2809609406 The Friends of the Children of Great Ormond Street LIBRARY ^ Institute of Child Health University College London 30 Guilford Street London WC IN lEH I THE DESCENT OF MAN, AND SELECTION IN EELATION TO SEX, 1 1 Digitized by the Internet Archive in 2014 https://archive.org/details/b21686555 THE .DESCENT OF MAN, AND SELECTION m KELATION TO SEL By CHAELES DAEWIN, M.A., F.E.S. SECO:fD'^ EDITION, REVISED AND AUGMENTED. TWENTY-THIRD THOUSAND. SSTitfj jmustratifltts. LONDON: JOHN MTJERAY, ALBEMARLE STREET. 1888. Thi right of Translation is reserved. WORKS BY THE SAME AUTHOR. A NATURALIST'S JOURNAL OF RESEARCHES INTO TUB Natural Histoky and Gkology of Counthiks vij-itkd during a Voyage Hound the Would. Scvenlecnth T/wusand. Woodouta. 7s. Gd. Mukiiay. THE ORIGIN OP SPECIES BY MEANS OF NATURAL SELECTION ; or. The Pukseuvation op F,i.vouBED Races ik the Struggle for Life. Thirly-lhird Thousand. Woodcuts. Large 'I'ype Edition. 2 vols. Crown 8vo., Vis. Clieap Edition, 6.5. MuuaAY. THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS. Fourtli Tlvousand. WoodcuU. Is. 6d. Murray. THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION. Sixtk Thousand. lilustratious. 15s. Murray. THE DESCENT OF MAN, AND SELECTION IN RELA- TION TO SEX. Twenty-third Thousand. lllu>tratious. Large Type Edition. 2 vols. Crown 8vo., 15s. Cheap Edition, 7s. 6d. Murray. THE EXPRESSION OF THE EMOTIONS IN MAN AND ANIMALS. Ninth Thousand. Illustrations. Murray. •INSECTIVOROUS PLANTS. Fourth Thousand. Hlustrations. Murray. THE MOVEMENTS AND HABITS OF CLIMBING PLANTS. Third Thousand. Woodcuts. 6s. Murray. THE EFFECTS OF CROSS AND SELF-FERTILIZATION IN THE VEGETABLE KINGDOM. Third Thousand. Illustrations. 9s. Murray. THE DIFFERENT FORMS OF FLOWERS ON PLANTS OP THE SAME SPECIES. Third Thousand. Illustrations. 7s. 6d. Murray. THE POWER OF MOVEMENT IN PLANTS. Third Tliomand- Woodcuts. Murray. THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS. Tenth Thousand. AVoodcuts. Crown svo., 6s. MUERAT. LIFE OF ERASMUS DARWIN. With a Study of his ScientiBc Works. Portrait. 7s. 6d. Muhray. THE STRUCTURE AND DISTRIBUTION OP CORAL REEFS. Second Edition, revised. Smith, Elder, & Co. GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS AND ON PARTS OF SOU TH AMERICA, visited during tbe VoyaRe of H.M.S. 'Beagle.' Second Edition. Smith, Elder, & Co. A MONOGRAPH OF THE CIRRIPEDIA. With numerous Illustrations. 2,vols. 8vo. Ray Society. Hardwicke. A MONOGRAPH OF THE FOSSIL LEPADID^, OR PEDUNCULATED CIRRIPEDS OF GRE.\T BRITAIN. PALJEONTOGRAl'niCAL SOCIETY. A MONOGRAPH OF THE POSSIL BALANID^ AND VERRUCIDiE OF GREAT BRITAIN. Pal^kiographical Socieit. FACTS AND ARGUMENTS FOR DARWIN. By Fritz MuLLBR. From the German, witli A(^d|,«oiis by the Author. Translated by W. S. Dallas, F.L.S. Illustrations. '6s. Murray. LOKDON: printed by WlLhUSl CLOWES and SONS, LIMITED, STAMFORD STREBT Aln> CUARIKG CROSS. PBEFACE TO THE SECOND EDITION. DtmnJG the successive reprints of the first edition of this "work, published in 1871, I was able to introduce several important corrections; and now that more time has elapsed, I have endeavoured to profit by the fiery ordeal through which the book has passed, and have taken advantage of all the criticisms which seem to me sound. I am also greatly indebted to a large number of correspondents for the communication of a surprising number of new facts and remarks. These have been so numerous, that I have been able to use only the more important ones ; and of these, as well as of the more important corrections, I will append a list. Some new illustrations have been introduced, and four of the old drawings have been replaced by better ones, done from life by Mr. T. W. Wood. I must especially call attention to some observations which I owe to the kindness of Prof. Huxley (given as a supplement at the end of Part I.), on the nature of the differences between the brains of man and the higher apes. I have been particularly glad to give these obser- vations, because during the last few years several memoirs on the subject have appeared on the Continent, and their importance has been, in some cases, greatly exaggerated by popular writers. I may take this opportunity of remarking that my critics frequently assume that I attribute all changes of corporeal structure and mental power exclusively to the natural selection of such variations as are often called spontaneous; whereas, even in the first edition of the ' Origin of Species,' I distinctly stated, that great Avcight must be attributed to the inherited effects of use and disuse, with respect both to the body and mind. I also attributed some amount of modification to the direct and prolonged action of changed conditions of life. Some allowance, too, must be made for occasional reversions of vi Preface to the :^econd Edition. 8tructui-o; nor must wo forgot what I have called "correlated" growth, moaning, thereby, that various parts of the organisation are in some unknown manner so connected, that when one part varifis, so do others; and if variations in the one are accu- mulated by selection, other parts will be modified. Again, it lias been said by several critics, that when I found that many details of structure in man could not be explained through natural selection, I invented sexual selection ; I gave, however, a tolerably clear sketch of this principle in the first edition oi the ' Origin of Species,' and I there stated that it was applicable to man. This subject of sexual selection has been treated at full length in the present work, simply because an opportunity was here first afforded me. I have been struck with the likeness of many of the half- favourable criticisms on sexual selection, with those which appeared at first on natural selection; such as, that it would explain some few details, but certainly was not applicable to the extent to which I have employed it. My conviction of the power of sexual selection remains unshaken ; but it is probable, or almost certain, that several of my con- clusions will hereafter be found erroneous ; this can hardly fail to be the case in the first treatment of a subject. When naturalists have become familiar with the idea of sexual selection, it will, as I believe, be much more largely accepted; and it has already been fully and favourably received by several capable judges. Down, Beckenuam, Kejjt, September l^li. TABLE PRINCIPAL ADDITIONS AND CORRECTIONS TO TBE PRESENT EDITION. First Kdition. Vol. I. Present Edition. Page Page 22 15-17 26 27, note. 29 19 20, note. 23 82, note. 24, note, 40 42 70 71 44 72-3 47 50 53 75 80 83 00 • 88-9 64 92 78 79 81 90, note. 104 104 105-G ai2-113,'l \ note. / 91 114 94 97 112 122 124, note. 125, note. 117, note. 120, note. 28 35-6 39, note. 36-8, note. 128-9 41-2 146 55, note. j Discussion on the rudimentary points in the \ human ear revised. Cases of men born with hairy bodies. Mantegazza on the last molar tooth in man. The rudiments of a tail in man. iBianconi on homologoxis structures, as ex- plained by adaptation on mechanical principles. Intelligence in a baboon. Sense of humour in dogs. iFurther facts on imitation in man and \ animals. Reasoning power in the lower animals. Acquisition of experience by animals. Power of abstraction iu animals. (■Power of farming concepts iu relation to \ language. ("Pleasure from certain sounds, colours, and \ forms. Fidelity in the elephant. Galton on gi-egariousness of cattle. Parental affection. Persistence of enmity and hatred, fNatme and strength of shame, regret, and \ remorse. Suicide amongst savages. The motives of conduct. Selection, as applied to primeval man. Resemblances between idiots and animals. Division of the malar bone. Suijemumerary mammra and digits. fFurther cases of muscles proper to animals \ appearing in man. IBroca: average capacity of slaill diminishect by the preservation of the inferior member* of society. I viii Table of the Principal Additions and First Edition. Vol. I. Present Edition. Page 149 150 169 180 193 208. note. 209 239 245 250 256 Pago 57 58-9 134-5 143 151 161, note. 163 188-190 195-6 199-206 209-210 275-6 224-5 290 235 301 243-4 314 254 315 255-6 327 264 338 272 339 273 345 277 349 280 350 281 351 282 354 284-5 359 288, note 366 292-3 387 308 397 315 401 319 412 324-5 417 326 (■Belt on advantages to man from his hair- \ lessness. (■Disappearance of the tail in man and certain \ monkeys. (Injurious forma of selection in civilised nations. Indolence of man, when free from a struggle for existence. jGorilla protecting himself from rain with his \ hands. Hermaphroditism in fish. Eudimentary raammfe in male mammals. (■Changed conditions lessen fertility and cause \ ill-health amongst savages. jDarkness of skin a protection against the \ sun. jNote by Professor Huxley on the develop- \ ment of the brain in man and apes. /Special organs of male parasitic worms for \ holding the female. Greater variability of male than female; direct action of the environment in causing differences between the sexes. Period of development of protuberances on birds' heads determines their trans- mission to one or both sexes. Causes of excess of male births. Proportion of the sexes in the bee family. /Excess of males perhaps sometimes deter- ( mined by selection. Bright colours of lowly organised animals. Sexual selection amongst spiders. Cause of smallness of male spiders. Use of phosphorescence of the glow-worm. The humming noises of flies. Use of bright colours to Hemiptera (bugs). Musical apparatus of Homoptera. /Development of stridulating apparatus in \ Orthoptera. /Hermann Miiller on sexual differences of \ bees. Sounds produced by moths. Display of beauty by butterflies. /Female butterflies, taking the more active \ part in courtship, brighter than their males. /Further cases of mimicry in butterflies and \ moths. /Cause of bright and diversified colours of \ caterpillars. Corrections to the Present Edition. First Kdition. Vol. II. l*resent Edition. Page Rage 2 331 o±i 23 347 26 349 30 352 32 353- 36 357 72 383 91 398 108 411 118 417 120 419 124 423 147-150 438-441 152 443 157 446 232 495-6 247 248 506 256 513-514 260 516 266 521 286 534 299 542-3 816 337 572 356 586 859 et acq. 588 et seq. 373 598-9 380 603 Brush-Uko scales of male Mallotus. (■Further facts on courtship of fishes, and the \ spawning of Macropus. Dufosse on the sounds made by fishes. Belt on a frog protected by bright colouring. Further facts on mental powers of snakes. Sounds produced by snakes ; the rattlesnake. Combats of Chameleons. Marshall on protuberances on birds' heads. (■Further facts on display by the Argus \ pheasant. Attachment between paired birds. Female pigeon rejecting certain males. (■Albino birds not finding partners, in a state \ of nature. Direct action of climate on birds' colours. (■Further facts on the ocelli in the Argus \ pheasant. Display by humming-birds in curtship. ("Cases with pigeons of colour transmitted to \ one sex alone. {Taste for the beautiful permament enough to allow of sexual selection with the lower animals. ("Horns of sheep originally a masculine \ character. Castration affecting horns of animals. Prong-horned variety of Cervus virginianus. (■Relative sizes of male and female whales and \ seals. Absence of tusks in male miocene pigs. Dcbson on sexual differences of bats. Eeeks on advantage from peculiar colouring. |Difference of complexion in men and women \ of an African tribe. Speech subsequent to singing. (■Schopenhauer on importance of courtship to \ mankind. (■Revision of discussion on communal marriages \ and promiscuity. (Power of choice of woman in marriage, \ amongst savages. |Long-continued habit of plucking out hairs \ may produce an inherited effect. CONTENTS. iNTRODrcTioN ........ Pages 1-4 PAET I. THE DESCENT OR ORIGIN OF MAN. CHAPTER I. Tub Evidesce of the Descent of Man fbom some Loweh Fobji. PAGH Nature of the evidence bearing on the origin of man — Homologous structm-es in man and the lower animals — Miscellaneous points of correspondence — Development — Rudimentary structures, muscles, sense-organs, hair, bones, reproductive organs, &c. — The bearing of these three great classes of facts on the origin of man 5 CHAPTER n. On the Manner of Development of Man from some Loweu Form. Variability of body and mind in man — Inheritance — Causes of variability — Laws of variation the same in man as in the lower animals— Direct action of the conditions of life — Effects of the increased use and disuse of parts — Arrested development — Re- version— Correlated variation — Rate of Increase — Checks to increase — Natural selection — Man the most dominant animal in the world — Importance of his corporeal structure — The causes which Lave led to his becoming erect — Consequent changes of structure — Decrease in size of the canine teeth — Increased size and altered shape of the skull — Nakedness — Absence of a tail — Defenceless condition of man . , . , . 26 CHAPTER m. Comparison of the Mental Powers of Man and the Lower Animals. The difference in mental power between the highest ape and the lowest savage, immense — Certain instincts in common — Tho emotions — Curiosity — Imitation — Attention — Memory — Imagi- nation— ^Reason — Progressive improvement — Tools and weapons Contents. used by animals— Abstraction, Sell-consciousness— Language —Sense of beauty— Belief in God, spiritual agencies, super- Btitions 65 CHAPTEK IV. COKPAEISON OJT THE AIeNTAL PoWERS OF MaN AND THE LoWEn Animals — continued. The moral sense— Fundamental proposition— The qualities of social animals— Origin of sociability— Struggle between opposed instincts — Man a social animal — The more enduring social in- stincts conquer other less persistent instincts — The social virtues alone regarded by savages— The self-regarding virtues acquired at a later stage of development — The importance of the judg- ment of the members of the same community on conduct — Transmission of moral tendencies — Summary . 97 CHAPTEE V. On the Development op the Intellectual and Moral Faculties during Primeval and Civilised Times. Advancement of the intellectual powers through natural selec- tion— Importance of imitation — Social and moral faculties — Their development within the limits of the same tribe — Natural selection«as aflecting civilised nations — Evidence that civilised nations were once barbarous . ... 1 27 CHAPTER VI. On THE Affinities and Genealogy of Man. Position of man in the animal series — The natural system genea- logical— Adaptive characters of slight value — Various smaU points of resemblance between man and the Quadrumana — Eank of man in the natural system — Birthplace and antiquity of man — Absence of fossil connecting-links — Lower stages in the genealogy of man, as inferred, firstly from his afBnities and secondly from his structure — Early androgynous condition of the Vertebrata — Conclusion ..... 1 46 CHAPTER VII. On the Races op Man. The nature and value of specific characters — ^Application to the races of man — Arguments in favour of, and opposed to, ranking the so-called races of man as distinct species — Sub-species — ]iIonogenists and polygenists — Convergence of character — Contents. xiii Numerous points of resemblance in body and mind between the moat distinct races of man — The state of man when he fii'st spread over the earth — Each race not descended from a single pair — The extinction of races — The formation of races — The efiects of crossing — Slight influence of the direct action of the conditions of life — Slight or no influence of natural selectioT> Sexual selection . . . • PART II. SEXUAL SELECTION. CHAPTER VIII. PiuNapLES OF Sexual Selection. Secondary sexual characters — Sexual selection — ^Manner of action — Excess of males — Polygamy — The male alone generally modified through sexual selection — Eagerness of the male — Variability of the male — Choice exerted by the female — Sexual compared -with natural selection — Inheritance at corresponding periods of life, at corresponding seasons of the year, and as limited by sex — Relations between the several forms of inheri- tance— Causes why one sex and the young are not modified through sexual selection — Supplement on the proportional num- bers of the two sexes throughout the animal kingdom — The proportion of the sexes in relation to natural selection . 207 CHAPTER IX. Secondary Sexual Chabacteks in the Lower Classes op THE Animal Kingdom. These characters absent in the lowest classes — Brilliant coloui-s — • MoUusca — Annelids — Crustacea, secondary sexual characters strongly developed; dimorphism; colour; characters not ac- quired before maturity — Spiders, sexual colours of ; stridulation by the males — ^Myriapoda ...... 260 CHAPTER X. Secondary Sexual Characters of Insects. Diversified structures possessed by the males for seizing the females — Differences between the sexes, of which the mean- ing is not understood— Difference in size between the sexes — Thysanuia — Diptera — ^Hemiptera — Homoptera, musical powers Contents. possessed by the males alone— Orthoptera, musical instniments of tlie males, much di versified in structure ; pugnacity ; colours — Neuroptora sexual differences in colour— Hymenoptera, pug- nacity and colours— Coleoptera, colours; furnished with great horns, apparently as an ornament; baltlos; fctrididating organs generally common to both sexes .... 274 CHAPTER XL Insects, continued. — Okdeu Lepidoptera. (butteuflies and moths.) Courtship of butterflies — Battles — Ticking noise — Colours common to both sexes, or more brilliant in the males — Examples — Not due to the direct action of the conditions of life — Colours adapted for protection — Colours of moths — Display — Perceptive powers of the Lepidoptera — Variability — Causes of the difference in colour between the males and females — Mimicry, female butterflies more brilliantly coloured than the males — Briglit colours of caterpillars — Summary and concluding remarks on the secondary sexual characters of insects — Birds and insects compared ........ 307 CHAPTER Xn. Seoondaey Sexual Chabaoteks of Fishes, Amphibians, anu Reptiles. Fishes: Courtship and battles of the males — Larger size of the females — ^Jlales, bright colours and ornamental appendages: other strange characters — Colours and appendages acquired by the males during the breeding-season alone — Fishes with both sexes brilliantly coloured — Protective colours — The less con- spicuous colours of the female cannot be accounted for on the principle of protection — Male fishes building nests, and taking charge of the ova and young. Amphibians: Differences in structure and colour between the sexes — Vocal organs. Rep- tiles: Chelonians — Crocodiles — Snakes, colours in some cases protective — Lizards, battles of — Ornamental appendages — Strange differences in structure between the sexes — Colours — Sexual differences almost as great as with birds . r 330 CHAPTER XIIL Secondaet Sexual Charactebs op Bibds. Prxual differences — Law of battle — Special weapons — Vocal organs — Instrumental music — Love-antics and dances — Deco- rations, permanent and seasonal — Double and single annual moults— Display of ornaments by the males . . 868 Contents, XV CHArTER XIV. BiiiDS — continued. TACB C'liowo exerted by the female— Length of courtship— Unpaired birds Mental qualities and taste for the beautiful— Preference or antipathy shewn by tlie female for particular males — Vari- ability of birds — ^Variations sometimes abrupt — Laws of varia- tion Formation of ocelli — Gradations of character — Case of Peacock, Argus pheasant, and Urosticte . . 401 CHAPTER XV. B iBDS — continued. Discussion as to why the males alone of some speciea, and both sexes of others are brightly coloured — On sexually-limited inheritance, as applied to various structures and to brightly- coloured plumage — Nidification in relation to colour — Loss of nuptial plumage during the winter .... 444 CHAPTER XVI. Birds — concluded. The immature plumage in relation to the character of the plumage in both sexes when adult — Six classes of cases — Sexual diiFer- ences between the males of closely-allied or representative species — The female assuming the characters of the male — Plumage of the young in relation to the summer and winter plumage of the adults — On the increase of beauty in the birds of the world — Protective colouring — Conspicuously-coloured birds — Novelty appreciated — Summary of the four chapters on birds 463 CHAPTER XVII. Secondary Sexual Characters of Mammals. The law of battle — Special weapons, confined to the males — Cause of absence of weapons in the female — "Weapons common to both sexes, yet primarily acquired by the male — Other uses of such weapons — Their high importance — Greater size of the male — Means of defence — On the preference shewn by either sex in the pairing of quadrupeds 500 CHAPTER XVIII. Secondary Sexual Characters of Mammals — continued. Voice — Remarkable sexual peculiarities in seals — Odour — Develop- ment of the hair— Colour of the hair and skin— Anomalous XVI Co7itents. case of the female being more ornamented than the male— Colonr and ornaments due to sexual selection— Colour acquired for tho sake of protection— Colour, though common to both sexes, often due to sexual selection— On tho disappearance of spots and stripes in adult quadrupeds— On tho colours and orna- ments of the Quadrumana — Summary . , . 525 PAET in. SEXUAL, SELECTION IN EELATION TO MAN, AND CONCLUSION. CHAPTER XIX. Secondaey Sexual Cuaeacters op Man Differences between man and woman — Causes of such diiferences, and of certain characters common to both sexes — Law of battle — Differences in mental powers, and voice — On the influence of beauty in determining the marriages of mankind — Attention paid by savages to ornaments — Their ideas of beauty in woman — The tendency to exaggerate each natural peculiarity . 556 CHAPTER XX. Secondaey Sexual Chakactees of Man — continued. On the effects of the continued selection of women according to a different standard of beauty in each race — On tho causes which interfere with sexual selection in civilised and savage nations — Conditions favourable to sexual selection during primeval times — On the manner of action of sexual selection with man- kind— On the women in savage tribes having some power to choose their husbands — Absence of hair on the body, and development of the beard — Colour of the skin — Summary . 585 CHAPTER XXI. General Summabt and Conclusion. Main conclusion that man is descended from some lower form — Manner of development — Genealogy of man — Intellectual and moral faculties — Sexual selection — Concluding remarks . 606' Supplemental Note ........ 620 Index C25 THE DESCENT OF MAN; AMD SELECTION IN EELATION TO SEX. INTRODUCTION. The nature of the following work will be best understood by a brief account of how it came to be written. During many years I collected notes on the origin or descent of man, without any intention of publishing on the subject, but rather with the determination not to publish, as I thought that I should thus only add to the prejudices against my views. It seemed to me sufficient to indicate, in the first edition of my ' Origin of Species,' that by this work " light would be thi'own on the " origin of man and his history ;" and this imphes that man must be included with other organic beings in any general conclusion respecting his manner of appearance on this earth. Now the case wears a wholly different aspect. When a naturalist like Carl Vogt ventui-es to say in his address as President of the National Institution of Geneva (1869), "personne, en Europe " au moins, n'ose plus soutenir la creation independante et de " toutes pieces, des especes," it is manifest that at least a large number of naturalists must admit that species are the modified descendants of other species ; and this especially holds good with the younger and rising naturalists. The greater number accept the agency of natural selection ; though some urge, whether with justice the future must decide, that I have greatly overrated its importance. Of the older and honoured chiefs in natural science, many unfortunately are still opposed to evolution in every form. In consequence of the views now adopted by most naturalists, and which will ultimately, as in every other case, be followed by B 3 Introduction. others who are not scientific, I have been led to put together my notes, so as to see how far the general conclusions arrived at in my former works were apphcable to man. This seemed all the more desirable, as I had never deUberately appUed these views to a species taken singly. When we confine our attention to any one form, we are deprived of the weighty arguments derived from the nature of the affinities which connect together whole groups of organisms— their geographical distribution in past and present times, and then* geological succession. The homological structure, embryological development, and rudi- mentary organs of a species remain to be considered, whether it be man or any other animal, to which our attention may be directed ; but these great classes of facts afford, as it appears to me, ample and conclusive evidence in favour of the principle of gradual evolution. The strong support derived from the other arguments should, however, always be kept before the mind. The sole object of this work is to consider, firstly, whether man, like every other species, is descended fi-om some pre- existing form; secondly, the manner of his development; and thirdly, the value of the differences between the so-called races of man. As I shall confine myself to these points, it will not be necessarj'' to describe in detail the differences between the several races — an enormous subject which has been fully discussed in many valuable works. The high antiquity of man has recently been demonstrated by the laboui's of a host of eminent men, beginning with M. Boucher de Perthes ; and this is the indis- pensable basis for understanding his origin. I shall, therefore, take this conclusion for granted, and may refer my readers to the admirable treatises of Sir Charles Lyell, Sir John Lubbock, and others. Nor shall I have occasion to do more than to allude to the amount of difference between man and the anthropomor- phous apes ; for Prof. Huxley, ia the opinion of most competent judges, has conclusively she-\vn that in every visible character man differs less from the higher apes, than these do from the lower members of the same order of Primates. This work contahis hardly any original facts in regard to man; but as the conclusions at which I arrived, after drawing up a rough draft, appeared to me interesting, I thought that they might interest others. It has often and confidently been asserted, that man's origin can never be known: but ignorance more frequently begets confidence than does knowledge : it is those who know Uttle, and not those who know much, who so positively assert that this or that problem will never be solved by science. The conclusion that man is the co-descendant with other species of some ancient, lower, and extinct form, is not in Introductio7i. 3 liny degree new. Lamarck long ago came to this conclusion, ■whicli has lately been maintained by several eminent naturalists and philosophers ; for instance, by Wallace, Huxley, Lyell, Vogt, Lubbock, Biichner, EoUe, &c.,^ and especially by Hackel. This last naturalist, besides his great work, ' Generelle Morphologie ' (1866), has recently (1868, with a second edit, in 1870), pub- lished his ' Natiirliche Schopfimgsgeschichte,' in which he fully discusses the genealogy of man. If this work had appeared before my essay had been written, I should probably never have completed it. Almost aU the conclusions at which I have arrived I find confii-med by this naturalist, whose knowledge on many points is much fuller than mine. "Wherever I have added any fact or view from Prof, flackel's writings, I give his autho- rity in the text ; other statements I leave as they originally stood in my manuscript, occasionally giving in the foot-notes references to his works, as a confii-mation of the more doubtful or interesting points. Diu-ing many years it has seemed to me highly probable that sexual selection has played an important part in differentiating the races of man ; but in my ' Origin of Species ' (first edition, p. 199) I contented myself by merely alluding to this belief. When I came to apply this view to man, I found it indispensable to treat the whole subject in fuU detail.^ Consequently the second part of the present work, treating of sexual selection, has ex- tended to an inordinate length, compared with the first part; but this could not be avoided. I had intended adding to the present volumes an essay on the expression of the various emotions by man and the lower animals. My attention was called to this subject many years ago by Sir Charles Bell's admirable work. This illustrious anatomist ^ As the works of the first-named .luthors are so well known, I need not give the titles ; but as those of the latter are less well known in England, I will give them : — ' Sechs Vorlesungen liber die Darwin'sche Theorie :' zweite Auflage, 1868, von Dr. L. Biichner; translated into French under the title ' Conferences sur la Theorie Darwinienne,' 1869. 'Der Mensch, im Lichte der Dar- -svin'sche Lehre,' 1865, von Dr. F. RoUe. I will not attempt to give references to all the authors who have taken the same side of the question. Thus G. Canestrini has published ('Annuario della Soc. d. Nat.,' Modena, 1867, p. 81) a very curious paper on rudimentary cha- racters, as bearing on the origin of man. Another work has (1869) been published Jby Dr. Francesco Barrago, bearing in Italian the title of " Man, made in the ima^e of God, " was also made in the image of the " ape." ^ Prof. Hackel was the only author who, at the time when this work first appeared, had discussed the subject of sexual selection, and had seen its full importance, since the publication of the ' Origin '; and this he did in a very able manner in his various works. B 2 4 Intro dttction. maintains that man is endowed with certain muscles solely for the sake of expressing his emotions. As this view is obviously opposed to the belief that man is descended from some other and lower form, it was necessary for me to consider it. I likewise wished to ascertain how far the emotions are expressed in the same manner by the different races of man. But owing to the length of the present work, I have thought it better to reserve my essay for separate pubLicatiou. ( 5 ) Part I. THE DESCENT OK ORIGIN OF MAN. OHAPTEE I. The Etidenob of the Descent op Man feom some Lower Foem. Nature of the evidence bearing on the origin of man — Homologoua structures in man and the lower animals — Miscellaneous points of correspondence — Development — Rudimentary structures, muscles, sense- organs, hair, bones, repi'oductive organs, &c. — The bearing of these three great classes of facts on the origin of man. He who wishes to decide whether man is the modified descendant of some pre-existing form, would probably first enquire whether man varies, however shghtly, in bodily structure and in mental faculties; and if so, whether the variations are transmitted to his offspring in accordance with the laws which prevail with the lower animals. Again, are the variations the result, as far as our ignorance permits us to judge, of the same general causes, and are they governed by the same general laws, as in the case of other organisms ; for instance, by correlation, the inherited effects of use and disuse, &c. ? Is man subject to similar mal- conformations, the result of arrested development, of reduplication of parts, &C.J and does he display in any of his anomalies rever- sion to some former and ancient type of structure ? It might also naturally be enquired whether man, like so many other animals, has given rise to varieties and sub-races, differing but slightly from each other, or to races differing so much that they must be classed as doubtful species? How are such races distributed over the world; and how, when crossed, do they react on each other in the first and succeeding generations ? And so with many other points. The enquirer woidd next come to the important point, whether man tends to increase at so rapid a rate, as to lead to occasional severe struggles for existence; and consequently to 6 TJie Descent of Man. Past I. beneficial variations, whether in body or mind, being preserved, and injui-ious ones eliminated. Do the races or species of men, whichever term may be applied, encroach on and replace one another, so that some finally become extinct ? We shall see that all these questions, as indeed is obvious in respect to most of them, must be answered in the afiarmative, in the same manner as with the lower animals. But the several considerations just referred to may be conveniently deferred for a time : and we will first see how far the bodily structure of man shows traces, more or less plain, of his descent from some lower form. In succeeding chapters the mental powers of man, in comparison with those of the lower animals, will be considered. The Bodily Structure of Man. — It is notorious that man is constructed on the same general type or model as other mam- mals. All the bones in his skeleton can be oompared with corresponding bones in a monkey, bat, or seal. So it is with his muscles, nerves, blood-vessels and internal viscera. The brain, the most important of aU the organs, follows the same law, as shewn by Huxley and other anatomists. Bischoff,* who is a hostile witness, admits that every chief fissure and fold in the brain of man has its analogy in that of the orang ; but he adds that at no period of development do their brains perfectly agree ; nor could perfect agreement be expected, for otherwise their mental powers would have been the same. Yulpian ^ remarks : " Les differences reelles qui existent entre I'encephale de " I'homme et celui des singes superieurs, sont bien minimes. II " ne faut pas se faire d'illusions a cet egard. L'homme est bien " plus pres des singes anthropomorphes par les caracteres " anatomiques de son cerveau que ceux-ci ne le sont non- "seulement des autres mammiferes, mais meme de certains " quadrumanes, des gueuons et des macaques." But it would be superfluous here to give further details on the correspondence between man and the higher mammals in the structure of the brain and all other parts of the body. It may, however, be worth while to specify a few points, not directly or obviously connected with structui-e, by which this correspondence or relationship is well shewn. Man is liable to receive from the lower animals, and to com- 1 ' Grosshirnwindungen des Men- in the Preface to this edition, schen,' 1868, s. 96. The conclusions ^ ' Le?. sur la Pliys.' 1866, p. 890, of this author, as well as those of as quoted by M. Dally, ' L'Ordre des Gratiolet and Aeby, concerning the Primates et le Transformism'',' 1868, brain, will be discussed by Prof. p. 29. Huxley in the Appendix alluded to Cha?. I. Homological Structures. 7 municate to them, certain diseases, as hydrophobia, variola, the glanders, syphilis, cholera, herpes, &c. ; ^ and this fact proves the close similarity* of their tissues and blood, both in minute structure and composition, far more plainly than does their compai'ison under the best microscope, or by the aid of the best chemical analysis. Monkeys are liable to many of the same non- contagious diseases as we are; thus Eengger,* who carefully observed for a long time the Cebus Azarce in its native land, found it Hable to cataiTh, with the usual symptoms, and which, when often recui-rent, led to consumption. These monkeys suffered also from apoplexy, inflammation of the bowels, and catai-act in the eye. The younger ones when shedding their milk-teeth often died from fever. Medicines produced the same effect on them as on its. Many kinds of monkeys have a strong taste for tea, coffee, and spirituous liquors : they will also, as I have myself seen, smoke tobacco with pleasure." Brehm asserts that the natives of north-eastern Africa catch the wild baboons by exposing vessels with strong beer, by which they are made di'unk. He has seen some of these animals, which he kept in confinement, in this state ; and he gives a laughable account of their behaviour and strange grimaces. On the following moining they were very cross and dismal ; they held their aching heads with both hands, and wore a most pitiable expression : when beer or wine was offered them, they turned away with disgust, but reHshed the juice of lemons.' An American monkey, an Ateles, after getting drunk on brandy, would never touch it again, and thus was wiser than many men. These trifling facts prove how similar the nerves of taste must be in monkeys and man, and how similarly their whole nervous system is affected. Man is infested with internal parasites, sometimes causing ' Dr. W. Lauder Lindsay has treated this subject at some length in the ' Journal of Mental Science,' July 1871 ; and in the ' Edinburgh Veterinary Review,' July 1858. * A Reviewer has criticised (' British Quarterly Review,' Oct. 1st, 1871, p. 472) what I have here said with much severity and con- tempt ; but as I do not use the term identity, I cannot see that I am greatly in error. There appears to me a strong analogy between the same infection or contagion pro- ducing the same result, or one closely similar, in two distinct ani- mals, and the testing of two dis- tinct fluids by the same chemical reagent. ^ ' Naturgeschichte der Siiuge- thiere von Paraguay,' 1830, s. 50. * The same tastes are common to some animals much lower in the scale. Mr. A. Nicols informs me that he kept in Queensland, in Aus- tralia, three individuals of the Phaseolarctus cinereus ; and that, without having been taught in any way, they acquired a strong taste for rum, and for smoking tobacco. ' Brehm, * Thierleben,' B. i. 1864, s. 75, 86. On the Ateles, s. 105. For other analogous statenieuls, sea s, 25, 107. 8 The Descent of Man. r fatal effects ; aud is plagued by external parasites, all of which belong to the same genera or families as those infesting other mammals, and in the case of scabies to the same species.* Man is subject, like other mammals, birds, and even insects," to that mysterious law, which causes certain normal processes, such as gestation, as well as the maturation and duration of various diseases, to follow lunar periods. His wounds are repaired by the same process of healing; and the stumps left after the amputation of his limbs, especially during an early embryonic period, occasionally possess some power of regeneration, as in the lowest animals.'" The whole process of that most important function, the reproduction of the species, is strikingly the same in all mam- mals, from the first act of courtship by the male," to the birth and nurturing of the young. Monkeys are born in almost as helpless a condition as our own infants ; and in certain genera the young differ fully as much in appearance from the adults, as do our children from their fuU-grown parents.'- It has been urged by some writers, as an important distinction, that with man the young arrive at maturity at a much later age than with any other animal : but if we look to the races of mankind which inhabit tropical countries the difference is not great, for the orang is believed not to be adult till the age of from ten to fifteen years." Man differs from woman in size, bodily strength, hairiness, &c., as weU as in mind, in the same manner as do the * Dr. W. Lauder Lindsay, ' Edin- " sagas, hoc mihi certissime pro- burgh Vet. Eeview-,' July 1858, " bavit, et curatores ejusdem loci et p. 13. " alii e ministris confirmarernnt. ' With respect to insects see Dr. " Sir Andrew Smith et Brehm no- Laycock," On a General Law of Vital " tabant idem in Cynocephalo. II- Periodicity," ' British Association,' " lustrissimus Cuyier etiam narrat 1842. Dr. Macculloch, ' Silliman's " multa de hac re, qua ut opinor, North American Journal of Science,' " nihil turpius potest indicari inter vol. xvii. p. 305, has seen a dog " omnia hominibus et Quadrumanis suffering from tertian ague. Here- " communia. Narrat enim Cyno- after I shall return to this subject. " cephalum quendam in furorem in- I have given the evidence on " cidere aspectu feminarum ali- this head in my ' Variation of Ani- " quarum, sed nequaquam accend: mals and Plants under Domestica- " tanto furore ab omnibus. Sem- tion,' vol. ii. p. 15, and more could " per eligebat juniores, et dignos- be added. " cebat in turba, et advooabat voce " " Mares e diversis generibus " gestuque." " Quadrumanorum sine dubio di- This remark is made wth re- " gnoscunt feminas humanas a ma- spect to Cynocephalus and the an- " ribus. Primum, credo, odoratu. thvopomorphous apes by Gcoffroy " postea aspectu. Mr. Touatt, qui Saint-Hilaire and F. Cuvier, ' Hist. « diu in Hortis Zoologicis (Besti- Nat. des Mammiferes,' torn. i. 1824. « ariis) medicus animalium erat, " Huxley, ' Man's Place in Na- " virin rebus observandis cautus et ture,' 1863, p. 34. Chap. I. Homological Structures. 9 two sexes of many mammals. So that the correspondence in general structure, in the minute structure of the tissues, in • chemical composition and in constitution, between man and the higher animals, especially the anthropomorphous apes, is ex- tremely close. Embryonic Development. — Man is developed from an ovule, about the 125th of an inch in diameter, which differs in no respect from the ovules of other animals. The embryo itself at a very early period can hardly be distinguished from that of other members of the vertebrate kingdom. At this period the arteries run in arch-like branches, as if to carry the blood to branchiae which are not present in the higher vertebrata, though the slits on the sides of the neck still remain (/, g, fig. 1), marking their former position. At a somewhat later period, when the extremities are developed, " the feet of lizards and " mammals," as the illustrious Von Baer remarks, " the wings " and feet of birds, no less than the hands and feet of man, all " arise from the same fundamental form." It is, says Prof. Huxley," " quite in the later stages of development that the young human being presents marked differences from the young " ape, while the latter departs as much from the dog in its " developments, as the man does. Startling as this last assertion " may appear to be, it is demonstrably true." As some of my readers may never have seen a drawing of an embryo, I have given one of man and another of a dog, at about the same early stage of development, carefully cojpied from two works of undoubted accuracy.'* After the foregoing statements made by such high autho- rities, it would be superfluous on my part to give a number of borrowed details, shewing that the embryo of man closely resembles that of other mammals. It may, however, be added, that the human embryo likewise resembles certain low forms when adult in various points of structure. For instance, the heart at first exists as a simple pulsating vessel; the excreta are voided through a cloacal passage ; and the os coccyx projects " 'Man's Place in Nature,' 1863, magnified, the embryo being twenty- p. 67. five days old. The internal viscera The human embryo (upper havebeenomitted, and the uterine ap- fig.) is from Ecker, ' Icones Phys.,' pendages in both drawings removed. 1831-1859, tab. xxx. fig. 2. This I was directed to these figures by embryo was ten lines in length, so Prof. Huxley, from whose work, that the drawing is much magnified. ' Man's Place in Natm-e,' the idea of The embryo of the dog is from giving them was taken. Hiickel has BischofT, ' Entwicklungsgeschichte also given analogous drawings in his des HunJe-Eies,' 1845, tab. xi. fig. ' Schopfungsgeschichte.' i2 B. This drawing is five times The Descent of Man. Pabt I, Fig. I. Upper figure human embryo, from Kcker. Lower figure that of a dog, from Bischoff. a. Fore-brain, cerebral hemispheres, &c. 6. Mid-brain, corpora qundrigemina. c. Hind-brain, cerebellum, medulla ob- longata. d. Eye. e Knr. ; First visceral arch. p. Second visceral arch. H. Vertebral columns and muscles ia process of development. i. Anterior K. Posterior L. Tail or os coccyx. \ extremities. J Chap. I. Rudiments. II like a true tail, "extending considerably beyond the rudi- '■' meutary legs.'"^ In the embryos of all air-breathing vertebrates, certain glands, called the corpora Wolffiana, correspond with, and act like the kidneys of matiu-e fishes." Even at a later embryonic period, some striking resemblances between man and the lower animals may be observed. Bischoff says that the convolutions of the brain in a human foetus at the end of the seventh month reach about the same stage of development as in a baboon when adult.^* The great toe, as Prof. Owen remarks,'^ " which forms the fulcrum when standing or walking, is " perhaps the most characteristic peculiarity in the human structure;" but in an embryo, about an inch in length. Prof. "Wyman^" found " that the great toe was shorter than the others ; " and, instead of being parallel to them, projected at an angle " from the side of the foot, thus corresponding with the per- " manent condition of this part in the quadrumana." I will conclude with a qtiotation from Huxley,"^ who after asking, does man originate in a different way from a dog, bii-d, frog or fish? says, "the reply is not doubtful for a moment; without " question, the mode of origin, and the early stages of the " development of man, are identical with those of the animals " immediately below him in the scale : without a doubt in " these respects, he is far nearer to apes than the apes are to " the dog." Rudiments. — This subject, though not intrinsically more important than the two last, will for several reasons be treated here more fully."^ Not one of the higher animals can be named which does not bear some- part in a rudimentary condition ; and man forms no exception to the rule. Eudimentary organs must be distinguished from those that are nascent ; though in some cases the distinction is not easy. The former are either abso- lutely useless, such as the mammae of male quadrupeds, or the incisor teeth of ruminants which never cut through the gums ; or they are of such slight service to their present possessors, that we can hardly suppose that they were developed under the " Prof. Wyman in ' Proc. of American Acad, of Sciences,' vol. iv. 1860, p. 17. " Owen, ' Anatomy of Verte- brates,' vol. i. p. 533. ' Die Grosshirnwindungen des Menschen,' 1868, s. 95. " ' Anatomy of Vertebrates,' vol. li. p. 553. 20 ' Proc. Soc. Nat. Hist.' Boston, 1863, vol. ix. p. 185. ' Man's Place in Nature,' p. 65. I had written a rough copy of this chapter before reading a valu- able paper, " Caratteri rudimentali in ordine all' origine del uomo" ('Annuario della Soc. d. Nat.,' Mo- dena, 1867, p. 81), by G. Canestrini, to which paper I am considerably indebted. Hackel has given admir- able discussions on this whole sub- ject, under the title of D3'steleologyj in his ' Gnnerelle Morphologie' and ' Schopfungsgeschiohta.' The Descent of Man. Paet 1, conditions which now exist. Organs in this latter state are not strictly rudimentary, but they are tending in this direction. Nascent organs, on the other hand, though not fully developed, are of high service to their possessors, and are capable of further development. Eudimentary organs arc eminently variable ; and this is partly intelligible, as they are useless, or nearly useless, and consequently are no longer subjected to natural selection. They often become wholly suppressed. When this occurs, they are nevertheless hable to occasional reappearance through reversion — a circumstance well worthy of attention. The chief agents in causing organs to become rudimentary seem to have been disuse at that period of life when the organ is chiefly used (and this is generally during maturity), and also inheritance at a coiTesponding period of Ufe. The term " disuse " does not relate merely to the lessened action of muscles, but includes a diminished flow of blood to a part or organ, fi-om being subjected to fewer alternations of jiressm-e, or from becoming in any way less habitually active. Eudiments, however, may occur in one sex of those parts which are normaUy present in the other sex; and such rudiments, as we shall hereafter see, have often originated in a way distinct fi'om those here referred to. In some cases, organs have been reduced by means of natural selection, from having become injurious to the species under changed habits of hfe. The process of reduction 's probably often aided through the two principles of compensa- tion and economy of growth ; but the later stages of reduction, after disuse has done all that can faMy be attributed to it, and when the saving to be effected by the economy of growth would be very small,^^ are difficult to tmderstand. The final and complete suppression of a part, already useless and much reduced in size, in which case neither compensation nor economy can come into plaj', is perhaps intelligible by the aid of the hypothesis of pangenesis. But as the whole subject of rudimentary organs has been discussed and illustrated in my former works,^* I need here say no more on this head. Eudiments of various muscles have been observed in many parts of the human body and not a few muscles, which are Some good criticisms on this Zoolog. 1852, tom. xviii. p. 13) de- subject have been given by Messrs. scribes and figures rudiments of Murie and Mivart, in ' Transact, what he calls the " muscle pe'dieus Zoolog. Soc' 1869, vol. vii. p. 92. de la main," which he says is some- 2^ ♦ Variation of Animals and times " infiniment petit." Another Plants under Domestication,' vol. ii. muscle, called " le tibial postdrieur," pp. 317 and 397 See also ' Origin is generally quite absent in the of Species,' 5th edit. p. 535. hand, but appears from time to time For instance M. Ricnard (' An- in a more or less rudimentary cou- aales des Sciences Nat. 3rd series, dition. ClIAP. I. 13 regularly present in some of .the lower animals can occasionally be detected in man in a greatly reduced condition. Every one must have noticed the power which many animals, especially horses, possess of moving or twitching then." skin; and this is effected by the panniculus carnosus. Eemnants of this muscle in an efficient state are found in various parts of our bodies ; for instance, the muscle on the forehead, by which the eyebrows are raised. The platysma myoides, which is well developed on the neck, belongs to this system. Prof. Turner, of Edinbm-gh, has occasionally detected, as he informs me, muscular fasciculi in five different situations, namely in the axillse, near the scapulae, &c., all of which must be referred to the system of the panni- culus. He has also shewn that the musculus sternalis or sternalis irutorum, which is not an extension of the rectus dbdominalis, but is closely allied to the pannicidus, occurred in the proportion of about three per cent, in upwards of 600 bodies : he adds, that this muscle affords "an excellent illustration of the statement " that occasional and rudimentary structures are especially " liable to variation in arrangement." Some few persons have the power of contracting the super- ficial muscles on their scalps ; and these muscles are in a vai'iable and partially rudimentary condition, M. A. de Candolle has communicated to me a cuiious instance of the long-continued persistence or inheritance of this power, as well as of its unusual development. He knows a family, in which one member, the present head of the family, could, when a youth, pitch several heavy books from his head by the movement of the scalp alone ; and he won wagers by performing this feat. His father, uncle, gi-andfather, and his three children possess the same power to the same unusual degree. This family became divided eight generations ago into two branches; so that the head of the above-mentioned branch is cousia in the seventh degree to the head of tho other branch. This distant cousin resides in another part of France ; and on being asked whether he possessed the same faculty, immediately exhibited his power. This case offers a good illustration how persistent may be the transmission of an absolutely useless faculty, probably derived from our remote semi- human progenitors ; since many monkeys have, and frequently use the power, of largely moving their scalps up and down.^'' The extrinsic muscles which serve to move the external ear, and the intrinsic muscles which move the different parts, are in a rudimentary condition in man, and they all belong to the system ^'^ Prof. W. Turner, ' Proc. Royal Emotions in Man and Animals./ Soc. Edinburgh,' 1866-67, p. 65. 1872, pu 144. Se« my ' Espression cf the The Descent of Man. Past I. of the panniculm ; they are also variable in development, or at least in function. I have seen one man who could draw the whole ear forwards; other men can di-aw it upwards; another who could draw it backwards ;-8 and from what one of these persons told me, it is probable that most of us, by often touching our ears, and thus dii-ectmg our attention towards them, could recover some power of movement by repeated trials. The power of erecting and dkecting the shell of the ears to the various points of the compass, is no doubt of the highest service to many animals, as they thus perceive the direction of danger; but I have never heard, on sufficient evidence, of a man who possessed this power, the one which might be of use to him. The whole external shell may be considered a rudiment, together with the various folds and prominences (helix and anti-helix, tragus and anti-tragus, &c.) which in the lower animals strengthen and support the ear when erect, without adding much to its weight. Some authors, however, suppose that the cartilage of the shell serves to transmit vibrations to the acoustic nerve; but Mr. Toynbee,-^ after collecting aU the known evidence on this head, concludes that the external shell is of no distinct use. The ears of the chimpanzee and orang are curiously like those of man, and the proper muscles are hkewise but very shghtly developed.''*' I am also assured by the keepers in the Zoological Gardens that these animals never move or erect their ears ; so that they are in an equally rudimentary condition with those of man, as far as function is concerned. Why these animals, as well as the progenitors of man, should have lost the power of erecting their ears, we cannot say. It may be, though I am not satisfied with this view, that owing to their arboreal habits and great strength they were but little exposed to danger, and so during a lengthened period moved their ears but httle, and thus gradually lost the power of moving them. This would be a parallel case with that of those large and heavy birds, which, from inhabiting oceanic islands, have not been exposed to the attacks of beasts of prey, and have consequently lost the power of using their wings for flight. The inability to move the ears in man and several apes is, however, partly com- pensated by the freedom with which they can move the head in Canestrini quotes Hyrtl. ('An- lately been experimenting on the nuario della See. del Naturalisti, function of the shell of the ear, Modena, 1867, p. 97) to the same and has come to nearly the same effect. conclusion as that given here. 29 ' The Diseases of the Ear,' by " Prof. A. Macalister, ' Annals J. Toynbee, F.R.S., 1860, p. 12. and Mag. of Nat. History,' vol vii., A distinguished physiologist. Prof. 1871, p. 342. Preyer, informs me that he had Chap. I. Rudiments. 15 a horizontal plane, so as to catch sounds from all directions. It has been asserted that the ear of man alone possesses a lobule ; but "a rudiment of it is found in the gorilla and, as I hear from Prof. Preyer, it is not rarely absent in the negro. The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity in the external ear, which he has often observed both in men and women, and of which he perceived the full signi- ficance. Bis attention was first called to the subject whilst at work on his figure of Puck, to which he had given pointed ears. He was thus led to examine the ears of various monkeys, and sub- sequently more carefully those of man. The peculiarity consists in a little blunt point, projecting from the inwardly folded margin, or helix. When present, it is developed at birth, and, according to Prof. Ludwig Meyer, more frequently in man than in woman. Mr. "Woolner made an exact model of one such case, and sent me the accompanying drawing. (Fig. 2.^ These points not only project inwards towards the centre of the ear, but often a little outwards from its plane, so as to be visible when the head is viewed from directly in front or behind. They are variable in size, and somewhat in position, standing either a little higher or lower; and they sometimes occur on one ear and not on the other. They are not confined to mankind, for I ob- served a case in one of the spider- monkeys (^Ateles heelzebuth') in our Zoological Gardens; and Dr. E. Pay Lankester informs me of another ease in a chimpanzee in the gardens at Hamburg. The helix obviously con- sists of the extreme margin of the ear folded inwards ; and this folding appears to be in some manner connected with the whole external ear being permanently pressed backwards. In many monkeys, which do not stand high in the order, as baboons and some species of macacus,^^ the upper portion of the ear is slightly pointed, and the margin is not at all folded inwards ; but if the margin were to be thus folded, a slight point would necessarily project inwards towards the centre, and probably a little outwards from the plane of the ear ; and this I believe to Fig 2. Human Ear, modelled and drawn by Mr. Woolner. o. The projecting point. ^' Mr. St. George Mivart, 'Ele- mentary Anatomy,' 1873, p. 396. See also some remarks, and the drawings of the ears of the Lemuroidea, in Messrs. Murie and Mivart's excellent pnper in ' Tran- sact. Zoolog. Soc' vol. vii. 1869, pp. 6 and 90. TJu Descent of Man, Paut I. be their origin in many cases. On the other hand, Prof. L. Meyer, in an able paper recently piibhshed,'^ maintains that the whole case is one of mere variability ; and that the projections are not real ones, but are due to the internal cartilage on each side of the points not having been fully developed. I am quite ready to admit that this is the correct explanation in many instances, as in those figured by Prof. Meyer, in which there are several minute points, or the whole margin is sinuous. I have myself seen, through the kindness of Dr. L. Down, the ear of a micro- cephalous idiot, on which there is a projection on the outside of the helix, and not on the inward folded edge, so that this point can have no relation to a former apex of the ear. Never- theless in some cases, my original view, that the points are vestiges of the tips of formerly erect and pointed ears, still seems to me probable. I think so £i-om the frequency ot their occurrence, and from the general correspondence in position with that of the tip of a pointed ear. In one case, ot which a photograph has been sent me, the projection is so large, that supposing, in accordance with Prof. Meyer's view, the ear to be made jDerfect by the equal development of the cartilage throughout the whole extent of the margin, it would have covered fully one-third of the whole ear. Two cases have been communicated to me, one in North America, and the other in England, in which the upper margin is not at all folded inwards, but is pointed, so that it closely resembles the pointed ear of an ordinary quadruped in outline. In one of these cases, which was that of a young child, the father compared the ear with the drawing which I have given^* of the ear of a monkey, the Cynopithecus niger, and says that their outHnes are closely similar. If, in these two cases, the margin had been folded inwards in the normal manner, an inward projection must have been formed. I may add that in two other cases the oiitline still remains somewhat pointed, although the margin of the upper part of the ear is normally folded inwards — in one of them, however, very narrowly. The following woodcut (No. 3) is an accm-ate copy of a photograph of the foetus of an orang (kindly sent me by Dr. Nitsche), in which it may be seen how different the pointed outhne of the ear is at this period from its adult condition, when it bears a close general resemblance to that of man. It is evident that the folding over of the tip of such an ear, unless it changed greatly during its further development, would give rise to a point projecting inwards. On the whole, it still seems to Ueber dasDarwin'sche Spitzohr, 'The Expression of the Emo- Ai-chiv fur Path, Anat. und Phys, tions,' p. 136. 1871, p. 485. Chap. I. Rudiments. 17 me pi-obabie that the points in question are in some cases, botli in man and apes, vestiges of a former condition. Fig. 3. Foetus of an Drang. Exact copy of a photograph, shewing the form of the ear at this early age. The nictitating membrane, or third eyelid, with its accessory muscles and other structures, is especially -well developed in birds, and is of much functional importance to them, as it can be rapidly drawn across the whole eye-ball. It is found in some reptiles and amphibians, and in certain fishes, as in sharks. It is fairly well developed in the two lower divisions of the mam- malian series, namely, in the monotremata and marsupials, and in some few of the higher mammals,- as in the walrus. But in man, the quadrumana, and most other mammals, it exists, as is admitted by all anatomists, as a mere rudiment, called the semilunar fold.^° The sense of smell is of the highest importance to the greater number of mammals — to some, as the ruminants, in warning them of danger; to others, as the carnivora, in finding their prey; to others, again, as the wild boar, for both purposes combined. But the sense of smell is of extremely slight service, if any, even to the dark coloured races of men, in whom it is Miiller's 'Elements of Physi- Knox, 'Great Artists and Anato- ology,' Eng. translat., 1842, vol. ii. mists,' p. 106. This rudiment ap p. 1117. Owen, ' Anatomy of Verte- parently is somewhat larger in brates,' vol. iii. p. 260; ibid, on Negroes and Australians than in the Walrus, ' Proc. Zoolog. Soc' Europeans, see Carl Vogt, ' Lectures November 8th, 1854. See also E. on Man,' Eng. translat. p. 129. C i8 Part I. much more highly developed than in the white and civilised races.5* Nevertheless it does not warn them of danger, nor guido them to their food ; nor does it prevent the Esquimaux from sleeping in the most fetid atmosphere, nor many savages from eating half-putrid meat. In Europeans the power differs greatly in different individuals, as I am assured by an eminent naturalist who possesses this sense highly developed, and who has at- tended to the subject. Those who believe in the principle of gradual evolution, will not readily admit that the sense of smell in its present state was originally acquired by man, as he now exists. He inherits the power in an enfeebled and so far rudimentary condition, from some early progenitor, to whom it was highly serviceable, and by whom it was con- tinually used. In those animals which have this sense highly developed, such as dogs and horses, the recollection of persons and of places is strongly associated with their odour ; and we can thus perhaps understand how it is, as Dr. Maudsley has truly remarked,^^ that the sense of smell in man " is singularly effective " in recalling vividly the ideas and images of forgotten scenes " and places." Man differs conspicuously from all the other Primates in being almost naked. But a few short straggling hairs are found over the greater part of the body in the man, and fine down on that of the woman. The different races differ much in hairiness ; and in the individuals of the same race the hairs are highly variable, not only in abundance, but likewise in position : thus in some Europeans the shoulders are quite naked, whilst in others they bear thick tufts of hair.^' There can be little doubt that the hau'S thus scattered over the body are the rudiments of the uniform hairy coat of the lower animals. This view is rendered aU the more probable, , as it is known that fine, short, and pale- coloured hairs on the limbs and other parts of the body, occasion- The account given by Humboldt of the power of smell possessed by the natives of South America is well known, and has been confirmed by others. M. Houzeau (' Etudes sur les Faculte's Mentales,' &ic., torn. i. 1872, p. 91) asserts that he re- peatedly made experiments, and proved that Negroes and Indians could recognise persons in the dark by their odour. Dr. W. Ogle has made some curious observations on the connection between the power of smell and thi colouring matter ©f the mucous membrane of the olfactory region, as well as of the skin of the body. I have, therefore, spoken in the text of the dark- coloured races having a finer sense of smell than the white races. See his paper, ' Medico-Chirurgical Tran- sactions,' London, vol. liii., 1870, p. 276. ^' ' The Physiology and Pathology of Mind,' 2nd edit. 1868, p. 134. 3' Eschricht, Ueber die Richtung der Haare am menschlichen Korper, ' Mailer's Archiv fiir Anat. und Phvs.' 1837, s. 47. I shall often have" to refer to this very curious paper. Chap, I. Rndivieiits. 19 ally become developed into "thickgct, long, and rather coarse " dark hairs/' when abnormally nourished near old-standing inflamed smfaces.^^ I am informed by Sir James Paget that often several members of a family have a few hairs in their eyebrows much longer than the others; so that even this sUght peculiarity seems to be inherited. These hairs, too, seem to have their representatives : for in the chimpanzee, and in certain species of Macacus, there are scattered hairs of considerable length rising from the naked ekin above the eyes, and corresponding to our eyebrows ; similar long hairs project from the haiiy covering of the superciliary ridges in some baboons. The fine wool-like hair, or so-called lanugo, with which the human foetus during the sixth month is thickly covered, offers a more cm-ious case. It is first developed, during the fifth month, on the eyebrows and face, and especially round the mouth, where it is much longer than that on the head. A moustache of this kind was observed by Eschricht*" on a female foetus; but this is not so surprising a circumstance as it may at fii'st appear, for the two sexes generally resemble each other in all external characters during an early jDeriod of growth. The direction and arrangement of the hairs on all parts of the foetal body are the same as in the adult, but are subject to much variability. The whole surface, including even the forehead and ears, is thus thickly clothed ; but it is a significant fact that the palms of the hands and the soles of the feet are qtiite naked, like the inferior surfaces of all four extremities in most of the lower animals. As this can hardly be an accidental coincidence, the woolly cover- ing of the foetus probably represents the first permanent coat of hair in those mammals which are born hairy. Three or four cases have been recorded of persons born with their whole bodies and faces thickly covered with fine long hairs ; and this strange condition is strongly inherited, and is correlated with an abnor- mal condition of the teeth Prof. Alex. Brandt informs me that he has compared the hair from the face of a man thus charac- terised, aged thirty-five, with the lanugo of a foetus, and fibids it quite similar in texture ; therefore, as he remarks, the case may be attributed to an arrest of development in the hair, together with its continued growth. Many delicate children, as I have 3» Paget, 'Lectures on Surgical has recently sent me an additional rathology,' 1853, vol. i. p. 71. case of a father and son, horn in •'O Eschricht, ibid. s. 40, 47. Russia, with these peculiarities. I See my 'Variation of Animals have received drawings of both from and Plants sader Domestication,' Paris vcL ii. p. 327. Prof. Alex. Brandt 20 The Descent of Man. Part I. been assured by a surgeon -to a hospital for children, have their backs covered by rather long sillcy hairs ; and such cases pro- bably como under the same head. It appears as if the posterior molar or wisdom-teeth were tending to become rudimentary in the more civilised races of man. These teeth are rather smaller than the other molars, as is likewise the case with the corresponding teeth in the chim- panzee and orang ; and they have only two separate fangs. They do not cut through the guins till about the seventeenth year, and I have been assured that they are much more liable to decay, and are earlier lost than the other teeth ; but this is denied by some eminent dentists. They are also much more liable to •vary, both in structure and in the period of their development, than the other teeth.*^ In the Melanian races, on the other hand, the wisdom-teeth are usually furnished with three separate fangs, and are generally sound ; they also differ from the other molars in size, less than in the Caucasian races.*^ Prof. Schaaffhausen accounts for this difference between the races by " the posterior dental portion of the jaw being always- " shortened" in those that are civihsed,''* and this shortening may, I presume, be attributed to civilised men habitually feeding on soft, cooked food, and thus using their jaws less. I am informed by Mr. Brace that it is becoming quite a common practice in the United States to remove some of the molar teeth of children, as the jaw does not grow large enough for the perfect development of the normal number.^^ With respect to the alimentary canal, I have met with an account of only a single rudiment, namely the vermiform append- age of the caecum. The caecum is a branch or diverticulum of the intestine, ending in a cul-de-sac, and is extremely long in many of the lower vegetable-feeding mammals. In the marsupial koala it is actually more than thrice as long as the whole body.'"' It is sometimes produced into a long gradually-tapering poinii, and is sometimes constricted in parts. It appears as if, in con- sequence of changed diet or habits, the cascum had become much ■«2 Dr. Webb, 'Teeth in Man and the Anthropoid Apes,' as quoted by Dr. C. Carter Blake in ' Anthropo- logical Review,' July 1867, p. 299. Owen, ' Anatomy of Verte- brates,' vol. iii. pp. 320, 321, and 325. ' On the Primitive Form of the Skull,' Eng. translat. in ' Anthropo- logical Review,' Oct. 1868, p. 426. *s Prof. Montegazza writes to me from Florence, that he has lately been studying the last molar teeth in the different races of man, and has come to the same conclusion as that given in my text, viz., that in the higher or civilised races they are on the road towards atrophy or elimination. *^ Owen, ' Anatomy of Verte- brat»s,' vol. lii. pp. 416, 434. 441. Chap I. Riidiments. 21 ghoi-tened in various animals, the vermiform appendage being left as a rudiment of the shortened part. That this appendage is a rudiment, we may infer from its small size, and fi-om the evidence which Prof. Canestrini*'' has collected of its variability ia man. It is occasionally quite absent, or again is largely developed. The passage is sometimes completely closed for half or two-thirds of its length, with the terminal part consisting of a flattened solid expansion. In the orang this appendage is long and convoluted: in. man it arises from the end of the short caecum, and is commonly from four to five inches in length, being only about the third of an inch in diameter. Not only is it useless, but it is sometimes the cause of death, of which fact I have lately heard two instances : this is due to small hard bodies, such as seeds, entering the passage, and causing inflam- mation.'** In some of the lower Quadrumana, in the Lemuridse and Carnivora, as well as in many marsupials, there is a passage near the lower end of the humerus, called the supra-condyloid fora- men, through which the great nerve of the fore limb and often the great artery pass. Now in the humerus of man, there is generally a trace of this passage, which is sometimes fairly well developed, being formed by a depending hook-Like process of bone, completed by a band of ligament. Dr. Struthers,^^ who has closely attended to the subject, has now shewn that this peculiarity is sometimes inherited, as it has occurred in a father, and in no less than four out of his seven children. When pre- sent, the great nerve invariably passes through it; and this clearly indicates that it is the homologue and rudiment of the supra-condyloid foramen of the lower animals. Prof. Tui'ner estimates, as he informs me, that it occurs in about one per cent, of recent skeletons. But if the occasional development of this structui'e in man is, as seems probable, due to reversion, it is a retm-n to a very ancient state of things, because in the higher Quadrumana it is absent. There is another foramen or perforation in the humerus. 'Annuario della Soc. d, Nat.' Modena, 1867, p. 94. ' " M. C. Martins (" De rUnite Organique," in 'Revue des Deu.\ Moudes,' June 15, 1862, p. 16), and Hiickel (' Generelle Morphologie,' B. ii. s. 278), have both remavked on the singular fact of this rudi- ment sometimes causing death. ^ With respect to inheritance, see Dr. Stvuthers in the 'Lancet,' Feb. 15, 1873, and another im- portant paper, ibid., Jan. 24, 1863, p. 83. Dr. Knox, as I am informed, was the first anatomist who drew attention to this peculiar structure in man ; see his * Great Ai'tists and Anatomists,' p. 63. See also an im- portant memoir on this process by Dr. Grubei-, in the ' Bulletin da I'Acad. Imp. de St. Pc'tersbourg, torn. sii. 1867, p. 448. The Descent of Man. Pabt i occasionally present in man, which may be called the inter- condyloid. This occurs, but not constantly, in various anthro- poid and other apes,'^'' and likewise in many of the lower animals. It is remarkable that this perforation seems to have been present in man much more frequently during ancient times than recently. Mr. Busk" has collected the following evidence on this head : Prof. Broca " noticed the perforation in four and a " half per cent, of the arm-bones collected in the ' Cimetiere du " Sud,' at Paris ; and in the Grotto of Orrony, the contents of "which are referred to the Bronze period, as many as eight "humeri out of thirty-two were perforated ; but this extraordi- " nary proportion, he thinks, might be due to the cavern having " been a sort of ' family vault.' Again, M. Dupont found thirty " per cent, of perforated bones in the caves of the Valley of tho " Lesse, belonging to the Eeindeer period ; whilst M. Leguay, m " a sort of dolmen at Argenteuil, observed twenty-five per cent, "to be perforated; and M. Pruner-Bey found twenty-six per " cent, in the same condition in bones from Vaureal. Nor should " it be left unnoticed that M. Pruner-Bey states that this con- " dition is common in Guanche skeletons." It is an interesting- fact that ancient races, in this and several other cases, more frequently present structures which resemble those of the lower animals than do the modern. One chief cause seems to be that the ancient races stand somewhat neai'er in the long line of descent to their remote animal-like progenitors. In man, the os coccyx, together with certain other vertebras hereafter to be described, though functionless as a tail, plainly represent this part in other vertebrate animals. At an early embryonic period it is free, and projects beyond the lower extremities ; as may be seen in the drawing (Fig. 1.) of a human embryo. Even after birth it has been known, in certain rare and anomalous cases,°^ to form a small external rudiment of a tail. The os coccyx is short, usually including only foui- vertebrse, all anchylosed together: and these are in a rudi" *° Mr. St. George Mivart, ' Trans- Quatrefages has lately collected act. Phil. Soc' 1867, p. 310. the evidence on this subject. 'Revue " "On the Caves of Gibraltar," des Cours Scientifiques,' 1867-1868, ' Transact. Internat. Congress of p. 625. In 1840 Fleischmann ex- Prehist. Arch.' Third Session, 1869, hibited a human fcetus bearing a p. 159. Prof. Wyman has lately free tail, which, as is not always the shewn (Fourth Annual Report, Pea- case, incladed vertebral bodies; and body Museum, 1871, p. 20), that this this tail was critically e.xamined by perforation is present in thirty-one the many anatomists present at the per cent, of some human remains meeting of naturalists at Erlangen from ancient mounds in the Western (see Miu-shall in Niederliindischeii United States, and in Florida. It Archiv fur Zoologie, Decern berl 871). frequently occurs in the negro. Chaf. I. Rtidiments. 23 mentary condition, for they consist, with the exception of the basal one, of the centrum alone.^* They are furnished with some small muscles ; one of which, as I am informed by Prof. Tui'ner, has been expressly described by Theile as a rudimentary repetition of the extensor of the tail, a muscle which is so largely developed in many mammals. The spinal cord in man extends only as far downwards as the last dorsal or first lumbar vertebra; but a thread-like struc- ture (the filum terminale) runs down the axis of the sacral pari of the spinal canal, and even along the back of the coccygeal bones. The upper part of this filament, as Prof. Turner informs me, is undoubtedly homologoas with the spinal cord • but the lower part apparently consists merely of the pia mater, or vascular investing membrane. Even in this case the os coccyx may be said to possess a vestige of so important a structure as the spinal cord, though no longer enclosed within a bony canal. The followiug fact, for which I am also in- debted to Prof. Turner, shews how closely the os coccyx corre- sponds with the ti'ue tail in the lower animals : Luschka has recently discovered at the extremity of the coccygeal bones a very pecuhar convoluted body, which is continuous with the middle sacral artery ; and this discovery led Krause and Meyer to examine the tail of a monkey (Macacus), and of a cat, in both of which they found a similarly convoluted body, though not at the extremity. The reproductive system offers various rudimentary struc- tures; but these differ in one important respect from the foregoing cases. Here we are not concerned with the vestige of a part which does not belong to the species iu an efficient state, but with a part efllcient iu the one sex, and represented in the other by a mere rudiment. Nevertheless, the occiu-rence of such rudiments is as difficult to explain, on the belief of the separate creation of each species, as in the foregoing cases. Hereafter I shall have to recur to these rudiments, and shall shew that their presence generally depends merely on inheri- tance, that is, on parts acquired by one sex having been partially transmitted to the other. I wUl in this place only give some instances of such rudiments. It is well known that in the males of all mammals, including man, rudimentary mammse exist. These in several instances have become well developed, and have yielded a copious supply of milk. Their essential identity in the two sexes is likewise shewn by their occasional sympathetic enlargement in both during an attack of the Owen, ' On the Nature of Limbs,' 1349, p. 114. 24 The Descent of Man. Past l measles. The vesicula proslatica, which has been observed in many male mammals, is now universally acknowledged to be the homologue of the female uterus, together with the con- nected passage. It is impossible to read Leuckart's able description of this organ, and his reasoning, without admitting the justness of his conclusion. This is especially clear in the case of those mammals in which the true female uterus bifurcates, for in the males of these the vesicula likewise bifurcates.^' Some other rudimentary structui'es belonging to the reproductive system might have been here adduced." The bearing of the three great classes of facts now given if, unmistakeable. But it would be superfluous fully to recapitulate the line of argument given in detail in my ' Origin of Species/ The homological construction of the whole frame in the members of the same class is intelligible, if we admit their descent from a common progenitor, together with their subsequent adaptation to diversified conditions. On any other view, the similarity of pattern between the hand of a man or monkey, the foot o*" a horse, the flipper of a seal, the wing of a bat, &c., is utterly inexplicable It is no scientific explanation to assert that they have all been formed on the same ideal plan. With respect to development, we can clearly understand, on the principle of ^* Leuckart, in Todd's 'Cyclop, of Anat.' 1849-52, vol. iv. p. 1415. In man this organ is only from three to six lines in length, but, like so many other rudimentary parts, it is variable in development as well as in other characters. See, on this subject, Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 675, 676, 706. '° Prof. Bianconi, in a recently published work, illustrated by ad- mirable engravings ('La The'orie Darwinienne et la crdation dite in- de'pendante,' 1874), endeavours to show that homological structures, in the above and other cases, can be fully explained on mechanical prin- ciples, in accordance with their uses. No one has shewn so well, how ad- mirably such structures are adapted for their final purpose ; and this adaptation can, as I believe, be explained through natural selection. In considering the wing of a bat, he brings forward (p. 218) what appears to nie (lo use Auguste Comte's words) a mere metaphysical prin- ciple, namely, the preservation " in " its integrity of the mammalian " nature of the animal." In only a few cases does he discuss rudiments, and then only those parts which are partially rudimentary, such as the little hoofs of the pig and ox, which do not touch the ground ; these he shews clearly to be of service to the animal. It is unfortunate that he did not consider such cases as the minute teeth, which never cut through the jaw in the ox, or the mamma: of male quadrupeds, or the wings of certain beetles, existing under the soldered wing-covers, or the vestiges of the pistil and stamens in various flowers, and many other such cases. Although I greatly admire Prof. Bianconi's work, yet the belief now held by most natural- ists seems to me left unshaken, that homological structures are iu- explicable on the principle of mere adaptation. Chap. T. Kudiments. 25 variations supervening at a rather late embryonic period, and being inherited at a corresponding period, how it is that the embryos of wonderfully different forms should still retain, more or less perfectly, the structure of their common progenitor. No other explanation has ever been given of the marvellous fact that the embryos of a man, dog, seal, bat, reptile, &c., can at first hardly be distinguished from each other. In order to understand the existence of rudimentary organs, we have only to suppose that a former progenitor possessed the parts in question in a perfect state, and that under changed habits of life they became greatly reduced, either from simple disuse, or through the natural selection of those individuals which were least encumbered with a superfluous part, aided by the other means previously in- dicated. Thus we can understand how it has come to pass that man and all other vertebrate animals have been constructed on the same general model, why they pass through the same early stages ot development, and why they retain certain rudiments in common. Consequently we ought frankly to admit their community of descent; to take any other view, is to admit that our own structure, and that of all the animals around us, is a mere snare laid to entrap oui' judgment. This conclusion is greatly strengthened, if we look to the members of the whole animal series, and consider the evidence derived from their afi&nities or classification, their geographical distribution and geolo- gical succession. It is only our natural prejudice, and that arrogance which made our forefathers declare that they were descended from demi-gods, which leads us to demur to this conclusion. But the time will before long come, when it will be thought wonderful that naturalists, who were well acquainted with the comparative structure and development of man. and other mammals, should have believed that each was the work of a separate act of creation. The Descent of Man. Paet L CHAPTER n. On the Manneb of Development op Man feom some Lower Form. Variability of body and mind in man — Inheritance — Causes of variability — Laws of variation the same in man as in the lower animals — Direct action of the conditions of life— Effects of the increased use and disuse of parts — Arrested development — Reversion — Correlated variation — Rate of increase — Checks to increase — Natural selection — Man the most dominant animal in the world — Importance of his corporeal structure — The causes which have led to his becoming erect — Consequent changes of structure — Decrease in size of the canine teeth — Increased size and altered shape of the skull — Nakedness — Absence of a tail — Defenceless condition of man. It is manifest that man is now subject to much variabLlity. No two individuals of the same race are quite alike. We may- compare millions of faces, and each will be distinct. There is an equally gi-eat amount of diversity ia the proportions and dimensions of the various parts of the body ; the length of the legs being one of the most variable points.^ Although in some quarters of the world an elongated skull, and in other quarters a short skull prevails, yet there is great diversity of shape even within the limits of the same race, as with the aborigines of America and South Austraha — the latter a race " probably as " pure and homogeneous ia blood, customs, and language as any " in existence" — and even with the inhabitants of so confined an area as the Sandwich Islands.^ An eminent dentist assures me that there is nearly as much diversity in the teeth as in the features. The chief arteries so fi-equently run in abnormal courses, that it has been found useful for surgical purposes to calculate from 1040 corpses how often each course prevails.^ The muscles are eminently variable: thus those of the foot were found by Prof. Turner* not to be strictly alike in any two out of fifty bodies ; and in some the deviations were considerable. * ' Investigations in Military and Anthropolog. Statistics of American Soldiers,' by B. A. Gould, 1869, p. 256. * With respect to the "Cranial forms of the American aborigines," see Dr. Aitken Meigs in ' Proc. Acad. Nat. Sci.' Philadelphia, May, 1868. On the Australians, see Huxley, in Lyell's 'Antiquity of Man,' 1863, p. 87. On the Sand- wich Islanders, Prof. J. Wyman, ' Observations on Crania,' Boston, 1868, p. 18. ' 'Anatomy of the Arteries,* by R. Quain. Preface, vol. i. 1844. * 'Transact. Royal Soc. Edin- burgh,' vol. xsiv. pp. 175, 180. Chap. II. Marnier of Development. 27 He adds, that the power of performiug the appropriate moye- ments miast have been modified in accordance with the several deviations. Mr. J. Wood has recorded^ the occurrence of 295 muscular variations in thirty-six subjects, and in another set of the same number no less than 558 variations, those occurring on both sides of the body being only reckoned as one. In the last set, not one body out of the thirty-six was "found totally " wanting in departures from the standard descriptions of the " muscular system given in anatomical text books." A single body presented the extraordinary number of twenty-five distinct abnormalities. The same muscle sometimes varies in many ways: thus Prof. Macalister describes^ no less than twenty distinct variations in the palmaris accessorius. The famous old anatomist, Wolff,^ insists that the internal viscera are more variable than the external parts : Nulla parti- ciila est quiB non aliter et aliter in aliis se habeat hominibus. He has even written a treatise on the choice of typical examples of the viscera for representation. A discussion on the beau-ideal of the liver, lungs, kidneys, &c., as of the human face divine, sounds strange in our ears. The variability or diversity of the mental faculties in men of the same race, not to mention the greater dinerences between the men of distinct races, is so notorious that not a word need here be said. So it is with the lower animals. All who have had charge of menageries admit this fact, and we see it plainly in our dogs and other domestic animals. Brehm especially insists that each individual monkey of those which he kept tame in Africa had its own peculiar disposition and temper ; he men- tions one baboon remarkable for its high intelUgence ; and the keepers in the Zoological Gardens pointed out to me a monkey, belonging to the New World division, equally remarkable for intelligence. Eengger, also, insists on the diversity in the various mental characters of the monkeys of the same species which he kept in Paraguay ; and this diversity, as he adds, is partly innate, and partly the result of the manner in which they have been treated or educated.* I have elsewhere^ so fully discussed the subject of Inheritance, that I need here add hardly anything. A greater number of * 'Pioc. Royal Soc' 1867, p. » Biehm, ' Tliierleben,' B. i. s. 544; also 1868, pp. 483, 524. There 58,87. Eengger, ' Saugethieve von Is a previous paper, 1866, p. 229. Paraguay,' s. 57. « ' Proc. R. Irish Academy,' vol. » ' Variation of Animals and X. 1868, p. 141. Plants under Domestication,' vo) ' ' Act. Acad. St. Petersburg,' ii. chap. sh. 1778, pai-t ii. p. 217 28 The Descent of Man. Taut I. facts have been collected witli respect to the transmission of the most trifling, as well as of the most important characters in man, than in any of the lower animals ; though the facts are copious enough with respect to the latter. So in regard to mental quaUties, their transmission is manifest in oui- dogs, horses, and other domestic animals. Besides special tastes and habits, general intelligence, courage, bad and good temper, &c., are certainly transmitted. With man we see similar facts in almost every family ; and we now know, through the admirable laboui-s of Mr. Galton,i° that genius which implies a wonderfully complex combination of high faculties, tends to be inherited; and, on the other hand, it is too certain that insanity and deteri- orated mental powers likewise run in families. With respect to the causes of variability, we are in all cases very ignorant; but we can see that in man as in the lower animals, they stand in some relation to the conditions to which each species has been exposed, during several generations. Domesticated animals vary more than those in a state of nature ; and this is apparently due to the diversified and changing natui-e of the conditions to which they have been subjected. In this respect the different races of man resemble domesticated animals, and so do the individuals of the same race, when inhabiting a very wide ai-ea, like that of America. We see the influence of diversified conditions in the more civilised nations; for the members belonging to different grades of rank, and following different occupations, present a greater range of character than do the members of barbarous nations. But the imiformity of savages has often been exaggerated, and in some cases can haidly be said to exist." It is, nevertheless, an error to speak of man, even if we look only to the conditions to which he has been exposed, as "far more domesticated"^^ than any other animal. Some savage races, such as the Australians, are not exposed to more diversified conditions than are many species which have a wide range. In another and much more important respect, man differs widely from any strictly domesticated animal; for his breeding has never long been controlled, either by methodical or unconscious selection. No race or body of men has been so ' Hereditary Genius : an In- " man had an oval visag.e with fine quiry into its Laws and Conse- " features, and another was quite quences,' 1869. " Mongolian in breadth and pro- " Mr. Bates remarks (' The Natu- " minence of cheek, spread of nos- ralist on the Amazons,' 1863, vol. ii. " trils, and obliquity of eyes." J). 159), with respect to the Indians " Blumenbach, ' Treatises on An- of the same South American tribe, thropolog.' Eng. translal., 1865, p. " 110 two of them were at all similar 205. " In the shape of the head ; one Chap. II. Manner of Development. 29 cjompletely subjugated by other men, as that certain individuals should be preserved, and thus unconsciously selected, from some- how excelling in utility to their masters. Nor have certain male and female individuals been intentionally picked out and matched, except in the well-known case of the Prussian grena- diers ; and in this case man obeyed, as might have been ex- pected, the law of methodical selection ; for it is asserted that many tall men were reared ia the villages inhabited by the grenadiers and their tail wives. In Sparta, also, a form of selec- tion was followed, for it was enacted that all children should be examined shortly after birth; the well-formed and vigorous being preserved, the others left to perish." If we consider aU the races of man as forming a single species, his range is enormous ; but some separate races, as the Americana and Polynesians, have very wide ranges. It is a well-known law that widely-ranging species are much more variable than species with restricted ranges ; and the variability of man may with more truth be compared with that of widely-ranging species, than with that of domesticated animals. Not only does variability appear to bo induced in man and the lower animals by the same general causes, but in both the same parts of the body are affected in a closely analogous manner. This, has been proved in siTch full detail by Godron and Mitford's 'History of Greece,' vol. i. p. 282. It appears also from a passage in Xenophon's 'Memora- bilia,' B. ii. 4 (to which my atten- tion has been called by the Kev. J. N. Hoare), that it was a well recognised principle with the Greeks, that men ought to select their wives with a view to the health and vigour of their children. The Gre- cian poet, Theognis, who lived 550 B.C., clearly saw how important selection, if carefully applied, would be for the improvement of mankind. He saw, likewise, that wealth often checks the proper action of sexual selection. He thus writes : " With kine and horses, Kurnus ! we proceed By reasonable rules, and choose a breed For profit and increase, at any price ; Of a sound stock, without defect or vice. But, in the daily matches that we make, The price is everything : for money's sake, Men marry : women are in marriage given The churl or ruffian, that in wealth has thriven, May match his offspring with the proudest race : Thus everything is mix'd, noble and base ! If then in outward manner, form, and mind, You find us a degraded, motley kind, "Wonder no more, my friend 1 the cause is plain, And to lament the consequence is vain." (The "Woi-ks of J. Hookham Frere, vol. ii. 1872, p. 334.) The Descent of Man. Past L Qnatrefages, that I need here only refer to their works.^* Mon- strosities, which gi-aduate into slight variations, are likewise so similar in man and the lower animals, that the same classification and the same terms can be used for both, as has been shewn by Isidore Geoffroy St.-Hilaire.^* In my work on the variation of domestic animals, I have attempted to arrange in a rude fashion the laws of variation imder the following heads : — The dii-ect and definite action of changed conditions, as exhibited by all or nearly all the individuals of the same species, varying in the same manner under the same circumstances. The effects of the long-continued use or disuse of parts. The cohesion of homologous parts. The variability of multiple parts. Compensation of growth ; but of this law I have found no good instance in the case of man. The effects of the mechanical pressure of one part on another ; as of the pelvis on the cranium of the infant in the womb. Arrests of development, leading to the diminution or suppression of parts. The reappearance of long-lost characters through reversion. And lastly, correlated variation. All these so-called laws apply equally to man and the lower animals ; and most of them even to plants. It would be superfluous here to discuss all of them -^^ but several are so important, that they must be treated at con- siderable length. !Z%e direct and definite action of changed conditions. — This is a most perplexing subject. It cannot be denied that changed con- ditions produce some, and occasionally a considerable effect, on organisms of all kinds ; and it seems at first probable that if sufficient time were allowed this would be the invariable result. But I have failed to obtaia clear evidence in favour of this con- clusion ; and valid reasons may be urged on the other side, at least as far as the innumerable structures are concerned, which are adapted for special ends. There can, however, be no doubt that changed conditions induce an almost indefinite amount of fluctuating variability, by which the whole organisation is rend- ered in some degree plastic. In the United States, above 1,000,000 soldiers, who served in the late war, were measured, and the States in which they were 14 Godron, 'De I'Espece,' 1859, torn. ii. livre 3. Quatrefages, ' Unite de I'Espfece Humaine,' 1861. Also Lectures on Anthropology, given in the ' Revue des Cours Scientifiques,' 1866-1868. " 'Hist. G^n. si Part, des Ano- malies de rOrganisation,' in three volGir.es, tors. i. 1832, 18 I have fully discussed these laws in my ' Variation of Animals and Plants under Domestication,' vol. ii. chap. xxii. and xxiii. M. J. P. Durand has lately (1868) pub- lished a valuable essay 'De I'ln- fluence des Milieux,' &c. He lays much stress, in the case of plauis, on the nature of the soil. Chap. II. Manner of Developmetit. 31 bom and reared were recorded." From this astonishing numboy of observations it is proved that local inSuences of some kind act directly on stature ; and we further learn that " the State " where the physical growth has in great measure taken place, " and the State of birth, which indicates the ancestry, seem to " exert a marked influence on the stature." For instance, it is estabhshedj " that residence in the "Western States, during the • " years of growth, tends to produce increase of stature." On the other hand, it is certain that with sailors, their Life delays growth, as shewn " by the great difference between the statures of soldiers " and sailors at the ages of seventeen and eighteen years." Mr. B. A. Gould endeavoui'ed to ascertain the nature of the influences which thus act on stature ; but he arrived only at negative results, namely, that they did not relate to climate, the elevation of the land, soil, nor even " in any controlling degree " to the abundance or the need of the comforts of life. This latter conclusion is directly opposed to that arrived at by ViUerme, from the statistics of the height of the conscripts in different parts of France. When we compare the differences in stature between the Polynesian chiefs and the lower orders vrithin the same islands, or between the inhabitants of the fertile volcanic and low barren coral islands of the same ocean,'^ or again between the Fuegians on the eastern and western shores of their country, where the means of subsis- tence are very different, it is scarcely possible to avoid the con- clusion that better food and greater comfort do influence stature. But the preceding statements shew how difficult it is to arrive at any precise result. Dr. Beddoe has lately proved that, with the inhabitants of Britain, residence in towns and certain occupa- tions have a deteriorating influence on height; and he infers that the result is to a certain extent inherited, as is likewise the case in the United States. Dr. Beddoe further believes that "wherever a " race attains its maximmn of physical development, it rises "highest in energy and moral vigour."" Whether external conditions produce any other direct effect on man is not known. It might have been expected that dif- ferences of climate would have had a marked influence, in as much as the lungs and kidneys are brought into activity under a low " ' Investigations in Military and 289. There is also a remarkable Anthrop. Statistics,' &c. 1869, by difference in appearance between B. A. Gould, p. 93, 107, 126, 131, the closely-allied Hindoos inhabiting 134. the Upper Ganges and Bengal ; sea " For the Polynesians, see Prich- Elphinstone's « History of India,' vol, ard's ' Physical Hi^t. of Mankind,' i. p. 324. vol. V. 1847, p. 145, 283. Also " 'Memoirs, Anthropolog. Soc Godron, ' De I'Espfece,' torn. ii. p. vol. iii. 1867-69, pp. 561, 565, 567, 32 The Descent of Man. Pabt 1. temperature, and the liver and skin under a high one." It was formerly thought that the colour of the skin and the character of the hair were determined by light or heat ; and although it can hardly be denied that some effect is thus produced, almost all observers now agree that the effect has been very small, even after exposure during many ages. But this subject will be more properly discussed when wo treat of the different races of man- kind. With our domestic animals there are grounds for believing that cold and damp directly affect the growth of the hair ; but I have not met with any evidence on this head in the case of man. Effects of the increased Use and Disuse of Parts. — It is well known that use strengthens the muscles in the individual, and complete disuse, or the destruction of the proper nerve, weakens them. "When the eye is destroyed, the optic nerve often becomes atrophied. "When an artery is tied, the lateral channels increase not only in diameter, but in the thickness and strength of their coats. "When one kidney ceases to act from disease, the other increases in size, and does double work. Bones increase not only in thickness, but in length, from carrying a greater weight.^' Different occupations, habitually followed, lead to changed proportions in various parts of the body. Thus it was ascertained by the United States Commission that the legs of the sailors employed in the late war were longer by 0'217 of an inch than those of the soldiers, though the sailors were on an average shorter men; whilst their arms were shorter by 1'09 of an inch, and therefore, out of proportion, shorter in relation to their lesser height. This shortness of the arms is apparently due to their greater use, and is an unexpected result : but sailors chiefly rise their arms in puUing, and not in supporting weights. "With sailors, the girth of the neck and the depth of the instep are greater, whilst the circumference of the chest, waist, and hips is less, than in soldiers. "Whether the several foregoing modifications would become hereditary, if the same habits of life were followed during many generations, is not known, but it is probable. Eengger attri- butes the thin legs and thick arms of the Payaguas Indians to Dr. Brakenridge, 'Theory of Dr. Jaeger, "Ueber das Langen- Diathesis,' 'Medical Times,' June 19 wachsthum der Knochen," 'Jena- aad July 17, 1869. ischeD Zeitschrift,' B. v. Heft i. 21 I have given authorities for ' Investigations,' &c. By B. A, these several statements in my Gould, 1869, p. 288. 'Variation of Animals under Do- " 'Saugethiere von Paraguay, inestication,' vol. ii. pp. 297-300. 1830, s. 4. Chap. II. Maimer of Development. 33 successive generations having passed nearly their whole lives in canoes, with their lower extremities motionless. Other wi-iters liave come to a similar conclusion in analogous cases. According to Cranz,-* who lived for a long time with the Esquimaus, " tha " natives believe that ingenuity and dexterity in seal-catching " (their highest ai-t and vu-tue) is hereditary ; there is really " something in it, for the son of a celebrated seal-catcher will " distinguish himself, though he lost his father in childhood." But in this case it is mental aptitude, quite as much as bodily structure, which appears to be inherited. It is asserted that the hands of English labourers are at bii'th larger than those of the gentry.-' From the correlation which exists, at least in some cases,-" between the development of the extremities and of the jaws, it is possible that in those classes which do not labour much with their hands and feet, the jaws would be reduced in size from this cause. That they are generally smaller in refined and civilised men than in hard-working men or savages, is certain. But with savages, as Mr. Herbert Spencer ^ has remarked, the greater use of the jaws in chewing coarse, uncooked food, would act in a direct manner on the'masticatory miiscles, and on the bones to which they are attached. In infants, long before birth, the skin on the soles of the feet is thicker than on any other part of the body ; and it can hardly be doubted that this is due to the inherited effects of pressure during a long series of generations. It is familiar to every one that watchmakers and engravers are liable to be short-sighted, whilst men living much out of doors, and especially savages, are generally long-sighted.^^ Short- sight and long-sight certainly tend to be inherited.'" The inferiority of Europeans, in comparison with savages, in eye- sight and in the other senses, is no doubt the accumulated and transmitted effect of lessened use during many generations ; for Rengger'^ states that ho has repeatedly observed Europeans, 'History of Greenland,' Eng. translat. 1767, vol. i. p. 230. ' Intermarriase.' By Alex. Walker, 1838, p. 377. 'The Variatiou of Animals under Domestication, vol. i. p. 173. -'' ' Principles of Biology,' vol. i. p. 455- 2' Paget, 'Lectures on Surgical Pathology,' vol. ii. 1853, p. 209. It is a singular and unex- pected fact that sailors are inferior to landsmen in their mean distant of distinct vision. Dr. B. A. Gould (' Sanitary Memoirs of the War of the Rebellion,' 1869, p. 530), has proved this to be the case ; and he accounts for it by the ordinary range of vision in sailors being " re- " stricted to the length of the vessel " and the height of the masts." 3° 'The Variation of Animals under Domestication,' vol. i. p. 8. 'Saugethiere von Paraguay,' s. 8, 10. I have had good opportuni- ties for observing the extraordinary power of eyesight in tlie Fuegians. See also Lawrence (' Lectures on D 34 The Descent of Man. who had beon brought up and spent their whole lives with the wild Indians, who nevertheless did not equal them in the sharp- ness of their senses. The same naturalist observes that the cavities in the skull for the reception of the several sense-organs are larger in the American aborigines than in Europeans ; and this probably indicates a corresponding difference in the dimen- sions of the organs themselves. Blumenbach has also remarked on the large size of the nasal cavities in the skulls of the American aborigines, and connects this fact with their remarkably acute power of smell. The Mongolians of the plains of Northern Asia, according to Pallas, have wonderfully perfect senses ; and Prichard believes that the great breadth of their skulls across the zygomas follows from their highly-developed sense-organs.^^ The Quechua Indians inhabit the lofty plateaux of Peru ; and Alcide d'Orbigny states*^ that, from continually breathing a highly rarefied atmosphere, they have acquired chests and lungs of extraordinary dimensions. The cells, also, of the lungs are larger and more numerous than in Europeans. These observa- tions have been doubted ; but Mr. D. Forbes carefully measured many Aymaras, an allied race, living at the height of between 10.000 and 15,000 feet; and he informs me" that they differ conspicuously from the men of all other races seen by him in the circumference and length of their bodies. In his table of measurements, the stature of each man is taken at 1000, and the other measurements are reduced to this standard. It is here seen that the extended arms of the Aymaras are shorter than those of Europeans, and much shorter than those of Negroes. The legs are likewise shorter ; and they present this remarkable peculiarity, that in every Aymara measured, the femur is actually shorter than the tibia. On an average, the length of the femur to that of the tibia is as 211 to 252 ; whilst in two Europeans, measured at the same time, the femora to the tibise were as 244 to 230 ; and in three Negroes as 258 to 241. The hmnerus is likewise shorter relatively to the forearm. This shortening of that part of the Hmb which is nearest to the body, appears to be, as suggested to me by Mr. Forbes, a case of compensation in Physiology,' &c., 1822, p. 404) on this same subject. M. Giraud-Teulon has recently collected (' Revue des Cours Scieutifiques,' 1870, p. 625) a large and valuable body of evidence proving that the cause of short- sight, " Cerf le travail assidu, de "pres." Prichard, ' Phys. Hist, of Man- kind,' on the authority of Blumen- bach, vol. i. 1851, p. 311; for the statement by Pallas, vol. iv. 1844, p. 407. " Quoted by Prichard, ' P.e- searches into the Phys. Hist, of Man- kind,' vol. V. p. 463. 3< Mr. Forbes' valuable paper is now published in the ' Journal of the Ethnological Soc. of London, new series, vol. ii. 1870, p. 193. Chap. II. Manner of Development. 35 relation with the greatly increased length of the trunk. The Aymaras present some other singular points of structure, for instance, the very small projection of the heel. These men are so thoroughly acclimatised to their cold and lofty abode, that when formerly carried down by the Spaniards to the low eastern plains, and when now tempted down by high wages to the gold-washings, they suffer a frightful rate of mor- tahty. Nevertheless Mr. Torbes found a few pure famihes which had survived during two generations : and he observed that they still raherited their characteristic pecuharities. But it was manifest, even without measui'ement, that these peculiarities had all decreased ; and on measui-ement, their bodies were found not to be so much elongated as those of the men on the high plateau ; whilst their femora had become somewhat lengthened, as had then." tibias, although in a less degree. The actual measurements may be seen by consulting Mr. Forbes's memoir. Trom these observations, there can, I thiuk, be no doubt that residence dui-ing many generations at a great elevation tends, both directly and iudirectly, to induce inherited modifications in the proportions of the body.^^ Although man may not have been much modified dm-ing the latter stages of his existence through the increased or de- creased use of parts, the facts now given shew that his liability in this resjDect has not been lost ; and we positively know that the same law holds good with the lower animals. Consequently we may infer that when at a remote epoch the progenitors of man were in a transitional state, and were changing from quadrupeds into bipeds, natui-al selection would probably have been greatly aided by the iuherited effects of the increased or diminished use of the different parts of the body. Arre&ts of Developvie7it. — There is a difference between arrested development and arrested growth, for parts in the former state continue to grow whilst still retaining their early condition. Various monstrosities come under this head ; and some, as a cleft-palate, are known to be occasionally inherited. It will suffice for our purpose to refer to the arrested brain-development of microcephalous idiots, as described in Vogt's memoir.^" Their skulls are smaller, and the convolutions of the brain are less complex than in normal men. The frontal sinus, or the *' Dr. "Wilckens (' Landwirth- regions, have their fi'ames modified, schaft. Wochenblatt,' No. 10, 1869) 36 « Me'tnoire sur les Microc6- has lately published an interesting phales,' 1867, pp. 50, 125, 169, 171, Essay shewing how domestic ani- 184-198. mals, which live in mountainous D 2 36 TIte Descent of Man. Part 1. projection over tho eye-brows, is largely developed, and the jaws are prognatlious to an " effrayant" degree ; so tbat these idiots somewhat resemble the lower types of mankind. Their in- telligence, and most of their mental faculties, are extremely feeble. They cannot acquire tho power of speech, and are wholly incapable of prolonged attention, but are much given to imitation. They are strong and remarkably active, continually gamboUng and jumping about, and making gi-imaces. They often ascend stairs on all-fours; and are curiously fond of climling up furniture or trees. ^Ve are thus reminded of the delight shewn by almost all boys in climbing trees; and this again rcmmds us how lambs and kids, originally alpine animals, delight to frisk on any hillock, however small. Idiots also resemble the lower animals in some other respects ; thus several cases are recorded of their carefully smelling every mouthful of food before eating it. One idiot is described as often vising his mouth in aid of his hands, whilst himting for lice. They are often filthy in their habits, and have no sense of decency ; and several cases have been published of their bodies being re- markably hairy Reversion. — Many of the cases to be here given, might have been introduced under the last heading. "When a structui-e is arrested in its development, but still continues growing, until it closely resembles a corresponding structm-o in some lower and adult member of the same group, it may in one sense be considered as a case of reversion. The lower members in a group give us some idea how the common progenitor was probably constructed ; and it is hardly credible that a complex part, arrested at an early phase of embryonic development, should go on growing so as tiltimately to perform its proper function, imless it had acquired such power dui-ing some earlier state of existence, when the present exceptional or arrested structm-e was normal. The simple brain of a microcephalous idiot, in as far as it resembles that of an ape, may in this sense be said to offer a case of reversion.^* There are other cases which come 3' Prof. Laycock sums up the character of brute-like idiots by calling them thcroid ; 'Jourual of Mental Science,' July 1863. Dr. Scott ('The Deaf and Dumb,' 2nd edit., 1870, p. 10) has often ob- served the imbecile smelling their food. See, on this same subject, and on the hairiness of idiots, Dr. Maudsley, 'Body and Mina,' 1870, pp. 46-51. Pinel has also given .i striking case of hairiness in an idiot. " In my ' Variation of Animals under Domestication ' (vol. ii. p. 57), I attributed the not very rare cases of supernumerary mamma; in women to reversion. I was led to this as a probable conclusion, by the addition.tl mamma! being generally p'.aced Chap. II. MaJiner of Development. 37 more strictly under our present lieacl of reversion. Certain structures, regularly occurring in the lower members of the group symmstrically on the breast; and more especially from one case, in ■which a single efficient mamma occurred in the inguinal region of a woman, the daughter of another woman witli supernumerary mam- ma;. But 1 now find (see, for in- stance, Prof. Preycr, ' Der Kampf um das Dasein,' 1869, s. 45) that vnammx crraticx occur in other situations, as on the back, in the armpit, and on the thigh ; the mamma; in this latter instance having given so much milk that the child was thus nourished. The pro- bability that the additional mamma; are due to reversion is thus much weakened ; nevertheless, it still Ecems to me probable, because two pairs are often found symmetrically on the breast ; and of this I myself have received information in several cases. It is well known that some Lemurs normally have two pairs of mamma; on the breast. Five cases have been recorded of the presence of more than a pair of mamma; (of course rudimentary) in the male sex of mankind ; see ' Journal of Anat. and Physiology,' 1872, p. 56, for a case given by Dr. Handyside, m which two brothers exhibited this peculiarity ; see also a paper by Dr. Bartels, in 'Reichert's and du Bois Reymond's Archiv.,' 1872, p. 304. In one of the cases alluded to by Dr. Bartels, a man bore five mamma;, one being medial and placed above the navel; Meckel von Hemsbach thinks that this latter case is illustrated by a medial mamma occurring in certain Cheiroptera. On the whole, we may well doubt if additional mammse would ever have been developed in both sexes of mankind, had not his early progenitors been provided with more t han a single pair. In the above work (vol. ii. p. 12), I also attributed, though with much hesitation, the frequent cases of polydactylism in men and various animals to reversion. I was partly' led to this through Prof. Owen's statement, that some of the Ichthy- opterygia possess more than five digits, and therefore, as I supposed, had retained a primordial condition; but Prof. Gegenbaur ('Jenaischen Zeitschrift,' B. v. Heft 3, s. 341), disputes Owen's conclusion. On the other hand, according to the opinion lately advanced by Dr. Giinther, on the paddle of Ceratodus, which is provided with articulated bony rays on both sides of a central chain of bones, there seems no great difficulty in admitting that six or more digits on one side, or on both sides, might reappear through reversion. Lam informed by Dr. Zouteveen that there is a case on record of a man having twenty-four fingers and twenty-four toes ! I was chiefly led to the conclusion that the presence of supei'numerary digits might be due to reversion from the fact that such digits, not only are strongly in- herited, but, as I then believed, had the power of regrowth after ampu- tation, like the normal digits of the lower vertebrata. But I have ex- plained in the Second Edition of my Variation under Domestication why I now place little reliance on the recorded cases of such regrowth. Nevertheless it deserves notice, in as much as arrested development, and reversion are intimately related processes ; that various structures in an embryonic or arrested con- dition, such as a cleft palate, bifid uterus, &c., are frequently accom- panied by polydactylism. This has been strongly insisted on by Meckel and Isidore Geoffroy St.-Hilaire. But at present it is the safest course to give up altogether the idea that there is any relation between the development of supernumeraiy di- gits and reversion to some lowly crganised progenitor of man. 38 The Descent of Man. Part I. to which man belongs, occasionally make their appearance in him, though not found in the normal human embryo; or, if normally present in the human embryo, they become abnormally developed, although in a manner which is normal in the lower members of the group. These remarks will be rendered clearer by the following illustrations. In various mammals the uterus graduates from a double organ with two distinct orifices and two passages, as in the marsupials, into a single organ, which is in no way double except from having a slight internal fold, as in the higher apes and man. The rodents exhibit a perfect series of gradations between these two extreme states. In all mammals the uterus is developed from two simple primitive tubes, the inferior portions of which form the cornua ; and it is in the words of Dr. Farre, " by the coalescence of the two cornua at their lower '•' extremities that the body of the uterus is formed in man; " while in those animals in which no middle portion or body " exists, the cornua remain ununited. As the develoj^ment of " the uterus proceeds, the two cornua become gi-adually shorter, " until at length they are lost, or, as it were, absorbed into the " body of the uterus." The angles of the uterus are still produced into cornua, even in animals as high up in the scale as the lower apes and lemurs. Now in women, anomalous cases are not very infrequent, in which the mature uterus is furnished with cornua, or is partially divided into two organs; and such cases, according to Owen, repeat "the grade of concentrative development," attained by certain rodents. Here perhaps we have an instance of a simple arrest of embryonic development, with subsequent growth and perfect functional development ; for either side of the partially double uterus is capable of performing the proper office of gestation. In other and rarer cases, two distinct uterine cavities are formed, each having its proper orifice and passage.^^ No such stage is passed through during the ordinary development of the embryo ; and it is difficult to believe, though perhaps not im- possible, that the two simple, minute, primitive tubes should know how (if such an expression may be used) to grow into two See Dr. A. Farre's well-known brates,' vol. iii., 1868, p. 687. Pro- article in the ' Cyclopseclia of Ana- fessor Turner in ' Edinburgh Medi- toiny and Physiology,' vol. v. 1859, cal Journal,' February 1865. p. 642. Owen, ' Anatomy of Verte- Chap. II. Manner of Development. 39 distinct uteri, each -Rath a ■well-constructed orifice and passage, and each fm-nished with numerous muscles, nerves, glands and vessels, if they had not formerly passed through a similar course of development, as in the case of existing marsupials. No one •will pretend that so perfect a structure as the abnormal double uterus in woman could be the result of mere chance. But tho principle of reversion, by which a long-lost structui'e is called back into existence, might serve as the guide for its full develop- ment, even after the lapse of an enormous interval of time. Professor Canestrini, after discussing the foregoing and various analogous cases, arrives at the ' same conclusion as that just given. He adduces another instance, in the case of the malar bone,*" which, in some of the Quadrumana and other mammals, normally consists of two portions. This is its condition in the human foetus when two months old ; and through arrested develop- ment, it sometimes remains thus in man when adult, more especially in the lower prognathous races. Hence Canestrini concludes that some ancient progenitor of man must have had this bone normally divided into two portions, which afterwards became fused together. In man the frontal bone consists of a single piece, but in the embryo, and in children, and in almost aU the lower mammals, it consists of two pieces separated by a distinct sutui'e. This suture occasionally persists more or less distinctly in man after maturity ; and more frequently in ancient than in recent crania, especially, as Canestrini has observed, in those exhumed from the Drift, and belonging to the brachyce^ phalic type. Here again he comes to the same conclusion as in the analogous case of the malar bones. In this, and other instances presently to be given, the cause of ancient races approaching the lower animals in certain characters more frequently than do the modern races, appears to be, that the latter stand at a somewhat ' Annuario della Soc. dei Natu- ralisti iu Modena,' 1867, p. 83. Prof. Canestrini gives extracts on tiiis subject from various authorities. Laurillard remarks, that as he has found a complete similarity in the form, proportions, and connection of the two malar bones in several human subjects and in certain apes, he cannot consider this disposition of the parts as simply accidental. Another paper on this same anomaly has been published by Dr. Saviotti ia the 'Gazzetta delle Cliniche,' Turin, 1871, where he says that traces of the division may be de- tected in about two per cent, of adult skulls ; he also remarks that it more frequently occurs in pro- gnathous skulls, not of the Aryan race, than in others. See also G. Delorenzi on the same subject ; ' Tre nuovi casi d' auomalia dell'osso, malare,' Toi'ino, 1872. Also, E. Morselli, ' Sopra una rara anomalia deir osso malare,' Modena, 1872. Still more recently Gruber has written a pamphlet on the division of this bone. I give these references because a reviewer, without any grounds or scruples, has thrown doubts on my statements. 40 The Descent of Man. Pabt I, greater distance in the long line of descent from their early semi- liuman progenitors. Various other anomalies in man, more or less analogous to the foregoing, have been advanced by different authors, as cases of J-eversion; but these seem not a little doubtful, for wo have to descend extremely low in the mammalian series, before we find such structures normally present.'" In man, the canine teeth are perfectly efficient instruments fo: mastication. But their true canine character, as Owen^^ re- marks, " is indicated by the conical form of the crown, which " terminates in an obtuse point, is convex outward and flat or " sub-concave within, at the base of which surface there is a " feeble prominence. The conical form is best expressed in the " Melanian races, especially the Australian. The canine is more " deeply implanted, and by a stronger fang than the incisors.'" Nevertheless, this tooth no longer serves man as a special weapon for tearing his enemies or prey ; it may, therefore, as far as its proper function is concerned, be considered as rudimentary. In every large collection of human skulls some may be found, as Hiickel^' observes, with the canine teeth projecting considerably beyond the others in the same manner as in the anthropomorphous apes, but in a less degree. In these cases, open spaces between the teeth in the one jaw are left for the reception of the canines of the opposite jaw. An interspace of this kind in a Kaffir iskull, figured by Wagner, is sui-prisingly wide.** Considering how few are the ancient skulls which have been examined, compared to recent skulls, it is an interesting fact that in at least three cases the canines project largely ; and in the Nauletto jaw they are spoken of as enormous.'"^ A whole series of cases is given if in any way serviceable, for in- by Isid. Geoffroy St.-Hilaire, ' Hist, stance, in shortening and simplifying des Anomalies,' torn. iii. p. 437. the course of development ? And A reviewer (' Journal of Anat. and again, why should not injurious ab- Physiology,' 1871, p. 366) blames normalities, such as atrophied or liy- me much for not having discussed pertrophied parts, which have no the numerous cases, which have relation to a former state of cxist- been recorded, of various parts ar- ence, occur at an early period, as rested in their development. He well as during maturity ? says that, according to my theory, ^- ' Anatomy of Vertebrates,' vol. " every transient condition of an iii. 1868, p. 323. " organ, during its development, is " ' Generelle Morphologie,' 1866, " not only a means to an end, but B. ii. s. civ. " once was an end in itself." This Carl Vogt's ' Lectures on Man,' does not seem to me necessarily to Eng. tiv.nslat. 1864, p. 151. hold good. Why should not varia- '•^ C. Carter Blake, on a jaw tions occur during an early period from La Naulette, ' Anthropolog. of development, having no relation Review,' 1867, p. 295. SchaalT- to reversion; yet such variations hausen, ibid. 1868, p. 426. might be preserved and accumulated. Chap, II. Marnier of Developmerit. 41 Of the anthropomorphous apes the males alone have their canines fully developed ; but in the female gorilla, and in a less degree in the female orang, these teeth project considerably beyond the others; therefore the fact, of wliich I have been assured, that women sometimes have considerably projecting canines, is no serious objection to the belief that their occasional great development in man is a case of reversion to an ape-liko progenitor. He who rejects with scorn the belief that the shape of his own canines, and their occasional great development in other men, are due to our early forefathers having been pro- vided with these formidable weapons, will probably reveal, by sneering, the line of his descent. For though he no longer intends, nor has the powei", to use these teeth as weapons, he will unconsciously retract his " snarling muscles" (thus named by Sir G. Bell),^" so as to expose them ready for action, like a dog prepared to fight. Many muscles are occasionally developed in man, which are proper to the Quadrumana or other mammals. Professor Ylacovich^'' examined forty male subjects, and found a muscle, called by him the ischio-pubic, in nineteen of them ; in three others there was a ligament which represented this muscle; and in the remaining eighteen no trace of it. In only two out of thirty female subjects was this muscl-e developed on both sides^ but in three others the rudimentary ligament was present. This muscle, therefore, appears to be much more common in the male than in the female sex ; and on the belief in the descent of man from some lower form, the fact is intelligible ; for it has been detected in several of the lower animals, and in all of these it serves exclusively to aid the male in the act of reproduction. Mr. J. Wood, in his valuable series of papers,*^ has minutelj' described a vast number of muscular variations ia man, which resemble normal structures in. the lower animals. The muscles ' The Anatomy of Expression,' 1844, pp. 110, 131. ^' Quoted by Prof. Canestrini in the 'Annuario,' &c., 1867, p. 90. These papers deserve careful study by any one who desires to learn how frequently our muscles vary, and in varying come to re- semble those of the Quadrumana. The following references relate to the few points touched on in my text : ' Proc. Royal Soc. vol. xiv. I860, pp. 379-384; vol. sv. 1866, pp. 241, 242 ; vol. XV. 1867, p. 544; vol. xvi. 1868, p. 524. I may here add that Dr. Murie and Mr. St. George Mivart have shewn in their Memoir on the Lemuroidea ('Tran- sact. Zoolog. Soc' vol, vii. 1869, p. 96), how extraordinarily variable some of the muscles are in these animals, the lowest members of the Primates. Gradations, also, in the muscles leading to structures found in animals still lower in the scale, are numerous in the Lemuroidea. 42 TJte Descent of Man. Part 1. which closely resemble those regularly present in our nearest allies, tho Quadi-umana, arc too numerous to be here even specified. In a single male subject, having a strong bodily frame, and well-formed skull, no less than seven musculsj varia- tions were observed, all of which plainly represented muscles proper to various kinds of apes. This man, for instance, had on both sides of his neck a true and powerful " levator daviculce" such as is found in all kinds of apes, and which is said to occur iu about one out of sixty human subjects.*^ Again, this man had " a special abductor of the metatarsal bone of the fifth " digit, such as Professor Huxley and Mr. Flower have shewn " to exist uniformly in the higher and lower apes." I will give only two additional cases; ih.e acromio-hasilar muscle is found in all mammals below man, and seems to be correlated vnth a quadrupedal gait,^" and it occui's in about one out of sixty human subjects. In the lower extremities Mr. Bradley found an abductor ossis metatarsi quinti in both feet of man ; this muscle had not up to that time been recorded in mankind, but is always present in the anthropomorphous apes. The muscles of the hands and arms — parts which are so eminently characteristic of man — are extremely liable to vary, so as to resemble the corresponding muscles in the lower animals.^^ Such resem- blances are either perfect or imperfect; yet in the latter case they arc manifestly of a transitional nature. Certain variations are more common in man, and others in woman, without oiu' being able to assign any reason. Mr. "Wood, after describing numerous variations, makes the following pregnant remark. " Notable departures from the ordinary type of the muscular " structures run in grooves or directions, which must be taken " to indicate some unknown factor, of much importance to a " comprehensive knowledge of general and scientific anatomy."^ See also Prof. Macalister in 'Proc. R. Irish Academy,' vol. i. 1868, p. 124. '» Mr. Champneys in ' Journal of Anat. and Phys.' Nov., 1871, p. 178. 'Journal of Anat. and Phys.' May, 1872, p. 421. " Prof. Macalister (ibid. p. 121) has tabulated his observations, and finds that muscular abnormalities are most frequent in the fore-arms, .•secondly, in the face, thirdly, in the foot, &c. " The Rev. Dr. Haughton, after giving ('Proc. R. Irish Academy,' June 27, 1864, p. 715) a remark- able case of variation in the human flexor pollicis longus, adds, "Thi> " remarkable example shews that " man may sometimes possess the " arrangement of tendons of thumb " and fingers characteristic of the " macaque ; but whether such a " case should be regarded as a " macaque passing upwards into a " man, or a man passing downwards " into a macaque, or as a congenital " freak of nature, 1 cannot undcr- " take to say." It is satisfactory to hear so capable an anatomist, and so embittered an opponent of evolutionism, admitting even the CiTAP. 11. Manner of Development. 43 That this -anknown factor is reversion to a former state of existence may be admitted as in the highest degree probable It is quite incredible that a man should thi-ough mere accident abnormally resemble certain apes in no less than seven of his muscleSj if there had been no genetic connection between them. On the other hand, if man is descended from some ape-like creature, no valid reason can be assigned why certain muscles should not suddenly reappear after an interval of many thou- sand generations, in the same manner as with horses, asses, and mules, dark-coloured stripes suddenly reappear on tbe legs, and shoulders, after an interval of hundreds, or more probably of thousands of generations. These various cases of reversion are so closely related to those of rudimentary organs given in the first chapter, that many of them might have been indifferently introduced either there or here. Thus a human uterus furnished with cornua may be said to represent, in a rudimentary condition, the same organ in its normal state in certain mammals. Some parts which are rudi- mentaiy in man, as the os coccyx in both sexes, and the mamma) in the male sex, are always present; whilst others, such as the supracondyloid foramen, only occasionally appear, and therefore might have been introduced under the head of reversion. These several reversionary structures, as well as the strictly rudi- mentary ones, reveal the descent of man from some lower form in an unmistakable manner. Correlated Variation. — In man, as in the lower animals, many structures are so intimately related, that when one part varies so does another, without our being able, in most cases, to assign any reason. We cannot say whether the one part governs the other, or whether both are governed by some earlier developed possibility of either of his first pro- positions. Prof. Macalister has also described (' Proc. R. Irish Acad.' vol. X. 1864, p. 138) variations in the flexor pollicis longus, remarkable from their relations to the same muscle in the Quadrumana. Since the first edition of this book appeared, Mr. Wood has pub- lished another memoir in the ' Phil. Transactions,' 1870, p. 83, on the varieties of the muscles of the human neck, shoulder, and chest. He here shews how extremely variable these muscles are, and how often and how closely the variations resemble the normal muscles of the lower ani- mals. He sums up by remarking, " It will be enough for my purpose " if I have succeeded in shewing " the more important forms which, " when occurring as varieties in the " human subject, tend to exhibit in " a sufficiently marked manner what " may be considered as proofs and " examples of the Darwinian prin- " ciple of reversion, or law of in- " heritance, in this department of " anatomical science." 44 The Descent of Man. Part I. part Various monstrosities, as I. Geoffroy repeatedly insists, are thus intimately connected. Homologous structures are par- ticularly liable to change together, as we see on the opposite sides of the body, and in the upper and lower extremities. Meckel long ago remarked, that when the muscles of the arm depart from their proper type, they almost always imitate those of the leg ; and so, conversely, with the muscles of the legs. The organs of sight and hearing, the teeth and haii-, the colour of the Bkin and of the hair, colour and constitution, are more or less cor- related.«5 Professor Schaaffhausen first drew attention to the relation apparently existing between a muscular frame and the strongly-pronounced supra-orbital ridges, which are so characteristic of the lower races of man. Besides the variations which can be grouped with more or less probabihty under the foregoing heads, there is a large class of variations which may be provisionally caUed spontaneous, for to our ignorance they appear to arise without any exciting cause. It can, however, be shewn that such variations, whether consisting of slight individual differences, or of strongly-marked and abrupt deviations of structure, depend much more on the constitution of the organism than on the nature of the condi- tions to which it has been subjected.'^ Hate of Increase. — Civilised populations have been known under favourable conditions, as in the United States, to double their numbers in twenty-five years ; and, according to a calcula- tion by Euler, this might occur in a little over twelve years." At the former rate, the present jjopulation of the United States (thirty millions), would in 657 years cover the whole terraqueous globe so thickly, that four men would have to stand on each square yard of surface. The primary or fundamental check to the continued increase of man is the diflBculty of gaining subsistence, and of living in comfort. We may infer that this is the case from what we see, for instance, in the United States, where subsistence is easy, and there is plenty of room. If such means were suddenly doubled in Great Britain, our number would be quickly doubled. With civilised nations this primary check acts chiefly by restraining marriages. The greater death-rate of infants in the poorest classes is also very important ; as well as The aiithorities for these seve- my 'Variation of Animals and Plants ral statements are given in my under Domestication.' ' Variation of Animals under Do- " See the ever memorable ' Essay raestication,' vol. ii. pp. 320-335. on the Principle of Population,' by This whole subject has been the Rev. T. Malthus, vol. i. 1826, p. discussed in chap, xxiii, vol. ii. of 6, 517. Chap. 11. Manner of Development. 45 tlio gi'eater mortality, from various diseases, of the Inhabitants of crowded and miserable houses, at all ages. The effects of severe epidemics and wars are soon counterbalanced, and more than counterbalanced, in nations placed under favourable conditions. Emigi-ation also comes in aid as a temporary check, but, "ivith the extremely poor classes, not to any great extent. There is reason to suspect, as Malthus has remarked, that the reproductive power is actually less in barbarous, than in civilised races. We know nothing positively on this head, for with savages no census has been taken; but from the concurrent testimony of missionaries, and of others who have long resided with such people, it appears that their families are usually small, and large ones rare. This may be partly accounted for, as it is beheved, by the women suckling their infants during a long time ; but it is highly probable that savages, who often suffer much hardship, and who do not obtain so miich nutritious food as civilised men, would be actually less prolific. I have shewn in a former work,'^ that all ovu- domesticated quadrupeds and birds, and all our cultivated plants, are more fertile than the corresponding species in a state of nature. It is no valid objection to this conclusion that animals suddenly supplied with an excess of food, or when grown very fat ; and that most plants on sudden removal from very poor to very rich soil, are rendered more or less sterile. We might, therefore, expect that civihsed men, who in one sense are highly domesticated, would be more prohfic than wild men. It is also probable that the increased fertility of civilised nations would become, as with our domestic animals, an inherited character : it is at least known that with mankind a tendency to produce twins runs in families.^' Notwithstanding that savages appear to be less prolific than civilised people, they would no doubt rapidly increase if their numbers were not by some means rigidly kept down. The San- tali, or hill-tribes of India, have recently afforded a good illustra- tion of this fact ; for, as shewn by Mr. Hunter,"" they have increased at an extraordinary rate since vaccination has been introduced, other pestilences mitigated, and war sternly repressed. This increase, however, would not have been possible had not these rude people spread into the adjoining districts, and worked for hire. Savages almost always marry; yet there is somo prudential restraint, for they do not commonly marry at the "'Variation of Animals and Foreign Medico-Chirm-ff. Renew,' Plants under Domestication,' vol. ii. July, 1863, p. 170. PP J w"-^ 1?',^^^- , °° ' The Annals of Rural Bengal, Mr, bcdgn-ick, 'British and by W. W. Hunter, 186S p. 259. 46 The Descent of Man. Part I. earliest possible age. The young men arc often required to shew that they can support a wife ; and they generally have first to earn the price with which to purchase her from her parents. With savages the difficulty of obtaining subsistence occasionally limits their number in a much more direct manner than with civilised people, for all tribes periodically suffer from severe famines. At such times savages are forced to devour much bad food, and their health can hardly fail to bo injui-ed. Many accounts have been published of their protruding stomachs and emaciated limbs after and during famines. They are then, also, compelled to wander much, and, as I was assured in Australia, their infants perish in large numbers. As famines are period- ical, depending chiefly on extreme seasons, all tribes must fluctuate in number. They cannot steadily and regularly increase, as there is no artificial increase ia the supply of food. Savages, when hard pressed, encroach on each other's territories, and war is the result ; but they are indeed almost always at war with their neighbours. They are hable to many accidents on land and water in theu- search for food ; and in some coimtries they suflier much fi-om the larger beasts of prey. Even in India, districts have been depopulated by the ravages o.' tigers. Malthus has discussed these several checks, but he does not lay stress enough on what is probably the most important of all, namely infanticide, especially of female infants, and the habit of procuring abortion. These practices now prevail in many quarters of the world ; and infanticide seems formerly to have prevailed, as ]\Ir. M'Lennan" has shewn, on a still more extensive scale. These practices appear to have originated in savages re- cognising the difficulty, or rather the impossibility of supporting all the infants that are born. Licentiousness may also be added to the foregoing checks ; but this does not follow from failing means of subsistence; though there is reason to believe that in some cases (as in Japan) it has been intentionally encoui"ag?d as a means of keeping down the population. If we look back to an extremely remote epoch, before man had arrived at the dignity of manhood, he would have been guided more by instinct and less by reason than are the lowest savages at the present time. Our early semi-human progenitors would not have practised infanticide or polyandi-y ; for the instincts of the lower animals are never so perverted as to lead them re- 'Primitive Marriage,' 1865. ments as follows on this passage : — A writer in the ' Spectator ' " Mr. Darwin tinds himself compelled (March 12th, 1871, p. 320) com- " to reintroduce a new doctrijie of the Chap. li. .Manner of Development. 47 gularly to destroy theii- own offspring, or to be quite devoid of jealousy. There would have been no prudential restraint from man-iagOj and the sexes would have freely united at an early age. Hence the progenitors of man would have tended to increase rapidly ; but checks of some kind, either periodical or constant, must have kept down their numbers, even more severely than with existing savages. What the precise nature of these checks were, we cannot say, any more than with most other animals. We know that horses and cattle, which are not extremely prolific animals, when first turned loose in South America, increased at an enormous rate. The elephant, the slowest breeder of all known animals, would in a few thousand years stock the whole world. The increase of every species of monkey must be checked by some means; but not, as Brehm remarks, by the attacks of beasts of prey. No one will assume that the actual power of reproduction in the wild horses and cattle of America, was at first in any sensible degree increased ; or that, as each disti'ict became fully stocked, this same power was diminished. No doubt in this case, and in aU others, many checks concur, and different checks under different circumstances ; periodical dearths, depending on unfavourable seasons, being probably the most important of all. So it will have been with the early pro- genitors of man. Natural Selection. — We have now seen that man is variable in body and mind; and that the variations are induced, either directly or indirectly, by the same general causes, and obey the same general laws, as with the lower animals. Man has spread widely over the face of the earth, and must have been exposed, during his incessant migrations,'® to the most diversified con- ditions. The inhabitants of Tierra del Fuego, the Cape of Good Hope, and Tasmania in the one hemisphere, and of the Arctic regions in the other, must have passed through many climates. " fall of man. He shews that the " instincts of the higher animals " are far nobler than the habits of " savage races of men, and he finds " himself, tharefore, compelled to " re-introduce, — in a form of the " s':bstantiai jrthodoxy of which he " appears to be quite unconscious, — " and to introduce as a scientific " hypothesis the doctrine that man's " gain of knowledr/e was the cause of " a temporary but long-enduring moral deterioration, as indicated " by the many foul customs, es- " pecially as to marriage, of savage " tribes. What does the Jewish " tradition of the moral degenera- " tion of man through his snatching " at a knowledge forbidden him " bj his highest instinct assert " beyond this?" °^ See some good remarks to this effect by W. btanley Jevons, " A " Deduction from Darwin's Theory, ' * Nature,' 1869, p. 231. 