W-WfiS^ 
 
The Study of Animal Life 
 
 PART I 
 
 &i5r 
 
 I30 
 
 domestications. (2) Nor is it u y dominant 
 
 began i"; -^^^ '^^^^^^ selection. 
 
 V l^ Jw! is more a luxury than a necessity, and 
 >°L not Ukdy to have been e^volved before the estab- 
 !• hment of the sterile caste of workers, who have no means 
 
 lV^!n»., mistake of an individual worker ant, but the 
 Imcle oT he community's progressive development ,n 
 "TnteUectual somnambulism," helped in some -neasur' ^j 
 the sSsh habits of the aphides. And, .f you wish, the 
 ferula C be added, " which was justified m the course 
 
 °' Tst«S-Not a few animals hide their prey or |he;r 
 eathertoT^d with marvellous memory for locahnes 
 Sum to them after a short time. But genmne stonng 
 wTmore Snt future is illustrated by the squirrels, wh.C, 
 Wde the"t«rrls like misers. Many mice and other rodents 
 do likewl^and in some cases the habit seems to become 
 f si« :f?»e, so large are the supplies la,d >n aganjst h 
 :«t*r'« .irarcitv Very quaint are the sacrc scaraDees 
 X'L ""^^^^^^^ of dung to their holes, an 
 
 Ifme^imercollect supplies at which they gnaw for a couple 
 of weeks Some anfs'(..^. Atta barhara) accumulate stores 
 of ^afn occasionally large enough to be worth robbing 
 and^heti is no doubt that they are able to keep the se d 
 from germinating for a considerable t-e, while thysto 
 he germination after it has begun ^Y gnawing off pbmd 
 Ind radicle and drying the seeds afresh. Dr. M Cooks 
 ^count of the agricdtural ant of Texas {Pogomynnex 
 nrJ.) gives even more marv.Uous illustrations 
 famitng habits, for these ants to a certain extent at least 
 cuSe in front of their nests a kind of grass with a ncc 
 
 ^-%^^=^!-^ 
 
CHAP. VII The Industries of Animals 121 
 
 like seed. They cut off all other plants from their fields, 
 aiid thus their crops flourish. 
 
 But animals store for their offspring as well as for 
 themselves. The habit is very characteristic of insects, 
 and is the more interesting because the parents in many 
 cases do not survive to see the rewards of their industry. 
 Sometimes, indeed, there is no industry, for the stores of 
 other insects may be utilised. Thus a little beetle {Sitaris 
 muralis) enters the nest of a bee {Anthophora pilifera) and 
 lays its eggs in the cells full of honey. More laudable are 
 the burying-beetles {Necrophorus), which unite in har- 
 monious labour to bury the body of a mouse or a bird, 
 which serves as a resting-place for their eggs and as a 
 larder for the larvae. The Spkex wasp makes burrows, 
 in which there are many chambers. Each chamber con- 
 tains an egg, and is also a larder, in which three or four 
 crickets or other insects, paralysed by a sting in the nervous 
 system, remain alive as fresh meat for the Sphex larva 
 when that is hatched. After the Sphex has caught and 
 stung its cricket and brought it to the burrow, it enters 
 at first alone, apparently to see if all is right within. 
 That this is thoroughly habitual is evident from Fabre's 
 experiment. While the Sphex was in the burrow, he stole 
 away the paralysed cricket, and restored it after a little ; 
 yet the wasp always reconnoitred afresh, though the trick 
 was played forty times in succession. Yet when he substi- 
 tuted an unparalysed cricket for the paralysed one, 
 the Sphex did not at once perceive what was amiss, but 
 soon awoke to the gravity of the situation, and made a 
 fierce onslaught on the recalcitrant victim. So it is not 
 wholly the slave of habit. 
 
 4- Ma ki n g of Homes. — Houssay arranges the dwellings 
 of animals in three sets — (a) those which are hollowed 
 out in the earth or in wood; (p) those which are 
 constructed of light materials often woven together ; and 
 (f) those which are built of clay or similar material. We 
 may compare these to the caves, wigwams, and buildings 
 in which men find homes. 
 
 Burrows are simplest, but they may be complex io 
 
 ■--. 
 Ifri 
 
 5». 
 
122 
 
 The Study of Animal Life 
 
 V.\RT 1 
 
 details Those of the land-crabs (Gccardnus), <h'= J"";!- 
 c S^S bees (Xy,oc.p.y .he sand-n,ar,ens t c „a™ , ; 
 rabbitt the prairie dogs, ilUrstrale th,» kmd of dwe.l.,r„ 
 
 ™XtSr:.SS'°o\.W«.) weaves and glues 
 
 FIG. ,7.-SwaUows iflulidonaria urkka) and their nest. (After lirch.n.) 
 
 the leaves and stems of water-plants ; the minutest mouse 
 
 ir/xs SeT -^' tosr;!"'-- 
 
 ""' WbuMings, the swallows' nests by the window, a.ul .k 
 
 
CHAP. VII The Industries of Animals 
 
 123 
 
 paper houses which wasps construct, are well known ; but we 
 should not forget the architecture of the mason-bees, the 
 gre.it towers of the termites, and the lodges of the beavers. 
 
 Perhaps I may be allowed to notice once again, whrit I 
 have suggested in another chapter, that while many of the 
 shelters which animals make are for the young rather than 
 for the adults, the hne of definition is not strict, and some 
 which were nests to begin with have expanded into homes 
 
 an instance of a kind of evolution which is recognisable 
 
 in many other cases. 
 
 5. Movements. — But animals are active in other ways. 
 All their ways of moving should be considered — the marvel- 
 
 FiG. 28.— Flight of crested heron, ten images per second. (From Chambers's 
 EncycloJ>. ; after Murey.) 
 
 lous flight of birds and insects, the power of swimming 
 and diving, the strange motion of serpents, the leap, the 
 heavy tread, the swift gallop of Mammals. All their 
 gainbolings and playful frolics, their travels in search of 
 food, and their migrations over land and sea, should be 
 reckoned up. 
 
 Most marvellous is the winged flight of birds. As a 
 boat is borne along when the wind fills the sails, or when 
 the oars strike the water, and as a swimmer beats the 
 water with his hands, so the bird beating the air backwards 
 with its wings Is borne onward in swift flight. But the 
 air is not so resistent as the water, and no bird can float in 
 the air as a boat floats in the water. Thus the stroke has 
 
 \n 
 
 
 'II 
 
 ■J 
 
 Hi 
 
 
mmmi 
 
 ^^wpMiiivg 
 
 i^w:0!m 
 
 124 T/ie Study of Animal Life part 1 
 
 a downward as well as a backward direction. When there 
 is more of the downward direction the bird rises, when there 
 is more of the backward direction it speeds forward ; but 
 usually the stroke is both downwards and backwards for 
 the lightest bird has to keep itseir from falling as it fl.es. 
 The hoUowness and sponginess of many of the bones com- 
 bine strength of material with lightness, and the balloon- 
 like air-sacs connected with the lungs perhaps help the 
 birds in rising from the ground; but, buoyant as many buds 
 are, all have to keep themselves up by an effort. But he 
 possibility of flight also depends upon the fac that the 
 raising of the wing in preparation for each stroke can be 
 accomplished with very little effort ; the whole wing and 
 its individual feathers are adjusted to present a^maxinuun 
 surface during the down-stroke, a minimuin surface dunng 
 the elevation of the wing. There are many different kmds 
 flight, which require special explanation— the fluttering 
 humming-birds, the soaring of the lark, the masterful 
 hovering of the kestrel, the sailing of the albatross. The 
 effortless sailing motion of many birds is comparable to 
 that of a kite, » the weight of the bird corresponding to the 
 tail of the kite ;" it is possible only when there is wind or 
 when great velocity has been previously attained. 
 
WW.'^^': 
 
 PART II 
 
 THE POWERS OF LIFE 
 
 CHAPTER VIII 
 
 VITALITY 
 
 'J 
 
 I- «! 
 
 I. The Task of Physiology— 2. The Seat of Life— i. The Eturgy of 
 Life — 4. Ceils, the Elements of Life — 5. The Machinery oj 
 Life — 6. Protoplasm — 7. Thi Chemical Elements of Life — 8. 
 Growth — 9. Origin of Life 
 
 I. The Task of Physiology. — So far we have been 
 considering the ways of living creatures, as they live and 
 move, feed and grow, love and fight ; as they build their 
 homes and tend their young. We shall now turn to 
 the inner mysteries, and seek, so far as we may, to fathom 
 the wisdom of the hidden parts. We shall describe the 
 machinery — the means by which the forces of life cause 
 those movements by which we recognise their presence. 
 
 This study is called physiology ; and the plan of our 
 sketch of present knowledge will be as follows : We shall 
 first try to realise what we mean by life ; we shall then 
 limit ourselves to the consideration of certain kinds of life, 
 and attempt to make plain in what parts of all living 
 creatures are the forces of life most active. Having done 
 this, we shall describe the life processes of the simplest 
 creatures, and then those of the higher animals. 
 
 It is not easy to say clearly what we mean by li^" ; but 
 we recognise as one of its characteristics the pt ^r of 
 movement. 
 
 
 ,'r; 
 
 ■yrxi 
 
126 The Study of Animal Lift partu 
 
 Stiil, this gives no distinction between the blowing of 
 wind and the life of man ; but the other charactenstics of 
 life wiU be realised as we proceed in our ^^^"^^ V^ 
 certain that without movement there is no life. Further 
 thought may lead us to define life as that 'complex of 
 forces which produces form." Thus the sta- like crystals 
 of a snowflake, the diamond drops of dew, the over- 
 shadowing mountains, wodd all be '^naged in our 
 minds as living, though of more lowly life than the 
 Uchens of the bare hill-tops, the grass of the plains, or man 
 himself. We have no space here to trace the connections 
 between such an idea and the beliefs of all simple peoples, 
 and the inspirations of aU poets, but the similarity is 
 evident, and the usefulness in philosophy of such general- 
 ised conceptions is great. 
 
 But the physiology which we shall sketch here will be a 
 narrower one; it will be confined to the life of plants and 
 animals, and we shall attempt to show precisely how that 
 life is separated from the life of the dust and of the air. 
 
 2 The Seat of Life.— Now in what parts within the 
 living body are the life forces most actively at work ? 
 
 When we look at any living creature we are all too 
 willing, even if the wonder of life stirs within us, to remain 
 satisfied with a vague apprehension of a mystery. It is 
 strange that so many generations of men passed away 
 befoi- any steps were taken towards a conception of the 
 intimate material processes of life and growth and death 
 The moving train has been watched, but the engine and 
 the stoker have been almost unnoticed. 
 
 Let us consider the growth of a tiee. The outward manner 
 of its growth we can observe, a few superficial details of its 
 inner life we already know, and of this knowledge we may 
 look fo- great expansion, but the ultimate processes of its 
 life are still a complete mystery to us. 
 
 The tree is alive, but is A all alive ? Cut a stake from 
 its heart and olant it in the ground ; it will not grow, and 
 shows no sig..J of life, but we are not puizled ; the tree, wc 
 think, can only live as a whole, and we know how easily 
 most Uving things are killed by local injuries. But if we 
 
CHA». VIII 
 
 Vitality 
 
 ta7 
 
 cat a stake from the outer part of the tree, leaving the 
 bark on, and set it in the ground, it may happen that buds 
 will appear, pushing through the bark, and stretching out 
 into shoots. 
 
 There is a mystery for us to begin with : some parts of 
 a tree may have a life of their own. Indeed, we all know 
 that gardeners do not rear geraniums and other plants from 
 seeds, but from cutti igs. Potatoes, as we know, will give 
 origin to new plan .3, and even small parts of potatoes will 
 do so. Roses are grafted into the stems of the wild brier, 
 and in this way two life -currents are mingled. We may 
 remember, too, that all seeds are only parts that have 
 become separated from the parent plant. We ourselves, 
 formed in the darkness of the womb, were separated at 
 birth from the mothers who bore us. 
 
 Let us think of the seeds of plants for a little. Formed 
 in the warmth and brightness of the summer sun, ripened in 
 the glow of autumn, they fall to the ground, are carried 
 hither and thither bv trickling runlets of water, by the 
 winds, by animals, and. scattered over new pastures. 
 Through the long chill of winter they remain asleep ; but 
 not dead, — slow preparation is being made for the new 
 day. With the warm winds of spring — when the birds 
 come back to us and sing their first songs of love and 
 courtship — the countless buds of the woods, the gardens, 
 and the hedgerows, all the seeds we sowed in the autumn, 
 all the com we scattered in the first hours of the new 
 morning, awake ; the buds burst, the tiny leaves unroll ; in 
 the seeds there is a great activity, — the slender shoots 
 stretch forth — spring passes into summer — and we await the 
 harvest. 
 
 3- The Eneivy of Life.— What is the cause ot this 
 strength of life ? How is it that in an acre of forest tons of 
 solid matter are lifted high into the air, while thf branches 
 waving under the blue sky seem to enjoy the bri^^^ iness of 
 the sun after the gloom of winter ? 1 his assertion of the 
 poets of the gladness of nature at the springtime is no mere 
 wandering fancy, it is simple truth ; the intensity of life at 
 that time is due entirely to the greater warmth of the air 
 
 
 / 
 
 X 
 
,a8 The Study of Animal Life 
 
 reason why '^ '"", . , creatures, that consciousness 
 3S°S.;"b^i«^ 1^- «iO.' inc^ased vigour or 
 
 ;;::^aX. "x^n^r 'energ, of sUJ^n jh.H by 
 
 --hanic^' .rsrj rr>,"t.*:uera"5 
 
 ;S' .h m^inTi" *e plant, b, which ^h. en.g, 
 
 ^ the sun', mys is transmuted ;>»o W'' J^S 
 
 answer to this riddle '^» 'J!"JZ'a J wUh a water 
 
 r ''^""u'roperatd «V XSmy stuff agai^ 
 shmy sap. If we open a duu ^.^ 
 
 under the l>ark of '«■=' ^.f * l^'teTnid-d. in all 
 .he tissues of a butt, and mgr^.nss« ^^ .^^^^^^^^ 
 
 lifrJ^afw^^ fin* vha we may call for the moment 
 
 li!, sTmy^'sT; while in the ha.. >-'„ P^ ° „f „ ^i 
 which we know can hve no more, we »";^ "°;" J". ^^ 
 
 Z^^Z^^^l rJorenTne. - we do ™. 
 
 •"'T'Sli."S/S»*' of Uf..-1-e. us ,ea.e .ho .aes 
 now'foTT'lMe, and turn to .he simplest of all 1> 
 ^«.,rM which Hve in water and In damp places. Ihcj 
 S^'r LthUt only a few of the larger ones can be . 
 
 »•«« .n#.fka movine about in the water m whicn mcy 
 L 'BuHhe; cTnXf seen quite easily with a micrcscop.^ 
 We find them to be little transparent drops f J « 
 matter. They are not really drops; many of them ha>e 
 
 iPx-msacrW^.r^^Xi:- "Jt;. 
 
 '^^r^pmrk^-^ 
 
CHAF. VIII 
 
 Vitality i«9 
 
 distinct shapes, others constantly change their form. They 
 move, indeed, by a kind of flowing ; one part of their body is 
 pushed out and a part on the farther side drawn in. Some 
 of these lowly creatures have skeletons or shells of lime or 
 of flint. Great numbers of these shells, when the little 
 inmates are dead, form beds of chalk and ooze. Now 
 all living creatures begin life in this way; at first they 
 are tiny masses of a jelly-like translucent stuflT. Each 
 mass gets a skin or surrounding wall ; if fed, it grows 
 hrger, and a wall is built up inside it, making its house a 
 two-roomed one. This process goes on and on ; the whole 
 mass grows larger and larger, and becomes divided up into 
 a corresponding number of compartments. The chambers 
 are not quite separated ; there are always holes left in the 
 walls, through which strands of the jelly-like stuff pass, and 
 so all of them are connected. The divisions in each 
 separaie kind of animal or plant take place in a special 
 way, until at last the whole body is built up, with all its 
 peculiarities of form and internal arrangement. The cells 
 of an animal's body do not, however, form walls as definitely 
 as do those of plants. 
 
 In an ordinary plant there are millions of those com- 
 partments ; they are called cells, from their likeness in 
 general appearance to the cells of a honeycomb ; and the 
 enclosed stuff that we have spoken of as jelly is called 
 protoplasm, because it is believed that the first living things 
 that were formed were little drops of jelly-like stuflT, not 
 unlike that within the cells, or composing the animalculae in 
 water. Protoplasm, wherever it occurs, from the highest 
 to the lowest forms of life, is supposed to have, within 
 certain limits, a similarity of nature. 
 
 In some plants the cells are large enough to be visible 
 to the naked eye, but the cells of most plants and animals 
 are so small that they can only be seen with a microscope. 
 
 We can now give a complete answer to the question, 
 What parts of a tree are alive ? It is only the protoplasm 
 of the cells. The walls of the cells are more or less dead. 
 As the cells grow older and larger, and the walls become 
 thicker, the amount of protoplasm within gets relatively 
 
 K 
 
The Study of Animal Life 
 
 FAKT II 
 
 ^^ 
 
 less • at last it slowly dies and withers awg^; the ceUs are 
 ^iiMtr and that is why the stake cut from the old hard 
 '^T£e toddle of the t Jee could not grow.-it was quite 
 
 ^^*f The Machinery of Idfe—We have found that, in 
 
 .om*; ^ Ae^rotoplasm within the cells is the machmery 
 
 of^L For sLplicity, we shall speak of protoplasm as 
 
 ?•«;%«»«« •Ais uUng matter in plants is such that 
 
 S t^^nn^eUrgy'of sunlight into potential en.^ 
 
 l.i'^mnlicated substances such as wood. This trans- 
 
 ? Tnn^lnerev is one of the chief labours of plants in 
 
 Horir A SSt d^l of the energy that reaches the.r 
 
 formatter is W for their own upward growth ; so that. 
 
 rweSJJ^ore, thousands of 1 >ns of matter are every 
 
 Tearover every acre of forest, raised high into the air. 
 
 ^nlimals^he Uvin^ ^c^^^^^^ X^ s^/h 
 
 f:Z:X:,o.^:^^trS^^or.^ - these is used by it 
 I^^llf about and so transformed into energy of motion. 
 CSSsIs chiefly shown in the storage of energy, 
 Xe life^o? aSm2s in the use of that store. Chiefly we say, 
 for itits X move to a slight extent; as a whole, when 
 hey tw^etround a tree or bend towards the sun ; and m 
 h'fr wS^ when the sap rises and falls. Animals also, to a 
 St^nV build up substances of high potential energy. 
 ^So S lis certain, but when we inquire by what an-angc 
 ment of parts the liv ng matter is able to be a machme for 
 r^isfo^ation of energy, we are unable to fo- any co. 
 xDc «*t discovery of the cells and their living 
 
 Sd fte nTessary physical condition,, arguing from * 
 
 Z .^vitie. of .h. living ■""'•'"nhr^U tht s«^ 
 from the stnictural arrangements of the ceUs , '"'J ' f; 
 ^ that the living matter, a part wuhm « "« '« 
 SScteus, and the cell-wall, were m A«™«''" *« Pf^„ 
 a mach ne, and that the various activities of the cells w«e 
 SuT^TlH^ing shapes of wall, and dispo«,t.on of, « ™.* 
 puts. It WM soon shown, however, that the wall «as "» 
 
CHAP. Till 
 
 Vitality 
 
 131 
 
 a necessary part of the living matter, and that the nucleus 
 did not always occur. The cell is a machine, not in virtue 
 of the disposition of its visible parts, but as a consequence 
 of the arrangement of its molecules. We know this much 
 about the living machinery, that it is far more perfect 
 than the machinery of our steam-engines, the perfection of a 
 machine being measured by the relation between the energy 
 which enters it and that which leaves it as work done. 
 
 «« Joule pointed out that not only does an animal much 
 more nearly resemble in its functions an electro-magnetic 
 engine than it resembles a steam-engine, but also that it is 
 a much more efficient engine ; that is to say, an animal, 
 for the same amount of potential energy of food or fuel 
 supplied to it— call it fuel to compare it with other engines 
 —gives you a larger amount converted into work than any 
 engine which we can construct physically," And Joly has 
 expressed the contrast between an inanimate material 
 system and an organism as follows : " While the transfer 
 of energy into any inanimate material system is attended 
 by effects retardative to the transfer and conducive to dis- 
 sipation, the transfer of energy into any animate material 
 system is attended by effects conducive to the transfer 
 and retardative of dissipation." 
 
 It is from protoplasm that we must start in our study 
 of living machinery ; let us see how far we can attain to 
 exact conceptions of its nature. We will first describe 
 shortly what is known as to the structure of protoplasm 01 
 living matter, chiefly to show how hopeless is any attempt 
 at a solution of the problem in terms of visible structure. 
 The powers of the microscope are limited by the physical 
 nature of light, and that limit has already nearly been 
 reached ; and yet we know the structure of matter is so ex- 
 cessively minute that within the compass of the finest fibre 
 visible with the microscope there is room for th- most intri- 
 cate structural arrangements. 
 
 6. Protoplasm.— Protoplasm used commonly to be de- 
 scnbed as a structureless mass ; we now know that it often 
 ^ structure somewhat like a heap of network. It is a 
 complex of finely-arranged strands, with knots or sweUings 
 
 'ia'fjsis^ 
 
,3a The Study of Animal Life part n 
 
 at the junctions of the strands, and with in each cell, one 
 nr more central and larger swellings, probably of a highly 
 sLda Used nSure, called nuclei. The size of the meshes 
 vE and they are filled "now with a fUud, now wjth a 
 mTre solid substance, or with a finer and more dehcate 
 network, minute particles or granules of vanable sue be.ng 
 someUmes lodged in the open meshes, sometimes deposited 
 
 identkal in refractive power with the bars or films .,f he 
 network, that the whole substance appears ho,„ogenc^^^^^ 
 The only means we have of getting any further kno.le 
 of this arrangement is by staining U wuh various d>cs and 
 observing the effects of the dyes upon the vanous part. 
 " A^l with various staining and other reagents leads to 
 
CHAT, irtti 
 
 Vifa/ify 
 
 «33 
 
 the conclusion that the substance of the network is of a 
 different character from the substance filling up the meshes. 
 Similar analysis shows that at times the bars or films of the 
 network are not homogeneous, but composed of different 
 kinds of stuff; yet even in these cases it is difl5cult, if not im- 
 possible, to recognise any definite relation of the components 
 to each other such as might deserve the name of structure." 
 Plainly there is not much light to be got by further investi- 
 gations in this direction. Ordinary chemical analysis, too, 
 is of little avail ; for how can we say what parts of the 
 mass are alive, even if we could separate part from part ? Is 
 it only the meshwork that is really living matter, or are the 
 granules part of it, or are the fluid contents the chiefly vital 
 substance ? 
 
 Let us turn now to the activities of the living stuff, and 
 see what we can learn from them. We have already spoken 
 of one of the activities of living matter, especially of plant 
 protoplasm, that of surrounding itself with a wall Now we 
 might at first be inclined to suppose that the wall was simply 
 due to a hardening and drying of the soft substance at those 
 places where it touched the air. It is possible that that may 
 have been the stimulus which caused, as a reaction, the 
 wall-making at the dawn of life, and which may still have 
 some connection with it ; but what we have to take note of 
 is the fact that the walls, as they are made by the higher 
 plants, have always a definite structure and chemical natur . 
 
 If we examine the cells of the leaves of a plant growing 
 in the sunlight, we find the green colouring matter to be 
 generally collected in little rounded masses. Looking more 
 closely, we find it to be the fluid which fills the meshwork 
 of the masses. At certain points in the meshwork we find 
 minute masses of starch constantly being formed. They seem 
 to pass along the strands and collect in the centre of the net- 
 work, until quite a large mass of starch is accumulated there. 
 If we examine the plant at night, some time afcer darkness 
 has set in, we find no traces of starch in the cells of the 
 Icares, There is evidence that the starch has been trans- 
 formed into sugar, and can then, by osmotic and perhaps 
 by other processes, be removed from the leaves, and 
 
;z TOar«^scscXEK»trS»i~:. 
 
 134 TAe Study of Animal Lift mm u 
 
 carried by -the vessds to aU parts of the plant. So we get 
 a first notion of how a plant is fed. Starch is a com- 
 pound containing carbon and the elements of water. The 
 carbon, we know, comes from the carbonic acid of the air; 
 the water is absorbed by the roots from the soil. In some 
 way the Uving matter of the cells, by means partly of the 
 green colouring matter, is able to transform the energy of the 
 sun's rays into potential energy of a combustible substance 
 
 starch ; so we get clear evidence of a machinery for the 
 
 transformation of energy. We have taken a plant as our 
 example throughout, partly because the cells are more 
 evident than in anunals, and partly because the chemical 
 processes give evidence of a transformation of kmetic mto 
 potential energy more clearly than do those of animals ; for 
 the animals eat the plants, and so by using the potential 
 energy of plant substance are able to live and move. 
 
 We have now some idea of the sources of the energy of 
 life. Plants get their food from the air by their leaves, and 
 from the soil by their roots, which absorb water and salts 
 dissolved in water. By aid of the energy of sunlight they 
 build these up into complex substances, which they use for 
 the growth of their living matter, for the formation of sup- 
 porting structures, and for other purposes. Animals eat 
 these substances. They build up their own bodies of living 
 matter and supporting structures, and they move about. 
 
 In order to get a clearer notion of the nature of living 
 matter we must attempt to trace the manner in which these 
 various substances are built up. We have first to discover 
 what arc the substances that are made. In all living 
 creatures there are, in addition to water and salts, such as 
 common salt and soda, three groups of stuffs :— ■ 
 
 Carbohydrates, such as starch and sugar, made of carbon 
 with hydrogen and oxygen in the same proportions as they 
 
 occur in water ; ' , , .c 
 
 F«/j— substances containing the same three elements, 
 
 but with a smaller proportion of oxygen ; 
 
 /»«?/«<&— substances containing always carbon, hydrogen, 
 oxygen, and nitrogen, with a small percentage of sulphur. 
 
 The constitution of protcids is difficult to determine. 
 
cbjlT. Tin 
 
 Vitality 
 
 «3S 
 
 The above elonents are always present, and in proportions 
 which vary within narrow limits; but in addition to 
 these substances there seem to be always present others 
 which, wheti the proteids are burnt, remain as ash in the 
 form of salts chiefly chlorides of sodium and potassium, but 
 also small quantities of calcium, magnesium, and iron, as 
 chlorides, phosphates, sulphates, and carbonates. The mole- 
 cule of a proteid must be very complex ; thus that of albumen 
 is, at its smallest, Cggg, H^gj, N^^,, Ogg, S^; most probably it 
 is some multiple of this. 
 
 The food-stuflFs of plants, then, are salts, water, and car- 
 bonic acid, and a certain amount of oxygen. Of these, by 
 means of the sun's energy, they build up complex substances 
 — carbohydrates, fats, proteids, which, with salts, water, and 
 oxygen, serve as the food of animals. The living matter, 
 the machinery by which all this is done, is, if it can be 
 classed at all, a proteid. But this only means that all 
 living matter contains the five essential elements and some 
 others which in the ash exist as salts. 
 
 The various services which the different food-materials 
 are set to within the body will be described later, when we 
 are considering the details of the animal economy. Here 
 we shall take note of the elements that enter into the 
 construction of the food-stuffs. 
 
 7. The Chemical Elements of Life. — There are sixty- 
 eight elements to be found in varying abundance upon the 
 earth, but by analysis of the food-stuffs and of living matter 
 itself, we find that only twelve of these occur with any con- 
 stancy in oi:ganisms. They are carbon, hydrogen, oxygen, 
 nitrogen, sulphur, phosphorus, chlorine, potassium, sodium, 
 calcium, magnesium, and iron. 
 
 Now nine of these elements form sixty-four per cent by 
 weight of the earth's crust; while aluminium and silicon, 
 substances that are only very occasionally found in living 
 creatures, form thirty-five per cent, being the chief consti- 
 tuents of quartz and felspar, sand and clay, in short the 
 greater part of all rocks. All the other elements, three of 
 which — hydrogen, nitrogen, and phosphorus — enter into 
 life, form the remaining one per cent 
 
13* 
 
 The Study of Animal Life part n 
 
 Since the ultimate analysis of the objective side of life 
 seems to show that life is to be pictured as matter in an 
 unstable and constantly altering condition, it will be of 
 interest to find the conditions that determine which of the 
 elements are to take part in it. 
 
 It seems that matter in order to enter into life must be — 
 
 (i) Common, (2) mobile, that is capable of easily 
 entering into solution or becoming gaseous, and (3) capable 
 of forming many combinations with other elements. 
 
 Nine of the elements fulfil the first condition ; a tenth, 
 nitrogen, is the chief constituent of the atmosphere; 
 while hydrogen is present everywhere in water. Why do 
 not aluminium and silicon take their share in life ? Because 
 they do not fulfil conditions (2) and (3). Their oxides are 
 quartz and aluminia, two of the hardest substances known. 
 Emery and ruby are two forms of aluminia ; while the oxide 
 of carbon, the source of all the carbon used in life, is a gas. 
 
 CsLrbon, which takes so great a part in life processes that 
 the chemistry of organic substances is commonly spoken of 
 as the chemistry of the compounds of carbon, fulfils all three 
 requirements in an eminent degree. For although in its 
 pure form a solid, and sometimes a very hard substance, yet 
 it readily forms an oxide which is present in the atmosphere, 
 and, as we know, serves as one of the chief foods of plants. 
 Its power of entering into combination with other elements 
 is practically infinite. Nitrogen, although by itself an inert 
 form of matter, is able to combine with carbon compounds 
 and add fresh complexity. 
 
 It is easy to see why water is so important in life. It 
 dissolves the other substances, and so allows them to come 
 into closer contact, and to change in position more easily, 
 than if they were solid. So the first stuff that was complex 
 and unstable enough to be properly described as living was 
 almost certainly formed in water, long ago, when the condi- 
 tions of greater heat, and consequently greater mobility of 
 all substances, made chemical changes more active. 
 
 The importance of the solvent power of water m a com- 
 plex organism is obvious when we think of the blood, the 
 great food stream and drain. It is shown in an interesting 
 
CHAP, vni 
 
 Vitality 
 
 m 
 
 way by the suspended animation of a dried seed, which will 
 remain for years dormant, but ready when moistened to 
 spring mto active life. 
 
 How, then, are these substances built" up into living 
 aeatures ? Let us, that we may see this matter clearly, 
 think for a moment of the conditions of life of the simplest 
 creatures, the formless masses of living matter. All that 
 the simplest plants need is water holding oxygen, carbonic 
 acid, and salts in solution. Out of these simple materials 
 by the magic touch of their living bodies, they can build up 
 
 Z' - ~- \ 
 
 B 
 
 P V- ... 
 
 y 
 
 ^ / 
 
 y" 
 
 / 
 
 X 
 
 the complex matter of which those bodies are made; so that 
 they can grow and divide until there may be hundreds in 
 place of a single one. The image we must form of this 
 •ncrease of hving matter is that step by step substances of 
 an ever-growing complexity are made, one from the other, 
 unt.l at last a substance so unstable is made that it begins 
 to break down into simpler forms of matter at the least 
 deviation from the precise conditions in which it was made 
 and perhaps also with a ferment-like action causes changed 
 
138 The Study of Animal Lift partii 
 
 in aU that it touches; and this we caU the living matter 
 As this living matter breaks down into simpler substances, 
 or as it causes surrounding substances to break down, 
 energy is set ffee for use in movement. We may make 
 a diagram of this process. The steps go up and down ; the 
 top one we call protoplasm (Fig. A). This shows only one 
 line of ascent and one of descent There niay be many, al 
 going on at the same time, as is shown m Fig. B. But 
 these are much too simple ; they show contmuou« ascending 
 and descending stairs, but each step does not really result 
 directly from the one below, but must result from two or 
 more stairs meeting; and at each meeting there must be 
 substances formed -^hich are useless, and begin to break 
 down, or are cast out of the system at once. 
 
 8 Orowth.— The power of growth, of adding to itself 
 subslance of the same nature as itself, is the real mystery 
 of living matter. A crystal grows out of its solution he 
 star or pyramid is built up with perfect regu anty, but the 
 process is much simpler than the growth of living matter. 
 The substance of which it will be formed is already there, 
 but the protoplasm has to make its own substance as U 
 grows. This is the true difference between the two pro- 
 cesses, and not, as is usually stated, that a crystal grows by 
 depositing matter on its surface, while a cell grows by putting 
 matter within itself. For when two cells fuse, which of en 
 occurs, growth is really as much by aggregation as in the 
 case of a crystal, and such manner of growth is made 
 possible simply because the two cells are masses of matter 
 of equal complexity. But when less complex matter is given 
 to a cell it cannot add that matter to itself until it has been 
 transformed into substance as complex as itself, ims 
 change can only be effected within the little laboratory of 
 the cell itself. The fact that the growth of a crystal may 
 be endless, while that of a cell is limited, which is usually 
 cited as the distinctive difference, is a consequence of the 
 necessity of the protoplasm for forming its own substance 
 within its own substance. For when a cell grows m sue 
 the ratio of its surface to its volume constantly decreases, 
 and therefore, since new material can only be absorbea 
 
CHAT. VIII 
 
 Vitality 
 
 139 
 
 through the surface, there must be a certain size of cell at 
 which the rate of absorption is just sufficient for the nourish- 
 ment of the protoplasm. Beyond this point a cell cannot 
 grow ; but if it divides, then the mass to be fed remains the 
 same, while the absorbing surface is increased. This, then, 
 is the necessitating cause of cell-division. But it would be 
 unwise to suppose that there are not other causes that help 
 to produce this result, which has as a consequence the 
 possibility 01 Timense variety of disposition of the daughter 
 cells, and therefore of organic forms ; for, to begin with, a 
 more obvious means of obtaining increased surface would 
 be for the cell merely to become flattened or to spread out 
 irregularly, which, indeed, we see in many of the Protozoa. 
 
 Since their growth implies cell-division as one of its con- 
 sequences, and since cell-division is the basis of reproduc- 
 tion, synonymous, indeed, in the Protozoa with reproduc- 
 tion, we get the idea of successive generations of animals as 
 merely the continued growth of former generations. This 
 makes intelligible to us all the facts of heredity which are 
 so surprising if we conceive of each generation as a number 
 of untried souls that have left some former dwelling-place to 
 come and live among us. Our children are, in truth, abso- 
 lutely portions of ourselves. If this be so, we must imagine 
 in the ovum — the tiny mass of protoplasm from which we 
 are formed by continued division — a most extraordinary 
 subtlety of constitution. 
 
 Try to picture the complexity of the arrangement of parts. 
 There are two tiny masses of protoplasm ; so far as we can 
 see they are the same, yet from one will grow a man, from 
 the other a tree. If the germ that will grow into a human 
 being could only properly be fed outside the body of the 
 mother, so far as we know it might leave that body as 
 an almost invisible cell, and would grow and divide, add 
 cell to cell, until the creature was fully formed — sculp- 
 tured out of dust and air. Our early life within the womb, 
 our nourishment by the blood of our mother, is only nature's 
 way of preserving us from injury. What we shall be is 
 already marked out before the t%% begins to grow. 
 
 It is only the highest animals who are thus shielded. 
 
 
 :ll;j 
 
I40 The Study of Animal Life »a»t n 
 
 The birds cover their eggs with their wings. The butterfly 
 lays hers where the grubs will find their food. The star- 
 fish cast theirs adrift in the sea. The same story is true 
 of the flowers. They are the nursing mothers. In their 
 heart the young plant grows until the first leaves appear ; 
 not till then does it drop away, and not without food 
 prepared and placed ready for use— enclosed in what we 
 call the seed. But the seaweed, like the star- fish that 
 crawls upon it, allows its young seeds quite unformed to be 
 floated away by the tide. 
 
 All seeds, then, are parts of the living matter of the 
 parent ; some leave naked and without food ; others are 
 protected by shells or by husks which are filled with food ; 
 others live within the mother until they have ceased really 
 to be seeds, and are fully formed new creatures. 
 
 Now the living matter of any sir'nie organism is so much 
 
 the same throughout the whole bouy that almost any part 
 
 of it will do to build the new generation om. Thus, 
 
 although the sea-anemone does sometimes set apart certain 
 
 cells as seeds, yet any part of the body will, if cut off, gi w 
 
 mto a complete creature. The same thing is true of a moss 
 
 pUnt But the more highly organised animals have their 
 
 living matter set to such different service in their various 
 
 organs that most of it does not keep all the qualities of the 
 
 whole creature, but only of that part to which it belongs. 
 
 Thus if a starfish lose its arm, another will grow from the 
 
 stump. A snail can in this way repeatedly regrow its horns. 
 
 Even so highly developed an animal as a lizard can grow a 
 
 new tail. With ourselves this power is confined to growing 
 
 new skin if we lose part of it, or mending a bone if it be 
 
 broken, and other similar processes. 
 
 When we clearly understand in what way the offspring 
 of all creatures arise from their parents, how they are, as 
 Erasmus Darwin said long ago, like separated buds, then 
 we see the truth of the often-made comparison between any 
 or all species of animals and an organism. The individuals 
 of a species are not indeed bound togethei by protoplasmic 
 strands, but thei? interdependence is not less complete. A 
 •ingle species utterly destroyed might modify the life of the 
 
CHAV. VIII 
 
 Vitality 
 
 141 
 
 whole earth. Life itself is dependent upon the invariable 
 presence of minute quantities of iron in the soil A wan- 
 dering tribe of savages is an organism not quite so high in 
 the scale of social organisms as is the hydra in the scale 
 of individuals ; for the cells of the hydra, although divided 
 broadly into an outer and an inner layer, are yet more 
 divided in their functions than are the members of a 
 savage tnL?. For there are only two kinds of person in 
 such a tribe — hunters and cooks ; while a highly civilised 
 community, with its immense variety of workmen, is prob- 
 ably not so well organised as any mammal ; for there are 
 in such a state thousands of persons, untrained to any special 
 labour, merely a burden to themselves and to the nation. 
 
 9. Origin of Life.— We have said that life probably 
 began when the conditions of heat and solubility of sub- 
 stance were more fovourable to the formation of peculiar 
 and complex matter than at present But such a state- 
 ment is often thought to be unphilosophical in view of the 
 fact that we have at present no experience of the foiiuation 
 of such substances, and that it has been conclusively proved 
 that living creatures always proceed from pre-existing life. 
 But those who urge such objections forget that all that has 
 been proved is, that the simplest creatures known to be alive 
 at present can be formed only by cell -division one from 
 another, and not from simple chemical materials. But we 
 must remember that those simplest animals are highly 
 developed in comparison with the complex matter from 
 which we conceive life to have sprung; and no one 
 would now expect that such comparatively highly developed 
 animals could arise from simple matter. There is certainly 
 no evidence of the formation at present of the very simplest 
 and original living matter. But, in the first place, could 
 we see it, even with a microscope, if it were to be formed ? 
 Might it not be formed molecule by molecule ? And, 
 secondly, what chance of survival would such elementary 
 creatures have among the voracious animals that swann in 
 all places where such simplest creatures might possibly be 
 formed ? Instantly they would be devoured, before they 
 could grow large enough to be seen. 
 
 ift 
 
f~ •■'?*i;;'*5 
 
 I4« 
 
 The Study of Animal Lift part ii 
 
 Lastly, let it be carefully observed, such a belief as this 
 as to the origin of life, and of the basis of all life in chemical 
 processes, carries with it no necessary adherence to the 
 doctrines of Materialism. The materialist analyses the 
 whole objective world of phenomena into matter and motion. 
 So fiu:, his conclusion is perfectly legitimate ; but when he 
 maintains that matter and motion are the only realities of 
 the world, he is making an unwarrantable assumption. 
 Matter in motion is accompanied by consciousness in our- 
 selves. We infer a similar consciousness in creatures like 
 ourselves. As the movements and the matter differ from 
 those that occur within our body, so will the accompanying 
 consciousness. The simplest state of affairs or " body " 
 we can imagine is that of a gas such as hydrogen. But 
 such a simple sUte of matter may have its accompanying 
 consciousness, as different from ours as is the structure of 
 our bodies from that of a hydrogen molecule. This is, of 
 course, also an assumption, but it is one that harmonises 
 with the facts of experience. 
 
 The opposite extreme to Materialism is Idealism, and in 
 this school of philosophy an assumption precisely similar, 
 and exactly opposite to that of Materialism, is made. The 
 idealist says the objective world of phenomena has no exist- 
 ence at all, it is the creation of mind. An objection to 
 such a theory lies in the question. If matter and energy are 
 the creation of mind, how is it that we find them to be 
 indestructible ? 
 
 Popular philosophy has mi.le an assumption which lies 
 midway between these extremes. It postulates two reali- 
 ties, matter and spirit, having little effect upon one another, 
 but acting harmoniously together. 
 
 But the view that is here set forth postulates neither 
 matter nor spirit, but an entity which is known objectively 
 as matter and energy, and subjectively as consciousness. 
 This philosophy goes by the name of Monism. The term 
 consciousness is used for lack of any other to express the 
 constant subjective reality. Carefull/ speaking, it is, of 
 course, only the more complex subjective processes that 
 form consciousneAt. 
 
CHAPTER IX 
 
 THE DIVIDED LABOURS OF THE BODY 
 
 I. Divisim of l3b<mr—%. The FutuHons of tkt Body : Movement; 
 Nutrition', Digestion; Absorption; The Work of the Liver 
 and th* Kidn^t; Respiralitn; Circulation; The Chtmges 
 within th* CeU$ ; The AcHvititt of th* Nervous System— 
 3. Shetch of Psychology 
 
 I. DiTision of Lftboor.— The simplest animals are one- 
 celled ; the higher animals are built up of numberless cells. 
 All the processes of life go on within a single cell In a 
 many-celled animal the labours of life are divided among 
 the various groups of cells which form tissues and organs. 
 The history of physiological development is the history of 
 this division of labour. 
 
 When a dividing cell, instead of separating into two 
 distinct masses, remained, after the division of its nucleus, 
 with the two daughter masses lying side by side, joined 
 together by strands of protoplasm, then the evolution of 
 organic form took a distinct step upwards, and at the same 
 time arose the possibility of greater activity, by means of 
 the division of labour. For when the process had resulted 
 in the formation of an organism of a few doien cells, 
 arranged very likely in the form of a cup, the outer cells 
 might devote the greater part of their energies to movement 
 Md the inner cells to the digestion of food. In the com- 
 men Hydru the body consists of two kyers of cells arranged 
 to form a tub^ the mouth <rf which is encircled by tentacle*, 
 
 ii 
 
 ^iL_ 
 
T:^^ 
 
 V;^,>. 
 
 144 
 
 TAe Study of Animal Life part n 
 
 The cells of the outer layer are protective, nervous, and 
 muscular ; the cells of the inner layer are digestive and 
 muscular. The cells of Hydra are therefore not so many- 
 sided in function as are Amoebae. In animals higher than 
 the simplest worms, a middle layer of cells is always formed 
 which discharges muscular, supporting, and other functions. 
 
 With advancing complexity of structure the specialisa- 
 tion of certain cells for the performance of certain functions 
 has become more pronounced. In the human body the 
 division of labour has reached a state of great perfection ; 
 we shall give a slight sketch of its arrangements. 
 
 2. Th« Functioiis of the Body.— Our objective life 
 consists of movement, and of feeding to supply the energy 
 for that movement Growth, reproduction, and decay are 
 elsewhere treated o£ 
 
 Movement. — We move by the contraction of cells massed 
 into tissues called muscles. Contractility is a property of 
 all living matter ; in muscle-cells this function is predomi- 
 nant This is all that need be said here of movement ; the 
 processes of nutrition we must follow more closely. 
 
 Nutrition.— AM the cells of our bodies are nourished by 
 the stream of fluid foodstuff, the blood, which flows in a 
 number of vessels called arteries, veins, or capillaries, 
 according to their place in the system. From this stream 
 each cell picks out its food; and into another stream— 
 the lymph stream — moving in separate channels — the 
 lymphatics, which, however, join the blood channels, each 
 cell casts its waste material ; just as a single-celled animal 
 takes food from the water in which it lives and casts its 
 waste into it 
 
 Nutrition must therefore consist of two series of activi- 
 ties. One series will have for its object the preparation 
 of food-matter so that it may enter the blood, and the 
 excretion of waste products out of the blood. The other 
 series will consist of the activities of the individual cells,— 
 the manner in which they feed themselves. 
 
 The first step in the preparation of the blood is digestion 
 Most food-stuff is solid and indiffusible ; before it can enter 
 the Wood it must be made soluble and diffusible. The 
 
CHAR a "^^ I>ivided Labours of the Bcdy 145 
 
 supply of ojqrgen to the tissues is also a part of these first 
 processes of nutntion. Being a gas, it is treated in a 
 special way which will be described imiiediately. 
 
 Dtgestwn.—T^^ various food-stuffs have various chemi- 
 cal qualities. After being swallowed they enter a.C 
 ube, the digestive tract or alimentary canal. ^Jithif 
 this canal they are subjected to the action of variois 
 digestive juices prepared by masses of cells called glands 
 Saliva IS one of these juices, gastric juice is another 
 pancreatic juice is another. The effect of these juices 
 upon the food IS that most of it is dissolved in the juice 
 and made diffusible. Thus we see an example of the 
 division of labour. An amoeba flows jound a soHd particle 
 of food and digests it. In the higher animals the Ss of 
 
 tt tTriiS^elr ^^^^"'^'"^' ^°^ '""^ ^^-'- «^- 
 
 AbsarpHoru-m^x the food is digested it leaves the 
 alimentary canal, and is absorbed into the blood-vessels 
 and lymphatics in the walls of the canal. Absorption Ts not 
 a mere process of diffusion. It is diffusion modified by ?he 
 cells hnmg the alimentary tract Certain chemical changes 
 are effected at the same time. Most of the absorb^ ?^ 
 
 TbUd t ""/' '",! *'^ '^* ^^^ not go directly t^ 
 the blood being first absorbed into that other system of 
 
 S\**u^'"P^"*'*^- Eventually it also getsTnto the 
 blood ; for the two streams are connected 
 
 .f2!v ^'^^ "-^ tf^ Liver and the Kidneys.~.T\,^ cells 
 of the liver secrete a juice called bile, which is poured into 
 ?n ^'T.*?"^ ^^^ "^^ «^^* ft^-^ction of this j^dis 
 
 u t° is ? • }' ''' ' '"^.^" "'* '" ^^« '^•^^^'on o" fat 
 .0 nc^^^' .K f ^^ ^" *'5''^''°"- "^^ »t^«^ of food-stuff 
 going to the hver contains sugar, the result of the digest"" 
 carbohydrates ; albumen, the result of the digest b^^S 
 absorption of proteids ; and certain waste Sgen^us 
 matter, formed during the digestion of proteids "'*'°^*"°" 
 
 themseh'e'^lli^' "'^"' "^'^ *^* '"^"' '^^''^ »» '^'thin 
 « InJ " •. ""' '°'* °^**y *^^» ^ Pot«^t° »to«s up 
 
 *r as IS known they do not affect the albumen in any way, 
 
«iS«j5::-.<«"#=«^«' ; 
 
 146 The Study of Animal Life part n 
 
 but the waste nitrogenous matter is altered and then sent 
 on in the blood stream to the kidneys. 
 
 The cells of the kidneys take this stuff, which was pre- 
 pared in the liver, and other waste nitrogenous products 
 out of the blood, pass them and a certain amount of water 
 along'to the urinary bladder, which empties itself from time 
 
 to time. 
 
 Respiration. — Breathing consists of two distinct acts, 
 inspiration and expiration. During an inspiration air is 
 drawn into lungs. Thence the oxygen passes by diffusion, 
 modified by the fact that the essential membrane is a living 
 one, into the blood. There it enters into a loose combina- 
 tion with haemoglobin, the red colouring matter of the 
 blood cells, and is thus carried to the cells of the tissues to 
 be absorbed into their living matter. During an expiration 
 we breathe out air which has less oxygen and more carbonic 
 acid gas than normal air. The carbonic acid is a waste- 
 product formed by the cells of the body ; it first enters the 
 blood, is then carried to the lungs, and leaves the blood- 
 vessels by a process of diffusion similar to that by which 
 the oxygen entered. The close association of these two 
 processes is simply due to the fact that an organ fitted for 
 the diffusion of one gas in one direction will do for the 
 diffusion of all gases in any direction. 
 
 Circulation. — The blood is maintained in a healthy state 
 by the processes we have described. By the active con- 
 traction of the heart it is pumped round and round the 
 body, continually carrying with it fresh food to the tissues, 
 and carrying away with it the waste matter cast out of the 
 tissues. All the blood-vessels, except the very smallest, 
 have muscular walls. The heart is a large hollow mass of 
 muscles, is a part of a pair of large blood-vessels that have 
 been bent upon themselves, and arranged so as to foni\ 
 four separate chambers, two upper and two lower, an upper 
 and a lower opening directly into one another on exich side. 
 By the contraction of the lower chamber of the left pair the 
 blood is forced through all the vessels of the body ; these 
 collect and empty the blood into the upper chamber of the 
 right pair ; from this it passes into the lower chamber on 
 
CHAP. « Tks Divided Labours of the Body 147 
 
 the »me side, and from this it is forced through the vessels 
 of the lungs, returning to the upper chamber of the left 
 side, and so to the lower chamber of the left side 
 
 The way in which the blood is able to nourish the 
 
 tissues isasfollowsr—The outgoing vessels-arteries-enter 
 each mass of tissue; within it they break up into number- 
 less very small, very thin-walled vessels-capiUaries ; the 
 blood oozes through these into the smaU spaces— lymph 
 spaces-that occur throughout the tissues ; adjacent to these 
 
 rf?n"l *" "^^.l^'' ^^•'^^ ^^''^ ^•^""^ ^^^ lymph-the fluid 
 that fills the small spaces and the vessels connected with 
 them— what they need, and cast into it their waste. The 
 lymph spaces open into lymph vessels, which, as has been 
 noted, jom the blood-vessels. Oxygen and carbonic acid, 
 being gases, pass directly from the blood through the walls 
 of the vessels to the tissues, and from the tissues to the 
 Dlood. 
 
 The Changes within the Cells.-ln speaking of proto- 
 pbsm an outhne of the kind of knowledge that ^ve possess 
 of the chemical changes that take place within the cells 
 has been given. We know little more than the sub- 
 stances that enter the cells and the substances that leave 
 tnem. 
 
 Perhaps even this is too much to say ; n ,re exacUy, we 
 know the substances that enter the body by the mouth and 
 nose, and through the alimentary canal and lungs: we 
 know the substances that leave the body through the 
 kidneys, and, in expiration, through the nose. A laree 
 amount of water and traces of other matters leave the body 
 M perspiration ; but the chief use of sweating is probably 
 7ZT IT °/»^« temperature of the body, and the skin 
 
 way that the kidneys are. The undigested matter that 
 
 ^^ITa '*'' ^"^-"^J^^ ^''^ "ever been within the 
 blood, and does not therefore concern us in this inquiry. • 
 But we know very little more than this ; the analysis of 
 
 ur^n'Z'J,*'^"^'^ *\" *"y particular mass of tissue exerts 
 u^n he blood-,.* the differences that must exist between 
 "« substances entering it and the substances leaving it— i« 
 
 i 
 I 
 
148 
 
 Thi Study of Animal Lift faet n 
 
 very difficult of detenzunation, because of the immense 
 quantity of blood that passes through any tissue in a short 
 time. This concludes our sketch of the interchange of 
 matter within the body. 
 
 The Activities of the Nervous Systetn. — We have now 
 to consider the arrangement of the nervous system — first 
 merely as the means by which all the varied activities of 
 the tissues of the separate parts of the body are co-ordi- 
 nated and wrought into an harmonious series of artions, 
 and then as the associate of consciousness and of mental 
 processes. 
 
 Just as protoplasm may be called the physical basis of 
 life, so is nervous tissue par excellence the physical basis of 
 consciousness and of mind. Throughout the whole animal 
 kingdom it has a superficial similarity of structure, and 
 consists of the same three parts. 
 
 (i) First there are cells adapted to receive notice of 
 change in the outer world. Changes in the sur- 
 rounding medium and affecting such cells are 
 called stimuli. These cells sensitive to stimuli 
 form the chief part of the sense organs — the 
 eyes, ears, nose, tongue. Also in the skin 
 there are cells sensitive to alterations of touch 
 and temperature. The effect of stimuli upon 
 such cells is probably to set them into a state of 
 molecular agitation, which may or may not result 
 in chemical changes. 
 (3) There are connecting fibres or nerves, which, 
 being connected with the sensory cells, take up 
 the vibrations or possibly the chemical changes 
 of the sensory cells and transmit them to the 
 « centre." 
 (3) There are "central" cells, in which the nerves 
 end, and which are set in molecular agitation by 
 the vibrations of the nerves. This molecular 
 agitation is often, when the central cells are in 
 the brain, accompanied by consciousness. Ap- 
 parently also agitations may arise <* spontane- 
 ously" within these central cells and stimulate 
 
CHAP. IX The Divided Labours of the Body 149 
 
 Aft outgobg neives, and cause muscular move, 
 ments, or the activity of glands, or other cellular 
 activities. 
 
 In many ways analogous to the nervous system is 
 
 i%hlT^^ ^^^ °^ * ^°""^' *^« receiving rt^ons 
 are the nerve cells, among which are the cells of the se^se 
 organs; the connecting wires are the nerve fibres ^he 
 cen^ stations are the groups of cells called ^ll ?« 
 ch,ef of wh.ch are in the brain and spinal corA^fhe less 
 important gangha are like the bmnch offices, they recdve 
 
 are like the offices of a government, in which messages are 
 received, plans elaborated on the strength of the news and 
 orders sent out to various parts of the country Tl 'such 
 
 anUL'lr?'" '''.' ?^^^ •" ''^ nervouTsysVl are 
 called reflex actions, whether a received messasre be s^nf 
 
 on unaltered, or whether the receiving cTu refSla^s the 
 body. The analogy of telegraph stations, even with the 
 iS^f .V°/'' them and with responiible pe"o„s to 
 
 t^^^ti^^S'nt: -"ir ' "^"^^ '"- --^'^^ ^^- ^ 
 
 3- Sketch of Psychoicgy.—The following is lanrelv 
 
 iT^' to which we refer the reader, and to which^e 
 acknowledge our indebtedness. ' 
 
 caulLr*b!^°tL^P^"!.*** "^^"S^'^^ » "ervous matter. 
 »used by changes m the outer world, result in what we 
 call a change of consciousness * m wnai we 
 
 ner^t^er t^'cllirs^^^^^^^^^ ^'^^^ '^^ ^^-^^-- «' 
 imp^reSs.°^'°°'''*'"'"*'' P"^"^^^ ^^ »*'°^"»' "* called 
 
 WvL orllJ • "P°° ™'"°'^' "^^ memory is the re 
 
 '^val of past impressions, which, we must suppose, have b 
 
-■-v-;rg<Vi'.!^t^^j«lg 
 
 I i 
 
 1 
 
 ! 
 
 150 The Study of Animal Life part n 
 
 some way been stored within the cells of the brain in the 
 form, from the objective point of view, of a certain 
 arrangement of its particles. 
 
 When, after the revival of past impressions, we are able 
 to discriminate between them, we call them sensations. 
 
 Now sensations are referred, in consciousness, not to 
 
 Fig. 31.— Attitude of a hen protecting her brood against a dog 
 (From Darwin's Expression 0/ Emotions.) 
 
 the brain cells which discriminate between them, but to the 
 cells of the sense organs which received them. 
 
 Further, we refer, by experience, the causes of sen- 
 sations to the outer world. We do this by a mental pro- 
 cess which is called perception. 
 
 Now out of perceptions, and through associations, there 
 arise expectations. The mental process involved in the 
 formation of an expectation is called inference. 
 
CHAP. IX The Divided Labours of the Body 151 
 
 Inference is of two kinds : 
 
 (1) Perceptual, drawn from direct experience, as in 
 
 the inference as to a rain storm from a black 
 cloud. 
 
 (2) Conceptual, which, though based upon experience, 
 
 yet can predict events that have never been 
 experienced. For instance, one who had studied 
 in books only the causes of volcanic activity, 
 might predict with a certain amount of confidence 
 a flow of lava from a volcano, when he saw it in 
 that state of activity which he knew usually pre- 
 ceded an eruption of lava. 
 What we call the emotions, love, hate, fear, and others, 
 are, so far as we can tell, agitations of nervous matter 
 which affect consciousness. Their exciting stimuli— infer- 
 ences for example— proceed, immediately, from within the 
 brain, ultimately, from changes in the outer world. 
 
 We have, therefore, the following orders of conscious- 
 ness, which are easily distinguishable in theory : 
 
 (1) Impressions, or the effects of environmental 
 
 changes upon nervous matter ; the retaining and 
 revival of these constitutes the basis of memory. 
 
 (2) Sensations, which occur when the differences that 
 
 exist between impressions are discriminated. 
 
 (3) Perceptions, which are the outward projections 
 
 into the world, by mental acts, of the molecular 
 disturbances caused in the brain by environ- 
 mental changes. For example, light falls upon 
 the retina, stimulates the optic nerve, and causes 
 a molecular disturbance in the brain, but the 
 consciousness excited in us is not of the brain 
 disturbance, but of the light. 
 It is most essential that the distinction between per- 
 ceptual and conceptual inference be cleariy realised, as it is 
 probable that it is the faculty for the latter which more 
 than anything else separates man from the lower animals. 
 We may be nearly certain that many animals exercise per- 
 ceptual inference, and we may affirm with little doubt that 
 none has ever performed a conceptual one. It has been 
 
iSa 
 
 Th Study of Animal Lift pakt ii 
 
 stated that a monkey that had learned to screw and 
 unscrew a handle from a broom had learned " the principle 
 of the screw." This is entirely erroneous. The monkey 
 merely observed that a certain move-^-^nt given to the 
 handle caused it to separate from the bioom, and inferred 
 perceptually that the same result would always follow from 
 the same action. 
 
 It is evident that a sound comparative psychology of 
 the animal kingdom, or even of a few of the highest 
 species, is beyond the present possibilities of science. 
 
 A^as^^aaa^'szz-.^ sx.- 
 
^I^» 
 
 
 CHAPTER X 
 
 INSTINCT 
 
 '% 
 
 X i.,fii-rai 
 
 3- 
 
 U 
 
 lagsofthe Term— 2. Carefvl Usage of the Term— 
 rumples of Instinct-^ TAeOrigii^fiJsii^''^^ 
 
 --iuermg the mental life of animals, we must settle 
 /ar r. is comparable to that of man. We judge of the 
 v.er.J p ocesses of human beings, other thin furSveT 
 dTr '^'''?i^''^^^\^^ we can only do the sa^e whe2 
 deahng with ammals. If we often err in irSiiT Ae 
 mental states of our feUow-men, how much more^^efiaSe 
 
 uX: ItiTw ~""'^""^ ^"^^""^ different Sm 
 h1 kTI u?^ believmg as we do in the continuity of 
 
 IS probable that m time we may arrive at a certain state 
 ^^Z"^t^T'^ '" comparative psycho^ 
 
 surely from sensations, the world of every creatui/mtS 
 be largely constructed from its dominant sense ; i^ a X 
 for instance, fro: . scent. . m a aog, 
 
 ta 5l".^°!^°2n*^ '^'^^ *^* *^^'*^"« o^ animals are all ascribed 
 
 wW^e the a^^' r °° "'^^ ""^^^"^ '^- termis £tt 
 While the actiors of men are determined by reason, those of 
 
 hTt ^' f \P«>°»Pted by a blind power of doing Sat which 
 « fitted to the successful conduct of their livl This. aS 
 
 iT' ?T? "°*'°° *"* ^'^"»«» modification. ' 
 • «neS^ y!^*^'''*?* **™ Iiurtliict-Every one has 
 •geneml notion of what is meant by insimct, but few ar^ 
 
 l.-y 
 
 X i k 
 
MHii 
 
 i|P 
 
 iiMM 
 
 I 
 I 
 
 »54 
 
 The Study of Animal Lift part n 
 
 agreed as to the precise usage of the word ; thus when the 
 birds build their nests, or when the bees collect honey and 
 form the:: combs, their acts are vrith one accord said to be 
 mstinctive ; but some would demur at using such a term to 
 describe the love of parents for their children, the courage 
 of brave men, or the artisf s perception of beauty. But, 
 even supposing we agree to mean by instinct all those actions 
 which are neither simply reflex nor purely rational, there 
 will still remain great difference of opinion as to its origin. 
 Thus the love of parents will not be imagined as due to 
 practice, either in the individual or its ancestors, but rather 
 to take origin in some hidden necessity of nature ; while 
 the rapid closure of the eyes as protection from an expected 
 blow would seem in all likelihood to have begun in a rapid 
 exercise of intelligence, which, by being often repeated, 
 had ceased to be accompanied by conscious effort. 
 
 It seems to us that there is still need of a vast amount 
 of observation and experiment before a theory of the origin 
 of instinct that will be at all satisfactory can be framed. As 
 already remarked, it is not easy to decide even in what 
 sense the term ought to be used. This being so, we shall 
 content ourselves with mapping the field of thought and 
 indicating the lines of inquiry that must be followed before 
 a just view of the subject will be possible. 
 
 If we arrange examples of all the movements of animals 
 in the order in which they are performed in the lifetime of 
 the individuals, not limiting ourselves to those acts which 
 involve the whole organism, but considering also those which 
 a single organ or mass of tissue may execute, wi shall see 
 at a glance all the possible varieties of activity with which 
 we can be concerned. It is, of course, only the move- 
 ments of comparatively large masses of tissue with which 
 we can deal at present. The molecular movements which 
 lie at the base of all the visible ones are as yet a'nost 
 unknown. 
 
 Even before birth, visible movements of the parts of the 
 higher animals occur ; as, for instance, the beating of the 
 heart Such movements may be either " automatic " or 
 reflex. At birth, in addition to such movements of its parts, 
 
OUBiZ 
 
 InsHttct 
 
 "55 
 
 VA 
 
 % 
 
 (2 
 
 (3) 
 
 the oisranism a^ as a whole ; it reacts to its environment, 
 and m fame performs " voluntary " actions. 
 
 The acts of the parts of an organism may be— 
 
 (1) "Automatic," as, for example, the beating of the 
 
 heart 
 
 (2) Reflex, as, for example, the intestinal movements 
 
 which force the food through the alimentary 
 canal, or the movements involved in sneezing. 
 
 (3) Mixed actions which are partly automatic and 
 
 partly reflex, such as the respiratory movements. 
 The movements of the entire organism may be of a verv 
 complex nature. They may be— 
 
 (i) Reflex ; as when we start at a sudden noise. 
 