48 The Descent of Man. Part L and changed their habits many times, before they reached their present homes."' The early progenitors of man must also have tended, like all other animals, to have increased beyond their means of subsistence ; they must, therefore, occasionally have been exposed to a struggle for existence, and consequently to tho rigid law of natural selection. Beneficial variations of all kinds Avill thus, either occasionally or habitually, have been preserved and injui'ious ones eliminated. I do not refer to strongly-marked deviations of structure, which occur only at long intervals of time, but to mere individual differences. We know, for instance, that the muscles of our hands and feet, which determine our powers of movement, are liable, like those of the lower animals,** to incessant variability. If then the progenitors of man inhabit- ing any district, especially one undergoing some change in its conditions, were divided into two equal bodies, the one half which included all the individuals best adapted by their powers of movement for gaiuing subsistence, or for defending themselves, would on an average survive in greater numbers, and procreate more offspring than the other and less well endowed half. Man in the rudest state in which he now exists is the most dominant animal that has ever appeared on this earth. He has spread more widely that any other highly organised form : and all others have yielded before him. He manifestly owes this immense superiority to his intellectual faculties, to his social habits, which lead him to aid and defend his fellows, and to his corporeal structure. The supreme importance of these characters has been proved by the final arbitrament of the battle for life. Through his powers of intellect, articulate language has been evolved; and on this his wonderful advancement has mainly depended. As Mr. Chauncey "Wright remarks " a psychological " analysis of the faculty of language shews, that even the smallest " proficiency in it might require more braia power than the " greatest proficiency in any other direction." He has invented and is able to use various weapons, tools, traps, &c., with which he defends himself, kills or catches prey, and otherwise obtains food. He has made rafts or canoes for fishing or crossing over to neighbouring fertile islands. He has discovered the art of Latliam, ' Man and his Migra- tions,' 1851, p. 135. Messrs. Murie and Mivart in their 'Anatomy of the Lemuroidea' (' Transact. Zoolog. Soc' vol. vii. 1869, pp. 96-98) say, "some muscles " are so irregular in their distribu- " lion that they cannot be well " classed in any of the above " groups." These muscles difler even on the opposite sides of the same individual. Limits of Natural Selection, ' North American Eeview,' Oct. 1870, p. 295. Chap. IT. Manner of Development. 49 rualdng fire, by which hard and stringy roots can be rendered digestible, and poisonous roots or herbs innocuous. This dis- covery of fire, probably the greatest ever made by man, excepting language, dates from before the dawn of history. These several inventions, by which man in the rudest state has become so pre- eminent, are the direct results of the development of his powers of observation, memory, curiosity, imagination, and reason. I cannot, therefore, understand how it is that ]\Ir. Wallace " main- tains, that "natural selection could only have endowed the " savage with a brain a little superior to that of an ape." Although the intellectual powers and social habits of man are of paramount importance to him, we must not underrate the importance of his bodily structure, to which subject the remain- dor of this chapter will be devoted ; the development of the in- tellectual and social or moral faculties being discussed in a later chapter. Even to hammer with i^recision is no easy matter, as every one who has tried to learn carpentry will admit. To throw a stone with as true an aim as a Fuegian in defending himself, or in killing biixls, requires the most consummate perfection in the correlated action of the muscles of the hand, arm, and shoulder, and, fui'ther, a fine sense of touch. In throwing a stone or spear, and in many other actions, a man mnst stand firmly on his feet ; and this again demands the perfect co-adaptation of numerous muscles. To chip a flint into the rudest tool, or to form a barbed spear or hook from a bone, demands the use of a perfect hand ; for, as a most capable judge, Mr. Schoolcraft,^' remarks, the shaping fragments of stone into kni a p. 132. G 2 84 Tlie Descent of Man. attention, association, and even some imagination and reason. If these powers, which differ much in different animals, are capable of improvement, there seems no great improbability in more complex faculties, such as the higher forms of abstraction, and self-consciousness, &c., having been evolved through the development and combination of the simpler ones. It has been urged against the views here maintained, that it is impossible to say at what point in the ascending scale animals become capable of abstraction, &c. ; but who can say at what age this occurs in our young children ? We see at least that such powers ire developed in children by imperceptible degrees. That animals retain their mental individuality is unquestion- able. When my voice awakened a train of old associations in the mind of the before-mentioned dog, he must have retained his mental individuality, although every atom of his brain had probably undergone change more than once during the interval of five years. This dog might have brought forward the argument lately advanced to crush aU evolutionists, and said, " I abide amid all mental moods and all material changes. . . . " The teaching that atoms leave their impressions as legacies to " other atoms falling into the places they have vacated is con- " tradictory of the utterance of consciousness, and is therefore " false ; but it is the teaching necessitated by evolutionism, con- " sequently the hypothesis is a false one."'"' Language. — This faculty has justly been considered as one of the chief distinctions between man and the lower animals. But man, as a highly competent judge, Archbishop Whately remarks, " is not the only animal that can make use of language to express " what is passing in his mind, and can understand, more or less, "what is so expressed by another."''^ In Paraguay the Celuf. azarcB when excited utters at least six distinct soimds, which excite in other monkeys similar emotions.''^ The movements of the features and gestures of monkeys are imderstood by us, and they partly understand ours, as Eengger and others declare. It is a more remarkable fact that the dog, since being domesticated, has learnt to bark^' in at least four or five distinct tones. Although barking is a new art, no dowbt the wild parent-species of the dog expressed their feelings by cries of various kinds. With the domesticated dog we have the bark of eagerness, as in the chase ; that of anger, as well as growling ; the yelp or howl of despair, as when shut up ; the baying at night ; the bark of joy, as The Rev. Dr. J. M'Cann, ' Anti- Rengger, ibid. s. 45. Darwinism,' 1869, p. 13. " See my ' Variation of Aui- Quoted in 'Anthropological Re- mals and Plants under Domesticr.- rievr ' 1864, p. 158. tion,' vol. i. p. 27, 3hap. III. Me7ital Powers. when starting on a walk with his master ; and the very distinct one of demand or supphcation, as when wishing for a door or window to be opened. According to Houzeau, who paid par- ticnJar attention to the subject, the domestic fowl utters at least a dozen significant sounds.^" The habitual use of articulate language is, howeTsr, peculiar to man ; but he uses, in common with the lower animals, inarti- culate cries to express his meaning, aided by gestures and the movements of the muscles of the face.**^ This especially holds good with the more simple and vivid feelings, which are but little connected with oui higher intelligence. Our cries of pain, fear, stu'prise, auger, together with their appropriate actions, and the murmur of a mother to her beloved child, are more expressive than any words. That which distinguishes man from the lower animals is not the understanding of articulate sounds, for, as every one knows, dogs tmderstand many words and sentences. In this respect they ai-e at the same stage of development as infants, between the ages of ten and twelve months, who understand many words and short sentences, but cannot yet utter a single word. It is not the mere articulation which is our distinguishing character, for parrots and other birds possess this power. Nor is it the mere capacity of con- necting definite sounds with definite ideas ; for it is certain that some parrots, which have been taught to speak, connect un- eiTingly words with things, and persons with events.*^ The lower animals differ from man solely in his almost infinitely larger power of associating together the most diversified 'Facultds Mentales des Ani- maux,' torn. ii. 1872, p. 346-349. See a discussion on this subject in Mr. E. B. Tyler's very interesting work, ' Researches into the Early History of Mankind,' 1865, chaps, ii. to iv. I have received several detailed accounts to this effect. Admiral Sir J. Sulivan, whom I know to be a careful observer, assures me that an African parrot, long kept in his father's house, invariably called certam persons of the household, as iveli as visitors, by their names. He said "good morning" to every one at breakfast, and " good night " to each as they left the room at night, and never reversed these salutations. To Sir J. Sulivan's father, he used to ada to the " good morning " a short sentence, which was never once repeated after his father's death. He scolded violently a strange dog which came into the room through the open window; and he scolded another parrot (say- ing "you naughty polly") which had got out of its cage, and was eating apples on the kitchen table. See also, to the same effect, Houzeau on parrots, 'Faculte's Mentales,' torn. ii. p. 309. Dr. A. Moschkau informs me that he knew a starling which never made a mistake in saying in German " good morning " to persons arriving, and " good- bye, old fellow," to those departing. I could add several other such cases. 86 The Descent of Man. Paht I. Bounds and ideas; and this obviously depends on the high development of his mental powers. As Horne Took, one of the founders of tlio noble science of philology, observes, language is an art, like brewing or baking; but writing would have been a better simile. It certainly is not a true instinct, for every language has to be learnt. It diifers, however, widely from all ordinary arts, for man has an in- stinctive tendency to speak, as wo see in the babble of our young children ; whilst no child has an instinctive tendency to brew, bake, or write. Moreover, no philologist now supposes that any language has been deliberately invented ; it has been slowly and unconsciously developed by many steps.^^ The sounds uttered by birds offer in several respects the nearest analogy to language, for all the members of the same species utter the same instinctive cries expressive of their emotions ; and all the kinds which sing, exert their power instinctively ; but tho actual song, and even the call-notes, are learnt from their parents or foster-parents. These sounds, as Daines Barrington'* has proved, " are no more innate than language is in man." The first attempts to sing " may be compared to the imperfect " endeavour in a child to babble." The young males continue practising, or as the bird-catchers say, " recording," for ten or eleven months. Their first essays show hardly a rudiment of the future song ; but as they grow older we can perceive what they are aiming at ; and at last they are said " to sing their " song round." Nestlings which have learnt the song of a distinct species, as with the canary-birds educated in the Tyrol, teach and transmit their now song to their offspring. The slight natural differences of song in the same species ir habiting different districts may be appositely compared, as Barrington remarks, " to provincial dialects ;" and the songs of allied, though distinct species may be compared with the languages of distinct races of man. I have given the foregoing details to shew that an instinctive tendency to acquire an art is not peculiar to man. With respect to the origin of articulate language, after having read on the one side the highly iateresting works of Sir. Hens- See some good remarks on this " gards the immediate end to be head by Prof. Whitney, in his " attained ; unconsciously as regards ' Oriental and Linguistic Studies,' " the further consequences of the 1873, p. 354. He observes that the " act." desire of communication between Hon. Daines Barrington in man is the living force, which, 'Philosoph. Transactions,' 1773, p. in the devekpmeut of language, 262. See also Bureau de la Malle, " works both consciously and un- iu ' Ann. des. Sc. Nat.' 3rd aeries, " '.•onseionsly consciously as re- Zoolog. torn. x. p. 119. Chap. III. Mental Powers. 87 leigh Wedgwood, the Eev. F. Farrar, and Prof. Schleicher,** and the celebrated lectures of Prof. Max Miiller on the other side, I cannot doubt that language owes its origin to the imitation and modification of Tarious natural sounds, the voices of other animals, and man's own instinctive cries, aided by signs and gestures. When we treat of sexual selection we shall see that primeval man, or rather some early progenitor of man, probably first used his voice in producing true musical cadences, that is in singing, as do some of the gibbon-apes at the present day ; and we may conclude from a widely-spread analogy, that this power would have been especially exerted during the courtship of the sexes, — would have expressed various emotions, such as love, jealousy, triumph, — and would have served as a challenge to rivals. It is, therefore, probable that the imitation of musical cries by articulate sounds may have given rise to words expres- sive of various complex emotions. The strong tendency in our nearest allies, the monkeys, in microcephalous idiots,^" and in the barbarous races of mankind, to imitate whatever they hear deserves notice, as bearing on the subject of imitation. Since monkeys certainly understand much that is said to them by man, and when wHd, utter signal-cries of danger to their fellows ; and since fowls give distinct warnings for danger on the ground, or in the sky fi-om hawks (both, as well as a third cry, intelligible to dogs),'^* may not some unusually wise ape-like animal have imitated the growl of a beast of prey, and thus told his fellow-monkeys the nature of the expected danger ? This would have been a first step in the formation of a language. As the voice was used more and more, the vocal organs would have been strengthened and perfected through the principle of the inherited effects of use ; and this would have reacted on the power of speech. But the relation between the continued use of language and the development of the brain, has no doubt been far more important. The mental powers in some early pro- genitor of man must have been more highly developed than in " ' On the Origin of Language,' by H. Wedgwood, 1866. ' Chapters on Language,' by the Rev. F. W. Farrar, 1865. These works are most interesting. See also * De la Phys. et de Parole,' par Albert Lemoine, 1865, p. 190. The work on this subject, by the late Prof. Aug. Schleicher, has been translated by Dr. Bikkers into English, under the title of ' Darwinism tested by the Science of Language,' 1869 " Vogt, ' Memoirs sur les Micro- cephales,' 1867, p. 169. With re- spect to savages, I have given some facts in my ' Journal of Researches,' &c., 1845, p. 206. " See clear evidence on this head in the two works so often quoted, by Brehm and Rengger. Houzeau gives a very curious account of his observations on this subject in his ' Facultes Mentalcs lies Animau.x,' tom. ii., p. 348. 88 7 he Descent of Man. Part I, any existing ape, before even the most imperfect form of speech could have come into use ; but we may confidently beheve that the continued use and advancement of this power would have reacted on the mind itself, by enabling and encouraging it to carry on long trains of thought. A complex train of thought can no more bo carried on without the aid of words, whether spoken or silent, than a long calculation without the use of figures or algebra. It appears, also, that even an ordinary train of thought ahnost requires, or is greatly facilitated by some form of language, for the dumb, deaf, and blind girl, Lam-a Bridgman, was observed to use her fingers whilst dreaming.*^* Nevertheless, a long succession of vivid and connected ideas may pass through the mind without the aid of any form of language, as we may infer from the movements of dogs during their di-eams. We have, also, seen that animals are able to reason to a certain extent, manifestly without the aid of language. The intimate connection between the brain, as it is now developed in us, and the faculty of speech, is well shewn by those curious cases of brain-disease in which speech is specially affected, as when the power to remember substantives is lost, whilst other words can be correctly used, or where substantives of a certain class, or all except the initial letters of substantives and proper names ai-e forgotten.*^ There is no more improb- ability in the continued use of the mental and vocal organs leading to inherited changes in their structure and functions, than in the case of handwriting, which depends partly on the form of the hand and partly on the disposition of the mind ; and hand-writing is certainly inherited.^' Several writers, more especially Prof. Max Miiller,^- have lately insisted that the use of language implies the power of forming general concepts ; and that as no animals are supposed to possess this power, an impossible barrier is formed between them and man.'* With respect to animals, I have already " See remarks on this head by Dr. Mau-dsley, 'The Physiology and Pathology of Mind,' 2nd edit. 1868, p, 199. Many curious cases have been recorded. See, for instance. Dr. Bateman ' On Aphasia,' 1870, p. 27, 31, 53, 100, &c. Also, 'Inquiries Concerning the Intellectual Powers,' by Dr. Abercrombie, 1838, p. 150. "1 'The Variation of Animals and Plants under Domestication,' vol. ii. p. 6. ^- Lectures on ' Mr. Dai-win's Phi- losophy of Language,' 1873. The judgment of a distin- guished philologist, such as Prof. Whitney, will have far more weight on this point than anything that I can say. He remarks (' Oriental and Linguistic Studies,' 1873, )? 297), in speaking of Bleek's views . " Because on the grand scale lan- " guage is the necessary auxiliary " of thought, indispensable to the " development of the power al Chap. HI. Mental Powers. 89 endeavoured to show that they have this power, at least in a rude and incipient degree. As for as concerns infants of from ten to eleven months old, and deaf-mutes, it seems to me in- credible, that they should be able to connect certain sounds with certain general ideas as quickly as they do, unless such ideas were ah-eady formed in their minds. The same remark may be extended to the more intelligent animals ; as Mr. Leshe Stephen observes," " A dog frames a general concept of cats or sheep, " and knows the corresponding words as well as a philosopher. " And the capacity to understand is as good a proof of vocal " intelligence, though in an inferior degree, as the capacity to " speak." Why the organs now used for speech should have been originally perfected for this purpose, rather than any other organs, it is not difficult to see. Ants have considerable powers of intercommunication by means of their antennas, as shewn by Huber, who devotes a whole chapter to their language. Wo might have used our fingers as efficient instruments, for a person with practice can report to a deaf man every word of a speech rapidly delivered at a public meeting; but the loss of our hands, whilst thus employed, would have been a serious inconvenience. As all the higher mammals possess vocal organs, constructed on the same general plan as ours, and used as a means of communication, it was obviously probable that these same organs would be still further developed if the power of communication had to be improved ; and this has been effected by the aid of adjoining and well adapted parts, namely the tongue and lips."^* The fact of the higher apes not using their vocal organs for speech, no doubt depends on their intelligence not having been sufficiently advanced. The possession by them of " thinking, to the distinctness and " variety and complexity of cogni- " tions to the full mastery of con- " sciousness ; therefore he would " fain make thought absolutely im- " possible without speech, identify- " ing the faculty with its instru- " ment. He might just as reason- " ably assert that the human hand " cannot act without a tool. With " such a doctrine to start from, he " cannot stop short of Miiller's " worst paradoxes, that an infant " (in fans, not speaking) is not a " human being, and that deaf-mutes " do not become possessed of reason " until they learn ;o twist their " fingers into imitation of spoken " words." Max Miiller gives in italics ('Lectures on Mr. Darwin's Philosophy of Language,' 1873, third lecture) the following aphoi-- ism: "There is no thought with- " out words, as little as there arf " words without thought." What a strange definition must here be given to the word thought I ' Essays on Free-thinking,' &c., 1873, p. 82. °^ See some good remarks to thia effect by Dr. Maudsley, ' The Phy- rtiology and Pathology of Mind, 1868, p. 199. 90 The Descent of Man. Part 1. organs, which with long-continued practice might have been used for speech, although not thus used, is paralleled by the case of many bii'ds which possess organs fitted for singing, though they never sing. Thus, the nightingale and crow have vocal organs similarly constructed, these being used by the former for diversified song, and by the latter only for croaking.^' If it be asked why apes have not had their intellects developed to the same degree as that of man, general causes only can be assigned in answer, and it is unreasonable to expect anything more definite, considering our ignorance with respect to the successive stages of development through which each creature has passed. The formation of different languages and of distmct species, and the proofs that both have been developed through a gradual process, are curiously parallel." But we can trace the formation of many words further back than that of species, for we can perceive how they actually arose from the imitation of various sounds. We find in distinct languages striking homologies due to community of descent, and analogies due to a similar process of formation. The manner in which certain letters or sounds change when others change is very like correlated growth. We have in both cases the reduplication of parts, the effects of long- continued use, and so forth. The frequent presence of rudi- ments, both in languages and in species, is still more remarkable. The letter m in the word am, means I ; so that in the expres- sion / am, a superfluous and useless rudiment has been retained. In the spelling also of words, letters often remain as the rudi- ments of ancient forms of pronunciation. Languages, like organic beings, can be classed in groups under groups ; and they can be classed either naturally according to descent, or arti- ficially by other characters. Dominant languages and dialects spread widely, and lead to the gradual extraction of other tongues. A language, like a species, when once extinct, never, as Sir C. Lyell remarks, reappears. The same language never has two birth-places. Distinct languages may be crossed or blended together.** We see variability ia every tongue, and new «» Macgillivray, ' Hist, of British Birds,' vol. ii. 1839, p. 29. An excellent observer, Mr. Blackwall, remarks that the magpie learns to pronounce single words, and even short sentences, more readily than almost any other British bird ; yet, as he adds, after long ana ciosely investigating its habits, he has never knowc it, in a state of nature, display any unuscal capacity for imitation. ' Researches in Zoology,' 1834, p. 158. See the very interesting pa- rallelism between the development of species and languages, given bv Sir C. Lyell in 'The Geolog. Evi- dences of the Antiquity of Man,' 1863, chap, xsiii. See remarks to this eflect by Mental Powers. 91 words are continually cropping up ; but as there is a limit to the powers of the memory, single words, like whole languages, gradually become extmct. As Max Miiller^^ has well re- maa-ked :— " A struggle for life is constantly going on amongst "the words and grammatical forms in each language. The " better, the shorter, the easier forms are constantly gaining the " upper hand, and they owe their success to their own inherent " virtue." To these more important causes of the survival of certain words, mere novelty and fashion may be added; for there is in the mind of man a strong love for slight changes in all things. The survival or preservation of certain favoured words in the struggle for existence is natural selection. The perfectly regular and wonderfully complex construction of the languages of many barbarous nations has often been advanced as a proof, either of the divine origin of these lan- guages, or of the high art and former civilisation of their founders. Thus P. von Schlegel wi-ites : " In those languages " which appear to be at the lowest grade of intellectual culture, " we frequently observe a very high and elaborate degree of art "in their grammatical structure. This is especially the case " with the Basque and the Lapponian, and many of the Ame- " rican languages."'" But it is assuredly an error to speak of any language as an art, in the sense of its having been elabor- ately and methodically formed. Philologists now admit that conjugations, declensions, &c., originally existed as distinct words, since joined together; and as such words express the most obvious relations between objects and i^ersons, it is not surprising that they should have been used by the men of most races during the earUest ages. With respect to perfection, the following illustration will best shew how easily we may err : a Criaoid sometimes consists of no less than 150,000 pieces of shell,'^ all arranged with perfect symmetry in radiating lines ; but a naturalist does not consider an animal of this kind as more perfect than a bilateral one with comparatively few parts, and with none of these parts alike, excepting on the opposite sides of the body. He justly considers the differentiation and special- isation of organs as the test of perfection. So with languages • the most symmetrical and complex ought not to be ranked abovo irregular, abbreviated, and bastardised languages, which have the Eev. F. W. Farrar, in aa in- " Quoted by C. S. Wake, ' Chap. terestiDg article, entitled ' Philo- ters on Man,' 1868, p. 101. logy and Darwinism' in 'Nature,' " Buckland, 'Bridaewater Trea- March 24th, 1870, p. 528. tise ' p 411 "5 ' Nature,' Jan. 6th, 187C -o. 257. ' 92 The Descent of Man. Paet 1, borrowed expressive words and useful forms of construction from various conquering, conquered, or immigrant races. From these few and imperfect remarks I conclude that the extremely complex and regular construction of many barbarous languages, is no proof that they owe their origin to a special act of creation." Nor, as we have seen, does the faculty of articulate speech in itself offer any insuperable objection to the belief that man has been developed from some lower form. Sense of Beauty. — This sense has been declared to be peculiar to man. I refer here only to llie pleasm-e given by certain colours, forms, and sounds, and which may fairly be called a sense of the beautiful ; with cultivated men such sensations are., however, intimately associated with complex ideas and trains of thought. When we behold a male bird elaborately displaying his graceful plumes or splendid colours before the female, whilst other birds, not thus decorated, make no such display, it is impossible to doubt that she admires the beauty of her male partner. As women everywhere deck themselves with these plumes, the beauty of such ornaments cannot be disputed. As we shall see later, the nests of humming-birds, and the playing passages of bower-birds are tastefully ornamented with gaily-coloured objects; and this shews that they must receive some kind of pleasure from the sight of such things. With the great majority of animals, however, the taste for the beautiful is confined, as far as we can judge, to the attractions of the opposite sex. The sweet strains poured forth by many male birds during the season of love, are certainly admired by the females, of which fact evidence will hereafter be given. If female birds had been incapable of appreciating the beautiful colours, the ornaments, and voices of their male partners, all the labour and anxiety exhibited by the latter in displaying their charms before the females would have been thrown away ; and this it is impossible to admit. Why certain bright coloui-s should excite pleasure cannot, I presume, be explained, any more than why certain flavour's and scents are agreeable ; but habit has something to do with the result, for that which is at first impleasant to our senses, ultimately becomes pleasant, and habits are inherited. With respect to sounds, Helmholtz has explained to a certain extent on physiological principles, why harmonies and certain cadenees are agreeable. But besides this, sounds frequently recurring at iiTCgular intervals are See some good remarks on the J. Lubbock, 'Origin of C.vilisatica, Biiaplific*lion of languages, by Sir 1870, p. 278. Chap. III. Mental Powers. highly disagi'eeablej as every one will admit who has listened at night to the irregiolar flapping of a rope on board ship. The same principle seems to come into play with vision, as the eye prefers symmetry or figures with some regular recurrence. Patterns of this kind are employed by even the lowest savages as ornaments; and they have been developed through sexual selection for the adornment of some male animals. Whether we can or not give any reason for the pleasure thus derived from vision and hearing, yet man and many of the lower animals are alike pleased by the same colours, graceful shading and forms, and the same sounds. The taste for the beaiitiful, at least as far as female beauty is concerned, is not of a special nature in the human mind ; for it differs widely in the different races of man, and is not quite the same even in the different nations of the same race. Judging from the hideous ornaments, and the equally hideous music admired by most savages, it might be urged that their aesthetic faculty was not so highly developed as in certain animals, for instance, as in bii-ds. Obviously no animal would be capable of admiring such scenes as the heavens at night, a beautiful land- scape, or refined music; but such high tastes are acquired through cultui-e, and depend on complex associations ; they are not enjoyed by barbarians or by uneducated persons. Many of the faculties, which have been of inestimable service to man for his progressive advancement, such as the powers of the imagination, wonder, curiosity, an undefined sense of beauty, a tendency to imitation, and the love of excitement or novelty, could hardly fail to lead to capricious changes of customs and fashions. I have alluded to this point, because a recent writer ''^ has oddly fixed on Caprice " as one of the most remarkable and "typical differences between savages and brutes." But not only can we partially understand how it is that man is from various conflicting influences rendered capricious, but that the lower animals are, as we shall hereafter see, likewise capri- cious m their affections, aversions, and sense of beauty. There is also reason to suspect that they love novelty, for it own sake. Belief in God— lieligion.— There is no evidence that man was aboriginally endowed with the ennobling belief in the existence of an Omnipotent God. On the contrary there is ample evidence, derived not from hasty travellers, but from men who have long resided with savages, that numerous races have existed, and still exist, who have no idea of one or more gods, and who have no " ' The Spectator,' Dec. 4th, 1869, p. 1430. 94 The Descent of Man. Pabt I. yords in their languages to express such an idea." The question is of course wholly distinct from that higher one, whether there exists a Creator and Ruler of the universe ; and this has bteu answered in the affirmative by some of the highest intellects that have ever existed. If, however, we include under the term " religion " the belief in unseen or spiritual agencies, the case is wholly different ; for this belief seems to be universal with the less civilised races. Nor is it difficult to comprehend how it arose. As soon as the important faculties of the imagination, wonder, and curiosity, together with some power of reasoning, had become partially developed, man would naturally crave to understand what was passing around him, and would have vaguely speculated on his own existence. As Mr. M'Lennan'* has remarked, " Some explan- " ation of the phenomena of life, a man must feign for himself • " and to judge from the universality of it, the simplest hypothesis " and the first to occur to men, seems to have been that natural " phenomena are ascribable to the presence in animals, plants, " and things, and in the forces of nature, of such spirits prompting " to action as men are conscious they themselves possess." It is also probable, as Mr. Tylor has shewn, that dreams may have first given I'ise to the notion of spirits ; for savages do not readily distinguish between subjective and objective impressions. "^Tien a savage dreams, the figures which appear before him are believed to have come from a distance, and to stand over him ; or " the soul of the dreamer goes out on its travels, and comes " home with a remembrance of what it has seen."^° But until See an excellent article on this subject by the Eev. F. W. Farrar, in the ' Anthropological Review,' Aug. 1864, p. ccxvii. For further facts see Sir J. Lubbock, ' Pre- historic Times,' 2nd edit. 1869, p. 564 ; and especially the chaptei's on Religion in his 'Origin of Civilisa- tion,' 1870. ' The Worship of Animals and Plants,' in the ' Fortnightly Review,' Oct. 1, 1869, p. 422. ^* Tylor, ' Early History of Man- kind,' 186.5, p. 6. See also the three striking chapters on the De- velopment of Religion, in Lubbock's ' Origin of Civilisation,' 1870. In a like manner Mi-. Herbert Spencer, in his ingenious essay in the 'Fort- nightly Review' (May 1st, 1870, p. 535), accounts for the earliest forms of religious belief throughout the world, by man being lerl through dreams, shadows, and other causes, to look at himself as a double essence, corporeal and spiritual. As the spiritual being is supposed to exist after death and to be power- ful, it is propitiated by various gifts and ceremonies, and its aid invoked. He then further shews that names or nicknames given from some animal or other object, to the early progenitors or founders of a tribe, are supposed after a long interval to represent the real progenitor of the tribe ; and such animal or object is then naturally believed still to exist as a spirit, is held sacred, and worshipped as a god. NeverthelesF I cannot but suspect that there is a still earlier and ruder stage, when Chap. III. Mental Powers. 95 the. faculties of imagination, curiosity, reason, &c., had been fairly well developed in the mind of man, his dreams would not have led him to beheve in spirits, any more than in the case of a dcg. The tendency in savages to imagine that natural objects and agencies are animated by spiritual or living essences, is perhaps illustrated by a little fact which I once noticed : my dog, a full- grown and very sensible animal, was lying on the lawn during a hot and still day ; but at a little distance a slight breeze occa- sionally moved an open parasol, which would have been wholly disregarded by the dog, had any one stood near it. As it was, every time that the parasol slightly moved, the dog growled fiercely and barked. He must, I think, have reasoned to himself in a rapid and unconscious manner, that movement without any apparent cause indicated the presence of some strange living agent, and that no stranger had a right to be on his territory. The belief in spiritual agencies would easily pass into the belief in the existence of one or more gods. For savages would naturally attribute to spirits the same passions, the same love of vengeance or simplest form of justice, and the same affections which they themselves feel. The Fuegians appear to be in this respect in an intermediate condition, for when the surgeon on board the "Beagle" shot some young ducklings as specimens, York Minster declared in the most solemn manner, " Oh, Mr. Eynoe, " much rain, much snow, blow much ;" and this was evidently a retributive punishment for wasting human food. So again he related how, when his brother killed a " wild man," storms long raged, much rain and snow fell. Yet we could never discover that the Fuegians beheved in what we should call a God, or practised any rehgious rites ; and Jemmy Button, with justifiable pride, stoutly maintained that there was no devil in his land. This latter assertion is the more remarkable, as with savages the belief in bad spirits is far more common than that in good ones. The feehng of religious devotion is a highly complex one, consisting of love, complete submission to an exalted and mysterious superior, a strong sense of dependence," fear, reverence, gratitude, hope for the future, and perhaps other elements. No being could experience so complex an emotion anything which manifests power or " See an able article on tLa movement is thought to be endowed ' Physical Elements of Religion,' by with some form of life, and with Mr. L. Owen Pike, in ' Anthropolav, mental faculties anakgcris to our EsTiew,' April, 1870. p. Isiii. own. 06 TJie Descent of Man. Paet 1. until advanced in his intellectual and moral faculties to at least a moderately high level. Nevertheless, we see some distant approach to this state of mind in the deep love of a dog for his master, associated with complete submission, some fear, and perhaps other feelings. The behaviour of a dog when returning to his master after an absence, and, as I may add, of a monkey to his beloved keeper, is widely different from that towards their fellows. In tho latter case the transports of joy appear to bo somewhat less, and the sense of equality is shewn in every action. Professor Braubach goes so far as to maintain that a dog looks on his master as on a god.''* The same high mental faculties which first led man to believe in unseen spiritual agencies, then in fetishism, polytheism, and ultimately in monotheism, would infallibly lead him, as long as his reasoning powers remained poorly developed, to various strange superstitions and customs. Many of these are terrible to think of — such as the sacrifice of human beings to a blood- loving god ; the trial of innocent persons by the ordeal of poison or fire ; witchcraft, &c. — yet it is well occasionally to reflect on these superstitions, for they shew us what an infinite debt of gratitude we owe to the improvement of our reason, to science, and to our accumulated knowledge. As Sir J. Lubbock has well observed, " it is not too much to say that the horrible dread of " unknown evil hangs hke a thick cloud over savage life, and " embitters every pleasure." These miserable and indirect consequences of our highest faculties may be compared with the incidental and occasional mistakes of the instincts of the lower animals. " ' Religion, Moral, &c., der Dar- " ' Prehistoric Times,' ^nd edit, win'schen Art-Lehre,' 1869, s. 53. p. 571. In this work (p. 571) It is said (Dr. W. Lauder Lindsay, there will be found an excellent 'Journal of Mental Science,' 1871, account of the many strange and p. 43), that Bacon long ago, and the capricious customs of .savages, poe ; Burns, held the same notion. CHAr. \ V Moral Sense. 97 CHAPTEE IV. COMPAinSON OF TUE MENTAL POWEES OP MAN AND THE Lower Animals — continued. The moral sense — Fundamental proposition — The qualities of social animals — Origin of sociability — Strucrgle between opposed instincts — Man a social animal — The more enduring social instincts conquer other less persistent instincts — The social virtues alone regarded by savages — The self-regarding virtues acquired at a later stage of development — The importance of the judgment of the members of the same community on conduct — ^Transmission of moral tendencies — Summary. I FULLY subscribe to the judgment of those writers^ who maintain that of all the differences between man and the lower animals, the moral sense or conscience is by far the most important. This sense, as Mackintosh' remarks, " has a "rightful supremacy oyer every other principle of human "action;" it is summed up in that short but imperious word ongU, so full of high significance. It is the most noble of all the attributes of man, leading him without a moment's hesita- tion to risk his Life for that of a fellow-creature ; or after due deliberation, impelled simply by the deep feeling of right or duty, to sacrifice it in some great cause, Immanuel Kant exclaims, " Duty ! Wondrous thought, that workest neither by "fond insinuation, flattery, nor by any threat, but merely by "holding up thy naked law in the soul, and so extorting for " thyself always reverence, if not always obedience ; before " whom all appetites are dumb, however secretly they rebel ; " whence thy original ?" * This great question has been discussed by many writers* of consummate ability ; and my sole excuse for touching on it, is the impossibility of here passing it over ; and because, as far as I know, no one has approached it exclusively from the side of natural history. The investigation possesses, also, some in- ' See, for instance, on this subject, Quatrefages, ' Unite' de I'Espfece Humaine,' 1861, p. 21, &c. ° ' Dissertation on Ethical Philo- sophy,' 1837, p. 231, &c. ^ ' Metaphysics of Ethics,' trans- lated by J. W. Semple, Edinburo-h, 1836, p. 136. * Mr. Baia gives a list (' Mental and Moral Science,' 1868, p. 543- 725) of twenty-six British authors who have written on this subject, and whose names are familiar to every reader ; to these, Mr. Bain's own name, and those of Mr. Lecky, Mr. Shadworth Hodgson, Sir J. Lubbock, and others, might be added. H 98 The Descoit of Man. Pabt I. dependent interest, as au attemi)t to see how far the Btudy of the lower anunals throws h'ght on one of the highest psychical faculties of man. , Tho following proposition seems to me in a high degree probable— namely, that any animal whatever, endowed with well-marked social instincts," the parental and filial affections being here included, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well, or nearly as well developed, as in man. Yor, firstly, the social instincts lead an animal to take pleasure in the society of its fellows, to feel a certain amount of sympathy with them, and to perform various services for them. The services may be of a definite and evidently instinctive nature ; or there may be only a wish and readiness, as with most of the higher social animals., to aid their fellows in certain general ways. But these feelings and services are by no means extended to all the individuals of the same species, only to those of the same association. Secondly, as Goon as the mental faculties had become highly developed, images of all past actions and motives would be incessantly passing through the brain of each individual ; and that feeling of dissatisfaction, or even misery, which invariably results, as we shall hereafter see, from any imsatisfied instinct, would arise, as often as it was perceived that the enduring and always present social instinct had yielded to some other instinct, at the time stronger, but neither enduring in its nature, nor leaving ' Sir B. Brodie, aftei observing that man is a social animal (' Psy- chological Enquiries,' 1854, p. 192), .isks the pregnant question, " ought " not this to settle the disputed " question as to the existence of a " moral sense ?" Similar ideas have probably occurred to many persons, as they did long ago to Marcus Aurelius. Mr. J. S. Mill speaks, in his celebrated work, 'Utilitarian- ism,' (1864, pp. 45, 46), of the social feelings as a "powerful natural " sentiment," and as " the natural " basis of sentiment fgr utilitarian " morality." Again he says, " Like " the other acquired capacities above " referred to, the moral faculty, if " not a part of our nature, is " a natural out-growth from it ; " capable, like them, in a certain " small degree of springing up spon- " taneously." But in opposition to all this, he also remarks, " if, as is " my own belief, the moral feelings " are not innate, but acquired, they " are not for that reason less natu- " ral." It is with hesitation that I venture to differ at all from so profound a thinker, but it can hardly be disputed that the social feelings are instinctive or innate in the lower animals ; and why should they not be so in man ? Mr. Bain (see, for instance, ' The Emotions and the Will,' 1865, p. 481) and others believe that the moral sense is ac- r quired by each individual dui-ing f his lifetime. On the general theory \ of evolution this is at least ex-l- tremely improbable. The ignoring: of all transmitted mental qualities ? will, as it seems to me, be hereafter r judged as a most serious blemish in i the works of Mi-. Mill. Chap. IT. Moral Sense. 99 behind it a very vivid impression. It is clear that many in- Btinctivo desires, such as that of hunger, are ia their nature of short dui-ation; and after being satisfied, are not readily or vividly recalled. Thirdly, after the power of language had been acquired, and the wishes of the community could be expressed, the common opinion how each member ought to act for the public good, would natui'ally become in a paramount degree the guide to action. But it should be borne in mind that how- ever great weight we may attribute to public opinion, our regard for the approbation and disapprobation of our fellows depends on sympathy, which, as we shall see, forms an essential part of the social instinct, and is indeed its foundation-stone. Lastly, habit in the individual would ultimately play a very important part in guiding the conduct of each member ; for the social in- stinct, together with sympathy, is, like any other instinct, greatly strengthened by habit, and so consequently would be obedience to the wishes and judgment of the community. These several subordinate propositions must now be discussed, and some of them at considerable length. It may be weU fii-st to premise that I do not wish to maintain that any strictly social animal, if its intellectual faculties were to become as active and as highly developed as in man, would acquire exactly the same moral sense as ours. In the same manner as various animals have some sense of beauty, though they admire widely different objects, so they might have a sense of right and wrong, though led by it to follow widely different lines of conduct. If, for instance, to take an extreme case, men were reared under precisely the same conditions as hive-bees, there can hardly be a doubt that our unmarried females would, like the worker-bees, think it a sacred duty to kUI their brothers, and mothers would strive to kill their fertile daughters ; and no one would think of interfering.^ Nevertheless, the bee, or any ^ Mr. H. Sidgwick remarks, in an able discussion on this subject (the 'Academy,' June 15th, 1872, (p. 231), " a superior bee, we may " feel sure, would aspire to a milder " solution of tho population ques- " tion." Judging, however, from the habits of many or most savages, man solves tho problem by female infanticide, po.yandry and promis- cnons intercourse ; therefore it may well be doubted whether it would be by a milder method. Miss Cobbe, in commenting (' Dai-winism in Morals,' 'Theological Review, April, 1872, p. 188-191) on the same illustration, says, the prin- ciples of social duty would be thus reversed ; and by this, I presume, she means that the fulfilment of a social duty would tend to the injury of individuals ; but she overlooks the fact, which she would doubtless admit, that the instincts of the bee have been acquired for the good of the community. She goes so far as to say that if the theory of ethics advocated in this chapter were ever H 2 100 TiLC Descent of Man. Paet I. other social animal, would gain in our supposed case, as i-t appears to me, some feeling of right or wrong, or a conscience. For each individual would have an inward sense of possessing certain stronger or more endui-ing instincts, and others less strong or enduring ; so that there would often be a struggle as to which impulse should be followed; and satisfaction, dissatis- faction, or even misery would be felt, as past impressions were compared during their incessant passage through the mind, lu this case an inward monitor would tell the animal that it would have been better to have followed the one impulse rather than the other. The one course ought to have been followed, and the other ought not ; the one would have been right and the other wrong ; but to these terms I shall recur. Socidbility. — Animals of many kinds are social ; we find even distinct species living together ; for example, some American monkeys; and united flocks of rooks, jackdaws, and starlings. Man shews the same feeling in his strong love for the dog, whic): the dog returns with interest. Every one must have noticed how miserable horses, dogs, sheep, &c., are when separated from their companions, and what strong mutual affection the two former kinds, at least, shew on their reunion. It is curious to speculate on the feeUngs of a dog, who will rest peacefully for hours in a room with his master or any of the family, withouJ the least notice being taken of him ; but if left for a short time by himself, barks or howls dismally. We will confine out attention to the higher social animals ; and pass over insects, ulthough some of these are social, and aid one another in many- important ways. The most common mutual service in the higher animals is to warn one another of danger by means ol the united senses of all. Every sportsman knows, as Dr. Jaeger remarks,'' how difficult it is to approach animals in a herd or troop. Wild horses and cattle do not, I believe, make an.9 danger-signal ; but the attitude of any one of them who fii-st discovers an enemy, warns the others. Eabbits stamp loudly on the ground with their hind-feet as a signal : sheep and chamois do the same with their forefeet, uttering likewise a whistle. Many birds, and some mammals, post sentinels, which ia the case of seals are said** generally to be the females. The leader generally Rccepted, " I cannot but earth is not held by many persons " believe that in the hour of their on so weak a tenure. " triumph would be sounded the ' ' Die Darwin'sche Theorie,' s. knell of the virtue of mankind t" 101. It is to 1>« hoped that the belief in ' Mr. R. Brown in ' Proc. Zooiog. ■ Hex permanence of virtue on this Soc' 1868, p. 409. Chap. IV. Moral Sense. lOl of a troop of monkeys acts as the sentinel, and utters cries expressive both of danger and of safety." Social animals perform many little services for each other : horses nibble, and cows lick each other, on any spot which itches: monkeys search each other for external parasites ; and Brehm states that after a troop of the Cercopithecus griseo-viridis has rushed through a thorny brake, each monkey stretches itself on a branch, and another monkey sitting by, " conscientiously " examines its fur, and extracts every thorn or burr. Animals also render more important services to one another : thus wolves and some other beasts of prey hunt in packs, and aid one another in attacking their victims. Pelicans fish in concert. The Hamadryas baboons turn over stones to find insects, &c. ; and when they come to a large one, as many as can stand round, turn it over together and share the booty. Social animals mutually defend each other. Bull bisons in N. America, when there is danger, di'ive the cows and calves into the middle of the herd, whilst they defend the outside. I shall also in a future chapter give an account of two young wild bulls at Chilhngham attacking an old one in concert, and of two stallions together trying to drive away a third stallion from a troop of mares. In Abyssinia, Brehm encountered a great troop of baboons, who were crossing a valley : some had already ascended the opposite mountain, and some were still in the valley : the latter were attacked by the dogs, but the old males immediately hui-ried down from the rocks, and with mouths widely opened, roared so fearfully, that the dogs quickly drew back. They were again encouraged to the attack ; but by this time all the baboons had reascended the heights, excepting a young one, about six months old, who, loudly calling for aid, climbed on a block of rock, and wpm sui-rounded. Now one of the largest males, a triae hero, came down again from the mountain, slowly went to the young one, coaxed him, and triumphantly led him away — the dogs being too much astonished to make an attack, I cannot resist giving another scene which was witnessed by this same naturahst ; an eagle seized a young Cercopithecus, which, by chnging to a branch, was not at once carried off; it cried xoudly for assistance, upon which the other members of the troop, vrith much uproar, rushed to the rescue, surrounded the eagle, 9 Brehm, ' Thierlcben,' B. i. 1864, the evidence of Alrarez, whose ob- s. 52, 79. For the case of the serrations Brehm thinks auit^ trust- ' monkeys extracting thorns from worthy. For the oases of che old each oth«r, see s. 54. With respect male baboons attacking tne dogs, to the Hamadryas turning over see s. 79; and with respect to the stones, the fact is given (s. 76) on Jig\e, s. 50, 102 The Descent of Man. PaetI and pulled out so many feathers, that he no longer thought of his prey, but only how to escape. This eagle, as Brehra remarks, assuredly would never again attack a single monkey of a troop. It is certain that associated animals have a feeling of love for each other, which is not felt by non-social adult animals. How far in most cases they actually sympathise in the pains and pleasures of others, is more doubtful, especially with respect to pleasures. Mr. Buxton, however, who had excellent means of observation," states that his macaw^s, which hved free in Norfolk, took " an extravagant interest " in a pair with a nest ; and when- ever the female left it, she was surrounded by a troop " scream- " ing horrible acclamations in her honour." It is often difficult to judge whether animals have any feeling for the sufferings of others of their kind. Who can say what cows feel, when they surround and stare intently on a dying or dead companion ; ap- parently, however, as Houzeau remarks, they feel no pity. That animals sometimes are far from feeling any sympathy is too certain ; for they will expel a wounded animal from the herd, or gore or worry it to death. This is almost the blackest fact in natural history, unless, indeed, the explanation which has been suggested is true, that their instinct or reason leads them to expel an injured companion, lest beasts of prey, including man, should be tempted to follow the troop. In this case their con- duct is not much worse than that of the North American Indians, who leave their feeble comrades to perish on the plains ; or the Kjians, who, when their parents get old, or faU ill, bury them alive.*^ Many animals, however, certainly sympathise with each other's distress or danger. This is the case even with birds. Capt. Stansbury " found on a salt lake in Utah an old and completely blind pehcan, which was very fat, and must have been well fed for a long time by his companions. Mr. Blyth, as he informs "> Mr. Belt gives the case of a " 'Annals and Mag. of Nat. Hist.,' spider-monkey (Ateles) in Nicara- November, 1868, p. 382. gua, which was heard screaming for Sir J. Lubbock, ' Prehistoric? nearly two hours in the forest, and Times,' 2nd edit. p. 446. was found with an eagle perched " As quoted by Mr. L. H. Morgan close by it. The bird apparently ' The American Beaver,' 1868, p. feared to attack as long as it re- 272, Capt. Stansbury also gives an mained face to face ; and Mr. Belt interesting account of the manner believes, from what he has seen of in which a very young pelican, the habits of these monkeys, that carried away by a sti-ong stream, they protect themselves from eagles was guided and encouraged in its by keeping two or three together, attempts to reach the shore by halt 'The Naturalist in Nicaragua,' 1874, a dozen old birds p. 118. Chap. IV. Moral Sense. 103 rae, saw Indian crows feeding two or three of their companions which wei-e blind ; and I have heard of an analogous case with the domestic cock. "We may, if we choose, call these actions instinctiTO ; but such cases are much too rare for the develop- ment of any special instinct.^' I have myself seen a dog, who never passed a cat who lay sick in a basket, and was a great friend of his, without giving her a few licks with his tongue, the surest sign of kind feeling in a dog. It must be called sympathy that leads a courageous dog to fly at any one who strikes his master, as he certainly will. I saw a person pretending to beat a lady, who had a very timid httle dog on her lap, and the trial had never been made before ; the little creature instantly jumped away, but after the pretended beating was over, it was really pathetic to see how perseveringly he tried to lick his mistress's face, and comfort her. Brehm states that when a baboon in confinement was pursued to be punished, the others tried to protect him. It must have been sympathy in the cases above given which led the baboons and Cercopitheci to defend their yoimg comrades from the dogs and the eagle, I will give only one other instance of sympathetic and heroic conduct, in the case of a httle American monkey. Several years ago a keeper at the Zoological Gardens shewed me some deep and scarcely healed wounds on the nape of his own neck, inflicted on him, whilst kneeling on the floor, by a fierce baboon. The little American monkey, who was a warm friend of this keeper, lived in the same large compartment, and was dreadfully afraid of the great baboon. Neverthelefis, as soon as he saw his friend in peril, he rushed to the rescue, and by screams and bites so distracted the baboon that the man was able to escape, after, as the surgeon thought, rmming great risk of his life. Besides love and sympathy, animals exhibit other qualities connected with the social instincts, which in us would be called moral ; and I agree with Agassiz that dogs possess something very like a conscience. Dogs possess some power of self-command, and this does not appear to be wholly the result of fear. As Braubach'^ remarks, they will refrain from steahng food in the absence of their master. They have long been accepted as the very type of fidehty and obedience. But the elephant is likewise very faith- ful to his driver or keeper, and probably considers him as the " As Mr. Bain states, "effective 'De I'Espfece et de la Classe,' " aid to a sufferer springs from sym- 1869, p. 97. " pathy proper :"' Mental and Moral "'Die Darwin'sche Art-Lehre, Science,' 1868, p. 245. 1869, s. 54. » 'Thierleben, B. i. s. 85. 104 The Descent of Man. PabtI leader of the herd. Dr. Hooker informs me that an elepliaut, ■which ho was riding in India, became so deeply bogged tliat ho remained stuck fast until tlie next day, ■when he was extricated by men with ropes. Under such circumstances elephants will seizo with their trunks any object, dead or alive, to place under their knees, to prevent their sinking deeper in the mud ; and tho driver was dreadfully afraid lest the animal should have seized Dr. Hooker and crushed him to death. But the driver himself, as Dr. Hooker was assured, ran no risk. This forbearance under an emergency so di-eadful for a heavy animal, is a wonderful proof of noble fidelity.^' All animals living in a body, which defend themselves or attack their enemies in concert, must indeed be in some degree faithful to one another ; and those that follow a leader must be in some degree obedient. When the baboons ia Abyssinia plunder a garden, they silently follow their leader ; and if an imprudent young animal makes a noise, he receives a slap from the others to teach him silence and obedience. Mr. Galton, who has had excellent opportunities for observing the half-wild cattle in S. Africa, says,-" that they cannot endure even a momentary separa- tion from the herd. They are essentially slavish, and accept the common determination, seeking no better lot than to be led by any one ox who has enough self-reliance to accept the position. The men who break in these animals for harness, watch assidu- ously for those who, by grazing apart, shew a self-reliant dis- position, and these they train as fore-oxen. Mr. Galton adds that such animals are rare and valuable ; and if many were born they would soon be eliminated, as lions are always on the look- out for the individuals which wander from the herd. With respect to the impulse which leads certaia animals to associate together, and to aid one another in many ways, ■n o may infer that in most cases they are impelled by the sami sense of satisfaction or pleasure which they experience in per- forming other instinctive actions ; or by the same sense of dissatisfaction as when other instinctive actions are checked. We see this in innumerable instances, and it is illustrated in a striking manner by the acquired instuicts of our domesticated animals ; thus a young shepherd-dog delights in driving and running round a flock of sheep, but not in woriying them ; a young fox-hound delights in hunting a fox, whilst some other kinds of dogs, as I have witnessed, utterly disregard foxes. What " See also Hooker's ' Himal.iynn See his extremely interesting Journals,' vol. ii., 1854, p. 333. paper on ' Gregariousness in Cattle, »» Brehm, * Thierlebcn,' B. i. s. and in Man," Wacmillan's Mig.'Feb, 76. 187], p. 353. ClIAP. IV. Moral Sense. a strong feeling of inwai-d satisfaction must impel a bii'd, so full of activity, to brood day after day over her eggs. Migratory birds aro quite miserable if stopped from migrating; perhaps they enjoy starting on their long flight ; but it is hard to believe that the poor pinioned goose, described by Audubon, which started on foot at the proper time for its journey of probably more than a thousand miles, could have felt any joy in doing so. Some instincts are determined solely by paiuful feelings, as by fear, •which leads to self-preservation, and is in some cases directed towards special enemies. No one, I presume, can analyse tlic sensations of pleasure or pain. In many instances, however, it is probable that iustiucts are persistently followed from the mere force of inheritance, without the stimulus of either pleasure or paiu. A young pointer, when it first scents game, apparently cannot help pointing. A squirrel in a cage who pats the nuts which it cannot eat, as if to bury them in the ground, can hardly be thought to act thus, either from pleasure or pain. Hence the common assumption that men must be impelled to every action by exiDcriencing some pleasure or pain may be erro- neous. Although a habit may be blindly and implicitly followed, independently of any pleasure or pain felt at the moment, yet if it be forcibly and abruptly checked, a vague sense of dissatisfaction is generally experienced. It has often been assumed that animals were in the first place rendered social, and that they feel as a consequence uncomfort- able when separated from each other, and comfortable whilst together ; but it is a more probable view that these sensations were first developed, in order that those animals which would profit by living in society, should be induced to Kve together, in the same manner as the sense of hunger and the pleasure ol eating were, no doubt, first acquired in order to induce animals to eat. The feeling of pleasure from society is probably an extension of the parental or filial afiections, since the social instinct seems to be developed by the young remaining for a long time with their parents ; and this extension may be attri- buted in part to habit, but chiefly to natui-al selection. With those animals which were benefited by hving in close association, the individuals which took the greatest pleasure in society would best escape various dangers; whilst those that cared least for their comrades, and lived solitary, would perisla in gi-eater numbers. With respect to the origin of the parental and filial affections, which apparently lie at the base of the social instincts, we know not the steps by which they have been gained; but we may infer that it has been to a large extent through natural selection. So it has almost certainly io6 The Descent of Man. Part 1. been ■with the unusual and opposite feeling of hatred between the nearest relations, as with the worker-bees which kill their brother-di'ones, and with the queen-bees which Mil their daughter-queens; the desire to destroy their nearest relations having been in this case of service to the community. Parental affection, or some feeling which replaces it, has been developed in certain animals extremely low in the scale, for example, in star-fishes and spiders. It is also occasionally present in a few members alone in a whole group of animals, as in the genus Forficula, or earwigs. The all-important emotion of sympathy is distinct from that of love. A mother may passionately love her sleeping and passive infant, but she can hardly at such times be said to fee) sympathy for it. The love of a man for his dog is distinct from sympathy, and so is that of a dog for his master. Adam Smith formerly argued, as has Mr. Bain recently, that the basis of sympathy lies in our strong retentiveness of former states of pain or pleasure. Hence, "the sight of another person en- " during hunger, cold, fatigue, revives in us some recollection of " these states, which are painful even in idea." We are thus impelled to relieve the sufferings of another, in order that our own painful feelings may be at the same time reheved. In like manner we are led to participate in the pleasures of others.-' But I cannot see how this view explains the fact that sympathy is excited, in an immeasurably stronger degree, by a beloved, than by an indifferent person. The mere sight of suffering, independently of love, would suffice to call up in us vivid recollections and associations. The explanation may lie in the fact that, with all animals, sympathy is du-ected solely towards the members of the same community, and therefore towards known, and more or less beloved members, but not to all the individuals of the same species. This fact is not more sur- prising than that the fears of many animals should be directed against special enemies. Species which are not social, such as lions and tigers, no doubt feel sympathy for the suffering of their own young, but not for that of any other animal. With 21 See the first and striking " or others in his stead, may malce chapter in Adam Smith's ' Theory " up, by sympathy and good offices of Moral Sentiments.' Also Mr. " returned, for all the sacrifice." Bain's ' Mental and Moral Science,' But if, as appears to be the case, 1868, p. 244, and 275-282. Mr. sympathy is strict'ly an instinct, Bain 'states, that "sympathy is, in- its exercise would give direct plea- " directly, a source of pleasure to sure, in the same manner as th« " the sympathiser ;" and he accounts exercise, as before remai-ked, of el. for this through reciprocity. He most every other instinct, remarks that " the person benefited, Chap. IV. Moral Seme. mankind, selfishness, experience, and imitation, probably add, as Mr. Bain has shewn, to the power of sympathy ; for we are led by the hope of receiving good in return to perform acts of sympathetic kindness to others ; and sympathy is much strengthened by habit. In however complex a manner this feehng 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 commu- nities, which included the greatest number of the most sympa- thetic members, would flourish best, and rear the greatest number of offspring. It is, however, impossible to decide in many cases whether certain social instincts have bei^n acquired through natural selection, or are the indirect result of other instincts and faculties, such as sympathy, reason, experience, and a tendency to imitation ; or again, whether they are simply the result of long-continued habit. So remarkable an instinct as the placing sentinels to warn the community of danger, can hardly have been the indirect result of any of these faculties ; it must, there- fore, have been directly acquired. On the other hand, the habit followed by the males of some social animals of defending the community, and of attacking their enemies or their prey in concert, may perhaps have originated from mutual sympathy ; but coui'age, and in most cases strength, must have been previously acquired, probably through natural selection. Of the various instincts and habits, some are much stronger than others ; that is, some either give more pleasure in their performance, and more distress in their prevention, than others ; or, which is probably quite as important, they are, through inheritance, more persistently followed, without exciting any special feeling of pleasure or pain. We are ourselves conscious that some habits are much more difficult to cure or change than others. Hence a struggle may often be observed in animals between different instincts, or between an instinct and some ( habitual disposition; as when a dog rushes after a hare, is rebuked, pauses, hesitates, pursues again, or returns ashamed to his master ; or as between the love of a female dog for her young puppies and for her master, — for she may be seen to slink away to them, as if half ashamed of not accompanying her master. But the most curious instance known to me of one instinct getting the better of another, is the migratory instinct conquer- ing the maternal instinct. The former is wonderfully strong ; a confined bird will at the proper season beat her breast against the wires of her cage, until it is bare and bloody. It causes yoxmg salmon to leap out of the fresh water, in which they could The Descent of Man. Pakt I. continue to exist, and thus unintentionally to commit suicide. Every one knows how strong the maternal instinct is, leading even timid birds to face great danger, though with hesitation, and in opposition to the instinct of self-preservation. Neverthe- less, the migratory instinct is so powerful, that late in the autumn swallows, house-martins, and swifts frequently desert their tender young, leaving them to perish miserably in their nests.^' "We can perceive that an uistinctive impulse, if it be in any way more beneficial to a species than some other or opposed instinct, would be rendered the more potent of the two thi-ough natural selection ; for the individuals which had it most strongly developed would survive in larger numbers. Whether this is the case with the migratory in comparison with the maternal instinct, may be doubted. The great persistence, or steady action of the former at certain seasons of the year during the whole day, may give it for a time paramount force. Man a social animal. — Every one will admit that man is a social being. We see this in his dislike of solitude, and in his wish for society beyond that of his own family. Solitary con- finement is one of the severest punishments which can be inflicted. Some authors suppose that man primevally hved in single families ; but at the present day, though single families, or only two or three together, roam the solitudes of some savage lands, they always, as far as I can discover, hold friendly relations with other families inhabiting the same district. Such families occasionally meet in council, and unite for their common defence. It is no argument against savage man being a social animal, that the tribes inhabiting adjacent districts are almost always at war with each other ; for the social instincts nevei extend to all the individuals of the same species. J udging from the analogy of the majority of the Quadrumana, it is probable that the early ape-like progenitors of man were likewise social ; but this is not of much importance for us. Although man, as " This fact, fhe Rev. L. Jenyns hatched. Many birds, not yet old states (see his edition of 'White's enough for a prolonged flight, are Nat. Hist, of Selborne,' 1853, p. likewise deserted and left behind. 204) was first recorded by the illus- See Blaclcwall, ' Researches in Zoo- Irious Jenner, in 'Phil. Transact.' logy,' 1834, pp. 108, 118. For some 1824, and has since been confirmed additional evidence, although this by several observers, especially by is not wanted, see Leroy, ' Lettres Mr. Blackwall. This latter careful Phil.' 1802, p. 217. For Swifts, observer examined, late in the Gould's 'Introduction to the Birds autumn, during two years, thirty- of Great Britain,' 1823, p. 5. Sim:- six nests; he found that twelve lar cases have been observed in contained young dead birds, five Canada by Mr. Adams; ;^Pop. contained eggs on the point of being Science Review,' July 1873, jk batched, and three, eggs not nearly 283. Chai'. IV. Moral Sense. 109 he now exists, has few special instincts, having lost any which his early progenitors may have possessed, this is no reason why he should not have retained from an extremely remote period some degree of instinctive love and sympathy for his fellows. We are indeed all conscious that we do possess such sympathetic feelings ; ^ but our consciousness does not tell us whether they are instinctive, having originated long ago in the same manner as with the lower animals, or whether they have been acquired by each of us during our early years. As man is a social animal, it is almost certain that he would inherit a tendency to be faithful to his comrades, and obedient to the leader of his tribe ; for these qualities are common to most social animals. He would consequently possess some capacity for self-command. He would from an inherited tendency be willing to defend, in concert with others, his fellow-men ; and would be ready to aid them in any way, which did not too greatly interfere with his own welfare or his own strong desires. The social animals which stand at the bottom of the scale are guided almost exclusively, and those which stand higher in the scale are largely guided, by special instincts in the aid which they give to the members of the same community ; but they are likewise in part impelled by mutual love and sympathy, assisted apparently by some amount of reason. Although man, as just remarked, has no special instincts to tell him how to aid his fellow-men, he still has the impulse, and with his improved intellectual faculties would naturally be much guided in this respect by reason and experience. Instinctive sympathy would also cause him to value highly the approbation of his fellows ; for, as Mr. Bain has clearly shewn,^* the love of praise and the strong feeling of glory, and the still stronger horror of scorn and infamy, " are due to the workings of sympathy." Conse- quently man would be influenced in the highest degree by the wishes, approbation, and blame of his fellow-men, as expressed by their gestures and language. Thus the social instincts, which must have been acquired by man in a very rude state, and probably even by his early ape-like progenitors, still give the impulse to some of his best actions ; but his actions are in a higher degree determined by the expressed wishes and judgment Hnme remarks (' An Enquiry " of the former . . . communicates Concerning the Principles of Morals,' "a secret joy ; the appearance of edit, of 1751, p. 132), "There seems " the latter . . . throws a melan- " a necessity fcr confessing that the " choly damp over the imagina- " happiness and misery of others " tion." " are not spectacles altogether in- ^* ' Mental and Moral Science^ *• Jiffemnt to us. but that the view 1863. p. 254. IIO The Descent of Mati. Pakt J, of his fellow-mon, and unfortunately very often by liis own strong selfish desires. But as love, sympathy and self-command become strengthened by habit, and as the power of reasoning becomes clearer, so that man can value justly the judgments of his fellows, he will feel himself impelled, apart from any transitory pleasure or pain, to certain lines of conduct. He might then declare — not that any barbarian or uncultivated man could thus think — I am the supreme judge of my own conduct, and in the words of Kant, I will not in my own person violate the dignity of humanity. The more enduring Social Instincts conquer the less persistent Instincts. — We have not, however, as yet considered the main point, on which, from our present point of view, the whole question of the moral sense turns. Why should a man feel that he ought to obey one instinctive desire rather than another? Why is he bitterly regretful, if he has yielded to a strong sense of self-preservation, and has not risked his life to save that of a fellow-creature ? or why does he regret having stolen food from hunger ? It is evident in the first place, that with mankind the instinc- tive impulses have different degrees of strength ; a savage will risk his own life to save that of a member of the same community, but wUl be wholly indifferent about a stranger : a young and timid mother urged by the maternal instinct will, without a moment's hesitation, run the greatest danger for her own infant, but not for a mere fellow-creature. Nevertheless many a civilized man, or even boy, who never before risked his life for another, but full of courage and sympathy, has dii-egarded the instinct of self-preservation, and plunged at once into a torrent to save a drowning man, though a stranger. In this case man is impelled by the same instinctive motive, which made the heroic little American monkey, formerly described, save his keeper, by attacking the great and dreaded baboon. Such actions as the above appear to be the simple result of the greater strength of the social or maternal instincts than that of any other instinct or motive; for they are performed too instan- taneously for reflection, or for pleasure or pain to be felt at the time ; though, if prevented by any cause, distress or even misery might be felt. In a timid man, on the other hand, the instinct of self-preservation might be so strong, that he would be unable to force himself to run any such risk, perhaps not even for his own child. I am aware that some persons maintain that actions performed impulsively, as in the above cases, do not come under the dominion of the moral sense^ and cannot be called moral. They CuAP. IT. Moral Sense. Ill confine this term to actions done deliberately, after a victory over opposing desires, or when prompted by some exalted motive. But it appears scarcely possible to draw any clear line of distinction of this kind.-^ As far as exalted motives are concerned, many instances have been recorded of savages, destitute of any feeling of general benevolence towards mankind and not guided by any religious motive, who have deliberately sacrificed their lives as prisoners,'^* rather than betray their comrades ; and surely their conduct ought to be considered as moral. As far as deliberation, and the victory over opposing motives are concerned, animals may be seen doubting between opposed instincts, in rescuing thoir offspring or comrades fi-om danger ; yet their actions, though done for the good of ©thers, are not called moral. Moreover, anything performed •very often by us, will at last be done withoiit deliberation or hesitation, and can then hardly be distinguished from an instinct; yet sxu'ely no one will i)i'etend that such an action ceases to be moral. On the contrary, we all feel that an act cannot be considered as perfect, or as performed in the most noble manner, unless it be done impulsively, without deliberation or efibrt, in the same manner as by a man in whom the requisite qualities are innate. He who is forced to overcome his fear or want of sympathy before he acts, deserves, however, in one way higher credit than the man whose innate disposition leads him to a good act without effort. As we cannot distinguish between motives, we rank all actions of a certain class as moral, if performed by a moral being. A moral being is one who is capable of comparing his past and future actions or motives, and of approving or disapproving of them. We have no reason to suppose that any of the lower animals have this capacity; therefore, when a Newfouiidland dog drags a child out of the water, or a monkey faces danger to rescue its comrade, or takes charge of an orphan monkey, we do not caU its conduct moral. But in the case of man, who alone can with certainty be ranked as a moral being, actions of a certain class are called moral, whether performed deliberately, after a struggle with opposing -* I refer here to the distinction between -what has been called ma- terial and formal morality. I am glad to find that Prof. Huxley ('Cri- tiques and Addresses,' 1873, p. 287) takes the same view on this subject as I do. Mr. Leslie Stephen re- marks (' Essays on Freethinking and Plain Speakin;:, 1873, p. 83), " the ** metaphysical distinction between " material and formal morality is " as irrelevant as other such dis- " tinctions." I have given one such case, namely of three Patagonian Indians who preferred being shot, one after the other, to betraying the plans of their companions in war ('Journal of Researches,' 1845, p. 103). 112 The Descent of Man. Part L motives, or impulsively through instinct, or from the effects of slowly-gaiucd habit. But to return to our more immediate subject. Althougli some instincts are more powerful than others, and thus lead to cor- responding actions, yet it is untenable, that in man tlie social instincts (including the love of praise and fear of blame) possess greater strength, or have, through long habit, acquired' greater strength than the instincts of self-preservation, hunger, lust, vengeance, &c. Why then does man regret, even though trying to banish such regret, that he has followed the one natural impulse rather than the other ; and why does he further feel that he ought to regret his conduct? Man in this respect differs profoundly from the lower animals. Nevertheless we can, I think, see with some degree of clearness the reason of this difference. Man, from the activity of his mental faculties, cannot avoid reflection : past impressions and images are incessantly and clearly passing through his mind. Now with those animals which live permanently in a body, the social instincts are ever present and persistent. Such animals are always ready to utter the danger-signal, to defend the community, and to give aid to their fellows in accordance with their habits ; they feel at all times, without the stimulus of any special passion or desire, some degree of love and sympathy for them ; they are unhappy if long separated from them, and always happy to be again in their company. So it is with ourselves. Even when we are quite alone, how often do we think with pleasure or pain of what others think of us, — of their imagined approbation or disapprobation; and this all follows from sympathy, afonda- mental element of the social instincts. A man who possessed no trace of such instincts would be an unnatural monster. On the other hand, the desire to satisfy hunger, or any passion such as vengeance, is in its nature temporary, and can for a time be fully satisfied. Nor is it easy, perhaps hardly possible, to call up with complete vividness the feeling, for instance, of hunger ; nor indeed, as has often been remarked, of any suffering. The instinct of self-preservation is not felt except in the presence of danger ; and many a coward has thought himself brave until he has met his enemy face to face. The wish for another man's property is perhaps as persistent a desire as any that can be named; but even in this case the satisfaction of actual pos- session is generally a weaker feeling than the desire : many a thief, if not a habitual one, after success has wondered why he stole some article.^ Enmity or hatred seems also perhaps more so than any other to be a highly persistent feeling, that can Vo named. Envy is de- 2UAV. IV, Moral Sense. A man cannot prevent past impressions often repassing through lis mind ; he will thus be driven to make a comparison between :he impressions of past hunger, vengeance satisfied, or danger shunned at other men's cost, with the almost ever-present nstinct of sympathy, and with his early knowledge of what )thers consider as praiseworthy or blameable. This knowledge ;annot be banished from his mind, and from instinctive sympathy s esteemed of great moment. He will then feel as if he had jeen baulked in following a present instinct or habit, and this vith all animals causes dissatisfaction, or even misery. The above case of the swallow affords an illustration, though )f a reversed nature, of a temporary though for the time strongly Dersistent instinct conquering another instinct, which is usually iominant over all others. At the proper season these birds ;eem all day long to be impressed with the desire to migrate ; ;heu- habits change ; they become restless, are noisy, and con- gregate in flocks. Whilst the mother-bird is feeding, or brooding )ver her nestlings, the maternal instinct is probably stronger ;han the migratory ; but the instinct which is the more persis- tent gains the victory, and at last, at a moment when her young )nes are not in sight, she takes flight and deserts them. When irrived at the end of her long journey, and the migratorj nstinct has ceased to act, what an agony of remorse the bird vould feel, if, from being endowed with gi-eat mental activity, ihe could not prevent the image constantly passing through her nind, of her young ones perishing in the bleak north from cold ind hunger. ined as hatred of anothar for some !xcellence or success; and Bacon nsists (Essay ix.), '•' Of all other ' affections envy is the most im- ' portune and continual." Dogs are rery apt to hate both strange men md strange dogs, especially if they ive near at hand, but do not belong ;o the same family, tribe, or clan ; ;his feeling would thus seem to be nnate, and is certainly a most per- iistent one. It seems to be the ;omplement and converse of the ;rue social instinct. From what s-e hear of savages, it would appear ;hat something of the same kind lolds good with them. If this be .0, it would be a small step in iny one to transfer such feelings to icy member of the same tribe if he had done him an injury and had become his enemy. Nor is it pro- bable that the primitive conscience would reproach a man fcr injuring his enemy : rather it would re- proach him, if he had not revenged himself. To do good in return for evil, to love your enemy, is a height of morality to which it may be doubted whether the social instincts would, by themselves, have ever led us. It is necessary that these in- stincts, together with sympathy, should have been highly cultivated and extended by the aid of reason, instruction, and the love or fear of God, before any such golden rule would ever be thought of and obeyed. I 114 The Descent of Man. I Pab-. i At the moment of action, man will no doubt be apt to follow the stronger impulse; and though this may occasionally prompt him to the noblest deeds, it will more commonly lead Mm to gratify his own desires at the expense of other men. But after their gratification, when past and weaker impressious are judged by the ever-enduring social instinct, and by his deep regard for the good opinion of his fellows, retribution will surely come. He will then feel remorse, repentance, regret, or shame this latter feeling, however, relates almost exclusively to the judgment of others. He will consequently resolve more or less firmly to act differently for the future ; and this is conscience ; for conscience looks backwards, and serves as a guide for the future. The nature and strength of the feelings which we call regret, shame, repentance or remorse, depend apparently not only on the strength of the violated instinct, but partly on the strengtli of the temptation, and often still more on the judgment of our fellows. How far each man values the appreciation of others, depends on the strength of his innate or acquired feeling of sympathy; and on his own capacity for reasoning ont the remote consequences of his acts. Another element is most important, although not necessary, the reverence or fear of the Gods, or Spirits believed in by each man : and this applic especially in cases of remorse. Several critics have objectcii that though some slight regret or repentance may be explained by the view advocated in this chapter, it is unpossible thus to account for the soul-shaking feeling of remorse. But I can see little force in this objection. My critics do not define what they mean by remorse, and I can find no definition implying more than an overwhelming sense of repentance. Eemorse seems to bear the same relation to repentance, as rage does to anger, or agony to pain. It is far from strange that an instinct so strong and so generally admired, as maternal love, should, if disobeyed, lead to the deepest misery, as soon as the impression of the past cause of disobedience is weakened. Even when an action is opposed to no special instinct, merely to know that our friends and equals despise us for it is enough to cause great misery. Who can doubt that the refusal to fight a duel through fear has caused many men an agony of shame ? Many a Hindoo, it is said, has been stirred to the bottom of his soul by having partaken of unclean food. Here is another case of what must, I think, be called remorse. Dr. Landor acted as a magistrate in West Australia, and relates,^' that a native on his farm, after losing one of his wives from disease, came and said that " he waa " ' Insanity in Relation to Law;' Ontario, United States, 1871, p. I'i. , Jhap. IV. Moral Sense. ' going to a distant tribe to spear a woman, to satisfy liis sense " of duty to his wife. I told him that if he did so, I would send him to prison for life. He remained about the farm for " soma months, but got exceedingly thin, and complained that he could not rest or eat, that his wife's spirit was haunting ' him, because he had not taken a life for hers. I was in- ' exorable, and assured him that nothing should save him if he ' did." Nevertheless the man disappeared for more than a year, md then returned in high condition ; and his other wife told Dr. Landor that her husband had taken the life of a woman belonging to a distant tribe; but it was impossible to obtain legal evidence of the act. The breach of a rule held sacred by Dhe tribe, will thus, as it seems, give rise to the deepest feelings, —and this quite apart from the social instincts, excepting in so far as the rule is grounded on the judgment of the community. How so many strange superstitions have arisen throughout the world we know not ; nor can we tell how some real and great crimes, such as incest, have come to be held in an abhorrence (which is not however quite universal) by the lowest savages. It is even doubtful whether in some tribes incest would be looked on with gi-eater horror, than would the marriage of a man with a woman bearing the same name, though not a relation. To " violate this law is a crime which the Austrahans hold in the ' greatest abhorrence, in this agi-eeing exactly with certain ' tribes of North America. When the question is put in either ' district, is it worse to kill a girl of a foreign tribe, or to marry ' a girl of one's own, an answer just opposite to ours would be ?iven without hesitation.'"^^ We may, therefore, reject the - belief, lately insisted on by some writers, that the abhorrence of incest is due to our possessing a special God -implanted con- science. On the whole it is intelligible, that a man urged by 30 powerful a sentiment as remorse, though arising as above explained, should be led to act in a manner, which he has been taught to believe serves as an expiation, such as delivering liimself up to justice. Man prompted by his conscience, will through long habit acquire such perfect self-command, that his desires and passions will at last yield instantly and without a struggle to his social sympathies and instincts, including his feeling for the judgment of bis fellows. The still hungry, or the still revengeful man wiil not think of stealing food, or of wreaking his vengeance. It is possible ar OS we shall hereafter see, even probable, that the habit of self- sommand may, like other habits, be inherited. Thus at last man » E. B. Tylor in ' Contemporary Review,' April, 1873, p. 707. The Descent of Man. Past 1 comes to feol, through acquired and pcrhaijs inherited habit, thai it is best for him to obey his moro persistent impulses. The imperious word oiujld seems merely to imply the consciousness of the existence of a rule of conduct, however it may have originated. Formerly it must have been often vehemently urged that an insulted gentleman ought to fight a duel. We even say that a pointer owjlit to point, and a retriever to retrieve game. If they fail to do so, they fail in their duty and act wrongly. If any desire or instinct leading to an action opposed to the good of others still appears, when recalled to mind, as strong as, or stronger than, the social instinct, a man -svill feel no keen regret at having followed it ; but he will be conscious that if his conduct were known to his fellows, it would meet with their disapprobation ; and few are so destitute of sympathy as not to feel discomfort when this is realised. If he has no such sympathy, and if his desires leading to bad actions are at the time strong, and when recalled are not over-mastered by the persistent social instincts, and the judgment of others, then he is essentially a bad man;^ and the sole restraining motive left is the fear of punishment, and the conviction that in the long iTin it would be best for his own selfish interests to regard the good of others rather than his own. It is obvious that every one may with an easy conscience gratify his own desires, if they do not interfere with his social instincts, that is with the good of others ; but in order to be quite free fi'om self-reproach, or at least of anxiety, it is almost neces- sary for him to avoid the disapprobation, whether reasonable or not, of his fellow-men. Nor must he break thi-ough the fixed habits of his life, especially if these are supported by reason : for if he does, he will assuredly feel dissatisfaction. He must likewise avoid the reprobation of the one God or gods in whom . according to his knowledge or superstition, he may believe; but in this case the additional fear of divine punishment ofteu supervenes. The strictly Social Virtues at first alone regarded. — The above view of the origin and nature of the moral sense, which tells us what we ought to do, and of the conscience which reproves us if we disobey it, accords well with what we see of the early and undeveloped condition of this faculty in mankind. The virtues which must bo practised, at least generally, by rude men, so Dr. Prosper Despine, in his many curious cases of the worst ' Psychologie Naturelle,' 1868 (torn, criminals, who apparently have beco i p. 243 ; torn. ii. 169) gives entirely destitute of conscience. Jhap. IV. Moral Sense. 1 17 that they may associate in a body, are those which are still roco"Tused as the most important. But they are practised almost exclusively in relation to the men of the same tribe ; and their opposites are not regarded as crimes in relation to the men of other tribes. No tribe could hold together if murder, robbery, treachery, &c., were common; consequently such crimes within the limits of the same tribe "are branded with "everlasting infamy;'"** but excite no such sentiment beyond these limits. A North-American Indian is well pleased with himself, and is honoured by others, when he scalps a man of another tribe ; and a Dyak cuts off the head of an unoffending person, and dries it as a trophy. The murder of infants has prevailed on the largest scale throughout the world,^^ and has met with no reproach ; but infanticide, especially of females, has been thought to be good for the tribe, or at least not injurious. Suicide during former times was not generally considered as a crime,'*^ but rather, from the courage displayed, as an honourable act ; and it is still practised by some semi-civihsed and savage nations without reproach, for it does not obviously concern others of the tribe. It has been recorded that an Indian Thug conscientiously regretted that he had not robbed and strangled as many travellers as did his father before him. In a rude state of civilisation the robbery of strangers is, indeed, generally considered as honourable. Slavery, although in some ways beneficial during ancient times,'* is a great crime ; yet it was not so regarded until quite recently, even by the most civihzed nations. And this was especially the case, because the slaves belonged in general to a race different from that of their masters. As barbarians do not regard the opinion of their women, wives are commonly treated like slaves. Most savages are utterly indifferent to the sufferings of strangers, or even delight in witnessing them. It is well See an f.ble article in the North British Review,' 1867, p. 395. See also Mr. W. Bugehot's articles on the Importance of Obe- dience and Coherence to Primitive Man, in the ' Fortnightly Review,' 1867, p. 529, and 1808, p. 457, &c. The fullest account which 1 have met with is by Dr. Gerland, in his ' Ucber dan Aussterben der Naturvolker,' 1868; but I shall have to recur to the subiect of infanticide in a future chapter. " See the very interesting discus- uon oa Suicide in Lecky's ' History of European Morals,' vol. i. 1869, p. 223. With respect to savages, Mr. Winwood Reade informs me that the negroes of West Africa often commit suicide. It is well known how common it was amongst the miserable aborigines of South America, after the Spanish conquest. For New Zealand, see the voyage ol the " Novara," and for the Aleutian Islands, Miiller, as quoted by Hou- zeau, ' Les Facult(!s Mentales,' &c., torn. ii. p. 136. See Mr. Bagehot, 'Piysics and Politics.' 187L', p. 7J. Il8 The Descent of Man. Pabt i. known that the women and children of the North-Americao Indians aided in torturing their enemies. Some savages take a horrid pleasure in cruelty to ani'nals,^ and humanity is au unknown virtue. Nevertheless, besides the family affections, kindness is common, especially during sickness, between the members of the same tribe, and is sometimes extended beyond these limits. Mungo Park's touching account of the kindness of the negro women of the interior to him is well known. Many instances could be given of the noble fideUty of savages towards each other, but not to strangers; common experience justifies the maxim of the Spaniard, "Never, never trust an Indian." There cannot be fideUty without truth ; and this fundamental virtue is not rare between the members of the same tribe : thus Mungo Park heard the negro women teaching their young children to love the truth. This, again, is one of the virtues which becomes so deeply rooted in the mind, that it is sometimes practised by savages, even at a high cost, towards strangers ; but to lie to your enemy has rarely been thought a sin, as the history of modem diplomacy too plainly shews. As soon as a tribe has a recognised leader, disobedience becomes a crime, and even abject submission is looked at as a sacred viiiue. As during rude times no man can be useful or faithful to his tribe without courage, this quality has universally been placed in the highest rank; and although in civilised countries a good yet timid man may be far more useful to the community than a brave one, we cannot help instinctively honouring the latter above a coward, however benevolent. Prudence, on the other hand, which does not concern the welfare of others, though a very useful virtue, has never been highly esteemed. As nc man can practise the vii'tues necessary for the welfare of his tribe without self-sacrifice, self-command, and the power ot endurance, these qualities have been at all times highly and most justly valued. The American savage voluntarily submits to the most horrid tortures without a groan, to prove and strengthen his fbrtitude and courage; and we cannot help admiring him, or even an Indian Fakir, who, from a foolisli religious motive, swings suspended by a hook buried in his flesh. The other so called self-regarding virtues, which do not obviously, though they may really, affect the welfare of the tribe, have never been esteemed by savages, though now highly appreciated by civilised nations. The greatest intemperance " See, for instance, Mr. Hamilton's account of the Kaffirs, ' Anthro- pological Review,' 1870, p. xv. Chap. IV. Moral Sense. 119 is no reproach with savages. Utter licentiousness, and un- natural crimes, prevail to an astounding extent.^* As soon, however, as marriage, whether polygamous, or monogamous, becomes common, jealousy will lead to the inculcation of female virtue; and this, being honoured, will tend to spread to the unman-ied females. How slowly it spreads to the male sex, we see at the present day. Chastity eminently requires self- command; therefore it has been honoured from a very early pei'iod iQ the moral history of civilised man. As a consequence of this, the senseless practice of celibacy has been ranked from a remote period as a virtue.**^ The hatred of indecency, which appears to us so natural as to be thought ionate, and which is so valuable an aid to chastity, is a modem vii'tue, appertaining exclusively, as Sir G. Staunton remarks,^^ to civilised life. This is shewn by the ancient religious rites of various nations, by the drawings on the walls of Pompeii, and by the practices of many savages. "We have now seen that actions are regarded by savages, and were probably so regarded by primeval man, as good or bad, Bolely as they obviously affect the welfare of the tribe, — not that of the species, nor that of an individual member of the tribe. This conclusion agrees well with the belief that the so-called moral sense is aboriginally derived from the social instincts, for both relate at first exclusively to the community. The chief causes of the low morality of savages, as judged by our standard, are, firstly, the confinement of sympathy to the same tribe. Secondly, powers of reasoning iosuflficient to recognise the bearing of many virtues, especially of the self-regarding virtues, on the general welfare of the tribe. Savages, for nstance, fail to trace the multiplied evils consequent on a ant of temperance, chastity, &c. And, thirdly, weak power :' self-conunand ; for this power has not been strengthened through long-continued, perhaps ioherited, habit, iostruction and religion. I have entered into the above details on the immorality of savages,^' because some authors have recently taken a high view of their moral nature, or have attributed most of their crimes to mistaken benevolence.^" These authors appear to rest their ^' Mr. M'Lennan has given ' Embassy to China,' vol. ii. p. ('Primitive Marriage,' 1865, p. 348. 176) a good collection of facts on ^' See on this subject copious this head. evidence in Chap. vii. of Sir J. Lab- s' Lecky, ' History of European bock, ' Origin of Civilisation,' 1870. Mcrals,' vol. 1. 1869, p. 109. i« For instance Lecky, 'HLit European Morals,' vol. i. p. 12'4. 120 The Descent of Man Past I. conclusion on savages possessing those virtues which arc ser- viceable, or even necessary, for the existence of the family and of tho tribe,— qualities which they undoubtedly do possess, and often in a high degree. Concluding Bemarhs. — It was assumed formerly by philosophers of the derivative" school of morals that the foundation of morality lay in a form of Selfishness ; but more recently the " Greatest " happiness principle " has been brought prominently forward. It is, however, more correct to speak of the latter principle as the standard, and not as the motive of conduct. Nevertheless, al 1 the authors whose works I have consulted, with a few excep- tions,*^ write as if there must be a distinct motive for every action, and that this must bo associated with some pleasure or displeasure. But man seems often to act impulsively, that is from instinct or long habit, without any consciousness of pleasure, in the same manner as does probably a bee or ant, when it blindly follows its instincts. Under circumstances of extreme peril, as during a fire, when a man endeavours to save a fellow- creature without a moment's hesitation, he can hardly feel pleasure ; and still less has he time to reflect on the dissatisfaction which he might subsequently experience if he did not make tho attempt. Should he afterwards reflect over his own conduct, he would feel that there lies within him an impulsive power widely dififerent from a search after pleasure or happiness; and this seems to be the deeply planted social instinct. In the case of the lower animals it seems much more appro- priate to speak of their social instincts, as having been developed This term is used in an able article in the ' WestBiinster Review,' Oct. 1869, p. 498. For the " Greatest " happiness principle," see J. S. Mill, ' Utilitarianism,' p. 17. Mill recognises (' System of Logic,' vol. ii., p. 422) in the clearest manner, that actions may be per- formed through habit without the anticipation of pleasure. Mr. H. Sidgwick also, in his Essay on Pleasure and Desire (' The Con- temporary Review,' April 1872, p. 671), remarks: "To sura up, in " contravention of the doctrine that " our conscious active impulses arc " always directed towards the pro- " duction of agreeable sensations in " ourselves, I would maintain that " we find everywhere in conscious- " ness extra-regarding impulse, di- " rected towards somethmg that is " not pleasure ; that in many cases " the impulse is so far incompatible " with the self-regaiding that th.. " two do not easily co-exist in the " same moment of consciousness." A dim feeling that our impulses do not by any means always arise from any contemporaneous or anticipated pleasure, has, I cannot but think, been one chief cause of the accept- ance of the intuitive theory of morality, and of the rejection of the utilitarian or " Greatest happiness " theory. With respect to the latter theory, the standard and the motive of conduct have no doubt often been confused, but they are really :3 some degree blended. Ohap. n Mofal Sense. for the general good rather than for the general happiness of the species. The term, general good, may be defined as the rearing of the greatest number of individuals in full vigour and health, with all their faculties perfect, under the conditions to which they are subjected. As the social instincts both of man and the lower animals have no doubt been developed by nearly the same steps, it would be advisable, if found practicable, to use the same definition in both cases, and to take as the standard of morality, the general good or welfare of the community, rather than the general happiness ; but this definition would perhai>s require some limitation on account of political ethics. "When a man risks his life to save that of a fellow-creature, it seems also more correct to say that he acts for the general good, rather than for the general happiness of mankind. No doubt the welfare and the happiness of the individual usually coincide ; and a contented, happy tribe will flourish better than one that is discontented and unhappy. We have seen that even at au early period in the history of man, the expressed wishes of tho community will have naturally influenced to a large extent the conduct of each member ; and as all wish for happiness, the "greatest happiness principle" will have become a most im- portant secondary giiide and object ; the social instinct, however, together with sympathy (which leads to ous regarding the approbation and disapprobation of others), having served as the primary impulse and guide. Thus the reproach is removed of laying the foundation of the noblest part of our nature in the base principle of selfishness; unless, indeed, the satisfaction which every animal feels, when it follows its proper instincts, and the dissatisfaction felt when prevented, be called selfish. The wishes and opinions of the members of the same community, expressed at first orally, but later by writing also, either form the sole guides of our conduct, or greatly reinforce the social instincts ; such opinions, however, have sometimes a tendency directly opposed to these instincts. This latter fact is well exemplified by the Law of Honour, that is, the law of the opinion of our equals, and not of all our countrymen. The breach of this law, even when the breach is known to be strictly accordant with true morality, has caused many a Tuan more agony than a real crime. We recognise the same influence in the burning sense of shame which most of us have felt, even after the interval of years, when calling to mind some accidental breach of a trifling, though fixed, rule of etiquette. The judgment of the community will generally be guided by some rude experience of what is best in the long run for all the members ; but this judg- ment will not rarely err from ignorance and weak powers of 122 The Descetit of Man. Part I. reasoning. Hence the strangest customs and superstitions, in complete opposition to the true welfare and happiness of man- kind, have become all-powerful throughout the world. Wo see this in the horror felt by a Hindoo who breaks his caste, and in many other such cases. It would be difficult to distinguish between the remorse felt by a Hindoo who has yielded to the temptation of eating unclean food, from that felt after committing a theft ; but the former would probably be the more seyere. How so many absurd rules of conduct, as well as so many absurd reUgious beliefs, have originated, we do not know ; nor how it is that they have become, in all quarters of the world, so deeply impressed on the mind of men; but it is worthy of remark that a belief constantly inculcated during the early years of life, whilst the brain is impressible, appears to acquire almost the nature of an instinct ; and the very essence of an instinct is that it is followed independently of reason. Neither can we say why certain admirable virtues, such as the love of truth, are much more highly appreciated by some savage tribes than by others nor, again, why similar differences prevail even amongst highly civilised nations. Knowing how firmly fixed many strange customs and superstitions have become, we need feel no surprise that the self-regarding virtues, supported as they are by reason, should now appear to us so natural as to be thought innate, although they were not valued by man in his early condition. Notwithstanding many sources of doubt, man can generally and readily distingTiish between the higher and lower moral rules. The higher are founded on the social instincts, and relate to the welfare of others. They are supported by the approbatiou of our fellow-men and by reason. The lower rules, though some of them when implying self-sacrifice hardly deserve to be called lower, relate chiefly to self, and arise from public opinion, ma- tured by experience and cultivation ; for they are not practised by rude tribes. As man advances in civilisation, and small tribes are united into larger communities, the simplest reason would tell each ji individual that he ought to extend his social instincts and II sympathies to all the members of the same nation, though personally unknown to him. This point being once reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races. If, indeed, such men are separated from him by great differences in appearance *^ Good instances arc given by in his 'Contributions to the Theory Mr. Wallace in 'Scientific Opinion,' of Natural Selection,' 1870, p. 353. Sept. 15, 1869 ; and more fully Chap. IY. Moral Sense. 123 or habits, experience unfortunately shews us how long it is, before we look at them as our fellow-creatures. Sympathy bevond the confines of man, that is, humanity to the lower animals, seems to be one of the latest moral acquisitions. It is appareEtly unfelt by savages, except towards their pets. How little the old Komans knew of it is shewn by their abhorrent gladiatorial exhibitions. The very idea of humanity, as far as I could observe, was new to most of the Gauchos of the Pampas. This virtue, one of the noblest with which man is endowed, seems to arise incidentally from our sympathies becoming more tender and more widely diffused, until they are extended to all sentient beings. As soon as this virtue is honoured and practised by some few men, it spreads through instruction and example to the young, and eventually becomes incorporated in pubKc opinion. The highest possible stage in moral culture is when we re- cognise that we ought to control our thoughts, and " not even in " inmost thought to think again the sins that made the past so " pleasant to us."** Whatever makes any bad action familiar to the mind, renders its performance by so much the easier. As Marcus Aurelius long ago said, "Such as are thy habitual " thoughts, such also will be the character of thy mind ; for the " soul is dyed by the thoughts."** Our great philosopher, Herbert Spencer, has recently explained his views on the moral sense. He says,*^ "I believe that the " experiences of utility organised and consolidated through all " past generations of the human race, have been producing " corresponding modifications, which, by continued transmission " and accumulation, have become in us certain faculties of " moral intuition — certain emotions responding to right and " wrong conduct, which have no apparent basis in the individual " experiences of utility." There is not the least inherent improbability, as it seems to me, in virtuous tendencies being more or less strongly inherited ; for, not to mention the various dispositions and habits transmitted by many of our domestic animals to their offspring, I have heard of authentic cases in which a desire to steal and a tendency to lie appeared to run in families of the upper ranks ; and as stealing is a rare crime in the wealthy classes, we can hardly account by accidental coinci- dence for the tendency occui-ring in two or three members of ** Tennyson, ' Idylls of the King,' Aurelius was born A.D. 121. p. 244. 46 Letter to Mr. Mill in Bain's « ♦ The Thoughts of the Emperor ' Mental and Moral Science,' 1868 M. Aurelius Antoninus,' Eng. trans- p. 722, lit., 2nd edit,, 1869, p. 112. Marcus 124 Tlie Descent of Man. Part L the same family. If bad tendencies are transmitted, it is pro- bable that good ones are likewise transmitted. That the state of the body by aifecting the brain, has great influence on the moral tendencies is known to most of those who have suffered from chronic derangements of the digestion or liver. The same- fact is likewise shewn by the " perversion or destruction of the " moral sense being often one of the earliest symptoms of mental "derangement;"^'' and insanity is notoriously often inherited. Except through the principle of the transmission of moral ten- dencies, we cannot understand the differences believed to exist in this respect between the various races of mankind. Even the partial transmission of virtuous tendencies would be an immense assistance to the primary impulse derived directly and indirectly from the social instincts. Admitting for a moment that virtuous tendencies are inherited, it appears probable, at least in such cases as chastity, temperance, humanity to animals, &c., that they become first impressed on the mental organization through habit, instruction and example, continued during several generations in the same family, and in a quite subordinate degree, or not at all, by the individuals possessing such virtues having succeeded best in the struggle for life. My chief source of doubt with respect to any such inheritance, is that senseless customs, superstitions, and tastes, such as the horror of a Hindoo for unclean food, ought on the same principle to be transmitted. I have not met with any evidence in support of the transmission of superstitious customs or senseless habits, although in itself it is perhaps not less probable than that animals should acquire inherited tastes for certain kinds of food or fear of certain foes. Finally the social instincts, which no doubt were acquired by man as by the lower animals for the good of the community, will from the first have given to him some wish to aid his fellows, some feeling of sympathy, and have compelled him \i< regard their approbation and disapprobation. Such impulses will have served him at a very early period as a rude rule of right and wrong. But as man gradually advanced in intellectual power, and was enabled to trace the more remote consequences of his actions ; as he acquired sufficient knowledge to reject baneful customs and superstitions; as he regarded more and more, not only the welfare, but the happiness of his fellow-men ; as from habit, following on beneficial experience, instruction and example, his sympathies became more tender and -widely diffused, extending to men of all races, to the imbecile, maimed, " Maadsley, ' Body and Mind,* 1870, p. 60. Chap. IV. Summary. and other useless members of society, and finally to the lower animals,— so would the standard of his morality rise higher and higher. And it is admitted by moralists of the derivative school and by some intuitionists, that the standard of morality has risen since an eai-ly period in the history of man.^^ As a struggle may sometimes be seen going on between the various instincts of the lower animals, it is not siu-prising that there should be a struggle in man between his social instincts, with their derived virtues, and his lower, though momentarily stronger impulses or desires. This, as Mr. Galton*' has remarked, : is all the less surprising, as man has emerged from a state of : barbarism within a comparatively recent period. After having 1 yielded to some temptation we feel a sense of dissatisfaction, shame, repentance, or remorse, analogous to the feelings caused by other powerful instincts or desires, when left unsatisfi.ed or baulked. We compare the weakened impression of a past temptation with the ever present social instincts, or with habits, gained in early youth and strengthened diu'ing om- whole lives, I until they have become almost as strong as instincts. If with ' the temptation still before us we do not yield, it is because either the social instinct or some custom is at the moment predominant, or because we have learnt that it will appear to us hereafter the stronger, when compared with the weakened im- pression of the temptation , and we realise that its violation would cause us suffering. Looking to future generations, there is no cause to fear that the social instincts will grow weaker, and we may expect that vii-tuous habits will grow stronger, becoming perhaps fixed by inheritance. In this case the struggle between our higher and lower impulses will bo less severe, and virtue will be triumphant. ' Summary of the last two Chapters.— ThevQ can be no doubt that the difference between the mind of the lowest man and that of the highest animal is immense. An anthropomorphous ape, if he could take a dispassionate view of his own case, would admit that though he could form an artful plan to plunder a garden- though he could use stones for fighting or for breaking open auts, yet that the thought of fashioning a stone into a tool was A writer in the ' North British coincide therein. Review' (July 1869, p. 531), well " See his remarkable work on capable of forming a sound judg- 'Hereditary Geni.xs,' 1869, p. 349. ment, expresses himself strongly in The Duke of Argyll (' Primeval favour of this concluiion. Mr. Man,' 1869, p. 188) has some good Lecky (' Hist, of Morals,' vol. i. p. remarks on the contest in man'a ■143) seems to a certair. extent to nature between right and wrong. 126 The Descent of Man. Paet I. quite beyond his scope. Still less, as he would admit, could he follow out a train of metaphysical reasoning, or solve a mathe- matical problem, or reflect on God, or admii-e a grand natural scene. Some apes, however, would probably declare that they could and did admire the beauty of the coloured skin and fur of their partners in marriage. They would admit, that though they could make other apes understand by cries some of their per- ceptions and simpler wants, the notion of expressing definite ideas by definite sounds had never crossed their minds. They miglit insist that they were ready to aid their fellow-apes of the same troop in many ways, to risk their lives for them, and to take charge of their orphans ; but they would be forced to acknow- ledge that disinterested love for all living creatures, the most noble attribute of man, was quite beyond their comprehension. Nevertheless the difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind. "We have seen that the senses and intuitions, the various emotions and feculties, such as love, memory, attention, curiosity, imitation, reason, &c., of which man boasts, may bc- found in an incipient, or even sometimes in a well-developed condition, in the lower animals. They are also capable of some inherited improvement, as we see in the domestic dog compared with the wolf or jackal. If it could be proved that certain high mental powers, such as the formation of general concepts, self-con- sciousness, &c., were absolutely peculiar to man, which seems extremely doubtful, it is not improbable that these qualities arc merely the incidental results of other highly-advanced intel- lectual faculties; and these again mainly the result of the continued use of a perfect language. At what age does the new-born infant possess the power of abstraction, or become self-conscious, and reflect on its own existence ? "We cannot answer ; nor can we answer in regard to the ascending organic scale. The half-art, half-instinct of language still bears the stamp of its gradual evolution. The ennobling belief in God is not universal with man; and the beUef in spiritual agencies naturally follows from other mental powers. The moral sense perhaps affords the best and highest distinction between man and •the lower animals ; but I need say nothing on this head, as I have so lately endeavoured to shew that the social instincts, — the prime principle of man's moral constitution ^ — with the aid of active intellectual powers and the effects of habit, naturally lead to the golden rule, " As ye would that men should do to you, do ye to them likewise ;" and this lies at the foundation of morality: »• ' The Thoughts of Marcus Aurelius,' &c., p. 139. r!HAP. V. Intellectual Faculties. 127 In the next chapter I shall make some few remarks on the probable steps and means by which the several mental and moral faculties of man have been gradually evolved. That such evolu- tion is at least possible, ought not to be denied, for we daily see these faculties developing in every infant ; and we may trace a perfect gradation from the mind of an utter idiot, lower than that of an animal low in the scale, to the mind of a Newton. CHAPTEE V. On the Development of the Intellectual and Mobal Faculties during Pbimeval and Civilised Times. Advancement of the intellectual powers through natural selection — Importance of imitation — Social and moral faculties — Their develop- ment within the limits of the same tribe — Xaturai selection as affecting civilised nations — Evidence that civilised nations were once barbarous. The subjects to be discussed in this chapter are of the highest interest, but are treated by me in an imperfect and fragmentary manner. Mr. Wallace, in an admirable paper before referred to,' argues that man, after he had partially acquired those intel- tectual and moral faculties which distinguish, him from the lower animals, would have been but little liable to bodily modifications through natural selection or any other means. For man is enabled through his mental faculties " to keep with " an unchanged body in harmony with the changing universe." He has great power of adapting his habits to new conditions of life. He invents weapons, tools, and various stratagems to procure food and to defend Mmself. When he migrates into a colder climate he uses clothes, builds sheds, and makes fires ; and by the aid of fire cooks food otherwise indigestible. He aids his fellow-men ia many ways, and anticipates future events. Even at a remote period he practised some division of labour. The lower animals, on the other hand, must have their bodily structure modified in order to survive under greatly changed conditions. They must be rendered stronger, or acquire more effective teeth or claws, for defence against new enemies; or' they must be reduced in size, so as to escape detection and danger. When they migrate into a colder climate, they must "become clothed with thicker fur, or have their constitutions altered. If they fail to be thus modified, they will cease to exist. ' 'Anthropological Review,' May 1864, p. clviii. £28 The Descent of Alan. rABT JL The case, however, is widely different, as Mr. Wallace has with justice insisted, iu relation to the intellectual and moral faculties of man. These faculties are variable; and we have every reason to believe that the variations tend to be inherited. Therefore, if they were formerly of high importance to primeval man and to his ape-like progenitors, they would have been perfected or advanced through natural selection. Of the high importance of the intellectual faculties there can be no doubt, for man mainly owes to them his predominant position in the world. We can see, that in the rudest state of society, the individuals who were the most sagacious, who invented and used the best weapons or traps, and who were best able to defend themselves, would rear the gi-eatest number of offspring. The tribes, which included the largest number of men thus endowed, would increase in number and supjjlant other tribes. Numbers depend primarily on the means of subsistence, and this depends Ijartly on the physical nature of the country, but in a much higher degree on the arts which are there practised. As a tribe increases and is victorious, it is often still further increased by the ab- sorption of other tribes.^ The stature and strength of the men of a tribe are likewise of some importance for its success, and these depend in part on the nature and amount of the food which can be obtained. In Europe the men of the Bronze period were supplanted by a race more powerful, and, judging from their sword-handles, with larger hands ;^ but their success was pro- Imbly still more due to their superiority \n the arts. All that we know about savages, or may infer from their ta-aditions and from, old monuments, the history of which is quite forgotten by the present inhabitants, shew that from the remotest limes successful tribes have supplanted other tribes. Eelics oi extinct or forgotten tribes have been discovered throughout the civilised regions of the earth, on the wild plains of America, and on the isolated islands in the Pacific Ocean. At the present day civilised nations are everywhere supplanting barbarous nations, excepting where the climate opposes a deadly barrier; and they succeed mainly, though not exclusively, through their arts, which are the prod ucts of the intellect. It is, therefore, highly probable that with mankind the intellectual faculties have been mainly and gradually perfected thi'ough natural selection ; and this con- clusion is sufficient for our purpose. Undoubtedly it would be interesting to trace the development of each separate faculty 3 After a time the members or 1861, p. 131), that they are the co- tribes whica are absorbed into descendants of the same ancestors, another tribe assume, as Sir Henry » Morlot, ' Son. Vaud. Sc. Nat. alaine remarks (' Ancient Law,' 1860, p. 294. Moral Faculties. 129 from the state in which it exists in the lower animals to that in which it exists in man; but neither my ability nor knowledge permits the attempt. It deserves notice that, as soon as the progenitors of man became social (and this probably occurred at a very early period), the principle of imitation, and reason, and experience would have increased, and much modified the intellectual powers in a way, of which we see only traces in the lower animals. Apes are much given to imitation, as are the lowest savages; and the simple fact previously referred to, that after a time no animal can be caught in the same place by the same sort of trap, shews that animals learn by experience, and imitate the caution of others. Now, if some one man in a tribe, more sagacious than the others, invented a new snare or weapon, or other means of attack or defence, the plainest self-interest, without the assistance of much reasoning power, would prompt the other members to imitate him ; and all would thus profit. The habitual practice of each new art must likewise in some slight degree strengthen the intellect. If the new invention were an important one, the tribe would increase in number, spread, and supplant other tribes. In a tribe thus rendered more numerous there would always be a rather greater chance of the birth of other superior and inventive members. If such men left children to inherit their mental superiority, the chance of the bii'th of still more ingenious members would be somewhat better, and in a very small tribe decidedly better. Even if they left no children, the tribe would still include their blood-relations ; and it has been ascertained by agriculturists * that by preserving and breeding from the family of an animal, which when slaughtered was found to be valuable, the desired character has been obtained. Turning now to the social and moral faculties. In order that primeval men, or the ape-Uke pregenitors of man, should become social, they must have acquired the same instinctive feelings, which impel other animals to live in a body ; and they no doubt exhibited the same general disposition. They would have felt uneasy when separated from their comrades, for whom they would have felt some degree of love ; they would have warned each other of danger, and have given mutual aid in attack or defence. AU this implies some degree of sympathy, fidelity, and courage. Such social quahties, the paramount importance of which to the lower animals is disputed by no one, were no doubt * 1 have given instances in my ' Variation of Animals under Domestica- tion,' vol. ii, p. 196, I30 The Descent of Man. Paet T. acquired by the progenitors of man in a similar manner, namely, through natural selection, aided by inherited habit. When two tribes of primeval man, living in the same country, came into competition, if (other circumstances being equal) the one tribe included a great number of courageous, sympathetic and faithful members, who were always ready to warn each other of danger, to aid and defend each other, this tribe would succeed better and conijuer the other. Let it be borne in mind how all-important in the never-ceasing wars of savages, fidelity and courage must be. The advantage which disciplined soldiers have over undis- ciplined hordes follows chiefly from the confidence which each man feels in his comrades. Obedience, as Mi-. Bagehot has well shewn,' is of the highest value, for any form of government is better than none. Selfish and contentious people will not cohere, and without coherence nothing, can be effected. A tribe rich in the above qualities would spread and be victorious over other tribes : but in the course of time it would, judging from all past history, be in its turn overcome by some other tribe still more highly endowed. Thus the social and moral qualities would tend slowly to advance and be diffused throughout the world. But it may be asked, how within the limits of the same tribe did a large number of members first become endowed with these social and moral qualities, and how was the standard of ex- cellence raised ? It is extremely doubtful whether the offspring of the more sympathetic and benevolent parents, or of those "who were the most faithful to their comrades, would be reared in greater numbers than the children of selfish and treacherous parents belonging to the same tribe. He who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature. The bravest men, who were always willing to come to the front in war, and who freely risked their lives for others, would on an average perish in larger numbers than other men. Therefore it hardly seems probable, that thd number of men gifted with such virtues, or that the standard of their excellence, could be increased thi-ough natural selection, that is, by the survival of the fittest ; for we are not here speaking of one tribe being victorious over another. Although the circumstances, leading to an increase in the number of those thus endowed within the same tribe, are too complex to be clearly followed out, we can trace some of the probable steps. In the fitrst place, as the reasoning powers and » See a remarkable series of arti- April 1, 1868 ; July 1, 1869, sir.cs; cles on ' Physics and Politics ' in the separately published, ♦Fortnightly Review,' Nov. 1867: Chap. V. Moral Faculties. foresiglit of the members became improved, each man would soon learn that if he aided his fellow-men, he would commonly receive aid in return. From this low motive he might acquire the habit of aiding his fellows ; and the habit of performing benevolent actions certainly strengthens the feeling of sympathy which gives the first impulse to benevolent actions. Habits, moreover, followed during many generations probably tend to be inherited. But another and much more powerful stimulus to the de- velopment of the social virtues, is afforded by the praise and the blame of our fellow-men. To the instinct of sympathy, as we have akeady seen, it is primarily due, that we habitually bestow both praise and blame on others, whilst we love the former and dread the latter when applied to oui'selves ; and this instinct no doubt was originally acquired, like all the other social instincts, through natural selection. At how early a period the progenitors of man in the course of their development, became capable of feeling and being impelled by, the praise or blame of their fellow-creatures, we cannot of course say. But it appears that even dogs appre- ciate encouragement, praise, and blame. The rudest savages feel the sentiment of glory, as they clearly show by preserving the trophies of then" prowess, by their habit of excessive boasting, and even by the extreme care which they take of their per- sonal appearance and decorations ; for unless they regarded the opinion of their comrades, such habits would be senseless. They certainly feel shame at the breach of some of their lesser rules, and apparently remorse, as shewn by the case of the Australian who grew thin and could not rest from having delayed to murder some other woman, so as to propitiate his dead wife's spirit. Though I have not met with any other recorded case, it is scarcely credible that a savage, who will sacrifice his life rather than betray his tribe, or one who will deliver himself up as a prisoner rather than break his parole,*' would not feel remorse in his inmost soul, if he had failed in a duty, which he held sacred. We may therefore conclude that primeval man, at a very remote period, was influenced by the praise and blame of his fellows. It is obvious, that the members of the same tribe would approve of conduct which appeared to them to be for the genera] good, and would reprobate that which appeared evil. To do good unto others — to do unto others as ye would they should do unto you— is the foundation-stone of morality. It is, therefore, hardly possible to exaggerate the importance during rude timea * Mr. Wallace gives cases in of Natural Selection,' 1870, p, ViB 'Contributions to the Theory 354. K 2 132 The Descent of Man. Faut I. of the love of praise and the dread of blame. A man who was not impelled by any deep, instinctive feeling, to sacrifice his life for the good of others, yet was roused to such actions by a sense of glory, would by his example excite the same wish for glory in other men, and would strengthen by exercise the noble feeling of admiration. He might thus do far more good to his tribe than by begetting offspring with a tendency to inherit his own high character. With increased experience and reason, man perceives the more remote consequences of his actions, and the self-regarding virtues, such as temperance, chastity, &c., which during early times are, as we have before seen, utterly disregarded, come to be highly esteemed or even held sacred. I need not, however, repeat what I have said on this head in the fourth chapter. Ultimately our moral sense or conscience becomes a highly complex sentiment— originating in the social instincts, largely guided by the approbation of our fellow-men, ruled by reason, self-interest, and in later times by deep religious feelings, and confirmed by instruction and habit. It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an increase in the number of well-endowed men and an advancement in the standard of morality will certaialy give an immense advantage to one tribe over another. A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes ; and this would be natural selection. At aU times throughout the world tribes have supplanted other tribes ; and as morahty is one important element in their success, the standard of morality and the number of well-endowed men will thus every- where tend to rise and increase. It is, however, very difficult to form any judgment why one particular tribe and not another has been successful and has risen in the scale of civilisation. Many savages are in the same condition as when first discovered several centuries ago. As Mr. Bagehot has remarked, we are apt to look at progress as normal in human society ; but history refutes this. The ancients did not even entertain the idea, nor do the Oriental nations at the present day. According to another high authority, Sir Henry Maine,'' " the greatest part of mankind has never shewn a ' 'Ancient Law,' 1861, p. 22. nightly Review,' ipril 1, 1868, p. For Mr. Bagehot's remarks, ' Fort 452, Chap. V. Civilised Natio?is. 133 " particle of desire that its civil institutions should be im- " proved." Progress seems to depend on many concurrent favourable conditions, far too complex to be followed out. But it has often been remarked, that a cool climate, from leading to industry and to the various arts, has been highly favourable thereto. The Esquimaux, pressed by hard necessity, have succeeded in many ingenious inventions, but their climate has been too severe for continued progress. Nomadic habits, whether over wide plains, or through the dense forests of the tropics, or along the shores of the sea, have in every case been highly detrimental. Whilst observing the barbarous inhabitants of Tierra del Fuego, it struck me that the possession of some property, a fixed abode, and the union of many families under a chief, were the indispensable requisites for civilisation. Such habits almost necessitate the cultivation of the ground ; and the first steps in. cultivation would probably result, as I have else- where shewn,^ from some such accident as the seeds of a fruit- tree falling on a heap of refuse, and producing an unusually fine variety. The problem, however, of the first advance of savages towards civilisation is at present much too difiBcidt to be solved. Natural Selection as affecting Civilised Nations. — I have hitherto only considered the advancement of man from a semi-human condition to that of the modern savage. But some remarks on the action of natural selection on civilised nations may be worth adding. This subject has been ably discussed by ]\Ir. W. E. Greg,^ and previously by Mr. "Wallace and Mr. Galton.^" Most of my remarks are taken from these three authors. With savages, the weak in body or mind are soon eliminated ; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination ; we build asylums for the imbecile, the maimed, and the sick ; we institute poor-laws ; and our medical ' ' The Variation of Animals and Plants under Domestication,' vol. i, p. 309. » ' Eraser's Magazine,' Sept. 1868, p. 353. This article seems to have struck many persons, and has given rise to two remarkable essays and a i'ejoinder in the 'Spectator,' Oct, 3rd and 17th, 1868. It has also been discussed in the ' Q. Journal of Science,' 1869, p. 152, and by Mr. Lawson Tait in the 'Dublin Q. lournai of Medical Science,' Feb. 1869, and by Mr. E. Ray Lankester in his ' Comparative Longevity,' 1870, p. 128. Similar views ap- peared previously in the 'Austra- lasian,' July 13, 1867. I have borrowed ideas from several of these writers. For Mr. Wallace, see ' Anthro- polog. Eeview,' as before cited. Mr. Gallon in ' Macraillan's Magazine,' Aug. 1865, p. 318 ; also his great work, ' Hereditary Genius,' 1870. 134 The Descent of Man. Pabt l men exert their utmost skill to save the life of every one to tho last moment. There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox. Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race ; but excepting in the case of man himself, hardly any one is so ignorant as to allow his worst animals to breed. The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but sub- sequently rendered, in the manner previously indicated, more tender and more widely diffused. Nor could we check our sympathy, even at the urging of hard reason, without deteriora- tion in the noblest part of our natui-e. The surgeon may harden himself whilst performing an operation, for he knows that he is acting for the good of his patient ; but if we were intentionally to neglect the weak and helpless, it could only be for a con- tingent benefit, with an overwhelming present evil. "We must therefore bear the undoubtedly bad effects of the weak surviving and propagating their kind; but there appears to be at least one check in steady action, namely that the weaker and inferior members of society do not mai-ry so freely as the sound ; and this check might be indefinitely increased by the weak in body or mind refraining from marriage, though this is more to be hoped for than expected. In every country in which a large standing army is kept up, the finest young men are taken by the conscription or are enlisted. They are thus exposed to early death during war, are often tempted into vice, and are prevented from marrying during the prime of life. On the other hand the shorter and feebler men, with poor constitutions, are left at home, and consequently have a much better chance of marrying and propagating their kind." Man accumulates property and bequeaths it to his children, so that the children of the rich have an advantage over the poor in the race for success, independently of bodily or mental su- periority. On the other hand, the children of parents who are short-lived, and are therefore on an average deficient in health and vigour, come into their property sooner than other children, 1' Prof. H. Tick ('Einfluss der on this head, and on other such Naturwissenschaft auf das Recht,' points. June, 1872) has some good remarks Chap. Y. Civilised Nations. 135 and will be likely to marry earlier, and leave a larger number of oifspring to inherit their inferior constitutions. But the in- heritance of property by itself is very far from an evil ; for ■without the accumulation of capital the arts octdd not progress; and it is chiefly through theii- power that the civilised races have extended, and are now everywhere extendmg their range, so as to take the place of the lower races. Nor does the moderate accumulation of wealth interfere with the process of selection. "When a poor man becomes moderately rich, his children enter trades or .professions in which there is struggle enough, so that the able in body and mind succeed best. The presence of a body of well-instructed men, who have not to labour for their daily bread, is important to a degree which cannot be over-estimated ; as all high intellectual work is carried on by them, and on such work, material progress of all kinds mainly depends, not to mention other and higher advantages. No doubt wealth when very great tends to convert men into useless drones, but their number is never large; and some degree of elimination here occurs, for we daily see rich men, who happen to be fools or profligate, squandering away their wealth. Primogeniture with entailed estates is a more du'ect evil, though it may formerly have been a great advantage by the creation of a dominant class, and any government is better than none. Most eldest sons, though they may be weak in body or mind, marry, whilst the younger sons, however superior in these respects, do not so generally marry. Nor can worth- less eldest sons with entailed estates squander their wealth. But here, as elsewhere, the relations of civilised life are so complex that some compensatory checks intervene. The men who are rich through primogenitui'e are able to select genera- tion after generation the more beautiful and charming women ; and these must generally be healthy in body and active in mind. The evil consequences, such as they may be, of the continued preservation of the same line of descent, without any selection, are checked by men of rank always wishing to increase their wealth and power; and this they effect by marrying heiresses. But the daughters of parents who have produced single children, are themselves, as Mr. Galton'^ has shewn, apt t& be sterile ; and thus noble families are continually cut off in the direct line, and their wealth flows into some side channel ; but unfortunately this channel is not determined by superiority of any kind. Although civilisation thus checks in many ways the action of " 'Hereditary Genius' 1870, pp. 132-140. 136 The Descent of Man. Paut I. Eaturai selection, it apparently favours the better development of the body, by means of good food and the freedom from occa- sional hardships. This may be inferred from civilised men having been found, wherever compared, to be physically stronger than savages.'^ They appear also to have equal powers of endurance, as has been proved in many adventurous ex- peditions. Even the great luxury of the rich can be but little detrimental ; for the expectation of life of our aristocracy, at all ages and of both sexes, is very little inferior to that of healthy English lives in the lower classes." "We will now look to the intellectual faculties. If in each grade of society the members were divided into two equal bodies, the one including the intellectually superior and the other the inferior, there can be little doubt that the former would succeed best in all occupations, and rear a greater number of children. Even in the lowest walks of life, skill and ability must be of some advantage; though in many occupations, owing to the great division of labour, a very small one. Hence in civilised nations there will be some tendency to an increase both in the number and in the standard of the intellectually able. But I do not wish to assert that this tendency may not be more than counterbalanced in other ways, as by the multiplica- tion of the reckless and improvident ; but even to such as these, ability must be some advantage. It has often been objected to views like the foregoing, that the most eminent men who have ever lived have left no offspring to inherit their great intellect. ]\Ir. Galton says,'^ " I regret I am " unable to solve the simple question whether, and how far, " men and women who are prodigies of genius are infertile. I have, however, shewn that men of eminence are by no means • ' so." Great lawgivers, the founders of beneficent religions, ^reat philosophers and discoverers in science, aid the progress of mankind in a far higher degree by their works than by leaving a numerous progeny. In the case of corporeal structures, it is the selection of the slightly better-endowed and the elimination of the shghtly less well-endowed individuals, and not the pre- servation of strongly-marked and rare anomalies, that leads to the advancement of a species." So it will be with the intellectual faculties, since the somewhat abler men in each grade of society " Quatrefages, « Eevue des Cours 1870, p. 115. Scientifiques,' 1867-68, p. 659. " 'Hereditar/ Genius,' 1870, p, " See the fifth and sixth columns, 330. compiled from good authorities, in " ' Origin of Species ' (fifth edi- the table given in Mr. E. R. Lan- tion, 1869), p. 104. kester's 'Comparative Longevity Chap. V. Civilised Nations. 137 succeed rather better than the less able, and consequently increase in number, if not otherwise prevented. When in any nation the standard of intellect and the number of intel- lectual men have increased, we may expect from the law of the deviation from an average, that prodigies of genius will, as shewn by Mr. Galton, appear somewhat more frequently than before. In regard to the moral qualities, some elimination of the worst dispositions is always in progress even in the most civilised nations. Malefactors are executed, or imprisoned for long periods, so that they cannot freely transmit their bad qualities. Melancholic and insane persons are confined, or commit suicide. Violent and quarrelsome men often come to a bloody end. The restless who will not follow any steady occupation— and this relic of barbarism is a great check to civilisation"— emigrate to newly-settled countries, where they prove useful pioneers. In- temperance is so highly destructive, that the expectation of life of the intemperate, at the age of thirty for instance, is only 13-8 years ; whilst for the rural labourers of England at the same age it is 40'59 years.^* Profligate women bear few children, and profligate men rarely marry ; both suffer from disease. In the breeding of domestic animals, the elimination of those individuals,, though few in number, which are in any marked manner inferior, is by no means an unimportant element towards success. This especially holds good with injurious characters which tend tc reappear through reversion, such as blackness in sheep; and with mankind some of the worst dispositions, which occasionally without any assignable cause make their appearance in families, may perhaps be reversions to a savage state, from which we are not removed by very many generations. This view seems indeed recognised in the common expression that such men are the black sheep of the family. With civilised nations, as far as an advanced standard of morality, and an increased number of fairly good men are con- cerned, natural selection apparently effects but little ; though the fundamental social instincts were originally thus gained. But I have already said enough, whilst treating of the lower races, on the causes which lead to the advance of morality, namely, the approbation of our fellow-men — the strengthening " 'Hereditary Genius,' 1870, p. Neison's 'Vital Statistics.' In re- 34:7. gcard to profligacy, see Dr. Farr, »• E. Ray Laniester, 'Compara- 'Influence of Marriage on Mor- tive Longevity,' 1?70, p. 115. The tality,' ' Nat. Assoc. for the Promc table of the intemperate is from tion of Social Science,' 18'j8. 138 TJic Descent of Man, Paht I. of our sympathies by habit — example and imitation — reason- experience, and even self-interest — instruction during youth, and religious feelings. A most important obstacle in ciYilised countries to an increase in the number of men of a superior class has been strongly insisted on by Mr. Greg and Mr. Galton," namely, the fact that the very poor and reckless, who are often degraded by vice, almost invari- ably marry early, -whilst the careful and frugal, who are generally ciherwise virtuous, marry late in life, so that they may be able to support themselves and their children in comfort. Those who marry early produce within a given period not only a greater number of generations, but, as shewn by Dr. Duncan,^ they pro- duce many more children. The children, moreover, that are bom by mothers during the prime of life are heavier and larger, and therefore probably more vigorous, than those bom at other periods. Thus the reckless, degraded, and often vicious members of society, tend to increase at a quicker rate than the provident and generally virtuous members. Or as Mr. Greg puts the case : " The careless, squalid, unaspiring Irishman multiplies like " rabbits : the frugal, foreseeing, self-respecting, ambitious Scot, "stern in his morality, spii-itual in his faith, sagacious and dis- " ciplined ia his intelligence, passes his best years in sti-uggle " and in celibacy, marries late, and leaves few behind him. " Given a land originally peopled by a thousand Saxons and a " thousand Celts — and in a dozen generations five-sixths of the ^ population would be Celts, but five-sixths of the property, of " the power, of the intellect, would belong to the one-sixth of " Saxons that remained. In the eternal ' struggle for existence,' " it would be the inferior and less favoui'ed race that had pre- " vailed— and prevailed by virtue not of its good qualities but of its faults." There are, however, some checks to this downward tendency. We have seen that the intemperate suffer from a high rate of mortality, and the extremely profligate leave few offspring. The poorest classes crowd into towns, and it has been proved by Dr. Stark from the statistics of ten years in Scotland,^^ that at all '° ' Fraser's Magazine,' Sept. 1868, p. 353. 'Macmillan's Maga- zine, Aug. 1865, p. 318. The Rev. F. W. Farrar (' Fraser's Mag.' Aug. 1870, p. 264) takes a different view. « « On the Laws of the Fertility of Women,' in ' Transact. Royal Soc' Edinburgh, vol. ssiv. p. 287 ; BOW published separately under the title of 'Fecundity, Fertility, and Sterility,' 1871. See, also, Mr Galton, 'Hereditary Genius,' pp. 35L-357, for observations to the above effect. ^' 'Tenth Annual Report oi Births, Deaths, &c., :d Scotland, 1867, p. sxa.. V. Civilised Nations. 139 ages the death-rate is higher in towns than in rural districts, " smd during the first five years of life the town death-rate is " almost exactly double that of the rural districts." As these re- turns include both the rich and the poor, no doubt more than twice the number of births would be requisite to keep up the number of the very poor inhabitants in the towns, relatively to those in the country. With women, marriage at too early an age is highly injurious ; for it has been found in France that, " twice as many wives under twenty die in the year, as died out " of the same number of the unmarried." The mortality, also, of husbands under twenty is " excessively high,"^^ but what the cause of this may be, seems doubtful. Lastly, if the men who prudently delay marrying until they can bring up their families in comfort, were to select, as they often do, women in the prime of life, the rate of increase in the better class would be only slightly lessened. It was established from an enormous body of statistics, taken during 1853, that the unmarried men throughout France, between the ages of twenty and eighty, die in a much larger, proportion than the married : for instance, out of every 1000 immarried men, between the ages of twenty and thirty, 11 "3 annually died, whilst of the married only 6'5 died.^^ A similar law was proved to hold good, during the years 1863 and 1864, with the entire population above the age of twenty in Scotland : for instance, out of every 1000 unmarried men, between the ages of twenty and thirty, li'QT annually died, whilst of the married only 7 '24 died, that is less than half.-^ Dr. Stark remarks on this, " Bachelorhood is more destructive to life than the most "unwholesome trades, or than residence in an unwholesome " house or district where there has never been the most distant "attempt at sanitary improvement." He considers that the lessened mortality is the direct result of " marriage, and the " more regular domestic habits which attend that state." He admits, however, that the intemperate, profligate, and criminal classes, whose duration of life is low, do not commonly marry ; and it must likewise be admitted that men with a weak constitii- These quotations are takeu from our highest authority on such questions, namely, Dr. Farr, in his paper 'On the Influence of Mar- riage on the Mortality of the French People,' read before the Nat. Assoc. for the Promotion cf Social Science, 1858. ^3 Dr. FaiT, ibid. The quota- tions given below are extracted from the same striking paper. "^^ I have taken the mean of the quinquennial means, given in ' The Tenth Annual Eeport of Births, Deaths, &c., in Scotland,' 1867. The quotation from Dr. Stark is copied from an article in the * Daily News,' Oct. 17th, 1868, which Dr. Farr considers very carefally writ- ten. 140 The Descent of Man. Paet T. tion, ill health, or any great infirmity in body or mind, will often not wish to marry, or will be rejected. Dr. Stark seems to have come to the conclusion that marriage in itself is a main cause of prolonged life, from finding that aged married men still have a considerable advantage in this respect over the unmarried of the same advanced age ; but every one must have known instances of men, who with weak health during youth did not marry, and yet have survived to old age, though remaining weak, and there- fore always with a lessened chance of hfe or of marrying. There is another remarkable circumstance which seems to support Dr. Stark's conclusion, namely, that widows and widowers in France suffer in comparison with the married a very heavy rate of mor- tality ; but Dr. I'arr attributes this to the poverty and evil habits consequent on the disruption of the family, and to grief. On the whole we may conclude with Dr. Farr that the lesser mortahty of married than of unmarried men, which seems to be a general law, "is mainly due to the constant elimination of imperfect " types, and to the skilful selection of the finest individuals out . " of each successive generation ;" the selection relating only to the marriage state, and acting on all corporeal, intellectual, and moral qualities.^^ We may, therefore, infer that sound and good men who out of prudence remain for a time unmarried, do not suffer a high rate of mortality. If the various checks specified in the two last paragraphs, and perhaps others as yet unknown, do not prevent the reckless, the vicious aud otherwise inferior members of society from increas- ing at a quicker rate than the better class of men, the nation wiU retrograde, as has too often occurred in the history of the world. We must remember that progress is no invariable rule. It is very diflScult to say why one civilised nation rises, becomes more powerful, and spreads more widely, than another ; or why the same nation progresses more quickly at one time than at another. We can only say that it depends on an increase in the actual number of the population, on the number of the men endowed with high intellectual and moral faculties, as well as on their standard of excellence. Corporeal structure appears to have little influence, except so far as vigour of body leads to vigour of mind. It has been urged by several writers that as high intellectual powers are advantageous to a nation, the old Greeks, who stood some grades higher in intellect than any race that has ever Dr. Duncan remarlcs (' Fecund- " from the unmarried side to the ity, Fertility,' &c., 1871, p. 334) on " married, leaving the unmarried this suhject ; " At every age the " columns crowded with the sickly " healthy and beautiful go over " and unfortunate." Chap V. Civilised Nations. 141 existed,^® ought, if the power of natural selection were real, to have risen still higher in the scale, increased in number, a.nd stocked the whole of Europe. Here we have the tacit assump- tion, so often made with respect to corporeal structures, that there is some innate tendency towards continued development in mind and body. But development of all kinds depends on many concurrent favourable circumstances. Natural selection acts only tentatively. Individuals and races may have acquired cer- tain indisputable advantages, and yet have perished from failing in other characters. The Greeks may have retrograded from a want of coherence between the many small states, from the small size of their whole country, from the practice of slavery, or from extreme sensuality ; for they did not succumb until " they were " enervated and corrupt to the very core." ''^ The western nations of Europe, who now so immeasurably surpass theu- formepr savage progenitors, and stand at the summit of civilisation, owe little or none of their superiority to direct inheritance from the old Greeks, though they owe much to the written works of that wonderful people. Who can positively say why the Spanish nation, so dominant at one time, has been distanced in the race. The awakening of the nations of Europe from the dark ages is a still more perplex- ing problem. At that early period, as Mr. Galton has remarked, almost all the men of a gentle nature, those given to meditation or culture of the mind, had no refuge except in the bosom of a Church which demanded celibacy;'*' and this could hardly fail to have had a deteriorating influence on each successive generation. During this same period the Holy Inquisition selected with extreme care the freest and boldest men in order to burn or imprison them. In Spain alone some of the best men — those who doubted and questioned, and without doubting there can be no progress — were eliminated during three cen- turies at the rate of a thousand a year. The evil which the Catholic Church has thus effected is incalculable, though no dctibt counterbalanced to a certain, perhaps to a large, extent in other ways; nevertheless, Europe has progressed at an un- paralleled rate. See the ingenious and original 257) advances arguments on the argument on this subject by Mr. other side. Sir C. Lyell had already Galton, 'Hereditary Genius,' 'pp. ('Principles of Geology,' vol. li. 340-342. 1868, p. 489) in a striking passage 2' Mr. Greg, 'Eraser's Magazine,' called attention to the evil influence Sept. 1868, p. 357. of the Holy Inquisition in having, *• ' Hereditary Genius,' 1870, pp. through selection, lowered the gene- 357-359. The Rev. F. W. Farrar ral standard of intelligence in Eu. C'Fraser's Mag.,' Aug. 1870, p. rope. 142 The Desce7it of Man. Paet I. The remarkable success of the English as colonists, compared toother European nations, has been ascribed to their "daring " and persistent energy ; " a result which is weU illustrated by comparing the progress of the Canadians of EngUsh and French extraction ; but who can say how the Enghsh gained their energy ? There is apparently much truth in the belief that the wonderful progress of the United States, as well as the character of the people, are the results of natural selection ; for the more ener- getic, restless, and courageous men from all parts of Europe have emigrated during the last ten or twelve generations to that great country, and have there succeeded best.^ Looking to the distant future, I do not think that the Eev. Mr. Zincke takes an exaggerated view when he says :^ " All other series of events — " as that which resulted in the culture of mind in Greece, and "that which resulted in the empire of Eome— only appear to " have purpose and value when viewed in connection with, or " rather as subsidiary to ... . the great stream of Anglo-Saxon " emigration to the west." Obscure as is the problem of the advance of civihsation, we can at least see that a nation which produced during a lengthened period the greatest number of highly intellectual, energetic, brave, patriotic, and benevolent men, would generally prevail over less favoured nations. Natural selection follows from the struggle for existence ; and this from a rapid rate of increase. It is impossible not to regret bitterly, but whether wisely is another question, the rpte at which man tends to increase ; for this leads in barbarous tribes to infanticide and many other evils, and in civilised nations to abject poverty, celibacy, and to the late marriages of the prudent. But as man suffers from the same physical evils as the lower animals, he has no right to expect an immunity from the evils consequent on the struggle for existence. Had he not been sub- jected during primeval times to natural selection, assuredly he would never have attained to his present rank. Since we see in many parts of the world enormous areas of the most fertile land capable of supporting numerous happy homes, but peopled only by a few wandering savages, it might be argued that the struggle for existence had not been sufficiently severe to force man up- wards to his highest standard. Judging from all that we know of man and the lower animals, there has always been sufficient variabihty in their intellectual and moral faculties, for a steady advance through natural selection. No doubt such advance w Mr. Galtoi!, ' Macmillan's and National Life,' Dec. 1869, p. 184. Magazine,' August, 1865, p. 325. vn countrieSj and yet have very rarely or never bred, is a more apposite in- stance, because of their relationship to man. It is remarkable how slight a change in the conditions often induces sterihty in a wild animal when captured ; and this is the more strange as all our domesticated animals have become more fertile than they were in a state of nature; and some of them can resist the most unnatural conditions with undiminished fertility.''^ Certain groups of animals are much more liable than others to be affected by captivity ; and generally all the species of the same group are affected in the same manner. But sometimes a single species in a group is rendered sterile, whilst the others are not so ; on the other hand, a single species may retain its fertility On the close relationship of the Scotland, Dr. JJitchell, 'Edinburgh Norfolk Islaudnrp, see Sir W. Deni- Medical Jouraal,' March to June, son, 'Varieties of Vice-Regal Life,' 186.5. vol. i. 1870, p. 410. For the Todas, <° For the evidence on this head, see Col. Marshall's work, 1873, p. see 'Variation of Animals' &c., 110. For the Western Islands of vol. ii. p. 111. IQO The Descent cf Man. Pabt L whilst most of the others fail to breed. The males and females of some species when confined, or when allowed to live almost, but not quite free, in their native country, never unite ; others thus circumstanced frequently unite but never produce offspring ; others again produce some offspring, but fewer than in a state of nature ; and as bearing on the above cases of man, it is important to remark that the young are apt to bo weak and sickly, or malformed, and to perish at an early age. Seeing how general is this law of the susceptibility of the reproductive system to changed conditions of life, and that it holds good with our nearest allies, the Quadrumana, I can hardly doubt that it applies to man in his primeval state. Hence if savages of any race are induced suddenly to change their habits of Ufe, they become more or less sterile, and their young offspring suffer in health, in the same manner and from the same cause, as do the elephant and hunting-leopard in India, many monkeys in America, and a host of animals of all kinds, on removal from their natural conditions. We can see why it is that aborigines, who have long ioha- bited islands, and who must have been long exposed to nearly uniform conditions, should be specially affected by any change in their habits, as seems to be the case. Civihsed races can certainly resist changes of all kiuds far better than savages; and in this respect they resemble domesticated animals, for though the latter sometimes suffer in health (for instance European dogs in India), yet they are rarely rendered sterile, though a few such instances have been recorded.*^ The immunity of civihsed races and domesticated animals is probably due to their having been subjected to a greater extent, and therefore having grown somewhat more accustomed, to diversified or varying conditions, than the majority of wild animals; and to their having formerly immigrated or been carried from country to country, and to different famihes or sub-races having inter-crossed. It appears that a cross with civihsed races at once gives to an aboriginal race an immunity from the evil consequences of changed conditions. Thus the crossed offspring from the Tahitians and Enghsh, when settled in Pitcairn Island, increased so rapidly that the island was soon overstocked ; and in June 1856 they were removed to Norfolk Island. They then consisted of 60 married persons and 131 children, making a total of 194. Here they likewise in- creased so rapidly, that although sixteen of them returned to Pit- cairn Island in 1859, they numbered in January 1868, 300 souls; «■ « Variation of Animals,' &e,, Tol. ii-, p 16. SuAP. VII. Extinction of Races. 191 tlio males and females being in exactly equal numbers. "What a contrast does this case present with that of the Tasmanians ; the Norfolk Islanders increased in only twelve and a half years from 194 to 300; whereas the Tasmanians decreased during fifteen years from 120 to 46, of which latter number only ten were children.'** So again in the interval between the census of 1866 and 1872 the natives of full blood in the Sandwich Islands decreased by 8081, whilst the half-castes, who are believed to be healthier, in- creased by 847 ; but I do not know whether the latter number includes the offspring from the half-castes, or only the half-castes of the fii'st generation. The cases which I have here given aU relate to aborigines, who have been subjected to new conditions as the result of the immigration of civilised men. But sterility and ill-health would probably foUow, if savages were compelled by any cause, such as the inroad of a conquering tribe, to desert their homes and to change their habits. It is an interestiag circumstance that the chief check to wild animals becoming domesticated, which imphes the power of their breeding freely when fitrst captured, and one chief check to wild men, when brought into contact with civilisation, surviving to form a civilised race, is the same, namely, sterility from changed conditions of hfe. Finally, although the gradual decrease and ultimate extinction of the races of man is a highly complex problem, depending on many causes which differ in different places and at different times ; it is the same problem as that presented by the extinc- tion of one of the higher animals — of the fossil horse, for in- stance, which disappeared from South America, soon afterwards to be replaced, within the same districts, by countless troops of the Spanish horse. The New Zealander seems conscious of this parallelism, for he compares his future fate with that of the native rat now almost exterminated by the European rat. Though the difficulty is great to our imagination, and really great, if we wish to ascertain the precise causes and their manner of action, it ought not to be so to our reason, as long as we keep steadily in mind that the increase of each species and each race is constantly checked in various ways ; so that if any new check, even a slight one, be superadded, the race will surely decrease in number; and decreasing numbers will sooner or " These details are taken from May 29th, 1863. The following 'The Mutineers of the " Bounty," ' statements about the Sandwich Is- by Lady Belcher, 1870; and from landers are from the 'Honcltlu * Pitcairn Island,' ordered to be Gazette,' and from Mr. Coaa. printed by the House of Commons, 192 The Descent of Man. 1'abt I later lead to extinction ; tlie end, in most cases, being promptly determined by the inroads of conquering tribes. On the Formation of the Races of Man. — In some cases the crossing of distinct races has led to the formation of a new race. The singular fact that Europeans and Hindoos, who belong to the same Aryan stock, and speak a language fundamentally the same, differ widely in appearance, whUst Europeans differ but little from Jews, who belong to the Semitic stock, and speak quite another language, has been accounted for by Broca,** through certain Aryan branches having been largely crossed by indigenous tribes during their wide diffusion. When two races ui close contact cross, the first result is a heterogeneous mixture : thus Mi". Hunter, in describing the Santali or hill-tribe, of India, Kays that hundreds of imperceptible gradations may be traced " from the black, squat tribes of the mountains to the tall " olive-coloured Brahman, with his intellectual brow, calm oyes, " and high but narrow head ;" so that it is necessary in courts of justice to ask the witnesses whether they are Santalis or Hindoos.^" Whether a heterogeneous people, such as the inhabi- tants of some of the Polynesian islands, formed by the crossing of two distinct races, with few or no pui-e members left, would ever become homogeneous, is not known from direct evidence. But as with our domesticated animals, a cross-breed can certainly be fixed and made uniform by careful selection" in the course of a few generations, we may infer that the free intercrossing of a heterogeneous mixture during a long descent would supply the place of selection, and overcome any tendency to reversion ; so that the crossed race would ultimately become homogeneous, though it might not partake in an equal degree of the characters of the two parent-races. Of all the differences between the races of man, the colour of the skin is the most conspicuous and one of the best marked. It was formerly thought that differences of this kind could bo accounted for by long exposure to different chmates; but Pallas first shewed that this is not tenable, and he has since been followed by almost all anthropologists.'^ This view has been rejected chiefly because the distribution of the variously coloured races, most of whom must have long inhabited their « 'On Anthropology,' transla- " Pallas, 'Act. Acid. St. Peters- tion ' Anthropolog. Review,' Jan. burg,' 1780, part ii. p. 69. He was 1868, p. 38. followed by Rudolphi, in his ♦ Bey- ''The Annals of Rural Bengal,' triige zur Anthropologie,' 1812. J 868, p. 134. -A^n excellent summary of the evi- '' The Variation of Animals and dence is given by Godion, 'De Plants under Domestication,' vol. ii. I'Espfece,' 1859, vol. ii. p. 246, &c. p. 95 Chap. VII. "^/'^ Formation of Races. 193 present homes, does not coincide with corresponding differences of climate. Some little weight may be given to such cases as that of the Dutch families, who, as we hear on excellent autho- rity,*^ have not undergone the least change of colour after residing for three centiiries in South Africa. An argument on the same side may likewise be drawn from the uniform appeai-- ance in various parts of the world of gipsies and Jews, though the imiformity of the latter has been somewhat exaggerated." A very damp or a very dry atmosphere has been supposed to be more influential in modifying the colour of the skin than mere heat ; but as D'Orbigny in South America, and Livingstone in Africa, arrived at diametrically opposite conclusions with respect to dampness and di'yness, any conclusion on this head must be considered as very doubtful.^^ Various facts, which I have given elsewhere, prove that the colour of the sMa and hair is sometimes correlated in a surpris- ing manner with a complete immunity from the action of certain vegetable poisons, and from the attacks of certain parasites. Hence it occurred to me, that negroes and other dark races might have acquired their dark tints by the darker individuals escaping from the deadly influence of the miasma of their native countries, during a long series of generations. I afterwards found that this same idea had long ago occurred to Dr. Wells.^" It has long been known that negroes, and even mulattoes, are almost completely exempt from the yellow-fever, so destructive in tropical America.*'' They likewise escape to a lai'ge extent the fatal intermittent fevers, that prevail along at least 2600 miles of the shores of Africa, and which annually cause one-fifth of the white settlers to die, and another fifth to return home invalided.** This immunity in the negro seems to be partly inherent, depending on some unknown peculiarity of constitution, and partly the result of acclimatisation. Pouchet*" Sir Andrew Smith, as quoted by Knox, ' Races of Man ' 1850, p. 473. See De Quatrefages on this head, 'Revue des Cours Scieati- fiques,' Oct. 17, 1868, p. 731. Livingstone's ' Travels and Re- searches in S. Africa,' 1857, pp. 338, 329. D'Orbigny, as quoted by Godron, ' De I'Espfece,' vol. ii. p. 266. See a paper read before the Royal Soc. in 1813, and published in his Essays in 1818. I have given an account of Dr. Wells' views in the Historical Sketch (p. xvi.) to my 'Origin of Species.' Various cases of colour correlated with constitu- tional peculiarities are given in my ' Variation of Animals under Do- mestication,' vol. ii. pp. 227, 335. See, for instance, Nott and Gliddon, ' Types of Mankind,' p. 68. " Major Tulloch, in a paper read before the Statistical Society, Apnl 20th, 1840, and given in the ' Athe- na:um,' 1840, p. 353. " 'The Plurality of the Human Race ' (translat.), 1864, p. 60. 0 194 The Descent of Man. Part I, states that the negro regiments recruited near the Soudan, and borrowed from the Viceroy of Egypt for the Mexican war, escaped the yellow-fever almost equally with the negroes origin- ally brought from various parts of Africa and accustomed to the climate of the West Indies. That acclimatisation plays a part, is shewn by the many cases in which negroes have become some- what liable to tropical fevers, after having resided for some time in a colder climate."" The nature of the climate under which the white races have long resided, likewise has some influence on them; for during the fearful epidemic of yellow-fever in Demerara during 1837, Dr. Blair found that the death-rate of the immigrants was proportional to the latitude of the country whence they had come. With the negro the immunity, as far as it is the result of acclimatisation, implies exposure during a prodigious length of time ; for the aborigines of tropical America who have resided there from time immemorial, are not exempt from yellow fever; and the Eev. H. B. Tristram states, that there are districts in Northern Africa which the native inhabit- ants are compelled annually to leave, though the negroes can remain with safety. That the immunity of the negro is in any degree correlated with the colour of his skin is a mere conjectui-e : it may be correlated with some difference in his blood, nervous system, or other tissues. Nevertheless, from the facts above alluded to, and from some connection apparently existing between complexion and a tendency to consumption, the conjecture seemed to me not improbable. Consequently I endeavoui'ed, with bnt Uttle success," to ascertain how far it holds good. The late Dr. Quatrefages, * Unite de I'Espfice Humaine,' 1861, p. 205. Waitz, ' Introduct. to Anthropology,' trans- lat. vol. i. 1863, p. 124. Living- stone gives analogous cases in his ' Travels.' In the spring of 1862 I ob- tained permission from the Director- General of the Medical department of the Army, to transmit to the surgeons of the various regiments on foreign service a blank tabic, with the following appended re- marks, but I hare received no re- turns. " As several well-marked " eases have been recorded with " our domestic animals of a relation " between the colour of the dermal " appendages and the constitution ; "ffad it being notorious that there " is some limited degree of relation " between the colour of the races of " man and the climate inhabited by " them ; the following investiga- " tion seems worth consideration. " Namely, whether there is any re- " lation in Europeans between the " colour of their hair, and their " liability to the diseases of tropical " countries. If the surgeons of the " several regiments, when stationed " in unhealthy tropical districts, " would be so good as first to count, " as a standard of comparison, how " many men, in the force whence " the sick are drawn, have dark " and light-coloured hair, and Lair " of intermediate or doubtful tints; " and if a similar account were " kept by the same medical gentle- Chap. VII. The Formation of Races. 195 DanieU, who had long lived on the West Coast of Africa, told me that he did not believe in any such relation. He "was himself nniisually fair, and had withstood the climate ia a wonderful manner. When he first arrived as a boy on the coast, an old and experienced negro chief predicted from his appearance that this would prove the case. Dr. Nicholson, of Antigua, after having attended to this subject, writes to me that he does not think that dai'k-coloured Europeans escape the yellow-fever more than those that are light-coloured. Mr. J. M. Harris altogether denies that Europeans with dark hair withstand a hot climate better than other men : on the contrary, experience has taught him in making a selection of men for service on the coast of Africa, to choose those with red hau-."^ As far, therefore, as these slight indications go, there seems no foundation for the hypothesis, that blackness has resulted from the darker and darker individuals having sui'vived better during long exposure to fever-generating miasma. Dr. Sharpe remarks,^^ that a tropical sun, which burns and blisters a white sMn, does not injure a black one at all ; and, as he adds, this is not due to habit in the individual, for children only six or eight months old are often carried about naked, and are not affected. I have been assured by a medical man, that some years ago during each summer, but not during the winter, his hands became marked with light brown patches, like. " men, of all the men who suffered " from malarious and yellow fevers, " or from dysentery, it would soon " be apparent, after some thousand " cases had been tabulated, whether " there exists any relation between " the colour of the hair and consti- " tutional liability to tropical dis- " eases. Perhaps no such relation " would be discovered, but the in- " vestigation is well worth making. " In case any positive result were " obtained, it might be of some " practical use in selecting men for " any particular service. Theoreti- " cally the result would be of high " interest, as indicating one means " by which a race of men inhabiting " from a remote period an un- " healthy tropical climate, might " have become dark-coloured by " the better preservation of dark- " haired or dark-complexioned in- " dividuals during a long succession " of generations." ' Anthropological Review,' Jan. 1866, p. xxi. Dr. Sharpe also says, with respect to India (' Man a Spe- cial Creation,' 1873, p. 118), that " it has been noticed by some medi- " cal officers that Europeans with " light hair and florid complexions " suffer less from diseases of tropical " countries than persons with dark " hair and sallow complexions ; " and, so far as I know, there ap- " pear to be good grounds for this " remark." On the other hand, Mr. Heddle, of Sierra Leone " who " has had more clerks killed under " him than any other man," by the climate of the West African Coast (W. Reade, ' African Sketch Book,' vol. ii. p. 522), holds a directly opposite view, as does Capt. Burton. " ' Man a Special Creation,' 1873 p. 119. 0 2 The Descent of Man. although larger than freckles, and that these patches were never affected by sun-burning, whilst the white parts of his skin have on several occasions been much inflamed and blistered. With the lower animals there is, also, a constitutional difference in liability to the action of the sun between those parts of the skin clothed with white hair and other parts.^* Whether the saving of the skin from being thus burnt is of sufiacient impor- tance to account for a dark tint having been gradually acquired by man through natural selection, I am unable to judge. If it be so, we should have to assume that the natives of tropical America have lived there for a much shorter time than the negroes in Africa, or the Papuans in the southern parts of the Malay archipelago, just as the lighter-coloured Hindoos have resided in India for a shorter time than the darker aborigines of the central and southern parts of the peninsula. Although with our present knowledge we cannot account for the differences of colour in the races of man, through any advantage thus gained, or from the direct action of climate ; yet we must not quite ignore the latter agency, for there is good reason to believe that some inherited effect is thus produced.'^' We have seen in the second chapter that the conditions of life affect the development of the bodily fi-ame in a direct manner, and that the effects are transmitted. Thus, as is generally admitted, the Eui'opean settlers in the United States undergo a shght but extraordinarily rapid change of appearance. Theii' bodies and limbs become elongated; and I hear from Col. Bernys that during the late war in the United States, good evidence was afforded of this fact by the ridiculous appearance presented by the German regiments, when dressed in ready-made clothes manufactured for the American market, and which were much too long for the men in every way. There is, also, a con- siderable body of evidence shewing that in the Southern States the house-slaves of the third generation present a markedly different appearance from the field-slaves.^'' ^* Variation of Animals and rtants under Domestication,' vol. ii. pp. 336, 337. See, for instance, Quatrefages (' Revue des Cours Scientifiques,' Oct. 10, 1868, p. 724) on the effects of residence in Abyssinia and Arabia, /.nd other analogous cases. Dr. Kolle (' Der Mensch, seine Abstam- mung,' &c., 1865, s. 99) states, on the authority of Khanikof, that the greater number of German families settled in Georgia, have acquired in the course of two generations dark hair and eyes. Mr. D. Forbes in- forms me that the Quichuas in the Andes vary greatly in colour, ac- cording to the position of the valleys inhabited by them. Harlan, 'Medical Researches,' p. 532. Quatrefages (' Unite de I'Espfece Humaine,' 1861, p. 128) has collected much evidence on this head. CiiAP. YII. The Formation of Races. 197 If, however, we look to the races of man as distributed over the world, we must infer that their characteristic differences can- not be accounted for by the direct action of different conditions of life, even after exposure to them for an enormous period of time. The Esquimaux live exclusively on animal food ; they are clothed in thick fur, and are exposed to intense cold and to prolonged darkness; yet they do not differ in any extreme degree from the inhabitants of Southern China, who live entirely on vegetable food, and are exposed almost naked to a hot, glaring climate. The unclothed Fuegians live on the marine produc- tions of their inhospitable shores; the Botocudos of Brazil wander about the hot forests of the interior and live chiefly on vegetable productions ; yet these tribes resemble each other so closely that the Fuegians on board the " Beagle " were mistaken by some Brazilians for Botocudos. The Botocudos again, as well as the other inhabitants of tropical America, are wholly different from the Negroes who inhabit the opposite shores of the Atlantic, ai-e exposed to a nearly similar climate, and follow nearly the same habits of life. Nor can the differences between the races of man be accounted for by the inherited effects of the increased or decreased use of parts, except to a quite insigniiicant degree. Men who habitu- ally live in canoes, may have their legs somewhat stunted ; those who inhabit lofty regions may have their chests enlarged ; and those who constantly use certain sense-organs may have the cavities in which they are lodged somewhat increased in size, and their features consequently a little modified. With civilised nations, the reduced size of the jaws from lessened use — the habitual play of different muscles serving to express different emotions — and the increased size of the brain from greater intellectual activity, have together produced a considerable effect on their general appearance when compared with savages.^'" Increased bodily stature, without any corresponding increase in the size of the brain, may (judging from the pre- viously adduced case of rabbits), have given to some races an elongated skull of the dolichocephalic type. Lastly, the little-understood principle of correlated develop- ment has sometimes come into action, as in the case of great muscular development and strongly projecting supra-orbital ridges. The colour of the skin and hair are plainly correlated, as is the texture of the hair with its colour in the Mandans of North America.^' The colour also of the skin, and the odour " See Prof. Schaaffhansen, trans- " Mr. Catlin states ('N, Aineri- lat. in 'Anthropological Review,' can Indians,' 3rd edit. 1342, vol. 1, Oct. 1868, p. 429, p. 49) that in the whole tribe of 198 The Descent of Man. Paet L emitted "by it, are likewise in some manner connected. With tlie breeds of sheep the number of hairs within a given space and the number of the excretory pores are related."' If we may judge from the analogy of our domesticated animals, many modifica- tions of structure in man probably come under this principle of correlated development. "We have now seen that the external characteristic differences between the races of man cannot be accounted for in a satisfac- tory manner by the direct action of the conditions of life, nor by the effects of the continued use of parts, nor through the principle of correlation. We are therefore led to inquire whether slight individual differences, to which man is emi- nently liable, may not have been preserved and augmented during a long series of generations through natural selection. But here we are at once met by the objection that beneficial variations alone can be thus preserved ; and as far as we arc enabled to judge, although always liable to err on this head, none of the differences between the races of man are of any direct or special service to him. The iutellectual and moral or social faculties must of course be excepted from this remark. The great variability of all the external differences between the races of man, likewise indicates that they cannot be of much importance ; for if important, they would long ago have been either fixed and preserved, or eliminated. In this respect man resembles those forms, called by naturalists protean or polymorphic, which have remained extremely variable, owing, as it seems, to suoh varia- tions being of an indifferent nature, and to their having thus escaped the action of natural selection. We have thus far been baffled in all our attempts to account for the differences between the races of man ; but there remains one important agency, namely Sexual Selection, which appears to have acted powerfully on man, as on many other animals. I do not intend to assert that sexual selection will account for all the differences between the races. An unexplained residuum is left, about which we can only say, in our ignorance, that as indivi- duals are continually born with, for instance, heads a little rounder or narrower, and with noses a little longer or shorter, such slight differences might become fixed and unifonn, if the the Mandans, about one in ten or fine and soft. twelve of the members, of all ages On the odour of the skin, and both sexes, have bright silvery Godron, ' Sur I'Espfece,' tom. ii. p. crrey hair, which is hereditary. 217. On the pores in the skin, Now this hair is as coarse and Dr. Wilckens, 'Die Aufgaben der harsh as that of a horse's mane, Landwirth. Zootechnik,' 1869, s. 7. whilst the hair of other colours, is Chap. VII. Strticticre of the Brain. 199 tinkno-\vn agencies which induced them were to act in a more constant manner, aided by long-continued intercrossing. Such variations come under the provisional class, alluded to in our second chapter, which for the want of a better term are often called spontaneous. Nor do I pretend that the effects of sexual selection can be indicated with scientific precision ; but it can be shewn that it would be an inexplicable fact if man had not been modified by this agency, which appears to have acted powerfully on' inmunerable animals. It can further be shewn that the differences between the races of man, as in colour, hairiness, form of features, &c., are of a kind which might have been expected to come under the influence of sexual selection. But in order to treat this subject properly, I have found it necessary to pass the whole animal kingdom in review. I have therefore devoted to it the Second Part of this work. At the close I shall return to man, and, after attempting to shew how far he has been modified through sexual selection, will give a brief summary of the chapters in this First Part. Note on the Eesemblances and Differences tn the Stkuctdee AND THE Development of the Brain in Man and Apes. By Professor Huxley, F.K.S. The conti'oversy respecting the nature and the extent of the differ- ences in the structure of the brain in man and the apes, which arose some fifteen years ago, has not yet come to an end, though the subject matter of the dispute is, at present, totally different from what it was formerly. It was originally asserted and re-asserted, with singular pertinacity, that the brain of all the apes, even the highest, diifers from that of man, in the absence of such conspicuous structures as the posterior lobes of the cerebral hemispheres, with the posterior cornu of the lateral ventiicle and the hippocampus minor, contained in those lobes, which are so obvious in man. But the truth that the three structures in question are as well deve- loped in apes' as in human brains, or even better ; and that it is character- istic of all the Primates (if we exclude the Lemurs) to have these parts well developed, stands at present on as secure a basis as any proposition in comparative anatomy. Moreover, it is admitted by every one of the long series of anatomists who, of late years, have paid special attention to the aiTangemcnt of the complicated sulci and gyri which appear upon the surface of the cerebral hemispheres in man and the higher apes, that they are disposed after the very same pattern in him, as in them! Every principal gyrus and sulcus of a chimpanzee's brain is clearly represented in that of a man, so that the terminology which applies to the one answers for the other. On this point there is no difierence of opinion. Some years since, Professor Bischoff published a memoir on 1he cerebral convolutions of man and apes; and as the purpose of my learned colleague was certainly not to diminish the value of the '» 'Die Grosshira-Windungen des Menschen;' ' Abhandlunger der K. Bayerischen Akadeccie.' Bd. x., 1868. 200 The Descent of Man. Part L clifferences between apes aud men in this respect, I am glad to make a citation from liim. " That the apes, iind especially the orang, chimpanzee and gorilla, " come very close to man in their organisation, much nearer than to an v " other animal, is a well known fact, disputed by nobody. Looking at " the matter from the point of view of organisation alone, no one probably " would ever have disputed the view of Linnajus, that man should bo " placed, merely as a peculiar species, at the head of the mammalia and ot those apes. Both shew, in all their organs, so close an aflSnity, that the " most exact anatomical investigation is needed in order to demonstrate " those differences which really exist. So it is with the brains. The " brains of man, the orang, the chimpanzee, the gorilla, in spite of all •' the important differences which they present, come very close to one- " another " (1. c. p. 101). Tliere remains, then, no dispute as to the resemblance in fundamental characters, between the ape's brain and man's ; nor any as to the won- derfully close similarity between the chimpanzee, orang and man, in even the details of the aiTangement of the gyri and sulci of the cerebral hemispheres. Nor, turning to the differences between the brains ot the highest apes and that of man, is there any serious question as to the nature and extent of these differences. It is admitted that the man's cerebral hemispheres are absolutely and relatively larger than those of the orang and chimpanzee ; that his frontal lobes are less excavated by the upward protnision of the roof of the orbits ; that his gjrri and sulci are, as a rule, less symmetrically disposed, and present a greater munbcr of seeondaiy plications. And it is admitted that, as a rule, in man, the temporo-occipital or "external perpendicular " fissure, which is usually so strongly marked a feature of the ape's brain is but faintly marked. But it is also clear, that none of these differences constitutes a sharp demarcation between the'man's and the ape's brain. In respect to th.- (3xtemal perpendicular fissure of Gratiolet, in the human brain, for instance. Professor Turner remarks " In some brains it appears simply as an indentation of the margin of " the hemisphere, but, in others, it extends for some distance more or less " transversely outwards. I saw it in the right hemisphere of a female " brain pass more than two inches outwards ; and in another specimen. " also the right hemisphere, it proceeded for four-tenths of an inch out- " wards, and then extended downwards, as far as the lower margin of the " outer surface of the hemisphere. The imperfect definition of this fissure " in the majority of human brains, as compared with its remarkable dis- " tinctness in the brain of most Quadrumana, is owing to the presence, in " the former, of certain superficial, well marked, secondary convolutions " which bridge it over and connect the parietal with the occipital lobe. " The closer the first of these bridging gyri lies to the longitudinal " fissure, the shorter is the external parieto-ocoipital fissure." (1. c. p. 12.^ The obliteration of the external perpendicular fissure of Gratiolet, therefore, is not a constant character of the hiunan brain. On the other hand, its full development is not a constant character of the higher ape's brain. For, in the chimpanzee, the more or less extensive oblitera- tion of the external perpendicular sulcus by " bridging convolutions," on 0^9 side or the other, has been noted over and over again by Prot. T» 'Convolutions of the Human Cerebrum Topographically Considered, 1866, p. 12. Chap. VII. Structure of the Brain. 20t Rolleston, Mr. Marshall, M. Broca and • Professor Tui-ner. At the conclusion of a special paper on this subject the latter writes •' The three specimens of the brain of a chimpanzee just described. ' prove, that the generalisation which Gratiolet has attempted to draw of " the complete absence of the first connecting convolution and tho •' concealment of the second, as essentially characteristic features in the " brain of this animal, is by no means universally applicable. In only one " specimen did the brain, in these particulars, follow the law which Gratiolet has expressed. As regards the presence of the superior bridg- •' ing convolution, I am inclined to think that it has existed in one hemi- •' sphere, at least, in a majority of the brains of this animal which have, up ■' to this time, been figured or described. The superficial position of tho " second bridging convolution is evidently less frequent, and has as yet, •• I believe, only been seen in the brain (A) recorded in this communi- '■ cation. The asymmetrical arrangement in the convolutions of tho '• two hemispheres, which previous observers have referred to in their '• descriptions is also well illustrated in these specimens." (pp. 8, 9.) Even were the presence of the temporo-occipital, or external per- pendicular, sulcus a mark of distinction between the higher apes and man, the value of such a distinctive character would be rendered very doubtful by the structure of the brain in the Platyrhine apes. In fact while the temporo-occipital is one of the most constant of sulci in the Catarhine, or Old World, apes, it is never very strongly developed in the New World apes ; it is absent in the smaller Platyi-hini ; rudimentary in Pithecia and more or less obliterated by bridging convolutions in Ateles. A character which is thus variable within the limits of a single group can have no great taxouomic value. It is further established, that the degree of asymmetry of the convolu- tion of the two sides in the human brain is subject to much individual variation ; and that, in those individuals of the Busliman race who have been examined, the gyri and sulci of the two hemispheres are consider- ably less complicated and more synunetrical than in the European brain, while, in some individuals of the chimpanzee, theii- complexity and asymmetry become notable. This is particularly the case in the brain of a young male chimpanzee figui-ed by M. Broca. (' L'ordro des Primates," p. 165, fig. 11.) Again, as respects the question of absolute size, it is established that the difference between the largest and the smallest healthy human brain is greater than the dilference between the smallest healthy human brain and the largest chimpanzee's or omng's brain. Moreover, there is one circumstance in which the orang's and chim- panzee's brains resemble man's, but in which they difler from the lower apes, and that is the presence of two corpora candicantia— tbt' Cynomorpha having but one. In view of these facts I do not hesitate in this year 1874, to repeat and insist upon the proposition which I enunciated in 1863.'* 'bo far as cerebral structure goes, therefore, it is clear that man • Notus more especially on the " Flower 'On the Anatomy of bridging convolutions m the Brain I'ithecia Monachus,' 'Proceedings of ot the Chimpanzee, 'Proceedings of the Zoological Society,' 1862. 186-6 ^^^^^ Edinburgh,' m 'Man's Place in Nature,' p. 102. 202 The Descent of Man. Paut I. dilfars less from the chimoauzeo or the orang, than these do even " from tho monkeys, and coat tbo difference between the brain of the " chimpanzee and of man is almost insignificant, when compared with " that between the chimpanzee brain and that of a Lemur." In the paper to which I have referred, Professor Bischoff does not deny tlie second part of this statement, but he first makes the irrelevant remark that it is not wonderful if the brains of an orang and a Lemur arc very difl'erent ; and secondly, goes on to assert that, " If we suoces- " sively compare the brain of a man with that of an orang; the brain of " this with that of a chimpanzee ; of this with that of a gorilla, and so "on of a Ihjlobates, Semnopitheous, Gynocephalus, Cercopithecus, Macacus, " Cehus, Callithrix, Lemur, Stenops, Hapale, we shall not meet with a " greater, or even as great a, break in the degree of development of the " convolutions, as we find between the brain of a man and that of an " orang or chimpanzee." To which I reply, firstly, that whether this assertion be true or false, it has nothing whatever to do with the proposition enunciated in ' Man's Place in Nature,' which refers not to the development of the convolutions alone, but to the structure of the whole brain. If Professor Bischoff had taken the trouble to refer to p. 96 of tho work he criticises, in fact, he would have found the following passage : " And it is a " remarkable circumstance that though, so far as our present know- '' ledge extends, there is one true structural break in the series of forms " of Simian brains, this hiatus does not lie between man and the " manlike apes, but between the lower and the lowest Simians, or in '' other words, between the Old and New World apes and monkeys and " the Lemurs. Every Lemur which has yet been examined, in fact, " has its cerebellum partially visible from above ; and its posterior lobe, " with the contained posterior cornu ahd hij^pocampus minor, more or "less rudimentary. Every marmoset, American monkey. Old World " monkey, baboon, or manlike ape, on the contrary, has its cerebellum " entirely hidden, posteriorly, by the cerebral lobes, and possesses a " large posterior cornu with a well-developeil hippocampus minor." This statement was a strictly accm-ate account of what was kno^Ti when it was made; and it does not appear to me to be more than apparently weakened by the subsequent discovery of the relatively small development of the posterior lobes in the Siamang and in the Howling monkey. Notwithstanding the exceptional brevity of tho posterior lobes in these two species, no one will pretend that their brains, in the slightest degree, approach those of the Lemurs. And if, instead of putting Eapale out of its natural place, as Professor Bischoff most unaccountably does, we write the series of animals he has chosen to mention as follows : Homo, Pitliecm, Troglodytes, Hylobates, Semnopithecus, Gynocephalus, Cercopithecus, Macacus, Cehus, Callithrix, Hapale, Lemur, Stenops, I venture to reafiirm that the great break in this series lies between Eapale and Lemur,, and that this break is considerably gi-eater than that between any other two terms of that series. Professor Bischoff ignores the fact that long before he -wrote, Gratiolet had suggested the separation of the Lemurs from the other Primates on the very ground of the difference in their cerebral characters; and that Professor Flower had made the following' observations in the course of his description of the brain of the Javan Loris " 'Transactions of the Zoological Society,' vol. v. 1862. Chap. VII. Structure of the Brain. 203 "And it is especially remarkable that, in the development of the ^ posterior lobes, there is no approximation to the Lemuriiie, short ^' Jiemisphered, brain, in those monkeys which are commonly supposed •' to approach this family in other respects, viz., the lower members ot •' (ie Platyrhine group." So far as the structure of the adult brain is concerned, then, the very considerable additions to oui- knowledge, which have been made by the researches of so many investigators, during the past ten years, fully justify the statement which I made in 1863. But it has been said that, admitting the similarity between the adult brains of man and apes, they are nevertheless, in reality, widely different, because they exhibit fundamental differences in the mode of their development. No one would be more ready than I to admit the force of this argument, if such fundamental differences of development really exist. But I deny that they do exist. On the contrary, there is a fundamental agree- ment in the development of the brain in men and apes. Gratiolet originated the statement that there is a fundamental difference in the development of the brains of apes and that of man — consisting in this ; that, in the apes, the sulci which first make their appearance are situated on the posterior region of the cerebral hemi- spheres, while, in the human foetus, the sulci first become visible on the frontal lobes.'* This general statement is based upon two observations, the one of a Gibbon almost ready to be born, in which the posterior gyri were " well " developed," while those of the frontal lobes were" hardly indicated (1. c. p. 39), and the other of a human foetus at the 22nd or 23rd week of uterogestation, in wliich Gratiolet notes that the insula was un- covered, but that nevertheless " des incisures sement le lobe anttrieur, " une scissure peu profoade indique la separation du lobe occipital, tres- " Chez tous les singes, les plis " posterieurs se ddveloppent les pre- *' miers ; les plis anterieurs se " developpent plus tard, aussi la *' vertfebre oecipitale et la pari^tale " sont-elles relativement tres-grandes " chez le fcetus. L'Homme presente *' une exception remarquable quant *' a I'dpoque de Tapparition des plis " frontaux, qui sont les premiers " indiquds ; mais le developpement " gdn6ral du lobe frontal, envisage " seulement par rapport \ son " volume, suit lesmemes lois que dans " les singes :" Gratiolet, ' Memoire sur les plis cerdbraux de I'Homme et des Primates,' p. 39, Tab. iv. fig. 3. ■' Gratiolet's words are (1. c. p. 39) : " Dans le foetus dont il s'agit " les plis cerdbraux posterieurs sont " bien developpds, tandis que les " plis du lobe frontal sont k peine " indiquds." the figui-e, however CPl. iv. fig. 3), shews the fissure of Eolando, and one of the front;il sulci, plainly enough. Nevertheless, M. Alix, in his 'Notice sur les travaux anthropologiques de Gratio- let' (Mdm. de la Societe d'Anthro- pologie de Paris,' 1868, page 32.), writes thus : " Gratiolet a eu ontre " les mains le cerveau d'un foetus de " Gibbon, singe dminemment su- " perieur, et tellement rapproch^ de " I'orang, que des naturalistes trfes- " compiStents I'ont range parmi les " anthropoides. M. Huxley, par ex- " emple, n'he'site pas sur ce point. " Eh bien, c'est sur le cerveau d'un " foetus de Gibbon que Gratiolet a " vu les circonvolutions du lobe tem- " poro-sphenoidal deja developpces " lorsqu'il n'existent pas encore deplis " sur le lobe frontal. II 6tait done " bien autorise a dire que, chez " I'homme les circonvolutions appa- " raissent d'a en ai, tandis que chez " les singes elles se develoupent " d'co en a." 204 The Descent of Man. PartL rdduit, d'ailleurs des cette dpoque. Le reste de la smface cerebrale " eat encore absoluiaent lisse." Three views of this brain are given in Plate II. figs, 1, 2, 3, of the work citud, showing the upper, lateral and inferior views of the hemi- siphercs, but not the inner view. It is worthy of note that the figure by no means bears out Gratiolet's description, inasmuch as tlie fissure (anterotempoi al) on the posterior half of the face of the hemisphere, is more marked than any of those vaguely indicated in the anterior half. If the figure is correct it in no way justifies Gratiolet's conclusion : " II y a done entre ces cerveaux [those of a Callithrix and of a Gibbon] et " celui du foetus humain une diti'e'rence fondamental. Chez celui-ci, long- " temps avant que les plis temporaux apparaissent, les plis frontaux " essayent d'exister." Since Gratiolet's time, however, the development of the gyri and sulci of the brain has been made the subject of renewed investigation by Schmidt, Bischotf, Pansch," and more particularly by Ecker,'* whose work is not only the latest, but by far the most complete, memoir on the subject. The final results of their inquiries may be summed up as follows : — 1. In the human foetus, the sylvian fissure is formed in the course of the third month of uterogestation. In this, and in the fourth month, the cerebral hemispheres are smooth and rounded (with the exception of the sylvian depression), and they project backwards far beyond the cerebellum. 2. The sulci, properly so called, begin to appear in the interval between the end of the fomth and the beginning of the sixth month of foetal life, but Ecker is careful to point out that, not only the time, but the order, of their appearance is subject to considerable individual variation. In no case, however, are either the frontal or the temporal sulci the earliest. The first which appears, in fact, lies on the inner face of the hemi- sphere (whencte doubtless Gratiolet, who does not seem to have examined that face in his foetus, overlooked it), and is either the internal perpen- dicular (occipito-parietal), or the calcarine sulcus, these two being close together and eventually running into one another. As a rule the occipito-parietal is the earlier of the two. 3. At the latter part of this period, another sulcus, the " posterio, parietal," or " Fissui-e of Eolando " is developed, and it is followed, in the course of the sixth month, by the other principal sulci of the frontal, parietal, temporal and occipital lobes. There is, however, no clear evidence that one of these constantly appears before the other and it is remarkable that, in the brain at the period described and figured by Ecker (I. c. p. 212-13, Taf. 11. figs. 1, 2, 3, 4), the antero- temporal sulcus (^soissure parallele) so characteristic of the ape's brain, is as well, if not better developed than the fissure of Eolando, and is much more marked than the proper frontal sulci. Taking the facts as they now stand, it appears to me that the order of the appearance of the sulci and gyri in the fcetal human brain is in perfect harmony with the general doctrine of evolution, and with the " ' Ueber die typische Anordnung " ' Zur Entwickelungs Geschichte lior Furchen und Windungen auf der Furchen und Windungen der den Grosshira-Hemisp..aren des Grosshirn-Hemispharen im Foetu.i Menschen und der Affen.' ' Archiv des Meuschen.' ' Archiv fiir Anthro- fiir Anthropologie,' iii., 1868. P'dogie,' iii., 1868. Ohap. YII. Stritcture of the Brain. 205 view that man lias been evolved from some ape- like form ; though there can be no doubt that that form was, in many respects, different from any member of the Primates now living. Von Baer taught us, half a century ago, that, in the course of theif development, allied animals put on, at first, the characters of the greater groups to which they belong, and, by degrees, assume those which restrict them within the limits of their family, genus, and species ; and he proved, at the same time, that no developmental stage of a higher animal is precisely similar to the adult condition of any lower animal. It is quite correct to say that a frog passes through the condition of a fish, inasmuch as at one period of its life the tadpole has all the cha- racters of a fish, and, if it went no further, would have to be grouped among fishes. But it is equally true that a tadpole is very different from any known fish. In like manner, the brain of a human foetus, at the fifth month, may correctly be said to be, not only the brain of an ape, but that of au Arctopithecine or marmoset-like ape ; for its hemispheres, with their great posterior lobster, and with no sulci but the sylvian and the calcarine, present the characteristics found only in the group of the Arctopithecine Primates. But it is equally true, as Gratiolet remarks, that, in its widely open syhian fissure, it difiers from the brain of any actual marmoset. No doubt it would be much more similar to the brain of an advanced foetus of a marmoset. But we know nothing whatever of the development of the brain in the marmosets. In the Platyrhini proper, the only observation with which I am acquainted is due to Pansch, who found in the brain of a foetal Cebus ApeUa, in addition to the sylvian fissure and the deep calcarine fissure, only a very shallow auterotempornl fissure (scissure parallele of Gratiolet.) Now this fact, taken together with the circumstance that the antero- temporal sulcus is present in such Platyrhini as the Saimiri, which present mere traces of sulci on the anterior half of the exterior of the cerebral hemispheres, or none at all, undoubtedly, so far as it goes, affords fair evidence in favour of Gratiolet's hypothesis, that the posterior sulci appear before the anterior, in the brains of the Platyrhini. But, it by no means follows, that the rule which may hold good for the Platyrhini extends to the Catarhini. We have no in- formation whatever respecting the development of the brain in the Cynomorpha; and, as regards the Anthropomorpha, nothing but the account of the brain of the Gibbon, near birth, already referred to. At the present moment, there is not a shadow of evidence to shew that the sulci of a chimpanzee's, or orang's, brain do not appear in the same order as a man's. Gratiolet opens his preface with the aphorism. " 11 est dangereux dans Ics sciences de conclure trop vite." I fear he must have for- gotten this sound maxim by the time he had reached the discussion of 1 ™en and apes, in the body of his work. No doubt, the excellent author of one of the most remarkable contributions to the just understanding of the mammalian brain which has ever been made would have been the first to admit the insufiSciency of his data had he lived to profit by the advance of inquiry. The misfortune is Innriif ^rfw^T''' ^^^^ employed by persons incompetent to appreciate their foundation, as arguments in favour of obscurantism." Ln'L!lfr'h^P'''^-^t^^1^^^ de I'Homme. in his terrible pamphlet 'Le Dar- 1873. 206 The Descent of Man. Part I. But it is important to remark that, whether Gratiolot was right or wrong iu his hypothesis respecting the relative order of appearance of the temporal and frontal sulci, the fact remains ; that, before either temporal or frontal sulci, appear, the foetal brain of man presents characters which are found only in the lowest group of the Primates (leaving out the Lemurs) ; and that this is exactly what we should expect to be the case, if man has resulted from the g^radual modifica- tion of the same form as that from which the other Frimates have sprung. C 207 ) Part II. SEXUAL SELECTION. CHAPTEE Vin. x'BmoiPLEs OF Sexual Selection. Secondary sexual characters — Sexual selection — Manner of action — Ex- cess of males — Polygamy — The male alone generally modified through sexual selection — Eagerness of the male — Variability of the male — Choice exerted by the female — Serual compared with natural selection Inheritance, at corresponding periods of life, at corresponding seasons of the year, and as limited by sex — Kelations between the several forms of inheritance — Causes why one sex and the young are not modified thi-ough sexual selection — Supplement on the proportional numbers 01 the two sexes throughout the animal kingdom — The proportion of the sexes in relation to natural selection. "With animals which have their sexes separatedj the males necessarily differ from the females in their organs of reproduction ; and these are the primary sexual characters. But the sexes often differ in what Hunter has called secondary sexual charac- ters, which are not directly connected with the act of reproduc- tion ; for instance, the male possesses certain organs of sense or locomotion, of which the female is quite destitute, or has them more highly-developed, in order that he may readily find or reach her ; or again the male has special organs of prehension for holding her secm-ely. These latter organs, of infinitely diversified kinds, graduate iato those which are commonly ranked as primary, and in some cases can hardly be distinguished from them ; we see instances of this in the complex appendages at the i apex of the abdomen in male insects. Unless indeed we confine 1 the term "primary" to the reproductive glands, it is scarcely j possible to decide which ought to be called primary and whicli ( secondary. 1 The female often differs ft'om the male in having organs for the nourishment or protection of her young, such as the mammary 208 The Descent of Man. Pabt i; glands of mammals, and the abdominal sacks of the marsupials. In some few cases also the male possesses similar organs, -which are wanting in the female, such as the receptacles for the ova in certain male fishes, and those temporarily developed in certain male frogs. The females of most bees are provided witli a special apparatus for collecting and carrying pollen, and their ovipositor is modified into a sting for the defence of the larvse and the community. Many similar cases could be given, but they do not here concern us. There are, however, other sexual differences quite unconnected with the primary reproductive organs, and it with is these that we are more especially concerned —such as the greater size, strength, and pugnacity of the male, his weapons of offence or means of defence against rivals, his gaudy colouring and various ornaments, his power of song, and other such characters. Besides the primary and secondary sexual differences, such as the foregoing, the males and females of some animals differ in structures related to different habits of life, and not at all, or only indirectly, to the reproductive functions. Thus the females of certain flies (Culicidfe and Tabanidss) are blood-suckers, whilst the males, living on flowers, have mouths destitute of mandibles.^ The males of certain moths and of some crustaceans {t.g. Tanais) have imperfect, closed mouths, and cannot feed. The complemental males of certain Ch-ripedes Hve like epiphytic plants either on the female or the hermaphrodite form, and are destitute of a mouth and of prehensile limbs. In these cases it is the male which has been modified, and has lost certain important organs, which the females possess. In other cases it is the female which has lost such parts ; for instance, the female glow-worm is destitute of wings, as also are many female moths, some of which never leave their cocoons. Many female parasitic crustaceans have lost their natatory legs. In some weevil-beetles (Curcu- Liouidse) there is a great difference between the male and female in the length of the rostrum or snout ; ^ but the meaning of thi? and of many analogous differences, is not at all understooci. Differences of structure between the two sexes in relation tu different habits of life are generally confined to the lower animals ; but with some few birds the beak of the male differs from that of the female. In the Huia of New Zealand the difference is wonderfully great, and we hear from Dr. BuHer 1 Westwood, 'Modern Class, of ''■ Kirby and Spenee, 'Introdu - Insects,' vol. ii. 1840, p. 541. For tion to Entomology,' vol. iii. 182 , the statement about Tanais, men- p. 309. tioned below, I am indebted to Fritz * ' Birds of New Zealand,' 1872 Miiller. p. 66. Ohap. YIII. Sexual Selection. 209 that the male uses his strong beak in chiselling the larvfe of insects out of decayed wood, whilst the female probes the softer parts with her far longer, much curved and pliant beak : and thus they mutually aid each other. In most cases, differences of structure between the sexes aje more or less directly connected with the propagation of the species : thus a female, which has to nourish a mtdtitude of ova, requires more food than the male, and consequently requires special means for procuring it. A male animal, which lives for a very short time, might lose its organs for procuring food through disuse, without detriment ; but he would retain his locomotive organs in a perfect state, so that ho might reach the female. The female, on the other hand, might safely lose her organs for flying, swimming, or walking, if she gradually acquired habits which rendered such powers useless. We are, however, here concerned only with sexual selection. This depends on the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction. When, as in the cases above mentioned, the two sexes differ in structure in relation lo different habits of life, they have no doubt been modified through natural selection, and by inheritance limited to one and the same sex. So again the primary sexual organs, and those for nourishing or protecting the young, come under the same influence ; for those individuals which generated or noiu-ished their offspring best, would leave, cceteris ■paribus, the greatest number to inherit their superiority ; whilst those which generated or noiirished their ofispring badly, would leave but few to inherit their wisaker powers. As the male has to ■find the female, he requires organs of sense and locomotion, but if these organs are necessary for the other purposes of life, as is generally the case, they will have been developed through natural selection. When the male has found the female, he sometimes absolutely reqiiires prehensile organs to hold her; thus Dr. Wallace informs me that the males of certain moths cannot unite with the females if their tarsi or feet are broken. The males of many oceanic crustaceans, when adult, have their legs and antennee modified in an extraordinary manner for the prehension of the female ; hence we may suspect that it is be- cause these animals are washed about by the waves of the open sea, that they reqixire these organs in order to propagate their kind, and if so, their development has been the result of ordinary or natural selection. Some animals extremely low in the scale have been modified for this same purpose ; thus the males of certain parasitic worms, when fully grown, have the lower surface of the terminal part of their bodies roughened 1' no The Descent of Man. Part II. like a rasp, and witli this they coil round and permanently hold the females.'' When the two sexes follow exactly the same habits of life, and the male has the sensory or locomotive organs more highly developed than those of the female, it may be that the perfection of these is indispensable to the male for finding the female ; but in the vast majority of cases, they serve only to give one male an advantage over another, for with sufficient time, the less well- endowed males would succeed in pairing with the females ; and judging from the structure of the female, they would be in all other respects equally well adapted for their ordinary habits of life. Since in such cases the males have acquii-ed theii- present structure, not from being better fitted to survive in the straggle for existence, but from having gained an advantage over other males, and from having transmitted this advantage to their male offspring alone, sexual selection must here have come into action. It was the importance of this distinction which led me to designate this form of selection as Sexual Selection. So again, if the chief service rendered to the male by his prehensile organs is to prevent the escape of the female before the arrival of other males, or when assaulted by them, these organs will have been perfected through sexual selection, that is by the advantage acquired by certain individuals over their rivals. But in most cases of this kind it is impossible to distinguish between the effects of natural and sexual selection. Whole chapters could be filled with details on the differences between the sexes in their sensoiy, locomotive, and prehensile organs. As, however, these structures are not more interesting than others adapted for the ordinary pm-poses of life I shall pass them over almost entirely, giving only a few instances under each class. There are many other structures and instincts which must have been developed through sexual selection — such as the weapons of offence and the means of defence of the males for fighting with and driving away their rivals— their courage and pugnacity — their various ornaments — their contrivances for pro- * M. Perrier advances this case claspers of certain male animals (' Revue Scientifique,' Feb. 1, 1873, could not have been developed p. 865) as one fatal to the belief in through the choice of the female I sexual selection, inasmuch as he Had I not met with this remark, I .<;',ipposes that I attribute all the should not have thought it possible differences between the sexes to for any one to h.ave read this chapter sexual selection. This distinguished and to have imagined that I main- naturalist, therefore, like so many tain that the choice of the female other Frenchmen, has not taken the had anything to do with the develop- trouble to understand even the first, ment of the prehensile organs in the piinciples of sexual selection. An male, itiglish naturalist insists that the Chap. YIU. Sextial Selection. 211 ducing TOCJiI or instrumental music — and their glands for emitting odours, most of these latter structures serving only to iillui'e or excite the female. It is clear that these characters are the result of sexual and not of ordinary selection, since unarmed, unomamented, or unattractive males would succeed equally "well in the battle for life and in leaving a numerous progeny, but for the presence of better endowed males. We may infer that this would be the case, because the females, which are unarmed and unornamented, are able to survive and procreate their kind. Secondary sexual characters of the kind just referred to, will be fully discussed in the following chapters, as being in many respects interesting, but especially as depending on the will, choice, and rivalry of the individuals of either sex. When we behold two males fighting for the possession of the female, or. several male birds displaying their gorgeous plumage, and per- forming strange antics before an assembled body of females, we cannot doubt that, though led by instinct, they know what they are about, and consciously exert then* mental and bodily powers. Just as man can improve the breed of his game-cocks' by the selection of those birds which are victorious in the cockpit, so it appears that the strongest and most vigorous males, or those provided with the best weapons, have prevailed under nature, and have led to the improvement of the natural breed or species. A slight degree of variability leading to some advantage, how- ever shght, in reiterated deadly contests would suffice for the work of sexual selection; and it is certain that, secondary sexual characters are eminently variable. Just as man can give beauty, accordmg to his standard of taste, to his male poultry, or more strictly can modify the beauty originally acquired by the parent species, can give to the Sebright bantam a new and elegant plumage, an erect and peculiar carriage— so it appears that female bu-ds m a state of nature, have by a long selection of the more attractive males, added to their beauty or other attractive quahties. No doubt tliis implies powers of discrimination and taste on the part of the female which Avill at first appear extremely improbable; but by the facts to be adduced here- after, I hope to be able to shew that the females actually have these powers. When, however, it is said that the lower ammals have a sense of beauty, it must not be supposed that such sense is comparable with that of a cultivated man, with his multiform and complex associated ideas. A more just com- parison would be between the taste for the beautiful in animals, and that in the lowest savages, who admire and deck themselves with any brilliant, glittering, or curious object. From our ignorance on several points, the precise manner in p 2 The Descent of Man. Part IL which sexual selection acts is somewhat uncertain. Neverthe- less if those naturahsts who already believe in the mutability of species, will read the following chapters, they will, I think, agree with me, that sexual selection has played an important part in the history of the organic world. It is certain that amongst almost all animals there is a straggle between the males for the possession of the female. This fact is so notorious that it would be superfluous to give instances, Hence the females have the opportunity of selecting one out of several males, on the suppo- sition that their mental capacity suffices for the exertion of a choice. In many cases special circumstances tend to make the straggle between the males particularly severe. Thus the males of our migratory birds generally arrive at their places of breeding before the females, so that many males are ready to contend for each female. I am informed by Mr. Jenner Weir, that the bird- catchers assert that this is invariably the case with the nightin- gale and blackcap, and with respect to the latter he can himself confirm the statement. Mr. Swaysland of Brighton has been in the habit, during the last forty years, of catching our migratory birds on their first arrival, and he has never known the females of any species to arrive before their males. During one spring he shot thirty -nine males of Eay's wagtail (^Budytes Raii) before he saw a single female. Mr. Gould has ascertained by the dissection of those snipes which arrive the fii'st in this country, that the males come before the females. And the Hke holds good with most of the migratory birds of the United States." The majority of the male salmon in oiir rivers, on coming up from the sea, are ready to breed before the females. So it appeal's to be with frogs and toads. Throughout the great class of insects the males almost always are the first to emerge from the pupal state, so that they generally abound for a time before any females can be seen." The cause of this difference between the males and females in their periods of arrival and maturity is sufficiently obvious. Those males which annually first migrated into any country, or which in the spring were first ready to breed, or were the most eager, would leave the largest number of offspring ; and these ' J. A. Allen, on the 'Mammalg rodite plants are dichogamous; that and Winter Birds of Florida,' Bull, is, their male and female organs are Comp. Zoology, Harvard College, p. not ready at the same time, so that 268. they cannot be self-fertilised. Now * Even with those plants in which in such flowers, the pollen is in 'he sexes are separate, the male general matured before the stigma, flowers are generally mature be- though there are exceptional cases fore the female. As first shewn in which the female oi-gans are by C. K. Sprengel, many hermaph- beforehand. Obap. VIII. Sexual Selection. 213 would tend to inherit similar instincts and constitutions. It must be borne in mind that it would have been impossible to change very materially the time of sexual maturity in the females, without at the same time interfering with the period of the production of the young — a period which must be determined by the seasons of the year. On the whole there can be no doubt that with almost all animals, in which the sexes are separate, there is a constantly recurrent struggle between the males for the possession of the females. Our difficulty in regard to sexual selection lies in imderstand- ing how it is that the males which conquer other males, or those which prove the most attractive to the females, leave a greater mmiber of offspring to inherit their superiority than their beaten and less attractive rivals. Unless this result does follow, the characters which give to certain males an advantage over others, could not be perfected and augmented through sexual selection. When the sexes exist in exactly equal numbers, the worst-endowed males will (except where polygamy prevails), ultimately find females, and leave as many offspring, as well fitted for their general habits of life, as the best-endowed males. Prom various facts and considerations, I formerly inferred that with most animals, in which secondary sexual characters are well developed, the males considerably exceeded the females in number; but this is not by any means always true. If the males were to the females as two to one, or as three to two, or oven in a somewhat lower ratio, the whole affair would be simple; for the better-armed or more attractive males would leave the largest number of offspring. But after investigating, as far as possible, the numerical proportion of the sexes, I do not believe that any great inequality in number commonly exists. In most cases sexual selection appears to have been effective in the following manner. Let us take any species, a bird for instance, and divide the females inhabitmg a district into two equal bodies, the one consisting of the more vigorous and better-nourished individuals, and the other of the less vigorous and healthy. The former, there can be little doubt, would be ready to breed in the spring before the others ; and this is the opinion of Mr. Jenner Weir, who has carefully attended to the habits of birds during many years. There can also be no doubt that the most vigorous, best-nourished and earUest breeders would on an average succeed m rearmg the largest number of fine offspring.^ The males, as we have seen, are generaUy ready to breed before the ' Here is excellent evidence on an experienced ornithologist. Mr. the character of the offspring from J. A. Allen, in speaking (' Mammals 214 Tfie Descent of Man. Paet It females ; the strongest, and with some species the best armed of the males, drive away the weaker ; and the former would then ■unite with the more vigorous and better-nourished females, be- cause they are the first to breed.* Such vigorous pairs would surely rear a larger number of offspring than the retarded females, which would be compelled to unite with the conquered and loss powerful males, supposing the sexes to be numerically equal ; and this is all that is wanted to add, in the course of successive generations, to the size, strength and courage of the males, or to improve their weajpons. But in very many cases the males which conquer their zivals, do not obtain possession of the females, independently of the choice of the latter. The courtship of animals is by no means so simple and short an affair as might be thought. The females are most excited by, or prefer pairing with, the more ornamented males, or those which are the best songsters, or play the best antics ; but it is obviously probable that they would at the same time prefer the more vigorous and lively males, and this has in some cases been confirmed by actual observation.* Thus the more vigorous females, which are the first to breed, will have the choice of many males ; and though they may not always select the strongest or best armed, they will select those which are vigorous and well armed, and in other respects the most at- tractive. Both sexes, therefore, of such early pairs would as above explained, have an advantage over others in rearing offspring ; and this apparently has sufficed during a long course of generations to add not only to the strength and fighting powei-s of the males, but likewise to their various ornaments or other attractions. In the converse and much rarer case of the males selecting particular females, it is plain that those which were the most vigorous and had conquered others, would have the freest choice ; and it is almost certain that they would select vigorous as well as attractive females. Such pairs would have an advan- and Winter Birds of E. Florida,' p. 229) of the later broods, after the accidental destruction of the first, says, that these " are found to be " smaller and paler-coloured than those hatched earlier in the sea- ^ son. In cases where several broods " are reared each year, as a general " rule the birds of the earlier broods " seem in all respects the most per- " feet and vigorous." ' Hermann Miiller has come to this same conclusion with respect to those female bees which are the first to emerge from the pupa each year. See his remarkable essay, 'Anwendung den Darwin'schen Lehre auf Bienen,' ' Verb. d. V. Jahrg.' xxis. p. 45. " With respect to poultry, I have received information, hereafter to be given, to this effect. Even with birds, such as pigeons, which pair for life, the female, as I hear frori; Mr. Jenner Weir, will desert her mate if he is injured or grows weak. Chap. VIII. Sexual Selection. 215 tago in rearing offspring, more especially if the male had the power to defend the female during the pairing-season as occurs with some of the higher animals, or aided her in providing for the young. The same principles would apply if each sex pre- ferred and selected certain individuals of the opposite sex ; supposing that they selected not only the more attractive, but likewise the more vigorous individuals. Numericai PropoHion of the Two Sexes. — I have remarked that sexual selection would be a simple affair if the males were con- siderably more numerous than the females. Hence I was led to investigate, as far as I could, the proportions between the two sexes of as many animals as possible; but the materials are scanty. I wiU here give only a brief abstract of the results, retaining the details for a supplementary discussion, so as not to interfere with the course of my argument. Domesticated animals alone afford the means of ascertaining the propor- tional numbers at birth; but no records have been specially kept for this purpose. By indirect means, however, I have collected a considerable body of statistics, from which it appears that with most of our domestic animals the sexes are nearly equal at bii'th. Thus 25,560 births of race-horses have been recoi'ded during twenty-one years, and the male bii'ths were to the female bitths as 99"7 to 100. In greyhounds the in- equality is greater than with any other animal, for out of 6878 bu'ths dm'ing twelve years, the male bii'ths were to the female as 110"1 to 100. It is, however, in some degree doubtful whether it is safe to infer that the jjroportion would be the same \mder natural conditions as nnder domestication ; for slight and unknown differences in the conditions affect the proportion of the sexes. Thus with mankind, the male births in England are as 104-5, in Eussia as 108"9, and with the Jews of Livonia as 120, to 100 female births. But I shall recur to this ciirious point of the excess of male births in the supplement to this chapter. At the Cape of Good Hope, however, male children of European extraction have been born during several years in the proportion of between 90 and 99 to 100 female children. For our present purpose we are concerned with the proportion of the sexes, not only at birth, but also at maturity, and this adds another element of doubt ; for it is a Avell-ascertained fact that with man the number of males dying before or during birth, and during the first few years of infancy, is considerably larger than that of females. So it ahnost certainly is with male lambs, and probably with some other animals. The males of some species kill one another by fighting ; or they drive one another about 2l6 The Descent of Man. Pakt Ii. until they become greatly emaciated. They must also be Often exposed to various dangers, whilst wandering about in eager search for the females. In many kinds of fish the males are much smaller than the females, and they are beheved often to be devoured by the latter, or by other fishes. The females of some bu'ds appear to die earlier than the males; they art also liable to be destroyed on then- nests, or whilst in charge of their young. With insects the female larvae are often larger than those of the males, and would consequently be more likely to be devoured. In some cases the mature females are less active and less rapid in their movements than the males, and could not escape so well from danger. Hence, with animals in a state of nature, we must rely on mere estimation, in order to judge of the proportions of the sexes at maturity ; and this is but Uttle trustworthy, except when the inequality is strongly marked. Nevertheless, as far as a judgment can be formed, we may conclude from the facts given in the supplement, that the -males of some few mammals, of many bii-ds, of some fish and insects, are considerably more numerous than the females. The proportion between the sexes fluctuates shghtly during successive years : thus with race-horses, for every 100 mares born the stallions varied from 107"1 in one year to y2'6 in another year, and with greyhounds from 116'3 to 95-3. But had larger num- bers been tabulated thi-oughout an area more extensive than England, these fluctuations would probably have disappeared ; and such as th/jy are, would hardly sufiice to lead to effective sexual selection in a state of nature. Nevertheless, in the cases of some few wild animals, as shewn in the supplement, the proportions seem to fluctuate either duiing different seasons or in different locaUties in a sufficient degree to lead to such selection. For it should be observed that any advantage, gained during certain years or in certain localities by those males which were able to conquer their rivals, or were the most attractive to the females, would probably be transmitted to the offspring, and would not subsequently be eliminated. Dm-ing the succeeding seasons, when, from the equality of the sexes, every male was able to procure a female, the stronger or more at- tractive males previously produced would still have at least as good a chance of lea^dng offspring as the weaker or less attractive. Polygamy. — The practice of polygamy leads to the same results as would foUow from an actual inequality in the number of the sexes; for if each male secui-es two or more females, many males cannot pair ; and the latter assuredly will be the weaker or less attractive individuals. Many mammals and some few birds ara Chap. VIIL Sexual Selection. 217 polygamous, but with animals belonging to the lower classes 1 have^found no evidence of this habit. The intellectual powers of such animals are, perhaps, not sufficient to lead them to collect and guard a harem of females. That some relation exists between polygamy and the development of secondary sexual characters, appears nearly certain ; and this supports the view- that a numerical preponderance of males Avould be eminently favoui-able to the action of sexual selection. Nevertheless many animals, which are strictly monogamous, especially bii-ds, display strongly-marked secondary sexual characters ; whilst some few animals, which are polygamous, do not have such characters. "We will first briefly run through the mammals, and then turn, to birds. The gorilla seems to be polygamous, and the male differs considerably from t'he female; so it is with some baboons, which live in herds contaimng twice as many adult females as males. In South America the Mycetes caraya presents well- marked sexual differences, in colour, beard, and vocal organs ; and the male generally Hves with two or three wives : the male of the Cehus capucinus differs somewhat from the female, and appears to be polygamous.'" Little is known on this head with respect to most other monkeys, but some species are strictly monogamous. The ruminants are eminently polygamous, and they present sexual differences more frequently than almost any other group of mammals; this holds good, especially in their weapons, but also in other characters. Most deer, cattle, and sheep are polygamous ; as are most antelopes, though some are monogamous. Sir Andrew Smith, in speaking of the antelopes of South Africa, says that in herds of about a dozen there was rarely more than one mature male. The Asiatic Antilope saiga appears to be the most inordinate polygamist in the world ; for Pallas'' states that the male drives away all rivals, and collects a herd of about a hundred females and kids together ; the female is hornless and has softer hair, but does not otherwise differ much from the male. The mid horse of the Falkland Islands and of the "Western States of N. America is polygamous, but, except in his greater size and in the proportions of his body, differs but little from the mare. The wild boar presents w^ell-marked sexual On the Gorilla, Savage and Wyman 'Boston Journal of Nat. Hist.' vol. V. 1845-47, p. 423. On Cynocephalus, Brehm, 'Illust. Thier- leben,' B. i. 1864, s. 77. On My- cetes, Rengger, 'Naturgesch.: Saage- thiere von Paraguay,' 1830, s. 14, 20. Cebns, Bj-ehm, ibid. s. 108. " Pallas, 'Spicilegia Zoolog., Fasc. xii. 1777, p. 29. Sir Andrew- Smith, ' Illustrations of the Zoology of S. Africa,' 1849, pi. 29, on the Kobus. Owen, in his ' Anatomy of Vertebrates ' (vol. iii. 1868, p. 633) gives a table shewing incidentally which species of antelopes are gre- garious. 2l8 The Descent of Man. Part 11. characters, in his great tusks and some other points. Ifl Europe and in India ho leads a solitary life, except during the breeding- season ; but as is believed by Sir W. Elhot, who has had many opportunities in India of observing this animal, he consorts at this season "with several females. Whether this holds good in Europe is doubtful, but it is supported by some evidence. The adult male Indian elephant, like the boar, passes much of his time in solitude ; but as Dr. Campbell states, when with others, " it is rare to find more than one male with a whole herd " of females ;" the larger males expelling or killing the smaller and weaker ones. The male differs from the female in liis immense tusks, greater size, strength, and endurance; so great is the difference in these respects, that the males when caught are valued at one-iifth more than the females.^^ The sexes of other pachydermatous animals differ very little or not at all, and, as far as known, they are not polygamists. Nor have I heard of any species in the Orders of Cheiroptera, Edentata, Insectivora and Eodents being polygamous, excepting that amongst the Eodents, the common rat, according to some rat-catchers, lives with several females. Nevertheless the two sexes of some sloths (Edentata) differ in the character and colour of certain patches of hau' on their shoulders.^' And many kinds of bats (Chehoptera) present well-marked sexual differences, chiefly in the males possessing odoriferous glands and pouches, and by their being of a lighter colour." In the great order of Eodents, as far as I can learn, the sexes rarely differ, and when they do so, it is but shghtly in the tint of the fur. As I hear fi-om Sir Andrew Smith, the lion in South Africa sometimes lives with a single female, but generally with more, and, in one case, was found with as many as five females; so that he is polygamous. As far as I can discover, he is the only polygamist amongst all the terrestrial Carnivora, and he alone presents well-mai-ked sexual characters. If, however, we tui-n toTthe marine Carnivora, as we shall hereafter see, the case is widely different; for many species of seals offer extraordinary sexual differences, and they are eminently polygamous. Thus, according to Peron, the male sea-elephant of the Southern Ocean always possesses several females, and the sea-lion of Eorster is said to be surrounded by from twenty to thirty females. In the North, the male sea-bear of Steller is accompanied by even a 12 Dr. Campbell, in ' Proc. Zoo- " Dr. Gray, in ' Annals and log Soc' 1869, p. 138. See also an Mag;, of Nat. Hist.' 1871, p. 302. interesting paper, by Lieut. Joha- '» See Dr. Dobson's excellent Btone, in 'Proc. Asiatic Soc. of paper, in ' Proc. Zoolog. ooc. 18(3. Bengal,' May. 1868. p- -'H. CUAP. Vill. 219 gi-oater number of females. It is an interesting fact, as Dr. Gill remarks/^ that in the monogamous species, "or those " living in small communities, there is little difference in size " between the males and females ; in the social species, or rather " those of which the males have harems, the males are vastly " larger than the females." Amongst birds, many species, the sexes of which differ greatly from each other, are certainly monogamous. In Great Britain: we see well-marked sexual differences, for instance, in the wild- duck which pairs with a single female, the common blackbird, and the bullfinch which is said to pair for life. I am informed by Mr. Wallace that the Kke is true of the Chatterers or Cotingidte of South America, and of many other birds. In several groups I have not been able to discover whether the species are polygamous or monogamous. Lesson says that birds of paradise, so remarkable for their sexual differences, are polygamous, but Mr. Wallace doubts whether he had sufficient evidence. IMr. Salvia tells me he has been led to beheve that humming-birds are polygamous. The male widow-bird, remarkable for his caixdal plumes, certainly seems to be a polygamist.^" I have been assui-ed by Mr. Jenner Weii- and by others,, that it is somewhat common for three starlings to frequent the same nest ; but whether this is a case of polygamy or polyandry has not been ascertained. The GalLLnacese exhibit almost as strongly marked sexual differences as birds of paradise or humming-birds, and many of the species are, as is well known, polygamous ; others being strictly monogamous. What a contrast is presented between the sexes of the polygamous peacock or pheasant, and the mono- gamous guinea-fowl or partridge ! Many similar cases could bo given, as in the grouse tribe, in which the males of the poly- gamous capercailzie and black-cock differ greatly from the females; whilst the sexes of the monogamous red grouse and ptarmigan differ very Mttle. In the Oursores, except amongst the bustards, few species offer strongly-marked sexual dif- ferences, and the great bustard (^Otis tarda) is said to be poly- gamous. With the Grallatores, extremely few species differ sexually, but the ruff {Machetes puc/nax) affords a marked " The Eared Seals, ' American Great Bustard, see L. Lloyd, ' Game >faturalist,' vol. iv., Jan. 1871. Birds of Swedea,' 1867, p. 19, and •« ' The Ibis,' vol. iii. 1861 p. 182. Montagu and Selby speak of 133, on the Progne Widow-bird, the Black Grotise as polygamous See also on the Vidua axillaris, and of the Red Grouse as mcno- ibid. vol. ii. 1860, p. 211. On the gamous. polygamy of the Capercailzie and 220 The Descent of Man. Part II. exception, and this species is believed by Montagu to be a polygamist. Hence it appears that amongst birds there often exists a close relation between polygamy and the development of strongly-marked sexual differences. I asked Mr. Bartlett, of the Zoological Gardens, vrho has had very large experience with bii-ds, whether the male tragopan (one of the Gallinacese) was polygamous, and I was struck by his answering, "I do not " know, but should think so from his splendid colours." It deserves notice that the instinct of pairing with a single female is easily lost under domestication. The wild-duck Ls strictly monogamous, the domestic-duck highly polygamous. The Eev. W. D. Fox informs me that out of some half-tamed wild-ducks, on a large pond in his neighbourhood, so many mallards were shot by the gamekeeper that only one was left for every seven or eight females ; yet unusually large broods were reared. The guinea-fowl is strictly monogamous ; but Mr. Fox finds that his birds succeed best when he keeps one cock to two or three hens. Canary-birds pair in a state of natui'e, but the breeders in England successfully put one male to four or five females. I have noticed these cases, as rendering it probable that wild monogamous species might readily become either temporarily or permanently polygamous. Too little is known of the habits of reptiles and fishes to enable us to speak of their marriage arrangements. The stickle-back (Gasterosteus), however, is said to be a polygamist •^'^ and the male during the breeding season differs conspicuously from the female. To sum up on the means through which, as far as we can judge, sexual selection has led to the development of secondary sexual characters. It has been shewn that the largest number of vigorous offspring will be reared from the pairing of the strongest and best-ai-med males, victorious in contests over other males, with the most vigorous and best-nomished females, which are the first to breed in the spring. If such females select the more attractive, and at the same time vigorous males, they will rear a larger number of offspring than the retarded females, which must pair with the less vigorous and less attractive males. So it will be if the more vigorous males select the more attractive and at the same time healthy and vigorous females ; and this will especially hold good if the male defends the female, and aids in providing food for the young. The ad- vantage thus gained by the more vigorous pairs in rearing a larger number of offspring has apparently sufficed to render sexual selection efficient. But a large numerical preponderance " Noel Humphreys, ' River G.irdens,' 1857. Chap. VHI. Sexual Selection. 221 of males over females will be still more efficient ; whether the pi-eponderance is only occasional and local, or permanent; whether it occurs at birth, or afterwards from the greater de- struction of the females ; or whether it indirectly follows from the practice of polygamy. The Male generally more modified than the Female. — Throughout the animal kingdom, when the sexes differ in external appearance, it is, with rare exceptions, the male which has been the more modified ; for, generally, the female retains a closer resemblance to the young of her own species, and to other adult members of the same group. The cause of this seems to lie in the males of almost all animals having stronger passions than the females. Hence it is the males that fight together and sedulously display their charms before the females ; and the victors transmit their superiority to their male offspring. Why both sexes do not thus acquire the characters of their fathers, will be considered here- after. That the males of all mammals eagerly pursue the females is notorious to every one. So it is with bu'ds ; but many cock birds do not so much pursue the hen, as display their plumage, perform strange antics, and pour forth their song in her presence. The male in the few fish observed seems much more eager than the female ; and the same is true of alligators, and apparently of Batrachians. Throughout the enormous class of insects, as Kirby remarks," " the law is, that the male shall seek " the female." Two good authorities, Mr. Blackwall and Mr. 0. Spence Bate, tell me that the males of spiders and crustaceans are more active and more erratic in their habits than the females. When the organs of sense or locomotion are present in the one sex of insects and crustaceans and absent in the other, or when, as is frequently the case, they are more highly developed in the one than in the other, it is, as far as I can discover, almost invariably the male which retains such organs, or has them most developed; and this shews that the male is the more active member in the courtship of the sexes." '* Kirby and Spence, 'Introduc- tion to Entomology,' vol. iii. 1826 p. 342. ' " One parasitic Hymenopterous insect (Westwood, ' Modern Class, of Insects:,' vol. ii. p. 160) forms an exception to the rulr, as the male has rudimentary wmgs, and never quits the cell in which it is born, whilst the female has well-developed wings. Audouin believes that the females of this species are impreg- nated by the males which are born in the same cells with them ; but it is much more probable that the females visit other cells, so that close interbreeding is thus avoided. We shall hereafter meet in various classes, with a few exceptional cases, in which the female, instead of the male, is the seeker and wooer. 222 The Descent of Man. Pakt IL The female, on the other hand, with the rarest exceptions, is less eager than the male. As the illustrious Hunter ^ long ago observed, she generally " requires to be courted ;" she is coy, and may often be seen endeavouring for a long time to escape from tho male. Every observer of the habits of animals will be able to call to mind instances of this land. It is shown by various facts, given hereafter, and by the results fahly attributable to sexual selection, that the female, though comparatively passive, generally exerts some choice and accepts one male in preference to others. Or she may accept, as appearances would sometimes lead us to believe, not the male which is the most attractive to her, but the one which is the least distasteful. The exertion of some choice on the part of the female seems a law almost as general as the eagerness of the male. We are natui'ally led to enquire why the male, in so many and such distinct classes, has become more eager than the female, so that he searches for her, and plays the more active part in court- ship. It would be no advantage and some loss of power if each sex searched for the other; but why should the male almost always be the seeker? The ovules of plants after fertili- sation have to be nourished for a time; hence the pollen is necessarily brought to the female organs — being placed on the stigma, by means of insects or the wind, or by the spontaneous movements of the stamens ; and in the Algae, &c., by the loco- motive power of the antherozooids. With lowly-organised aquatic animals, permanently affixed to the same spot and having their sexes separate, the male element is invai'iably brought to the female ; and of this we can see the reason, for even if the ova were detached before fertilisation, and did not require subsequent nourishment or protection, there would yet be greater difficulty in transporting them than the male element, because, being larger than the latter, they are produced in far smaller numbers. So that many of the lower animals are, in this re- spect, analogous with plants.^^ The males of affixed and aquatic animals having been led to emit their fertilising element in this way, it is natui'al that any of their descendants, which rose in the scale and became locomotive, should retain the same habit ; and they would approach the female as closely as pos- sible, in order not to risk the loss of the fertilising element in a long passage of it through the water. With some few of tho lower 'Essays and Observations.' of the male and female reproductive edited by Owen, vol. i. 1861, \, cells, remarks, " verhalt sich die 194. 2' Prof. Sachs (' Lehrbuch de.* Botanik,' 1870, s. 633) in speaking " eine bei der Vereinigung activ, " . . . die audero erscheint bei der " Vereinigung passiv." ciHAP. vin. Sexual Selection. 223 animals, the females alone are fixed, and the males of these must be the seekers. But it is difficult to understand why the males of species, of which the i)rogenitors were primordially free, should invariably have acquired the habit of approaching the females, instead of being approached by them. But in all cases, in order that the males should seek efficiently, it would be necessary that they should be endowed with strong passions ; and the acquire- ment of such passions would naturally follow from the more eager leaving a larger number of offspring than the less eager. The great eagerness of the males has thus indirectly led to their much more frequently developing secondary sexual characters than the females. But the development of such characters would be much aided, if the males were more liable to vary than the females — as I concluded they were — after a long study of domesticated animals. Von Nathusius, who has had very wide experience, is strongly of the same opinion.''^ Good evidence also in favour of this conclusion can be produced by a comparisoE of the two sexes in mankind. During the Novara Expeditions^ a vast number of measurements was made of various parts of the body in different races, and the-men were found in almost every case to present a greater range of variation than the women ; but I shall have to reciu* to this subject in a future chapter. Mr. J. Woodj^* who has carefully attended to the variation of the muscles in man, puts in italics the conclusion that " the greatest number of abnormalities in each subject is found in the males." He had previously remarked that "altogether in 102 subjects, the varieties " of redundancy were found to be half as many again as in " females, contrasting widely with the greater frequency of " deficiency in females before described." Professor Macalister likewise remarks that variations in the muscles " are probably " more common in males than females." Certain muscles which are not normally present in mankind are also more frequently developed in the male than in the female sex, although exceptions to this rule are said to occur. Dr. Burt Wilder has tabulated the cases of 152 individuals with supernumerary digits, of which 86 were males, and 39, or less than half, females, the remaining 27 bemg of unknown sex. It should not, however, be overiooked " 'Voi-trage Uber Viehzucht,' 1872, p. 63. ' my 'Variation of Animals and Plants under Domestication,' vol, ii. " 'Eeise der Novara: Anthro- polog. Theil,' 1867, s. 216-269. The results were calculated by Dr. Weisbach from measurements made by Drs. K. Scherzer and Schwarz. On the greater variability of the ciales of domesticated animals, see vol. ii. No. 3, 1868, p. 9. svi. July 1868, pp. 519 and 524. " 'Proc. Royal Insh Academy, vol. s. 1868, p. 123. 'Massachusetts Medical Soc 1868, p. 75. ' Proceedings Royal Soc' vol. 224 The Descent of Man. Part IL that women would more frequently endeavour to conceal a deformity of this kind than men. Again, Dr. L. Meyer asserts that the ears of man are more variable in form than those of woman.*' Lastly the temperature is more variable in man than in woman.** The cause of the greater general variability in the male sex than in the female is unknown, except in so far as secondary sexual characters are extraordinarily variable, and are usually confined to the males; and, as we shall presently see, this fact is to a certain extent, intelligible. Through the action of sexufil and natural selection male animals have been rendered in very many instances widely different from their females; but in- dependently of selection the two sexes, from differing constitu- tionally, tend to vary in a somewhat different manner. The female has to expend much organic matter in the formation of her ova, whereas the male expends much force in fierce contests with his rivals, in wandering about in search of the female, in exerting his voice, pouring out odoriferous secretions, &c. : and this expenditure is generally concentrated within a short period. The great vigour of the male during the season of love seems often to intensify his colours, independently of any marked dif- ference from the female.^* In mankind, and even as low down in the organic scale as in the Lepidoptera,, the temperature of the body is higher in the male than in the female, accompanied in the case of man by a slower pulse.^ On the whole the expenditure of matter and force by the two sexes is probably nearly equal, though effected in very different ways and at different rates. From the causes just specified the two sexes can hardly fail to differ somewhat in constitution, at least during the breeding season; and, although they may be subjected to exactly the same conditions, they will tend to vary in a different manner. If such variations are of no service to either sex, they will not be accumulated and increased by sexual or natural selection. Never- theless, they may become permanent if the exciting cause acts " 'Archiv fur Path. Auat. und Phys.' 1871, p. 488. ^' The conclusions recently ar- rived at by Dr. J. Stockton Hough, on the temperature of man, are given in the ' Pop. Science Review,' Jan. 1st, 1874, p. 97. 2' Prof, ilantegazza is inclined to believe (' Lettera a Carl o Darwin,' ' Archivio per 1' Anthr opologia,' 1871, p. 306) that the bright colours, common in so many male animals, are due to the presence and retention by them of the sperm- atic fluid ; but this can hardly be the case ; for many male birds, for instance young pheasants, become brightly coloured in the autumn of their first year. For mankind, see Dr. J. Stock- ton Hough, whose conclusions are given in the 'Pop. Science Review,' 1874, p. 97. See Girard's observa- tions on the Lepidoptera, as given in the ' Zoological Record,' 1869, p. 347. (Jhap. Vlll. Sexual S elect ioji. 225 permanently ; and in accordauco with a frequent form of inheri- tance they may be transmitted to that sex alone in which they first appeared. In this case the two sexes will come to pj'esent permanent, yet unimportant, differences of character. For instance, Mr. Allen shews that with a large number of birds inhabiting the northern and southern United States, the speci- mens from the south are darker-coloured than those from the north ; and this seems to be tho direct result of the difference in temperature, hght, &c., between the two regions. Now, in some few cases, the two sexes of the same species appear to have been differently affected ; in the AgeJoeus phwniceus the males have had their colours greatly intensified in the south; whereas with Car- dinalis virginianus it is the females which have been thus affected ; with Qidscalus maj'm- the females have been rendered extremely variable in tint, whilst the males remain nearly uniform.*' A few exceptional cases occur in various classes of animals, in which the females instead of the males have acquired well pronounced secondaiy sexual characters, such as brighter colours, greater size, strength, or pugnacity. With bii'ds there has some- times been a complete transposition of the ordinary characters proper to each sex ; the females having become the more eager in coui'tship, the males remaining comparatively passive, ■ but apparently selecting the more attractive females, as we may infer from the results. Certain hen birds have thus been rendered more highly coloured or otherwise ornamented, as well as more powerful and pugnacious than the cocks ; these characters being transmitted to the female offspring alone. It may be suggested that in some cases a double process of selection has been carried on; that the males have selected the more attractive females, and the latter the more attractive males. This process, however, though it might lead to the modification of both sexes, would not make the one sex different from the other, unless indeed their tastes for the beauti- ful differed ; but this is a supposition too improbable to be worth considering in the case of any animal, excepting man. There are, however, many animals in which the sexes resemble each other, both being furnished with the same ornaments, which analogy would lead us to atti-ibute to the agency of sexual selection. In such cases it may be suggested with more plausi- bility, that there has been a double or mutual process of sexual selection ; the more vigorous and precocious females selecting the more attractive and vigorous males, the latter rejecting all except tho more attractive females. But from what we know »' ♦ ilammals and Birds of E. Florida,' pp. 234, 280, 295. Q 226 The Descent of Man. Pakt II of tLo habits of animals, this view is hardly probable, for the male is generally eager to pair with any female. It is more probable that the ornaments common to both sexes were acquire-- by one sex, generally the male, and then transmitted to the ofi- spring of both sexes. If, indeed, during a lengthened period the males of any species were gi-eatly to exceed the females in aumber, and then dm-ing another lengthened period, but under different conditions, the reverse were to occur, a double, but not simultaneous, process of sexual selection might easily be carried on, by which the two sexes might be rendered widely different. We shall hereafter see that many animals exist, of which neither sex is brilliantly coloured or provided with special orna- ments, and yet the members of both sexes or of one alone have probably acquired simple colours, such as white or black, through sexual selection. The absence of bright tints or other ornaments may be the result of variations of the right kind never having occurred, or of the animals themselves having preferred plain black or white. Obscure tints have often been developed through natural selection for the sake of protection, and the acquirement thi'ough sexual selection of conspicuous colours, appears to have been sometimes checked from the danger thus incurred. But in other cases the males during long ages may have struggled together for the possession of the females, and yet no effect wiU have been produced, unless a larger number of offspring were left by the more successful males to inherit their superiority, than by the less successful : and this, as previously shewn, depends on many complex contingencies. Sexual selection acts in a less rigorous manner than natural selection. The latter produces its effects by the life or death at all ages of the more or less successful individuals. Death, indeed, not rarely ensues from the conflicts of rival males. But generally the less successful male merely fails to obtain a female, or obtains u retarded and less vigorous female later in the season, or, if poly- gamous, obtains fewer females ; so that they leave fewer, less vigor- ous, or no offspring. In regard to structures acquired through ordinary or natural selection, there is in most cases, as long as the conditions of life remain the same, a limit to the amount of advantageous modification in relation to certain special purposes ; but in regard to structures adapted to make one male victorious over another, either in fighting or in charming the feniale, there is no definite limit to the amount of advantageous modification ; so that as long as the proper variations arise the work of sexual selection will go on. This circumstance may partly account for the frequent and extraordinary amount of variability presented Chap. YIIl. Sexual Selection. 227 by secondary sexual characters. Nevertheless, natural selection -n'ill determine that such characters shall not be acquired by the Yictorious males, if they would be highly injurious, either by oxpendiug too mucb of their vital powers, or by exposing them to any great danger. The development, however, of certain Btructures— of the horns, for instance, in certain stags — has been carried to a wonderful extreme ; and in some cases to an extreme which, as far as the general conditions of life are concerned, must be slightly injurious to the male. From this fact we learn that the advantages which favoured males derive from conquer- ing other males in battle or coui'tship, and thus leaving a nimierous progeny, are in the long run greater than those derived fi'om rather more perfect adaptation to their conditions of life. We shall further see; and it could never have been anticipated, that the power to charm the female has sometimes been more important than the power to conquer other males in battle. LAWS OF INHEl'JTANOE. In order to understand how sexual selection has acted on many animals of many classes, and in the course of ages has produced a conspicuous result, it is necessary to bear in mind the laws of inheritance, as far as they are known. Two distinct elements are included under the term " inheritance " — the transmission, and the development of characters; but as these generally go together, the distinction is often overlooked. We see this dis- tinction in those characters which are transmitted through the early years of life, but are developed only at maturity or duruag old age. We see the same distinction more clearly with secondary sexual characters, for these are transmitted through both sexes, though developed in one alone. That they are present in both sexes, is manifest when two species, having strongly-marked sexual characters, are crossed, for each trans- mits the characters proper to its own male and female sex to the hybrid offsprmg of either sex. The same fact is likewise mani- fest, when characters proper to the male are occasionally deve- loped in the female when she grows old or becomes diseased, as, for instance, when the common hen assumes the flowing tail- feathers, hackles, comb, spurs, voice, and even pugnacity of the cock. Conversely, the same thing is evident, more or less plainly with castrated males. Again, mdependently of old age or disease' characters are occasionally transferred from the male to the female, as when, in certain breeds of the fowl, spurs regularly appear in the young and healthy females. But in truth they are Bimply developed in tL. female; foi- in every breed each detail (4 2 228 The Descent of Man. Pabt n. in tho structure of the spur is transmitted through tlie female to her male oiTspring. Many cases will hereafter be given, where; the female exhibits, more or less perfectly, characters proper to the male, in whom they must have been first developed, and then transferred to the female. The converse case of the first de- velopment of characters in the female and of transference to the male, is less frequent ; it will therefore be well to give one strik- ing instance. With bees the pollen-collecting apparatus is used by the female alone for gathering pollen for the larvsB, yet in most of the species it is partially developed in the males to whom it is quite useless, and it is perfectly developed in the males of Bombus or the humble-bee.^ As not a single other Hymenopterous insect, not even the wasp, which is closely allied to the bee, is provided with a pollen-collecting apparatus, we have no grounds fof supposing that male bees primordially collected pollen as well as the females ; although we have some reason to suspect that male mammals primordially suckled their young as well as the females. Lastly, in all cases ol reversion, characters are transmitted through two, three, or many more generations, and are then developed under certain unknown favourable conditions. This important distinction between transmission and development will be best kept in mind by the aid of the hypothesis of pangenesis. According to this hypothesis, every unit or cell of the body throws off gemmules or undeveloped atoms, which are transmitted to the offspring of both sexes, and are multipUed by self-division. They may remain undeveloped during the early years of life or during successive generations; and their development into units or cells, like those from which they were derived, depends on their affinity for, and union with other imits or cells previously developed in the due order of growth. ■ Inheritance at corresponding Periods of Life. — This tendency is well established. A new character, appearing in a young animal, whether it lasts thi-oughout life or is only transient, will, in general, reappear in the offspring at the same age and last for the same time. If, on the other hand, a new character appears at matui-ity, or even during old age, it tends to re- appear in the offspring at the same advanced age. When devia- tions from this rule occur, the transmitted characters much oftener appear before, than after the corresponding age. As I have dwelt on this subject sufficiently in another work,'' I will H. Milller, ' Anwendung der '' 'The Variation of Animals Darwin'schen Lehre,' &c. Verh. and Plants under Domestication,' d. n. V. Jahrg xxix. p. 42. vol. ii. 1868, p. 75. In the lant Uhaf. VITI. Sexual Selection. 229 here merely give two or three instances, for the sake of recalling the subject to the reader's mind. In seyeral breeds of the Fowl, the down-covered chickens, the young birds in their first true plumage, and the adults differ greatly from one another, as well as from their common parent-form, the Gallus hankiva ; and these characters are faithfully transmitted by each breed to their offspring at the corresponding periods of life. For instance, the chickens of spangled Hamburgs, whilst covered with down, have a few dark spots on the head and rump, but are not striped longitudinally, as in many other breeds ; in their fii'st true plu- mage, " they are beautifully pencilled," that is each feather is transversely marked by numerous dark bars ; but in their second plumage the feathers all become spangled or tipped with a dark round spot.'* Hence in this breed variations have occurred at, and been transmitted to, three distinct periods of life. The Pigeon offers a more remarkable case, because the aboriginal parent species does not undergo any change of plumage with advancing age, excepting that at maturity the breast becomes more ii-idescent ; yet there are breeds which do not acquire their characteristic coloui-s until they have moulted two, three, or four times ; and these modifications of plumage are regularlj^ transmitted. Inheritance at corresponding Seasons 0/ the Year. — With animals in a state of nature, innumerable instances occur of characters appearing periodically at different seasons. We see tliis in the horns of the stag, and in the fur of arctic animals which becomes thick and white during the winter. Many birds acquire bright colours and other decorations during the breeding-season alone. Pallas states,^^ that in Siberia domestic cattle and horses become lighter-coloured during the winter; and I have myself observed, and heard of sunilar strongly marked changes of colour, that is] from brownish cream-colour or reddish-brown to a perfect white' in several ponies in England. Although I do not know that this tendency to change the colour of the coat during different seasons chapter but one, the provisional hypothesis of pangenesis, above alluded to, is fully explained. ^* These facts are given on the high authority of a groat breeder, Mr. Teebay ; see Tegetmeier's ' Poul- try Book,' 1868, p. 158. On the characters of chickens of different breeds, and on the breeds of the pigeon, alluded to in the following paragraph, see 'Variation of Anit mals,' &c., vol. i. pp. 160, 249 ; vol. ii. p. 77. " ' Novae species Quadrupedum e Glirium ordiue,' 1778, p. 7. Ou the transmission of colour by the ht rse, see ' Variation of Animals, &c., under Domestication,' vol. i. p. 51. Also vol. ii. p. 71, for a gene- ral discussion on ' Inheritance us limited by Sex.' The Vesccni .>/ Mati. Pakt II, is traiismittcd, yet it probably is so, as all shades of colour are strongly inherited by the horso. Nor is this form of inheritance, as limited by the seasons, more remarkable than its limitation by age or sex. Inheritance as Limiled hy /Sea:.— The equal transmission of characters to both sexes is the commonest form of inheritance, at least with those animals which do not present strongly-marked sexual differences, and indeed with many of these. But characters are somewhat commonly transferred exclusively to that sex, in which they first appear. Ample evidence on this head has been advanced in my work on ' Variation under Domestication,' but a few instances may here be given. There are breeds of the sheep and goat, in which the horns of the male differ greatly in shape from those of the female ; and these differences, acquii'ed under domestication, are regularly transmitted to the same sex. As a rule, it is the females alone in cats which are tortoise-shell, the corresponding colour in the males being rusty-red. With most breeds of the fowl, the characters proper to each sex are transmitted to the same sex alone. So general is this form of transmission that it is an anomaly when variations in certain breeds are transmitted equally to both sexes. There are also certain sub-breeds of the fowl in which the males can hardly be distinguished from one another, whilst the females differ con- siderably in colour. The sexes of the pigeon in the parent-species do not differ in any external character ; nevertheless, in certain domesticated breeds the male is coloured differently from the female.'' The wattle in the English Carrier pigeon, and the crop in the Pouter, are more highly developed in the male than in the female ; and although these characters have been gained through long-continued selection by man, the slight differences between the sexes ai'e wholly due to the form of inheritance which has prevailed ; for they have arisen, not from, but rather in opposi- tion to, the wish of the breeder. Most of our domestic races have been formed by the accumula- tion of many slight variations; and as some of the successive steps have been transmitted to one sex alone, and some to both sexes, we find in the different breeds of the same species all gradations between great sexiial dissimilarity and complete similarity. Instances have already been given with the breeds of the fowl and pigeon, and under nature analogous cases are Dr. Chapuis, ' Le Pigeon Voya- similar differences in certain breeds geur Beige,' 1865, p. 87. Boitard at Modena, ' Le variazioni dei •t Corbie, ' Les Pigeons de Volifere,' Colombi domestici,' del Paolo Bo- &c., 1824, p. 173. See, also, on nizzi, 1873. Chaf. vin. Sexual Selection 231 common. With animals under domestication, but whether in nature I will not venture to say, one sex may lose characters proper to it, and may thus come somewhat to resemble the opposite sex ; for instance, the males of some breeds of the fowl have lost their masculine tail-plumes and hackles. On the other hand, the differences between the sexes may bo increased under domestication, as with merino sheep, in which the ewes have lost their horns. Again, characters proper to one sex may suddenly appear in the other sex ; as in those sub- breeds of the fowl in which the hens acquire sjours whilst young ; or, as in certain Polish sub-breeds, in which the females, as there is reason to believe, originally acquired a crest, and sub- sequently transferred it to the males. All these cases are in- telligible on the hypothesis of pangenesis ; for they depend on the gemmules of certain parts, although present in both sexes, becoming, through the influence of domestication, either dormant or developed in either sex. There is one difficult question which it will be convenient to defer to a future chapter ; namely, whether a character at first developed in both sexes, could through selection be limited in its development to one sex alone. If, for instance, a breeder observed that some of his pigeons (of which the characters are usually transferred in an equal degree to both sexes) varied into pale blue, could he by long-continued selection make a breed, in which the males alone should be of this tint, whilst the females remained unchanged ? I will here only say, that this, though perhaps not impossible, would be extremely diflicult; for the natural result of breeding from the pale-blue males would be to change the whole stock of both sexes to this tint. If, how- ever, variations of the desii'ed tint appeared, which were fi'om the first limited in theii* development to the male sex, there would not be the least difficulty in making a breed with the two sexes of a different colour, as indeed has been effected with a Belgian breed, in which the males alone are streaked with black. In a similar manner, if any variation appeared in a female pigeon, which was from the first sexually limited in its development to the females, it would be easy to make a breed with the females alone thus characterised ; but if the variation was not thus originally limited, the process would be extremely difficult, per- haps impossible.*' Since the publication of the pericnceJ a breeder as Mr. Teget- first edition of this work, it has meier. After describing some cu- been highly satisfactory to me to rious cases iu pigeons, of the trans- Cnd the following remarks (the mission of colour by one sex alone, ?ield,' Sept. 1872) from so ex- and the formation of a sut>-bree.l 232 The Descent of Man. On the Bdation letween the Period of Development of a Character and its Transmission to one Sex or to both Sexes.— Why certain characters should be inherited by both sexes, and other charac- ters by one sex alone, namely by that sex in which the character first appeared, is in most cases quite unknown. We cannot even conjecture why with certain sub-breeds of the pigeon, black strias, though transmitted through the female, should be deve- loped in the male alone, whilst every other character is equally transferred to both sexes. Why, again, with cats, the tortoise- shell colour should, with rare exceptions, be developed in the female alone. The very same character, such as deficient or su- pernumerary digits, colour-blindness, &c., may with mankind be inherited by the males alone of one family, and in another family by the females alone, though in both cases transmitted through the opposite as well as through the same sex.'* Although we are thus ignorant, the two following rules seem often to hold good — that variations which first appear in either sex at a late period of life, tend to be developed in the same sex alone ; whilst variations which first appear early in life in either sex tend to be developed in both sexes. I am, however, far from supposing that this is the sole determining cause. As I have not elsewhere discussed this subject, and as it has an important bearing on sexual selection, I must here enter into lengihy and somewhat intricate details. It is in itself probable that any character appearing at au early age would tend to be inherited equally by both sexes, for the sexes do not differ much in constitution before the power of reproduction is gained. On the other hand, after this power has been gained and the sexes have come to differ in constitution, the gemmules (if I may again use the language of pangenesis) which are cast off from each varying part in the one sex would be much more likely to possess the proper affinities for uniting with the tissues of the same sex, and thus becoming developed, than with those of the opposite sex. I was first led to infer that a relation of this kind exists, from the fact that whenever and in whatever manner the adult male differs from the adult female, he differs in the same manner from the young of both sexes. The generality of this fact is quite remai-kable: it holds good with almost all mammals, birds. with this character, he says : " It is " facts that I have related ; but it a singular circumstance that Mr. " is remarkable how very closely " Darwin should have suggested the " he suggested the right method of " possibility of modifying the sexual " procedure." colours of birds by a course of References are given in my " artificial selection. When he did Variatton of Animals under Domes- " 60, he was in ignorance of those ti'-ation," vol. ii. p. 72. Chap. Yill. Sexual Selection. 