 "Innate," commonly called instinctive ; these are 
 best observed in newly-born animals, for in them 
 intelligence, which must be based upon experience. 
 IS necessarily at a minimum. 
 "Habitual," such as are rapidly learned and are 
 then performed without mental effort, which imply 
 an mnate capacity, and are therefore allied to (2) 
 
 (4) Intelligent, such as imply mental activity, which 
 
 consists in the combining and rearranging all the 
 other possible acts of the order— (i), (2) or (3) • 
 and which may be recognised in all adaptations 
 to novel circumstances. 
 ^ This classification possesses most obvious faults, but it 
 
 tlT^'^l "^^Tl' J^ '^""^^^ »«'"« °f th«= difficulties 
 th deUy the would-be definer of instinct. For the essen- 
 tial criterion of an instinctive action is that all the machinery 
 
 ^'.H %^ L""''"^^ " * '^^^'' *° * ""**" «i'«"Iu», lies 
 ^ady formed within the organism ; but the apparently in- 
 soluble questions present themselves, How soon may not 
 actions be modified by intelligence ? "and How in a mature 
 ^rirT- "^"'"^'^•■^♦''^ experience i. one to separate 
 L^inTvlract'sr'" "'' '^°" ^'^ •"^^"'^^"''y "^^^''«-^ 
 Also it !, evidem that "habitual- actions may be "instinct- 
 ive actions deferred until the creature be further dev-1- 
 opeu, as the flight of many birds is deferred j or they may 
 
 '■i 
 
156 
 
 The Study of Animal Life »a»t i 
 
 be actions in the formatiott of which intelligence has had a 
 cosiidetable share. 
 
 Now all these activities of an entire oigmnism may be 
 studied from four points of view : — 
 
 (i) Of natural history, or general description, such as 
 
 occurs here and there throughout this work : 
 (a) Of physiology, or the analysis of the muscular, 
 nervous, and other mechanisms involved ; as 
 treated generally in the last chapter : 
 
 (3) Of psychology, or the investigation into the states 
 
 of consciousness and mental processes concerned ; 
 as sketched in the last chapter : 
 
 (4) Of aetiology, or study of the factors in their origin 
 
 and development. 
 
 We shall first define more carefully than we have yet 
 done what we shall speak of as instinct, then give a few 
 examples, and finally discuss the aetiology of it. 
 
 2. The Oareftil Uiage of tbe term Instinct.— We Iiave 
 enumerated all the possible varieties of action, and the pos- 
 sible states of consciousness with which they may be asso- 
 ciated have been described in the last chapter. If we retain 
 the use of the term instinct we must explain to what ordei 
 of activity we shall apply it. In our use of the term we 
 shall not strive after any great precision ; for, as already 
 noted, the difficulty of precision seems to us to be at present 
 msurmountable. In a general way we shall call any action 
 which does not require for its execution any immediate 
 exertion of perceptual inference an instinctive action. Thus 
 a burned child dreads the fire ; such dread and its const 
 quent avoidance of fires may, with propriety, be termed 
 instinctive. After the first bum the avoidance will, for a 
 short time, be the result of perceptual inference ; but in 
 perhaps a few days only the avoidance becomes " instinct- 
 ive" ; or it might be called " habitual," as hinted previoubiy. 
 It is, of course, to be understood that an "instinctive"' 
 action is not necessarily the result of this *' lapsed intelli 
 gence," as it has been called. Thus, when a worci 
 wrigg!es away from a fire it probably has not at any tin« 
 reasoned out to itself the advantages of such procedure, 
 
JV.-:: 
 
 dUK t 
 
 Tmsimei 
 
 '57 
 
 yrt It may wdl be said to avoid the fire instinctively. It is 
 obvious that, If we agree to use the tenn as defined, we 
 must call aU the actions of the lower animals, whose con- 
 saousness has never risen to the level of perceptual infer- 
 jaice, instinctive. This definition is based upon the assump- 
 Uon that we can determine the CMiscious states of animals • 
 but, as we have repeatedly said, it ,s only within very wide' 
 limits that we can with any certainty do this. The inten- 
 tion, however, is to preclude all those actions which are 
 certainly or probably rational, and at the same time include 
 adaptive reflex actions. 
 
 Mr. Herbert Spencer has defined instinct as compound 
 reflex action, while Mr. Romanes separates it from reflex 
 
 action and from reason as follows : 
 
 •• Reflex action is non-mentai neuro-muscular adjustment 
 due to the inherited mechanism of the nervous system, 
 which IS found to respond to particular and often-recurring 
 sttmuli, by giving nse to particular movements of an 
 adaptive though not of an intentional kind." 
 
 " Instinct is reflex action into which there is imported 
 the element of consciousness. The term is therefore a 
 generic one, comprismg all these faculties of mind which 
 are concerned in consciousness and adaptive action, 
 antecedent to individual experience, without necessary 
 knowledge of the relation between means employed and 
 ends attained, but similarly performed under similar and 
 requently-recurring circumstances by all the individuals of 
 the same species." 
 
 "Reason or intelligence is the faculty which is con- 
 amed m the intentional adaptation of means to ends. It 
 ^rcfore imphes the conscious knowledge of the relation 
 Detween means employed and ends attained, and may be 
 "wcised m adaptauon to circumstances novel alike to the 
 ttpcncnce of the individual and that of the species." 
 
 Mr. Romanes therefore separates reflex action from 
 ^mct,ve action by limiting the term instinct to th"^ 
 
 Hbd,fin^?' •^'^' ^ * '"^"" °^ *^«' 'conscious reflexes. 
 «tt definition is open to objection on the same ground that 
 «« 's. only m a greater degree ; for it it easier to deter 
 
rsd 
 
 The Study of Animal Life »a»t ii 
 
 mine the presence of perceptual inference than the absence 
 of consciousness; this criterion may be of theoretical 
 interest, — ^it is of no practical use. The other attributes he 
 enumerates should be carefully studied. 
 
 Pro£ Lloyd Morgan also separates, but by no hard-and- 
 fast line, the automatic and reflex actions, which are 
 reactions to definite stimuli, from instinctive actions, which, 
 according to him, are ♦* sequences of co-ordinated activities, 
 performed by the individual in common with all the mem- 
 bers of the same more or less restricted group, in adaptation 
 to certain circumstances, oft recurring or essential to the 
 continuance of the species." 
 
 He separates these from intelligent actions, which are 
 ••performed in special adaptation to special circumstances." 
 Instinctive activities he conceives to be perfonned 
 " without learning or practice." If the actions need a Httle 
 practice he calls them •• incomplete instincts" ; if a great deal 
 of practice be necessary they are called " habitual activities' ; 
 if they are not perfectly developed at birth but after further 
 development can be performed without practice they may be 
 called "deferred instincts." A further useful classification 
 of instincts is into " perfect " and •' imperfect," according to 
 the precision of their adaptation to the desired end. 
 
 Mr. Lloyd Morgan's definition, like the others, implies that 
 one can separate rational from non-rational actions ; but he 
 safeguards himself by defining instincts as " oft-recurrin!,' or 
 essential to the continuance of the species," in ciutra- 
 distinction to intelligent actions which are performed in 
 special adaptation to special circumstances. It is important 
 to notice that the terms of the definition are that instincts 
 are either oft-recurring or essential, and not oft-recurrins,- 
 and essential, for many instincts are only either one or the 
 other and not both. But it is not always possible to say of 
 a certain action that it is a special adaptation to a special 
 circumstance, and is therefore rational, and not in reality 
 an instinctive adaptation to circumstances that are of frequeiu 
 occurrence although we have not observed them to be so. 
 
 This definition, however, emphasises the fact that instincts 
 are common to species ; it is, however, not easy to cstimaie 
 
CRAP. X 
 
 Instinct 
 
 «59 
 
 the exact significance of this fact, for the apparent similarity 
 m the actions of individuals of the same species must, to a 
 certam taUao^ be due to incomplefeness of observation. 
 
 It IS after <^SHi^ring all these definitions that we have 
 come to the c<*c?usv>n that it is convenient to describe all 
 those actions of animals which are not immediately rational 
 or mtelhgent as instincts, li we classify an instinct as 
 reflex m cases where the exact chain of internal events is 
 known and use the other <^ifications already enumerated, 
 we reach a simplicity and pw^^ioo of speech that is 
 convenient 
 
 At the same time all such enteral m adaptiveness and 
 similarity of performance in all the individuals of a species 
 can obviously be applied as they are discovered. 
 
 The essential distinction, we believe, between non- 
 mtelhgent, that is, instinctive, and intelligent actions, is 
 that non-intelligent actions are performed in virtue of the 
 innate and co-ordinated mechanisms of the organism 
 whereas for an intelligent action the organism has to do a 
 greater or less amount of the co-ordination for itself. 
 
 3. Ettmples of Inatinct-If we classify aU the actions 
 
 of animals accordmg to the period of life at which they are 
 
 performed, we shall find that there are three distinct clLses 
 
 Laratd ""^ *'*^ convenience be considered 
 
 They are — 
 
 (1) Those which are performed at birth, or shortly 
 
 afterwards, as perfectly, or neariy so, as at anv 
 future time ; ' 
 
 (2) Thoso more varied actions which are characteristic 
 
 of tiie mature life of any animal : 
 
 Ti^^/:^**°^* ^^'"^^ ^'■'^ associated with reproduction 
 ihe first of these classes must evidently consist of very 
 
 pure mstmcts since the creature cannot be supposed to 
 
 reason before it has any store of experience 
 
 actions' n^•°"^ "'''".'' ^"" 'yP'^^*^ ^y '^^ marvellous 
 actions of insects, such as ants, bees, and wasps. These 
 
 «iv l)e instinctive, but it is very probable that many of 
 
 Acni are, at least, improved by intelligence ^ 
 
i6e 
 
 TJIt Studf of Animal Lift paut u 
 
 (a) They may be perfected by perceptual inferences on 
 the part of the individuals, and die mental efforts may or 
 may not, after a certain number of repetitions, be replaced 
 by reflexes. 
 
 {b) They may be perfected by less complex mental 
 efforts, such as those involved in imitation or in receiving 
 instruction from other members of the species. 
 
 Actions of the third class may be as purely instinctive 
 as any of those in the first class, or may be improved by 
 intelligence like those of the second class; but among 
 them are many ot the most wonderfril performances of 
 animals, for they often seem to show a prevision of an 
 unknown future. 
 
 Some interesting experiments have been made upon 
 instincts of the first class. The observations show that the 
 precision of the neuro- muscular co-ordinations of some 
 newly-born creatures is very surprising. Mr. Spalding 
 blindfolded some chickens immediately after they were 
 hatched, and removed the hood after two or three days 
 when they were stronger. He says that " almost invariably 
 they seemed a little stunned by the light, remained motion- 
 less for several minutes, and continued for some time less 
 active than before they were unhooded. Their behaviour, 
 however, was in every case conclusive against the theory 
 that the perceptions of distance and direction by the eye 
 are the result of experience, or of associations formed in the 
 history of each individual life." 
 
 «« Often at the end of two minutes they followed with 
 their eyes the movements of crawling insects, turning their 
 heads with all the precision of an old fowl. In from two to 
 fifteen minutes they pecked at some speck or insect, show- 
 ing not merely an instinctive perception of distance, but an 
 original ability to judge, to measure distance, with some- 
 thing like infallible accuracy. They did not attempt to 
 seize things beyond their reach, as babies are said to grasp 
 at the moon , and they may be said to have invariably hit 
 the objects at which they struck, they never missed by a 
 hair's-breadth, and that too when the specks at which they 
 aimed were no bigger and less visible than the smallest A(A 
 
CBAP. X 
 
 Instinct 
 
 i6z 
 
 of an i To seize between the points of the mandibles at 
 the very instant of striking, seemed a more difficult opera- 
 non. I have seen a chicken seize and swallow an insect at 
 Uie first attempt; most frequentiy, however, they struck 
 ive or SIX times, lifhng once or twice before they succeeded 
 in swaUowing their first food." Again, « The art of scrap- 
 mg m «»rch of food, which, if anything, might be acquired 
 by mutation, for a hen with chickens spends the half of her 
 time m scratching for them, is nevertheless another indis- 
 puti^ case of instinct Without any opportunities of 
 umtatioo, when kept quite isolated fi:Dm their kind, chickens 
 began to scrape when from two to six days old. GeneraUy 
 the condition of the ground was suggestive; but I have 
 several tunes seen the first attempt, which consists of a sort 
 of ntfvous dance, made on a smooth table." Another 
 eiyerunenter "hatched out some chickens on a carpet 
 where he kept them for several days. They showed no 
 inclination to scrape, because the stimulus supplied by the 
 carpet to the soles of their feet was of too novel a character 
 to caU mto action the hereditary instinct ; but when a litUe 
 gravel was sprinkled on the carpet, and so the appropriate 
 or customary stimulus supplied, the chickens immediately 
 Degan their scraping movements." 
 
 Another instance of the first class of instincts is the fear 
 wd to be shown by many animals for their natural foes • 
 but on this pomt we find a certain conflict of evidence' 
 S"blS!!'o! "^ «5'd t° 'how disgust at a dog, and, while 
 «»U blind, at a hand that has touched and smells of a dog. or 
 to tremble with excitement at the smell of a mouse. A chicken 
 « young turkey wiU show evident signs of fear at hearing 
 «« cry of a hawk. Ants of various species that are mutually 
 hosnle recognise an enemy, and fight; but, on the other 
 ftand, there are observations to the effect that, if taken youne 
 enough, ants of several such species may be brought up 
 together as a happy family. orougnt up 
 
 ,J^ instinctive lameness or wildness of many animals 
 towards man is probably the effect of intelligence L infor 
 
 ZTLT?* '"^ T ^"°''''''= ^ » ^^*= «^°i<ian^« of the 
 wae kmd of trap, after a short experience of its properties, by 
 
II' '■ 
 
 11 i 
 
 itffl TA€ Study of Animal Lift part ii 
 
 all the mice of a house or birds of a district The wild rabbit 
 is extremely timid, but the domesticated variety is as tame 
 as possible. In explanation of such cases we might easily 
 invoke the ud of " the principle of cessation of natural selec- 
 tion" when the safety of the species ceased to depend upon 
 wildness, but we prefer to suppose that the direct action 
 of intelligence is to a great extent operative. 
 
 As already noted, what are perhaps the most striking 
 examples of instinct of the second class occur among in- 
 sects. The comb-building of bees, the wars, the slave-using, 
 the agricultural pursuits of ants, have been so often de- 
 scribed that they need not detain us here. The brain of an 
 ant was to Darwin the most wonderful piece of matter in 
 the world. Wonderful, indeed, it would be if we supposed 
 that all the acts of an ant were truly instinctive, that is, 
 that the nervous machinery of co-ordination was ready, 
 waiting only the appropriate stimulus to evoke any one of 
 that scries of nicely-adjusted actions. But if we suppose 
 that individual intelligence has a considerable share in that 
 co-ordination, then the brain of an ant, though still very- 
 wonderful, is not to us quite so astounding an arrangement 
 of particles as it was to Darwin. 
 
 The third class of instincts, those connected with 
 reproduction, comprise such actions as the building of 
 homes and nests, the storage of food for the use of 
 young that may never be seen, and the care of young after 
 
 birth. 
 
 The nest-building of birds would form a very good sub- 
 ject upon whjch to experiment, in order to determine how 
 far such a complex act may be truly instinctive, and how 
 far it is perfected by training, by imitation, and by intelli- 
 gent practice and observation. The method would be to 
 isolate young birds from their parents and firom all other 
 creatures of their kind, so as to preclude training and 
 imitation, and then see how far the nests that they 
 built resembled the typical nest of their species. Then one 
 might remove other birds from their parents but allow them 
 the society of the members of an allied species, but one 
 whose nests diflfered to some observable extent from thoM 
 
CHAP. X 
 
 Instinct 
 
 i«3 
 
 It IS stated tJiat the nests of RriHeiT u- j . 
 Australia differ very grea!w from thl ^"'''u '^' ^"^"^ "" 
 build at home. No«f S mt^ hi h "'''' '^' '''"^ *°"'^ 
 training and the possil^Hues ^f' imitate thl' ^'^ ^^ °' 
 or it may be due to th.. ah««^ 'minting the specific nest, 
 
 to build the charaJJeristifn:^^^^^ °'^^ ""^^"^^ "'^^ -^ch 
 
 or the selection S^rbune'r^^ofThrlt "'" "^^^^ ^^'^ ' 
 lays her eggs, the only sort ofkaf it J.^LTk" ^^'"'^ ^'^^ 
 the grubs, when hatched for ft^' f I^^>,*''^* '"'" ^^"^e 
 butterfly herself d^s not eat^' Jl 1? ^'"^ ^^^'^^^ ^^e 
 of instincts most ^vonderfunn Tk '^ ^^°'^ "' '^^"'P'w 
 obscure in their or^^^ The ?J^' • ^"^^^^'^^ and most 
 Plex for us to believe that th! nt' "'^°''''^ ^'"'^ *°° ^"n^- 
 intelligence. sHa^as we c^nrat'" ''^ "^"'^ °^ 
 mstmcts can only be accounted for by ^e Natu^%"!', T' 
 of fortunate varieties of habit Th^/o T Selection 
 habit of incubation are Sinrf? '^ °^J°""S^ ^"^ the 
 amount of thought harLenS^^^ /'"'^ ^ *^^«-" 
 incline to the idea whiVh ml ^°'* ourselves, we 
 
 such habits ar;t.:'o LTeSeT';^ ? ^°'"^' ^^^^ 
 nearly related to the ^■^^ ^sTlf^'"'' '"^ ^^^*'* ^° 
 
 an explanation of suchlla^s'in tetsTat;. '''^ '^^^?« 
 naturalists have suggested thi- '" ^™s of affect,on^ certain 
 
 that birds sit upon their ee«t ^J^^^^'^ ^'^^"^^ "ot'°n 
 breast. If such were her o£ th^ *' '° '*^' ^ ^^^'^'^ 
 a bird could select as her S m "l ""^^^ P'*^« ^^at 
 nest containing egi whtl .'^^^°"'d ^e a wooUy hairy 
 
 changes gene^:^^aronhem^^^^^^^^^ °^ ^"^^^^ ^^--S 
 
 tion'o f instin^s t^^t^^i:^^' '''^^^ °^ ^''^ -- 
 'J^y by various otheTau^hnr! ^'■^1^^'^'^^ and since his 
 A- R. Wallace and Prl^ ' ""^-^^'^ ^^- Romanes. Mr. 
 
 Weismann's S^trines hale T ^'"^^^ ' "''"^ ^^^^^^^o 
 certain plausibirhy^^'er ^''^''''^'^^ '^^ revision of 
 
 '"""' o^ course, supposed that Natural Selection 
 
i64 The Study of Animal Lift part ii 
 
 was the means of the evolution of habit as much as of 
 
 form. . 
 
 Mr. Romanes, starting from this as a basis, has con- 
 structed a well-reasoned and lucid theory. He supposes that 
 while many instincts have been evolved by Natural Selection, 
 such instincts being called Primary, other habits become 
 instinctive through the " lapse of intelligence." Actions 
 performed at first with mental effort, becoming after suffi 
 cient repetition so ingrained upon the nervous system that 
 a mechanism of neuro- muscular co-ordination has been 
 established, are referred to as Secondary Instincts. He 
 imagines also a third class of Mixed Instincts in which 
 there are primary instincts that have been altered and 
 improved by intelligent variations of habit, or secondary 
 instincts that have been modified by natural selection. 
 
 Obviously, therefore, he supposes that intelligence may 
 be a factor in the formation of any habit that may be under 
 consideration. 
 
 But this theory of instinct becomes impossible if we accept 
 Professor Weismann's doctrine that acquired characters can 
 not be inherited (this doctrine will be discussed in a later 
 chapter). If this be true, the only possibilities are primar>' 
 instincts, and secondary instincts formed afresh during each 
 individual lifetime, and mixed instincts of the same nature. 
 The exact antithesis to Professor Weismann's theory is 
 upheld by Professor Eimer, who believes that instincts have 
 been evolved chiefly by the perpetuation of what Mr. 
 Romanes calls secondary instincts. There is little evidence 
 that this is the case. The value of Elmer's work really lies 
 in his insistence upon the intelligent action of animals as 
 apart from purely instinctive action. 
 
 Mr. Wallace has begun the analysis of the particular 
 forms which the intelligence of animals takes. He supposes 
 that imitation of parents and other members of the species 
 has a great influence upon the actions of individuals He 
 has dwelt especially upon such cases as the song and nest- 
 building of birds. . , .u,, 
 It may be pointed out as a matter for consideration t.iat. 
 granted that parents teach their offspring, as, for instance, 
 
 ^vSiB^S?- 
 
CHAP. X 
 
 Instinct 
 
 '<SS 
 
 birds teach the.r fledglings to fly, and ants their young their 
 place m the community of the nest, and that animals imi- 
 tate each other, it is quite possible, and indeed probable 
 that an mstmct may be steadily improved throughout sud 
 
 !• 10. j..-Vuui.g duck* calcliiDg mollis. (iVom St. JoJu.s lyud S^U.) 
 
 cessivc generations by the intelligence of the individuals of 
 a sivecies, without any acqiiirccl character being inherited 
 therefore^"'''''' ^'''''"''' '" ''"' evolution of instinct are 
 (0 Natural Selection, which miKht develop innate 
 capacity; this is certainly insufficient for the 
 devciopnient of form, and therefor.,-, probably, also 
 of mind. 
 
 ^Sfe:>^*^sw 
 
 lamesms^^^. 
 
MICROCOPY RBOIUTION TEST CHART 
 
 (ANSI and ISO TEST CHART No. 2) 
 
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 ^ /IF PLIED IVMGE Inc 
 
 16&.] lOil Main Slrnt 
 
 Roch«»:*r. N«» York (♦eOS USA 
 
 (716) 482 - 0300 - Phone 
 
 (716) 268- 5989 ■ To. 
 
 ^ 
 
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 i66 
 
 The Study of Animal Life part n 
 
 (2) Individual intelligence, which directly modifies the 
 
 actions of individuals, and is also used when, by 
 imitation and education, the habits of a species 
 are steadily improved. 
 
 (3) The " lapsing of intelligence," forming " second- 
 
 ary," and helping to form " mixed " instincts. 
 But the probable factors are the first twa 
 

 m 
 
 i ii 
 
 PART III 
 
 THE FORMS OF ANIMAL LIFE 
 CHAPTER XI 
 
 THE ELEMENTS OF STRUCTURE 
 
 I. ThtResemblanca and Contrasts between Plaftts and Animals- 
 2. The Relation of the simplest Animals to those which are 
 
 I^f 'f"^^K°^ ^T? ^"? '*™'=*"'"^ (Morphology), and the 
 study of habu and function (Physiology), are both as essen- 
 tial to science as the realities are in life. It is with the 
 forms of animal life and their structure that we have now 
 to do, but It seems useful at the outset to compare plants 
 and animals. 
 
 i.ThB Besomblances and Contrasts between Plants 
 and Animals.— Every one could point out some differences 
 between a tree and a horse, but many might be puzzled to 
 d.stmgursh clearly between a sponge and a mushroom, 
 while all have to confess their inability to draw a firm line 
 between the simplest plants and the simplest animals. For 
 the tree of life is double like the letter V, with divergent 
 branches, the ends of which, represented, let us say by 
 a daisy and a bird, are far apart, while the bases gradually 
 approach and unite in a common root. 
 
 Plants and animals are alike, though not equally, alive 
 
 i 
 
 .41 
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1 68 
 
 The Study of Animal Life part m 
 
 Diverse as are the styles of animal and vegetable archi- 
 tecture, the materials are virtually the same, and the 
 individuals in both cases grow from equally simple 
 beginnings. 
 
 Even movement, the chief characteristic of animals, 
 occurs commonly, though in a less degree, among plants. 
 Young shoots move round in leisurely circles, twining 
 stems and tendrils bend and bow as they climb, leaves 
 rise and sink, flowers open and close with the growing 
 and waning light of day. Tendrils twine round the 
 lightest threads, the leaves of the sensitive plant respond 
 to a gentle touch, the tentacles of the sundew and 
 the hairs of the fly-trap compare well with the sensitive 
 structures of many animals. The stamens of not a few 
 flowers move when jostled by the legs of insects, and the 
 stigma of the musk closes on the pollen. 
 
 Plants and animals alike consist of cells or unit masses 
 of living matter. The structure of the cell and the apparent 
 structure of the living stuff is much the same in both. We 
 may liken plants and animals to two analogous manufac- 
 tories, both very complex ; we study the raw materials 
 which pass in, many of the stages and by-products of 
 manufacture, and the waste which is laid aside or thrown 
 out, but in neither case can we enter the secret room where 
 the mystery of the process is hidden. 
 
 In the pond we find the eggs of water-snails and water- 
 insects attached to the floating leaves of plants; in the 
 ditches in spring we see in many places the abundant 
 spawn of frogs and toads ; we are familiar with the heavily 
 yolk-laden eggs of birds. Now, with a little care it is quite 
 easy to convince ourselves that an egg or ovum is to begin 
 with a simple mass of matter, in part, at least, alive, and that 
 by division after division the egg gives rise to a young animal. 
 We are also well aware that in mosi cases the egg-cell, for 
 cell it is, only begins to divide after it has been penetrated, 
 and in some subtle way stimulated, by a male unit or sperm. 
 The great facts of individual history or development tlicn 
 are, the apparent simplicity in the beginning, the joc 
 liminary condition that the egg-cell be united with a male 
 

 CHAP. XI ne Elements of Structure ,69 
 
 unit, and the mode of growth by repeated division of the 
 ovum and its daughter-cells. In those plants with wh ch 
 we arc most familiar, the facts seem different, for we wa ch 
 bean and oak growing from seeds which, in tead ofben^ 
 simple units, are very complex structures. But the seed"! 
 not the begmnmg of a plant, it has already a long Sil 
 behmd ,t, and when that history is traced back tofhe sleZ 
 box and possible seeds of the parent plant, there t wilt be 
 seen that the beginning of the future he'rb o; tree is a s^'e 
 cell This IS the equivalent of the animal ovum, and ifke 
 •t, begins Its course of repeated divisions after k has been 
 joined by a kernel or nucleus from the pollen g^n 
 
 Thus, to sum up, along three different paths we reach 
 th same conclusion, that there is a fundament umty 
 
 T^^rttl thf st'"'"^^\ '" *'^ ^"^"^'^^ -'-" - 
 .IhTm • u '^°"^^ ^"^ '"ortar of their structure 
 and lastly, m the way in which each individual berins and 
 grows, there is a real unity. ^ 
 
 ThJf' *f^.^'/"'.PJa"ts and animals are very different 
 
 wide^ and bear diffelt^U^.^^Tie^'cTs^or^^^^^^^^^ 
 and diversity are as undeniable as the inseparable S^ol 
 he basal trunk and the genuine sameness of life throughout 
 the whole tree. I have stated the chief contrast between 
 plants and animals in a tabulated summary— 
 
 > III 
 
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CHAP. XI The Elements of Structure 17, 
 
 The net result of this contrast is that animals are more 
 active than plants. Life slumbers in the plant; it wakes 
 and works m the animal. The changes associated with the 
 
 2T ? 'i^"''"^^^''^ seemingly more intense and 
 rapid , the ratio of disruptive, power-expending changes to 
 constructive power-accumulating changes is greater? most 
 
 nlan'tsdo %r"r "'''■^^. "^ ^° '''''' '^"-^ ^^an most 
 plants do. They live on richer food ; they take the pounds 
 
 which plants have accumulated in pence, and spend them 
 Of course plants also expend energy, but for the most paT 
 w.thin their own bodies ; they neither toil nor spin. They 
 stoop to conquer the elements of the inorganic world but 
 have comparatively little power of moving or feeling. They 
 are more conservative and miserly than the liberally spend 
 thnft animals, and it is possible that some of the most 
 chZvlTf ' r'^'^'-f °f plants, e.g. cellulose, may be 
 chemical expressions of a marked preponderance of con- 
 structive and up-building vital processes. It is enough, 
 however If we have to some extent realised the common^ 
 places that plants and animals live the same sort of life 
 but that the animals are on an average more active and 
 wide-awake than the plants. 
 
 whi'.'w! ^'^^*i?'' °{ *^' ®^Pl«»* ^inials to those 
 r^Jat tnhT' ^rfle^-F'-on^ the pond-water catch in 
 
 t.Sfl °"' '^^ '"'^" ^"''"''*'^' ^"PP«^^ '^ ^^ ^ tiny 
 
 uater-flea or a mmute " worm » ; how does it differ from one 
 
 nnnv n,T 'f T^"^"' '"'^ "' ^" Ir^in.on^r. ? It consists of 
 
 nst is L i'Tf T'^' '"''^•'^^ °^«"'y °"^- The con- 
 
 hitchoH f '^^.\^*^^!^-^^" an ^^^ and the bird which is 
 
 cds J^I fr r'""."- '^'^^ ^'"^P'^^' '-^"""als are single 
 cells, a 1 he others from sponge to man are many-celled. 
 
 cmlnJ? ^'■' """' '■ ^" others-the Metazoa-are 
 
 coniposite aggregates of units, or cities of cells 
 
 •I uormTf'*'' "'"' "f-°:^° "^ '•^^ Protozoa with that of 
 ien Z' \ ^\ -^ ''"■^- ^^"'h ^'-^ ^'i^«. both may be 
 
 Se, S'^ " "sefu,, engulfing food, and getting rid of 
 
 1 nn %n??i T ^^^^'^'"S-' ^o-- «^^rbonic acid will poison 
 
 t'^nn. and dearth of oxygen will kill them ; both grow and 
 
 4^ 
 
 a 
 
 !-i«1 
 
 .iJ« 
 
17a 
 
 Tfie Study of Animal Life part m 
 
 multiply. But in the single -celled Protozoon all the pro- 
 cesses of life occur within a unit mass of living matter. In 
 the many-celled Metazoon the various processes occur at 
 different parts of the body, are discharged by special sets of 
 cells, among which the labour of life has been divided. The 
 life of the Protozoon is like that of a one-roomed house 
 which is at once kitchen and work-room, nursery and coal- 
 cellar. The life of the Metazoon is like that of a mansion 
 where there are special rooms for diverse purposes. 
 
 In having no " body " the Protozoa are to some extent 
 relieved from the necessity of death. Within the compass 
 of a single cell they perform a crowd of functions, but tear 
 and wear are often made good again, the units have great 
 power of self-recuperation. They may, indeed, be crushed 
 to powder, and they lead no charmed life safe from the 
 appetite of higher forms. But these are violent deaths. 
 What Weismann and others have insisted on is that 
 the unicellular Protozoa, in natural conditions, need never 
 die a natural death, being in that sense immortal. It 
 is true that a Protozoon may multiply by dividing into two 
 or more parts, but only a sort of metaphysical individuality 
 is thus lost, and there is nothing left to bury. We would 
 not, however, give much prominence to a strange idea of 
 this kind. For the " immortality of the Protozoa " is little 
 more than a verbal quibble ; it amounts to saying that our 
 common idea of death, as a change which makes a living 
 body a corpse, is hardly applicable to the unit organisms. 
 I believe, moreover, that the idea has been exaggerated ; 
 for instance, the Protozoa in the open sea, in their natural 
 conditions, seem to die in large numbers. 
 
 The combination of all the vital activities within the 
 compass of a single-cell involves a very complex life within 
 the unit, — not more complex than the entire life of a many- 
 celled animal, but fuller than that of one of its component 
 cells. While a Protozoon is relatively simple in structure, 
 its life of crowded functions, such as moving, digesting, 
 breathing, is exceedingly complex. The simpler an organism 
 is in structure the more difficult will it be to study its separate 
 functions. Physiological or functional simplicity is in inverse 
 
CHAP. XI The Elements of Structure 173 
 
 ratio to structural or morphological simplicity Thus the 
 physiologist makes most progress when he seeks to under- 
 stand animals with many parts, for there he can find a large 
 number of units, all as it were working, at one task. The 
 life of a Protozoon is more manifold and complex than that 
 of any unit from a higher animal, just as the daily life o 
 the savage-at once hunter, shepherd, warrior-is more 
 varied than ours. 
 
 Already it has been recognised that every many-celled 
 ammal begins ts life as a single cell,.-as an egg-cell with 
 .hich a male element has united. Every Metazoon begins 
 Its hfe as a Protozoon, no matter how large the animal 
 
 Iti: t" f?''r"^ °^" ""° '^^^^^ ^han fern-seS" 
 no matter how lofty the result, for man himself has to beg n 
 his life at the literal beginning. The fertilised egg-ceH 
 divides and re-divides, its daughter-cells also divide, the 
 resultant units are arranged in layers, clubbed together to 
 form tissues compacted to form young organs, and the 
 result IS such a multicellular body as we possess ; but whHe 
 this body-making proceeds, certain units are ke^t apart in 
 some way insulated from the process of growth, to form 'the 
 future reproductive elements, which, freed from the aduU 
 body, will begin a new generation. Back to the beginning 
 again every Metazoon has to go, and if we believe that thf 
 Protozoa are not only the simplest, but also represent the first 
 ninials we have here the first and perhaps most importan 
 .llustration of the fact that in its developnfent the individua 
 more or less recapitulates the history of the race The 
 simplest animals are directly comparable with the repro- 
 luu .e cells of higher animals, but the divided cells of the 
 ovum remain clubbed together to form a young animal while 
 the daughter-cells of a Protozoon separate from 0^0^^ 
 each as a new life. «t"uiner, 
 
 The gulf between the single-celled and many-celled 
 an.mals IS a deep one, but it has been bridged. Otherwise 
 we should net exist. Trace, of the bridge now rema n n 
 
 l?t"tf '"' 'I'i^if"' ^^°*°^°^'" -hichfhowever tTo?bl " 
 some to those who like cnsp distinctions, are most instruc- 
 tive to those who would appreciate the continuity of the 
 
 m 
 
 \\ 
 
 ^ilil 2i 
 
 i 
 
 i 
 
 
174 
 
 The Study of Animal Life part hi 
 
 tree of life. These exceptional Protozoa are loose colonies 
 of cells, descendants or daughter- cells of a parent unit, 
 which have remained persistently associated instead of 
 going free with the usual individualism of Protozoa. They 
 illustrate to some minds a primitive co-operation of cells ; 
 they show us how the Metazoa or multicellular animals may 
 have arisen. 
 
 3. The Parts of the Animal Body. — The physioloj^ist 
 investigates life or activity at different levels, passing from 
 his study of the animal as a unity with habits and a tem- 
 perament, to consider it as an engine of organs, a web of 
 tissues, a city of cells, or finaliy as a whirlpool of livitiL; 
 matter. So the morphologist investigates the form of the 
 intact animal, then in succession its organs, their component 
 tissues, the minuter elements or cells, and finally the struc- 
 ture of the living stuff itself. Moreover, as there is no real 
 difference between studying a corpse and a fossil, the pale- 
 ontologist is also among the students of morphology ; and 
 most of embryology consists of studies of structure at dif- 
 ferent stages in the animal's life-history. 
 
 The o\x\.tx form of normal animals seems to be always 
 artistically harmonious. It has a certain hardly definable 
 crystalline perfection which pleases our eyes, but those who 
 have not already perceived this will not see much meaning 
 in the assertion, nor in Samuel Butler's opinion that "foim 
 is mind made manifest in flesh through action." 
 
 " I believe a leaf of grass is no less than the journey-work of tht 
 stars, 
 And the pismire is equally perfect, and the grain of sand, and 
 
 the egg of the wren, 
 And the tree-toad is a chef-d'oeuvre for the highest, 
 And the running blackberry would adorn the parlours of heaven, 
 And the narrowest hinge in my hand puts to scorn all machinny, 
 And the cow cruhching with depressed head surpasses any si.', no, 
 And a mouse is miracle enough to stagger sextillions of infukl> !' 
 
 Walt Whitman. 
 
 It is also important to think of the differ nt kind? of 
 symmetry, how for instance the radiating sea-anemones and 
 jellyfishes, which are the same all round, differ m rkedly 
 
CHAP. XI The Elements of Structure 175 
 
 from bilaterally symmetrical worms, lobsters, fishes and 
 most other animals. Then there is 'the differ^.ce beJween 
 unsegmented anniials which are all one piece (like the 
 lower worms and the molluscs), and those\vhose bodies 
 consist, as m earthworm and crayfish, of a series of nwe o 
 less snmlar nngs or segments, due to conditions of growth 
 of which we know almost nothing {,ro\Mn 
 
 Organs are well-defined parts, such as hmb or liver hean 
 or bram m which there is a predominance of one or a few 
 
 and fnl: ""T''l '"''^^"^"y' ^"^^^ '" ^he ind v!du^ 
 and in the race do they take form and function. There is 
 contractility before there are definite contractile organTo 
 muscles ; there ,s diffuse sensitiveness before the^e are 
 defined nerves or sense-organs. The progress of structure 
 ahke m the individual and in the race, i^ from siS^ c ty 
 to complexity, as the progress of function is from homo^ 
 
 twoTreLt H^r '" ^^^^^^^ us specialisatio" The 
 uvo great kinds of progress may be illustrated by contrastim! 
 a sea-anemone and a bird. The higher animal ha mort 
 numerous parts or organs, the division of labour withiri s 
 body has brought about more differentiation of st ull 
 but It IS also a more perfect unitv it<; n^rfc , ^'"'^^' 
 Ujoroughly knit together^nrha^Jiisel '^TLrisTo' 
 gress in integration as well as in differentiation ^ 
 
 " The shoulder-girdle of the skate," W. K. Parker savs " mo„ 1 
 
 for^s ^the .obile front waif of the ILS, "^l^ ^^^^ 
 
 we«'^SL'''' xf '^'"^r '^^-^'^^^ °^ ^--^ appeared 
 can say little. The simplest sponges and polypes are 
 
 .H.'l 
 
 1 1« k K 
 
 IJf 
 
 * . ■f^:i 
 
•M ' .' 
 
 176 
 
 The Study of Animal Life part in 
 
 little more than two-layered cups of cells, the cavity of the 
 cup being the primitive food -canal. A parallel sta^e 
 occurs in the early life-history of most animals, when the 
 embryo has the form of a two-layered sac of cells, or is in 
 technical language a gastrula. Both in the racial and 
 individual life-history the formation of this primitive food- 
 canal occurs very early. But it is not certain that it— the 
 primitive stomach— was not at a still earlier stage an in- 
 ternal brood-cavity ! 
 
 But instead of speculating about this, let us seek to 
 understand what is meant by ae correlation of organs. 
 Certain parts of the body stand or fall together, they are 
 physiologically knit, they have been evolved in company. 
 Thus heart and lungs, muscles and nerves, are closely 
 correlated. Sometimes it is obvious why two or three 
 structures should be thus connected, for it is of the very 
 essence of an organism that its parts are members one of 
 another. In other cases the reason of the connection is 
 
 obscure. . 
 
 When organs either in the same or in different animals 
 have a similar origin, anc' are built up on the same funda- 
 mental plan, they are called homologous. Those whose 
 resemblance is merely that they have similar functions are 
 termed analogous. Even Aristotle recognised that some 
 structures apparently different were fundamentally the 
 same, and no small part of the progress of morphology has 
 consisted in the recognition of homologies. Thus it was a 
 great step hen Goethe and others showed that the sepals, 
 petals, stamens, and carpels of a flower were really modified 
 leaves, or when Savigny discerned that the three pairs of 
 jaws besidt an insect's mouth were really modified legs. 
 To Owen tiie precision of our conceptions in regard to 
 homologies is in great part due, though subsequent studies 
 in development have added welcome corroboration to many 
 of the comparisons which formerly were based solely on the 
 results of anaton < . Thus an organ derived from the outer 
 emVryonic layer cannot be homologous with one derived 
 from the innermost stratum of embryonic cells. Homo- 
 logous organs in one animal are well illustrated by the 
 
CHAP. XI The Elements of Structure 177 
 
 all homo OKOUS. So tri^ rl.o ,!;«• . f ' ^ *^ 
 
 the oeclor-H fin „f , «l ;''^,'''''if™' forms of fore-limb, 
 
 analogous „„. homolo'o *\ .hi^: oT a'"bW ^hUe't 
 iZr' "''= '"^ ''^"^ -' ^°"> analogous and' W 
 
 Fig. 33.— Bones of the wing in pigeon CA) h:,t iv.\ 
 
 (Frol ChambeA^^:^^:.^J.g;.;^""^' pterodactyl (C). 
 
 hvHr,« f *• nsfies, seems usua v to bp t 
 
 ■mportant respiratory (and sometimes yolk-absorbing) bLth^ 
 
 i , 
 
 IP''. 
 
 }? 
 
 
 
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 ^ 
 
 i 
 
 1 
 
 fl 
 
 1 
 
 ■ || 
 
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 '1 
 
 1 
 
 ( 
 
 J 
 
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 : 
 
 
 
 
 
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 ^^^ 
 
1 i 
 
 178 The Study of Animal Life part in 
 
 robe, and in almost aU mammals by part of the placenta 
 which unites mother and unborn oflFspring. 
 
 Substitution of Organs.~To the embryologist Klemen- 
 berg we owe a suggestive conception of organic change, 
 which he speaks of as the development of organs by sub- 
 stitution: An organ may supply the stimulus and the 
 necessary condition for another which gradually supersedes 
 and replaces it. In the simplest backboned animals, such 
 as the lancelet, there is a supporting gristly rod along the 
 back • among fishes the same rod or notochord is largely 
 replaced by a backbone; in yet higher Vertebrates the 
 adults have almost no notochord, its replacement by the 
 backbone is almost complete. So in the individual life- 
 history, all vertebrate embryos have a notochord to begin 
 with ; in the U ncelet and some others this is retained 
 throughout life, in higher forms it is temporary and serves 
 as a scaffolding around which, from a thoroughly distinct 
 embn'ological origin, the backbone develops. What is the 
 relation between these two structures — notochord anu 
 backbone? According to Kleinenberg, the notochord 
 supplies the necessary stimulus or condition for the 
 development of the backbone which replaces it. 
 
 Rudimentary Organs. -{a) Through some ingrained 
 
 defect it sometimes happens that an organ does not 
 
 develop perfectly. The heart, the brain, the eye may be 
 
 spoilt in the making. Such cases are illustrations of 
 
 arrested development, {b) A parasitic crustacean, such as 
 
 the Sacculina which shelters beneath the tail of a crab, 
 
 begins life with many equipments such as legs, food-canal, 
 
 eye, and brain, which are afterwards entirely or nearly 
 
 lost • the sedentary adult sea-squirt or ascidian has lost the 
 
 tail 'the notochord, the spinal cord which its free-swimmmg 
 
 tadpole-like larva possessed. Such cases are illustrations 
 
 of degeneration. In these instances the retrogression is 
 
 demonstrable ia each lifetime, in other casf^s we havx to 
 
 compare the animal with its ancestral ideal. Thus there 
 
 are many cave-anim.ils whose eyes are always blind and 
 
 abortive. The little kiwi of New Zealand has only apologies 
 
 for wings. We need have no hesitation in calling these 
 
CHAF. XI The Elements of Structure ,79 
 
 animals degenerate in eyes and fore-limbs respectively 
 if) But somewhat different are such structures as the 
 
 «!•■ Jhkh t'^^"'^ ^'"-^^^^^^ °^ reptiles birds ^d 
 mammals, which have no respiratory significance, oJ the 
 embryonic teeth of whalebone whales, of £me paiTots and 
 turtles, which in no case come to anything. ^ They ^e 
 vestigia^ structures, which are partly expllined on t^e 
 
 n!^ Li ', ^'^'' ^^ "'^'"^'^ "^^d ^h« &i»<lefts as fishes 
 and tadpoles do, that the ancestors of whalebone unales 
 birds, and turtles had functional teeth. No one can sav 
 with certamty of vestigial structures that they are entirely 
 useless, nor can one precisely say why they persist S 
 their original usefulness has ceased. They remairbecmise 
 of necessities of growth of which we are ignomnt and 
 they may be useful in relation to other struSureTthough 
 m themselves functionless. mougn 
 
 Classification of Organs.~^Ne may arrange omans 
 according to their work, some, such as limbs and wea^ns 
 being busied with the external relations of the orS^^ ' 
 
 bte^L "It- ^ n "" '"' ^'^^^' ^^'"^ concen^fT whh 
 ntemal affairs. Or we may classify them according o 
 heir development from the outer, middle, or inner layfr of 
 he embryo. Thus brain and sense-organs 'are ar/ys maTnly 
 due to the outer stratum (ectoderm or epiblast); muscles 
 and skeleton arise from the middle mesodeL or ^^1' 
 the gut and its outgrowths such as lungs and liver primarilv 
 ongmate from the inner endodenn or hypoblast Or we 
 may arrange the various structures more oVless arbitr^nMy 
 In ?."""'" °^ description as follows : the skin and its 
 outgrowths, appendages, skeleton, muscular system"nervcu 
 h hoH '""^.'=-°'-«;^"«' the food-canal and its outgrowths 
 the body-cavity, the heart and blood-vessels, the resoirrton; 
 organs, the excretory system, the reproductive organ ^ 
 rtssues.-To the school of Cuvier we owe the analvsis 
 
 t^yTZ\ bS" T^ r^"^"^ organ:;'S'^;^ 
 whichThi . ^ ^ published his^««/^;«,> G^„^rale,\n 
 
 w organs to their component tissues, and maintained that 
 
 i i 
 
 li 
 
 t . 
 
 J 
 
 I i 
 
ido The Study of Animal Life part m 
 
 the function of an organ might be expressed in terms of the 
 
 properties of its tissues. , .,• i r *u 
 
 If we pass to the next step of analysis, and thmk of the 
 body as a complex city of cells, we are better able to 
 understand what tissues are. Each cell corresponds to a 
 house, a tissue corresponds to a street of similar houses 
 In a city like Leipzig many streets are homogeneous, formed 
 by houses or shops in which the predominant activity is the 
 same throughout. A street is devoted to the making of 
 clothes, or of bread, or of books. So m the ammal body 
 aggregates of contractile cells form muscular tissue, of 
 supporting cells skeletal tissue, of secreting cells glandular 
 
 tissue, and so on. .,,.•• 
 
 It is enough to state the general idea that a tissue is an 
 aggregate of more or less similar cells, and to note that the 
 different kinds may be grouped as follows :— 
 
 I. Nervous tissue, consisting of ceUs which receive, 
 
 transmit, or originate nerve-stimuli. 
 II Muscular tissue, consisting of contractile cells. 
 III'. Epithelial tissue, consisting of lining and covering 
 cells, which often become glandular, exuding the 
 products of their activity as secretions. 
 IV. Connective tissue, including cells which bind, 
 
 support, and store. 
 Cells —To the discovery and perfecting of the micro- 
 scope we owe the analysis of the body into its unit masses 
 of living matter or cells. From 1838-39, when Schwann 
 and Schleiden stated in their -cell doctrine" that al 
 organisms-plants and animals alike-were bu.lt up of 
 cells, cellular biology may be said to date It was soon 
 shown as a corollary that every organism which reproduced 
 in the ordinary fashion arose from a single egg-cell or 
 ovum which had Loen fertilise-! by union with a male-eel. 
 or spermatozoon. Moreover, the position of the snnple. 
 animals and plants was more clearly appreciated ; they are 
 sinjfle cells, the higher organisms are multicellular 
 
 Now the cells of the animal body are necessarily varied. 
 for the existence of a body involves division of lalxjur 
 
CHAP. XI Tfte Elements of Structure ,8i 
 
 among the units. Some, such as the lashed cells lining 
 t e w.ndp.pe, are very active, like the I nfusorfan Protozoa^ 
 
 t sue ' te'"?"" ''' ''^"^"^ '^"^ ^"^^'-^^»« of connective 
 tissue, are very passive, something like the Greearines 
 
 1 bet^efn tL^'^ "''^ '^'^"^ ^°'p"-'- or irufo^'s; 
 But it is true of most of them that they consist (.) of a 
 
 complex and in part living cell -substance, in which keen 
 e>es lookmg through good microscopes detect an TmnW 
 
 «t: c^rsir" tc~= '^^^'^ 
 
 H atoenl, through which conimunicalions wiih neiKh- 
 
 lii 
 
 I 1 
 
 ill 
 1 I 
 
 .1 
 
x8a The Study of Animal Life part in 
 
 boating cells are often established ; and (4) of cell cc ents, 
 whkh can be chemically analysed, and which are pr. lucts 
 Tnhe Tal activity rather than parts of the hymg substance, 
 such as pigment, fat, and glycogen or animal starch. 
 
 The RrS^th if all multicellular animals depends upon a 
 mul iplication of the component cells. Like organisms, 
 Tells have definite limits of growth which they rarely exceed 
 gta^ts among the units are rare. When the hmu ot 
 erowth is reached the cell divides. 
 
 The necessity for this division has been partly explained 
 by Spencer and Leuckart. If you take a round lump of 
 dough, weighing an ounce- another of two ounces, a third 
 o?fou ounL,you obvi-.-si have three masses success- 
 °vdy doubled but in oouoling the mass you have not 
 doubled the surface. The mass increases as the cube^^the 
 surface only as the square of the radius. Suppose these 
 lumos aU^ the second has twice as much living matter as 
 hTfirst but not twice the surface. Yet it is through the 
 Surface Ihat the living matter is fed, aerated, and P-^^^^^ 
 The unit will therefore get into physiological difficulties a 
 itLws bigger, because its increase of surface does not 
 kee^ pace with its increase of mass. Its waste tends to 
 exceed its repair, its expenditure gams on its income. 
 What are the alternatives ? It may go on growing and d.e 
 ^b- this is not likely), it may cease growing at the fit 
 £nit it may greatly increase its surface by outflowmg 
 pTo^Us (which thus may be regarded as I'fe-saving) or 
 it may divide. The last is the usual course. When the 
 unit has grown as large as it can conveniemly grc.-, 
 divides; in other words, it reproduces at the l.m t 
 growth, when proce ~s of waste are gaining on th s 
 of construction i iding, the mass is lessened, the 
 
 surface increased, the nfe continued. ^..^ . ,^11- 
 
 But although we thus get a general rationale of oil 
 division, we are not much nearer a conception of th 
 fnS forces which operate when a cell divi^^^^ ; or . 
 most cases the process is orderly and complex, and is 
 rmehow governed by the behaviour of the nucleus, f e. 
 rLTs of the modem study of minute structure are more 
 
CHAP. XI The Elements of Structure 183 
 
 marvellous than those which relate to dividing cells From 
 Protozoa to man, and also in plants, the process 'is strik- 
 ingly uniform. The nucleus of the cell becomes more 
 active, the coil or network of threads which it contains is 
 undone and takes the new and more regular form of a 
 spindle or barrel. The division is most thorough, each of 
 the two daughter- cells getting an accurate half of the 
 original nucleus. Recent investigators, moreover, assert 
 that from certain centres in the cell-substance an influence 
 IS exerted on the nuclear threads, and they talk of an archo- 
 plasm within the protoplasm, and of marked individuality of 
 behaviour m the nuclear threads. 
 
 From the cell as a unit element we penetrate to the 
 protoplasm which makes it what it is. Within this we 
 discern an intricate network, within this, special centres of 
 force— "attractive spheres" and "central corpusd^s » or 
 an "archoplasm" within the protoplasm! We study the 
 nucleus, first as a simple unit which divides, years after- 
 wards as composed of a network or coil of nuclear threads 
 which seem ever to become more and more marvellous, 
 'behaving like little organisms." We split these up 
 into "microsomata," and so on, and so on. But we do 
 not catch the life of the cell, we cannot locate it, we -annot 
 give an account of the mechanics of cell-division. It is a 
 mystery of life. After all our analysis we have to confess 
 that the cell, or the protoplasm, or the archoplasm, or the 
 chromatin threads of the nucleus, or the " microsomata " 
 which compose them, baffle our analysis ; they behave as 
 they do because they are alive. Were we omniscient 
 chemists, such as Laplace imagined in one of his specula- 
 tions, and knew the secret of protoplasm, how its touch 
 upon the simpler states of matter is powerful to give them 
 ife, we should but have completed a small part of those 
 labours that even now lie waiting us ; what further investi- 
 gations will present themselves we cannot telL 
 
 «• ,■■■ 
 
 M 11 
 
 :i#|| 
 
 
 ■rq] 
 
 
 i-% 
 
CHAPTER XII 
 
 THE LIFE-HISTORY OF ANIMALS 
 
 I Modti of ReproducHon—z. Divergent Modes of Reproduction- 
 3. Historical— A- The Egg- Cell or Ovum—S- The Malt- 
 Cell or Spermatozoon— 6. Maturation of the Ovum—'j. 
 Fertilisation — %. Segmentation and the first stages in 
 Developnunt—g. Some Generalisations— The Ovum Tkcfy, 
 the Gastrtea Theory^ Fact of Recapitulation, Organic Con- 
 tinuity 
 
 In his exercitation "on the efficient cause of the 
 chicken," Harvey (1651) confesses that "al'^-ough it be a 
 known thing subscribed by all, that the fcEtus assumes i:s 
 original and birth from the male and female, and conse- 
 quently that the egge is produced by the cock and henne. 
 and the chicken out of the egge, yet neither the schools ox 
 physicians nor Aristotle's discerning brain have disclosea 
 the manner how the cock and his seed doth mint an. 
 coine the chicken out of the egge." The marvellov.; 
 facts of growth are familiar to us — the sproutmg corn 
 and the opening fl< weis, the growth of the chick within 
 the egg and of the child within the womb; yet so 
 ditficult is the task of inquiring wisely into this nianei- 
 lous renewal of life that we must reiterate the cd 
 confession: «' ingratissimum opus scribere ab lis qu-t, 
 multis a natura circumjectis tencbris velata, sensuun 
 lucis inaccessa, hominum agitantur opinionibus." 
 
 1. Modes of Eeproduction.— The simplest animals 
 divide into two or into many parts, each of which becomes a 
 full-grown Protozoon. There is no difficulty in understanding 
 
CHAP. XII The Life-History of Animals ,85 
 
 why <^ch part should be able to regrow the whole, for each 
 IS a fair sample of the original whole. Indeed, when a 
 large Protozoon is cut into two or three pieces with a knife 
 each fragment .s often able to retain the movements and 
 life of the intact organism. Among the Protozoa we find 
 some .n which the multiplication looks like the rupture of a 
 cell which has become too large ; In others numerous buds 
 are set free from the surface ; in others one definitely-formed 
 bud (hke an overflow of the living matter) is set free; in 
 others the cell divides into two equal parts, after the 
 manner of -ost cells; and numerous divisions may also 
 occur in rapid succession and within a cyst, that is in 
 limited time and space, with the result that maily " spo^s " 
 are formed. These modes of multiplication form a natural 
 series. 
 
 In the many<elled animals multiplication may still pro- 
 ceed by the separation of parts ; indeed the essence of 
 reproduction always is the separation of part of an organ- 
 ism to form-or to help to form_a new life. Sponges bud 
 profusely, and pieces are sometimes set adrift ; W Hydra 
 fonns daughter polypes by budding, and these are set free • 
 sea-anemones and several worms, and perhaps even some' 
 star-fishes multiply by the separation of Comparatively large 
 
 S It i ". Tl' °' -"l^'Pl'-tion-which is'calle'd 
 a.exual-has eviden limitations. It is an expensive way 
 of multiplying. It is possible only among comparatively 
 ^'-mple animals m which there is no very high degree of 
 
 of a sponge, Hydra sea-anemone, or simple worm may 
 grw mo adult animals, this is obviousl/not the case 
 
 t'o^ nf ?H ;;' * '"^'^' ""' ^ ^'^- Thus with the exceo- 
 12 V degenerate Tunicates there is no budding 
 
 Spolr'^^^^^' "°^ --^ ^o"--. nor an.onf 
 
 Ta ;?vs ^IT"''"'', ^"'iP^^^'b'^ °"'y in ^'-"Pler animals, 
 m4ti^ th^t nf' "^^'^ r ^«=*^on.panied by anothe; 
 m .hod-that of sexual reproduction. The phrase " sexua' 
 reproduction » covers several distinct (acts : (a) the separ^.' 
 
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 t 
 
 1 
 
 
 i 
 
 •* 
 
 ftp 
 
 t 
 
 % 
 
 i 
 
 m 
 
1 86 The Study of Animal Life part ii! 
 
 tion of special reproductive cells ; (*) the production of two 
 different kinds of reproductive cells (spermatozoa and ova), 
 which are dependent on one another, for in most cases an 
 ovum comes to nothing unless it be united with a male-cell 
 or spermatozoon, and in all cases the spermatozoon comes 
 to nothing unless it be united with an ovum ; {c) the pro- 
 duction ot spermatozoa and ova by different (male and 
 female) organs or individuals. ,, j • i 
 
 (rt) It is easy to think of simple many-celled animals 
 beinc multiplied by liberated reproductive cells, which 
 differed but little from those of the body But as mo.e 
 and more division of labour was established m the bodies 
 of animals, the distinctness of the reproductive eel s om 
 the other units of the body became greater. Finally, the 
 prevalent state was reached, in which the only cells able 
 to begin a new life when liberated are the reproductive 
 cells They owe this power to the fact that they have not 
 shared in making the body, but have preserved intact the 
 characters of the fertilised ovum from which the parent 
 
 itself arose. , • r „ 
 
 (*) But, in the second place, it is easy to conceive of a 
 simple multicellular animal whose liberated reproductive 
 cells were each and all alike able to grow into new 
 organisms. In such a case, we might sP^aT^^of sexua 
 reproduction in one sense, for the process would be different 
 from the asexual method of liberating more or less large 
 Darts But yet there would be no fertilisation and no sex, 
 for fertilisation means the union of mutually dependent 
 reproductive cells, and sex means the existence of two 
 physiologically different kinds of individuals, or at least 
 of organs producing different kinds of reproductive cells. 
 We can infer from the Protozoa how fertilisation or the union 
 of the two kinds of reproductive cells may have had a 
 .gradual origin. For in some of the simplest Protozoa, ^.^. 
 Protomyxa, a large number of similar cells sometimes flow 
 together ; in a few cases three or more combine ; m most a 
 couple of apparently similar units unite; while m a few 
 instances, eg. Vorticella, a small cell fuses with a large one, 
 just as a spermatozoon unites with an ovum. 
 
CHAP. XII The Life-History of Animals 
 
 187 
 
 (r) But the higher forms of sexual reproduction imply 
 more than the liberation of special reproductive cells, more 
 than the union of two different and mutually dependent 
 kinds of reproductive cells, — they imply the separation 
 of the sexes. The problem of sexual reproduction becomes 
 less difficult when the various facts are discussed separ- 
 ately, and if you grant that there is no great difficulty 
 in understanding the liberation of special cells, and 
 no great difficulty in understanding why two different 
 kinds should in most cases have to unite if either is to 
 develop, then I do not think that the remaining fact — 
 the evolution of male and female individuals— need remain 
 obscure. 
 
 If we study those interesting Infusorian colonies, of 
 which Volvox is a good type, the riddle may be at least 
 partially read. Though Protozoa, they are balls of cells, in 
 which the component units are united by protoplasmic 
 bridges and show almost no division of labour. From 
 such a ball of cells, units are sometimes set free which 
 divide and form new colonies. In other conditions a less 
 direct multiplication occurs. Some of the cells— apparently 
 better fed than their neighbours— become large; others, 
 less successful, divide into many minute units. The large 
 kind of cell is fertilised by the small kind of cell, and there 
 IS no reason why we should not call them ova and sperma- 
 tozoa respectively. In such a Volvox, two different kinds 
 of reproductive cell are made within one organism. But 
 we also find Volvox balls in which only ova are being 
 made, and others in which only spermatozoa are being 
 made. The sexes are separate. Indeed we have in Vol- 
 vox, as Dr. Klein— an enthusiastic investigator of this form 
 — nglitly says, an epitome of all the great steps in the 
 evolution of sex. 
 
 So far I have stated facts ; now I shall briefly state the 
 theory by which Professor Geddes has sought to rationalise 
 these facts. 
 
 AH through the animal series, from the active Infusorians 
 and passive Gregarines, to the feverish birds and sluggish 
 reptiles, and down into the detailed contrasts between ordei 
 
 III; 
 
 til! 
 
 •' 1 
 
 ■J il 
 
 1 h\ 
 
i88 The Study of Animal Life part m 
 
 and order, species and species, an antithesis may be read 
 between predominant activity and preponderant passivity, 
 between lavish expenditure of energy and a habit of storing, 
 between a relatively more disruptive {katabolic) and a re- 
 latively more constructive {anabolic) series of changes in 
 the protoplasmic life of the creature. The contrast between 
 the sexes is an expression of this fundamental alternative of 
 
 variation. 
 
 The theory is confirmed by contrasting the characteristic 
 product of female life— passive ova, with the characteristic 
 product of male life— active spermatozoa ; or by summing 
 up the complex conditions (abundant food, favourable 
 temperature, and the like) which favour the production of 
 female offspring, with the opposite conditions which favour 
 maleness ; or by contrasting the secondary sexual char- 
 acters of the more active males {e.g. bright colours, smaller 
 size) with the opposite characteristics of their more passive 
 
 mates. 
 
 Apart from the general problem of the evolution of sex, 
 those who find the subject interesting should think about 
 the evolution of the so-caUed » sexual instincts," as illus- 
 trated in the attraction of mate to mate. As to the actual 
 facts of pairing and giving birth, it seems to me that 1 have 
 suggested the most profitable way of considering these in a 
 former part of this book where courtship and parental care 
 are discussed, though 1 believe firmly with Thoreau, that 
 " for him to whom sex is impure, there are no flowers in 
 
 nature." 
 
 2. Divergent Modes of Reproduction.— (a) //;?mrf- 
 i>;iro^V«w.— Especially among lower animals, both ova 
 and spermatozoa may be produced by one individual, 
 which is then said to be hermaphrodite. So most common 
 plants produce both seeds and pollen. Some sponges and 
 stinging animals, many " worms," e.g. earthworm and leech, 
 barnacles and acorn-shells among crustaceans, one of the 
 edible oysters, the snail, and many other molluscs, the sea- 
 squirts, and the hagfish, are all hermaphrodite. But it 
 should be noted that the organs in which ova and sperma- 
 tozoa are produced are in most cases separate, that the two 
 
CHAP. XII The Life-History of Animals 189 
 
 l5!"?!i,°^/^-!' ^'■^ "'"*"y ^°'™*^** ** ^'flferent times, and 
 that the fertihsation of ova by spermatozoa from the same 
 animal very rarely occurs. It is very likely that the 
 bisexu^i or hermaphrodite state of periodic maleness and 
 femaleness is more primitive than that of separate sexes, 
 which, except m tunicates, a few fishes and amphibians 
 and casual abnormalities, is constant among the backboned 
 animals. 
 
 iP) Parthenogenesis seems to be a degenerate form of 
 sexual reproduction in which the ova produced by female 
 organisms develop without being fertilised by male cells. 
 Thus 'the drones have a mother but no father," for they 
 develop from ova which are not fertilised. In some rotifers 
 the niales have never been found, and yet the fertility of the 
 females is very great; in many small crustaceans («« water- 
 fleas ) the males seem to die off and are unrepresented for 
 long penods; m the aphides males maybe absent for a 
 summer (or in a greenhouse for years) without affecting the 
 rapid succession of female generations. 
 
 (^) Alternation of Generations.— Ps. fixed asexual zoophyte 
 or hydroid sometimes buds off and liberates sexual swim- 
 ming bells or medusoids, whose fertilised ova develop into 
 embryos which settle down and grow into hydroids. This is 
 perhaps the simplest and clearest illustration of alternation 
 of generations. 
 
 In autumn the fi-eshwater sponge {Spongilla) begins 
 to suffer from the cold and the scarcity of food. It dies 
 away; but some of the units club together to form 
 
 norT 7T ^'"'^ •" ^P""^ '"^•^ -"d female 
 sponges are developed. The males are short-lived, but 
 
 their spermatozoa fertilise the ova of the females The 
 
 fertilised ovum develops into a ciliated embryo, and this 
 
 into the asexual sponge, which produces the gemmules. 
 
 ihe large free-swimming and sexual jellyfishes of the 
 genus Aureba produce ova and spermatozoa j from the 
 fertilised ovum an embryo develops not into a jellyfish, but 
 mto a sessile ^j^^ra-like animal. This grows and divides 
 and gives origin asexually to jellyfish. 
 