233 amphibians, and fishes ; also with many crustaceans, spiders, and some few insects, such as certain orthoptera and libellulas. In all these cases the variations, through the accumulation of which the male acquired his proper masculine characters, must have occui-red at a somewhat late period of life ; otherwise the young males would have been similarly characterised ; and conformably with our rule, the variations are transmitted to and developed in the adult males alone. When, on the other hand, the adult male closely resembles the young of both sexes (these, with rare exceptions, being alike), he generally resembles the adult female ; and in most of these cases the variations through which the young and old acquii'ed their present characters, probably occurred, according to our rule, dui'ing youth. But there is here room for doubt, for characters are sometimes transferred to the offspring at an earlier age than that at which they first appeared in the parents, so that the parents may have varied when adult, and have transferred theu- characters to their offspring whilst young. There are, moreover, many animals, in which the two sexes closely resemble each other, and yet both differ from their young ; and here the characters of the adults must have been acquired late in life ; nevertheless, these characters, in apparent contradiction to our rule, are transferred to both sexes. We must not, however, overlook the possibihty or even probability of successive varia- tions of the same nature occurring, under exposure to similar conditions, simultaneously in both sexes at a rather late period of life ; and in this case the variations would be transferred to the offspring of both sexes at a corresponding late age ; and there would then be no real contradiction to the rule that variations occui-ring late in life are transferred exclusively to the sex in which they first appeared. This latter rule seems to hold true more generally than the second one, namely, that variations which occur in either sex early in life tend to be transferred to both sexes. As it was obviously impossible even to estimate in how large a number of cases throughout the animal kingdom these two propositions held good, it occurred to me to investigate some striking or crucial instances, and to rely on the result. An excellent case for investigation is afforded by the Deer family. In all the species, but one, the horns are developed only in the males, though certainly transmitted through the females, and capable of abnormal development in them. In the reindeer, on the other hand, the female is provided with horns ; so that in this species, the horns ought, according to our rule, to appear early in hfe, long before the two sexes are mature and have come to differ much in constitution. In all the other species the horns ought to appear later in life, which 234 The Descent of Man. Part II would lead to their development in that sex alone, in which they first appeared in the progenitor of the whole Family. Now in seven species, belonging to distinct sections of the family and inhabiting different regions, in which the stags alone bear horns, I find that the horns first appear at periods, vaiying from nine months after birth in the roebuck, to ten, twelve or even more months in the stags of the six other and larger species.** But with the reindeer the case is widely different ; for, as I hear from Prof. Nilsson, who kindly made special enquiries for me in Lapland, the horns appear in the young animals within four or five weeks after birth, and at the same time in both sexes. So that here we have a structure, developed at a most unusually early age in one species of the family, and likewise common to both sexes in this one species alone. In several kinds of antelopes, only the males are provided with liorns, whilst in the gi-eater number both sexes bear horns. With respect to the period of development, Mr. Blyth informs me that there was at one time in the Zoological Gardens a young koodoo {Ant. strepsiceros), of which the males alone are homed, and also the young of a closely-allied species, the eland (Ant. oreus), in which both sexes are horned. Now it is in strict conformity with our rule, that in the young male koodoo, although ten months old, the horns were remarkably small, con- sidering the size ultimately attained by them; whilst in the young male eland, although only three months old, the horns were already very much larger than in the koodoo. It is also a noticeable fact that in the prong-horned antelope,^'' only a few of the females, about one in five, have homs, and these are in a, rudimentary state, though sometimes above four inches long ; so that as far as concerns the possession of horns by the males alone, this species is in an intermediate condition, and the horns do not appear until about five or six months after birth. Therefore in comparison with what little we know of the development of the horns in ether antelopes, and from what ^' I am much obliged to Mr. tinent, see J. D. Caton, in ' Ottawa Cupples for having made enquiries Acad, of Nat. Sc. 1868, p. 13. For for me in regard to the Roebuck Ce>-ctis ElJi of Pegu, see Lieut, ind Red Deer of Scotland from Mr. Beavan, ' Proc. Zoolog. Sec' 1867, Robertson, the experienced head- p. 762. forester to the Marquis of Breadal- " Antilocapra Americana. I have bane. In regard to Fallow-deer, I to thank Dr. Canfield for informa- have to thank Mr. Eyton and tion with respect to the horns of the others for informf.tion. For the female: see also his paper in ' Proc. Cervus alces of N. America, see Zoolog. Soc' 1866, p. ICfl. Also 'Land and Water,' 1868, pp. 221 Owcn^ 'Anatomy of Vertebrates, aud 254; and for the C. Virginianus vol. iii. p. 627. nad strongyloceros of the same con- Chap. VJII. Sexual Selection. 235 we do know with respect to the horns of deer, cattle, &c>., fhoso of the pron{?-horned antelope appear at an intermediate period of life,— that is, not very early, as in cattle and sheep, nor very late, as in the larger deer and antelopes. The horns of sheep, goats, and cattle, which are well developed in both sexes, though not quite equal in size, can be felt, or even seen, at birth or soon afterwards." Our rule, however, seems to fail in some breeds of sheep, for instance merinos, in which the rams alone are horned; for I cannot find on enquiry that the horns are developed later in life in this breed than in ordinary sheep in which both sexes are horned. But with domesticated sheep the presence or absence of horns is not a firmly fixed character ; for a certain proportion of the merino ewes bear small horns, and some of the rams are hornless; and in most breeds hornless ewes are occasionally produced. Dr. W. Marshall has lately made a special study of the pro- tuberances so common on the heads of birds,''^ and he comes to the following conclusion ; — that with those species in which they are confined to the males, they are developed late in life; whereas with those species in which they are common to the two sexes, they are de-veloped at a very early period. This is certainly a striking confirmation of my two laws of inheritance. In most of the species of the splendid family of the Pheasants, the males differ conspicuously from the females, and they acquire their ornaments at a rather late period of life. The eared pheasant (Crossoptilon aurituvi), however, ofi'ers a remarkable exception, for both sexes possess the fine caudal plumes, the large ear-tufts and the crimson velvet about the head ; I find that all these characters appear very early in life in accordance with rule. The adult male can, however, be distinguished from the adult female by the presence of spurs; and conformably I have been assured that the horns of the sheep in North Wales can always be felt, and are some- times even an inch in lenprth, at birth. Youatt says (' Cattle",' 1834, p. 277), that the prominence of the frontal bone in cattle penetrates the cutis at birth, and that the horny matter is soon formed over it. " I am greatly indebted to Prof. Victor Carus for having made en- quiries for me, from th3 highest authorities, with respect to the meiino sheep of Saxony. On the Ouinea coast of Africa there i.=, however, a breed of sheep in which, as with merinos, the rams alone bear horns ; and Mr. Winwood Reade informs me that in one case observed by him, a young ram, born on Feb. 10th, first shewed horns on March Gth, so that in this instance, in conformity with rule, the development of the horns oc- curred at a later period oi life than in Welsh .sheep, in which both sexes are horned. " ' Ueber die knochernen Schiidel- hbcker der \'6gel' in the ' Nieder- landistnen Archiv fiir Zoologie,' Baud 1. Iloft 2, 1872. 236 The Descent of Man. Pabt II. with our rule, these do not begin to be developed before the age of six months, as I am assured by Mr. Bartlett, and even at this age, the two sexes can hardly be distinguished." The male and female Peacock differ conspicuously from each other in almost every part of their plumage, except in the elegant head-crest, which is common to both sexes ; and this is developed very early in life, long before the other ornaments, which are confined to the male. The -nild-duck offers an analogous case, for the beautiful green speculum on the wings is common to both sexes, thougli duller and somewhat smaller in the female, and it is developed early in life, whilst the curled tail-feathers and other ornaments of the male are developed later. « Between such extreme cases of close sexual resemblance and wide dissimilarity, as those of the Crossoptilon and peacock, many intermediate ones could be given, in which the characters follow our two rules in their order of development. As most insects emerge from the pupal state in a mature condition, it is doubtful whether the period of development can determine the transference of their characters to one or to both sexes. But we do not know that the colom-ed scales, for instance, in two species of butterflies, in one of which the sexes differ in colour, whilst in the other they are alike, are developed at the same relative age in the cocoon. Nor do we know whether all the scales are simultaneously developed on the wings of the same species of butterfly, in which certain coloured marks are confined In the common peacock (Pauo cristatus) tlie male alone possesses spurs, whilst both sexes of the Java Peacock (P. muticus) offer the un- usual case of being furnished with spurs. Hence I fully expected that in the latter species they would have been developed earlier in life than in the common peacock ; but M. Hegt of Amsterdam informs me, that with young birds of the pre- vious year, of both species, com- pared on April 23rd, 1869, there was no difference in the develop- ment of the spurs. The spurs, however, were as yet represented merely by slight knobs or eleva- tions. I presume that I should liave been informed if any difference in the rate of development, had been observed subsequently. *^ In some other species of the Duck family the speculum differs ill a greater degree in the two sexes; but I have not been able to discover whether its full develop- ment occurs later in life in the males of such species, than in the male of the common duck, as ought to be the case according to our rule. With the allied Mei-gtis cu- cullatus we have, however, a case of this kind : the two sexes differ con- spicuously in general plumage, and to a considerable degree in the speculum, which is pure white in the male and greyish-white in the female. Now the young males at first entirely resemble the females, and have a greyish-white speculum, which becomes pure white at an earlier age than that at which the adult male acquires his other and more strongly-marked sexual dif- feren-ces : see Audubon, ' Ornitho- logical Biography,' vol. iii. 183^ pp\ 249-250. Chap. VIII. Sexual Selection. 237 to one sex, whilst others are common to both sexes. A difference of this kind in the period of development is not so improbable as it may at fii'st appear ; for with the Orthoptera, which assume their adult state, not by a single metamorphosis, but by a suc- cession of moults, the young males of some species at first resemble the females, and acquire their distinctive masculine characters only at a later moult. Strictly analogous cases occur at the successive moults of certain male crustaceans. We have as yet considered the transference of characters, re- latively to their period of development, only in species in a natui'al state; we will now tui'n to domesticated animals, and first touch on monstrosities and diseases. The presence of super- numerai-y digits, and the absence of certain phalanges, must be determined at an early embryonic period— the tendency to profuse bleeding is at least congenital, as is probably colour-blindness — yet these peculiarities, and other similar ones, are often limited in their transmission to one sex ; so that the rule that characters, developed at an early period, tend to be trans- mitted to both sexes, here wholly fails. Eut this rule as before remarked, does not appear to be nearly so general as the converse one, namely, that characters which appear late in life in one sex are transmitted exclusively to the same sex. From the fact of the above abnormal peculiarities becoming attached to one sex, long before the sexual functions are active, we may infer that there must be some difference between the sexes at an extremely early age. With respect to sexually-limited diseases, we know too little of the period at which they originate, to di'aw any safe conclusion. Gout, however, seems to fall under our rule, for it is generally caused by intemperance diu-iug manhood, and is transmitted from the father to his sons in a much more marked manner than to his daughters. In the various domestic breeds of sheep, goats, and cattle, the males differ from theu- respective females in the shape or develop- ment of then: horns, forehead, mane, dewlap, tail, and hump on the shoulders ; and these peculiarities, in accordance with our rule, are not fully developed until a rather late period of life. The sexes of dogs do not differ, except that in certain breeds, especially in the Scotch deer-hound, the male is much larger and heavier than the female; and, as wo shall see in a future chapter, the male goes on increasing in size to an unusually late period of life, which, according to rule, will account for his in- creased size being transmitted to his male offspring alone On the other hand, the tortoise-shell colour, which is confined to female cats, is quite distinct at bii-th, and this case violates the rule. There is a breed of pigeons in which the males alone ara 7'Jic Descent of Mmi. Pabt II. streaked with black, and the streaks can be detected even in the nestlings ; but they become more conspicuous at each successive moult, so that this case partly opposes and partly supports the rule. With the English Carrier and Pouter pigeons, the full development of the wattle and the crop occurs rather late in life, and conformably with the rule, these characters are transmitted in full perfection to the males alone. The following cases perhaps come within the class previously alluded to, in which both sexes have varied in the same manner at a rather late period of life, and have consequently transferred their new characters to both sexes at a corresponding late period ; and if so, these cases are not opposed to our rule :— there exist sub-breeds of the pigeon, described by Neumeister," in which both sexes change their colour during two or three moults (as is likewise the case with the Almond Tumbler), nevertheless, these changes, though occurring rather late in life, are common to both sexes. One variety of the Canary-biid, namely the London Prize, offers a nearly analogous case. With the breeds of the Fowl the inheritance of various charac- ters by one or both sexes, seems generally determined by the period at which such characters are developed. Thus in all the many breeds in which the adult male differs gi-eatly in colour from the female, as well as from the wild parent-species, he differs also from the young male, so that the newly-acquireei characters must have appeared at a rather late period of life. On the other hand, in most of the breeds in which the two sexes resemble each other, the young are coloured in nearly the same manner as their parents, and this rendtrs it probable that their colours fii'st appeared early in life. We have instances of this fact in all black and white breeds, in which the young and old of both sexes are alike ; nor can it be maintained that there is something pecuhar in a black or whito plumage, which leads to its transference to both sexes; for the males alone of many natural species are either black or white, the females being differently coloured. With the so-ealled Cuckoo sub-breeds of the fowl, in which the feathers are transversely pencilled with dark stripes, both sexes and the chickens are coloured in nearly the same manner. The laced plumage of the Sebright bantam is the same in both sexes, and in the yoimg chickens the wing- feathers are distinctly, though imperfectly laced. Spangled Hamburgs, however, offer a partial exception ; for the two sexes, though not quite alike, resemble each other more closely than " ' Das Ganze der Taubenzucht,' puis, * Le pigeon voyageur Beige,' 1837, s. 21, 24. For the case of 186.=i, p. E7. the streaked pigeons, see Dr Cha- OHAr. Vlll. Sexual Selection. do the sexGS of the aborigical parent-species ; yet they acquire their characteristic plumage late in life, for the chickens are distinctly pencilled. With respect to other characters besides colour, in the wild-parent species and in most of the domestic breeds, the males alone possess a well-developed comb; but in the young of the Spanish fowl it is largely developed at a very early age, and, in accordance with this early development in the male, it is of unusual size in the adult female. In the Game breeds pugnacity is developed at a wonderfully early age, of which curious proofs could be given ; and this character is trans- mitted to both sexes, so that the hens, from iheii' extreme pugnacity, are now generally exhibited in separate pens. With the Polish breeds the bony protuberance of the skull which supports the crest is partially developed even before the chickens are hatched, and the crest itself soon begins to gi'ow, though at first feebly;*^ and in this breed the adults of both sexes are characterised by a great bony protuberance and an immense crest. Finally, from what we have now seen of the relation which exists in many natural species and domesticated races, between the period of the development of their characters and the manner of their transmission — for example, the striking fact of the early growth of the horns in the reindeer, in which both sexes bear horns, in comparison with their much later growth in the other species in which the male alone bears horns — we may conclude that one, though not the sole cause of characters being exclusively inherited by one sex, is their development at a late age. And secondly, that one, though apparently a less efficient cause of characters being inherited by both sexes, is their development at an early age, whilst the sexes differ but little in constitution. It appears, however, that some difference must exist between the sexes even during a very early embryonic period, for characters developed at this age not rarely become attached to one sex. Summary and concluding remarks. — From the foregoing dis- cussion on the various laws of inheritance, we learn that the characters of the parents often, or even generally, tend to become developed in the offspring of the same sex, at the same age, and periodically at the same season of the year, in which they iirst For full particulars and re- 250, 256. In regard to the higher ferences on all these points respect- animals, the sexual differences which ing the several bi-eeds of the Fowl, have arisen uader domestication are see 'Variation of Animals and Plants described in the same work under Knder Dome^ticatior. vol. i. pp. the head of each species. The Descent of Man. Paut II. appeared in the parents. But these rules, owing to unknown causes, are far from being fixed. Heuce during the modification of a species, the successive changes may readily be transmitted in different ways; some to one sex, and some to both ; some to the offspring at one age, and some to the offspring at all ages. Not only are the laws of inheritance extremely complex, but so are the causes which induce and govern variability. The variations thus induced are preserved and accumulated by sexual selection, which is in itself an extremely complex affair, depending, as it does, on the ardour in love, the courage, and the rivalry of the males, as well as on the powers of perception, the taste, and will of the female. Sexual selection will also be largely dominated b.y natural selection tending towards the general welfare of the species. Hence the manner in wliich the individuals of either or both sexes have been affected through sexual selection cannot fail to be complex in the highest degree. "When variations occur late in life in one sex, and are trans- mitted to the same sex at the same age, the other sex and the young are left unmodified. When they occur late in life, but are transmitted to both sexes at the same age, the young alone are left unmodified. Yariations, however, may occur at any period of hfe in one sex or in both, and be transmitted to both sexes at all ages, and then all the individuals of the species are similarly modified. In the following chapters it wiU be seen that all these cases frequently occur in nature. Sexual selection can never act on any animal befoie the age for reproduction arrives. From the great eagerness of the male it has generally acted on this sex and not on the females. The males have thus become provided with weapons for fighting with their rivals, with organs for discovering and securely holding the female, and for exciting or charming her. When the sexes differ in these respects, it is also, as we have seen, an extremely general law that the adult male differs more or less from the young male ; and we may conclude from this fact that the successive variations, by which the adult male became modi- fied, did not generally occur much before the age for reproduction. "Whenever some or many of the variations occurred early in life, the young males would partake more or less of the charac- ters of the adult males; and differences of this kind between the old and young males may be observed in many species of animals. It is probable that young male animals have often tended to vary in a manner which would not only have been of no use to them at an early age, but would have been actually injurious— 5hap. VIII. Scxiul Selection. 241 «s by acquiring bright coloiu-s, which would render them con- r)icuous to their enemies, or by cacquii-ing structures, such as /reat liorus, which would expend much vital force in their deTelopmeut. Variations of this kind occurring in the young males would almost certainly be eliminated through natural selection. With the adult and experienced males, on the other hand, the advantages derived from the acquisition of such characters, would more than counterbalance some exposure to danger, and some loss of vital force. As variations which give to the male a better chance 01 conquering other males, or of finding, securing, or charming th(? opposite sex, would, if they happened to arise in the female, be of no service to her, they would not be preserved in her through sexual selection. We have also good evidence with domesticated animals, that variations of all kinds are, if not carefully selected, soon lost through intercrossing and accidental deaths. Conse- quently in a state of nature, if variations of the above kind chanced to arise in the female line, and to be transmitted exclusively in this line, they would be extremely liable to be lost. If, however, the females varied and transmitted their newly acqiured characters to their offspring of both sexes, the characters which were advantageous to the males would be preserved by them through sexual selection, and the two sexes would in consequence be modified in the same manner, although such characters were of no use to the females ; but I shall hereafter have to recur to these more inti-icate contingencies. Lastly, the females may acquire, and apparently have often acquired by transference, characters from the male sex. As variations occurring late in life, and transmitted to one sex alone, have incessantly been taken advantage of and accumu- lated through sexual selection in relation to the reproduction of the species ; therefore it appears, at first sight, an unaccountable fact that similar variations have not fi-equently been accumu- lated through natural selection, in relation to the ordinary habits of life. If this had occurred, the two sexes would often have been differently modified, for the sake, for instance, of capturing prey or of escaping from danger. Differences of this kind between the two sexes do occasionally occur, especially in the lower classes. But this unpHes that the two sexes follow different habits in their struggles for existence, which is a rare circumstance with the higher animals. The case, however, is widely different with the reproductive functions, in which respect the sexes necessarily differ. For variations in structure which are related to these functions, have often proved of value to one and from having arisen at a late period of hfe, have beeu a 242 The Descent of Man. Part IL transmitted to one sex alone ; and such variations, thus preserved and transmitted, have given rise to secondary sexual characters. In the following chapters, I shall treat of the secondary sexual characters in animals of all classes, and shall endeavour in each case to apply the i)rinoiples explained in the present chapter. The lowest classes will detain us for a very short time, but the higher animals, especially birds, must be treated at considerable length. It should be borne in mind that for reasons already assigned, I intend to give only a few illustrative instances of the innumerable structures by the aid of which the mal-e finds the female, or, when found, holds her. On the other hand, all structures and instincts by the aid of which the male conquers other males, and by which he allures or excites the female, will be fully discussed, as these are in many ways the most interesting. Supplement on the proportional numbers of the two sexes in animals belonging to various classes. As no one, as far as I can discover, has paid attention to the relative numbers of the two sexes throughout the animal kingdom, I will here give such materials as I have been able tc collect, although they are extremely imperfect. They consist in only a few instances of actual enumeration, and the numbers are not very large. As the proportions are known with certainty only in mankind, I will fii'st give them as a standard of comparison. Man. — In England during ten years (from 1857 to 1866) the: average number of children born alive yearly was 707,120, in the proportion of 104-5 males to 100 females. But in 1857 the male bii-ths throughout England were as 105 2, and in 1865 as 104-0 to 100. Looking to separate districts, in Buckingham- shire (where about 5000 children are annually born) the mean proportion of male to female births, during the -whole period of the above ten years, was as 102-8 to 100 ; whilst in N. Wales (where the average annual births are 12,873) it was as high as 106-2 to 100. Taking a still smaller district, viz., Eut- landshire (where the annual births average only 739), in 1864 the male births were as 114-6, and in 1862 as only 97-0 to 100 ; but even in this small district the average of the 7385 births during the whole ten years, was as 104-5 to 100 ; that is in the same ratio as throughout England.'" The proportions are sometimes slightly disturbed by unknown causes; thus Prof. « ' Twcntv-nic*.h Annual Report In this report (p. xii.) a special de- of the Kegistrar-General for 1866.' ceuni.'»l table is giveiu Chap. VIII. Proportion of the Sexes. 243 Faye states " that in some disti'icts of Norway there has been " during a decennial period a steady deficiency of boys, whilst in others the opposite condition has existed." In Franco during forty-four years the male to the female births have been as 106'2 to 100; but during this period it has occurred five times in one department, and six times in another, that tho female bii-ths have exceeded the males. In Russia the average proportion is as high as 108'9, and in Philadelphia in the United States as 110-5 to 100.'*^ The average for Europe, deduced by Bickes from about seventy million births, is 106 males to 100 females. On the other hand, with white children born at the Cape of Good Hope, the proportion of males is so low as to fluctuate during successive years between 90 and 99 males for every 100 females. It is a singular fact that with Jews the proportion of male births is decidedly larger than with Christians : thus in Prussia the proportio7i is as 113, in Breslau as 114, and in Livonia as 120 to 100; the Chi-istian births in these countries being the same as usual, for instance, in Livonia as 104 to lOO.'*" Prof. Faye remarks that " a still greater preponderance of " males would be met with, if death struck both sexes in equal " proportion in the womb and during birth. But the fact is, that " for every 100 stiU-born females, we have in several countries " from 134-6 to 144-9 still-born males. During the firpt four or " five years of life, aluo, more male children die than females ; for example in England, during the first year, 126 boys die for " every 100 girls — a proportion which in France is stUl more " unfavourable."" Dr. Stockton-Hough accounts for these facts in part by the more frequent defective development of males than of females. We have before seen that the male sex is more For Norway and Russia, see abstract of Prof. Faye's researches, in 'British and Foreign Medico- Chirurg. Review,' April, 1867, pp. 343, 345. For France, the ' An- nuaire pour I'An 1867,' p. 213. For Philadelphia, Dr. Stockton- Hough, 'Social Science Assoc' 1874. For the Cape of Good Hope, Quetelet as quoted by Dr. H. H. Zouteveen, in the Dutch Translation of this work (vol. i. p. 417), where much information is given on the propor- tion of the sexes. In regard to the Jews, see M, fhury, 'La Loi de Production des Sexes',' 1863, p. 25. 'British and Foreign Medico- Chlruri:. Review,' April, 1867, p. 343. Dr. Stark also remarks ('Tenth Annual Report of Births, Deaths, &c., in Scotland,' 1867, p. xxviii.) that " These examples may " suffice to shew that, at almost " every stage of life, the males in " Scotland have a greater liability " to death and a higher death-rate " than the females. The fact, how- " ever, of this peculiarity being " most strongly developed at that " infantile period of life when the " dress, food, and general treatment " of both sexes are alike, seems to " prove that the higher maledeath- " rate is an impressed, natural, and " constitutional peculiarity due to " sex alone." R 2 244 The Descent of Man. Pabt 11. variable in structure than tlic female; and variations in im- portant organs would generally be injurious. But the size of the body, and e.si)ecially of the head, being greater in male than lemale infants is another cause; for the males are thus more Uable to be injured during parturition. Consequently the still- born males are more numerous; and, as a highly competent judge, Dr. Crichton Browne,'^ believes, male infants often suffer in health for some years after birth. Owing to this excess in the death- rate of male childi-en, both at birth and for some time sub- sequently, and owing to the exposure of grown men to various dangers, and to their tendency to emigrate, the females in all old-settled countries, where statistical records have been kept,'^ are found to preponderate considerably over the males. It seems at first sight a mysterious fact that in different nations, under different conditions and cUmates, in Naples, Prussia, Westphalia, Holland, France, England and the United . States, the excess of male over female births is less when they are illegitimate than when legitimate.*^* This has been explained by different writers in many different ways, as from the mothers - being generally yonng, from the large proportion of first preg- nancies, &c. But wc have seen that male infants, from the large size of their- heads, suffer more than female infants during parturition ; and as the mothers of illegitimate children must be more liable than other women to undergo bad labours, from various causes, such as attempts at concealment by tight lacing, hard work, distress of mind, &c., their male infants would proportionably suffer. And this probably is the most efiicient of aU the causes of the proportion of males to females boru alive being less amongst illegitimate childi-en than amongst the legitimate. With most animals the greater size of the adult male than of the female, is due to the stronger males having conquered the weaker in then.' stniggles for the possession of the females, and no doubt it is owing to this fact that the twOv seses of at least some animals differ in size at birth. Thus-- ' West Riding Lunatic Asylum Reports,' vol. i. 1871, p. 8. Sir J. Simpson has proved that the head of the male infant exceeds that of the female by 3-8ths of an inch in circumference, and by l-8th in transverse diameter. Quetelet has shewn that woman is born smaller than man ; see Dr. Duncan, ' Fe- cundity, Fertility, Sterility,' 1871, p. 382. " With the savage Guaracys of Paraguay, according to the accurate Azara (' Voyages dans I'Amprique me'rid.' torn. ii. 1809, p. 60, 179). the women are to the men m the proportion of 14 to 13. Babbage, ' Edinburgh Journal of Science,' 1829, vol. i. p. 88 ; al^ p. 90, on still-born children. <-'u illegitimate children in England, see ' Report of Registrar-Generil for 18t>(j,' p. XV. Proportion of the Sexes. 245 we havo the curious fact that we may attribute the more frequent deaths of male than female infants, especially amongst the illegitimate, at least in pai-t to sexual selection. It has often been supposed that the relative age of the two parents determines the sex of the offspring ; and Prof. Leuckart'''' has advanced what he considers sufficient evidence, with respect to man and certain domesticated animals, that this is one impor- tant though not the sole factor in the result. So again the period of impregnation relatively to the state of the female has been thought by some to be the efficient cause ; but recent observa- tions discountenance this belief. According to Dr. Btockton- Hough,^^ the season of the year, the poverty or wealth of the parents, residence in the country or in cities, the crossing of foreign immigrants, &c., all influence the proportion of the sexes. With mankind, polygamy has also been supposed to lead to the birth of a greater proportion of female infants ; but Dr. J . Campbell"^ carefully attended to this subject in the harems of Siam, and concludes that the proportion of male to female births is the same as from monogamous unions. Hardly any animal has been rendered so highly polygamous as the English race- horse, and we shall immediately see that his male and female offspring f|re almost exactly equal in number. I will now give the facts which I have collected with respect to the proportional numbers of the sexes of various animals ; and will then briefly discuss how far selection has come into play in determining the result. Horses. — Mr. Tegetmeier has been so kind as to tabulate for me from the ' Racing Calendar ' the births of race-h(jrses during a period of twenty-one years, viz., from 1846 to 1867 ; 1849 being omitted, as no returns were that year published. The total births were 25,560,^^ con- sisting of 12,763 males and 12,797 females, or in the proportion of 99'7 males to 100 females. As these numbers are tolerably large, and as they are drawn from all parts of England, during several years, we may ■with much confidence conclude that with the domestic horse, or at least with the race-horse, ttie two sexes are produced in almost equal numbers. The fluctuations in the proportions doling successive years '* Leuckart (in Wagner ' Hand- wiirterbuch der Phys.' B. iv. 1853, s. 774. Social Science Assoc. of Phila- delphia, 1874. " ' Anthropological Review,' April, 1870, p. cviii. During eleven years a record was kept of the number of mares ■which proved barren or prematurely s!lpp«d their foals ; and it deserves notice, as shewing how infertile these highly-nurtured and rathei closely-interbred animals have be- come, that not far from one-third o{ the mares failed to produce living foals. Thus during 18G6, 809 male colts and 816 female colts were born, and 743 mares failed to produce otfsprin';. During 1807, 830 males and 90-2 females wore born, and 794 mares failed. 246 The Descent of Man. Part II. are closely like tlinte which occur witli mankind, when a auiall and thinly-populatiid area is considered; thus in 1856 the male horses were as lOyi, and in 18U7 as only 92 6 to 100 females. In the tabulated roturns the proportions vary in cycles, for the males exceeded the females during bix successive years ; and the females exceeded the males during two periods each of four years : this, however, may be accidental ; at least I can detect nothing of the kind with man in the decennial table in the Registrar's lleport for 1866. Boys. — During a period of twelve years, from 1857 to 1868, the birtlia of a largo number of greyhounds, throughout England, were sent to the ' Field' newspaper ; and I am again indebted to Mr. Tegetmeier for carefully tnbulating tho results. The recorded biiths were 6878, consisting of 3605 males and 3273 females, that is, in the proportion of llO'l males to 100 females. The greatest fluctuations occurred in 1864, when the proportion was as 95'3 males, and in 1867, as 116-3 males to 100 females. The above average proportion of 110*1 to 100 ia probably nearly correct in the case of the greyhound, but whether it would hold with other domesticated breeds is in some degree doubtful. Mr. Cupples has enquired from several great breeders of dogs, and finds that all without exception believe that females are produced in excess; but he suggests tbat this belief may have arisen from females being less valued, and from the consequent disappointment producing a stronger impression on the mind. Sheep. — The sexes of sheep are not ascertained by agriculturists until several months after birth, at the period when the males are castrated ; so that the following returns do not give the proportions at birth. Moreover, I find that several great breeders in Scotland, who annually raise some thousand sheep, are firmly convinced that a larger proportion of males than of females die during the first year or two. Therefore tho proportion of males would be somewhat larger at bu th than at the age of castration. This is a remarkable coincidence with what, as we Lave seen, occurs with mankind, and both cases probably depend on the same cause. I have received returns from four gentlemen in England who have bred Lowland sheep, chiefly Leicesters, during the last ten to sixteen years; they amount altogether to 8C65 births, consisting of 4i07 males and 4558 females; that is in the proportion of 96 7 males to 100 females. With respect to Cheviot and black-faced sheep bred in Scotland, I have received returns from six breeders, two of them on a large scale, chiefly for the years 1867-1869, but some of the returns extend back to 1862. The total number recorded amounts to 50,685, consisting of 25,071 males and 25,614 females, or in the proportion of 97.9 males to 100 females. If we take the English and Scotch returns together, the total number amounts to 59,650, consisting of 29,478 males and 30,172 females, or as 977 to 100. So that with sheep at tho age of castration the females are certainly in excess of the males, but probably this would not hold good at birth.*" , „„ , . Of Cattle I have received returns from nine gentlemen of 982 birtM, too few to be trusted ; these consisted of 477 buU-calves and 505 cow- s' I am much indebted to Mr. Cupples for having procured for me the above returns from Scotland, as well as some of the following re- turns on cattle. Mr. R. Elliot, of Laighwood, first called my atten- tion to the premature deaths of the males, — a statement subsequently confirmed by Mr. Aitchison and others. To this latter gentleman, and to Mr. Payan, I owe my thanks for 1 irge returns as to sheep. Chap. VI 11. Proportiofi of the Sexes. 247 calves; i.e., iu the proportion of 91 '4 males to 100 females. The Rev. W. D. Fox int'orms me "ihiit in 1867 out of 34 calves born on a farm in Derbyshire only one was a bull. Mr. Harrison Wuir has enquired from several bret dors of P**/*') i^nd mobt of them estimate the male to the female births as about 7 to 6. This same gentleman has bred Jtabbits for many years, and has noticed that a far greater number of bucks are produced than does. But estimations arc of little value. Of mammalia in a state of nature I have been able to learn very little. In regard to the common rat, I have received conflicting statements. Mr. R. Elliot, of Luighwood, informs me that a rat-catcher assured him that he had always found the males in great excess, even with the youug in the nest. In consequence of this, Mr. Elliot himself subsequently examined some hundred old ones, and found the statement true. Mr. F. Buckland has bred a large number of white rats, and he also believes that the male.'j greatly exceed the females. In regard to Moles, it is said that " the males are much more numerous " than the females ;" and us the catching of these animals is a special occupation, the statement may perhaps be trusted. Sir A. Smith, in describing an antelope of S. Afiica"' (^Kobus ellipsiprymnus), remarks, that in the herds of this and other species, the males are few in niunber compared with the females : the natives believe that they are born in this proportion ; others believe that the younger males are expelled from the herds, and Sir A. Smith says, that though he has himself never seen herds consisting of young amies alone, others affirm that this does occur. It appears probable that the young when expelled from the herd, would often fall a prey to the many beasts of prey of the country. BIRDS. With respect to the Fowl, I have received only one account, namely, that out of 1001 chickens of a hifjhly-bred stock of Cochins, reared during eight years by Mr. Stretch, 487 proved males and 514 females; i.e., as 94-7 to 100. In regard to domestic pigeons there is good evidence either that the males are produced in excess, or that they live longer; for these birds invariably pair, and single males, as Mr. Teget- meier informs me, can always be purchased cheaper than females. Usually the two birds reared from the two eggs laid in the same nest are a male and a female ; but Mr. Harrison Weir, who has been so large u breeder, says that he has often bred two cocks from the same nest, and seldom two hens ; moreover, the hen is generally the weaker of the two, and more liable to perish. AVith respect to birds in a state of nature, Mr. Gould and others" are convinced that the males are generally the more numerous ■ and as the young males of many species resemble the females, the latter would naturally appear to be the more numerous. Large numbers of pheasants are reared by Mr. Baker of Leadenhall from eggs laid by wUd birds and he miorms Mr. Jenner Wtu: that four or five males to one female are generally produced. An experienced observer remarks," «» Bell, ' History of British Quad- iv. s. 990) comes to the same con- rupeds, p. 100. elusion. „/' \^}^^'^^foT' f 2°°l«gy " On the authority of L. Lloyd, of b. Africa, 1849, rd. 29. r;...j„ r q ■ > 10,.- - Brehm' (' Illust. Thierleben,' B. 12,732 248 TJie Descent of Man. Paht II. that in Scandinavia the broods of the capercailzie and black-cock contiiiii more males than females ; and that with the Dal-ripa (a kind of ptarmigan) inon! mules than femuled attend the lain or places of courtship; but this latter circumstuncu is accounted for by some observers by a greater number of hen birds being killed by vermin. From various facts given by Wliite of Selbcirne,"^ it seems clear that the males of the partridge must be in considerable excess in (he south of England; anil 1 have been assured that this is the case in Scotland. Mr. Weir on enquiring from the dealers, who receive at certain sc-asons largo numbers of rufl's (Machetes pugnax), was told that tlie males are mucli the more numerous. This same naturalist has also enquired for me fiom the birdcatchers, who annually catch an astouisliiug number of various small species alive for the London market, and he was un- hesitatingly answered by an old and trustworthy man, that with the chaffinch the males are in large excess; he thoughtas high as 2 males to 1 female, or at least as high as 5 to 3."' The males of the blackbird, he likewise maintained, were by far the more numerous, whether caught by traps or by netting at night. These statements maj apparently be trusted, because this same man said that the sexes are about equal with the lark, the twite {Linaria moidana), and goldfinch. On the other hand, he is certain that with the common linnet, the females preponderate greatly, but unequally during dilferent years ; dmiKg some years be has found the females to the males as four to one. It should, however, be borne in mind, that the chief season for catching birds does not begin till September, so that With some species partial migrations may have begun, and the flncks at this period often consist of hens alcne. Mr. Salvin paid particular attention to the sexes of the humming-birds in Central America, and he is convinced that with most of tiie species the males are in excess ; thus one year he procured 204 specimens belonging to ten species, and these consisted of 166 males and of only 38 females. With two other species the females were in excess : but the proportions apparently vary either during diflerent seasons or in dilferent localities; for on one occasion the males of Campylopturus hemileucurus were to the females as 5 to 2, and on another occasion °" in exactly the reversed ratio. As bearing on this latter point, I may add, that Mr. Powys found in Corfu and Epirus the sexes of the chaflSnch keeping apart, and " the females by far the " most numerous;" whilst in Palestine BIr. Tristram found "the male *' flocks api earing greatly to exceed the female in number.'"^' So ai^ain with the Quiscalus major, Mr. G. Taylor"' says, that iu Florida tiiere were " very few females in proportion to the males," whilst iu Honduras the proportion was the other way, the species there having the character of a polygamist. ' Nat. Hist, of Selborne,' letter xxix. edit, of 1825, vol. i. p. 139. " Mr. Jenner Weir received similar information, on making en- quiries during the follcwing year. To shew the number of living chaf- tlnches caught, I may mention that iu 1869 there was a match between two experts, and one man caught in a day 62, and another 40, male chalHnches. ' The g.i-eatest number ever caught by one man in a single day was 70. ' Ibis,' vol. ii. p. 260, ns quoted m Gould's 'TrochilidaV 1861, p. 52. For the foregoing proportions, I am indebted to Mr. Salvia for a table of his results. 'Ibis,' 1860, p. 137; and 1S67 p. 369. " 'Ibis,' 1862, p. 1J7. CUAl'. VIII. Proportion of the Sexes. 249 FISH. Wich Fish the proportiozjcil numbers of the sexes can be ascer tabled only by catching :hem iu the adult or nearly adult state ; and there are many difficulties in arriving at any just conclusion.'^' Infertile females might readily be mistaken for males, as Dr. Giinther has remarked- to me in regai'd to trout. With hOme species the males are believed to die soon after fertilising the ova. Witli many species the males are of much smaller size than the females, so that a large number of males would escape from the same net by which tlie females were caught. M. Carbonnier," who has especially attended to the natural history of the pike (J5.sox lucius), states that many males, owing to their small size, are devoured by the larger females ; and he believes that the males of almost all fish are exposed from this same cause to greater danger thau the females. Nevertheless, in the few cases in which the proportional numbers have been actually observed, the males ai)poar to be largely in excess. Thus Mr. K. Buist, the superin- tendent of the Stormontfield experiments, says that in 1865, out of 70 salmon first landed for the purpose of obtaining the ova, upwards of 60 were males. Iu 1867 he again " calls attention to the vast disproportion •' of the males to the females. We had at the outset at least ten males " to one female." Afterwards females sulMcient for obtaining ova were procured. He adds, " from the great proportion of th^ males, they arc "constantly fighting and tearing each other on the spawning-beds."" This dispropoi tion, no doubt, ean be accounted for in part, but whether wholly is doubtful, by the males asceudiHg the rivers before the females. Mr. F. Buckland remarks iu regard to trout, that " it is a curious fact that the males preponderate very largely iu number over " the females. It invariably happens that when the first rush of fish is " made to the net, there will be at least seven or eight males to one female found captive. I cannot quite account for this ; either the '■ males are more numerous than the females, or the latter seek safety " by concealment rather than flight." He then adds, that by carefully searching the banks, sufi&cicnt females for obtaining ova can be found."' Mr. H. Lee informs me that out of 212 trout, taken for this purpose in Lord Portsmouth's park, 150 were males and 62 females. The males of the Cyprinidse likewise seem to be in excess ; but several members of this Family, viz., the carp, tench, bream and minnow, appear regularly to follow the practice, rare in the animal kingdom, of polyandry ; for the female whilst spawning is always attended by two males, one on each side, and in the case of the bream by three or four males. This fact is so well known, tliat it is always recommendtd to stock a pond with two male tenches to one female, or at least with three males to two females. With the minnow, an excellent observer states, that on the spawuing-beds the males are ten times as numerous as the females; when a female comes amongst the Leuuk.trt quotes Bloch (Wag. 18, 1869, p. 369. ner, ' Handworterbuch dev Phys.' " 'The Stormontfield Piscicnl- B. IV. 1833, s. 775), that with fish tural F.xporinients,' 1866, p. -23. there are twice as many males as The 'Field' newspaper, June 29111, females. I8U7. Quoted in the 'Farmer,' March " ' Land and Water,' 1868, p. 41 250 The Descent of Man. p^et II. males, "she is immcdiutely pressed closely by a mde on each side; "aud wLen thoy have been in that situation for a time, are auperseded " by other two males." " INSECTS. In this great Class, the Lepidoptera almost alone afford means for juilgiiig of the proportional numbers of the sexes ; for they have been collected with special care by many good observers, and have been largely bred from the egg or caterpillar state. I had hoped that some breeders of silk-moths might have kept an exact record, but after writing to France and Italy, and consulting various treatises, I cannot find that this has ever been done. The general opinion appears to be that the sexes are nearly equal, but in Italy, as I hear from Professor Canestrini, many breeders are convinced that the females are produced in excess. This same naturalist, however, informs me, that in the two yearly broods of the Ailanthus silk-moth (Bombyx cynthiu), the males greatly preponderate iu the first, whilst in the second the two sexes are nearly equal, or the females rather in excess. In rej;ard to Butterflies iu a state of nature, several observers have been much struck by the apparently enormous preponderance of the males." Thus Mr. Bates," in speaking of several species, about a hundred in number, which inhabit the Upper Amazons, says that the males are much more numerous than the females, even in the propor- tion of a hundred to one. Iu North America, Edwards, who had great experience, estimates in the genus Papilio the males to the females as four to one ; and Mr. Walsh, who informed me of this statement, says that with P. turitus this is certainly the case. In South Africa, Mr. K. Trimeu found the males in excess in 19 species and in one of these, which swarms in optn places, he estimated the number of males as fifty to one female. With another species, in which the males are numerous in certain localities, he collected only five females during seven years. In the island of Bourbon, M. Maillard states that the males of one species of Papilio are twenty times as numerous as the females.'' Mr. Trimen informs me that as far as he has himself seen, or heard from others, it is rare for the females of any butterfly to exceed the males in nimiber ; but three South African species per- haps ofier an exception. Mr. Wallace " states that the females of Ornitlioptera crcesus, in the Malay archipelago, are more common and more easily caught than the males ; but this is a rare butterfly. I may " Yarrell, ' Hist. British Fishes,' vol. i. 18'26, p. 307 ; on the Cyprinus carpio,^. 331; on the Tinea vulgaris, p. 331 ; on the Abramis brama, p. 33G. See, for the minnow {Leu- ciscus phoxinns), ' Loudon's Mag. of Nat. Hist.' vol. v. 1832, p. 682. '* Leuckart quotes Meinecke (Wagner, ' Handworterbuch der Phys.' B. iv. 1853, s. 775) that the males sf Butterflies are three or four times as numerous as the females. " 'The Naturalist on the Ama- zons,* vol. ii. 1863, p. 228, 347- '° Four of these cases are given by Mr. Trimen in his ' Khopalocera Africae Australis.' " Quoted by Trimen, ' Transact. Ent. Soc' vol. T. part iv. 1866, p. 330. " ' Transact. Linn. Soc,' vol. xxv. p. 37. Chap. VIII. Proportion of the Sexes. 251 here add, that iu Hyperyfhra, a genus of moths, Guenee says, that fioni four to five females are sent in collections from India for one wiien this subject of the proportional numburs of the sexes of insects was brought before the Entomological Society," it was generally admitted that the males of most Lepidoptera, in the adult or imago state, are caught in greater numbers than the females : but_ this fact was attributed by various observers to the more retiring habits of the females, and to the males emerging earlier from the cocoon. This latter circumstiince is well known to occur with most Lepidoptera, as well as with other insects. So that, as M. Personnat remarks, the males of the domesticated Bombyx Yamamai, are useless at the begin- ning of the season, and the females at the end, from the want of mates.'" I cannot, however, persuade myself that these causes suffice to explain the great excess of males, in the above cases of certain butter- fliee which are extremely common in their native countries. Mr. Stainton, who has paid very close attention during many years to the smaller moths, informs me that when he collected them in the imago state, he thought that the males were ten times as numerous as the females, but that since he has reared them on a large scale from the caterpillar state, he is convinced that the females are the more numerous. Several entomologists concur in this view. Mr. Double- day, however, and some others, take an opposite view, and are con- vinced that they have reared from the eggs and caterpillars a larger proportion of males than of females. Besides the more active habits of the males, their earlier emergence from the cocoon, and in some cases their frequenting more open stations, other causes may be assigned for an apparent or real diffiirence iu the proportional numbers of the sexes of Lepidoptera, when cap- tured in the imago state, and when reared from the egg or caterpillar state. I hear from Professor Canestrini, that it is believed by many breeders in Italy, that the female caterpillar of the silk-moth suffers more from the recent disease than the male ; and Dr. Staudinger informs me that iu rearing Lepidoptera more females die in the cocoon than males. With many species the female caterpillar is lat'ger than the male, and a collector would naturally choose the linest specimens, and thus unintentionally collect a larger number of i'emales. Three collectors have told me that this was their practice ; but Dr. Wallace is sure that most collectors take all the specimens which they can find of the rarer kinds, which alone are wortii the trouble of rearing. Birds when surrounded by caterpillars would probably devour the largest ; and Professor Canestrini informs me that in Italy some breeders believe, though on insufficient evidence, that in the first broods of the Ailanthus silk-moth, the wasps destroy a larger number of the female than of the male caterpillars. Dr. Wallace fm-lher remarks that female caterpillars, from being larger than the males, require more time for their development, aud consume more food and mois ture; and thus they would be exposed during a longer time to danger from ichneumons, birds, &c., and in times of scarcity would perish in greater numbers. Hence it appears quite possible thai ' Proc. Entomolog. Soc.' Feb. 17th, 18G8. Quoted by Dr. Wallace in ' Proc. Ent. boc' 3rd seiies, toI. t 1S67, 1. 487. 252 TIte Descent of Man. Part IT. in a btale of natuie, fewer female Lepidoptsra may reacb maturitv than males; ami for our Bpeeial object we are conctnierl with tlici'r relative numbers at maturity, when the sexes are leady to propagate their kind. The manner in which the males of certain moths coiigri'^iate in extraordinary numbers round a bingle female, Apparently indioates h great excess of males, though this fact may perhaps be accounted for by _1he earlier emergence of the msdes from then- cocoons. Mr. Stainton informs me lhat from twelve to twenty male?, may often be seen congrcgatid round a female Elachida rufocinerea. It is well known that if a virgin Lasiocainpa quercus or Saturitia carjniii be exposed in a cage, vast numbers of males collect round her, and if confined in a room will even come down the chimney to her. Mr Doubleday bdieves lhat he has seen from fifty to a hundred males of both these spe( ies attracted in the course of a single day by a female in confinement. In the Isle of Wight Mr. Trimen exposed a box in which a female of the Lasiocampa hud been confined on the previous day, and five males soon endeavoured to gain admittance. In Australia, M. Verreaux, having placed the female of a small Bombyx in a box in his pocket, was followed bj a crowd of males, so that about 200 entered the house with him." Mr. Doubleday has culled my attention to i)/L. Staudinger's list of Lepidoptera, which gives the prices of the males and females of 300 species or well-marked varieties of butterflies (Ehopalocera). The prices for both sexes of tlie very common species are of course the same ; but in 114 of the rarer species they differ; the males being in all cases, excepting one, the cheaper. On an average of the prices of the 113 species, the price of the male to that of the female is as 100 to 149 ; and this apparently indicates that inversely the males exceed the females in the same proportion. About 2000 species or varieties of moths (Heterocera) are catalogued, those with wingless females being here excluded on acc(runt of the difference iu habits between the two sexes : of these 2000 species, 141 differ in price according to sex, the males of 130 being cheaper, and those of only 11 being dearer than the females. The average price of the males of the 130 species, to that of the females, is as lOU to 143. With respect to the butterflies in this priced list, Mr. Doubleday thinks (and no man in England has had more experience), that there is nothing in the habits of the species which can account for the difl'erence in the prices of the two sexes, and that it can be accounted for only by an excess in the number of the males. But I am bound to add that Dr. Staudinger informs me, that he is himself of a different opinion. Ho thinks that the less active habits of the females and the earher emc rgence of the males will account for his collectors securing a larger number of males than of females, and consequently for the lower prices of the former. With respect to specimens reared from the caterpillar-state, Dr. Staudinger believes, as previously stated, that a greater number of females than of males die whilst confined in the cocoons. He adds that with certain species one sex seems to preponderate over the other during certain years. Of direct observations on the sexes of Lepidoptera, reared either Blacchard, ' Metamorphoses, ' Lepidopteren - Doulletten Maurs des Insectes,' J8(-8, pp. 2 .5- Liste,' Beriiu, No. x. 18G6. 226 CuAP. VJT.. Proportion of the Sexes. 253 from eg{j3 or catorpillai-s, I have received only tbe few following cases : — I MbIcs. Females. The fiev. J. Hellins'^ of Exeter reared, during 1868, imagos of 73 species, which consisted of. Mr. Albert Jones of Eltham reared, during 1868 images of 9 species, which consisted of . During 1869 he reared imagos from 4 species, con sisting of Ml". Buckler of Emsworth, Hants, during 1869 reared imagos from 74 species, consisting of. Dr. Wallace of Colchester reared from one brood Bombyx cynthia Dr. Wallace raised, from cocoons of Bombyx Pernyil sent from China, during 1869 J Dr. Wallace raised, during 1868 and 1869, from two^ lots of cocoons of Bombyx yama-mai . . , J Total i 153 137 izo 1 It: 119 180 169 52 48 224 123 52 46 934 761 So that in these eight lots of cocoons and eggs, males were produced in excess. Taken together the proportion of males is as 122'7 to 100 females. But the numbers are hardly large enough to be trustworthy. On the whole, from these various sources of evidence, all pointing in the same direction, I infer that with most species of Lepidoptera, the matm-e males generally exceed the females in number, whatever the proportions may be at their first emergence from the egg. With reference to the other Orders of insects, I have oeen able to collect very little reliable information. With the stag-beetle {Lucanuz cervus) " the males appear to be mucU more numerous " than the females ;" but when, as Cornelius remarked during 1867, an unusual number of these beetles appeared in one part of Germany, the females appeared to exceed the males as six to one. With one of the Elateridje, the males are said to be much more numeroiis than the females, and " two or three are often found united with one female " so that here polyandry seems to prevail." With Siagonium (Staphy- ILnidse), in which the males are furnished with horns, " t.ie females are " far more numerous than the opposite sex." Mr. Janson stated at the Entomological Society that the females of the bark- feeding Tomtom villosug are so common as to be a plague, whilst the males are so rare tts to be hardly known. This naturalist has been so kind as to send me some results from former years, in which the females seemed to preponderate ; but so many of the figures were estimates, that I fcund it impossible to tabulate them. Giinther's ' Record of Zoo- logical Literature,' 1867, p. 260. On the excess of female Lucanus, ibid..p. 230. On the males of Luc;i- nus in England, Westwood, ' Jlodcni Class, of Insects,' vol. i. p. 187. Ou the Siagonium, ibid. p. 172. 254 T)te Descent of Man. Part II. It is liardly worth while saying anything alxmt the proportion of the sexes in certain spefies and even groups of insects, for the males are unknown or very rare, and the females are parthenogenetic, tliat is, fertile without sexual union; examples of this are aflforded by several of the Cynipidaj." In all the gall-making Cyni]jidffl known to Mr. Walsh, the females are four or live times as numerous as the males ; and so it is, as he informs me, with the gall-making Cecidomyiiaj (Diptera). With some common tpecies of Saw-flies (Tenthredlnffi) Mr. F. Smith has reared hundreds of specimens from larvas of all sizes, but hat, novcr reared a single male : on the other hand, Curtis says," that with certain species (Athalia), bred by him, the msiles were to the females as six to one ; whilst exactly the reverse occurred with the mature insects of the same species caught in the fields. In the family of Bt:es, Hermann Miiller," collected a large number of specimens of many siiecies, and reared others from the cocoons, and counted the sexes. He found that the males of some species greatly exceeded the females in number ; in others the reverse occurred ; and in others the two sexes were nearly equal. But as in most cases the males emerge from the cocoons before the females, they are at the commencement of the breeding season practically in excess. Miiller also observed that the relative number of the two sexes in some species differed much in different localities. But as H. Miiller lias himself remarked to me, these remarks must be received with some caution, as one sex might more easiiy escape observation than the other. Thus his brother Fritz Miiller has noticed in Brazil that the two sexes of the same species of bee sometimes frequent different kinds of flowers. With respect to the Orthoptera, I know hardly anything about the relative number of the sexes : Korte," however, says that out of 500 locusts which he examined, the males were to the females as five to six. With the Neuroptera, Mr. Walsh states that in many, but by no means in all the species of the Odonutous group, there is a great overplus of males : in the genus HetaRrina, also, the males are generally at least four times as numerous as the females. In certain species in the genus Gomphus the males are equally in excess, whilst in two other species, the females are twice or thrice OS numerous as the males. In some European species of Psocus thousands of females may be collected without a single male, whilst \wth other species of the same genus both sexes are common." In England, Mr. MacLachlan has captured hundreds of the female Apalania muliebris, but has uever seen the male; and of Boreus hyemalis only four or five males hare been Seen here.°° With most of thi se species (excepting the Tenthredinae) there is at present no evidence that the females are subject to parthenogenesis ; and thus we see how ignorant we are of the causes of the apparent discrepancy in the proportion of the two sexes. In the other Classes of the Articulata t have been able to collect still Walsh, in ' The American En- tomologist,' vol. i. 1869, p. 103. F. Smith, ' Record of Zoological Literature,' 1867, p. 328. ' Farm Insects,' pp. 45-46. ' Anweudung der Darwinschen I^hre Verh. d. n. V. Jahrg. xxiv.' •* 'Die Strich, Zug odor Wan- derheuschrecke,' 1828, p. 20. ' Observations on N. American Neuroptera,' by H. Hagen and B. D. Walsh, ' Proc. Ent. Soc. Phila- delphia,' Oct. 1863, pp. 168, 223, 239. »• ' Proc. Ent. Soc Londcn,' FeU 17, 1868. Ohap. VIII. Proportion oj the Sexes. 255 less information. With Spiders, Mr. Blackwall, who has carefully attended to this olaas during many years, writes to me that the males from their more erratic habits are more commonly seen, and therefore appear mure numerous. This is actually the case with a few species ; but he mentions several species in six genera, in wliirh the females appear to be much more mimerous than the aiales."' 'I'he small size of the males in comparison with the females (a peculiarity which is some- times carried to an extreme degree), and their widely dilierent appear- ance, may account Ln some instances for their rarity in collections."^ Some of the lower Crustaceans are able to propitgate their kind asexuiilly, and this will account for the extreme rarity of the males : thus Von Siebold"' carefully examined no less than 13,000 specimens of Apus from twenty-one localities, and amongst these he found only 319 males. With some other forms (as Tanais and Cypris), as Fritz Milliter informs me, there is reason to believe that the males are much shorter-lived than the females ; and this would explain their scarcity, supposing the two sexes to be at first equal in number. On the other hand, Miiller has invariably taken far more males than females of the Diastylid£e and of Cypridina on the shores of Brazil; thus with a species in the latter genus, 63 specimens caught the same day included 57 males ; but he suggests that this preponderance may be due tc some unknown difference in the habits of the two sexes. With one of the higher Brazilian crabs, namely a Gelasimus, Fritz Miillei found the males to be more numerous than the females. According to the Luge experience of Mr. 0. Spence Bate, the reverse seems tc be the caso with six common British crabs, the names of which he has given me. The proportion of the sexes in relation to naturiil selection. There is reason to suspect that in some cases man has by selection indirectly influenced his own sex-producing powers. Certain women tend to produce during their whole lives more children of one sex than of the other : and the same holds good of many animals, for instance, cows and horses ; thus Mr. Wright of Yeldersley House informs me that one of his Arab mares, though put seven times to different horses, produced seven fillies. Though I have very little evidence on this head, analogy would lead to the belief, that the tendency to produce either sex would be inherited like almost every other peculiarity, for instance, that of producing twins ; and concerning the above tendency a good authority, Mr. J. Downing, has communicated to me facts which seem to prove that this does occur in certain families of short-horn cattle. Col. Marshall has recently found on careful examination that the Todas, a hill-tribe of India, " Another great authority with 0. P. Cambridge, as quoted ii respct to this class. Prof. Thorell of 'Quarterly Journal of Science, Upsala (' On European Spiders,' 1868, p. 429 1869-70, part i. p. 205) speaks as if «3 < Beitrage zur Parthencjenesi^ temale spiders were generally com- p. 174 a — » moner than the males. '.4 .'xhe Tcdas.' 1873. pp. 100 " bee, on this subject, Jlr. 194^ igg. 2S6 The Descent of Man. Pabt II. consist of 112 males and 84 females of all ages— that is in a ratio of 133-3 males to 100 females. The Todas, who are polyandroua in their marriages, during former times invariably practised female infanticide ; but this practice has now been discontinued for a considerable period. Of the children born within late years, the males are more numerous than the females, in the proportion of 124 to 100. Colonel Marshall accounts for this fact in the following ingenious manner. " Let us for the purpose of illustra- " tion take three families as representing an average of the " entire tribe ; say that one mother gives birth to six daughters " and no sons ; a second mother has six sons only, whilst the " third mother has three sons and three daughters. The first " mother, following the tribal custom, destroys four daughters " and preserves two. The second retains her six sons. The third " kills two daughters and keeps one, as also her three sons. We " have then from the three families, nine sons and three daughters, " with which to continue the breed. But whilst the males " belong to families in which the tendency to produce sons is " great, the females are of those of a converse inclination. Thus " the bias strengthens with each generation, until, as we find, " families grow to have habitually more sons than daughters." That this result would follow from the above form of infanticide seems almost certain ; that is if we assume that a sex-producing tendency is inherited. But as the above numbers are so ex- tremely scanty, I have searched for additional evidence, but cannot decide whether what J have found is trustworthy ; nevertheless the facts are, perhaps, worth giving. The Maories of New Zealand have long practised infanticide ; and Mr. Fenton'' states that he " has met with instances of women who have de- "stroyed four, six, and even seven children, mostly females. ' However, the universal testimony of those best qualified to " judge, is conclusive that this custom has for many years been " almost extinct. Probably the year 1835 may be named as the " period of its ceasing to exist." Now amongst the New Zea- ianders, as with the Todas, main bii-ths are considerably in excess. Mr. Fenton remarks (p. 3Uj, " One fact is certain, although the " exact period of the commencement of this singular condition of " the disproportion of the sexes cannot be demonstratively fixed, " it is quite clear that this course of decrease was in full opera- " tion during the years 1830 to 1844, when the non-adult " population of 1844 was being produced, and has continued " with great energy up to the present time." The following statements are taken from Mr. Fenton (p. 26), but as the numbers »5 'Aboriginal Inhabitants of New Zealand ; Government Report,' 1853, p. 36. Chap. VIH. i^roporti07i of the Sexes. iire not large, and as the census was not accurate, uniform results cannot be expected. It should be borne in mind in this and the following cases, that the normal state of every population ■is an excess of women, at least in all civilised countries, chiefly owing to the greater mortaUty of the male sex during youth, and partly to accidents of all kinds later in life. In 1858, the native population of New Zealand was estimated as consistiag of 31,667 males and '24,803 females of all ages, that is in the i-atio of 130-3 males to 100 females. But during this same year, and in certain limited districts, the numbers were ascertained with much care, and the males of all ages were here 753 and the females 616 ; that is in the ratio of 122-2 males to 100 females. It is more important for us that during this same year of 1858, the non-adult males within the same district were found to be 178, and the non-adult females 142, that is in the ratio of 125-3 to 100. It may be added that in 184.4, at which period female infanticide had only lately ceased, the non-adult males in one district were 281, and the non-adidt females only 194, that is in the ratio of 144-8 males to 100 females. In the Sandwich Islands, the males exceed the females in number. Infanticide was formerly practised there to a frightful 3xtent, but was by no means confined to female infants, as is shewn by Mr. Ellis,'° and as I have been informed by Bishop Staley and the Eev. 'BIi-. Coan. Nevertheless, another apparently trustworthy writer, Mr. Jarves,^^ whose observations apply to the whole archipelago, remarks : — " Numbers of women are to " be found, who confess to the murder of from three to six or eight children;" and he adds, " females from being considered less '•' useful than males were more often destroyed." From what is known to occur in other parts of the world, this statement is probable; but must be received with much caution. The practice of infanticide ceased about the year 1819, when idolatry was aboUshed and missionaries settled in the Islands. A careful census ia 1839 of the adult and taxable men and women in the island of Kauai and in one district of Oahu ( Jarves, p. 404), gives 4723 males and 8776 females; that is in the ratio of 125-08 to 100. At the same time the number of males under fourteen years in Kauai and under eighteen ia Oahu was 1797, and of females of the same ages 1429 ; and here we have the ratio of 125-75 males to 100 females. In a census of all the islands in 1850,^^ the males of all ages ' Narrative of a Tour through "8 xhis is given in the Eev. H. T. ■Hawaii,' 18-26, p. 298. Cheever's ' Life in the Sandwich l»- " ' History of the Sandwich lands,' 1851. v. 277 Islands,' 1843, p. 93. ' ) S 258 Tfie Descent of Man. Pabt n. amount to 36,272, and the females to 33,128, or as 109-49 to 100. The males under seventeen years amounted to 10,773, and the females under the same ago to 9593, or as 112"3 to 100. From the census of 1872, the proportion of males of all ages (including half-castes) to females, is as 125u6 to 100. It must be borne i6 mind that all these returns for the Sandwich Islands give the proportion of living males to living females, and not of the births ; and judging from all civilised countries the proportion of males would have been considerably higher it the numbers had referred to bh-ths.*' From the several foregoing cases we have some reason to believe that infanticide practised in the manner above explained, tonds to make a male-producing race ; but I am far from sup- posing that this practice in the case of man, or some analogous process with other species, has been the sole detei-mining cause of an excess of males. There may be some unknown law leading to this result in decreasing races, which have akeady become somewhat infertile. Besides the several causes previously " Dr. Coulter, in describing (' Journal R. Geograph. Soc.,' vol. V. 1835, p. 67) the state of Cali- fornia about the year 1830, says that the natives, reclaimed by the Spanish missionaries, have nearly all perished, or are perishing, al- though well treated, not driven from their native land, and kept from the use of spirits. He at- tributes this, in great part, to the undoubted fact that the men greatly exceed the women in number ; but he does not know whether this is ilue to a failure of female offspring, or to more females dying during early youth. The latter alternative, according to all analogy, is very improbable. He adds that " in- " fanticide, properly so called, is " not common, though very fre- " quent recourse is had to abor- " tion." If Dr. Coulter is correct about infanticide, this case cannot bn advanced in support of Col. ^Nlarshall's view. From the rapid decrease of the reclaimed natives, we may suspect that, as in the cases lately given, their fertility has been diminished from changed jiabits of life. I had hoped to gain some light on this subject from the breeding of dogs ; inasmuch as in most breeds, with the exception, perhaps, of greyhounds, many more female puppies are destroyed than males, just as with the Toda infants. Mr. Cupples assures me that this is usual with Scotch deer-hounds. Unfortunately, I know nothing ot the proportion of the sexes in any breed, excepting greyhounds, and there the male births are to the female as 110-1 to 100. Now from enquiries made from many breeders, it seems that the females are in some respects more esteemed, though otherwise troublesome ; and it does not appear that the female puppies of the best-bred dogs are systematically destroyed more than the males, though this does sometimes take place to a limited extent. There- fore 1 am unable to decide whether we can, on the above principles, ac- count for the preponderance of male births in greyhounds. On the other hand, we have seen that with horses, cattle, and sheep, which are too valuable for the young of either sex to be destroyed, if there is any difference, the females are slightly in excess. Chap. VIH. Proportion of the Sexes. 259 alluded to, the greater facility of pai-turition anongst savages, and the less consequent injury to their male infants, would tend to increase the proportion of live-born males to females. There does not, however, seem to be any necessary connection between savage life and a marked excess of males ; that is if we may judge by the character of the scanty offspring of the lately existing Tasmanians and of the crossed offspring of the Tahltians now inhabiting Norfolk Island. As the males and females of many animals differ somewhat in habits and are exposed in different degrees to danger, it is probable that in many cases, more of one sex than of the other are habitually destroyed. But as far as I can trace out the com- plication of causes, an indiscriminate though large destruction of either sex would not tend to modify the sex-producing power of the species. With strictly social animals, such as bees or ants, which produce a vast number of sterile and fertile females in comparison with the males, and to whom this preponderance is of paramount importance, we can see that those communities would flourish best which contained females having a strong inherited tendency to produce more and more females ; and ia such cases an unequal sex-producing tendency would be ulti- mately gained through natural selection. "With animals living in herds or troops, in which the males come to the front and defend the herd, as with the bisons of North America and certain baboons, it is conceivable that a male-producing tendency might be gained by natural selection ; for the individuals of the better defended herds would leave more numerous descendants. In the case of mankind the advantage arising from having a pre- ponderance of men in the tribe is supposed to bo one chiof causo of the practice of female infanticide. In no case, as far as we can see, would an inherited tendency to produce both sexes in equal numbers or to produce one sex in excess, be a direct advantage or disadvantage to certain individuals more than to others ; for instance, an individual with a tendency to produce more males than females would not succeed better m the battle for life than an individual with an opposite tendency ; and therefore a tendency of this kind could not be gained through natural selection. Nevertheless, there are certam animals (for instance, fishes and cirripedes) in which two or more males appear to be necessary for the fertilisation of the female ; and the males accordingly largely preponderate, but it is by no means obvious how this male-producing tendency could have been acquired. I formerly thought that when a tendency to produce the two sexes in equal numbers was advantageous to the species, it would follow from natural selection, but I now s 2 260 The Descent of Man. Paet ir. Bee that the whole problem is so intricate that it is safer to leave its solution for the future. CHAPTER IX. Seoondaby Sexual Ciiaracteks in the Lower Classes of THE Animal Kingdom. These characters absent in the lowest classes — Brilliant colours — MoUusca — Annelids — Crustacea, secondary sexual characters strongly developed ; dimorphism ; colour ; characters not acquired before maturity— Spiders, sexual colours of; stridulation by the males — Myriapoda. With animals belonging to the lower classes, the two sexes are not rarely united in the same individual, and therefore secondary sexual characters cannot be developed. In many cases where the sexes are separate, both are permanently at- tached to some support, and the one cannot search or struggle for the other. Moreover it is almost certain that these animals have too imperfect senses and much too low mental powers, to appreciate each other's beauty or other attractions, or to feel rivalry. Hence in these classes or yub-kingdoms, such as the Protozoa, Ccelenterata, Echinodermata, Scolecida, secondary sexual cha- racters, of the kind which we have to consider, do not occur; and this fact agrees with the behef that such characters in the higher classes have been acquired thi'ough sexual selection, which depends on the will, desire, and choice of either sex. Nevertheless some few apparent exceptions occui- ; thus, as I hear from Dr. Eaird, the males of certain Entozoa, or internal parasitic worms, differ slightly in coloui- fi'om the females ; but we have no reason to suppose that such diiferences have been augmented through sexual selection. Contrivances by which tbo male holds the female, and which are indispensable for the propagation of the species, are independent of sexual selection, and have been acquu-ed through ordinary selection. Many of the lower animals, whetlier hermaphrodites or with separate sexes, are ornamented with the most brilliant tints, or are shaded and striped in an elegant manner ; for instance, many corals and sea-anemones (Actinire), some jelly-fish (Medusae, Porpita, &c.), some Planari£e, many star-fishes. Echini, Ascidiaus, &c. ; but wc may conclude from the reasons already indicated, namely the union of the two sexes in some of these animals, the permanently afi&xed condition of others, and the low mental powers of all, that such colours do not serve as a sexual attraction, and have not been acquired through sexual selection. Chap. IX. ttextial election. 261 It should be borne in mind that in no case have we siiffi- cient evidence that colours have been thus acquired, ex- cept where one sex is much more brilliantly or conspicuously coloured than the other, and where there is no difference in habits between the sexes sufficient to account for their different colours. But the evidence is rendered as complota as it can ever be, only when the more ornamented indivi- duals, almost always the males, voluntarily display their attractions before the other sex ; for we cannot believe that such display is useless, and if it be advantageous, sexual selection will almost inevitably follow. We may, however, extend this conclusion to both sexes, when coloured ahke, if their colours are plainly analogous to those of ono sex alone in certain other species of the same group. How, then, are we to account for the beautiful or even gorgeous colours of many animals in the lowest classes? It appears doubtful whether such colours often serve as a protec- tion ; but that we may easily err on this head, will be admitted by every one who reads Mr. Wallace's excellent essay on this subject. It would not, for instance, at first occur to any one that the transparency of the Meduste, or jelly-fishes, is of the highest service to them as a protection; biit when we are reminded by Hackel that not only the medusae, but many floating mollusca^ crustaceans, and even small oceanic fishes partake of this same glass-like appearance, often accompanied by prismatic colours, we can hardly doubt that they thus escape the notice of pelagic birds and other enemies. M. Giard is also convinced^ that the bright tints of certain sponges and ascidians serve as a protection. Conspicuous colours ai'e likewise beneficial to many am'mals as a warning to their would-be devourers that they are distasteful, or that they possess some special means of defence ; but this subject will bo discussed more conveniently hereafter. We can, in our ignorance of most of the lowest animals, only say that their bright tints result either from the chemical nature or the minute structure of their tissues, independently or any benefit thus derived. Hardly any colour is finer than that of arterial blood; but there is no reason to suppose that the colour of the blood is in itself any advantage; and though it adds to the beauty of the maiden's cheek, no one will pretend that it has been acquired for this purpose. So again with many animals, especially the lower ones, the bile is richly coloured'; thus, as I am informed by Mr. Hancock, the extreme beauty of the Eohdae (naked sea-slugs) is chiefly due to the biliary glands » ' Archives de Zoolog. Eip^r.,' Oct. 1872, p. 563. 262 The Descent of Man. Pakt II. . Sieing seen through the translucent integiunents— this beautjr being probably of no service to these animals. The tints of tho decaying leaves in an American forest are described by every one as gorgeous; yet no one supposes tliat these tmts are of the least advantage to the trees. Bearing in mind how many substances closely analogous to natural organic compounds have ■•^cen recently formed by chemists, and which exhibit the most splendid colours, it would have been a strange fact if substances similarly coloured had not often origmated, independently of any useful end thus gained, in the complex laboratory of living organisms. The sub-ldngdom of the Mollusca. — Throughout this great division of the animal kingdom, as far as I can discover, secondary sexual characters, such as we are here considering, never occur. Nor could they be expected in the three lowest classes, namely in the Ascidians, Polyzoa, and Brachiopods (constituting the MoUuscoida of some authors), for most of these animals are permanently ailixed to a support or have their sexes imited in the same individual. In the LamelUbranchiata, or bivalve shells, hermaphroditism is not rare. In the next higher class of the Gasteropoda, or univalve shells, the sexes are either united or separate. But in the latter case the males never possess special organs for finding, securing, or charming the females, or for fighting with other males. As I am informed by Mr. Gwyn Jeffreys, the sole external difference between the sexes consists in the shell sometimes difi'ering a little in form ; for instance, the shell of the male periwinkle {Littorina littorea) is narrower and has a more elongated spire than that of the female. But differences of this natui-e, it may be presumed, are directly connected with the act of reproduction, or with the development of the ova. The Gasteropoda, though capable of locomotion and furnished with imperfect eyes, do not appear to be endowed with sufficient mental powers for the members of the same sex to struggle together in rivalry, and thus to acquire secondary sexual characters. Nevertheless with the pulmoniferous gasteropods, or land-snails, the pairing is preceded by courtship; for these animals, though hermaphrodites, are compelled by then- structure to pair together. Agassiz remarks,- " Quiconque a eu I'occasion " d'observer les amours des lima5ons, ne saurait mettre en doute " la seduction deployee dans les mouvements et les allui-es qui " preparent et accomplissent le double embrassement de ces " hermaphrodites." These animals appear also susceptible of some degree of permanent attachment : an accurate observer, « ' De I'Espfece et de la Class.' &c., 1869, p. 106. Chap. IX. Molluscs. 263 Ml-. Lonsdale, informs mo that he placed a pair of land-snails, ( Helix pomatia), one of which was weakly, into a small and ill- provided garden. After a short time the strong and healthy individual disappeared, and was traced by its track of shme over a waU into an adjoining well-stocked garden. Mr. Lonsdale concluded that it had deserted its sickly mate; but after an absence of twenty-four hours it returned, and apparently communicated the result of its successful exploration, for both then started along the same track and disappeared over the waU. Even in the highest class of the MoUusca, the Cephalopoda or cuttlefishes, in which the sexes are separate, secondary sexual characters of the present kind do not, as far as I can discover, occur. This is a surprising circumstance, as these animals possess highly-developed sense-organs and have considerable mental powers, as will be admitted by every one who has watched their artful endeavoui'S to escape fi'om an enemy.* Certain Cephalopoda, however, are characterised by one extraordinary sexual character, namely, that the male element collects within one of the arms or tentacles, which is then cast off, and clinging by its sucking-discs to the female, lives for a time an independent life. So completely does the cast-off arm resemble a separate animal, that it was described by Cuvier as a parasitic worm under the name of Hectocotyle. But this marvellous structui'e may be classed as a primary rather than as a secondary sexual character. Although with the MoUusca sexual selection does not seem to have come into play; yet many univalve and bivalve shells, Buch as volutes, cones, scallops, &c., are beautifiilly coloiu-ed and shaped. The colours do not appear in most cases to be of any use as a protection ; they are probably the direct result, as in the lowest classes, of the nature of the tissues ; the patterns and the sculpture of the shell depending on its manner of gi-owth. The amount of light seems to be influential to a certain extent; for although, as repeatedly stated by Mr. Gwyn Jeffreys, the shells of some species living at a profound depth are brightly coloured, yet we generally see the lower surfaces, as well as the parts covered by the mantle, less highly-coloured than the tipper and exposed surfaces.* In some cases, as with shells 3 See for instance, the account influence of light on the colours of which I have given in my 'Journal a froudescent incrustation, de- of Researches, 1845 p. 7. posited by the surf on the coast- \ I have given (' Geolog. Obser- rocks of Ascension, and formed by Tations on Volcanic Islands,' 1844, the solution of triturated sea-shella. p. o3) a curious instance of the 2t>4 TJie Descent of Man. Pakt 11. living amongst corals or brightly-tinted sea-weeds, the bright colours may serve as a in-otection.* But that many of the nudi- branch mollusca, or sea-slugs, are as beautifully coloured as any shells, may bo seen in Messrs. Alder and Hancock's magnificent work ; and from information kindly given me by Mr. Hancock, it seems extremely doubtful whether these coloui-s usually serve as a protection. With some species this may be the case, as with one kind which lives on the green leaves of algas, and is itself bright-green. But many brightly-coloui-ed, white or otherwise conspicuous species, do not seelc concealment ; whilst again some equally conspicuous species, as well as other dull-coloured kinds, live under stones and in dark recesses. So that with these nudi- branch molluscs, colour apparently does not stand in any close- relation to the nature of the places which they inhabit. These naked sea-slugs are hermaphi-odites, yet they pair together, as do land-snails, many of which have extremely pretty shells. It is conceivable that two hermaphrodites, attracted by each other's greater beauty, might unite and leave offspring which would inherit their parents' gi-eater beauty. But with such lowly-organised creatures tliis is extremelj- improbable. Nor is it at all obvious how the offspring from the more beautiful pairs of hermaphrodites would have any ad- vantage over the offspring of the less beautiful, so as to increase in number, unless indeed vigour" and beauty generally coincided. AVe have not here the case of a number of males becoming mature before the females, with the more beautiful males selected by the more vigorous females. If, indeed, brilliant colours were beneficial to a hermaphi-odite animal in relation to its general habits of hfe, the more brightly-tinted indiv-iduals would succeed best and would increase in number; but tliis would be a case of natural and not of sexual selection. Sub-Mngdom of the Vermes : Class, Annelida (or Sea-worms). — In this class, although the sexes, when separate, sometimes differ from each other in characters of such importance that they have been placed under distinct genera or even families, yet the differences do not seem of the kind which can be safely at- tributed to sexual selection. These animals are often beaiiti- fully coloured, but as the sexes do not differ in this respect, we are but little concerned with them. Even the Nemertians, though so lowly organised, " vie in beauty and variety of " colouring with any other group in the invertebrate series;" yet' * Dr. Morse has lately ■ discussed ' Proc. Boston See. of Kat. Hist.* this subject in his paper on the vol. .xiv., April, 1871, Adaptive Coloration of Mollusca, Chap. IX. Crustaceans. 265: Dr. Mcintosh ° cannot discover that these colours are of any service. The sedentary annelids become duller- coloured, ac- cording to M. Quatrefages/ after the period of reproduction ; and this I presume may be attributed to their less vigorous condition at that time. All these worm-like animals apparently stand too low in the scale for the individuals of either sex to exert any choice in selecting a partner, or for the individuals of the same sex to struggle together in rivalry. Siib-hingdom of the AHliropoda: Class, Crustacea. — In this great class we fii-st meet with imdoubted secondary sexual characters, often developed in a remarkable manner. Unfortunately the habits of crustaceans are very imperfectly known, and we cannot explain the uses of many structures pecuhar to one sex. "With the lower parasitic species the males are of small size, and they alone are furnished with perfect swimming-legs, antennae and sense-organs ; the females being destitute of these organs, with their bodies often consisting of a mere distorted mass. But these extraordinary diiferences between the two sexes are no doubt related to their widely different habits of life, and con- sequently do not concern us. In various crustaceans, belonging to distinct families, the anterior antennte are furnished with i)eculiar thread-like bodies, which are believed to act as smelling-organs, and these are much more numerous in the males than in the females. As the males, without any unusual development of their olfactory organs, would almost certainly be able sooner or later to find the females, the increased number of the smelling- threads has probably been acquired thi'ough sexual selection, by the better provided males having been the more successful ii> finding partners and in producing offspring. Fritz Miiller has described a remarkable dimorphic species of Tanais, in which the male is represented by two distinct forms, which never gi'aduato into each other. In the one form the male is furnished with more numerous smelling-threads, and in the other form with more powcrftil and more elongated chelee or pincers, which servo to hold the female. Fritz Miiller suggests that these differences between the two male forms of the same species may have originated in certain individuals having varied in the number of the smelling-threads, whilst other individuals varied in the shape and size of their chelse; so that of the former, those which were best able to find the female, and of the latter, those whictt « See his beautiful monogr.-.ph on ? gee M. Perrier, « I'Orio-ine de ♦British Annelids, part i. 1873, I'Homme d'api-fes Darwin,' ' Rorue. ^- Scientifique,' Feb. 1873, p. 866. 266 The Descent of Mmu Paut II. were best able to hold her, have left the greatest number of progeny to inherit their respective advantages." In some of the lower crustaceans, the right anterior antenna of the male differs greatly in structure from the left, the latter resembling in its simple tapering joints the antenna of the female. In the male the modified antenna is either swollen in the middle or angularly bent, or converted (fig. 4) into an elegant, and sometimes wonderfully complex, prehensile organ.** It serves, as I hear from Sir J. Lubbock, to hold the female, and for this same purpose one of the two posterior legs (6) on the same side of the body is converted into a forceps. In another family the inferior or posterior antennae are " curiously zigzagged " in the males alone. In the higher crustaceans the an- terior legs are developed into chelae or pincers; and these are generally larger in the male than in the female, — so much so that the market value of the male edible crab {Cancer j^agurus). according to Mr. C. Spence Bate, m five times as great as that of the fe- male. In many species the chelae are of unequal size on the opposite side of the body, the right-hand one being, as I am informed by Mr. Bate, generally, though not invariably, the largest. This inequality is also often much greater in the male than in the female. The two chela of the male often differ in structure (figs. 5, 6, and 7), the smaller one resembling that of the female. What advantage is gained by their inequality in size on the opposite sides of the Fig. 4. Labidoeera Darwinii (from Lubbock). a. Part of right anterior an- tenna of male, forming a prehensile organ. !). Posterior pair of thoracic legs of male. c. Ditto of female. * ' Facts and Arguments for Darwin,' English translat. 1869, p. 20. See the preTious discussion on the olfactory threads. Sars has described a somewhat analogous case (as quoted in ' Nature,' 1870, p. 455) in a Norwegian crustacean, the Pontoporeia affinis. » See Sir J. Lubbock in ' Annals and Mag. of Nat. Hist.' vol. -^i. 1853, pi. i. and x. ; and vol. xii. (1853) pi. vii. See also Lubbock in 'Transact. Ent. Soc' vol. iv. now series, 1856-1858, p. 8. With re- spect to the zig-zagged antenn.-o montioued below, see Fritz Miiller, ' Facts and Arguments for Darwiu, 1869, p. 40, foot-note. Chap. IX. Crustaceans. 267 body and by the inequality being much greater in the male than in the female; and why, when they are of equal size, both are Fig. 5. Anterior part of body of Callianassa (from Milne-Edwards), showing the un- equal and differently-constructed right and left-hand cliela: of the male. The artist by mistalie has reversed the drawing, and made the left-hand chela the largest. n Fig. 6. Fig. 1. Fig. 6. Second leg of male Orchestia Tucuratinga (from Fritz Miiller). Fig. 7. Ditto of female. often much larger in the male than in the female, is not known. As I hear from Mr. Bate, the chelas are sometimes of such length and size that they cannot possibly be used for carrying food to the mouth. In the males of certain fresh-water prawns (Palremon) the right leg is actually longer than the whole body.^" The great size of the one leg with its chelaj may aid the male in fighting with his rivals; but this will not account for their " See a paper by Mr. C. Spence 585. I am greatly indebted to Mr. Bate, with figures, iu ' Proc. Zoolo^. Speuce Bate for nearly all the above Soc' 1868, p. 363 ; and on the statements with respect to the chela nomenclature of the genus, ibid. p. of the higher crustaceans. 268 The Descent of Man. Part II. inequality in the female on the opposite sides of of the Ijody. In Golasimus, according to a statement quoted by Milne-Edwards/"- the male and the female live in the same burrow, and this shews that tliey pair ; the male closes the mouth of the burro\v with one of its chete, which is enormously developed ; so that hero it indirectly serves as a means of defence. Their main use, however, is probably to seize and to secure the female, and this in some instances, as Avith Gammarus, is known to be the case. The male of the hermit or soldier crab (Parjurus) for weeks together, carries about the shell inhabited by the female.'^ The sexes, however, of the common shore-crab (Carcinus manas), as Mr. Bate informs me, unite directly after the female has moulted her hard shell, Avhen she is so soft that she would be injured if seized by the strong pincers of the male ; but as she is caught and carried about by the male before moulting, she could then be seized with impunity. Fritz Miiller states that certain species of Melita are distin- guished from all other amphipods by the females having " the coxal lamellsB of the penultimate pair of feet produced into ' hook-like processes, of which the males lay hold with the " hands of the first pair." The development of these hook-like processes has probably followed from those females which were the'most securely held diuing the act of reproduction, having left the largest number of offspring. Another Brazilian amplii- pod (Orchestia Baru'inii, fig. 8) jsresents a case of dimorphism, like that of Tanais ; for there are two male forms, which differ in the structure of their chelfe.'^ As either chela would certainly suffice to hold the female, — for both are now used for this jjui-pose, — the two male forms probably originated by some having varied in one manner and some in another ; both forms having derived certain special, but nearly equal advantages, from their differently shaped organs. It is not known that male crustaceans fight together for the possession of the females, but it is probably the case ; for with most animals when the male is larger than the female, he seems to owe his greater size to his ancestors having fought with other males during many generations. In most of the orders, especially in the highest or the Brachyura, the male is larger than the female ; the parasitic genera, however, in which the sexes follow different habits of life, and most of the Ento- mostraca must be excepted. The chelae of many crustaceans are n 'Hist. Nat. des Crust.' torn. ii. of S. Devon.' 1837, p. 50. Fritz Miiller, 'Facts and Argu- Mr. C. Spence Bate, * Brit, ments for Darwin,' 1869, pp. 25-2a ^gsoc, Fourth Report on the Fauna Chap. IX. Crustaceans. 269 -weapons well adapted for fighting. Thus when a Devil-crab ( Portunus puber) was seen by a son of Mr. Bate fighting with a Carciims mcenas, the latter was soon throAvn on its back, and had every limb torn from its body. When several males of a Brazilian Gelasimns, a species fui-nished with immense pincers, were placed together in a glass vessel by Fritz Miiller, they mutilated and killed one another. Mr. Bate put a large male Carcinus 8. Orchestia B.winU Kh. the a,0.rently-cons™ m^ms into a pan of water, inhabited by a female which was paared with a smaller male ; but the latter was soon dispossessed. 270 The Desce7it of Man, Part H. ]Mr. Bate adds, " if they fought, the victory was a bloodless one, " for I saw no wounds." This same naturabst separated a male sand-slcipper (so common on our sea-shores), Gammarus marinus, from its female, both of whom were imprisoned in the same vessel with many individuals of the same species. The female, when thus divorced, soon joined the others. After a tuiie the male was put again into the same vessel ; and he then, after swimming about for a time, dashed into the crowd, and without any fighting at once took aAvay his wife. This fact shews that in the Amphipoda, an order low in the scale, the males and females recognise each other, and are mutually attached. The mental powers of the Crustacea are probably higher than at first sight appears probable. Any one who tries to catch one of the shore-crabs, so common on tropical coasts, will perceive how wary and alert they are. There is a large crab {Birgus latro), found on coral islands, which makes a thick bed of the picked fibres of the cocoa-nut, at the bottom of a deep burrow. It feeds on the fallen fruit of this tree by tearing off the husk, fibre by fibre ; and it always begins at that end where the three eye-like depressions are sitxiated. It then breaks through one of these eyes by hammering with its heavy front pincers, and turning round, extracts the albimiinous core with its narrow posterior pincers. But these actions are probably instinctive, so that they would be performed as well by a young animal as by an old one. The following case, however, can hardly be so con- sidered : a trustworthy naturalist. Mi. Gardner," whilst watching a shore-crab (Gelasimus) making its burrow, threw some shells towards the hole. One rolled in, and three other shells remained within a few inches of the mouth. In about five minutes the crab brought out the shell which had fallen in, and carried it away to the distance of a foot ; it then saw the three other shells lying near, and evidently thinking that they might likewise roll in, carried them to the spot where it had laid the first. It would, I think, be difficult to distmguish this act from one performed by man by the aid of reason. Mr. Bate does not know of any well-marked case of difference of colour in the two sexes of oui- British crustaceans, in which respect the sexes of the higher animals so often differ. In some cases, however, the males and females differ slightly in tint, but Mr. Bate thinks not more than may be accounted for by then- different habits of life, such as by the male wandermg more about, and being thus more exposed to the Light. Dr. Power 11 ' Travels in the Interior of 463, ;in account of the hiibits of the Brazil,' 1846, p. 111. I have given, Birgus. in my 'Journal of Researches,' p. Ch.vp. IX. Crttstaceans. 271 tried to distingiiisli by colour the sexes of the several species which inhabit the Mauritius, but failed, except with one species of Sqtiilla, probably S'. stylifera, the male of which is described as being " of a beautiful bluish-green," with some of the appendages cherry-red, whilst the female is clouded with brown and gi'ey, " with the red about her much less vivid than in the male." In this case, we may suspect the agency of sexual selection. Fi'om M. Bert's observations on Daphnia, when placed in a vessel illuminated by a prism, we have reason to believe that even the lowest crustaceans can distinguish colours. With Saphirina (an oceanic genus of Entomostraca), the males are furnished with minute shields or ceU-hke bodies, which exhibit beautiful changuig colours ; these are absent in the females, and in. both sexes of one species." It would, however, be extremely rash to conclude that these curious organs serve to attract the females. I am informed by Fritz Miiller, that in the female of a Brazilian species of Gelasimus, the whole body is of a nearly uniform greyish-brown. In the male the posterior part of the cephalo-thorax is pure white, with the anterior part of a rich green, shading into dark brown ; and it is remarkable that these colours are liable to change in the coui'se of a few minutes — the white becoming dirty grey or even black, the green " losing much " of its brilliancy." It deserves especial notice that the males do not acquire their bright colours until they become mature. They appear to be much more numerous than the females; they differ also in the larger size of their chelae. In some species of the genus, probably in all, the sexes pair and inhabit the same burrow. They are also, as we have seen, highly intelligent animals. From these various considerations it seems probable that the male in this species has become gaily ornamented in order to attract or excite the female. It has just been stated that the male Gelasimus does not acquire his conspicuous colours until mature and nearly ready to breed. This seems a general rule in the whole class in respect to the many remarkable structtiral differences between the sexes. We shall hereafter find the same law prevailing throughout the great sub-kingdom of the Vertebrata ; and in all cases it is eminently distinctive of characters which have been acquired through sexual selection. Fritz MtiUer" gives some striking instances of this law ; thus the male sand-hopper (Orchestia) does not, until nearly full grown, acquire his large claspers, " Mr. Oh. Fraser, in 'Proc. Zoo- >« Glaus, 'Die freilebenden Cone- iog. See' 1869, p. 3. I am indebted poden,' 1863, s. 35. so Mr. Bate for Dr. Power's state- " ' Facts and Arguments,' kc, taent. p. 79. 272 Tlie Descent of Man. rAK'i ir. which are very differently constructed from those of the female; whilst young, his claspers resemble those of tlie female. Class, Arachnida (Spiders).— The sexes do not generally differ much in colour, but the males are often darker than the females, as may bo seen in Mr. Blackwall's magnificent work."* In some species, however, the difference is conspicuous : thus the female of Sparassus smaragdulus is dulhsh gi-een, whilst the adult male has the abdomen of a fine yellow, with three longitudinal stripes of rich red. In certain species of Thomisus the sexes closely resemble each other, in others they differ much ; and analogous cases occur in many other genera. It is often difficult to say which of the two sexes departs most from the ordinary coloration of the genus to which the species belong ; but Mr. Blackwali thinks that, as a general rule, it is the male ; and Canestrini remarks that in certain genera the males can be specifically dis- tinguished with ease, but the females with great difiiculty. I am informed by Mr. Blackwali that the sexes whilst young usually resemble each other ; and both often undergo great changes in colour during their successive moults, before arriving at maturity. In other cases the male alone appears to change coloiu'. Thus the male of the above bright-coloured Sparassus at first re- sembles the female, and acquii-es his pecuhar tints only when nearly adult. Spiders are possessed of acute senses, and exhibit much intelligence; as is well known, the females often shew the strongest affection for their eggs, which they carry about enveloped in a silken web. The males search eagerly for the females, and have been seen by Canestrini and others to fight for possession of them. This same author says that the union of the two sexes has been observed in about twenty species ; and he asserts positively that the female rejects some of the males who court her, thi'eatens them with open, mandibles, and at last after long hesitation accepts the chosen one. From these several considerations, we may admit with some confidence that the well-marked differences in colour between the sexes of certain species are the results of sexual selection ; though we have not here the best kind of evidence, — the display by the male of his ornaments. Fi'om the extreme variability of colour in the male of some sj)ecies, for instance of Theridion liiieatuin, it would appear that these sexual characters of the males have not as yet become well fixed. Canestrini draws the same conclusion from " ' A. History of the Spiders of ' Caratteri sessuali secondarii degli Great Britain,' 1861-G4. For the Arachnidi,' in the 'Atti della Soc. followiug foots, see pp. 77, 88, 102. Veneto-Trentina di Sc. >J.^t. Padova, This author has recently pub- vol. i. Fasc. 3, 1873. Kshed a valuable essay on the Chap. IX. Spiders. 2/3 the fact that the males of certain species present two forms, differing from each other in the size and length of their jaws ; and this reminds us of the above cases of dimorphic crustaceans. The male is generally much smaller than the female, sometimes to an extraordinary degree/" and he is forced to be extremely cautious in making his advances, as the female often carries her coyness to a dangerous pitch. De Geer saw a male that " in tho " midst of his preparatory caresses was seized by the object of " his attentions, enveloped by her in a web and then devoured, a " sight which, as he adds, filled him with horror and indignation." ''^ The Eev. 0. P. Cambridge accouuts in the following manner for the extreme smallness of the male in the genus Nephila. " M. Vinson gives a graphic account of the agile way in which " the diminutive male escapes from the ferocity of the female, by " gliding about and playing hide and seek over her body and " along her gigantic limbs : in such a pursuit it is evident that " the chances of escape would be in favour of the smallest males, " while the larger ones would fall early victims ; thus gradually " a diminutive race of males would be selected, until at last they " would dwindle to the smallest possible size compatible with the " exercise of their generative functions, — in fact probably to the " size we now see them, i.e., so small as to be a sort of parasite " upon the female, and either beneath her notice, or too agile and " too small for her to catch without great difficulty." Westring has made the interesting discovery that the males of several species of Theridion^ have the power of making a stridulating sound, whilst the females are mute. The ap- paratus consists of a serrated ridge at the base of the abdomen, against which the hard hinder part of the thorax is rubbed ; and of this structure not a trace can be detected in the females. It deserves notice that several writers, including the well-known arachnologist Walckenaer, have declared that spiders are attracted by music.2* From the analogy of the Orthoptera and Homoptera, tion to Entomology,' vol. i. 1818, p. 280. ^2 'Proc.Zoolog. Soc' 1871, p. 621. Theridion (Asagem, Sund.) scrratipes, A-punctatum et gutta- turn; see Westring, in Kroyer, ' Naturhist. Tidskrift,' vol. iv. 1842- 1843, p. 349; and vol. ii. 1846- 1849, p. 342. See, also, for other species, ' Aranea SueciciE,' p. 184. Dr. H. H. van Zoutaveen, ia his Dutch translation of this work (vol. i. p. 444), has collected several cases. Aug. Vinson ('Aran^ides des lies de la Reunion,' pi. vi. figs. 1 and 2) gives a good instance of the small size of the male, in Epeira nigra. In this species, as I may add, the male is testaceous and the female black with legs banded with red. Other even more striking cases of inequality in size between the sexes have been recorded (' Quarterly Journal of Science ' 1868, July, p. 429); but I have ■ot seen the original accounts. Kirby and Spence, ' Introduc- T 274 The Descent of Man. Paet IL to be described in the next chapter, we may feel almost sure tliat the Btridulation serves, as Westring also believes, to call or to excite the female ; and this is the first case known to me in the ascending scale of the animal kingdom of sounds emitted for this purpose.^^ Class, Myriapoda. — In neither of the two orders in this class, the millipedes and centipedes, can I find any well-mar kea instances of such sexual differences as more particularly concern us. In Glomeris limhata, however, and perhaps in some few other species, the males differ slightly in colour from the females; but this Glomeris is a highly variable species. In the males of the Diplopoda, the legs belonging either to one of the anterior or of the posterior segments of the body are modified into pre- hensile hooks which serve to secure the female. In some species of lulus the tarsi of the male are furnished with membranous suckers for the same purpose. As we shall see when we treat of Insects, it is a much more unusual circumstance, that it is the female in Lithobius, which is furnished with prehensile appendages at the extremity of her body for holding the male.*^" CHAPTEE X. Secondakt Sexual Chabaoteks op Insects. Diversified structures possesse'l by the males for seizing the females — Differences between the sexes, of which the meaning is not understood — Difference in size between the sexes — Thysanura — Diptera — Hemiptera — Homoptera, musical powers possessed by the males alone — Orthoptera, musical instruments of the males, mucli diversified in structure ; pugnacity ; colours — Neuroptera, sexual differences in colour — Hynie- noptera, pugnacity and colours — Coleoptera, colours ; furnished with great horns, apparently as an ornament ; battles ; stridulating organs generally common to both sexes. In the immense class of insects the sexes sometimes differ in their locomotive-organs, and often in their sense-organs, as in the pectinated and beautifully plumose antennae of the males of many species. In Chloeon, one of the Ephemerae, the male has great pillared eyes, of which the female is entirely destitute.' The ocelli are absent in the females of certain insects, as in the Hilg-endcrf, however, has lately called attention to an analogous structure in some of the higher crustaceans, which seems adapted to produce sound ; see ' Zoological Record,' 1869, p. 603. *• Walckenaer et P. Gervais, ' Hist. Nat. des Insectes : Apteres,* . tom. iv. 1847, pp. 17, 19, 68. 1 Sir J. Lubbock, ' Trausact. ' Linnean Soc' vol. xxv. 1866, p. 484. With respect to the Mu- tillidse see Westwood, ' Modera Class, of Insects,* vol. ii. p. 213. Chap. X. Insects. 275 Mutillidfe; and here the females are likewise wingless. But we are chiefly concerned with structui-es by which one male is enabled to conquer another, either in battle or courtship, thi'ough his strength, pugnacity, ornaments, or music. The innumerable contrivances, therefore, by which the male is able to seize the female, may be briefly passed over. Besides the complex structures at the apex of the abdomen, which ought perhaps to be ranked as primary organs,^ "it is astonishing," as LIr. B. D. Walsh ^ has remai'ked, " how many different organs are worked in by natui'e " for the seemingly insignificant object of enabling the male to " gi'asp the female firmly." The mandibles or jaws are some- times used for this pm-pose ; thus the male Corydalis cornutus (a neui'opterous insect in some degree allied to the Dragon-flies, &c.) has immense curved jaws, many times longer than those of the female ; and they are smooth instead of being toothed, so that he is thus enabled to seize her without injury.'' One of the stag-beetles of North America (Lucanus elaphus) uses his jaws, which are much larger than those of the female, for the same purpose, but probably likewise for fighting. In one of the sand-wasps (Ammophila) the jaws in the two sexes are closely alike, but are used for widely different purposes : the males, as Professor Westwood observes, " are exceedingly ardent, seizing " their partners round the neck with their sickle-shaped jaws;"" whilst the females use these organs for burrowing in sand-bariks and making their nests. The tarsi of the front-legs are dilated in many male beetles, or are furnished with broad cushions of hairs ; and in many genera of water-beetles they are armed with a round flat sucker, so that the male may adhere to the slippery body of the female. It is a ^ These organs in the male often differ in closely-allied species, and afford excellent specific characters. But their importance, from a func- tional point of view, as Mr. R. MacLachlan has remarked to me, has probably been overrated. It has been suggested, that slight dif- ferences in these organs would suffice to prevent the intercrossino- of well-marked varieties or incipient species, and would thus aid in their development. That this can hardly be the case, we may infer from the many recorded cases (see, for in- instance, Bronn, ' Geschichte der Natnr,' B. ii. 1843, s. 164; and Westwood, * Transact. Ent. Soc' Tol. iii. 1842, p. 195) of distinct species having been observed in union. Mr. MacLachlan informs me (vide ' Stett. Ent. Zeitung,' 1867, s. 155) that when several species of Phryganidte, which pre- sent strongly-pronounced differences of this kind, were confined together by Dr. Aug. Meyer, they coupled, and one pair produced fertile ova. ' ' The Practical Entomologist,' Philadelphia, vol. ii. May, 1867, p. 88. * Mr. Walsh, ibid. p. 107. * 'Modern classification of In- sects,' vol. ii. 1840, pp. 205, 206. Mr. 'Walsh, who called my attention to the double use of the jaws, says that he has repeatedly observed this fact. T 2 276 The Descent of Man. Part 11, much more unusual circumstance that tlie female of some water- boetles (Dytiscus) have their elytra deeply grooved, and inr Adlim sulcatiis thickly set with hau\s, as an aid to the male. The females of some other water- beetles (Hydroporus) have their elytra punctured for the same purpose." lu the male of Crahro- crihrurius (fig. 9), it is the tibia- which is dilated into a broad- horny plate, with minute mem- braneous dots, giving to it a sin- gular appearance like that of a riddle.'' In the male of Penthe (a genus of beetles) a few of the middle joints of the antennae are dilated and furnished on the in- ferior surface with cushions of hair, exactly like those on the tarsi of the Carabidas, " and obviously for " the same end." In male di'agon- flies, "the appendages at the tip " of the tad are modified in au " almost infinite variety of curious " patterns to enable them to em- " brace the neck of the female." Lastly, in the males of many in- sects, the legs are furnished with peculiar spines, knobs or spurs ; or the whole leg is bowed or thickened, but this is by no means invariably a sexual character ; or one pair, or all thi'ee pairs are elongated, sometimes to an extravagant length.* The sexes of many s]pecies in all the orders present differences, of which the meaning is not understood. One curious case is that of a beetle (fig. 10), the male of which has the left mandible much enlarged; so that the mouth is greatly distorted. In another Carabidous beetle, Eurygnathus,^ we have the case,. * We have here a curious and inexplicable case of dimorphism, for Fig. 9. Crabro cribrarius. Upper figure, male; lower liguie, female. some of the females of four Euro- jjean species of Dytiscus, and of certain species of Hydroporus, have their elytra smooth ; and no inter- mediate gradations between the sulcated or punctured, and the quite smooth elytra have been observed. See Dr. H. Schaum, as quoted in the ' Zoologist,' vol. v.-vi. 1847-48, p. 1896, Also Kirby and Spence, ' Introduction to Entomology,' vol. iii. 1826, p. 305. ' West wood, 'Modern Class.' vol. ii. p. 193. The following state- ment about Penthe, and others in- inverted commas, are taken fronr Mr. Walsh, 'Practical Entomolo- gist,' Philadelphia, vol. ii. p. 88. ' Kirby .and Spence, 'Introduct.' &c., vol. iii. pp. 332-336. » 'Jnsecta Maderensia,' 1854, p» 20. Chap. X. Insects. rjiiqiie as far as known to Mr. Wollaston, of the head of the female being much broader and larger, though in a variable degree, than that of the male. Any number of such cases could be given. They abound m the Lepidoptera: one of the most extra- ordinaiy is that certain male butterflies have their fore-legs more or less atrophied, with the tibife and tarsi reduced to mere ru- dimentary knobs. The wings, also, in the two sexes often differ in neuration," and some- times considerably in outline, as in the Ari- coris epitus, which was shewn to me in the ^British Museum by Mr. A. Butler. The males of certain South American butterflies have -tufts of hair on the margins of the wings, and horny excrescences on the discs of the posterior pair.^^ In several British butter- flies, as shewn by Mr. Wonfor, the males alone are in j)arts clothed with peculiar scales. The use of the bright light of the female ^low-worm has been subject to much discus- 'Sion. The male is feebly luminous, as are the ilarvffi and even the eggs. It has been sup- iposed by some authors that the light serves to frighten away enemies, and by others to guide the male to the female. At last, Mr, Belt '2 appears to have solved the difficulty, he finds that all the Lampyrida3 which he has ■tried are highly distasteful to insectivorous mammals and birds. Hence it is in accordance •with Mr. Bates' view, hereafter to be explained, that many insects mimic the Lampyrida3 closely, in order to be mistaken for them, and -thus to escape destruction. He further be- lieves that the luminous species jDrofit by once recognised as unpalatable. being at Fig. 10. Tapbroderes distort us (much en- larged). Upper fig- ure, male ; lower figure, female. It is probable that the same explanation may be extended to the " E. Doubleday, ' Annals and Mag. of Nat. Hist.' vol. i. 1848, 1. i04», p. 3.79. I may add that the wings in ■ certain Hymenoptera (see Shuckard, ■'Fossorial Hymenop.' 1837, pp. 39- 43) differ in neuration according to sex. " H. W. Bates, iw 'Jonraai of Proc. Linn. Soc' vol, vi. 1862, p. 74. Mr. Wonfor's observations are quoted in ' Popular Science Eeview/ 1868, p. 343. 'The Naturalist in Nicai-agua^- 1874, pp. 316-320. On the phos- phorescence of the eggs, see ' Annals and Mag. of Nat. Hist.' 1871,' Nov,, p. 372. 278 TJie Descent of Man, Pabt 11. Elaters, both sexes of which are highly luminous. It is not known why the wings of the female glow-worm have not been developed; but in her present state she closely resembles a larva, and as larvte are so largely preyed on by many animals, we can understand why she has been rendered so much more luminous and conspicuous than the male ; and why the Iarva> themselves are likewise luminous. Difference in Size between the Sexes. — With insects of all kinds the males are commonly smaller than the females; and this difference can often be detected even in the larval state. So considerable is the difference between the male and female cocoons of the silk-moth (Bomhyx mori), that in Prance they are separated by a particular mode of weighing.'^ In the lower classes of the animal kingdom, the greater size of the females seems generally to depend on their developing an enormous number of ova ; and this may to a certain extent hold good with insects. But Dr. "Wallace has suggested a much more probable explanation. He finds, after carefully attending to the develop- ment of the caterpillars of Bombyx cynthia and yamamai, and especially to that of some dwarfed caterpillars reared from a second brood on unnatural food, " that in proportion as the in- " dividual moth is finer, so is the time required for its metamor- "phosis longer; and for this reason the female, which is the " larger and heavier insect, from having to carry her numerous " eggs, will be preceded by the male, which is smaller and has " less to mature." ^* Now as most insects are short-lived, and as they are exposed to many dangers, it would manifestly be ad- vantageous to the female to be impregnated as soon as possible. This end would be gained by the males being first matured in large numbers ready for the advent of the females ; and this again would naturally follow, as Mr. A. E. "Wallace has re- marked,^^ through natural selection; for the smaller males would be first matured, and thus would procreate a large number of offspring which would inherit the reduced size of then- male parents, whilst the larger males from being matiued later would leave fewer offspring. There are, however, exceptions to the rule of male insects being smaller than the females : and some of these exceptions are intelligible. Size and strength would be an advantage to the males, which fight for the possession of the females; and in those cases, as with the stag-beetle (Lucanus), the males are larger than the females. There are, however, other beetles 1' Robmet, '"7ers a Soie,' 1848, vol. v. p. 486. p. 207. " ' Journal af Proc. Eat. Sco " 'Transact. Ent. Soc' 3rd series, Feb. 4th, 1867-, p. Ixxi. Chap. X. Thysamira. ■which are not known to fight together, of which the males exceed the females in size ; and the meaning of this fact is not known; but in some of these cases, as with the huge Dynastes and Megasoma, we can at least see that there would be no necessity for the males to be smaller than the females, in order to be matured before them, for these beetles are not short-lived, and there would be ample time for the pairing of the sexes. So again, male dragon-flies (Libellulidse) are sometimes sensibly larger, and never smaller, than the females;^" and as Mr. MacLachlan believes, they do not generally pair with the females until a week or fortnight has elapsed, and until they have asstmaed their proper masculine coloui's. But the most curious case, shewing on what complex and easily-overlooked relations, so trifling a character as difference in size between the sexes may depend, is that of the aculeate Hymenoptera ; for Mr. F. Smith informs me that throughout nearly the whole of this large group, the males, in accordance with the general rule, are smaller than the females, and emerge about a week before them ; but amongst the Eees, the males of A'pis melUfica, Anthidiunt, manicatimi, and AntkopJiora acervoriim, and amongst the FossoreSj the males of the Methoca ichneumonides, are larger than the females. The explanation of this anomaly is that a marriage flight is absolutely necessary with these species, and the male requu'es great strength and size in order to carry the female tlirough the air. Increased size has here been acquired in op- position to the usual relation between size and the period of development, for the males, though larger, emerge before the smaller females. We will now review the several Orders, selecting such facts as more particularly concern us. The Lepidoptera (Butterflies and Moths) will be retained for a separate chapter. Order, Thysanura.—Ihe members of this lowly organized order are wingless, dull-coloured, muaute insects, with ugly, almost misshapen heads and bodies. Their sexes do not differ but they are interesting as shewmg us that the males pay sedulous court to the females even low down in the animal scale. Sir J. Lubbock " says : "it is very amusing to see these " little creatures (Smynthurus luteus) coquetting together. The " male, which is much smaller than the female, runs round her, " and they butt one another, standing face to face and moving " For this and other statements see p. 344. on the size of the sexes, see Kirby w ' Transact. Linnean Soc.' vnL and Spence, ibid. vol. iii. p. 300 ; xsvi. 1868, p. 296. ' on the duration of life in insects, ' 28o TJie Descent of Alan. Pabt IL " backward and forward like two playful lambs. Then the " female pretends to run away and the male runs after her with " a queer appearance of anger, gets in front and stands facing " her again ; then she turns coyly round, but he, quicker and " more active, scuttles round too, and seems to whip her " with his antenna ; then for a bit they stand face to face, " play with their antermje, and seem to be all in all to one " another." Order, Bii^tera (Flies).— The sexes differ little in colour. The greatest difference, known to Mr. P. Walker, is in the genus Bibio, in which the males arc blackish or quite black, and the females obscure brownish-orange. The genus Elaphomjda, dis- covered by Ml-. Wallace i« in New Guinea, is highly remarkable, as the males are furnished with horns, of which the females are quite destitute. The horns spring from beneath the eyes, and curiously resemble those of a stag, being either branched or pal- mated. In one of the species, they equal the whole body in length. They might be thought to be adapted for fighting, but as in one species they are of a beautiful pink colour, edged with black, with a pale central stripe, and as these insects have altogether a very elegant appearance, it is perhaps more probable that they serve as ornaments. That the males of some Diptera fight together is certain ; for Prof. Westwood " has several times seen this with the Tipulse. The males of other Diptera ap- parently try to win the females by their music : H. Miiller watched for some time two males of an Eristalis courting a female; they hovered above her, and flew from side to side, making a high humming noise at the same time. Gnats and mosquitoes (Culicidfe) also seem to attract each other by hum- ming ; and Prof. Mayer has recently ascertained that the haks on the antennae of the male vibrate in unison with the notes of a tuning-fork, within the range of the sounds emitted by the female. The longer hairs vibrate sympathetically with the graver notes, and the shorter haii's with the higher ones. Landois also asserts that he has repeatedly drawn down a whole swarm of gnats by tittering a particular note. It may be added that the mental faculties of the Diptera are probably higher than in most other in- sects, in accordance with their highly developed nervous system.-' " ' The Malay Archipelago,' vol. " See Mr. B. T. Lowne's interest- "^^ Anwenduug, &c., ' Verh. d. n. " captured flies utter a peculiar V. Jahrg.' x.\ix. p. 80. Mayer, in " plaintive note, and that this sound 'American Naturalist,' 1874, p. 236. " causes other flies to disappear." ii, 1869, p. 313. 1" ' Modern Classification of In- sects,' vol. ii. 1840, p. 526. ing work, ' On the Anatomy of the Blow-fly, Musca vomitoria,' 1870, p. 14. He remarks (p. 33) that, " the Hemiptera and Homoptera, 281 Order, Eemipiera (Field-Bugs).— Mr. J. W. Douglas, who haa paa-ticularly attended to the British species, has kindly given me an account of their sexual differences. The males of some species ai-e fiu'nished with wings, whilst the females are wingless ; ths ^exes differ in the form of their bodies, elytra, antennae and tarsi ; but as the signification of these differences are unknown, they may be here ijassed over. The females are generally larger and more robust than the males. With British, and, as far as iVTt. Douglas knows, with exotic species, the sexes do not commonly differ much in colour; but in about six British species the male is considerably darker than the female, and in about four other species the female is darker than the male. Both sexes of some species are beautifully coloured; and as these insects emit an extremely nauseous odour, their con- spicuous colour's may serve as a signal that they are unpalat- able to insectivorous animals. In some few cases their colours appear to be directly protective : thus Prof. Hoffmann informs me that he could hardly distinguish a small pink and green species from the buds on the trunks of lime-trees, which this insect frequents. Some species of Eeduvidfe make a stridulating noise; and, in the case of Pirates stridulus, this is said to be effected by the movement of the neck within the ijro-thoracic cavity. Accord- ing to Westring, Eeduvius personatus also stridulates. But I have no reason to suppose that this is a sexual character, ex- cepting that with non-social insects there seems to be no use for sound-producing organs, unless it be as a sexual call. Order, Homoptera. — Every one who has wandered in a tropi- cal forest must have been astonished at the din made by the male Cicadse. The females are mute; as the Grecian poet Xenarchus says, " Happy the Cicadas live, since they all have voiceless wives." The noise thus made could be plainly heard ■on board the " Beagle," when anchored at a quarter of a mile from the shore of Brazil ; and Captain Hancock says it can be heard at the distance of a mile. The Greeks formerly kept, and the Chinese now keep these insects in cages for the sake of their song, so that it must be pleasing to the ears of some men.^^ The Cicadidag usually sing during the day, whilst the FulgoridsB •appear to be night-songsters. The sound, according to Landois,"- " Westwood, 'Modern Class, of also, on the Fulgoridaj, Kirby and ,f rn? P- Spence, ' Introduct.' vol. ii. p. 401. " These particulars are taken 'Zeitschrift f ticus (from Laudois). I'espect to the formation of these teeth. Dr. Gruber has shewn that they have been de- veloped by the aid of selection, from the minute scales and hairs with which the wings and body are covered, and I came to the . same conclusion with respect to those of the Coleoptera. But Dr. Gruber further shews that their development is in part • directly due to the stimulus from the friction of one wing over the other. In the Locustidfe the opposite wing-covers differ from each other in structure (fig. 13), and the action cannot, as in the last family, be reversed. The left wing, which acts as the bow, hes over the right wing which serves as the fiddle. One .of the nervures («) on the under surface of the former is 'finely serrated, and is scraped across the prominent nervures on the upper surface of the opposite or right wing. In our British Fhasgonura viridissima it appeared to me that the serrated nervure is rubbed against the rounded hind-corner of the opposite wing, the edge of which is thickened, coloured brown, and very shariJ. In the right wing, but not in the left, there is a little plate, as transparent as talc, surrounded by nervures, and called the speculum. In Ephipjnger vitium., a member of this same family, we have a curious subordinate modification ; for the wing-covers are greatly reduced in size, but " the posterior part of the pro-thorax is elevated into a kind * Zeitschrift fiir wi.ssenschaft. 2" 'Ueber der Tonappar.it der .Zoolocr.' B. xvii. 18G7, s. 117. Locustiden, ein Beitrag zum Dar- '5 Westwood, 'Jlodern Class, of wiuisnius,' 'Zeitsch. fiir wissensch. Insects,' vol. i. p. 440. Zoolog.' B. .x.xii. 1872, p. 100. Chap. X. Orthoptera. 285 " of dome over the wing-covers, and wMch has probably the effect of increasing the sound." ^' Fig. 13. Chlorocoelus Tanana (from Bates), a, h. Lobes of opposite wing-covers. We thus see that the musical apparatus is more differentiated or specialised in the Locustidaj (which include, I believe, the most powerful performers in the Order), than in the Achetidee, in which both wing-covers have the same structure and the same function.^* Landois, however, detected in one of the Locustidas, namely in Decticus, a short and narrow row of small teeth, mere rudiments, ou the inferior surface of the right wing- cover, which underlies the other and is never used as the bow. I observed the same rudimentary structure on the under side of ' the right wing-cover In Phasgoniwa viridissima. Hence we may infer with confidence that the liocustidas are descended from a foi-m, in which, as in the existing Achetidte, both wing-covers had serrated nervures on the under siu-face, and could be - indifferently used as the bow ; but that in the Locustidee the two wing-covers gradually became differentiated and perfectedj • " Westwood, 'Modern Class, of Insects,' vol. i. p. 453. landois, 'Zeitsch. f. wiss. Zoolog.' B. .wii. 1867, s. 121, 122. The Descent of Man. Paet IL on the principle of the division of labour, the one to act ex- clusively as the bow, and the other as the fiddle. Dr. Gruber takes the same view, and has shewn that rudimentary teeth are commonly found on the inferior surface of the right wing. By ■what steps the more simple apparatus in the Achetidse originated, we do not know, but it is probable that the basal portions ol the wing-covers originally overlapped each other as they do at present; and that the friction of the nervures produced a grating sound, as is now the case with the wing-covers of the females.^^ A grating sound thus occasionally and accidentally made by the males, if it served them ever so little as a love-call to the females, might readily have been intensified through sexual selection, by variations in the roughness of the nervures having been continually preserved. In the last and third Family, namely the Acridiidse or grasshoppers, the stridulation is produced in a very different manner, and according to Dr. Scudder, is not so shrill as in the preceding Families. The inner surface of the femur (fig. 14, r) is furnished with a longitudinal row of minute, elegant, lancet- shaped, elastic teeth, from 85 to 93 in number and these are scraped across the sharp, projecting nervures on the wing-covers, ■R'hich are thus made to vibrate and resound. Harris*^ says that when one of the males begins to play, he first " bends " the shank of the hind-leg " beneath the thigh, where it " is lodged in a furrow de- " signed to receive it, and " then draws the leg briskly " up and down. He does not " play both fiddles together, " but alternately, first upon " one and then on the other." In many species, the base of the abdomen is hollowed out into a great cavity which is believed to act as a re- sounding board. In Pneu- mora (fig. 15), a S. African family, ;we meet with a new " wing-covers together." Landois, ibid. s. 113. ' Insects of New England," 1842, p. 133. rig. 14. Hind-legof Stenotiotliruspratorum.- i-j'the stridulatiiig ridge ; lower figure, the teeth forming the ridge, much magniflcd (from Landois). belonging to the same ™ Mr. "Walsh also informs me that he has noticed that the female of the Platyphyllum concavum, ■"when captured makes a feeble ■" grating noise by shuffling her Chap. X. Orthoptera. and remarkable modification; in the males a small notched ridge projects obliquely from each side of the abdomen, against which the hind femora are rubbed.*^ As the male is furnished with wings (the female being wingless), it is re- markable that the thighs are not rubbed in the usual manner against the wing-covers ; but this may perhaps be accounted for by the unusually small size of the hind-legs. I have not been able to examine the inner surface of the thighs, which, judging Fig. 15. Pneumora (from specimens in the British Museum). Upper figure, male lower ligurc, I'emale. from analogy, would be finely serrated. The species of Pneumora have been more pi^foundly modified for the sake of stridulation than any other orthopterous insect; for in the male the whole body has been converted into a musical instrument, being « Westwood, ' Modei'ii Classification,' vol. i. p. 4G2. TJie Descent of Maji. Part IL distended witli aii-, like a great pellucid bladder, so as to increase the resonance. Mr. Trimen informs me that at the Cape of Good Hope these insects make a wonderful noise during the night. In the three foregoing families, the females are almost always- destitute of an efficient musical apparatus. But there are a few exceptions to this rule, for Dr. Gruber has shewn that both sexes of EpMppiger vitium are thus provided; though the organs differ in the male and female to a certain extent. Hence wo cannot suppose that they have been transferred from the male to the female, as appears to have been the case with the secondary sexual characters of many other animals. They must have been independently developed in the two sexes, which no doubt mutually call to each other diuing the season of love. In most other Locustidse (but not according to Landois in Decticus) the females have rudiments of the stridulatory organs proper to the male ; from whom it is probable that these have been transferred. Landois also found such rudiments on the under sm-face of the wing-covers of the female Achetidse, and on the femora of the female Acridiidse. In the Homoptera, also, the females have the proper musical apparatus in a functionless state ; and we shall hereafter meet in other divisions of the animal kingdom with many instances of structures proper to the male being present in a rudimentary condition in the female. Landois has observed another important fact, namely, that in the females of the Acridiidfe, the stridulating teeth on the- femora remain throughout life in the same condition in which they fii'st appear during the larval state in both sexes. In the males, on the other hand, they become fui'ther developed, and acquire their perfect structure at the last moult, when the insect is matui'e and ready to breed. From the facts now given, we see that the means by which the males of the Orthoptera produce their sounds are extremely diversified, and are altogether different from those employed by the Homoptera.'*' But throughout the animal kingdom we often find the same object gained by the most diversified means ; this seems due to the whole organisation having undergone mul- tifarious changes in the course of ages, and as part after part varied different variations were taken advantage of for the same general purpose. The diversity cf means for producing sound, in the three families of the Orthoptera and in the- *' Landois has recently found in moptera; and this is a surprising certain Orthoptera rudimentary fact. See ' Zeitschr. fiir wissensch. structures closely similar to the Zoolog.' B. xxii. Heft 3, 1871, J>^ sooB.d-prod icing organs in the Ho- 348. CliAr. X. Orthoptera. .Homoptera, impresses the mind with the high importance of these structures to the males, for the sake of calling or alluring the females. We need feel no surprise at the amount of modification which the Orthoptera have undergone in this respect, as we now inow, from Dr. Scudder's remarkable discovery," that there has been more than ample time. This naturalist has lately found a fossil insect in the Devonian formation of New Brunswick, which is furnished with " the well-known tympanum or stridu- " latiQg apparatus of the male Locustidse." The insect, though in most respects related to the Neuroptera, appears, as is so often the case with very ancient forms, to connect the two related Orders of the Neuroptera and Orthoptera. I have but little more to say on the Orthoptera. Some of tho species are very pugnacious: when two male field-crickets {Gryllus campestris) are confined together, they fight till one kills the other; and the species of Mantis are described as manoeuvring with their sword-like front-limbs, like hussars with their sabres. The Chinese keep these insects in little bamboo cages, and match them like game-cocks." With respect to colour, some exotic locusts are beautifully ornamented; the posterior wings being marked with red, blue, and black ; but as •throughout the Order the sexes rarely differ much in colour, it is not probable that they owe their bright tints to sexual selection. Conspicuous colours may be of use to these insects, by giving notice that they are unpalatable. Thus it has been observed*" that a bright-coloui-ed Indian locust was invariably rejected when offered to birds and lizards. Some cases, however, are known of sexual differences in colour in this Order. The male of an American cricket'" is described as being as white as ivory, whilst the female varies from almost white to greenish- yellow or dusky. Mr. Walsh informs me that the adult male of Spectrum femoratum (one of the Phasmidse) "is of a shining " brownish-yellow colour ; the adult female being of a dull, " opaque, cinereous brown; the young of both sexes being green." Lastly, I may mention that the male of one curious kind of cricket*^ is furnished with "a long membranous appendage, " which falls over the face like a veil;" but what its use may be' is not known. " ' Transact. Ent. Soc' 3rd series, The (Ecanthus nivalis. Harris, vol. II. ('Journal of Proceedings,' 'Insects of New England,' 1842, p. . , c^r ^2*- The two se.xes of pe^MCidiis " VVestwood, 'Modern Class, of of Europe difiFer, as I hear from Insects, vol. i. p. 427 ; for crickets, Victor Carus, in nearly the same P- inauner. " Mr. Ch. Horne, in 'Proc. Ent. •"> Platyblemnus : Westwood, 8oc. May 3, 1869. p. xii. ' Modern Class.' vol. i. p. 447. U 290 Tlie Descent of Man. Pakt II. Order, ^ewropiera.— Little need here be said, except as to colour. In the EphemcridaB the sexes often differ slightly in their obscure tints;*" but it is not probable that the males are thus rendered attractive to the females. The Libellulid£e, or dragon-flies, are ornamented with splendid green, blue, yellow, and vermilion metallic tints ; and the sexes often differ. Thus' as Prof. Westwood remarks,"" the males of some of the AgrionidsB, " are of a rich blue with black wings, whilst the " females are fine green with colourless wings." But in Agrixm Bamhurii these colours are exactly reversed in the two sexes." In the extensive N. American genus of Hetserina, the males alone have a beautiful carmine spot at the base of each wing. In Anax Junius the basal part of the abdomen in the male is a vivid ultramarine blue, and in the female grass-green. In the allied genus Gomphus, on the other hand, and ia some other genera, the sexes differ but little in coloui". In closely-allied forms thi-oughout the animal kingdom, similar cases of the sexes differing greatly, or very little, or not at all, are of frequent occurrence. Although there is so wide a difference in colour between the sexes of many Libellulidse, it is often difficult to say which is the more brilliant ; and the ordinary coloration of the two sexes is reversed, as we have just seen, in one species of Agrion. It is not probable that their colours in any case have been gained as a protection. Mr. MacLachlan, who has closely attended to this family, writes to me that cbagon-flies — the tyrants of the iasect-world — are the least liable of any insect to be attacked by birds or other enemies, and he believes that their bright colours serve as a sexual attraction. Certaia dragon-flies apparently are attracted by particular colours : Mi'. Patterson observed that the Agrionidae, of which the males are blue, settled in numbers on the blue float of a fishing line ; whilst two other species were attracted by shining white colours. It is an interesting fact, first noticed by Schelver, that, in several genera belonging to two sub-families, the males on first emergence from the pupal state, are coloured exactly like the females; but that their bodies in a short time assume a con- spicuous milky-blue tint, owing to the exudation of a kind of oil, soluble in ether and alcohol. Mr. MacLachlan believes that in the male of Libellula depressa this change of colour does not occur until nearly a fortnight after the metamorphosis, when the sexes are ready to pair. " B. D. Walsh, the ' Pseudo-neu- indebted to this naturalist for the roptera of Illinois,' in ' Proc. Ent. following facts on Hetterina, Anax, Son. of Philadelphia,' 1862, p. 361. and Gomphas. M ' Modern Class.' vol. ii. p. 37. " < Transact. Ent. Soc' vol. >. AValsh, ibid. p. 381. 1 am 1836, p. Ixxxi. ClIAl'. X. Hyme7iopte}'a. 291 Certain species of Neurothemis present, according to Brauer, '"^ a curious case of dimorphism, some of the females having ordinary wings, whilst others have them " very richly netted, as in the " males of the same species." Brauer " explains the phenomenon on Darwinian principles by the supposition that the close " netting of the veins is a secondary sexual character in the " males, which has been abruptly transferred to some of tho " females, instead of, as generally occurs, to all of them." Mr. MacLachlan informs me of another instance of dimorphism in several species of Agrion, in which some individuals are of an orange colour, and these are invariably females. This is probably a case of reversion; for in the true Libellulae, when the sexes differ in coloiu', the females are orange or yellow ; so that supposing Agrion to be descended from some primordial form which resembled the typical Libellulse in its sexual cha- racters, it would not be surprising that a tendency to vary in this manner should occur in the females alone. Although many dragon-flies are large, powerfcil, and fierce insects, the males have not been observed by Mr. MacLachlan to fight together, excepting, as he believes, in some of tho smaller species of Agi-ion. In another group in this Order, namely, the Termites or white ants, both sexes at the time of swarming may be seen running about, " the male after the female, sometimes " two chasing one female, and contending with great eagerness " who shall win the prize."^* The Atrcypos pulsatorius is said to make a noiso with its jaws, which is answered by other individuals.*^ Order, Eymenoptera. — That inimitable observer, M. Fabre,*" in describing the habits of Cerceris, a wasp-like insect, remarks that " fights frequently ensue between the males for the possession of " some particular female, who sits an apparently unconcerned " beholder of the struggle for supremacy, and when the victory " is decided, quietly flies away in company with the conqueror." Westwood^'' says that the males of one of the saw-flies (Tenthre- din£E) " have been found fighting together, with their mandibles " locked." As M. Fabre speaks of the males of Cerceris striving to obtain a particular female, it may be well to bear in mind that insects belonging to this Order have the power of recognising " See abstract in the ' Zoological See an interesting article. Record' for 1867, p. 450. «The Writings of Fabre,' in 'Nat. " Kirby and Spence, 'Introduct. Hist. Review,' April 1862, p. 122. to Entomology,' vol. ii. 1818, p. 35. < Journal of Proc. of Entomolog " Houzeau, 'Les Faculty Men- Soc' Sept. 7th, 1863, p. 169. teles,' &c. Tom. i. p. 104. ' ^ u 2 292 The Descent of Man. Pakt II. each other after long intervals of time, and are deeply attached- For instance, Pierre Hubcr, whose accuracy no one doul)t8, Bcpaitited some ants, and when, after an interval of four months, ihey met others which had formerly belonged to the same community, they recognised and caressed one another with their antenna3. Had they been strangers they would have fought together. Again, when two communities engage in a l)attle, the ants on the same side sometimes attack each other in the general confusion, but they soon perceive their mistake, and the one ant soothes the other.*^* In this Order slight differences in colour, according to sex, are common, but conspicuous differences are rare except in the family of Bees ; yet both sexes of certain groups are so brilliantly coloured— for instance in Chrysis, in which vermilion and metallic greens prevail — that we are tempted to attribute the result to sexual selection. In the Ichneumonidae, according to Ml". Walsh,°^ the males are almost universally lighter-colovired than the females. On the other hand, in the Tenthredinidse the males are generally darker than the females. In the Siricidfe the sexes frequently differ ; thus the male of Sirex juvencus is banded with orange, whilst the female is dark purple ; but it is difficult to say which sex is the more ornamented. In Tremex columbce the female is much brighter-coloured than the male. I am informed by Mr. F. Smith, that the male ants of several species are black, the females being testaceous. In the family of Bees, especially in the solitary species, as I hear from the same entomologist, the sexes often differ in colotu-. The males are generally the brighter, and in Bombus as well as in Apathus, much more variable in colour than the females. In Anthophora retusa the male is of a rich fulvous-brown, whilst ihe female is quite black : so are the females of several species of Xylocopa, the males being bright yellow. On the other hand the females of some species, as of Andrcena fulva, are much brighter-coloured than the males. Such differences in col'our can hardly be accounted for by the males being defenceless and thus requiring protection, whilst the females are well defended uy theii" stings. H. Miiller, who has particularly attended to the haoits of bees, attributes these differences in colour in chief part to sexual selection. That bees have a keen perception of colour is certain. He says that the males search eagerly and tight for the possession of the females ; and he accounts through 53 p. Huber, ' Recherches sur les Philadelphia,' 1866, pp. 238-239. Mceurs des Fouimis,' 1810, pp. 150, ' Anwendung der Darwinschen 165. Lehre auf Bienea.' Verh. Q. n. " ' Proc. Entomolog. Soc, of J.-ihrg. xiix. Ckap. X. Hymcnoptera. 293 such contests for the mandibles of the males being in certain opecies larger than those of the females. In some cases the males are far more numerous than the females, either early in the season, or at all times and places, or locally ; whereas the females in other cases are apparently in excess. In some species the more beautiful males appear to have been selected by the females ; and in others the more beautiful females by the males. Consequently in certain genera (Miiller, p. 42), the males of the several species differ much in appearance, whilst the females are almost indistinguishable; in other genera the reverse occui's. H. Miiller believes (p. 82) that the coloui-s gained by one sex through sexual selection have often been transferred in a variable degree to the other sex, just as the pollen-collecting apparatus of the female has often been transferred to the male, to whom it is absolutely useless." Mutilla Europxa makes a stridulating noise ; and according to Goureau both sexes have this power. He attributes the sound to the friction of the thii'd and preceding abdominal segments, and I find that these surfaces are marked with very fine con- centric ridges ; but so is the projecting thoracic collar, into which the head articulates, and this collar, when scratched with the point of a needle, emits the proper sound. It is rather surprising that both sexes should have the power of stridulating, as the male is winged and the female wingless. It is notorious that Bees express certain emotions, as of anger, by the tone of their humming; and according to H. Miiller (p. 80), the males of some species make a peculiar singing noise whilst pursuing the females. " M. Perrier in his article ' la Se- lection sexuelle d'aprfes Darwin ' ('Re- vue Scientifique,' Feb. 1873, p. 868), without apparently having reflected much on the subject, objects that as the males of social bees are known to be produced from unfertilised ova, they could not transmit new characters to their male oft'spring. This is an extraordinary objection. A female bee fertilised by a male, which presented some character fa- cilitating the union of the sexes, or rendering him more attractive to the female, would lay eggs which would produce only females ; but these young females would next year produce males; and will it be pretended that such males would not inherit the characters of their male grandfiithers ? To take a case with ordinary animals as nearlv parallel as possible: if a female oi any white quadruped or bird were crossed by a male of a black breed, and the male and female ofiFspring were paired together, will it be pretended that the grandchildren would not inherit a tendency to blackness from their male grand- father? The acquirement of new characters by the sterile worker-beoa is a much more difficult case, but I have endeavoured to show m my ' Origin of Species,' how these sterile beings are subjected to the power o\ natural selection. Quoted by Westwood, ' Modern Chiss. of Insects,' vol. ii. p. 214 294 The Descent of Man. Pabt U Order, ColeapUra (Beetles). — Many beetles are coloured so as to resemble the surfaces which they habitually frequent, and they thus escape detection by their enemies. Other species, for instance diamond-beetles, are ornamented with splendid colours, which are often arranged in stripes, spots, crosses, and other elegant patterns. Such colours can hardly servo directly as a protection, except in the case of certain flower-feeding species ; but they may serve as a warning or means of recognition, on the same principle as the phosphorescence of the glow-worm. As with beetles the colours of the two sexes are generally alike, we have no evidence that they have been gained through sexual selection ; but this is at least possible, for they may have been developed in one sex and then transferred to the other; and this view is even in some degree probable in those groups which possess other well-marked secondary sexual characters. Blind beetles, which cannot of course behold each other's beauty, never, as I hear from Mr. Waterhouse, jun., exhibit bright colours, though they often have polished coats ; but the expla- nation of their obscurity may be that they generally inhabit caves and other obscure stations. Some Longicorns, especially certain Prionidse, offer an excep- tion to the rule that the sexes of beetles do not differ in colour. Most of these insects are large and splendidly coloured. The males in the genus Pyrodes,^^ which I saw in Mr. Bates's col- lection, are generally redder but rather duller than the females, the latter being coloured of a more or less splendid golden-green. On the other hand, in one species the male is golden-green, the female being richly tinted with red and pui-ple. In the genus Esmeralda the sexes differ so greatly in colour that they have been ranked as distinct species ; in one species both are of a beautiful shining green, but the male has a red thorax. On the whole, as far as I could judge, the females of those PrionidaB, in "3 Pyrodes pulcherrmus, in which the sexes differ conspicuously, tins been described by Mr. Bates in 'Transact. Ent. Soc' 1869, p. 50. I will specify the few other cases in ■which I have heard of a difference in colour between the sexes of beetles. Kirby and Spence (' In- troduct. to Entomology,' vol. iii. p. 301) mention a Cantharis, Meloe, Rhagium, and the Leptura testacea ; the male of the latter being tes- taceous, with a black thorax, and the female of a dull red all ovei. Those two latter beetles belong to the family of Longicorns. Messrs. R. Trimen and Waterhouse, jun., inform me of two Lamellicorns, viz., a Peritrichia and Trichius, the male of the latter being more obscurely coloured than the female. In Tillus elongatiis the male is black, and the female always, as it is believed, of a dark blue colour, with a red thorax. The male, also, of Orsodacna atra, as I hear from Mr. Walsh, is black, the female (the so-called 0. ruficollis) having a "Tifous thor.\x. Chap. X. Coleoptera. 295 ■which the sexes differ, are coloured more richly than the males, and this does not accord with the common rule in regard to colour, when acquired through sexual selection. A most remarkable distinction between the sexes of many- beetles is presented by the great horns which rise from the head, ■ thorax, and clypeus of the males ; and in some few cases from the under surface of the body. These horns, in the great family of the Lamellicorns, resemble those of various quadrupeds, such as stags, rhinoceroses, &c., and are wonderful both from their size and diversified shapes. Instead of describing them, I have given figiu'es of the males and females of some of the more re- markable forms. (Figs. 16 to 20.) The females generally ex- hibit rudiments of the horns in the form of small knobs or ridges ; but some are destitute of even the slightest rudiment. On the other hand, the horns are nearly as well developed in the female as in the male of Phanceus lancifer ; and only a little less well developed in the females of some other species of this genus and of Copris, I am informed by Mr. Bates that the horns do not differ ia any manner corresponding with the more important characteristic differences between the several subdivisions of the family : thus within the same section of the genus Onthophagus, there are species which have a single horn, and others whicli have two. JFig, 16. Ctalcosoma atlas. Upper flpire, tn.ile (rcduc'd) ; lower figure, female (lUl. sizi-j. Phana:us faunus. Fig. 20. OnthophiiCTS rangifcr. enlarged. Chap. X. Coleoptera. 297 In almost all cases, the horns are remarkable from their ex- cessive variability; so that a graduated series can be formed, from the most highly developed males to others so degenerate that they can barely be distinguished from the females. Mr. Walsh found that in Phanceus carniftx the horns were thiice as- long in some males as iu others. Mr. Bates, after examining above a hundred males of Onthophagus mngifer (fig. 20), thought that he had at last discovered a species in which the horns did not vary ; but fui'ther research proved the contrary. The extraordinary size of the horns, and their widely different structure iu closely-allied forms, indicate that they have been formed for some purpose ; but their excessive variability iu the- males of the same species leads to the inference that this purpose cannot be of a definite nature. The horns do not show marks of friction, as if used for any ordinary work. Some authors sup- pose"^ that as the males wander about much more than the females, they require horns as a defence against their enemies ; but as the horns are often blunt, they do not seem well adapted for defence. The most obvious conjecture is that they are used by the males for fighting together ; but the males have never been observed to fight; nor could Mr. Bates, after a careful examiaation of numerous species, find any sufficient evidence, iu their mutilated or broken condition, of their having been thus used. If the males had been habitual fighters, the size of their bodies would probably have been increased through sexual selection, so as to have exceeded that of the females; but Mr. Bates, after comparing the two sexes in above a hundred species of the Oopridse, did not find any marked difference in this respect amongst well-developed individuals. In Lethrus, moreover, a beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female. The conclusion that the horns have been acquired as ornaments is that which best agrees with the fact of their having been so immensely, yet not fixedly, developed,— as shewn by their extreme- variability in the same species, and by their extreme diversity in closely-allied species. This view will at fii-st appear extremely improbable; but we shall hereafter find with many animals standing much higher in the scale, namely fishes, amphibians, reptiles and birds, that various kmds of crests, knobs, horns and combs have been developed apparently for this sole purpose. The males of Onitis furcifer (fig. 21), and of some other ** ' Proc. Entomolog. Soc. of Philadelphia,' 1864, p. 228. Kirby and Spence, ' Introduct. Entomolog.' vol. iij. p. 300. The Descent of Man. Part IT. species of tlie genus, are furnished with singular projections on their anterior femora, and with a great fork or pair of horns on the lower surface of the thorax. Judging from other insects, these may aid the male in clinging to the female. Although the males have not even a trace of a horn on the upper surface of the body, yet the fe- males plainly exhibit a rudiment of a single horn on the head (fig. 22, a), and of a crest (&) on the thorax. That the shght thoracic crest in the female is a rudiment of a pro- jection proper to the male, though entirely absent in the male of this particular species, is clear : for the female of Bubas hison (a genus which comes next to Onitis) has a similar slight crest on the thorax, and the male bears a great projection in the same situation. So, again, there can hardly be a doubt that the little point (a) on the head of the female Onitis fig 21. Onitis furcifer, male viewed from be- neath. Fig. 22. Left-hand figure, male of Onitis furcifer, viewed laterally. Eight-hand figure, female, o. Rudiment of cephalic horn. &. Trace of thoracic horn or crest. furcifer, as well as on the head of the females of two or three allied species, is a rudimentary representative of the cephalic horn, which is common to the males of so many Lamellicorn beetles, as in Phanfeus (fig. 18). The old belief that rudiments have been created to complete the scheme of nature is here so far from holding good, that we have a complete inversion of the ordinary state of things in the family. We may reasonably suspect that the males originally bore horns and transferred them tc the females in a rudimentary condition, as in so many other Lamellicorns. Why the males subsequently lost their horns, we know not ; but this may have been caused through the principle of compensation, owing to the development of the large horns and projections on the lower surface ; and as these are confined to the males, the rudiments of the upper horns on the females would not have been thus obliterated. Chap. X. Coleoptera. 299 The cases Mtherto given refer to the Lamellicorns, but the males of some few other beetles, belonging to two widely distinct groups, namely, the Curculionida3 and Staphylinid^, are fur- nished with horns — in the former on the lower surface of the body/'^ in the latter on the upper surface of the head and thorax. In the Staphylinidfe, the horns of the males are extraordinarily Tariable in the same species, just as we hare seen with the Lamellicorns. In Siagonium we have a case of dimorphism, for the males can be divided into two sets, differing greatly in the size of their bodies and in the development of their horns, without intermediate gradations. In a species of Bledius (fig. 23), also belonging to the Staphylinid^e, Professor Westw;ood Fig. 23. Elediiis taurus, magnified. Left-hand figure, male ; right-hand^flgure female. states that, "male specimens can be found in the same locality " in which the central horn of the thorax is very large, but the " horns of the head quite rudimental ; and others, in which the "thoracic horn is much shorter, whilst the protuberances on " the head are long." ^'^ Here we apparently have a case of compensation, which throws light on that just given of the supposed loss of the upper horns by the males of Onitis. Law of Battle. — Some male beetles, which seem ill-fitted for fighting, nevertheless engage in conflicts for the possession of the females. Mr. Wallace ''^ saw two males of Leptorhynchus angustatus, a linear beetle with a much elongated rostrum, *' fighting for a female, who stood close by busy at her boring. " They pushed at each other with their rostra, and clawed and " thumped, apparently in the greatest rage." The smaller male, however, " soon ran away, acknowledging himself vanquished." In some few cases male beetles are well adapted for fighting, by possessing great toothed mandibles, much larger than those of the females. This is the case with the common stag-beetle (Lucamts cervus), the males of which emerge from the pupal state about a week before the other sex, so that several may often be seen pursuing the same female. At this season they Kirby and Spence, ' Introduct. gonium in an intermediate condi- Entomolog.' vol. iii. p. 329, tion, so that the dimorphism is not ' Modern Classification of In- strict, sects,' vol. i. p. 172 : Siagonium, < ^he Malay Archipelago,' vol. p. 172. In the British Museum I ii. 1869, p. 276. Eiloy, Sixth ' Report noticed one male specimen of Sia- on insects of Missouri,' 1874, p. llSk 300 The Descent of Man. Paet II. engage in fierce conflicts. When Mr. A. H. Davis*' enclosed two males with one female in a box, the larger male severely pinched the smaller one, until he resigned his pretensions. A friend informs mo that when a boy he often put the males together to see them fight, and he noticed that they were much bolder and fiercer than the females, as with the higher animals. The males would seize hold of his finger, if held in front of them, but not so the females, although they have stronger jaws. The males of many of the Lucanidae, as well as of the above-mentioned Leptorhynchus, are larger and more powerful insects than the females. The two sexes of Lethrus cephalotes (one of the Lamellicorns) inhabit the same burrow; and the male has larger mandibles than the female. If, duiing the breeding-season, a strange male attempts to enter the burrow, he is attacked ; the female does not remain passive, but closes the mouth of the burrow, and encoui-ages her mate by con- tinually pushing him on from behind ; and the battle lasts until the aggressor is killed or runs away.'" The two sexes of another LamelUcorn beetle, the Ateuchus cicatricosus, live in pairs, and seem much attached to each other ; the male excites the female to roll the balls of dung in which the ova are deposited ; and if she is removed, he becomes much agitated. If the male is removed the female ceases all work, and as M. Brulerie" believes, would remain on the same spot until she died. The great mandibles of the male Lucanidaa are extremely variable both in size and structure, and in this respect resemble the horns on the head and thorax of many male Lamellicorns and StaphylinidsB. A perfect series can be formed from the best-provided to the worst-provided or degenerate males. Al- though the mandibles of the common stag-beetle, and probably of many other species, are used as efficient weapons for fighting, it is doubtful whether their great size can thus be accounted for. We have seen that they are used by the Lucanus elapJms of N. America for seizing the female. As they are so con- spicuous and so elegantly branched, and as owing to their gi-eat length they are not well adapted for pinching, the suspicion has crossed my mind that they may in addition serve as an ornament, like the homs on the head and thorax of the various species above described. The male Chiasognathus Grant ii of S. Chile— a splendid beetle belonging to the same family — has 'Entomological Magazine,' vol. " Quoted from Fischer, in ' Diet, i. 1833, p. 82. See also on the Class, d'llist. Nat.' torn. s. p. 324. conflicts of this species, Kiiby and " ' Ann. Soc. Entoinolog. France,* Spence, ibid. vol. iii. p. 314; and 1866, as quoted in 'Journal of Westw'ood, ibid. vol. i. p. 187. Travel,' by A. Murray, 1868, p. 135-. Chap, X. Coleoptera, enormously developed mandibles (fig. 24) ; he is bold and pug- Dacious ; when thi-eatened he faces round, opens his great jaws, and at the same time stridulates loudly. But the mandibles were not strong enough to pinch my finger so as to cause actual pain. Sexual selection, which implies the possession of considerable perceptive powers and of strong passions, seems to have been more effective with the Lamellicorus than with any other family of beetles. With some species the males are provided with weapons for fighting; some live in pairs and show mutual affection; many have the power of stridulating when excited ; many are furnished with the most ex- traordinary horns, apparently for the sake of ornament; and some, which are diurnal in their habits, are gor- geously coloured. Lastly, several of the largest beetles in the world belong to this family, which was placed by Linnaeus and Fabricius at the head of the Order.'2 Stridulating organs. — Beetles belong- ing to many and widely distinct families possess these organs. The sound thus produced can sometimes he heard at the distance of several feet or evenyai-ds," but it is not comparable with that made by the Orthoptera. The rasp generally consists of a narrow, shghtly-raised surface, crossed by very fine, parallel ribs, sometimes so fine as to cause iridescent colours, and having a very elegant appearance under the microscope. In some cases, as with Typhosus, minute, bristly or scale-like prominences, with which the whole surrounding surface is covered in approximately parallel hnes, could be traced passing into the ribs of the rasp. The J'i YIqT"'^' Cui-culionida>,"AnnalsandMag. oi " Wii r < n ^^t. Hist.' vol. vi. 1860, p. 14. Wollaston, ' On certain Musical Fi?. 24. Chiasognathus grantii, reduced. Upper figure, male 5 lower figure, female. 302 The Descent of Man. Paet IL transition takes place by their becoming confluent and straight, and at the same time more prominent and smooth. A hard ridge on an adjoining part of the body serves as the scrapei for the rasp, but this scraper in some cases has been specially modified for the purpose. It is rapidly moved across the rasp, or conversely the rasp across the scraper. Fig. 25. Necrophorus (from Landois). r. The two rasps. Left-hand figure, part of the rasp highly magnified. These organs are situated in widely different positions. In the carrion-beetles (Necrophorus) two parallel rasps (r, fig. 25) stand on the dorsal stu-face of the fifth abdominal segment, each rasp" consisting of 126 to 140 fine ribs. These ribs are scraped against the posterior margins of the elytra, a small portion of which projects beyond the general outline. In many Crioceridte, and in Clythra ^punctata (one of the Chrysomehd^), and in some Tenebrionidse, &c.,''^ the rasp is seated on the dorsal apex of the abdomen, on the pygidium or pro-pygidium, and is scraped in the same manner by the elytra. In Heterocerus, which belongs to another family, the rasps are placed on the sides of the first abdominal segment, and are scraped by ridges on the femora." In certain Curculionidte and Carabidse," the parts been described by Dr. Chapman as a stridulator, in the 'Entomolo- gist's Monthly Magazine,' vol. vi. p. 130. Schiodte, translated in ' Annals and Mag. of Nat. Hist.' vol. ss. 1867, p. 37. " Westringhas described (Kroyer, ' Naturhist. Tidskrift,' B. ii. 1848- 49, p. 334) the stridulating organs in these two, as well as in other families. In the CarabidiB I have examined Maphrus uliginosus and Blethisa multipunctata, sent to me by Mr. Crotch. In Blethisa the transverse ridges on the furrowed border of the abdominal segment do " Landois, ' Zeitschrift filr wiss. Zoolog.' B. xvii. 1867, s. 127. '° I am greatly indebted to Mr. G. E. Crotch for having sent me many prepared specimens of various beetles belonging to these three families and to others, as well as for. valuable mformation. He believes that the power of stridulation in the Clythra has not been previously observed. I am also much indebted to Mr. E. W. Janson, for informa- tion and specimens. I may add that my son, Mr. F. Darwin, finds that Dcrmcstes murinus stridulates, but he searched in vain for the apparatus. Scolytus has lately Chap. X. Coleoptera. 303 are completely reversed in position, for the rasps are seated on the inferior sui-face of the elytra, near their apices, or along their outer margins, and the edges of the abdominal segments serve as the scrapers. In Peldbius Hermanni (one of Dytiscidse or water-beetles) a strong ridge runs parallel and near to , the sutural margin of the elytra, and is crossed by ribs, coarse in the middle part, but becoming gradually finer at both ends, especially at the upper end; when this insect is held under water or in the air, a stridulating noise is produced by the extreme horny margin of the abdomen being scraped against the rasps. In a great number of long-horned beetles (Longi- cornia) the organs are situated quite otherwise, the rasp being on the meso-thorax, which is rubbed against the pro-thorax; Landois counted 238 very fine ribs on the rasp of Ceramhyx heros. Many LameUicoms have the power of stridulating, and the organs differ greatly in position. Some species stridulate very loudly, so that when Mr. F. Smith caught a Trox sdbulosus, a gamekeeijer, who stood by, thought he had" caught a mouse ; but I failed to discover the proper organs in ^ this beetle. In Geotrupes and Typhceus a / narrow ridge runs obliquely across (r, fig. 26) the coxa of each hind-leg (having in G. ster- corarius 84 ribs), which is scraped by a specially projecting part of one of the ab- dominal segments. In the nearly allied Copris lunaris, an excessively narrow fine rasp runs along the sutural margin of the elytra, with another short rasp near the basal outer mar- gin; but in some other Coprini the rasp is seated, according to Leconte,''^ on the dorsal siTrface of the abdomen. In Oryctes it is seated on the pro-pygidium ; and, according to the same entomologist, in some other Dynastini, on the under surface of the elytra. Lastly, "Westring states that in OmalopUa hrunnea the rasp is placed on the pro-sternum, and the scraper on the meta-sternum, the parts thus occupying the under surface of the body, instead of the upper surface as m the Longicorns. We thus see that in the^rent coleopterous families the not, as far as I could judge, come of Illinois, for having sent me cs- into play m scraping the rasps ou tracts from Leconte's ' Introductiou the elytra. to Entomology,' pp. 101, 143. " 1 am indebted to Mr. Walsh, =-J' i'i' Fig. 26. Hind-leg of Geotrupes stercora- rius (from Landois). r. Easp. c. Coxa. /. Femur, t. . Tibia, tr. Tarsi. 304 The Descent of Man. PabtIL stridulating organs are wonderfully diversified in position, but not much in structure. Within the same family some species are provided with these organs, and others are destitute of them. This diversity is intelligible, if we suppose that originally various beetles made a shufBing or hissing noise by the rubbing together of any hard and rough parts of their bodies, which happened to be in contact ; and that from the noise thus produced being in some way useful, the rough surfaces were gradually developed into regular stridulating organs. Some beetles as they move, now produce, either intentionally or unintentionally, a shTiffliug noise, without possessing any proper organs for the purpose. Mr. Wallace informs me that the Euchirus longimanus (a Lamellicorn, with the anterior legs wonderfully elongated in the male) " makes, whilst moving, a low hissing sound by the pro- " trusion and contraction of the abdomen; and when seized it " produces a grating sound by riibbing its hind-legs against the " edges of the elytra." The hissing sound is clearly due to a narrow rasp running along the sutural margin of each elytron ; and I could likewise make the gi'ating soimd by rubbing the shagreened surface of the femtu" against the granulated margin of the corresponding elytron ; but I could not here detect any proper rasp ; nor is it likely that I could have overlooked it in so large an insect. After examining Cychrus, and reading what Westring has written about this beetle, it seems very doubtful whether it possesses any true rasp, though it has the power of emitting a sound. From the analogy of the Orthoptera and Homoptera, I expected to find the stridulating organs in the Coleoptera differing according to sex; but Landois, who has carefully examined several species, observed no such difference ; nor did Westring; nor did Mr. G. E. Crotch in preparing the many specimens which he had the kindness to send me. Any difference in these organs, if shght, would, however, be difficult to detect, on account of their great variability. Thus, in the first pair of specimens of Necrophorus humator and of Pelohius which I ex- amined, the rasp was considerably larger in the male than in the female; but not so with succeeding specimens. In Geo- trupes stercorarius the rasp appeared to me thicker, opaquer, and more prominent in three males than in the same number of females; in order, therefore, to discover whether the sexes differed in their power of stridulating, my son, Mr. F. Darwin, collected fifty-seven living specimens, which he separated into two lots, according as they made a greater or lesser noise, when held in the same manner. He then examined all these specimens, •and found that the males were very nearly in the same pi-oportion Chap. X. Coleopfera. 305 to the females in both the lots. Mr. F. Smith has kept alive numerous specimens of Monoynchus pseudacori (Curculionidse), and is convinced that both sexes stridulate, and apparently in an equal degree. Nevertheless, the po"wer of stridulating is certainly a sexual character in some few Coleoptera. Mi*. Crotch discovered that the males alone of two species of Heliopathes (Tcnebrionidae) possess stridulating organs. I examined live males of E. gibbus, and in all these there was a well-developed rasp, partially divided into two, on the dorsal surface of the terminal abdominal segment ; whilst in the same number of females there was not even a rudiment of the rasp, the membrane of this segment being transparent, and much thinner than in the male. In E. cribratostriatus the male has a similar rasp, excepting that it is not partially divided into two portions, and the female is completely destitute of this organ ; the male in addition has on the apical margins of the elytra, on each side of the suture, three or four short longitudinal ridges, which are crossed by extremely fine ribs, parallel to and resembling those on the abdominal rasp ; whether these ridges serve as an independent rasp, or as a scraper for the abdominal rasp, I could not decide : the female exhibits no trace of this latter structure. Again, in three species of the LamelUcorn genus Oryctes, we have a nearly parallel case. In the females of 0. gryplms and nasicornis the ribs on the rasp of the pro-pygidium are less continuous and less distinct than in the males ; but the chief difference is that the whole upper surface of this segment, when held in the proper light, is seen to be clothed with hairs, which are absent or are represented by excessively fine down in the males. It should be noticed that in all Coleoptera the effective part of the rasp is destitute of hairs. In 0. senegalensis the difference between the sexes is more strongly marked, and this is best seen when the proper abdominal segment is cleaned and viewed as a transparent object. In the female the whole surface is covered with little separate crests, bearing spines ; whilst in the male these crests in proceeding towards the apex, become more and more confluent, regular, and naked ; so that three- fourths of the segment is covered with extremely fine parallel ribs, which are quite absent m the female. In the females, however, of all three species of Oryctes, a slight grating or stridulating sound is produced, when the abdomen of a softened specimen is pushed backwards and forwards. In the case of the Heliopathes and Oryctes there can hardly be a doubt that the males stridulate in order to call or to excite the females; but with most beetles the stridulation 3o6 The Descent of Man. P^IIT II. apparently serves both sexes as a mutual call. Beetles stridu- late under various emotions, in the same manner as birds use their voices for many purposes besides singing to their mates. ■Jhe great Chiasognathus stridulates in anger or defiance ; many species do the same from distress or feai', if held so that they cannot escape; by striking the hollow stems of trees In the Canary Islands, Messrs. Wollaston and Crotch were able to discover the presence of beetles belonging to the genus Acalles by their stridulation. Lastly, the male Ateuchus stridulates to encourage the female in her work, and from distress when she is removed.™ Some naturalists believe that beetles make this noise to frighten away their enemies ; but I cannot think that a quadruped or bird, able to devour a large beetle, would be frightened by so slight a sound. The behef that the stridu- lation serves as a sexual call is supported by the fact that death- ticks (Anobium tessellatum) are well known to answer each other's ticking, and, as I have myself observed, a tapping noise artificially made. Mi". Doubleday also informs me that he has sometimes observed a female ticking,* and in an hour or two afterwards has found her united with a male, and on one occasion surrounded by several males. Fiaally, it is probable that the two sexes of many kinds of beetles were at first enabled to find each other by the slight shuffling noise produced by the rubbing together of the adjoining hard parts of their bodies; and that as those males or females which made the greatest noise succeeded best in finding partners, rugosities on various parts of their bodies were gradually developed by means of sexual selection into true stridulatiag organs. " M. P. de la Brulerie, as quoted in * Journal of Travel,' A. Mui-ray, vol. i. 1868, p. 135. According to Mr. Doubleday, " the noise is produced by the in- " sect raising itself on its legs as " high as it can, and then striking " its thorax five or six times, in " rapid succession, against the sub- " stance upon which it is sitting." For references on this subject see Landois, ' Zeitschrift fiir wissen. Zoolog.' B. xvii. s. 131. Oliver says (as quoted by Kirby and Spence, ' Introduct.' vol. ii. p. 395) that the female of Pimelia striata produces a rather loud sound by striking her abdomen against any hard substance, " and that the male, " obedient to this call, soja attends " her, tnd they pair." Chap. XI. Biitte7'Jlies and Moths. 307 CHAPTER XI. Insects, continued. — Obdkr Lepidopteea. (butterflies and moths.) Courtshtp of butterflies — Battles — ^Ticking noise — Colours common to both sexes, or more brilliant in the males — Examples — Not due to the direct action of the conditions of life — Colours adapted for pi'otection — Colours of moths — Display — Perceptive powers of the Lepidoptera — Variability — Causes of the difference in colour between the males and females — Mimicry, female butterflies more brilliantly coloured than the males — Bright colours of caterpillars — Summary and concluding remarks on the secondary sexual characters of insects — Birds and insects compared. In this great Order the most interesting points for us are the differences in coloiu* between the sexes of the same species, and between the distinct species of the same genus. Nearly the "vrhole of the following chapter will be devoted to this subject ; but I will fii'st make a few remarks on one or two other points. Several males may often be seen pui'suing and crowding round the same female. Their courtship appears to be a prolonged affair, for I have frequently watched one or more males pirouet- ting round a female until I was tired, without seeing the end of the courtship. Mr. A. G. Butler also informs me that he has several times watched a male courting a female for a full quarter of an hour ; but she pertinaciously refused him, and at last settled on the ground and closed her wings, so as to escape from his addi-esses. Although butterflies are weak and fi-agile creatures, they are pugnacious, and an Emperor butterfly ^ has been captured with the tips of its wings broken from a conflict with another male. Mr. Collingwood, in speaking of the frequent battles between the butterflies of Borneo, says, " They whirl round each other with " the greatest rapidity, and appear to be incited by the greatest " ferocity." The Ageronia feronia makes a noise like that produced by a toothed wheel passing under a spring catch, and which can be heard at the distance of several yards : I noticed this sound at Eio de Janeiro, only when two of these butterflies were chasmg each other in an irregular course, so that it is probably made during the courtship of the sexes.^ ' Apaturalris: 'The Entomolo- Naturalist,' 1868, p 183 gtst s Weekly Intelligence,' 1839, p. = See my ' Journal of Researches, n n\-^.^^ Bornaan Butterflies, 1845, p. 33. Mr. Doubleday has 8c-e t. Collmgwood, RamDles of a detected (' Proc. Ent. Soc' March 3o8 The Descent of Man. Pabt It ^ Some moths also produce sounds ; for instance, the males of Thecophora fovea. On two occasions Mr. F. Buchanan White* heard a sharp quick noise made by the male of Uyhphila prasinana, and which he believes to be produced, as in Cicada by an elastic membrane, furnished with a muscle. He quotes' also, Guenee, that Setina produces a sound like the ticking of a watch, apparently by the aid of « two large tympaniform " vesicles, situated in the pectoral region ; " and these " are much " more developed in the male than in the female." Hence the sound-producing organs in the Lepidoptera appear to stand in some relation with the sexual functions. I have not alludal to the well-known noise made by the Death's Head Sphinx, for it is generally heard soon after the moth has emerged from 'its cocoon. Girard has always observed that the musky odour, which is omitted by two species of Sphinx moths, is pecuUar to the males and in the higher classes we shall meet with many instances of the males alone being odoriferous. Every one must have admired the extreme beauty of many butterflies and of some moths ; and it may be asked, are their colours and diversified patterns the result of the direct action of the physical conditions to which these insects have been exposed, without any benefit being thus derived ? Or have successive vai'iations been accumulated and determined as a protection, or for some unknown pui-pose, or that one sex may be at- tractive to the other ? And, again, what is the meaning of the colours being widely different in the males and females of, certain species, and alike in the two sexes of other species of the •• same genus ? Before attempting to answer these questions a body of facts must be given. "With our beautiful English butterflies, the admiral, peacock, and painted lady (Vanessee), as weU as many others, the sexes are alike. This is also the case with the magnificent Hehconidae,. and most of the Danaidaa in the tropics. But in certain other tropical groi;ps, and in some of our English butterflies, as the- purple emperor, orange-tip, &c. {Apatura Iris and Anthocharis cardamines), the sexes difi'er either greatly or slightly in colour. No language suffices to describe the splendour of the males of ord, 1845, p. 123) a peculiar mem- observations, ' The Scottish Natural- liranous sac at the base of the ist,' July 1872, p. 214. front vings, which is probably con- ' ' The Scottish Naturalist,' July nected with the production of the 1872, p. 213. sound. For the case of Thecophora, * 'Zoological Record,' 1869, p. see 'Zoological Record,' 1869, p. 347. 401. For Mr. Buchanan Wleiv'a jChap. XL Butterflies and Motlis. 309 •eome tropical species. Even within the same genus we often ifind species presenting extraordinary differences between the «exes, whilst others have their sexes closely alike. Thus in the •South American genus Epicaha, Mr. Bates, to whom I am indebted for most of the following facts, and for looking over this whole discussion, informs me that he knows twelve species, the two sexes of which haunt the same stations (and this is not always the case with butterflies), and which, therefore, cannot have been differently affected by external conditions.^ In nine of these twelve species the males rank amongst the most brilliant of .aU butterflies, and differ so greatly from the comparatively plain females that they were formerly placed in distinct genera. The •females of these nine species resemble each other in their general type of coloration; and they likewise resemble both sexes of the species in several alhed genera, found in various parts of the world. Hence we may infer that these nine species, and probably all the others of the genus, are descended from an -ancestral form which was coloured in nearly the same manner. In the tenth species the female still retains the same general colouring, but the male resembles her, so that he is coloured in a much less gaudy and contrasted manner than the males of the previous species. In the eleventh and twelfth species, the females depart from the usual type, for they are gaily decorated iihnost like the males, but in a somewhat less degree. Hence in these two latter species the bright colours of the males seem to have been transferred to the females; whilst in the tenth species the male has either retained or recovered the plain ^colours of the female, as well as of the parent-form of the genus. ;The sexes in these three cases have thus been rendered nearly alike, though in an opposite manner. In the allied genus Eubagis, both sexes of some of the species are plain-coloured and nearly ^like ; whilst with the greater number the males are decorated with beautiful metalHc tints in a diversified manner, and differ much from their females. The females throughout the genus retain the same general style of colouring, so that they resemble one another much more closely than they resemble their own males. In the genus Papilio, all the species of the .ffineas group .are remarkable for their conspicuous and strongly contrasted colours, and they illustrate the frequent tendency to gradation, in the amount of difference between the sexes. In a few species, for instance in P. ascanius, the males and females are alike ; in » See also Mr. Bates's paper m the same subject, in regard tc Proc. Ent. Soc. of Philadelphia,' DIadema, in ' Transact. Entomolog, i860, p. 206. Also Mr. Wallace on Soc. of London," 1869, p. 278. 310 The Descent of Man. Paet II, others the males are either a little brighter, or very mucli mora superb than the females. The genus Junonia, allied to our Vanessse, offers a nearly parallel case, for although the sexes of most of the species resemble each other, and are destitute of rich colours, yet in certain species, as in J. oenone, the male is rather more bright- coloui-ed than the female, and in a few (for instance J. andremiaja) the male is so different from the female that he might be mistaken for an entirely distinct species. Another striking case was pointed out tome in the British Museum by Mr. A. Butler, namely, one of the tropical American Theclse, in which both sexes are nearly alike and wonderfully splendid ; in another species the male is coloured in a similarly gorgeous manner, whilst the whole upper surface of tha female is of a dull uniform brown. Our common little Enghsh blue butterflies of the genus Lycsena, illustrate the various dif- ferences in colour between the sexes, almost as well, though not in so striking a manner, as the above exotic genera. In Lycxna agestis both sexes have wings of a brown colour, bordered with smaU ocellated orange spots, and are thus alike. In L. oegon the wings of the male are of a fine blue, bordered with black ' whilst those of the female are brown, with a similar border, closely resembUng the wings of L. agestis. Lastly, in L. arion both sexes are of a blue colour and are very like, though in the female the edges of the wings are rather duskier, with the black spots plainer ; and in a bright blue Indian species both sexes are still more alike. I have given the foregoing details in order to show, in the fii-st place, that when the sexes of butterflies differ, the male as a i general rule is the more beautiful, and departs more from the i usual type of colouring of the gi'oup to which the species s belongs. Hence in most groups the females of the several " species resemble each other much more closely than do the males. In some cases, however, to which I shall hereafter r allude, the females are coloured more splendidly than the? males. In the second place, these details have been given to ? bring clearly before the mind that within the same genus, the ? two sexes frequently present every gradation from no difference s in colour, to so great a difference that it was long before the two :> were placed by entomologists in the same genus. In the third i place, we have seen that when the sexes nearly resemble each other, this appears due either to the male having transferred i his colours to the female, or to the male having retained, or r perhaps recovered, the primordial colom'S of the group. It also deserves notice that in those groups in which the sexes differ, the females usually somewhat resemble the males, so that when Chap. XI, Butterflies and Moths. 311 the males ai-e beautiful to an extraordinary degree, the females almost invariably exhibit some degree of beauty. Erom the many cases of gradation in the amount of difference between the sexes, and from the prevalence of the same general type of coloration throughout the whole of the same group, we may con- clude that the causes have generally been the same which have determined the brilliant colouring of the males alone of some species, and of both sexes of other species. As so many gorgeous butterflies inhabit the tropics, it has often been supposed that they owe their colours to the great heat and moisture of these zones ; but Mr. Bates ^ has shewn by the comparison of various closely-allied groups of insects from the temperate and tropical regions," that this view cannot be maintained ; and the evidence becomes conclusive when bril- liantly-coloiu-ed males and plain-coloured females of the same species inhabit the same district, feed on the same food, and follow exactly the same habits of life. Even when the sexes resemble each other, we can hardly believe that their brilliant and beautifully-arranged colours are the purposeless result of the nature of the tissues and of the action of the surrounding conditions. , With animals of all kinds, whenever colour has been modified for some special purpose, this has been, as far as we can judge, either for direct or indirect protection, or as an attraction between the sexes. With many species of butterflies the upper surfaces of the wings are obscure; and this in all probability leads to their escaping observation and danger. But butterflies woiild be particularly liable to be attacked by their enemies when at rest ; and most kinds whilst resting raise their wings vertically over their backs, so that the lower surface alone is exposed to view. Hence it is this side which is often coloured so as to imitate the objects on which these insects commonly rest. Dr. Ebssler, I believe, first noticed the similarity of the closed wings of certain Vanessse and other butterflies to the bark of trees. Many analogous and striking facts could be given. The most interesting one is that recorded by Mr. Wallace of a common Indian and Sumatran butterfly (Kallima), which disappears like magic when it settles on a bush ; for it hides its head and antennfe between its closed wings, which, in form, colour and veining, cannot be distinguished from a withered leaf with its footstalk. In some other cases the lower « 'The Naturalist oa the Ama- 1867, p. 10. A woodcut of the zons/ vol. :. 1863, p. 19. Kallima is given by Mr. Wallace in ' See the interesting article in ' Hardwicke's Science Gossip,' SepL the 'Westminster Review,' July 18G7, p. 19G. 312 Tlie Descejit of Man. Part VL surfaces of the wings arc brilliantly coloured, and yet are protective ; thus in Thecla ruhi the wings when closed are of au emerald green, and resemble the young leaves of the bramble, on which in spring this butterfly may often be seen seated. It is also remarkable that in very many species in which the sexes differ greatly in colour on their upper surface, the lower surface is closely similar or identical in both sexes, and serves as a protection.* Although the obscure tints both of the up])er and under sides of many butterflies no doubt serve to conceal them, yet we cannot extend this view to the brilliant and conspicuous colours on the upper surface of such species as our admiral and peacock Vanessaj, our white cabbage-butterflies (Pieris), or the great swallow-tail Papilio which haunts the open fens — for these butterflies are thus rendered visible to every living creature. In these species both sexes are alike ; but in the conmaon brim- stone butterfly (^Gonepteryx rhamni), the male is of an intense yellow, whilst the female is much paler; and in the orange- tip (Anthocharis cardamines) the males alone have their wings tipped with bright orange. Both the males and females in these cases are conspicuous, and it is not credible that their difference in colour should stand in any relation to ordinary protection. Prof. Weismann remarks,^ that the female of one of the Lycaenas expands her brown wings when she settles on the ground, and is then almost invisible ; the male, on the other hand, as if aware of the danger incurred from the bright blue of the upper surface of his wings, rests with them closed ; and this shews that the blue colour cannot be in any way protective. Nevertheless, it is probable that conspicuous colours are in- directly beneficial to many species, as a warning that they are unpalatable. For in certain other cases, beauty has been gained through the imitation of other beautiful species, which inhabit the same district and enjoy an immunity from attack by being in some way offensive to their enemies ; but then we have to account for the beauty of the imitated species. As Mr. Walsh has remarked to me, the females of our orange- tip butterfly, above referred to, and of an American species (^Anth. genutia) probably shew us the primordial colours of the parent-species of the genus; for both sexes of four or five widely-distributed species are coloured in nearly the same manner. As in several previous cases, we may here infer that it is the males of Anth. cardamines and genutia which have departed from the usual type of the genus. In the Anth. sara » Mr. G. Fraser, in ' Nature,' ' ' Einfluss der Isolirung auf di. April 1871, p. 489. Artbildung,' 1872, p. 58. CiiAP. XI, Butterflies and Moths. 313 from California, the orange-tips to the wings have been partially developed in the female ; but they are paler than in the male, and slightly different in some other respects. In an allied Indian form, the Iphias glaucippe, the orange-tips are fully developed in both sexes. In this Iphias, as pointed out to me by Mr. A. Butler, the under surface of the wings marvellously resembles a pale- coloured leaf; and in our English orange-tip, the under surface resembles the flower-head of the wild parsley, on which the butterfly often rests at night.^" The same reason which compels us to believe that the lower surfaces have here been coloured for the sake of protection, leads tis to deny that the wings have been tipped with bright orange for the same piirpose, especially when this character is confined to the males. Most Moths rest motionless during the whole or greater part of the day with their wings depressed ; and the whole upper sui'face is often shaded and coloured in an admirable manner, as Mr. Wallace has remarked, for escaping detection. The front- wings of the Bombycidse and Noctuidse," when at rest, generally overlap and conceal the hind- wings ; so that the latter might bo brightly coloured without much risk; and they are in fact often thus coloxu-ed. Duiing flight, moths would often be ablo to escape from their enemies ; nevertheless, as the hind-wings are then fully exposed to view, their bright colours must generally have been acquired at some little risk. But the following fact shews how cautious we ought to be in drawing conclusions on this head. The common Yellow Under-wings (Triphsena) often fly about during the day or early evening, and are then conspicuous from the colour of their hind-wings. It would natui'ally be thought that this would be a source of danger; but Mr. J. Jenner Weir beUeves that it actually serves them as a means of escape, for birds strike at these brightly coloui-ed and fragile surfaces, instead of at the body. For in- stance, Mr. Weir turned into his aviary a vigorous specimen of Triphcena j>ronuba, which was instantly pursued by a robin; but the bird's attention being caught by the coloured wings, the moth waj3 not captured until after about fifty attempts, and small portions of the wings were repeatedly broken off. He tried the same experiment, in the open air, with a swallow and T. fimbria; but the large size of this moth probably interfered with its capture.''^ We are thus reminded of a statement made '0 See the interesting observations Science Gossip,' Sept. 1867, p. 193. hy Mr. T. W. Wood, ' The Student,' 12 See also, on this subject, Mr. Bept. 1868, p. 81. Weir's pnper in ' Transnct. Ent. Soc' " Mr. WaUace in ' Hfxrdwickc's 18G9. p. 23. 3^4 TJie Descent of Man. Paht ij^ by Mr. Wallace," namely, that in the Brazilian forests and Malayan islands, many common and highly-decorated butterflies are weak flyers, though furnished with a broad expanse of wing; and they " are often captured with pierced and broken wings' " as if they had been seized by birds, from which they had " escaped : if the wings had been much smaller in proportion " to the body, it seems probable that the insect would more " frequently have been struck or pierced in a vital part, and " thus the increased expanse of the wings may have been in- " directly beneficial." Display. — The bright colours of many butterflies and of some moths are specially arranged for display, so that they may be readily seen. During the night colours are not visible, and there can be no doubt that the nocturnal moths, taken as a body, are much less gaily decorated than butterflies, all of which are diurnal in their habits. But the moths of certain families, such as the Zygsenidee, several SphingidaB, UraniidEe, some Arctiidse and Satm-niidse, fly about during the day or early evening, and many of these are extremely beautiful, being far brighter coloured than the strictly nocturnal kinds. A few exceptional cases, however, of brighihcoloured nocturnal species have been recorded." There is evidence of another kind in regard to display. Butterflies, as before remarked, elevate their wings when at rest, but whilst basking in the simshine often alternately raise and depress them, thus exposing both smfaces to full view ; and although the lower sui-face is often coloui'ed in an obscure manner as a protection, yet in many species it is as highly decorated as the upper surface, and sometimes in a very different manner. In some tropical species the lower surface is even more brilliantly coloured than the upper. In ti:e Eng- lish fritillaries (Argynnis) the lower surface alone is orna- mented with shining silver. Nevertheless, as a general rule, the upper surface, which is probably more fully exposed, is coloured more brightly and diversely than the lower. Hence the lower surface generally affords to entomologists the more " ' Westminster Review,' July 1867, p. 16. ^ For instance, Lithosia ; but Prof. Westwood (' Modern Class, of Insects,' vol. ii. p. 390) seems sur- prised at this case. On the relative colours of diurnal and nocturnal Lepidoptera, see ibid. pp. 333 and a92 ; also Harris, ' Treatise on the Insects of New England,' 1842, p. 315. Such differences between ths upper and lower surfaces of the wings of several species of Papilio, may be seen in the beautiful plates to Mr. Wallace's ' Memoir on the Papilionidee of the Malayan Region," in 'Transact. Linn. Soc' vol. xiv. part i. 1865. Chap. XJ Butterflies and Moths. 315 useful character for detecting the affinities of the varioua species. Fritz Miiller informs me that three species of Castnia are found near his house in S. Brazil : of two of them the hind- wings are obscure, and are always covered by the front- wings when these butterflies are at rest; but the third species has black hind-wings, beautifully spotted with red and white, and these are fully expanded and displayed whenever the butterfly rests. Other such cases could be added. If we now turn to the enormous group of moths, which, as I hear from Mr. Stainton, do not habitually expose the under surface of their wings to full view, we find this side very rarely coloiu-ed with a brightness greater than, or even equal to, that of the upper side. Some exceptions to the rule, either real or apparent, must be noticed, as the case of Hypopyra." IMr, Trimen informs me that in Guenee's great work, thi-ee moths are figured, in which the under surface is much the more brflliant. For instance, in the Australian Gastrophora the upper surface of the fore-wing is pale greyish-ochreous, while the lower surface is magnificently ornamented by an oceUus of cobalt-blue, placed in the midst of a black mark, surrounded by orange-yellow, and this by bluish-white. But the habits of these thi-ee moths are unknown ; so that no explanation can be given of their unusual style of colouring. Mr. Trimen also informs me that the lower surface of the wings in certain other Geomctrae" and quadrifid Noctuse are either more variegated or more brightly-coloured than the upper surface ; but some of these species have the habit of " holding their wings quite erect " over their backs, retaining them in this position for a con- " siderable time," and thus exposing the under surface to view. Other species, when settled on the ground or hei-bage, now and then suddenly and slightly lift up their wings. Hence the lower surface of the wings being brighter than the upper surface in certain moths is not so anomalous as it at first appears. The Saturniidse include some of the most beautiful of all moths, their wings being decorated, as in our British Emperor moth, with fine ocelli ; and Mr. T. W. Wood" observes that they resemble butterflies in some of their movements; "for " instance, in the gentle waving up and down of the wings as M " for display, which is more cLaracteristic of diurnal than of " nocturnal Lepidoptera." >« See Mr. Worraald on this the Geometi-ffi) in 'Transact. Eat, moth : ' Proc. Ent. Soc' March 2nd, Soc' new series, vol. v. pi. xv. and 1868. xvi. " See also an account of the S. '» ' Proc. Ent. Soc. of Londoo,' American genus Erateina (one of July 6, IS68, p. xxvii. 3 16 The Descent of Man. Part IL It is a singular fact that no British moths which are bril- liantly coloured, and, as far as I can discover, hardly any foreign species, differ much in colour according to sex ; though this is the case with many brilliant butterflies. The male, however, of one American moth, the Saturnia lo, is described as having itfi fore-wings deep yellow, curiously marked with purplish-red spots ; whilst the wings of the female are purple-brown, marked with grey lines." The British moths which differ sexually in colour are all brown, or of various dull yellow tints, or nearly white. In several species the males are much darker than the females,^" and these belong to groups which generally fly about during the afternoon. On the other hand, in many genera, as Mr. Stainton informs me, the males have the hind-wings whiter than those of the female — of which fact Agrotis exclamationis offers a good instance. In the Ghost Moth (Ilepialus humuli) tJie difference is more strongly marked ; the males being white, and the females yellow with darker markings.^' It is probable that in these cases the males are thus rendered more conspicuous, and more easily seen by the females whilst flying about in the dusk. From the several foregoing facts it is impossible to admit that the brilliant colours of butterflies, and of some few moths, liave commonly been acquired for the sake of protection. "We have seen that theii- colours and elegant patterns are arranged a,nd exhibited as if for display. Hence I am led to believe that the females prefer or are most excited by the more brillinjit " Harris, 'Treatise,' &c., edited by Flint, 1862, p. 395. For instance, I observe in my son's cabinet that the males are darker than the females in the Lasiocampa quercus, Odoncstis pota- ioria, Hijpogymna dispar, Dasychira pudibunda, and Cycnia mcndica. In this latter species the difference in colour between the two sexes is strongly marked ; and Mr. Wallace informs me that we here have, as he believes, an instance of protective mimicry confined to one sex, as will hereafter be more fully ex- plained. The white female of the Cycnia resembles the very common Spilosoma menthrasti, both sexes of which are white ; and Mr. Stainton observed that this latter moth was rejected with utter disgust by a whole brood of young turkeys, which were fond of eating othei moths; so that if the Cycnia was commonly mistaken by British birds for the Spilosoma, it would escape being devoured, and its white de- ceptive colour would thus be highly beneficial. It is remarkable, that in the Shetland Islands the male of this moth, instead of differing widely from the female, frequently re- sembles her closely in colour (see Mr. MacLachlan, ' Transact. Ent. Soc' vol. ii. 1866, p. 459). Sir. G. Fraser suggests ('Nature,' April 1871, p. 489) that at the season of the year when the ghost-moth ap- pears in these northern islands, the whiteness of the males would not be needed to render Lliem visible to the females in the ttviiight Dight. Chap. XI. Butterflies and Moths. males ; for on any other supposition tlie males would, as far as. we can see, be ornamented to no purpose. We know that ants, and certain Lamellicorn beetles are capable of feeling an attach- ment for each other, and that ants recognise their fellows after an interval of several months. Hence there is no abstract improbability in the Lepidoptera, which probably stand nearly or quite as high in the scale as these insects, having sufficient mental capacity to admire bright colours. They certainly discover flowers by colour. The Humming-bird Sphinx may often be seen to swoop down from a distance on a bunch of flowers in the midst of green foliage ; and I have been asstired by two persons abroad, that these moths repeatedly visit flowers painted on the walls of a room, and vainly endeavour to insert their proboscis into them. Fritz Miiller informs me that several kinds of butterflies in S. Brazil shew an unmistakable prefer- ence for certain colours over others : he observed that they very often visited the brilhant red flowers of five or six genera of plants, but never the white or yellow flowering species of the same and other genera, growing in the same garden; and I have received other accounts to the same effect. As I hear from Mr. Doubleday, the common white butterfly often flies down to a bit of paper on the ground, no doubt mistaking it for one of its own species. Mr. CoUingwood"^ in speaking of the difficulty in collecting certain butterflies in the Malay Archipelago, states that " a dead specimen jDinned upon a " conspicuous twig will often arrest an insect of the same species " in its headlong flight, and bring it down within easy reach of " the net, especially if it be of the opposite sex." The courtship of butterflies is, as before remarked, a prolonged affair. The males sometimes fight together in rivalry; and many may be seen pui'suing or crowding round the same female. Unless, then, the females prefer one male to another, the pairing must be left to mere chance, and this does not appear probable. If, on the other hand, the females habitually, or even occasionally, prefer the more beautiful males, the colours of the latter will have been rendered brighter by degrees, and will have been transmitted to both sexes or to one sex, according to the law of inheritance which has prevailed. The process of sexual selection will have been much facilitated, if the conclusion can be trusted, arrived at from various kinds of evidence in the supplement to the ninth chapter; namely, that the males of many Lepidoptera, at least in the imago state, greatly axceed the females in number. (Some facts, however, are opposed to the belief that female " ' Rambles of a Naturalist in the Chinese Seas,' 1868, p. 182. 3i8 The Descent of Man. Paet II. biTtterflies prefer tlio more beautiful males ; thus, as I have been assured by several collectors, fresh females may frequently be seen paired with battered, faded, or dingy males; but this is a circumstance which could hardly fail often to follow from the males emerging from their cocoons earlier than the females. With moths of the family of the Bombycidse, the sexes pair immediately after assuming the imago state; for they cannot feed, owing to the rudimentary condition of their mouths. The females, as several entomologists have remarked to me, lie in an almost torpid state, and appear not to evince the least choice in regard to their partners. This is the case with the common silk-moth {B. mori), as I have been told by some continental and English breeders. Dr. Wallace, who has had great experience in breeding Bombyx cynthia, is convinced that the females evince no choice or preference. He has kept above 300 of these moths together, and has often found the most vigorous females mated with stunted males. The reverse appears to occur seldom ; for, as he believes, the more vigorous males pass over the weakly females, and are attracted by those endowed with most vitality. Nevertheless, the Bombycidas, though obscurely-coloured, are often beautifid to our eyes fi'om their elegant and mottled shades. I have as yet only referred to the species in which the males are brighter coloured than the females, and I have attributed their beauty to the females for many generations having chosen and paired with the more attractive males. But converse cases occur, though rarely, in which the females are more brilliant than the males ; and here, as I believe, the males have selected the more beautiful females, and have thus slowly added to their beauty. We do not know why in various classes of animals the males of some few species have selected the more beautiful females instead of having gladly accepted any female, as seems to be the general rule in the animal kingdom ; but it, contrary to what generally occurs with the Lepidoptera, the females were much more numerous than the males, the latter would be likely to pick out the more beautiful females. Mr. Butler shewed me several species of Calhdryas in the British Museum, in some of which the females equalled, and in others gi-eatly surpassed the males in beauty; for the females alone have the borders of their wings suffused with crimson and orange, and spotted with black. The plainer males of these species closely resemble each other, showing that here the females have been modified ; whereas in those cases, where the males are the more ornate, it is these which have been modified, the females remaining closely alike. Chap. XL Butterflies and Moths. 319 In England we liave some analogons cases, thongh not bo marked. The females alone of two species of Thecla have a bright-purple or orange patch on their fore-wings. In Hip- parchia the sexes do not differ much ; but it is the female of H. janira which has a conspicuous light-brown patch on her \dngs ; and the females of some of the other species are brighter coloui-ed than then.' males. Again, the females of Colias edusa and hyale have " orange or yellow spots on the black marginal " border, represented in the males only by thin streaks ; " and in Pieris it is the females which " are ornamented with black " spots on the fore-wings, and these are only partially present " ui the males." Now the males of many butterflies are known to support the females during their marriage flight ; but in the species just named it is the females which support the males ; so that the part which the two sexes play is reversed, as is their relative beauty. Throughout the animal kingdom the males commonly take the more active share in wooing, and their beauty seems to have been increased by the females having accepted the more attractive individuals ; but with these but- terflies, the females take the more active part in the final mai-- riage ceremony, so that we may suppose that they likewise do so in the wooing ; and in this case we can understand how it is that they have been rendered the more beautiful. Mr. Meldola, from whom the foregoing statements have been taken, says in conclusion ; " Though I am not convinced of the action of " sexual selection in producing the colours of insects, it cannot " be denied that these facts are strikingly corroborative of " Mr. Darwin's views." As sexual selection primarily depends on variability, a few words must be added on this subject. In respect to coloui- there is no diflaculty, for any nuihber of highly variable Lepi- doptera could be named. One good instance will suffice. Mr. Bates shewed me a whole series of specimens of Papilio sesostris an i P. childrencB ; in the latter the males varied much in the extent of the beautifully enamelled green patch on the fore- wings, and in the size of the white mark, and of the splendid crimson stripe on the hind-wings; so that there was a great contrast amongst the males between the most and the least gaudy. The male of Papilio sesostris is much less beautiful than of P. childrence ; and it likewise varies a little ia the size of P- "^liilst pairing. See also Mr. G. 508. Mr. Meldola quotes Donzol, Frascr, in 'Nature,' April 20th in 'Soc. Ent. de France,' 1837, p. 1871, p. 489, on the sexual difler- 77, on the flight of butterflies ences of se- oral British butterflies. 320 The Descent of Man. Pakt D the green patch on the fore-wings, and in the occasional ap- pearance of the small crimson stripe on the hind-wings, borrowed, as it would seem, from its own female ; for the females of this and of many other species in the JEncas group iwssess this crimson stripe. Hence between the brightest specimens of P. sesostris and the dullest of P. children^, there was but a small interval ; and it was evident that as far as mere varia- bility is concerned, there would be no difiaculty in permanently increasing the beauty of either species by means of selection. The variability is here almost confined to the male sex; but Mr. Wallace and Mr. Bates have shewn'^* that the females of some species are extremely variable, the males being nearly constant. In a future chapter I shall have occasion to shew that the beautiful eye-like spots, or ocelli, found on the wings of many Lepidoptera, are eminently variable. I may here add that these ocelli offer a difficulty on the theory of sexual selection ; for though appearing to us so ornamental, they are never present in one sex and absent in the other, nor do they ever differ much in the two sexes.-^ This fact is at present inexphcable ; but if it should hereafter be found that the for- mation of an ocellus is due to some change in the tissues of the wings, for instance, occui-ring at a very early period oi development, we might expect, from what we know of the laws of inheritance, that it would be transmitted to both sexes, though arising and perfected in one sex alone. On the whole, although many serious objections may be lu'ged, it seems probable that most of the brilliantly coloured species of Lepidoptera owe theii* coloui-s to sexual selection, excepting in certain cases, presently to be mentioned, in which conspicuous colours have been gained through mimicry as a protection. From the ardour of the male tkroughout the animal kingdom, he is generally wiUing to accept any female ; and it is the female which usually exerts a choice. Hence, if sexual selection has been efficient with the Lepidoptera, the male, when the sexes differ, ought to be the more brilliantly coloured, and this undoubtedly is the case. When both sexes are brilliantly coloured and resemble each other, the characters acquired by the males appear to have been transmitted to both. "^^ Wallace on the Papilionida; of f omolog. Soc' Nov. 19th, 1866, p. the Malayan Region, in ' Transact, xl. Linn. Soc.' voi. xxv. 1865, pp. 8, Mr. Bates was so kind as to '36. A striking case of a rare lay this subject before the Entomo- pariety, strictly intermediate be- logical Society, and I have receired tween two other well-marked female answers to this eflect from sereral varieties, is given by Mr. Wallace, entomologists. See also Mr. Bates, in ' Proc. En- Chap. XI. Butterflies and Moths. 321 We are led to this conclusion by cases, even within the same genus, of gradation from an extraordinary amount of difference to identity in colour between the two sexes. But it may be asked whether the differences in colour between the sexes may not be accounted for by other means besides sexiial selection. Thus the males and females of the same species of butterfly are in several cases known to inhabit different stations, the former commonly basking in the sunshine, the latter haunting gloomy forests. It is therefore possible that different conditions of life may have acted directly on the two sexes ; but this is not probable,^'' as in the adu't state they are exposed to different conditions during a very short period ; and the larvae of both are exposed to the same conditions. Mr. Wallace believes that the difference between the sexes is due not so much to the males having been modified, as to the females having in all or almost all cases acquired dull colours for the sake of protection. It seems to me, on the contrary, far more probable that it is the males which have been chiefly modified through sexual selection, the females having been comparatively little changed. We can thus understand how it is that the females of allied species generally resemble one another so much more closely than do the males. They thus shew us ap- proximately the primordial colouring of the parent-species of the gi-oup to which they belong. They have, however, almost always been somewhat modified by the transfer to them of some of the successive variations, through the accumulation of which the males were rendered beautiful. But I do not wish to deny that the females alone of some species may have been specially modified for protection. In most cases the males and females of distiact species will have been exposed during their prolonged larval state to different conditions, and may have been thus affected; though with the males any slight change of colour thus caused will generally have been masked by the brilliant tints gained through sexual selection. When we treat of Birds, I shaU have to discuss the whole question, as to how far the differences in colour between the sexes are due to the males having been modified through sexual selection for ornamental purposes, or to the females having been modified through natural selection for the sake of protection, so that I will he°re say but little on the subject. Id all the cases in which the more common form of equal " H. W. Bates 'The Naturalist " On this whole subject see 'The ooo"'^^S'^';^°f,' P- Variation of Animals and Plants 228. A. R. Wallace, in 'Transact, uader Domesticat on,' 1868, vol. ii. Lmn. Soc' vol. .x.w. 1865, p. 10. chap, ixiii. Y 322 The Descent of Man. Part IJ. inlieritance hy botli sexes has prevailed, the selectiou of bright- coloured malds would tend to make the females bright-coloured ; and the selection of dull-coloured females would tend to malco the males dull. If both processes were carried on simultaneously, they would tend to counteract each other; and the final result would depend on whether a greater number of females from being well protected by obscure colours, or a greater number of males by being brightly-coloured and thus finding partners, succeeded in leaving more numerous offspring. In order to account for the frequent transmission of character.s to one sex alone, Mr. "Wallace expresses his beUef that the more- common form of equal inheritance by both sexes can be changed through natural selection into inheritance by one sex aloue, but in favour of this view I can discover no evidence. "We know from what occurs under domestication that new characters often appear, which from the first are transmitted to one sex alone ; and by the selection of such variations there would not be the slightest difficulty in giving bright colours to the males alone, and at the same time or subsequently, dull colours to the females alone. In this manner the females of some butterflies and moths have, it is probable, been rendered inconspicuous for the sake of protection, and widely different from their males. I am, however, unwilling without distinct evidence to admit that two complex processes of selection, each requiring the transference of new characters to one sex alone, have been carried on with a multitude of species, — that the males have been rendered more brilliant by beating their rivals, and the females more dull-coloured by having escaped from their enemies. The male, for iastance, of the common brimstone butterfly (Gonepteryx), is of a far more intense yellow than the female, though she is equally conspicuous ; and it does not seem probable that she specially acquired her pale tints as a protec- tion, though it is probable that the male acquired his bright colours as a sexual attraction. The female of Anthochuris ear- damines does not possess the beautiful orange wing-tips of the male ; consequently she closely resembles the white butterflies (Pieris) so common in our gardens ; but we have no evidence that this resemblance is beneficial to her. As, on the other hand, she resembles both sexes of several other species of the genus inhabiting various quarters of the world, it is probable that she has simply retained to a large extent her primordial colours. rinally, as we have seen, various considerations lead to the conclusion that with the greater number of brilliantly-coloured Lepidoptera it is the male which has been chiefly modified through Koxual selection; the amouDt of difference between Chap. XI. Butterflies and Moths. 323 the sexes mostly clepen(iing on the form of inheritance which \jas prevailed. Inheritance is governed by so many unknown laws or conditions, that it seems to us to act in a capricious manner ; ^ and we can thus, to a certain extent, understand how it is that with closely allied species the sexes either differ to an astonishing degree, or are identical in colour. As all the suc- cessive steps in the process of variation are necessarily trans- mitted through the female, a greater or less number of such steps might readily become developed in her ; and thus we can imderstand the frequent gradations from an extreme difference to none at all between the sexes of allied species. These cases of gi-adation, it may be added, are much too common to favour the supposition that we here see females actually undergoing the process of transition and losing their brightness for the sake of protection ; for we have every reason to conclude that at any one time the greater number of species are in a fixed condition. Mimicry. — This principle was first made clear in an admirable paper by Mr. Bates,"' who thus threw a flood of light on many obscure problems. It had previously been observed that certain butterflies in S. America belonging to quite distinct familieb,_ resembled the Heliconidas so closely in every stripe and shade of " colour, that they could not be distinguished save by an ex- perienced entomologist. As the Hehconidse are coloured in their usual manner, whilst the others depart from the usual colouring of the groups to which they belong, it is clear that the latter are the imitators, and the Heliconidse the imitated. Mr. Bates further observed that the imitating species are com- paratively rare, whilst the imitated abound, and that the two sets live mingled together. From the fact of the Heliconidse being conspicuous and beautiful insects, yet so numerous in individuals and species, he concluded that they must be pro- tected from the attacks of enemies by some secretion or odour ; and this conclusion has now been amply confirmed,"" especially by Mr. Belt. Hence Mr. Bates inferred that the butterflies which imitate the protected species have acquired their present marvellously deceptive appearance through variation and natural selection, in order to be mistaken for the protected kinds, and thus to escape being devoured. No explanation is here attempted of the brilliant colours of the imitated, but only of the imitating butterflies. We must account for the colours of the former in the same general manner, as in the cases previously discussed ' The Variation of Animals and xxiii. 18()2, p. 495. Piauts under Domestication,' vol. ii. « Prcc. Ent. Soc* Deo. 3rd, chap. Tii. p. 17. 18(30, p. xlv. ' Transact. Linn. Soc' vol. T 2 324 The Descent of Man. Pabt II, in this chapter. Since the publication of Mr. Bates' paper, similar and equally striking facts have been observed by Mr, "Wallace in the Malayan region, by Mr. Trimen in South Africa, and by Mr. Eiley in the United States.^* As some writers have felt much difficulty in understanding how the first steps in the process of mimicry could have been effected through natural selection, it may be well to remark that the process probably commenced long ago between forms not widely dissimilar in colour. In this case even a slight variation would be beneficial, if it rendered the one species more like the other ; and afterwards the imitated species might be modi- fied to an extreme degree through sexual selection or other means, and if the changes were gradual, the imitators might easily be led along the same track, until they differed to au equally extreme degree from their original condition ; and they would thus ultimately assume an appearance or colouring wholly unlike that of the other members of the group to which they belonged. It should also be remembered that many species of Lepidoptera are liable to considerable and abrupt variations in colour. A few instances have been given in this chapter ; and many more may be found in the papers of Mr. Bates and Mr. Wallace. With several species the sexes are alike, and imitate the two sexes of another species. But Mi-. Trimen gives, in the paper already referred to, three cases in which the sexes of the imitated form differ from each other in colour, and the sexes of the imitating form differ in a like manner. Several cases have also been recorded where the females alone imitate brilliantly- coloured and protected species, the males retaining "the " normal aspect of their immediate congeners." It is here obvious that the successive variations by which the female has been modified have been transmitted to her alone. It is, however, probable that some of the many successive variations would have been transmitted to, and developed in, the males had not such males been eliminated by being thus rendered less attractive to the females; so that only those variations were preserved which were from the first strictly limited in their transmission to the female sex. We have a partial illus- tration of those remarks in a statement by Mr. Belt;'* that " Wallace, ' Transact. Linn. Soc' 163-168. This latter essay is valu- vol. XIV. 1865, p. 1 ; also ' Transact, able, as Mr. Riley here discusses all Ent. S'jc' vol. iv. (3rd series), 1867, the objections which have been p 301. Trimen, ' Linn. Transact.' raised against Mr. Bates' theory. roL xxvi. 1869, p. 497. Riley, < xhe Naturalist in Nicaragof., 'Third Annual Report on the Noxi- 1874, p. 385. ous Insects of Missouri,' 1871, pp. Chap. XI. 325 the males of some of the Leptalides, which imitate protected species, still retain in a concealed manner some of their original characters. Thus in the males " the upper half of the lower " wing is of a pure white, whilst all the rest of the wings is " barred and spotted with black, red and yellow, like the species " they mimic. The females have not this white patch, and the " males usually conceal it by covering it with the upper wing, " so that I cannot imagine its being of any other use to them " than as an attraction in courtship, when they exhibit it to the " females, and thus gratify their deep-seated preference for the " normal colour of the Order to which the Leptalides belong." Bright Colours of Caterpillars. — Whilst reflecting on the beauty of many butterflies, it occurred to me that some cater- pillars were splendidly coloured ; and as sexual selection could not possibly have here acted, it appeared rash to attribute the beauty of the mature insect to this agency, unless the bright colours of their larvae could be somehow explained. In the first place, it may be observed that the colours of caterpillars do not stand in any close correlation with those of the mature insect. Secondly, their bright colours do not serve in any ordinary manner as a protection. Mr. Bates informs me, as an instance of this, that the most conspicuous caterpillar which he ever beheld (that of a Sphinx) lived on the large green leaves of a tree on the open llanos of South America ; it was about four inches in length, transversely banded with black and yellow, and with its head, legs, and tail of a bright red. Hence it caught the eye of any one who passed by, even at the distance of many yards, and no doubt that of every passing bird. I then applied to Mr. Wallace, who has an innate genius foj solvmg difiSculties. After some consideration he replied : " Most " caterpillars require protection, as may be inferred from some " kinds being furnished with spines or ii-ritating haii-s, and " from many being coloured green like the leaves on which they " feed, or being curiously like the twigs of the trees on which they " live." Another instance of protection, furnished me by Mr. j. Mansel Weale, may be added, namely, that there is a caterpillar of a moth which lives on the mimosas in South Africa, and fabricates for itself a case quite indistinguishable from the surrounding thorns. From such considerations Mr. Wallace thought it probable that conspicuously-coloured caterpillars were protected by having a nauseous taste; but as their skin is extremely tender, and as then- intestines readily protrude from a wound, a slight peck from the beak of a bird would be as fatal to them as if they liad been devoured. Hence, as 326 rr„e jyescent Of Man. Pabt LI. Mr. Wallace remarks, " distastefulness alone would be insufficient " to protect a caterpillar unless some outward sign indicated to " its would-be destroyer that its prey was a disgusting morsel." Under these circumstances it would be highly advantageous to a caterpillar to be instantaneously and certainly recognised as unpalatal)lo by all birds and other animals. Thus the most gaudy coloui's would be serviceable, and might have been gained by variation and the survival of the most easily-re- cognised individuals. This hypothesis appears at first sight very bold, but when it was brought before the Entomological Society ^'^ it was supported by various statements ; and Mr. J. Jenner Weir, who keeps a large number of birds in an aviary, informs me that he has made many trials, and finds no exception to the rule, that all caterpillars of nocturnal and retiring habits with smooth sktns, all of a green colour, and all which imitate twigs, are greedily devoured by his birds. The hairy and spinose kinds are invariably rejected, as were four conspicuously-coloured species. When the birds rejected a caterpillar, they plainly shewed, by shaking their heads, and cleansing their beaks, that they were disgusted by the taste.** Three conspicuous kinds of cater- pillars and moths were also given to some lizards and frogs, by Mr. A. Butler, and were rejected, though other kinds were eagerly eaten. Thus the probability of Mr. Wallace's view is confirmed, namely, that certain caterpillars have been made conspicuous for their own good, so as to be easily recognised by their enemies, on nearly the same principle that poisons are sold in coloured bottles by di'uggists for the good of man. We cannot, however, at present thus explain the elegant diversity in the colours of many caterpillars ; but any species which had at some former period acquired a dull, mottled, or striped appear- ance, either in imitation of surrounding objects, or from the direct action of climate, &c., almost certainly would not become uniform in colour, when its tints were rendered intense and bright ; for in order to make a caterpillar merely conspicuous, there would be no selection in any definite direction. Summary and Concluding Remarks on /wsecfc.-r-Looking back ' Proc. Entomolog. Soc' Dec. 3rd, 1866, p. xlv., and March •ith, 1867, p. lixx. See Mr. J. Jenner Weir's paper on Insects and Insectivorous Birds, in ' Transact. Ent. Soc' 1869, p. 21 ; also Mr. Butler's paper, ibid. p. 27. Mr. Riley has given analogous facts in the ' Third An- nual Report on the Noxjous Insects of Missouri,' 1871, p. 148. Some opposed cases are, however, given by Dr. Walla.'e and M. H. d'Orville; see ' Zoological Record,' i869, p. 349, Chap. XI. Siivn7ta7-y on Insects. 327 to the several Orders, we see that the sexes often differ in. varions chai-acters, the meaning of which is not in the least understood. The sexes, also, often differ in their organs of sense and means of locomotion, so that the males may quickly discover and reach the females. They differ still oftener in the males possessing diversified contrivances for retaining the females when found. We are, however, here concerned only in a secondary degree with sexual differences of these kinds. In almost all the Orders, the males of some species, even of weak and delicate kinds, are knoAvn to be highly pugnacious ; and some few are furnished with special weapons for fighting with their rivals. But the law of battle does not prevail nearly so widely with insects as with the higher animals. Hence it probably arises, that it is in only a few cases that the males have been rendered larger and stronger than the females. On the contrary, they are usually sjnaller, so that they may be developed within a shorter time, to be ready in large numbers for the emergence of the females. In two famines of the Homoptera and in three of the Orthop- tera, the males alone possess sound-producing orj^.T,ns in an efficient state. These are used incessantly during the breeding- season, not only for calling the females, but apparently for charming or exciting them in rivalry with other males. No one who admits the agency of selection of any kind, will, after reading the above discussion, dispute that these musical instru- ments have been acquired through sexual selection. In four other Orders the members of one sex, or more commonly of both sexes, are provided with organs for producing various .sounds, which apparently serve merely as call-notes. When both sexes are thus provided, the individuals which were able to make the loudest or most continuous noise would gain partners before those which were less noisy, so that their organs have probably been gained through sexual selection. It is instructive to reflect on the wonderful diversity of the means for producing sound, possessed by the males alone, or by both sexes, in no less than six Orders. We thus leai-n how effectual sexual selection has been in leading to modifications which sometimes, as with the Homoptera, relate to important parts of the organisation. From the reasons assigned in the last chapter, it is probable that the great horns possessed by the males of many Lamel- licorn, and some other beetles, have been acquired as ornaments. From the smaU size of insects, we are apt to undervalue their appearance. If we could imagine a male Chalcosoma (fig. 16), With its polished bronzed coat of mail, and its vast comples 328 The Descent of Man. Paiit II, horns, magnified to the size of a horse, or even of a dog, it would bo one of the most imposing animals in the world. The colouring of insects is a complex and obscure subject. "When the male dififers slightly from the female, and neither are brilliantly-coloured, it is probable that the sexes have varied in a slightly different manner, and that the variations have been transmitted by each sex to the same, without any benefit or evil thus accruing. When the male is brilliantly-coloured and differs conspicuously from the female, as with some dragon-flies and many butterflies, it is probable that he owes his colours to sexual selection ; whilst the female has retained a primordial or very ancient type of colouring, slightly modified by the agencies before explained. But in some cases the female has apparently been made obscure by variations transmitted to her alone, as a means of direct protection; and it is almost certain that she has sometimes been made brilliant, so as to imitate other protected species inhabiting the same district. When the sexes resemble each other and both are obscurely coloured, there is no doubt that they have been in a multitude of cases so coloured for the sake of protection. So it is in some instances when both are brightly-coloured, for they thus imitate protected species, or resemble surrounding objects such as flowers; or they give notice to their enemies that they are unpalatable. In other ca^es in which the sexes resemble each other and are both brilliant, especially when the colours are arranged for display, we may conclude that they have been gained by the male sex as an attraction, and have been transferred to the female. We are more especially led to this conclusion whenever the same type of coloration prevails throughout a whole group, and we find that the males of some species differ widely in colour from the females, whilst others differ slightly or not at all, with intermediate gradations connecting these extreme states. In the same manner as bright colours have often been partially transferred from the males to the females, so it has been with the extraordinary horns of many Lamellicorn and some other beetles. So again, the sound-producing organt proper to the males of the Homoptera and Orthoptera have generally been transferred in a rudimentary, or even in a nearly perfect condition, to the females ; yet not sufficiently perfect to be of any use. It is also an interesting fact, as bearing on sexual selection, that the stridulating organs of certain male Orthoptera are not fully developed until the last moult; and that the colours of certain male dragon-flies are not fully developed until some little time after their emergence from the pupal state, and when they are ready to breed. Ohap. XL Szimniary on 'Insects 329 Sexual selection implies that the more attractive individuals are prefen-ed by the opposite sex ; and as with insects, when tne sexes differ, it is the male which, with some rare exceptions, is the more ornamented, and departs more from the type to which the species belongs ; — and as it is the male which searches eagerly for the female, we must suppose that the females habitually or occasionally prefer the more beautiful males, and that these have thus acquired their beauty. That the females in most or all the orders would have the power of rejecting any pai'ticular male, is probable from the many singular con- trivances possessed by the males, such as great jaws, adhesive cushions, spines, elongated legs, &c., for seizing the female ; for these contrivances shew that there is some difficulty in the act, so that her concurrence would seem necessary. Judging from what we know of the perceptive powers and affections of various insects, there is no antecedent improbability in sexual selection having come largely into play ; but we have as yet no direct evidence on this head, and some facts are opposed to the belief. Nevertheless, when we see many males pursuing the same female, we can hardly believe that the pairing is left to blind chance — that the female exerts no choice, and is not influenced by the gorgeous colours or other ornaments with which the male is decorated. If we admit that the females of the Homoptera and Orthoptera appreciate the musical tones of their male partners, and that the various instruments have been perfected through sexual se- lection, there is little improbability in the females of other insects appreciating beauty in form or colour, and consequently in such characters having been thus gained by the males. But from the circumstance of colour being so variable, and from its having been so often modified for the sake of protection, it is difficult to decide in how large a proportion of cases sexual selection has played a part. This is more especially difficult in those _ Orders, such as Orthoptera, Hymenoptera, and Coleop- tera, in which the two sexes rarely differ much in colour; for we are then left to mere analogy. With the Coleoptera, however, as before remarked, it is in the great Lamellicorn group, placei by some authors at the head of the Order, and in which we sometimes see a mutual attachment between the sexes, that we find the males of some species possessing weapons for sexual strife, others furnished with wonderful horns, many with stridu- latmg organs, and others ornamented with splendid metallic tints. Hence it seems probable that all these characters have been gamed through the same means, namely sexual selection. With butterflies we have the best evidence, as the males 320 The Descmt of Man. Paet II. Kometimes take pains to display their beautiful colours ; and we cannot believe that they would act thus, unless the display was of use to them in their courtship. When wo treat of Birds, we shall see that they present in their secondary sexual characters the closest analogy witli insects. Thus, many male birds are highly pugnacious, and some are furnished with special weapons for fighting with their rivals. They possess organs which are used dui-ing the breeding- season for producing vocal and instrumental music. They are frequently ornamented with combs, horns, wattles and plumes of the most diversified kinds, and are decorated with beautiful colours, all evidently for the sake of display. We shall find that, as with insects, both sexes in certain groups are equally beautiful, and are equally provided with ornaments which are usually confined to the male sex. In other groups both sexes are equally plain-coloured and unornamented. Lastly, in some few anomalous cases, the females are more beautiful than the males. We shall often find, in the same group of birds, every gi'adation from no difference between the sexes, to an extreme difference. We shall see that female birds, like female insects, often possess more or less plain traces or rudiments of characters which properly belong to the males and are of use only to them. The analogy, indeed, in all these respects between birds and insects is curiously close. Whatever explanation applies to the one class probably applies to the other ; and this explanation, as we shall hereafter attempt to shew in further detail, is sexual selection. CHAPTEE Xn. Secondary Sexual Charaotehs of Fishes, Amphibians, AND Eeptiles. Fishes : Courtship and battles of the males — Larger size of the females — Males, bright colours and ornamental appendages; other strange characters — Colours and appendages acquired by the males durind the breeding-season alone — Fishes with both sexes brilliantly coloured — Protective colours — The lass conspicuous colours of the female cannot be accounted for on the principle of protection — Male fishes building nests, and taking charge of the ova and young. Ai.ipiiibians : Dif- ferences in structure and colour between the sexes — Vocal organs. Reptiles : Chelonians — Crocodiles — Snakes, colours in some cases pro- tective— Lizards, battles of — Ornamental appendages — Strange dif- ferences in structure between the sexes — Coloiu's — Sexual diiferences almost as great as with birds. We have now arrived at the great sub-kingdom of the Vertebrata, and will commence with the lowest class, that of Fishes. The Chap. XIJ. FisJtes. males of Plagiostomons fishes (sharks, rays) and of Chimferoid fishes are provided with claspers which serve to retain the female, like the various structures possessed by many of the lower animals. Besides the claspers, the males of many rays have clusters of strong sharp spines on their heads, and several rows along " the upper outer surface of their pectoral fins." These are present in the males of some species, which have other parts of their bodies smooth. They are only temporarily developed during the breeding-season; and Dr. Giinther suspects that they are brought into action as prehensile organs by the doubling inwards and downwards of the two sides of the body. It is a remarkable fact that the females and not the males of some species, as of Raia davata, have their backs studded with large hook-formed spines.^ The males alone of the capelin {Mallotus villosus, one of Salmonidfe), are provided with a ridge of closely-set, brush-like scales, by the aid of which two males, one on each side, hold the female, whilst she runs with great swiftness on the sandy beach, and there deposits her spawn.^ The widely distinct Monacanthus scopas presents a somewhat analogous structure. The male, as Dr. Giinther informs me, has a cluster of stiff, straight spines, like those of a comb, on the sides of the tail ; and these in a specimen six inches long were nearly one and a half inches in length ; the female has in the same place a cluster of bristles, which may be compared with those of a tooth-brash. In another species, M. peronii, the male has a brush like that possessed by the female of the last species, whilst the sides of the tail in the female are smooth. In some other species of the same genus the taU can be perceived to be a little roughened in the male and perfectly smooth in the female; and lastly in others, both sexes have smooth sides. The males of many fish fight for the possession of the females. Thus the male stickleback (Oasterosteus leiurus) has been de- scribed as " mad with delight," when the female comes out of her hiding-place and surveys the nest which he has made for her. " He darts round her in every direction, then to his accumulated materials for the nest, then back again in an instant ; and as " she does not advance he endeavours to push her with his snout, " and then tries to pull her by the tail and side-spine to the nest."^ • Yarrell's 'Hist, of British 1871. p. 119. Fishes,' vol. ii. 1836, pp. 417, 425, 3 See Mr. R. Warington's in- 436. Dr. Giinther informs me that terestmg articles in ' Annals and ths spines in H. clavata are peculiar Mag. of Nat. Hist.' Oct. 1852 and to the female. Kov. 1855. ^ ' The American Naturalist,' April 332 The Descent of Man. Pabf II, The males are said to be polygamists they are extraordinarily bold and pugnacious, whilst "the females are quite pacific." Their battles are at times desperate; "for these puny com- " batants fasten tight on each other for several seconds, tumbling " over and over again, until their strength appears completely " exhausted." With the rough-tailed stickleback (G. trachurus) the males whilst fighting swim round and round each other, biting and endeavouring to pierce each other with their raised lateral spines. The same writer adds,'* " the bite of these little " fui-ies is very severe. They also use their lateral spines with " such fatal effect, that I have seen one during a battle absolutely " rip his opponent quite open, so that he sank to the bottom and " died." When a fish is conquered, " his gallant bearing forsakes " him ; his gay colours fade away ; and he hides his disgrace "among his peaceable companions, but is for some time the " cnnstant object of his conqueror's persecution." The male salmon is as pugnacious as the little stickleback ; and so is the male trout, as I hear from Dr. Giinther. Mr. Shaw saw a violent contest between two male salmon which lasted the whole day ; and Mr. E. Buist, Superintendent of Fisheries, informs me that he has often watched from the bridge at Perth the males driving away theu- rivals, whilst the females were spa'miing. The males " are constantly fighting and tearing each " other on the spawning-beds, and many so injure each other as " to cause the death of numbers, many being seen swimming near " the banks of the river in a state of exhaustion, and apparently " in a dying state."^ Mr. Buist informs me, that in June 1868, the keeper of the Stormontfield breeding-ponds visited the northern Tyne and found about 300 dead salmon, all of which with one exception were males ; and he was convinced that they had lost their lives by fighting. The most curious point about the male salmon is that during the breeding-season, besides a slight change in colour, " the " lower jaw elongates, and a cartilaginous projection turns " upwards from the point, which, when the jaws are closed, " occupies a deep cavity between the intermaxillary bones of the -ipper jaw." ' (Figs. 27 and 28.) In oui' salmon this change of structure lasts only during the breeding-season: but in the * Noel Humphreys, ' River Gar- experienced observer (Scrope's ' Days dens,' 1857. of Salmon Fishing,' p. 60) remarks * Loudon's ' Mag. of Nat. History,' that like the stag, the m.ile would, vol. iii. 1830, p. 331. if he could, keep all other malei « 'Th» Field,' June 29th, 1867. away. For Mr. Shaw's statement, see ' Yarrell, 'History of British •Eilmburgh Revipw,' 1843. Another Fishes,' vol. ii. 1836, p. 10. Chap. XH. Fishes. 333 BaXmo lycaodon of jST.-W. America the change, as Mr. J. K. Lord^ believes, is permanent, and best marked in the older males which have previously ascended the rivers. In these old males the jaw becomes developed into an immense hook-like projection, and Fig. 27. Head of male common salmon {Salmo solar) during the breediiiE;-seasoii, lh';kindfie?SS^nfeo'?Dr''ba^^^^^^^^^^ 'P^^^'"^"^ Museum, under the teeth grow into regular fangs, often more than half an inch m length. With the European salmon, according to Mr. Lloyd," the temporary hook-like structure serves to strengthen and llll^^ f '"^"/oll;'* Vancouver's » < Scandinavian Adventures,' voL Island, vol. 1866, p 1,4. i. 18.H, pp. 100, 104. 334 The Descent of Man. Part IL protect the jaws, wlien one male charges another -with -wonderful violence ; but the greatly developed teeth of the male American salmon may be compared with the tusks of many male mammals, and they indicate an offensive rather than a protective purpose. Fig 28. Head of female Balmon. The salmon is not the only fish in which the teeth differ in the two sexes ; as this is the case with many rays. In the thomback {Raia clavata) the adult male has sharp, pointed teeth, directed backwards, whilst those of the female are broad and flat, and form a pavement ; so that these teeth differ in the two sexes of the same species more than is usual m distmct genera of the same family. The teeth of the male become sharp only when he is adult: whilst young they are broad and flat Chap. XIT. Fishes. 335 like those of the female. As so frequently occurs with secondary sexual characters, both sexes of some species of rays (for instance R. latis), when adult, possess sharp pointed teeth ; and here a character, proper to and primarily gained by the male, appears to have been transmitted to the offspring of both sexes. The teeth are likewise pointed in both sexes of R. maadatu, but only when quite adult ; the males acquiring them at an earlier age than the females. We shall hereafter meet with analogous cases in certain birds, in which the male acquires the plumage common to both sexes when adult, at a somewhat earlier age than does the female. With other species of rays the males even when old never possess sharp teeth, and consequently the adults of both sexes are provided with broad, flat teeth hke those of the young, and like those of the mature females of the above-mentioned species.'" As the rays are bold, strong and voracious fish, we may suspect that the males require their sharp teeth for fighting with their rivals ; but as they possess many parts modified and adapted for the prehension of the female, it is possible that their teeth may be used for this purpose. In regard to size, M. Carbonnier " maintains that the female of almost all fishes is larger than the male ; and Dr. Gunther does not know of a single instance in which the male is actually larger than the female. With some Cyprinodonts the male is not even half as large. As in many kinds of fishes the males habitually fight together, it is surprising that they have not generally become larger and stronger than the females through the effects of sexual selection. The males suffer from their smaU size, for according to M. Carbonnier, they are liable to be devoured by the females of their own species when carnivorous, and no doubt by other species. Increased size must be in some manner of more importance to the females, than strength and size are to the males for fighting with other males; and this perhaps is to allow of the production of a vast number of ova. In many species the male alone is ornamented with bright colours; or these are much brighter in the male than the female. The male, also, is sometimes provided with appendages which appear to be of no more use to him for the ordinary purposes of life, than are the tail feathers to the peacock. I am indebted for most of the following facts to the kindness of Di Giinther. There is reason to suspect that many tropical fishes differ sexually in colour and structure; and there are some striking cases with our British fishes. The male Qallionymus hjra See Yarrell's account of the cellent figure, and p. 422, 432. rays in his ' Hist, of British Fishes,' n As quoted in 'The Fanner, vol. ii. 1836, p. 416, with an ei- 1868, p. 369. 336 The Descent of Man. Pabt 1L has been called the (jemmeoua dragonet " from its brilliant gem- " like colours." When fresh caught from the sea the body is yellow of various shades, striped and spotted with vivid blue on the head ; the dorsal fins arc pale brown with dark longitudinal < bands; the ventral, caudal, and anal fins being bluish-black. . The female, or sordid dragonet, was considered by Linnajus. and j by many subsequent naturalists, as a distinct species ; it is of a ; dingy reddish-brown, with the dorsal fin. brown and the other i Fig. 29. Callionyimis lyra. Upper figure, male ; lower figure, female. N.B. The lower figure is more reduced than the upper. •fins white. The sexes difier also in the proportional size of the head and mouth, and in the position of the eyes f but the most striking difference is the extraordinary elongation in the male (fig. 29) of the dorsal fin. Mr. W. Saville Kent remarks that this " singular appendage appears from my observations of the species in confinement, to be subservient to the same end as the wattles, crests, and other abnormal adjuncts ot " the male in gallinaceous birds, for the purpose of fascmatmg « I have drawn np this description from Yarrell's ' British Fishes.'vol. i. 1836, pp. 261 and 266. I, Chap. XII. Fishes. 337 their mates."" The young males resemble the adult females in sti-ucture and colour. Throughout the genus Callionymus/- the male is generally much more brightly spotted than the female, and in several species, not only the dorsal, but the anal fin is much elongated in the males. The male of the Cottus scorpius, or sea-scorpion, is slenderer and smaller than the female. There is also a great difference in coloui" between them. It is difficult, as Mr. Lloyd remarks, " for any one, who has not seen this fish during the spawning- " season, when its hues are brightest, to conceive the admixture " of brilliant colours with which it, in other respects so ill- " favoured, is at that time adorned." Both sexes of the Ldbrus mixtus, although very different in colour, are beautiful; the male being orange with bright blue stripes, and the female bright red with some black spots on the back. Fig. 30. Xiphophorus Hellerii. Upper figure, male ; lower figure, female. In the very distinct family of the Cyprinodontid£e— inhabitants of the fresh waters of foreign lands— the sexes sometimes differ much in various characters. In the male of the MoUievesia ^etenensis,^^ the dorsal fin is greatly developed and is marked '3 'Nature,' July 1873, p. 264. With respect to this and the ' Catalogue of Acanth. Fishes following species I am indebted to in the British Museum,' by Dr. Dr. Giinther for information: see Oiinther, 1861, pp. 138-151. also his paper on the 'Fishes of ^ ' Game Birds of Sweden,' &c.. Central America,' in 'Transact. 1867, p. 466. Zoolog. Soc' vol. vi 1868, p. 485. Z 33S Tlie Descent of Matt. PAHTa with a row of large, round, ocellated, bright-coloured spots; whilst the same fin in the female is smaller, of a diflerent shape, and marked only with irregularly curved brown spots. In the male the basal margin of the anal fin is also a little produced and dark coloured. In the male of an allied form, the Xijiho- pJiorus Hellerii (fig. 30), the inferior margin of the caudal fin is developed into a long filament, which, as I hear from Dr. Giinther, is striped with bright colours. This filament does not contain any muscles, and apparently cannot be of any direct use to the fish. As in the case of the Callionymus, the males whilst young resemble the adult females in colour and structure. Sexual differences such as these may be strictly compared with those which are so frequent with gallinaceous birds." In a siluroid fish, inhabiting the fresh waters of South America, the Plecostomus barbatus (fig. 31), the male has its mouth and inter-operculum fringed with a beard of stiff hairs, of which the female shows hardly a trace. These hairs are of the nature of scales. In another species of the same genus, soft flexible ten- tacles project froru the front part of the head of the male, which are absent in the female. These tentacles are prolongations of the true skin, and therefore are not homologous with the stiff hairs of the former species ; but it can hardly be doubted that both serve the same purpose. What this purpose may be, it is difficult to conjecture^, ornament does not here seem probable, but we can hardly suppose that stiff hairs and flexible filaments can be useful in any ordinary way to the males alone. In that strange monster, the Chimcera monstrosa, the male has a hook- shaped bone on the top of the head, directed forwards, with its end rounded and covered with sharp spines ; in the female " this " crown is altogether absent," but what its use may be to the male is utterly imknown.^^ The structures as yet referred to are permanent in the male after he has arrived at maturity ; but with some Blennies, and in another allied genus,^" a crest is developed on the head of the male only during the breeding-season, and the body at the same time becomes more brightly-coloured. There can be little doubt that this crest serves as a temporary sexual ornament, for the female does not exhibit a trace of it. In other species of the same genus both sexes possess a crest, and in at least one species " Dr. Giinther makes this re- Water,' July 1868, p. 377, with a mark; 'Catalogue of Fishjs in the figure. Many other cases could be British Museum,' vol. iii. 1861, p. added of structures peculiar to the 141. male, of which the uses are not '* See Dr. Giinther on this genus, known, in 'Proc. Zoolog. Soc' 1868, p. 232. =» Dr. Giinther, ' Catalogue ot F. Buckland, in ' Land and Fishes,' vol. iii. pp. 221 and 240. Chap. XII. Fishes. 339 fig. 31. Plccostomus barbatus. Upper figure, head of male ; lower figure, female Z 2 340 The Descent of Man. ?\et U. neither sex is thus provided. In many of the Chromidse, for instance in Geophagus and especially in Cichla, the males, as 1 hear from Professor Agassiz,'"'' have a conspicuous protuberance on the forehead, which is wholly wanting in the females and in the young males. Professor Agassiz adds, " I have often " observed these fishes at the time of spawning when the pro- " tuberance is largest, and at other seasons when it is totally " wanting, and the two sexes shew no difference whatever in the " outline of the profile of the head. I never could ascertain that " it subserves any special function, and the Indians on the " Amazon know nothing about its use." These protuberances resemble, in their periodical appearance, the fleshy caruncles on the heads of certain birds ; but whether they serve as ornaments must remain at present doubtful. I hear from Professor Agassiz and Dr. Giinther, that the males of those fishes, which differ permanently in colour from the females, often become more brilliant during the breeding-season. This is likewise the case with a multitude of fishes, the sexes of which are identical in colour at all other seasons of the year. The tench, roach, and perch may be given as instances. The male salmon at this season is "marked on the cheeks with " orange-coloured stripes, which give it the appearance of a " Labrus, and the body partakes of a golden orange tinge. The " females are dark in colour, and are commonly called black- "fish."*^ An analogous and even greater change takes place with the Salmo eriox or bull trout; the males of the char (S. umUa) are likewise at this season rather brighter in colour than the females.^^ The colours of the pike {Esox reticulatus) of the United States, especially of the male, become, during the breeding-season, exceedingly intense, brilliant, and mdescent."^ Another striking instance out of many is afforded by the male stickleback (Gasterosteus leiurus), which is described by Mr. Warington,^^ as being then "beautiful beyond description." The back and eyes of the female are simply brown, and the belly white. The eyes of the male, on the other hand, are " of the " most splendid green, having a metallic lustre hke the green " feathers of some humming-birds. The throat and belly are " of a bright crimson, the back of an ashy-green, and the whole " fish appears as though it were somewhat translucent and =' See also ' A Journey in Brazil,' llag. of Nat. Hittory,' vol. vi. 1841, by Prof, and Mrs. Agassiz, 1868, p. p. 440. 220. ' The American Agriculturist, •■arrell, ' British Fishes,' vol. 1868, p. 100. ii. 1836, pp. 10, 12, 35. " 'Annals and Mag. cf Nat. Hist. " W. ThoHipson, in ' Annals and Oct. 1852. CHAr. XII. Fishes. 341 " glowed with an internal incandescence." After the breeding- season these colours all change, the throat and belly become of a paler red, the back more green, and the glowing tints subside. "With respect to the coui-tship of fishes, other cases have been observed since the first edition of this book appeared, besides that aheady given of the stickleback. Mr. W. S. Kent says that the male of the Lahrus mixtus, which, as we have seen, differs in colour from the female, makes " a deep hollow in the sand of the " tank, and then endeavours in the most persuasive manner to in- " duce a female of the same species to share it with him, swim- " ming backwards and forwards between her and the completed " nest, and plainly exhibiting the greatest anxiety for her to follow." The males of Cantharus lineatus become, during the breeding- season, of deep leaden-black ; they then retire from the shoal, and ■excavate a hollow as a nest. " Each male now mounts vigilant " guard over his respective hollow, and vigorously attacks and drives away any other fish of the same sex. Towards his com- " panions of the opposite sex his conduct is far different; many of " the latter are now distended with spawn, and these he endeavours " by all the means in his power to lure singly to his prepared " hollow, and there to deposit the myriad ova with which they are " laden, which he then protects and guards with the greatest care.^" A more striking case of courtship, as well as of dispky, by the males of a Chinese Macropus has been given by M. Carbonnier, who carefully observed these fishes under confinement.^'' The males are most beautifully coloured, more so than the females. During the breeding-season they contend for the possession of the females ; and, in the act of coui-tship, expand their fins, which are spotted and ornamented with brightly coloured rays, in the same manner, according to M. Carbonuier, as the peacock! They then also bound about the females with much vivacity, and appear by " I'etalage de leui's vives couleurs chercher a attirer '•^ I'attention des femelles, lesquelles ne paraissaient indifferentes " a ce manage, elles nageaient avec une molle lenteur vers les " males et semblaient se complaire dans leur voisinage." After the male has won his bride, he makes a little disc of froth by blowmg air and mucus out of his mouth. He then collects the fertilised ova, dropped by the female, in his mouth ; and this caused M Carbonnier much alarm, as he thought that they were going to be devoured. But the male soon deposits them in the disc of froth, afterwards guarding them, repairing the froth, and taking care of the young when hatched. I mention these par- ticulars because, as we shall presently sot, there are fishes, the « ' Nature,' May, 187.3, p. 25. " . Bull, de la Soc. d'Acclimat.' Paris, July 1869, and J.aa. 1870. 342 The Descent of Man. Pabt II, males of which hatch their eggs in their mouths ; and those who do not believe in the principle of gradual evolution might ask how could such a habit have originated; but the difficulty is mucli iliminishcd when we know that there are fishes which thus collect and carry the eggs; for if delayed by any cause in depositing them, the habit of hatching them in their moutlis might have been acquired. To return to our more hnmediatc subject. The case stands thus : female fishes, as far as I can learn, never willingly spawn except in the presence of the males ; and the males never fertilise the ova except in the presence of the females. The males fight for the possession of the females. In many species, the males whilst young resemble the females in colour ; but when adult become much more brUhant, and retain their colours throughout life. In other species the males become brighter than the females and otherwise more highly ornamented, only during the season of love. The males sedulously court the females, and in one case, as we have seen, take pains in displaying their beauty before them. Can it be believed that they would thus act to no purpose during their courtship ? And this would be the case, unless the females exert some choice and select those males which please or excite them most. If the female exerts such choice, all the above facts on the ornamentation of the males become at once intelligible by the aid of sexual selection. We have next to enquire whether this view of the bright colours of certain male fishes having been acquired through sexual selection can, through the law of the equal transmission of characters to both sexes, be extended to those groups in which the males and females are brilhant in the same, or nearly the same degree and manner. In such a genus as Labrus, which includes some of the most splendid fishes in the world — for instance, the Peacock Labrus {L. pavo), described,^* with pardonable exaggera- tion, as formed of polished scales of gold, encrusting lapis-lazuli, rubies, sapphires, emeralds, and amethysts — we may, with much probability, accept this belief; for we have seen that the sexes in at least one species of the genus differ greatly in colour. With some fishes, as with many of the lowest animals, splendid colours may be the direct result of the nature of their tissues and of the .surrounding conditions, without the aid of selection of any kind. The gold-fish {Cyprinus auratus), judging from the analogy of the golden variety of the common carp, is perhaps a case in point, as it may owe its splendid colours to a single abrupt variation, due to the conditions to which this fish has been subjected under IJory de Saint Vincent, in 'Diet. Class. d'Hist. Nat.' torn. ii. 1826 p. 151. Chap. XII. 343 confinement. It is, however, more probable that these coloiu's have been intensified through artificial selection, as this species has been carefully bred, in China from a remote period.^* Under natural conditions it does not seem probable that beings so highly organised as fishes, and which Live under such complex relations, should become brilliantly coloured without suffering iBome evil or receiving some benefit from so great a change, and consequently without the intervention of natural selection. What, then, are we to conclude in regard to the many fishes, both sexes of which are splendidly coloured? Mr. Wallace** believes that the species which frequent reefs, where corals and other brightly-colom'cd organisms abound, are brightly coloured in order to escape detection by their enemies ; but according to my recollection they were thus rendered highly conspicuous. In the fresh-waters of the tropics there are no brilhantly- coloured corals or other organisms for the fishes to resemble; yet many species in the Amazons are beautifully coloured, and many of the carnivorous Cyprinidse in India are ornamented with "bright longitudinal Hnes of various tints." Mr. M'Clel- land, in describing these fishes, goes so far as to suppose that " the peculiar brilliancy of their colours " serves as " a better " mark for king-fishers, terns, and other birds which are " destined to keep the number of these fishes in check;" but at the present day few naturalists will admit that any animal has been made conspicuous as an aid to its own destruction. It is possible that certain fishes may have been rendered conspicuous in order to warn birds and beasts of prey that they were unpalatable, as explained when treating of caterpillars; but it is not, I believe, known that any fish, at least any fresh-water fish, is rejected from being distasteful to fish-devouring animals, On the whole, the most probable view in regard to the fishes, of which both sexes are brilhantly coloured, is that their colours were acquired by the males as a sexual ornament, and were transferred equally, or nearly so, to the other sex. Owing to some reraark.s on this has been " produced at Hangchow a subject, made in my work ' On the " variety called the fire-fish, from its Variation of Animals under Domesti- "intensely red colour. It is uni- cation,' Mr. W. F. Mayers (' Chinese " versally admired, and there is not Notes and Queries,' Aug. 1868, p. " a household where it is not cul- 123) has searched the ancient " tivated, in rivalry as to its colour, Chinese encyclopedias. He finds " and as a source of profit." that gold-fish were first reared in 'Westminster Review,' July confinement during the Sung Dy- 1867, p. 7. nasty, which commenced a.d. 960. 3i ' Indian Cyjuinida;,' by Mr. In the year 1129 these fishes M'Clelland, 'Asiatic Researches, abonnded. In another place it is vol. part Ij. 1839, p. 230. said that since the vear 1548 there 344 We liavo now to consider whether, when the ma!(! differs in a marked manner from the female in colour or in other orna- ments, he alone has been modified, the variations being inherited by his male olfspring alone; or whether the female has been specially modified and rendered inconspicuous for the sake of protection, such modifications being inherited only by the females. It is impossible to doubt that colour has been gained by many fishes as a protection : no one can examine the speckled upper surface of a flounder, and overlook its resemblance to the sandy bed of the sea on which it lives. Certain fishes, moreover, can through the action of the nervous system, change their colours in adaptation to surrounding objects, and that within a short time.'* One of the most striking instances ever recorded of an animal being protected by its colour (as far as it can be judged of in preserved specimens), as well as by its form, is that given by Dr. Gunther^' of a pipe-fish, which, with its reddish streaming filaments, is hardly distinguishable from the sea-weed to which it clings with its prehensile tail. But the question now under consideration is whether the females alone have been modified for this object. We can see that one sex will not be modified through natural selection for the sake of protection more than the other, supposing both to vary, unless one sex is exposed for a longer period to danger, or has less power of escaping from such danger than the other; and it does not appear that with fishes the sexes differ in these respects. As far as there is any difference, the males, from being generally smaller and from wandering more about, are exposed to greater danger than the females; and yet, when the sexes differ, the males are almost always the more conspicuously coloured. The ova are fertilised immediately after being deposited ; and when this process lasts for several days, as in the case of the salmon,'* the female, during the whole time, is attended by the male. After the ova are fertilised they are, in most cases, left unprotected by both parents, so that the males and females, as far as oviposition is concerned; are equally exposed to danger, and both are equally important for the production of fertile ova ; consequently the more or less brightly-coloured individuals of either sex would bo equally liable to be destroyed or preserved, and both would have an equal influence on the colours of their offspring. Certain fishes, belonging to several families, make nests, and some of them take care of their young when hatched. Both »» G. Pouchet, L'Institut. Nov. 1, 327, pi. xiv. and xv. 1871, p. 134. " Yarroll, 'British Fishes,' vol. ■■»» '' Proc. Zoolog. Soc.' 1865, p. ii. p. ' I Chap. XII. Fishes. 345 sexes of the bright coloui-ed Crenilabrus massa and melons work together in building their nests with sea-weed, shells, &g.^^ Bat the n^ales of cei-tain fishes do all the work, and afterwards tdke exclusive charge of the young. This is the case with the duU- coloui-ed goliies,^'^ in which the sexes are not known to differ in colour, and likewise with the sticklebacks (Gasterosteus), in which the males become brilliantly coloured during the spawning season. The male of the smooth-tailed stickleback (G. leiurus) performs the duties of a nurse with exemplary care and vigilance during a long time, and is continually employed in gently leading back the young to the nest, when they stray too far. He courageously diives away all enemies, including the females of his own species. It would indeed be no small relief to the male, if the female, after depositing her eggs, were immediately devoured by some enemy, for he is forced incessantly to drive her from the nest." The males of certain other fishes inhabiting South America and Ceylon, belonging to two distinct Orders, have the extra- ordinary habit of hatching within their mouths or branchial cavities, the eggs laid by the females.^' I am informed by Professor Agassiz that the males of the Amazonian species which follow tliis habit, " not only are generally brighter than " the females, but the difference is greater at the spawning-season " than at any other time." The species of Geophagus act in the same manner; and in this genus, a conspicuous protuberance becomes developed on the forehead of the males during the breeding-season. With the various species of Ghromids, as Professor Agassiz Likewise informs me, sexual differences in colour may be observed, " whether they lay their eggs in the " water among aquatic plants, or deposit them in holes, leaving " them to come out without further care, or build shallow nests " in the river mud, over which they sit, as our Pomotis does. " It ought also to be observed that these sitters are among the " brightest species in their respective families ; for instance, " Hygrogonus is bright green, with large black ocelli, encircled " with the most brilliant red." Whether with all the species of Ghromids it is the male alone which sits on the eggs is not known. It is, however, manifest that the fact of the eggs being " According to the observations of M. Gerbc ; see Giinther's ' Reconl of Zoolog. Literature,' 1865, p 194-. " Cuvier, ' Rfegne Animal,' iroJ. j, 1829, p. 242. " See Mr. Waringtou's most interesting description of the habits of the Oasterosieus leiurus, in 'An- nals and Mag. of Nat. Hist.' Novem- ber 1855. " Prof. Wvman, in * Proc. Boston Soc. of Nat. 'Hist.' Sept. 15, 1857. Also Prof. Turner, in 'Journal of Anatomy and Phys.' Nov. 1, 1866, p. 78. Dr. Gilnther has lilcewise described other cases. 346 . The Descent of Man. p^bt u, protected or unprotected by the parents, has had little or no influence on the differences in colour between the sexes. It is further manifest, in all the cases in which the males take exclusive charge of the nests and young, that the destruction of the blighter-coloured males would be far more influential on the character of the race, than the destruction of the brighter- coloured females ; for the death of the male during the period of incubation or nursing would entail the death of the young, bo that they could not inherit his peculiarities; yet, in many of these very cases the males are more conspicuously coloured than the females. Inmost of the Lophobranchii (Pipe-fish, Hippocampi, &c.) the males have either marsupial sacks or hemispherical de- pressions on the abdomen, in which the ova laid by the female are hatched. The males also shew great attachment to their young.'* The sexes do not commonly differ much in colour; but Dr. Gunther believes that the male Hippocampi are rather brighter than the females. The genus Solenostoma, however, offers a curious exceptional case,*" for the female is much more vividly-coloured and spotted than the male, and she alone has a marsupial sack and hatches the eggs; so that the female of Solenostoma differs from all the other Lophobranchii in this latter respect, and from almost all other fishes, in being more brightly-coloured than the male. It is improbable that this remarkable double inversion of character in the female should be an accidental coincidence. As the males of several fishes, which take exclusive charge of the eggs and young, are more brightly coloured than the females, and as here the female Sole- nostoma takes the same charge and is brighter than the male, it might be argued that the conspicuous colours of that sex which is the more important of the two for the welfare of the offspring, must be in some manner protective. But from the large number of fishes, of which the males are either permanently or period- ically brighter than the females, but whose life is not at all more important for the welfare of the species than that of the female, this view can hardly be maintained. "When we treat of birds we shall meet with analogous cases, where there has been a complete inversion of the usual attributes of the two sexes, and we shall then give what appears to be the probable explanation, namely, that the males have selected the more attractive females, instead of the latter having selected, in » Yarrell, * Hist, of British Fishes of Zanzibar,' by Col. Playfair, Fishes,' vol. ii. 1836, pp. 329, 338. 1866, p. 137, has re-eiamined the ^' Dr. GUnther, since publishing specimens, and has given me the jn sccount of this spccias in ' The above information. Chap. XII. Fishes. 34; Rccordance with the usual rule thi'oughout the animal kingdom, the more attractive males. On the whole we may conclnde, that with most fishes, in which the sexes differ in colour or in other ornamental charac- terSj the males originally varied, with their variations trans- mitted to the same sex, and accumulated through sexual selection by attracting or exciting the females. In many cases, however, such characters have been transferred, either partially or completely, to the females. In other cases, again, both sexes have been coloured alike for the sake of protection; but in no instance does it appear that the female alone has had her colours or other characters specially modified for this latter purpose. The last point which need be noticed is that fishes are known to make various noises, some of which are described as being- musical. Dr. Dufosse, who has -especially attended to this subject, says that the sounds are voluntarily produced in several ways by different fishes : by the fi'iction of the pharyngeal bones — by the vibration of certain muscles attached to the swim- bladder, which serves as a resounding boai'd — and by the vibra- tion of the intrinsic muscles of the swim-bladder. By this latter means the Trigla produces pure and long-drawn sounds which range over nearly an octave. But the most interesting case for us is that of two species of Ophidium, in which the males alone are provided with a sound-producing apparatus, consisting of small movable bones, with proper muscles, in connection with the swim-bladder." The drumming of the Umbrinas in the European seas is said to be audible ftom a depth of twenty fathoms ; and the fishermen of Eochelle assert " that the males " alone make the noise during the spawning-time ; and that it " is possible by imitating it, to take them without bait."*^ From this statement, and more especially from the case of Ophidium, it is almost certain that in this, the lowest class of the Verte- brata, as with so many insects and spiders, sound-producing instruments have, at least in some cases, been developed through sexual selection, as a means for bringing the sexes together. " ' Comptes Rendus.' Tom. xlvi. the Dutch translation of this work 1858, p. 353. Tom. ilvii. 