 Similar but sometimes more complicated alternations 
 
 f 31 
 
 m 
 
 \li il 
 
 iil 
 
IIMiiil I lii 11 iiiiii 
 
 ¥'• > 
 
 T/ie Study of Animal Life 
 
 I'ART 111 
 
 'Xu an^ogous alternations are very common, e.g. m .l,o 
 life-cycles of fern and moss. 
 
 liberated. 
 
 , Wiatorical— In the seventeenth and eighteenth cen- 
 turie;, na u\TsU had a short and easy method of deahng .n 
 embryology. They maintained that w.thm t. . seed o a 
 
 HrjLn^n^Lntnrr^^^^^^^^^ 
 mtaUture' mSl of the adult, which in development .a. 
 
CHAP, xii The Life-History of Animals 191 
 
 simply unfolded. It was to this unfolding that the word 
 evolution (as a biological term) was first applied. But not 
 only did they compare the germ to a complex bud hiding 
 the already formed organs within its hull, they maintained 
 that It included also the next generation and the next and 
 the next Some said that the ovum was most important, 
 that it required only the sperm's awakening touch and it 
 began to unfold; others said that the animalcules or 
 spermatozoa produced by male animals were most im- 
 portant, that they only required to be nourished by the 
 ova. The two schools nicknamed one another "ovists" 
 and "aninialculists." The preformation-theories were false, 
 as Harvey in the middle of the seventeenth century discerned^ 
 and as Wolff a century later proved, because germs are 
 demonstrably simple, and because embryos grow gradually 
 part lay part But in a later chapter we shall see that the 
 theories were also strangely true. 
 
 4. The Egg-cell or Ovum pro„ ed by a female animal, 
 or at least by a female organ (cary), exhibits the usual 
 charactenstics of a cell. It often begins like an Amoeba, 
 and may absorb adjacent ceUs ; in most cases it becomes 
 surrounded by an envelope or by several sheaths; in 
 many cases it is richly laden with yolk derived from various 
 sources. In the t.%z of a fowl, the most important part 
 (out of which the embryo is made) is a smaU area of trans- 
 parent living matter which lies on the top of the yeUow 
 yolk and has a nucleus for its centre; round about 
 there is a coating of white-of-egg ; this is surrounded by 
 a double membrane which forms an air-chamber at the 
 broad end of the ^%g ; outermost is the porous shell of 
 lime. 
 
 While there must be a general relation between the size 
 of the bird and that of the ^g%, there are many inconsisten- 
 cies, as you will soon discover if you compare the eggs 
 of several birc^ j of the same size. It is said that the eggs 
 of birds which are rapidly hatched and soon leave the nest 
 tend to be large, and that there is some relation between the 
 sue of eggs and the number which the bird has to cover. 
 It seems probable, however, from what oce notices in the 
 
 ■II 
 
 'ir 
 
 ■ll 
 
 -A]' 
 
 II 
 
 
 III 
 
 •"fill' 
 
 km 
 
The Study of Animal Life 
 
 PART III 
 
 ooultry yard and in comparing the constitution of different 
 Wrds th^ a highly-nourished and not very energetic b.rd 
 wm hat larger eggs than one of more active habits and 
 
 '^X'^egg-shell consists almost ^vholIy of carbonate of 
 
 limJ and tfe experiments of Irvine have shown that a hen can 
 hme, ana ine «ji ^^^ ^^^^ g^^g jt is 
 
 X'o^ b.tfS^>".c.^.=U^ n,a„,.a., absorWoo 
 young u ^ different sizes of egg usually 
 
 d^ nd' poT^^^^^^^ of yolk, for the really vital portion 
 
 nufof which the embryo is -nade is always very small. 
 There a^e many differences also in regard to the outer 
 
 to a minute monad Infusorian. It is a very sn 
 bearing at one end a "head," which consists mo b of 
 nucleus, prolon,'ed at the other end into a mobile tail. 
 which lashes the head along. 
 
 iK.'m~^.jij^A^i& 
 
CHAP. XII The Life- History of Animals 193 
 
 The spermatozoon, though physiologically t'l" -omple- 
 ment of the ovum, is not its morphological equivalent 
 I he precise equivalent of the ovum is a primitive male-cell 
 or mother-sperm-cell, which divides repeatedly and forms a 
 ball or clump of spermatozoa. This division is to be com- 
 pared with the division or segmentation of the ovum, which 
 we shall afterwards discuss. 
 
 In some cases spermatozoa which have been transferred 
 10 a female may lie long dormant there. Thus those 
 received by the queen-bee during her nuptial flight may last 
 for a whole season, or even for three seasons, during which 
 they are used in fertilising those ova which develop into 
 workers or queen-bees. Quite unique is the case of one of 
 Sir John Lubbock's queen-ants, which, thirteen years after 
 the last sexual union with a male, laid eggs which 
 developed. 
 
 6. Maturation of the Ovum.— Most ova before they are 
 fertilised are subject to a remarkable change, the precise 
 meaning of which is not certainly known. The nucleus of 
 the ovum moves to the surface and is halved twice in rapid 
 succession. Two minute cells or polar globules are thus 
 extruded, and come to nothing, while the bulk of the 
 nucleus is obviously reduced by three-fourths. It may be 
 that th- ovum is only behaving as other cells do at the 
 hm;; of growth, or that it is exhibiting in an ineffective sort 
 of way the power of independent division which all the re- 
 P'-oduct=ve cells of very simple many-celled animals perhaps 
 possessed ; it may be that it is parting with some surplus 
 material which is inconsistent with or no longer necessary 
 to Its welfare, and there are other theories. One fact 
 however, seems well established, that parthenogenetic ova' 
 "hii:h are able to develop into embryos without being 
 lertihsed, extrude only one polar globule, a fact which 
 suggests that the amount of nucleus thus retained some- 
 how makes up for the aljsence of a spermatozoon. 
 
 7. Fertilisatios.- -When a pollen grain is carried by an 
 'nsect or by the wind to the stigma of a flower, it grows 
 down through the tissue of the pistil until it reaches the 
 ovu'e and the egg-cell which that contains. Then a nuclear 
 
 O 
 
 it 
 
 1 
 
 I 
 
 illil 
 
 
 I 
 
 If 
 
 A 
 
 1; 
 
 
 1; 
 
 
194 TJie Study of Animal Life part hi 
 
 element belonging to the pollen cell f ^- ^^^^^^f ^^^^^ 
 of the egg-cell. The union is intimate and coniplete. 
 
 Whef spermatozoa come in contact with the egg-shell 
 of a cockroach ovum, they move round and -und 't m 
 varying orbits until one finds entrance through a minute 
 apeVtufe in the shell. It works its way inwards ur^ul Us 
 nuclear part unites with that of the ovum. The union ,s 
 again intimate and complete. 
 
 -■ 3--s;:^s.t;fer i£=(S^?&i"'^ °"'" 
 
 ^rr\ "T^iii^r;^) Vn^.s.^h' '^^^^^ 
 
 the tir>t pol; lx)il> Kr > """ '^' A.j. . nucleus («-) now 
 ox.rusionof theseconl polar '-^> ^ )• «h;,:;;^„, dVidins t 
 
 .,, „vum extnuling 
 ■educed by half ; C, 
 
 I polar body ^A^,. me ""— '.N^j), -* -f;;^"=V^.o 
 
 s,*rmalozoa (x/») ; D, '^^^"V f ,.„?leu, 0^\ 'u-proach one ancther, and 
 i^\!;-l^":^i^l^;'h.!rT^:un;;;:^u>rt^e^fcniU.tio„. (Kro. ... 
 
 Evolution o/ic.r.) 
 
 Both in plants and in animals the male cell is attracted 
 to he female cell, the two nuclei unite t-roughly^ui , 
 when fertilisation is thus effected, the egg-cell ,s usually 
 
 ^T:i::erl::L^S^r.ble origin is tlnis establ^M 
 •md the egg-cell begins to divide. Some idea both ol 
 •^rdcHy complexity 'of the nuclear anion and o the caic^ 
 net of modern investigation may be ^'^'"-^ /rom tU ^^ 
 That the nuclei of the two daughter-cells which re.ult from 
 
CHAP. XII The Life-History Of /inimals 195 
 
 the first division of the egg-cell have been shown to consist 
 .n equal proportions of material derived from the male 
 nucleus and from the ovum-nucleus. 
 
 Yet in the last century naturalists still spoke of an "aura 
 semmahs," and believed that a mere breath, as it were of 
 the male cell was sufficient to fertilise an l^^, and it was 
 onlym 1843 that Martm Barry discerned the presence of 
 the spermatozoon within the ovum. 
 
 8. Segmentation and Development. — The fertiliseH 
 egg-cell divides, and by repeated division and grow h'^^f 
 cells every embryo, of herb and tree, of bird and beast is 
 
 Zalr ?? tt '"'"'^^ ^"' arrangement of the She 
 character c« the segmentation depends. When there is 
 httle or no yolk the whole ovum divides into equa" parts a 
 m sponge, ' rthworm, starfish. lancelet, and higher mamriia! 
 VVhen there is more than a little yolk, and when tSs sii^ks 
 to the lower part of the egg-cell, the division is complete 
 fr"e hi "r", ; '"'^ '^'' ""'' ^^ ''^'^^y ^^^" by exaZing 
 
 ^e oi of ?hV''""- n'"^!^^" ^'^ y°"^ '^ accumulated in 
 the core of the egg-cell, the more vital superficial nart 
 d.vides, as m insects and crustaceans. LastfyT when the 
 yoHc IS present in large quantity as in the ovL ofTistlv 
 fishes, reptiles, and birds, the division is very partial ^einl 
 
 onfined to a small but rapidly extending ar7a of fonnaZ 
 hving matter, which lies like a drop ol the surface o? the 
 
 As the resuh of continued division, a ball of cells is 
 formed. This may be hollow (a ^/aW/J.r.) or olid 
 
 Tlnis in the hen\ t^g^lL" "s^ ^^VS r^s^c of c^lt 
 rrd t Jot' ''' ''-''''--' -'^^^^ ^-^-"^ teat 
 The hollow ball of cells almost always becomes dimnLH 
 . or mvagmated, as an india-rubbe, ball rth a Li "" k 
 might be pressed into a cuo-like form tk» ^- i- . 
 result of inequalities of erowth TlT; ,^^ "^'TP''"^ '^ ^^"^ 
 
 -ii: 
 
inij 
 
 1 
 
 ^^^^^B| 
 
 ' 
 
 H 
 
 
 ^ni 
 
 
 ^Hcl» 
 
 
 mR 
 
 196 
 
 The Study of Animal Life part m 
 
 food-canal Where there is no hollow ball of cells but 
 some other result of segmentation, the formation of a gaslrula 
 
 is not so obvious. \et 
 in most cases some 
 analogous infolding i> 
 demonstrable. 
 
 In the hollow sar 
 of cells there arc 
 already two layers. 
 The outer, which is 
 called the ectoderm 
 or epiblast, forms in 
 the adult the outer 
 skin, the nervou. 
 system, and the incist 
 important parts of the 
 sense - organs. 'I'he 
 inner, which is called 
 ( j) the endodcrm or hypo- 
 blast, forms the linini; 
 of the most import- 
 ant part of the food- 
 cana!, and (f ^ueh 
 appendages as lunj^s. 
 liver, and paii< reas 
 
 Fic. „._The formation of the two-l.-jyereJ ps- 
 
 Ilia 
 
 m.la from the invagination of a hollow sphere 
 of cells. (From the Evolution 0/ Six ; .liter 
 Haeckel.) 
 
 which are outgntwth- 
 from it. lUit in all 
 animals above the 
 Sponges and Cci;lentcrates, a middle layer appears beiAeen 
 the other two. From th-s— the mesoderm or mesobla^t- 
 the muscles, the internal skeleton, the connective-tissue, etc.. 
 
 are formed. 
 
 9. Some Oeneralisations.— 00 The " Ot •;/;«- 7 ^vn. 
 To realise that almost every organism from the spon^i' i" 
 the highest begins i's life as a fertilised egg-cell, and i^ 
 built up by the divisic. and arrangement, layering aiul loUl- 
 iag of cells, should not lessen, but should greatly tnlunce 
 the wonder with which we look upon life. If the end 
 of this constantly repeated process of development be 
 
CHAP. XII The Life-History of Animals ,97 
 
 Teginninl '° "'"'' '^ *^ ^^"^ '^ ^^-">^ ^-« °^ its 
 (^) 77.^ Ga^/r^a Theory, From the frequent, though 
 not universal occurrence of the two-layered gastrula stage In 
 the development of animals, Haeckel concluded that the 
 first stable foroi of many-celled an.mal must have been 
 somethmg very hke a gastrula. He called this hypotheS 
 ancestor of all many-celled animals a Gastrcea, and his infer 
 ence has found favour with many naturalists. Some of the 
 
 (0 Recapitulation. When we take a general survey 
 jf the animal senes, we recognise that the simplest aS 
 are smgle cells, that the next simplest are balls of cenTke 
 
 retrr^d t Th"'^ ' 'P°"^''' P^'^P^^' ^"^ *°""^ above 
 referred to These represent the three lowest steps in the 
 
 evolution of the race. They are not hypothetical sfeps in a 
 hypothefcal ladder of ascent, they are realities ^ 
 
 When we take a general survey of the individual 
 
 development of many-celled animals, we recognise that aU 
 
 f';e".ir S tr^-'^'.-^ ^^^^ ^^e ova div^tntotn 
 
 cells lttrh.rf'°"'' -If "'"f *^^'^^ two-layered sacs of 
 
 v-A "'^ therefore evident that the first three chapters in 
 
 .n^^v^dual history are precisely the first three stepsT^rdLl 
 
 Von Baer, one of the pioneer embryoloj^jsts in the first 
 ha^o this century, discemed that the individual lif^hLto^ 
 
 he LT ^h""""* '°""'/ recapitulation of the history Z 
 the race He recognised that even one of the hi/her 
 an.mals. let us say a rabbit, began at the beginning fs a 
 
 vc^I fil' A ^"bsequently showed the character of a 
 
 MZJtl^ T^' °^ ^ y^""^ ^^P^"«' then of a young 
 mammal, then of a young rodent, finally of a younjr rabbit 
 He confessed his inability to distinguish\vhethlr t'ee ve^ 
 cm'lTT;, "' '"'" ^'"^ --oundin«s, were thL^ 
 vivid Idea of development as progress irom the simple 
 
 \t 
 
 %\ 
 
 lil 
 
tgi 
 
 The Study of Animcd Life part hi 
 
 to the complex, from the general to the special, we must 
 be careful to notice that he did not say that the young 
 mammal was once like a little fish, afterwards like a reptile, 
 and so on ; he compared the embryo mammal at one stage 
 with the embryo fish, at another stage with the embryo 
 reptile, which is a very different matter. 
 
 Fig. 38.-Embryos of fowl, a ; dog, b ; mane. (From Chambers's EmyckK ; 
 ' after Haeckel.) 
 
 Fritz MuUer, in his Facts for Darwin, illustrated the 
 same idea in relation to Crustacea. When a young cray- 
 fish is hatched, it is practically a miniature adult. When 
 a young lobster is hatched, it differs not a little from the 
 adult, and is described as being at a Mysis stage, — Vysis 
 being a prawn-like crustacean. It grows and moults and 
 becomes a little lobster. When a crab is hatched, it is 
 quite unlike the adult, it is liker one of the humblest 
 Crustacea such as the common water-flea Cyclops, and is 
 described as a Zoea. This Zoea grows and moults and 
 becomes, not yet a crab but a prawn-like animal with ex- 
 tended tail, a stage known as the Megalopa. This grows anc 
 moults, tucks in its tail, and becomes a young crab. And 
 again, when the shrimp-like crustacean, known as rcmnis, 
 is hatched, it is simpler than any known crustacean, it is 
 an unringed somewhat shield-shaped little creature with 
 three pairs of appendages and a median eye. It is kno\\n 
 as a Nauplius and resembles the larvie of most of the simpier 
 crustaceans. It grows and moults and becomes a '-^oea, 
 grows and moults and becomes a Mysis, grows nd moults 
 and becomes a Penceus, 
 
CHAP. XII The Life-History of Animals 199 
 
 Now these life-histories are hardly intelligible at all 
 unless we believe that Penaus does in some measure recapi- 
 tulate the steps of racial progress, that the crab does so 
 to a slighter extent, that the lobster has abbreviated its 
 obvious recapitulation much more, while the crayfish has 
 found out a short cut in development. Let us exercise our 
 imagination and think of the ancestral rrustacea perhaps 
 not much less simple than the Nauplius larvae which many 
 
 Fig. 39--Life.historyof/'*«««j; the Nauplius. 
 
 Of them exhibit. In the course of time some pushed for- 
 ward in evolution and attained to the level of structure 
 represented by the Zoea larv.c. At this station some 
 remained and we have already mentioned the " water-flea " 
 tychps as a crustacean which persists near this level But 
 others pushed on and reached a stage represented by 
 Mysts, and finally the highest crustaceans were evolved 
 
 i\ow to a certain extent these highest crustacean^, have 
 
 o travel in their individual development along the rails 
 
 laid down m the progress of the race. Thus Penaus 
 
 1 11 
 
 »* 
 
 li 
 
 
 ,f 
 
I 
 
 200 The Study of Animal Life part m 
 
 starting of course as an ovum at the level of the Protozoa, 
 has to stop as it were at the first distinctively crustacean 
 station— the Nauplius stage. After some change and 
 delay, it continues to progress, but again there is a halt and 
 a change at the Zoea station. Finally there is another 
 
 Fici. 3S«-— Life-lu^>lory of I\iufus ; the Zoea. 
 
 delay at the Afysis stage before the Pcn:rus reaches its 
 destination. The crab, on the other hand, stops first at 
 the Zoea station, the lobster at the Mysis station, while tlie 
 crayfish though progressing very gradually like a!! the 
 others has— if you do not find the simile too grotesque -a 
 through-carriage all the way. 
 
/ i\\y\\ 
 
 I \ 
 
 i'lr,. j9^. -Life history o( I'eitiru^; a later 
 
 stage. 
 
 /I 
 
 1^;- 
 
 m 
 
 - ? 
 
 
 \* 1 
 
 il 
 
202 The Study of Animal Life part m 
 
 One must l)c careful not to press the idea of recapitulation 
 too far, (i) because the individual life-history tends to skip 
 
 stages which occurred in the an- 
 cestral progress ; (2) because the 
 young animal may acquire new- 
 characters which are peculiar to 
 its own near lineage and have 
 little or no importance in connec- 
 tion with the general evolution of 
 its race ; (3) because, in short, 
 the resemblance between the indi- 
 vidual and raciul history (so far 
 as we know them) is general, not 
 precise. Thus we regard Nauplius 
 and Zoea rather as adaptive larval 
 forms than as representatives of 
 ancestral crustaceans. More- 
 over, if one insists too much on 
 the approximate parallelism be- 
 tween the life-history of the indi- 
 vidual and the progress of the 
 race, one is apt to overlook the 
 deeper problem — how it is that 
 the recapitulation occurs to the 
 extent that it undoubtedly does. 
 The organism has no feeling for 
 history that it should tread a 
 sometimes circuitous path, be- 
 cause its far-off ancestors did so. 
 To some extent we may think of 
 inherited constitution as if it ^ere 
 the hand of the past upon the 
 organism, compelling it to become 
 thus or thus, but we must realise 
 that this is a living not a dead 
 hand ; in other words these imta- 
 morphoses have their efficient causes in the actual cun- 
 dilions of growth and development. The suggestion of 
 Kleinenberg referred to in a preceding chapter helps U5, for 
 
CHAP. XII The Life-History of Animals 203 
 
 if we ask why an animal develops a notochord only to have 
 It rapidly replaced by a backbone, part of the answer surely 
 IS that the notochord which in the historical evolution supplied 
 the stimulus necessary for the development of a backbone is 
 still necessary in the individual history for the same purpose 
 But there is no doubt that the idea of recapitulation is a 
 very helpful one, m regard to our own history as well as in 
 regard to animals, and we would do well to think of it 
 much, and to read how Herbert Spencer {Principles of 
 Bw/ogy Land. 1864-66) has discussed it in harmony with his 
 general formula of evolution as a progress from the homo- 
 geneous to the heterogeneous ; how Haeckel {Generelie Mor- 
 pho/o^e Berhn, 1866) has illustrated it, and pithily summed 
 It up in his "fundamental law of biogenesis » {Biogenetisches 
 Grundgesetz\ saying tha. ontogeny (individual develop- 
 ment) recapitulates phylogeny (racial history); how Milnes 
 Marshall (see Nature, Sept. 1890) has recently tested and 
 criticised It, defining the limits within which the notion 
 can be regarded as true, and searching: for a deeper rationale 
 of the facts than the theory supplies. 
 
 id) Organic Continuity. In a subsequent chapter on 
 heredity, which simply means the relation of organic 
 continuity between successive generations, I shall explain 
 the fundamental idea that the reproductive cells owe their 
 powtr of developing, and of developing into organisms like 
 the parents, to the fact that they are in a sense continuous 
 with those which gave origin to the parents. A fertilised 
 egg-cell with certain qualities divides and forms a "body" 
 m which these qualities are expressed, distributed, and 
 altered m many ways by division of labour. But it also 
 forms reproductive cells, which do not share in the up- 
 building of the body, which are reproductive cells in fact 
 because they do not do so, because they retain the intrinsic 
 qualities of the original fertilised ovum, because they 
 preserv-e its protoplasmic tradition. If this be so, and 
 there is much reason to believe it, then it is natural and 
 necessary that these cells, liberated in due time, should 
 behave as those behaved whose qualities they retain. It is 
 necessary that like should beget like. 
 
 I 
 
 il 
 
 Ml 
 
 
 m 
 
 I > 6 1 
 
CHAPTER XIII 
 
 THE PAST HISTORY OF ANIMALS 
 
 I. ne two Records — 2. Imperfection of the Geological Record— 
 3. Palceontological Series — 4. Extinction of Tyfes — 5. Variom 
 Difficulties — 6. Relative Antiquity of Animals 
 
 I. The Two Becords. — Reviewing the development of the 
 chick, W. K. Parker said, "Whilst at work I seemed 
 to myself to have been endeavouring to decipher a palimp- 
 sest, and that not erased and written upon just once, but 
 five or six times over. Having erased, as it were, the 
 characters of the culminating type — those ot the gaudy 
 Indian bird — I seemed to be amongst t^" sombre g;0JS- 
 and then, towards incubation, the characters of the Sand- 
 Grouse and Hemipod stood out before me. Rubbing these 
 away, in my downward walk, the form of the Tinamou 
 looked me in the face ; then the aberrant Ostrich :ieemed 
 to be described in large archaic characters ; a little while 
 and these faded into what could just be read oflf as per- 
 taining to the Sea Turtle ; whilst, underlying the whole, 
 the Fish in its simplest Myxinoid form could be traced 
 in morphological hieroglyphics." 
 
 There is another palimpsest — the geological record 
 written in the rocks. For beneath the forms which dis- 
 appeared, as it were, yesterday, — the Dodo and the Solitaire, 
 the Moa and the Mammoth, the Cave Lion and the Irish 
 Elk, — there are mammals and birds of old-fashioned type the 
 like of which no longer live. Beneath these lie the giant 
 
 '5<«3?S' 
 
205 
 
 CHAP, xin The Past History of Animals 
 
 reptiles, beneath these great amphibians, preceded by hosts 
 of armoured fishes, beyond the first traces of which only 
 backboneless animals are found. Yet throughout the 
 chapters of this record, written during different sons on the 
 earths surface, persistent forms recur from age to aee 
 many of them, such as some of the lamp-shells or Brachio^ 
 pods, hvmg on from near the apparent beginning even until 
 now. But other races, like the Trilobites, have died out 
 leaving none wh.ch we can regard as in any sense thei; 
 direct descendants. Other sets of animals, like the Ganoid 
 fishes, grow m strength, attain a golden age of prosperous 
 success, and wane away. As the earth grew older nobler 
 forms appeared, and this history from the tombs like 
 that from the cradles of animals, shows throughout a 
 gradual progress from simple to complex. 
 
 2. Imperfection of the Geological Record.— If complete 
 records of past ages were safely buried in great treasure- 
 houses such as Frederic Harrison proposes to make for the 
 enlightenment of posterity, then palceontology would be ea^y 
 Then a genealogical tree connecting the Protist and Man 
 would be possible, for we should have under our eyes what 
 ■s now but a dream— a complete record of the past 
 
 • V u^T^ °^ ^^'^ "^^^^ ^' °^^^" compared to a library 
 m wh,ch shelves have been destroyed and confused, in 
 which most of the sets of volumes are incomplete, and 
 most of the individual books much damaged. wlTen we 
 consider the softness of many animals, the chances against 
 their being entombed, and the history of the earth's crust 
 our wonder ,s that the record is so complete as it is that' 
 rem the strange graveyards of the buried past" we can 
 learn so much about the life that once was 
 
 We must not suppose the record to be as imperfect as 
 
 su2rh ''^K °' "• "^^"^ "^'""y ^^^'^"^ °^ the earth's 
 surface have been very partially studied, many have not 
 
 been explored at all, many are inaccessible benelth the sea! 
 
 As to the record, the rocks in which fossils are found 
 
 are sedimentary rocks formed under water, often they have 
 
 been unmade and remade, burnt and denuded. The 
 
 Chances against preservation are many. 
 
 I M 
 
 ' 
 
 t 
 
2o6 
 
 The Study of Animal Life part m 
 
 Soft animals rarely admit of preservation, those living 
 on land and in the air are much less likely to be preserved 
 than those living in water, the corpses of animals are 
 often devoured or dissolved. Again the chances against 
 preservation are many. 
 
 3. Palaontological Series. — Imperfect as the geological 
 record is, several marvellously complete series of related 
 animals have been disentombed. Thus, a series of fossilised 
 freshwater snails {Planorbis) has been carefully worked 
 out ; its extremes are very different, but the distinctions 
 between any two of the intermediate forms are hardly 
 perceptible. The same is true in regard to another set of 
 freshwater snails {Paludwa), and on a much larger scale 
 among the extinct cuttlefishes (Ammonites, etc.) whose shells 
 have been thoroughly preserved. The modern crocodiles 
 are linked by many intermediate forms to their extinct 
 ancestors, and the modern horse to its pigmy progenitors. 
 In cases like these, the evidences of continuously progress- 
 ive evolution art conclusive. 
 
 4. Extinction 01 Types. — A few animals, such as some 
 of the lamp-shells or Brachiopods, have persisted from almost 
 the oldest rock-recorded ages till now. In most cases, 
 however, the character of the family or order or class lias 
 gradually changed, and though the ancient forms art no 
 longer represented, their descendants are with us. There 
 is an extinction of 'ndividuals and a slow chani;e of 
 species. 
 
 On the other baud there are not a few fossil animals 
 which have become wholly extinct, whose type is not 
 represented in the modern fauna. Thus there are no 
 animals alive that can be regarded as the lineal descendants 
 of Trilobit^s and Eurypterids, or of many of the ancient 
 reptiles. There is no doubt that a rare may die out. 
 Many different kuuls of heavily armoured Ganoiil tisbrs 
 abounded in the ages when the Old Red Sandstone was 
 formed, but only seven different kinds are now alive. 
 The lamp-shells and the sea-lilies, once very numerous, are 
 now greatly restricted. Once there were giants ainon^ 
 Amphibians, now almost all are pigmies. 
 
CHAP, xm The Past History of Animals 207 
 
 It is difficult to explain why some of the old types 
 disappeared. The extinction was never sudden. Formid- 
 able competitors may have helped to weed out some • for 
 cuttlefish would tend to exterminate trilobites, and voracious 
 fishes would decimate cuttlefish, just as man himself is 
 rapidly and inexcusably an"':,. ..i;„.. many kinds of beasts 
 and birds. But, apart fro n the sivn^^, with competitors, 
 it IS hkely that some types wc o ins .fnclcatly plastic to save 
 themselves from changes ol . n. ..o.hncnt, P.r.J it s°ems likely 
 that others were victims to their own -..istitutions, becominL^ 
 too large, or too sluggish, or too calcareous ; or on the 
 otner hand, too feverishly active. The '« scouts " of evolution 
 woula be apt to become martyrs to progress ; the " laggards " 
 m the race would tend to become pillars of salt • the 
 path of success was oftenesi a via media of compromise 
 Samuel Butler has some evidence for saying that " the race 
 IS not in the long run to the phenomenally swift, nor the 
 battle to the phenomenally strong ; but to the good average 
 a 1-round organism that is ar' e shy of radLal crotchets and 
 old world obstructiveness ' 
 
 5. Various Difficulties.— Nowadays it seems natural 
 to us to regard the fossils in the rocks as vestiges of a 
 gradual progress or evolution. As some still find difficulty 
 I., accepting this interpretation, I shall refer to three 
 clifllculties occasionally raised. 
 
 («) It is said that the number of fossils in successive- 
 strata does not increase steadily as we ascend to modern 
 times-that the numerical strength uf the fauna is stran-elv 
 irregular. Thus (in 1872) it was computed that 10,000 
 species were known from the early Silurian rocks, while the 
 much later Permian yielded only 300. But those who use 
 such arguments should mention that a large number of the 
 Silurian species were discovered by the marvellous industry 
 of one man in a .avourable locality, and that the rocks of 
 he Permian system are ill adapt.,! for the preservation of 
 lossils Moreover, we cannot compute the relative dura- 
 tion of the diflferent periods, we cannot infer evolutionary 
 progress from the number of species, and we must make 
 many allowances for the imperfections of the record. 
 
 WW ' 
 
 
 -I ^ 
 
 ■Mi 
 
 ■ t 
 

 ■a.* 
 
 2o8 
 
 The Study of Animal Life part m 
 
 (b) It is said that the occurrence of Fishes in the 
 Silurian, and of many highly organised Invertebrates in the 
 still earlier Cambrian, is inconsistent with a theory which 
 would lead us to expect very simple fossil forms to begin 
 with. But to say so is to forget that we have no concep- 
 tion of the vast duration of periods like the Silurian and 
 Cambrian, while the antecedent Archaean rocks in which we 
 might look for traces of simple ancestral organisms have 
 been shattered and altered too thoroughly to reveal any 
 important secrets as to the earliest animals. 
 
 (f) It is maintained that organic evolution proceeds very 
 Slowly, and that the geologists and biologists demand more 
 millions than the experts in astronomical physics can grant 
 them. But there is considerable difference of opinion as to 
 the unthinkable le.igth of time during which the earth may 
 have been the home of life ; we are apt to measure the rate 
 of evolutionary ch inge by the years of a man's lifetime which 
 lasts but for a geological moment ; and there is reason to 
 believe that the simpler animals would change and take 
 great steps of progress much more rapidly than those ol 
 high degree. 
 
 6. Relative Antiquity of Animals. — I have not much 
 satisfaction in submitting the following table showing 
 the relative antiquity of the higher .\nimals. Such a table 
 is only an approximation ; it does not suggest the -^rcat 
 differences in the duration of the various periods, nor how 
 the classes of animals waxed and waned, nor how some types 
 in these classes dropped off while others persisted. But tlie 
 general fad which the table shows is true, — in the course 
 of time higher and higher forms of life have come into 
 being. It is true that the remains of mammals are of more 
 ancient date than those of birds, but it is likely that the 
 remains of the earliest birds have still escaped discover)' ; 
 moreover, the earliest known mammalian remains seem to 
 be of those of very simple types. 
 
CHAP. XIII The Past History of Aniniu 
 
 Primary or Pahrozoi. 
 
 »* 
 3 
 
 3 
 
 73 
 
 P 
 
 3 
 
 O 
 
 3 
 
 S' 
 
 3 
 
 u 
 
 c 
 
 3 
 
 o 
 
 c 
 
 "3 
 
 p 
 
 3 
 
 3 
 
 -a 
 
 -3 
 
 Secondary or 
 
 JMesozoic 
 
 n 
 
 n 
 
 p 
 o 
 
 o 
 o 
 
 c 
 
 2; 
 
 p 
 
 3 
 
 3 
 p 
 
 7/s 
 
 Tertiary or 
 Cainozoic 
 
 209 
 
 ^ 3 
 
 o 
 
 n 
 
 3 
 
 O 
 o 
 ft 
 3 
 O 
 
 n 
 
 f» 
 
 3 
 
 o = 
 
 a p 
 
 ^ 2 
 
 1^ 
 
 -•' 
 
 4 n| 
 
 fl4W7tjtt!iv^fll^ 
 
I 
 
 CHAPTER XIV 
 
 THE SIMPLEST ANIMALS 
 
 I. The Simplest Forms of Life— 2. Survey of Protozoa— i. The com- 
 mon Amn-ba—^. Structure of the Prolozon-S- Life of Protozoa 
 —6. Psychical Life of the Pro^^zoa—I. History of the Protozoa 
 8. Relation to the Earth— <). Relation to other Forms of Life - 
 lo. Relation to Man 
 
 I. The Simplest Forms of Life.— It is likely that the first breati. 
 of life was in the water, for there most of the simplest animals and 
 plants have their haunts. Simple they are, as an egg Is simplf 
 when contrasted with a bird. They are (almost all) unit specks o: 
 living matter, each comparable to, but often more complex than, or.e 
 of the numerous unit elements or cells which compose any highei 
 plant or animal, moss or oak-tree, spont;e or man. It is not merely 
 because they are small that we cannot split them into separate parts 
 different from one another,— size has little to do with complexity, - 
 but rather because they are unit specks or single cells. But they are 
 not "structureless" ; in fact, old Ehrenberij, who described some c! 
 them in 1838 as " perfect organisms" and fancied he sawstoniac!i?. 
 vessels, hearts, and other organs within them, was nearer tlie tmth 
 than those who reduce the Protozoa to the level of white of cgi;. 
 
 Nor are they omnipresent, swarming in any drop of water. I lis 
 clear water of daily use will generally disappoint, or rather plc.ise 
 us by showing little trace of living things. Hut take a test-tul-e of 
 water from a stagnant pool, hold it between your eyes and theluht. 
 and it is likely that you will see many forms of life. Simple iilant? 
 and simple animals are there, the former represented by threah 
 ovals, and spheres in green, the latter by more mobde almost 
 colourless specks or whitish moles which dance in the water. Hut 
 besides these there are jerky swimmers v hose appearance alnios^ 
 suggests their popular name of " water-Heas," and wriggling "worms, 
 
 .im^^'^^i^ 
 
mt 
 
 CHAP. xTv T^g Simplest Animals 
 
 an 
 
 .mSi^Wll^"''"'^ ^^ "•'''■' '^"" ^^'^ = ^°'h of these may be very 
 small, bat closer examination shows that thevhavp nnrf.o^^ ^ 
 
 that they are many-celled not single-cSd animal?"''' '"' °^"'' 
 
 Vary the observations by taking water in which h-iv .^t^m. «, «.», 
 
 parts of dusty dead plants have been steeped fo a few davran 1 v 
 
 wuh the unaided eye you will see a thick^crowd of he Sile 1 iS 
 
 motes which from their frequent occurrence in such inA Ins 1 
 
 usually called Infusorians. Or if a piece of flesh be allowed to rVfn 
 
 an open vessel of water, the fluid becomes cloudy and a hrfl yscum 
 
 ga hers on the surface. If a drop of this turbkl liquid be examined 
 
 pracdcally omn.present microbes, soma of which as disease ~™^ 
 
 Jlif cLLterri.iS/e';",t"Vr„ sr"' •""> -"' ^ 
 
 mobile lashe, of living ™,'L, C™ as ci ia'^oTZ^na "tH ''' 
 Ae sl,pper-animalcale l,Par<,m,t,lum) is covered wUh r^w. „f S' 
 
 :l„g* i"=oX'eSa°"%t''!' r""'"?'', '"°''™»' "' »"= °" 
 u. i, wiups or nagella. The bell-anmia cu es {VortuflIn\ u,hi,^j, 
 
 .rfilre;"-;Lii:r.'°.'t:.rtsTi*r:o^^^^^ 
 
 .•aip":i^frtz'=of'rz't"er"t'i„zr'°^V" 
 »..s, whieh'rn' .tar^fr,,°7^,?jf;/'« ?/j"'"'f "s p- 
 
 ^ '5 rnv.iun, and are siilj 
 
 I- 
 
 * 
 
 . 3 IT 
 
 ■ i 
 
 ■|l^.-*^ 
 
 I' 
 
 
 
 1 
 ,1 
 
 31^ 
 
 ,i i 
 
 IP 
 
 111 
 
 
 I i I 
 
 ■ \ ; 
 
 
 ''':rt^>l 
 
The Study of Anmal Life 
 
 PART ni 
 
 'f>?^; 
 
 „,orc useful in surnuuvUng — ^/:^yC^cv.l.lc. often alnu.; 
 like processes, which ate capable ot vcy ^^^^^^^^^ ^^^^^^^^^ ^,^^,^^ 
 
 Trolo/oa owe llicir i;c-.-. 
 cml name of Rlu/.opo>.>. 
 In contrast to the iw 
 im-coiling tyiH-s ^^lv,.: 
 \\:\\i' (Iclinitc bouml.iru: 
 „i- "sixins," the Rhi.-, 
 nods arc naked, and i!a. 
 
 living matter may i'\~ 
 llow at any point. 
 
 As the I nt'usoi ';.-.', 
 aie for il>e mo^t i- 
 piovidca with cilia l.,! 
 which llagclla *lilTor w 
 in detail, wc may ^p^. 
 of the type as cili:.u 
 the self-contained i. ■• 
 giwines, often wra. . . 
 up within a sheath. \ 
 may call prodomin.v.. 
 encysted ; while •.: 
 forms whicli axe i; ' 
 juediate between .: 
 two extremes, an.; 
 hibit outt^owins 
 
 cesses of living i". 
 
 flowing out on .XII r'"^;^ ,,^ . ^fter Max 
 
 (From Ch.^mb<;rs> A«0'''A. 
 
 Schultze.) are called anwix . 
 
 units may become encysted. 
 
 5 
 
 lit-- 
 
 , <.nc^•<t«l: 2, dividing into many unit. ;:-.t^ 
 
 Fig. 41.— Protomyx.i. 
 ing as tlagel' 
 t,lai.modium. ,- , 
 
 ,-_-^^» t>^A three physiological p. 
 As the three pnascs rci-rese..-. ^ »- - 
 

 CHAP, xrv Tk£ Simplest Animals 2,3 
 
 of cell-life, it is natural lo find that the very simplest Protoroa, rach 
 :.,Protomyxa, exhibit a cycle of amaboid, encysted, and fljellate 
 phases, not hanng taken a decisive step along any one of the three 
 great paths. Moreover, the cells of higher animals mny be classTfiS 
 m the same way. The ci!....ed cells of the windpipe or the mobSe 
 spermatozoa correspond to Infusorians ; mature ova fat-cells d" 
 generate muscle-cells, correspond to Gregarines, while white bl'ood. 
 corpuscles and young ova are amceboid. 
 
 3- The common Amoeb0..-To find Amoebae, which is not 
 alwaj-s easy, some wraer and mud from a pond should be allowed 
 to seule m a glass vessel. Samples from the surface of the sediment 
 should then be removed m a gl.xss lube or pipette, dropped on a 
 s .de, and patiently examined under the microscope: Among the 
 .kbns, traversed in most cases by swift InfusoiianCtlie sou^ht-for 
 .-^«^ia may be seen, ..s an irregular mass of living matter? often 
 obscured With vanouskmds of particles and minute Alg^ which k 
 has engulfed, but hardly mistakable as it ploughs its way lei urely 
 among the sediment, sending out b!unt nnd changeful fingerdike 
 processes in the direction towards which it moves, and d^rawing 
 m similar processes at the opposite side. From some objects il 
 reco>ls, whUe others of an edible sort ,t surrounds with it b un 
 processes and gets outside of. Intense light makes it contract, and 
 a rriinu.e drop of some obnoxious reagent causes it to round itsHf off 
 and i.e quiescent. Such is the simple animal which, in 1755, an 
 early microscopist Rosel von Rosenhof was del,g!ued to describe 
 calling It the " Proteus animalcule." ^"escriue, 
 
 4. StTUCtnre of the Protozoa. -Most of these Protozoa are 
 ^.nus or single cells^ but this contrast l.etween them and the higher 
 an;mas is lessened by the fact that manv Infusorians. tme 
 Kaaiolanans. and some of the verj- lowest forms live inclose comU " 
 00-.;^"^^"% fP""'"'' individuals being substar/iully united in 
 o-operanon. In two quite different wavs this com,, .^.id'lif- of som- 
 
 o'l" theLrL nf T> ' '""'T "'""'^^' 'P'""^'' "^ ^ ^•e.\o^^■\^. slime 
 
 ■h Snl"! ■ """''"^ ^/undifferentiated protoplasm." arises fn,„, 
 dua..v„ng together ana fusion of a nun.lH.r of ..nalier amo.lK.id 
 Jn.-. But in some Infusorians and Kadiolarians the colonv 
 
 S:" t^\ °''""'T- , '''"T' '""'''P'^ ^y division ; eacL^^ 
 bv tlmil"" 7'-f' tlienceforth live separate lives, and bv and 
 f:^ '.!::™ '^'"^^ ^'^''d'=- -^"PP^.- however, that the unit d.vid. 
 un evr?-li- '^^P°'' ''''"^^ ^^"^ claughter-unitb, distni.t thou.di 
 
 thev ir "^"''- ^" *'"' "'^ t*^*^ ""i'^ do not flow togwhe- 
 
 iney were never seiaratwl k... .^^ .. ...„j_^ - . ^^>, "c, 
 
 '^ I: 
 
 '■: I 
 
The Study of Animal Life 
 
 PART in 
 
 ^ 
 
 «>4 
 
 early associations has been justified in their far-off children, for in 
 this wav the many-celled animals began. 
 
 tTic cell substance of a Protozoon is living matter, along v.".!. 
 uutrive materials which are approaching that chmax, and was e 
 materilh So which some of the cell substance has d.sm cgrate . 
 The ce 1 has a kernel or nucleus, or more than one. essenl.al to >u 
 complete life. There are bubbles of water taken m along with 
 foS particles, and in nearly all freshwater orms there are one or 
 wo special r gions of internal activity, pulsat.ng cavit.es oco,v 
 ^ctile vacuole^ which become large and -[^^ --^^^ l^yi^;;;:; 
 -illv and may burst open on the surface of the cell. They are 1k- 
 & to h^lp in gettiig rid of waste, and also m mterna crculalu^n 
 There s a iLl in the Infusorlans and Gregar.nes, and shells of fhn: 
 Tnd itme are characteristic of most Foramin. crs and Kadiolanans. 
 ana nnje . protoZOa— The life -histories of the Protozoa ar 
 
 very v.^^. fut^me Sters are common to most. They expend 
 eneUyn movement ; they regain this by feedmg ; their income 
 exceSs their expenditure, and they grow ; at the lumt of gro« 1 
 Sey eproduce by dividing into two or many daughter- unUs : m 
 certain stages two individuals combine, either interchangmg nuclei 
 Sments ( n the ciliated Infusorians) or fusing together (as in sc..e 
 Riropods) ; in drought or in untoward conditions, or belore 
 mSld division, they often draw themselves together and encvst 
 within a sweated-off sheath. j- -j . ;.,.„ 
 
 The Protozoa often muUiply very rapidly. One divides no 
 two the two become four, and in rapid progression the num.a. 
 ncr'eas^ On Maupas's calculuion a single Infus.nan may in fcur 
 days have a progeny of a million. The same observer has shed a 
 new St on^ a 'other process-that of conjugation, the temporan- 
 or percent union of t\vo Protozoa, which in thecihated Inhisona . 
 ?n?ouis an interchange of nuclear particles. In November iS^,. 
 Maupi isoht d an Infusorian {Stylonichia) and observed its genera^ 
 Monstm March i8S6. By that time there had been two hundied and 
 fften generations produced by ordinaiy division, but smce t:ese 
 owTy organisms do not conjugate with near relatives, conjug. a^ 
 hadU^occurred. The result, «>"°borated m other case., v^ 
 strikin- The whole family became exhaust.!, small, ^^ 
 ''senile " ; they ceased to divide or even to feed ; their r.v.. 
 underwen a strange degeneration; they began to die. B.. 
 ndivSs removed' before the process had gone too far ... 
 observed to conjugate with unrelated forms and to live on lb 
 Sference was obvious. Conjugation in these Infusorians is of .tth 
 moment t^any two individuals ; during l-g P-ods it need ne.« 
 occur, but it is essential to the continued life of the species. 
 is a necessary condiUon of their eternal youth. 
 
 11 V: 
 
CHAP. XIV The Simplest Animals 215 
 
 We must return, however, to the eveiyday life of the Protozoa 
 Rhizopods move by means of outflowing processes of tlieir livinL' 
 matter winch stream out at one corner and are drawn in ac another • 
 tlie Infusorians move more rapidly by undulating flagella or by 
 numerous cilia wliich work like flexible oars; the parasitic 
 Gregarines without any defmite locomotor structures sometimes 
 writhe sluggishly. A few Infusorians have a spasmodic leaping or 
 springing motion, while the activity of others (like Vorticelld)ss\nc\i 
 in adult hfe are fixed, is restricted to the contraction and expansion 
 of a stalk and to the action of cilia around the opening which serves 
 as a mouth. Arcella is aided in its movements by the formation of 
 ^'as (nubbles in different parts of its cell-substance. 
 
 'Ihe food consists of other Protozoa, of minute Algce, and of 
 organic debris, simply engulfed by the AmoebK, wafted by cilia 
 into the " mouth " of most Infusorians. The parasitic Gregarines 
 absDrb the debris ol the cells or tissues of the animals in which they 
 live, while not a few suck the cell-contents of freshwater Algje like 
 Spirogyra. A few Protozoa are green, and some are able to use 
 carbonic acid after the manner of plants. Almost all Radiolarians 
 and a few I-oraminifers live in constant and mutually helpful 
 partnership or symbiosis with small Algae which flourish within 
 their cell-substance. 
 
 As to the other functions, the celk absorb oxygen and liberate 
 carbonic acid, digest the food-particles and excrete waste, produce 
 cysts or elaborate shells, 
 
 6. Psychical Life of the Protozoa.— We linger over the 
 
 Protozoa because they illumine the beginnings of many activities, 
 and we cannot leave them without asking what light they cast upon 
 the conscious life of higher animals. Is the future quite hidden in 
 these simple organisms or are there hints of it ? 
 
 According to some, the 'Votozoa, with frequently rapid and 
 useful movements, with cap...i[ies for finding food and avoiding 
 I'.anger, with beautiful and intricate shells, are endowed with the 
 will and intelligence of higher forms of life. According to others, 
 their motions are arbitraiy and without choice, they are only much 
 more complex than those of the potassium ball which darts about 
 on the surface of water, the organisms are c^awn by their food 
 instead of finding it, their powers of selection art jublimcd chemical 
 aifimties, their protective cysts are quite necessary results of partial 
 <icath, and their houses are but crystallisations. In both interpreta- 
 tions there is some truth, but the first credits the Protozoa with too 
 much, the second with too little. 
 
 Cienkow^ki marvelled over the way in which Vampyrella sought 
 and found a Spirogyra filament and proceeded to suck its contents ; 
 t-ngelmann emphasiseii the wonderful power of sdjustiv-ent in Aralla 
 
 \ 1 
 
 I 
 
 ill 
 
 
 I : 
 
i 
 
 I i 
 
 216 The Study of Animal Life part m 
 
 which evolves gas bubbles and thus rises or rights itself when cap- 
 sized, and also detected perception and decision in the motions of 
 young Vorticella or in the pursuit of one unit by another ; Oscar 
 Schmidt granted them only "a very dim general feeling" and the 
 power of responding in different ways to definite stimuli ; Schneider 
 believed that they acted on impulses based upon definite impressions 
 of contact ; Moebius would credit them with the power of reminis- 
 cence and Eimer with will. 
 
 Romanes finds evidence of the power of discriir " lative selection 
 among the protoplasmic organisms, and he quotes in illustration Dr. 
 Carpenter's account of the making of shells. «• Certain minute 
 particles of living jelly, having no visible differentiation of organs 
 . . . build up • tests ' or casings of the most regular geometrical 
 symmetry of form and of the most artificial construction. . . . 
 From the same sandy bottom one species picks up the coarser quartz 
 grains, cements them together with phosphate of iron (?) which must 
 be secreted from their own substance, and thus constructs a flask - 
 shaped 'test' having a short neck and a single large orifice. Another 
 picks up the finer grains and puts them together with the same 
 cement into perfectly spherical ' tests * of the most extraordinary 
 finish, perforated by numerous small tubes, disposed at pretty regular 
 intervals. Another selects the minutest sand-grains and the terminal 
 points of sponge spicules, and works these up together apparently 
 with no cement at all, but by the ' laying * of the spicules into 
 perfect spheres, like homoeopathic globules, each having a single 
 fissured orifice." This selecting power is marvellous ; we cannot 
 explain it ; the animals are alive and they behave thus. But it 
 must be remembered that even * dead * substances have attractive 
 atnnities for some things in preference to others, that the cells of 
 roots and those lining the food-canal of an animal or floating in its 
 blood show a power of selection. Moreover, if we begin will) a 
 unit which provides itself with a coating of sponge spicules, 
 at first perhaps because they were handiest, it is not difficult to 
 understand why the future generations of that species should con- 
 tinue to gather these minute needles. Being simply separated parts 
 of their parents, whose living matter had become accustomed to 
 the stimulus of sponge spicules, the descendants naturally sustain 
 the tradition. This organic memory all Protozoa must have, 
 for the young are separated parts of the parents. 
 
 Haeckel was one of the first (1876) to urge the necessity o( 
 recognising the ''soul" of the cell. He maintained that the con- 
 tinuity of organic life led one to assume a similar continuity of 
 psychical life, that an egg-cell had in it not only the potency of 
 forming tissues and organs but the rudiments of a higher life as well, 
 tiiat liie Protozoa likewise must be regarded not only as physical 
 
CHAP. XIV The Simplest Animals 
 
 217 
 
 but as psychical, in fact that the two are inseparable aspects of one 
 reality. "The cell-soul in the monistic sense is the sum-total of 
 the energies emlwdied in the protoplasm, and is as inseparable 
 from the cell-substance as the human soul from the nervous 
 system." For several years Verwom has been investigatinc the 
 psychical hfe of the Protozoa. He has conducted his researclies 
 with great care and thoroughness, observing tlie animals both in 
 their natural life and m artificial conditions. I shall cite his con- 
 elusions, translating them freely : "An investigator of the psychical 
 processes in Pro...^ts (simple forms of life) has to face two distinct 
 problems. Tne first is comparative, and inquires into the grade of 
 psychical development which the Protists may exhibit— the known 
 standard being found of course in man ; the second is physiological, 
 and inquires into the nature of these psycliical processes. Since 
 we know these only through the movements in which they are 
 expressed, the investigation is primarily a study of the movements 
 of Protists. 
 
 " On a superficial observation of these movements the impression 
 arises in the observer's mind that they are the result of higher 
 psychical processes, like the consciously willed activities of men. 
 Especially the spontaneous movements of advance and recoil of 
 testmg and searching, give us the impression of being intentional 
 atul voluntary, since no external stimulus can account for them • 
 while even some of the movements provoked by stimuli appear on 
 account of their marked aptness to arise from conscious sensation 
 nnd determination. 
 
 " But a critical study of the results yielded by an investigation 
 of spontaneous and stimulated movements warrants a more secure 
 judgment than that of the superficial observer, and leads to a con- 
 elusion opposed to his. To this conclusion we are led, that none 
 of the higher psychical processes, such as conscious sensations, 
 representations, thoughts, determinations, or conscious acts of will 
 are exhibited by Protists. A numl;er of criteria show that the 
 movements are in part impulsive and automatic, and in part reflex, 
 ^" ./xi:° '^^^^ expressions of unconscious psychical processes. 
 
 This opmion is corroborated by an examination of the structure 
 of these Protists, for this does not seem such as would make it 
 possible for the individual to have an idea of its own unified self, 
 and the absence of self-consciousness excludes the higher psychical 
 processes. Small fragments cut from a Protist cell continue to 
 make the same movements as they made while parts of the intact 
 organism. Each fragment is an independent centre for itself 
 1 here is no evidence that the nucleus of the organism is a psychical 
 centre. There is no unified Psyche. 
 
 "Since the characteristic movements persist in such small frag- 
 
 r 
 
 T"; 
 
 
 M. 
 
 w 
 
ai8 The Study of Animal Life part in 
 
 ments, they cannot be the expression of any individual consciousnesa 
 for the individuality has been cut in pieces." 
 
 The dilemma is obvious ; either there are no psychical processes 
 in the Protists, or they are inseparable from the molecular changes 
 which occur in the parts of the material substance. 
 
 If no psychical processes occur in the Protists, where do they 
 begin ? There is no distinct point in the animal series at which a 
 nervous system may be said to make its first appearance. If there 
 are none, even rudlmentarily, in the Protists, then these simple 
 organisms do not potentially include the life of higher organisms. 
 If theie are none in the Protists, are there any in the germs from 
 which men develop ? .... 
 
 Verworn seizes the other horn of the dilemma, mamtaming that 
 the superficial observers are wrong in crediting the Protozoa with 
 their own intelligence or with some of it, but right in concluding 
 that psychical processes of some sort are there. But since lie 
 cannot in any way locate these processes, since he finds that even 
 small fragments retain their life for a time and behave much as the 
 entire cells did, he maintains that all life is psychical. 
 
 7. History of the Protozoa.— We know that the Protozoa 
 have lived on the earth for untold ages, for the shells of Fora- 
 minifera and others may be disentombed from almost the oldest 
 rocks. The word Protozoa, a translation of the German Urthicre or 
 primitive animals, suggests that the Protozoa are not only tie 
 simplest, but the first animals, or the unprogre"ive descendants ot 
 these. Nowadays we can hardly feign to consider this proposition. 
 startling, for we know that all the higher animals, including ot;r- 
 selves, begin life at the beginning again as single cells. Fiom the 
 division and redivision of an apparently simple fertilised egg-cell rx 
 embryo is built up which grows from stage to stage till it 1- 
 hatched, let us say, as a chick. It is only necessary to extend t! '.^ 
 to the wider history of the race. What the egg is to the chick the 
 original Protozoa were to the animal series ; the present Protoza 
 are like eggs which have lived on as such without making much 
 progress. 
 
 We do not know how the Protozoa began to be upon the e.u: .. 
 whether they originated from not living matter or in some yet more 
 mysterious way. The German naturalist Oken, a prominent ty; : 
 of the school of "Natural Philosophers" who flourished about t.: 
 beginning of this century, dreamed of a primitive living shtre 
 (Urschleim) which arose in the sea from inorganic material. Mi-- 
 dream was prophetic of the modern discoveiy of very simple ;or'.r.s 
 of life, in connection with one of which there is an interesimj sr.a 
 instructive story. That one, perhaps I should say that supposea 
 one, was called Batkybius, and since those who are eager to nr..-:e 
 
mijiJl 
 
 CHAP. XIV TAe Simplest Anintals 219 
 
 points against science (that is to say against knowledge) always tell 
 the stojy wrongly, I shall make a digression to tell it rightly 
 
 In 1857 Captam Dayman, in charge of a vessel engaged in con- 
 nection with cab e - laying, discovered on the submarine Atlantic 
 plateau the abundant presence of slimy material which looked as if 
 It were al.ve. Preserved portions of this formless slime were after- 
 wards descnb. d by Huxley, and he named the supposed organism, 
 
 Haeckelu. On the /Va///«^expeduion Professors Wyville Thomson 
 and Carpenter observed it in its fresh state, and Haeckel afterwards 
 described some preserved specimens. Its interest lay in its 
 simplicity and apparent abundance; Oken's dream seemed to be 
 
 But when the Challenger expedition went forth, and the bed of 
 the ocean was explored for the first time carefully, the organism 
 Bathybius v^;,^ nowhere to be found. But this was not M : the 
 
 ™? . r R T, ^'' '° '=°'"'- ^'- J°^" ^^""-y '^-' reason to 
 suspect that Bathybius was not an organism at all, that it could be 
 made in a test-tube, and was nothing but a gelatinous form of 
 sulpha e of lime precipitated from the sea water by the action of the 
 ttt T"h P^«^^y>"g 7^f «Js- He renounced Bathybius, 
 
 llri ^ °^ acquiesced, Huxley surrendered his organism to 
 the chemists, and the obscurantists rejoiced exceedingly over the 
 mares nest. Bathybius became famous, it was trotted out to 
 1 ustrate the fallibility of science, a useful if it were not a some^hS 
 superfluous service. 
 
 th.f';hi^^n""''''"'',°'"^''''>'^''"'^"^^ "°' P^°^'^d by the fact 
 
 ha the Chall^ger explorers failed to find it. nor was it certain 
 
 that Murray's destructive criticism covered all the facts. Haeckel 
 
 l"nMr Kf' '"'''^ pertinacity to Bathybius. and his con- 
 
 S ^ ^Tr Vrf "^'"' J"'''^''-' '^y the fact that in 1875 
 
 tarerV^'w'^^/^'f \'P''^^''°"''^^^^eed from 92 fathoms of 
 
 TZ '"^""^^ ^o""^ abundant quantities cf a closely- similar 
 
 fiTkr,,.,- n ""'"^ ''l^''^' movements, and called it Protc 
 
 Bathy,us. It may be that it consists of the broken-off portions 
 
 of Foraminifera ; we require to know yet more about it. but I have 
 
 aid enough to show that it is unfair to stop telling th; s"ory wi h 
 
 the words "mare's nest." But whether there lia Bathybhr . 
 
 IZlillT^r' °r "° ^'"'^^'"' ""' ^"' ''^ "^^ ^^ ^'"d^"«s of science 
 compelled to confess our complete ignorance as to the origin 
 
 8. Relation to the Earth. — The floor of the sea for a 
 
 o"e?ed^T'a VI """ (-t exceeding 300) from thHlJ:: i 
 
 ^"""■^•■•-jr'wa" 3"ciis of i-oraminilcia usually 
 
 ^ 
 
 i i 
 
 :1L1: 
 
 1 
 
 ill 
 
 ni, 
 
 
 u 
 r 
 I 
 I 
 
 11 
 
 iiit 
 
330 
 
 TJie Study of Animal Life ^-art m 
 
 oocur, bu; they become more numerous farther from the land, 
 where the floor of the sea is often covered with a whitish "ooze," 
 most of which consists of Foraminifera which in dying have sunk 
 from the surface to the bottom. ihey are ferming the chalk of a 
 possible future, just as many dialk-cliffs and pure limestones repre- 
 sent the ooie of a distant past. In other regions the hard parts 
 of Radiolarians or Diatoms (small plants) or Pteropods (minute mol- 
 luscs) are very abundant. As the Foraminifers have made much 
 of the chalk, so Radiolarians have formed less important siliceous 
 deposits, such as the Barbados Earth, from which Ehrenberg 
 described no fewer than 278 species. At marine depths greater 
 than 2500 fathoms the Globigerina or other Foraminifer shells are 
 no longer present, not because there are none at the surface, but 
 apparently owing to the solution of the shells before they reach 
 such a vast depth. Here the floor is covered with a very fine 
 reddish or brownish deposit, often called "red- clay," a very 
 heterogeneous deposit of meteoric and volcanic dust and of residues 
 of surface-animals. Along with this, in some of the very deepest 
 parts, e.g. of the Central Pacific, there are accumulations of Radio- 
 larian shells, which do not readily dissolve. ^ 
 
 9. Belation to other Forms of Life.— On the one hand 
 
 the Protozoa are devourers of oi^nic debris and the enemies of 
 many small plants ; on the other hand they form the fundamental 
 food of higher animals, helping, for instance, to make that thin sea- 
 soup on which many depend. Moreover, among them there are 
 many parasites both on vegetable and animal hosts. 
 
 10. Belation to Man. —in many indirect ways these firstlings 
 affect human life, nor are there wanting direct points of contact ; 
 witness a few Protozoa parasites in man, an .^nioeba, some Gie 
 garines, and some Infusorians, which are very trivial, however, in 
 comparison with the numerous plant-parasites— the Bacteria. 
 
 Among the earliest human records of Protozoa is the notice 
 which Herodotus and Strabo take of the large coin-like N unimu 
 lites, the " Pharaoh's beans " of popular fancy. But the minute- 
 ness of most Protozoa kept them out of sight for ages. Thty were 
 virtually discovered by Leeuwenhoek (b. 1632) about the middle o( 
 the seventeenth century, and soon afterwards demonstrated by 
 Hooke to the Royal Society of London, the members of which 
 signed an «ffidavit that they had really seen them ! In 1755 Kosc[ 
 von Rosenhof discovered the Amoeba, or "Proteus animalcule:" 
 but his discovery was ineffective till Dujardin in 1835 demonstraied 
 the simplicity of the Foraminifers, and till Von Siebold in 184S 
 
 » For details, see conveniently H. R. Mill's Realm of Nature (Lend. 
 1893). 
 
CHAP, xnr The Simplest Animats an 
 
 sb'^'ved that Infusoria were single celli comparable to those whicli 
 make up a higher animal. For the resemblance between some of 
 the spirally twisted shells of Foraminifera and those of the 
 immensely larger MoUuscan Ammonites and Nautili led many to 
 mamtain that the Foraminifera were minute predecessors or else 
 dwindling dwarfs of the Ammonites. So Ehrenberg (1838) figured 
 the presence of many organs within the Infusorian cell. But as 
 the microscope was perfected naturalists were soon convinced that 
 the Protozoa were uni^ masses of living matter. This is their great 
 interest to us ; they are, as it were, higher organisms analysed into 
 their component elements. We see them passing through cycles 
 of phases, from ciliated to amoeboid, from amoeboid to encysted, 
 cycles which shed light upon changes both of health and of disease 
 in higher animals. Again, they seem like ova and spermatoiot 
 which have never got on any farther. 
 
 m 
 
 m 
 
 m ^ 
 
, 
 
 I 
 
 
 Ir 
 
 CHAPTER XV 
 
 BACKBONELESS ANIMALS 
 
 Spends — 2. Stitigittg-Animah or Ccelenterata — 3. " Worms''— 
 4. Echitioderms—l. Arthropods— (t. Molluscs 
 
 I. Sponges.— Sponges are many- celled animals without organs, 
 with little division of labour among their cells. A true " body " is 
 only beginning among sponges. 
 
 Adult sponges are sedentary, and plant -like in their growth. 
 With the exception of the freshwater sponge {Spongilla) they live 
 in the sea fixed to the rocks, to seaweeds and to animals, or to the 
 muddy bottom at slight or at great depths. They feed on micro- 
 scopic organisms and particles, borne in with currents of water 
 which continually flow through the sponge. The sponge is a 
 Venice-like city of cells, penetrated by canals, in which incoming 
 and outflowing currents are kept up by the lashing activity of 
 internal ciliated cells. These ciliated cells, on which the whole hie 
 of the sponge depends, line the canals, but are especially develoi-ed 
 in little clusters or ciliated chambers. The currents are drawn in 
 through very small pores all over the surface ; they usually flow on 
 through much larger crater-like openings. 
 
 Sponges feed easily and well, and many of them grow out in 
 buds and branches. A form which was at first a simple cup may 
 grow into a broad disc or into a tree-like system. And as trees art 
 blown out of shape by the wind, so sponges are influenced by the 
 currenU which play around them, as well as by the nature o\ ti e 
 objects on which they are fixed. Like many other ia:,>r.e 
 organisms, sponges almost always have a well-developed skclcKn. 
 made of flinty needles and threads, of spicules of lime, or of tilres 
 of horn -like stuff. While sponges do not rise high in oiganic 
 rank, they have many internal complications and much beauty. 
 
 Sponges may be classified according to their skeleton, m 
 
CHAP. XT 
 
 BackboneUss Animals 
 
 "3 
 
 calcareous, ainty, and horny, (o) The calcareous forms with 
 needles of bme have a world-wide distribution in the sea, from 
 between tide-marks to depths of 300 to 400 fathoms. They often 
 retain a cup -like form, but vary greatly in the complexity of their 
 
 « ■•.• u t !.fc'"^''* (°' Grantia) com/r»sa is common 
 
 on Brifsh shores (*) The siliceous sponges are more numerous, 
 diverse, and comphcated, and the flinty needles or threads are often 
 combined with a fibrous " horny " skeleton. Venus'-Flower-Basket 
 [EupUctella) hzs, a glassy skeleton of great beauty. Mermaids' 
 Gloves (CAa//«a oculata) with needles of flint and horny fibres Ls 
 often thrown up on the beach, the Crumb-of- Bread Sponge 
 {Haltchondna pamcea) spreads over the low -tide rocks. Some 
 have strange habits, witness Clione which bores holes in oyster 
 shells, or Subentes domuncula which clothes the outside of a whelk 
 or buckle shell tenanted by a hermit-Crab. Unique in habitat is 
 the freshwater sponge {SpongHla) common in some canals and lakes, 
 notable for plant-hke greenness, and for the vicissitudes of its life- 
 history, (c) The " horny " sponges which have a fibrous skeleton 
 
 ^f "ilP'^^u't''." "* **" represented by the bath-sponges 
 (Euspongta) which thrive well off Mediterranean coasts, whe- they 
 are farmed and even bedded out. ' 
 
 Sponges are ancient but unpiogiessive animals. Their sedentary 
 habits from which only the embryos for a short time escape, have 
 been fatal to further progress. They show tissues as it were in the 
 making They are living thickets in which many small animals 
 play hide-and-seek. Burrowing worms often do them much harm, 
 
 ? • '^°i "^"^ *"*™'" ^^"^ "* Protected by their skeletons and by 
 tneir bad taste. ' 
 
 2. Stinging- Anixnals or Ooelenterata.— It U difficult to 
 
 fin. a convenient name for the jellyfish and zoophytes, sea-anemones 
 and corals, and many other beautiful animals which are called 
 Ccelenterates; but the fact that almost all have poisonous stincine 
 lassoes in some of their skin-cells suggests that which we now use 
 
 Representatives of the chief divisions may be sometimes found 
 n a pool by the shore. Ruddy sea-anemones, which some call 
 ea-roses, nestle m the nooks of the rocks ; floating in the pool and 
 hrohbmg gently IS a jellyfish left by the tide ; fringing thTrocks 
 
 e various toophytes, or if we construe the name backwards plant! 
 iKc animals ; besides these, and hardly visible in the clear water 
 are minute translucent bells some of which have a strange relation 
 s .p wuh .oophyte, ; and there are yet other exquiSdSe' 
 
 Si. ly iridescent globes-the Ctenophore, which mo.thyTmt 
 
 7y^at^.iV "7''»» ™^"^b«." of this dass-the neshwatei 
 a^dra which hangs from the floating duckweed and other planta. 
 
 ill* 
 
 m 
 
 ■i- 
 
 -..a t i 
 
ii4 The Study of Animal Life part hi 
 
 TKU H^ra is a tubular animal often about quarter of an inch in 
 
 Th» ^'•<» » * S thTtXis fixed, the other bears the mouth 
 
 ^'"^^a.?°bv a crSln of m^b?e tentacles. It is so simple that 
 
 StLlt. tf^t tc^ minute may grow into complete animals ; 
 
 wh^n wdf?S the Hydra buds out little polypes hke Uself. and 
 
 ''TfweTpS^'the budding of Hydra continued a hundred- 
 
 "°Som:tirer tZ^^:^^'^^^^^o.oi^.^..r^n such 
 Sometimes however in ^^^^.^.^^^ reproductive, 
 
 S n a special interest in the case of many zoophytes. Fo 
 this nas a spcuim uu^ tnown as Tulm arians and 
 
 -Li..,.H-« hi«i« of hvdrod colonies. Some wnicn are 
 
 lik. lh« P^* « /Sm, .« "he M. jellyfish^ «hich are 
 somelimei superficially l«e i"'™" "= ' . ni „,ednst 
 
 sometimes stranded in great numl.ers on "« ?«?*• '"' ,i„k their. 
 talone 10 a different series, and some of tlieir fcattres hnit 
 r,.her^th..«.-.nem«ne,.han.„theMro.d. ^^^ 
 
 moilS: :::-=^^;"fjv5C'XroS"^^^^ 
 s.rt;Seru-roSs^'.Hro»^^^^^^^^ 
 
 man, radiating partition, "r ,,"'? °' """'iir R^lal d > • -l^ 
 
CHAF. XV Backboneless Animals 
 
 225 
 
 as relatives (S.phonophora). which are colonies of more or Lss 
 meduscMd ind.v.duals with much division of labour. TdLuv the 
 Ctenophores, such as Beroe and Pleurobrackia, which XS tJe 
 climax of activity among Coelenterates. "^n represent the 
 
 A brief recapitulation will be useful • 
 /»vr/ j-^,,_Hydroid and Medusoid types (Hydrozoa):- 
 I The freshwater Hydra and a few forms like it 
 
 (2) The hydroids or zoophytes, each of which maybe regarded 
 
 as a compound much-branched Hydra ; including af many 
 whose -eproductive persons are not liberated, espedaSy 
 Se uwians and I'lumularians ;-(3) many whose^repro^ 
 ductive persons are liberated as swimming bells or 
 medusoids, especially Tubularians and Campanularians 
 
 (3) tree meduso.ds. anatomically like the liberated bells o? 2 i) 
 
 but without any connection with zoophytes. ^ '' 
 
 (5) A few hydroid corals or Millepores. 
 Wj^/«_JeIIyfish and Sea-Anemone types (Scyphozoai- 
 
 (!) The true jellyfishes or Medus.. including S a formlke 
 Pelasta which is free-swimming all its life IhioUgh,?^) £e 
 common ^«,W.a who.se embiyos settle down and become 
 polypes from which the future free -swimming jellyfishes 
 are budded off. (.) the more or less sedenta^ry jeUyfish 
 known as Lucernarians. ^ j-^^yjisn 
 
 The sea -anemones and their relatives, including r«) sea- 
 anemones proper ie.g. Aainia) and their relat;d reef- 
 building coral-colonies {e.g. star-corals Astr^a, brain-coral 
 
 clT /r V • '''° ^"h'^'-'^'l ^"r->«. 'S. the organ-pipe 
 coral (Tubtpora musua) ^nA the '« noble coral" of com- 
 merce (Ct>/a//,«w „,^;^;,;). *' 01 com- 
 Third Series— 
 Ti,e Ctenophores, which a: e n.arkedly contrasted with corals, 
 l^mg free and bght and active. Many (e.g. Beroi and 
 I^letirobrachm) swarm in our seas in summer, iride> ♦ in 
 daylight, phosphorescent at night. Tlu-y differ in . ny 
 Q 
 
 f2) 
 
 M 
 
 I 
 
 
 ill 
 
 IB. 
 
 
 
226 Th£ Study of Animal Life part in 
 
 ways from other Coelenterates, thus the characteristic 
 stinging cells are modified into adhesive cells. 
 The first and second series, separated by diflferences of structure 
 and development, are yet parallel. In both there are polype-types ; 
 in both medusoid types ; in both there are single mdividuals and 
 colonies of individuals; in both there are "corals. ^ ^^e n;--*)' 
 compare a Hydra with a sea -anemone, a medusoid with a jelly- 
 fish a hydroid colony with Dead -men's- fingers, Millepores wiih 
 
 the Evolution o/Stx ; after Haeckel.) 
 
 lll-Ol 
 
 the commoner reef-corals. Moreover, we may compare a mod 
 liberated from a hydroid with Aurelia liberated from its fixed polyp. 
 stage, and permanently-free medusoids with jellyfishes like Vda^ta, 
 These arc physiological parallels. 
 
 The sedentary polypes arc somewhat sluggish, with a tondomy 
 to bud and to form shells or skeletons of some kind. 'I ho free- 
 swimming medusoid types are active, they rarely bud, they d) not 
 form skeletons, but their activity is sometijncs expressed m 
 
CHAP. XV Backboneless Animals 
 
 phosphorescence, and their fuller life 
 
 227 
 
 J associated with the develnn 
 wh,ch ftMe„„clcs and .h'e S^" .ST^H Zr"" » -"""« 
 
 occurs in brackish water and in .;„ni "y^'™''* f-o> dyhphora which 
 
 which is pan^siticinTts youth "n .ri.: ^fThf R°™ '''''^^'^"'" 
 or sterlet, and a freshwater iellvfi.jf^f / • ^^^^^^^'^n sturgeon 
 found in the tanks at Kew ^rlt ^Ltmnocodtum) which was 
 
 \^x them company Siphonophores and Ctenophores 
 
 Various kinds of corals should be contra<;tPH n . 
 fingers with aumerous jagged suicules oMi " • •. ^,^^'|-™ens- 
 l^nning to be coralline SimiUrc•^i™^'" "' ^^^^ '- J"st 
 i7an external t°ut" i^' tl I'^^an 'pTp^L'rT t" S"' '^^'^J 
 the calcareous material form.; nn a vJc*^ j "... , *^^ ""^^ '^o"' 
 are clustered. Ve.y diSnt nr^ ^.^'"""^^M'f^ '^^ individuals 
 the cup in which e^IhlnSuaUivxd'ir:^"'''^^ ~'^'^' "'^"^ 
 according as it has remaiS di inct 1 "fZ' ^h^ "'" T^''' 
 and where an imatre of the fliv. ..'"^^^ ^^'^^ "s neighbours, 
 .ike anima, is ^::^t^l^:SZt^:tl^, '>- ™one- 
 
 ca.^":irK.T; hot'do^ trVef r °^''""^' ^-^^^^ »'- 
 
 which these are composed^ Is h^f ^1 ^^ '''^°"^*'^ ^^ '™« of 
 sea-water-plentiful nS cLl ree^ or "T^'iL"^^ ^ n' ^'""'^"' '" 
 tion between the abunHmt ^.\l- °^'V"^'^ ^ double-decomposi- 
 
 products, a: hls\t""suggS'b^? i'^^^^^^^^ ''^ '^^^"'^ --'- 
 do the corals feed, for therseem alwn s f^h '"■'^^ ^" ^"'''''' 
 bright pigmenU enable them T/r^ ^^ ^""P^^' ^° »heir 
 plants on carbonic acid ? ' ''''°" '"^gests. to feed like 
 
 water. """' '^'"S J'ttle more than animated sea- 
 
 11 
 
 'I 
 
 1' 
 
 M 
 
 ,1 
 
 ]^ 
 
 iif 
 
 WS^Z^ 
 
2a8 The Study of Animal Life part m 
 
 As sDonces showed tissues in the making, so among Stinging- 
 As sponges snow nerve- rings, and special 
 
 animals o'g"^ ^8^°-?^ ^lo^t has much to leam in regard 
 "P/v^T™.S orhydS^dTedusoid in one life-cycle, the 
 to he ^'7?^*^° °\„^^^^^ and other colonies, and the 
 
 division °f }*^" JV a skSe on. Nor can we forget the long 
 meaning and makmg oj J «^;'«° ^^^j „,f,, ^^d types of coral 
 
 Sirretrett^^^^^^^^^^^ Graptolites whose nature we 
 
 '°W ?ln'?il's^ritro?m;uy-celled animals with Sponges and 
 rXteS par?^ ic-re they are on the whole simplest, but 
 OElenteraes. partly / ^^.^^^.yyxft are leest removed 
 
 ZmtCtt^S reT.cS^ or gastrula which recurs .n 
 
 Se Wsto^ of most animals, and which we have mucn warran 
 the life-tastory oi mus successful many-celled 
 
 for regardmg as a hint of what ^he ^^^^^^^^ ^.^^^ ^^^^ ^j,^ 
 animals ^ere 'ke The f ?on|es ^^ ^^.^ ^^^^^^^^ .^^ 
 
 S^r^ttdii ly ^ymS^^^^^ and'in so gVowing that the axis 
 eSi from the mouth to the opposite pole corresponds o the 
 extending iromuic two -layered animals, for 
 
 '"'y°'Wo™^This title is one of convenience, ^vithout 
 .3 . r^r'., Vnr there is no class of "worms," but an 
 
 sides. The ""P^'^/iSSstently head foremost, thus acquiring 
 
CHAP. XV 
 
 Backhondess Antmals 
 
 329 
 
 by budding forms temporary chains of eight or sixteen individuals 
 as if suggesting how a ringed wonn might arise ; Gunda, with a hint 
 of internal s^mentation ; and two parasitic genera — Grc^la and 
 Amplodium — may be mentioned as representatives of this class. 
 You will find specimens by collecting the waterweeds from a pond 
 or seaweeds from a shore-pool, and the simplicity of some may be 
 demonstrated by observing that when they are cut in two each half 
 lives and grows. 
 
 2nd Class. — Trematoda or Flukes. These are parasitic "worms," 
 living outside or inside other animals, often fiat or leaf- like in 
 form, provided with adhesive and absorbing suckers. Those which 
 live as ectoparasites, e.g. on the skin of fishes, have usually a 
 simple history ; while those which are internal boarders have an 
 intricate life-cycle, requiring to pass from one host to another of a 
 different kind if their development is to be fulfilled. Thus the 
 liver-fluke {Distornum hepaiicum), which causes the disease of liver- 
 rot in sheep, and sometimes destroys a million in one year in Britain 
 alone, has an eventful history. From the bile-ducts of the sheep 
 the embryos pass by the food-canal to the exterior. If they reach a 
 pool of water they develop, quit their egg-shells, and become for 
 a few hours free-swimming. They knock against many things, but 
 when they come in contact with a small water -snail (Lymtueus 
 tmncatulus) they fasten to it, bore their way in, and, losing their 
 locomotor cilia, encyst themselves. They grow and multiply in a 
 somewhat asexual way. Cells within the body of the encysted 
 embryo give rise to a second generation quite different in form. 
 The second generation similariy produces a third, and so on. 
 Finally, a generation of little tailed flukes arises ; these leave the 
 water-snail, leave the water too, settle on blades of grass, and lose 
 their tails. If they be eaten by a sheep they develop into adult 
 sexual flukes. Others have not less eventful life-cycles, but that of 
 the liver-fluke is most thoroughly known. If you dissect a frog 
 you are likely to find Polystomum integerrimum in the lungs or 
 bladder ; it begins as a parasite of the tadpole, and takes two or 
 three years to become mature in the frog. Quaint are the little 
 forms known as Diporpa which fasten on the gills of minnows, and 
 unite in pairs for life, forming double animals (Diplotoon) ; and 
 hardly less strange is Gyrodactylm, another parasite on freshwater 
 fishes, for three generations are often found together, one within 
 the other. The most formidable fluke-parasite of man is Bilhartia, 
 or Distomum kamatobium, common in Africa. 
 
 3rd Class. Ccstoda or Tapeworms. These are all internal 
 parasites, and, with the exception of one {Ankigctes), which fulfils 
 its life in the little river-worm Tubifex, the adults always occur in 
 the food-canal of backboned animals. Like the flukes, they have 
 
 mk 
 
 tf 
 
 i <'i 
 
836 The Study of Animal Life part ih 
 
 adhesive suckers, and sometimes hooks as well ; unlike aukes and 
 planarians, which have a food-canal, they absorb the juices of their 
 hosU through their skins, and have no mouth or gut. Like 
 the endo-parasitic flukes, the tapeworms have (except Archigttes) 
 intricate life -histories. Both Turbellarians and Trematodes are 
 small, rarely more than an inch at most in length, but the tape- 
 worms may measure several feet. In the adult Tania solium, 
 which is sometimes found in the intestines of man, we see a small 
 head like that of a pin ; it is fixed by hooks and suckers to the 
 wall of the food-canal ; it buds off a long chain of "joints," each 
 of which is complete in itself. As these joints are pushed by con- 
 tinued budding farther and farther from the head, they become 
 larger, and distended with eggs, and even with embryos, for the 
 bisexual tapeworm seems able to fertilise itself, which is a very rare 
 thing among animals. The terminal joints of the chain are set free, 
 one or a few at a time, and they pass down the food-canal to the 
 exterior. The tiny embryos which they contain when fully ripe 
 are encased in firm shells. It may be that some of them are eaten 
 by a pig. tbe shells are dissolved away in the food-canal, small six- 
 ncoked embryos emerge. These bore their way into the muscles of 
 the pig and lie dormant, increasing in size however, becoming 
 little bladders, and forming a tiny head. They are called bladder- 
 worms, and it was not till about the middle of this century that they 
 were recognised as the young stages of the tapeworm. For if the 
 diseased pig be killed and its flesh eaten (especially if half-cooked) 
 by man, then each bladder-worm may become an adult sexual tape- 
 worm. The bladder part is of no importance, but the head fixes 
 itself and buds off a chain. For many others the story is similar ; 
 the bladder-worm of the ox becomes another tapeworm {Tania 
 saginata) in man ; the bladder-worm of the pike or turbot becomes 
 another (Bothriocephaltis lotus) ; the tladder-worm of the rabbit 
 becomes one of the tapeworms of the dog, that of the mouse passes 
 to the cat, and so on. A bladder-worm which forms many heads 
 destroys the brain of sheep, etc., and has its tapeworm stage ( Tattia 
 ccenunis) in dog or wolf. Another huge bladder- worm, which has also 
 many heads, and sometimes kills men, has also its tapeworm stage 
 {Tania echinococcus) in the dog. But enough of these vicious 
 cycles. 
 
 2nd Set of Worms. Bibbon Worms or Nemerteans— 
 
 4th Class, Nemcrtea.— In pleasing contrast to the flukes and tape- 
 worms, the Nemerteans are free -living "worms." They are 
 mostly marine, often brightly coloured, almost always elongated, 
 always covered \vith cilia. There is a distinct food-canal with 
 a posterior opening, a blood-vascular system for the first time, 
 a well-develop nervous system, a remarkable protrusible " pro- 
 
CHAt. XV 
 
 BcukboneUss Animals 
 
 a3* 
 
 boscu lying in a sheath along the back, a pair of enigmatical 
 ciliated piU on the head. The sexes are almost always separate. 
 Almost all Nemerteans are carnivorous, but two or three haunt other 
 animals in a manner which leads one to suspect some parasitism ; 
 thus AfalacobJella lives within the shells of bivalve molluscs. We 
 find many of them under loose stones by the sea-shore; one 
 beautiful form, Lineus marinus, sometimes measures over twelve 
 feet in length. Some, such as Cerebratulm, break very readily into 
 parts, even on slight provocation, and these parts are said to be 
 able to r^row the whole. To speculative zoologists, the Nemer- 
 teans are of great interest on account of the vertebrate affinities 
 which some of their structures suggest. Thus the sheath of the 
 ''proboscis" has been compared with the vertebrate notochord 
 (the structure which precedes and is replaced by a backbone), and 
 the two ciliated head -pits with gill-slits. 
 
 3rd Set of Worms. Nematbelmintlies or Bound- 
 Worms— sth Class, Nematoda or Thread - Worms.— The 
 " worms " of this class are usually long and cylindrical, and the 
 small ones are like threads. The skin is firm, the body is 
 muscular ; in most a simple food-canal extends from end to end of 
 the body-cavity now for the first time distinct; the sexes are 
 separate. Many of the Nematodes live in damp earth and in 
 rottenness ; many are, during part of their life, parasitic in animals 
 or plants. We have already noticed how long some of them — 
 "paste -eels," "vinegar -eels," etc.— may lie in a dried-up state 
 without dying. The life-histories are often full of vicissitudes ; thus 
 the mildew- worm {Tylmchus tritict) passes from the earth into the 
 ears of wheat, and many others make a similar change ; the female 
 of Sphttrularia bombi migrates from damp earth into humble-bees, 
 and there produces young which find their way out ; others, e.g. 
 some of the thread-worms found in man {Oxyurii, Trichocephalus), 
 pass from water into their hosts ; others are transferred from one 
 host to another ; as in the case of the Trichina with which pigs 
 are infected by eating rats, and men infected by eating diseased 
 pigs, or the small Filaria sanguinis hominis, sometimes found in 
 the blood of man, which seems to pass its youth in a mosquito. 
 Somewhat different from the other Nematodes are those of which 
 the horse-hair worm Gordius is a type. They are sometimes found 
 inside animals (water-insects, molluscs, fish, frog, etc), at other 
 times they appear in great numbers in the pools, being, according 
 to popular superstition, vivified horse-hairs. 
 
 6th Class, Acanthocephsla. — Including one peculiar genus of 
 parasites {Echinorkynchus). 
 
 4th Series of Worms. The Annelids or Ringed Wonns 
 
 -7lh Class, Chsetopoda or Bristle - footed "worms."— In the 
 
«3« The Study of Animal Life part m 
 
 earthworms {Liimbricus, etc.), in the freshwater worms {Nais, 
 
 Tubifex, etc.), in the \o\yfioxxa& {Arenicola piscatorum), and in the 
 
 »ea-worms (Nereis, Aphrodite, etc.), all of which are ranked as 
 
 Ch8etopods,\he body is divided into a series of similar rings or 
 
 segments, and there are always some, and often very many, bristles 
 
 on the outer surface. The segments are not mere external rings, 
 
 but divisions of the body often partially partitioned off" internally, 
 
 and there is usually some repetition of internal organs. Thus in 
 
 each segment there are often two little kidney-tubes or nephridia, 
 
 while reproductive organs may occur in s^ment after segment. 
 
 Moreover, there are often two feet on each ring. The nervous 
 
 system consists of a dorsal brain and of a double nerve-cord lying 
 
 along the ventral surface. The nerve-cord has in each segment a 
 
 pair of nerve-centres or ganglia, and divides in the head region to 
 
 form a ring round the gullet united with the brain above. The 
 
 existence of nerve-centres for each segment makes each ring to some 
 
 extent independent, but the brain rules all. This type of nervous 
 
 system represents a great step of progress ; it is very different from 
 
 that of Stinging-animals, which lies diffusely in the skin or forms 
 
 a ring around the circumference ; different from that of the lower 
 
 "worms," where the nerve-cords from the brain usually run alonj,' 
 
 the sides of the body ; different from that of molluscs, where the 
 
 nerve-centres are fewer and tend to be concentrated in the head ; 
 
 different finally from the central nervous system of backboned animals, 
 
 for that is wholly dorsal. But the type characteristic of ringed 
 
 "worms" — a dorsal brain and a ventral chain of ganglia — is also 
 
 characteristic of crustaceans, insects, and related forms. 
 
 Of bristle-footed "worms," there are two great sets, the earth- 
 worms and the sea-worms. The former, including the common 
 soil-makers and a few giants, such as the Tasmanian Megascolides, 
 sometimes about six feet long, have bristles but no feet ; sense- 
 organs, feelers, and breathing organs are undeveloped as one would 
 expect in subterranean animals. The sea-worms, on the other 
 hand, have usually stump-like bristly feet, and eyes and tentacles 
 and gills, but there is much difference between those which swim 
 freely in the sea (e.g. Alciope and Tomopteris and some Nereids) 
 and the lobworms which burrow and make countless castings upon 
 the flat sandy shores, or those which inhabit tubes of lime or 
 sandy particles (e.g. Serpula, Spirorbis, and Lattice or Terebdli 
 cotichilegd). The earthworms with comparatively few bristles 
 (Oligochseta) are bisexual, while almost all the marine worms with 
 many bristles (Polychaeta) have separate sexes. Moreover, those of 
 the first series usually lay their eggs in cocoons, within which the 
 embryos develop without any metamorphosis, while the sea- worms, 
 though they sf-metirr.PF. form r.ocoons, have free-swimming l.irva! 
 
CHAP. XV 
 
 Backboneless Animals 
 
 m 
 
 usually v^ry different from the adults-little barrel-shaped or pear, 
 shaped ci.iated creatures known as Trochospheres. 
 
 Some of the Chjetopods multiply not only sexually, but asexually 
 by dividing into two or by giving off buds from various parts of 
 their body Strange branching growths, which eventually separate 
 mto individuals, are well illustrated by the freshwater A^a/JTand 
 
 Fig. 43.-A budding marine worm (6>//« ramosa). From Evolution of Sex ■ 
 after M 'Intosh's Challenger Report.) ' 
 
 still better by a marine worm, Syllis nvuosa, which almost forms 
 •I iictwoi k. 
 
 Many sea-worms have much beauty, which some of their names 
 hlv^ In'n "J"' ^Phjodiu, Alao/e, suggest, and which is said to 
 ha^e mduced a specialist to call his seven daughters after them 
 
 Along with the Chstopods, we include some other forms' too 
 
 ™" 'iTut ' "r *^^" --^'°" '^-^. ^he Myzostomata which 
 or ^-ill-Uke growths on the feather-stars which they infest, the 
 
 wiEk T^'^"^ '" '"^''^ '^^ >»icroscopic male lives as a para i,e 
 uuhin thefemale, and some very simple forms which are so .times 
 ^ -.iv.. -Aiciii-.vnnends. 
 
 ^'1' 
 
 
»34 
 
 The Study of Animal Life part hi 
 
 8th Class, Hirudinea or Discophora or Leeches. — These are 
 blood-sucking animais, which often cling for a long time to their 
 victims. They live in salt and in fresh water, and sometimes on 
 land. The body is elastic and ringed, but the external markings 
 do not correspond to the internal segments. There are no legs, 
 but the mouth is suctorial, and there is another adhesive sucker 
 posteriorly. The body-cavity is almost obliterated by a growtli 
 of spongy tissue, whereas that of Chaetopods is roomy. Leeches 
 are hermaphrodite, and lay their eggs in cocoons, within which 
 the young develop without metamorphosis. 
 
 The medicinal leeches {Hirudo medicinalii) live in slow streams 
 and marshes, creeping about with their suckers or sometimes 
 swimming lithely, preying upon fishes and amphibians, and both 
 laiger and smaller animals. They fix themselves firmly, bite with 
 their three semicircular saw-like tooth-plates, and gorge themselves 
 with blood. When they get an opportunity they make the most 
 of it, filling the many pockets of their food-canal. The blood is 
 kept from coagulating by means of a secretion, and on its store the 
 leech may live for many months. 
 
 The horse-leech {Hamopis sanguisuga) is common in Britain 
 and ilsewhere The voracious Aulastoma is rather carnivorous 
 than parasitic The land -leeches (e.g. Hamadipsa ceylonica\ 
 though small and thin, are very troublesome, sucking the blood of 
 man and beast Among the others are the eight-eyed Nepkelis of 
 our ponds, the little Clepsim which sometimes is found with its young 
 attached to it, the warty marine PontMella which fastens on rays, 
 Piideola on perch and carp, BranchtUion with numerous lateral 
 leaflets of skin, and the largest leech— the South American Macro- 
 bdtlla valdiviana which is said to attain a length of over two 
 
 feet. 
 
 Possibly related to the Annelid series are two other 
 
 classes — 
 
 9th Class— Chxtognatha, including two genera of small arrow- 
 like marine '• worms," Sagitta and Spadella. 
 
 loth Class — Rotifera, " wheel animalcvUes," abundant and 
 exquisitely beautiful animals inhabiting fresh and salt 
 water and damp moss. The head-region bears a ciliated 
 structure, whose activity produces the impression of a 
 swiftly rotating wheel. Many of them seem to !« 
 entirely parthenogenelic. Some can survive being made 
 as dry as dust. 
 Fifth set of Worms— a doubtful combination including— 
 
 I ith Class— Sipunculoidea, " spoon-worms" living In the sea, 
 freely or in tubes, e.g. Siputuulus. 
 
 lath Claa— Phoronidea, including one genus, Pk^vnis. 
 
cHAf. XV BackboneUss AnimcUs 
 
 13th Class-Polyzoa or Bryozoa, with one exception forming 
 colonies by budding, in fresh water or in the sea «. p. the 
 common sea-mats or horn-wracks (Flustra) 
 
 '*''*.?«'7^'^\°P°*^* °' Lamp-shells, a clLs of marine 
 
 shelled animals once much richer in members, now 
 
 decadent. They have a superficial, but only a superficial 
 
 resemblance to Molluscs. F<:rn«ai, 
 
 I have net catalogued all these classes of "worms » without a 
 
 purpose. To ignore their diversity would have lent a false simplicity 
 
 to our survey If you gain only this idea that there U a great 
 
 Za^^TL"^"^ worm-like animals, which zoologists have not yet 
 
 reduc-;d to order, you have gained a true idea. The " worms "lie 
 
 as It were m a central pool among backboncless animals, from which 
 
 whh Frhllr"^ '""T? °^ P'^S'*^"^* "f*- They have affinities 
 with Echinoderms, with Insects, with Molluscs, with Vertebrates. 
 To practi<al people the study of " worms » has no little interest. 
 The work of earthworms is pre-eminently important ; the sea- 
 
 constant companion ; numerous parasitic i^orms injure man. his 
 domesticated ock, and the crops of his fielc'?. 
 
 .'♦• .EcWn<^erm»t» -in contrast to the " Worms," the series 
 mcluding starfishes, brit -stars, feather- stars, sea-urchins, and 
 sea-cucumbers, is well defined. "renins, ana 
 
 The Echinodermata are often ranker next the stinging animals, 
 mainly becau«s many of the adults have « radiate fyi^metra; 
 jellyfishes and sea-anemones have. But radiate sySr/b a 
 
 ?K wlh olf" •*;• ^l^T *'VP'«'"y due to a sedemary habit of 
 life in which all sid« of the animal were equally affected. More- 
 
 saT'tiel -T:?-^ Echmoderms are bilaterally symmetrical, that is to 
 
 olL /.h^n., ''"'"r '"'° >''" *'°"e . median pline. We 
 place Echinodeims after and not before "worms." because the 
 simplest worm-like animals are much simpler, much near" the 
 l.yponiet.c.1 gastrula-like ancestor than are any Echinoderms. and 
 
 io^troroth^erl'^^'^''" "^''^"°''^""' ^^^^^ ^-™ «- 
 
 wa™ 's'^L'S '" i°''^ '. '''•^'^v"^ ?« *^"«^ ^'''^h *" in «»"« 
 ways suggestive. You know the five-rayed appearance of the 
 
 animal like a conventional .tar; you ha\e perhapi watched il 
 
 moving slowly in a deep ,xH:k pJol by the^shoiT; yrtve 
 
 perhaps ducovered that it will surrender one of its armi ihen you 
 
 tor to capture it. No;v Haeckel compared the s.arfish toTcolZ 
 
 of five worms united in the centre. Each •• arm " or •« ray""^ 
 
 complete in itself. £.,:h hM . nerve-cord aSng the ^tra 
 
 '::^^ Li? r • 23 ■' .*'• ^'P' P~'o"8»»ton. of the fo^.clrSiI.ro^ ' 
 vessels, and reproductive organs Each i. wiatomically comparable 
 
 ill 
 
 if 
 if 
 
236 
 
 The Study of Animal Life part m 
 
 to a worm. Furthermore, when an arm is separated, it may bud 
 out other four arms and thus recreate an entire starfish. Each arm 
 has therefore some physiological independence. 
 
 But there is no likelihood that a starfish arose as a colony of 
 worms; the facts of development do not corroborate the sug- 
 gestion. - , , , 
 
 Of Echinoderms there are seven classes, two of which are 
 wholly extinct. These— the Cystoids and Blastoids— are of great 
 interest because of their relationship with the feather- stars or 
 Crinoids, which stand somewhat apart from the other four extant 
 classes. The Cystoids are more primitive than the Crmoids, and 
 connect them with the starfishes or Asteroids. The Asteroids are 
 nearly related to the brittle-stars or Ophiuroids, and they are also 
 linked to the sea-urchins or Echinoids. These in turn are the 
 nearest allies of the Holothuroids or sea-cucumbers. 
 
 The Echinoderms are all marine. The sea-urchins and Holo- 
 thurians are mud-cleansing scavengers; the Holothurians and 
 Crinoids feed for the most part on small organisms, though tlie 
 former are sometimes mud-eaters ; the starfishes are more tmphatic- 
 ally carnivorous, and often engulf small molluscs. 
 
 Among starfishes, sea-urchins, and sea -cucumbers, we find 
 occasional cases of prolonged external connection between the 
 
 mothers and the young. . , , . u •.., 
 
 The Echinoderms are sluggish animals, though many bnttie- 
 stars are lithe gymnasts, and though the commonest Crinoids 
 (Comatulids, such as the rosy feather-star, Anttdon rosacea), differ 
 from their stalked relatives and adolescent stages in being to some 
 extent swimmers. Perhaps the sluggishness is expressed m the 
 abundance of lime in the skin and other parts ; for, as the name 
 suggests, the Echinoderms are thorny-skinned, being usually pro- 
 tected by calcareous plates and spines. The sea-cucumbers are the 
 most muscular and the least limy, indeed in some almost the only 
 calcareous parts are a few anchors and plates scattered in the skm. 
 Another frequent characteristic is the radial symmetry, but we 
 remember that the larvae are bilateral. 
 
 Very important is the development ot a peculiar systciu oi 
 canals and suctorial " tube-feet "—the water-vascular system. Hy 
 means of the tube-feet the starfishes and sea-urchins move, m the 
 others their chief use seems to be in connection with respir.it ion, 
 and it is likely that in some at least they also help in excretion. 
 
 Another characteristic of the Echinoderms is the strangeness of 
 the larval forms. For not only are they very different from the 
 parenU, and v-iy remarkable in form, but in no case do they 
 erow directly into the adult. The development U '''nfi'f' 
 th€ larva does not li«:ome the adult } the fwindttioM of the 
 
CHAP. XV 
 
 Backboneless Animals 
 
 237 
 
 Fic. 44. —A Holothurian (Cucumaria ertcfa) with iu young attached »o it't 5kin. 
 (From Ev«iiilhH 0/Stx ; after ChailtHger Narrative.) 
 
 wx 
 
 m 
 , I 
 
 ■A'i 
 
 } 4 s. 
 
 tf 
 
 l.ii'-'".liiMl 
 
2$6 
 
 The Study of Animal Life part m 
 
 adult are laid anew within the body of the larva, which is absorbed 
 or partly rejected. 
 
 Not only the starfishes but also the brittle -stars and the 
 Teather-stan often surrender their arms when captured, or even 
 when slightly irritated, and a part or a remnant can in favourable 
 conditions regrow the whole. The Holothurian Synapta breaks 
 readily into pieces, and others contract themselves so forcibly that 
 the internal organs are extruded. 
 
 The relations of Echinoderms t other animals are many. A 
 little fish, Fierasfer, goes in and out of Holothurians ; the de- 
 generate Myzostomata form galls on the arms of Crinoids ; star- 
 fishes are deadly enemies of oysters. On the other hand, some 
 sea-snails and fishes prey upon Echinoderms in spite of their 
 grittiness. Except that the unlud eggs of some sea-urchins are 
 edible, and that some sea-cucumbers are considered delicacies, the 
 Echinoderms hardly come into direct contact with human life. 
 
 5. Arthropods. — Lobsters, centipedes, insects, spiders, agree 
 with the Annelid " worms " in V ing built up of a series of rings 
 or segments. .Some or all of iUv.i segments bear limbs, and these 
 limbs are jointed, as the term Arthropod implies. The skin 
 forms an external sheath or cuticle of a stuff called chitin, an>l 
 this firm sheath helps us to understand how thfc limbs became 
 well-jointed. The chiti.i seems in some way antagonistic to tlic 
 occurrence of ciliated cells, for none seem to occur in this large 
 series unless it be in the strange type Peripatus. The chitin \\^> 
 also to do with the moulting or cuticle-casting which is common 
 in the series, for the cuticle is generally rigid and does not expand 
 as the body grows, hence it has to be cast and a new one made. 
 Finally, Arthropods have a nervous system Kke that of Annelids— 
 ft double dorsal brtiin connected by a ring round the gullet with a 
 double chain of ganglia along the ver.lral surface. But the life ol 
 most Arthropods is more highly pitched than that of Annelid>. 
 The sense-organs are more highly developed, brains are larger and 
 more complex, the ganglia of the ventral chain tend to become 
 concentrated ; there is division of labour among the appendages : 
 there are new internal organs s .ch as a heart ; the wliole bo<.!v 
 is better knit together. A crayfish may part with his claw and 
 grow another in its place, but the animal will not survive being cut 
 in two as some kinds of Annelids do. 
 
 The series includes at least five classes :— 
 
 Crustacea, almost all aquatic, and breathing by gills. 
 
 Protrachcata, represented by the genus Ptripaiui. 
 
 Myriapoda, centipedes and millipedes. 
 
 Insecta, more or less aerial 
 
 Aracbnida, Riders, scorpions, mites, etc. 
 
CHAP. XV 
 
 Backhoneless Animals 
 
 239 
 
 The members of the last four classes usually breathe by means 
 of air-tubes or tracheae, which penetrate into every part of the body, 
 or in the case of spiders and scorpions, by " lung-books," which 
 seem like concentrated and plnited trachere. The King-crab 
 (Limulus), which is very often ranked along witli Arachnids is 
 aquatic, and breathes by peculiar "gill-books." ' 
 
 (a) Omstacea.— Except the wood-lice, which live under bark 
 .ind stones, the land-CMl)s which visit the sea only at the breeding 
 
 Fig. 45.— Nauplius of Sacculina. (From Fritz Mailer.) 
 
 time, and some shore-forms which live in great part above the tide- 
 mark, the Crustaceans are aquatic animals, and usually breathe by 
 gills. Each segment of the body usually bears a pair of append- 
 ages and each aj.iwndage is typically double. Among these ap- 
 I'tndagcs much division of labour is often exhibited, some l)eing 
 sensoiy, others masticatory, others locomotor. In the higher forms 
 the hfe-hjstory is often long and circuitous, with a succession of 
 larval stages. 
 
 The lower Crustaceans arc grouped together as Enfnmostraca. 
 riiey are often small and simple in structure; the number of 
 
 ^y^^,'^ 
 
24© Tht Study of Animal Life part m 
 
 segments and appendages varies greatly. The little larva whidi 
 hatches from the egg is usually a " Nauplius "— an unsegmentc.l 
 creature with only three pairs of appendages and a median eye. 
 
 The brine -shrimps (A Hernia), the related genus Branchipus, 
 the old-fashioned freshwater Apus ; the common water-flea Daphui^ 
 and its relatives, like Lcptodora and Moina, are united in the okkt 
 of Phyllopods. 
 
 The small "water-fleas"' of which Cyptis is a very comii\on 
 representative, and which arc very abundant in sea and lake, foim 
 the order of Ostr.icods. 
 
 Another " water-flea" Cyclops and many more or less degeneiaie 
 " fish-lice " and other ectoparasites (e.g. Chondral ant hus, Cali^^u;., 
 Lernaa) are known as Copepods. The free-swimming forms often 
 occur in great swarms and are devoured by fishes. 
 
 The acorn -shells {Balanns) crusting the rocks, the barn.-iclcs 
 (Ijspas) pendent from floating "timl)er," and the degenerate ^a^vw//;/,; 
 under the tail of crabs, represent the order Cirrij^dia. 
 
 The higher Crustaceans are grouped together as Malacostracn. 
 The bo<ly usually consists of nineteen segments, five forming the 
 he.-id, eight the thorax, six the abdomen or tail. In most cases the 
 larva is hatchetl at a higher level of structure than the Naupliii- 
 represents, but the shrimp-like Peniais l)egins life as a Naupliu- 
 while the crab is hatched as a Zoea, the lobster in a yet liighes 
 form, and the craytish as a miniature adult. 
 
 Simplest of these higher Crustaceans, in some ways lil^i- :> 
 survivor of their hypothetical ancestors, is the marine genus .\V/,;.'/.j, 
 but we are more familiar with the Amphipmls (e.g. Gnnimaru \ 
 which jerk themselves along sideways or shelter under stones luitli 
 in fresh and salt water. The wood-louse Onisais has counieriui;-> 
 {Asellus, LioUa) on the shore, and several remarkable paraMiic 
 relatives. Among the highest forms are the long-tailed lob^te^^ 
 (/lomartis, ralinitnis), and crayfishes (As/aats), and slirimi» 
 (Crangon), and prawns {PaUcmon, randalus)\ the sofltailea 
 hermit crabs (Pagitrns) ; and the short tailed crabs (e.g. Cuiiu-y. 
 Carcinus, Diomia). 
 
 {h) Protracheata.— Z''''"'/'''"^- This remarkable genus. iei>rc- 
 
 FiG. 46.— Peripaiu*. (From C! ambers's Encychp. ; after Mo*«ley ) 
 
 sented by about a dozen widely-distributed species, seems to ! e n 
 survivor of the ancestral insects. Worm-like or caterpillar like sn 
 
CHAP. XV 
 
 BackboneUss Animals 
 
 24t 
 
 app^rance, with a soft and beautiful skin, with unjointed legs, with 
 the halves of the ventral nerve-cord far apart, and with many other 
 remarkable features, it has for us this special interest that it 
 jjossesses the air- tubes characteristic of insects and also little 
 kidney-tubes similar to those of Annelids. 
 
 (0 Msrriapoda.— Centipedes and Millipedes.— These animals 
 have very uniform bodies, there is little division of labour among the 
 numerous appendages. The head is distinct, and bears besides the 
 pair of antenncE (which Peripatus and Insects also have) two pairs 
 of jaws. The Centipedes are flattened, carnivorous, and poisonous ; 
 the Millipedes are cylindrical, vegetarian, and innocuous ; moreover, 
 they have two pairs of legs to most of their segments. 
 
 Fiu. 47.-\Vinsed male and wingless female of Pneumora. a kind of 
 grasshopper. (From Darwin.) 
 
 ('0 Insecta.— Insects are the birds of the backboneless series. 
 Like birds they are on an average active, most have the power of 
 Hiyht, many are gaily coloured, sense-organs and brains are often 
 highly developed. 
 
 Contrasted with Peripatus and Myriapods, 'hey have a more 
 compact Ixxly, with fewer but more efficient lirSs. They are 
 Arthropods, which are usually winged in adult life, breathe air 
 'y means of tracheoe, and have frequently a metamorphosis in their 
 ijfe-history. To this definition must be added the anatomical facts 
 "at the adult body is divided into three regions, (i) a head with 
 tliree pairs of mouth -appendage* { = leg8) and a pair of sensitive 
 < '"'growths (antennae or feelers) in front of the mouth, (2) a thorax 
 with three pairs of walking legs, and usually two pairs of wings, 
 and (3) an abdomen without appendages, unless occasional stings, 
 cgg-laying organs, etc., be remnants of these. 
 
 *"ffl 
 
 
 ■ t a 
 
 
 itHll 
 
 
 -Tf« 
 
 
 ' - 1 
 
 
 • Hi 
 
 
243 TJie Study of Animal Life part in 
 
 The wings "are very characteristic. "They are flattened sacs of 
 skin, into which air-tubes, blood-spaces, and nerves extend. It is 
 possible that they had originally a respiratory, rather than a 
 locomotor function, and that increased activity induced by bettered 
 respiration made them into flying wings. 
 
 The breathing is effected by means of the numerous air-tubes 
 or tracheae which open externally on the sides and send branches 
 to every corner of the body. As the air is thus taken to all 
 the tissues, the blood-vascular system has little definiteness, though 
 there is (as in other Arthropods) a dorsal contractile heart. The 
 larvae of some insects, e.g. dragonflies, mayflies, etc., live in 
 the water, and the tracheae cannot open to the exterior (else the 
 creature would drown), but they are sometimes spread out on 
 wing-like flaps of skin (" tracheal plls "), or arranged around the 
 terminal portion of the food-canal in which currents of water are 
 kept up. 
 
 The student should learn something about the different mouth- 
 organs of insects and the kinds of food which they eat ; about the 
 various modes of locomotion, for insects " walk, run, and jump with 
 the quadrupeds, fly with the birds, glide with the serpents, and 
 swim with the fish ;" about the bright colours of many, and the 
 development of their senses. 
 
 In the simplest insects — the old-fashioned wingless Thysanura 
 and Collembola — the young creature which escapes from the egg 
 shell is a miniature adult. There is no metamorphosis. So with 
 cockroaches and locusts, lice and bugs ; except that the young are 
 small, have undeveloped reproductive organs, and have no wings, 
 they are like the parents, and all the more when the parents (e.g. 
 lice) also are wingless. 
 
 In cicadas there is a slight but instructive difference betwctn 
 larvae and adults. The full-grown insects live among herbage, the 
 young live in the ground, and the anterior legs of the larvre ue 
 adapted for burrowing. Moreover, the larral life ends in a sleep 
 from which an adult awakes. But much mure marked is the differ- 
 ence between the aquatic larvae of mayflies and dragonflies and the 
 aerial adults, in which we have an instance of mere thorough though 
 still incomplete metamorphosis. 
 
 Different, however, is the life of all higher insects — butterflies 
 and beetles, flies and bees. From the egg-shell there emerges a 
 larva (maggot, grub, or caterpillar), which often lives an active 
 voracious life, growing much, and moulting often. Rich in stores 
 of fatty food, it falls ini- a longer quiescence than that associated 
 with previous moults and becomes a pupa, nymph, or chrysalis. 
 In this stage, often within the shelter of a silken cocoon, great 
 transformations occur ; the body is undont and rebuilt, wings bud 
 
4XAr. XV 
 
 Sackboneiess Antmats 
 
 *43 
 
 out, the appendages of the adult are formed, and out of the pupal 
 husk there emerges an imago, an insect fully formed. 
 
 (/) Aradmida.— Spiders, Scorpions, Mites, etc.— This ctss is 
 unmtisfactorily large and heterc^eneous. In many the body is 
 divided into two regions, the head and breast (cephalothorax), with 
 two pairs of mouth parts and four pairs of walking legs, the 
 abdomen with no appendages. Respiration may be effected by 
 the skin in some mites, by tracheae in other mites, by trarhete plus 
 "lung-books" in many spiders, by "lung-books" alone in other 
 spiders, by "gill-books" in the divergent king-crab. 
 
 The scorpions with a poisoning weapon at the tip of the tail, 
 the little book-scorpions {Cktlifer), the long-legged harvest-men 
 (e.g. Phalangium)', the spiders proper— spinners, nest -makers, 
 hunters; the mites; the strange parasite {Pentastomum) in the 
 dog's nose ; the quaint king-crab (Z»/w«/«x)— last of a lost race, 
 with which the ancient Trilobites and Eurypterids were connected ; 
 all these are usually ranked as Arachnids ! 
 
 6. Molluscs. — It seems strange that animals, the majority of 
 which are provided with hard shells of lime, should be called 
 mollusca ; for that term first used by Linnaeus is a Latinised version 
 of the Greek malakia^ which means soft. Aristotle applied it 
 originally to the cuttlefish, which are practically without shells, so 
 that iU first use was natural enough, but the subsequent history of 
 the word has been strange. 
 
 Cockle, mussel, clam, and oyster; snail and slug, whelk and lim- 
 pet ; octopus, squid, and pearly nautilus ; what common character- 
 istics have they? Most of them have a bias towards slu^hness, 
 and on the shields of lime which most of them bear, do we not read 
 the legend, «« castles of indolence " ? But this sluggishness is only 
 an average character, and the shell often thins away. The scallop 
 (Pecten) and the swimming Lima are active compared with the 
 oyster, and they have thinner shells ; the snails which creep slowly 
 between tides or on the floor of the sea are heavily weighted, while 
 the sea-butterflies (Pteropods) have light shells, and most cuttlefish 
 nave none at all. 
 
 The shell is very distinctive, but we are not able to state 
 definitely how it is formed or what it means. In most of the 
 embryo molluscs which have been studied there is a little pit or 
 "shell-gland" in which a shell begins to be formed, but the shell 
 of the adult is in all cases made by a single or double fold of skin 
 known as the " mantle." In some cases where the shell seems to 
 be absent, e.g. in some slugs, a degenerate remnant is still to be found 
 beneath the skin, while in other cases (e.g. most cuttlefish) its 
 absence it to be explained as a loss, since related ancestral species 
 possess it. There are, how«yer, two or three primitive forms 
 
,44 The Study of Animal Life part hi 
 
 sutetance called ""*»''" •■*r^,toe, Sile'.he innc,n,», 
 S.raTe"i:::S /n'V^.eSwfiK;? ... .he. „e ™„, 
 
 uUi;i 
 
 F.G. 48.-The common octopus (From ChamWs Encyclop. ; nfter I'.rc 
 
 Cuestions about shells whicl. we --^ jnsv^ Where .Ws^|hc 
 
 carbonate of lime come f^o".. since tha sal ^. 
 
 abundant in the water m which '"-^^J^^^^^^j/ ^^ ;, sca-ua.cr 
 
 the power of changing the =^h""^'^"^. ^"'P'^^^^^^^^^ 
 
 into'carbonate of lime. V^^^^^l^^^;"^::'^:,^^^ ^^ cons.itu- 
 
 excreted from the skm ? Is the "j" ^^//^^^ °„ ,he whole to k 
 
 tional sluggishness of the animal nee u eems on ^_^^_^^^, 
 
 most massive in the most ^ "88'^'^' '^!\* ^^ '" ' ', J open sea, in the 
 Most molluscs are marine on the ^ho e ^ t'le op ^^^^ 
 
 great depths; there are also manyj^^^^^^^^^^ 
 mussels ^noa'on and Lnt>}, ana .1- -"'!"» - 
 
CHAP. XT 
 
 Backhoneless Animals 
 
 a45 
 
 and Paludina ; the terrestrial snails and slugs are legion. Among 
 those of the shore the naked Nudibranchs are often in colour and 
 form protectively adapted to their surroundings ; those of the open 
 sea , .leteropods, Pteropods, and many cuttlefish) are active and 
 carnivorous, with light shells or none ; in the dark depths many 
 are blind or in other ways rudimentary, but food seems to be so 
 abundant that there is almost no need to struggle for it. 
 
 As to diet, there are three kinds of eaters — carnivores, such as 
 the active swimmers we have mentioned besides the whelks and 
 many other burglars who bore through their neighbours' shells, and 
 the Testacella slugs ; vegetarians, like the periwinkle, the snail, and 
 most slugs; and thirdly, almost all the bivalves, which feed on 
 microscopic plants and animals, and on organic debris wafted to 
 the mouth by the lashing of the cilia on the gills and lips. In this 
 connection it is important to not.ce that all molluscs except bivalves 
 have in their mouths a rasping r.bbon or toothed tongue {radulu, 
 odontophore) by which they grate, file, or bore with marked effect. 
 Of parasites there are few, but one Gasteropod, Entoconcha 
 mirabilis, which lives inside the Ilolothurian Synapta, is very 
 remarkable in its degeneration. It starts in life as a. vigorous 
 embryo like that of most marine snails, it becomes a mere sac of 
 reproductive oi^ns and elements. 
 
 In structure, molluscs differ remarkably from the arthropods 
 and higher "worms" in the absence of segments and serial 
 appendages. They are not divided into rings, and they have no 
 legs. 
 
 To begin with, they were doubtless (bilaterally) symmetrical 
 animals, and this symmetry is retained in primitive forms like the 
 eight-shelled Chiton and in the bivalves. But most of the snails 
 are twisted and lop-sided, they cannot be symmetrically halved. 
 For this asymmetry the strange dorsal hump formed by the viscera, 
 and the tendency that the single shell would have to fall to one side, 
 are sometimes blamed. That this lop-sidedness is not necessarily 
 a defect, but rather the reverse, is evident from the success not 
 only of the snail tribe but of many other asymmetrical animals. 
 
 The skin has a remarkable fold (double in the bivalves) known 
 as the " mantle," the importance of which in making the shell we 
 have already recognised. Another very characteristic structure is 
 the so-called "foot," a muscular protrusion of the ventral surface, 
 an organ used in creeping and swimming, leaping and boring, but 
 almost absent in the sedentary oysters. 
 
 We rank the molluscs high among backhoneless animals, partly 
 l)ecause of the nervous system, which here as elsewhere is a 
 dominating characteristic. There are fewer nerve centres than in 
 most .'\rthropod3 or in higher " worms," but this is m most casca 
 
 {■=. f 
 
 ■I I 
 
,46 Tht Study of Animal Life vakj iu 
 
 the sides and visara, a ^""°y««« ' ^ , . j^ ^ ^ important 
 
 foot, -jj^'^*" j^jf;^2:SpTS^^^^^ cA'^o'^^^ ^^^ 
 
 are vuceral. In the «o'»«*™*»?7" most readily harmonised with 
 thai of other InvMt™»i», m^j,,, ,i,e thrM «re con. 
 
 first »}"*"** .f°~Z.» It is a barrel -shaped or pear-hke 
 :X-r.'ri.ro?5^»l"dU.infrontofthe.outh....U 
 
 '" M." "whutffcSe" to>o . mo,, ch^acterbtic fom <aUe<l 
 
 '° '^T^ ofc uSfoh dift. r™,n those of othe, -l^ '" S 
 ine egg!»" f prolonged period as capita 
 
 J^h^^ fS, »^«.s *. in.»»«.y of F. "'- '4- 
 
 tSW "te •l>»n'i>"' f-O"" "« S""''° °°T^5 „, L» Tver Mh! 
 go,? on tacreMing, and are now "^ore ,.b«nd.mt thj" »«' • * 
 
 =hiv.l«s cannot be said «»o,''»^t ^^^mIJ^ f Cep^'oV>. 
 SrlSh t^ercltds oTf^iSl on,; he pea^ Na..J-s 
 :lw sunrives. and though there are ">->' ''"'f ^^.^.tfj^'.^^ 
 fish in on- -^;" - ^ 'rrdloTStSrw'e shcld 
 i:™iin'5.c.y?h/.bXb;Lh|ng snait. and the fresh.,..- 
 blval»es were ^c«hat late In appearing. ^^.^ 
 Prof. Ray lankester has reconstracted ".'^™ " »°.f.<^inr, 
 combiiK> the wrioos moUtucan cbaraccensliB .n a « ' 
 
CHAP. XV 
 
 Backbonehss Animals 
 
 847 
 
 lightning," 
 
 u IV :.nv others, 
 
 dP,: 
 
 fashion, and may lie something like the original mollusc. Whence 
 that original sprang is uncertain, but the common occurrence of the 
 trochosphere larva and some of the characters of the primitive 
 Gasteropods {Neovienia^ C/uefod'-rnia, Chiton) suggest the origin 
 of molluscs from son.j " worm " type or other. We can be sure ol 
 this, however, that i iC series must have divid-^d at a very early 
 epoch into two sets, the sluggish, sedentary, headless bivalves on 
 the one hand, and the more active and aggressive snails and cuttle- 
 fish on the other. 
 
 Relation to Man. — Irresbtibly we think first of oysters, which 
 Huxley describes as "gustatory flashes of su 
 and over which neolithic man smacked his I'ps 
 cuttlefish, ear -shells (Haiiotis), mussels (A ,'//?' 
 winkles (Littorina httorea), cockles ( Cardium <ji J-it.i 
 used as food, and many more as bait. In iiroic 
 now, the shells of many were used for ■ r v >. 
 lamps, vessels, coins, etc. ; the inner law r ■! 
 mother-of pea.l ; concretions around i tntiiu, <.; 
 pearls in the pearl-oyster (/!/ar^an/(7«<j cl ii 
 TjTian purple was a secretion of the . h.ik v, 
 related Murex ; and the attaching byssus thi. ad., o; • ' e (,iv;.V»e 
 Pinna may be woven like silk. 
 
 On the other hand, a few cuttlefish are \..^g" nca;..!: to )e 
 somewhat langerous ; the bivalve Teredo boring iu.^ ^jiii^-'uottoms 
 £td p'ers is a formidable pest, baulked, however, by the pre- 
 valent use of metal sheathing ; the snails and blugs are even more 
 voradou* than the birds which decimate them. 
 
 Conchology was for a while a craze, rare shells have changed 
 hands at the cost of hundreds of pounds, such is the human " mania 
 of owning things." But the shells are often fascinating in their 
 beauty, a^-l poetic fancy has played lovingly with such as the 
 Nautilus. 
 
 rr; 
 
 '■■ ■■er 
 
 . Whf: 
 
 :1 the 
 
 if 
 If 
 
 li 
 
 
 'm 
 
CHAPTER XVI 
 
 BACKBONED ANIMALS 
 
 I. Balanegtosius—2. Tunuates—y The Lanceld—i,. Koinu- 
 Mouths or Cyclostomata — S- Fishes — b. AMiphibuws ~ 
 7. Reptiles— i. Birds— 9. Mammals 
 
 A'x:oRDiNG to Aristotle, fishes and all higher animals were •« blood 
 containing," and thus distinguished from the lower anmials, which 
 he regarded as • ' bloodless." He was mistaken as to the abseiKc uf 
 blood in lower animals, for in most it U present, but the line which 
 he drew between higher and lower animals has been recognisc.l m 
 all subsequent classifications. Fishes, amphibians, reptiles. bird>. 
 and mammals differ markedly from molluscs, insects, crustaceans. 
 "worms," and yet simpler animals. The former are backbuiicd 
 (Vertebrate), the latter backboneless (Invertebrate). 
 
 It is necessary to make the contrast more precise. («) ^'^"'y 
 Invertebrates have a well-developed nerve-cord, but this lies on tin 
 ventral surface of the body, and is connected anteriorly, by a >>"t; 
 round the gullet, with a dorsal brain in the head. In \ trti- 
 bralss the whole of the central nervous system lies along the dur^al 
 
 
 -^ 
 
 Fir, 4o.-DiMr»m of " Ideal Vertebrate " ihowing the Mgment* of the 1k.,Iv 
 the spinal cordTthe nolochord, the gill-ciefU, the ventral heart. (After H..«cUI.) 
 
 surface of the body, forming the brain and spinal cord. Tlu -. 
 arise by the infolding of a skin groove on the dorsad surfiue .f tlu 
 embryo, {p) Underneath the nerve-cord in the Vertebrate ciidr)- 
 
ft 
 
 CHAP. XVI 
 
 Backboned Animals 
 
 249 
 
 is a supporting rod or uij:t>. .< ul. It arses along the roof of the 
 Axxl-canal, and serves as ^ supporting axis to the Ixxly. It i>er- 
 sists in some of the lowest Vertebrates (f.^'. thelancelet) ; it i>ersists 
 in part in some fishes ; but in most Verte!)rates it is replaced by a 
 new growth — the backlxinc — wliich ensheaths and constricts it. 
 (c) From the anterior region of the food-canal in fishes and tadpoles 
 Klits, bordered by gills, open to the exterior. Through the slits 
 water flows, washing the outsidcs of blood -ves.' -Is antl aerating the 
 blood. These slits or clefts are represented ai the young of all 
 Vertebrate animals, but in reptiles, birds, and mammals they are 
 transitory and never used. Amphibians arc 'he highest animals in 
 which they are used for breathing, and even then they may be 
 entirely replaced by lungs in adult life. They are evident in tad- 
 ))oles, they have disappeared in frogs. (./) Many an Invertebrate 
 has a well-develojied heart, but this always lies on the dorsal 
 surface of the lx)dy, while that of fish or inv^, bird or man, lies 
 ventrally. (<•) It is characteristic of the eye of 1 ickboned animals 
 that the greater i>art of it arises as an outgrowt!. from the brain, 
 while that of b.acklKjneless animals is directly derived from the skin, 
 liut this fMffcrence is less striking when we rememlxr that it is fn)iu 
 an infolding of skin that the brain of a b.-ickboned animal arises. 
 
 Hut while the rliaractcristics of backlxjned animals can now \vi 
 staled with a precision greater than tliat of sixty yea s igo, it is no 
 longer possil>le to draw with a firm hand the dividing line Ulween 
 b.icklKmed and backboneless. Thus fishes are not the simplest 
 \'ertebrates ; the lamprey aixl tlie glutinous hag belong to a more 
 primitive type, and are called fishes only by courte^y ; simpler stiil 
 is the lancelet ; the Tunicates hesitate on the border line, K'ing 
 tadpoledike in their youth, but mostly degenerate when adults ; 
 and the w irm-like Halano^^lo'^sia is perhaps to be ranked as an 
 incipient Vertebrate. The extension of knowledge and the appli- 
 cation of evolutionary conceptions obliterate tiie ancient landmarks 
 of vinrc rigid but K-ss natural classification. 
 
 1. BAlftnOCloSSttS. — lialino:;li).uMis is a worm - like animal, 
 npresented by some half-dozen species, which ea. their way 
 
 Y\yi. 50. — B.ili«not!liJ'«»«s> 4i"wiiiK probDHcl-., collar, ami gill-slitt. 
 
 tlirnugh sandy imi<l olT the coasts of the (.'hannel Islands, Krittany, 
 ChcsajH-ake ll-.y, and o'.hcr regions, lis In^ly i> ciliated and divided 
 into distinct regions- a large •' piolioscis "' in front of the mouth, a 
 
 ^iMx^ 
 
 s t 
 
 ■%v 
 
 
»5Q The Study of Animal Life part m 
 
 firm collar behind the nouth, a part with numerous gill-slits behind 
 the collar, and finally a soft coiled portion with the intestme and 
 reproductive organs. The size varies from alwut an mch to 6 
 inches, the colours are bright, the odour is peculiar ; the sexes art- 
 separate. But Bcdanoglossus is most remarkable m havmg a dorsal 
 supporting rod (like a notochord) in the "proboscis" regon, a 
 dorsal nerve-cord running along the back and especially devclopc.l 
 in the collar, and a series of giU-clefls on the anterior part of ti.e 
 food-canal. It is therefore difficult to exclude Balamglosms fr.Mu 
 
 Fig ,,.--Cephal«!i«cus a single individual, isolated from a colony, li i~ mi 1> 
 m.i({nifiea. KV^om Chanibcrsr. tncydo/'-, after cArt//.«i'.' Kci-i > 
 M'liilosh and Karmer.) 
 
 the Vertebrate series, and it i> likely that the same :mi-i be vii.l 
 of another strange animal, Cfhahhiiuiis, discovered by liic <'■■■>'■ 
 
 Unger explorers. 
 
 2. Tunicates. Hanging; to the jicnnon like stawtoN >^ii. t- 
 fringe the rocky shore and arc rarely uncovercl Uy Uie ndi-. liij^i 
 sea-sciuirls sometimes lixe. They are shaped like dnul.k-muu'.lK.; 
 wine l«gs 2 or 3 inches in length, antl water »-. aUva>> \ i.i; 
 drawn in at one a|M:rlure and exiK-lkd at the other. I >.uaii} !.a) 
 live in dusters, and their life is very i^ssive. We call liuiu -•... 
 Mjuirts localise water may si>out forth when wc squee/r i..v,i 
 
CHAF. xn 
 
 Backboned Animals 
 
 251 
 
 bodies, while the tnle Tunicate refers to a characteristic cloak ot 
 tunic which envelops the whole animal. 
 
 There is not much to suggest backbonedness about these Tuni- 
 cates, and till 1866 no one dreamt that they could Ik: included in 
 the Vertebrate series. But then the Russian naturalist Kowalevsky 
 discovered their life-history. The young forms are free-swimming 
 creatures like miniature tad]X)les, with a dorsal nerve-cord, a sup- 
 porting rod in the tail region, gill-slits opening from the food canal, 
 a little eye arising as an outgrowth of the brain, and a ventral 
 heart. 
 