1858, p. (vol. ii., p. 36), gives some further 916. Tom. hv. 1862, p. 393. The particulars on the sounds made by noist made by the Umbrinas {Scxaina fishes. (viuila), is said by some authors to « The Rev. C. Kingsley, in be more like that of a flute or organ, ' Nature,' May 1870, p. 40. than drummintf: Dr. JCouteveen, in 348 The Descent of Man. Paet IL Amphibians. TJrodela.—l will begin with the tailed amphibians. The sexes? of salamanders or newts often diflfcr much both in colour and structure. In some species prehensile claws are developed on the fore-legs of the males during the breeding-season : and at this season in the male Triton palmipes the hind-feet are pro- vided with a swimming-web, which is almost completely absorbed during the winter; so that their feet then resemble Fig, 32. Triton cristalus (half nntiirul size, from B.'U's ' British Reptiles ')• Upper ligure, male during the breeding-season ; lower figure, female. those of the female.''^ This structure no doubt aids the male in his eager search and pursuit of the female. Whilst courting her he rapidly vibrates the end of his tail. With our common newts {Triton punctatus and cristatus) a deep, much indented crest is developed along the back and tail of the male during the breeding-season, which disappears during the winter. Mr. St. George Mivart informs me that it is not furnished with muscles, and therefore cannot be used for locomotion. As during the season of courtship it becomes edged with bright colours, there can hardly be a doubt that it is a masculine ornament. In many species the body presents strongly contrasted, though lurid tints, and these become more vivid during the breeding- season. The male, for instance, of our common little newt (Triton punctatus) is "brownish-grey above, passing into yellow " Bell, 'History of Bi-itish Reptiles,' 2nd edit. 1849, pp. 156-159. OuAP. XII A inp}ubia7is. 349 " beneatli, -whicli in tho spring becomes a rich bright orange, " marB.ed everywhere with round dark spots." The edge of the crest also is then tipped with bright red or violet. The female is usually of a yellowish-brown colour with scattered brown dots, and the lower surface is often quite plain.''* The young are obscurely tinted. The ova are fertilised during the act of deposition, and are not subsequently tended by either parent. We may therefore conclude that the males have acquired their strongly-marked coloui'S and ornamental appendages through sexual selection ; these being transmitted either to the male offepring alone, or to both sexes. Anura or Batracliia. — With many fi'ogs and toads the colours evidently serve as a protection, such as the bright green tints of tree-frogs and the obscure mottled shades of many terrestrial species. The most conspicuously-coloured toad which I ever saw, the Phrynisaus n iyricans,*^ had the whole upper sui'face of the body as black as ink, with the soles of the feet and parts of the abdomen spotted with the brightest vermilion. It crawled about the bare sandy or open gi'assy plains of La Plata under a scorching sun, and could not fail to catch the eye of every pass- ing creature. These colours are probably beneficial by making this animal known to all birds of prey as a nauseous mouthful. In Nicaragua there is a little frog " dressed in a bright livery " of red and blue " which does not conceal itself like most other species, but hops about during the daytime, and Mr, Belt says" that as soon as he saw its happy sense of security, he felt sure that it was uneatable. After several trials he succeeded ia tempting a young duck to snatch up a young one, but it was- instantly rejected ; and the duck " went about jerking its head, " as if trymg to throw off some unpleasant taste." With respect to sexual differences of colour. Dr. Giinther does not know of any striking instance either with frogs or toads ; yet he can often distinguish the male from the female, by the tints of the former being a little more intense. Nor does he know of any striking difference in external structure between the sexes, excepting the prominences which become developed durmg the breedmg-season on the front-legs of tho male, by which he is enabled to hold the female." It is surprising that .•i".^o"j 'Hiftory of British Rep- sikimmensis (Dr. Anderson, ' Proe, tiles, 2nd edn. 1849, pp. 146, 151. Zoolog. Soc.,' 1871, p. 204) has two .< u f"" ?%.°o ^'^I^Ti^y-t?? °^ '^"^ plate-like callosities on the tbora. «^^T1: V 1 • xv"^- ^"-i rugosities on the fangers, 18^4 ^ '° Nicaragua,' which perhaps subserve the samlo»-' L ' »? , , , , „ as the above-meiit'oned prominences, *' The male alone . of the Bufo 350 The Descent of Man. PabtII, these animals have not acquired more strongly-marked sexual characters; for though cold-blooded their passions are strong. Dr. Giinther intorms me that he has several times found aii unfortunate female toad dead and smothered from having been so closely embraced by three or four males. Frogs have been observed by Professor Hoffman in Giessen fighting all day long during the breeding-season, and with so much violence^, that one had its body ripped open. Frogs and toads offer one interesting sexual difference, namely, in the musical powers possessed by the males; but to speak of music, when applied to the discordant and overwhelming; sounds emitted by male bull-frogs and some other species, seems, according to our taste, a singularly inappropriate expression. Nevertheless, certain frogs sing in a decidedly pleasing manner Near Eio Janeiro I used often to sit in the evening to listen to a number of little Hylse, perched on blades of grass close to tho water, which sent forth sweet chirping notes in harmony. Tho various sounds are emitted chiefly by the males during tho breeding-season, as in the case of the croaking of our common frog.*' In accordance with this fact the vocal organs of the males are more highly-developed than those of the females. In some genera the males alone are provided with sacs which open into the larynx." For instance, in the edible frog (liana esculenta) " the sacs are peculiar to the males, and become, when fiUed " with air in the act of croaking, large globular bladdeis, stand- " ing out one on each side of the head, near the corners of the mouth." The croak of the male is thus rendered exceedingly powerful ; whilst that of the female is only a slight groaning noise."" In the several genera of the family the vocal organs differ considerably m structure, and their development in all cases may be attributed to sexual selection. C%eZonta.— Tortoises and turtles do not offer well-marked sexual differences. In some species, tho tail of the male is longer than that of the female. In some, the plastron or lower surface of the shell of the male is slightly concave in relation to the back of the female. The male of the mud-turtle of tho United States (Chrysemys picta) has claws on its front-fect twice as long as those of the female ; and these are used whcu KffiPTILES. <• Bell, 'History of British Heptiles,* 1849, p. 93. " J. Bishop, in 'Todd's Cyclop, cf Anat. and Phvs.' vol. iv. p. 1.^03 « Bell, ibid. p. 112-114. Chap. XJ 1. Reptiles. 351 the sexes miiio.** With the huge tortoise of the Galapagoa Islands (Testudo nigra) the males are said to grow to a larger size than the females: dming the pairing-season, and at no other time, the male utters a hoarse bellowing noise, which can be heard at the distance of more than a hundred yards ; the female, on the other hand, never uses her voice.'^^ "With the Testudo elegans of India, it is said " that tho combats " of the males may be heard at some distance, from the noise " they produce in butting against each other." ^ Crocodilia. — The sexes apparently do not differ in colour ; nor do I know that the males fight together, though this is pro- bable, for some kinds make a prodigious display before the females. Bartram*^ describes the male alligator as striving to win the female by splashing and roaring in the midst of a lagoon, " swollen to an extent ready to burst, with its " head and tail lifted up, he spins or twii-ls round on the " surface of the water, like an Indian chief rehearsing his feats of war." During the season of love, a musky odour is emitted by the submaxillary glands of the crocodile, and pervades their haunts.''* Ophidia.—'Dx. Giinther informs me that the males are always smaller than the females, and generally have longer and slenderer tails ; but he knows of no other difference in external structure. In regard to colour, he can almost always distinguish the male from the female by his more strongly-pronounced tints ; thus the black zigzag band on the back of the male English viper is more distinctly defined than in the female. The difference is much plainer in the rattle-snakes of N. America, the male of which, as the keeper in the Zoological Gardens shewed me, can at once be distinguished from the female by having more lurid yeUow about its whole body. In S. Africa the Bucephalus capensis presents an analogous difference, for the female "is " never so fuUy variegated with yellow on the sides as the " male."^^ The male of the Indian Dipsas cynodon, on the other hand, is blackish-brown, with the belly partly black, whilst the female is reddish or yeUowish-olive, with the belly either uniform yellowish or marbled with black. In the Tragops dispar of the same country, the male is bright green, and the " Mr. C. J. Maynard, ' The British India,' 1864, p. 7. American Naturahst,' Dec. 1869, p. " < Travels through Carolina, 555. &c., 1791, p. 128. " See niy ' Journal of Researches " Owen, 'Anatomy of Verte- during the Voyage of the " Beagle," ' brates,' vol. i.' 1866, p. 615. 1845, p. 384. Sir Andrew Smithi, ' Zoolog. cf " Dr GUnther, 'Reptiles of S.Africa: Repdlia,' 1849, pi. x. 352 Pabt 11, fomalo bronze-coloured." No doubt the colours ol some snakes are protective, as shewn by the green tints of tree-snakes, and the various mottled shades of the species which livo in sandy places ; but it is doubtful whether the colours of many kinds, for instance of the common English snake and viper, serve to conceal them; and this is still more doubtful witli the many foreign species which are coloured with extreme elegance. The colours of certain species are very different in the adult and young states.^* Dui'ing the breeding-season the anal scent-glands of snakes are in active function and so it is with the same glands in Uzards, and as we have seen with the submaxillary glands of crocodiles. As the males of most animals search for the females, these odoriferous glands probably serve to excite oi- charm the fear ale, rather than to giiide her to the spot where the male may be foimd. Male snakes, though appearing so sluggish, are amorous ; for many have been observed crowding round the same female, and even round her dead body. They are not known to fight together from rivalry. Their intellectual powers are higher than might have been anticipated. In the Zoological Gardens they soon learn not to strike at the iron bar with which their cages are cleaned ; and Dr. Keen of Philadelphia informs me that some snakes which he kept, learned after four or five times to avoid a noose, with which they were at first easily caught. An excellent observer in Ceylon, Mr. E. Layard, saw a cobra thrust its head through a narrow hole and swallow a toad. " With this encumbrance he could not withdraw him- " self; finding this, he reluctantly disgorged the precious mor- " sel, which began to move off; this was too much for snake " philosophy to bear, and the toad was agaia seized, and again " was the snake, after violent efforts to escape, compelled to part " with its prey. This time, however, a lesson had been learnt, " and the toad was seized by one leg, withdrawn, and then " swallowed in triumph." The keeper in the Zoological Gardens is positive that certain snakes, for instance Crotalus and Python, distinguish liim from all other persons. Cobras kept together in the same cage apparently feel some attachment towards each other."' " Dr. A. Gilnther, 'Reptiles of bi-ates,' vol. i. 1866. p. 615. British India,' Ray Soc. 1864, pp. '» 'Rambles in Ceylon,' in 'Atnals 304, 308. and Mag. of Nat. Hist.' 2nd senes, »• Dr. Stoliczka, ' Journal of vol. is. 1852, p. 3^.i. Asiatic Soc. of Bengal,' vol. xxsii. »' Dr. GUntner, Kepfiles ol 1870, pp. 205, 211. British India,' 1864, p 340. Owen, 'Anatomy of Veite- ohap. xn. Reptiles. 353 It does not, however, follow because snakes have some reasoning power, strong passions and mutual aifection, that they should likewise be endowed with sufficient taste to admire brilliant colours in their partners, so as to lead to the adorn- ment of the species through sexual selection. Nevertheless, it is difficult to account in any other manner for the extreme beauty of certain species ; for instance, of the coral-snakes of S. America, which are of a rich red with black and yellow transverse bands. I well remember how much surprise I felt at the beauty of the first coral-snake which I saw gliding across a path in Brazil. Snakes coloured in this peculiar manner, as Mr. Wallace states on the autnority of Dr. Giinther,*^ are found nowhere elser in the world except in S. America, and here no less than four genera occur. One of these, Elaps, is venomous ; a second and widely-distinct genus is doubtfully venomous, and the two others are quite harmless. The species belonging to these distinct genera inhabit the same districts, and are so like each other, that no one "biit a naturalist would distinguish the " harmless from the poisonous kinds." Hence, as Mr. Wallace beheves, the innocuous kinds have probably acquired their colours as a protection, on the principle of imitation ; for they would naturally be thought dangerous by their enemies. The cause, however, of the bright colours of the venomous Elaps remains to bo explained, and this may perhaps be sexual selection. Snakes produce other sounds besides hissing. The deadly Ediis carinata has on its sides some oblique rows of scales of a peculiar structure with serrated edges ; and when this snake is excited, these scales are rubbed against each other, which pro- duces " a curious prolonged, almost hissing sound." Wath respect to the rattling of the rattle-snake, we have at last some definite information : for Professor Aughey states,'* that on twc occasions, being himself unseen, he watched from a little distance, a rattle-snake coiled up with head erect, which continued to rattle at short intervals for half an hour : and at last he saw another snake approach, and when they mot they paired. Hence he is satisfied that one of the uses of the rattle is to bring the sexes together. Unfortunately he did not ascertain whether it was the male or the female which remained stationary and called for the other. But it by no means follows from the above fact that the rattle may not be of use to these snakes in other ways, as a warning to animals which would otherwise " ' Westminster Review,'July 1st, Soc' 1871, p. 196. 1867, p. 32. «* . The Amei-ican Naturalist,' "Dr. Anderson, ' Proc. Zoolog. 1873, p. 85. 2 A 354 Tfie Descent of Man. Pabt n, attack them. Nor can I quite disbelieve tlie several accounts which have appeared of their thus paralysing their prey with fear. Some other snakes also make a distinct noise by rapidly vibrating their tails against the surrounding stalks of plants ; and I have my- self heard this in the case of a Trigonocephalus in S. America. Lacertilia. — The males of some, probably of many kinds of lizards fight together from rivalry. Thus the arboreal Anolis, cristatellus of S. America is extremely pugnacious : " During the " spring and early part of the summer, two adult males rarel; " meet without a contest. On fii-st seeing one another, they nod " their heads up and down three or four times, and at the same " time expanding the frill or pouch beneath the throat ; their " eyes gUsten with rage, and after waving their tails fi-om " side to side for a few seconds, as if to gather energy, they dart " at each other furiously, rolling over and over, and holding firmly with their teeth. The conflict generally ends in one of the combatants losing his tail, which is often devoured by the " victor." The male of this species is considerably larger than tiie female and this, as far as Dr. Gunther has been able to ascertain, is the general rule with lizards of all kinds. The males alone of the Cyrtodadylns rubidus of the Andaman Islands possesses pre-anal pores ; and these pores judging from analogy probably serve to emit an odour."^ The sexes often differ greatly in various external characters. The male of the above-mentioned Anolis is furnished with a crest which runs along the back and tail, and can be erected at pleasure ; but of this crest the female does not exhibit a trace. In the Indian Cophotis ceylanica, the female has a dorsal crest, though much less developed than in the male ; and so it is, as Dr. Giinther informs me, with the females of many Iguanas, Chameleons, and other lizards. In some species, however, the crest is equally developed in both sexes, as in the Iguana tubercu- lata. In the genus Sitana, the males alone are furnished with a large throat-pouch (fig. 33), which can be folded up like a fan, and is coloured blue, black, and red ; but these splendid colours are exhibited only dui-ing the pairing-season. The female does not possess even a rudiment of this appendage. In the Anolis cristatellus, according to Mr. Austen, the tlu'oat pouch, which is bright red marbled with yellow, is present in the female, though in a rudimental condition. Again, in certain other lizards, both sexes are equally well provided with throat pouches. Here we Mr. N. L. Austen kept these Stoliczka, 'Journal of Asiatic animals alive for a considerable Soc. of Bengal,' vol. ixxiv. 1870, p. time ; see ' Land and Water.' July 166. 1867, p. &. Chap. XH. Reptiles. 355 Fig. 33. Sitana minor. Male with the gular pouch expanded (from Giinther's ' Reptiles of India '). see with species belonging to the same group, as in so many previous cases, the same character either confined to the males, or more largely developed in them than in the females, or again equally developed in both sexes. The little lizards of the genus Draco, which ghde thi'ough the air on their rib- supported parachutes, and ■which in the beauty of their coloiu's baflfle description, are fiu-nished with skinny appen- dages to the throat " like the •wattles of gallinaceous birds." These become erected when the animal is excited. They occur in both sexes, but are best developed -when the male arrives at maturity, at which age the middle appendage is sometimes twice as long as the head. Most of the species like- ■wise have a low crest running along the neck ; and this is much more developed in the full-grown males, than in the females or young males." A Chinese species is said to live in pairs during the spring ; " and if one is caught, the other falls from " the tree to the ground, and allows " itself to be captured with imjDu- " nity,"— I presume from despair.^^ There are other and much more remarkable differences between the sexes of certain lizards. The male of Ceratophora aspera bears on the extremity of his snout an appendage half as long as the head. It is cylindrical, covered with scales, flexible, and apparently capable of erection : in the female it is quite rudimental. In a second species of the same genus a terminal scale • foi-ms a minute hom on the summit of the flexible appendage; " All the foregoing statements nificent work on the ' Reptiles of British India,' Ray Soc. 1864, pp. 122, 130, 135. «« Mr. Swinhoe, *Proc. Zoolog, See' 1870, p. 240. And quotations, in regard to Cophotis, Sitana and Draco, as well as the' following facts in regard to Cerato- phora and Cham.-cleon, are from Dr. GUnther himseli^ or from his mag- Fig. 34. Ceratophora Stoddartii Upper figure, male ; lower figure, female. 2 A 2 35^ T^Jis Descent of Man. Paet 11. and in a third species (C. Stoddartu, fig. 34) the whole appen- dage is converted into a horn, which is usually of a white- coloui", but assumes a purplish tint whea the animal is excited. In the adult male of this latter species the horn is half an inch in length, but it is of quite minute size in the female and in the young. These appendages, as Dr. GUnther lias remarked to me, may be compared with the combs of gallinaceous birds, and apparently serve as ornaments. Fig. 35. Chatnjeleon bifurcns. Upper figure, male ; lower figure, female. In the genus Chamseleon we come to the acme of difference : between the sexes. The upper part of the skull pf the male C.Mfurcus (fig. 35), an inhabitant of Madagascar is V^odu f di into' two great, solid, bony projections, covered with scales iiKC SeMt ?f the head; and of this wonderful i^odifica ion o^' Structure the female exhibits only a rudmient. Again, m Chap. XII. Reptiles. 357 Chamodeon Owenii (fig. 36), from the West Coast of Africa, the male beai-s on his snout and forehead thi-ee cui-ious horns, of Tvhich the female has not a trace. These homs consist of an excrescence of bone covered with a smooth sheath, forming part of the general integu- ments of the body, go that they are identical in struc- ture with those of a bull, goat, or other sheath -horned ru- minant. Although the three horns differ so much in appearance from the two great pro- longations of the skull in C. hif urcus, we can hardly doubt that they serve the same general pur- pose in the economy J,,.,, 33 ohan^a^leonOwenli. Upper iigure, male of these two am- lower figure, female. mals. The first con- jectm-e, which will occur to every one, is that they are used by the males for fighting together; and as these animals are very quarrelsome,^^ this is probably a correct view. Mr. T. "W. Wood also informs me that he once watched two individuals of C. fumilus, fighting violently on the branch of a tree ; they flung then' heads about and tried to bite each other ; they then rested for a time, and afterwards continued their battle. With many lizards, the sexes differ slightly in colour, the tints and stripes of the males being brighter and more distinctly defined, than in the females. This, for instance, is the case with the above Cophotis and with the Acanthodactylus capensis of S. Africa. In a Cordylus of the latter country, the male is either much redder or greener than the female. In the Indian dalotes nigrilabris there is a still greater difference ; the lips also of the male are black, whilst those of the female ai'e green. In our common little viviparous lizard (Zootocc vivipara) "the ^ under side of the body and base of the tail in the male aro bright orange, spotted with black ; in the female these parts "are pale-greyish-gTeen without spots." ^° We have seen that Dr. Bucholz, ' IVIonatsbovicht, Bell, ' History of British K. Prenss. Akad.' Jan. 1874, p. 78. Reptiles,' 2Dd edit. 1849, p. 40. 358 The Descent of Man. Past IL tho males alono of Sitana possess a throat-pouch ; and this is splendidly tinted with blue, black, and red. In the Prodolrdm tenuis of Chile the male alone is marked with spots of blue, green, and coppery-red.'^ In many cases the males retain the same colours throughout the year, but in others they become much brighter during tho breeding-season ; I may give as an additional instance the Calotes maria, which at this season has a bright red head, the rest of the body being green." Both sexes of many species are beautifully coloiu-ed exactly alike ; and there is no reason to suppose that such colours are protective. No doubt with the bright green kinds which live in the midst of vegetation, this colour serves to conceal them ; and in N. Patagonia I saw a lizard (Proctotretus multimaculatus) which, when frightened, flattened its body, closed its eyes, and then from its mottled tints was hardly distinguishable from the surrounding sand. But the bright colours with which so many lizards are ornamented, as well as their various curious appen- dages, were probably acquired by the males as an attraction, and then transmitted either to their male offspring alone, or to both sexes. Sexual selection, indeed, seems to have played almost as important a part with reptiles as with birds ; and the less conspicuous colours of the females in comparison with the males cannot bo accounted for, as Mr. Wallace believes to be the case with birds, by the greater exposure of the females to danger during incubation. CHAPTER Xm. Secondaet Sexual Chaeactehs of Birds. Sexual differences — Law of battle — Special weapons — Vocal organs — Instrumental music — Love-antics and dances — Decorations, permanent and seasonal — Double and single annual moults — Display of ornaments by the males. Secondary sexual characters are more diversified and con- spicuous in birds, though not perhaps entailing more important changes of structure, than in any other class of animals. I shall, therefore, treat the subject at considerable length. Male birds sometimes, though rarely, possess special weapons for fighting " For Proctotretus see ' Zoology the Indian Calotes, see ' Reptiles of of the Voyage of the "Beagle:" British India,' by Dr Giinther, c. r.eptiles,' by Mr. Bell, p. 8. For 143. tho Lizards of S. Africa, see ' Zoology " Giinther in ' Proc. Zcolog. Soc. of S. Africa: Reptiles,' by Sir 1870, p. 778, with a coloured Andrew Smith, pi. 25 and 39. For ligiire. Chai-. XIII. Birds. 359 with each other. They charm the female by vocal or instru- mental music of the most varied kinds. They are ornamented by all sorts of combs, wattles, protuberances, horns, air-distended sacks, top-knots, naked shafts, plumes and lengthened feathers gi-acefully springing from all parts of the body. The beak and naked skin about the head, and the feathers are often gorgeously coloured. The males sometimes pay their coui-t by dancing, or by fantastic antics performed either on the ground or in the air. In one instance, at least, the male emits a musky odour, which we may suppose serves to charm or excite the female ; for that excellent observer. Mi-. Eamsay,* says of the Australian musk- duck (Biziura lobuta) that "the smell which the male emits " during the summer months is confined to that sex, and in " some individuals is retained throughout the year ; I have " never, even in the breeding-season, shot a female which had " any smell of musk." So powerful is this odour during the paii-ing-season, that it can be detected long before the bird can be seen.2 On the whole, birds appear to be the most aesthetic of aU animals, excepting of course man, and they have nearly the same taste for the beautiful as we have. This is shewn by our enjoyment of the singing of bii-ds, and by our women, both cirilised and savage, decking their heads with borrowed plumes, and using gems which are hardly more brilliantly coloured than the naked skin and wattles of certain birds. In man, however, when cultivated, the sense of beauty is manifestly a far more complex feeling, and is associated with various intellectual ideas. Before treating of the sexual characters with which we are here more particularly concerned, I may just allude to certain differences between the sexes which apparently depend on differences in their habits of life; for such cases, though common in the lower, are rare in the higher classes. Two humming-birds belonging to the genus Eustephanus, which inhabit the island of Juan Fernandez, were long thought to be specifically distinct, but are now known, as Mr. Gould informs me, to be the male and female of the same species, and they differ slightly in the form of the beak. In another genus of humming-birds {Grypus), the beak of the male is serrated along the margin and hooked at the extremity, thus differing much from that of the female. In the Neomorpha of New Zealand, there is, as wo have seen, a still wider difference in the form of the beak in relation to the manner of feeding of the two sexes. Something of the same kind has been observed with the gold- ' 'Ibis,' vol. iivr (new scries) 1867, « Gould, ' Handbook to the Birds P- "^l"*- of Australia,' 1805, vol. ii. p. 383. 36o The Descent of Man. Part IL. finch (Carduelia elegans), for I am assured by Mr. J. Jenner Weir that the birdcatchers can distinguish the males by their slightly louger beaks. The flocks of males are often found feeding on the seeds of the teazle (Dipsacus), which they can reach with their elongated beaks, whilst the females more commonly feed on the seeds of the betony or Scrophularia. With a slight difference of this kind as a foundation, we can see how the beaks of the two sexes might be made to differ greatly through natural selection. In some of the above cases, however, it is possible that the beaks of the males may have been first modified in relation to then- contests with other males; and that this afterwards led to slightly changed habits of life. Law of Battle. — Almost all male birds are extremely pug- nacious, using their beaks, wings, and legs for fighting together. We see this every spring with our robins and sparrows. The smallest of all birds, namely the humming-bird, is one of the most quarrelsome. Mr. Gosse^ describes a battle in which a pair seized hold of each other's beaks, and whirled round and round, till they almost fell to the ground ; and M. Montes de Oca, in speaking of another genus of humming-bird, says that two males rai-ely meet without a fierce aerial encounter: when kept in cages " their fighting has mostly ended in the spUtting of " the tongue of one of the two, which then surely dies from " being unable to feed."* With Waders, the males of the common water-hen ( Qallinula cMoropus) " when pairing, fight " violently for the females : they stand nearly upright in the " water and strike with their feet." Two were seen to be thus engaged for half an hour, until one got hold of the head of the other, which would have been killed, had not the observer interfered ; the female all the time looking on as a quiet spec- tator.^ Mr. Blyth informs me that the males of an allied bird (Gallicrex cristatus) are a third larger than the females, and are so pugnacious during the breeding-season, that they are kept by the natives of Eastern Bengal for the sake of fighting. "Various other birds are kept in India for the same purpose, for instance, the bulbids {Fycnonotus hxinorrhous) which " fight with great " spirit." The polygamous ruff {Machetes pugnax, fig. 37) is notorious for his extreme pugnacity ; and in the spring, the males, which are considerably larger than the females, congregate day after ' Quoted by Mr. Gould, ' lutro- Ireland : Birds,' vol. ii. 1850, p. Auction to the Trochilida,' 1861, 327. p_ 29. ° Jerdon, ' Bii-ds of India,' 186S, ♦ Gould, ibid. p. 52. vol. ii. p. 96. » W. Thompson, 'Nat. Hist, of Chap. XIII. Lazv of Battle. 361 day at a particular spot, where the females propose to lay their eggs. The fowlers discoTer these spots by the turf being trampled somewhat bare. Here they fight very much like game- cocks, seizing each other with thoir beaks and striking with then- wings. The great ruff of feathers round the neck is then erected, and according to Col. Montagu " sweeps the ground as " a shield to defend the more tender parts ;" and this is the only 362 The Descent of Man. I'AUT IL iiiBtauco known to mo in the case of birds, of any structure serving as a shield. The ruff of feathers, however, from its varied and rich colours probably serves in chief part as an ornsi- ment. Like most pugnacious birds, they seem always ready to fight, and when closely confined often kill each other; but Montagu observed that their pugnacity becomes greater during the spring, when the long feathers on their necks are fully developed ; and at this period the least movement by any one bird provokes a general battled Of the pugnacity of web-footed birds, two instances will suffice : in Guiana " bloody fights occur " dui-ing the breeding-season between the males of the wild " musk-duck (Camna moschata); and where these fights have " occurred the river is covered for some distance with feathers."' Birds which seem ill-adapted for fighting engage in fierce con- flicts ; thus the stronger males of the pelican drive away the weaker ones, snapping with their huge beaks and giving heavy blows with their wings. Male snipe fight together, " tugging " and pushing each other with their bills in the most curious " manner imaginable." Some few birds arc believed never to fight ; this is the case, according to Audubon, with one of the woodpeckers of the United States (Picus auratus), although " the " hens are followed by even half a dozen of their gay suitors." " The males of many bii-ds are larger than the females, and this no doubt is the result of the advantage gained by the larger and stronger males over then- rivals during many generations. The difference in size between the two sexes is carried to an extreme point in several Austrahan species ; thus the male musk-duck (Biziura) and the male Oi7icloram2yhits cruralis (alhed to our pipits) are by measui'ement actually twice as large as then- respective females.'" With many other bii-ds the females are larger than the males ; and as formerly remarked, the explana- tion often given, namely, that the females have most of the work in feeding their young, will not suffice. In some few cases, as we shall hereafter see, the females apparently have acquired their greater size and strength for the sake of conquering other females and obtaining possession of the males. The males of many gallinaceous birds, especially of the poly- gamous kinds, are furnished with special weapons for fighting ■with theii- rivals, namely spurs, which can be used with fearful ' Macgillin-ay, * Hist. Bi-it. i. p. 191. For pelicans and snipes, Birds,' vol. iv. 1852, pp. 177-181. see vol. iii. pp. 138, 477. « Sir R. Schomburgk, in ' Journal "> Gould, ' Handbook of Buds of of R. Geosraph. See' vol. xiii. 1843, Australia,' vol. i. p. 395 ; vol. ii. p. p. 31. 383 * ' Ornithological Biography,' vol. Chap. XUI. Law of Battle. 3^3 effect. It has been recorded by a trustworthy writer " that in Derbyshii-e a kite struck at a game-hen accompanied by her chickenSj when the cock rushed to the rescue, and droTe his spur right thi-ough the eye and skull of the aggressor. The spur was with difficulty drawn from the skull, and as the kite though dead retained his grasp, the two birds were fii-mly locked together; but the cock when disentangled was very little injured. The invincible courage of the game-cock is notorious : a gentleman who long ago witnessed the brutal scene, told me that a bird had both its legs broken by some accident in the cockpit, and the owner laid a wager that if the legs could be spliced so that the bird could stand upright, he would continue fighting. This was effected on the spot, and the bird fought with undaunted courage until he received his death- stroke. In Ceylon a closely allied, wild species, the Oallm Stanleyi, is known to fight desperately "in defence of his " seraglio," so that one of the combatants is fi-equently found dead.^^ An Indian partridge ( Ortygornis gularis), the male of which is fturnished with strong and sharp spxu's, is so quarrel- some, " that the scars of former fights disfigure the breast of " ahnost eveiy bird you kill." " The males of almost all gallinaceous birds, even those which are not furnished with spurs, engage during the breeding-season in fierce conflicts. The Capercailzie and Black-cock (^Tetrao urogallus and T. tetrix), which are both polygamists, have regular appointed places, where during many weeks they congregate in numbers to fight together and to display their charms before the females. Dr. W. Kovalevsky informs me that in Eussia he has seen the snow all bloody on the arenas where the capercailzie have fought ; and the black-cocks " make the feathers fly in every " direction," when several " engage in a battle royal." The elder Brehm gives a curious account of the Balz, as the love- dances and love-songs of the Black-cock are called in Germany. The bird utters almost continuously the strangest noises : " he " holds his tail up and spreads it out like a fan, he lifts up his " head and neck with all the feathers erect, and stretches his " wings from the body. Then he takes a few jumps in different " directions, sometimes in a circle, and presses the under part of " his beak so hard against the ground that the chin feathers are " rubbed off. During these movements he beats his wings and " turns round and round. The more ardent he grows the moro " lively he becomes, until at last the bird appears like a frantio " Mr. Hewitt in the 'Poultw Nat. Hist.' vol. sir. 185-i, p. 63. Book by Tegetmeier,' 1866, p. 3 37. » Jerdon, 'Birds cf India,' rol. ■'• Layord, 'Anaals and Mag. of iii. p. 574. 364 The Descent of Man. Part IL " creature." At such times the black-cocks are so absorbed that thoy become almost blind and dea/, but less so than the caper- cailzie : hence bird after bird may be shot on the same spot, or even caught by the hand. After ])erforming these antics the males begin to fight : and the same black-cock, in order to prove his strength over several antagonists, will visit in the course of one morning several Balz-places, which remain the same diu'ing successive years." The peacock with his long train appears more like a dandy than a warrior, but he sometimes engages in fierce contests : the Eev. W. Darwin Fox informs me that at some little distance from Chester two peacocks became so excited whilst fighting, that they flew over the whole city, still engaged, until they alighted on the top of St. John's tower. The spur, in those gallinaceous birds which are thus provided, is generally single ; but Polyplectron (see fig. 51, p. 397) has two or more on each leg ; and one of the Blood-pheasants (Ithughiis cruentus) has been seen with five spui's. The spurs are generally confined to the male, being represented by mere knobs or rudi- ments in the female ; but the females of the Java peacock (Pavo muticus) and, as I am informed by Mr. Blyth, of the small fii-e- backed pheasant (Euplocamus erythropthalmus) possess spurs. In Galloperdix it is usual for the males to have two spurs, and for the females to have only one on each leg.^* Hence spurs may be considered as a masculine structure, which has been occasion- ally more or less transferred to the females. Like most other secondary sexual characters, the spurs are highly variable, both in number and development, in the same species. Various birds have spurs on their wings. But the Egyptian goose {Chenalopex cegyptiacus) has only "bai"e obtuse knobs," and these probably shew us the first steps by which true spui's have been developed in other species. In the spur-winged goose, Pledropterus ganihensis, the males have much larger spui-s than the females; and they use them, as I am informed by Mi-. Bartlett, in fighting together, so that, in this case, the wing-spui's serve as sexual weapons ; but according to Livingstone, they are chiefly used in the defence of the young. The Palamedea (fig. 38) is ai-med with a pair of spurs on each wing ; and these are such formidable weapons, that a single blow has been known to drive a dog howhng away. But it does not appear that the spurs in this case, or iu that of some of the spur-winged rails, " Brehm, ' Illust. Thierleben, Sweden,' &c., 1867, p. 79. 1867, B. iv. s. 351. Some of the Jerdon, 'Birds of India: on foregoing statements are taken from Ithaginis, vol. iii. p. 523 ; on Gallo- L. Lloyd, 'The Game Birds of perdix, p. 541. Chap. XIII. Law of Battle. are larger in the male than in the female.^" In certain plovers, however, the wing-spurs must be considered as a sexual cha- Fig. 38. Palamedea cornuta (from Brehm), shewing the double wing-spnrs. and the nUmcnt on the head. ^^^^Syptian soose, see p. 639. For Plectropterus, ' Livinff- Macgilhvray, ' British Birds,' vol. iv. stone's Travels,' p. 254. For Pala- 366 TJie Descent of Man. Part IL racter. Thus in tlio male of our common peewit ( Vandlus cri^ tatus) the tubercle on the shoulder of the wing becomes more prominent during the breeding-season, and the males fight together. In some species of Lobivanellus a similar tubercle becomes developed during the breeding-season "into a short " horny spur." In the Austrahan L. lobatus both sexes have spurs, but these are much larger in the males than in the females. In an allied bird, the Iloplopterus wnnatm, the spurs do not increase in size during the breeding-season ; but these birds have been seen in Egypt to fight together, in the same manner as our peewits, by turning suddenly ia the air and striking sideways at each other, sometimes with fatal results. Thus also they drive away other enemies." The season of love is that of battle ; but the males of some birds, as of the game-fowl and ruff, and even the young males of the wild turkey and grouse," are ready to fight whenever they meet. The presence of the female is the teterrima belli causa. The Bengali baboos make the pretty little males of the amadavat {Estrelda ainandava) fight together by placing three small cages in a row, with a female in the middle ; after a httle time the two males are turned loose, and immediately a desperate battle en- sues.'' When many males congregate at the same appointed spot and fight together, as in the case of grouse and various other bu'ds, they are generally attended by the females,^" which after- wards pair with the victorious combatants. But ia some cases the pairing precedes instead of succeeding the combat : thus accord- ing to Audubon,'^ several males of the Virginian goat-sucker {Caprimulgus virginianus) "court, in a highly entertaining " manner the female, and no sooner has she made her choice, " than her approved gives chase to all intruders, and diives medea, Brehm's ' Tliierleben,' B. iv. s. 740. See also on this bird Azara, ' Voyages dans I'Ame'rique me'rid.' toro. iv. 1809, pp. 179, 263. See, on our peewit, Mr. R. Carr in ' Land and Water,' Aug. 8th, 1868, p. 46. In regard to Lobi- vanellus, see Jerdon's ' Birds of India,' vol. ill. p. 647, and Gould's * Handbook of Bird." "f Australia, Tol. ii. p. 220. For the Holopterus, see Mr. Allen in the 'Ibis,' vol. v, 1863, p. 156. Audubon, ' Ornith. Biography, vol. ii. p. 492 ; vol. i. pp. 4-13. '» Mr. Blyth, ' Land and Water, ■i;867, p. 212. Richardson on Tetrao unibellus 'Fauna Bor. Amer. : Birds,' 1831, p. 343. L. Lloyd, ' Game Birds of Sweden,' 1867, pp. 22, 79, on the capercailzie and black-cock. Brehm, however, asserts (' Thierleben,' &c., B. iv. s. 352) that in Germany the grey-hens do not generally attend the Balzen of the black-cocks, but thia is an exception to the common rule; possibly the hens may lie hidden in the surrounding bushes, as IS known to be the case with the grey-hens in Scandinavia, and with other species in N. America. 2' 'Ornithological Biography, vo\. ii. p, 275. Chap. XHI. Law of Battle. 367 " them beyond his dominions." Generally the males try to drive a'way or kill their rivals before they pair. It does not, however, appear that the females invariably prefer the victorious males. I have indeed been assured by Dr. "W. Kovalevskj' that the female capercailzie sometimes steals away with a yoimg male who has not dared to enter the arena with the older cocks, in the same manner as occasionally happens with the does of the red-deer in Scotland. When two males contend in presence ot a single female, the victor, no doubt, commonly gains his desire ; but some of these battles are caused by wandering males trying to distract the peace of an already mated pair.^ Even with the most pugnacious species it is probable that the pairing does not depend exclusively on the mere strength and courage of the male ; for such males are generally decorated with various ornaments, which often become more brilliant during the breeding-season, and which are sedulously displayed before the females. The males also endeavour to charm or excite their mates by love-notes, songs, and antics ; and the courtship) is, in many instances, a prolonged affair. Hence it is not probable that the females are indifferent to the charms of the opposite sex, or that they are invariably compelled to yield to the victorious males. It is more probable that the females are excited, either before or after the conflict, by certain males, and thus un- consciously prefer them. In the case of Tetrao umhellus, a good observer goes so far as to believe that the battles of the males " are all a sham, performed to show themselves to the greatest " advantage before the admiring females who assemble around ; for " I have never been able to find a maimed hero, and seldom more " than a broken feather." I shall have to recur to this subject, but I may here add that with the Tetrao cupido of the Uniteo States, about a score of males assemble at a particular spot, ano strutting about, make the whole air resound with their extra ordinary noises. At the first answer from a female the males begin to fight furiously, and the weaker give way ; but then, according to Audubon, both the victors and vanquished search for the female, so that the females must either then exert a choice, or the battle must be renewed. So, again, with one of the field-starlings of the United States (Sturnella ludoviciana) the males engage in fierce conflicts, " but at the sight of a female " they all fly after her, as if mad." • 'i9«7''^"''QQ7^i"'','^,'°' ^r^-^ ''Audubon's 'Oi-nitholog. Bio- .J. 1867 p 990. Audubon, ' Ornith. gvaphy on Tetrao cupido,%ol ii. Biography vol .up 492 p. 492Yon the Sturnus, vol. ii. p. " 'Land and Water,' July 25th, 219 1868, p. 14. 368 The Descent of Man. Part IL Vocal and instrumental music. — "With birds the voice serves to express various emotions, such as distress, fear, anger, triumph, or mere happiness. It is apparently sometimes used to excito terror, as in the case of the hissing noise made by some nestling- birds. Audubon relates that a night-heron (Ardtu mjcticorax, Linn.) which he kept tame, used to hide itself when a cat approached, and then " suddenly start up uttering one of the " most frightful cries, apparently enjoying the cat's alarm and " flight." The common domestic cock clucks to the hen, and the hen to her chickens, when a dainty morsel is found. The hen, when she has laid an egg, " repeats the same note very often, " and concludes with the sixth above, which she holds for a longer time ; " ^° and thus she expresses her joy. Some social birds apparently call to each other for aid ; and as they flit from tree to tree, the flock is kept together by chirp answering chirp. During the nocturnal migrations of geese and other water-fowl , sonorous clangs from the van may be heard in the darkness overhead, answered by clangs in the rear. Certain cries serve as danger signals, which, as the sportsman knows to his cost, are understood by the same species and by others. The domestic cock crows, and the humming-bird chirps, in triumph over a defeated rival. The true song, however, of most birds and various strange cries are chieily uttered during the breed- ing-season, and serve as a charm, or merely as a call-note, to the other sex. Naturalists are much divided with respect to the object of the singing of bu'ds. Few more careful observers ever lived than ■ftlontagu, and he maintained that the " males of song-birds and " of many others do not in general search for the female, but, " on the contrary, their business in the spring is to perch on some '•' conspicuous spot, breathing out their fall and amorous notes, " which, by instinct, the female knows, and repaii-s to the spot to " choose her mate." Mr. Jenner Weir informs me that this is certainly the case with the nightingale. Bechstein, who kept bii-ds during his whole life, asserts, "that the female canary " always chooses the best singer, and that in a state of nature " the female finch selects that male out of a hundred whoso " notes please her most." There can be no doubt that birds closely attend to each other's song. Mr. Weir has told me of " ' Ornithological Biograph.' vol. vogel,' 1840, s. 4. Mr. Harrison V. p. 601. Weir likewise writes to me: — " i 20 The Hon. Daines Barrington, "am informed that the best singing •Philosoph. Transact.' 1773, p. 252. "males gener.illy get a mate first, " < Ornithological Dictionary,' " when they are bred in the same 1833, p. 475. " room." 2« ' Naturgeschichte der Stuben- Chap. XIII. Vocal Mzisic. 369 the case of a bullfinch which had been taught to pipe a German waltz, and who was so good a performer that he cost ten guineas ; when this bird was first introduced into a room where other bii'ds were kept and he began to sing, all the others, con- sisting of about twenty linnets and canaries, ranged themselves on the nearest side of their cages, and listened with the greatest interest to the new performer. Many naturalists believe that the singing of bii-ds is almost exclusively " the effect of rivalry " and emulation," and not for the sake of charming their mates. This was the opinion of Daines Barrington and White of Selborne, who both especially attended to this subject.-^ Bar- riagton, however, admits that " superiority in song gives to " bu-ds an amazing ascendancy over others, as is well known to " bird-catchers." It is certain that there is an intense degree of rivalry between the males in their singing. Bird-fanciers match their birds to see which will sing longest; and I was told by Mr.Yarrellthat a first-rate bird will sometimes sing till he di'ops down almost dead, or according to Bechstein,^" quite dead from ruptm-ing a vessel in the lungs. Whatever the cause may be, male birds, as I hear fi'om Mr. Weir, often die suddenly during the season of song. That the habit of singing is sometimes quite independent of love is clear, for a sterile, hybrid canary-bii-d has been de- scribed ^' as singing whilst viewing itself in a miiTor, and then dashing at its own image; it likewise attacked with fury a female canary, when put into the same cage. The jealousy excited by the act of singing is constantly taken advantage of by bird-catchers; a male, in good song, is hidden and protected, whilst a stuffed bird, surrounded by limed twigs, is exposed to view. In this manner, as ]\Ir. Weir informs me, a man has in the course of a single day caught fifty, and in one instance seventy, male chaffinches. The power and inclination to sing differ so greatly with birds that although the price of an ordinary male chaffinch is only sixpence, Mr. Weir saw one bird for wliich the bird-catcher asked three pounds; the test of a really good singer being that it will continue to sing whilst the cage is swung round the owner's head. That male birds should sing from emulation as well as for charming the female, is not at all incompatible; and it might have been expected that these two habits would have concurred, like those of display and pugnacity. Some authors, however, ^» 'Philosophical Transactions,' ao « Naturgesch. der Stubenvogel,' 1773, p. 263. White's 'Natural 1840, s. 252 History of Selborne,' 1825, vol. i. p. si Mr. Bold, ' Zoologist,' 1843-44^ 24G. p. 659. 2 B 370 The Descent of Man. I'ABT II. argue that tlie song of tLe male cannot serve to charm the female, because the females of some few species, such as of the canary, robin, lark, and bullfinch, especially when in a state of widow- hood, as Bechstein remarks, pour forth fairly melodious strains. In some of these cases the habit of singing may be in part attributed to the females having been highly fed and confined,^'' for this disturbs all the usual functions connected with the repro- duction of the species. Many instances have already been given of the partial transference of secondary masculine characters to the female, so that it is not at all surprising that the females of some species should possess the power of song. It has also been argued, that the song of the male cannot serve as a charm, be- cause the males of certain species, for instance of the robin, sing during the autumn.** But nothing is more common than for animals to take pleasui-e in practising whatever instinct they follow at other times for some real good. How often do we see birds which fly easily, gliding and sailing through the air ob- viously for pleasure ? The cat plays with the captured mouse, and the cormorant with the captured fish. The weaver-bird (Ploceus), when confined in a cage, amuses itself by neatly weaving blades of grass between the wires of its cage. Bii-ds which habitually fight dui'ing the breeding-season are generally ready to fight at alJ times; and the males of the capercailzie sometimes hold their Balzen or lelcs at the usual place of as- semblage during the autumn.^'' Hence it is not at all surprising that male birds should continue singing for their own amuse- ment after the season for courtship is over. As shewn in a previous chajpter, singing is to a certain extent an art, and is much improved by practice. Birds can be taught various tunes, and even the unmelodious sparrow has learnt to sing like a linnet. They acquire the song of their foster IDarents,*^ and sometimes that of their neighbours.-'' All the common songsters belong to the Order of Insessores, and their vocal organs are much more complex than those of most other birds ; yet it is a singular fact that some of the Insessores, such as ravens, crows, and magpies, possess the proper apparatus,'" D. Barrington, ' PhiU Transact.' 1773, p. 262. BecbsToin, 'Stuben- vogel,' 1840, s. 4. 33 This is likewise the case with the water-ouzel, see Mr. Hepburn in the 'Zoologist,' 1845-1846, p. 1068. " L. Lloyd, 'Game Birds of Sweden,' 1867, p. 25. " Barrington, ibid. p. 264. Bechstein, ibid. s. 5. Dureau de la Malle gives a curious instance ('Aunales des Sc.. Nat.' 3rd series, Zoolog. torn. x. p. 118) of some wild blackbirds in his garden in Paris, which naturally learnt a republican air from a cageil bird. Bishop, in ' Todd's Cyclop. «rf Anat. and Phys.' vol. iv, p. 1496. Chap. XIII. Vocal Music. 371 though they never sing, and do not naturally modulate their voices to any great extent. Hunter asserts that with the true Bongsters the muscles of the larynx are stronger in the males than in the females ; but with this slight exception there is no difference in the vocal organs of the two sexes, although the males of most species sing so much better and more continuously than the females. It is remarkable that only small birds properly sing. The A.ustralian genus Menura, however, must be excepted ; for the Menura Albert i, which is about the size of a half-grown tui'key, not only mocks other birds, but " its own whistle is exceedingly " beautiful and varied." The males congregate and form " cor- roborying places," where they sing, raising and spreading their tails like peacocks, and drooping their wings.^^ It is also remark- able that birds which sing well are rarely decorated with brilliant colours or other ornaments. Of our British birds, excepting the buUfinch and goldfinch, the best songsters are plain-coloured. The kingfisher, bee-eater, roller, hoopoe, woodpeckers, &c., utter harsh cries ; and the brilliant birds of the tropics are hardly ever .songsters.*" Hence bright colours and the power of song seem to replace each other. We can perceive that if the plumage did not vary in brightness, or if bright colours were dangerous io tho species, other means would be employed to charm the females ; and melody of voice offers one such means. In some birds the vocal organs differ greatly in the two sexes. In the Tetrao cupido (fig. 39) the male has two bare, orange- coloured sacks, one on each side of the neck; and these are largely inflated when the male, during the breeding-season, makes his curious hoUow sound, audible at a great distance. Audubon proved that the sound was intimately connected with this apparatus (which reminds us of the air-sacks on each side ot tho mouth of certain male frogs), for he found that the sound was much diminished when one of the sacks of a tame bird was pricked, and when both were pricked it was altogether stopped. The female has " a somewhat similar, though smaller naked space " of skin on the neck : but this is not capable of inflation." ^ The As stated by Harrington in Philosoph. Transact.' 1773, p. 262. 3" Gould, ' Handbook to the Birds of Australia,' vol. i. 1865, pp. 308- aiO. Sevj also Mr. T. W. Wood in the ' Student,' April 1870, p. 125. See remarks to this eflect in (lonld's ' Introduction to the Trochi- lidae,' 1861, p. 22. ' TLa Sportsman and Naturalist in Canada,? by Major "W. Eoss King, 1866, pp. 144-146. Mr. T. W. Wood gives in the 'Student' (April, 1870, p. 116) an excellent account of the attitude and habits of this bird during its courtship. He states that the ear-tufts or neck- plumes are erected, so that thov meei over the crown of the heni. See his drawing, tig. 39. 2 B 2 372 The Descent of Man. Past II. male of another kind of grouse (JFeirao urophasianus), whilst courting the female, has his " bare yellow oesophagus inflated to " a prodigious size, fully half as large as the body ; " and he then utters various grating, deep, hollow tones. With his neck- feathers erect, his wings lowered, and buzzing on the gound, and his long pointed tail spread out like a fan, he displays a variety of grotesque attitudes. The oesophagus of the female is not in any way remarkable." « Richardson, ' Fauna Bor. American: Birds,' 1831, p. 359. Audubot bid. vol. iv. p. 507. Chap. XIU. Vocat Music. 373 It seems now well made out that the great throat pouch of the European male bustard {Otis tarda), and of at least four other species, does not, as was formerly supposed, serve to hold water, but is connected with the iitterance durmg the breeding- Fig. 40. The Umbrella-bird or Cephalopterus ornatus male from Brelim). season of a peculiar sound resembling "oak."*^ A crow-like bird inhabiting South America {Cephalopterus ornatus, fig. 40) is called the umbrella-bird, from its immense top knot, formed of ' The following: papers have been lately written on this subject : Prof. A Newton, in the ' Ibis,' i8B2, p. 107 , Dr. Cullen, ibid. 1865, p. 145 ; Mr Flower, in ' Proc. Zool. Soc' 18B.5, p. 747; and Dr Murie, ui 'Proc. Zool. Soc. 18GB, p. 471. In this latter paper an excellent figure is given of the male Austra/^ lian Bustard in full display with the sack distended. It is a singular fact that the sack is not developed in all the males of the same species. 374 The Descent of Man. Part W. bare white quills sui-mounted by dark-blue plumes, which it cau elevate into a great dome no less than five inches in diameter, covering the whole head. This bird has on its neck a long, thin, cylindrical fleshy appendage, which is thickly clothed with scalt!- like blue feathers. It probably serves in part as an ornament, but likewise as a resounding apparatus; for Mr. Bates found that it is connected " with an unusual development of the " trachea and vocal organs." It is dilated when the bird utters its singularly deep, loud and long sustained fluty note. The head- crest and neck-appendage are rudimentary in the female.'** The vocal organs of various web-footed and wading birds, are extraordinarily complex, and differ to a certain extent in the two sexes. In some cases the trachea is convoluted, Mke a French horn, and is deeply embedded in the sternum. In the wild swan ( Cygnus ferns) it is more deeply embedded in the adult male, than in the adult female or young male. In the male Merganser the enlarged portion of the ti-achea is fui'nished with an additional pair of muscles.*® In one of the ducks, however, namely Anus punctata, the bony enlargement is only a little more developed in the male than in the female.*" But the meaning of these differences in the trachea of the two sexes of the Anatidse is not understood; for the male is not always the more vociferous; thus with the common duck, the male hisses, whilst the female utters a loud quack.*^ In both sexes of one of the cranes (^Gras virgo) the trachea penetrates the sternum, but presents " certain " sexual modifications." In the male of the black stork there is also a well-marked sexual difference in the length and curvatui-e of the bronchi.** Highly important structures have, therefore, in these cases been modified according to sex. It is often difficult to conjecture whether the many strange cries and notes uttered by male birds dui-ing the breeding- season, serve as a charm or merely as a call to the female. The soft cooing of the turtle-dove and of many pigeons, it may be presimied, pleases the female. When the female of the wild Bates, ' The Naturalist on the of eight, and yet this bird (Jerdon, Amazons,' 1863, vol. ii. p. 284; ' Birds of India,' vol. iii. p. 7G3) is Wallace, in ' Proc. Zool. Soc' 1850, mute ; but Mr. Blyth informs me X. 206. A new species, with a still that the convolutions are not con- larger neck-appendage {C. pendu- stantly present, so that perhaps iiger), has lately been discovered, they are now tending towards see ' Ibis,' vol. i. p. 457. abortion. <5 Bishop, in Todd's 'Cyclop, of " 'Elements of Comp. Anat.' by inat. and Phys.' vol. iv. p. 1499. R. Wagner, Eng. translat. 1845, p. " Prof. Itewton, 'Proc. Zociog. 111. With respect to the sw.in, as Soc' 1871, p. 651. ° given above, Yarrell's 'Hist, of The spoonbill (Platalea) has British Birds,' 2nd edit. 1S46, vo- lts trachea convoluted into a figure iii. p. 193. / Cjiap. XIII. Instrumental Music. 375 tiirkey utters her call in the mornmg, the male answers by a note which diflers from the gobbling noise made, when with erected feathers, rustling wings and distended wattles, he puffs and struts before her.^^ The spd of the black-cock certaioly serves as a call to the female, for it has been known to bring four or five females from a distance to a male under confinement; but as the black-cock contmues his spel for hours during successive days, and in the case of the capercailzie " with an agony of " passion," we are led to suppose that the females which are present are thus charmed.'" The voice of the common rook is known to alter during the breeding-season, and is therefore in some way sexual." But what shall we say about the harsh screams of, for iastance, some kinds of macaws; have these birds as bad taste for musical sounds as they apparently have for colour, judging by the inharmonious contrast of their bright yellow and blue plumage ? It is indeed possible that without any advantage being thus gained, the loud voices of many male bii-ds may be the result of the inherited effects of the continued use of their vocal organs, when excited by the strong passions of love, jealousy and rage; but to this point we shall recm: when we treat of quadrupeds. We have as yet spoken only of the voice, but the males of various birds practise, during their courtship, what may be called instrumental music. Peacocks and Birds of Paradise rattle their quiUs together. Turkey-cocks scrape their wings against the ground, and some kinds of grouse thus produce a buzzing sound. Another North American grouse, the Tetrao umhellus, when with liis tail erect, his ruffs displayed, "he shows off his finery to the " females, who lie hid in the neighbourhood," drums by rapidly striking his wings together above his back, according to Mr. R. Haymond, and not, as Audubon thought, by striking them against his sides. The sound thus produced is compared by some to distant thunder, and by others to the quick roll of a drum. The female never drums, " but Sies dii-ectly to the place " where the male is thus engaged." The male of the Kalij- pheasant, in the Himalayas, " often makes a singular drumming " noise with his wings, not unlike the sound produced by shaking " a stiff piece of cloth." On the west coast of Africa the little l,>lack-weavers (Ploceus?) congregate in a small party on tho bushes round a smaU open space, and sing and glide thi-ough C. L. Bonnparte, quoted in the Sweden,' &c., 1867, pp. 22, 81. 'Naturalist Library: Birds,' vol. '-^ Jenner, ' Philosooh. Traasac- Eiv. p. 126. lions,' 1824, p. 20. L. Lloyd, ' The Game Birds of \ The Descent of Man. Tart H the air with quivering wings, " which make a rapid whirring " sound like a child's rattle." One bird after another thus performs for hours together, but only during the courting-season. At this season and at no other time, the males of certain night-jars (Capri- mulgus) make a strange booming noise with their wings. The various species of wood-peckers strike a sonorous branch with their beaks, with so rapid a vibratory movement that " the head " appears to be in two places at once." The sound thus pro- duced is audible at a considerable distance, but cannot be described ; and I feel sure that its source would never be con- jectured by any one hearing it for the first tune. As tliis jarring sound is made chiefly during the breeding-season, it has been considered as a love-song; but it is perhaps more strictly a love-call. The female, when driven from her nest, has been observed thus to call her mate, who answered in the same manner and soon appeared. Lastly, the male Hoopoe (JJpupa epops) combines vocal and instrumental music ; for during the breeding-season this bird, as Mr. Swinhoe observed, fii-st draws in air, and then taps the end of its beak perpendicularly down against a stone or the trunk of a ti'ce, " when the breath being " forced down the tubular bill produces the correct sound." If the beak is not thus struck against some object, the sound is quite different. Air is at the same time swallowed, and the oesophagus thus becomes much swollen ; and this probably acts as a resonator, not only with the hoopoe, but with pigeons and other birds.^^ In the foregoing cases sounds are made by the aid of structures already present and otherwise necessary ; but in the following cases certain feathers have been specially modified for the express purpose of producing soimds. The drumming, bleating, neigh- ing, or thundering noise (as expressed by different observers) made by the common snipe (^Scolopax gallinago) must have sur- prised every one who has ever heard it. This bird, during the pairing-season, flies to " perhaps a thousand feet in height," and *- For the foregoing facts see, Weavers, 'Livingstone's Expedition on Birds of Paradise, Brehm, to the Zambesi,' 1865, p. 425. On ' Thierleben,' Band iii. s. 325. On Woodpeckers, Macgillivray, « Hist. Grouse, Richardson, ' Fauna Bor. of British Birds,' vol. iii. 1840, pp. Americ. ; Birds,' pp. 343 and 359 ; 84, 88, 89, and 95. On the Hoopoe, Major W. Ross King, ' The Sports- Mr. Swinhoe, in ' Proc. Zoolog. Soc' man in Canada,' 1866, p. 156; Mr. June 23, 1863 and 1871, p. 348, Raymond, in Prof. Cox's ' Geol. On the Night-jar, Audubon, ibid. Survey of Indiana,' p. 227 ; Audu- vol. ii. p. 255, and ' American Natu- bon, 'American Ornitholog. Bio- ralist,' 1873, p. 672. The English graph.' vol. i. p. 216. Ou the Night-jar likewise makes in the Kalij-pheasant, Jerdon, 'Birds of spring a curious noise during its India,' vol. iii. p. 533. On the rapid fligiit. Chap. XIIL InstnmientaL Mtisic, 377 after zig-zagging about for a time descends to the earth in a cui'ved line, with outspread taU and quivering pinions, and surprising velocity. The sound is emitted only during this rapid descent. No one was able to explain the cause, until M. Meves observed that on each side of the tail the outer feathers are peculiarly formed (fig. 41), having a stiif sabre-shaped shaft Fig. 42. Outer tail-feather of Scolopax frenata. Fig. 41. Outer tail-rcather of Scolopax gallinngo (from ' Proc. Zool. Soc.' 1858). with the oblique barbs of unusual length, the outer webs being strongly bound together. He found that by blowing on these feathers, or by fastening them to a long thin stick and waving them rapidly through the air, he could reproduce the drumming- noise made by the living bird. Both sexes are furnished with these feathers, but they are generally larger in the male than in the female, and emit a deeper note. In some species, as in B. frenaca (fig. 42), four feathers, and in S. javensis (fig. 43), no less than eight on each side of the tail are greatly modified. Different tones are emitted by the feathers of the different species when waved through the air; and the Scolopax Wihonii of the United States makes a switching noise whilst descendine; rapidly to the earth.'^^ 5 f j In the male of the Chamce'petes unicolor (a large gallinaceous bird ot America) the first primary wing-feather is arched towards the tip and is much more attenuated than in the female. In an alhed bird the Penelope nicira, Mr. Salviu observed a male, which, whilst It flew do^Tiwards "with outstretched wings, gave forth a kind of crashing rushing noise," like the fallmg of a tree.«* Fig. 43. Outer taU-feather of Scolopax javensis. " See M. Meves' interestino- paper in ' Proc. Zool. Soc' 1858, p. 199. For the habits of the snipe, Macgillivray, ' Hist. British Birds,' vol. iv. p. 371. For the American •snipe, Capt. Blakiston, ' Ibis,' vol. v. 1863, p. 131. Mr. Salvin, in -jars, the shafts of the elon- gated wing-feathers are naked, except at the extremity, where there is a disc.** Again, in another genus of night-jars, the tail-feathers are even still more prodigiously developed. In general the feathers of the tail are more often elongated than those of the wings, as any great elongation of the latter impedes flight. "We thus see that in closely-allied birds ornaments of the same kind have been gained by the males through the development of widely different feathers. It is a curious fact that the feathers of species belonging to very distinct groups have been modified in almost exactly the same peculiar manner. Thus the wing-feathers in one of the above-mentioned night-jars are bare along the shaft, and ter- minate in a disc ; or are, as they are sometimes called, spoon or racket-shaped. Feathers of this kind occur in the tail of a motmot (hJumomota superciliaris), oi a king-fisher, finch, hum- ming-bird, parrot, several Indian drongos (Dicrurus and Edolius, in one of which the disc stands vertically), and in the tail of certain birds of paradise. In these latter birds, similar feathers, i beautifully ocellated, ornament the head, as is likewise the case I with some gallinaceous birds. In an Indian bustard (Sypheotides auritus) the feathers forming the ear-tufts, which are about four inches in length, also terminate in discs."* It is a most singular fact that the motmots, as Mr. Salvm has clearly shewn,'" give to their tail feathers the racket-shape by biting off the barbs, and, further, that this contiaued mutilation has produced a certain amount of inherited effect. ««Dr W.Marshall, 'ULer den Vog- 1864, p. 114. LiringstDne, 'Eipedi- elschwanz,' ibid. B. I. Heft 2, 1872. tion to the Zambesi,' 1865, p. 66. «" Jai'dine's 'Naturalist Library: " Jerdon, 'Birds of India,' vol. Birds,* vol. siv. p. 166. ' iii. p. 620. ^ .oo «8 Sclater, in the 'Ibis,' vol. vi. •» 'Proc.Zoolog.So(;.*1873,p.429. Chap. XIII. Decoration. 385 ARain, tlie barbs of the feathers in various -widely-distinct birds are fUamentous or plumose, as with some herons, ibises, bii-ds of paradise, and Gallinacese. In other cases the barbs disappear, leaving the shafts bare from end to end ; and these in the tail of the Paradiaea apoda attain a length of thirty-four inches in P. Papuana (fig. 47) they are much shorter and thin. Smaller feathers when thus denuded appear like bristles, as on the breast of the turkey-cock. As any fleeting fashion in dress comes to be admired by man, so with birds a change of almost any kind in the structure or colouring of the feathers in the male appears to have been admired by the female. The fact of the feathers in widely distinct groups, having been modified in an analogous manner, no doubt depends primarily on all the feathers having neai'ly the same structure and manner of development, and consequently tending to vary in the same manner. We often see a tendency to analogous variability in the plumage of our domestic breeds belonging to distinct species. Thus top-knots have appeared in several species. In an extinct variety of the turkey, the top-knot consisted of bare quills surmounted with plumes of down, so that they somewhat resembled the racket-shaped feathers above described. In certain breeds of the pigeon and fowl the feathers are plumose, with some tendency in the shafts to be naked. In the Sebas- topol goose the scapular feathers are greatly elongated, curled, or even spirally twisted, with the margins plumose.''"^ In regard to colour hardly anything need here be said, for every one knows how splendid are the tints of many birds, and how harmoniously they are combined. The coloxu's are often metal Uc and iridescent. Circular spots are sometimes sur- rounded by one or more differently shaded zones, and are thus converted into ocelH. Nor need much be said on the wonderful difiierence between the sexes of many bii-ds. The common peacock ofiFers a striking instance. Female birds of paradise are obscurely coloured and destitute of all ornaments, whilst the males are probably the most highly decorated of all birds, and in so many different ways, that they must be seen to be appre- ciated. The elongated and golden-orange plumes which spring from beneath the wings of the Paradisea apoda, when vertically erected and made to vibrate, are described as forming a sort of halo, in the centre of which the head " looks like a little emerald " sun with its rays formed by the two plumes." In another " Wallace, in ' Annals and Mag. " See my work on ' The Variation of Nat. Hist.' vol. xx. 1857, p. 416 of Animals and Plants under Domes- and in his ' Malay Archipelago, ticatiou,' vol. i. pp. 289, 293. vol. 11. 1869, p. 390. 71 Quoted from M. de Lafresnaye 2 0 386 The Descent of Man. PaktIT most beautiful species the head is bald, " and of a rich cobalt " blue, crossed by several lines of black velvety feathers."''* in 'Annals and JIag. of Nat. Hist.' Tol. xiii. 1854, p. 157 : see also Mr. Wallace's much fnllei- account in vol. 2x. 1857, p. 412, and in his ' ;\Ialay Archipelago.' Wallace, 'The Malar Archi- pelago,' vol. ii. 1869, p. 405. Chap. XUI. Decoration. 387 Male humming-birds (figs. 48 and 49) almost vie with birds of imradise in their beauty, as every one will admit who has seen. 1 \\x. Gould's splendid volumes, or his rich collection. It is very remarkable in how many different ways these birds are orna- mented. Almost every part of their plumage has been taken advantage of, and modified; and the modifications have been 388 The Descent of Man. Paet 11. carried, as Mr. Gould shewed me, to a wonderful extreme in some species belonging to nearly every sub-group. Such cases are curiously like those which we see in our fancy breeds, reared by man for the sake of ornament: certain individuals originally varied in one character, and other individuals of the ¥lg. 49. Spathura underwoodi, male and female (from Breb'B). Chap. Xni, Decoration. same species in other characters ; and these have been seized on by man and much augmented— as shewn by the tail of the fan- tail-pigeon, the hood of the jacobin, the beak and wattle of the carrier, and so forth. The sole difference between these cases is that in the one, the result is due to man's selection, whilst in the other, as with htimming-birds, birds of paradise, &c., it is due to the selection by the females of the more beautiful males. I will mention only one other bird, remarkable from the ex- treme contrast in colour between the sexes, namely the famous bell-bird (Ghasmorhynchus niveus) of S. America, the note of which can be distinguished at the distance of nearly three miles, and astonishes every one when first hearing it. The male is pure white, whilst the female is dusky-gi-een ; and white is a very rare colour in terrestrial species of moderate size and in- offensive habits. The male, also, as described by Water ton, has a spiral tube, nearly three inches in length, which rises from the base of the beak. It is jet-black, dotted over with minute downy feathers. This tube can be inflated with air, through a communication with the palate; and when not inflated hangs down on one side. The genus consists of four species, the males of which are very distinct, whilst the females, as described by Mr. Sclater in a very interesting paper, closely resemble each other, thus offering an excellent instance of the common rule that within the same group the males differ much more fi'om each other than do the females. In a second species (C. nudi- coUis) the male is Likewise snow-white, with the exception of a large space of naked skia on the throat and round the eyes, which dm-ing the breeding-season is of a iine green colour. In a third species (C. tricar unculatus) the head and neck alone of the male are white, the rest of the body being chesnut-brown, and the male of this species is provided with three filamentous projections half as long as the body— one rising from the basa uf the beak, and the two others from the corners of the mouth.'" The coloured plumage and certain other ornaments of the adult males are either retained for hfe, or are periodically re- newed dui-ing the summer and breeding-season. At this same season the beak and naked skin about the head frequently change colour, as with some herons, ibises, gulls, one of tho bell-birds just noticed, &c. In the white ibis, the cheeks, the inflatable skin of the throat, and the basal portion of the beak then become crimson.''^ In one of the rails, Gallicrex cristatus, a » Mr. Sclater, 'Intellectual Ob- plate, in the « Ibis,' 1865, p. 90. server,' Jan. 1867. ' VVaterton's "'Land and Water,' 1867, iv Wanderings,' p. 118. See also Mr. 394. Salvin'a interesting paper, with u 390 The Descent of Man. Part U. large red caruncle is developed during this period on the head of the male. So it is with a thiu horny crest on the beak of one of the pelicans, P. erythrorhynchm ; for after the breeding- season, these horny crests are shed, like horuB from the heads of stags, and the shore of an island in a lake in Nevada was found covered with these cui-ious exuvia).'^ Changes of colour in the plumage according to the season depend, firstly on a double annual moult, secondly on an actual change of colour in the feathers themselves, and thirdly on their dull-coloured margins being periodically shed, or on these three processes more or less combined. The shedding of the de- ciduary margins may be compared with the shedding of their down by very young birds ; for the down m most cases arises from the summits of the first true feathers.'* With respect to the birds which annually undergo a double moult, there are, fii'stly, some kinds, for instance snipes, swallow- plovers (Glareolae), and curlews, in which the two sexes resemble each other, and do not change colour at any season. I do not know whether the winter plumage is thicker and warmer than th® summer plumage, but warmth seems the most probable end attained of a double moidt, where there is no change of colour. Secondly, there are birds, for instance, certain species of Tetanus and other Grallatores, the sexes of which resemble each other, but in which the summer and winter plumage difl:"er slightly in colour. The difference, however, in these cases is so small that it can hardly be an advantage to them ; and it may, perhaps, be attributed to the direct action of the different conditions to which the birds are exposed during the two seasons. Thirdly, there are many other birds the sexes of which ai'e alike, but which are widely different in their summer and winter plumage. Tourthly, there are birds, the sexes of which differ from each other in colour ; but the females, though moulting twice, retain the same colours throughout the year, whilst the males undergo a change of colour, sometimes a great one, as with certain bustards. Fifthly and lastly, there are birds the sexes of which differ from each other in both their summer and winter plumage ; but the male undergoes a greater amount of change at each recui-rent season than the female — of which the ruff (Machetes pugnax) offers a good instance. With respect-to the cause or purpose of the differences in colour between the summer and winter plumage, this may in some instances, as with the ptarmigan,'' serve during both " Mr. D. G. EHiot, in ' Proc. edited by P L. Sclater. Kay Soc Zool. Soc' 1869, p. 589. 1867, p. 14. Nitzsch's ' Pterylogi-aphy,' " The brown mottled summei Chap. XIII. Double Anmial Moult. 391 seasons as a pretection. When the difference between the two plumages is shght, it may perhaps be attributed, as already- remarked, to the dii-ect action of the conditions of life. But with many bkds there can hardly be a doubt that the summer plumage is ornamental, even when both sexes are alike. We may conclude that this is the case with many herons, egrets, Ac, for they acquire their beautiful plumes only during the breeding-season. Moreover, such plumes, top-knots, &c., though possessed by both sexes, are occasionally a little more developed in the male than in the female ; and they resemble the plumes and ornaments possessed by the males alone of other birds. It is also known that confinement, by affecting the reproductive system of male birds, frequently checks the development of their secondary sexual characters, but has no immediate influence on any other characters ; and I am informed by Mr. Bartlett that eight or nine specimens of the Knot (Tringa canutus) re- taiaed their unadorned winter plumage ia the Zoological Gardens throughout the year, from which fact we may infer that the summer plumage though common to both sexes partakes of the nature of the exclusively masculine plumage of many other birds.*" From the foregoing facts, more especially from neither sex of certain birds changing colour dui'iug either annual moult, or changing so slightly that the change can hardly be of any service to them, and from the females of other species moulting twice yet retaining the same colours tliroughout the year, we may conclude that the habit of annually moulting twice has not been acquired in order that the male should assume an orna- mental character during the breeding-season; but that the double moult, having been originally acquired for some distinct purpose, has subsequently been taken advantage of in certain cases for gaining a nuptial plumage. It appears at first sight a surprising circumstance that some closely-aUied species should regularly undergo a double annual plumage of the ptarmigan is of as much importance to it, as a pro- tection, as the white winter plu- mage; for in Scandinavia, during the spring, when the snow has disappeared, this bird is known to sufler greatly from birds of prey, before it has acquired its summer dress : see Wilhelm von Wright, in Lloyd, 'Game Birds of Sweden,' 1867, p. 125. ** Id regard to the previous statements on moulting, see, on snipes, &c., Macgillivray, ' Hist. Brit. Birds,' vol. iv. p. on Glareolie, curlews, and bustards, Jerdon, ' Birds of India,' vol. iii. pp. 615, 630, 683; on Totanus, ibid. p. 700 ; on the plumes of herons, ibid, p. 738, and Macgillivray, vol. iv. pp. 435 and 444, and Mr. Stafford Allen, in the ' Ibis,' vol. v. 1863, p.. 392 The Descent of Mmu 1'art IL moult, and others only a single one. The ptarmigan, for instance, moults twice or even thrice in the year, and the black- cock only once : some of the splendidly coloured honey-suckers (Nectarim'as) of India and some sub-genera of obscurely coloured pipits (Anthus) have a double, whUst others have only a single annual moult." But the gradations in the manner of moulting, which are known to occur with various birds, shew us how species, or whole groups, might have origmally acquired thek double annual moult, or having once gained the habit, have again lost it. With certain bustards and plovers the vernal moult is far from complete, some feathers being renewed, and some changed in colour. There is also reason to believe that with certain bustards and rail-like bkds, which properly under- go a double moult, some of the older males retam their nuptial plumage throughout the year. A few highly modified feathers may merely be added dui-ing the spring to the plumage, as occurs with the disc-formed tail-feathers of certain drongos (Bhringa) in India, and with the elongated feathers on the back, neck, and crest of certain herons. By such steps as these, the vernal moult might be rendered more and more complete, until a perfect double moult was acquii-ed. Some of the bu-ds of paradise retain their nuptial feathers throughout the year, and thus have only a single moult ; others cast them directly after the breeding-season, and thus have a double moult; and others again cast them at this season dui-ing the first year, but not afterwards ; so that these latter species are intermediate iu their manner of moulting. There is also a great difference with many bii'ds in the length of time dui-ing which the two annual plumages are retained ; so that the one might come to be vg- tained for the whole year, and the other completely lost. Thus in the spring Machetes pugnax retains his ruff for barely two months. In Natal the male widow-bird (Chera progne) acquires his fine plumage and long tail-feathers in December or January, and loses them in March; so that they are retained only for about three months. Most species, which undergo a double moult, keep their ornamental feathers for about six months. The male, however, of the wild Gallus hankiva retains his neck- hackles for nine or ten months ; and when these are cast oflj the underlying Mack feathers on the neck are fully exposed to view. But with the domesticated descendant of this species, the neck- hackles of the male are immediately replaced by new ones ; so On the moulting of the ptar- 359, 365, 369. On the moulting of migan, sae Gould's 'Birds of Great Anthus, see BIyth, in 'Ibis,' 1867, Britain.' On the honey-suckers, p. 32. Jerdon, * Birds of India,' vol. i. pp. Cha?. :xtII. Double A wual M oulf. 393 that we here see, as to part of the plumage, a double moult changed under domestication into a single moult.*^ The common drake {Anas boschas) after the breeding-season is well known to lose his male plumage for a period of three months, during which time he assumes that of the female. The male pintail-duck (Anas acuta) loses his plumage for the shorter period of six weeks or two months ; and Montagu remarks that " this double moult within so short a time is a most extra- ' ordinary circumstance, that seems to bid defiance to all human " reasoning." But the behever in the gi-adual modification of species will be far from feeling surprise at finding gi-adations of all kinds. If the male pintail were to acquire his new plumage within a still shorter period, the new male feathers would almost necessarily be mingled with the old, and both with some proper to the female ; and this apparently is the case with the male of a not distantly-allied bird, namely the Merganser serrator, for the males are said to " undergo a change of plumage, which " assimilates them in some measure to the female." By a little further acceleration in the process, the double moult would bo completely lost.*^ Some male burds, as before stated, become more brightly coloured in the spring, not by a vernal moult, but either by an actual change of coloiu* in the feathers, or by their obscurely- coloured deciduary margins being shed. Changes of colour thus caused may last for a longer or shorter time. In the Pelecanus onocrotalus a beautiful rosy tint, with lemon-coloured marks on the breast, overspreads the whole plumage in the spring ; but these tints, as Mr. Sclater states, " do not last long, disappearing " generally in about six weeks or two months after they have " been attained." Certain finches shed the margins of theii* feathers in the spring, and then become brighter coloiu'ed, while other finches undergo no such change. Thus the Fringilla tristis of the United States (as well as many other American species) For the foregoing statements of the Herodias bubulcus, Mr. S. S. in regard to partial moults, and Allen, in 'Ibis,' 1863, p. 33. On on old males retaining their nuptial Gallus bankim, Blyth, in ' Annals plumage, see Jerdon, on bustards and Mag. of Nat. Hist.' vol. i. 1848, and plovers, in ' Birds of India,' vol. p. 45.5 ; see, also, on this subject, iii. pp. 617, 637, 709, 711. Also my 'Variation of Animals under iilyth in ' Land and Wat^.-,' 1867, Domestication,' vol. i. p. 236. p. 84, On the moulting of Para- " ggg Macgillivray, ' Hist. British disea, see an interesting article by Birds ' (vol. v. pp. 34, 70, and 223), Dr. W. Marshall, ' Archives Neerlan- on the moulting of the Anatida.. daises,' torn. vi. 1871. On the Vidua, with quotations from Waterton and 'Ibis,' vol. iii. 1861, p. 133. On Montagu. Also Yarrell, 'Hist, oi the Drongo-shrikes, Jerdon, ibid. British Birds,' vol. iii. p, 243. vol. i. p. 435. On the vernal moult 394 The Descent of Man. Paht IL exhibits its bright colours only when the winter is past, whilst our goldfinch, which exactly represents this bird in habits, and our siskin, which represents it still more closely in structure, undergo no such annual change. But a difference of this kind in the plumage of alUed species is not surprising, for with the common Linnet, which belongs to the same family, the crimson forehead and breast are displayed only during the summer in England, whilst in Madeira these colours are retained through- out the year.'* Disxjlay ly Male Birds of their Plumage. — Ornaments of all kinds, whether permanently or temporarily gained, are sedulously displayed by the males, and apparently serve to excite, attract, or fascinate the females. But the males will sometimes display their ornaments, when not in the presence of the females, as occasionally occurs with grouse at their balz-places, and as may be noticed with the peacock; this latter bird, however, evidently wishes for a spectator of some kind, and, as I have often seen, will shew off his finery before poultry, or even pigs.*^ All natu- ralists who have closely attended to the habits of birds, whether in a state of nature or under confinement, are unanimously of opinion that the males take delight in displaying their beauty. Audubon frequently speaks of the male as endeavouring in various ways to charm the female. Mr. Gould, after describing some peculiarities in a male humming-bird, says he has no doubt that it has thepowerof displaying them to the greatest advantage before the female. Dr. Jerdon insists that the beautiful plum- age of the male serves " to fascinate and attract the female." Mr. Bartlett, at the Zoological Gardens, expressed himself to mo in the strongest terms to the same effect. It must be a gi'and sight in the forests of India " to come " suddenly on twenty or thirty pea-fowl, the males displaying " their gorgeous trains, and strutting about in aU the pomp ot ' pride before the gratified females." The wild tui-key-cock .erects his glittering plumage, expands his finely-zoned tail and banned wing-feathers, and altogether, with his crimson and blue wattles, makes a superb, though to our eyes, grotesque On the pelican, see Sclater, in 1863, p. 230. 'Proc. Zool. Soc' 1868, p. 265. " See also ' Ornamental Poultrj,' On the American finches, see Au- by Rev. E. S. Dixon, 1848, p. 8. dsbon, ' Ornith. Biography,' vol. i. '° ' Birds of India,' introduct. vol. pp. 174, 221, and Jerdon, 'Birds of i. p. xiiv. ; on the peacock, vol. iii. India,' vol. li. p. 383. On the p. 507. See Gould's ' Introduction Fringilla cannahina of Madeira, Mr. to the Trochilidae,' 1861, pp. 15 and E, Vernon Harcourt, Ibis,' vol. v., 111. Chap. XIIT, Display by the Male. 395 appearance. Similar facts have already been given with respect to gi'otise of various kinds. Turning to another Order. The male Bupicdla crocea (fig. 50) is one of the most beautiful birds in the world, being of a splendid orange, with some of the feathers curiously truncated and plumose. The female is brown- ish-green, shaded with red, and has a much smaller crest. Sir B. Schombui-gk has described their courtship; he found one Eupicola crocea, male (T. W. Wood). of their meeting-places where ten males and two females were present. The space was from four to five feet in diameter, and appeared to have been cleared of every blade of grass' and smoothed as if by human hands. A male " was capering, to the apparent delight of several others. Now spreading its'wings, throwing up its head, or opening its tail liJve a fan ; now struttmg about with a hopping gait until tired, when it 396 The Descent of Man. Paht ii. " gabbled some kind of note, and was relieved by another. Thus " three of them successively took the field, and then, with self- " approbation, withdrew to rest." The Indians, in order to obtain their skins, wait at one of the meeting-places till the birds are eagerly engaged in dancing, and then are able to kill with their poisoned arrows four or five males, one after the other." With bu-ds of paradise a dozen or more fuU-plumaged males congregate in a tree to hold a dancing-party, as it is called by the natives : and here they fly about, raise their wings, elevate their exquisite plumes, and make them vibrate, and the whole tree seems, as Mr. Wallace remarks, to be filled wi:h waving plumes. When thus engaged, they become so absorbed that a skilful archer may shoot nearly the whole party. These birds, when kept in confinement in the Malay Archipelago, arc said to take much care in keeping their feathers clean; often spreading them out, examining them, and removing every specie of dirt. One observer, who kept several pairs alive, did not doubt that the display of the male was intended to please the female.*" The Gold and Amherst pheasants dui-ing their courtship not only expand and raise their splendid frills, but twist them, as I have myself seen, obliquely towards the female on whichever side she may be standing, obviously in order that a large surface may be displayed before her.*^ They likewise turn their beautiful tails and tail-coverts a little towards the same side. Mi'. Bartlett has observed a male Polyplectron (fig. 51) in the act of court- ship, and has shewn me a specimen stufied in the attitude then assumed. The tail and wing-feathers of this bii-d are ornamented with beautiful ocelli, like those on the peacock's train. Now when the peacock displays himself, he expands and erects his tail transversely to his body, for he stands in front of the female, and has to shew off, at the same time, his rich blue throat and breast. But the breast of the Polyplectron is obscurely coloured, and the ocelli are not confined to the tail- feathers. Consequently the Polyplecti'on does not stand in front of the female ; but he erects and expands his tail-feathers a little obbquely, lowering the expanded wing on the same side, and raising that on the opposite side. In this attitude the ocelli over the whole body are exposed at the same time before the ' Journal of R. Geograph. Soc' " jjj.^ -p. W. Wood has given vol. T.. 1840, p. 236. (' The Student,' April 1870, p. 115) ' Annals and Mag. of Nat. Hist.' a full account of this manner of vol. xiii. 1854, p. 157 ; also Wallace, display, by the Gold pheasant and ibid, vol, XX. 1857, p. 412, and 'The by tlie Japanese pheasant, Ph. Malay k rchipelago,' vo[. ii. 1869, p. versicolor ; and he calls it the lateral 252. Also Dr. Bennett, as quoted or one-sided display, by Brehm, 'Thierleben,' B. iii. s. 326. Cbaf. XIII. Display by the Male. 397 eyes of the admiring female in one grand bespangled expanse. To whichever side she may turn^ the expanded wings and the obliquely-held tail are turned towards her. The male Tragopan pheasant acts in nearly the same manner, for he raises the feathers of the body, though not the wing itself, on the side Fig- 51. Polyplectron chinquis, male (T. W. Wood). 398 The Descent of Man. PabtIL which is opposite to the female, and which would otherwise be concealed, so that nearly all the beautifully spotted feathers aro exhibited at the same time. The Argus pheasant aflfords a much more remarkable case. The immensely developed secondary wing-feathers are confined to the male ; and each is ornamented with a row of from twenty to twenty-three ocelli, above an inch in diameter. These feathera are also elegantly marked with oblique stripes and rows of spots of a dark colour, like those on the skin of a tiger and leopard combined. These beautiful ornaments are hidden until the male shews himself off before the female. He then erects his tail, and expands his wiog-feathers into a great, almost upright, circular fan or shield, which is carried in front of the body. The neck and head are held on one side, so that they are concealed by th& fan; but the bird in order to see the female, before whom he is displaying himself, sometimes pushes his head between two of the long wing-feathers (as Mr. Bartlett has seen), and then pre- sents a gi'otesque appearance. This must be a frequent habit with the bird in a state of nature, for Mr. Bartlett and his son on examining some perfect skins sent from the East, found a place- between two of the feathers, which was much frayed, as if the' head had here frequently been pushed through. Mr. Wood thinks that the male can also peep at the female on one side, beyond the margin of the fan. The ocelli on the wing-feathers are wonderful objects ; for they are so shaded that, as the Duke of Ai-gyll remarks,'" they stand out like balls lying loosely within sockets. When I looked at the specimen in the British Museum, which is mounted with the wings expanded and trailing downwards, I was however greatly disappointed, for the ocelli appeai-ed flat, or even concave. But Mr. Gould soon made the case clear to me, for he held the feathers erect, in the position in which they would naturally be displayed, and now, from the light shining on them from above, each ocellus at once resembled the ornament called a ball and socket. These feathers have been shewn to several artists, and all have expressed their admiration at the perfect shading. It may well be asked, could such artisticaUy shaded ornaments have been formed by means of sexual selection ? But it will be convenient to defer giving an answer to this question, until we treat in the next chapter of the principle of gi-adation. The foregoing remarks relate to the secondary wing-fcathers, but the primary wing-feathers, which in most galUnaceous bii'ds are uniformly coloured, are in the Argus pheasant equally wonderful. They are of a soft brown tint with numercus dai-k »» ' The Keign of Lnw,' 1867 p. 203. Chap. XIII. Display by the Male. 399 spots, each of which consists of two or three black dots with' a STirrounding dark zone. But the chief ornament is a space parallel to the dark-blue shaft, which in outline forms a perfect second feather lying within the true feather. This inner part is coloured of a lighter chesnut. and is thickly dotted with minutai Tlie Descent of Man. Pabt JUL. ■white ix)ints. I have shewn this feather to several persons, and many have admired it even more than the ball and socket feathers, and have declared that it was more like a work of art than of natm-e. Now these feathers are quite hidden on all ordinary occasions, but are fully displayed, together with the long secondary feathers, when they are all expanded together so as to form the great fan or shield. The case of the male Argus pheasant is eminently interesting, becaiise it affords good evidence that the most refined beauty may serve as a sexual charm, and for no other purpose. We must con- clude that this is the case, as the secondai-y and primary wing- feathers are not at all displayed, and the ball and socket orna- ments are not exhibited in full perfection, imtil the male assumes the attitude of courtship. The Ai-gus pheasant does not possess brilliant colours, so that his success in love appears to depend on the great size of his plumes, and on the elaboration of the most elegant patterns. Many will declare that it is utterly incredible that a female bii'd should be able to appreciate fine shading and exquisite patterns. It is tmdoubtedly a marvellous fact that she should possess this ahnost human degree of taste. He who thinks that he can safely gauge the discrimination and taste of the lower animals may deny that the female Argus pheasant can appreciate such refined beauty ; but he will then be compelled to admit that the extraordinary attitudes assumed by the male during the act of courtship, by which the wonderful beauty of his plumage is fully displayed, are pui-poseless ; and this is a conclusion which I for one will never admit. Although so many pheasants and alhed gallinaceous bu-ds carefully display their plumage before the females, it is remark- able, as Sir. Bartlett informs me, that this is not the case with the duU-coloured Eared and Cheer pheasants ( Crossoptilon auritum and Phasianus ivallichii); so that these birds seem conscious that they have little beauty to display. Mr. Bartlett has never seen the males of either of these species fighting together, though he has not had such good opportunities for observing the Cheer as the Eared pheasant. IMi'. Jenner Weii-, also, finds that all male birds with rich or strongly-characterised plumage are more quarrelsome than the dull-coloured species belonging to the same groups. The goldfinch, for instance, is far more pugnacious than the linnet, and the blackbu-d than the thrush. Those birds which undergo a seasonal change of plumage like- wise becomes much move pugnacious at the period when they are most gaily ornamented. No doubt the males of some obscurely-coloured birds fight desperately together, but ^ it appears that when sexual selection has been highly influential, Chap. XIII. Display by the Male. 401 and has given Lrighit colours to the males of any species, it has also very often given a strong tendency to pugnacity. We shall meet with nearly analogous cases when we ti-eat of mammals. On the other hand, with birds the power of song and brilliant colours have rarely been both acquired by the males of the same species ; but in this case, the advantage gained would have been the same, namely, success in charming the female. Nevertheless it must bo owned that the males of several brilUantly coloured birds have had theii' feathers specially modified for the sake ot producing instrumental musiC; though the beauty of this cannot be compared, at least according to our taste, with that of the vocal music of many songsters. We will now turn to male bii'ds which are not ornamented in any high degree, but which nevertheless display during their courtship whatever attractions they may possess. These cases are in some respects more cuiious than the foregoing, and have been but little noticed. I owe the following facts to Mr. Weir, who has long kept confined birds of many kinds, including all tho British Fringillidaj and Emberizidse. The facts have been selected from a large body of valuable notes kindly sent me by him. Tho buUfinch makes his advances in fi-ont of the female, and then pufis out his breast, so that many more of the crimson feathers are seen at once than otherwise would be the case. At the same time he twists and bows his black tail from side to side in a ludicrous manner. The male chaffinch also stands in front of the female, thus shewing his red breast and " blue beU," as the fanciers caU his head ; the wings at the same time being shghtly expanded, with the pure white bands on the shoulders thus rendered conspicuous. The common linnet distends his rosy breast, slightly expands his brown wings and tail, so as to make the best of them by exhibiting theu' white edguigs. We must, however, be cautious in concluding that the wings are spread out solely for display, as some birds do so whose wings are not beautiful. This is the case with the domestic cock, but it is always the wing on the side opposite to the female which i? expanded, and at the same time scraped on the ground. The male goldfinch behaves difierently from all other iinches : his wings are lieautiful, the shoulders being black, with the dark- tipped wing-feathers spotted with white and edged with golden yellow. When ho courts the female, he sways his body from side to side, and quickly turns his slightly expanded wings first to one side, then to the other, with a golden flashing effect. Mr. Weir informs me that no other British finch tru-ns thus from side to side during his courtship, not even the closely- allied male siskin, for he would not thus add to bis beauty. 2 D 402 The Descent of Man. Pabt II. Most of the British Buntings are plain coloured birds ; but in the spring the feathers on the head of the male reed-bunting (^Eriiberiza schcenicuhcs) acquii-e a fine black colour by the abrasion of the dusky tips; and these are erected during the act of courtship. Mr. Weu- has kept two species of Amadina from Australia : the A. castanotis is a very small and chastely coloui-ed finch, with a dark tail, white rump, and jet-black upper taU-coverts, each of the latter being marked with three large con- spicuous oval spots of white.^* This species, When courting the female, slightly spreads out and vibrates these parti-coloured tail-coverts in a very pecuhar manner. The male Amadina Latliami behaves very differently, exhibiting before the female Ms brilliantly spotted breast, scarlet rump, and scarlet upper tail-coverts. I may here add from Dr. Jerdon that the Indian bulbul (^Pycnonotus lixmorrhoiis) has its under tail-coverts of a <,'rimson colour, and these, it might be thought, coiild never be well exhibited ; but the bird " when excited often spreads them " out laterally, so that they can be seen even from above." The crimson imder tan-coveris of some other birds, as with one of the woodpeckers, Ficus major, can be seen without any such display. The common pigeon has ii-idescent feathers on the breast, and every one must have seen how the male iuflates his breast whilst courting the female, thus shewing them off to the best advantage. One of the beautifid bronze-winged pigeons of Australia {Ocyplia'ps lophotes) behaves, as described to me by Mr. "Weir, very differently: the male, whilst standing before the female, lowers his head almost to the ground, spreads out and raises his tail, and half expands his wings. He then alternately and slowly raises and depresses his body, so that the iridescent metallic feathers are all seen at once, and glitter in the sun. Sufficient facts have now been given to shew with what care male birds display their various charms, and this they do with the utmost skill. Whilst preening their feathers, they have frequent opportunities for admiring themselves, and of studying how best to exhibit their beauty. But as all the males of the same species display themselves in exactly the same manner, it appears that actions, at first perhaps intentional, have become instinctive. If so, we ought not to accuse bii-ds of conscious vanity ; yet when we see a peacock strutting about, with ex- panded and quivering tail-feathers, he seems the very emblem of pride and vanity. •1 For the description of these p. 417. ibirds, see Gould's ' Handboolv to the 'Birds of India,' vol. ii. p. 96. BirdB of Australia,' vol. i. 1865, Ohap. XUI. Display by the Male. 403 The vai-ious ornaments possessed by the males are certainly of the highest importance to them, for in some cases they have been acquii-ed at the expense of greatly impeded powers of flight or of running. The African night-jar (Cosmetornis), which during the pairing-season has one of its primary wing-feathers developed into a streamer of very great length, is thereby much retarded in its flight, although at other times remarkable for its swiftness. The " unwieldy size " of the secondary wing-feathers of the male Ai-gus pheasant are said " almost entirely to deprive *" the bird of flight." The fine plumes of male birds of paradise trouble them during a high wind. The extremely long tail- feathers of the male widow-bu-ds (Vidua) of Southern Afi-ica render " their flight heavy ; " but as soon as these are cast off they fly as well as the females. As birds always breed when food is abundant, the males probably do not suffer much in- convenience in seai'ching for food from their impeded powers of movement ; but there can hardly be a doubt that they must be much more hable to be struck down by birds of prey. Nor can we doubt that the long train of the peacock and the long tail and wing-feathers of the Ai'gus pheasant must render them an easier prey to any prowling tiger-cat, than would otherwise be the case. Even the bright colours of many male bu-ds cannot fail to make them conspicuous to their enemies of all kinds. Hence, as Mr. Gould has remarked, it probably is that such birds are generally of a shy disposition, as if conscious that their beauty was a source of danger, and are much more difficult to discover or approach, than the sombre coloui'ed and comj)a- ratively tame females, or than the young and as yet unadorned males.^* It is a more curious fact that the males of some birds which are provided with special weapons for battle, and which in a state of nature are so pugnacious that they often kill each other, suffer from possessing certain ornaments. Cock-fight€rs trim the hackles and cut oif the combs and giUs of then- cocks ; and the birds are then said to be dubbed. An undubbed bu-d, as Mr. Tegetmeier insists, " is at a fearful disadvantage ; the comb and " gills offer an easy hold to his adversary's beak, and as a cock " always strikes where ho holds, when once he has seized his foe. On the Cosmetornis, see Living- widow-bird, Barrow's ' Travels m stone's ' Expedition to the Zambesi,' Africa,' vol. i. p. 243, and ' Ibis,' 1865, p. 0(3. On the Argus pheasant, vol. iii. 1861, p. 133. Mr. Gould, Jardine's 'Nat. Hist. Lib.: Birds,' on the shyness of male birds, ' Hand- vol, xiv. p. 167. On Birds of book to Birds of Australia,' vol. i. Paradise, Lesson, quoted bj Brehm, 1865, pp. 210 457 ' Thierleben,' B. iii. s. 325. On the 2 D 2 404 The Descent of Man. " he has him entirely in his power. Even supposing that the " bird is not killed, the loss of blood sufiered by an undubbed " cock is much greater than that sustained by one that has been " trimmed." Young turkey-cocks in fighting always seize hold of each other's wattles ; and I presume that the old birds fight in the same manner. It may perhaps be objected that the comb and wattles are not ornamental, and cannot be of service to the birds in this way ; but even to om- eyes, the beauty of the glossy black Spanish cock is much enhanced by his white face and crimson comb ; and no one who has ever seen the splendid blue wattles of the male Tragopan pheasant, distended in courtship, can for a moment doubt that beauty is the object gained. From the foregoing facts we clearly see that the plumes and other ornaments of the males must be of the highest importance t(v them ; and we fiu'ther see that beauty is even sometimes more important than success in battle. CHAPTEE XIV. Birds — con tinned. Choice exerted by the female — Length of courtship — Unpaired birds — Mental qualities and taste for the beautiful — Preference or antipathy shewn by the female for particular males — Variability of birds — Varia- tions sometimes abrupt — Laws of variation — Formation of ocelli — Gradations of character — Case of Peacock, Argus pheasant, and Urosticte. When the sexes differ in beauty, or in the power of singing, or in producing what I have called instrumental music, it is almost invariably the male who surpasses the female. These qualities, as we have just seen, are evidently of high importance to the male. When they are gained for only a part of the year it is always before the breeding-season. It is the male alone who elaborately displays his varied attractions, and often performs strange antics on the ground or in the air, in the presence of the female. Each male drives away, or if he can, kills his rivals. Hence we may conclude, that it is the object Of the male to induce the female to pair with him, and for this purpose he tries to ex- cite or charm her in various ways ; and this is the opinion of all those who have carefully studied the habits of living birds. But there remains a question which has an all-important bearing on sexual selection, namely, does every male of the same species excite and attract the female equally? Or does she exert a choice, and prefer certain males ? This latter question can be answered in the affirmative by much direct and indu-ect evidence. It is far Tegetmeier, ' The Poultry Book,' 1866, p. 139. Chap. XIY. Length of Courtship. 405 more difficult to decide what qualities determine the choice of tho females ; but here again we have some direct and indirect evi- dence that it 13 to a large extent the external attractions of the male; though no doubt his vigour, courage, and other mental qualities come into play. We will begin with the indirect evidence. Length of Courtship— The lengthened period duriag which both sexes of certain birds meet day after day at an appointed place probably depends partly on the courtship being a pro- longed affair, and partly on reiteration in the act of pairing. Thus in Germany and -Scandinavia the balzing or leks of the black-cocks last from the middle of March, all through April into May. As many as forty or fifty, or even more birds con- gregate at the leks; and the same place is often frequented during successive years. The lek of the capercailzie lasts from the end of March to the middle or even end of May. In North America "the partridge dances" of the Tetrao phasianellus " last for a month or more." Other kinds of grouse, both in North America and Eastern Siberia,^ follow nearly the same habits. The fowlers discover the hillocks where the ruffs con- gregate by the grass being ti-ampled bare, and this shews that the same spot is long frequented. The Indians of Guiana are well acquainted with the cleared arenas, where they expect to find the beautiful cocks of the Eock ; and the natives of New Guinea know the trees where from ten to twenty male birds of paradise in full plumage congregate. In this latter case it is not expressly stated that the females meet on the same trees, but the hunters, if not specially asked, would probably not mention their presence, as their skins are valueless. Small parties of an African weaver (Ploceus) congregate, during the breeding-season, and perform for hours their graceful evolutions. Large numbers of the Solitary snipe (^Scolopax major) assemble during dusk in a morass ; and the same place is frequented for the same purpose during successive years ; here they may be seen running about " like so many large rats," puffing out their feathers, flapping their wings, and uttering the strangest cries.^ ' Nordman describes (' Bull. Soc. Imp. des Nat. Moscou,' 1861, torn, xxxiv. p. 264) the balzen of Tetrao urcgalloides in Amur Land. Ho estimated the number of birds assembled at above a hundred, not counting the females, which lie hid in the surrounding bushes. The noises uttered differ from those of T. urogallus. * With respect to the assemblages of the above named grouse see Brehm, ' Thierleben,' B. iv. s. 350 ; also L. Lloyd, ' Game Birds of Sweden,' 1867, pp. 19, 78. Richard- son, ' Fauna Bor. Americana,' Birds, p. 362. References in regard to the assemblages of other birds have already been given. On Paradises see Wallace, in ' Annals and Mag, of Nat. Hist.' vol. xx. 1857, p. 412, Ou the snipe, Lloyd, ibid. p. 221. 406 The Descent of Man. Part IL Some of the above birds, — the black-cock, capercailzie, pheasant-grouse, ruff. Solitary snipe, and perhaps others, — are, as is believed, polygamists. With such birds it might have been thought that the stronger males would simply have driven away the weaker, and then at once have taken possession of as many females as possible ; but if it be indispensable for the male to excite or please the female, we can understand the length of the courtship and the congregation of so many individuals of both sexes at the same spot. Certaia strictly monogamous species likewise hold nuptial assemblages ; this seems to be the case in Scandinavia Avith one of the ptarmigans, and theii' leks last from the middle of March to the middle of May. In Australia the lyre-bird {Menura superba) forms " small round hillocks," and the M. Alherti scratches for itself shallow holes, or, as they are called by the natives, corrdborying places, where it is believed both sexes assemble. The meetings of the M. superha are some- times very large ; and an account has lately been published ' by a traveller, who heard in a vaUey beneath him, thickly covered with scrub, "a din which completely astonished" him; on crawling onwards he beheld to his amazement about one hun- dred and fifty of the magnificent lyre-cocks, " ranged in order of " battle, and fighting with indescribable fury." The bowers of the Bower-birds are the resort of both sexes during the breeding- season ; and " here the males meet and contend with each other " for the favours of the female, and here the latter assemble and " coquet with the males." With two of the genera, the same bower is resorted to during many years.* The common magpie {Corvus pica, Linn.), as I have been in- formed by the Eev. W. Darwin Fox, used to assemble from all parts of Delamere Forest, in order to celebrate the " great mag- pie marriage." Some years ago these birds abounded in extra- ordinary numbers, so that a gamekeeper killed in one morning nineteen males, and another killed by a single shot seven bii-ds at roost together. They then had the habit of assembling very early in the spring at particular spots, where they could be seen in flocks, chattering, sometimes fighting, busthug and flying about the trees. The whole affair was evidently considered by the birds as one of the highest importance. Shortly after the meeting they aU separated, and were then observed by Mr. Fox and others to be paired for the season. In any district in which a species does not exist m large numbers, great assemblages cannot, of course, be held, and the same species may have 8 Quoted by Mr. T. W. Wood in of Australia,' vol. i. pp. 300, 308, the ' Student,' April, 1870, p. 125. 448, 451. On the ptarmigan, abore ♦ Gould, ' Handbook to the Birds alluded to, see Lloyd, ibid. p. 129. CJHAP. XIV. Unpaired Birds. 407 different habits in different countries. For instance, I have heard of only one instance, from llr. Wedderburn, of a regular assemblage of black game in Scotland, yet these assemblages are so well known in Germany and Scandinavia that they have received special names. Unpaired Birds. — From the facts now given, we may conclude that the courtship of birds, belonging to widely different groups, is often a prolonged, dehcate, and troublesome affair. There is even reason to suspect, improbable as this will at first appear, that some males and females of the same species, inhabiting the same district, do not always please each other, and consequently do not pair. Many accounts have been published of either the male or female of a pair having been shot, and quickly replaced by another. This has been observed more frequently with the magpie than with any other bird, owing perhaps to its conspic- uous appearance and nest. The illustrious Jenner states that in Wiltshire one of a pair was daily shot no less than seven times successively, "but all to no purpose, for the remaining " magpie soon found another mate " ; and the last pair reared their young. A new partner is generally foimd on the succeed- ing day ; but Mr. Thompson gives the case of one being replaced on the evening of the same day. Even after the eggs are hatched, if one of the old bii-ds is destroyed a mate will often be found ; this occurred after an interval of two days, in a case recently observed by one of Sir J. Lubbock's keepers.*^ The first and most obvious conjecture is that male magpies must be much more numerous than females ; and that in the above cases, as well as in many others which could be given, the males alone had been killed. This apparently holds good in some instances, for the game- keepers in Delamere Forest assured Mr. Fox that the magpies and carrion-crows which they formerly killed in succession in large numbers near their nests, were all males ; and they accounted for this fact by the males being easily lolled whilst bringing food to the sitting females. Macgillivray, however, gives, on the authority of an excellent observer, an instance of three magpies successively killed on the same nest, which were all females ; and another case of sis magpies successively killed whilst sitting on the same eggs, which renders it probable that most of them were females ; though, as I hear from Mr. Fox, the male will sit on the eggs when the female is killed. Sir J. Lubbock's gamekeeper has repeatedly shot, but how often he could not say, one of a pair of ^\ys (Oarrulus glandarius), = On magpies, Jenner, in 'Phil. p. 570. Thompson, in 'Annals and Transact.' 1824, p. 21. Macgil- Mag. of Nat. Hist.' vol. riii, 1 842, uvray, ' Hist. Britisk Birds,' vol. i. p. 494. 408 The Descent of Man. Parz JI. and has never failed shortly afterwards to find the survivor re-matched. Mr. Fox, Mr. P. Bond, and others have shot one of a pair of carrion-crows (Corvus corone), but the nest was soon again tenanted by a pair. These birds are rather common; but the peregrine-falcon (Falco peregrinun) is rare, yet Mr. Thompson states that in Ireland " if either an old male or female be killed " in the breeding-season (not an uncommon circumstance), " another mate is found within a very few days, so that the " eyries, notwithstanding such casualties, are sure to tui-n out " their complement of young." Mr. Jenner Weir has known the same thing with the peregrine-falcons at Beachy Head. The same observer informs me that three kestrels ( Falco tinnunculus), all males, were killed one after the other whilst attending the same nest ; two of these were in mature plumage, but the third was in the plumage of the previous year. Even with the rare golden eagle {Aquila chrysaetos), Mr. Bii-kbeck was assured by a trustworthy gamekeeper in Scotland, that if one is killed, another is soon found. So with the white owl (Strix flammea), " the " survivor readily found a mate, and the mischief went on." White of Selborne, who gives the case of the owl, adds that he knew a man, who from believing that partridges when paired were distm-bed by the males fighting, used to shoot them ; and though he had widowed the same female several times, she always soon found a fresh partner. This same naturalist ordered the sparrows, which deprived the house-martins of their nests, to be shot ; but the one which was left, " be it cock or hen, " presently procured a mate, and so for several times following." I could add analogous cases relating to the chaffinch, nightingale, and redstart. With respect to the latter bird {Fhcenicura ruti- cilla), a writer expresses much sm-prise how the sitting female could so soon have given effectual notice that she was a widow, for the species was not common in the neighbourhood. Mi-. Jenner Weir has mentioned to me a nearly similar case; at Blackheath he never sees or hears the note of the wild bullfinch, yet when one of his caged males has died, a wild one in the course of a few days has generally come and perched near the widowed female, whose call-note is not loud. I will give only one other fact, on the authority of this same observer ; one of a pair of starUngs (^Sturnus vulgaris) was shot in the morning ; by noon a new mate was found ; this was again shot, but befdre night the pair was complete ; so that the disconsolate widow or widower was thrice consoled during the same day. Mr. Englcheart also informs me that he used dui-ing several years to shoot one of a ixair of starlings which built in a hole in a house at Blackheath ; but the loss was always immediately repaired. During one Chap. XI 7 Unpaired Birds. 409 season he kept an account, and found that he had shot thirty-five birds from the same nest; these consisted of both males and females, but in what proportion he could not say : nevertheless/ iifter all this destruction, a brood was reared.^ These facts well deserve attention. How is it that there are birds enough, ready to replace immediately a lost mate of either sex ? Magpies, jays, carrion-crows, partridges, and some other birds, are always seen during the spring in paii's, and never by themselves ; and these offer at first sight the most perplexing cases. But birds of the same sex, although of coui-se not truly paired, sometimes Uve ia pairs or in small parties, as is known to be the case with pigeons and partridges. Birds also sometimes live in triplets, as has been observed with starlings, carrion-crows, parrots, and partridges. "With partridges two females have been known to hve with one male, and two males with one female. In all such cases it is probable that the union would be easily broken ; and one of the three would readily pair with a widow or widower. The males of certaia birds may occasionally be heard pouring forth their love-song long after the proper time, shew- ing that they have either lost or never gained a mate. Death from accident or disease of one of a pair, would leave the other free and single ; and there is reason to believe that feniale birds during the breeding-season are especially liable to prematui-e death. Again, birds whicli have had their nests destroyed, or barren pairs, or retarded individuals, would easily be induced to desert their mates, and would probably be glad to take what share they could of the pleasm-es and duties of rearing offspring although not their own.'^ Such contingencies as these probably explain most of the foregoing cases.* Kevertheless, it is a strange * On the peregrine falcon see 1824. In regard to birds living in Thompson, ' Nat. Hist, of Ireland, triplets, I owe to Mr. Jenner Weir Birds,' vol. 1. 1849, p. 39. On owls, the cases of the starlings and parrots, sparrows, and partridges, see White, and to Mr. Fox, of partridges ; on 'Nat. Hist, of Selborne,' edit, of carrion-crows, see the ' Field,' 1868 1825, vol. i. p. 139. OnthePhoeni- p. 415. On various male birds cura, see Loudon's ' Mag. of Nat. singing after the proper period, see Hist.' vol. vii. 1834, p. 245. Brehm Eev. L. Jenyns, ' Observations in (' Thierleben,' B. iv. s. 991) also Natural History,' 1846, p. 87. .alludes to cases of birds thrice mated « The following case has been during the same day. given (' The Times,' Aug. 6th, ISoS) ' See White (' Nat. Hist, of Sel- by the Rev. F. 0. Moms on the borne,' 1825, vol. i. p. 140) on the authority of the Hon. and' Rev 0 existence, early in the season, of W. Forester. "The gamekeeper small coveys of male partridges, of " here found a hawk's nest this year, which fact I have heard other in- " with five youno- ones on it Ha stances. See Jenner, on the retarded "took four and" killed them, but state of the generative organs in " left one with its winces clipped a» certain biris, in ' Phil. Transact.' « a decoy to destroy the old ones by. 410 The Descent of Man. Paet IL fact that within the same district, during the height of the breeding-season, there should be so many males and females always ready to repair the loss of a mated bird. Why do not such spare birds immediately pair together ? Have we not some reason to suspect, and the suspicion has occurred to Mr. Jenner Weir, that as the courtship of birds appears to be in many cases prolonged and tedious, so it occasionally happens that certain males and females do not succeed during the proper season, in exciting each other's love, and consequently do not pair ? This suspicion will appear somewhat less improbable after we have seen what strong antipathies and preferences female birds occasionally evince towards particular males. Mental Qualities of Birds, and their Taste for the Beautiful. — Before we further discuss the question whether the females select the more attractive males or accept the first whom they may encounter, it will be advisable briefly to consider the mental powers of birds. Their reason is generally, and perhaps justly, ranked as low ; yet some facts could be given ^ leading to an opposite conclusion. Low powers of reasoning, however, are compatible, as we see with mankind, with strong affections, acute perception, and a taste for the beautiful ; and it is with these latter qualities that we are here concerned. It has often been said that parrots become so deeply attached to each other that when one dies the other pines for a long time; but Mr. Jenner Weir thinks that with most birds the strength of their affection has been much exaggerated. Nevertheless when one of a pair in a state of nature has been shot, the survivor has been heard for days afterwards uttering a plaintive call ; and Mr. St. John, gives yarious fkcts proving the attachment of mated birds.^" " They were both shot next day, in " the act of feeding the young one, " and the keeper thought it was " done with. The next day he came " again and found two other chari- " table hawks, who had come with " an adopted feeling to succour the " orphan. These two he killed, and " then left the nest. On returning " afterwards he found two more " charitable individuals on the same " errand of mercy. One of these he " killed ; the other he also shot, "but could not find. No more "came on the like fruitless errand." • I am indebted to Prof. Newton for the following passage from Mr. Adam's 'Travels of a Natiiralist,' 1870, p. 278. Speaking of Japanese nut-hatches in confinement he says : " Instead of the more yielding fruit " of the yew, which is the usual " food of the nut-hatch of Japan, at " one time I substituted hard hazel- " nuts. As the bird was unable " to crack them, he placed them one " by one in his water-glass, evidently " with the notion that they would " in time become softei' — an interest- " ing proof of intelligence on the " part of these birds." «A Tour in Sutherlandshire, vol. i. 1849, p. 185. Dr. Buller says ('Birds of New Zealand,' 1872, p. 56) that a male King Lory was killed ; and the female " fretted and Chap. XIV. Mental Qualities. 411 Mr. Bennett relates" that in China after a drake of the beautiful mandailn Teal had been stolen, the duck remained disconsolate, though sedulously courted by another mandarin drake, who dis- played before her all his charms. After an interval of thi'ee weeks the stolen drake was recovered, and instantly the pair recognised each other with extreme joy. On the other hand starlings, as we have seen, may be consoled thrice in the same day for the loss of their mates. Pigeons have such excellent local memories, that they have been known to return to their former homes after an interval of nine months, yet, as I hear from Mr. Harrison "Weir, if a pair which naturally would remain mated for life be separated for a few weeks during the winter, and afterwards matched with other birds, the two, when brought together again, rarely, if ever, recognise each other. Birds sometimes exhibit benevolent feelings*, they will feed the deserted young ones even of distinct species, but this perhaps ought to be considered as a mistaken instinct. They will feed, as shewn in an earher part of this work, adult birds of their own species which have become blind. Mi*. Buxton gives a curious account of a parrot which took care of a frost-bitten and crippled' bird of a distinct species, cleansed her feathers, and defended her from the attacks of the other parrots which roamed freely about his garden. It is a still more curious fact tliat these birds apparently evince some sympathy for the pleasures of their feUows. When a pair of cockatoos made a nest in an acacia tree, " it was ridiculoiis to see the extravagant interest taken in " the matter by the others of the same species." These parrots, also, evinced unbounded curiosity, and clearly had " the idea of " property and possession." They have good memories, for in the Zoological Gardens they have plainly recognised their former masters after an interval of some months. Birds possess acute powers of observation. Every mated bird, of course, recognises its fellow. Audubon states that a certain number of mocking-tkrushes (Mimus polygloUus) remain all the year round in Louisiana, whilst others migx-ate to the Eastern States ; these latter, on their return, are instantly recognised, and always attacked, by their southern brethren. Birds under confinement distinguish different persons, as is proved by the strong and permanent antipathy or affection which they shew, without any apparent cause, towards certain individuals, i moped, refused her food, and died " of a broken heart." " 'Wiindenngs in New Sou/,h Vale?,' vol. ii. 1834, p. 62. ' Acfilimatization of Parrots, by C. Buxton, M.P. 'Annals anil- Mag. of Nat. Hist.' Nov. 1868, p,, 381. 412 The Descent of Man. PAr.T 11. have heard of numerous instances with jays, partridges, canaries, and especially bullfinches. Mr. Hussey has described in how extraordinary a manner a tamed partridge recognised everybody ; and its likes and dislikes were very strong. This bird seemed " fond of gay colours, and no new gown or cap could be put on " without catching his attention." " Mr. Hewitt has described the habits of some ducks (recently descended from wild birds'*, which, at the approach of a strange dog or cat, would rush headlong into the water, and exhaust themselves in their attempts to escape ; but they knew Mr. Hewitt's own dogs and cats so well, that they would lie down and bask in the sun close to them. They always moved away from a strange man, and so they would from the lady who attended them, if she made any gi-eat change in her dress. Audubon relates that he reared and tamed a wild tui'key which always ran away from any strange dog; this bird escaped into the woods, and some days afterwards Audubon saw, as he thought, a wild turkey, and made his dog chase it ; but to his astonishment, the bird did not run away, and the dog, when he came up, did not attack the bird, for they mutually recognised each other as old friends." Ml". Jenner Weir is convinced that bu-ds pay particular atten- tion to the colour's of other bii'ds, sometimes out of jealousy, and sometimes as a sign of kinship. Thus he turned a reed-bunting {Emberiza schceniculus), which had acquired its black head-di"ess, into his aviary, and the new-comer was not noticed by any bird, except by a bullfinch, which is likewise black-headed. This bullfinch was a very quiet bii-d, and had never before quarrelled with any of its comrades, including another reed-bunting, which had not as yet become black-headed : but the reed-bunting with a black head was so iinmercifully treated, that it had to be removed. Spiza cyanea, during the breeding-season, is of a bright blue colour ; and though generally peaceable, it attacked S. ciris, which has only the head blue, and completely scalped the unfortunate bird. Mi'. Weir was also obliged to turn out a robin, as it fiercely attacked all the birds in his aviary with any red in their plumage, but no other kinds ; it actually killed a red-breasted crossbill, and nearly killed a goldfinch. On the other hand, he has observed that some birds, when first intro- duced, fly towards the species which resemble them most in colour, and settle by their sides. As male birds display their fine plumage and other ornaments " 'The Zoologist,' 1847-1848, p. p. 39. Auduton on the wild tarkey, 3G02. 'Ornith. Biography,' vol. i. p- l"^- 1* Hewitt on wild ducks, 'Journal On the mocking-thrush, ibid. vol. L of Horticulture,' Jan. 13, 18G3, p. 110. Chap. XIV. T aste for the Beautiftil. 413 ■with so rmicli care before the females, it is obviously p-obable that these appreciate the beauty of their suitors. It is, however, clifBcult to obtain direct evidence of their capacity to appreciate beauty. When birds gaze at themselves in a looking-glass (of which many instances have been recorded) we cannot feel sure that it is not from jealousy of a supposed rival, though this is not the conclusion of some observers. In other cases it is difficult to distinguish between mere curiosity and admiration. It is per- haps the former feeling which, as stated by Lord Lilford,'^ attracts the ruff towards any bright object, so that, in the Ionian Islands, " it will dart down to a bright-coloured handkerchief, regardless " of repeated shots." The common lark is drawn down from the sky, and is caught in large numbers, by a small mirror made to move and glitter in the sun. Is it admiration or cui'iosity which leads the magpie, raven, and some other birds to steal and secrete bright objects, such as silver articles or jewels ? Mr. Gould states that certain humming-birds decorate the outsides of their nests " with the utmost taste ; they instinctively " fasten thereon beautiful pieces of flat lichen, the larger pieces " in the middle, and the smaller on the part attached to the " branch. Now and then a pretty feather is intertwined or " fastened to the outer sides, the stem being always so placed, " that the feather stands out beyond the surface." The best evidence, however, of a taste for the beautiful is afforded by the three genera of Australian bower-birds akeady mentioned. Their bowers (see fig. 46, p. 382), where the sexes congregate and play strange antics, are variously constructed, but what most concerns us is, that they are decorated by the several species in a dijBFerent manner. The Satin bower-bird collects gaily-coloured articles, such as the blue tail-feathers of parrakeets, bleached bones and shells, which it sticks between the twigs, or arranges at the entrance. Mr. Gould found in one bower a neatly- worked stone tomahawk and a slip of blue cotton, evidently procured from a native encampment. These objects are continually re-arranged, and carried about by the birds whilst at play. The bower of the Spotted bower-bird " is beautifully Imed with tall grasses, so " disposed that the heads nearly meet, and the decorations are " very profuse." Eound stones are used to keep the grass-stems in their proper places, and to make divergent paths leading to the bower. The stones and shells are often brought from a great distance. The Ecgent bird, as described by Mr. Ramsay, ornaments its short bower with bleached land-shells belonging to five or six species, and with " berries of various colours, blue, red, " and black, which give it when fresh, a very pretty appearance, The 'Ibis,' vol. ii. I860, p. 344. 414 The Descent of Man. Pabt II. " Besides these there were sevei-al newly-picked leaves and " young shoots of a pinkish coloui-, the whole shewing a de- " cided taste for the beautiful." Well may Mr. Gould say, that " these highly decorated halls of assembly must be regarded as " the most wonderful mstances of biid-architecture yet dis- " covered ;" and the taste, as we see, of the several species certainly differs.'^ Freference for 'particular Males hy the Females. — Having made these preliminary remarks on the discrimination and taste of birds, I will give all the facts known to me, which bear on the preference shewn by the female for particular males. It is certain that distinct species of birds occasionally pair ia a state of nature and produce hybrids. Many instances could be given: thus Macgillivray relates how a male blackbird and female thrush "fell in love with each other," and produced offspring." Several years ago eighteen cases had been recorded of the occurrence in Great Britain of hybrids between the black grouse and pheasant ; but most of these cases may perhaps be accounted for by solitary birds not finding- one of their own species to pair with. With other birds, as Mr. Jenner Weir has reason to beheve, hybrids are sometimes the result of the casual intercourse of birds buUding in close proximity. But these remarks do not apply to the many recorded instances of tamed or domestic bu-ds, belonging to distinct species, which have become absolutely fascinated with each other, although living with their own species. Thus Waterton" states that out of a flock of twenty-three Canada geese, a female paired with a solitary Bernicle gander, although so different in appearance and size; and they produced hybrid offspring. A male widgeon {Mareca penelope), hving with females of the same species, has been known to pair with a pintail duck, Querquedula acuta. Lloyd describes the remarkable attachment between a shield- drake {Tadorna vulpanser) and a common duck. Many ad- '° On the ornamented nests of humming-birds, Gould, ' Introduc- tion to the Trochilidae,' 1861, p. 19. On the bower-birds, Gould, ' Hand- book to the Birds of Australia,' 1865, vol. i. pp. 444-461. Ramsay, in the ' Ibis,' 1867, p, 456. ' Hist, of British Birds,' vol. ii. p. 92. " 'Zoologist,' 1853-1854, p. 3946. ^' Waterton, 'Essays on Nat. Hist.' 2ud series, pp. 42 and 117. For the following statements, see on the widgeon, Loudon's ' Mag. of Nat. Hist.' vol. i.x. p. 616; L. Lloyd, 'Scan- dinavian Adventures,' vol. i. 1854, p. 452. Dixon, ' Ornamental and Domestic Poultry,' p. 137; Hewitt, in 'Journal of Horticulture,' Jan. 13, 1863, p. 40; Bechstein, 'Stu- benvogel,' 1840, s. 230. Mr. J. Jenner Weir has lately given me an analogous case with ducks of two species. Chap. XIV. Preference by the Female. 415 ditional instances could be given ; and the Eev. E. S. Dixon remarks that " those who have kept many different species of geese together, well know what unaccountable attachments " they are frequently forming, and that they are quite as likely " to pair and rear young with individuals of a race (species) " apparently the most alien to themselves, as with their own " stock." The Eev. W. D. Fox informs me that he possessed at the same time a pair of Chinese geese {^An&er cygnoides), and a common gander with three geese. The two lots kept quite separate, until the Chinese gander seduced one of the common geese to live with him. Moreover, of the young birds hatched from the eggs of the common geese, only four were pure, the other eighteen proving hybrids ; so that the Chinese gander seems to have had prepotent charms over the common gander. I will give only one other case ; Mi'. Hewitt states that a wHd duck, reared in captivity, " after breeding a couple of seasons with her " own mallard, at once shook him off on my placing a male " Pintail on the water. It was evidently a case of love at first " sight, for she swam about the new-comer caressingly, though " he appeared evidently alarmed and averse to her overtures of " affection. From that hour she forgot her old partner. Winter " passed by, and the next spring the Pintail seemed to have " become a convert to her blandishments, for they nested and " produced seven or eight young ones." What the charm may have been in these several cases, beyond mere novelty, we cannot even conjecture. Colour, however, sometimes comes into play ; for in order to raise hybrids from the siskin {Fringilla spinus) and the canary, it is much the best plan, according to Bechstein, to place birds of the same tint together. Mi-. Jenner Weir tui-ned a female canary into his aviary, where there were male linnets, goldfinches, siskins, greenfinches, chaffinches, and other birds, in order to see which she would choose; but there never was any doubt, and the greenfinch carried the day. They paired and produced hybrid offspring. The fact of the female preferring to pair with one male rather than with another of the same species, is not so likely to excite attention, as when this occurs, as we have just seen, between distinct species. The former cases can best be observed with domesticated or confined bu-ds ; but these are often pampered by high feeding, and sometimes have their instincts vitiated to an extreme degree. Of this latter fact I could give sufficient proofs with pigeons, and especially mth fowls, but they cannot be here related. Vitiated instincts may also account for some 4i6 TJie Descent of Man. Part H of the hybrid unions above mentioned ; but in many of those cases the birds were allowed to range freely over large ponds, and there is no reason to suppose that they were unnaturally stimulated by high feeding. With respect to birds in a state of nature, the first and most obvious supposition which will occur to every one is that the female at the proper season accepts the first male whom she may encounter ; but she has at least the opportunity for exerting a choice, as she is almost invariably pursued by many males. Audubon — and we must remember that he spent a long life in prowling about the forests of the United States and observing the birds — does not doubt that the female deUberately chooses her mate ; thus, speaking of a woodpecker, he says the hen is followed by half-a-dozen gay suitors, who continue performing strange antics, " until a marked preference is shewn for one." The female of the red-winged starling (Agelseus phceniceus) is likewise pursued by several males, " until, becoming fatigued, " she alights, receives their addresses, and soon makes a choice." He describes also how several male night-jars repeatedly plunge through the air with astonishing rapidity, suddenly turning, and thus making a singular noise ; " but no sooner has the female " made her choice, than the other males are driven away." With one of the vultures ( Calhartes aura) of the United States, parties of eight, ten, or more males and females assemble on fallen logs, " exhibiting the strongest desire to please mutually," and after many caresses, each male leads off his partner on the wing. Audubon likewise carefully observed the wild flocks of Canada geese {Anser canadensis), and gives a graphic description of their love-antics; he says that the birds which had been previously mated "renewed their courtship as early as the " month of January, while the others would be contending or " coquetting for hoiu's every day, until all seemed satisfied with " the choice they had made, after which, although they re- " mained together, any person could easily perceive that they " were careful to keep in pairs. I have observed also that the " older the birds, the shorter were the preliminaries of their " courtship. The bachelors and old maids, whether in regret, " or not caring to be disturbed by the bustle, quietly moved " aside and lay down at some distance from the rest."