 The.e are only two or three genera of Tunicates, especially one 
 called Apftndicularia, in which these Vertebrate characteristics are 
 retained throughout life. The others lose them more or less com- 
 pletely. The young Tunicates are active, perhaps too active, for a 
 short time ; then they settle down as if fatigued, fix themselves by 
 their heads, absorb their tails, and become deformed. The nervous 
 system is reduced to a single ganglion between the two apertures ; 
 the original gill-slits are replaced by a great number of a different 
 character ; the eye is lost. From the skin of the degenerate animal 
 the external tunic is exuded. It is a cutide, and consists, in part 
 at least, of cellulose, the sul»tance which forms the cell-walls of 
 plants. Thus this characteristically vegetable substance occurs 
 almost uniquely in the most passive part of a very passive animal. 
 The sea-squirt's metamorphosis, is one of the most signal instances 
 of degeneration ; the larva has a higher structure than the adult ; 
 the young Tunicate is a Vertebrate, the adult is a nondescript We 
 cannot tell how this fate has befallen the majority, nor why a few 
 are free-swimmers, nor why Apprndicularia retains throughout life 
 the Vertebrate characteristics of its youth. Do the majority over- 
 exert themselves when they are " tadpoles," or arc they constitu- 
 tionally doomed to become sedentary ? 
 
 'i unicates are hermaphrodite — a very rare condition among Ver- 
 tebrates ; some of them exhibit " alternation of generations," as the 
 [Kiet Chamisso first observed ; asexual multiplication by budding is 
 very common, and not only clusters but more or less intimate 
 colonies are thus formed. 
 
 Tunicates live in all seas, niostly near the coast from low water 
 to 20 fathoms, and usually fixed to stones and rocks, shells and sea- 
 weed. A few are free-swimming, such as the fire-flame {Pyivsoma)^ 
 a unified colony of tubular (orm, sometimes 2 or 3 feet in letigth, 
 and brilliantly phasphorcsccnt. Very beauiiPd are the swimming 
 thains of the genus Salpa, whose sti icture and life-history alike are 
 complicated. 
 
 Tunicates feed on the animalcules bt>me in by the wntet 
 currents, and some of them must feed well, so rapidly do they grow 
 
 li I 
 
 I: 
 
 
 II 
 
 f ' If 
 
 
as* The Study of Animal Life pa»t hi 
 
 and multiply. Unpleasant to taste, they are left in peace, though 
 a crab sometimes cuts a tunic off as a cloak for himself. 
 
 3 The LaiICel«t.-The lancelct {AmphioxusS is a simple 
 Vertebrate, far below the structural rank of fishes. It is only 
 about 2 inches in length, and, as both English and Greek names 
 suggest, it is pointed at both ends. On the sandy coasis of warm 
 and temperate seas it is widely distril>utcd. 
 
 From tip to tail of the translucent body runs a supporting noto- 
 chord ; above this U a spinal cord, with hardly a hint of brain. 
 The pl.a.7nx bears a hundred or so gill-shts, which m the aduh 
 are covered over by folds of skin, so that the water which enters 
 by the mouth finds its way out by a single postenor aperture. 
 Although Amphioxus has no skull, nor jaws, nor bram, nor linibs, 
 it deserves its position near the base of the Vertebrate series. The 
 sexes are separate, and the eggs are fertilised outside of the body. 
 The development of the embryo has been very carefully studie.l. 
 and is for a time very like that of Tunicates. 
 
 4. Eound-MotttllB or OyclOlt01liato.-The hag -fishes and 
 the lampreys and a few allied genera must be excluded from the 
 class of fishes. They are survivors of a more pnimtive race. 
 They are lawless, limbless, scaleless, and therefore not fishes. 
 
 The lampreys (Petromyzon) live in rivers and estuaries, and also 
 
 in the wider sea. They are eel-like, slimy animals. The skeleton 
 
 is gristly ; the simple brain is imperfectly roofed ; the single nostril 
 
 docs not open into the mouth ; the rounded mouth has homy teeth 
 
 on the lips and on the piston-like tongue ; there are seven pairs of 
 
 giU-pouches which open directly to the exterior and internally into 
 
 a tube lying beneath and communicating with the adult gullet : the 
 
 young are blind and otherwise different from the parents, and mny 
 
 remain so for two or three years. ,„ ,i , i 
 
 Though lampreys eat worms and other small fry, and even cieaa 
 
 animals/they fix themselves aggressively to fishes, ra.sping holes 
 
 in the skin, and sucking the flesh and juices. They aUo chng .o 
 
 stones, as the name Petromyion suggests. 
 
 Some si>ecics drag stones into a kind ot nest. They sp-awn i.i 
 spring, usually far up rivers, for at least some of the marine 
 lamprey, leave the sea at the time of breeding. The young are in 
 many ways different from the parents, and that of the small riv.r 
 lampem [Petromyion branchialU) used to be regarded as a distinct 
 ^visL\~Ammo^<,ta. The metamorphosis was discovered t«o 
 hundred years ago by Baklner. a Slrasburg fisherman, but vy 
 overlooked till the strange story was worked out in ihjO i)^ 
 August Muller. Country boys often call the young nine eyes, 
 miscounting the gill apertures, and the Germans alio speak oJ 
 munaugtn. 
 
CHAP. XVI 
 
 Backboned Animals 
 
 «53 
 
 The sea lamprey (/'. marinus) may measure three feet ; the 
 river lamprey (P. Jluviatilis) about two feet ; the small lampern or 
 stone-grig (P. brttHchialis or planeri) about a foot The flesh is 
 well known to be palatable. 
 
 The glutinous hag (Myxine gltUinosa) is an eel- like animal, 
 about a foot in length, of a livid flesh colour. It is common at 
 considerable depths (40 to 300 fathoms) oflf the coasts of Britain 
 and Norway, and, when not feeding, lie- buried in the mud witli 
 only its nostril protruded. Like the lamprey, it has a smooth 
 slimy skin, a gristly skeleton, a round suctorial mouth with teeth. 
 The single nostril communicates with the food-canal at the back 
 of the mouth, and serves for the inflowing of water ; the six gill- 
 pockets on each side open directly into the gullet, but each has an 
 excurrent tube, and the six tubes of each side open at a common 
 aperture. The animal lives away from the light, and its eyes are 
 rudimentary, hidden beneath skin and muscles. The skin exudes 
 so much slime that the ancients spoke of the hag " turning water 
 into glue." 
 
 In several ways the hag is strange. Thus J. T. Cunningham 
 discovered that it is hermaphrodite, first producing male elements, 
 and afterwards eggs, and Nansen hao corroborated this. The eggs 
 are large and oval, each enclosed in a •'horny" shell with knotted 
 threads at each end, by which a number are entangled together. 
 How they develop is unknown. The hags devour the bait and 
 even the fish from the fisherman's lines, and some say that they bore 
 their way into living flshes such as cod. 
 
 5. Fi(lh<>ff — Fishes .ire in the water as birds in the air, — swift, 
 buoyant, and graceful. They are the first backboned animals with 
 jaws, while scales, paired fins, and gills are their most character- 
 istic structures. The scales may lie hard or soft, scattered or 
 closely fitting, and are often very beautiful in foim and colour. 
 The paired fins are limbs, as yet wi :iout digits, varying much in 
 sire and position, and helping the fish to direct its course. The 
 gills are outgrowths of skin with a plaited surface, on which the 
 branching blood-vessels are washed by the water. They are the 
 breathing organs of all fishes, but in the double-breathing mud- 
 fishes {Dipnoi) the swim-bladder has come to serve as a lung, and 
 there are hints of this in a few others. 
 
 There are at least four orders of fishes : — 
 (l) The cartilaginous fishes (Elasmobranchs or Selachians) are for 
 the most part quite gristly, except in teeth antl scales. Among 
 them are the flattened skates and rays with enormous fore-fins, 
 while the sharks and dogfish are shaped like most other fishes. 
 Their pedigree goes back as far as the Silurian rocks, in which 
 remains of shark-like forms are found. A J apancse shark {Ckia- 
 
 'ik I 
 
 •SI f f 
 
254 The Study of Animal Life part iii 
 
 mydoselachm) is said to be very closely allied ^^/yP" J^J^Jj^X 
 in the Old Red Sandstone. Allied to the Elasmobranchs, but 
 ^metimes kept in a separate division, are two genera, the Cktmam 
 Tr Kt^-S-the-Herrin^ and Callorhynchus, iu relative in Southern 
 
 ^^''Si The Ganoid fishes are almost, if not quite, as ancient as the 
 Elasmobranchs, but their goldenage, long since past, ^^ »" D^^" 
 and Carboniferous ages. There are only some fJ^PJ^' J^^^J'^^J^ 
 now alive. Two of these are the sturgeons (^«A««r) and he 
 W pike (Lepidoslois). The latter has a bony skeleton ; the 
 Z^n is inVrt gristly. An armature of hard scales .s very 
 characteristic of this decadent order. ... ,11 
 
 S In Permian times, when Reptiles were begmn.ng, a thud 
 type of fish appeared, of which the Queensland mud-fish (Ceratodus) 
 leem to be Tdirect descendant. In this type the air-bladder ,s 
 used as a lung, thus suggesting the transition from Fishes to Am- 
 phlbiS^ PC haps thii order was always small m numbers ; now- 
 adlvsT^ least there are only two genera- ara/..//«, from the 
 S wate .f Queensland, and Protopterus, from west and trop.cal 
 AfrTcaTv le another form, sometimes called a d.fferen genus 
 is recorded from the Amazons. Double-breathers c.r 
 all them, for they do not depend wholly upon g>i>s. >^"l 
 ^ surface and gulp air into their air-bladder. Mud- 
 rt well named, for as the waters dry up they retire into 
 ming for themselves a sort of nest, within which they 
 
 {Ltpidosit 
 Dipnoi V 
 comr 
 fishes 
 
 the n Jii, 
 lie d' rma 
 
 ( I. 
 "^ -OStt 
 
 1 salm 
 est fi 
 >oats. 
 
 he Chalk period the characteristically modern fishes 
 
 will ompletely bony skeletons, begun. Ilcinni; 
 
 cod a' 1 pike, eel and minnow, and most of the com- 
 
 , belo to this order. Heavy ironclads yield to swilt 
 
 ai d 'I. le Teleosteans have succeeded better limn tin 
 
 T^rt ,vle lorm of most fishes is well adapted (or ra,.! 
 swimming! I^ ' flat fish, whether flattened from above down 
 wards like the .nslly bkale, or from side to side like the flounckp 
 Td plaice, live at the bottom; those of eel -like shape usua ly 
 "aloWlhe sand or mud; the quaint f^^ ^f.^^^^ 
 The chief organ of locomotion is the tad ; the P»'^«^^ "'^^^^ 
 raise or depress the fish, and serve as guiding oars. In he chml. 
 ing perch they are used in scrambling ; .n the flymg hsh tl .7 . 
 sometimes moved during the long swooping leaps. In ceK an 1 
 SsT they are absent; in the Dipnoi they have a re.narka hie 
 InSian axil' The unpaired fins on the back «.d Uil and un.cr 
 surface are fringes of skin 8upi»orted by rays. 
 
 Fishes are often rLsplendent in colours, which are partly ciue w 
 
CHAP. XVI 
 
 Backboned Animals 
 
 255 
 
 pigments, partly to silvery waste-products in the cells of the outer 
 skin, and partly to the physical structure of the scales. Some- 
 times the males are much brighter than the females, and grow 
 brilliant at the breeding season. In some cases the colours har- 
 monise with surrounding hues of sand and gravel, coral and sea- 
 weed ; while the plaice and some others have the jxjwer of rapidly 
 changing their tints. 
 
 Fishes feed on all sorts of things. Some are carnivorous, others 
 
 Vm. 32. —The gemmeoiis clr.ij.inet {Cnl/ioHviuus iyrtt), the male alwvc, 
 the fcmule beneath. (!• roiii Darwiu.) 
 
 \et;ctaiian, others swallow the mud. By niost of them worms, 
 « lustaceans, inscct-larv.v, jiiolluscs, and smallci fishes are greedily 
 tntcn. Stran-je are some of large appeti'e (<-.,(,■•. Chiasmodon niger\ 
 wlio manage to get outside tishes larger than their own normal 
 
 M/L- : 
 
 Of their mental life little is known. Vet the running of tiout, 
 the carefulness witli wliich llu- mother s.thnon selects a .spavvninj;- 
 ^'i-ntntl, the way the archer-fish {Toxotes) spits ujwn insects, the 
 lust. making and courtship of the stickleback and others, the img- 
 nacity of many, show that the brain of the fish is by no means asleep. 
 
 II 
 
 11 
 
«S6 
 
 Th€ Study of Animal Lifi pa»t in 
 
 The males are often different from the females— smaller, brighter, 
 and less numerous. In some cases they court their mates, and 
 fight with their rivals. Most of the females lay eggs, but a few 
 bony fishes and many sharks bring forth living young. In two 
 sharks there is a prophecy of that connection between mother and 
 offspring which is characteristic of mammals. The fishs egg is 
 usually a small thing, but those of Elasmobranchs are large, being 
 rich in yolk and often surrounded by a mermaid's purse. This 
 egg-case has long tendril-like prolongations at the comers, these 
 twine automatically around seaweed, and the embryos may be 
 rocked by the waves until the time of hatching. When the egg is 
 enclosed in a sheath, or when the young are hatched within the 
 body of the mother, fertilisation must take place internally, but in 
 most cases the male accompanies the female as she spawns, and 
 with his milt fertilises the eggs in the water or on the gravelly 
 spawning-ground. As love for offspring varies inversely with their 
 number, there is little parental care among the prohfic fishes. 
 
 Most fishes live either wholly in 4he sea or wholly in fresh 
 water, but some are indifferent, ard pass, at spawning time espe- 
 cially, from one to the other. A few, such as the climbing 
 perch, venture ashore, while the mud -fishes and » fc* ot\^" 
 can survive drought for a season. In caves several blind fishes 
 live, and species of Fierasfer find more or less habitual lodging 
 inside sea-cucumbers and some other animals. 
 
 The fishes which live in deep water are interesting m many 
 ways. Gunther has shown that from 80 to 200 fathoms the eyes 
 are rather larger than usual, as if to make the most of the dim 
 light. Beyond 200 fathoms ' ' small-eyed fishes as well as large-eyed 
 occur, the former having their want of vision compensated for l,y 
 tentacular orrans of touch, whilst the latter have no such accessory 
 organs," an-i can see only by the fitful light of phosphorescence. 
 "In the greatest depths blind fishes occur, with rudimentary eyes, 
 and without special organs of touch." The phosphorescence is pro- 
 duced by numerous marine animals and by the fishes themselves. 
 
 6 Amphibians —The Amphibians which now live are neither 
 numerous nor large, (iiant Amphibiai.s or Labyrinthodonts bepin 
 to appear in the Carboniferous period, but most of the modern 
 frogs and toads, newts and sjilamanders, are relatively pigmies. 
 
 Young Amphibians always breathe by gills, as Fishes do, and m 
 some cafes these gills persist in adult life. But whether they no 
 or not, the full-grown Amphibians have lungs and use them, i de 
 skin is characteristically soft, naked, and clammy. Amphibians 
 are the first Vertebrates with hands and feet, with fingers and tocs. 
 Unpaired fringes are sometimes present on the back and tail .as in 
 Fishes, but are never supported by f vrays. 
 
CHAP. XVI 
 
 Backboned Animals 
 
 as? 
 
 I 
 
 The class includes four orders, of which the Lab]rrinthodonts 
 are wholly extinct, the other three being represented by tail-less 
 frogs and toads (Anura), by newts and salamanders (Urodela) with 
 distinct tails, and by a few of worm-like form and burrowing 
 habit, e.g. Cacilia. Some, the last for example, are tensstriaJ, but 
 usually live in damp places ; most pass their youth at least in fresh 
 water ; none can endure saltness, and they are therefore absent from 
 almost all oceanic islands. The common British newts {Triton and 
 LissoiriUm), and the often brightly-coloured salamanders (Saia- 
 niandra) have in adult life no trace of gills ; the rice-eel {Amphiuma) 
 and the genus Menopoma lose their gills, but persistent clefts indi- 
 cate their position ; the blanched blind Proteus from caves and the 
 genus Menobranchus keep their gills throughout life. The remark- 
 able Axolotl from North American lakes occurs in two forms, both 
 of which may bear young ; the one form {Axoloi!) has persistent 
 gills, the other form {Amblystoma) loses them, asd the change 
 from the Axolotl to the Amblystoma is in part associated with the 
 passage from the water to the swampy shore. A large fossil dis- 
 covered by Scheuchzer in the beginning of the eighteenth century 
 was quaintly regarded as a fossil man and as a testimony of the 
 deluge. But Cuvier showed that Scheuchzer's Homo diluvii testis 
 was but a large newt. 
 
 The common frc^ {Ranct), the Surinam toad (JHfd), the 
 common toads {Bufo), and the tree-frogs {Hyla) illustrate the tail- 
 less order Anura. In none of them is there in adult life any trace 
 of gills. 
 
 The worm-like, limbless, burrowing Amphibians (Gymnophiona) 
 must not be confused with the blind- ^r slow-worms, which are 
 lizards. There are only very few genera, Siphonops, RhineUrema, 
 Epicrium, Cacilia. The newly-born Cacilia has external gills, 
 but these are soon lost. The eyes are covered with skin, but are 
 well developed. 
 
 The race of Amphibians began in the Carboniferous ages. 
 Most of the Labyrinthodonts which flourished then and in the two 
 succeeding periods were newt-like in form, but some were serpen- 
 tine. They seem to have been armoured, and were sometimes 
 large. 
 
 Amphibians are naturally sluggish. For long periods they can 
 fast and lie dormant ; they can survive being frozen ouite stif^, 
 and though tales of toads within stones are mostly due to mistakes 
 or fancies, there are some authentic cases of prolonged imprison- 
 ment. 
 
 Few are found far from water, and the gilled condition of 
 the young is s'iipped over only in a few cases. In the black 
 salamander {SalamanJra atra) of the Alps, which lives where 
 
 S 
 
 
258 The Study of Animal Life part 111 
 
 pools are scarce, the young, after living and breathing for a time 
 SSn the mother, are l^rn as lung-breathers; also m some 
 Tpecies of tree-frogs {JJylodes), ..-hich live m situations where water 
 
 ''''''^t^:£^^Tt^'^^o. frog should be studied by 
 every student of natural history. The eggs are fertilised as they 
 are being laid. The division of the ovum can be readily observed, 
 "n hs early stages the tadpole is fishlike. with a lamprey-l.ke 
 
 Fig. 53. -The life-history of the Frog. 
 
 mouth. External gills are replaced by an internal set. an-l as 
 metamorphosis is accomplished these disapiv^ar and the lui.t,'s 
 become active. The larva feeds first on its own yolk, then en 
 freshwater plants, then on small animals or even on its own 
 relatives ; then it fasts, absorbing its tail, and finally it becomes an 
 insect-catching frog. . 
 
 The food of adult Amphibians usually consists of insects, slugs. 
 and worms ; most of the larvx are for a time vegetarian. Though 
 Amphibians often live alone, crowds are often found together at the 
 breeding season. Then the sluggish life wakes up, as the croal:- 
 ings of frogs remind us. Quairt are many of their reproduMive 
 habits, to some of which allusion has already been made, buch 
 
CHAP. XVI 
 
 Backboned Animals 
 
 259 
 
 animals as the Surinam toad (Pipa amfricana) and the Obstetric 
 frog (Alyles obstetricans) suggest that the Amphibians make ex- 
 periments in eugenics. 
 
 7. Reptiles. — Fishes and Amphibians are closely allied ; so 
 Reptiles are linked to Birds, and more remotely to Mammals also. 
 Those three highest classes — Reptiles, Birds, and Mammals — are 
 very different from one another, but they have certain characters in 
 common. Most of them have passed from the water to dry land ; 
 none of them ever breathe by gills ; all of them have two embryonic 
 birth-robes — amnion and allantois — which are of great importance 
 in early life. Compared with the other Vertebrates, the brains are 
 more complex, the circulation is more perfect, the whole life has a 
 higher pitch. As symbols of mammal, bird, and reptile, take the 
 characteristic coverings of the skin — hair, feathers, and scales. 
 Hair typifies strength and perhaps also gentleness ; feathers suggest 
 swift flight, the beauty which wins love, and the down which lines 
 the warm nest ; scales speak of armour and cold-blooded stealth. 
 
 But we need not depreciate reptiles, nor deny the justice of that 
 insight which has found in tliem the fittest emblems of the omni- ' 
 potencc of the earth. If Athene of the air possesses the birds, 
 surely the power of the dust is in the grovelling snakes. Few 
 colour arrangements are more beautiful than those which adorn the 
 lithe lizards. The tortoise is an example of passive energy, self- 
 contained strength, and all but impenetrable armature. The 
 crocodiles more than the others recall the strong ferocity of the 
 ancient extinct dragons. Nor should we judge reptiles exclusively 
 by their living representatives, any more than we should judge 
 the Romans by those of the decadent Empire. It is interesting to 
 remember the long-tailed toothed Archctopteryx, the predecessor of 
 modern birds, just as it is to recall the giant sloths which pre- 
 ceded the modern Edentate mammals ; but it is essential to include 
 in our appreciation of Reptiles the giant dragons of their golden 
 age. Most modern forms are jiigmies beside an Ichthyosaurus 25 
 feet long, a Megalosaurus of 30, a Titanosaurus of 60, or an 
 Atlantosaums of loo, all fairly broad in proportion. We have still 
 pythons and crocodiles and other reptiles of huge size, and we do 
 not deny Grant Allen's remark that a good blubbery " right whale" 
 could give points to any deinosaur that ever moved upon Oolitic 
 continents, but the fact remains that in far back times (Triassic, 
 Jurassic, and Cretaceous) reptiles had a golden age with a pre- 
 dominance of foi-ms larger than any living members of the class, 
 liesides size, however, the ancient saurians had another virtue, 
 apparently possessed by both small and great — they were pro- 
 gressive. Yox, with toothed birds on the one hand and flying or 
 flopping reptiles on the other, it seems probable that birds had 
 
 i>TI 
 
 81 
 
 t. i 
 
MiciocorY nsoiuTiON tbt chart 
 
 (ANSI and ISO TEST CHART No. 2) 
 
 ^ 
 
 /APPLIED IM^OE li 
 
 nc 
 
 !6S3 East Main StrMi 
 
 Roch«»t«r. N«« York 14609 USA 
 
 (716) 482 -0300 - Phon* 
 
 (716) 268-3989 -Tax 
 

 a6o The Study of Animal Life part in 
 
 their origin from feverish saurians which acquired the power of 
 flight, and it is also possible that some, perhaps pathological, 
 mother reptile, overflowing in the milk of animal kindness, and 
 retaining her young for a long time within her womb, was the fore- 
 runner of the mammalian race. 
 
 While there are many orders of extinct reptiles — Ichthyosaurs, 
 Plesiosaurs, Deinosaurs, Pterosaurs, and other saurians not yet 
 classified with certainty— the living forms belong to four sets— the 
 lizards, the snakes, the tortoises, and the crocodiles— to which a 
 fifth order should perhaps be added for the New Zealand "lizard" 
 Hatteria or Sphenodon, which is in several respects a living fossil. 
 
 The Lizards (Lacertilla).— The lizards form a central order of 
 Reptiles, but the members are a motley crowd, varied in detailed 
 structure and habit. Usually active in their movements, though 
 fond, too, of lying passive in the sunshine, they are often ver>' 
 beautiful in form and colour, and not uncommonly change their 
 tints in sympathetic response to their surroundings. Most lay eggs, 
 but in some, e.g. the common British lizard {Lacerta or Zooto^a 
 mvipara), and the slow-worm, the young are hatched within the 
 
 mother. . ^ , v v • l 
 
 Among the remarkable forms are the Geckos, which with 
 plaited adhesive feet can climb up smooth walls ; the large Monitors 
 [yaranus\ which may attain a length of 6 feet, and prey upon 
 small mammals, birds, frogs, fishes, and eggs; the poisonous 
 Mexican lizard {Heloderma hoiridum), with large venom glands 
 and somewhat fang -like teeth; the worm-like, limbless Amphis- 
 bam', the likewise snake-like slow-worm (Anptis fragilis), which 
 well illustrates the tendency lizards have to break in the spasms of 
 capture; the large Iguanas, which frequent tropical American 
 forests, and feed on leaves and fruit; the slugijish and spiny 
 " Horned Toad " (Phryiiosonta) ; the Agamas of the Old World 
 comparable to the Iguanas of the New ; the Flying Dragon (Draco 
 volatts), which, with skin outstretched on extended nbs, swoops 
 from tree to tree; the Australian frilled lizards (Chlamydosaunts) 
 and the quaint thorny Moloch ; the single marine lizard {Oreo- 
 cephaUu or Amblyrhynchm cristatus) from the Galapago and the 
 divergent Chameleons, flushing with changeful colour. 
 
 The New Zealand Hatteria or Sphenodon is quite unique, and 
 seems to be the sole survivor of an extinct order— Rhynchocephalia. 
 It was in it first of all that the pineal body—an upgrowth from the 
 mid-brain of backboned animals— was seen to be a degenerate 
 upward-looking eye. 
 
 Snakes or Serpents (Ophidia). — These much modified 
 
 reptiles mostly cleave to the earth, though there are among tliem 
 devcr climbers, swift swimmers, and powerful burrowers. Though 
 
CHAP. XVI 
 
 Backboned Animals 
 
 261 
 
 ; j! 
 
 m 
 
 i . I 
 
 t 
 
 I ; 
 
 
 
 1! 
 
 1 '■ !i 
 
 i 
 
 '}•" 
 
a6a 
 
 The Study of Animal Life part hi 
 
 they are all limbless, unless we credit the little hind claws of some 
 hooi and pythons with the title of legs, they flow like swift living 
 streams along the ground, using ribs and scales instead of their lost 
 appendages, pushing themselves forward with jerks so rapid that 
 the movement seems continuous. Without something on which to 
 raise themselves they must remain at least half prostrate, but in the 
 forest or on rough ground there are no lither gymnasts. Their 
 united eyelids give them an unlimited power of staring, and, accord- 
 ing to uncritical observers, of fascination ; yet most of them seem 
 to see dimly and hear faintly, trusting mainly for guidance to the 
 touch of their restless protrusible tongue and to their sense of 
 smell. Their only language is a hiss or a whine. Most of them 
 have an annual period of torpor, and all periodically cast off their 
 scales in a normally continuous slough, which they turn outside-in 
 as they crawl out. Almost all lay eggs, but in a few cases [e.g. 
 the adder) the young are hatched within 'le mothers, and this 
 mode of birth may be induced by artificial conditions. Think not 
 meanly of the serpent, "it is the very omnipotence of the earth. 
 That rivulet of smooth silver — how does it flow, think you? It 
 literally rows on the earth with every scale for an oar ; it bites the 
 dust with the ridges of its body. Watch it when it moves slowly — 
 a wave, but without wind I a current, but with no fall ! all the 
 body moving at the same instant, yet some of it to one side, some 
 to another, or some forward, and the rest of the coil backwards j 
 but all with the same calm will and equal way — no contraction, no 
 extension ; one soundless, causeless, march of sequent rings, and 
 spectral procession of spotted dust, with dissolution in its fangs, 
 dislocation in its coib. Startle it — the winding stream will become 
 a twisted arrow ; the wave of poisoned life will lash through the 
 grass like a cast lance. It scarcely breathes with its one lung (the 
 other shrivelled and abortive) ; it is passive to the sun and shade, 
 and cold or hot like a stone ; yet • it can outclimb the monkey, 
 outswim the fish, outleap the zebra, outwrestle the athlete, and 
 crush the tiger.' It is a Divine hiero-jlyph of the demoniac power 
 of the earth — of the entire eartlily nature. As the bird is the 
 clothed power of the air, so this is the clothed power of the dust ; 
 as the bird is the symbol of the spirit of life, so this of the grasp and 
 sting of death."* 
 
 This well-known and eloquent passage is not perfectly true,— 
 thus the serpent breathes not scarcely but strongly with its one 
 lung, — but, while you may correct and complete it as you will, I am 
 sure that you will find here more insight into the nature of serpents 
 than in pages of anatomical description. 
 
 Ruskin's Quttn of the Air. 
 
CttAP. XVI 
 
 Backboned Animals 
 
 263 
 
 A few snakes have mouths which do not distend, skull bones 
 which are slightly movable, teeth in one jaw (upper or lower) 
 only, and rudiments of hind legs. These are included in the 
 genera Typhlops and Anomakpsis, and are small simple ophidians. 
 
 Many are likewise non-venomous snakes, but with wider gape 
 and more mobile skull bones, and with simple teeth on both jaws. 
 Some are very large and have great powers of strangling. Such 
 are the Pythons, the Boa, and the Anaconda. To these our grass 
 snake {Tropidonotus natrix) is allied. 
 
 Many poisonous snakes have large permanentlyerect grooved fangs 
 in the upper jaw, and a salivary gland whose secretion is venomous. 
 Such are the cobra {Naja tripudians), the Egyptian asp (Naj'a haje)y 
 the coral snakes (Elaps), and the sea snakes {Hydrophis). 
 
 Other poisonous snakes have perforated fang teeth, which can 
 be raised and depresseJ. Such are the vipers ( Vipera), the British 
 adder [.Pelias derus), the copperhead (Ancisirodon contortrix), the 
 rattlesnakes (Crota/us). 
 
 Tortoises and Turtles (Chelonia).— Boxed in by a bony 
 shield above and by a bony shield below, and often with partially 
 retractile head and tail and legs, the Chelonians are thoroughly 
 armoured. On the average the pitch of their life is low, but their 
 tenacity of life is great. Slow in growth, slow in movement, slow 
 even in reproduction are many of them, and they can endure long 
 fasting. It is said that a tortoise walked at least 200 yards, twenty- 
 four hours after it was decapitated, while it is well known that the 
 heart of a tortoise will beat for two or three days after it has been 
 isolated from the animal. In connection with their sluggishness it 
 is significant that the ribs which help to some extent in the respira- 
 tory movements of higher animals are soldered into the dorsal 
 shield, thus slu^sh respiration may be in part the cause, as it is 
 in part the result, of constitutional passivity. All the Chelonians 
 lay eggs in nests scooped in the earth 01 sand. 
 
 The marine turtles {«.g. Sphargis, Chelone), the estuarine soft- 
 shelled turtles {e.g. Aspidonectes\ the freshwater turtles {e.g. 
 Emys), and the snapping turtle {Chelydra) are more active than the 
 land tortoises, such as the European Testudo graca, often kept as 
 a pet. The tortoise of the Galapagos Islands ( Testudo elephautopus), 
 the river tortoise {Podocnemys expattsa) of the Amazon, the bearded 
 South American turtle (Chelys matamata), and the green turtle 
 {Chelone mydas) attain a large size, sometimes measuring about 
 3 feet in length. 
 
 Oroccdilians (Crocodilia). — Crocodiles, alligators, and gavials 
 •eem in our present perspective very much alike— strong, large, 
 heavily armoured reptiles, at home in tropical rivers, but clumsy 
 snd stiff-necked on land, feeding on fishes and small mammals, 
 
 V f 
 
 rt 
 
 f.'% m 
 
264 
 
 The Study of Animal Life part m 
 
 growing slowly and without that definite limit which punctuates 
 the life -history of most animals, attaining, moreover, a great 
 age, freed after youth is past from the attacks of almost every 
 foe but man. The teeth are firmly implanted in sockets ; the 
 limbs and tail are suited for swimming, and also for crawling ; the 
 heart is more highly developed than in other reptiles, having four 
 instead of three chambers. The animals lie in wait for victims, 
 and usually drown them, being themselves able to breathe whilo 
 the mouth is full of water, if only the nostrils be kept above the 
 surface. 
 
 In many ways Reptiles touch human life, the poisonous snakes 
 are very fetal, especially in India ; crocodilians are sometimes 
 destructive ; turtles afford food and " tortoise shell ;" lizards arc 
 delightfully beautiful. 
 
 8. Birds. — What mammals are to the earth, and fishes to the 
 sea, birds are to the air. Has anything truer ever been said of 
 
 fio. 55.— The Collocalia, whicli from the secreted juice of its salivary glands 
 builds the cdiblc-l'iid's-ncst. (Adapted from Brehiii.) 
 
 them than this sentence from Ruskin's Queen of tic Air? "'I'hc 
 bird is little more than a drift of the air brought into form by 
 plumes; the air is in all its quills, it breathes through its whole 
 frame and flesh, and glows with air in its flying, like a bluwn 
 
CHAP. XVI 
 
 Backboned Animals 
 
 265 
 
 flame : it rests upon the air, subdues it, surpasses it, outraces it ; 
 
 is the air, conscious of itself, conquering itself, ruling itself." 
 
 Birds represent among animals the climax of activity, an index to 
 which may be found in their high temperature, from 2"- 14' Fahren- 
 heit higher than that of mammals. In many other ways they rank 
 high, for whether we consider the muscles which move the wings 
 in flight, the skeleton which so marvellously combines strength 
 with lightness, the breathing powers perfected and economised by a 
 set of balloons around the lungs, or the heart which drives and 
 receives the warm blood, we recognise that birds share with 
 mammals the position of the highest animals. And while it is true 
 that the brains of birds are not wrinkled with thought like 
 those of mammals, and that the close connection between mother 
 and offspring characteristic of most mammals is absent in birds, it 
 may be urged by those who know their joyousness that birds feel 
 more if they think less, while the patience and solicitude con- 
 nected with nest-making and brooding testify to the strength of 
 their parental love. Usually living in varied and beautiful sur- 
 roundings, birds have keen eyes and sharp ears, tutored to a sense 
 of beauty, as we may surely conclude from their cradles and love 
 songs. They love much and joyously, and live a life remarkably 
 free and restless, qualities symbolised by the voice of the air in 
 their throat, and by the sunshine of their plumes. There is more 
 than zoological truth in saying that in the bird «' the breath or spirit 
 is niore full than in any other creature, and the earth power least," 
 or in thinking of birds as the purest embodiments of Athene of 
 the air. 
 
 But just as there are among mammals feverish bats with the power 
 of true flight, and whales somewhat fish-like, so there are excep- 
 tional birds, runners like the ostriches and cassowaries, swimniers 
 like the penguins, criminals too like the cuckoos and cow-birds in 
 which the maternal instincts are strangely perverted. As we go 
 back into the past, strange forms are discovered, with teeth, long 
 tails, and other characteristics which link the birds of the air to the 
 grovelling reptiles of the earth. Even to-day there lives a 
 " reptilian-bird "—0/tjM<7f<?w«j— -which has retained more than 
 any other indisputable affinities with the reptiles. Professor W. K. 
 Parker, one of the profoundest of all students of birds, described 
 this form in one of his last papers, and there used a comparison 
 which helps us to appreciate birds. They are among backboned 
 animals what insects are among the backboneless— winged pos- 
 sessors of the air, and just as many insects pass through a cater- 
 pillar and chrysalis stage before reaching the acme of their life as a 
 flying imago, so do the young birds within the veil of the egg- 
 »hell pass through somewhat fish-like and somewhat reptile-like 
 
i66 
 
 The Study of Animal Life part hi 
 
 Fig. 56.— Decorative male and less adorned female of Spafhura— a genus of 
 Humming-birds. (From Darwin, after Urehm.) 
 
CrtAP. XVI 
 
 Backboned Animals 
 
 267 
 
 f ; 
 
 stages before they attain to the possession of wings and the enjoy- 
 ment of freedom. 
 
 The great majority of birds are fliers, and possess a keeled 
 breast-bone, to which arc fixed the muscles used in flight. To 
 this keel or carina they owe their name Carinatae. The flying 
 host includes the gulls and grebes, the plovers and cranes, the 
 ducks and geese, the storks, and herons, the pelicans and cormo- 
 rants, the partridges and pheasants, the sand grouse, the pigeons, 
 the birds of prey, the parrots, the pies, and about 6000 Passerine or 
 sparrow-like birds, including thrushes and warblers, wrens and 
 swallows, finches and crows, starlings and birds of paradise. To 
 these orders we have to add Opisthocomiis, from which it is perhaps 
 easier to pass to some of the keeled fossil birds, some of which 
 possessed teeth. 
 
 Distinct from the keeled fliers, both ancient and modem, 
 are the running-birds, which 
 ai'e incapable of flight, and 
 therefore possess a flat raft- 
 like breast bone, to vvhicli 
 they owe their title Ratita;. 
 Nowadays these are few in 
 number, the Ostrich and the 
 Rhea, the Cassowary and 
 Kmu, and the small Kiwi. 
 Heside these must be ranked 
 the giant Moa of New Zea- 
 land, not long extinct, and 
 the more ancient, not less 
 gigantic yEpyornis of Mada- 
 gascar, while farther back 
 still, from the Chalk strata 
 of America, the remains of 
 toothed keelless birds have 
 been disentombed. 
 
 The most reptilian, least 
 bird -like of birds is the 
 oldest fossil of al, placed in 
 a sub-cKass by itself, the 
 Archaopteryx (lit. ancient 
 bird) from strata of Jurassic 
 age. 
 
 9. Mammalia.— Of the 
 
 highest class of animals — the Mammalia — I need say least for they 
 are most familiar. Most of them are terrestrial, four-footed, and 
 hairy. Bats and whales, seals and sea-cows, are obviously excep- 
 
 Fig. 57. — Restoration of the extinct moa (/)/«- 
 ornts ingens), and alongside of it the little 
 kiwi {Apteryx iiiantelii). (From Cham- 
 bers's A^ktj'c/o/. ; after F. v. Hochstetter.) 
 
 t 
 i . 
 
 i1 
 
 < f 
 
368 
 
 Tfu Study of Animal Life part 114 
 
 tional. The brain of mammals is more highly developed thap 
 that of other animals, and in the great majority there is a prolonged 
 (placental) connection between the unborn young and the mother. 
 In all cases the mothers feed the tender young with milk. 
 In the class there are three grades : — 
 
 (1) In the Duckmole {Omithorhynchus) and the Porcupine 
 Ant-Eater lEchtdtta\ and perhaps another genus Proechidna, the 
 females lay eggs. In many other ways these exclusively Austral- 
 asian mammals are primitive, exhibiting affinities with reptiles. 
 
 (2) In the Marsupials, which, with the exception of some 
 American Opossums, are also Australasian, the young are born at 
 a very tender age, as it were, prematurely. In the great majority 
 of genera, the mothers stow them away in an external pouch, where 
 they are fed and sheltered till able to fend for themselves. In 
 Australia the Marsupials have been saved by insulation from stronger 
 mammals, which seem to have exterminated them in other parts 
 of the earth, the Opossums which hide in American forests being 
 the only Marsupials surviving outside Australasia, though fossils 
 show that the race had once a much wider distributioii. In their 
 Australian retreat, apart from all higher Mammalia (mice, rabbits, 
 and the like being modern imports) the Marsupials have evolved 
 along many lines, prophetic of the higher orders of mammals. 
 There are "carnivores" like the Thylacine and the Dasyure, 
 "herbivores" like the Kangaroos, " insectivores " like the banded 
 ant-eater Mynnecobius^ and "rodents" like the Wombat. 
 
 (3) In all the other orders of mammals there is a close con- 
 nection between mother and unborn offspring. 
 
 Two orders are lowly and distinctly separate from the others 
 and from one another — the Edentata represented by sloths, 
 ant-eaters, armadillos, pangolins, and the Aard-Vark ; and the 
 Sirenia or Sea-Cows which now include only the dugong and the 
 manatee. 
 
 Along one fairly definite line we may rank three other orders 
 — the Insectivores, the Bats, and the Carnivores. The hedgehog, 
 which is at once a lowly and a central type of -nammal, may be 
 taken as the beginning of this line. Along with shrews, moles, 
 porcupines, the hedgehogs form the order Insectivora. To these 
 the Bats (Cheiroptera), with their bird-like powers of flight, are 
 linked, while the Camivora (cats, dogs, bears, and seals), though 
 progressive in a different direction, seem also related. 
 
 Comparable to the Insectivores, but on a different line, are the 
 gnawing Rodents, rabbits and hares, rats and mice, squirrels and 
 beavers. This line leads on to the Elephants, from the company 
 of which the mammoths have disappeared since man arose on the 
 earth. With the Elephants, the rock-co' jys or Hyraxes— " a feeble 
 
CHAP. XVX 
 
 Backboned Animals 
 
 269 
 
 folk " — seem to be allied. Both are often included in the great 
 order of hoofed animals or Ungulates, along w-th the odd-toed 
 
 Fig. i%.—Phenacoelus f>rimarms, a primitive extinct mammal from the lower 
 Eocene of N. America. The actual .size of the slab of rock on which it rested 
 was 49 inches in length. (From Chambers's Encyclop. ; after Cope.) 
 
 animals — horse, rhinoceros, and tapir, and a larger number of 
 even-toed forms, hog and hippopotamus, camel and dromedary. 
 
 Fig. 59. --Head of gorilla. (From Du Chaillu.) 
 
 and the true cud-chewers or ruminants such as sheep and cattle, 
 deer and antelopes. From the ancient predecessors of the modern 
 
 \%\ i 
 
 , ! a I 
 
 ! t 
 
 111 
 
 i * i 
 
27° 
 
 The Study of Animal Life part m 
 
 Ungulates, it seems likely enough that the Cetaceans (whales and 
 dolphins) diverged. 
 
 A third line, which we may call median, leads through the 
 Lemurs on to Monkeys. It must be noted, however, that these 
 lines, which seem distinct from one another if we confine our 
 attention to living mammals, are linked by extinct forms. Thus a 
 
 Fig. 6o.— Head of male Semnopithecus. (From Darwin.) 
 
 remarkable fossil type, Pkenacodus, is regarded by Cope as pre- 
 senting affinities with Ungulates, Lemurs, and Carnivores. 
 
 The monkeys which most closely resemble man in structure, 
 habits, and intelligence, are the so-called anthropoid apes, the 
 gori i t, the chimpanzee, the orang-utan, and the gibbon. A 
 second grade is represented by the more dog-like, narrow-nosed 
 Old World apes, such as the baboons and mandrills. Lower in 
 many ways are the broad-nosed New World or American monkeys, 
 e.^. the numerous species of Cebus, some of which are the familiar 
 
CHAP. XVI 
 
 Backboned Animals 
 
 II 
 
 271 
 
 companions of itinerant musicians, while lowest and smallest among 
 true monkeys are the South American marmosets. Distinct from 
 all these, probably outside the monkey order altogether, are the 
 so-called half-monkeys or Lemurs. 
 
 We might describe the clever activities of monkeys, the shelters 
 which some of them ipake, their family life, parental care and 
 sociality, their docility, their intelligent habits of investigation, and 
 their quickness to profit by experience ; but it would all amount to 
 this, that their life at many points touches the human, that they 
 are in some ways like growing children, in other ways like savage 
 men, though with more circumscribed limits of progress than either. 
 
 ORDERS OF MAMMALS. 
 
 MON 
 
 unXgulates 
 
 KEYS 
 
 \ 
 CARNI/VORES 
 
 URS 
 
 CETACEANS 
 
 BATS b 
 
 \ td 
 
 IN/SECTIVORES 
 
 SIRENIA 
 
 EDENTATA 
 
 MARSUPIALS 
 
 \ 
 
 MONOTREMES 
 
a7a The Study of Animal Life part in 
 
 SURVEY OF THE ANIMAL KINGDOM 
 T 
 
 BIRDS. 
 Flying-Birds. Running-Birds, 
 
 Placentals. 
 MAMMALS. Marsupials. 
 Monotremes. 
 
 Snakes. Lizards. REPTILES. &ocodiles. Tortoises 
 
 Double-Breathers. 
 Bony-Fishes. 
 
 Elasmobranchs. 
 
 AMPHIBIANS. 
 Newt. Frog. 
 
 LANCELET. 
 
 CrcLOSTOMATA. 
 Lamprey. Hagfish. 
 
 TUNICATES 
 
 Insects. Arachnids 
 
 Myriapods. 
 Peripatus. 
 
 ARTHROPODS, 
 Crustaceans. 
 
 BALANOGLOSSUS. 
 
 ANNELIDS. 
 "WORMS." 
 
 FLAT-WORMS. 
 
 Cuttlefish. 
 Gasteropods. 
 
 MOLLT'SCS. 
 
 Bivalves. 
 
 Feather-stars. 
 
 Brittle-stp-s. 
 
 Starfish. 
 
 ECHINODERMS, 
 
 Sea-urchins. 
 Sea-cucumbers. 
 
 Ctenophorcs. Jellyfish. Sea-Anemones. Corals. 
 
 STINGING-ANIMALS or CCELENTERATES. 
 
 Medusoids and Hydroids. 
 
 SPONGES. 
 
 Infusorians. Rhiropods. Gregarines. 
 
 SIMPLEST ANIMALS. 
 
 I 
 
 O 
 
 "•3 
 
PART IV 
 
 THE EVOLUTION OF \NIMAL LIFE 
 
 CHAPTER XVII 
 
 THE EVIDENCES OF EVOLUTION 
 
 I. The Idea of Evolution — 2. Arguiiunts for Evolution : Physio- 
 logical, Morphological, Historical — 3. Origin of Lift 
 
 We observe animals in their native haunts, and study their 
 growth, their maturity, their loves, their struggles, and their 
 death ; we collect, name, preserve, and classify them ; we 
 cut them to pieces, and know their - organs, tissues, and 
 cells ; we go back upon their life and inquire into the secret 
 working of their vital mechanism ; we ransack the rocks for 
 the remains of those animals which lived ages ago upon the 
 earth ; we watch how the chick is formed within the tgg, 
 and yet we are not satisfied. We seem to hear snatches of 
 music which we cannot combine. We seek some unifying 
 idea, some conception of the manner in which the world of 
 life has become what it is. 
 
 I. The Idea of Evolution. — We do not dream now, 
 as men dreamed once, that ill has been as it is since all 
 emerged from the mist of an unthinkable beginning ; nor 
 can we believe now, as men believed once, that all came 
 into its present state of being by a flash of almighty volition. 
 We still dream, indeed, of an unthinkable beginning, but 
 we know that the past has been full of change ; we still 
 
 
 1: 
 
274 The Study of Animal Life part iv 
 
 believe in almighty volition, but rather as a continuous reality 
 than as expressed in any event of the past. Thus Erasmus 
 Darwin (i794), speaking of Hume, says "he concluded 
 that the world itself might have been generated rather than 
 created ; that it might have been gradually produced from 
 very small beginnings, increasing by the activity of its 
 inherent principles, rather than by a sudden evolution of 
 the whole by the Almighty fiat." In short, we have 
 extended to the world around us our own characteristic 
 perception of human history ; we have concluded that in all 
 things the present is the child of the past and the parent 
 
 of the future. 
 
 But while we dismiss the theory of permanence as 
 demonstrably false, and the theory of successive cataclysms 
 and re-creations as improbable,^ without feeling it necessary 
 to discuss either the falsity or the improbability, we must 
 state on what basis our conviction of continuous evolution 
 rests. "La nature ne nous offre le spectacle d'aucune 
 creation, c'est d'une continuation dtemelle." "As in the 
 development of a fugue," Samuel Butler says, "where, 
 when the subject and counter-subject have been announxd, 
 there must thenceforth be nothing new, and yet all must 
 be new, so throughout organic nature— which is a fugue 
 developed to great length from a very simple subject— 
 everything is linked on to and grows out of that which 
 comes next to it in order— errors and omissions excepted." 
 2. Arguments for Evolution.— What then are the facts 
 which have convinced naturalists that the plants and the 
 animals of to-day are descended from others of a simpler 
 sort, and the latter from yet simpler ancestors, and so on, 
 back and back to those first forms in which all that suc- 
 ceeded were implied ? I refer you to Darwin's Origin oj 
 Species (1859), where the arguments were marshalled in 
 sue' a masf^rly fashion that they forced the conviction 
 1 1 uie the word in its literal sense-- not admiuingof proof." It is 
 not my duty nor my desire to discuss the poetical, or philosophical, 
 or religious conceptions which lie behind the concrete cMmogomes of 
 diffaxSt ages and minds. To many modem theologians creatior, 
 nMdirmeanTthe institution of the order of nature, the possibility of 
 natural evdutioa included. 
 
CBAP. XVII The Evidences of Evolution 375 
 
 of the wwld. To the statements of the case by Spencer, 
 Haeckel, Huxley, Romanes, and others, I have given 
 references in the chapter on books. Darwin's arguments 
 were derived {a) from the distribution of animals in space ; 
 (p) from their successive appearance in time, {c) from actual 
 variations observed in domestication, cultivation, and in 
 nature ; {d) from facts of structure, e.g. homologous and 
 rudiiiiftntary organs, {e) from embryology. I shall simply 
 illustrate the different kinds of evidence, and that under 
 three heads— (a) physiological, {b) structural, {c) his- 
 torical. 
 
 {a) PhysiologicaL— A study of the life of organisms 
 shows that the ancient and even Linnaean dogma of the 
 constancy or immutability of species was false. Organisms 
 change under our eyes. They are not like cast-iron ; they 
 are plastic. One of the most striking cases in the Natural 
 History Collection of the British Museum is that near the 
 entrance, where on a tree are perched domesticated pigeons 
 
 of many sorts— fantail, pouter, tumbler, and the like 
 
 while in the centre is the ancestral rock-dove Columba livia, 
 from which we know that all the rest have been derived! 
 In other domesticated animals, even when we allow that 
 some of them have had multiple origins, we find abundant 
 proof of variability. But what occurs under man's super- 
 vision in the domestication of animals and in the culti- 
 vation of plants occurs also in the state of nature. Natural 
 " varieties " which link species to species are very common, 
 and the offspring of one brood differ from one another and 
 from their parents. How many strange sports there are 
 and grim reversions I and, as we shall afterwards see, 
 modifications of individuals by force of external conditions 
 are not uncommon. Those who say they see no variation 
 now going on in nature should try a month's work at identi- 
 fying species. I have known of an ancient man who dwelt 
 in a small town ; he did not believe in the reality of railways 
 and to him the testimony of observers was as an idle tale ; 
 he was not daunted in his scepticism even when the railway 
 was extended to his town, for he was aged, and remained 
 at home, dying a professed unbeliever in that which he had 
 
 * 
 \ 
 
 
 \\\ 
 
276 
 
 The Study of Animal Life part iv 
 
 F.G 6. -Varieties of domestir J.igeon arr.ngejl arou.,.l f--^f^ ^'^■^•'' ''^ 
 
CHAP. XVII The Evidences of Evolution 
 
 211 
 
 never seen. Conviction depends on more than intelligence, 
 often on emotional vested interests. 
 
 (J>) Morphological. — There are said to be over a million 
 species of living animals, about half of them insects. 
 Even their number might suggest blood-relationship, but our 
 recognition of this becomes clear when we see that species 
 is often united to species, genus to genus, and even class 
 to class, by connecting links. The fact that we can make 
 at least a plausible genealogical tree of animals, arranging 
 them in series along the lines of hypothetical pedigree, is 
 also suggestive. 
 
 Throughout long series, structures fundamentally the 
 same appear with varied form and function ; the same bones 
 and muscles are twisted into a variety of shapes. Why this 
 adherence to type if animals are independent of one 
 another ? How necessary it is if all are branches of one 
 tree. 
 
 By rudimentary organs also the same conclusion is 
 suggested. What mean the unused gill-clefts of reptiles, 
 birds, and mammals, unless the ancestors of these classes 
 were fish-like ; what mean the teeth of very young whale- 
 bone whales, of an embryonic parrot and turtle, unless they 
 are vestiges of those which their ancestors possessed ? There 
 are similar vestigial structures among most animals. In 
 man alone there are about seventy little things which might 
 be termed rudimentary ; his body is a museum of relics. We 
 are familiar with unsounded or rudimentary letters in many 
 words ; we do not sound the " o " in leopard nor the " 1 " 
 in alms, but from these rudimentary letters we read the 
 history of the words, 
 
 (0 Historical. — Every one recognises that animals have 
 not always been as they now are ; we have only to dig to 
 be convinced that the fauna of the earth has had a history. 
 But it does not follow that the succession of fauna after 
 fauna, age after age, has been a progressive development. 
 What evidence is there of this ? 
 
 In the first place, there is the general fact that fishes 
 appear before amphibians, and these before reptiles, and 
 these before birds, and that the same correspondence 
 
 I >: i 
 
278 
 
 The Study of Animal Life part iv 
 
 6 
 
 between order of appearance and structural rank is often 
 true in detail within the separate classes of animals. There 
 are some marvellously complete series of fos- 
 sils, especially, perhaps, that of the extinct 
 cuttlefishes, in which the steps of progressive 
 evolution are still traceable. Moreover, the 
 long pedigree of some animals, such as the 
 horse, has been worked out so perfectly that 
 more convincing demonstration is hardly pos- 
 sible. In Professor Huxley's American Ad- 
 dresses, or in that pleasant introduction to 
 zoology afforded by Professor W. H. Flower's 
 little book on the horse (Modern Science 
 Series, Lond., 1891), you will find the story 
 of the horse's pedigree most lucidly told: 
 how in early Eocene times there lived small 
 quadrupeds about the size of sheep that 
 walked securely upon five toes, how these 
 animals lost, first the inner toe, while the 
 third grew larger, and then the fifth ; how the 
 third continued to grow larger and the second 
 and fourth to become smaller until they dis- 
 appeared almost entirely, remaining only as 
 small splint bones ; and how thus the light- 
 footed runn-rs on tiptoe of the dry plains 
 were evolved from the short -legged splay- 
 footed plodders of the Eocene marshes. Fin- 
 ally, there are many extinct types which link 
 ■!!;dhrndfeet°o'f order to order and even class to class, such 
 th-^ horse and as that Strange mammal Phenacodtts, which 
 TestLf show: seems to occupy a central position in the 
 ine the gradual ^qx\qs, SO uumerous are its affinities, or such 
 [he numVr uf as thosc sauriaus which link crawling reptile 
 soaring bird. 
 
 Another historical argument of great im- 
 portance is that derived from the study of 
 the geographical distribution of animals, but this cannot be 
 appreciated without studying the detailed facts. These 
 suggest that the various types of animals have spread from 
 
 SU-s"«" to soaring bird. 
 
 cyclot. ; after 
 Marsh.) 
 
CHAP. XVII The Evidences of Evolution 279 
 
 definite centres, along convenient paths of diffusion, varying 
 into species after species as their range extended. 
 
 But the history of the individual is even more instructive. 
 The first three grades of structure observed among living 
 animals are: (i) Single cells (most Protozoa), (2) balls of 
 cells (a few Protozoa which form colonies), and (3), two- 
 layered sacs of cells {e.g. the simplest sponges). But these 
 three grades correspond to the first three steps in the indi- 
 vidual life-history of any many-celled animal. Every one 
 begins as a single cell, at the presumed beginning again ; 
 this divides into a ball of cells, the second grade of struc- 
 ture ; the ball becomes a two-layered sac of cells. The 
 
 Fig. 63. — Antlers of deer (1-5) in successive years ; but the figure might almost 
 represent at the same time the degree of evohition exhibited by tne antlers 
 of deer in successive ages. (From Chambers's Encyclof.) 
 
 correspondence between the first three grades of structure 
 and the first three chapters in the individual's life-history is 
 complete. It is true as a general statement that the indi- 
 vidual development proceeds step by step along a path 
 approximately parallel to the presumed progress of the 
 race, so far as that is traceable from the successive grades 
 of structure and from the records of the rocks. Even in 
 regard to details such as the development of antlers on stags 
 the parallelism of racial and individual history may be 
 observed. Of this correspondence it is difficult to see any 
 elucidation except that the individual in its life-history in 
 great part re-treads the path of ancestral evolution. 
 
 I have illustrated these evidences of evolution very 
 
 f 
 
 i 
 
38o The Study of Animal Life part iv 
 
 briefly, for they have been stated many times of late years. 
 The idea of evolution has also justified itself by the ligbt 
 which it has cast not only on biological, but on physical, 
 psychological, and sociological facts. There has never been 
 a more germinal idea ; it is fast becoming organic m all 
 
 our thinking. , j . • / 
 
 To those who feel a repugnance to the doctrine of 
 descent, I suggest the following considerations :— 
 
 (i) In so far as conclusions do not affect conduct, it 
 seems wise to conserve what makes one happiest. If your 
 intellectual and emotional necessities are better satisfied, 
 for instance, by any one of the creationist theories than 
 by that of a gradual and natural progress from simple 
 beginnings to implied ends, and if you feel that your sense 
 of the marvel, beauty, and sacredness of life would be 
 impoverished by a change of theory, then I should not seek 
 
 to persuade you. 
 
 (2) But as we do not think a tree less stately because 
 we know the tiny seed from which it grew, nor any man 
 less noble because he was once a little child, so we ought 
 not to look on the world of life with eyes less full of wonder 
 or reverence, even if we feel that we know something of its 
 
 humble origins. . , , . 
 
 (3) Finally, we should be careful to distinguish between 
 the doctrine of natural descent, which, to most naturalists, 
 seems a solemn fact, and the theories of evolution which 
 explain how the progressive descent was brought about. 
 For in regard to the causal, as distinguished from the modal 
 explanation of the worid, we are or ought to be uncertain. 
 
 3. Origin of Life.— It is no dogma, nor yet a " law 
 of Biogenesis," but a fact of experience, to which no excep- 
 tion has been demonstrated, that living organisms arise 
 from pre-existent organisms— Ow«^ vivum e vivo. 
 
 As to the origin of life upon the earth we know nothing, 
 but hold various opinions, (i) Thus it is believed that life 
 began independently of those natural conditions which come 
 within the ken of scientific inquirers; in other words, it is 
 believed that the first living things were created. That 
 this belief presents intellectual difficulties to many minds 
 
CHAP. XVII The Evidences of Evolution 
 
 281 
 
 may mean that its fittest expression in words has not been 
 attained, or is unattainable. (2) It has been suggested 
 that germs of life reached this earth in the bosom of 
 meteorites from somewhere else. This at least shifts the 
 responsibility of the problem off the shoulders of this planet. 
 (3) It is suggested that living matter may have been evolved 
 from not-living matter on the earth's surface. If we accept 
 this suggestion, we must of course suppose that in not-living 
 matter the qualities characteristic of living organisms are 
 implicit. The evolutionist's common denominator is then 
 as inexpressibly marvellous as the philosopher's greatest 
 common measure. 
 
 \ 
 
 \ 
 
 f!' 
 
 \ \ 
 
 ■ ji '. 
 
 I 
 
CHAPTER XVIII 
 
 THE EVOLUTION OF EVOLUTION THEORIES 
 
 I. Greek Philosophers -2. Aristotle-l. Lucretius-^, Evolution, 
 ists before Darwin-^. Three old Masters: Buffon, Erasmus 
 Darwin, Lamarck-6. Charles Darwin— 1. Darwin s Fellom- 
 workers-^. The Present State of Opinion 
 
 THE conception of evolution is no new idea, it is the human 
 idea of history grown larger, large enough to cover the 
 whole world. The extension of the idea was gradual, as 
 men felt the need of extending it ; and at the same moment 
 we find men believing in the external permanence of one 
 set of phenomena, in the creation of others, in the evolution 
 of others. One authority says human institutions have been 
 evolved ; man was created ; the heavens are eternal. Ac- 
 cording to another, matter and motion are eternal ; life was 
 created ; the rest has been evolved, except, perhaps, the 
 evolution theory which was created by Darwin. 
 
 I. Greek Plulosopliers.— Of the wise men of Greece 
 and what they thought of the nature and ongin of 
 things, I shall say little, for I have no direct acquaintance 
 with the writings of those who lived before Aristotle. 
 Moreover, though an authority so competent as Zeller has 
 written on the «« Grecian predecessors of Darwin, most ot 
 them were philosophers not naturalists, and we are apt to 
 read our own ideas into their words. They thought, indeed, 
 as we are thinking, about the physical and organic universe, 
 and some of them believed it to be, as we do, the result ot 
 
cH. XVIII The Evolution of Evolution Theories 283 
 
 a process ; but here in most cases ends the resemblance 
 between their thought and ours. 
 
 Thus when Anaximander spoke of a fish-like stage in the 
 past history of man, this was no prophecy of the modem 
 idea that a fish-like form was one of the far-off ancestors of 
 backboned animals, it was only a fancy invented to get over 
 a difficulty connected with the infancy of the first human 
 being. 
 
 Or, when we read that several of these sages reduced 
 the world to one element, the ether, we do the progress of 
 knowledge injustice if we say that men are simply returning 
 to this after more than two thousand years. For that 
 conception of the ether which is characteristic of modem 
 physical science has been, or is being, slowly attained by 
 precise and patient analysis, whereas the ancient conception 
 was reached by metaphysical speculation. If we are 
 retuming to the Greeks, it is on a higher turn of the spiral, 
 so far at least as the ether is concerned. 
 
 When we read that Empedocles sought to explain the 
 world as the result of two principles — love- and hate — 
 working on the four elements, we may, if we >o inclined, 
 call these principles " attractive and repulsive orces " ; we 
 may recognise in them the altruistic and individualistic 
 factors in organic evolution, and what not ; but Empedocles 
 was a poetic philosopher, no far-sighted prophet of evolu- 
 tion. 
 
 But the student cannot afford to overlook the lesson 
 which Democritus first clearly taught, that we do not 
 explain any result until we find out the natural conditions 
 which bring it about, that we only understand an effeci. 
 when we are able to analyse its causes. We require a so- 
 called " mechanical," or more strictly, a dynamical explana- 
 tion of results. It is easy to show that it is advantageous 
 for a root to have a root-cap, but we wish to know how the 
 cap comes to be there. It is obvious that the antlers of a 
 stag are useful weapons, but we must inquire as precisely 
 as possible how they first appeared and still grow. 
 
 2. Aristotle. — As in other departments of knowledge, 
 so in zoology the work of Aristotle is fvindamental It is 
 
 In 
 
a«4 
 
 The Study of Animal Life part iv 
 
 wonderful to think of his knowledge of the forms and ways 
 of life, or the insight with which he foresaw such useful dis- 
 tinctions as that between analogous and homologous organs, 
 or his recognition of the fact of correlation, of the advan- 
 tages of division of labour within organisms, of the gradual 
 differentiation observed in development. He planted seeds 
 which grew after long sleep into comparative anatomy and 
 classification. Yet with what sublime humility he says : " I 
 found no basis prepared, no models to copy. Mine is the 
 first step, and therefore a small one, though worked out with 
 much thought and hard labour." Aristotle was not an 
 evolutionist, for, although he xccognisedthe changefulness of 
 life, the world was to him an eternal fact not a stage m a 
 process. 
 
 " In nature, the passage from inanimate things to animals is so 
 gradual that it is impossible to draw a hard-and-fast line between 
 them. After inanimate things come plants, which differ from one 
 another in the degree of life which they possess. Compared with 
 inert bodies, plants seem endowed with life; compared with 
 animals, they seem inanimate. From plants to animals the passage 
 is by no means sudden or abrupt ; one finds living things m the 
 sea about which there is doubt whether they be animals or plants. 
 «« Animals are at war with one another when they live m the same 
 place and use the same food. If the food be not sufficiently 
 abundant they fight for it even with those of the same kind.' 
 