^" Many similar statements with respect to other birds could be cited from this same observer. Turning now to domesticated and confined birds, I will commence by giving what little I have learnt respecting the 2» Audubon * Ornitholog. Biography, vol. i. pp. 191, 349 ; vol. ii. pp. 42, 275 ; vol. iii. p. 2. Chap. XIV. Preference by the Female. 417 courtsliip of fowls. I have received long letters on tMs subject from Messrs. Hewitt and Tegetmeier, and almost an esBay from the late Mr. Brent. It will be admitted by every one that these gentlemen, so well known from their published works, are careful and experienced observers. They do not believe that the females prefer certain males on account of the beauty of their plumage ; but some allowance must be made for the arti- ficial state under which these bu-ds have long been kept. Mi-. Tegetmeier is convinced that a game-cock, though disfigured by being dubbed and with his hackles trimmed, would be accepted as readily as a male retaining all his natural ornaments. Mr. Brent, however, admits that the beauty of the male probably aids in exciting the female ; and her acquiescence is necessary. j\Ir. Hewitt is convinced that the union is by no means left to mere chance, for the female almost invariably prefers the most vigorous, defiant, and mettlesome male ; hence it is almost useless, as he remarks, " to attempt true breeding if a game-cock in good health and condition runs the locality, for almost " every hen on leaving the roosting-place will resort to the " game-cock, even though that bu-d may not actually drive " away the male of her own variety." Under ordinary circum- stances the males and females of the fowl seem to come to a mutual understanding by means of certain gestures, described to me by Mr. Brent. But hens will often avoid the officious attentions of young males. Old hens, and hens of a pugnacious disposition, as the same writer informs me, dislike strange males, and will not yield until well beaten into compliance. Ferguson, however, describes how a quarrelsome hen was subdued by the gentle courtship of a Shanghai cock.^' There is reason to believe that pigeons of both sexes prefer pairing with birds of the same breed; and dovecot-pigeons dislike all the highly improved breeds.^^ Mr, Harrison Weir has lately heard from a trustworthy observer, who keeps blue pigeons, that tbese drive away all other coloured varieties, such as white, red, and yellow ; and from another observer, that a female dun carrier could not, after repeated trials, be matched with a black male, but immediately paired with a dun. Again. Mr. Tegetmeier had a female blue tm-bit that obstinately refused to pair with two males of the same breed, which were successively shut up with her for weeks ; but on being let out she would have immediately accepted the fii'st blue dragon that offered. As she was a valuable bird, she was then shut up for " ' Rare and Prize Poultry,' 1854, Plants under Domestication,' vol. ii p. 27. p. 103. " 'The Viiriation of Animals anl 2 E 4i8 The Descent of Man PaetIL many weeks with a silver (i.e., very pale blue) male, and at last mated with him. Nevertheless, as a general rule, colour appears to have little influence on the pairing of pigeons. Mr. Teget- meier, at my request, stained some of his birds with magenta . but they were not much noticed by the others. Female pigeons occasionally feel a strong antipathy towards certain males, without any assignable cause. Thus MM. Boitard and Corbie, whose experience extended over forty-five years, state: "Quand une femelle eprouve de I'antipathie pour un " male avec lequel on veut I'accoupler, malgre tons les feux " de I'amour, malgre I'alpiste et le chenevis dont on la noun-it " pour augmenter son ardeur, malgre un emprisonnement de " six mois et meme d'un an, elle refuse constamment ses " caresses ; les avances empressdes, les agaceries, les tournoie- " mens, les tendres roucoulemens, rien ne pent lui plaire ni " I'emouvoir ; gonflee, boudeuse, blottie dans un coLq de sa " prison, elle n'en sort que pour boire et manger, ou pour re- " pousser avec une espece de rage des caresses devenues trop pres- santes." On the other hand, Mr. Harrison Weir has himself observed, and has heard from several breeders, that a female pigeon will occasionally take a strong fancy for a particular male, and will desert her own mate for him. Some females, accord- ing to another experienced observer, Eiedel,-* are of a profligate disposition, and prefer almost any stranger to their own mate. Some amorous males, called by our Enghsh fanciers " gay birds," are so successful in their gallantries, that, as Mr. H. Weir informs me, they must be shut up on account of the mischief which they cause. Wild tui-keys in the United States, according to Audubon, " sometimes pay their addresses to the domesticated females, " and are generally received by them with great pleasure." So that these females apparently prefer the wild to their oWn males.^ Here is a more curious case. Sir E. Heron dui-ing many years kept an account of the habits of the peafowl, which he bred in large numbers. He states that " the hens have frequently great " preference to a particular peacock. They were all so fond " of an old pied cock, that one year, when he was confined " though still in view, they were constantly assembled close to " the trellice-walls of his prison, and would not suffer a japanned "Boitard and Corbid, 'Les "4 < Die Taubenzucht,' 1S24, j. 86. Pigeons, &c.,* 1824, p. 12. Prosper " 'Ora'thological Bicgraphy,' Lucas (' Traits de I'Hdrdd. Nat.' voL i. p. 13. See to the saoie efiFect, torn. ii. 1850, p. 296) has himself Dr. Bryant, in ' Allen's Maxmals and observed nearly similar facts with Birds of Florida,' p. 344. pigeoLs 5)hap. XIV. Preference by the Female. 419 " peacock to touch them. On his being let out in the autumn, " the oldest of the hens instantly courted him, and was success- " fulin her courtship. The next year he was shut up in a stable, " and then the hens all courted his rival." This rival was a japanned or black-winged peacock, to our eyes a more beautiful bird than the common kind. Lichtensteia, who was a good observer and had excellent opportunities of observation at the Cape of Good Hope, assured Kudolphi that the female widow-bird ( Chera progne) disowns the male, when robbed of the long tail-feathers with which he is ornamented during the breeding-season. I presume that this observation must have been made on birds under confinement.^" Here is an analogous case ; Dr. Jaeger/* director of the Zoological Gardens, of Yienna, states that a male silver-pheasant, who had been triumphant over all other males and was the accepted lover of the females, had his ornamental plumage spoiled. He was then immediately superseded by a rival, who got the upper hand and afterwards led the flock. It is a remarkable fact, as shewing how important colour is iu the courtship of bu-ds, that Mr. Boardman, a well-known col- lector and observer of birds for many years in the Northern United States, has never in his large experience seen an albino paired with another bird; yet he has had opportunities of observing many albinos belonging to several species.-^ It can hardly be maintained that albinos in a state of nature are incapable of breeding, as they can be raised with the greatest facility under confinement. It appears, therefore, that we must attribute the fact that they do not pair, to their rejection by their normally coloured comrades. Female birds not only exert a choice, but in some few cases they court the male, or even fight together for his possession. Sir E. Heron states that with peafowl, the first advances are always made by the female ; something of the same kind takes place, according to Audubon, with the older females of the wild turkey. With the capercailzie, the females flit round the male whilst he is parading at one of the places of assemblage, and sohcit his attention.'" We have seen that a tame wild-duck Proc. Zool. Soc' 1835, p. 54. ihre Stellung zu Moral und Re- The japanned peacock is considered ligion,' 1869, s. 59. by Mr. Sclater as a distinct species, 2» This statement is given by Mr and has been named Paw nigri- A. Leith Adams, in his ' Field and pennis; but the evidence seems to Forest Rambles,' 1873, p. 76, and me to shew that it is only a variety, accords with his own experience " Rudolphi, 'Beytriige zur An- 3" In regard to peafowl, see Sir thropologie,' 1812, s. 184. R. Horon, ' Proc. Zoolog. Soc' 1835 »• 'Die Darwin'sche Theorie, und p. 54, and tiie Rev. E. S. Dixoa, 2 E 2' 420 The Descent of Man. Part II seduced an unwilling pintail drake after a long courtship, Mr. Bartlett believes that the Lophophorus, like many other gallina- ceous birds, is naturally polygamous, but two females cannot be placed in the same cage with a male, as they fight so much together. The following instance of rivalry is more surprising as it relates to bullfinches, which usually pair for hfe. Mr. Jenner "Weir introduced a dull-coloured and ugly female into his aviary, and she immediately attacked another mated female so unmercifully, that the latter had to be separated. The new female did all the courtship, and was at last successful, for she paired with the male ; but after a time she met with a just re- tribution, for, ceasing to be pugnacious, she was replaced by the old female, and the male then deserted his new and returned to his old love. In all ordinary cases the male is so eager that he wiU accept any female, and does not, as far as we can judge, prefer one to the other ; but, as we shall hereafter see, exceptions to this rule apparently occur in some few groups. With domesticated birds, I have heard of only one case of males shewing any preference for certain females, namely, that of the domestic cock, who, according to the high authority of ]\Ir. Hewitt, prefers the younger to the older hens. On the other hand, in etfecting hybrid unions between the male pheasant and common hens, Mr. Hewitt is convinced that the pheasant invariably prefers the older birds. He does not appear to be in the least influenced by their colour, but " is most capricious in his attachments :" ^' from some inexphcable cause he shews the most determined aversion to certain hens, which no care on the part of the breeder can overcome. Mr. He^vitt informs me that some hens are quite unattractive even to the males of their own species, so that they may be kept with several cocks during a whole season, and not one egg out of forty or fifty will prove fertile. On the other hand, with the Long-tailed duck {Harelda glacialis), " it has been remarked," says M. Eksh-om, " that certain females " are much more courted than the rest. Frequently, indeed, " one sees an individual surrounded by six or eight amorous " males." Whether this statement is credible, I know not ; but the native sportsmen shoot these females in order to stuff them as decoys.^ With respect to female birds feeling a preference for particular Ornamental Poultry,' 1848, p. b'. " Mr. Hewitt, quoted in 'Tegct- For the turkey, Audubon, ibia. p. 4. meier's Poultry Book,' 1866, p. 165. For the capercailzie, Lloyd, ' Game " Quoted in Lloyd's ' Game Birds Bird of Sweden,' 1807, p. 23. of Sweden,' p. 345. Chap. XIV. Preference by the Female. 421 males, we must bear in mind that we can judge of choice being exerted, only by analogy. If an inhabitant of another pknofc were to behold a number of young rustics at a fair courting a pretty girl, and quarrelling about her like birds at one of their places of assemblage, he would, by the eagerness of the wooers to please her and to display their finery, infer that she had the power of choice. Now with birds, the evidence stands thus; they have acute powers of observation, and they seem to have some taste for the beautiful both in colour and sound. It is certain that the females occasionally exhibit, from unknown causes, the strongest antipathies and preferences for particular males. When the sexes differ in colour or in other ornaments the males with rare exceptions are the more decorated, either permanently or temporarily during the breeding-season. They sedulously display their various ornaments, exert their voices, and perform strange antics in the presence of the females. Even well-armed males, who, it might be thought, would altogether depend for success ou the law of battle, are in most cases highly ornamented; and their ornaments have been acquired at the expense of some loss of power. In other cases ornaments have been acquired, at the cost of increased risk from birds and beasts of prey. With various species many individuals of both sexes congregate at the same spot, and their courtship is a pro- longed afi"air. There is even reason to suspect that the males and females within the same district do not always succeed in pleasing each other and pairing. What then are we to conclude from these facts and considera- tions ? Does the male parade his charms with so much pomp and rivalry for no purpose ? Are we not justified in beheving that the female exerts a choice, and that she receives the addresses of the male who pleases her most ? It is not probable that she consciously deUberates ; but she is most excited or attracted by the most beautiful, or melodious, or gallant males. Nor need it be supposed that the female studies each stripe or spot of colour ; that the peahen, for instance, admires each detail in the gorgeous train of the peacock— she is probably struck only by the general effect. Nevertheless, after hearing how carefully the male Argus pheasant displays his elegant primary wing-feathers, and erects Ms ocellated plumes in the right position for their lull effect ; or again, how the male goldfinch alternately displays his gold-bespangled wihgs, we ought not to feel too sure that the female does not attend to each detail of beauty. We can judge, as already remarked, of choice being exerted, only from analogy; and the mental powers of birds do not differ fundamentally from' ours. From these various considerations we may conclude that 422 The Descent of Man. Paet II. the pairing of birds is not left to chance ; but that those malee, "which are best able by their various charms to please or excite the female, are under ordinary circumstances accepted. If this be admitted, there is not much diflaculty ia understanding how male birds have gi-adually acquired their ornamental characters. All animals present individual differences, and as man can modify his domesticated birds by selecting the individuals which appear to him the most beautiful, so the habitual or even occasional preference by the female of the more attractive males ■would almost certainly lead to their modification; and such modifications might ia the course of time be augmented to almost any extent, compatible with the existence of the species. Variahility of Birds, and especially of their Secondary Sexual Characters. — Variability and inheritance are the foundations for the work of selection. That domesticated birds have varied greatly, their variations being inherited, is certain. That birds in a state of nature have been modified into distinct races is now universally admitted.'^ Variations may be divided into two classes ; those which appear to our ignorance to arise spon- taneously, and those which are directly related to the surrounding conditions, so that all or nearly all the individuals of the same species are similarly modified. Cases of the latter kind have recently been observed with care by IVIr. J. A. AUen,^* who shews According to Dr. Blasius ('Ibis,' vol. ii. 1860, p. 297), there are 425 indubitable species of birds which breed in Europe, besides sixty forms, which are frequently regarded as distinct species. Of the latter, Blasius thinks that only ten are really doubtful, and that the other fifty ought to be united with their nearest allies ; but this shews that there must be a considerable amount of variation with some of our Euro- pean birds. It is also an unsettled point with naturalists, whether several North American birds ought to be ranked as specifically distinct from the corresponding European .species. So again many North Ame- rican forms which until lately were named as distinct species, are now considered to be local races. " ' Mammals and Birds of East Florida,' also an ' Ornithological Re- connaissance cf Kansas, &c. Not- withstanding the influence of cli- mate on the colours of birds, it is diSicult to account for the dull or dark tints of almost all the species inhabiting certain countries, for instance,' the Galapagos Islands under the equator, the wide temperate plains of Patagonia, and, as it ap- pears, Egypt (see Mr. Hartshorne in the ' American Naturalist,' 1873, p. 747). These coxintries are open, and afford little shelter to birds ; but it seems doubtful whether the absence of brightly coloured species can be explained on the principle of protection, for on the Pampas, which are equally open, though covered by green grass, and where the birds would be equally exposed to danger, many brilliant and conspicuously coloured species are common. I have sometimes speculated whether the prevailing dull tints of the scenery in the above named countries may not have affected the appreci.-i- tion of bright colours by the birds inhabiting them. Chap. XIV. Variability. 423 that in the United States many species of birds gradually become more strongly coloured in proceeding southward, and more lightly coloured in proceeding westward to the arid plains of the interior. Both sexes seem generally to be affected in a like manner, but sometimes one sex more than the other. This result is not incompatible with the behef that the colours of birds are mainly due to the accumulation of successive varia- iions through sexual selection; for even after the sexes have seen greatly differentiated, cUmate might produce an equal effect on both sexes, or a greater effect on one sex than on the other, owing to some constitutional difference. Individual differences between the members of the same species are admitted by every one to occur under a state of nature. Sudden and steongly marked variations are rare ; it is also doubtful whether if beneficial they would often be preserved through selection and transmitted to succeeding generations.'® Nevertheless, it may be worth while to give the few cases which I have been able to collect, relating chiefly to colour, — simple albinism and melanism being excluded. Mr. Gould is well known to admit the existence of few varieties, for he esteems very slight differences as specific; yet he states that near Bogota certain humming-birds belonging to the gfenus CynanUius are divided into two or three races or varieties, which differ from each other in the colouring of the tail — " some having the " whole of the feathers blue, while others have the eight central " ones tipped with beautiful green." It does not appear that intermediate gradations have been observed in this or the following cases. In the males alone of one of the Australian parrakeets "the thighs in some are scarlet, in others grass- " green." In another parrakeet of the same country " some " individuals have the band across the wing-coverts bright- 35 ' Origin of Species,' fifth edit. 1869, p. 104. I had always per- ceived, that rare and strongly- marked deviations of structure, de- serving to be called monstrosities, could seldom be preserved through natural selection, and that the pre- servation of even highly-beneficial variations would depend to a certain extent on chance. I had also fully appreciated the importance of mere individual differences, and this led me to insist so strongly on the im- portance of that unconscious form of selection by man, which follows from the preservation of tha most valued individuals of each breed, without any intention on his part to modify the characters of the breed. But until I read an ablo article in the ' North British Re- view ' (March 1867, p. 289, et seq.), which has been of more use to me than any other Review, I did not see how great the chances were against the preservation of varia- tions, whether slight or strongly pronounced, occurring only in smgi« individuals. " ' Introduct. to the Trochilida, p. 102. 424 The Descent of Man. Part II. "yellow, while in others the same part is tinged with red."=" In the United States some few of the males of the Scarlet Tanager {TarMgra r«6j-a) have "a beautiful transverse band of glowing "red on the smaller wing-coverts ;" but this variation seems to be somewhat rare, so that its preservation through sexual selection would follow only under vmusually favourable circum- stances. In Bengal the Honey buzzard (Pernis mstata) has either a small rudimental crest on its head, or none at all : so slight a difference, however, would not have been worth notice, had not this same species possessed in Southern India " a well- " marked occipital crest formed of several graduated feathers." ^' The following case is in some respects more interesting. A pied variety of the raven, with the head, breast, abdomen, and parts of the wings and tail-feathers white, is confined to the Feroe IslUnds. It is not very rare there, for Graba saw during his visit from eight to ten living specimens. Although the characters of this variety are not quite constant, yet it has been named by several distinguished ornithologists as a distinct species. The fact of the pied birds being pui'sued and persecuted with much clamour by the other ravens of the island was the chief cause which led Briinnich to conclude that they were specifically distinct ; but this is now known to be an error.^" This case seems analogous to that lately given of albino birds not pairing from being rejected by theii' comrades. In various parts of the northern seas a remarkable variety of the common Guillemot ( Uria troile) is found ; and in Feroe, one out of every five birds, according to Graba's estimation, presents this yariation. It is characterised by a pui-e white ring round the eye, with a curved narrow white line, an inch and a half in length, extending back from the ring. This conspicuous cha- racter has caused the bird to be ranked by several ornithologists as a distinct species under the name of U. lacrymans, but it is now known to be merely a variety. It often pau-s with the common kind, yet intermediate gradations have never been seen ; nor is this surprising, for variations which appear suddenly, are often, as I have elsewhere shewn," transmitted either unaltered or not at all. We thus see that two distinct forms of the same species may co-exist in the same district, and we cannot doubt " Gould, ' Handbook to Birds of Faro,' 1830, s. 51-54. Jlacgillivray, Australia,' vol. ii. pp. 32 and 68. ' Hist. British Birds,' vol. iii. p. " Audubou, 'Ornitholog. Bio- 745. ' Ibis,' vol. v. 1SG3, p. 469. graphy,' 1838, vol. iv. p. 389. ■" Graba, ibid. s. 54. Macgil- " Jerdon, ' Birds of India,' vol. i. livvay, ibid. vol. v. p. 327. p 108- and Mr. Blyth, in 'Land 'Variation of Animals .autl and Water,' ]868, p. 381. Plants under Domestication,' toI. u. <» Graba ' Tagebuch Reise nach p. 92. Chap. XIV. Variability. 425 that if the one had possessed any advantage ever the other, it would soon have been multiplied to the exclusion of the latter. If, for instance, the male pied ravens, instead of being persecuted by their comrades, had been highly attractive (like the above pied peacock) to the black female ravens, their numbers would have rapidly increased. And this would have been a case of sexual selection. With respect to the slight individual differences which are common, in a greater or less degree, to all the members of the same species, we have every reason to believe that they are by far the most important for the work of selection. Secondary sexual characters are eminently liable to vary, both with animals in a state of nature and under domestication.^^ There is also reason to believe, as we have seen in our eighth chapter, that variations are more apt to occur in the male than in the female SGx. All these contingencies are highly favourable for sexual selection. Whether characters thus acquired are transmitted to one sex or to both sexes, depends, as we shall see in the following chapter, on the form of inheritance which prevails. It is sometimes difficult to form an opinion whether certain slight differences between the sexes of birds are simply the result of variability with sexually-limited inheritance, without the aid of sexual selection, or whether they have been augmented through this latter process. I do not here refer to the many instances where the male displays splendid colours or other ornaments, of which the female partakes to a slight degree ; for these are almost certainly due to characters i^rimarily acquired by the male having been more or less transferred to the female. But what are we to conclude with respect to certain birds in which, for instance, the eyes differ shghtly in colour in the two sexes In some cases the eyes differ conspicuously; thus with the storks of the genus Xenorhynchus, those of the male are blackish- hazel, whilst those of the females are gamboge-yellow; with many hornbills (Buceros), as I hear from Mr. Blyth," the males have intense crimson eyes, and those of the females are white. In the Buceros hicornis, the hind margin of the casque and a stripe on the erest of the beak are black in the male, but not so in the female. Are we to suppose that these black marks and the crimson colour of the eyes have been preserved or augmented Oirough sexual selection in the males ? This is very doubtful ; " On these points see also • Varia- of a Podica and Gallicrex in ' Ibis,' tion of Animals and Plants under vol. ii. 1860, p. 206 ; and vol. t. Domestication,' vol. i. p. 253; vol. ii. 1863, p. 426. PP- 73, 75. " See also Jerdon. ' Birds of ** See, for instance, on the irides India,' vol. i. pp. 243-245. 426 The Descent of Man. Part II, for Mr. Bartlett shewed me in the Zoological Gardens that tho inside of the mouth of this Buceros is black in the male and flesh-coloured in the female; and their external appearance or beauty would not be thus affected. I observed in Chili " that the u-is in the condor, when about a year old, is dark-brown, but changes at maturity into yellowish-brown in the male, and into bright red in the female. The male has also a small, longitu- dinal, leaden-coloured, fleshy crest or comb. The comb of many gallinaceous birds is highly ornamental, and assumes vivid coloui-s during the act of coui-tship ; but what are we to think of the dull-coloured comb of the condor, which does not appear to lis in the least ornamental ? The same question may be asked in regard to various other characters, such as the knob on the base of the beak of the Chinese goose (^Anser cygnoides), which is much larger in the male than in the female. No certain answer can be given to these questions ; hut we ought to be cautious in assuming that knobs and various fleshy appendages cannot be attractive to the female, when we remember that with savage races of man various hideous deformities— deep scars on the face with the flesh raised into protuberances, the septum of the nose pierced by sticks or bones, holes in the ears and lips stretched widely open — are all admired as ornamental. Whether or not unimportant differences between the sexes, such as those just specified, have been preserved through sexual selection, these differences, as well as all others, must primarily depend on the laws of variation. On the principle of correlated development, the pltmiage often varies on different parts of the body, or over the whole body, in the same manner. "We see this well illustrated in certain breeds of the fowl. In all the breeds the feathers on the neck and loins of the males are elongated, and are called hackles ; now when both sexes acquire a top-knot, which is a new character in the genus, the feathers on the head of the male become hackle-shaped, evidently on the principle of correlation ; whilst those on the head of the female are of the ordinary shape. The colour" also of the hackles forming the top-knot of the male, is often correlated with that of the hackles on the neck and loins, as may be seen by comparing these feathers in the Golden and Silver-spangled Polish, the Houdans, and Creve-coeur breeds. In some natural species we may observe exactly the same correlation in the colours of these same feathers, as in the males of the splendid Gold and Amherst pheasants. The structure of each individual feather generally causes any « ' Zoology of the Voyage of H.M.S. Beagle,' 1841, p. 6, Chap. XIV. Ocelli. I 427 change in its colouring to be symmetrical ; we see this in the various laced, spangled, and pencilled breeds of the fowl ; and on the principle of correlation the feathers oyer the whole body ai'e often coloui-ed in the same manner. We are thus enabled without much trouble to rear breeds with their plumage marked almost as symmetrically as in natural species. In laced and spangled fowls the coloured margins of the feathers are abruptly [lefined ; but in a mongrel raised by me from a black Spanish cock glossed with green, and a white game-hen, aU the feathers were greenish-black, excepting towards their extremities, which were yellowish- white ; but between the white extremities and the black bases, there was on each feather a symmetrical, curved zone of dark-brown. In some instances the shaft of the feather determines the distribution of the tints; thus with the body- feathers of a mongrel from the same black Spanish cock and a silver-spangled Polish hen, the shaft, together with a narrow space on each side, was greenish-black, and this was surrounded by a regular zone of dark-brown, edged with brownish-white. In these cases we have feathers symmetrically shaded, like those which give so much elegance to the plimiage of many natural species. I have also noticed a variety of the common pigeon with the wing-bars symmetrically zoned with tkree bright shades, instead of being simply black on a slaty-blue ground, as in the parent-species. In many gi-oups of birds the plumage is differently coloured in the several species, yet certain spots, marks, or stripes are retained by all. Analogous cases occur with the breeds of the pigeon, which usually retain the two wing-bars, though they may be coloured red, yellow, white, black, or blue, the rest of the plumage being of some wholly different tint. Here is a more curious case, in which certain marks are retained, though coloured in a manner almost exactly the opposite of what is natural ; the aboriginal pigeon has a blue tail, with the terminal halves of the outer webs of the two outer tail feathers white ; now there is a sub-variety having a white instead of a blue tail, with precisely that part black which is white in the parent-species.'''' Formation and Variability of the Ocelli or eye-like Spots on the Plumage of Birds— As no ornaments are more beautiful than the ocelli on the feathers of various birds, on the hairy coats of some mammals, on the scales of reptiles and fishes, on the skin of amphibians, on the wings of many Lepidoptera and other insects, they deserve to be especially noticed. An ocellus consists of a spot within a ring of another colour, like the pupil within the " Bechstein, 'Naturgeschichte DeutsoUaads,' B. iv. 1795, s. 31, ou a sub-rariety of the Monak pigeon. 428 The Descent of Man. Part 11, iris, but the central spot is often surrounded by additional con- centric zones. The ocelli on the tail-coverts of the peacock offer a familiar example, as well as those on the wings of the peacock- butterfly (Vanessa). Mr. Trimen has given me a description of a S. African moth {Gyananis isis), allied to our Emperor moth, in which a magnificent ocellus occupies nearly the whole surface of each hinder wing ; it consists of a black centre, including a semi-transparent crescent-shaped mark, surrounded by successive, ochre-yellow, black, ochre-yellow, pink, white, pink, brown, and whitish zones. Although we do not know the steps by which these wonderfully beautiful and complex ornaments have been developed, the process has probably been a simple one, at least with insecis ; for, as Mi'. Trimen wi-ites to me, " no characters of " mere marking or coloration are so unstable in the Lepidoptera " as the oeeUi, both in number and size." Mr. Wallace, who first called my attention to this subject, shewed me a series of specimens of our common meadow-brown butterfly (HipparcMa janim) exhibiting numerous gradations from a simple minute black spot to an elegantly-shaded ocellus. In a S. African butterfly {Qyllo leda, Linn.), belonging to the same family, the ocelli are even still more variable. In some specimens (A, fig. 53) large spaces on the upper surface of the wings are coloured black, and include irregular white marks ; and from this state a complete gradation can be traced into a tolerably perfect ocellus (A'), and this results from the contraction of the irregular blotches of colour. In another series of specimens a gradation can be followed from excessively minute white dots, surrounded by a scarcely visible black line (B), into perfectly symmetrical and large ocelli (B')." In cases Hke these, the development of a perfect ocellus does not require a long course of variation and selection. With birds and many other animals, it seems to foUow fi-om the comparison of allied species that circular spots are often generated by the breaking up and contraction of stripes. In the Tragopan pheasant faint white lines in the female represent the beautiful white spots in the male ; and something of the same land may be observed in the two sexes of the Argus pheasant. However this may be, appearances strongly favour the belief that on the one hand, a dark spot is often formed by the colouring " Tliis woodcut has been en- wings of this butterfly, in hi« jiraved from a beautiful drawing, ' Rhopalocera Africa; Australi.s,' p. most Icindly made for me by Mr. 180. Trimen ; see also his description of *^ Jerdon, ' Birds of India,' vol the wonderful amount of variation iii. p. 517. in the coloration and shape of the Chap, XIV. Ocelli. 429 TYintter bein- drawn towards a central point from a surrounding Tone which latter is thus rendered lighter; and, on the other hand that a white spot is often formed by the colour being driven away from a central point, so that it accumulates m a surround- ing darker zone. In either case an ocellus is the result The colouring matter seems to be a nearly constant quantity, but is redistributed, either centripetally or centrifugally. The leathers Fig. 53. Cyllo leda, Linn., from a drawing by Mr. Trimen, shewing the extreme range of variation in the ocelli. A. Specimen, from Mauritius, upper surface of fore-wing. Ai. Specimen, from Natal, ditto. B. Specimen, from Java, upper surface of hind-wing. Bi. Specimen, from Mauritius, ditto. of the common guinea-fowl offer a good instance of white spots surrounded by darker zones ; and wherever the white spots are large and stand near each other, the surrounding dark zones become confluent. In the same wing-feather of the Argus pheasant dark spots may be seen surrounded by a pale zone, and white spots by a dark zone. Thus the formation of an ocellus in its most elementary state appears to be a simple affair. By what further steps the more complex ocelli, which are sur- rounded by many successive zones of colour, have been generated, I will not pretend 'to say. ' But the zoned feathers of the mongrels from differently coloured fowls, and the extraordinary variability of the ocelli on many Lepidoptera, lead us to conclude that their formation Is not a complex process, but depends on some slight and graduated change in the nature of the adjoining tissues. 43^ TJte Descent of Mati. Part II. Gradation of Secondary Bexual Characters.— Cases of gradation are important, as shewing us that highly complex ornaments may be acquired by small successive steps. In order to discover the actual steps by which the male of any existing bird has acquired his magnificent colours or other ornaments, we ought to behold the long line of his extinct progenitors ; but this is obviously impossible. We may, however, generally gain a clue by comparmg all the species of the same group, if it be a largo one ; for some of them will probably retain, at least partially, traces of their former characters. Instead of entering on tedious details respecting various groups, in which striking instances of gradation could be given, it seems the best plan to take one or two strongly marked cases, for instance that of the peacock, in order to see if hght can be thrown on the steps by which this bii-d has become so splendidly decorated. The peacock is chiefly remarkable from the extraordinary length of his tail-coverts ; the tail itself not being much elongated. The barbs along neai-ly the whole length of these feathers stand separate or are decomposed ; but this is the case with the feathers of many species, and with some varieties of the domestic fowl and pigeon. The barbs coalesce towards the extremity of the shaft forming the oval disc or ocellus, which is certainly one of the most beautiful objects in the world. It consists of an iridescent, in- tensely blue, indented centre, surrounded by a rich green zone, this by a broad coppery-brown zone, and this by five other narrow zones of slightly different iridescent shades. A trifling character in the disc deserves notice ; the barbs, for a space along one of the concentric zones are more or less destitute of their barbules, so that a paii of the disc is surrounded by an almost transparent zone, which gives it a highly finished aspect. But I have else- where described ^° an exactly analogous variation m the hackles of a sub-variety of the game-cock, in which the tips, having a metallic lustre, "are separated from the lower part of the " feather by a symmetrically shaped transparent zone, composed " of the naked portions of the barbs." The lower margin or base of the dark-blue centre of the oceUus is deeply indented on the liue of the shaft. The surrounding zones Likewise shew traces, as may be seen in the drawing (fig. 54), of indentations, or rather breaks. These indentations aire common to' the Indian and Javan peacocks (Pavo cristatus and P. muticus) ; and they seemed to deserve particular attention, as probably connected with the development of the ocellus ; but for a long time I could not conjecture their meaning. ♦ Variatiou of Animals and Plants under Domestication," vol. i. p. 254 Chap. XIV. Gradation of Characters. 431 If we admit the principle of gradual evolution, there must formerly have existed many species which presented every suc- cessive step between the wonderfully elongated tail-coverts of the peacock and the short tail-eoverts of all ordinary birds ; and again between the magnificent ocelli of the former, and the simpler ocelH or mere coloured spots on other birds ; and so with aU the other characters of the peacock. Let us look to the aUied Gallinaceas for any stiU-existing gradations. The species and Big. 54. Feather of Peacock, about two-thirds of natural size, drawn by Mr. Ford The transparent zone is represented by the outermost white zone, confined to the tipper end of the disc. sub-species of Polyplectron inhabit countries adjacent to the native land of the peacock ; and they so far resemble this bird that they are sometimes called peacock-pheasants. I am also in- formed by Mr. Bartlett that they resemble the peacock in their voice and in some of their habits. During the spring the males, as previously described, strut about before the comparatively plain-coloured females, expanding and erecting their tail and 432 The Descent of Man. rABT IT, wing-feathers, which are ornamented with numerous ocelli. I request the reader to turn back to the drawing (fig. 51, p. 397) of a Polyplectron. In P. napoleonis the ocelli are confined to the tail and the back is of a rich metallic blue ; in which re- spects this species approaches the Java peacock. P. hardvdckii possesses a peculiar top-knot, which is also somewhat like that of the Java peacock. In all the species the ocelli on the wings and tail are either circular or oval, and consist of a beautiful, iridescent, greenish-blue or greenish-purple disc, with a black border. This border in P. chinquis shades into brown, edged with cream-colour, so that the ocellus is here surrounded with variously shaded, though not bright, concentric zones. The unusual length of the tail-coverts is another remarkable character in Polyplectron ; for in some of the species they are half, and in others two-thirds as long as the true tail-feathers. The tail- coverts are ocellated as in the peacock. Thus the several species of Polyplectron manifestly make a graduated approach to the peacock in the length of their tail-coverts, in the zoning of the ocelli, and in some other characters. Notwithstanding this approach, the first species of Polyplectron which I examined almost made me give up the search; for I found not only that the true tail-feathers, which in the peacock are quite plain, were ornamented with ocelli, but that the ocelli on all the feathers differed fundamentally from those of the peacock, in there being two on the same feather (fig. 55), one on each side of the shaft. Hence I concluded that the early pro- genitors of the peacock could not have resembled a Polyplectron. But on continuing my search, I observed that in some of the species the two ocelli stood very near each other ; that in the tail-feathers of P. hardwickii they touched each other; and. finally, that on the tail-coverts of this same species as well as of P. malaccense (fig. 56) they were actually confluent. As the central part alone is confluent, an indentation is left at both the upper and lower ends ; and the surrounding coloured zones are likewise indented. A single ocellus is thus formed on each tail- covert, though still plainly betraying its double origin. These confluent ocelli differ from the single ocelli of the peacock in having an indentation at both ends, instead of only at the lower or basal end. The explanation, however, of this difference is not diflBcult; in some species of Polyplectron the two oval ocelli on the same feather stand parallel to each other ; in other species (as in P. chinquis') they converge towards one end; now the partial confluence of two convergent ocelli would manifestly leave a much deeper indentation at the divergent than at the convergent end. It is also manifest that if the convergence were Chap. XIV. Birds— Gradation of Characters. 433 gtrongly pronounced and the confluence complete, the indentation at the convergent end would tend to disappear. The tail-feathers in both species of peacock are entirely destitute of ocelli, and this apparently is related to their being covered up and concealed by the long tail- coverts. In this respect they di£fer remarkably from the tail- feathers of Polyplectron, which in most of the species are or- namented with larger ocelli than those on the tail-coverts. Hence I was led carefully to examine the tail-feathers of the several species, in order to discover whether their ocelli shewed any tendency to dis- appear; and to my great satis- faction, this appeared to be so. The central tail-feathers of P. napoleonis have the two ocelli on each side of the shaft perfectly developed ; but the inner ocellus becomes less and less conspicuous on the more exterior -tail-feathers, until a mere shadow or rudiment is left on the inner side of the outermost feather. Again, in P. malaccense, the ocelli on the tail- coverts are, as we have seen, confluent ; and these feathers are of unusual length, being two- thirds of the length of the tail- feathers, so that in both these respects they approach the tail- soverts of the peacock. Now in P. malaccense the two central tail- feathers alone are ornamented, each with two brightly-coloured ocelli, the inner ocellus having completely disappeared from all the other tail-feathers. Conse- quently the tail-coverts and tail-feathers of this species of Poly- plectron make a near approach in structure and ornamentation to the corresponding feathers of the peacock. 2 F Fig. 55. Part of a t;\il-covi?rt ol' Poly- plectron chinquis, with the two ocelli of nat. size. Fig. 56. Part of a tail-covert of Poly- plectron malaccense, with the two ocelli, partially conilueut, of nat. size. 434 The Descent of Ma?i. I'aet U. As far, thou, as gradation throws light on the steps by which the magnificent train of the peacock has been acquired, hardly anything more is needed. If we picture to ourselves a progeni- tor of the peacock in an almost exactly intermediate condition between the existing peacock, with his enormously elongated tail-coverts, ornamented with single ocelli, and an ordinary gallinaceous bird with short tail-coverts, merely spotted with some colour, we shall see a bii-d allied to Polyplectron — that is, with tail-coverts, capable of erection and expansion, ornamented with two partially confluent ocelli, and long enough almost to conceal the tail-feathers, the latter having already partially lost their ocelli. The indentation of the central disc and of the surrounding zones of the ocellus, in both species of peacock, speaks plainly in favour of this view, and is otherwise in- explicable. The males of Polyplectron are no doubt beautiful birds, but their beauty, when viewed from a little distance, cannot be compared with that of the peacock. Many female progenitors of the peacock must, during a long line of descent, have appreciated this sui^eriority ; for they have unconsciously, by the continued preference of the most beautiful males, rendered the peacock the most splendid of hving birds. Argus pheasant. — Another excellent case for investigation is offered by the ocelli on the wing-feathers of the Argus pheasant, which are shaded in so wonderful a manner as to resemble balls lying loose within sockets, and consequently differ from ordinary ocelli. No one, I presume, will attribute the shading, which has excited the admiration of many experienced artists, to chance — to the fortuitous concourse of atoms of colouring matter. That these ornaments should have been formed through the selection of many successive variations, not one of which was originally intended to produce the ball-and-socket effect, seems as incredible, as that one of Eaphael's Madonnas should have been formed by the selection of chance daubs of paint made by a long succession of young artists, not one of whom intended at first to draw the human figure. In order to discover how the ocelli have been developed, we cannot look to a long line ot progenitors, nor to many closely-allied forms, for such do not now exist. But fortunately the several feathers on the wing- suffice to give us a clue to the problem, and they prove to de- monstration that a gradation is at least possible from a mere spot to a finished ball-and-socket ocellus. The wing- feathers, bearing the oceUi, are covered with dark stripes (fig. 57) or with rows of dark spots (fig. 59), each stripe or row of spots running obliquely down the outer side of the Chap. XIV. Birds— Gradation of Characters. 435 shaft to one of the ocelli. The spots are generally elongated in a hne transverse to the row in which they stand. They often become confluent, either in the line of the row— and then they form a longitudinal stripe— or transversely, that is, with the spots in the adjoining rows, and then they form transverse stripes. A spot sometimes breaks up into smaller spots, which still stand in their proper places. It will be convenient first to describe a per- fect ball - and - socket ocellus. This consists of an intensely black circular ring, surround- ing a space shaded so as exactly to resemble a ball. The figure here given has been ad- mirably drawn by Mr. Ford and well engraved, but a woodcut cannot exhibit the exqiusite shading of the original. The ring is almost always slightly broken or interrupted (see fig. 57) at a point in the upper half, a little to the right of, and above the white shade on the enclosed ball ; it is also sometimes broken to- wards the base on the right hand. These little breaks have an important meaning. The ring is always much thickened, with the edges ill-defined towards the left- hand upper corner, the feather being held erect, in the posi- tion in which it is here drawn. Beneath this thickened part there is on the surface of the ball an oblique almost pure-white mark, which shades off downwards into a pale-leaden hue, and this into yellowish and brown tints, which insensibly become 2 F 2 Fig. 5Y. Part of secondary wing-feather of Argiis pheasant, shewing two perfect ocelli, a and 6. A, B, C, D, &c., are dark stripes running obliquely down, each to an ocellus. [Much of the web on both sides, especially to the left of the shaft, has been cut off.] 436 The Descent of Man. Paet II. darker and darker towards the lower part of the ball. It is this shading which gives so admirably the effect of light shining on a convex surface. If one of the balls be examined, it will be seen that the lower part is of a brown tint and is indistinctly sepa- rated by a curved oblique line from the upper part, which is yellower and more leaden ; this curved oblique line runs at right angles to the longer axis of the white patch of light, and indeed of aU the shading ; but this difference in colour, which camiot of course be shewn in the woodcut, does not in the least interfere with the perfect shading of the ball. It should be particularly observed that each ocellus stands in obvious connection either with a dark stripe, or with a longitudinal row of dark spots, for both occur indifferently on the same feather. Thus iu fig. 57 stripe A runs to ocellus a ; B runs to ocellus b ; stripe C is broken in the upper part, and runs down to the next succeeding ocellus, not represented in the wood- cut ; D to the next lower one, and EO with the stripes E and F. Lastly, the several ocelli are separated from each other by a pale sui'face bear- ing irregular black marks. I will next describe the other extreme of the series, namely, the first trace of an ocellus. The short se- condary wing -feather (fig. 58), nearest to the body, is marked like the other feathers, with oblique, lon- gitudinal, rather irregular, rows of very dark spots. The basal spot, or that near- est the shaft, in the five lower rows (excluding the lowest one) is a little larger than the other spots of the same row, and a little more elon- gated in a transverse direc- tion It differs also from the other spots by being bordered on its upper side with some dull fulvous shading. But this '•pot is not in any way more remarkable than those on the plumage of many birds, and might easily be overlooked. The next Mgher spot does not differ at all from the upper ones id Fig. 58. Basal part of the secondary-wing feather, nearest to the body. Chap. XIV. Birds — Gradation of Characters. 437 the same row. The larger basal spots occupy exactly the same relative position on these feathers, as do the perfect ocelli on the longer wing-feathers. By looking to the next two or three succeeding wing-feathers, an absolutely insensible gradation can be traced from one of the last-described basal spots, together with the next higher one in the same row, to a curious ornament, which cannot be called an ocellus, and which I will name, from the want of a better term, an " elliptic ornament." These are shewn in the accompanying figure (fig. 59). We here see several oblique rows. A, B, C, D, A B c c Fig. 59. Portion of one of the Becond.iry wing featbcrs near to the body, shewing the 80-called elliptic ornaments. The right-hand figure is given merely as a diagram for the sake of the letters of reference. A, H, C, I), &c. Bows of spots running c. The next succeeding spot or mark in down to and forming the elliptic the same row. ornaments. d. Apparently a broken prolongation of 6. Lowest spot or mark in row B. the spot c in the same row B. &c. (see the lettered diagram on the right hand), of dark spots of the usual character. Each row of spots runs down to and is connected with one of the elliptic ornaments, in exactly the same manner as each stripe in fig. 57 runs down to, and is connected with, one of the ball-and-socket ocelli. Looking to any one row, for instance, B, in fig. 59, the lowest mark (6) is thicker and considerably longer than the upper spots, and has its left extremity pointed and curved upwards. This black mark 438 The Descent of Man Paut IL is abruptly bordered on its upper side by a rather broad space of richly shaded tints, beginning with a narrow brown zone, which passes into orange, and this into a pale leaden tint, with the end towards the shaft much paler. These shaded tints together fill up the whole inner space of the elliptic ornament. The mark (&) corresponds in every respect with the basal shaded spot of the simple feather described in the last paragraph (fig. 58), but is more highly developed and more brightly coloured. Above and to the right of this spot (6 fig. 59), with its bright shading, there is a long narrow, black mark (c), belonging to the same row, and which is arched a little downwards so as to face (i). This mark is sometimes broken into two portions. It is also narrowly edged on the lower side with a fulvous tint. To the left of and above c, in the same oblique direction, but always more or less distinct from it, there is another black mark (cZ). This mark is generally sub-triangular and irregular in shape, but in the one lettered in the diagram it is xmusually narrow, elongated, and regular. It apparently consists of a lateral and broken prolongation of the mark (c), together with its confluence with a broken and prolonged part of the next spot above ; but I do not feel sure of this. These three marks, 6, c, and cZ, with the intervening bright shades, form together the so-called elliptic ornament. These ornaments placed parallel to the shaft, manifestly correspond in position with the ball-and-socket ocelli. Their extremely elegant appearance can- not be appreciated in the drawing, as the orange and leaden tints, contrasting so well with the black marks, cannot be shewn. Between one of the elliptic ornaments and a perfect ball-and- socket ocellus, the gi-adation is so perfect that it is scarcely possible to decide when the latter term ought to be used. The passage from the one into the other is effected by the elongation and greater curvature in opposite directions of the lower black mark (& fig. 59), and more especially of the upper one (c), together with the contraction of the elongated sub-triangular or narrow mark (c?), so that at last these three marks become con- fluent, forming an irregular elliptic ring. This ring is gradually rendered more and more circiilar and regular, increasing at the same time in diameter. I have here given a drawing (fig. 60) of the natural size of an ocellus not as yet quite perfect. The lower part of the black ring is much more curved than is the lower mark in the elliptic ornament (& fig. 69). The upper part of the ring consists of two or three separate portions ; and there is only a trace of the thickening of the portion which forms the black mark above the white shade. This white shade itself is pot as yet much concentrated; and beneath it the surface is brighter coloui'ed than in a perfect ball-and-socket ocellus. Even Chap. XIV. Birds— Gradation of Characters. 439 m axx the most perfect ocelU, traces of tlie junction of three or four elon-ated black marks, by which the ring has been formed, may often be detected. The irregular sub-triangular or narrow mark fig. 59), manifestly forms, by its contraction and equalisation, the thickened portion of the ring above the white shade on a perfect ball- and-socket ocellus. The lower part of the ring is invariably a httle thicker than the other parts (see fig. 57), and this follows from the lower black mark of the elliptic ornament (b fig. 59) having origi- nally been thicker than the upper mark (c). Every step can be fol- lowed in the process of confluence and modification; and the black ring which surrounds the ball of the ocellus is unquestionably formed by the union and modification of the three black marks, i, c, d, of the elliptic ornament. The hre- gular zigzag black marks between the successive ocelli (see again fig. 57) are plainly due to the breaking up of the somewhat more regular but similar marks between the elliptic ornaments. The successive steps in the shading of the ball-and-socket ocelli can be followed out with equal clearness. The brown, orange, and pale leaden narrow zones, which border the lower black mark of the elliptic ornament, can be seen gradually to become more and more softened and shaded into each other, with the upper lighter part towards the left-hand corner ren- dered still hghter, so as to become almost white, and at the same time more contracted. But even in the most perfect ball-and- socket ocelli a sUght difference in the tints, though not in the shading, between the upper and lower parts of the ball can be perceived, as before noticed ; and the line of separation is oblique, in the same direction as the bright-coloured shades of the elliptic ornaments. Thus almost every minute detail in the shape and colouring of the ball-and-socket ocelli can be shewn to follow from gradual changes in the elliptic ornaments ; and the development of the latter can be traced by equally small steps from the union of two almost simple spots, the lower one (fig. 58) having some dull fulvous shading on its upper side. An ocellus in an inter- mediate condition between the elliptic ornament and the perfect ball-and-socket oceUuB. 44-0 The Descejit of Man. PabtII. The extremities of the longer secondary feathers which bear the perfect ball-and-socket ocelli, are peculiarly ornamented (fig. 61). The oblique longitudinal stripes suddenly cease upwards and become confused ; and above this limit the whole upper end of the feather (a) is covered with white dots, sur- rounded by little black rings, standing on a dark ground. The oblique stripe belonging to the uppermost ocellus (ft) is barely represented by a very short irregular black mark with the usual, curved, tranverse base. As this stripe is thus abruptly cut off, we can perhaps under- stand from what has gone before, how it is that the upper thickened part of the ring is here absent ; for, as before stated, this thickened part apparently stands in some relation with a broken prolonga- tion from the next higher spot. From the absence of the upper and thickened part of the ring, the uppermost ocellus, though perfect in all other respects, appears as if its top had been ol)liquely sliced off. It would, I think, perplex any one, who beheves that the plumage of the Argus-pheasant was created as we now see it, to account for the imperfect condition of the uppermost ocellus. I should add that on the secondary wing- feather farthest from the body, all the ocelli are smaller and less perfect than on the other feathers, and have the upper part of the ring deficient, as in the case just mentioned. The imperfection here seems to be connected with the fact that the spots on this feather shew less tendency than usual to become confluent into stripes ; they are on tlie contrary, often broken up into smaller spots, so that two or three rows run down to the same ocellus. Fig. 61. Puvtiou near summit of one of the secondary wing-feathers, bearing perfect ball-and-socket ocelli. a. Ornamented upper part. 6. Uppermost, imperfect ball-and-socket ocellus. (The shading above the white mark on the summit of the ocellus is here a little too dark.) c. Perfect ocellus. Chap. XIY. Birds — Gradation of ChatActers 44 1 There still remains another very cnrioias point, first observed by Mr. T. W. Wood," which deserves attention. In. a photograph, given me by Mr. Ward, of a specimen mounted as in the act ol display, it may be seen that on the feathers which are held perpendicularly, the white marks on the ocelli, representing light reflected from a convex surface, are at the upper or fm-ther end, that is, are directed upwards ; and the bird whilst displaying himself on the ground would naturally be illuminated fi'om above. But here comes the curious point, the outer feathers are held almost horizontally, and their- ocelli ought like- wise to appear as if illuminated from above, and consequently the white marks ought to be placed on the upper sides of the ocelli ; and wonderful as is the fact they are thus placed ! Hence the ocelli on the several feathers, though occupying very different positions with respect to the hght, all appear as if illuminated from above, just as an artist would have shaded them. Never- theless they are not illuminated from strictly the same point as they ought to be ; for the white marks on the ocelli of the feathers which are held almost horizontally, are placed rather too much towards the further end ; that is they are not suffi- ciently lateral. We have, however, no right to expect absolute perfection in a part rendered ornamental through sexual selec- tion, any more than we have in a part modified through natural selection for real use ; for instance in that wondrous organ the human eye. And we know what Helmholtz, the highest authority in Europe on the subject, has said about the human eye ; that if an optician had sold him an instrument so carelessly made, he would have thought himself fully justified in returning it.**^ We have now seen that a perfect series can be followed, fi'om simple spots to the wonderful ball-and-socket ornaments. Mr. Gould, who kindly gave me some of these feathers, fully agrees with me in the completeness of the gradation. It is obvious that the stages in development exhibited by the feathers on the same bird, do not at all necessarily shew us the steps passed through by the extinct progenitors of the species; but they probably give us the clue to the actual steps, and they at least prove to demonstration that a gradation is possible. Bearing in mind how carefully the male Argus pheasant displays Ms plumes before the female, as well as the many facts rendering it probable that female birds prefer the more attractive males, no one who admits the agency of sexual selection in any case, will deny that a simple dark spot with some fulvous shading might be converted, through the approximation and modification of two adjoining " The 'Field,' May 28, 1870. Subjects,' Eng. trans. 1873, pp. 219, 'Popular Lectures on Scientific 227, 269, 390. 442 The Descent of Ma7u Pabt II. spots, together with some slight increase of colour, into one of the so-called elliptic ornaments. These latter ornaments have been shewn to many persons, and all have admitted that they are beautiful, some thinking them even more so than the ball-and- socket ocelli. As the secondary plumes became lengthened through sexual selection, and as the elhptic ornaments increased in diameter, their colom-s apparently became less bright ; and then the ornamentation of the plumes had to bo gained by an improvement in the pattern and shading ; and this process was carried on until the wonderful ball-and-socket ocelli were finally developed. Thus we can understand — and in no other way as it seems to me — the present condition and origin of the orna- ments on the wing-feathers of the Argus jpheasant. From the light afforded by the principle of gradation — from what we know of the laws of variation — from the changes which have taken place ia many of our domesticated birds — and, lastly, fi'om the character (as we shall hereafter see more clearly) of the immature plumage of young birds — we can sometimes indicate with a certain amount of confidence, the probable steps by which the males have acquired their brilliant plumage and various ornaments ; yet in many cases we are involved in complete darkness. Mr. Gould several years ago pointed out to me a humming-bird, the Urostide lenjamini, remarkable for the curious differences between the sexes. The male, besides a splendid gorget, has greenish-black tail-feathers, with the four central ones tipped with white ; in the female, as with most of the allied species, the three outer tail-feathers on each side are tipped with white, so that the male has the four central, whilst the female has the six exterior feathers ornamented with wliite tips. What ■makes the case more cmious is that, although the colouring of the tail differs remarkably in both sexes of many kinds of humming-birds, Mr. Gould does not know a single species, be- sides the Urosticte, in which the male has the four central feathers tipped with white. The Duke of Argyll, in commenting on this case,^ passes over sexual selection, and asks, " What explanation does the law of " natm-al selection give of such specific varieties as these ?" He answers " none whatever ;" and I quite agree with him. But can this be so confidently said of sexual selection ? Seeing in how many ways the tail-feathers of humming-birds difier, why should not the four central feat'hers have varied in thi.3 one species alone, so as to have acquired white tips ? The variations ■may have been gradual, or somewhat abrupt as in the case »» « The Reign of Law,' 1867, p. 247. Chap. XIV. Birds — Gradation of Characters. 443 recently given of the humming-birds near Bogota, in which certain individuals alone have the " central taU-feathers tipped " with beautiful green." In the female of the Urosticte I noticed extremely minute or rudimental white tips to the two outer of the four central black tail-feathers ; so that here we have an indication of change of some kind in the plumage of this species. If we grant the possibility of the central tail- feathers of the male varying in whiteness, there is nothing strange in such variations having been sexually selected. The white tips, together with the small white ear-tufts, certainly add, as the Duke of Argyll admits, to the beauty of the male ; and whiteness is apparently appreciated by other birds, as may be inferred from such cases as the snow-white male of the Bell-bird. The statement made by Sir E. Heron should not be forgotten, namely, that his peahens, when debarred from access to the pied peacock, would not unite with any other male, and during that season produced no offspring. Nor is it strange that variations in the tail-feathers of the Urosticte should have been specially selected for the sake of ornament, for the next succeeding genus in the family takes its name of Metallura from the splendour of these feathers. We have, moreover, good evidence that humming- birds take especial pains in displaying their tail-feathers ; Mi-. Belt,°* after describing the beauty of the Florisuga mellivora, says, " I have seen the female sitting on a branch, and two males " displaying their charms in front of her. One would shoot up " hke a rocket, then suddenly expanding the snow-white tail, like " an inverted parachute, slowly descend in front of her, turning " round gradually to shew off back and front The " expanded white tail covered more space than all the rest of the " bird, and was evidently the grand feature in the performance, " Whilst one male was descending, the other would shoot up " and come slowly down expanded. The entertainment would " end in a fight between the two performers ; but whether the " most beautiful or the most pugnacious was the accepted " suitor, I know not." Mr. Gould, after describing the peculiar plumage of the Urosticte, adds, " that ornament and variety is " the sole object, I have myself but little doubt." If this bo admitted, we can perceive that the males which during former times were decked in the most elegant and novel manner would have gained an advantage, not in the ordinary struggle for life, but in rivalry with other males, and would have left a larger number of offspring to inherit their newly-acquii-ed beauty. " ' The Naturalist in Nicaragua, ' Introduction to the Trochi- t874, p. 112 Hdae,' 1861, p. 110. 444 The Descent of Man. Pabt II CHAPTER XV. BIRDS — continued. Discussion as to why the males alone of some species, and both seiea oi others, are brightly coloured — On sexually-limited inheritance, as applied to various structures and to brightly-coloui-ed plumage — Nidification in relation to colour — Loss of nuptial plumage during the winter. Y/b have in this chapter to consider, why the females of many birds have not acquired the same ornaments as the male ; and why, on the other hand, both sexes of many other bu-ds are equally, or almost equally, ornamented? In the following chapter we shall consider the few cases in which the female is more conspicuously coloured than the male. In my ' Origin of Species I briefly suggested that the long taU of the peacock would be inconvenient, and the conspicuous black colour of the male capercailzie dangerous, to the female during the period of incubation; and consequently that the transmission of these characters from the male to the female offspring had been checked through natural selection. I stiU think that this may have occurred in some few instances : btat after mature reflection on all the facts which I have been able to collect, I am now inclined to beheve that when the sexes differ the successive variations have generally been from the first hmited in their transmission to the same sex ia which they first arose. Since my remarks appeared, the subject of sexual coloration has been discussed in some very interesting papers by Mr. Wallace,^ who believes that in almost all cases the successive variations tended at first to be transmitted equally to both sexes; but that the female was saved, through natural selection, from acquiring the conspicuous colours of the male, owing to the danger which she would thus have incurred during incubation. This view necessitates a tedious discussion on a diflScult point, namely, whether the transmission of a character, which is at first inherited by both sexes, can be subsequently limited in its transmission to one sex alone by means of natural selection. We must boar in mind, as shewn in the preliminary chapter on sexual selection, that characters which are limited in tbcir development to one sex are always latent in the other. An ' Fourth edition, 1866, p. 241. 1867. ' Journal of TraTcJ," voL L 2 ' Westminster Review,' July, 1868, p. 73. Chap. XV. Birds — Sexually Limited Inherita?tce. 445 imaginary illustration will best aid us in seeing the difficulty of the case : we may suppose that a fancier wished to make a breed of pigeons; in which the males alone should be coloured of a pale blue, whilst the females retained their former slaty tint. As with pigeons characters of all kinds are usually trans- mitted to both sexes equally, the fancier would have to try to convert this latter form of inheritance into sexuaUy-limited transmission. All that he could do woiild be to persevere in selecting every male pigeon which was in the least degree of a paler blue; and the natural result of this process, if steadily carried on for a long time, and if the pale variations were strongly inherited or often recurred, would be to make his whole stock of a lighter blue. But our fancier would be com- pelled to match, generation after generation, his pale blue males with slaty females, for he wishes to keep the latter of this colour. The result would generally be the production either of a mongrel piebald lot, or more probably the speedy and complete loss of the pale-blue tint; for the primordial slaty colour would be transmitted with prepotent force. Supposing, however, that some pale-blue males and slaty females were produced during each successive generation, and were always crossed together ; then the slaty females would have, if I may tise the expression, much blue blood in their veins, for their fathers, grandfathers, &c., will all have been blue birds. Under these circumstances it is conceivable (though I know of no distinct facts rendering it probable) that the slaty females might acquire so strong a latent tendency to pale-blueness, that they would not destroy this colour in their male offspring, their female offspring still inheriting the slaty tint. If so the desired end of making a breed with the two sexes permanently different in colour might be gained. The extreme importance, or rather necessity in the above case of the desired character, namely, pale-blueness, being present though in a latent state in the female, so that the male offspring should not be deteriorated, will be best aispreciated as follows : the male of Soemmerring's pheasant has a tail thirty-seven inches in length, whilst that of the female is only eight inches ; the tail of the male common pheasant is about twenty inches, and that of the female twelve inches long. Now if the female Scemmerring pheasant with her short tail were crossed with the male common pheasant, there can be no doubt that the male hybrid offspring would have a much longer tail than that of the pure offspring of the conunon pheasant. On the other- hand, if the female common pheasant, with a tail much longer than that of the female Scemmerring pheasant, were crossed witJa the male 446 The Descent of Man. Part 11. of the latter, the male hybrid offspring would have a much slwrter tail than that of the pure offspring of Soemmerring's pheasant.' Our fancier, in order to make his new breed with the males of a pale-blue tint, and the females unchanged, would have to continue selecting the males during many generations; and each stage of paleness would have to be fixed in the males, and rendered latent in the females. The task would be an extremely difficult one, and has never been tried, but might possibly be successfully carried out. The chief obstacle would be the early and complete loss of the pale-blue tint, from the necessity of reiterated crosses -Nvith the slaty female, the latter not having at first any latent tendency to produce pale-blue offspring. On the other hand, if one or two males were to vary ever so slightly in paleness, and the variations were fi-om the first limited in their transmission to the male sex, the task of making a new breed of the desii-ed kind would be easy, for such males would simply have to be selected and matched with ordinary females. An analogous case has actually occurred, for there are breeds of the pigeon in Belgium* in which the males alone are marked with black strise. So again Mr. Tegetmeier has recently shewn ^ that dragons not rarely produce silver-coloured bii'ds, which are almost always hens; and he himself has bred ten fuch females. It is on the other hand a very unusual event when a silver male is produced; so that nothing woiild be easier, if desired, than to make a breed of dragons with blue males and silver females. This tendency is indeed so strong that when Mr. Tegetmeier at last got a silver male and matched him with one of the silver females, he expected to get a breed with both sexes thus coloured; he was however disappointed, for the young male reverted to the blue colour of his grand- father, the young female alone being silver. No doubt with patience this tendency to reversion in the males, reared from an occasional silver male matched with a silver hen, might be eliminated, and then both sexes would be coloured ahke ; and this very process has been followed with success by Mr. Esquilant in the case of silver turbits. With fowls, variations of colour, limited in their transmis- sion to the male sex, habitually occur. When this form of 3 Temrainck says that the tail of For the common pheasant, se*" the female Phasianus Smmmerringii Macgillivray, ' Hist. Brit. Birds,' is only six inches long, 'Planches vol. i. pp. 118-121. colorizes,' vol. v. 1838, pp. 487 and ♦ Dr. Chapuis, 'Le Pigeon Voya- 488: the measurements above given geur Beige,' 18(35, p. 87. urere made for me by Mr. Sclater. » The ' Firld,' Sept. 1872. Chap. XV. Birds — Sexually Limitea Inheritance. 447 iaheritance prevails, it might well happen that some of the successive variations -would be transferred to the female, who would then slightly resemble the male, as actually occurs in some breeds. Or again, the greater number, but not all, of the successive steps might be transferred to both sexes, and the female would then closely resemble the male. There can hardly be a doubt that this is the cause of the male pouter pigeon having a somewhat larger crop, and of the male carrier pigeon having somewhat larger wattles, than their respective females ; for fanciers have not selected one sex more than the other, and have had no wish that these characters should be more strongly displayed in the male than in the female, yet this is the case with both breeds. The same process would have to be followed, and the same difficulties encountered, if it were desired to make a breed with the females alone of some new colour. Lastly, our fancier might wish to make a breed with the two sexes difiering fi'om each other, and both from the parent- species. Here the difficulty would be extreme, unless the suc- cessive variations were from the first sexually limited on both sides, and then there would be no difficulty. We see this with the fowl ; thus the two sexes of the pencilled Hambui-ghs differ greatly from each other, and from the two sexes of the abori- ginal GaUus bankiva ; and both are now kept constant to their standard of excellence by continued selection, which would be impossible unless the distinctive characters of both were limited in their transmission. The Spanish fowl offers a more curious case ; the male has an immense comb, but some of the successive variations, by the accumulation of which it was acquired, appear to have been transferred to the female ; for she has a comb many times larger than that of the females of the parent-species. But the comb of the female differs in one respect from that of the male, for it is apt to lop over ; and within a recent period it has ^ea ordered by the fancy that this should always be the case, and success has quickly followed the order. Now the lopping of the comb must be sexually limited in its transmission, otherwise it would prevent the comb of the male from being perfectly upright, which would be abhorrent to every fancier. On the other hand, the uprightness of the comb in the male must likewise be a sexually-Umited character, otherwise it would prevent the comb of the female from lopping over. From the foregoing illustrations, we see that even with almost unlimited time at command, it wculd be an extremely difficult and complex, perhaps an impossiVJe process, to change one form of transmission into the other through selection. Therefore, 448 The Descent of Man. Pabt U. without distinct evidence in each case, I am unwilling to admit that this has been effected in natural species. On the other hand, by means of successive variations, which were from the fii'st sexually limited in their transmission, there would not be the least difficulty in rendering a male bird widely different in colour or in any other character from the female; the latter being left unaltered, or slightly altered, or specially modijEled for the sake of protection. As bright colours are of service to the males in their rivalry with other males, such colours would be selected, whether or not they were transmitted exclusively to the same sex. Conse- quently the females might be expected often to partake of the brightness of the males to a greater or less degree; and this occurs with a host of species. If all the successive variations were transmitted equally to both sexes, the females would be indistinguishable from the males ; and this likewise occurs with many birds. If, however, dull colours were of high importance for the safety of the female during incubation, as with many ground birds, the females which varied in brightness, or which received through inheritance from the males any marked ac- cession of brightness, would sooner or later be destroyed. But the tendency in the males to continue for an indefinite period transmitting to their female offspring their own brightness, would have to be eliminated by a change in the form of in- heritance ; and this, as shewn by our previous illustration, would be extremely difficult. The more probable result of the long-continued destruction of the more brightly-coloured females, supposing the equal form of transmission to prevail, would be the lessening or annihilation of the bright colours of the males, owing to their continual crossing with the duller females. It would be tedious to follow out all the other possible results; but I may remind the reader that if sexually-limited valuations in brightness occurred in the females, even if they were not in the least injurious to them and consequently were not eUmi- nated, yet they would not be favoured or selected, for the male usually accepts any female, and does not select the more at- tractive individuals; consequently these variations would be liable to be lost, and would have little influence on the character of the race ; and this wiU aid in accounting for the females being commonly duller-coloured than the males. In the eighth chapter instances were given, to which many might here be added, of variations occurring at various ages, and inherited at the corresponding ago. It was also shewn that va- riations which occur late in life are commonly transmitted to the same sex in which they first appear ; whilst variations occurring Chap. XV. Birds— Dex elopinent of Spurs. 449 cftrly in life ai-e apt to be transmitted to both sexes ; not that all the cases of sexually-limited transmission can thus be accounted for. It was further shewn that if a male bird varied by be- coming brighter whilst yoimg, such variations would be of no service until the age for reproduction had arrived, and there was competition between rival males. But in the case of birds living on the groiind and commonly in need of the protection of dull colours, bright tints would be far more dangerous to the young and inexperienced, than to the adult males. Conse- quently the males which varied ia brightness . whilst young would suffer much destruction and be eliminated through natural selection ; on the other hand, the males which varied in this manner when nearly mature, notwithstanding that they were exposed to some additional danger, might survive, and from being favoured through sexual selection, would procreate their kind. As a relation often exists between the period of variation and the form of transmission, if the bright-coloui'ed young males were destroyed and the mature ones were suc- cessful ia their courtship, the males alone would acquire bril- liant colours and would transmit them exclusively to their male offspring. But I by no means wish to maintain that the influence of age on the form of transmission, is the sole cause of the great difference in brilliancy between the sexes of many birds. When the sexes of birds differ in colour, it is interesting to determine whether the males alone have been modified by sexual selection, the females having been left unchanged, or only partially and indh-ectly thus changed ; or whether the females have been specially modified through natm-al selection for the sake of pro- tection. I will therefore discuss this question at some length, even more fully than its intrinsic importance deserves ; for various curious collateral points may thus be conveniently considered. Before we enter on the subject of colour, more especially in reference to Mr. Wallace's conclusions, it may be useful to discuss some other sexual differences under a similar point of view. A breed of fowls formerly existed in Germany * in which the hens were furnished with spurs ; they were good layers, but they so greatly disturbed their nests with their spurs that they could not be allowed to sit on their own eggs. Hence at one time it appeared to me probable that with the females of the wild Gallinaceee the development of spurs had been checked through natural selection, from the injury thus caused to their nests. This seemed all the more probable, as wing-spurs, which would pot be injurious during incubation, arc often as well-developed • Bcchstein, 'Naturgesch. Deutschlands," 1793, B. iii. s. 339. 2 Q 450 The Descent of Man. m the female as in the male; though in not a few cases they are rather larger in the male. When the male is furnished with log-spurs the female almost always exhibits rudiments of them, — the rudiment sometimes consisting of a mere scale, as in Gallus. Hence it might be argued that the females had abori- ginally been furnished with well-developed spui-s, but that these had subsequently been lost through disuse or natural selection. But if this view be admitted, it would have to be extended to innumerable other cases; and it implies that the female pro- genitors of the existing spur-bearing species were once encum- bered with an injurious appendage. In some few genera and species, as in Galloperdix, Acomus, and the Javan peacock {Favo muticus), the females, as well as the males, possess well-developed leg-spm-s. Are we to infer from this fact, that they construct a different sort of nest from that made by their nearest allies, and not liable to be injured by their spurs ; so that the spurs have not been removed. Or are we to suppose that the females of these several species especially require spui's for their defence ? It is a more probable conclusion that both the presence and absence of spurs in the females result from different laws of inheritance having prevailed, indepen- dently of natural selection. "With the many females in which spurs appear as rudiments, we may conclude that some few of the successive variations, through which they were developed in the males, occurred very early in life, and were consequently transferred to the females. In the other and much rarer cases, in which the females possess fully developed sptu's, we may conclude that all the successive variations were ti-ansferred to them ; and that they gradually acquired and inherited the habit of not disturbing their nests. The vocal organs and the feathers variously-modified for pro- ducing sound, as well as the proper instincts for using them, often differ in the two sexes, but are sometimes the same in both. Can such differences be accounted for by the males having acquired these organs and instincts, whilst the females have been saved from inheriting them, on account of the danger to which they -would have been exposed by attracting the attention of birds or beasts of prey ? This does not seem to me probable, when we think of the multitude of birds which with impunity gladden the country with their voices during the spring.' It is 7 Daines Barrington, however, cubation. He adds, that a similar thought it probable ('Phil. Transact.' view may possibly account for the 1773, p. 164) that few female birds inferiority of the female to the cing, because the talent would have male in plumage, been dnugorous to them during iu- Chap. XV. Birds — Length of Female' s Tail. 451 a safer conclusion that, as vocal and instrumental organs are of special service only to the males during their courtship, these organs were developed through sexual selection and their con- stant use in tlaat sex alone — the successive variations and the eifects of use having been from the first more or less limited in transmission to the male offspring. Many analogous cases could be adduced ; those for instance of the plumes on the head being generally longer in the male than in the female, sometimes of equal length in both sexes, and occasionally absent in the female, — these several cases occuring in the same group of birds. It would be difficult to account for such a difference between the sexes by the female having been benefited by possessing a slightly shorter crest than the male, and its consequent diminution or complete suppression through natural selection. But I will take a more favourable case, namely the length of the tail. The long train of the peacock would have been not only inconvenient but dangerous to the peahen during the period of incubation and whilst accompany- ing her young. Hence there is not the least a priori improba- bility in the development of her tail having been checked through natural selection. But the females of various phea- sants, which apparently are exposed on their open nests to as much danger as the peahen, have tails of considerable length. The females as well as the males of the Menura superba have long tails, and they build a domed nest, which is a great anomaly in so large a bird. Naturalists have wondered how the female Menura could manage her tail during incubation ; but it is now known * that she " enters the nest head first, and then " turns round with her tail sometimes over her back, but more " often bent round by her side. Thus in time the tail becomes " quite askew, and is a tolerable guide to the length of time the " bird has been sitting." Both sexes of an Australian kingfisher (Tanysiptera sylvia) have the middle tail-feathers greatly length- ened, and the female makes her nest in a hole ; and as I am informed by Mr. E. B. Sharpe these feathers become much crumpled during incubation. In these two latter cases the great ler^th of the tail- leathers must be in some degree inconvenient to the female ; and as in both species the tail-feathers of the female are somewhat shorter than those of the male, it might be argued that their full development had been prevented through natural selection. But if the development of the tail of the peahen had been checked only when it became inconveniently or dangerously great, she would haye retained a much longer tail than she actually possesses; * Mr. Ramsay, in ' Proc. Zoolog. Soc' 1868, p. 50. 2 G 2 452 The Descent of Man. I'AET 11. for her tail is not nearly so long, relatively to the size of her bo(iy, as that of many female pheasants, nor longer than that of the female turkey. It must also be borne in mind, that in accordance with this view as soon as the tail of the peahen became dangerously long, and its development was consequently checked, she would have continually reacted on her male pro- geny, and thus have prevented the peacock from acquu-ing his present magnificent train. We may therefore infer that the length of the tail in the peacock and its shortness in the pea- hen are the result of the requisite variations in the male having been from the first transmitted to the male offspring alone. We are led to a nearly similar conclusion with respect to the length of the tail in the various species of pheasants. In the Eared pheasant (Crossoptilon auritum) the tail is of equal length in both sexes, namely, sixteen or seventeen inches ; in the common phea- sant it is about twenty inches long in the male and twelve in the female ; in Soemmerring's pheasant, thirty-seven inches in the male and only eight in the female ; and lastly in Eeeve's phea- sant it is sometimes actually seventy-two inches long in the male and sixteen in the female. Thus in the several species, the tail of the female differs much in length, irrespectively of that of the male ; and this can be accounted for, as it seems to me, with much more probability, by the laws of inheritance, — that is by the successive variations having been from the first more or less closely limited in their transmission to the male sex, than by the agency of natural selection, resulting from the length of tail being more or less injurious to the females of these several allied species. We may now consider Mr. Wallace's arguments in regard to the sexual coloration of bu'ds. He believes that the bright tints originally acquired thi'ough sexual selection by the males, would in all, or almost all cases, have been transmitted to the females, unless the transference had been checked through natural selec- tion. I may here remind the reader that various facts opposed to this view have already been given under reptiles, amphibians, fishes, and lepidoptera. Mr. Wallace rests his belief chiefly, but not exclusively, as we shall see in the next chapter, on the following statement,* that when both sexes are coloured in a very conspicuous manner, the nest is of such a nature as to conceal the sitting bird; but when there is a marked contrast of colour between the sexes, the male being gay and the female dull-coloured, the nest is open and exposes the sitting bird to view. This coincidence, as far as it goes, cer- tainly seems to favour the belief that the females which sit on » 'Journal of Travel,' edited by A. Murray, vol. i. 1868, p. 78. CiiAP- XV. Birds — Colour and Nidificatioji. 453 open nests have been specially modified for the sake of protec- tion ; but we shall presently see that there is another and more probable explanation, namely, that conspicuous females have acquired the instinct of building domed nests oftener than dull- coloured birds. Mr. "Wallace admits that there are, as might have been expected, some exceptions to his two rules, but it is a '^y^-<'A^^f',P-^^V 108. Gould's 'Handbook oi Audubon, Orni«nolcgical Bio- the Birds cf Australia,' vol. i. p. 463. graphy, t;1. i. p. 233. la for instance, the female Fupff' 454 Tlie Descent of Man. PabtIL In regard to birds whicli build in holes or construct domed nests, other advantages, as Mr. Wallace remarks, besides con- cealment are gained, such as shelter from the rain, greater warmth, and in hot countries protection from the sun;" so that it is no valid objection to his view that many birds having both sexes obscurely coloured build concealed nests."' The female Horn-bill {Buceros), for instance, of India and Africa is protected dui-ing incubation with extraordinary care, for she plasters up with her own excrement the orifice of the hole in which she sits on her eggs, leaving only a small orifice through which the male feeds her ; she is thus kept a close prisoner during the whole period of incubation ; " yet female horn-bills are not more con spicuously coloured than many other birds of equal size which build open nests. It is a more serious objection to IVIr. Wallace's view, as is admitted by him, that in some few groups the males are brilLiantly colom-ed and the females obscure, and yet the latter hatch their eggs in domed nests. This is the case with, the Grallin£B of Australia, the Superb Warblers (Malui-idse) of the same country, the Sun-birds (Nectarinise), and with several of the Australian Honey-suckers or Meliphagidse.^'' If we look to the birds of England we shall see that there is no close and general relation between the colours of the female and the natiu'e of the nest which is constructed. About forty of our British birds (excluding those of large size which could defend themselves) build in holes in banks, rocks, or trees, or construct domed nests. If we take the colours of the female goldfinch, bullfinch, or blackbird, as a standard of the degree of con- spicuousness, which is not highly dangerous to the sitting female, then out of the above forty birds, the females of only twelve can be considered as conspicuous to a dangerous degree. tomena macroura has the head and tail dark blue with reddish loins ; the female Lampornis poi-phyrwus is blackish-green on the upper surface, with the lores and sides of the throat crimson; the female Eulampis jugularis has the top of the head and back green, but the loins and the tail are crimson. Many other instances of highly conspicuous females could be given. See Mr. Gould's magnificent work cn this family. " Mr. Salvin noticed in Guate- mala ('Ibis,' 1864, p. 375) that humming-birds were much more unwilling to leave their nests during very hot weather, when the sun was shining brightly, as if their eggs would be thus injured, than during cool, cloudy, or rainy weather. I may specify, as instances of dull-coloured birds building con- cealed nests, the species belonging to eight Australian genera, de- scribed in Gould's ' Handbook of the Birds of Australia,' vol. i. pp. 340, 362, 365, 383, 387, 389, 391, 414. Mr. C. Horne, 'Proc. Zoolog. Soc' 1869, p. 243. On the nidification and colours of these latter species, see Gould's ' Handbook,' &c., ToL. i. pp. 504 527, Chap XV. Birds — Colour and Nidification. 455 the remaining twenty-eight being inconspicuous.^^ Nor is there any close relation within the same genus between a well-pro- nounced difference in colour between the sexes, and the nature of the nest constructed. Thus the male house sparrow {Passer domesticus) differs much from the female, the male tree-sparrow (P, montanus) hardly at all, and yet both build well-concealed nests. The two sexes of the common fly-catcher {Musicapa grisola) can hardly be distinguished, whilst the sexes of, the pied fly-catcher {M. luctuosa) differ considerably, and both species buUd iu holes or conceal their nests. The female black- bh'd {Turdus merula) differs much, the female ring-ouzel (T. torquatus) differs less, and the female common thrush (T. musicus) hardly at all from their respective males ; yet all build open nests. On the other hand, the not very distantly-allied water-ouzel {Cindus aquaticus') builds a domed nest, and the sexes differ about as much as in the ring-ouzel. The black and red grouse (Tetrao tetrix and T. scoticus) build open nests in equally well- concealed spots, but in the one species the sexes differ gi-eatly, and in the other very little. Notwithstanding the foregoing objections, I cannot doubt, after reading Mr. Yfallace's excellent essay, that looking to the bu'ds of the world, a large majority of the species in which the females are conspicuously coloured (and in this case the males with rare exceptions are equally conspicuous), build concealed nests for the sake of protection. Mr. Wallace enumerates" a long series of groups in which this rule holds good ; but it wlU suffice here to give, as instances, the more familiar groups of kingfishers, toucans, trogons, puff- birds (Gapitonidse), plantain- eaters (Musophagse), woodpeckers, and parrots. Mr. Wallace believes that in these groups, as the males gradually acquired through sexual selection their brilliant colours, these were transferred to the females and were not eliminated by natural selection, owing to the protection which they already enjoyed ^' I have consulted, on this sub- ject, Macgillivray's ' British Birds,' and though doubts may be enter- tained in some cases in regard to the degree of concealment of the nest, and to the degree of coa- spicuousness of the female, yet the following birds, which all lay their eggs in holes or in domed nests, can hardly be considered, by the above standard, as conspicuous : Passer, 2 species ; Sturnus, of which the female is considerably less brilliant than the male ; Cinclus ; Motacilla boarula (?); Erithacus (?) ; Fru- ticola, 2 sp. ; Saxicola ; Ruticilla, 2 sp. ; Sylvia, 3 sp. ; Parus, 3 sp. ; Mecistura ; Anorthura ; Certhia ; Sitta; Yunx; Muscicapa, 2 sp. ; Hirundo, 3 sp. ; and Cypselus. The females of the following 12 birds may be considered as conspicuous, according to the same standard, viz., Pastor, Motacilla alba, Parus major and P. caruleus, Upupa, Picus, 4 .sp., Coracias, Alcedo, and Merops. ' Journal of Travel,' edited by A. Murray, vol. i. p. 78. 456 The Descent of Man. f AKT II, from their manner of nidification. According to this view, their present manner of nesting was acquired before their present colours. But it seems to me much more probable that in most cases, as the females wore gradually rendered more and more brilliant from partaking of the colours of the male, they were gradually led to change their instincts (supposing that they originally built open nests), and to seek protection by building domed or eoncealed nests. No one who studies, or mstance, Audubon's accoxmt of the differences in the nests of the same species in the Northern and Southern United States,-" feel any great difficulty in admitting that birds, either by a change (in the strict sense of the word) of their habits, or through the natural selection of so-called spontaneous variations of instinct, might readily be led to modify their manner of nesting. This way of viewing the relation, as far as it holds good, between the bright colom's of female bii-ds and their manner of nesting, receives some support from certain cases occurring in the Sahara Desert. Here, as in most other deserts, various birds, and many other animals, have had their colours adapted in a wonderful manner to the tints of the surrounding surface. Nevertheless there are, as I am informed by the Eev. Mr. Tristram, some curious exceptions to the rule ; thus the male of the Monticola cyanea is conspicuous from his bright blue colour, and the female almost equally conspicuous from her mottled brown and white plumage; both sexes of two species ofDro- molsea are of a lustrous black ; so that these three species are far from receiving protection from their colours, yet they are able to survive, for they have acquired the habit of taking refuge from danger in holes or crevices in the rocks. With respect to the above groups in which the females are conspicuously coloured and build concealed nests, it is not necessary to suppose that each separate species had its nidifying instinct specially modified ; but only that the early progenitors of each group were gradually led to build domed or concealed nests, and afterwards transmitted this instinct, together with their bright colours, to their modiiied descendants. As far as it can be trusted, the conclusion is interesting, that sexual selection, together with equal or nearly equal inheritance by both sexes, have indirectly determined the manner of nidification of whole groups of birds. According to Mr. Wallace, even in the groups in which the females, from being protected in domed nests during incubation, ^'o See many statements in the the nests of Italian birds by Eugcn:o •Ornithological Biography.' See, Bettoni, in the ' Atti dcll:i Socicti also, some curious obserrations ou Italiana,' vol. xi. 18(59, p. -IS?. Chap. XY. Birds — Colour and Nidificai ion. 457 have not had their bright colours eliminated through njiitural selection, the males often differ in a slight, and occasionally in a considerable degree, from the females. This is a significant fact, for such differences in colour must be accounted for by some of the -variations in the males having been from the first limited in transmission to the same sex ; as it can hardly be maintained that those differences, especially when very slight, seiTC as a protec- tion to the female. Thus all the species in the splendid gi'ouij of the Trogons build in holes ; and Mr. Gould gives figures of both sexes of twenty -five species, in all of which, ^vith one partial exception, the sexes differ sometimes slightly, sometimes con- spciuously, in colour, — the males being always finer than the females, though the latter are likewise beautiful. All the species of kingfishers build in holes, and with most of the species the sexes are equally brilliant, and thus fai- Mr. Wallace's rule holds good ; but in some of the Australian species the colours of the females are rather less vivid than those of the male ; and in one splendidly- coloured species, the sexes differ so much that they were at first thought to be specifically distinct.^^ Mr. E. B. Sharpe, who has especially studied this group, has shewn me some American species (Ceryle) in which the breast of the male is belted with black. Again, in Carcineutes, the difference between the sexes is conspicuous : in the male the upper surface is dull- blue banded with black, the lower surface being partly fawn- coloured, and there is much red about the head ; in the female the upper sui-face is reddish-brown banded with black, and the lower surface white with black markings. It is an interesting fact, as shewing how the same peculiar style of sexual coloui'ing often characterises allied forms, that in three species of Dacelo the male differs from the female only in the tail being dull-blue banded with black, whilst that of the female is brown with blackish bars ; so that here the tail differs in colour in the two sexes in exactly the same manner as the whole upper surface in the two sexes of Carcineutes. With parrots, which likewise build in holes, we find analogous cases : in most of the species both sexes are brilhantly coloured and indistinguishable, but in not a few species the males are coloured rather more vividly than the females, or even very differently from them. Thus, besides other strongly-marked diiferences, the whole under sm-face of the male King Lory (Ajjrosmictus scapulatus) is scarlet, whilst the throat and chest of the female is green tinged with red: in the Euphema sidendidn See his 'Monograph of the 'Handbook to the Firds of Aivs- Trogonida;,' first edition. tnilia,' vol. i. p. 13? ; see, also, i.ix, " Nnmeiy Cyanalcvon. Gould's loO, 458 The Descent of Man. Pabt n. there is a similar difference, the face and •wing-coverts moreover of the female being of a paler blue than in the male.^ In the family of the tits (Farince), which build concealed nests, the female of our common blue tomtit (Parus cceruleus) is " much " less brightly coloured " than the male ; and in the magnificent Sultan yellow tit of India the difference is greater.''* Again in the great group of the woodpeckers,^ the sexes are generally nearly ahke, but in the Meyapicus validus all those parts of the head, neck, and breast, which are crimson in the male are pale brown in the female. As in several woodpeckers the head of the male is bright crimson, whilst that of the female is plain, it occurred to me that this colour might possibly make the female dangerously conspicuous, whenever she put her head out of the hole containing her nest, and consequently that this colour, in accordance with Mr. Wallace's behef, had been elimi- nated. This view is strengthened by what Malherbe states with respect to Indopicus carlotta ; namely, that the young females, like the young males, have some crimson about their heads, but that this colour disappears in the adult female, whilst it is intensified in the adult male. Nevertheless the following con- siderations render this view extremely doubtful : the male takes a fair share in incubation,^" and would be thus almost equally exposed to danger ; both sexes of many species have their heads of an equally bright crimson ; in other species the difference between the sexes in the amount of scarlet is so slight that it can hardly make any appreciable difference in the danger incui-red ; and lastly, the colouring of the head in the two sexes often differs slightly in other ways. The cases, as yet given, of slight and graduated differences in colour between the males and females in the groups, in which as a general rule the sexes resemble each other, all relate to species which build domed or concealed nests. But similar gradations may likewise be observed in groups in which the sexes as a general rule resemble each other, but which build open nests. As I have before instanced the Australian parrots, so I may here instance, without giving any details, the Austrahan pigeons.-' It deserves especial notice that in all these cases the shght Every gradation of difference bstwcen the sexes may be followed in the parrots of Australia. See Gould's ' Handbook,' kc, vol. ii. pp. 14-102. ^< Macgillivray's ' British Birds,' vol. ii. p. 433. Jordon, 'Birds of India,' vol. ii. p. 282. =" All the following facts arc taken from M. Malherbe's mag- nificent ' Monographie des Picidees,' 1861. Audubon's ' Ornithological Bio- graphy,' vol. ii. p. 75; see also the ' Ibis,' vol. i. p. 268. " Gould's 'Handbook to the Birds of Australia,' vol. ii. pp. 109- 149. Chap. XV. Birds — Colour and Nidification. 459 differences in plumage between the sexes are of the same generai natui-e as the occasionally gxeater differences. A good illustra- tion of this fact has already been afforded by those kingfishers in which either the tail alone or the whole upper surface of the plumage differs in the same manner in the two sexes. Similar cases may be observed with parrots and pigeons. The differ- ences in colour between the.sexes of the same species are, also, of the same general nature as the differences in colom" between the distinct species of the same group. For when in a group in which the sexes are usually alike, the male differs considerably from the female, he is not coloiu-ed in a quite new style. Hence we may infer that within the same group the special colours of both sexes when they are alike, and the colours of the male, when he differs sUghtly or even considerably from the female, have been in most cases determined by the same general cause ; this being sexual selection. It is not probable, as has already been remarked, that differ- ences in colour between the sexes, when very slight, can be of service to the female as a protection. Assuming, however, that they are of service, they might be thought to be cases of transition ; but we have no reason to beheve that many species at any one time are undergoing change. Therefore we can hardly admit that the numerous females which differ very shghtly in colour from their males are now all commencing to become obscure for the sake of protection. Even if we consider somewhat more marked sexual differences, is it probable, for instance, that the head of the female chaffinch, — the crimson on the breast of the female bullfinch,— the green of the female greenfinch, — the crest of the female golden-crested wren, have all been rendered less bright by the slow process of selection for the sake of protection ? I cannot think so ; and still less with the slight differences between the sexes of those birds which build concealed nests. On the other hand, the differences in colour be- tween the sexes, whether great or small, may to a large extent be explained on the principle of the successive variations, acquired by the males through sexual selection, having been from the first more or less limited in their transmission to the females. That the degree of limitation should differ in different species of the same group will not sm-prise any one who has studied the laws of inheritance, for they are so complex that they appear to us in our ignorance to bo capricious in their action.^" As far as I can discover there are few lauge groups of birds in which all the species have both sexes alike and brilliantly '» See rcmai-ks to this effect in my work on ' Vamtion vnder Domesti- cation,' vol. ii. chap. xii. 4-60 TJic Descent of Man, Pabt n. coloured, but I hear from Mr. Sclater, that this appears to be the case with the Musopbagaj or plantain-eaters. Nor do I btjliove that any large group exists in which the sexes of all the species arc widely dissimilar in colour : Mr. Wallace informs me that the chatterers of S. America {Cotingidoe) offer one of the best instances ; but with some of the species, in which the male has a splendid red breast, the female exhibits some red on her breast ; and the females of other species shew traces of the green and other colours of the males. Nevertheless we have a near approach to close sexual similarity or dissimilarity throughout several groups : and this, from what has just been said of the fluctuating nature of inheritance, is a somewhat surprising circumstance. But that the same laws should largely prevail with allied animals is not surprising. The domestic fowl has produced a great number of breeds and sub-breeds, and in these the sexes generally differ in plumage; so that it has been noticed as an unusual circumstance when in certain sub-breeds they resemble each other. On the other hand, the domestic pigeon has likewise produced a vast number of distinct breeds and sub-breeds, and in these, with rare exceptions, the two sexes are identically alike. Therefore if other species of Gallus and Columba were domesticated and vari-ed, it would not be rash to predict that similar rules of sexual similarity and dissimilarity, depending on the form of transmission, would hold good in both cases. In like manner the same form of transmission has gene- rally prevailed under nature thi-oughout the same groups, although marked exceptions to this rule occur. Thus within the same family or even genus, the sexes may be identically alike, or very different in colour. Instances have already been given in the same genus, as with sparrows, fly-catchers, thrushes and grouse. In the family of pheasants the sexes of almost all the species are wonderfully dissimilar, but are quite ahke in the eared pheasant or Crossoptilon auritum. In two species of Chloephaga, a genus of geese, the male cannot bo distinguished from the females, except by size ; whilst in two others, the sexes are so unlike that they might easily be mistaken for distinct species.^^ The laws of inheritance can alone account for the following cases, in which the female acquires, late in life, certain characters proper to the male, and ultimately comes to resemble him more or less completely. Here protection can hardly have come into iilay. Mr. Blyth informs me that the females of Oriolus melano- ctphalus and of some alhed species, when sufficiently mature to breed, differ considerably in plumage from the adult males; btt •'^ 71ic ' Ibis,' vol. vi. iff the peacock, with some of the bii'ds of paradise, and with the crest tnd plumes of certain herons, for instance, the Ardea ludovicana.^" But it is doubtful whether the continued development of such feathers is the result of the selection of successive beneficial variations (though this is the most probable view with birds of paradise) or merely of con- tinuous growth. Most fishes continue increasing in size, as long as they are in good health and have plenty of food ; and a somewhat similar law may prevail with the plumes of birds. Class V. When the adults of both sexes have a distinct winter and $ummer plumage, whether or not the male differs from the female, the young resemble the adults of both sexes in their ivinter dress, or much more rarely in their summer dress, or they resemble the females alone. Or the young may have an intermediate character ; or, again, they may differ greatly from the adults in both their seasonal plumages. — The cases in this class are singularly complex ; nor is this surprising, as they depend on inheritance, limited in a greater or less degree in three difl'erent ways, namely, by sex, age, and the season of the year. In some cases the individuals of the same species pass through at least five distinct states of plumage. With the species, in which the male differs from the female during the summer season alone, or, which is rarer, during both seasons,*' the young generally resemble the females, — as with the so-called goldfinch of North America, and apparently with the splendid Maluri of Australia.''- With those species, the sexes of which are alike during both the summer and winter, the young may '° Other animals, belonging to quite distinct classes, are either habitually or occasionally capable of breeding before they have fully acquired their adult characters. This is the case with the young males of the salmon. Several am- phibians have been known to breed whilst retaining their larval struc- ture. Fritz Miiller has shewn (' Facts and Arguments for Darwin,' Eng. trans. 1869, p. 79) that the males of several amphipod crusta- ceans become sexually mature whilst voung; and I infer that this is a case of premature breeding, because they have not as yet acquired their fully-developed claspers. All such facts are highly interestiug, as bearing on one means by which species may undergo great modifi- cations of character. *^ Jerdon, 'Birds of India,' vol. iii. p. 507, on the peacock. Dr. Marshall, thinks that the older and more brilliant males of birds of paradise, have an advantage over the younger males; see 'Archives Neerlandaises,' tom. vi. 1871. — On Ardea, Audubon, ibid. vol. iii. p. 139. " For illustrative cases see vol. iv. of Macgillivray's 'Hist. Brit. Birds ;' on Tringa, &c., pp. 229, 271 ; on the Machetes, p. 172; on the Charadrius hiaticula, p. 118 ; on the Charadrius pluvialis, p. 94. " For the goldfinch of n! America, Fringilla tristis, Linn., see Audubon. ' Ornith. Biography,' vol. i. p. 17£. For the Maluri, Gould's ' Handbook to the Birds of Austr.alia, vol. i. Tk 318 486 The Descent of Man. Part 1L resemble the adults, firstly, in their winter dress ; secondly, and this ia of much rarer occurrence, in their summer dress ; thirdly, they may be intermediate between these two states ; and, fourthly, they may differ greatly from the adults at all seasons. We have aii instance of the first of these four cases in one of the egrets of India {Buphus coro- mandus), in which the young and the adults of both sexes are white during the winter, the adults becoming golden-bufi" duriug the summer. "With the gaper (Aiiastomus oscitans) of India we have a similar case, but the colours are reversed: for the young and the adults of both sexes are grey and black dm-ing the winter, the adults becoming white during the summer." As an instance of the second case, the young of the razor-bill {Alca tarda. Linn.), in an early state of plumage, are coloured like the adults duriog the summer ; and the young of the ■white-crowned sparrow of North America (Fringilla leucophrys), as soon as fledged, have elegant white stripes on then- heads, which are lost by the young and the old during the wiater." With respect to the thud case, namely, that of the yormg having an intermediate character between the summer and winter adult plumages, Yarrell insists that this occurs with many waders. Lastly, in regard to the young differing greatly from both sexes in their adult summer and winter plumages, this occurs with some herons and egrets of North America and India, — the young alone being white. I wUl make only a few remarks on these complicated cases. When the young resemble the females in their summer di-ess, or the adults of both sexes in their winter dress, the cases differ from those given under Classes I. and III. only in the characters originally acquired by the males during the breeding-season, having been limited iu thek trans- mission to the corresponding season. When the adults have a distinct summer and winter plumage, and the young differ from both, the case is more difficult to understand. We may admit as probable that the young have retaiaed an ancient state of plumage ; we can account by sexual selection for the summer or nuptial plumage of the adults, but how are we to account for their distinct winter plumage ? If we could admit that this plumage serves in aU cases as a protection, its ac- quirement would be a simple affair ; but there seems no good reason for this admission. It may be suggested that the widelj different conditions of life during the winter and summer have acted in a direct manner on the plumage ; this may have had some effect, but I have not much confidence in so great a difference as we sometimes see between the two plumages, having been thus caused. A more probable explanation is, that an ancient style of plumage, partially modified through the transference of some characters from the summer plumage, has been retained by the adults diuing the winter. Fiaally, aU the cases in our present class apparently depend on characters acquired by the adult males, having been variously limited in their transmission according to age, season, and sex ; but it would not be worth while to attempt to follow out these complex relations. " I am indebted to Mr. Blyth for information as to the Buphus ; see also Jerdon, ' Birds of India,' vol. iii. p. 749. On the Anastomus, see Blyth, in 'Ibis,' 1867, p. 173. ■•^ On the Alca, see Macgillivray, Hist. Brit. Birds,' vol. v. p. 3^7. On the Fringilla leucophrys, Au- dubon, ibid. vol. ii. p. 89. I shall have hereafter to refer to the young of certain herons and egrets being white. « ' History of British Birds, vol « p. 159. Chap. XV J. Birds — Young like both Adults. 487 Class VI. Ths young in their first plumage differ from ^.ach other aecordiTig to sex ; the young males resembling more or less closely the adult males, and the young females more or less closely the adult females. — The cases in the present class, though occun'ing in various groups, ai-c. not nmneraus ; yet it seems the most natural thing that the young should at first somewhat resemble the adults of the same sex, and gradually become more and more like them. The adult male blackcaji [Sylvia atricapilla) has a black head, that of the female being reddish - brown ; and I am informed by Mr. Blyth, that the young of both sexe.-j caa be distinguished by this character even as nestlings. In the family of thrushes an unusual mimber of similar cases have been noticed ; thus, the male blackbird (^Turdus merula) can be distinguished in the nest from the female. The two sexes of the mocking bird {Turdus polyglottm, Linn.) differ very little from each other, yet the males can easily be distinguished at a very early age from the females by shewing moru pure white." The males of a forest-thrush and of a rock-thrush (Orooetes erythrogastra and Petrocincla cyanea) have much of their plumage of a fine blue, whilst the females are brown ; and the nestling males of both species have their main wing and tail-feathers edged with blue, whilst those of the female are edged with brown."' In the young blackbird the wing feathers assume their mature character and become black after the others ; on the other hand, in the two species just named the wing- feathers become blue before the others. The most probable view with reference to the cases in the present class is that the males, differently from what occurs in Class I., have transmitted their colom-s to their male offspring at an earlier age than that at which they were first acquired ; for, if the males had varied whilst quite young, their characters would probably have been transmitted to both sexes.'" In Aithurus polytmus, a humming-bird, the male is splendidly coloured black and green, and two of the taU-feathers are immensely lengthened ; the female has an ordinary tail and inconspicuous colours; now the young males, instead of resembling the adult female, in accordance with the common rule, begin from the first to assume the colours proper to their sex, and their taU-feathers soon 6ecome elongated. I owe this information to Mr. Gould, who has given me the following more striking and as yet unpublished case. Two humming-birds belonging to the genus Eustephanus, both beautifully coloured, inhabit the smaU island of Juan Fernandez, and have always been ranked as specifically dis- tmct. But it has lately been ascertained that the one, which is of a rich chesnut-brown colour with a golden-red head, is the male, whilst the other, which is elegantly variegated with green and white with a, metallic-green head is the female. Now the young firom the first Audubon, ' Ornith. Biography,' vol. i. p. 113. Mr. C. A. Wright, in 'Ibis,' vol. vi. 1864, p. 65. Jerdon, ' Birds of India,' vol. i. p. 515. See also on the blackbird, Blyth in Charles- worth's ' Mag. of Nat. History,' vol. i. 1837, p. 113. The following additional cases may be mentioned ; the young males of Tanagra rubra can be distinguished from the younjz females (Axidubon. 'Ornith. Biography,' vol. iv. p. 392), and so it is with the nestlings of a blue nuthatch, Dendrophila frontalis of India (Jerdon, ' Birds of India,' vol. i. p. 359). Mr. Blyth also informs me that the se-xes of tho stonechat, Saxicola rubicola, are distinguishable at a very early age. Mr. Salvin gives (' Proc. Zoolog. Soc' 1870, p. 206 ), the case of a hum- ming-bird, like the following one of Eustephanus. 488 The Descent of Man. Paht IL somewhat resemble tlie adults of tlie corresponding sex, the resemblaLce griidually becoming more and more complete. lu considering this last case, if as before we take tlie plumage of th« young as our guide, it w ould appear that both sexes have been rendered peautiful independently; and not that one sex has partially transferre\ Its beauty to the other. The male apparently has acquired liis bright solours through sexual selection in the same manner as, for instance, the peacock or pheasant in our first class of cases ; and the female in the same manner as the female Rhynchsea or Turnix in our second 3lass of cases. But there is much difficulty in understanding how this oould have been effected at the same time with the two sexes of the same species. Mr. Salvin states, as we have seen in the eighth chapter, that with certain humming-birds the males greatly exceed the females in number, whilst with other species inhabiting the same coimtry the females greatly exceed the males. If, then, we might assume that during some former lengthened period the males of the Juan Fernandez species had greatly exceeded the females in number, but that during another lengthened period the females had far exceeded the males, we could understand how the males at one time, and the females at another, might have been rendered beautiful by the selection of the brighter-coloured individuals of either sex; both sexes transmitting their characters to their young at a rather earlier age than usual. Whether this is the true explanation I will not pretend to say ; but the case is too remarkable to be passed over without notice. Vf e have no"w seen in all six classes, that an intimate relation exists between the plumage of the young and the adults, either of one sex or both. These relations ai'e fairly well explained on the principle that one sex — this being in the gi-eat majority of cases the male — fii'st acquired thi'ough variation and sexual selection bright colours or other ornaments, and transmitted them in various ways, in accordance with the recognised laws of inheritance. Why variations have occurred at different periods of life, even sometimes with species of the same group, we do not know, but with respect to the form of transmission, one important determining cause seems to be the age at which the variations first appear. From the principle of inheritance at corresponding ages, and from any variations in colour which occui'red in the males at an early age not being then selected — on the contrary being often eliminated as dangerous — whilst similar variations occurring at or near the period of reproduction have been presei-ved, it follows that the plumage of the young will ofteu have been left' unmodified, or but little modified. We thus get some insight into the colouring of the progenitors of our existing species. In B vast number of species in five out of our six classes of cases, the adults of one sex or of both are bright coloured, at least during the breeding-season, whilst the young are invariably less Drigh^^Iy coloured than the adults, or are quite dull coloured ; Chap. XVI. Birds — Colour and Protectio 489 for no instance is known, as far as I can discover, ot the young of dull-coloured species displaying bright colours, or of the young of bright-coloured species being more brilliant than their parents. In the foui-th class, however, in which the young and the old resemble each other, there are many species (though by no means all), of which the young are bright-coloured, and as these form whole groups, we may infer that their early progenitors were likewise bright. With this exception, if we look to the birds of the world, it appears that their beauty has been much increased since that period, of which their immature plumage gives us a partial record. On the Colour of the Plumage in relation to Protection. — It wiD have been seen that I cannot follow Mr. Wallace in the belief that dull colours, when confined to the females, have been in most cases specially gained for the sake of protection. There can, however, be no doubt, as formerly remarked, that both sexes of many birds have had their colours modified, so as to escape the notice of their enemies ; or in some instances, so as to approach their prey unobserved, just as owls have had their plumage rendered soft, that the^r flight may not be over- heard. Mr. Wallace remarks that " it is only in the tropics, " among forests which never lose their foliage, that we find " whole gi'oups of birds, whose chief colour is green." It will be admitted by every one, who has ever tried, how difficult it is to distinguish parrots in a leaf-covered tree. Nevertheless, we must remember that many parrots ai-e ornamented with crimson, blue, and orange tints, which can hardly be protective. Wood- peckers are eminently arboreal, but besides green species, there are many black, and black-and-white kinds — all the species being apparently exposed ttf'^early the same dangers. It is therefore probable that with tree-haunting birds, strongly-pro- nounced colour's have been acquired through sexual selection, but that a green tint has been acquired oftener than any other, from the additional advantage of protection. In regard to birds which live on the ground, every one admits that they are coloured so as to imitate the surrounding surface. How difficult it is to see a partridge, snipe, woodcock, certain plovers, larks, and night-jars when crouched on ground. Animals inhabiting deserts offer the most striking cases, for the bare surface affords no conceahnent, and nearly all the smaller quad- rupeds, reptiles, and birds depend for safety on their colours. Mr. Tristram has remarked in regard to the inhabitants of the dahara, that all are protected by their "isabelline or sand- " 'Westminster Review,' July, 1867, p. 5. 49^ The Descent of Man. Pabt II " colour." Calling to my recollection the desert-birds of South America, as well as most of the ground-birds of Great Britain, it appeared to me that both sexes in such cases are generally coloured nearly alike. Accordingly, I apphed to Mr. Tristram with respect to the birds of the Sahara, and he has kindly given me the following information. There are twenty-six species belonging to fifteen genera, which manifestly have their plumage coloured in a protective manner; and this colouring is all the more striking, as with most of these bii-ds it differs from that of their congeners. Both sexes of thirteen out of the twenty-six species are coloured in the same manner ; but these belong to genera in which this rule commonly prevails, so that they teU us nothing about the protective colours being the same in both sexes of desert-birds. Of the other thirteen species, three belong to genera in which the sexes usually differ from each other, yet here they have the sexes aUke. In the remaining ten species, the male differs from the female ; but the difference is confined chiefly to the under surface of the plumage, which is concealed when the bird crouches on the ground ; the head and back being of the same sand-coloured hue in the two sexes. So that in these ten species the upper surfaces of both sexes have been acted on and rendered alike, through natural selection, for the sake of protection ; whilst the lower surfaces of the males alone have been diversified, through sexual selection, for the sake of ornament. Here, as both sexes are equally well pro- tected, we clearly see that the females have not been prevented by natural selection from inheriting the colours of their male parents; so that we must look to the law of sexually-Kmited transmission. In all parts of the world both sexes of many soft-billed bii-ds, especially those which frequent reeds or sedges, ai-e obscurely coloured. No doubt if their colours had been brilliant, they would have been much more conspicuous to their enemies ; but whether their dull tints have been specially gained for the sake of protection seems, as far as I can judge, rather doubtful. It is stiU more doubtful whether such dull tints can have been gained for the sake of ornament. We must, however, bear in mind that male bii-ds, though dull-coloured, often differ much from their females (as with the common sparrow), and this leads to the belief that such colours have been gained thi-ough sexua! selection, from being attractive. Many of the soft-billed birds are songsters ; and a discussion in a former chapter should not " ' Ibis,' 1859, vol. i. p. 429, et his eiperieuce of the Sahara, this teq. Dr. Rohlfs, however, rem.avks statement is too stwng. to me in a letter that, accordins *" Chai'. XVI. Birds — Cojispicicous Colours. 491 be forgotten, in which it was shewn that the best songstei's are rarely ornamented with bright tints. It would appear that female birds, as a general rule, have selected their mates either for their sweet voices or gay colours, but not for both charms combined. Some species, which are manifestly coloured for the sake of protection, such as the jack-snipe, woodcock, and night-jar, are likewise marked and shaded, according to our standard of taste, with extreme elegance. In such cases we may conclude that both natural and sexual selection have acted conjointly for protection and ornament. Whether any bird exists which does not possess some special attraction, by which to charm the opposite sex, may be doubted. When both sexes are so obscurely coloured that it would be rash to assume the agency of sexual selection, and when no direct evidence can be advanced shewing that such colours serve as a protection, it is best to own complete ignorance of the cause, or, which comes to nearly the same thing, to attribute the result to the direct action of the conditions of life. Both sexes . of many birds are conspicuously, though not brilliantly coloured, such as the niimerous black, white, or piebald species; and these colours are probably the result of sexual selection. With the common blackbird, capercailzie, blackcock, black scoter-duck (Oidenaia), and even with one of the bii'ds of paradise (^Loplwrina atra), the males alone are black, whilst the females are brown or mottled ; and there can hardly be a doubt that blackness in these cases has been a sexually selected character. Therefore it is in some degree probable that the complete or partial blackness of both sexes in such birds as crows, certain cockatoos, storks, and swans, and many marine birds, is likewise the result of sexual selection, accompanied by equal transmission to both sexes ; for blackness can hardly serve .in any case as a protection. With several birds, iu which the male alone is black, and in others in which both sexes are black, the beak or skin about the head is brightly coloured, and the contrast thus afforded adds much to their beauty ; we see this ia the bright yellow beak of ^he male blackbird, in the crimson skin over the eyes of the black-cock and capercailzie, in the brightly and variously coloured beak of the scoter-drake (Oidemia), in the red beak of the chough (Corvus graculus, Linn.), of the black swan, and the black stork. This leads me to remarJc that it is not incredible that toucans may owe the enormous size of their beaks to sexual selection, for the sake of displaying the diversified and vivid stripes of colour, with which theso organs are ornamented.^^ The naked skin, also, at the base of the " No satisfactory explanation has size, and still less of the bright ever been offered of the immense colours, cf the toucan's beak., Mr. 492 TJie Descejit of Man. Past IL oeak and round the eyes is likewise often brilliantly coloured ; and Mr. Gould, in speaking of one species,'^ says that the colours of the beak " are doubtless in the finest and most brilliant state " during the time of pairing." There is no greater improbability that toucans should be encumbered with immense beaks, though rendered as light as possible by their cancellated structure, for the display of fine colours, (an object falsely appearing to us unimportant), than that the male Argus pheasant and some other birds should be encumbered with plumes so long as to impede their flight. In the same manner, as the males alone of various species are black, the females being dull-coloured ; so in a few cases the males alone are either wholly or partially white, as with the several bell-birds of South America (Chasm orhynchus), the Antarctic goose {Bernida antarcUca), the silver-pheasant, &c., whilst the females are brown or obscurely mottled. Therefore, on the same principle as before, it is probable that both sexes of many birds, such as white cockatoos, several egrets with their beautiful plumes, certain ibises, gulls, terns, &c., have acquired their more or less completely white plumage through sexual selection. In some of these cases the plumage becomes white only at maturity. This is the case with certain gannets, tropic- birds, &c., and with the snow-goose {Anser hyperboreus). As the latter breeds on the " barren grounds," when not covered with snow, and as it migrates southward during the winter, there is no reason to suppose that its snow-white adult plumage sei'ves as a protection. In the Anastomua oscitans, we have still better evidence that the white plumage is a nuptial character, for it is developed only during the summer ; the young in their imma- ture state, and the adults in their winter dress, being grey and black. With many kinds of gulls (Larus), the head and neck become pure white dui-ing the summer, being grey or mottled during the winter and in the young state. On the other hand. Bates ('The Naturalist oa the Amazons,' vol. ii. 1863, p. 341) states that they use their beaks for reaching fruit at the extreme tips of the branches; and likewise, as stated by other authors, for ex- tracting eggs and young birds from the nests of other birds. But, as Mr. Bates admits, the beak " can " scarcely be considered a very per- " fectly-forraed instrument for the " end to which it is applied." The great bulk of the beak, as shewD by its breadth, depth, as well as length, is not intelligible on the view, that it serves merely as an organ of prehension. Mr. Belt believes ('The Naturalist in Nica- ragua,' p. 197), that the principal use of the beak is as a defence against enemies, especially to the female whilst nesting in a hole in a tree. " Ramphastos carmatus, Gonld'i ' Monograjih of Ramphastidae.' Chap. XVI. Birds — Conspiaiotis Colours 493 with the smaller gulls, or sea-mews (Gavia), and with some terns (Sterna), exactly the reverse occurs ; for the heads of the young birds during the first year, and of the adults during the winter, are either pure white, or much paler coloured than during the breeding-season. These latter cases offer another instance of the capricious manner in which sexual selection appears often to have acted.^^ That aquatic birds have acquired a white plumage so much oftener than terrestrial birds, probably depends on their large size and strong powers of flight, so that they can easily defend themselves or escape from birds of proy, to which moreover they are not much exposed. Consequently, sexual selection has not here been interfered with or guided for the sake of protection. No doubt with birds which roam over the open ocean, the males and females could find each other much more easily, when made conspicuous either by being perfectly white or intensely black ; so that these colours may possibly serve the same end as the call-notes of many land-birds.^* A white or black bird when it discovers and flies down to a carcase floating on the sea or cast up on the beach, will be seen fi-om a great distance, and will guide other birds of the same and other species, to the prey ; but as this would be a disadvantage to the first finders, the indi- viduals which were the whitest or blackest would not thua procure more food than the less strongly coloured individuals. Hence conspicuous colours cannot have been gradually acquired for this purpose through natural selection. As sexual selection depends on so fluct'aating an element as taste, we can understand how it is that, within the same group of birds having nearly the same habits, there should exist white or nearly white, as well as black, or nearly black species,— for instance, both white and black cockatoos, storks, ibises, swans, terns, and petrels. Piebald birds likewise sometimes occur in the same groups together with black and white species: for instance, the black-necked swan, certain terns, and the common magpie. That a strong contrast in colour- is agreeable to birds, we may conclude by looking through any large collection, for the sexes often differ from each other in the male having the pale On Larus, Gavia, and Steraa, see Macgillivray, ' Hist. Brit. Birds,' vol. V. p. 515, 584, 626. On the Anser hyperboreus, Audubon, ' Or- nith. Biography,' vol. iv. p. 562. On the Anastomus, Mr. Blyth, in ' Ibis,' 1867, p. 173. It may be noticed that with vultures, which roam far and wide high in the air, like marine birds over the ocean, three or four species are almost wholly or largely white, .'md that many others are black. So that here again conspicuous colours may possibly aid the sexes in finding each other during the breeding- season. 494 The Descent of Man. Part H. parts of a purer white, and the variously coloured dark parts of still darker tints than the female. It would even appear that mere novelty, or slight changes for the sake of change, have sometimes acted on female bii-ds as a charm, like changes of fashion with us. Thus the males of some parrots can hardly be said to be more beautiful than the females, at least according to our taste, but they differ in such points, as ia having a rose-coloured collar instead of " a bright " emeraldine narrow green collar;" or in the male having a black collar instead of " a yellow demi-collar in fi-ont," with a pale roseate instead of a plum-blue head.'^ As so many male birds have elongated, tail-feathers or elongated crests for their chief ornament, the shortened tail, formerly described in the male of a humming-bird, and the shortened crest of the male goosander, seem like one of the many changes of fashion which we admii-e in our own dresses. Some members of the heron family offer a still more curious case of novelty in colouring having, as it appears, been appre- ciated for the sake of novelty. The young of the Ardta asha are white, the adults being dai'k slate-coloured; and not only the young, but the adults in their winter plumage, of the aUied Buphus coromandus are white, this colour changing into a rich golden-buff during the breeding-season. It is incredible that the young of these two species, as weU as of some other members of the same family,^'' should for any special purpose have been rendered pure white and thus made conspicuous to their enemies ; or that the adults of one of these two species should have been specially rendered white during the winter in a country which is never covered with snow. On the other hand we have good reason to beheve that whiteness has been gained by many birds as a sexual ornament. "We may therefore conclude that some early progenitor of the Ardea asha and the Buphus acquired a white plumage for nuptial pm-poses, and transmitted this colour to their young; so that the young and the old. became white Uke certain existing egrets ; and that the whiteness was afterwards retained by the young, whilst it was exchanged by the adults for more strongly-pronounced tints. But if we could look still further back to the still earlier progenitors of these two species, we should probably see the adults dark- See Jei'don on the genus specific names. Audubon (' Ornith. Palasornis, 'Birds of India,' vol. i. Biography,' vol. iii. p. 416 ; vol. iv. p. 258-260. p. 58) seems rather pleased at the The young of Ardea rufesccns thought that this remarkable change and A. ccerulca of the U. States are of plumage will greatly " disconcert likewise wliite, the adults being " the systematists." ijolonrad in accordance with their Chap. XYI. Birds— Novelty admired. 