 3. Lucretius.— Among the Romans Lucretius gave 
 noble expression to the philosophy of Epicurus. I shall 
 not try to explain his materialistic theory of the concourse 
 of atoms into stable and well-adapted forms, but rather 
 quote a few sentences in which he states his belief that the 
 earth is the mother of all life, and that animals work out 
 their destiny in a struggle for existence. He was a cosmic, 
 but hardly an organic evolutionist, for, according to his 
 poetic fancy, organisms arose from the eaith's fertile bosom 
 and not by the gradual transform?tion of simpler predecessors. 
 
 «• In the beginning the earth gave forth all kinds of herbage and 
 verdant sheen about the hills and over all the plains ; the flowery 
 meadows glittered with the bright green hue, and next in order to 
 the f?:fferent trees was given a strong and emulous desire of grow- 
 
CH. xviii The Evolution of Evolution Theories 285 
 
 ing up into the air with full unbridled powers. . . . With good 
 reason the earth has gotten the name of mother, since all things 
 have been produced out of the earth. . . . 
 
 " We see that many conditions must meet together in things in 
 order that they may beget and continue their kinds ; first a supply 
 of food, then a way in which the birth-producing seeds throughout 
 the frame may stream from the relaxed limbs. . . . And many 
 races of living things must then have died out and been unable to 
 beget and continue their breed. For in the case of all things which 
 you see breathing the breath of life, either craft or courage or else 
 speed has from the beginning of its existence protected and pre- 
 served each particular race. And there are many things which, 
 recommended to us by their useful services, continue to exist con- 
 signed to our protection. 
 
 *' In the first place, the first breed of lions and the savage races 
 their courage has protected, foxes their craft, and stags their prone- 
 ness to flight. But light-sleeping dogs with faithful heart in breast, 
 and every kind which is born of the seed of beasts of burden, and at 
 the same time the woolly flocks and the horned herds, are all con- 
 signed to the protection of man. For they have ever fled with 
 eagerness fro:" ''/'. beasts, and have ensued peace, and plenty of 
 food obtained w :out their own labour, as we give it in requital of 
 their useful services. But those to whom nature has granted none 
 of these qualities, so that they could neither live by their own 
 means nor perform for us any useful service, in return for which 
 we should suffer their kind to feed and be safe under our protection, 
 those, you are to know, would lie exposed as a prey and booty 
 of others, hampered all in their own death-bringing shackles, until 
 nature brought that kind to utter destruction." 
 
 4. Evolutionists before Darwin. — From Lucretius I 
 shall pass to BufTon, for the intervening centuries were un- 
 eventful as regards zoology. Hugo Spitzer, one of the histo- 
 rians of evolution, finds analogies between certain mediaeval 
 scholastics and the Darwinians of the nineteenth century, 
 but these are subtle comparisons. Yet long before Darwin's 
 day there were evolutionists, and the first of these who can 
 be called great was BufTon. 
 
 We must guard against supposing that the works of 
 BufFon, or Lamarck, or Darwin were inexplicable creations 
 of genius, or that they came like cataclysms, without warning, 
 to shatter the conventional traditions of their time. For all 
 great workers have their forenmners, who prepare their 
 
 ! 
 1 
 
 1 
 
 
 j 
 
 
 ! 
 
 
 \ 
 
 ! 
 
 
 
 
 ttj- 
 
 
 
s86 The Study of Animal Life part r? 
 
 paths. Therefore xa thinking out the history of evolutionist 
 theories before that of Buffon, we must take account of 
 many forces which began to be influential from the twelfth 
 century onwards. "Evolution in social affairs has not 
 only suggested our ideas of evolution in the other sciences, 
 but has deeply coloured them in accordance with the 
 particular phase of social evolution current at the time." i 
 In other words, we must abandon the idea that we can 
 understand the history of any science as such, without 
 reference to contemporary evolution in other departments 
 of activity. The evolution of theories of evolution is bound 
 up with the whole progress of the world. 
 
 In trying to determine those social and intellectual forces 
 of which the modern conception of organic evolution has 
 been a resultant, we should take account of social changes, 
 such as the collapse of the feudal system, the crusades, the 
 invention of printing, the discovery of America, the French 
 Revolution, the beginning of the steam age ; of theological 
 and religious movements, such as the Protestant Reforma- 
 tion and the spread of Deism ; of a long series of evolu- 
 tionist philosophers, some of whom were at the same time 
 students of the physical sciences, — notably Descartes, 
 Spinoia, Leibnitz, Herder, Kant, and Schelling ; of the 
 acceptance cf evolutionary conceptions in regard to other 
 orders of facts, especially in regard to the earth and the 
 solar system ; and, finally, of those few naturalists, like De 
 Maillet .nd Robinet. who, before Buffon's day, whispered 
 evolutionist heresies. The history of an idea is like that 
 of an organism in which cross-fenilisation and composite 
 inheritance complicate the pedigree, 
 
 5 Three old Masters.— Among the evolutionists before 
 Darwin I shall speak of only three— Buffon, Erasmus Darwin, 
 
 and Lamarck. 
 
 Buffon (1707- 17 88) was bom to wealth andwas wcddeu 
 
 to Fortune. He sat in kings' houses, his statue adorned their 
 gardens. As Director of the Jardin du Roi he had oppor- 
 tunity to acquire a wide knowledge of animals. He com- 
 manded the assistance of able coUaborateurs, and his own 
 1 Article "EvoluUon" (P. Geddei) in Chambers*! Encyciofadia. 
 
 :^=^K:'aKrA •• ^A«;^J'MTtf.K£~~V'W-"y ' 
 
CH. XVIII The Evolution of Evolution Theories 287 
 
 industry was untiring. He was about forty years old when 
 he began his gfreat Natural ^''«tory, and he worked till he 
 was fourscore. He lived a full life, the success of which 
 we can almost read in the strong confidence of his style. 
 ' Le style, c'est I'homme m6me," he said ; or again, " Le 
 style est comme le bonheur ; il vient de la douceur de I'Ame." 
 Rousseau called him " La plus belle plume du si^cle ; " 
 Mirabeau said, " Le plus grand homme de son sifecle et de 
 bien d'autres ; " Voltaire first mocked and then praised him ; 
 and Diderot also eulogised. EufTon was first a man then 
 a zoologist, which seems to be the natural, though by no 
 means universally recognised, order of precedence, and we 
 have pleasant pictures of his handsome person, his magnifi- 
 cence, his diplomatic manners, and a splendid genius, which 
 he himself called " a supreme capacity for taking pains." 
 
 Buffon's culture was very wide. He had an early 
 training in mathematics, and translated Newton's Fluxions ; 
 he seems to have been familiar with the chemistry and 
 physics of his time ; he was curious about everything. 
 Before Laplace, he elaborated an hypothesis as to the origin 
 of the solar system ; before Hutton and Lyell, he realised 
 that causes like those now at work had in the long pasi. 
 sculptured the earth ; he had a special theory of heredity 
 not unlike Darwin's, and a by no means narrow theory of 
 evolution, in which he recognised the struggle for existence 
 and the elimination of the unfit, the influence of isolation 
 and of artificial selection, but especially the direct action of 
 food, climate, and other surrounding influences upon the 
 organism. It is generally allowed that there is in Bufibn's 
 writings something of that indefiniteness which often charac- 
 terises pioneer works, and a lack of depth not unnatural in 
 a survey so broad, but they exhibit some remarkable illustra- 
 tions of prophetic genius, and a lively appreciation of 
 nature. 
 
 It is probable that Bufibn's treatment of zoology gained 
 freedom because he wrote in French, having shaken oflF the 
 shackles which the prevalent custom of writing in Latin 
 imposed, and it cannot be doubted that his works did some- 
 thing to prepare the way for the future reception of the 
 
 \ h 
 
a88 The Study of Animal Life part iv 
 
 doctrine of descent He had a vivid feeling of the unity 
 of nature, throwing out hints in regard to the fundamental 
 similarity of different forms of matter, suggestmg that heat 
 and light are atomic movements, denying the existence of 
 hard-and-fast lines—" Le vivant et I'animd est une propn^t^ 
 physique de la mati^re !" protesting against crude distmctions 
 between plants and animals, and realising above all that 
 there is one great family of life. Naturalists had been 
 wandering up and down the valleys studying their charac- 
 teristic contours ; Buflfon took an eagle's flight and saw the 
 connected range of hills,—" I'enchainement des ^tres. 
 
 Erasmus Darwin (1731-1802), grandfather to the 
 author of the Origin of Species, was a large-hearted, thought- 
 ful physician, whose life was as full of pleasant eccentricities, 
 as his stammc rjng speech of wit, and his books of wisdom. 
 We have pleasant pictures of the philosophical physician 
 of Lichfield and Derby, driving about in a whimsical un- 
 stable carriage of his own contrivance, prescribing abundant 
 food and cowslip wine, rich in good health and generosity. 
 Comparing his writings with those of Buffon, an acquaint- 
 ance with which he evidently possessed, we find more 
 emotion and intensity, more of the poet and none of the 
 diplomatist He approached the study of organic life on 
 the one hand as a physician and physiologist, on the other 
 hand as a gardener and lover of plants ; and, apart from 
 poetic conceits, his writings are characterised by a direct- 
 ness and simplicity of treatment which we often describe as 
 " common-sense " . , • 1 
 
 He beUeved that the different kinds of plants and animals 
 were descended from a few ancestral forms, or possibly 
 from one and the same kind of "vital filament," and tnat 
 evolutionary change was mainly due to the exertious which 
 organisms made to preserve or better themselves. He 
 showed that animals were driven to exertion by hunger, by 
 love and by the need of protection, and explained theit 
 progress as the result of their endeavours. Buffon under- 
 rated the transfon.iing influence of action, and laid emphasis 
 upon the direct influence of surroundings ; Erasmus Darwin 
 emphasised function, and regarded the influence of the 
 
CH. XVIII The El lution of Evolution Theories 289 
 
 environment as for the most part indirect Let us quote 
 some conclusions from his Zoonomia (1794): 
 
 "Owing to the imperfection of language the offspring is termed 
 a new animal, but is in truth a branch or elongation of the 
 parent, since a part of the embyron animal is, or was," a part of the 
 parent, and therefore in strict language cannot be said to be entirely 
 new at the time of its production; and therefore it may retain 
 some of the habits of the parent-system." 
 
 "The fetus or embryon is formed by apposition of new parts, 
 and not by the distention of a primordial nest of germs included 
 one withm another like the cups of a conjuror." 
 
 "From their first rudiment, or primordium, to the termination 
 ot tneir lives, all animals undergo perpetual transformations ; which 
 are in part produced by their own exertions in consequence of 
 their desires and aversions, of their pleasures and their pains, or 
 of irritations, or of associations ; and many of these acquired forms 
 or propensities are transmitted to their posterity." 
 .1. "^"' ^"^ w^'<^f are supplied to animals in sufficient profusion, 
 the three great objects of desire, which have changed the forms of 
 many animals by their exertions to gratify them, are those of lust, 
 hunger, and security." 
 
 " This idea of the gradual generation of all ti,ings seems to hi/e 
 been as familiar to the ancient philosophers r the modern ones, 
 and to have given rise to the beautiful hieroy.yphic figure of the 
 rpwToy if6y, or first great egg, produced by night, that is, whose 
 ongrn IS involved in obscurity, and animated by ip^s, that is, by 
 Divine Love ; from whence proceeded all things which exist." 
 
 On Lamarck (i 744-1 829) success did not shine as it 
 did on the Comte de liuffon or on Dr. Erasmus Darwin. 
 His life was often so hard that we wonder he did not say 
 more about the struggle for existe ice. As a youth of six- 
 teen, destined for the Church, ' rides off on a bad horse 
 to jo... the French r.rmy, then fighting in Germany, and 
 bravely wms promotion on his first battle-field. After the 
 peace he is sent into garrison at Toulon and Monaco, 
 where his scientific enthusiasm is awakened by the Flora 
 of the south. Retiring in weakened health from military 
 service, he earns his living in a Parisian banker's office, 
 devotes his spare energies to the study of plants, and 
 writes a F/ore frafiiaise in three volumes, the publica- 
 Hon of which (1778) at the royal press was secured by 
 
 U 
 
 ill' ^ 
 
 f 
 
 I: 
 
 V 
 
 M 
 
 hi 
 
 * 
 
 Ml 
 
 it i 
 
 I 
 
 II! 
 
ago The Study of Animal Life part iv 
 
 Buffon's patronage. As tutor to Buffon's son, he travels 
 in Europe and visits some of the famous gardens, and we 
 can hardly doubt that Buflfon influenced Lamarck m many 
 wavs After much toil as a literary hack and scientific 
 drudge he is elected to what we would now call a Professor- 
 ship of Invertebrate Zoology, a department at that time 
 chaotic. In 1794 he began his lectures and each year 
 brought increased order to his classification and museum 
 alike At the same time, however, he was liftmg his anchors 
 from the orthodox moorings, relinquishing his behef in the 
 constancy of species, following (we know not with what 
 consciousness) the current which had already borne Buffon 
 and Erasmus Darwin to evolutionary prospects. In i8o. 
 he published Researches on the Organisation of Uvtng 
 Boies', in 1809 a Philosophie Zoologique , from 1816- 
 1 822 his Natural History of Invertebrate Animals, a large 
 work in seven volumes, part of which the blind na -.list 
 dictated to his daughter. Busy as he must have beea wuh 
 zoology, his restless intellect found time to speculaie-.t 
 must be confessed to little purpose-on chemical, physical 
 and meteorological subjects. Thus he ran an unsuccessful 
 tilt against Lavoisier's chemistry, and published for ten 
 years annual forecasts of the weathe^ which seem to have 
 been almost always wrong. Nor d.d Lamarck add to his 
 reputation by a theory of Hydrogeology, and his scientific 
 Sends who were loyal specialists shrugged their shoulders 
 more and more over bis intellectual knight-errantry. 
 
 . 1 J- J !.:_ 1™**... voarc his tr 
 
 Poverty 
 
 lore over ma ini*,..*,..*— o- - • 
 
 roveny also clouded his later years, his treasured 
 collections had to be sold for bread, his theories made no 
 headway, his merits were unrecognised Yet now a La- 
 marckian school is strong in France and ,n Amei.ca, and 
 even those who deny his doctrines admit that he was one 
 
 of the bravest of pioneers. „ u 1 c-,v>. 
 
 Of Lamarck's Philosophie Zoologtque, Haeckel sa>s, 
 « This admirable work is the first connected and thoroughly 
 logical exposition of the theory of descent." And again he 
 savs "To Lamarck will remain the immonal glory 
 havi'ng for the first time established the theory of descent 
 as an independent scientific generalisation of the first order, 
 
cn.xvni The Evolution of Evolution Theories 291 
 
 as the foundation of the whole of Biology." But the verdict 
 of the majority of naturalists in regard to Lamarck's doctrines 
 has not tended to be eulogistic Cuvier, in his iloge de M. 
 i'^T^ ^^^'^^'■ed before the French Academy in 1832' 
 said, "A system resting on such foundations may amuse 
 the imagmafon of a noet, etc., ... but it cannot for a 
 moment bear the examination of any one who has dissected 
 the hand, the viscera, or even a feather." The great Cuvier 
 was a formidable obscurantist. 
 
 But let us hear Lamarck himself: 
 
 ducl'SfZ '"■^" ^' """'^ P'°'"^' gradually, and could not pre 
 duce all the ammals at once. At first she formed only the simplest 
 and passed from these on to the most complex " amplest, 
 
 \SJ^^ ^™"' °^ f"'^"^'^ 'P^''"' "« "°' so <^onstant and unvary- 
 mg as IS commonly supposed. Spontaneous generation staS 
 each particular series, but thereafter one form givi rise to aulcher 
 In hfe we should see, as it were, a ramified continuity if ierta'n 
 species had not been lost." """.luuy u cenam 
 
 "The operations of Nature in the production of animals show 
 Int.l Tr ':." P"""""^ '"'^ predominant cause which gves to 
 amma hfe the power of progressive organisation, of gfadual V 
 comphcating and perfecting not only the organism as a whole bu^ 
 each system of organs in particular." ' 
 
 incrla^^'lhf Ti ^'^^ ^) ''' '"^"^'"' P°^" *^"^^ continually to 
 mcrease the volume of every living body, and to extend the 
 d.mensions of its parts up to a self-regulated limit, 
 resultf fi:om fhJ^J^" Production of a new organ in an animal body 
 Se itseTfe \n l"r"'"'' °^ '°'^' "^^ "^'^^ ^'^''^h continues to 
 
 ;• rAini Law. The development of organs and their power of 
 
 Fourth Law. All that has been acquired, begun, or -handed in 
 the structure of individuals during ,he course ofShi life f pre 
 
 wnich spring f om tho.se which have experienced the changes." 
 
 These four aws I have cited from limarck's HistoinNXrelle 
 nd'Lt;'?';r'.h'^ir'"'^*'''"^''^^ ^« in^lste^tnt; 
 
 'It 
 
 
 iii 
 
 II 
 
292 
 
 The Study of Animal Life 
 
 PART rv 
 
 creature by iU own efforts '"■" ""'!'%,„,„„„en,, due to use or 
 
 descended." , 
 
 The historian of the evolution of evolution theones 
 .ho^d taije account of many w^^rsb^^^^^^^^ Buff „, 
 
 S:n5. flugh.'U'^^Vie'r. *e fellow-worker of his you^h 
 Udmn' ; bloT^S But we must now recogn.se the work 
 
 Siw sill laboratory, his yellow-back novels h,s «^uff. 
 
 ^isi%rrn-r^s^t?;ri^ - -^^^^^^^^ 
 »?rr.rrc-»rrerr. 
 
CH. XVIII The Evolution of Evolution Theories 293 
 
 hood. We read the curve of his moods, steadier than that 
 of most men, without any climax of speculative ecstasy, free 
 from any fall to a depth of pessimism. We hear his own 
 sincere voice in his simple autobiography, and even more 
 clearly perhaps in the unconstrainedness of his abundant 
 letters. There was seldom a great life so devoid of little- 
 ness, seldom a record of thought so free from subtlety. 
 There seems to be almost nothing hid which we could 
 wish revealed, or uncovered which we could wish hidden. 
 Darwin's life was as open as the country around his her- 
 mitage. 
 
 Marcus Aurelius gives thanks in his roll of blessings 
 that he had not been suffered to keep quails ; so Darwin, in 
 recounting his mercies, does not forget to be grateful for 
 having been preserved from the snare of becoming a 
 specialist. From a more partial point of view, we have 
 reason to be thankful that he became a specialist, not in 
 one department, but in many. As a disciple of Linnsus, 
 he described the species of barnacles in one volume, and 
 followed in the steps of Cuvier in anatomising them in 
 another. Of tissues and cells he knew less, being as 
 regards these items an antediluvian, and outside the guild 
 of those who dexterously wield the razor, and in so doing 
 observe the horoscope of the organism. Of protoplasm, 
 in regard to which modern biology says so much and knows 
 so little, he .as not ignorant, for did he not study the 
 marvels of the state known as " aggregation " ? 
 
 But it is not for special research that men are most 
 grateful to Darwin. Undoubtedly, if c^ear insight into the 
 world around us be esteemed in itself of value, the author 
 of Insectivorous Plants, The Fertilisation of Orchids The 
 Movements of Plants, The Origin of Coral Reefs, The 
 Formation of Vegetable Mould, etc., runs no risk of being 
 forgotten. But though our possession of these results swells 
 the meed of praise, we usually regard them as outside of 
 Darwin's real work, which, as every one knows was his 
 contribution to the theory of organic life. 
 
 This contribution was threefold —(a) He placed the 
 theory of descent on a sure basis ; {b) he shed the light 
 
 rU ; 
 
 ^t ; 
 
 II 
 
 5 s; 
 
 M 
 
,54 The Study of Animal Lift fart iv 
 
 of this doctrine on various groups of i^'^'^^ '' ""^ ^'^ *" 
 l^^^y^^^''V">^'^\^'^^''^tZT:\c^ Is to us 
 
 sin«^u:ro;n«£^^^ 
 
 caption was no ne» ""^^^f rKavel to many. He did 
 L"-o. J^nt';h:e"s2b^i:kea."'Hf convened natu,a>ists to 
 
 A }rL the thfory of development out of preceding 
 
 hfe, It was eage ^^.^ ^^^^^^^ ^^^ Aew 
 
 itrthinUe. and '^^^^^^'^^ T£^ 
 how the conception to» ^"^ fven found expression In 
 ro*e: o-flSlra^.tdJ^sC-Uan ofte^n-tepeate. 
 
 "«r,":rSd'rtx^;t«:e:"'"- 
 
N 
 
 CH. xvm The Evolution of Evolution Theories 295 
 
 satisfied ; he advanced to one of his own — to the theory of 
 natural selection, the characteristic feature of Darwinism. 
 
 Let us state this theory, which was foreseen by Matthew, 
 Wells, Naudin, and others, was developed simultaneously 
 by Darwin and by Alfred Russel Wallace, and has attained 
 remarkable acceptance throughout the world. 
 
 All plants and animals produce offspring which, though 
 like their parents, usually differ from them in possessing 
 some new features or variations. These are of more or 
 less obscure origin, and are often termed fortuitous or in- 
 definite. But throughout nature there is a struggle for 
 existence in which only a small percentage of the organisms 
 bom survive to maturity or reproduction. Those which 
 survive do so because of the individual peculiarities which 
 have made them in some way more fit to survive than their 
 fellows. Moreover the favourable va-iation possessed by 
 the survivors is handed on as an inheritance to their oflT- 
 spring, and tends to be intensified when the new generation 
 is bred from parents both possessing the happily advan- 
 tageous character. This natural fostering of advantageous 
 variations and natural elimination of those less fit, explain 
 the general modification and adaptation of species, as well 
 as the general progress from simpler to higher forms of 
 life. 
 
 This theory that favourable variations may be fostered 
 and accumulated by natural selection till useful adaptations 
 result is the chief characteristic of Darwinism. Of this 
 theory Prof Ray Lankester says : " Darwin by his discovery 
 of the mechanical principle of organic evolution, namely, the 
 survival of the fittest in the struggle for existence, completed 
 the doctrine of evolution, and gave it that unity and au- 
 thority which was necessary in order that it should reform 
 the whole range of philosophy." And again he says : '• The 
 history of zoology as a science is therefore the history of 
 the great biological doctrine of the evolution of living things 
 by the natural selection of varieties in the struggle for exist- 
 ence, — since that doctrine is the one medium whereby all 
 the phenomena of life, whether of form or function, are 
 rendered capable of explanation by the laws of physics and 
 
 
 
 1' 
 
 II- 
 
 to 
 
296 The Study of Animal Life partita 
 
 chemistry, and so made the subject-matter of a true science 
 or study of causes." I have quoted these two sentences 
 because they illustrate better than any others that I have 
 seen to what exaggeration enthusiasm for a theory will lead 
 a strong intellect. But listen to a few sentences from 
 Samuel Butler, which I quote because they well illustrate 
 that the critics of Darwinism may also be extreme, and m 
 the hope that the contrast may be sufficiently interesting to 
 induce you to think out the question for yourselves. 
 
 "Buffon planted, Erasmus Darwin and Lamarck watered, 
 but it was Mr. Darwin who said 'That fruit is ripe,' and 
 shook it into his lap Darwin was heir to a dis- 
 credited truth, and left behind him an accredited fallacy 
 Do animals and plants grow into conformity with 
 'their surroundings because they and their fathers and 
 mothers take pains, or because their uncles and aunts go 
 away? ... The theory that luck is the mam means of 
 organic modification is the most absolute denial of God 
 which it is possible for the human mind to conceive. . . . 
 7 Daxwin'8 FeUow-workers.— But we must bring this 
 historical sketch to a close by referring to four of the more 
 prominent of Darwin's fellow- workers— Wallace, Spencer, 
 
 Haeckel, and Huxley. 
 
 ALFRED RUSSEL WALLACE, contemporary with Darwin, 
 not only in years, but in emphasising the truth of evolution- 
 ary conceptions, and in recognising the fact of natural 
 selection, has been justly called the Nestor of Biolo^. No 
 one will be slow to appreciate the splendid unselfishness 
 with which he has for thirty years sunk himself ^ the Dar- 
 winian theory, or the scientific disinterestedness which leads 
 him from the very title of his last work^ to its close, co 
 say so little-perhaps too little— of the important part 
 which he has played in evolving the doctrine. " It was 
 Romanes says, «'in the highest degree dramatic that the 
 great idea of natural selection should have occurred inde- 
 pendently and in precisely the same form to two working 
 naturaUsts ; that these naturalists should have been country- 
 men ; that they should have agreed to publish their theory 
 1 Darwinism, London, 1889. 
 
CH. xviii The Evolution of Evolution Theories 297 
 
 on the same day ; and last, but not least, that, through the 
 many years of strife and turmoil which followed, these two 
 English naturalists consistently maintained towards each 
 other such feelings of magnanimous recognition that it is 
 hard to say whether we should most admire the intellectual 
 or the moral qualities which, in relation to their common 
 labours, they have displayed," 
 
 Mr. Wallace is a naturalist in the old and truest sense, 
 rich in a world-wide experience of animal life, at once 
 specialist and generaliser, a humanist thinker and a social 
 striver, and a man of science who realises the spiritual 
 aspect of the world. 
 
 He believes in the " overwhelming importance of natural 
 selection over all other agencies in the production of new 
 species," differs from Darwin in regard to sexual selection, 
 to which he attaches little importance, and agrees with 
 Weismann in regard to the non- inheritance of acquired 
 characters. 
 
 But the exceptional feature in Wallace's scientific philo- 
 sophy is his contention that the higher characteristics of 
 man are due to a special evolution hardly distinguishable 
 from creation. 
 
 Wallace finds their only explanation in the hypothesis 
 of "a spiritual essence or nature, capable of progressive 
 development under favourable conditions." 
 
 Herbert Spencer must surely have been an evolution- 
 ist by birth ; there was no hesitation even in the first strides 
 he took with the evolulion-torch uplifted. A ponderer on 
 the nature of things, and the possessor of encyclopaedic 
 knowledge, he grasped what was good in Lamarck's work, 
 and as early as 1852 published a plea for the theory of 
 organic evolution which is still remarkable in its strength 
 and clearness. The work of Darwin supplied corroboration 
 and fresh material, and in the Principles of Biology (i 863-66) 
 the theory of organic evolution first found philosophic, as 
 distinguished from merely scientific expression. To Spencer 
 we owe the familiar phrase "the survival of the fittest," 
 and that at first sight puzzling generalisation, " Evolution is 
 an integration of matter and concomitant dissipation of 
 
 
 ' 11 
 
 ^ 
 
 , 
 
 II 
 
298 
 
 The Study of Animal Life part iv 
 
 motion, during which the matter passes from an indefinite 
 incoherent homogeneity to a definite coherent heterogeneity, 
 and during which the retained motion (energy) undergoes a 
 parallel transformation." He has given his life to establish- 
 ing this generalisation, and applying it to physical, biological, 
 psychological, and social facts. As to the factors in organic 
 evolution, he emphasises the change-producing influences of 
 environment and function, and recognises that natural selec- 
 tion has been a very important means of progress. 
 
 Ernst Haeckel, Professor of Zoology in Jena, and 
 author of a great series of monographs Radiolarians, 
 Sponges, Jellyfish, etc., may be well called the Darwin of 
 Germany. He has devoted his life to applying the doctrme 
 of descent, and to making it current coin among the people. 
 Owing much of his motive to Darwin, he stood for a time 
 almost alone in Germany as the champion of a heresy. 
 Before the publication of Darwin's Descent of Man, Haeckel 
 wa? the only naturalist who had recognised the import of 
 sexual selection ; and of his Natural History of Creation 
 Darwin writes : " If this work had appeared before my 
 essay had been written, I should probably never have com- 
 pleted it." His most important expository works are the 
 above-mentioned Naturliche ScKopfungsgeschichte (ist ed. 
 1868 ; 8th ed. 1889) ; and his Anthrcpor'-'ie {I'i^l %, trans- 
 lated as The Evolution ./ Man). These books are very 
 brilliantly written, though they offend many by their remorse- 
 less consistency, and by their impatience with theological 
 dogma and teleological interpretation. His greatest work, 
 however, is of a less popular character, namely, the Generellc 
 Morphologic (2 vols., Beriin, 1866), which in its reasoned 
 orderiiness and clear generalisations ranks beside Spencer's 
 Principles of Biology. 
 
 Huxley, by whose work the credit of British schools of 
 zoology has been for many years enhanced, was one of the first 
 to stand by Darwin, and to wield a sharp intellectual sword 
 in defence and attack. No one has fought for the doctrme 
 of descent in itself and in its consequences with more keen- 
 ness and success than the author of Man's Place in Nature 
 (1863), American Addresses, Lay Sermons, etc., and no one 
 
CH. xvin The Evolution of Evolution Theories 299 
 
 has championed the theory of natural selection with more 
 confident consistency or with more skilfully handled 
 weapons. 
 
 8. The Present State of Opinion.— As Wallace says in 
 the preface to his work on Darwinism^ " Descent with 
 modification is now universally accepted as the order of 
 nature in the organic world." But, while this is true, there 
 remains much uncertainty in regard to the way in which the 
 progressive ascent of life has come about, as to the mechan- 
 ism of the great nature-loom. The relaiive importance of 
 the various factors in evolution is very uncertain. ^ 
 
 The condition of evolution is variability, or the tendency 
 which animals have to change. The primary factors of 
 evolution are those which produce variations, which cause 
 organic inequilibrium. Darwin spoke of variations as 
 " fortuitous," " indefinite," " spontaneous," etc., and frankly 
 confessed that he could not explain how most of them arose. 
 
 Ultimately all variations in organisms must be due to 
 variations in their environment, that is to say, to changes in 
 the system of which organisms form a part But this is 
 only a general truism. 
 
 > All naturalists, however uncertain in regard to the factors in 
 evolution, accept the doctrine of descent — the general conception of 
 evolution— as a theory which has justified itself. It is not indeed so 
 demonstrable as is the doctrine of the conservation of energy, but it is 
 almost as confidently accepted, lew naturalists, however, have 
 attempted any philosophical justification of their belief This is strange, 
 since it should surely give pause to the dogmatic evolutionist to reflect 
 that his own theory has been evolved like other beliefs, that his 
 scientific demonstration of it rests upon assumptions which have also 
 been evolved, that the entire system of evolutionary thought must be a 
 phase in the development of opinion, that, in short, he cannot be 
 dogmatic without being self-contradictory. See A. J. Balfour's Defence 
 of Philosophic Doubt, pp. 260-274 (London, 1879). In regard to the 
 philosophical aspects of the doctrine of evolution see Prof. Knight's 
 essay on " Ethical Philosophy and Evolution" in \<\s Studies in Philo- 
 sophy and Literature (Lond. 1879), and, with additions, in Essays in 
 Philosophy (Boston and New York, 1890) ; Prof. St. George Mivart's 
 Contemporary Evolution (Lond. 1876) ; E. von Hartmann's Wahrheit 
 und Irrthum im Darwinismus ; an article by Prof. Tyndall on " Vir- 
 chow and Evolution" in Nineteenth Century, Nov. 1878 ; and articles 
 on " Evolution" by Huxley and Sully in Encyclopcedi^ Dritauri. :, 
 
 li 
 
 ^ 
 
 .11 U' 
 
 m 
 ill 
 
 I -if 
 
 i'l 
 
 K 
 
 i 
 
 f 
 ■» 
 
 jl j 
 
 iilll: 
 
30O The Study of Animal Life part iv 
 
 There are evidently three direct ways in which organic 
 changes may be produced: (i) From the nature of the 
 organism itself; i.e. from constitutional or germinal peculiar- 
 ities which are ultimately traceable to influences from 
 without ; (2) from changes in its functions or activity, in 
 other words, from use and disuse ; or (3) from the direct 
 influence of the external conditions of life — food, temperature, 
 moisture, etc. 
 
 Thus some naturalists follow Buffbn in emphasising the 
 moulding influence of the environment, or agree with 
 Lamarck in maintaining that change of function produces 
 change of structure. But at present the tide is against 
 these opinions, because of the widespread scepticism as to 
 the transmissibility of characters thus acquired. 
 
 Those who share this scepticism refer the origin of 
 variations to the nature of the organism, to the mingling 
 of the two different cells from which the individual life 
 begins, to the instability involved in the complexity of the 
 protoplasm, to the oscillating balance between vegetative 
 and reproductive processes, and so on. 
 
 One prevalent opinion regards vari- tions as arbitrary 
 sports in " a chapter of accidents," but according to the 
 views of a minority variations are for the most part definite 
 occurring in a few directions, fixed by the constitutional 
 bias of the organism. The minority are '« Topsian '| evolu- 
 tionists who believe that the modification of species has 
 taken place by cumulative growth, influ< need by function 
 and environment, and pruned by natural selection. To the 
 majority the theory that new species result from the action 
 of natural selection on numerous, spontaneous, indefinite 
 variations, is the " quintessence of Darwinism " and of truth. 
 Until we know much more about the primary factors 
 which di'-ectly cause variations it will not be possiole to 
 decide in regard to the precise scope of natural selection 
 and the other secondary factors which foster or accumulate, 
 thin or prune, which in short establish a new organic 
 equilibrium. The argument has been too much in regard 
 to possibilities, too little in regard f^ observed facts 0/ 
 variation. 
 
cH. XVIII The Evolution of Evolution Theories 301 
 
 The secondary factors of evolution niay be ranked under 
 two heads : — 
 
 I. Natural Selection, or the survival of the fittest in the 
 struggle for existence, and 2. Isolation, or the various means 
 by which species tend to be separated into sections which 
 do not inteiL'^ei 
 
 Natuiai selection i<; '\ phrase descriptive of the course of 
 nature, ( mV a survival of the tit and the elimination of the 
 unfit in li-e struggle fci existence. It involves on the one 
 hand the survivHi. /.•♦. the nutriti/e and reproductive success 
 of the variations fittest to survive in given conditions, and 
 on the other hand the destruction or elimination of forms 
 less fit. Suitable variations pay ; nature or natural selection 
 justifies and fosters them. Maternal sacrifice or cunning 
 cruelty, the milk of animal kindness or teeth strong to 
 rend, distribution in space or rate of reproduction, are all 
 affected by natural selection. But it is another thing to say 
 that all the adaptations and well-endowed species that we 
 know hav- been produr°d by the action of natural selection 
 on fortuitous, indefinite variations. This is what Samuel 
 Butler calls the '• accredited fallacy." 
 
 Secondly, there seem to be a great many ways by which 
 a species may be divided into two sections which do not 
 interbreed, and if this isolation be common it must help 
 greatly in divergent evolution. 
 
 Thus Romanes, who has been the chief exponent of the 
 importance of isolation, on which Gulick has also insisted, 
 says : " Without isolation, or the prevention of free inter- 
 crossing, organic evolution is in no case possiMe. It is 
 isolation that has been • the exclusive means of modifica- 
 tion,* or more correctly, the universal condition to it. 
 Heredity and variability being given, the whole theory of 
 organic evolution becomes a theory of the causes and con- 
 ditions which lead to isolation." 
 
 
 I. 
 I • 
 
 \\- 
 
 ( • 
 
 •Ss- 
 ?! 
 
 ^^ 
 
 i 
 
 III 
 
 I 
 
$oi 
 
 The Study of Animal Life part iv 
 
 SUMMARY OF EVOLUTION THEORIES. 
 
 hi 
 
 o 
 
 e 
 
 iS 
 o 
 
 I 
 
 g 
 
 I Variations all ultimately due to External Influences. 
 
 Direct 
 action of the 
 environment 
 produces 
 environ- 
 mental 
 variations, 
 
 wh ich 
 if trans;missible, 
 
 Organismal, 
 
 constitutional, 
 
 congenital, 
 
 or germinal 
 
 variations 
 
 may be either 
 
 definite or indefinite. 
 
 Use and 
 disuse and 
 
 chanf^e 
 
 of function 
 
 produce 
 
 functional 
 
 variations 
 
 (certainly 
 transmis- 
 sible). 
 
 may 
 accumulate 
 as 
 environ- 
 mental 
 modifications 
 of 
 species. 
 
 All cases 
 
 By the 
 
 persistence 
 
 of the original 
 
 editions 
 
 iheso may 
 
 grow into 
 
 new 
 
 species. 
 
 By natural 
 
 selection in 
 
 the --truggle 
 
 for existence 
 
 these may 
 
 give rise to 
 
 new 
 
 species. 
 
 wh':ich, 
 if transimissible. 
 
 B' 
 
 o 
 
 — ^ 
 
 < 
 
 may 
 
 be aflfectied by 
 
 may 
 accumulate 
 
 as 
 functional 
 modi- 
 fications 
 
 of 
 species. 
 
 "isolation." 
 
 02_ 
 
 5' 
 
 o 
 
 •-\ 
 
 The process of natural selection will affect all cases, but i» 
 less essential for those marked • . 
 
CHAPTER XIX 
 
 THE INFLUENCE OF HABITS AND SURROUNDINGS 
 
 I. The Influence of Function — 2. The Influen,. of Surroundings — 
 3, Our own Environment 
 
 I. The Influence of Fnnction. — A skilled observer can 
 often discern a man's occupation from his physiognomy, 
 his shoulders, or his hands. In some unhealthy occupa- 
 tions the death-rate is three times that in others. Disuse 
 of such organs as muscles tends to their degeneration, for 
 the nerves which control them lose their tone and the 
 circulation of blood is affected ; while on the other hand 
 increased exercise is within certain limits associated with 
 increased development. A force de forger on devient 
 forgeron. 
 
 If we knew more about animals we might be able to cite 
 many cases in which change cf function produced change of 
 structure, but there are few careful observations bearing on 
 this questior. 
 
 Even if we could gather many illustrations of the 
 influence of use and disuse on individual animals, we should 
 still have to find out whether the precise characters thus 
 acquired by individuals were transmissible to the offspring, 
 or whether any secondary effects of the acquired characters 
 were transmissible, or whether these changes had no effect 
 upon succeeding generations. As there are few facts to argue 
 fhsm, the answers given to these questio*^'- are not reliable. 
 
 It is easy to find hundreds of cases in which the constant 
 
 j p 
 
 ■■ f 
 
 
 I pi 
 
 Mi III 
 
 \ 1 
 
 f^ 
 
304 The Study of Animal Life paxt iv 
 
 characters of animals may be hypothetically interpreted as 
 the result of use or disuse. Is the torpedo ' shape of 
 swift swimmers due to their rapid motic nrough the 
 water, do burrowing animals necessarily become worm-like, 
 has the giraffe lengthened its neck by stretching it, have 
 hoofs been developed by running on hard ground, are horns 
 responses to butting, are diverse shapes of teeth the results 
 of chewing diverse kinds of food, are cave-animals blmd 
 because they have ceased to use their eyes, are snails lop- 
 sided because the shell has fallen to one side, is the 
 asymmetry in the head of flat fishes due to the efforts made 
 by the ancestral fish to use its lower eye after it had formed 
 the habit of lying flat on the bottom, is the woodpecker's 
 long tongue the result of continuous probing into holes, are 
 webbed feet due to swimming efforts, has the food-canal m 
 vegetarian anin.als been mechanically lengthened, do the 
 wing bones and muscles of the domesticated duck compare 
 unfavourably with those of the wild duck because the habi* 
 of sustained flight has been lost by the former ? 
 
 But these interpretations have not been venfied ; they 
 are only probable. " It is infinitely easy," Semper says, 
 «' to form a fanciful idea as to how this or that fact may be 
 hypothetically explained, and very little trouble is needed to 
 imagine some process by which hypothetical fundamental 
 causes— equally fanciful— may have led to the result which 
 has been actually observed. But when we try to prove by 
 experiment that this imaginary process of development is 
 indeed the true and inevitable one, much time and laborious 
 research are indispensable, or we find ourselves wrecked on 
 insurmountable difficulties." 
 
 Not a few naturalists believe in the inherited effects 
 of functional change mainly because the theory is simple 
 and logically sufficient. If use and disuse alter the 
 structure of individuals, if the results are transmitted and 
 accumulate in similar conditions for generations, we require 
 no other explanation of many structures. 
 
 The reasons why not a few naturalists disbeheve m tne 
 inherited effects of functional change are (i) that definite 
 proof is wanting, (a) that it is difficult to understand how 
 
CH. XIX Influence of Habits and Surroundings 305 
 
 changes produced in the body by use or disuse can be 
 transmitted to the offspring, (3) that the theory of the 
 accumulation of (unexplained) favourable variations in the 
 course of natural selection seems logically sufficient. I 
 should suspend judgment, because it is unprofitable to argue 
 when ascertained facts are few. 
 
 But if you like to argue about probabilities, the following 
 considerations may be suggestive : — 
 
 The natural powers of animals — h rses, dogs, birds, and 
 others — can be improved by training and education, and 
 animals can be taught tricks more or less new to them, but 
 we have no precise information as to any changes of 
 structure associated with these acquirements. 
 
 Individual animals are sometimes demonstrably affected 
 by use or disuse. Thus Packard cites a few cases in which 
 some animals — usually with normal eyes — have had these 
 affected by disuse and darkness ; he instances the variations 
 in the eyes of a Myriapod and an Insect living in partial 
 daylight near the entrance of caves, the change in the eyes 
 of the common Crustacean Gammarus pulex after confine- 
 ment in darkness, the fact that the eyes of some other 
 Crustaceans in a lake were smaller the deeper the habitat. 
 
 There are many more or less blind animals, and Packard 
 says " no animal or series of generations of animals, wholly 
 or in part, can lose the organs of vision unless there is some 
 appreciable physical cause for it." If so, it is probable that 
 the appreciable physical cause has been a direct factor in 
 producing the blindness. 
 
 Not a few young animals have structures, such as eyes 
 and legs, which are not used and soon disrippear in adult 
 life. Thus the little crab Pinnotheres^ which lives inside 
 bivalves and sea -cucumbers, keeps its eyes until it has 
 established itself within its host. Then they are completely 
 covered over and degenerate. The same is true of many 
 internal parasites, and Semper concludes that "we must 
 refer the loss of sight to disuse of the organ." Perhaps the 
 same is true of some blind cave-animals, in which the eyes 
 are less degenerate in the young, and of the mole, whose 
 embryos have between the eyes and the brain normal optic 
 
 f Si 
 III 
 
3o6 The Study of Animal Life part iv 
 
 nerves which usually degenerate in each individual life- 
 
 ™The theory that many structures in animals are due to 
 the inherited results of use and disuse has this advantage, 
 that it suggests a primary cause of change, whereas the 
 other theory assumes the occurrence of favourable variations 
 and proceeds to show how they might be accumulated m 
 the course of natural selection, that is to say by a secondary 
 
 factor in evolution. . , j- .• . 
 
 When we find in a large number of entirely distinct 
 forms that the same habit of life is associated with the same 
 peculiarities, there is a likelihood that the habit is a direct 
 factor in evolving these. Thus sluggish and sedentary 
 animals in many different classes tend to develop skeletons 
 of lime, as in sponges, corals, sedentary worms, lamp-shells, 
 Echinoderms, barnacles, molluscs. Professor Lang has re- 
 cently made a careful study of sedentary creatures, and this 
 result at least is certain that the same peculiarity often occurs 
 in many different types with little in common except that 
 they are sedentary. But till one can show that sedentary life 
 necessarily involves for instance a skeleton of lime or some- 
 thing equivalent, we are still dealing only with probabilities. 
 2 The Influence of Surroundings.— In ancient times 
 men saw the threads of their life passing through the hands 
 of three sister-fates-of one who held the distaff, of another 
 who offered flowers, and of a third who bore the abhorred 
 shears of death. In Norseland the young child was visited by 
 chree sister Noms, who brought characteristic gifts of past 
 present, and future, which ruled the life as surely as did 
 the hands of the three Fates. So too in days of scientihc 
 illumination, we think of the dread three, but, clothing our 
 thoughts in other words, speak of life as determined by the 
 organism's legacy or inheritance, by force of habit or 
 function, and by the influences of external conditions or 
 environment. What the living orgrnism is to begin with 
 what it does or does not in the course of its life, and what 
 surrounding influences play upon it, -these are the three 
 Fates, the three Noms, the three Factors of Life. Organ- 
 ism, function, and environment are the $»des of the Die- 
 
B 
 
 I 
 
 CH. XIX Influence of Habits and Surroundings 307 
 
 logical prism. Thus we try to analyse the light of life. But 
 inheritance in its widest sense is only another name for the 
 organism itself, and function is simply the organism's activity. 
 The organism is real ; the environment is real, in it we live 
 and move ; function consists of action and reaction between 
 these two realities. Yet the capital which the organism 
 has to begin with is very important ; conduct has some 
 relation to character, and function to structure ; the sur- 
 roundinto — the dew of earth and the sunshine of heaven 
 — silently mould the individual destiny. 
 
 A living animal is almost always either acting upon its 
 surroundings or being acted upon by them, and life is the 
 relation between two variables— a changeful organism and 
 a changeful environment. And since animals do not and 
 cannot live in vacuoy they should be thought of in relation 
 to their surroundings. You may kill the body and cut it to 
 pieces, and the result may be interesting, but you have lost 
 the animal just as you lose a picture if you separate figure 
 from figure, and all from the associated landscape or interior. 
 The three Fates are sisters, they are thoroughly intelligible 
 only as a Trinity. 
 
 The most certain of all the relations between an organism 
 and its surroundings is the most difficult to express. We 
 see a small whirlpool on a river, remaining for days or 
 weeks apparently constant, with the water circling round 
 nnceasingly, bearing the same flotsam of leaves and twigs. 
 But though the eddy seems the same for many days, it is 
 always changing, currents are flowing in and out ; it is the 
 constancy of the stream and it: bed which produces the 
 apparent constancy of the whiripool. So, in some measure, 
 is it with an animal in relation to its surroundings. Streams 
 of matter and energy are continually passing in and out. 
 Though we cannot see it with our eyes, the organism is 
 indeed a whirlpool. It is ever being unmade and remade, 
 and owes much of its apparent constancy to the fact that 
 the conditions in which it lives— the curre.Us of its stream 
 — are within certain limits uniform. 
 
 But as we cannot understand the material aspects of an 
 animal's life without considering the streams of matter and 
 
 i . 
 
 iii _ 
 
3o8 The Study of Animal Life part tv 
 
 energy which pass in and out, neither can we understand 
 its higher life apart from its surroundings. 
 
 To attempt a natural history of isolated animals, whether 
 alive or dead, is like trying to study man apart from society. 
 For it is only when we know animals as they live and move 
 that we discover how clever, beautiful, and human they 
 are Thus Gilbert White's Selbome is a natural history ; and 
 therefore we began our studies with the natural life of 
 animals-their competition and helpfulness, their adaptations 
 to diverse kinds of haunts, their shifts and tricks, their 
 industries and their loves. 
 
 At present, however, we have to do with the relation 
 between external and internal changes. We must find ou 
 what the environment of an organism is, and what power . 
 has In a smithy we see a bar of hot iron bemg hammered 
 into useful form. Around a great anvil are four smiths 
 with their hammers. Each smites in his own fashion as 
 the bar passes under his grasp. The first hammer falls, 
 and while the bar is still quivering like a l.vmg thing u 
 receives another blow. This is repeated many times till the 
 thing of use is perfected. By force of smiting one becomes 
 a smith, and by dint of blows the bar of iron becomes 
 an anchor. So is it with the organism. In its youth 
 esoecially. it omes under the influence of nature s hammers ; 
 it may become fitter for life, or it may be battered out of 
 existence altogether. Let us try to analyse the various 
 environmental factors. 
 
 {a\ Pressures.— r\x%\. we may consider those lateral and 
 vertical pressures due to air or water currents and to 
 th" gentle but potent force of gravity. The shriek of the 
 w^nd as It pruSes the trees, the swish of the water as it 
 moulds the sponges and water-'eaves, illustrate the tunes o 
 those pressure-hammers. Under artificial pressure embryos 
 have been known to broaden ; even the division of the egg .s 
 affected by gravity ; water currents mould shells and corals. 
 The Influence of want of room must also be noticed, for by 
 artificial overcrowding naturalists have slowed the rate of 
 d^efopment and reared dwarf broods ; and the rate of 
 human mortality sometimes vanes with the sue of the 
 
H I 
 
 CH. XIX Influence of Habits and Surroundings 309 
 
 dwelling. It is difficult, however, to abstract the influence 
 of restricted space from associated abnormal conditions. 
 
 (J)) Chemical Influences. — Quieter, but more potent, are 
 the chemical influences which damp or fan the fire of life, 
 which corrode the skin or drug the system, which fatten or 
 starve, depress or stimulate. Along with these we must 
 include that most important factor — food. 
 
 When a lighted piece of tinder is placed in a vessel 
 full of oxygen it burns more actively. Similarly, super- 
 abundance of oxygen makes insects jump, makes the 
 simplest animals more agile, and causes the " phosphores- 
 cent " lights of luminous insects to glow more brightly ; 
 and young creatures usually develop more or less rapidly 
 according as the aeration is abundant or deficient. The 
 most active animals — birds and insects — live in the air and 
 have much air in their bodies ; sluggish animals often live 
 where oxygen is scarce ; changes in the quality of the 
 atmosphere may have been of importance in the historical 
 evolution of animals. Fresh air influences the pitch of 
 human life, and lung diseases increase in direct ratio to 
 the amount of crowded indoor labour in an area. 
 
 By keeping tadpoles in unnatural conditions the usual 
 duration of the gilled stage may be prolonged for two or three 
 years. The well-known story of the Axolotl and the Atnbly- 
 stoma is suggestive but not convincing of the influence of 
 surroundings. These two newt-like Amphibians differ slightly 
 from one another, in this especially that the Axolotl retains 
 its gills after it has developed lungs, while the Amblystoma 
 loses them. Both forms may reproduce, and they were 
 originally referred to different genera. But some Axolotls 
 which had been kept with scant water in the Jardin des 
 Plantes in Paris turned into the Amblystoma form ; the two 
 forms are different phases of the same animal. It was a 
 natural inference that the Axolotls were those which had 
 remained or had been kept in the water, the Amblystoma 
 forms were those which got ashore. But both kinds may 
 be found in the water of the same lake and the metamor- 
 phosis may take place in the water as well as on the shore. 
 For these and for other reasons this oft -told tale is not 
 
 I \ 
 
310 The Study of Animal Life part iv 
 
 cogent. In another part of this book I have given examples 
 of the state of lifelessness which drought induces in some 
 
 F;<;. 64.-AxoIotl (in the water) and Amblystoma (on the land). 
 
 simple animals, and from which returning moisture can 
 after many days recall them. 
 
 Changes may also be due to the chemical composition 
 of the medium, as was established by the experiments ot 
 
 p,(-, 6, —Side view of male Atlnnia saliiin (uulaiged). 
 (From Chambers's Kiicychp.) 
 
 Schmankewitsch on certain small Crustaceans. Aniong the 
 numerous species of the brine-shrimp ^;■Av,//.^ the mos 
 unlike are A. salina and A. milhausemt ; they difter m the 
 
CH. XIX Influence of Habits and Surroundings 311 
 
 shape and size of the tail and in the respiratory appendages 
 borne by the legs ; they are not found together, but live in 
 pools of different degrees of saltness. Now Schmankewitsch 
 took specimens of ^. salina »vhich live in the less salt water, 
 
 Fi(j. 66. — Tail-lobcs of Artciiiia saiiiia (to the left)and o( Arte/in'a titilhausetiii 
 (to the right) : between these four stages in the transformation of the one into 
 the other. (From Chambers's Encyclop. ; after Schmank.:witsch.) 
 
 11 
 
 F 
 
 added salt gradually to the medium in which they were 
 living, and in the course of generations turned them into 
 A. milhausenii. He also reversed the process by freshening 
 the water little by little. Moreover, he accustomed A. salina 
 to entirely fresh water, and then found that the form had 
 changed towards that of a related genus, Branchipus. This 
 last step has been adversely criticised, but it is allowed that 
 one species of brine-shrimp was changed into another. 
 
 Many interesting experiments have been made on the 
 effect of chemical reagents on cells, but these are perhaps 
 of most interest to the student of drugs. Still the fact that 
 the form of a cell and its predominant phase of activity 
 may be entirely changed in this way is important, especially 
 when we remember that it was in single cells that life first 
 began, and is now continued. Even Weismann agrees with 
 Spencer's conclusion that " the direct action of the medium 
 was \h& primordial factor of organic evolution."' 
 
 To Claude Bernard, the main proljJem of evolution 
 seemed to be concerned with variations in nutrition : 
 " L'evolution, c'est I'ensemble constant dc ces alternatives 
 dc la nutrition ; c'est la nutrition considerde dans sa 
 reality, embrassde d'un coup d'oeil ii travers le temps."' 
 John Hunter and others have shown how the walls of the 
 
 
 I: 
 
 It 
 
 li' 
 
 
3ia The Study of Animal Life part iv 
 
 stomach of gulls and other birds may be experimentally 
 altered by cliange of diet, and the same is seen in nature 
 when the Shetland gull changes from its summe.- diet of 
 grain to its winter diet of fish. The colours of birds' feathers, 
 as in canaries and parrots, are affected by their food. A 
 slight difference in the quantity and quality of food deter- 
 mines whether a bee -grub is to become a queen or a 
 worker, royal diet evolving the reproductive queen, sparser 
 less rich diet evolving the more active but unfertile worker. 
 Abundant food favours the production of female offspring, 
 while sparser food tends to develop males. Thus, in frogs, 
 the proportion of the sexes is normally not very far from 
 equal ; in three lots of tadpoles an average of 57 per hun- 
 dred became females, 43 males. But Yung has shown that 
 the nutrition of the tadpoles has a remarkable influence on 
 the sex of the adults. In a set of which one half kept in 
 natural conditions developed into 54 females to 46 males, 
 the other half fed with beef had 78 females to 22 males. 
 In a second set of which one half left to themselves 
 developed 61 females to 39 males, the other half, fed with 
 fish, had 81 females to 19 males. Finally, in a third set, 
 of which one half in natural conditions developed 56 females 
 to 44 males, the other half, to v xiich the especially nutritious 
 flesh of frogs was supplied, had no less than 92 females 
 
 to 8 males. 
 
 When food is abundant, assimilation active, and mcome 
 above expenditure, the animal grows, and at the limit of 
 growth in lower animals asexual multiplication occurs. 
 Checked nutrition, on the other hand, favours the higher 
 or sexual mode of multiplication. Thus the gardener 
 prunes the roots of a plant to get better flowers or repro- 
 ductive leaves. The plant-lice or Aphides, which infest 
 our pear-trees and rose-bushes, well illustrate the combined 
 influence of food and warmth. All through the summer, 
 when food is abundant and the warmth pleasant, the 
 Aphides enjoy prosperity, and multiply rapidly. For an 
 Aphis may bring forth young every few hours for days 
 together, so rapidly that if all the offspring of a mother 
 Aphis survived, and multiplied as she did, there would 
 
ill 
 
 CH. XIX Influence of Habits and Surroundings 313 
 
 in the course of a year be l. progenv which would weigh 
 down 500,000,000 stout men. \. i. all through the 
 summer these Aphides are wholly female, and therefore 
 wholly parthenogenetic ; no males occur. In autumn, how- 
 ever, when hard times set in, when food is scarcer, and the 
 weather colder, males are bom, parthenogenesis ceases, 
 ordinary sexual reproduction recurs. Moreover, if the 
 Aphides be kept in the artificial summer of a greenhouse, 
 as has been done for four years, the parthenogenesis con- 
 tinues without break, no males being bom to enjoy the 
 comforts of that environment. Periods of fasting occur 
 in the life-history of many animals, and these are very 
 momentous and progressive periods in the lives of some, 
 for the tadpole fasts before it becomes a frog, and the 
 chrysalis before it becomes a butterfly. Lack of food, how- 
 ever, may stunt development, as we see every day in the 
 streets of our towns. 
 
 if) Radiant Energy. — Of the forms of radiant energy 
 which play upon the organism, we need take account only 
 of heat and light, for of electrical and magnetic influence 
 the few strange facts that we know do not make us much 
 wiser. 
 
 We know that increased warmth hastens motion, the 
 development of embryos, and the advent of sexual maturity. 
 An Infusorian {Stylonichia) studied by Maupas was seen 
 to divide once a day at a temperature of 7°- 10° C, twice 
 at lo'-is", thrice at is'-ao", four times at 2o''-24°, five 
 times at 24°-27° C. At the last temperature one Infusorian 
 became in four days the ancestor of a million, in six days 
 of a billion, in seven days and a half of 100 billions, weigh- 
 ing 100 kilogrammes. By consummately patient experi- 
 ments, Dallinger was able to educate Monads which lived 
 normally at a temperature of 65° Fahr., until they could 
 flourish at 158° Fahr. 
 
 Cold has generally a reverse action, checking activity, 
 producing coma and Hfelessness, diminishing the rate of 
 development, tending to produce dwarf or larva-like forms. 
 The cold of winter acting through the nervous system 
 changes the colour of some animals, like Ross's lemn^ing, 
 
 d i 
 
 
 ^- i i 
 
 J k\ 
 
 ttVf 
 
 WA 
 
 % i 
 
314 Tlie Study of Animal Life part iv 
 
 to advantageous white. Not a few animals vary slightly 
 with the changing seasons. Thus many cases are known 
 where a butterfly produces in a year more than one brood, 
 
 (variety Telamouide^, to tl.e ri^ht I v; Nammer form (variety Marccllu.). 
 (From Chambers's Eucydop. \ after Weismann.) 
 
 of which the winter forms are so different from those born 
 in summer that they have often been described as different 
 spe-ics It is possible that this is a remmiscence of past 
 climatic changes, such as those of the Ice Ages, as the 
 
 Fig. 68.-Se.-isonal chnnse. <.f the hill in the puffin {rraU,XHln»rcik«)\ to the 
 left the -opting form, to the right the winter form, both .idult malen. (Altir 
 Dureau.) 
 
 result of which a species became split up into two varieties. 
 Thus Araschnia kvana and Araschnia prorsa are respect- 
 ively the winter and summer forms of one species. In the 
 
CH, XIX Influence of Habits and Surroundings 315 
 
 glacial epoch there was perhaps only A. levana^ the winter 
 form; the change of climate has perhaps evolved the 
 summer variety A. prorsa. Both Weismann and Edwards 
 have succeeded, by arti6cial cold, in making the pupse which 
 should become the summer A. prorsa develop into the winter 
 A. levana. Nor can we forget the seasonal moulting and 
 the subsequent change of the plumage in birds, so marked 
 in the case of the ptarmigan, which moults three times in 
 the year. In the puffins even the bill is moulted and 
 appears very difterent at dilTerent seasons. But in these 
 last cases the influence of environment must be very 
 indirect. 
 
 Light is very healthful, but it is not easy to explain its 
 precise influence. Our pulses beat faster when we go out 
 into the sunlight. Plants live in part on the radiant 
 energy of the sun, and perhaps some pigmented animals do 
 the same. Perhaps the hundreds of eyes which some mol- 
 luscs have are also useful in absorbing the light. It is also 
 possible that light has a direct influence on the formation of 
 some animal pigments, as it seems to have in the develop- 
 ment of chlorophyll. We know, from Poulton's experiments, 
 that the light reflected from coloured bodies influen s the 
 colouring of caterpillars and pupae, but this influence seems 
 to be subtle and indirect, operating through the nervous 
 system. It is also certain that living in darkness tends to 
 bleach some animals, and it is probable that the absence 
 of light stimulus has a directly injurious effect upon the 
 eyes of those animals which live in caves or other dark 
 places. But I have already explained why dogmatism in 
 regard to these cases should be avoided. 
 
 One case of the influence of light seems very instructive. 
 It is well known tha. flat fishes like flounders, plaice, and 
 soles lie or swim in adult life on one side. This lower side 
 is unpigmented ; the upper side bears black and yellow 
 pigment-containing cells. 
 
 One theory of the presence of pigment on the upper 
 side ai d its absence on the other is that the difference is 
 a protective adaptation evolved by the natural selection of 
 indefinite variations. But it is open to question whether the 
 
 1 1 
 
 If ■ 
 
 I . 
 
 ■' 
 
 i 
 
 f \ , 
 
 Ml 
 
3i6 The Study of Animal Life part iv 
 
 characteristic is so advantageously protective as is usually 
 imagined : thus the coloured upper side in soles is very 
 often covered with a layer of sand. Soles come out most 
 at night, most live at depths at which differences of colour 
 are probably indistinct. In shallower water the advantage 
 is likely to be greater, though the white under-side slightly 
 exposed as the fish rises from the bottom may attract atten- 
 tion disadvantageously. Moreover, if we find in a large 
 number of different animals that the side away from the 
 light is lighter than that which is exposed, and if we can 
 show that this has in many cases no protective advantage 
 whatever— and I believe that a few hours' observation will 
 convince you that both my assumptions are correct— then 
 there is a probability that the absence of light has a direct 
 influence on the absence of pigment. 
 
 But we are not left to vague probabilities ; Mr. J. T. 
 Cunningham has recently made the crucial experiment of 
 illuminating the under sides of young flounders. Out of 
 thirteen, whose undersides were thus illumined by a mirror 
 for about four months, only three failed to develop black 
 and yellow colour-cells on the skin of the under-sides. It 
 is therefore likely that the normal whiteness of the under- 
 sides is due in some way to the fact that in nature little light 
 can fall on them, for they are generally in contact with the 
 
 ground. - 
 
 (</) Animate Surroundings.— ^t have given a few 
 instances showing how mechanical or molar pressures, 
 chemical and nutritive influences, and the subtler physical 
 energies of heat and light, affect organisms. There is a 
 fourth set of environmental factors— the direct influence of 
 organism upon organism. In a previous chapter we spoke 
 of the indirect influences different kinds of organisms exert 
 on one another, and these are most important, but there are 
 also results of direct contact. 
 
 Much in the same way as insects produce galls on 
 plants, so sea- spiders {JPycnogonida) affect hydroids, a 
 polype deforms a sponge, a little worm {Mysostoma) makes 
 galls on Crinoids. Prof. Giard has described how certain 
 degenerate Crustaceans parasitic on crabs injuriouajy affect 
 
CH. XIX Influence of Habits and Surroundings 317 
 
 their hosts, and some internal parasites produce slight 
 modifications of structure. Interesting also are the shelters 
 or domatia of some plants, within which insects and mites 
 find homes. 
 
 We can speak more confidently about the influence of 
 surroundings than we could in regard to the influence of 
 use and disuse, because the ascertained facts are more 
 numerous. Those interested in the theoretical importance 
 of these facts should attend to the following considerations. 
 
 It is essential to distinguish between cases in which 
 we know that external conditions influence the organism 
 and those in which we think they may have done so. Thus 
 it is probable that the degeneracy and other peculiarities of 
 many parasites are results of external influence and of 
 feeding, and also in part of disuse, but we cannot state 
 this as a fact. 
 
 Most of the observations on the influence of external 
 conditions give us no information as to the transmissi- 
 bility of the results. It is not enough to know that a 
 peculiarity observed to occur in peculiar surroundings was 
 observed to recur in successive generations living in the 
 same surroundings. For (i) it might be an indefinite 
 variation — a sport due to some germinal peculiarity — 
 which happened to suit. In such a case it would be 
 transmissible, but it would not be a change due to the 
 environment. And (2) even when it has been proved that 
 the peculiarity is due to the direct influence of the environ- 
 ment, and observed to recur in successive generations, still 
 its transmissibility is not proven, for it may be hammered 
 on each successive generation as it was on the first. We 
 can say little about the transmissibility or evolutionary 
 importance of changes of structure due to surroundings 
 because most of the observations were made before the 
 scepticism as to the inheritance of acquired characters 
 became dominant. Only in a few cases, such as that of the 
 brine-shrimps, was the cumulative influence traced through 
 many generations. In dearth of facts we should not be 
 confident, but eager for experiment. 
 
 Surroundings may influence the organism in varying 
 
3i8 
 
 The Study of Animal Life part iv 
 
 ^'.egrees. There may be direct results, rapid parries after 
 thrusts, or the results may be indirect ; they may affect the 
 organism visibly in the course of one generation, or only 
 after several have passed. 
 
 Some animals are more susceptible and more plastic 
 than others. Young organisms, such as caterpillars and 
 tadpoles, are more completely in the grasp of their environ- 
 ment than are the adults. Thus Treviranus, who believed 
 very strongly in the influence of surroundings, distinguished 
 two periods of vita minima— in youth and in old age— 
 during which external conditions press heavily, from the 
 period of vita maxima— m adult life— when the organism 
 is more free. To some kinds of influence, e.g. mechanical 
 pressures, passive and sedentary organisms such as sponges, 
 corals, shell-fish, and plants, are more susceptible than are 
 those of active life. And it is during a period of quiescence 
 that surrounding colour tells on the sensitive caterpillars. 
 
 3. Our own Environment. — The human organism, like 
 any other, may be modified by its environment, for we 
 lead no charmed life. Those external influences which 
 touch body and mind are to us the more important, since 
 we have them to some extent within our own hands, and 
 because our lives are relatively long. Even if the changes 
 thus wrought upon parents are not transmissible, it is to 
 some extent possible for us to secure that our children grow 
 up open to influences known to be beneficial, sheltered from 
 forces known to be injurious. 
 
 As the influence of surroundings is especially potent on 
 young things— such as caterpillars and tadpoles— all care 
 should be taken of the young child's environment during 
 the earliest months and years, when the grip that externals 
 have is probably much greater than is imagined by those 
 who believe themselves emancipated from the tyranny of 
 the present.* 
 
 As passive organisms are more in the thrall of their 
 surroundings than are the more active, we feel the import- 
 ance of beauty in the home, that the organism may be 
 » Cf. Matthew Arnold's poem, ' ' The Future," and Walt Whitman's 
 •' AMim!latii»s." 
 
CH. XIX Influence of Habits and Surroundings 319 
 
 saturated with healthful influence during the periods in 
 which it is most susceptible. The efforts of Social Unions, 
 Kyrle Societies, Verschonerungs-Vereine, and the like, are 
 justified not only by their results,^ but by the biological 
 facts on which they more or less unconsciously depend. 
 There would be more progress and less invidious com- 
 parison of ameliorative schemes, if we realised more vividly 
 that the Fates are three. Though it is not easy to appre- 
 ciate the three sides of a prism at once, of what value is 
 liberty on an ash-heap, or equality in a hell, or fraternity 
 among an overpopulated community of weaklings ? Organ- 
 ism, function, and environment must evolve together, and 
 surely they shall. 
 
 Poets have often compared human beings to caterpillars ; 
 it may be that no improvement in constitutions, functions, 
 T surroundings w"" make us winged Psyches, yet it may be 
 possible for us to be ennobled like those creatures which in 
 gilded surroundings became golden. Surely art is warranted 
 by the results of science, as these in time may justify them- 
 selves in art. 
 
 > Ideally stated in Emerson's well-known poem of "Art." 
 
 I i 
 
 i \ 
 
 I 
 
 h 
 
 * 
 f ' 
 
 1 
 
CHAPTER XX 
 
 HEREDITY 
 
 I. The Facts of Heredity —%. Theories of Heredity: theological^ 
 metaphysical, mystical^ and the hypothesis of pangenesis — 
 3. The Modem Theory of Heredity—^. The Inheritance of 
 Acquired Characters — 5. Social and Ethical Aspects — 6. Social 
 Inheritance 
 
 We have spoken of the three Fates which were believed to 
 determine of what sort a life should be. With the decay 
 of poetic feeling, and in the light of common science, the 
 forms of the three sisters have faded. But they are realities 
 still, for men are thinking more and more vividly about the 
 factors of life, which to some are "powerful principles," 
 to others living and personal, to others unnameable. 
 Biologists speak of them as Heredity, Function, and En- 
 vironment : the capital with which a life begins, the 
 interest accruing from the investment of this in varied vital 
 activities, and the force of circumstances. But while it is 
 useful to think of Heredity, Function, and Environment as 
 the three fates, we must not mystify matters by talking as 
 if these were entities acting upon the organism. They 
 are simply aspects of the fact that the animal is bom and 
 lives. The inheritance is the organism itself, and heredity 
 is only a name for the relation between successive genera- 
 tions. Moreover, the function of an organism depends 
 upon the nature of the organism, and so does its suscep- 
 tibility to influences from without. 
 
 I would at present define heredity as the organic relation 
 
CHAP. XX 
 
 Heredity 
 
 3ai 
 
 between successive generations^ choosing this definition 
 because it is misleading to talk about "heredity" as a 
 "basal principle ia evolution," as - "great law," as a 
 "power," or as a "cause." When I call heredity a 
 " Fate," it is plain that I speak fancifully, but " principle " 
 and " law " are dangerous words to play with. We cannot 
 think of life without this organic relation between parents 
 and offspring, and had species been created instead of being 
 evolved there would still be heredity. 
 
 I. The Facts of Heredity. — An animal sometimes 
 arises as a bud from its parent, and in rare cases from an 
 egg which requires no fertilisation, but apart from these 
 exceptions, every animal develops from an egg-cell with 
 which a male-cell has united in an intimate way. The 
 egg-cell supphes most of the living matter, but the nucleus 
 of the fertilised egg-cell is formed in half from the nucleus 
 of the immature ovum, in half from the nucleus of the 
 spermatozoon. Let us emphasise this first fact that each 
 parent contributes the same amount of nuclear material to 
 the offspring, and that this nuclear stuff is very essential. 
 
 Another fact is more obvious, the offspring is very like 
 its kind. One of the first things that people say about an 
 infant is that it is like its father or its mother, and the 
 assertion does not arouse any surprise, although the truer 
 verdict that the infant is like any other of the same race is 
 received with contempt. But every one admits that " like 
 begets like." 
 
 This likeness between offspring and parent is often far 
 more than a general resemblance, for peculiar features and 
 minute idiosyncrasies are frequently reproduced. Yet one 
 must not assume that because a child twirls his thtimbs 
 in the same way as his father did the habit has been 
 inherited. For peculiar habits and structures may readily 
 reappear by imitation, or because the offspring grow up in 
 conditions similar to. those in which the parents lived. 
 
 Abnormal as well as normal characters, " natural " to 
 the parents, may reappear in their descendants, and the list 
 of weaknesses and malformations which maybe transmitted 
 is long and grim. But care is required to distinguish 
 
 Y 
 
 { i 
 
322 The Study of Animal Life part iv 
 
 between reappearartce due to inheritance and reappearance 
 due to similar conditions of life. 
 
 Then there is a strange series of facts showing that an 
 organism may reproduce characteristics which the parents 
 did not exhibit, but which were possessed by a grandparent 
 or remoter ancestor. Thus a lizard in growing a new 
 tail to replace .one that has been lost has been known to 
 grow one with scales like those of an ancestral species. To 
 find out a lizard'? nedigree, a wit suggests that we need only 
 pull off its tail. When such ancestral resemblance in ordi- 
 
 Fig. 6a.— Devonshire pony, showing the occasional occurrence of ancestral 
 stripes. (From Darwin.) 
 
 nary generation is very marked, we call it •' atavism " or 
 «« reversion," but of this there are many degrees, and 
 abnormal circumstances sometimes force reversion even 
 upon an organism with a normal inheritance. A boy 
 " takes after his grandfather " ; a horse occasionally exhibits 
 stripes like those of a wild ancestor ; a blue pigeon like the 
 primitive rock-dove sometimes turns up unexpectedly in a 
 pure breed ; or a cultivated flower reverts to the simpler 
 and more normal wild type. So children bom dunng 
 famine sometimes show reversions, and some types of 
 criminal and insane persons are to be thus regarded. 
 
CHAP. XX 
 
 Heredity 
 
 323 
 
 But every animal is usually a little different from its 
 parents, and except in cases of "identical twins" cannot be 
 mistaken for one of its fellow-offspring. The proverbial 
 " two peas " may be very unlike. Organisms are variable, 
 and this is natural, for life begins in the intimate 
 mingling of two units of living matter perhaps very dif- 
 ferent and certainly very complex. The relation between 
 successive generations is such that the offspring is like 
 its parents, but various causes producing change diminish 
 this likeness, so that we no longer say " like begets like," 
 but " like tends to beget like." 
 
 There are, I think, two other important facts in regard 
 to heredity, but both require discussion — the one because 
 some of the most authoritative naturalists deny it, the other 
 because it is difficult to understand. 
 
 I believe that some characters acquired by the parent as 
 the result of what it does, and as impacts from the surround- 
 ing conditions of life, are transmissible to the offspring. In 
 other words, some functional and environmental variations 
 in the body of the parents may be handed on to the 
 offspring. This is denied by Weismann and many others. 
 
 The other fact, which has been elucidated by Galton, 
 is that through successive generations there is a tendency 
 to sustain the average of the species, by the continual 
 approximation of exceptional forms towards a mean. 
 
 2. Theories of Heredity — historical retrospect. — 
 Theories of heredity, like those about many other facts, 
 have been formulated at different times in different kinds 
 of intellectual language — theological, metaphysical, and 
 scientific — and the words are often more at variance than 
 the ideas. 
 
 (a) Theological T/ieories. — It was an old idea, that the 
 germ of a new human life was possessed by a spirit, some- 
 times of second-hand origin, having previously belonged to 
 some ancestor or animal. So far as this idea persists in the 
 minds of civilised men, it is so much purified and sublimed 
 that if the student of science does not believe it true, 
 he cannot wisely call it false. 
 
 {b) " Metaphysical Theoties." — For a time it was com- 
 
 r 
 
 IS I 
 
324 The Study of Animal Life part iv 
 
 mon to appeal to <^ vires formativai* " hereditary tendencies," 
 and "principles of heredity," by aid of which the germ 
 grew into the likeness of the parent, and this tendency 
 to resort to verbal explanations is hardly to be dnven from 
 the scientific mind except by intellectual asceticism. For 
 my own part, I prefer such "metaphysical" mist to the 
 frost of a «« materialism » which blasts the buds of wonder. 
 
 {c\ ''Mystical Theories."— Tivinvii the eighteenth cen- 
 tury and even within the limits of the enlightened nineteenth, 
 a quaint idea of development prevailed, according to which 
 the germ (either the ovum or the sperm) contained a miniature 
 organism, preformed in all transparency, which only required 
 to be unfolded (or "evolved," as they said), in order to 
 become the future animal. Moreover, the ^^% of a fowl 
 contained not only a micro-organism or miniature model of 
 the chick, but likewise in increasing minuteness similar 
 models of future generations. Microcosm lay within micro- 
 cosm, germ within germ, like the leaves within a bud 
 awaiting successive unfolding, or like an infinite juggler^s 
 box to the « evolution " of which there was no end. This 
 «« preformation theory" or "mystical hypothesis" was virtu- 
 ally but not actually shattered by WolfTs demonstration of 
 " Epigenesis » or gradual development from an apparently 
 simple rudiment. But the preformationists were right m 
 insisting that the future organism lay (potentially) within 
 the germ, and right also in supposing that the germ involved 
 not only the organism into which it grew but its descendants 
 as well. The form of their theory, however, was crude and 
 
 false. .- . . ex. 
 
 (d) Theories of Pangenesis.—ScitnWfic theories of here- 
 dity really begin with that of Herbert Spencer, who in 
 1864 suggested that "physiological units" derived from 
 and capable of growth into cells were accumulated from the 
 body into the reproductive elements, there to develop the 
 characters of structures like those whence they arose. At 
 dates so widely separate as are suggested by the names of 
 Democritus and Hippocrates, Paracelsus and BufTon, the 
 same idea was expressed— that the germs consist of samples 
 from the various parti of the body. But the theories of 
 
CHAP. XX 
 
 Htredity 
 
 3*5 
 
 these authors were vague and in some respects entirely 
 erroneous suggestions. The best-known form of this type 
 of theory is Darwin's " provisional hypothesis of pan- 
 genesis" (1868), according to which (a) every cell of the 
 body, not too highly differentiated, throws off characteristic 
 gemmules, which (*) multiply by fission, retaining their 
 peculiarities, and (f) become specially concentrated in the 
 reproductive elements, where (rf) in development they grow 
 into cells like those from which they were originally given 
 off. This theory was satisfactory in giving a reasonable 
 explanation of many of the facts of heredity, it was unsatis- 
 factory because it involved many unverified hypotheses. 
 
 The ingenious Jaeger, well known as the introducer of 
 comfortable clothing, sought (1876) to replace the "gem- 
 mules " of which Darwin spoke, by characteristic " scent- 
 stuffs," which he supposed to be collected from the body 
 into the reproductive elements. 
 
 Meanwhile (1872) Francis Galton, our greatest British 
 authority on heredity, had been led by his experiments 
 on the transfusion of blood and by other considerations 
 to the conclusion that "the doctrine of pangenesis, pure 
 and simple, is incorrect." As we shall see, he reached 
 forward to a more satisfactory doctrine, but he still allowed 
 the possibility of a limited pangenesis to account for those 
 cases which suggest that some characters acquired by the 
 parents are *' faintly heritable." He admitted that a cell 
 ♦' may throw off a few germs" {i.e. " gemmules ") " that 
 find their way into the circulation, and have thereby a 
 chance of occasionally finding their way to the sexual 
 elements, and of becoming naturalised among them." 
 
 W. K. Brooks, a well-known American naturalist, pro- 
 posed in 1883 an important modification of Darwin's theory, 
 especially insisting on the following three suppositions : 
 that it is in unwonted and abnormal conditions that the cells 
 of the body throw off gemmules ; that the male elements 
 are the special centres of their accumulation ; and that the 
 female cells keep up the general resemblance between 
 offspring and parents. For further modifications ?.nd for 
 criticism of the theories of pangenesis, I refer the student 
 
 V. 
 
 t 
 
 \ 
 
 \ 
 
3a6 
 
 The Study of Animal Life vkxi iv 
 
 to the works of Galton, Ribot, Brooks, Herdman, Plarre, 
 Van Bemmelen, and De Vries. 
 
 3 The Modem Theory of Heredity.— In the midst of 
 much debate it may seem strange to speak of the modern 
 theory of heredity, but while details are disputed, one clear 
 fact is generally acknowledged, the increasing realisation of 
 which has shed a new light on heredity. This fact is the 
 organic continuity of generations. 
 
 In 1876 Jaeger expressed his views explicitly as follows : 
 "Through a long series of generations the germinal proto- 
 plasm retains its specific properties, dividing in develop- 
 ment into a portion out of which the individual is built up, 
 and a portion which is reserved to form the reproductive 
 material of the mature ofifspring." This reservation, by 
 which some of the germinal protoplasm is kept apart, dunng 
 development and growth, from corporeal or external influ- 
 ences and retains its specific or germinal characters intact 
 and continuous with those of the parent ovum, Jasger 
 regarded as the fundamental fact of heredity. 
 
 Brooks (1876, 1877, 1883) was not less clear: "The 
 ovum gives rise to the divergent cells of the organism, but 
 also to cells like itself. The ovarian ova of the offspring 
 are these latter cells or their direct unmodified descendants. 
 The ovarian ova of the ofifspring thus share by direct 
 inheritance all the properties of the fertilised ova." 
 
 But before and independently of either Jaeger or Brooks 
 or any one else, Galton had reached forward to the same 
 idea We have noticed that he was led in 1872 to the 
 conclusion that "the doctrine of pangenesis, pure and 
 simple, is incorrect." His own view was that the fertihsed 
 ovum consisted of a sum of germs, gemmules, or organic 
 units of some kind, to which in entirety he apphed the 
 term stirp. But he did not regard this nest of organic 
 units as composed of contributions from all parts of the 
 body. He regarded it as directly derived from a previous 
 nest, namely, from the ovum which gave rise to the parent. 
 He maintained that in development the bulk of the stirp 
 grew into the body— as every one allows— but that a cer- 
 toin residue was kept apart from the development of the 
 
CHAP. XX 
 
 Heredity 
 
 327 
 
 " body " to form the reproductive elements of the offspring. 
 Thus he said, in a sense the child is as old as the parent, 
 for when the parent is developing from the ovum a residue 
 of that ovum is kept apart to form the germ-cells, one of 
 which may become a child. Besides Galton, Jaeger, and 
 Brooks, several other biologists suggested this fertile idea 
 of the organic continuity of generations. Thus it is ex- 
 pressed by Erasmus Darwin and by Owen, by Hacckel, 
 Rauber, and Nussbaum. But it is to Weismann that the 
 modem eaiphasis on the idea is chiefly due. 
 
 Let us try to realise more vividly this doctrine of organic 
 continuity between generations. Let us begin with a fertil- 
 ised egg-cell, and suppose it to have qualities abcxyz. This 
 endowed egg- cell divides and redivides, and for a short 
 time each of the units in the ball of cells may be regarded 
 as still possessed of the original qualities abcxyz. But 
 division of labour, and rearrangement, infolding and out- 
 folding, soon begin, and most of the cells form the " body." 
 They lose their primitive characters and uniformity, they 
 become specialised, the qualities ab predominate in one 
 set, be in another, xy in another. But meantime certain 
 cells have kept apart from the specialisation which results 
 in the body. They have remained embryonic and un- 
 differentiated, retaining the many-sidedness of the original 
 egg-cell, preserving intact the qualities abcxyz. They form 
 the future reproductive cells — let us say the eggs. 
 
 Now when these eggs are liberated, with the original 
 qualities abcxyz unchanged j having retained a continuous 
 protoplasmic tradition with the parent ovum, they are evi- 
 dently in almost the same position as that was. There- 
 fore they develop into the same kind of organism. Given 
 the same protoplasmic material, the same inherent quali- 
 ties, the same conditions of birth and growth, the results 
 must be the same. A single-celled animal with qualities 
 abcxyz divides into two ; each has presumably the qualities 
 of the original unit ; each grows rapidly into the form of 
 the full-grown cell. We have no difficulty in understanding 
 this. In the sexual reproduction of higher animals, the 
 case is complicated by the form?*'on of the " body," but 
 
 Wxi' ■■■■■ 
 
 
328 
 
 The Study of Animal Life part iv 
 
 logically the difficulty is not greater. A fertilised egg-cell 
 with qualities abcxyz divides into many cells, which, becom- 
 ing diverse, express the original qualities in various kinds 
 of tissue within the forming body. But if at an early stage 
 certain cells are set apart, retaining the qualities or charac- 
 ters abcxyz in all their entirety, then these, when liberated 
 after months or years as egg-cells, will resemble the original 
 ovum, and are able like it to give rise to an organism, 
 which is necessarily a similar organism. 
 
 To call heredity ««the relation of organic continuity 
 between successive generations," as I define it, seenis a 
 truism to some, but it is in the realisation of this truistic 
 fact that the modem progress in regard to heredity consists. 
 To ask how the inherent qualities of the ovum become 
 divergent in the different cells of the body, or how some 
 units remain embryonic, or how the egg-cell divides at 
 all, is to raise the deepest problems of biology, not of 
 heredity. To answer such questions is the more or less 
 hopeless task of physiological embryology, not that of the 
 student of heredity. Recognising the fact of organic con- 
 tinuity, various writers such as Samuel Butler, Hering, 
 Haeckel, Geddes, Gautier, and Bcrthold, have sought in 
 various ways to make it clearer, e.g. by regarding the re- 
 production of like by like as an instance of organic memory. 
 As these suggestions are unessential to our argument, I 
 shall merely notice that there are plenty of them. 
 
 How far has this early separation of the future repro- 
 ductive cells from the developing body been observed ? It 
 has been observed in several worm-types— leeches, Sagitta^ 
 thread-worms, Polyzoa, — in some Arthropods {e.g. Moina 
 among crustaceans, Chironomus among Insects, Phalangid;E 
 among spiders), and with less distinctness in a number of 
 other organisms, both animal and vegetable. In most of 
 the higher animals, however, the future reproductive cells 
 are not observable till development has proceeded for some 
 days or weeks. To explain this difficulty, VVeismann has 
 elaborated a theory which he calls " the continuity of the 
 germ-plasma:* The general idea oi this theory is that of 
 oi^anic continuity between generations, and this Weismann 
 
CHAP. XX 
 
 Heredity 
 
 3*9 
 
 has done momentous service in expounding. But for the 
 detailed theory by which he seeks to overcome the diffi- 
 culty which has been noticed above I refer those interested 
 to Weismann's Papers on Heredity (Trans. Oxford, 1889). 
 4. The Inheritance of Acquired Characters.— («) His- 
 torical. We have seen that variations, or changes in char- 
 acter, may be constituHonal, i.e. innate in the germ ; or 
 functional., i.e. due to use or disuse ; or environmental, i.e. 
 due to influences of nutrition and surroundings. Many 
 naturalists have believed that gains or losses due to any of 
 these three sources of change might be transmitted from 
 parent to offspring. But nowadays the majority, with 
 Profs. Weismann and Lankester at their head, deny the 
 transmissibility of either functional or environmental 
 changes, and believe that inborn, germinal, or constitu- 
 tional variations alone are transmissible. 
 
 This scepticism is not strictly modem. The editor, 
 whoever he was, of Aristotle's Historia Animalium, differed 
 from \ master as to the inheritance of injuries and the 
 like. Avant maintained the non- inheritance of extrinsic 
 variations, and Blrnenbach cautiously inclined to the same 
 negative position. In more recent times the veteran morpho- 
 logist His expressed a strong conviction against the inherit- 
 ance of acquired characters, and the not less renowned 
 physiologist Pfliiger is also among the sceptics. A few 
 sentences from Gallon (1875), whose far-sightedness has 
 been insufficiently acknowledged, may be quoted : " The 
 inheritance of characters acquired during the lifetime of the 
 parents includes much questionable evidence, usually diffi- 
 cult of verification. We might almost reserve our belief 
 that the structural cells can react on the sexual elements at 
 all, and we may be confident that at the most they do so in 
 a very faint degree— in other words, that acquired modifica- 
 tions are barely, if at all, inherited in the correct sense of 
 
 that word." 
 
 But Weismann brought the discussion to a climax by 
 altogether denying the transmissibility of acquired charac- 
 ters. 
 
 (*) Weismann's position. — Weismann't reasons for 
 
 
33© The Study of Animal Life part iv 
 
 maintaining that no acquired characters are transmissible 
 are twofold, — first because the evidence in favour of such 
 transmission conusts of unverifiable anecdotes ; second 
 because the "germ -plasma," early set apart in the de- 
 velopment of the body, remains intact and stable, unaffected 
 by the vicissitudes which beset the body. 
 
 It is natural that Weismann, who realised so vividly the 
 continuity between germ and germ, should emphasise the 
 stability of the "germ-plasma," that he should regard it 
 as leading a sort of charmed life within the organism un- 
 affected by changes to which the body is subject But has 
 he not exaggerated this insulation and stability ? 
 
 Of course Weismann does not deny that the body may 
 exhibit functional and environmental variations, but he 
 denies that these can spread from the body so as to affect 
 the reproductive cells thereof, and unless they do so, they 
 cannot be transmitted to the offspring. 
 
 On the other hand, innate or germinal characters 
 must be transmitted. They crop up in the parent be- 
 cause they are involved in the fertilised egg-cell. But as 
 the cell which gives rise to the offspring is by hypothesis 
 similar to and more or less directly continuous with the 
 cell which gave rise to the parent, similar constitutional 
 variations will crop up in the offspring. 
 
 We must admit that most of the old evidence adduced 
 in fitvour of the transmission of acquired characters may 
 be called a "handful of anecdotes." For scepticism was 
 undeveloped, and when a character acquired by a parent 
 reappeared in the offspring, it was too readily regarded as 
 transmitted, whereas it may often have been acquired by 
 the offspring just as it was by the parent. 
 
 Weismann has two saving clauses, which make argu- 
 ment against his position peculiarly difficult. (i) He 
 admits that the germ -plasma may be modified "ever so 
 little " by changes of nutrition and growth in the body ; 
 but may not an accumulation of many "ever -so -littles" 
 amount to the transmission of an acquired character ? (2) 
 He admits that external conditions, such as climate, may 
 influence the reproductive cells along with^ though not 
 
CHAP. ZX 
 
 Heredity 
 
 331 
 
 exacUy throu^ the body ; but this is a distinction too 
 subtle to be verified. 
 
 These two saving-clauses seem to me to affect the strin- 
 gency of Weismann's conclusion, but in his view they do 
 not affect the main proposition that definite somatic modifi- 
 cations or changes in the body due to function cr enmon^ 
 ment have no effect on the reproductive cells, and therefore 
 no transmission to offspring. 
 
 lc\ Arguments against Weismann's position.— In arguing 
 against Weismann's position that no acquired characters 
 are inherited, I shall first illustrate the arguments of others, 
 and then emphasise that which appears to me at present 
 
 most cogent. 
 
 (O Some have cited against Weismann various cases 
 where the effects of mutilation seemed to be transmitted 
 and Weismann has spent some time in experimenting with 
 mice in order to see whether cutting off the tails tor severa 
 generations did not eventually make ^^ V* .' 1?°^;, Jl 
 did not— a result which might have been foretold. For we 
 have known for many years that the mutilations mflicted 
 on sheep and other domesticated animals had no measur- 
 able effect on the offspring. Even the numerous cases of 
 tailless kittens produced from artificially curtailed oits have 
 no cogency in face of the fact that taiUess sports often arise 
 from normal parents. Moreover, it is for many reasons not 
 to be expected that the results of curtailment and the like 
 should be inherited. For there is great power of regener- 
 ating lost parts even in the individual lifetime ; the result 
 of cutting off a tail is for mtst part merely a minus quantity 
 to the organism; the imperfectly known physiological re- 
 action on nerves and blood-vessels might perhaps result m 
 a longer rather than a shorter tail in the offspring. 
 
 (2) Various pathologists, led by Virchow, have empha- 
 sised the fact that many diseases are inherited, but their 
 arguments have usually* shown how easy it is to misunder- 
 stand Weismann's position. No doubt many malformations 
 and diseases reappear through successive generations, bu 
 there is lack of evidence to show that the pathological 
 variations were not genninal to begin with. It is tadly 
 
 V 
 
 I 
 
 I 
 
 I 
 
 kii 
 
 MP^ 
 
332 
 
 The Study of Animal Life part iv 
 
 interesting to learn that colour-blindness has been known 
 to occur in the males only of six successive generations, 
 deaf mutism for three, finger malformations for six, and so 
 with harelip and cleft palate, and with tendencies to con- 
 sumption, cancer, gout, rheumatism, bleeding, and so on. 
 liut these facts do not prove the transmission of functional or 
 environmental variations ; they only corroborate what every 
 one allows, that innate, congenital, constitutional characters 
 
 Fig. 70.— HalWop rabbit, an abnormal variation, which by artificial selection 
 has become ronstant in a breed. (From Darwin.) 
 
 tend to be transmitted. Ve* some cases recently stated by 
 Prof. Bertram Windle seem to suggest that some patho- 
 logical conditions acquired by function may be transmitted. 
 IJut even if a ncn-constitutional pathological state acquired 
 by a parent reappeared in the oflTspring, we require to show 
 that the offspring did not also acquire it by his work or 
 from conditions of life, as his parent did before him. 
 
 (3) Some individual cases seem to stand some criticism. 
 
 Two botanists, Hoffmann and Detmer, have noted such 
 facts as the following — scant nutrition influenced the flowers 
 of poppvj Nigella, dead-nettle., and the result was trans- 
 
CHAP. XX 
 
 Heredity 
 
 333 
 
 mitted; peculiar soil conditions altered the root of the 
 carrot, and the result was transmitted. 
 
 Semper gives a few cases such as Schmankewitsch's 
 transformation of one species of brine-shrimp (Ariemia) into 
 another, throughout a series of generations during which 
 the salinity of the water was slowly altered. 
 
 Eimer has written a book of which even the title, " The 
 Origin of Species, according to the laws of organic growth, 
 through the inheritance of acquired characters," shows how 
 strongly he supports the aflfirmative side of our question. 
 But much as I admire and agree with many parts of Eimer's 
 work, 1 do not think that all his examples of the inheritance 
 of acquired characters are cogent One of the strongest 
 is that cereals from Scandinavian plains transplanted to 
 the mountains become gradually accustomed to develop 
 more rapidly and at a lower temperature, and that when 
 returned to the plains they retain this power of rapid 
 development I am inclined to think that the strongest 
 part of Eimer's argument is that in which he maintains that 
 certain effects produced upon the nervous system by peculiar 
 habits are transmissible. 
 
 (4) Another mode of argument may be considered. To 
 what conception of evolution are we impelled if we deny 
 the inheritance of acquired characters ? Weismann believes 
 that he has taken the ground from under the feet of 
 Lamarckians and Buffonians, who believe in the inheritance 
 of functional and environmental variations. The sole fount 
 of change is to be found in the mingling of the kernels of 
 two cells* at the fertilisation of the ovum. On these varia- 
 tions natural selection works. 
 
 But even if we do not believe in the inheritance of 
 acquired characters, it is open to us to maintain that by 
 cumulative constitutional variations in definite directions 
 species have grown out of one another in progressive evolu- 
 tion. Thus we are not forced to restrict our interpreta- 
 tions of the marvel and harmony of organic nature to the 
 theory of the action of natural selection on indefinite for- 
 tuitous variations. 
 
 Prof. Ray Lankester*! convictions on this subject are to 
 
 |i 
 
334 The Study of Animal Life part iv 
 
 strong, and his dismissal of Lamarckian theory is so 
 emphatic, that I shall select one of his illustrations by way 
 of contrasting his theory with that of Lamarckians. 
 
 Many blind fishes and crustaceans are found in caves, 
 Lamarckians assume, as yet with insufficient evidence, that 
 the blindness is due to the darkness and to the disuse 
 of the eyes. Changes thus produced are believed, again 
 with insufficient evidence, to be transmitted and increased, 
 generation after generation. This is a natural and simple 
 theory, but it is not a certain conclusion. 
 
 What is Prof. Ray Lankester's explanation ? 
 
 " The facts are ftiUy explained by the theory of natural 
 selection acting on congenital fortuitous variations. Many 
 animals are bom with distorted or defective eyes whose 
 parents have not had their eyes submitted to any peculiar 
 conditions. Supposing a number of some species of Arthro- 
 pods or fish to be swept into a cavern, those individuals with 
 perfect eyes would follow the glimmer of light and eventually 
 escape to the outer air, leaving behind those with imperfect 
 eyes to breed in the dark place. In every succeeding 
 generation this would be the case, and even those with 
 weak but still seeing eyes would in the course of time 
 escape, until only a pure race of eyeless or blind animals 
 would be left in the cavern." This is a possible explanation, 
 but it is not a certain conclusion. 
 
 (5) The argument which I would urge most strongly is 
 based on general physiological considerations. It gives 
 no demonstration, but it seems to establish a presump- 
 tion against Weismann's conclusion. He maintains that 
 functional and environmental changes in the body cannot 
 be transmitted because such changes cannot reach the 
 stable and to some extent insulated reproductive elements. 
 But this cannot requires proof, just as much as the converse 
 
 can. 
 
 The organism is a unity ; cell is often linked to cell by 
 bridges of living matter ; the blood is a common medium 
 carrying food and waste ; nervous relations bind the whole 
 in harmony. Would it not be a physiological miracle if the 
 reproductive cells led a charmed life unaffected even by 
 
CItAP. XX 
 
 Heredity 
 
 335 
 
 influences which touch the very heart of the organism ? Is 
 it unreasonable to presume that some influences of habit and 
 conditions, of training and control, saturate the organism 
 thoroughly enough to affect every part of it ? 
 
 A slight change of food affects the development of the 
 reproductive organs in a bee-grub, and makes a queen out of 
 what otherwise would have been a worker. A difference of 
 diet causes a brood of tadpoles to become almost altogether 
 female. There is no doubt that some somatic changes 
 affect the reproductive cells in some way. Is it incon- 
 ceivable that they affect them in such a precise way that 
 bodily changes may be transmitted ? 
 
 It must be admitted that it is at present impossible to 
 give an explanation of the way in which a modification 
 of the brain can affect the cells of the reproductive organs. 
 The only connections that we know are by the blood, by 
 nervous thrills, by protoplasmic continuity of cells. But 
 there are many indubitable physiological influences which 
 spread through the body of which we can give no rationale. 
 Because we cannot tell how an influence spreads, we need 
 not deny its existence. 
 
 It is at least conceivable that a deep functional or 
 environmental change may result in chemical changes 
 which spread from cell to cell, that characteristic products 
 may be carried about by the blood and absorbed by the 
 unspecialised reproductive cells, that nervous thrills of 
 unknown efficacy may pass from part to part. Nor do we 
 expect that more than a slight change will be transmitted 
 in one generation. 
 
 Weismann traces all variations ultimately to the action 
 of the environment on the original unicellular organisms. 
 These are directly affected by -.unrounding influences, and 
 as they have no "body" nc* specialised reproductive 
 elements, but are single cells, it is natural that the char- 
 acters acquired by a parent-cell should also belong to the 
 daughter-units into which it divides. And if so, is it not 
 possible that the reproductive cells of higher animals, being 
 equivalent to Protozoa, may be definitely afiiected by their 
 immediate environment, the body? Moreover, if it were 
 
33< 
 
 The Study of Animal Life part iv 
 
 proved that the definite changes produced on an individual 
 by influences of use, disuse, and surroundings, do not reach 
 the reproductive cells, and cannot, therefore, be transmitted, 
 it is not thereby proved that secondary results or some results 
 of such definite changes may not have some effect on the 
 germ-cells. The conditions are so complex that it seems 
 rash to deny the possibility of such influence. 
 
 Certainly it is no easy task to explain all the adapta- 
 tions to strange surroundings and habits, or the majority of 
 animal instincts, or the progress of men, apart fi-om the 
 theory that some of the results of environmental influence 
 and habitual experience are transmitted. I am certainly 
 unable to reconcile myself to the opinion that the progress 
 of life is due to the action of natural selection on fortuitous, 
 indefinite, spontaneous variations. 
 
 I believe that the conclusion of the whole matter should 
 be an emphatic "not proven" on either side, while the 
 practical corollary is that we should cease to talk so much 
 about possibilities (in regard to which one opinion is often 
 as logically reasonable as another), and betake ourselves 
 with energy to a study of the facts. 
 
 5. Social and Ethical Aspects.— All the important 
 biological conclusions have a human interest 
 
 The fact of organic continuity between germ and germ 
 helps us to realise that the child is virtually as old as the 
 parent, and that the main line of hereditary connection 
 is not so much that between parent and child as •' that 
 between the sets of elements out of which the personal 
 parents had been evolved, and the set out of which the 
 personal child was evolved." "The main line," Galton 
 says, " may be rudely likened to the chain of a necklace, 
 and the personalities to pendants attached to the links." 
 To this fact social inertia is largely due, for the organic 
 stability secured by germinal continuity tends to hinder 
 evolution by leaps and bounds either forwards or backwards. 
 There is some resemblance between the formula of heredity 
 and the fir-t law of motion. The practical corollary is 
 respect for a good stock. 
 
 That each parent contributes almost equally to the off- 
 
CHAV. XX 
 
 Heredity 
 
 337 
 
 spring suggests the two-sided responsibility of parentage ; 
 but the fact has to be corrected by Galton's statistical con- 
 clusion that the offspring inherits a fourth from each 
 parent, and a sixteenth from each gram narent ! Inherited 
 capital is not merely dual, but multiple like a mosaic. 
 
 If we adopt a modified form of Weismann's conclusion, 
 and believe that only the more deeply penetrating acquired 
 characters are transmitted, we are saved from the despair 
 suggested by the abnormal functions and environments of 
 our civilisation. 
 
 And just in proportion as we doubt the transmission of 
 desirable acquired characters, so much the more should we 
 desire to secure that improved conditions of life foster the 
 individual development of each successive generation. 
 
 That pathological conditions, innate or congenital in the 
 organism, tend to be transmitted, suggests that men should 
 be informed and educated as to the undesirability of 
 parentage on the part of abnormal members of the com- 
 munity. 
 
 But while no one will gainsay the lessons to be drawn 
 from the experience of past generations, it should be noticed 
 that Virchow and others have hinted at an " optimism of 
 pathology," since some of the less adequately known abnor- 
 mal variations may be associated with new beginnings not 
 without promise of possible utility. It seems, moreover, 
 that by careful environment and function, or by the inter- 
 crossing of a slightly tainted and a relatively pure stock, a 
 recuperative or counteractive influence may act so as to 
 produce comparatively healthy offspring, thus illustrating 
 what may be called " the forgiveness of nature." 
 
 6. Social Inheritance. — The widest problems of 
 heredity are raised when we substitute " fraternities " for 
 individuals, or make the transition to social inheritance — 
 the relation between the successive generations of a society. 
 The most important pioneering work is that of Galton, 
 whose unique papers have been recently summed up in a 
 work entitled Natural Inheritance. Galton derived his 
 data from his Records of Family Faculties, especially con- 
 cerning stature, eye-colour, and artistic powers ; and his 
 
 
 t 
 
338 
 
 The Study of Animal Life pa»t i^ 
 
 work has been in great part an application of the statistical 
 law of Frequency of Error to the records accumulated. 
 
 The main problem of his work is concerned with the 
 strange regularity observed in the peculiarities of great 
 populations throughout a series of generations. "The 
 large do not always beget the large, nor the smaU the 
 small ; but yet the observed proportion between the large 
 and the small, in each degree of size and in every quality 
 hardly varies from one generation to another." A specific 
 average is sustained. This is not because each individuM 
 leaves his like behind him, for this is not the case. It is 
 rather due to the fact of a regular regression or deviation 
 which brings the offspring of extraordinary parents in a 
 definite ratio nearer the average of the stock. .... 
 
 " However paradoxical it may appear at first sight, it is 
 theoretically a necessary fact, and one that is clearly con- 
 firmed by observation, that the stature of the adult offspring 
 must on the whole be more mediocre than the stature of 
 their parents— that is to say, more near to the median 
 stature of the general population. Each peculiarity of a 
 man is shared by his kinsmen, but on an average in a less 
 degree. It is reduced to a definite fraction of its amount, 
 quite independently of what its amount might be. The 
 fraction differs in different orders of kinship, becoming 
 smaller as they are more remote." 
 
 Yet it must not be supposed that the value of a good stock 
 is under-estimated by Galton, for he shows how the offspring 
 of two ordinary members of a gifted stock will not regress 
 like the offspring of a couple equal in gifts to the former, 
 but belonging to a poorer stock, above the average of which 
 
 they have risen. , , „ 
 
 Yet the fact of regression tells against the full transmission 
 of any signal talent Children are not Ukely to differ from 
 mediocrity so widely as their parents. " The more bounti- 
 fully a parent is gifted by nature, the more rare will be his 
 good fortune if he begets a son who is as richly endowed as 
 himself, and still more so if he has a son who is endowed 
 more largely." But " The law is even-handed ; it levies an 
 equal succession-tax on the transmission of badness as of 
 
CHAP. XX 
 
 Heredity 
 
 339 
 
 goodness. If it discourages the extravagant hope of a gifted 
 parent that his children will inherit all his powers, it no less 
 discountenances extravagant fears that they will inherit all 
 his weakness and disease." 
 
 The study of individual inheritance, as in Gallon's 
 Hereditary Genius^ may tend to develop an aristocratic and 
 justifiable pride of race when a gifted lineage is verifiable 
 for generations. It may lead to despair if the records of 
 family diseases be subjected to investigation. 
 
 But the study of sc cial inheritance is at once more demo- 
 cratic and less pessimistic. The nation is a vast fraternity, 
 with an average towards which the noble tend, but to which 
 the offspring of the under-average as surely approximate. 
 Measures which affect large numbers are thus more hopeful 
 than those wl '^h artificially select a few. 
 
 Even when we are doubtful as to the degree in which 
 acquired characters are transmissible, we cannot depreciate 
 the effect on individuals of their work and surroundings. 
 In fact there should be the more earnestness in our desire to 
 conserve healthful function and stimulating environment of 
 every kind, for these are not less important if their influences 
 must needs be repeated on each fresh generation. " There 
 was a child went forth every day ; and the first object he 
 looked upon, that object he became; and that object 
 became part of him for the day, or a certain part of the 
 day, or for many years, or for stretching cycles of years." ^ 
 
 Nor can we forget how much a plastic physical and 
 mental education may do to counteract disadvantageous 
 inherited qualities, or to strengthen characters which are 
 useful. 
 
 Every one will allow at least that much requires to be 
 done in educating public opinion, not only to recognise all 
 the facts known in regard to heredity, but also to admit the 
 value and necessity of the art which Mr. Galton calls 
 •« eugenics," or in frank English " good-breeding." 
 
 ^ Walt Whitman's ' ' Assimilations." 
 
 iL ii^j 
 
APPENDIX I 
 
 ANIMAL LIFE AND OURS 
 
 A. Our Relation to Animals 
 
 I AfSnities and Differences between Man and Monkeys. 
 
 ; one^ the woAs of Broca. a pioneer anthropologist of renown, 
 fjere is an eloquent apology for those who find U useful to con- 
 
 ''^'l ^^i:^V]^ «'wS!; one of the most characteristic trait. 
 
 of our nature, has prevailed with many minds over the calm tesU- 
 
 Iny of reason. Like the Roman emperors who. enervated by dl 
 
 S uowen ended by denying their character as men, in fact, by 
 
 iliev?n7th;mSve8 demigod^ so the king of our planet pltttfes 
 
 Ss^ ?IJ im^ning tha^the vile animal, subject to his caprice 
 
 rlniJ^t have alwthing in common with kis peculiar nature. The 
 
 uSity of the monkey vexes him. it is not enough to be kmg of 
 
 '^ °^!?c . he wishes to separate himself from his subjects by a deep 
 
 ShnriaWe abvS • aXturning his back upon the earth, he takes 
 
 ;et« ^h his ^nLtf ;^^^ a nebulous sphere, 'the human 
 
 tS^' But anatomy, like that slave who followed the con- 
 
 nJSort chariot crying, Mmento te hominem ««, anatomy comes 
 
 double mTn in his 'naive self-admiration, reminding him of the 
 
 visible tangible facts which bind him to the animals. 
 
 visible tang ^^^^^ ^ j.^^j^^ remembenng Fa^als 
 
 maxiSs "ItTdangerous to show man too planly how like he is 
 ^T animals without, at the same time, reminding h.m of his 
 IreSnei Is Vlly unwise to impress him with h.s greatness, 
 fid not with hU LliLs. It is worse to leave him m ignorance 
 ?iL?»S B?i* it is very profitoble to recognise the two facts." 
 
 nt m^y yean sine? Owen-now a veteran among anatomists 
 -i^SId the "all-pervading simiUtade of structure" between 
 
APP. I 
 
 Animal Life and Ours 
 
 341 
 
 vU .1 
 
 .X 
 
 The 
 
 act that man is peculiarly 
 less pro*' '"ive face, smaller 
 '.(I >ore uniform 
 '., ':.< ever, is the 
 ;Kt ' i he smallest 
 -\\.: a /est human 
 > ave a brain 
 of a healthy 
 .-s : the average 
 
 ; ■ ,.ir:, .1 
 
 }arv 
 
 •,'1 i 
 
 1, 
 
 m 
 
 ir •;-/ ou 
 
 tavie 
 
 man and the highest monkeys. Subsequent research ha« continued 
 to add corroborating details. As far as structure is concerned, 
 ihere is much less difference between man and the gorilla than 
 between the gorilla and a monkey like a mamoset. Yet differences 
 between man and the anthropoid apes do exist. Thus man alone 
 is thorciglily trect after his infancy is past, his head weighted with 
 a heu.y brain does not droop forward, and with his erect attitude 
 his peiiect development of vocal mechanism is perhaps connected. 
 We plant the soles of our feet flat on the ground, our great toes 
 are usuaily in a line with the rest, and we have better heels than 
 monkeys have, but no emphasis can be laid on the old distinction 
 which separated two-handed men (P! . ana) from the four-handed 
 monkeys (Quadrumana), nor on ' it- 
 naked. We have a bigger foreh'M 
 cheek-bones and eyebrow ridg • , a 
 teeth than the anthropoid aper M 
 fact that the weight of the grr'^ . ' '-.' 
 brain of an adult man the i a" <>i : 
 brain the ratio of I : 3 ; i. 
 three times as heavy as 1 
 human adult never we-gh. I- -^ 
 human brain weighs 48 or 40 
 does not exceed 20 ounces. ' 
 than 55 cubic inches in any ncri ir 1 . ... m 
 orang and the chimpanzee it is u ' ar 
 respectively." 
 
 But differences which can be measured and weighed give us little 
 hint of the characteristically human powers of building up ideas and 
 of cherishing ideals. It is not merely that man profits by his 
 experience, as many animals do, but that he makes some kind of 
 theory of it. It is not merely that he works for ends which are 
 remote, as do birds and beavers, but that he controls his life 
 according to conscious ideals of conduct. But I need not say much 
 in regard to the r laracter'stics of huu.an personality, we are all 
 conscious of them, though w? may differ as to the words in which 
 they may be expressed ; nor need I talk about man's power of 
 articulate speech, nor his realisation of history, nor his inherent 
 social sympathies, nor his gentleness. Fov all recognis hat the 
 higher life of men has a loftier pitch than that of animi.":, while 
 many think that the difference is in kind, not merely 'n dejjree. 
 
 2. Descent of Man. — 'I'he arg^-ments by whicl Darwin and 
 others have sought to show that man urose from an ancestral type 
 common to him and to the higher apes are the same as those used 
 to substantiate the general doctrine of descent. For the Descent 
 of Man was but the expansion of a chapter in the Origin o/Speeiu ; 
 
 cnniai cd 
 
 gorilla brain 
 
 );...! 'v is never less 
 
 I'njcjt, while in the 
 
 , ^ cubic inches 
 
The Study of Animal Life 
 
 KTt. 
 
 34« 
 
 the argumenU used to prove the origin of animal from animal were 
 adapted to rationalise the ascent of man. 
 
 (a) Physiological.— 1\it bodily life of man is like that of mon- 
 keys ; both are subject to the same diseases ; various human traits, 
 such as ges ares and expressions, are paralleled among the " brut ;s ; 
 and chil'.ren bom during famine or in disease are often sadly 
 
 (u) Morphological.— The structure of man is like that of the 
 anthropoid apes, none of his distinctive characters except that of 
 a heavy brain being momentous, and there are about seventy 
 vestigial structures in the muscular, skeletal, and other systems. 
 
 (<■) Historical.— TYittt is little certAinty in regard to the fossil 
 remains of prehistoric man, but some of these suggest more primi- 
 tive skulls, while the facU known about ancient life show at kast 
 that there has been progress along certain lines. Moreover, there 
 is the progress of each individual life, from the apparently simple 
 egg-cell to the minute embryo, which is fashioned withm the womb 
 into the likeness of a child, and being bom grows from stage to 
 stage, all in a manner which it is hard to understand if man be 
 not the outcome of a natural evolution. 
 
 3. Various Opinions about the Descent of Man.— But 
 
 opinion in regard to the origin of man is by no means unanimous. 
 
 (a) A few authorities, notably A. de Quatrefagcs, maintain a 
 conservative position, believing that the evolutionist's case has not 
 been sufficiently demonstrated. But the majority of naturalists 
 believe the reverse, and think that the insufficiencies of evidence in 
 regard to man are counterbalanced by the force of the argument 
 
 from analogy. . ... 
 
 (b) Alfred Russel Wallace has consistently maintained a position 
 which seems 10 many a very strong one. '• I fully accept," he 
 says, " Mr. Darwin's conclusion as to the essentia' identity of man s 
 bodi'ly structure with that of the higher mammalia, and his descent 
 from some ancestral form common to man and the anthropoid apes. 
 The evidence of such descent appears to me overwhelming and 
 conclusive. Again, as to the cause and method of such descent 
 and modification, we may admit, at all events provisionally, that 
 the laws of variation and natural selection, acting through the 
 struffile for existence and the continual need of 1, ore perfect 
 adaptation to the physical and biological environments, may have 
 brought about, first that perfection of bodily structure in which he 
 is so far above all other animals, and in co-ord'nation with it the 
 larger and more developed brain, by means of which he has been 
 able to utilise that structure in the more and more complete sub- 
 jection of the whole animal and vegetable kingdoms to bis 
 service." 
 
Animal Life and Ours 
 
 343 
 
 ••But .^K*uie man's physical structure has been developed 
 from an .r^; al form bynitoral selection it doc. not neces^n^r 
 fXw that i-,:. mental Lure, even though d«v«loped /or, A««^ 
 with it. has been developed by the same causes only." WaU.ce 
 Thw gie. on to .how that m«n's mathemat-cal, "»««<=*> f^istic 
 mToS« higher faculties could not be developed by vanat.on and 
 Stural .election alone. - Therefore some °'her mfluence law.^ 
 aeency U required to account for them." Indeed this unknown 
 S^r^er may have had a much wider influence ex ending 
 To the whSe cour« of his dev. : .pmerit. " Jhe Jove of ,ru h he 
 delight in beauty, the passion for justice, and the J*"» « ""'»J 
 tion with which we hear of any act of courageous «lf-«"ifice. are 
 the workings within us of a higher nature which has not been 
 deve7oid^ means of the struggle for material ««»«<=«•" ft 
 ?he orik^n of Uving things, at ihe introduction of consc.ousn^s, in 
 he development of man's higher faculties. •• a change ;««««« 
 nature (due, probably, to causes of a higher order than those of the 
 "ateriai universe) toik place." ;« i;hc P^^g-^"^^^^"!*^!"! 
 of life in the vegetable, the animal and ,«>^°-''J ?L^* "^W 
 chusilya. unconscious, conscious, and mtellectual hfe-ptobably 
 depend upon different degrees of spiritual influx. „5^-a„. 
 
 In di.cus.ing problems such as this there .s apt to be «n«unrte' 
 standing, for worf. are " but feeble light on the depth of the an- 
 iken'^' ani^rhapsno man appreciates hi. brother'. phdo«,phy. 
 Wiretl rSrainVm seeking to -ontrovert wjat Wallace ha. 
 Mid esoedally as I also beUeve that the nature of life and mind 
 SI ;J?rS.Ti. all. and that the higher life of man cannot be 
 explained by indefinite variations which happened to prosper m tne 
 courM of natural Klection. „ , . , .r •_._ 
 
 Xt it «em. to me (.) to be difficult to divide man'. «lf mo 
 an animal nature which has been naturally evolved and a 
 Ipirl^lHature which ha. been .uperadded " or to ;^™'^;«»« 
 higher life from that of wme of the beaatfc (a) When we find 
 IL any fact in our exprrience. such -^^ ^f«" '«"^"' «S"° 
 be expliined on the theory of evolution which we l'«r »'»oP»«i,»» 
 doe. not follow that the reality in question has not been naturtlly 
 JJSvSd, it only follows that our theory of evolution is imperfect 
 AiheorV i. not proved to be complete because it rxpla ns many 
 factsr^t U U pLed to be incomplete if it faiU to "P ;in^-y- 
 Thui if man's higher nature cannot be «P>*'"«f. ''> J* 'J^Y ° 
 natural selection ir the struggle for existence. «hen that theory s 
 incomplete, but there may be other theories of «^"'"'7 *'»'^,'', "* 
 Xent. '(3) It i» difffcult to l'"^^ -»1*'^- "l**"^'^^^^^^ 
 in(lux-for our opinion, in regard to those matter, vary with 
 Sdoal .xperieSce. We may mean to «igge*t the mterpola- 
 
 V^-^'.^^ '^^■: 
 
344 The Study of Animal Life app. 
 
 tion of a power of a secret and supersensory nature, distinct from 
 that power whi'*h is everywhere present in sunbeam and rain- 
 drq), bird and flower. Then we are abandoning the theory of a 
 continuous natural evolution. Or we may mean to vi^vA that wL -n 
 life and mind and man began to be, then possibilities of action and 
 reaction hitherto latent became real, and all things bjcame in a 
 sense new. Then, while maintaining that life and mind are new 
 realities with new powers, we are still consistent believf.rs in a con- 
 tinuous natural evolution. (4) Perhaps the simpK-^st conception is 
 that more than once su^ested in thU book, that the world is one 
 not twofold, that the spiritual influx is the primal reality, that there 
 is nothing in the end which was not also in the beginning. 
 
 (e) Prof. Calderwood has recently stated with clearness and 
 conciseness what difficulties surround the task of those who would 
 explain the evolution of man. " So far as the human organism is 
 concerned, there seem no overwhelming obstacles to be encountered 
 by an evolution theory ; but it seems impossible under such a theory 
 to account for the appearance 0I homo sapiens— ihe thinking, self- 
 regulating life, distinctively human." Again, I have no desire to 
 enter into controversy, for I recognise the difficulties which the 
 student of comparative psychology must Uckle, but it seems 
 important that the following consideration should be kept in mind. 
 
 It is not the first basiness of the evolutionist to find out how one 
 reality has grown out of another, but to marshal the arguments 
 which lead him to conclude that one reality Aas so evolved. We 
 have only a vague idea how a backbone arose, but that need not 
 hinder us from l>elieving that Ixickboned animals were evolved from 
 bockboneless if there be sufficient evidence in favour of this con- 
 clusion. We do not know how birds arose from a reptile stock, 
 but that tlicy did so arise is fairly certain. We cannot explain the 
 intelligence of m.-»n in terms of the activify of the brain ; we are 
 equally at a loss in regard to the intelligence of an ant. What we 
 have to do is to compare the structure of man's brain with that .>f 
 the neare?t animals, and the nature of human intelligence with th.u 
 of the closest approximations, drawing from the results of our 
 comparison what conclusion we can. The general doctrine of 
 descent may be establisheil independently of the investigations of 
 physiologist and psychologist, valuable as these may l)e in elucidat- 
 ing the way in which the great steps of prepress have been made. 
 
 (d) Finally there is the opinion of matiy that man is altogether 
 too marvellous a l>eing to have arisen from any humbler form of 
 life. But to others this ascent seems the tump of man's nobility. 
 
 4. Ancestors of Man.— Of these we know notliing. The 
 anthropoid a|)es approach hitji most closely, each in some particular 
 respect, but none of them nor any known form of life can be callcil 
 
Animal Life and Ours 
 
 345 
 
 man's ancestor. It is possible that the race of men— for of a 
 first mr^n evolutionists cannot speak— began in Miocene times, 
 as offshoots from an ancestral stock common to them and to the 
 anthropoids. We often hear of " the missing link," but surely no 
 one expects to find him alive. And while we have still much to 
 learn from the imperfect geological record, it must be remembered 
 that what most distinguishes man will not be remarkable in a fossil, 
 for brains do not petrify except metaphorically, nor can we look for 
 fossilised intelligence or gentleness. 
 
 Kii.. 71. -Young gorilla. (From I>u Chaillu) 
 
 5. Possible Factors in tho Ascent of Man.— in regard to 
 
 tlie factors which secured man's ascent from a humbler form of life 
 we can only si>eculatc. 
 
 (a) We have already explained that organisms vary, that the 
 offspring differ from their paients, that the more favourable changes 
 prosper, and that the loss fit die out of the struggle. Thus the race 
 is lifted. Now, from what we know of men and monkeys, it seems 
 likely that in the struggles of primitive man cunning was nxire 
 imixjrtnnt than strength, .ind if intelligence now U-cauic, more than 
 ever U-fore, the condition of life or death, wits would tend to 
 develop ra)>idly. 
 
 (/.) When h.ibits of using sticks and stones, of building shelters, 
 of living in families, l)egan- and some monkcyscxhil.it these— it is 
 likely that wits wouUl increase by leaps and Inninds. 
 
 (c) Professor Fiske and others have emphasised the importance of 
 prolongetl infancy, and this must surely have helped to evolve the 
 ncntlciiess of mankind. 
 
 n 
 
 '4 
 
346 
 
 The Study of Animal Life 
 
 APF. 
 
 («/) Among many monkeys society has begun. Families com- 
 bine for protection, and the combination favoors the derelopment 
 botfi of emotional and intellectual strength. Surely " man did not 
 make society, society made man." 
 
 B. Our Relation to Bioiogy. 
 
 6. The Utility of Sdeiice.— As life is short, all too short for 
 learning the art of Uving, it is well that we should cntiase our 
 activities, and favour those which seem to yield most return of 
 health and wealth and wisdom. 
 
 We are so curious about all kinds of things, so omnivorously 
 hungry for information, that the most trivial department of know- 
 ledge or science may afford exercise and mental satisfaction to its 
 votaries. The interest and pleasantness of science is therefore no 
 
 criterion. . , . u . i 
 
 Nor can we be satisfied with the assertion that saence should 
 be pursued for science's sake. As in regard to the kindred dictum, 
 " art for art's sake," we require further explanation— some ideal ot 
 science and art. For it is not evident tiiat knowledge is a good in 
 itself, especially if that knowledge be gained at the expense of the 
 emotional wealth which is often associated with healthy ignorance. 
 Nor is it safe to judge scientific activity by the material results 
 which the application of knowledge to action may yield. For a seed 
 of knowledge may Ue dormant for centuries before it sends lU shoots 
 into life, and many of the material results of applied science are not 
 unmixed blessings. Moreover, too narrow a view may be taken of 
 material results, so-called " necessaries " of existence may be exalted 
 over the "super-necessaries" essential to life; in short, w.mi ues 
 about the mouth— the nose, the ears, the eyes, the brain— u:?y be 
 
 °' WeTrc nearer the truth if we combine the different standards of 
 science, and unify them by reference to the human ideal.* The utility 
 of science, and of biology among the other kinds of knowledge, is 
 to supply a basis of fact — ... i 
 
 (a) For the practice of useful arts (such as hygiene and 
 
 education), and for the guidance of conduct : 
 
 (b) For the satisfaction of our desire to understand and enjoy 
 
 the world and our life in it. 
 
 7. Practical Jmstiflcation of Biology.-The world of life 
 
 is so web-like that almost any part may touch or thrill iw. it is 
 therefore well ihat we should learn what we can about it. 
 
 On plants we are very dependent for food and dnnk, for shelter 
 
 » See Ruskin. Tkt EagUt Nttt (1880). 
 
Animal Life and Ours 
 
 347 
 
 and clothing, and for delight. Thdr evil influen^ .s almost 
 restricted to that of disease germs and poisonons herbfc 
 
 Animals likewise furnish food (perhaps to an unwholesoaie 
 extent) ; and parts of their bodies are used (sometimes cafelessly) 
 in manifold ways. Among those which are domesti<ated, some, 
 such as canary and parrot, cat and dog, are kept for thepie^^ure 
 they give to many ; others, such as dog, horse, elei*a«t, -mfi 
 falcon, are used in the chase ; others, notably the dog, a*Mst .<> 
 shepherding; horse and ass, reindeer and cattle, camei anf! 
 elephant, are l)easts of burden ; others yield useful producte, the 
 milk of cows and goats, the eggs of birds, the silk of silkworms, 
 and the honey of bees. 
 
 Formerly of much greater imj ortance for good and lU as direct 
 rivals, animals have, through man's increasing mastery of life, become 
 less dangerous and more directly useful. Only in primitive con- 
 ditions of life and in thinly-peopled territories is something of the 
 old struggle still experienced. Their influence for ill is now for the 
 most part indirect,— on crops and stocks. Parasites are common 
 enough, but rarely fatal. The serpent, however, still bites the 
 heel of progressive man. 
 
 Man's relations with living creatures are so close that systentiatic 
 knowledge about them is evidently of direct use. Indeed it is in 
 practical lore that both botany and zoology have their primal roots, 
 and from these, now much strengthened, impulses do not cease to 
 give new life to science. 
 
 If increase of food-supply be desirable, biology has something to 
 say about soil and cereals, about fisheries and oyster-culture. The 
 art of agriculture and breeding has been influenced not a little by 
 scientific advice, though much more by unrationalised experience. 
 If wine be wanted, the biologist has something to say about grafting 
 and the Phylloxera, about mildew and Bacteria. It is enough to 
 point to the succession of discoveries by which Pasteur alone has 
 enriched science and benefited humanity. , u u i i 
 
 But if we take higher ground and consider as an ideal the healtli- 
 fulness of men, which is one of the most obvious and useful 
 standards of individual and social conduct, the practical justification 
 of biological science becomes even more apparent. 
 
 Medicine, hygiene, physical education, and good-breeding (or 
 " eugenics ') are the arts which correspond to the science of 
 biology, just as education is applied psychology, as government is 
 applied sociology, and as many industries arc applied chemistry and 
 physics. It would be historically untrue to say that the progreM in 
 these arts was due to progress in the parallel sciences ; in fact the 
 propretsive impulse has often been from art to science. ' La 
 pratique a partout devanc^ la thiorie," Espinas says, and all 
 
 -ff^^t.^- 
 
 m 
 
 :^i*jr.ras?: 
 
 ¥^-m 
 
348 
 
 The Study of Animal Life 
 
 APP. 
 
 historians of science would in the main confirm this. But it is 
 also true that science reacts on the arts and sometimes improves 
 
 There may be peculiar aberrations of the art of medicine due to 
 the progress of the science thereof, but these are because the science 
 is partial, and hardly affect the general fact that scientific prc^ess 
 has advanced the art of healing. The results of science have like- 
 wise suppUed a basis to the endeavours to prevent disease and to 
 increase healthfulness, not only by definite hygienic practice but 
 perhaps still more by diffusing some precise knowledge of the 
 
 conditions of health. , • , » • 
 
 The generalisations of biology, realised m men s minds, must in 
 some measure affect practice and public opinion. Spencer's 
 inducUon that the rate of reproduction varies inversely with the 
 degree of development sheds a hopeful light on the population 
 question ; the recognition of the influence which function and sur- 
 roundings have upon the organism suggests criticism of many 
 modes of economic production ; a knowledge of the facts and 
 theory of heredity must have an increasing influence on the art of 
 eugenics. Nor can I believe that the theory of evolution which 
 mei lold, granting that it is in part an expression of their life and 
 soc environment, does not also react on these. 
 
 . short, the direct application of biological knowledge in the 
 
 ja» arts of medicine, hygiene, physical education, and eugenics, 
 
 us to perfect our environment and our relations with it, helps 
 
 discover— if not the "elixir vitie"— some not despicable 
 
 sui tute. And likewise, a realisation of the facts and principles of 
 
 bio ijy helps us to criticise, justify, and regulate conduct, suggest- 
 
 in. V the ft of life may be better learned, how human relations 
 
 ml <; mor wisely harmonised, how we may guide and help the 
 
 Ia*«^ HJtnal JuBtillcation of Biology.— But another 
 
 r»n!: ym» ?ion of Biology is found in our desire to understand 
 thing -' >ur dislike of obscurities, in our inlwrn curiosity. There 
 is an in- actual as well as a practical and ethical justification of 
 the stucy of organic life. 
 
 Through our senses we liecome aware of the world of which we 
 form a part. We cannot know it in itself, for we are part of it and 
 only know it as it becomes part of us. We know only fractions of 
 reality- real at least to us- and these are unified in our experience. 
 
 (I) Intheworid around us we are accustomed to distinguish 
 four orders of facts, • ' Matter " and ' ' energy " we call those which 
 seem to us fundamental, because all that we know by our senses 
 are forms of these. The study of matter and energy-or i^erhaps 
 we may say the study of matter in motion— considered apart from 
 
, Animal Life and Ours 349 
 
 life, we call Phyria and Chemistty, of which astronomy, geology, 
 etc. are special departments. . . , j 
 
 (2) But we also know something about plants and animals, and 
 while all that we know about them is stiU dependent upon chuiges 
 of matter and motion, yet we recogni^ that the acUv.tie. of the 
 onanism cannot at present be expressed in terms of these. There- 
 foTJre find it convenient to speak of life as a new reality, while 
 believing that it U the result of some combination of matters and 
 energies, the secret of which is hidden. • a c\( 
 
 (?) But we are also aware of another reahty, our own mmd. Of 
 this we have direct consciousness and greater certamty than about 
 anvthine else. And while some would say that what we are 
 conscious of when we think is a protoplasmic change in our brain 
 cells or is a subtle kind of motion, it U truer to say that we are 
 conscious of ourselves. It U our thought that we know .t is our 
 feeling that we feel, and as we cannot explam the thought or the 
 feeling in terms of protoplasm or of motion, we find it convenient o 
 speak of mind as Tnew reality, while believing it to be essentudly 
 associated with some complex activity of protoplasm the secret of 
 which is hidden. For our knowledge of our own mental processes, 
 and of those inferred to be similar in our fellows, and of those 
 inferred to be not very different in intelligent animals, we establish 
 another science of Psychology. . ,., r .u u 
 
 (4l But we also know something about the life of the human 
 society of which we form a part. We recognise that it has a umty 
 of its own. and that its activities are more than those of its 
 individual members added up. We find it '^o")'*"'*"* »° '^^'J 
 society as another synthesis or un.ty-though less definite than 
 either organism or mind- and to our knowledge of the life and 
 erowth of society as a whole, we apply the term soaology. 
 
 Thus we recognise four orders of facts and four great sciences— 
 
 4. Society Sociology. 
 
 3. Mind Psychology. 
 
 2. Life Biology. 
 
 I. Matter and Energy . • Physics and Chemistry. 
 
 Each of these sciences is dependent upon its predecessor. Ihe 
 student of organisms requires help from the student of chemistry 
 and physics ; mind cannot be discussed apart from body ; nor can 
 society be studied apart from the minds of its component members. 
 Each order of realities we may regard as a subtle synthesis of 
 those which we call simpler. Life is a secret synthesis of matter 
 and energy ; mind is a subtle form of life ; society u a unity of 
 
 ""'But it must be clearly recognised that the " matter and energy" 
 which we regard as the fundamental realities are only known to us 
 
 II 
 
The Study of Animal Life 
 
 APP. 1 
 
 through whiU is for us the supreme reality— ourselves— mind. And 
 as in our brain activity we know matter and enei^ as thought, I 
 have adopted throughout this book what may be called a monistic 
 
 philosophy. . , ,>• • u 
 
 Having recognised the central position of Biology among the 
 other sciences, we have still to inquire what its task precisely is. 
 
 Our scientific data are (i) the impressions which we gather 
 through our senses about living creatures, and (2) the deductions 
 which we directly draw in regard to these. Our scientific aim 
 is to arrange these data so that we may have a mental picture of 
 the life around us, so that we may be better able to understand 
 what that life is, and how it has come to be what it seems to be. 
 Pursuing what are called scientific methods, we try to make the 
 world of life and our life as organisms as intelligible as possible. 
 We seek to remove obscurities of perception, to make the world 
 translucent, to make a working thought-model of the world. 
 
 But we are apt to forget how ignorant we are about the realities 
 themselves, for all the time we are dealing not with realities, but 
 with impressions of realities, and with inferences from these im- 
 pressions. On the other hand, we are apt to forget that our deep 
 desire is not merely to know, but to enjoy the world, that the heart 
 of things is not so much known by the man as it is felt by the child. 
 
APPENDIX 11 
 
 SOME OF THE «« BEST BOOKS" ON ANIMAL LIFE 
 
 To recommend the "best books" on any subject is apt to be like 
 prescribing the " best diet." Both depend upon age, constitution, 
 and opportunities. The best book for ine is that which does me 
 most good, but it may be tedious reading for you. Moreover, 
 books are often good for one purpose and not for another ; that 
 which helps us to realise the beauty and marvel of animal life may 
 be of little service to those who are preparing for any of the 
 numerous examinations in science. But the greatest difficulty is 
 that we are often too much influenced by contemporary opinion, 
 •o that we lose our power of appreciating intellectual per- 
 spective. 
 
 The best way to begin the study of Natural History is to 
 observe animal life, but the next best way is to read such accounts 
 of observation and travel as are to be found in the works of 
 Gilbert White, Thoreau, Richard JefTeries, and John Burroughs, 
 or in Bates's Naturalist on the Amazons, Belt's Naturalist tn 
 Nuaragua, and Darwin's Voyage cf the*' Beagle." Sooner or later 
 the student will seek more systematic books, but it is not natural 
 that he should begin with a text-book of elementary biology. 
 
 In introducing you to the literature devoted to the study of 
 animals, I shall avoid the bias of cunent opinion by following the 
 history of too\ogf. I shall first name some of the more technical 
 books ; secondly, some of the more popular ; thirdly, some of the 
 more theoretical. If I may make the distinction, I shall first 
 mention books on toology, secondly those on natural history, 
 thirdly thc«e on biology. 
 
 A. Zoolcgy, 
 
 (i) We can form a vivid conception of the history of toology 
 by cseiparing it with our own. In our childhood we knew and 
 
The Study of Animal Life 
 
 APP. 
 
 35« 
 
 eaicd more about the useful, dangerous, and strange animals than 
 about those which were humble and fiimiliar ; we had more in- 
 terest in haunts and habits than in structure and history ; we 
 were content with rough-and-ready classification, and cherished 
 a feeling of superstitious awe in regard to the indistinctly-known 
 forms of life. We were inquisitive rather than critical; we 
 accepted almost any explanation of facts, and, if we tried to inter- 
 pret, forced our borrowed opinions upon nature instead of trying 
 to study things for ourselves. So was it with those naturalists who 
 lived before Aristotle. .... 
 
 We must also recognise that the science of sool<^ had its 
 beginnings in a practical acquaintance with animals, just as botany 
 sprang from the knowledge of ancient agriculturists and herb- 
 gatherers. Much information in regard to the earliest zoological 
 knowledge has been gathered from researches into the history of 
 words, art, and religious customs, and there is still much to be 
 gleaned. Therefore I should recommend the student to dip into 
 those books which discuss the early history of man, such as 
 Lubbock's Prehistoric Times (1865), and Origin of Ctviluatton 
 (1870); Tylor's Primitive Culture (1871), and Anthropology 
 (1881) ; Andrew Lang's Myths, Ritual, and Religion ; besides 
 works on the history of philosophy, such as those of Schwegler and 
 of Zeller, which give some account of ancient cosmogonies. 
 
 (2) But just as there are precocious children, so there was an 
 early naturalist, whose works form the most colossal monument to 
 the intellectual prowess of any one thinker. The foundations of 
 loology were laid by Aristotle, who lived 384-322 B.C. He 
 collected many observations, and argued from them to general 
 statements. He records over five hundred animals, and describes 
 the structure and habits, the struggles and friendUness, of some 
 of these. His is the first definite classification. His work 
 was dominated by the idea that animal Ufe is a unity and part 
 of a larger system of things. In part his works should be read, 
 and besides the great edition by Bekker (Berlin, 183 1-40), 
 there is a translation of The Parts of Animals by Dr. Ogle, and 
 of The History of Animals by R. Cresswell. See also G. J. 
 Romanes's " Aristotle as a NaturalUt," Nineteenth Century (Feb. 
 
 1891, pp. 275-289). , . 
 
 (3) After the freedom of early childhood, and m most cases 
 after precocity too, there comes a lull of inquisitiveness. Other 
 affaira, practical tasks, games and combats, engross the attention, 
 and parents sigh over dormant intellects; so the historian of 
 toology sighs over the fifteen centuries during which science 
 slumbered. The foundations which Aristotle had firmly laid 
 remained, but the waUs of the temple of knowledge did not nse. 
 
n Sonu of the **Best Books " on Animal Life 353 
 
 The seeds which he had sown were alive, but they did not germi- 
 nate. Men were otherwise occupied, with practical affairs, with 
 the tasks of civilisation alike in peace and war, though some at 
 their leisure played with ideas which they did not verify. There 
 were some exceptions; such as Pliny (23-79 a.d.), a diligent but 
 uncritical collector of facts, and Galen (130-200 A.D.), a medical 
 anatomist, who had the courage to dissect monkej-s ; besides the 
 Spanish bishop Isidor in the seventh century, and various Arabian 
 inquirers. It will not be unprofitable to look into the Natural 
 History of Pliny, which has been translated by Bostock and 
 Riley. 
 
 (4) But just as there is in our life a stage — happy are those who 
 prolong it— during which we delight in fables and fairy tales, so 
 there was a long period of mythological zoology. The schoolboy 
 who puts horse-hairs into the brook, and returns after many days 
 to find them eel-like worms, is doing what they did in the Middle 
 Ages. For then fact and fiction were strangely jumbled ; credulity 
 ran riot along the paths of science ; allegorical interpretations and 
 superstitious symbolisms were abundant as the fancies which flit 
 through the minds of dreamers. Scientific inquiry was not en- 
 couraged by the theological mood of the time ; and just as Scotch 
 children cherish The Beasts of the Bible as a pleasantly secular book 
 with a spice of sacredness which makes it legitimate reading on 
 the Sabbath, so many a mediaeval naturalist had to cloak his 
 observations in a semi-theological style. 
 
 In illustration of the mood of the medieval naturalists, which 
 is by no means to be carelessly laughed at, read John Ashton's 
 Curious Creatures (Lond., 1890), in which much old lore is retold, 
 often in the words of the original writers. The most characteristic 
 expression of mythical Zoology is a production often called Physio- 
 b^ts. It is found in about a dozen languages and in many 
 diH'erent forms, being in part merely a precipitate of floating 
 traditions. It is partly like a natural history of the beasts of the 
 Bible and prototype of many similar works, partly an account of 
 the habits of animals, the study of which modern zoologists are 
 apt to neglect, partly a collection of natural history fables and 
 anecdotes, partly a treatise on symbolism and suggestive of the 
 poetical side of zoology, partly an account of the medicinal and 
 magical uses of animals. For many centuries it seems to have 
 served as a text-l)Ook, a fact in itself an index to the slow progress 
 of the science. Its influence on art and literature has been con- 
 siderable, and it well illustrates the attempt to secure for the 
 unextinguishable interest in living things a sanction and foothold 
 under the patronage of theology. A series of fifty emblems is 
 described, among others the lion wliich sleeps with its eyes ojien, 
 
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TJu Study of Animal Life 
 
 APP. 
 
 354 
 
 the lizard which recovers its sight by looking at the sun, the eagle 
 which renews its youth, the tortoise mistaken for an island, the 
 serpent afraid of naked man, and the most miserable ant-lion, 
 which is not able either to take one kind of food or digest the 
 
 other. 
 
 (5) But delight in romance is replaced by a feeling of the need 
 for definite knowledge, and the earlier years of adolescent man- 
 hood and womanhood are often very markedly characterised by a 
 thirst and hunger for information. Which of us— now perhaps 
 blast with too much learning— does not recall the enthusiasm for 
 knowing which once swayed our minds? Stimulated in a hundred 
 ways by new experiences and responsibilities, our appetite for facts 
 was once enormous. This was the mood of naturalists during the 
 next great period in the history of zoology. 
 
 The freer circulation of men and thoughts associated with the 
 Crusades ; the discovery of new lands by travellers like Marco 
 Polo and Columbus; the founding of universities and learned 
 societies ; the establishment of museums and botanic gardens ; the 
 invention of printing and the reappearance of Aristotle's works in 
 dilution and translation ; and many other practical, emotional, and 
 intellectual movements gave fresh force to science, and indeed to 
 the whole life of man. If we pass over some connectmg links, 
 such as Albertus Magnus in the thirteeenth century, we inay call 
 the period of gradual scientific renaissance that of the Encyclo- 
 paedists. This somewhat cumbrous title suggests the omnivorous 
 habits of those early workers. They were painstaking collectors 
 of all information about all animals; but their appetite was 
 greater than their digestion, and the progress of science was 
 in quantity rather than in quality. Prominent among them were 
 these four, the Englishman Edward Wotton (1492-1 555). w^o 
 wrote a treatise De Differetttiis Animalium ; the Swiss Conrad 
 Gesner (1516-65), author of a well-known Historia Animalium ; 
 the Italian Aldrovandi (b. 1522); and the Scotsman Johnston 
 
 (b. 1603). , , . , . 
 
 About the middle of the eighteenth century the best aims of the 
 Encyclopaedists were realised in Buffon's Histoire NaturelU, which 
 appeared in fifteen volumes between 1749 and 1767. This work 
 not only describes beasts and birds, the earth and man, with an 
 eloquent enthusiasm which was natural to tlie author and pleasing 
 to his contemporaries, but is the first noteworthy attempt to 
 expound the history or evolution of animals. Its range was very 
 wide ; and its successors are not so much single books as many 
 different kinds of books, on geology and physical geography, on 
 classification and physiology, on anthropology and natural histoiy. 
 There is a goo4 French edition of Buffon's complete works by 
 
II Some of the " Best Books " on Animal Life 355 
 
 A. Richard 1825-28), and at least one English translation. Three 
 large modem books on natural history correspond in some degree 
 to the Histoire Naturell:, viz. CasselPs Natural History, edited by 
 P. Martin Duncan (6 vols. ; London, 1882) ; The Standard or 
 Riverside Natural History, edited by J. S. Kingsley (6 vols. ; 
 London, 1888) : and a remarkable work well known as Brehm's 
 Thierleben, of which a new (3rd) edition is at present in progress 
 {10 vols.; Leipzig and Wien, 1890). Those who read German 
 will find in Caius Sterne's (Ernst Krause's) Werden und Vergehtn 
 (3rd ed. ; Berlin, 1886) the most successful attempt hitherto 
 made to combine in one volume a history of the earth and its 
 inhabitants. 
 
 (6) From BuflFon till now the history of biology shows a pro- 
 gressive analysis, a deeper and deeper penetration into the structure 
 and life of organisms. From external form to the internal organs, 
 from organs to the tissues which compose them, from tissues to 
 their elementary units or cells, and from cells to the living matter 
 itself, has been the progress of the science of structure — Mor- 
 phology. From habit and temperament to the work of organs, 
 from the functions of organs to the properties of tissues, from these 
 to the activities of cells, and from these finally to the chemical and 
 physical changes in the living matter or protoplasm, has been the 
 progress of the science of function — Physiology. Such is the lucid 
 account which Prof. Geddes has given of the last hundred years' 
 progress ; see his article " Biology " in the new edition of 
 Chambers's Encydopadia. Following the metaphor on which we 
 have already insisted, we may compare this century of analjrsis to 
 the period of ordered and more intense study which in the individual 
 life succeeds the abandonment of encyclopaedic ambitions. 
 
 We should clearly understand the histoiy of this gradually 
 deepening analysis of animals ; for if we would be naturalists 
 we must retread the same path. The history of biology has still 
 to be written, but there are already some useful books and papers, 
 notably — J. V. Carus, Geschichte der Zoologie (MUnchen, 1872) ; 
 J. Sachs, Geschichte der Botanik (MUnchen, 1875), translated 
 into English (Oxford, 1890); W. Whewell, History of the 
 Inductive Sciences (London, 1840) ; articles " Morphology " 
 and •• Physiology," Eneyclopadia Britannica, by P. Geddes and 
 M. Foster H. A. Nicholson, Natural History: its Rise and 
 Progi.u in Britain (Edinburgh, 1888); A. B. Buckley, Short 
 History tf Natural Science ; E. Terrier, La Philcsophie Zoologique 
 avant Darwin (Paris, 1884); Ernst Krause (Carus Sterae), Die 
 Allgemeine IVeltanschauung in ihrer historischen Entwitkelung 
 (Stuttgart, 1889). Very instructive, not least so in contrast, 
 are two articles, "Biology" (in Chambers's Encyclopadia), by 
 
356 
 
 The Study of Animal Life 
 
 APP. 
 
 P. Geddes, and "Zool(^" (in Emyclopadia Briiannica^f by E. 
 Ray Lankester. 
 
 If we think over the sketch which Professor Geddes has given, 
 we shall see how easy it is to arrange the literature — the first step 
 towards mastering it. {a) The early anatomists were chiefly 
 occupied with the study of external and general features, very 
 largely moreover with the purpose of establishing a classification. 
 The Systema Naturce of Linnaeus (ist ed., 1735 ; 12th, 1768) is 
 the typical work on this heavily-kden shelf of the zoological 
 library. It is to such books that we turn when we wish to 
 identify some animal, but the shelf is very long and most of the 
 volumes are very heavy. Each chapter of Linn^'s Systema h.is 
 been expanded into a series of volumes, or into some gigantic 
 monograph like those included in the series of " Challenger" Reports, 
 or The Fauna and Flora of the Gulf of Naples. If I am asked 
 to recommend a volume from which the eager student may identify 
 some British flower, I can at once place Hooker's Flora in his 
 hands. But it is more difficult to help him to a work by which he 
 may identify his animal prize. There are special works on Britisli 
 Mammals, Birds, Fishes, Molluscs, Insects, etc., but a compact 
 British Fauna is much wanted. I shall simply mention Bronn's 
 /Classen und Ordnungen des Thierreiches, a series of volumes still 
 in pr(^ess ; Leunis, Synopsis des Thierreiches (Hanover, 1886) ; 
 the British Museum Catalogues (in progress) ; and P. H. Gosse's 
 Manual of Marine Zoology of the British Islands (1856). 
 
 (A) Cuvier's Rigne Animal (1829)13 the typical book on the 
 next plane of research — that concerned with the anatomy of organs. 
 I should recommend the student on this path to begin with Pro- 
 fessor F. Jeffrey Bell's Comparative Anatomy atid Physiology (Lond. , 
 1886); after which he will more readily appreciate the text-books 
 on Comparative Anatomy by Huxley, Gegenbaur, Claus, Wieders- 
 heim, Lang, etc. As an introduction I may also mention my 
 Outlines of Zoology (Edin., 1892). As a book of reference 
 Hatchett Jackson's edition of Rolleston's Forms of Animal Life 
 (Oxford, 1888) is of great value, not least on account of its 
 scholarly references to the literature of zoology. The zoological 
 articles in the Encychp^tdia Britannua, many of which are pub- 
 lished separately, are not less useful. As guides in serious practical 
 work may be loticed- -A Course of Elementary Instruction in 
 Practical Biology by Profs. T. H. Huxley and H. N. Martin, 
 revised by Profs. G. B. Howes and D. H. Scott (Lond., 1888); 
 Howes's Atlas of Practical Elementary Biology (Lend., 1885); 
 A Course of Practical Zoology by Prof. A. Milnes Marshall and 
 Dr. C. H. Hurst (jtti ed'., I^nd., 1892); Prof. C. Lloyd 
 'ULax^xit Animal Biology [,UmA.^ 1889); Vogt and Yung, Traiti 
 
II Some of the " Best Books " on Animal Life 357 
 
 d^ Anatomic comparie pratique (Paris, 1885-92) or" in German 
 (Braunschweig) ; Prof. W. K. Brooks's Handbook of ItwerUbrate 
 Zoology for Laboratories and Seaside Work (Boston, 1882); Prof. 
 T. J. Parker's Zootomy (Lond., 1884) and Practical Biology 
 (Lend., 1891), 
 
 {c) As early as 1801, Bichat had penetrated beneath the organs 
 to the tissues which compose tliem, and his Anatomie GhiSrale is 
 the forerunner of many works on minute anatomy or histology. 
 From the comparative histology of animals by Leydig {Histologie, 
 1867) the zoological student must begin, but to follow it up he must 
 have recourse to the pages of scientific journals. As a guide in 
 microscopic work. Dr. Dallinger's new edition of Carpenter's well- 
 known work, The Microscope (Lond., 1 891) may be cited. 
 
 (d) In 1838-39, Schwann and Schleiden, two German naturalists, 
 clearly stated a doctrine towards which investigation had been 
 gradually tending, namely, that each organism was built up of 
 cells, and originated from a fertilised egg-cell. In the establish- 
 ment of this "cell theory" the study of structure became deeper, 
 imd the investigation of animal cells still becomes more and more 
 intense. To gain an appreciation of this step in analysis, the 
 student may well begin with the article " Cell " in the new edition 
 of Chambers's Etuyclopadia, and with the articles "Morphology" 
 and "Protozoa" in the Encyclopadia Britannica. From these he 
 will discover how his studies may be deepened. 
 
 («) Finally, with the improvement of microscopic instruments 
 and technique, investigation has touched the bottom, as far as 
 biology is concerned, in the study of the living stuff or protoplasm 
 itself. Again, I refer you to the articles "Protoplasm" in the 
 Encyclopadia Britannica ai:d in Chambers's Enc^'chpadia. 
 
 I shall not follow the history of physiology in detail, but content 
 myself with saying that [a) from the conception of a living body 
 ruled by spirits or dominated by a temperament, physiologists passed 
 •.o consider it {b) as an engine of living organs, then {c) as a com- 
 plex web of tissues, then (d) as a city of cells, and finally {e) as a 
 •.vhirlpool of living matter. I recommend you to read first the 
 article " Physiology " in the Encyclopcedia Britannica, then Huxley's 
 Crayfish (International Science Series), and his Elementary Text- 
 book of Physiolog}', then Jeffrey Bell's Comparative Anatomy and 
 Physiology and Lloyd Morgan's Animal Biology, after which you 
 may pass to larger works such as the text-books of Kirkes (new ed., 
 1892); Bunge(Lond., 1890); Landois and Srirling, McKendrick, 
 and Foster, and to the studies on comparative phj liology by 
 Krukenberg, Vergleichend - Physiologischt Studien and Vortrda 
 (Heidelberg, 1882-88). 
 
 In the above summary nothing has been said about the history 
 
358 The Study of Animal Life app. 
 
 of animals in their individ-l life^^^^^^^^^^ 
 
 appearance upon the ^''''^t^ jf JXrlolofv Sn with the article 
 buiion in space As regards embo'ology begin ^^^^^^^ 
 
 ^"r A^r H^L?? ttirot rUstrand F. M. Balfour 
 
 l^^nwTneiL and ^^^ teilpif^-=« of 
 distribution in time wU be found >" A «« p„n ^^^^^^^^ 
 
 students --y P-^;° Jj^^f ;oir. Ld. and Edin., ,889), to 
 Nicholson and R. ^S" ^z« emhainements du monde animal 
 the French work of Gaudry, /-« ««^«» j^ German 
 
 remains the principal w"'"^ °/ ^^^"7"' ^^^ ^t^dent to the>«m«/ 
 For progressive research I may re er tne suiuc" y 
 
 which gives summanes -J-^'^^^'^^^^] ^y Lankester. Klein. 
 ^/Mfr.5../»»Va/5«.«^« (edited by P;°'«- '^^^ ^ ^^^ ;„ ^hich 
 4dgwick, and Milnes Marshall) and of cou^^^^^^^ ,^ 
 summaries and d.scus.^^^^^ are oft n .o^J^ral ScUnce. 
 ^-SJ^IlUletnl^^^^^^ 
 
 mention other ways of begmnmg. 
 
 B. Natural History. 
 
 rory\:^r::S.^s s;:;:itrcut ^^ :z^ 
 
 them, they are seized w,th ^^^^J^^e^Sh a learned^ book about 
 it. to get it under the microscope »« P« J^ ^^^^^ ,exicon, and 
 it which no one can read w't^out an "P«"^'^*^j^ ^,1; ^j ,„ an 
 to put up its remains m «"^^"%^"^th on a pterygoid pro- 
 abnormal hxmapophysts ; ^^^^ P'" ^^JiVJ^, ^bT/of^ubeTc^^ 
 
„ Some of the " Best Books " on Animal Life 359 
 part of it. and is neither less nor jnore v^duable th^^^^^ tV.at^ of .the 
 Lid naturalist, ^e may crmcise the d^^^^ ^^^^^ ^^^^ 
 analysis we may believe that "^^P^^^^j^ ^m to be less 
 unnaturally upon students, we may ^^ ^^^^^^^„ ,^q„i,es 
 
 pedantic; but »« "mmd ^»^^^^^^^^^^^^^^ field 
 
 iJrllLTtrJJ-ls Mnes and muscles. Both are true 
 
 '' ^l^ ^^d \ rhSeTa^JetrlutThe^^^^^^^^^ and activities 
 our knowledge what 1'^ can tea ^ combinations of organs, 
 
 of animals aUke «« umtxes and a^ co^pl"^ ^^^^^ 
 
 tissues, and cells. Let us ag^f« |" j^j^h we have already 
 
 the morphological and PlS:i>°^°g\^^^^^^^^^ that few of us can 
 
 explained, "zoology." We ^^f ^f*^"";";^^^^ binder us from per- 
 become zoological experts. But ^^^ Jjj ^J^^wards what end and 
 ceiving that it is not ^i'^'^";' *° "^j^^ Sa^^^^^^^ Claude Bernard, 
 by what method Lmn^us and O^^^^^^^ ^^ j.^^„ „3i„g 
 
 and the other great masters worked, n^^^^^^ ^^^^ ^^^ 
 
 all natural opportumt.es o^ pact c^^^^^^^^ ...oology" is 
 
 powers of ammal life. ^« .j*"^" ,_.=-! j^an the work of the 
 Neither less interesting nor le« ^^^\^^^ ^^^^^^ is not more 
 field naturalist, we shall '«<=°et»se that its^ermi ogy ^^^^ 
 
 complex than that ^^ 5\^'"^"^J ?' *" Jk^^^^^^ nature acquires 
 from clear zoologica^ *»f ^"^ ?« *=°^^*'™^^^^^^^ cachait plus 
 
 an additional intensity o .en>c^ °°; ^ JloJ^« » What Hamerton 
 
 ou moins "\-'"»^«'^' ^^'"'^t^ ^ also to the 
 
 says with reference to an art^ts educa PP ^ 
 
 fo^r^^To^lS^:^^^^^^^^^^ --^^-" ^°" 
 
 their sense of perspective. those who have little time or 
 
 Now. however I YO^^,.f^^f;'J„7ave « interest in the life 
 opportunity for -zoolc^, but who have ^^^^ ^^^^ 
 
 and habits °f ^^^^^J^i^^^^^^ personalities -in 
 
 thoroughly. T">s Jcnowieagc ^^ ^^^y^^ 
 
 struggle and friendhneg. in ha e and ^^^J^J^^j j, ..,,,iogy" 
 I would call •• natural history, m c°°"^^ „ '^^ ^ther. For 
 
 on the one hand, and g^;"^^'"!, J°Sory of life-its nature 
 I restrict the latter term to ^J\« general tneo y ^.^^^^ ^^^^ 
 
360 The Study of Animal Life app. 
 
 the three as essential, and to cease from drawing prejudiced com 
 parisons between them. 
 
 Their relations may be summarised as follows : — 
 
 ••NATURAL HISTORY." 
 
 Study of the 
 
 real life 
 
 of 
 
 I 
 
 fauna 
 
 class 
 
 order 
 
 genus 
 
 species 
 
 families 
 
 pairs 
 
 individuals 
 
 in relation 
 
 to 
 one another 
 and to their 
 surroundings. 
 
 (S) Organism. 
 (4) Organs. 
 (3) Tissues, 
 (2) Cells, 
 (i) Protoplasm. 
 
 Study of Structure 
 (Morphological) 
 
 Study of Activities 
 (Physiological). 
 
 ZOOLOGY.' 
 
 To those interested in " Natural History," there is little need 
 to give the primary word of counsel " Observe," for to do so is 
 their delight ; nor do they need to be told that sympathetic feeling 
 with animals, delight in their harmonious beauty, and poetical 
 justice of insight which recognises their personality, are qualities 
 of a true naturalist, as every one will allow, except those who are 
 given up to the idolatry of that fiction called •« pure science." 
 
 There is a maniacal covetousness of knowledge which one has 
 no pleasure in encouraging. We do not want to know all that is 
 contained even in Chambers's Encyclopcedia, though we wish to 
 gain the power of understanding, realising, and enjoying the 
 various aspects of the world around us. We do not wish brains 
 laden with chemistry and physics, astronomy and geology, botany 
 
,1 Some of the " Best Books " on Animal Life 361 
 
 and roology, and other sciences, though we would have our eyes 
 lightened so that we may see into the heart of things our brains 
 cleared so that we may understand what is known and unknown 
 when we are brought naturally in face of problems, and our emotions 
 purified so that we may feel more and more fully the joy of life. 
 Therefore I would, in the name of education, urge students to 
 begin naturally, with what interests them, with the near at hand, 
 with the practically important. A circuitous course of study, 
 followed with natural eagerness, will lead to better results than he 
 most logical of programmes if that take no root in the life of the 
 
 ^^Let'me suggest some of these indirect ways of beginning. 
 Begin with domesticated animals and their histoiy. See Darwin s 
 Vanation of A mm ah and Plants under Domestication (l866), etc. 
 Concentrate your attention on some common animals. See, for 
 instance, Darwin's Formation of Vegetable Mould through the 
 action of Worms (i88l); Mivart's /r^^ (Nature Series, Lon^'on); 
 Huxley's Crayfish (Internat. Sci. Series, London) ; M«Cook s 
 North American S/^iders {2 vols., Philadelphia, 1889-90) ; f- 
 Cheshire's Bees and Bee-keeping (vol. i., Lond., 1886) ; Lubbock s 
 Ants, Bees, and Wasps (IniGrnvii. Sci. Series, London); Flowers 
 
 /A»r5«(Lond., 1891). ,,. , , „, 
 
 Enjoy your seaside holiday. See Charles Kingsley ^Glaucus-, 
 
 J. G. Wood's Common Objects of the Sea-Shore (1857); P. H. 
 
 Gosse's Manual of Marine Zoology (1856), and Tenby-, G. H. 
 
 Lewes's Seaside Studies (mm. 1858); L. Fred^ricq, La Lutte pour 
 
 rexistence chez les Animaux Marins {Vaxxs, 1889). 
 
 Form an aquarium. See J. G. Wood's Fresh and Salt Watei 
 
 Aquarium ; P. H. Gosse, The Aquarium (1854), and many similar 
 
 Begin a naturalist's year-book. See the Naturalist's Diary 
 by Roberts; the Field Naturalise s Handbook, by J. G. and 
 Th. Wood {Lond., 1879); and K. Russ, Das hetmtsche 
 Naturleben im Kreislauf des Jahres ; Ein Jahrbuch der Natur. 
 
 (Berlin, 1889). „ _ 
 
 Observe the inimals you see on your country walks. &ee 
 T. G. Wood's Common Objects of the Country (1858), The Brook 
 and its Bank (1889); Life of a Scotch NaturaHt, Thomas 
 Edward, by Samuel Smiles; The Moor and the Loch, hy J. 
 Colquhoun (Edin. 1840, 8th ed. 1878); Wild Sports and Natural 
 History of the Highlands, by Charles St. John (Lond., illust. ed., 
 1878); Woodland, Moor, and Stream, edited by J. A. Owen 
 (Lond., 1889); W. Marshall, Spaziergange eifus Natutforschers 
 (Leipzig, 1888); Lloyd Morgan's Sketches of Animal Life (Lond., 
 1892), etc. etc. 
 
The Study of Animal Life 
 
 KVV. 
 
 Another natural way of beginning is to work out some subject 
 which attracts you. It becomes a centre round which a crystal 
 erows. Muybridge's photographic demonstrations of animal loco- 
 motion have interested us in the Hight of birds, et us follow this 
 ^p iy observation and by reading, e.g., Ruskin's Z^.V Mann 
 (i88i); Pettigrew's Animal Locomotion (Internat. Sci. Series 
 \%Tiy,U»xti% Animal Mechanism (Internat Sci. Series. 1874); 
 Marey's Le Vol des 0«wi«r (Paris, 1890). 
 
 The colours of animals appeal to many people. Read E. B. 
 Poulton's volume (1890) in the Internat. Sci. Series, and Grant 
 STcolour 5*L. aid F. E. Beddard's Animal Colo,naUon 
 
 ^^The lelaUons between plants and animals are ent'^ncingly 
 interesting Watch the bees and other insects in their flight, 
 anSDarS volumes on the Fertilisation of OrcAJds {1S62) 
 ^oTcross.FertilisationiiS76); Hermann Umiers Fertzhs^^on 
 of Flowers (transl. by Prof. D'Arcy Thompson, Lond., 883) . 
 Kemer's Flowers and their Unbidd^ Guests; the arUcles on 
 '« Insectivorous Plants," in Encyclop. Brttanntca, and m Chambers s 
 ^Mrvf/oA, or Darwin's work (1875). , . , . » •„, 
 
 XSn, manyof us are directly interested in foreign countries 
 Let^e practical interest broaden, it naturally becomes geographical 
 a^d physiograpWcal. and extends to the natural history o he 
 rSon No more peasant and sane way of learning about the 
 wSs and distribution of animals could be suggested than that 
 Sh follows as a gradual extension of physiographcal knowledge. 
 See Dr H. R. Mill's Realm of Nature, and the following samples 
 from Xh" long list of books by exploring naturalists :— 
 A. Agassiz. nree Cruises of the "Blake" (Boston and New York. 
 
 S W.^ Baker. Wild Beasts and Ways: Reminiscences of Europe, 
 
 jitia Africa, and America VUinAon, \Z<io). 
 H. ^^^^ Naturalist on the Amazons (sth ed.. London. 
 
 T iJlt Naturalist in Nicaragua (2nd ed., London. 1888). 
 liiirT:S^ioTobservatiom on Geology and Zoology of Abyss.nta 
 
 P B^^ci^m%xplorations and Adventures in Equatorial Afnca, 
 
 ^ rCutln|Sll= l!^:Zl!:^ilTut^l History of the Straits of 
 
 Magellan (EAia., 1871). . 
 
 Darwin. rW e^'** " -»# '^^J "^^g^" '^^°^- 
 
 H. Drummond. Tropical Afnca (Umd. , 1888). 
 
 h! O. Forbes. A Naturalists Wanderings %n the Eastern Arc/it 
 
 ptlago {Uind. , xBSs)- ^ „ ,. . ,on^v 
 
 Gm\ltm^Td, Cruise of the -Marchesa' (Lond.. 1886). 
 
„ Sofiu of the " Best Books " oh Animal Lift 363 
 
 187Q, new ed. Lond., 189a). .. /i «„^ tRRt^ 
 
 unternommmen Reiser (L;^>Pf!S; J^^'- .^ .„ ^,,.^ 
 
 H. Seebohm. 5j*ma m Europe (Lond.. i88oj . ana 
 
 J. E.^Tennent. ^'^'-ral History of Ceylon {l.c^^^^^ 
 VyviUe Thomson. The Depths of t/ie S a (M ^1^73) .^^^ ^J^ 
 the Voyage of the \C>taUenger (r^^S)^ Cf A^ oe ^^^.^^^^^^ 
 
 Tristram. V/i/ Flora and Fauna of Palestine. 
 
 Tschndi, Thierleien der A Ipenwelt. Trotical Nature 
 
 A R. Wallace. Malay Archipelago {Lond.. 1869) . Tropicat na, 
 
 (1878) ; hland Life (i88°)- America (ed. by T. G. Wood. 
 
 Ch. Waterton, Wanderings m South America ^ea. oy j 
 
 C. M^'woodford, Naturalist among the Head-hunters (London. 
 1890). 
 Prominent among those who have helped many to «alise the 
 marveland beauty of nature, a widely-felt gratitude ranks Gilbert 
 WWte Henry Thoreau. Charles Kingsley. Richard JefTenes. J. G. 
 Wood, John Ruskin, and John Burroughs. 
 
 'Lento, .888), buf .her. Is a cheaper one. edited b, R,cha,d 
 Jefferies, in the Camelot Series. 
 
 Henry Thoreau (1817-1862). the author of Walden, A Week 
 on Concord, and other much-loved books. 
 
 CHARLES KINGSLEY (l8l9-i«75)- See his Glaucus 
 1854) ; Water-Babies ; and popular lecturer 
 
 (Lend., 
 
3^4 
 
 The Study of Animal Life 
 
 APP. 
 
 Richard Jefferies (1848- 1887). 
 
 See The Eulogy of Richard Jefferies, by Walter Besant (London, 
 1 883), and the following works, some of which are published in 
 cheap editions: The Gamekeeper at Home (1878); Wild Lift 
 in a Southern County (1879); The Amateur Poacher (1880); 
 Round about a Great Estate (t88i) ; Nature near London 
 (1883) ; Life of the Fields (1884) ; Red Deer (1884) ; The Open 
 ^iV(i885). 
 
 J. G. Woou, whom we have lately lost, has done more than 
 any other to popularise natural history in Britain. 
 
 See Life of J. G. Wood, by his son, Theodore V/ood (Lond., 1890) ; 
 My Feathered Friends (1856); Common Objects of the Seashore 
 (1857); Common Objects of the Country (1858): his large 
 Natural History (1859-63) ; Glimpses into Petland (1862) ; Homes 
 without Hands (1864) ; The Dominion of Man (1887) ; and other 
 works. 
 John Ruskin. See the Eagle's Nest, Queen of the Air, Love's 
 
 Meinie, Proserpina, Deucalion, and Ethics of the Dust. 
 
 John Burroughs. 
 See the neat shilling editions of Wake Robin (1871), Winter Sun- 
 shine (1875), ^»'''^-' ^"^ P"^*^ (1877). iLocusts and Wild Honey 
 (1879). Pepacton (1881), Fresh Fields (1884), Signs and Seasons 
 (1886). 
 
 See also : — 
 
 Grant Allen, The Evolutionist at Large; Vignettes from 
 Nature, etc. 
 
 FraNK Buckland, Curiosities of Natural History (London, 
 1872-77), and his Life. 
 
 P. H . GOSSE. Romance of Natural History' ( London, 1 860-6 1 ). 
 
 P. G. Hamerton, Chapters on Animals : The Sylvan Year 
 (3rd ed., London, 1883). 
 
 W. Kirby and W. Spence, Introdui.'ion to Entomology 
 (London, 1815). 
 
 F. A. Knight, By Leafy Ways; Idylls of the Field (London, 
 1889). 
 
 Phil Robinson, The Poet's Birds (London, i8«3); and The 
 Poet's Beasts (London, 1885). 
 
 Andrew Wilson, Leaves from a Naturalist's Note-Books; 
 Chapters on Evolution, etc. 
 
 -■**»«!« 
 
II 
 
 So7ne of the " Best Books " on Animal Life 365 
 
 C. Biology. 
 
 Having offered counsel to those who would study the literature 
 of Zoology and of Natural History, I shall complete my task of 
 giving advic- by addressing those who are strong enough to 
 Tnquire into the nature, continuance, and progress of life. It is 
 to students of mature years that this •♦biological" study is most 
 natural, for young folks should be left to see and enjoy as much 
 as possible, till theories grow in them as naturally as "wisdom 
 teeth." This also should be noted in regard to the study of 
 evolution and the related problems of biology, that though all the 
 generalisations reached must be based on the research and observa- 
 tion of zoologists, botanists, and naturalists, and are seldom fully 
 appreciated by those who have little personal acquaintance with 
 the facts, yet sound and useful conclusions may be, and often are, 
 obtained by those who have had no discipline in concrete scientific 
 
 work. 
 
 Besides the general question of organic evolution there are 
 special subjects which the student of biology must learn to think 
 about: Protoplasm, or "the physical basis of life;" Repro- 
 duction, Sex, and Heredity, or "the continuance of life>" and 
 Animal Intelligence, or "the growth of mind." Before passing 
 to the literature on these subjects, it may be noted that there are 
 two general works of pioneering importance, namely, Herbert 
 Spencer's Principles of Biology (2 vols., Lond., 1864-66), and 
 Ernst Haeckel's GemrelU Morphologie {2. vols., Berlin, 1866). 
 
 Protoplasm.— Of this the student should learn how little we 
 know. Yet this is not very easy, since the most important recent 
 contributions, such as those of Professors Hering and Gaskell, are 
 inaccessible to most. The gist of the matter, however, may be 
 got hold of by reading : (a) three articles in the Encychpadia 
 ffritannica, "Physiology" (Prof. M. Foster), "Protoplasm" 
 (Prof. P. Geddes), and " Protozoa"— the large type— (Prof. E. Ray 
 Lankester) ; {p) the Presidential Address to the Biological Section 
 of the British Association, 1889, by Prof. Burdon Sanderson 
 {Nature, xl., September 1889, pp. 521-526); and {c) the article 
 "Protoplasm" in the new edition of Chambers's Etuyclopadia. 
 Of the abundant literature on the philosophical questions which 
 the scientific conception of living matter raises, I shall mention 
 Huxley's address on "The Physical Basis of Life," published 
 among his collected essays; Hutchison Stirling's tract, "As 
 regards Protoplasm;" the chapter on "VitUiism" in Bunge's 
 Physiological Chemistry (translated, London, 1890). 
 
 Beprodnction, Sex, and Heredity.— For adult students, 
 
 and no others should be encouraged to face the responsibility of 
 
 t 
 
366 The Study of Animal Life app. 
 
 inquiry into such matters, the most convenient introductionj.'iU 
 Kund n The Evolution of Sex p^ni^^^or^rj S^^^^^^n^^ 
 llnd 1880V by Prof. Geddes and myself. In that work there 
 ^e ifeJcncel' Z others. A survey of modem op.mons and co„ 
 1 • « ;« r^Torrl to heredity may be obtamed Kom the article in 
 
 ffm^JmeriliL (Lo„d„ .889), and to other „„po.ta„t 
 '^*n^°tot<;CD'SJ-rS wo* by Professor C. iJo,d 
 
 also mention that Brehm t n«rkU« ('S^S »9 S „„„, 
 
 in process of re-edition (10 "«''■• "^f '"'"J' ,'\„j „i,dom of 
 „««ur, of inf«mat»n - J=8«d 'o * . X^.V-l-i-'.' 
 
 C't'o^ 'Vr >: =n'io»sTo',."of ir,.T„'''aW terse 
 Protozoa. Ol ^^^ '"8^" „-„«av's Les Industries des Antmaux 
 I^S^m. '''Z 5~HeJo^.i„ct «e esg=^.. K„™.cs, 
 
 in regwd to Evolution is to make mmseu »t4u».ut 
 
II 
 
 Some of the " Best Books " on Animal Life 367 
 
 arguments ^^hich show that the animals and plan now ahve are 
 descended from simpler ancestors, these from still s™Pl". ^J" 
 soTback into the mists of life's begimiings. To realise that the 
 
 (Nature Series, Lond.) gives a convenient statement of the case, 
 S hfs RSbTry Lectures will be more exhaustive. CU^d s 
 ?LvofcLli7n: a plain accoun: of Evolution (Lond., 1888) 
 S UP the evSence in small compass ; another very terse state- 
 ment wm be found in H. De Varigny's Experimental EvoMxm 
 Sd 892); Haeckel's Natural Hilary ./ Cr.a/«^ (Berim, 
 te^tne -St popular of his works, now in its ^f ^h f mon 
 (Tena i89o)-is available in translation (Lond.. 1879) ; Huxley s 
 ^^AnuH^an Addressee (Lond., 1877) have even peater «:h^m f 
 f^e; Carus Sterne's Werden und Vergehen (3rd ed.. Berlin 
 1886 is perhaps the best of all popular expositions; while the 
 thorougb Sent will find most satisfaction in the relevaii 
 iTrJbnso. Darwin's Origin of Species, and Spencer's Pnnctples 
 
 "^mZtl Of Evolution Theories.- As the idea of Evolution 
 is v^Snt, and as it was expounded in relation to animal Ufe 
 byTa. c^Smpetent naturalists "before Darwin's inteHectual com 
 Scame current throughout the world, it is unwise that students 
 S restrict tl..ir reading to Darwinian and Pos^Damiman 
 literature. The student of Evolution should know ho«r Buffon 
 Erasmu- Darwin. Lamarck. Treviranus. the St. Hila.res Goethe 
 
 even Robert Chambers, and many other P'^^f^^^"'''"^ .'^f ^^ ^^ 
 the problem. Those who desire to preserv;- their sense of historical 
 Ssti'ce should read one or more of the following : Huxley Y^^^^^^ 
 in " Evolution " in the Encyclopadxa Bntannua ; Samuel Butler s 
 interesting volume on Evolution Old and ^«7^(L*>"f«'- 'f J^) ; 
 Perrkr'8/'-4.-^x«'/A'V Zoologique avant Darwtn (Pans. 1884) the 
 hSorical chapters of H^e^kel'. Natural History of Creatton-, 
 SZTcescLte der ZoologU, and some other histon^ works 
 already referred to (p. 355) ; /. de CandoUe's g'^""' ^" 
 
 Sciences et des Savants d^P''"/^*' ^\i' l^ ^ h^^hL^^^^^^ 
 Carus Sterne's (Ernst Krausc's excellent work, Dte Allgemetne 
 mZnschauung (Stuttgart. ,889) ; De Quatrefages. CkarUs 
 Darwin et sesprJcurseursfranfats {Funs, liJO). ., 
 
 Darwinisnu-The best account of the Darwinian theory of 
 EvolSTespecially of the theoiy of natural selwtion which 
 ChSs Darwi? and Alfred Russel W-Uace independently^cj^ 
 rated, is Wallace's Darwinism (Lond.. 1889). From this the 
 
368 
 
 The Study of Animal Life 
 
 A pp. 
 
 Student will naturally pass to the works of Darwm himself— 7A« 
 Origin of Species by means of Natural SeUction ; or, the Pre- 
 servation of Favoured Races in the Shuggle for Life (Lond., 
 1859) • The Variation of Animals and Plants under Domestuatton 
 (2 vols., Lond., 1868); The Descent of Man, and SeUction in 
 Relation to Sex (Lond., 1871), etc. ; the earlier works of Wallace, 
 especially his Contrilmtions to the Theory of Natural Selection 
 (Lond., 1 871); Spencer's Principles of Biology— cf his articles 
 on "Thf Factors of Organic Evolution" {Nineteenth Century, 
 1886); Haeckel's Generelle Morphologie, and Natural History of 
 Creation. As a popular account of Darwin's life and work. Grant 
 Allen's Charles Danvin (English Worthies Series, 3rd ed., Lond., 
 1886) has a deserved popularity; G. T. Bettany's similar work 
 (Great Writers Series, Lond., i886) has a very valuable biblio- 
 eraphy ; but for full personal and historical details reference must 
 be made to the Life and Letters of Charles Darwin, by his son 
 Francis Darwin (3 vols., Lond., 1887). 
 
 Becent Contributions to the Theory of Bvolutioa— 
 
 At the present time there is much discussion m r^ard to the 
 factors of organic Evolution. The theory of Evolution is still 
 being evolved ; there is a struggle between opinions. On the 
 one hand, many naturalists are more Darwinian than Darwin was, 
 —that is to say, they lay more exclusive emphasis upon the theory 
 of natural selection ; on the other hand, not a few are less Darwinian 
 than Darwin was, and emphasise factors of Evolution and aspects 
 of Evolution which Darwin regarded as of minor importance. 
 
 Of those who are more Darwinian than Darwin, I may cite as 
 representative : Alfred Russel Wallace who, in his Darwinism, 
 subjects Darwin's subsidiary theory of sexual selection to destructive 
 criticism; August Weisma.m wlio, in his Essays on Heredity, 
 denies the transmissibiiity of characters acquired by the individual 
 oreanism, as the results of use or disuse or of external influence ; 
 and E. Ray Lankester, see his article "Zoology" m iht Enc^-clo. 
 padia Britannica, and his work on tlie Advancement of Science 
 fLond., 1890). The student should also read an article by Prof. 
 Huxley, "The Struggle for Existence, and its Bearing upon Man 
 in the Nineteenth Century, Feb. 1888. 
 
 Samuel Butler. Evolution Old and New (Lond., 1 /9). Luck or 
 
 C«««»»r (Lond.. 1887) and other works. 
 Prof E. D. Cope. Origin of the Fittest {ii^yt \oxV., 1887). 
 Prof G H T Elmer, Organic Evolution, as the Result of the 
 
 Inheritance of Acquired Characters, according to the Laws of 
 
 Organic Growth (Jena. 1888). Trans, by J. T. Cunnmgnam 
 
 (Lond., 1890). 
 
II Scm4 of the " Best Books " on Animal Life 369 
 
 Ptot T. Ffake, Outlims tf Cosmic PhUmophy (Lund.. 1874). Dor- 
 wMsm, amdoOtr Essays {Ifnd., »*75). ., „_^^,^^i, 
 
 i>r«f P Reddes Article "Variation and Sdection, MHcyeUf^ata 
 5^*^^' '^ution." Chambers-s Encyclopedia n^ ^. 
 OLmEiloluHon of Sex. and forthcoming work on Evolutton, 
 
 Organic and Social. 
 V Oflon La LutU fiour le Bien-ltrt (1090). 
 Rc^T'Tfo^dH Divergent Evolution, through CumulaHve Segre- 
 
 P ^.^Z^'^uZ^^^^^T^r,^'' Nineteenth century 
 Lan.S' Z'L:ur^^\E.istence et rAssociaHon pour la LutU 
 
 Prof^^^'c^rgc Mivart. The Genesis if ^pecies{U>f- . Xr"*' 
 
 U^sonsfJi Nature (U>nA., 1876). On Truth (^n±, 1889). 
 Prof C. lioyd Morgan, Animal Life and Intelligence {Lond., 
 
 Prof.*C°^V. NBgeU. Mechanisch . physiologischc Abstammungslehre 
 
 '(MUnchen and Leipzig. 1884). pi«„,idt 
 
 Prof. A. S. Packard, Introduction to the Standard or Rtverstde 
 
 Natural History (New York and Lond., 1885). 
 Dr G T Romanes, Physiological Selection (Joum. Linn. Soc. xu.. 
 
 1886). Sd forthcoming'^Rosebery I^tures on the PhUosophy 
 
 ^ToL^liLt^Tnl'Natural Conditions of Existence as they affect 
 J timal Life (Intrmt. Sci. Series, Lond., 18B1). 
 
 Dr. J B LtSi! Jr Int,vducHon 'to General Pathol^ (Lond, 
 x886). Evolution and Disease (Contempor. Sci. Senes, Lond.. 
 1890). 
 
 3 B 
 
INDEX 
 
 Absorption, 145 
 Acacias guarded by ants, 29, 30 
 Acquired characters, 339-336 
 Actions, automatic, 155 
 
 habitual, 155 
 
 innate, 155 
 
 intelligent, 155 
 Alternation of generations, 189 
 
 Amoeba, 213 
 Amphibians, 9, 256, 257 
 
 parental care among, no, in 
 Amphioxus, 252 
 Angler-fish, 118 
 Animalculists, 191 
 Animals, everyday life of, 1-124 
 
 domestic life of, 05, 116 
 
 industries of, 1 17-124 
 
 life-history of, 184-203 
 
 past history of, 204-209 
 
 social life of, 67-94 
 
 and plants, resemblances and 
 contrasts, 167-171 
 
 relation of simplest to more 
 complex, 1 71-174 
 Ann lids, 231-234 
 Antic. . 279 
 Ants, J '-84 
 
 and av- ides, 119, 120 
 
 and plants, 29 
 Aphides, 8a, 31a 
 
 mnltipUcation of, 38 
 Anchnida, 243 
 Archoplaun, 183 
 
 Aristotle, 283, 284 
 Armour of animals, 34, 35 
 Artemia, 310, 311 
 Arthropods, 10, 238 
 Atavism, 322 
 Autotomy, 64-66 
 Axolotl, 309 
 
 Backboned animals, 9, 222-247 
 Backboneless animals, 9, 10, 248- 
 
 272 
 Bacteria, 21, 2a 
 Balance of nature, 19-21 
 Balanoglossus, 9, 249, 250 
 Bathybius, 219 
 Beauty of animals, 15-17 
 Beavers, 25, 74, 7S 
 Bees, 78-84 
 
 Biology, justification of, 34-50 
 
 Birds, 9, 264-267 
 parental care among, 114, 115 
 
 Blind animals, 305 
 
 Body, functions of, 144-149 
 parts of, 174-183 
 
 Books, 351-369 
 
 Boring animals, 25 
 
 Bower birds, 98 
 
 Brachiopoda, 235 
 
 Brine-shrimp, 310, 311 
 
 BufTon, 286 
 
 Caddis worms, 6z 
 Carbohydrates, 134 
 
37« 
 
 The Study of Animal Lift 
 
 Caterpillars, 50. 51 
 Cau and dover. 39 
 Cave-animals. 334 
 Cdl-divMon. 158-183 
 Cells, ia8, 147. 179-183 
 Centipedes, 341 
 Cestoda, 339 
 Chsetopoda, 331-233 
 Challenger Expedition, 5, 6 
 Chamseleons, 53 
 Chemical elements, 135 
 
 influences in environment, 309, 
 
 313 
 
 Circulation, 146 
 Classification of animals, 8-ix 
 Coelenterates, 222-228 
 Cold, effect of, 313 
 Colonies, 70, 71 
 Colour-change, 52, 53 
 Colouring, protective, 48, 49 
 
 variable, 49-51 
 Colours of animab, 49-53 
 
 of flat-fishes, 315 
 Commensalism, 68, 69 
 Competition, internal, 67 
 Concealment of animals, 47 
 Conjugation, 314 
 Consciousness, 150-153 
 Co-operation, 69 
 Corals, 26, 27, 227 
 Coral snakes, 59 
 Courtship of birds, 96 
 mammals, 96 
 spiders, 101-105 
 Crabs, masking of, 61, 62 
 
 and sea-anemones, 68, 69 
 Cranes, gregarious life of, 73 
 Crayfish, 35 
 Crocodilians, 363, 364 
 Cruelty of nature, 43-45 
 CnisUcea, 339> 34° 
 
 life-history of, 198-202 
 Cuckoo, 114. "5 
 Cuttlefish, 53, 66 
 Cyclostomata, 35a 
 
 Darwin. Charles, 393-396 
 Brftsmuf, 388, 389 
 
 Deep-sea fishes, 356 
 
 life, 6 
 Descent of man, 34X>34S 
 Desiccation. 41-43 
 Digestion, 145 
 Distribution of animals, 3-8 
 Disuse, results of. 305, 306 
 Division of labour, 69-71, 143' 
 
 144 
 Dormant life, 41-43 
 Drought, effect of. 41-43 
 
 Earthworms, 23-34 
 
 Echinoderms, 10, 65, 66, 235-238 
 
 Ectoderm, 196 
 
 Eggs, 191, 19a 
 
 Elaps, 59 
 
 Elephant hawk-moth, 59 
 
 Encystation, 41 
 
 Endoderm, 196 
 
 Environment, 306-319 
 
 Ephemerides, 106, 107 
 
 Epiblast, 196 
 
 Epigenesis, 324 
 
 Evolution, evidences of, 373-281 
 
 factors of, 399-303 
 
 theories, history of, 383-301 
 
 of sex, 188 
 Extinct types, 206, 207 
 
 Family, evolution of, 91 
 
 life, 91 
 Fats, 134 
 Feigning death, 66 
 Fertilisation. 193-19S 
 Filial regression, 3^8 
 Fishes, 9, 253-25" 
 
 parental care among, 109, 110 
 Flight of birds, 123, 124 
 Flowers and insects, 28, 39 
 Flukes, 229 
 
 Food, influence of, 310-313 
 Freshwater fauna, 6-8 
 Friar-birds, 59 
 Frog, 258 
 Ftmction, influence of,. 303 
 
 Oastra^ theoty. X97 
 
Index 
 
 373 
 
 Gastnila, 195, 196 
 Genealogical tree, la, 13 
 Geological record, imperfection of, 
 
 ao5 
 Germ-plasma, 338 
 Giant reptiles. 359 
 Glow-worm, courtship of, 100 
 Greg^nes, an 
 Gregarious animals, 71-74 
 Grouse attacked by weasel, 40 
 
 Habitat, change of, 47 
 Habitual actions, 155 
 Haeckel, 398 
 Hagfish, 353 
 Halcyon, 116 
 Hatteria, 260 
 Heat, influence of, 313 
 Heredity, 320-339 
 Hermaphroditism, 188 
 Hermit-crabs, masking of, 63 
 Hirudinea, 334 
 Homes, making of, 121-123 
 Hombill, brooding of, 114 
 Horse, pedigree of, 278 
 Hunting, 118, 119 
 Huxley, 298 
 Hydractinia, 69, 70 
 Hypoblast, 196 
 
 Ichneumon flies, 64 
 Idealism, 14a 
 Impressions, 151 
 Industries of animals, 116-124 
 Infiisorians, an 
 
 multiplication of, 38 
 Innate actions, 155 
 Insects. 341-343 
 
 parental care of, 108 
 
 and flowers. 38 
 Instinct, 153-166 
 
 origin of, 163-166 
 Instinct defined, n 
 
 incomplete, 158 
 
 mixed. 163 
 
 primary, 163 
 
 secondary, 163 
 Insulation of animals, 46 
 
 Intelligence, lapse of. 166 
 Intelligent actions, 155 
 Iron, importance of, 19 
 Isolation, 300, 30X 
 Ivory. 31 
 
 Jellyfish, 226 
 
 Kallima, S3 
 Kidneys, work of, 145 
 
 Lamarck, 289-292 
 
 Lamprey. 252 
 
 Lar;cdet. 9, 252 
 
 Land animals. 8 
 
 Leaf insects. 54 
 
 Leeches, 234 
 
 Lemming, Ross's, 50 
 
 Lemurs, 46 
 
 Life, chemical elements of, 135- 
 
 137 
 
 energy of, 127 
 
 haunts of, 3-8 
 
 machinery of, 130, 131 
 
 origin of. 140-142, 280 
 
 struggle of. 32-45 
 
 variety of. 3 
 
 wealth of. 1-17 
 Light, influence of, 315, 316 
 Liver, work of, 145 
 Living matter, 131-135 
 Lizards, 260 
 Love of mates. 90, 91, 96 
 
 and care for offspring. 105-116 
 
 and death. 106 
 Luciola. courtship of, 100 
 Lucretius, 284, 285 
 
 Macrofod, parental care of, no 
 Mammals, 9, 267-271 
 Man as a social person, 94 
 
 considered loologically, 340- 
 
 346 
 Marine life, 3-6 
 Marsupials. 46 
 Masking, 61-63 
 Materialism. 141, 14* 
 
374 
 
 The Study of Animal Life 
 
 Mates, love of, 90, 91, 96 
 Mayflies, 106, 107 
 Metamorphosis of Insects, 243 
 Meaoderm or mesoblast, 196 
 Migration of birds, 74 
 MiUepedes, 241 
 Mimicry, 57-61 
 Mites, desiccation oi, 41, 43 
 Molluscs, 10, 243-'247 
 Monkeys, 370, 271, 341 
 
 gregarious life of, 71 
 Monogamous mammals, 96 
 Moss-insect, 55 
 Moulting, 315 
 Movement, 144 
 
 Movements of animals, 123, 124 
 Mud-fish, 8 
 Mygale, 36 
 Myriapoda, 241 
 
 Natural selection, 295 
 Nematoda, 231 
 Nemerteans, 230 
 Nervous system, 148 
 Nudibranchs, 56 
 Number of animals, 14, 15 
 Nutrition, 144 
 Nutritive relations, 27, 28 
 
 Odours and sexual attraction, 
 
 Offspring, care for, 105-116 
 
 Ontogeny, 203 
 
 Ooze, 220 
 
 Organic continuity, 203, 326-329 
 
 Organs, 175 
 
 change of function of, 178 
 
 classification of, 178 
 
 correlation of, 176 
 
 order of appearance of, 175, 
 176 
 
 rudimentary, 178, 179 
 
 substitution of, 178 
 Orioles, 59 
 Ovists, 191 
 Ovum, 191-193 
 
 theory, 196 
 Oysters, nuMttality of, 43 
 
 Palaontological series, so6 
 Pftteeontology, 304-209 
 Pangenesis, 334 
 Parasitic worms, 229-331 
 Parasitism, 47, 48 
 Parthenogenesis, 189-193 
 Partnerships among animals, 68; 
 
 69 
 Perception, 151 
 Peripatus, 10, 240 
 Phasmidse, 53 
 Phenacodus, 269, 270 
 Phyllopteryx, 54 
 Phylogeny, 203 
 Physiology, 125-153 
 Pigeon, 27s, 276 
 Pineal body, 260 
 Plants and animals, 19, 20, 28-31, 
 
 168-171 
 Polar globules, 193 
 Polyzoa, 235 
 
 Preformation theories, 191, 324 
 Pressures, effect of, 300 
 Protective resemblance, 53 
 Proteids, 134, 135 
 Protomyxa, 212 
 Protoplasm, 131-135 
 Protopterus, 41 
 Protozoa, 11, 210-221 
 
 colonial, 173, 174 
 
 classes of, 211 
 
 life of, 214 
 
 "immortality" of, 172 
 
 psychical life of, 215-318 
 
 structure of, 213 
 
 andMetazoa, transition between, 
 88, 89, 171-174 
 Psychology, 149 
 Pupae of caterpillars, 50 
 Puss-moth, 63, 64 
 
 Radiant energy, influence of, 
 
 313-316 
 Recapitulation, 197, 279 
 Reflex actions, 155 
 Reproduction, 184-190 
 Reptiles, 9, 359-364 
 RespiratioD, 146 
 
Index 
 
 375 
 
 Revenion, ^;a» 
 Rhinpods, ais 
 Rotifer*, 7. 4a, 334 
 Round-mouths, 9, 353 
 Rudimentaiy organs, 377 
 
 Saccophora, 62 
 
 Sacculina, 48 
 
 Sea-borso, parental care of, no 
 
 Seasonal dimorphism, 314 
 
 Segmentation, 195 
 
 Sensations, 151 
 
 Sex, 96 
 
 Sexual reproduction, 186-188 
 
 selection, 98 
 Shells of molluscs, 243 
 Shepherding, 119, 120 
 Shifts for a living, 46-66 
 Skunk, SS 
 
 Snails and plants, 30 
 Snakes, 260-263 
 Social inheritance, 337-339 
 
 life of animals, 67-94 
 
 organism, 93, 94 
 Societies, evolution of, 87 
 Song of birds, 96 
 Spencer, 297, 298 
 Spermatozoon, 192, 193 
 Sphex, 131 
 Spiders, courtship of, iot-105 
 
 bird-catching, 36 
 Sponges, iz, 323 
 Spongilla, 186 
 Spring, biolo^ of. 95, 96 
 Starfish, 335 
 
 Stickleback, courtship of, 99 
 
 parental care of, 109, no, 133 
 Stinging-animals, xz, 323-338 
 Storing, zao, Z3X 
 Struggle for existence. 33-45 
 Surrender of parts, 64-66 
 Symbiosis, 69 
 
 Tapeworms, 229 
 Termites, 34, 84-87 
 Tissues, 179, 180 
 Tortoises, 263 
 Toxotes, 118 
 Trematoda, 229 
 Tunicates, 9, 250, 251 
 Turbellaria, 328 
 
 Variation, 299 
 
 Vertebrata, characters of, 19, 348, 
 
 349 
 Vital force, X9 
 Vivarium, so, 3i 
 Volvox, 187 
 
 Wallace, 296, 397 
 Warning colours, 55, 56 
 Weapons of animals, 34 
 Web of Life, 18-31 
 White Ants. See Termites 
 Worms, zo, zx, 338-335 
 
 Yolk, 195 
 
 Zoology, history of, 352-357 
 
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