495 coloured. I infer that this would be the case, from the analog} of many other birds, which are dark whilst young, and when adult are white ; and more especially from the case of the Arde^x gularis, the colours of which are the reverse of those of A. asha, for the young are dark-coloured and the adults white, the young having retained a former state of plimiage. It appears there- fore that, during a long line of descent, the adult progenitors of the Ardea asha, the Buphus, and of some alUes, have under- gone the following changes of colour: first, a dark shade; secondly, pure white ; and thirdly, owing to another change of fashion (if I may so express myself), their present slaty, reddish, or golden-buff tints. These successive changes are inteUigible only on the principle of novelty having been admired by birds for its own sake. Several writers have objected to the whole theory of sexual selection, by assuming that with animals and savages the taste of the female for certain colours or other ornaments would not remain constant for many generations; that first one colour and then another would be admired, and con- sequently that no permanent effect could be produced. We may admit that taste is fluctuating, but it is not quite arbitrary. It depends much on habit, as we see in mankind ; and we may infer that this would hold good with birds and other animals. Even in our own dress, the general character lasts long, and the changes are to a certain extent graduated. Abundant evidence will be given in two places in a future chapter, that savages of many races have admired for many generations the same cicatrices on the skin, the same hideously perforated hps, nostrils, or ears, distorted heads, &c. ; and these deformities present some analogy to the natural ornaments of various animals. Nevertheless, with savages such fashions do not endure for ever, as we may infer from the differences in this respect between allied tribes on the same continent. So again the raisers of fancy animals certainly have admired for many generations and still admire the same breeds ; they earnestly desire slight changes, which are considered as improvements, but any great or sudden change is looked at as the greatest blemish. With birds in a state of nature we have no reason to suppose that they would admire an entirely new style of coloration, even if great and sudden variations often occurred, which is far from being the case. We know that dovecot pigeons do not willingly associate with the variously coloured fancy breeds ; that albino birds do not commonly get partners in marriage ; and that the black ravens of the Feroe Islands chase away their piebald brethren. But this dislike of a sudden change would not 49*5 The Descent of Man. p^ j. n preclude their appreciating slight changes, any more than it does in the case of man. Hence with respect to taste, which depends on many elements, but partly on habit and' partly on a love of novelty, there seems no improbability in animals admiring for a very long period the same general style of ornamen- tation or other attractions, and yet appreciating slight changes in colours, form, or sound. Summary of the Four Chapters on Birds. — Most male birds are liighly pugnacious during the breeding-season, and some possess weapons adapted for fighting with their rivals. But the most pugnacious and the best armed males rarely or never depend for success solely on their power to drive away or kill their rivals, but have special means for charming the female. With some it is the power of song, or of giving forth strange cries, or instrumental music, and the males in consequence differ from the females in their vocal organs, or in the structure of certain feathers. From the curiously diversified means for producing various sounds, we gain a high idea of the importance of this means of courtship. Many birds endeavour to charm the females by love-dances or antics, performed on the ground or in the air, and sometimes at prepared places. But ornaments of many kinds, the most brilliant tints, combs and wattles, beautiful plumes, elongated feathers, top-knots, and so forth, are by far the coromonest means. In some cases mere novelty appears to have acted as a charm. The ornaments of the males must be highly important to them, for they have been acquired in not a few cases at the cost of increased danger from enemies, and even at some loss of power in fighting with their rivals. The males of very many species do not assume their ornamental dress until they arrive at maturity, or they assume it only during the breeding-season, or the tints then become more vivid. Certain ornamental appendages become enlarged, turgid, and brightly coloured during the act of courtship. The males display their charms with elaborate care and to the best efi'ect ; and this is done in the presence of the females. The courtship is sometimes a prolonged affair, and many males and females congregate at an appointed place. To suppose that the females do not appreciaie the beauty of the males, is to admit that their splendid decorations, all their pomp and display, are useless ; and this is incredible. Birds have fine powers of discrimination, and in some few instances it can be shewn that they have a taste for the beautiful. The females, moreover, are known occasionally to exhibit a marked preference or antipathy for certain individual males. If it, be admitted that the females prefer, or are unconscioualj Chap. XYI, Birds — Suvi niary. 497 excited by the more beautiful males, then the males would slowly but surely be rendered more and more attractive through eexual selection. That it is this sex which has been chiefly modified, we may infer from the fact that, in almost every genua where the sexes differ, the males differ much more from one another than do the females ; this is well shewn in certain closely-allied representative species, in which the females can hardly be distinguished, whilst the males are quite distinct. Birds in a state of nature offer individual differences which would amply suffice for the work of sexual selection; but we have seen that they occasionally present more strongly-marked variations which recur so frequently that they would imme- diately be fixed, if they served to allure the female. The laws of variation must determine the nature of the initial changes, and will have largely influenced the final result. The grada- tions, which may be observed between the males of allied species, indicate the nature of the steps through which they have passed. They explain also in the most interesting manner how certain characters have originated, such as the indented ocelli on the tail-feathers of the peacock, and the ball and socket ocelli on the wing-feathers of the Argus pheasant. It is evident that the brilhant colours, top-knots, fine plumes, &c., of many male birds cannot have been acquired as a protection; indeed, they sometimes lead to danger. That they are not due to the direct and definite action of the conditions of life, we may feel assui-ed, because the females have been exposed to the same conditions, and yet often differ from the males to an extreme degree. Although it is probable that changed conditions acting dming a lengthened period have in some cases produced a definite effect on both sexes, or sometimes on one sex alone, the more important result will have been an increased tendency to vary or to present more strongly marked individual differences ; and such differences will have afforded an excellent groimd- work for the action of sexual selection. The laws of inheritance, irrespectively of selection, appear to have determined whether the characters acquired by the males for the sake of ornament, for producing various sounds, and for fighting together, have been transmitted to the males alone or to both sexes, either permanently, or periodically during certain seasons of the year. Why various characters should have been transmitted sometimes in one way and sometimes in another, is not in most cases known ; but the period of variability seems often to have been the determining cause. When the two sexes have inherited all characters in common they necessarily resemble each other ; but as the successive variations may be differently 2 K 498 The Descent of Maj'i,. Pabt II. transmitted, every possible gradation may be found, even within the same genus, from the closest similarity to the widest dis- similarity between the sexes. With many closely-allied species, following nearly the same habits of life, the males have come to differ from each other chiefly through the action of sexual selection; whilst the females have come to differ chiefly from partaking more or less of the characters thus acquired by the males. The effects, moreover, of the definite action of the conditions of life, will not have been masked in the females, as in the males, by the accumulation through sexual selection of strongly-pronounced colours and other ornaments. The indi- viduals of both sexes, however affected, will have been kept at each successive period nearly uniform by the free intercrossing of many individuals. "With species, in which the sexes differ in colour, it is possible or probable that some of the successive variations often tended to be transmitted equally to both sexes; but that when this occurred the females were prevented from acquiring the bright colours of the males, by the destruction which they suffered during incubation. There is no evidence that it is possible by natural selection to convert one form of transmission into another. But there would not be the least difficulty in rendering a female dull-coloured, the male being stiU kept bright-coloured, by the selection of successive variations, which were from the first limited in their transmission to the same sex. Whether the females of many species have actually been thus modified, must at present remain doubtful. When, through the law of the equal transmission of characters to both sexes, the females were rendered as conspicuously coloured as the males, their instincts appear often to have been modified so that they were led to bund domed or concealed nests. In one small and curious class of cases the characters and habits of the two sexes have been completely transposed, for the females are larger, stronger, more vociferous and brighter coloured than the males. They have, also, become so quarrel- some that they often fight together for the possession of the males, like the males of other pugnacious species for the possession of the females. If, as seems probable, such females habitually drive away their rivals, and by the display of their bright colours or other charms endeavour to attract the males, w^e can ' understand how it is that they have gradually been rendered, by sexual selection and sexually-limited transmission, more beautiful than the males — the latter being left unmodified or only slightly modified. Whenever the law of inheritance at corresponding ages prevails. Chap. XVL Birds — Summary. but not that of sexually-limited transmission, then if the parents vary late in life — and we know that this constantly occurs with our poultry, and occasionally with other birds — the young will be left unaffected, whilst the adults of both sexes win be modified. If both these laws of inheritance prevail and either sex varies late in life, that sex alone will be modified, the other sex and the young being unaffected. When variations in brightness or in other conspicuous characters occur early in life, as no doubt often happens, they will not be acted on through sexual selection until the period of reproduction arrives ; con- sequently if dangerous to the young, they will be eliminated through natural selection. Thus we can understand how it is that variations arising late in life have so often been pre- served for the ornamentation of the males; the females and the young being left almost unaffected, and therefore like each other. With species having a distinct summer and winter plumage, the males of which either resemble or differ from the females during both seasons or during the summer alone, the degrees and kinds of resemblance between the young and the old are exceedingly complex ; and this complexity apparently depends on characters, first acquired by the males, being transmitted in various ways and degrees, as limited by age, sex, and season. As the young of so many species have been but little modified in colour and in other ornaments, we are enabled to form some judgment with respect to the plumage of their early progenitors ; and we may infer that the beauty of our existing species, if we look to the whole class, has been largely increased since that period, of which the immature plumage gives us an indirect record. Many birds, especially those which live much on the ground, have undoubtedly been obscurely coloured for the sake of protection. In some instances the upper exposed surface of the plumage has been thus coloured in both sexes, whilst tho lower surface in the males alone has been variously ornamented through sexual selection. Finally, from the facts given in these four chapters, we may conclude that weapons for battle, organs for producing sound, ornaments of many kinds, bright and conspicuous colours, have generally been acquired by tho males through variation and sexual selection, and have been transmitted in various ways according to the several laws of inheritance— the females and the young being left comparatively out little modified." *^ I am greatly indebted to the kindness of Mr. Sclater for having looked over these foui- chapters on birds, and the two following ones on mammals. In this way I have been saved from making inistak'js 2 K 2 The Desce7it of Man. Pakt II. CHAPTEK XVn. Secondary Sexual Charactebs of Mammals. The iaw of battle — Special weapons, confined to the males— Cause of absence of weapons in the female — Weapons common to both sexes, yet primarily acquired by the male — Other uses of such weapons — Their high importance — Greater size of the male — Means of defence — On the preiereace shewn by either sex in the pairing of quadrupeds. With mammals the male appears to win the female much more through the law of battle than through the display of his charms. The most timid animals, not provided with any special weapons for fighting, engage in desperate conflicts during the season of love. Two male hares have been seen to fight together vrntU one was killed; male moles often fight, and sometimes with fatal results ; male squirrels engage in frequent contests, " and often wound each other severely ;" as do male beavers, so that " hardly a skin is without scai's." ^ I observed the same fact with the hides of the guanacoes in Patagonia ; and on one occasion several were so absorbed in fighting that they fearlessly rushed close by me. Livingstone speaks of the males of the many animals in Southern Africa as almost invariably shewing the scars received in former contests. The law of battle prevails with aquatic as with terrestrial mammals. It is notorious how desperately male seals fight, both with their teeth and claws, during the breeding-season; and their hides are likewise often covered with scars. Male sperm-whales are very jealous at this season; and in their battles " they often lock their jaws together, and turn on their " sides and twist about ;" so that their lower jaws often become distorted.^ about the names of the species, and from stating anything as a fact which is known to this distinguished naturalist to be erroneous. But of course he is not at all answerable for the accuracy of the statements quoted by me from various autho- rities. ' See Waterton's account of two hares fightiug, ' Zoologist,' vol. i. 1843, p. 211. On moles. Bell, < Hist, of British Quadrupeds,' 1st odit. p. 100. On squirrels, Audubon and Bachman, 'Viviparous Quad- rupeds of N. America,' 1846, p. 269. On beavers, Mr. A. H. Green, in ' Journal of Lin. Soc. Zoolog.' vol. x. 186S, p. 362. ° On the battles of seals, see Capt. C. Abbott in ' Proc. Zool. Soc' 1868, p. 191; also Mr. R. Brown, ibid. 1868, p. 436 ; also L. Lloyd, ' Gams Birds of Sweden,' 1867, p. 412 also Pennant. On the sperm-whale see Mr. J. H. Thompson, in ' Proc. Zool. Soc' 1867, p. 246. Chap. XYII. Mammals — Law of Battle. 501 All male animals which are furnished with special weapons for fighting, are well known to engage in fierce battles. The courage and the desperate conflicts of stags have often beeu described ; their skeletons have been found in various parts of the world, with the horns inextricably locked together, shewing how miserably the victor and vanquished had perished.^ No animal ia the world is so dangerous as an elephant in must. Lord Tankerville has given me a graphic description of the battles between the wild bulls in Chillingham Park, the descen- dants, degenerated in size but not in courage, of the gigantic Bos primigenius. In 1861 several contended for mastery ; and it was observed that two of the younger bulls attacked in concert the old leader of the herd, overthrew and disabled him, so that he was believed by the keepers to be lying mortally wounded in a neighbouring wood. But a few days afterwards one of the yoimg bulls approached the wood alone ; and then the " monarch " of the chase," who had been lashing himself up for vengeance, came out and, m a short time, killed his antagonist. He then quietly joined the herd, and long held undisputed sway. Admiral Sir J. B. Sulivan informs me that, when he lived in the Falk- land Islands, he imported a young English stallion, which frequented the hiUs near Port William with eight mares. On these hills there were two wild staUions, each with a small troop of mares ; " and it is certain that these stallions would never " have approached each other without fighting. Both had tried " singly to fight the English horse and di'ive away his mares, " but had failed. One day they came in together and attacked " him. This was seen by the capitan who had charge of the " horses, and who, on riding to the spot, found one of the two " stallions engaged with the English horse, whilst the other was " driving away the mares, and had already separated four from " the rest. The capitan settled the matter by driving the whole " party into the corral, for the wild stallions would not leave " the mares." Male animals which are provided with eflScient cutting or tearing teeth for the ordinary purposes of life, such as the carnivora, insectivora, and rodents, are seldom furnished with weapons especially adapted for fighting with their rivals. The case is very different with the males of many other animals. We see this in the horns of stags and of certain kinds of ' See Scrope (' Art of Deer-stalk- wapiti, moose, and rem-deer have ing,' p. 17) on the locking of the been found thus locked together, ^orns with the Cervus elaphus. Sir A. Smith found at the Ciipe ot Richardson, in ' Fauna Bor. Ameri- Good Hope the skeletons of two CMi, 1829, p. 252, says that the gnus in the same condition. 502 The Descent of Mzn. Pabt 11, antelopes in which the females are hornless. With many animalB the canine teeth in the upper or lower jaw, or in both, are mucl? larger in the males than in the females, or are absent in the latter, with the exception sometimes of a hidden rudiment. Certain antelopes, the musk-deer, camel, horse, boar, various apes, seals, and the wahnis, offer instances. In the females of the walrus the tusks are sometimes quite absent.* In the male elephant of India and in the male dugong^ the upper incisors form offensive weapons. In the male narwhal the left canine alone is developed into the well-known, spirally-twisted, so- called horn, which is sometimes from nine to ten feet in length. It is believed that the males use these horns for fighting to- gether ; for " an unbroken one can rarely be got, and occasionally " one may be found with the point of another jammed into the " broken place." ^ The tooth on the opposite side of the head in the male consists of a rudiment about ten inches in length, which is embedded in the jaw ; but sometimes, though rarely, both are equally developed on the two sides. In the female both are always rudimentary. The male cachalot has a larger head than that of the female, and it no doubt aids Viim in his aquatic battles. Lastly, the adult male ornithorhynchus is pro- vided with a remarkable apparatus, namely a spur on the foreleg, closely resembling the poison-fang of a venomous snake ; but ac- cording to Harting, the secretion from the gland is not poisonous ; and on the leg of the female there is a hoUow, apparently for the reception of the spui-.'' When the males are provided with weapons which in the females are absent, there can hardly be a doubt that these serve for fighting with other males; and that they were acquired through sexual selection, and were transmitted to the male sei alone. It is not probable, at least in most cases, that the females have been prevented from acquiring such weapons, on account of their being useless, superfluous, or in some way injurious. On the contrary, as they are often used by the males for various * Mr. Lamont ('Seasons with the * Mr. E. Brown, in 'Proc. Zool. Sea-Horses,' 1861, p, 143) says that Soc' 1869, p. 553. See Prof. Turner, a good tusk of the male walrus in Journal of ' Anat. and Phys.' 1872, weighs 4 pounds, and is longer than p. 76, on the homological nature of that of the female, which weighs these tusks. Also Mr. J. W. Clarke about 3 pounds. The males are on two tusks being developed in the described as fighting ferociously, males, in ' Proc. Zoolog. Soc' 1871, On the occasional absence of the p. 42. tusks in the female, see Mr. R. ' Owen on the cachalot and Brown, 'Proc. Zool. Soc' 1868, p. Ornithorhynchus, ibid. vol. iii. pp. 429. 638,641. Harting is quoted by Dr. s Owen, 'Anatomy of Vertebrates, Zouteveen in the Dutch translat. ol in. p. 283. this work, toI. ii. p. -92. Ceap. XVIL Mammals — Law of Battle, 503 purposes, more especially as a defence against their enemies, it is a sui'prising fact that they are so poorly developed, or quite absent, in the females of so many animals. With female deei the development during each recurrent season of great branching horns, and with female elephants the development of immense tusks, would be a great waste of vital power, supposing that they were of no use to the females. Consequently, they would have tended to be eliminated in the female thi'ough natural selection ; that is, if the successive variations were limited in their transmission to the female sex, for otherwise the weapons of the males would have been injuriously affected, and this would have been a greater evil. On the whole, and from the consideration of the following facts, it seems probable that when the various weapons differ in the two sexes, this has generally depended on the kind of transmission which has prevailed. As the reindeer is the one species in the whole family of Deer, in which the female is furnished with horns, though they are somewhat smaller, thinner, and less branched than in the male, it might naturally be thought that, at least in this case, they must be of some special service to her. The female retains her horns from the time when they are fully developed, namely, in September, tkroughout the winter until April or May, when she brings forth her young. Mr. Crotch made particular enquiries for me in Norway, and it appears that the females at this season conceal themselves for about a fortnight in order to bring forth their young, and then reappear, generally hornless. In Nova Scotia, however, as I hear from Mr. H. Eeeks, the female some- times retains her horns longer. The male on the other hand casts his horns much earher, towards the end of November. As both sexes have the same requirements and foUow the same habits of life, and as the male is destitute of horns during the winter, it is improbable that they can be of 'any special service to the female during this season, which includes the larger part of the time during which she is horned. Nor is it probable that she can have inherited horns from some ancient pro- genitor of the family of deer, for, from the fact of the females of so many species in all quarters of the globe not having homSr we may conclude that this was the primordial character of the group.* The horns of the reindeer are developed at a most unusually « On the structure and shedding regard to the American variety or of the horns of the reindeer, Holl- species ; also Major W. Ross King, bcvg, 'Amoenitates Acad.' vol. iv. 'The Sportsman in Canrda,' 1866, 17S8, p. 149. See Richardson, p. 80. Fauna Bor. Americana,' p. 241, iu 504 Tlie Descent of Man. Part II. early age; but what the cause of this may be is not knowiu The eflfect has apparently been the transference of the horns to both sexes. We should bear in mind that horns are always transmitted through the female, and that she has a latent capacity for their deTelopment, as wo see in old or diseased females.* Moreover the females of some other species of deer exhibit, either normally or occasionally, rudiments of horns ; thus the female of Cervulus moschatus has " bristly tufts, ending in a " knob, instead of a horn ;" and " in most specimens of the " female wapiti {Cervus canadensis) there is a sharp bony pro- " tuberance in the place of the horn."'" From these several considerations we may conclude that the possession of fairly well-developed horns by the female reindeer, is due to the males having first acquired them as weapons for fighting with other males; and secondarily to their development fi-om some un- known cause at an unusually early age in the males, and theii- consequent transference to both sexes. Turning to the sheath-horned ruminants: with antelopes a graduated series can be formed, beginning with species, the females of which are completely destitute of horns — passing on to those which have horns so small as to be almost rudimentary, (as with the Antilocapra americana, in which species they are present in only one out of four or five females ") — to those which have fairly developed horns, but manifestly smaller and thinner than in the male and sometimes of a difierent shape,'^ — and ending with those in which both sexes have horns of equal size. As with the reindeer, so with antelopes there exists, as pre- viously shewn, a relation between the period of the development of the horns and their transmission to one or both sexes ; it is therefore probable that thek presence or absence in the females of some species, and their more or less perfect condition in the females of other species, depends, not on their being of any special use, but simply in inheritance. It accords with this » Isidore Geoffrey St. Hilaire, 'Essais de Zoolog. Gdn^rale,' 1841, p. 513. Other masculine characters, besides the horns, are sometimes similarly transferred to the female ; thus Mr. Boner, in speaking of an old female chamois (' Chamois Hunting in the Mountains of Ba- varia,' 1860, 2nd edit. p. 363), says, " not only was the head very male- " looking, but along the back there "■was a ridge of long hair, usually " to be found only in bucks." >» On the Ccvvi-lus, Dr. Gray, ' Catalogue of Mammalia in the British Museum,' part. iii. p. 220. On the Cervus canadensis or wapiti see Hon. J. D. Caton, ' Ottawa Acad, of Nat. Sciences,' May, 1868, p. 9. " I am indebted to Dr. Canfield, for this information, see also his paper in ' Proc. Zoolog. Soc.,' 1866, p. 105. For instance the horns of the female Ant. euchore resemble those of a distinct species, viz. the Ant. dorcas var. Coring, see Desmarest, ' Mammalogie,' p. 455. Chap. XVII. Mammals — LaTv oj Dattle. view that even in the same restricted genus both sexes of some species, and the males alone of others, are thus provided. It is also a remarkable fact that, although the females of Antilope bezoartica are normally destitute of horns, Mr. Blyth has seen no less than three females thus furnished ; and there was no reason to suppose that they were old or diseased. In all the wild species of goats and sheep the horns are larger in tho male than in the female, and are sometimes quite absent in the latter.^^ In several domestic breeds of these two animals, the males alone are furnished with horns; and in some breeds, for instance, in the sheep of North "Wales, though both sexes are properly horned, the ewes are very liable to be hornless. I have been informed by a trustworthy witness, who purposely inspected a flock of these same sheep during the lambing season, that the horns at birth are generally nr.ore fully developed in the male than the female. Mr. J. Peel crossed his Lonk sheep, both sexes of which always bear horns, with hornless Leicesters and hornless Shropshire Downs; and the result was that the male offspring had their horns con- siderably reduced, whilst the females were wholly destitute of them. These several facts indicate that, with sheep, the horns are a much less firmly fixed character in the females than in the males ; and this leads us to look at the horns as properly of masculine origin. With the adult musk-ox (Ovihos moschdtus) the horns of the male are larger than those of the female, and in the latter the bases do not touch." In regard to ordinary cattle Mr. Blyth remarks : " In most of the wild bovine animals the horns are " both longer and thicker in the bull than in the cow, and in " the cow-banteng (Bos sondaicus) the horns are remarkably " small, and inclined much backwards. In the domestic races " of cattle, both of the humped and humpless types, the horns " are short and thick in the bull, longer and more slender in the " cow and ox ; and in the Indian buffalo, they are shorter and " thicker in the bull, longer and more slender in the cow. In " tho wild gaour (5. gaurus) the horns are mostly both longer " and thicker in the bull than in the cow."^^ Dr. Forsyth Major also informs me that a fossil skull, believed to be that of the female Bos etruscus, has been found in the Val d'Arno, which is wholly without horns. In the Rhinoceros simus, as I may add, the horns of the female are generally longer but less powerful than in the male; and in some other species of rhinoceros they " Gray, ' Catalogue Mamm. Brit, ricana,' p. 278. Mus.' pan iii. 1852, p. 160. is ' Land and Water,' ISST, u. '* Richardson, ' Fauna Bor. Ame- 5o6 The Descent of Man. Past II. are said to be shorter in the female.'" From these various facts we may infer as probable that horns of all kinds, even when they are equally developed in the two sexes, were primarily acquired by the itale in order to conquer other males, and have been transferred more or less completely to the female. The eflfects of castration deserve notice, as throwing light on this same point. Stags after the operation never renew their horns. The male reindeer, however, must be excepted, as after castration he does renew them. Tlds fact, as well as the pos- session of horns by both sexes, seems at fii-st to prove that the horns in this species do not constitute a sexual character but as they are developed at a very early age, before the sexes differ in constitution, it is not sui'prising that they should be imaffected by castration, even if they were aboriginally acquired by tlie male. With sheep both sexes properly bear horns ; and 1 am informed that with Welch sheep the horns of the males are considerably reduced by castration; but the degree depends much on the age at which the operation is performed, as is like- wise the case with other animals. Merino rams have large horns, whilst the ewes " generally speaktug are without horns ;" and in this breed, castration seems to produce a somewhat greater effect, so that if performed at an early age the horns " remain " almost undeveloped." On the Guinea coast there is a breed in which the females never bear horns, and, as Mr. Winwood Reade informs me, the rams after castration are quite desti- tute of them. With cattle, the horns of the males are much altered by castration; for instead of being short and thick, they become longer than those of the cow, but otherwise re- semble them. The Antilope hezoartica offers a somewhat ana- logous case : the males have long straight spiral horns, nearly parallel to each other, and directed backwards; the females occasionally bear horns, but these when present are of a very different shape, for they are not spiral, and spreading widely, bend rotmd with the points forwards. Now it is a remarkable fact that, in the castrated male, as Mi-. Blyth informs me, the horns are of the same peculiar shape as in the female, but longer and thicker. If we may judge from analogy, the female probably shews us, in these two cases of cattle and the antelope, the former Sir Andrew Smith, ' Zoology quiries for me in S.axony on this of S. Africa,' pi. six. Owen, 'Ana- subject. H. von Nathusius (' Vieh- tomy of Vertebrates,' vol. iii. p. 624. zucht,' 1872, p. 64) says that the This is the conclusion of horns of sheep castrated at an early Seidlitz, ' Die Darwinsche Theorie,' period, either altogether disappea- 1871, p. 47. remain as mere rudiments; but f8 I am much obliged to Prof. I do not know whether he retera Victor Carus, for having naade en- to merinos or to ordinary breeds. CnAi>. XVII. Mammals — Law of Battle. 507 condition of the horns in some early progenitor of each species. But why castration should lead to the reappearance of an early condition of the horns cannot be explained with any certainty. Nevertheless, it seems probable, that in nearly the same manner as the constitutional disturbance in the offspring, caused by a cross between two distinct species or races, often leads to the reappearance of long-lost characters ; so here, the disturbance in the constitution of the individual, resulting from castration, produces the same effect. The tusks of the elephant, in the different species or races, differ according to sex, nearly as do the horns of ruminants. In India and Malacca the males alone are provided with weU- (leveloped tusks. The elephant of Ceylon is considered by most naturalists as a distinct race, but by some as a distinct species, and here " not one in a hundred is found with tusks, the few " that possess them being exclusively males." The African elephant is undoubtedly distinct, and the female has large well- developed tusks, though not so large as those of the male. These differences in the tusks of the several races and species of elephants — the great variability of the horns of deer, as notably in the wild reindeer — the occasional presence of horns in the female Antilope bezoartica, and their frequent absence in the female of Antilocapra americana — the presence of two tusks in some few male narwhals — the complete absence of tusks in some female walruses— are aU instances of the extreme variability of secondary sexual characters, and of their habiUty to differ in closely-allied forms. Although tusks and horns appear ia all cases to have been primarily developed as sexual weapons, they often serve other purposes. The elephant uses his tusks in attacking the tiger ; according to Bruce, he scores the trunks of trees until they can be thrown down easily, and he likewise thus extracts the fari- naceous cores of palms ; in Africa he often uses one tusk, always the same, to probe the ground and thus ascertain whether it will bear his weight. The common bull defends the herd with his horns; and the elk in Sweden has been known, according to Lloyd, to strike a wolf dead with a single blow of his great horns. Many similar facts could be given. One of the most curious secondary uses to which the horns of an animal may be occasionally put, is that observed by Captain Hutton*i with '» I have given various expei-i- =» Sir J. Emerson Tennent, ' Cey- ments and other evidence proving ]on,' 1859, vol. ii. p 274. For that this is the case, in my ' Varia- Malacca, 'Journal of Indian Archi- tion of Animals and Plants under pelago,' vol. iv. p. 35-7. Domestication,' vol. ii., 18G8, pp. 39 'Calcutta'jo'urnalof Nat.HLit. 'ol. ii. 1843, p. 626. 508 TJie Descent of Man. Paht II. tlie wild goat (Capra xgagrus) of the Himalayas and, as it is also said, with the ibex, namely, that when the male accidentally fall? from a height he bends inwards his head, and by alighting on his massive horns breaks the shock. The female cannot thus use her horns, which are smaller, but from her more quiet disposition she does not need this strange kind of shield so much. Each male animal uses his weapons in his own peculiar fashion. The common ram makes a charge and butts with such force with the bases of his horns, that I have seen a power- ful man knocked over like a child. Goats and certain species of sheep, for instance the Ovis cycloceros of Afghanistan,'^ rear on their hind legs, and then not only butt, but " make a cut down " and a jerk up, with the ribbed front of their scimitar-shaped " horn, as with a sabre. When the 0. cycloceros attacked a large " domestic ram, who was a noted bruiser, he conquered him by " the sheer novelty of his mode of fighting, always closing at " once with his adversary, and catching him across the face and " nose with a sharp drawing jerk of the head, and then bounding " out of the way before the blow could be returned." In Pembrokeshire a male goat, the master of a flock which during several generations had run wild, was known to have killed several males in single combat; this goat possessed enormous horns, measuring thirty-nine inches in a straight line from tip to tip. The common bull, as every one knows, goi-es and tosses his opponent ; but the Italian buffalo is said never to use his horns, he gives a tremendous blow with his convex forehead, and then tramples on his fallen enemy with his knees — an instinct which the common buU does not possess.^ Hence a dog who pins a buffalo by the nose is immediately crushed. We must, however, remember that the Italian buffalo has been long domesticated, and it is by no means certain that the wild parent-form had similar horns. Mr. Bartlett informs me that when a female Cape buffalo (Buhalus caffer) was turned into an enclosure "with a bull of the same species, she attacked him, and he in return pushed her about with great violence. But it was manifest to Mr. Bartlett that, had not the bull shewn dignified forbearance, he could easily have killed her by a single lateral thrust with his immense horns. The giraffe uses his short hair-covered horns, which are rather longer in the male than in the female, in a curious manner ; for, with his long neck, he swings his head to either side, almost upside down, with such « Mr. Blyth, in 'Land and goats see the ' Field,' 1869, p. 150. Water,' March, 1867, p. 134, on " m. E. M. Bailly, 'Sur I'usage the authority of Capt. Hutton and des Cornes,' &c., ' Annal. des Sc. others. For the wild Pembrokeshire Nat.' torn. ii. 1824, p. 369. Chap. XVII. Mamvials—Laiv of Battle. 509 force, that I have seen a hard plank deeply indented by a single blow. . . , With antelopes it is sometimes difficult to unagme how they san possibly use their cui-iously-shaped horns ; thus the spring- boo {Ant. euchore) has rather short upright horns, with the sharp points bent inwards almost at right angles, so as to face each other ; Mr. Bartlett does not know how they are used, but suggests that they would inflict a fearful wound down each side of the face of an antagonist. The slightly-curved horns of the Fig. 63. Oryx leucoryx, male (from the Knowsley Menagerie) Oryx leucoryx (fig. 63) are directed backwards, and are of such length that their points reach beyond the middle of the back, over which they extend in almost parallel lines. Thus they seem singularly ill-fitted for fighting ; but Mr. Bartlett informs me that when two of these animals prepare for battle, they kneel down, with their heads between their fore legs, and in this attitude the horns stand nearly parallel and close to the groundj with the points directed forwards and a little upwards. The com- batants then gradually approach each other, and each endeavours to get the upturned pomts under the body of the other; if one succeeds in doing this, he suddenly springs up, throwing up his head at the same time, and can thus wound or perhaps even transfix his antagonist. Both animals always kneel down, so as to guard as far as possible against this manoeuvre. It has been recorded that one of these antelopes has used his horns with effect even against a lion ; yet from being forced to place his head between the fore-legs in order to bring the points of the 510 The Descent of Man. Part il. horns forward, he would generally be under a great disadvantage when attacked by any other animal. It is, therefore, not probable that the horns have been modified into their present great length and pecuHar position, as a protection against beasts of prey. We can however see that, as soon as some ancient male progenitor of the Oryx acquired moderately Jong horns, directed a little backwards, he would be compelled, in his battles with rival males, to bend his head somewhat inwards or down- wards, as is now done by certain stags ; and it is not improbable that he might have acquired the habit of at first occasionally and afterwards of regularly kneeling down. In this case it is almost certain that the males which possessed the longest horns would have had a great advantage over others with shorter horns ; and then the horns would gradually have been rendered longer and longer, through sexual selection, until they acquired their present extraordinary length and position. With stags of many kinds the branches of the horns offer a curious case of difficulty ; for certainly a single straight point would inflict a much more serious wound than several diverging ones. In Sir Philip Egerton's museum there is a horn of the red-deer {Cervus elaphus), thirty inches in length, with "not " fewer than fifteen snags or branches and at Moritzburg there is still preserved a pair of antlers of a red-deer, shot in 1699 by Frederick I., one of which bears the astonishing number of thirty-three branches and the other twenty-seven, making altogether "sixty branches. Eichardson figures a pair of antlers of the wild reindeer with twenty-nine points.^* Fi'om tlie manner in which the horns are branched, and more especially from deer being known occasionally to fight together by kicking with their fore-feet,^^ M. Bailly actually comes to the conclusion that their horns are more injurious than useful to them ? But this author overlooks the -pitched battles between rival males. As I felt much perplexed about the use or advantage of the branches, I applied to Mr. McNeill of Colonsay, who has long and carefully observed the habits of red-deer, and he informs me that he has never seen some of the branches brought into use, but that the brow antlers, from inclining downwards, are a great protection to the forehead, and their points are likewise On the horns of red-deer, Acad, of Nat. Science,' May, 1868, Owen, ' British Fossil Mammals,' p. 9), says that the American deer 1846, p. 478; Richardson on the fight with their fore-feet, after horns of the reindeer, ' Fauna Bor. " the question of superiority has Americana,' 1829, p. 240. I am " been once settled and acknowledged indebted to Prof. Victor Carus, for " in the herd." Bailly, 'Sur I'us.i.jje the Moritzburg case. des Cornes,' ' Annales des So. Nat. "Hon. J. D. Caton ('Ottawa torn. ii. 1824, p. 371. Chap. XVII. Mammals — Law of Battle. used in attack. Sir Philip Egerton also informs me both as to red-deer and faUow-deer that, in fighting, they suddenly dash together, and getting their horns fixed against each other's bodies, a desperate struggle ensues. When one is at last forced to yield and turn round, the victor endeavours to plunge his brow antlers into his defeated foe. It thus appears that the upper branches are used chiefly or exclusively for pushing and fencing. Nevertheless in some species the upper branches are used as weapons of offence; when a man was attacked by a wapiti deer (JJervus canadensis) in Judge Caton's park in Ottawa, and several men tried to rescue him, the stag " never " raised his head from the ground ; in fact, he kept his face almost " flat on the ground, with his nose nearly between his fore feet, " except when he rolled his head to one side to take a new " observation preparatory to a plunge." In this position the ends of the, horns were directed against his adversaries. " lu " rolling his head he necessarily raised it somewhat, because his " antlers were so long that he could not roU his head without " raising them on one side, while, on the other side, they touched " the ground." The stag by this procedure gradually di-ove the party of rescuers backwards, to a distance of 150 or 200 feet ; and the attacked, man was killed.^^ Although the horns of stags are efficient weapons, there can. I think be no doubt that a single point would have been much more dangerous than a branched antler ; and Judge Caton, who has had large experience with deer, fully concurs in this conclu- sion. Nor do the branching horns, though highly important as a means of defence against rival stags, appear perfectly well adapted for this purpose, as they are Liable to become interlocked. The suspicion has therefore crossed my mind that they may serve in part as ornaments. That the branched antlers of stags as well as the elegant lyrated horns of certain antelopes, with their graceful double curvature, (fig. 64), are ornamental in our eyes, no one will dispute. If, then, the horns, hke the splendid accoutrements of the knights of old, add to the noble appearance of stags and antelopes, they may have been modified partly for this purpose, though mainly for actual service in battle ; but I have no evidence in favour of this belief An interesting case has lately been published, from which it appears that the horns of a deer in one district in the United Statesare now being modified through sexual andnatural selection. A writer in an excellent American Journal says, that he has 2« See a most interesting account " ' The American Naturalist, m the Appendix to Hon. J. D. Dec, 1869, p. 552. Caton's paper, as above quoted. 512 The Descent of Man. Part 11, limited for the last twenty-one years in the Adii'ondacks, ■where the Ctrvus virqinianus abounds. About fourteen years ago he first heard of spike-horn hucJes. These became frona year to year more common ; about five years ago he shot one, and afterwards another, and now they are frequently killed. " The spike-horn differs greatly from the common antler of the C. virginianus. Fig. G4. Strepsiceros Kudu (from Sir Andrew Smith's ■ Zoology of South Africa'). " It consists of a single spike, more slender than the antler, and "scarcely half so long, projecting forward from the ^^^J'f'l " terminating in a very sharp point. It gives a considemblo Chap. XVII. Mammals — Law of Battle. 513 " advantage to its possessor over the common buck. Besides " enabling him to run more swiftly through the thick woods and "■underbrush (every hunter knows that does and yearling " bucks run much more rapidly than the large bucks when " armed with their cumbrous antlers), the spike-horn is a more " effective weapon than the common antler. With this advantage " the spike-horn bucks are gaining upon the common bucks, and " may, in time, entirely supersede them in the Adirondacks. ■" Undoubtedly, the first spike-horn buck was merely an acci- " dental freak of nature. But his spike-horns gave him an ^' advantage, and enabled him to propagate his peculiarity. His " descendants having a like advantage, have propagated the " peculiarity in a constantly increasing ratio, till they are " slowly crowding the antlered deer from the region they " inhabit." A critic has well objected to this account by asking, why, if the simple horns are now so advantageous, were the branched antlers of the parent-form ever developed ? To this I can only answer by remarking, that a new mode of attack with new weapons might be a great advantage, as shewn by the case of the Ovis cydoceros, -who thus conquered a domestic ram famous for his fighting power. Though the branched antlers of a stag- are well adapted for fighting with his rivals, and though it might be an advantage to the prong-horned variety slowly to acquire long and branched horns, if he had to fight only with others of the same kind, yet it by no means follows that branched horns would be the best fitted for conquering a foe differently armed. In the foregoing case of the Oryx leucoryx, it is almost certain that the victory would rest with an antelope having short horns, and who therefore did not need to kneel down, though an oryx might profit by having still longer horns, if he fought only with his proper rivals. Male quadrupeds, which are furnished with tusks, use them in various ways, as in the case of horns. The boar strikes laterally and upwards; the musk-deer downwards with seTious effect.*? The walrus, though having so short a neck and so unwieldy a body, "can strike either upwards, or downwards, or sideways, with " -equal dexterity."^' J was informed by the late Dr. Falconer, that the Indian elephant fights in a different manner according to the position and curvature of his tusks. When they are directed forwards and upwards he is able to fling a tiger to a gnat distance— it is said to even thii-ty feet; when they are short and turned downwards he endeavours suddenly to pin the Pallas, 'Spicilegia Zoologica,' fasc. xiii. 1779, p. 18. ^ Lament, ' Seasons with the Sejw Horses,' 1861, p. 141. 2 L 514 The Descent of Mdn. PabtU. tiger to the ground and, in consequence, is dangerous to the rider, who is liable to be jerked off the howdah.^" Very few male quadrupeds possess weapons of two distinct Idnds specially adapted for fighting with rival males. The male muntjac-deer (Cervulus), however, offers an exception, as he is provided with horns and exserted canine teeth. But we may infer from wha-fc follows that one form of weapon has often been replaced in the course of ages by another. With ruminants the development of horns generally stands in an inverse relation with that of even moderately developed canine teeth. Thus camels, guanacoes, chevrotains, and musk-deer, are hornless, and they have efficient canines ; these teeth being " always of " smaller size in the females than in the males." The Camehdse have, in addition to their true canines, a pair of canine-shaped incisors in their upper jaws.^^ Male deer and antelopes, on the other hand, possess horns, and they rarely have canine teeth; and these, when present, are always of small size, so that it is doubtful whether they are of any service in their battles. In Antilope montana they exist only as rudiments in the young male, disappearing as he grows old ; and they are absent in the female at all ages ; but the females of certain other antelopes and of certain deer have been known occasionally to exhibit rudiments of these teeth.'^ Stalhons have small canine teeth, which are either quite absent or rudimentary in the mare ; but they do not appear to be used in fighting, for stallions bite with their incisors, and do not open their mouths wide like camels and guanacoes. Whenever the adult male possesses canines, now inefficient, whilst the female has either none or mere rudiments, we may conclude that the early male pro- genitor of the species was provided with efficient canines, which have been partially ti-ansferred to the females. The reduction of these teeth in the males seems to have followed from some change in their manner of fighting, often (but not in the horse) caused by the development of new weapons. Tusks and horns are manifestly of high importance to their 30 See also Corse ('Philosoph. Transact.' 1799, p. 212) on the manner in which the short-tusked Mooknah variety attacks other ele- phants. 3» Owen, * Anatomy of Verte- brates,' vol. iii. p. 349. »2 See Riippell (in ' Proc. Zoolog Soc' Jan. 12, 1836, p. 3) on tho canines in deer and antelopes, with n note by Mr. Martin on .i female American deer. See also Falconer (' PaljBont. Memoirs and Notes,' vol. i. 1868, p. 576) on canines in an adult female deer. In old males of the musk-deer the canines (Pallas, 'Spic. Zoolog.' fasc. xiii. 1779, p. 18) sometimes grow to the length of three inches, whilst in old females a rudiment projects scarcely half an inch above the gums. Chap. XVII. Mammals — Greater Size of Male. 515 possessors, for their development consumes much organised matter. A single tusk of the Asiatic elephant — one of the extinct woolly species — and of the African elephant, have been known to weigh respectively 150, 160, and 180 pounds ; and even greater weights have been given by some authors.^^ With deer, in which the horns are periodically renewed, the drain on the constitution must be greater ; the horns, for instance, of the moose weigh fi'om fifty to sixty pounds, and those of the extinct Irish elk from sixty to seventy pounds — the skuU of the latter weighing on an average only five pounds and a quarter. Although the horns are not periodically renewed in sheep, yet their development, in the opinion of many agriculturists, entails a sensible loss to the breeder. Stags, moreover, in escaping from beasts of prey are loaded with an additional weight for the race, and are greatly retarded in passing throiigh a woody country. The moose, for instance, with horns extending five and a half feet from tip to tip, although so skilful in their use that he wiU not touch or break a twig when walking quietly, cannot act so dexterously whilst rushing away from a pack of wolves. "During his progress he holds his nose up, so " as to lay the horns horizontally back ; and in this attitude " cannot see the ground distinctly."^* The tips of the horns of the great Irish elk were actually eight feet apart ! Whilst the horns are covered with velvet, which lasts with the red-deer for about twelve weeks, they are extremely sensitive to a blow ; so that in Germany the stags at this time somewhat change theii- habits, and avoiding dense forests, frequent young woods and low thickets.'^ These facts remind us that male birds have acquired ornamental plumes at the cost of retarded flight, and other ornaments at the cost of some loss of power in their battles with rival males. ^ With mammals, when, as is often the case, the sexes differ in size, the males are ahnost always larger and stronger. I am informed by Mr. Gould, that this holds good in a marked manner with the marsupials of Austraha, the males of which appear to continue growing until an unusually late age. But the most extraordinary case is that of one of the seals {Callor- hinus ursinus), a full-grown female weighing less than one-sixth of a full-grown male.=« Dr. Gill remarks that it is with the .Jn^'^f Tennent, 'Ceylon,' 143. See .also Owen, ' British 18.->9 vol. u. p. 275 ; Owen, ' Bri- Fossil Mammals,' on the Irish elk, tish Fossil Mammals,' 1846, p. 245. pp. 447 455. " Richardson, ' Fauna Bor. Ame- « ' ForestCreatures,' by C. Boner, ncana, on the moose, Alces palmata, 1861, p. 60. pp. 236, 237 ; on the expanse of the gg^ ^j^'g interostincr paper horni', 'Land and Water,' 1869, p. by Mr. J. A. Allen in ' Bull. Mu*. 2 L 2 5i6 The Descent of Man. Paet 11. polygamous seals, the males of wliich are well known to fight savagely together, that the sexes diflfer much in size ; the mono- gamous species dififering but little. Whales also afford evidence of the relation existing between the pugnacity of the males and their, large size compared with that of the female ; the males of the right-whales do not fight together, and they ai"e not larger, but rather smaller, than their females ; on the other hand, male sperm-whales, fight much together, and their bodies are " often " found scarred with the imprint of their rival's teeth," and they are double the size of the females. The greater strength of the male, as Hunter long ago remarked,^' is invariably displayed in those parts of the body which are brought into action in fighting with rival males — for instance, in the massive neck of the bull. Male quadrupeds are also more coui-ageous and pugnacious than the females. There can be little doubt that these characters have been gained, partly through sexual selec- tion, owing to a long series of victories by the stronger and more courageous males over the weaker, and partly thi'ough the inherited effects of use. It is probable that the successive variations in strength, size, and coui-age, whether due to mere variability or to the effects of use, by the accumulation of which male quadrupeds have acquii-ed these characteristic qualities, occurred rather late in life, and were consequently to a large extent limited in their transmission to the same sex. From these considerations I was anxious to obtain information as to the Scotch deerhound, the sexes of which differ more in size than those of any other breed (though bloodhounds differ considerably), or than in any vrild canine species known to me. Accordingly, I applied to Mr. Cupples, well-known for his success with this breed, who has weighed and measured many of his own dogs, and who has with great kindness collected for me the following facts from various sources. Fine male dogs, measured at the shoulder, range from 28 inches, which is low, to 33 or even 34 inches in height; and in weight from 80 pounds, which is light, to 120 pounds, or even more. The females range in height from 23 to 27, or even to 28 inches ; and in weight from 60 to 70, or even 80 pounds.^^ Mr. Cupples Comp. Zoolog. of Cambridge, United .'Jtat. s,' vol. ii. No. 1, p. 82. The weights were ascertained by a care- ful observer, Capt. Bryant. Dr. Gill in 'The American Naturalist,' Jan. 1871, Prof. Shaler on the relative size of the seses of whales, 'American Naturalist/ Jan. 1873. ♦ Animal Economy,' p. 45. 5' See also Richardson's ' ManuAi on the Dog,' p. 59. Much valuable information on the Scottish deci- hound is given by Mr. McNeill, who first called attention to ttie inequality in size between the sexes, in Scrope's ' Art of Deer Stalking." Chap. XVII, Mammals — Greater Size of Male. 517 concludes that from 95 to 100 pounds for the male, and 70 foi the female, would be a safe average; but there is reason to beheve that formerly both sexes attained a greater weight. Mr. Cupples has weighed puppies when a fortnight old ; in one litter the average weight of four males exceeded that of two females by six and a half ounces ; in another litter the average weight of four males exceeded that of one female by less than one ounce; the same males when thi'ee weeks old, exceeded the female by seven and a half ounces, and at the age of six weeks by nearly fourteen ounces. Mr. Wright of Yeldersley House, in a letter to Mr. Cupples, says : " I have taken notes on " the sizes and weights of puppies of many litters, and as far as " my experience goes, dog-puppies as a rule differ very little " from bitches till they arrive at about five or six months old ; " and then the dogs begin to increase, gaining upon the bitches " both in weight and size. At birth, and for several weeks " afterwards, a bitch-puppy will occasionally be larger than any " of the dogs, but they are invariably beaten by them later." Mr. McNeill, of Colonsay, concludes that "the males do not " attain their full growth till over two years old, though the " females attain it sooner." According to Mr. Cupples' expe- rience, male dogs go on growing in stature till they are from twelve to eighteen months old, and in weight till from eighteen to twenty-four months old ; whilst the females cease increasing in stature at the age of from nine to fourteen or fifteen months, and in weight at the age of from twelve to fifteen months. From these various statements it is clear that the full difference in size between the male and female Scotch deerhound is not acquired until rather late in life. The males almost exclusively are used for coursing, for, as Mr. McNeill informs me, the females have not sufficient strength and weight to pull down a full-grown deer. From the names xised iu old legends, it appears, as I hear from Mr. Cupples, that, at a very ancient period, tho males were the most celebrated, the females being mentioned only as the mothers of famous dogs. Hence, during many generations, it is the male which has been chiefly tested for strength, size, speed, and courage, and the best will have been bred from. As, however, the males do not attain their full dimensions until rather late in life, they will have tended, in accordance with the law often indicated, to transmit their characters to their male offspring alone; and thus the great inequality in size between the sexes of the Scotch deer-hound may probably be accounted for, I hope that Mr. Cupples will keep account and history of this famous to his intention of publishing a full breed. 5i8 The Descent of Man. Part II. The males of some few quadrupeds possess organs or pai-t8 developed solely as a means of defence against the attacks of other males. Some kinds of deer use, as we have seen, the upper branches of their horns chiefly or exclusively for de- fending themselves ; and the Oryx antelope, as I am infoi-med by Mr. Eartlett, fences most skilfully with his long, gently curved horns ; but these are likewise used as organs of offence. The same observer remarks that rhinoceroses in fighting, parry each other's sidelong blows with their horns, which clatter loudly together, as do the tusks of boars. Although wild boars fight desperately, they seldom, according to Brehm, receive fatal wounds, as the blows fall on each other's tusks, or on the layer of gristly skin covering the shoulder, called by the German hunters, the shield; and here we have a part spe- cially modified for defence. With boars in the prime of life (see fig. 65) the tusks in the lower jaw are used for fighting, but they become in old nge, as Brehm states, so much curved inwards and up- wai'ds over the snout, that they can no longer be used in this way. They may, however, still serve, and even more effectively, as a means of defence. In compensation for the loss of the lower tusks as weapons of offence, those in the upper jaw, which always project a little laterally, increase in old age so much in length and curve so much upwards, that they can be used for attack. Nevertheless, an old boar is not so dangerous to man as one at the age of six or seven years.^' In the full-grown male Baburisa pig of Celebes (fig. 66), the lower tusks are formidable weapons, like those of the EuroiJean boar in the prime of life, whilst the upper tusks are so long and have their points so much curled inwards, sometimes even touching the forehead, that they are utterly useless as weapons of attack. They more nearly resemble horns than teeth, and are so manifestly useless as teeth, that the animal was foimerly supposed to rest his head by hooking them on to a branch! Their convex surfaces, however, if the head were held a little « Brehm, ' Thierleben,' B. ii. s. 729-732. Fig. 65. Head of Common wild boar, in prime of life (from Brehm). Chap. XVII. Mammals — Means of Defence. 5^9 laterally, would serve as an excellent guard \ and hence, perhaps, it is that in old animals they " are generally broken off, as if by fighting."*" Here, then, we have the curious case of the upper tusks of the Babirusa regularly assuming during the prime of hfe, a structure which apparently renders them fitted only for defence ; whilst in the European boar the lower tusks assume in a less degree and only during old age, nearly the same form, and then serve in like manner solely for defence. Fig. 66. Skull ol the Babirusa Pig (from WaUace's ' Malay Archipelago ■> ,In the wart-hog {Phacocloerus cefhiopicus, fig. 67) the tusks in the upper jaw of the male curve upwards during the prime of hfe and from bemg pointed serve as formidable weapons The tusks in the lower jaw are sharper than those in the upper but from their shortness it seems hardly possible that they can be T^ed as weapons of attack. They must, however, greatly strengthen those m the upper jaw, from being ground so as to fit closely against their bases. Neither the upper nor the lower a::i^^'S::s. its:' ^'^^"^^^ '^^^ ^^^^^y 520 Tlie Descent of Man. Part II. tusks appear to have been specially modified to act as guards, though no doubt they are to a certain extent used for this pur- pose. But the wart-hog is not destitute of other special means of protection, for it has, on each side of the face, beneath the eyes, a rather stiff, yet flexible, cartilaginous, oblong pad (fig. 67), which projects two or three inches outwards; and it appeared to Mr. Bartlett and myself, when viewing the living animal, that these pads, when struck from beneath by the tusks of an opponent, would be turned upwards, and would thus admirably protect the somewhat prominent eyes. I may add, on the authority of Mr. Bartlett, that these boars when fighting stand directly face to face. Fig. 67. Heart of female Ethiopian wart-hog, from 'Proc. Zool. Soc' 1809, shewing- the same cbaracters as the male, though on a reduced scale. N.B. When the engraving was first made, 1 was under the impression that it repre- sented the male. Lastly, the African river-hog (Pofomochoenis penicillatus) has a hard cartilaginous knob on each side of the face beneath the eyes, which answers to the flexible pad of the wart-hog ; it has also two bony prominences on the upper jaw above the nostrils. A boar of this species in the Zoological Gardens recently broke into the cage of the wart-hog. They fought all night long, and were found in the morning much exhausted, but not seriously wounded. It is a significant fact, as shewing the purpose of the above-described projections and excrescences, that these were covered with blood, and were scored and abraded in an extra- ordinary manner. . Although the males of so many members of tho pig family aio Cbap. XVII, Mammals — Means of Defence. 521 provided with weapons, and as we have just seen with means ol defence, these weapons seem to have been acquired within a rather late geological period. Dr. Forsyth Major specifies" several miocene species, in none of which do the tusks appear to have been largely developed in the males ; and Prof. Eiitimeyer was formerly struck with this same fact. The mane of the lion forms a good defence against the attacks of rival Hons, the one danger to which he is hable; for the males, as Sir A. Smith informs me, engage ia terrible battles, and a young hon dares not approach an old one. In 1857 a tiger at Bromwich broke into the cage of a lion and a fearful scene ensued : " the lion's mane saved his neck and head from " being much injured, but the tiger at last succeeded in ripping " up his belly, and in a few minutes he was dead." The broad ruff round the throat and chin of the Canadian lynx {Fdis canadensis) is much longer in the male than in the female ; but whether it serves as a defence I do not know, Male seals are well known to fight desperately together, and the males of certain kinds ( Otaria jubata) *^ have great manes, whilst the females have small ones or none. The male baboon of the Cape of Good Hope {Cynocephalus porcarius) has a much longer mane and' larger canine teeth than the female ; and the mane probably serves as a protection, for, on asking the keepers in the Zoo- logical Gardens, without giving them any clue to my object, whether any of the monkeys especially attacked each other by the nape of the neck, I was answered that this was not the case, except with the above baboon. In the Hamadryas baboon, Ehi-enberg compares the mane of the adult male to that of a young lion, whilst in the young of both sexes and in the female the mane is almost absent. It appeared to me probable that the immense woolly mane of the male American bison, which reaches almost to the ground, and is much more developed in the males than in the females, served as a protection to them in their terrible battles ; but an experienced hunter told Judge Caton that he had never observed anything which favoured this behef. The stallion has a thicker and fuller mane than the mare; and I have made particular inquiries of two great trainers and breeders, who have had charge of many entire horses, and am assured that they " invariably t t- 2 M 2 532 The Descent of Man. Part IL monkeys attack each other by the throat ; but it is not probable that the beard has been developed for a distinct purpose from that served by the whiskers, moustache, and other tufts of hair on the face ; and no one will suppose that these are useful as a protection. Must we attribute all these appendages of hair or skin to mere pm-poseless variability in the male ? It cannot bo denied that this is possible ; for in many domesticated quad- rupeds, certain characters, apparently not derived through re- version from any wild parent-form, are confined to the males. Fig. 68. Pithecia satanas, male (from Brehm). or are more developed in them than in the females— for instance, the hump on the male zebu-cattle of India, the tail of fat-tailed rams, the arched outline of the forehead in the males of several breeds of sheep, and, lastly, the mane, the long hairs on the hind-legs, and the dewlap of the male of the Berbura goat.'* The mane, which occurs only in the rams of an African breed of See the chapters on these ' Vari.ntion of Animals under Domes- several animals in vol. i. of my tication ; ' also vol. ii. p. 73 ; also Ghap. X7III. Mammals — Ornamental Colours. 533 sheep, is a true secondary sexual character, for, as I hear from Ml". Winwood Eeade, it is not developed if the animal be castrated. Although wo ought to be extremely cautious, as shewn in my work on 'Variation under Domestication,' in concluding that any character, even with animals kept by semi-civilised people, has not been subjected to selection by man, and thus augmented, yet in the cases just specified this is improbable ; more especially as the characters are confined to the males, or are more strongly develoijed in them than in the females. If it were positively known that the above African ram is a descendant of the same primitive stock as the other breeds of sheep, and if the Berbui'a male-goat with his mane^ dewlap, &c., is descended from the same stock as other goats, then, assuming that selection has not been applied to these characters, they must be due to simple variability, together T/ith sexually-limited inheritance. Hence it appears reasonable to extend this same view to all analogous cases with animals in a state of natui'e. Nevertheless I cannot persuade myself that it generally holds good, as in the case of the extraordinary development of hair on the throat and fore-legs of the male Ammotragus, or in that of the immense beard of the male Pithecia. Such study as I have been able to give to nature makes me believe that parts or organs which are highly developed, were acquired at some period for a special pui'pose. With those antelopes in which the adult male is more strongly-coloured than the female, and with those monkeys in wliich the hair on the face is elegantly arranged and coloured in a diversified manner, it seems probable that the crests and tufts of hair were gained as ornaments ; and this I know is the opinion of some natm-alists. If this be correct, there can be little doubt that they were gained or at least modified through aexual selection ; but how far the same view may be extended to other mammals is doubtful. Colour of the Hair and of the Naked Skin.— I vnll fitst give briefly all the cases known to me, of male quadrupeds differing in colour from the females. "With Marsupials, as I am informed by Mr. Gould, the sexes rarely differ in this respect; but the great red kangaroo offers a striking exception, " delicate blue " being the prevailing tint in those parts of the female, which " in the male are red."i» In the Didelphis opossum of Cayenne chap. XX. on the practice of selection logue,' ibid. p. 157. Jjy gemiKiivillsed people. For the OspAra.iier ru/us, Gould, ' Mam- iJetbura goat, s%e Dr. Gray, < Cata- mals of Australia,' 1863, vol. il 534 The Descent of Man. Part II. the female is said to be a little more red than the male. Of the Rodents Dr. Gray remarks : " African squirrels, especially those " found in the tropical regions, have the fur much brighter " and more vivid at some seasons of the year than at others, " and the fur of the male is generally brighter than that of " the female."-" Dr. Gray informs me that he specified the African squirrels, because, from their unusually bright colours, they best exhibit this difference. The female of the Mu& minutus of Eussia is of a paler and dirtier tint than the male. In a large number of bats the fur of the male is lighter than in the female.^* Mr. Dobson also remarks, with respect to these animals : " Dif- " ferences, depending partly or entirely on the possession by the " male of fur of a much more brilliant hue, or distinguished by " different markings or by the greater length of certain portions, " are met only, to any appreciable extent, in the frugivorous bats " in wliich the sense of sight is well developed." This last remark deserves attention, as bearing on the question whether bright colours are serviceable to male animals from being orna- mental. In one genus of sloths, it is now established, as Dr. Gray states, "that the males are ornamented differently from the " females— that is to say, that they have a patch of soft short " hair between the shoulders, which is generally of a more or less " orange colour, and in one species pure white. The females on " the contrary, are destitute of this mark." The terrestrial Carnivora and Insectivora rarely exhibit sexual differences of any kind, including colour. The ocelot {Felis pardalis), however, is exceptional, for the colotu's of the female, compared with those of the male, are "moins apparentes, le ' fauve etant plus terne, le blanc moins pur, les raies ayant moins de largeur et les taches moins de diametre."^ The sexes of the allied Felis mitis also differ, but in a less degree ; the general hues of the female being rather paler than in the male, with the spots less black. The marine Carnivora or seals, on the other hand, sometimes differ considerably in colour, and they present, as we have ah-eady seen, other remarkable sexual differences. Thus the male of the Otaria nigrescens of the southern hemisphere is of a rich brown shade above; whilst the On the Didelphis, Desmarest, * Mammalogie,' p. 256. 20 ' Annals and Mag. of Nat. Hist.' Nov. 1867, p. 325. On the Mus minutus, Desmarest, ' Mammalogie,' p. 304. «» J. A. Allen, in ' Bulletin of Mufi. Comp. Zoolog. of Cambridge, United States,' 1869, p. 207. Mr. Dobson on se.^ual characters in the Chiroptera, 'Proc. Zoolog. Soc' 1873, p. 241. Dr. Gray on Slothg, ibid. 1871, p. 436. =2 Desmarest, ' Mammalogie,' 1820, p. 220. On Fclis mitis, Kenggejj ibid. s. 194. Chap. XVIII. Mammals — Ornamental Colours. 535 female, who acqtiires her adult tints ea,rlier in life than the male, is dark-grey above, the young of both sexes being of a deep chocolate coloui'. The male of the northern Fliom groenlandica is tawny grey, with a curious saddle-shaped dark mark on the hack; the female is much smaller, and has a very different appearance, being " dull white or yellowish straw-colour, with a tawny hue on the back ;" the young at first are pure white, and can " hardly be distinguished among the icy hummocks and " snow, their colour thus acting as a protection." With Euminants sexual differences of colour occur more commonly than in any other order. A difference of this kind is general in the Strepsicerene antelopes ; thus the male nilghau (Portax pida) is bluish-grey and much darker than the female, with the square white patch on the throat, the white marks on the fetlocks, and the black spots on the ears all much more distinct. We have seen that in this species the crests and tufts of hair are likewise more developed in the male than in the hornless female. I am informed by Mr. Blyth that the male, without shedding his hau', periodically becomes darker during the breediag-season. Young males cannot be distinguished from young females until about twelve months old ; and if the male is emasculated before this period, he never, according to the same authority, changes colour. The importance of this latter fact, as evidence that the colouring of the Portax is of sexual origin becomes obvious, when we hear^* that neither the red summer- coat nor the blue winter-coat of the Virginian deer is at all affected by emasculation. With most or all of the highly-orna- mented species of Tragelaphus the males are darker than the hornless females, and their crests of hair are more fully developed. In the male of that magnificent antelope, the Derbyan eland, the body is redder, the whole neck much blacker, and the white band which separates these colours, broader, than in the female. In the Cape eland also, the male is slightly darker than the female.^® In the Indian black-buck {A. bezoartica), which belongs to another tribe of antelopes, the male is very dark, almost black ; whilst the hornless female is fawn-coloured. Wo meet in this Dr. Murie on the Otaria, ' Proc. Zool. Soc' 1869, p. 108. Mr. R. Brown, on the P, groenlandica, ibid. 1868, p. 417. See also on the colours of seals, Desmarest, ibid. p. 243, 249. ■* Judge Caton, in ' Trans. Ottawa Acad, 'of Nat. Sciences,' 1868, p. 4. Dr. Gray, * Cat. of Mamm. in Brit. Mus.' part iii. 1852, pp. 134- 142 ; .also Dr. Gray, ' Gleanings from the Menagerie of Knowsley, in which there is a splendid drawing of the Orcas derbiafius : see the text on Tragelaphus. For the Cape eland (Oreas canna), see Andrew Smith, ' Zoology of S. Africa,' pi. 41 and 42. There are also many of these antelopes in the Zoological Gardens. 53^ The Descent of Man. Pakt IL species, as Mr. Blyth informs me, witli an exactly similar series of facts, as in the Portax pir.la, namely, in the male periodically changing colour during the breeding-season, in the effects of emasculation on this change, and in the young of both sexes being indistinguishable from each other. In the Antilope niger the male is black, the female, as well as the young of both sexes, being brown ; in A, sing-sing the male is much brighter coloured than the hornless female, and his chest and belly are blacker; in the male A. caama, the marks and lines which occur on various parts of the body are black, instead of brown as in the female; in the brindled gnu (A. gorgon) "the colours of the " male are nearly the same as those of the female, only deeper " and of a brighter hue." Other analogous cases could be added. The Banteng bull {Bos sondaicus') of the Malayan Archipelago is almost black, with white legs and buttocks ; the cow is of a bright dun, as are the young males until about the age of three years, when they rapidly change colour. The emasculated bull reverts to the colour of the female. The female Kemas goat is paler, and both it and the female Capra cegagrus are said to be more tmiformly tinted than their males. Deer rarely present any sexual differences in colour. Judge Caton, however, informs me that in the males of the wapiti deer (Cervus canadensis) the neck, belly, and legs are much darker than in the female ; but during the winter the darker tints gradually fade away and disappear. I may here mention that Judge Caton has in his park thi'ee races of the Vii'ginian deer, which differ shghtly in colour, but the differences are almost ex- clusively confined to the blue winter or breeding coat ; so that this case may be compared with those given in a previous chapter of closely-allied or representative species of birds, which differ from each other only in their breeding plumage.^ The females of Cervus pcdudosus of S. America, as well as the young of both sexes, do not possess the black stripes on the nose and the blackish-brown line on the breast, which are characteristic of the adult males.^' Lastly, as I am informed by Mr. Blyth, the ,28 On the Ant. niger, see ' Proc. Zool. Soc' 1850, p. 133. With re- spect to an allied species, in which there is an equal sexual difference in colour, see Sir S. Baker, 'The Albert Nyanza,' 1866, vol. ii. p. 327. For the A. sing-sing, Gray, Cat. B. Mus.' p. 100. Desmarest, ' Mammalogie,' p. 468, on the A. caama. Andiew Smith, 'Zoology of S. Africa,' on the Gnu. ^7 ' Ottawa Academy of Sciences,' May, 21, 1868, pp. 3, 5. 28 S. Muller, on the Banteng, 'Zoog. Indischen Archipel.* 1839- 1844, tab. 35; see also Raffles, as quoted by Mr. Blyth, in ' Laud and Water,' 1867, p. 476. On goats. Dr. Gray, 'Cat. Brit. Mus.' p. 146 ; Desmarest, 'Mammalogie,' p. 482. On the Cervus paludosua, Rengger, ibid. 8. 345. Chap. XVIII. Mammals — Ornamental Colours. 537 mature male of the beautifully coloured and spotted axis deer is <5onsiderably darker than the female ; and this hue the castrated male never acquires. The last Order which we need consider is that of the Primates. The male of the Lemur macaco is generally coal-black, whilst the female is brown.^' Of the Quadrumana of the New World, the females and young of Myceies caraya are greyish-yeUow and Like «ach other ; in the second year the young male becomes reddish- brown ; ia the third, black, excepting the stomach, which, how- ever, becomes quite black in the fourth or fifth year. There is also a strongly-marked difference in colour between the sexes of Mycetes seniculus and Cehus capucinus ; the young of the former, and I believe of the latter species, resembling the females. With Pithecia leucocephala the young likewise resemble the females, which are brownish-black above and light rusty-red beneath, the adult males being black. The ruff of hair round the face of Ateles marginatus is tinted yellow in the male and white in the female. Turning to the Old World, the males of Hylohates Jwolock are always black, with the exception of a white band over the brows ; the females vary from whity-browii to a dark tint mixed with black, but are never wholly black.^" In the beautiful Cercopithecus diana, the head of the adult male is of an intense black, whilst that of the female is dark grey ; ia the former the fur between the thighs is of an elegant fawn- colour, in the latter it is paler. In the beautiful and curious moustache monkey (Cercopithecus cephus) the only difference between the sexes is that the tail of the male is chesnut and that of the female grey; but Mr. Bartlett informs me that all the hues becomes more pronounced in the male when adult, whilst in the female they remain as they were during youth. Ac- cording to the coloured figures given by Solomon Miiller, the male of Semnopithecus chrysomelas is nearly black, the female being pale brown. In the Cercopithecus cynosurus and griseo- viridis one part of the body, which is confined to the male sex, is of the most brilliant blue or green, and contrasts strikingly -with the naked skin on the hinder part of the body, which is vivid red. Lastly, in the baboon family, the adult male of Cynocephalus hamadryas differs from the female not only by his immense ? Sdater, ' Pi-oc. Zool. Soc' 1866, U ; and Brehm, ' Illustrirtes Thior- p. 1. The same fAct has also been leben,' B. i. s. 96, 107. On Ateles tully ascertained by MM. Pollen and Desmarest, ' Mamnialogie,' p. 75. -yan Dam. See, also Dr. Gray in Ou Hylobates, Blyth, 'Land and ' Annals and Mag. of Nat. Hist.' May Water,' 1867, p. 135. Ou the Sem- r nopithecus, S. MuUer, 'Zocg. In- On Mycetes, Keugger, ibid, s. dischen Archipel.' tab. x. 538 The Descent of Man. Part II. maue, but slightly in the colour ot the hair and of the naked callosities. In the drill (C. leucojjhceus) the females and young are much paler-coloured, with less green, than the adult males. No other member in the whole class of mammals is coloured in so extraordinary a manner as the adult male mandi-ill (C. mormon). The face at this age becomes of a fine blue, with the ridge and tip of the nose of the most briUiant red. According to some authors, the face is also marked with whitish stripes, and Fig. 69. Head of male Mandrill (from Gervais, ' Hist. Nat. des Mammifbres'). is shaded in parts with black, but the colours appear to be variable. On the forehead there is a crest of hair, and on the chin a yellow beard. " Toutes les parties sup^rieures de leurs " cuisses et le grand espace nu de leurs fesses sent .^galement " colores dn rouge le plus vif, avcc un melange dc bleu qui ne Chap, XVIII. Mammals — Ornamental Colours. 539 " manque reeUement pas d'elegance."^^ When the animal is excited aU the naked parts become much more yividly tinted. Several authors have used the strongest expressions in de- scribing these resplendent colours, which they compare with those of the most brilliant birds. Another remarkable pecu- liarity is that when the great canine teeth are fully developed, immense protuberances of bone are formed on each cheek, which are deeply furrowed longitudinally, and the naked skin over them is brilKantly-coloured, as just described. (Kg. 69.) In the adult females and in the young of both sexes these protuber- ances are scarcely perceptible ; and the naked parts are much less bright coloured, the face bemg almost black, tmged with blue. In the adult female, however, the nose at certain regular intervals of time becomes tinted with red. In all the cases hitherto given the male is more strongly or brighter coloured than the female, and differs from the young of both sexes. But as with some few bii'ds it is the female which is brighter coloured than the male, so with the Khesus monkey (Macacus rhesus) the female has a large surface of naked skin round the tail, of a brilhant camine red, which, as I was assured by the keepers in the Zoological Gardens, periodically becomes even yet more vivid, and her face also is pale red. On the other hand, in the adult male and in the young of both sexes, (as I saw in the Gardens) neither the naked skin at the posterior end of the body, nor the face, shew a trace of red. It appears, however, from some published accounts, that the male does occa- sionally, or during certain seasons, exhibit some traces of the red. Although he is thus less ornamented than the female, yet in the larger size of his body, lai-ger canine teeth, more developed whiskers, more prominent superciliary ridges, he follows the common rule of the male excelling the female. I have now given all the cases known to me of a difference in colour between the sexes of mammals. Some of these may be the result of variations confined to one sex and transmitted to the same sex, without any good being gained, and therefore without the aid of selection. We have instances of this with our domesticated animals, as in the males of certain cats being rusty-red, whilst the females are tortoise-shell coloured. Analo- gous cases occur in nature : Mr. Bartlett has seen many black varieties of the jaguar, leopard, vulpine phalanger, and wombat; " Gervais, ' Hist. Nat. des Mam- Desmarest, ' Mammalogie,' p. 70. miftres,' 1854, p. 103. Figures are Geoffroy St.-Hilaire and F. Cavier, givcE of the skull of the male. Also ' Hist. Nat. des Mamm ' 1 824, torn, i 540 Tlie Descent of Man. Pabt IL and he is certain that all, or nearly all these animals, were males. On the other hand, with wolves, foxes, and apparently American raqiiirrels, both sexes are occasionally born black. Hence it is quite possible that with some mammals a difference in colour Ixjtween the sexes, especially when this is congenital, may simply be the result, without the aid of selection, of the occurrence of 0 cie or more variations, which from the first were sexually limited jn their transmission. Nevertheless it is improbable that the diversified, vivid, and contrasted colours of certain quadrupeds, for instance, of the above monkeys and antelopes can thus bo accounted for. We should bear in mind that these colours do not appear in the male at birth, but only at or near maturity ; and that unUke ordinaiy variations, they are lost if the male be emasculated. It is on the whole probable that the strongly- marked colours and other ornamental characters of male quadrupeds are beneficial to them in their rivalry with other males, and have consequently been acquii-ed through sexual selection. This view is strengthened by the differences in colour between the sexes occurring almost exclusively, as may be collected from the previous details, in those groups and sub- groups of mammals, which present other and strongly-marked secondary sexual characters ; these being likewise due to sexual selection. Quadrupeds manifestly take notice of colour. Sir S. Baker repeatedly observed that the African elephant and rhinoceros attacked white or grey horses with special fury. I have else- where shewn that half- wild horses apparently prefer to pair with those of the same colour, and that herds of fallow-deer of different colours, though living together, have long kept distinct. It is a more significant fact that a female zebra would not admit the addresses of a male ass untU he was painted so as to resemble a zebra, and then, as John Hunter remarks, " she " received Mm very readily. In this curious fact, we have instinct excited by mere colour, which had so strong an effect " as to get the better of everything else. But the male did not " require this, the female being an animal somewhat similar tc " himself, was sufficient to rouse him."^^ In an earher chapter we have seen that the mental powers o: the higher animals do not differ in kind, though greatly ir degree, from the corresponding powers of man, especially of the lower and barbarous races ; and it would appear that even their taste for the beautiful is not widely different from that of the < The Variation of Animals and 'Essays and Observations by Plants under Domestication,' 1868, J. Hunter,' edited by Owen, 18ttL, Tol a. pp. 102, 103. vol. i. p. 194. Chap. XYlir. Matnnials — Ornaments. 541 Quadnimana. As tlie negro of Africa raises the flesh on his face into parallel ridges " or cicatrices, high above the natural "surface, which unsightly deformities, are considered great "personal attractions;"^* — as negroes and savages in many parts of tho world paint their faces with red, blue, white, or black bars, — so tho male mandrill of Africa appears to have acquired his deeply-farrowed and gaudOy-coloured face from having been thus rendered attractive to the female. No doubt it is to us a most grotesque notion that the posterior end of the body should be coloured for the sake of ornament even more brilliantly than the face ; but this is not more strange than that the tails of many bu'ds should be especially decorated. With mammals we do not at present possess any evidence that the males take pains to display their charms before the female ; and the elaborate manner in which this is performed by male birds and other animals, is the strongest argument in favour of the belief that the females admire, or are excited by, the ornaments and colours displayed before them. There is, however, a striking parallelism between mammals and birds in all their secondary sexual characters, namely in their weapons for fighting with rival males, in their ornamental appendages, and in their colours. In both classes, when the male differs from the female, the young of both sexes almost always resemble each other, and in a large majority of cases resemble the adult female. In both classes the male assumes the characters proper to his sex shortly before the age of reproduction ; and if emas- culated at an early period, loses them. In both classes the change of colour is sometimes seasonal, and the tints of the naked parts sometimes become more vivid during the act of courtship. In both classes the male is almost always more vividly or strongly coloured than the female, and is ornamented with larger crests of hair or feathers, or other such appendages. In a few exceptional cases the female in both classes is more highly ornamented than the male. With many mammals, and at least in the case of one bird, the male is more odoriferous than the female. In both classes the voice of the male is more powerful than that of the female. Considering this parallelism there can be little doubt that the same cause, whatever it may be, has acted on mammals and birds ; and the result, as far as ornamental characters are concerned, may be attributed as it appears to me, to the long-con tinned preference of the indi- viduals of one sex for certain individuals of the opposite sex, combmed with their success in leaving a larger number of offspring to inherit their superior attractions. ^ Sir S Baker, ' The Nile Tributaries of Abyssiaia,' 1867. 542 The Descent of Man. Paet II, Equal transmission of ornamental characters to both sexes. — Y/itk many birds, ornaments, ■which analogy leads us to believe were primarily acquired by the males, have been transmitted equally, or almost equally, to both sexes ; and we may now enquire how far this view applies to mammals. With a considerable number of species, especially of the smaller kinds, both sexes have been coloured, independently of sexual selection, for the sake of pro- tection ; but not, as far as I can judge, in so many cases, nor ia so striking a manner, as in most of the lower classes. Audubon remarks that he often mistook the musk-rat,'^ whilst sitting on the banks of a muddy stream, for a clod of earth, so complete was the resemblance. The hare on her form is a familiar instance of concealment through colour; yet this principle partly fails in a closely-aUied species, the rabbit, for when running to its burrow, it is made conspicuous to the sportsman, and no doubt .to all beasts of prey, by its upturned white tail. No one doubts that the quadi'upeds inhabiting snow-clad regions have been rendered white to protect them from iheir enemies, or to favour their steaUng on their prey. In regions where snow never lies for long, a white coat would be injurious; consequently, species of this colour are extremely rare ia the hotter parts of the world. It deserves notice that many quadrupeds inhabiting moderately cold regions, although they do not assume a white winter dress, become paler during this season ; and this appa- rently is the direct result of the conditions to which they have long been exposed. Pallas states that in Siberia a change of this nature occurs with the wolf, two species of Mustela, the domestic horse, the Eqims hemionus, the domestic cow, two species of antelopes, the musk-deer, the roe, elk, and reia- deer. The roe, for instance, has a red summer and a greyish- white winter coat; and the latter may perhaps serve as a protection to the animal whilst wandering through the leafless thickets, sprinkled with snow and hoar-fi-ost. If the above- named animals were gradually to extend their range into regions perpetually covered with snow, their pale winter-coats would probably be rendered through natural selection, whiter and whiter, until they became as white as snow. Mr. Eeeks has given me a curious instance of an animal profit- ing by beiug pecuharly coloured. He raised fi-om fifty to sixty white and brown piebald rabbits in a large walled orchard; and he had at the same time some similarly colom-ed cats in his Fiber zibethicus, Audubou and Glirium ordine,' 1778, p. 7. What Bachman, *Tha Quadrupeds of K I have called the roe is the Ca/ireoto America,' 1846, p. 109. sibiricus subeccnidatus of Pallas. ^ ' NovK species Quadrupedum e Chap. XYIII. Mammals — Spots and Stripes. 543 house. Sucli cats, as I liave often noticed, are very conspicuous during day ; but as they used to lie in watcli dui'ing the dusk at the mouths of the bui'rows, the rabbits apparently did not distinguish them from their parti-coloured brethren. The result was that, within eighteen months, every one of these parti- coloured rabbits was destroyed; and there was evidence that this was effected by the cats. Colour seems to be advantageous to another animal, the skiink, in a manner of which we have had many instances in other classes. No animal will voluntarily attack one of these creatui'es on account of the dreadful odour which it emits when irritated ; but duriog the dusk it would not easily be recognised and might be attacked by a beast of prey. Hence it is, as Mr. Belt believes,^'' that the skunk is provided with a great white bushy tail, which serves as a conspicuous warning. Although we must admit that many quadrujDeds have received their present tints either as a protection, or as an aid in procui'ing prey, yet with a host of species, the colour's are far too con- spicuous and too singularly arranged to allow us to suppose that they serve for these pm-poses. We may take as an illustration certain antelopes ; when we see the squai-e white patch on the throat, the white marks on the fetlocks, and the round black spots on the ears, all more distinct in the male of the Portax picta, than in the female ; — when we see that the colours are more vivid, that the narrow white lines on the flank and the broad white bar on the shoulder are more distinct in the male Oreas derhyanus than in the female ; — ^when we see a, similar difference between the sexes of the curiously-ornamented Tragelaphus scriptus (fig. 70), — we cannot believe that differences of this kind are of any service to either sex in their daily habits of Ufe. It seems a much more probable conclusion that the various marks were first acquh-ed by the males and their colours intensified through sexual selection, and then partially trausfen-ed to the females. If this view be admitted, there can be little doubt that the equally singular colours and marks of many other antelopes, though common to both sexes, have been gained and transmitted in a like manner. Both sexes, for instance, of the koodoo (Strepsiceros kudu) (fig. 64) have narrow white vertical lines on their hind flanks, and an elegant angular white mark on their foreheads. Both sexes in the genus Damalis are very oddly coloured ; in D. pygarga the back and neck are purplish-red, shading on the flanks into black ; and these colom-sare abruptly separated from the white belly and from a large white space on the buttocks; the head is still more oddly coloured, a large oblong whit<3 mask, narrowly-edged with black, covers the face 3' ' The Naturalist in Nicaragua,' p. 249. 544 The Descent of Man. Pakt II. ■up to the eyes (fig. 71) ; there arc three white stripes on the forehead, and the ears are marked with white. The fawns of this species are of a uniform pale yellowish-brown. In Damalis alhifrons the colouring of the head differs from that in the last species in a single white stripe replacing the three stripes, and in the ears being almost wholly white.^^ After having studied to the best of my ability the sexual differences of animals be- longing to all classes, I cannot avoid the conclusion that the curiously-arranged colours of many antelopes, though common to both sexes, are the result of sexual selection primarily applied to the male. " See the fine plates in A. Smith's « Gleanings from the Menagerie O'' ' Zoology of S. Africa,' and Dr. Gray's Knowsley .' Chap. XVIII. Mammals — Spots and Stripes. 545 The same conclusion may perhaps be extended to the tiger, one of the most beautiful animals in the world, the sexes of which cannot be distinguished by colour-, even by the dealers in wild beasts. Mr. Wallace believes^" that the striped coat of the tiger " so assimilates with the vertical stems of the bamboo, as to assist greatly in concealing him from his approaching prey." But this view does not appear to me satisfactory. We have .some sUght evidence that his beauty may be due to sexual Tig. 71 . Damalis pygarga, male (from the Knowsley Menagerie). selection, for in two species of Felis the analogous marks and ^'t''' ^^^^ tl^e female. Se protection on the open plams of South Africa. BurchelP in de- scriDing a nercl says, 'their sleek ribs glistened in the sun, and the brightness and regularity of their striped coats presented a picture of extraordinary beauty, in which probably they are 18G7 ^'^'"^^^ -^"'^ ^' " "J^'-'-^ve^^ in South Africa,' 1824. ' P- ^' vol. ii. p. 315. 2 N 546 llie Desce?it of Man. Pakt II. " not surpassed by any other quadruped." But as throughout the whole group of the Equidas the sexes are identical in colour, we have here no evidence of sexual selection. Nevertheless he who attributes the white and dark vertical stripes on the flanka of various antelopes to this process, will probably extend the same view to the Eoyal Tiger and beautiful Zebra. We have seen in a former chapter that when young animals belonging to any class follow nearly the same habits of life as their parents, and yet are coloured in a different manner, it may be inferred that they have retained the colouring of some ancient and extinct progenitor. In the family of pigs, and in the tapirs, the young are marked vrith longitudinal stripes, and thus differ from all the existing adult species in these two gi'oups. With many kinds of deer the young are marked with elegant white spots, of which their parents exhibit not a trace. A graduated series can be followed from the axis deer, both sexes of which at aU ages and during all seasons are beautifully spotted (the male being rather more strongly coloured than the female), to species in which neither the old nor the young aro spotted. I will specify some of the steps in this series. The Mantchurian deer (CerwMs mantchuricus) is spotted during the whole year, but, as I have seen in the Zoological Gardens, the spots are much plainer during the summer, when the general colour of the coat is lighter, than during the winter, when the general colour is darker and the horns are fully developed. In the hog-deer {Hyelaphus porcinus) the spots are extremely con- spicuous during the summer when the coat is reddish-brown, but quite disappear dui'ing the winter when the coat is brown." In both these species the young are spotted. In the Virginian deer the young are likewise spotted, and about five per cent, of the adult animals living in Judge Caton's park, as I am in- formed by him, temporarily exhibit at the period when the red summer coat is being replaced by the bluish winter coat, a row of spots on each flank, which are always the same in number, though very variable in distinctness. I'rom this condition there is but a very small step to the complete absence of spots in the adults at all seasons ; and, lastly, to their absence at all ages and seasons, as occurs with certain species. From the existence of this perfect series, and more especially from the fawns of so many species being spotted, we may conclude that the now living members of the deer family are the descendants of some ancient •«> Dr. Gray, ' Gleanings from the deer of Ceylon, says it is more Menagerie of Knowsley,' p. 64. brightly spotted with white than Mr. Blyth, in speaking (' Land and the common hog-deer, at the season Water,' 1869, p. 42) of the hog- when it renews its horns. Chap. XVIII, Mammals — Spots and Stripes. 547 species which, like the axis deer, was spotted at all ages and seasons. A still more ancient progenitor probably somewhat resembled the Eyomoschus aquaticus — for this animal is spotted, and the hornless males have large exserted canine teeth, of which some few true deer still retain rudiments. Hyomoschus. also, offers one of those interesting cases of a form linking to- gether two groups, for it is intermediate in certain osteological characters between the pachyderms and ruminants, which were formerly thought to be quite distinct.^^ A ciarious difficulty here arises. If we admit that coloiu'ed spots and stripes were first acquired as ornaments, how comes it that so many existing deer, the descendants of an aboriginally spotted animal, and all the species of pigs and tapir's, the descendants of an aboriginally striped animal, have lost in their adult state their former ornaments ? I cannot satisfactorily answer this question. Wo may feel almost sure that the spots and stripes disappeared at or near maturity in the progenitors of our existing species, so that they were still retained by the young ; and, owing to the law of inheritance at corresponding ages, were transmitted to the young of all succeeding generations. It may have been a great advantage to the hon and puma, from the open nature of their usual haunts, to have lost their stripes, and to have been thus rendered less conspicuous to their prey ; and if the successive variations, by which this end was gained, occurred rather late in life, the young would have retained their stripes, as is now the case. As to deer, pigs, and tapirs, Fritz Miiller has suggested to me that these animals, by the removal of their spots or stripes through natural selection, would have been less easily seen by their enemies ; and that they would have especially required this protection, as soon as the carnivora increased in size and number during the tertiary periods. This may be the true explanation, but it is rather strange that the young should not have been thus protected, and still more so that the adults of some species should liave retained their spots, either partially or completely, during part of the year. We know that, when the domestic ass varies and becomes reddish-brown, grey, or black, the stripes on the shoulders and even on the spine frequently disappear, though we cannot explain the cause. Vei-y few horses, except dun-coloxired kinds, have stripes on any part of theii- bodies, yet we have good reason to believe that the aboriginal horse was striped on the legs and spine, and probably on the shoulders.^^ Hence the dis- appearance of the spots and stripes in our adult existing deer, « Falconer and Cautley, ' Proc. ^ < ^he Variation of Animals and Geoloff. See' 1843; and Falconer's Plants under Domestication,' 1868, 'Pal. Memoirs,' vol. i. p. 19G. vol. i. p. 61-64. 2 N 2 548 TJie Descent of Man. Part IL pigs, and tapirs, may be due to a change in the general colour of their coats; but whether this change was effected tlu-ough sexual or natural selection, or was due to the direct action of the conditions of Life, or to some other unknown cause, it is impossible to decide. An observation made by IMr. Sclater well illustrates our ignorance of the laws which regulate the appearance and disappearance of stripes ; the species of Asinus which inhabit the Asiatic continent are destitute of stripes, not having even ^„ TT 1 f c.,„„«T.it>.M™s rubicundus. This and the following figures (from "^'^rorGe^rl^rf^vTrrew^toddarra^ and development of the ha>r on the head. the cross shoulder-stripe, whilst those which inhabit Africa Jii-e conspicuously striped, with the partial exception of A. tej»o^«.S which has only the cross shoulder-stripe and general ys^^^^^^^ faint bars on the legs ; and this species mhabits the almost mtei mediate region of Upper Egypt and Abyssinia. " ' Proc. Zool. See' 1862, p. 164. See, also, Dr. Hartmann, 'Ann. d. Landw.' Bd. xliii. s. 222. Chap. XVIII. Beauty of the Quadrumana. 549 Quadrumana. — Before we conclude, it will be weU to add a few remarks on the ornaments of monkeys. In most of the species the sexes resemble each other in colour, but in some, as we have seen, the males differ from the females, especially in the colour of the naked parts of the skin, in the development of the t)eard, whiskers, and mane. Many species are coloured either in so extraordinary or so beautiful a manner, and are furnished with such curious and elegant crests of hair, that we can hardly avoid looking at these characters as having been gained for the sake of ornament. The accompanying figures (figs. 72 to 76) Fig. 75. Hcaa of Atoles marsinatus. Fig. 76. Head of Cebus vcUcrosus. serve to shew the arrangement of the hair on the face and head m several species. It is scarcely conceivable that these crests of hair, and the strongly contrasted colours of the fur and skin, can bo the result of mere variability without the aid of selection; 550 The Descent of Man. Part U. and it is inconceivable that they can be of use in any ordinary way to these animals. If so, they have jorobably been gained through sexual selection, though transmitted equally, or almost equally to both sexes. With many of the Quadrumana, we have addi-' tional evidence of the action of sexual selection in the greater size and strength of the males, and in the greater development of their canine teeth, in comparison with the females. A few instances will sufiSce of the strange manner in which both sexes of some species are coloured, and of the beauty of others. The face of the Cercopithecus petaurista (fig. 77) is black, the whiskers and beard being white, with a defined, round, white spot on the nose, covered with short white hair, which gives to the animal an almost ludicrous aspect. The Semnopitheciis frontatus likewise has a blackish face with a long black beard, and a large naked spot on the forehead of a bluish- white colour. 'The face of Macacus lasiotus is dirty flesh-coloured, with a defined red spot on each cheek. The appearance of Cercocehus mthiops is grotesque, with its black face, white whiskers and collar, chesnut head, and a large naked white spot over each eyelid. In very many species, the beard, whiskers, and crests of hair round the face are of a different colour from the rest of the head, and when different, are always of a lighter tint,** being often pure white, sometimes bright yellow, or reddish. The whole face of the South American Brachyurus calvus is of a " glowing scarlet hue ; " but this colour does not appear until the animal is nearly mature.^* The naked skin of the face differs wonderfully in colour in the various sjDecies. It is often brown or flesh-colour, with parts perfectly white, and often as black as that of the most sooty negro. In the Brachyurus the scarlet tint is brighter than that of the most blushing Caucasian damsel. It is sometimes more distinctly orange than in any Mongolian, and in several species it is blue, passing into violet or grey. In all the species known to Mr. Bartlett, in which the adults of both sexes have strongly-coloured faces, the colours are dull or absent during early youth. This likewise holds good with the mandiill and Ehesus, in which the face and the posterior pai'ts of the body are brilliantly coloured in one sex alone'. In these latter cases we have reason to believe that the colours were acquired through sexual selection ; and we are naturally led to extend the same view to the foregoing species, though both sexes when adult have their faces coloured in the same manner. *' I observed this fact in the ' Hist. Nat. des Mammiftres.' torn. Zoological Gardens; and manj- cases i. 1824. maybe seen in the coloured plates in Bates, 'The Naturalist on the Geoffrey St.-Hilaire and F. Cuvier, Amazons,' 1863, vol. ii. p. 310. Chap. XVIII. Beauty of the Qziadrtcmana. 551 Although many kinds of monkeys are far from beautiful accord- ing to our taste, other species are universally admired for their .elegant appearance and bright colours. The Semnopithems nemceus, though peculiarly coloured, is described as extremely 552 The Descent of Man. Paht it. pretty ; the orange-tinted face is surrounded by long whiskers of glossy whiteness, with a line of chesnut-red over the eye- brows ; the fi;r on the back is of a delicate grey, with a square patch on the loins, the tail and the fore-aims being of a pure- white ; a gorget of chesnut surmounts the chest ; the thighs are black, with the legs chesnut-red. I will mention only two other monkeys for their beauty; and I have selected these as pre- senting slight sexual differences in colour, which renders it in some degree probable that both sexes owe their elegant appeai'ance to sexual selection. In the moustache-monkey ( Oercopitliecus cepkus) the general colour of the fur is mottled- greenish with the thi'oat white ; in the male the end of the tail is chesnut, but the face is the most ornamented part, the skin being chiefly bluish-gxey, shading into a blackish tint beneath the eyes, with the upper lip of a delicate blue, clothed on the lower edge with a thin black moustache; the whiskers are orange-coloured, with the upper part black, forming a band which extends backwards to the ears, the latter being clothed with whitish hairs. In the Zoological Society's Gardens I have often overheard visitors admiring the beauty of another monkey,^ deservedly called Cercopithecus diana (fig. 78) ; the general colour of the fur is grey ; the chest and inner surface of the forelegs are white; a large triangular defined space on the hinder part of the back is rich chesnut ; in the male the inner sides of the thighs and the abdomen are dehcate fawn-coloured, and the top of the head is black ; the face and ears are intensely black, contrasting finely with a white transverse crest over the eye-brows and a long white peaked beard, of which the basal portion is black.'''' In these and many other monkeys, the beauty and singular arrangement of their colours, and still more the diversified and elegant arrangement of the crests and tufts of hair on their heads, force the conviction on my mind that these characters liave been acquired through sexual selection exclusively as ornaments. Summary.— The law of battle for the possession of the female appears to prevail thjfoughout the whole great class of mammals j\lost naturalists will admit that the greater size, strength, courage, and pugnacity of the male, his special weapons ot offence, as well as his special means of defence, have been *^ I have seen most of the above Mr. W. C. M-irtin's 'Nat. Hist., of monkeys in the Zoological Society's Mammalid,' 1841, p. 460; »oe Gardens. The description of the pp. 47£ 523. SiimnojtAtliecus nemxus is taken from Dhap. XVIII. Mammals — Stcmmary. 555 acquired or modified through that form of selection which E have called sexual. This does not depend on any superiority in the general struggle for life, but on certain individuals of one sex, generally the male, being successful in conquering other males, and leaving a larger number of olfspring to inherit their superiority than do the less successful males. ^'f?- Cercopithecus diana (from Brehm). There is another and more peaceful kind of contest, in -which the males endeavour to excite or allure the females by various charms. This is in-obably carried on in some cases by the power- ful odours emitted by the males during the breeding-season; the- odoriferous glands having been acquired through sexual selection. Whether the same view can be extended to the voic©' :S54 The Descent of Man. Part II. is doubtful, for the vocal organs of the males must have been strengthened by use duiing maturity, under the jjowerful excite- ments of love, jealousy or rage, and will consequently have been transmitted to the same sex. Various crests, tufts, and mantles •of hair, which are either confined to the male, or are more developed in this sex than in the female, seem in most cases to be merely ornamental, though they sometimes serve as a defence against rival males. There is even reason to suspect that the branching horns of stags, and the elegant horns of certain ante- lopes, though properly serving as weapons of offence or defence, have been partly modified for ornament. When the male differs in colour from the female, he generally exhibits darker and more strongly-contrasted tints. "We do not in this class meet with the splendid red, blue, yellow, and green iints, so common with male birds and many other animals. The naked parts, however, of certain Quadrumana must be excepted ; for such parts, often oddly situated, are brilliantly coloui-ed in some species. The colours of the male in other cases may be due to simple variation, without the aid of selection. But when ihe colours are diversified and strongly pronounced, when they are not developed until near matui-ity, and when they are lost after emasculation, we can hardly avoid the conclusion that they have been acquired through sexual selection for the sake of ornament, and have been transmitted exclusively, or almost ■exclusively, to the same sex. When both sexes are coloured in ihe same manner, and the colours are conspicuous or curiously arranged, without being of the least apparent use as a protection, and especially when they are associated with various other orna- mental appendages, we ai-e led by analogy to the same conclusion, namely, that they have been acquired through sexual selection, although transmitted to both sexes. That conspicuous and ■diversified colours, whether confined to the males or common to both sexes, are as a general rule associated in the same groups and sub-groups with other secondary sexual characters serving for war or for ornament, will be found to hold good, if we look iDack to the various cases given in this and the last chapter. The law of the equal transmission of character? to both sexes, as far as colour and other ornaments are concerned, has prevailed far more extensively with mammals than with birds; but weapons, such as horns and tusks, have often been transmitted either exclusively or much more perfectly to the males than to the females. This is surprising, for, as the males generally use their weapons for defence against enemies of all kinds, their weapons would have been of service to the females. As far as we can sec, iheir absence in this sex can be accounted for only by tho Chap. XVIII. Mammals — Summary. 555 form of inheritance which has prevailed Finally, with quad- rupeds the contest between the individuals of the same sex, whether peaceful or bloody, has, with the rarest exceptions, been confined to the males ; so that the latter have been modified through sexual selection, far more commonly than the females, either for fighting with each other or for alluring the opposite sex. ( 556 ) Part III. SEXUAL SELECTION IN EELATION TO MAN, AND CONCLUSION. CHAPTER XIX. Secondaut Sexual Chakactebs of Man. Differences between man and woman — Causes of such differences and of certain characters common to both sexes — Law of battle — Differences in mental powers, and voice — On the influence of beauty in determining the marriages of mankind — Attention paid by savages to ornaments — ■ Their ideas of beauty in woman — The tendency to exaggerate each natural peculiarity. With mankind the differences between the sexes are greater than in most of the Quadi'umana, but not so great as in some., for instance, the mandrill. Man on an average is considerably taller, heavier, and stronger than woman, with squarer shoulders and more plainly-jjronounced muscles. Owing to the relation which exists between muscular development and the projection of the brows,' the superciliary ridge is generally more marked in man than in woman. His body, and especially his face, is more hairy, and his voice has a different and more powerful tone. In certain races the women are said to differ slightly in tint from the men. For instance, Schweinfurth, in speaking of a negress belonging to the Monbuttoos, who inhabit the interior of Africa a few degrees north of the Equator, says, " Like all her race, she had " a skin several shades lighter than her husband's, being some- " thing of the colour of half-roast«d coffee." * As the women labour in the fields and ar© quite unclothed, it is not hkely that they differ in colour from the men owing to less exposure to the weather. European women are perhaps the brighter coloured of the two sexes, as may be seen when both have been equally exposed. ' Schaaff hausen, iranslntlon in * ' The Heart of Africa,' English 'Anthropological Review,' Oct. 1868, Transl. 1873, vol. i. p. 544. pp. 419, 420, 427. Chap. XIX. Man — Sexual Differences. 557 Man is more courageous, pugnacious and energetic than woman, and has a more inventive genius. His brain is abso- lutely larger, but whether or not proportionately to his larger body, has not, I believe, been fully ascertained. In woman the face is roimder ; the jaws and the base of the skull smaller ; the outlines of the body rounder, in parts more prominent ; and her pelvis is broader than in man;* but this latter character may perhaps be considered rather as a primary than a secondary sexual character. She comes to matui'ity at an earlier age than man. As with animals of all classes, so with man, the distinctive characters of the male sex are not fully developed until he is nearly matm-e; and if emasculated they never appear. The beard, for instance, is a secondary sexual character, and male «hildi-en are beardless, though at an early age they have abun- dant hair on the head. It is probably due to the rather late appearance in life of the successive variations whereby man has iicquired his masculine characters, that they are transmitted to the male sex alone. Male and female children resemble each other closely, like the young of so many other animals in which the adult sexes differ widely ; they likewise resemble the mature female much more closely than the mature male. The female, however, ultimately assumes certain distinctive cha- racters, and in the formation of her skull, is said to be inter- mediate between the child and the man. * Again, as the young of closely alHed though distinct species do not differ nearly so much from each other as do the adults, so it is with the children of the different races of man. Some have even maintained that race- differences cannot be detected in the infantile skuli.^ In regard to colour, the new-born negro child is reddish nut-brown, which soon becomes slaty-grey ; the black colour being fully developed within a year in the Soudan, but not until three years in Egypt. The eyes of the negro are at first blue, and the hair chesnut- brown rather than black, being curled only at the ends. The children of the Australians immediately after birth are yellowish- brown, and become dark at a later age. Those of the Guaranys of Paraguay are whitish-yellow, but they acquire in the course of a few weeks the yellowish-brown tint of their parents. Similar observations have been made in other parts of America." » Ecker, translation in ' Anthro- 355 ; Vogt, ' Lectures on Man,' Eng. pological Review,' Oct. 1868, pp. 351- translat. p. 81. 356. The comparison of the form ' Schaaffhausen, ' Anthropolog. of the skull in men and women has Review,' ibid. p. 429. been followed out with much care « Pruner-Bey, on negro infants by Wclcker, .as quoted by Vogt, ' Lectures on * Ecker and Welcker, ibid. p. 352, Man,' Eng. translat. 1864, p. 189: 558 The Descent of Man. Part m. I have specified the foregoing differences between the male and female sex in mankind, because they are curiously like those of the Quadrumana. With these animals the female is mature at an earlier age than the male ; at least this is certainly the case in the Cehus azaroe? The males of most species are larger and stronger than the females, of which fact the gorilla affords a weU- known instance. Even in so trifling a character as the greater l^rominence of the superciliary ridge, the males of certain monkeys differ from the females,* and agi-ee in this respect with mankind. In the gorilla and certain other monkeys, the craniimi of the adult male presents a strongly-marked sagittal crest, which is absent in the female ; and Ecker found a trace of a similar difference between the two sexes in the Australians.' With monkeys when there is any difference in the voice, that of the male is the more powerful. We have seen that certain male monkeys have a well-developed beard, which is quite deficient, or much less developed in the female. No instance is known of the beard, whiskers, or moustache being larger in the female than in the male monkey. Even in the colour of the beard there is a curious parallelism between man and the Quadrumana, for with man when the beard differs in colour from the hair of the head, as is commonly the case, it is, I behe\e, almost always of a lighter tint, being often reddish. I have repeatedly observed this fact in England ; but two gentlemen have lately written to me, saying that they form an exception to the rule. One of these gentlemen accounts for the fact by the wide difference in colour of the hair on the paternal and maternal sides of his family. Both had been long aware of this peculiarity (one of them having often been accused of dyeing his beard), and had been thus led to observe other men, and were convinced that the exceptions were very rare. Dr. Hooker attended to this little point for me in Eussia, and found no exception to the rule. In Calcutta, Mr. J. Scott, of the Botanic Gardens, was so kind as to observe the many races of men to be seen there, as well as in some other parts of India, namely, two races in Sikhim, the Bhoteas, Hindoos, Burmese, and for further facts on negro infants, as quoted fi'om Winterbottom and Camper, see Lawrence, ' Lectures on Physiology,' &c. 1822, p. 451. For the infants of the Guaranys, see Eengger, ' Siiugethiere,' &c. s. 3. See also Godron, ' De I'Espfece,' torn, ii. 1859, p. 253. For the Austra- lians, Waitz, ' Introduct. to Anthro- pology,' Eng. translat. 1863, p. 99. 7 Eengger, ' Saugethiere,' &c. 1830, s. 49. * As in Macacus cynomolgus (Des- marest, ' Mammalogie,' p. 65), and in Hylohates agilis (Geofi'roy St.- Hilaire and F. Curier, ' Hist. Nat. des Mamm.' 1824, torn. i. p. 2). ° ' Anthropological Review,' Oct. 1868, p. 353. Chap. X1X_ Man — Sexual Differences. Chinese, most of which races have very little Tia'ir on the face and he always found that when there was any difference in coloui- between the hair of the head and the beard, the latter was inyariably lighter. Now with monkeys, as has ah-eady been stated, th(j beard frequently differs strikingly in colour from the hair of the head, and in such cases it is always of a lighter hue, being often pui-e white, sometimes yellow or reddish.^*^ In regard to the general hairiness of the body^ the women in all races are less hairy than the men; and in some fow Quadrumana the under side of the body of the female is less- hairy than that of the male." Lastly, male monkeys, like men, are bolder and fiercer than the females. They lead the troop, and when there is danger, come to the front. We thus see how close is the parallelism between the sexual differences of man and the Quadrumana. With some few species, however, as with certain baboons, the orang and the gorilla, there is a con- siderably greater difference between the sexes, as in the size of the canine teeth, in the development and colour of the hair, and especially in the colour of the naked parts of the skin, than in mankind. All the secondary sexual characters of man are highly variable, even within the limits of the same race ; and they differ much in the several races. These two rules hold good generally through- out the animal kingdom. In the excellent observations made on board the Novara, the male Australians were foimd to exceed the females by only 65 millim. in height, whilst with the Javans the average excess was 218 millim. ; so that in this latter race the difference in height between the sexes is more than thrice as great as with the Austrahans. Numerous measurements were carefully made of the stature, the circumference of the neck and chest, the length of the back-bone and of the arms, in various Mr. Blyth informs me that he has only seen one instance of the beard, whiskers, &c., in a monkey becoming white with old age, as is so commonly the case with us. This, however, occurred in an aged Macacus cynomolgus, kept in confinement, whose moustaches were " remarkably long and hu- " man-like." Altogether this old monkey presented a ludicrous re- semblance to one of the reigning itionarchs of Europe, after whom he w.is universally nick-named. In certain races of man the hair on the head hardly ever b;comes grey ; thus Mr. D. Forbes has never, as he informs me, seen an instance with the Aymaras and Quichuas of S. America. " This is the case with the fe- males of several species of Hylobates,. see GeofFroy St.-IIiliare and F. Cu- vier, 'Hist. Nat. des Mamm.'tom. i. See, also, on H. lar. 'Penny Cy- clopedia,' vol. ii. pp. 149, 150. ^2 The results were deduced by Dr. Weisbach from the measure- ments made by Drs. K. Scherzer and Schwarz, see ' Reise der Novara : Anthropolog. Theil,' 1867, bs. 216 231, 234, 236, 339, 269. £6o The Descent of Man. Part IlL races ; and nearly all these measui-emeuts shew that the malee differ much more from one another than do the females. This fact indicates that, as far as these characters are concerned, it is the male which has been chiefly modified, since the several races diverged from their common stock. The development of the beard and the hairiness of the body differ remarkably in the men of distinct races, and even in different tribes or families of the same race. We Europeans see this amongst ourselves. In the Island of St. Kilda, according to Martin," the men do not acquire beards until the age of thirty or upwards, and even then the beards are very thin. On the Europseo-Asiatic continent, beards prevail until vre pass beyond India ; though with the natives of Ceylon they are often absent, as was noticed in ancient times by Diodorus." East- ward of India beards disappear, as with the Siamese, Malays, Kalmucks, Chinese, and Japanese ; nevertheless the Ainos," who inhabit the northernmost islands of the Japan Archipelago, are the hairiest men in the world. With negroes the beard is scanty or wanting, and they rarely have whiskers ; in both sexes the body is frequently almost destitute of fine down.'" On the other hand, the Papuans of the Malay Archipelago, who are nearly as black as negroes, possess well-developed beards." In the Pacific Ocean the inhabitants of the Fiji Archipelago have lai'ge bushy beards, whilst those of the not distant archi- pelagoes of Tonga and Samoa are beardless; but these men belong to distinct races. In the Ellice group all the inhabitants belong to the same race; yet on one island alone, namely Nunemaya, "the men have splendid beards;" whilst on the other islands " they have, as a rule, a dozen straggling hairs for "a beard." 18 Throughout the great American continent the men may be .said to be beardless ; but in almost all the tribes a few short hairs are apt to appear on the face, especially in old age. With the tribes of North America, Catlin estimates that eighteen out of twenty men are completely destitute by nature of a beard ; ■3 'Voyage to St. Kilda' (3i-d remarkable that in the United States edit. 1753), p. 37. (' Investigations in Military and '* Sir J. E. Tennent, ' Ceylon,' Anthropological Statistics of Ame- Tol. ii. 1859, p. 107. rican Soldiers,' 1869, p. 569) the Quatrefagcs, ' Revue des Cours pure negroes and their crossed oH' Scientitiques,' Aug. 29, 1868, p. spring seem to have bodies almos 630; Vogt 'Lectures on Man,' as hairy as Europeans. Eng. translat. p. 127. " Wallace, ' The Malay Arch. '8 On the beards of negroes, Vogt, vol. ii. 1869, p. 178. ' Lectures,' &c. p. 127 ; Waitz, ' In- '» Dr J. Barnai-d Davis On Oce* troduct. to Anthropology,' Engl, anic Raoes, in 'Anthropolog. Review, translat. l&o3, vol. i. p. 96. It is April, 1870, pp. 185, 191. Dhap. XIX. Man — Law of Battle. 561 but occasioually there may be seen a man, -who lias neglectai to pluck out the haii's at puberty, with a soft beard an inch or two in length. The Guaranys of Paraguay differ from all the surrounding tribes in having a small beard, and even some hair on the body, but no whiskers.^^ I am informed by Mr. D. Forbes, who particularly attended to this point, that the Aymaras and Quichuas of the Cordillera are remarkably hauiess, yet in old age a few straggUng hairs occasionally appear on the chin. The men of these two tribes have very little hair on the various parts of the body where hair grows abundantly in Europeans, and the women have none on the corresponding parts. The hair on the head, however, attains an extraordinary length in both sexes, often reaching almost to the ground; and this is likewise the case with some of the N. American tribes. In the amount of hair, and in the general shape of the body, the sexes of the American aborigines do not differ so much from each other, as in most other races.^" This fact is analogous with what occurs with some closely allied monkeys; thus the sexes of the chimpanzee are not as different as those of the orang or gorilla.*' In the previous chapters we have seen that with mammals, birds, fishes, insects, &c., many characters, which there is every reason to believe were primarily gained through sexual selection by one sex, have been transferred to the other. As this same form of transmission has apparently prevailed much with mankind, it will save useless repetition if we discuss the origin of cha- racters peculiar to the male sex together with certain other characters common to both sexes. Law of Battle. — With savages, for instance the Australians, the women are the constant cause of war both between members of the same tribe and between distinct tribes. So no doubt it was in ancient times ; " nam fuit ante Helenam mulier teterrima belli " causa." With some of the North American Indians, the con- test is reduced to a system. That excellent observer, Hearne,=^ " Catlin, 'North American In- dians,' 3rd edit. 1842, vol. ii. p. 227. On the Guaranys, see Azara, ' Voy- ages dans TAme'rique M^rid.' torn, li. 1809, p. 58 ; also Renggcr, ' Saugethiere von Paraguay,' s. 3. Prof, and Mrs. Agassiz (' Jour- ney in Brazil,' p. 530) remark that the sexes of the American Indians differ less than those of the negroes and of the higher races. See also K«ngger, ibid. p. 3, on the Guaranys. Riitimeyer, 'Die Grenzen der Thierwelt ; eine Betrachtung za Darwin's Lehre,' 1868, s. 54. 'A Journey from Prince cf Wales Fort.' 8vo. edit. Dublin, 1796. p. 104. Sir J. Lubbock (' Origin of Civilisation,' 1870, p. 69) gives other and similar cases in North America. For the Guanas of S. America see Azara, ' Voyages," &c, torn, ii. p. 94. 2 o 562 The Descent of Man. Paet 111. Bays : — " It has ever been the custom among these people for " the men to wrestle for any woman to whom they are at- " tached ; and, of coui-so, the strongest party always carries oft " the prize. A weak man, unless he be a good hunter, and well- " beloved, is seldom permitted to keep a wife that a stronger " man thinks worth his notice. This custom prevails thi-ough- " out -all the tribes, and causes a great spirit of emulation among " their youth, who ai-e upon all occasions, from their childhood, " trying their strength and skill in wrestUng." With the Guanas of South America, Azara states that the men rarely marry till twenty years old or more, as before that age they cannot conquer their rivals. Other similar facts could be given ; but even if we had no evidence on this head, we might feel almost sui-e, from the analogy of the higher Quadrumana,^^ thf^t the law of battle had prevailed with man during the early stages of his development. The occasional appearance at the present day of canine teeth which project above the others, with traces of a diastema or open space for the reception of the opposite canines, is in all probability a case of reversion to a former state, when the progenitors of man were provided with these weapons, like so many existing male Quadrumana. It was remarked in a former chapter that as man gradually became erect, and continually used his hands and arms for fighting with sticks and stones, as well as for the other purposes of life, he would have used his jaws and teeth less and less. The jaws, together with then- muscles, would then have been reduced through disuse, as would the teeth thi-ough the not well understood principles of correlation and economy of growth ; for we everywhere see that parts, which are no longer of service, are reduced in size. By such steps the original inequality between the jaws and teeth in the two sexes of mankind would ultimately have been oblite- rated. The case is almost parallel with that of many male Euminants, in which the canine teeth have been reduced to mere rudiments, or have disappeared, apparently in consequence of the development of horns. As the prodigious difference between the skulls of the two sexes in the orang and gorilla stands in close relation with the development of the immense canine teeth in the males, we may infer that the reduction of the jaws and teeth in the early male progenitors of man must have led to a most striking and favourable change in his appearance. -3 On the fighting of the male p. 423. On Presbytis cntelhs, see gorillas, see Dr. Savage, in ' Boston the ' Indian Field,' 1859, p. 146 Journal of Nat. Hist.-' vol. v. 1847 ■Chap. XIX. Mental powers of Man and Woman.. 563 There can be little doubt that the greater size and strength of oiian, in comparison with woman, together with his broader shoulders, more developed muscles, rugged outline of body, his greater coiu'age and pugnacity, are all due in chief part to in- heritance from his half-human male ancestors. These characters would, however, have been preserved or even augmented during the long ages of man's savagery, by the success of the strongest iind boldest men, both in the general struggle for life and in their contests for wives ; a success which would have ensured •their leaving a more numerous progeny than their less favoured brethren. It is not probable that the greater strength of man was primarily acquired through the inherited effects of his having worked harder than woman for his own subsistence and that of his family ; for the women in all barbarous nations are compelled to work at least as hard as the men. With civilised people the arbitrament of battle for the possession of the women has long ceased ; on the other hand, the men, as a ^general rule, have to work harder than the women for their joint subsistence, and thus their greater strength will have been iept up. IDiffermce in the Mental Foiuers of the tiuo Sexes. — With respect to differences of this nature between man and woman, it is probable that sexual selection has played a highly important part. I am aware that some writers doubt whether there is any such inherent difference ; but this is at least probable from the analogy of the lower animals which present other secondary sexual characters. No one disputes that the bull differs in 'disposition from the cow, the wild-boar from the sow, the stallion from the mare, and, as is well known to the keepers of menageries, the males of the larger apes from the females. Woman seems to difi'er from man in mental disposition, chiefly an her greater tenderness and less selfishness ; and this holds good even with savages, as shewn by a well-known passage in .Mungo Park's Travels, and by statements made by many other ■travellers. Woman, owing to her maternal instincts, displays these qualities towards her infants in an eminent degree ; there- fore it is likely that she would often extend them towards her fellow-creatures. Man is the rival of other men ; he delights in competition, and this leads to ambition which passes too easily into selfishness. These latter qualities seem to be his natural and unfortunate birthright. It is generally admitted uhat with woman the powers of intuition, of rapid perception, and perhaps of imitation, are more strongly marked than in umn; but some, at least, of these faculties are charactoristio 2 0 2 564 The Descent of Man. Paet in. of the lower races, and therefore of a past and lower state of eivilisation. The chief distinction in the intellectual powers of the two sexes is shewn by man's attaining to a higher eminence, in whatever he takes up, than can woman — whether requiring deep thought, reason, or imagination, or merely the use of the senses and hands. If two lists were made of the most eminent men and women in poetry, painting, sculpture, music (inclusive both of composition and performance), history, science, and philosophy, with half-a-dozen names under each subject, the two lists would not bear comparison. We may also infer, from the law of the deviation from averages, so well illustrated by Mr. Galton, in his work on ' Hereditary Genius,' that if men are capable of a decided pre-eminence over women in many subjects, the average of mental power in man must be above that of woman. Amongst the half-human progenitors of man, and amongst savages, there have been struggles between the males during many generations for the possession of the females. But mere bodily strength and size would do little for victory, unless associated with coui-age, perseverance, and determined energy. With social animals, the young males have to pass through many a contest before they win a female, and the older males have to retain their females by renewed battles. They have, also, in the case of mankind, to defend their females, as well as their young, from enemies of all kinds, and to hunt for theii- joint subsistence. But to avoid enemies or to attack them with success, to capture wild animals, and to fashion weapons, requires the aid of the higher mental faculties, namely, observation, reason, invention, or imagination. These various faculties will thus have been continually put to the test and selected during manhood ; they will, moreover, have been strengthened by use during this same period of life. Consequently, in accordance with the principle often alluded to, we might expect that they would at least tend to be transmitted chiefly to the male offspring at the corresponding period of manhood. Now, when two men are put into competition, or a man with a woman, both possessed of every mental quality in equal per- fection, save that one has higher energy, perseverance, an-, courage, the latter will generally become more eminent in every pursuit, and will gain the ascendancy.^^ He may be said to possess genius — for genius has been declai-ed by a great J. Stuart Mill remarks ('The "require most plodding, and long Subjection of Women,' 1869, p. 122), " hammering at single thoughts." *' The things in which man most What is this but energy and per- " eicels woman are those which severance ? Chap. XIX. Mental powers of Man and Woman. 565 authority to be patience; and patience, in this sense, means tmflinching, undaunted perseverance. But this view of genius is perhaps deficient ; for without the higher powers of the imagi- nation and reason, no eminent success can be gained in many subjects. These latter faculties, as well as the former, will have been developed in man, partly through sexual selection, — that IS, through the contest of rival males, and partly through natural •selection, — that is, from success in the general struggle for life ; and as in both cases the struggle will have been during maturity, the characters gained will have been transmitted more fully to the male than to the female offspring. It accords in a striking manner with this view of the modification and re-inforcement of many of our mental faculties by sexual selection, that, firstly, they notoriously undergo a considerable change at puberty,-^ and, secondly, that eunuchs remain throughout Ufe iaferior in these same quahties. Thus man has ultimately become superior to woman. It is, indeed, fortunate that the law of the equal transmission of characters to both sexes prevails with mammals ; otherwise it is probable that man would have become as superior in mental endowment to woman, as the peacock is in ornamental •plumage to the peahen. It must be borne in mind that the tendency in characters acquired by either sex late in life, to be transmitted to the same sex at the same age, and of early acquired characters to be transmitted to both sexes, are rules which, though general, do not always hold. If they always held good, we might conclude (but I here exceed my proper bounds) that the inherited effects of the early education of boys and girls would be transmitted equally to both sexes ; so that the present inequahty in mental power between the sexes would not be effaced by a similar course of early training ; nor can it have been caused by their dissimilar early training. In order that woman should reach the same standard as man, she ought, when nearly adult, to be trained to energy and perseverance, and to have her reason and imagination exercised to the highest point; and then she would probably transmit these qualities chiefly to her adult daughters. All women, however, could not be thus raised, unless dui-mg many genera- tions those who excelled in the above robust virtues were married, and produced offspring in larger numbers than other women. As before remarked of bodily strength, although men do not now fight for their wives, and this foiTQ of selection has passed away, yet during manhood, they generally undergo a severe struggle in order to maintain themselves and their families; and this will tend to keep up or even increase their MaudsJey, 'Mind and Body,' p. 31. 566 The Descent of Man. Paut I£L mental powers, and, as a consequence, the present inequality between the sexes.-^ Voice and Musical Powers. — In some species of Quadramana there is a great difference between the adult sexes, in tlie power of their voices and in the development of the vocal organs ; and man appears to have inherited this difference from his early progenitors. His vocal cords are about one-third longer than in woman, or than in boys ; and emasculation produces the same effect on him as on the lower animals, for it " arrests that pro- " minent growth of the thyroid, &c., which accompanies the " elongation of the cords." ^ With respect to the cause of this difference between the sexes, I have nothing to add to tho remarks in the last chapter on the probable effects of the long- continued use of the vocal organs by the male under the ex- citement of love, rage and jealousy. According to Sir Duncan Gibb,^' the voice and the form of the larynx differ in the different races of mankind ; but with the Tartars, Chinese, &c., the voice of the male is said not to differ so much from that of the female, as in most other races. The capacity and love for singing or music, though not a sexual character in man, must not here be passed over. Although the sounds emitted by animals of all kinds serve many purposes, a strong case can be made out, that the vocal organs were jjrimarily used and perfected in relation to the propagation of the species. Insects and some few spiders are the lowest animals which voluntarily produce any sound; and this is generally effected by the aid of beautifully constructed stridulating organs, which are often confined to the males. The sounds thus pro- duced consist, I believe in all cases, of the same note, repeated rhythmically ; ^ and this is sometimes pleasing even to the ears of man. The chief and, in some cases, exclusive purpose appears to be either to call or charm the opposite sex. The sounds produced by fishes are said in some cases to be made only by the males during the breeding-season. All the An observation by Vogt bears " skulls." But Vogt admits (' Lec- oa this subject : lie says, " It is a tures on Man,' Eng. translat. 18G4, " l emarkable circ-jnistance, that the p. 81) that more observations are " diflerence betwaen the sexes, as requisite on this point, "regards the cranial cavity, in- Owen, 'Anatomy of Verte- " creases with the development of bratcs,' vol. iii. p. 603. "the race, so that the male Euro- 'Journal of the Anthropolog. " pean excels much more the female, Soc' April, 1869, p. Ivii. and l.wi. " than the negro the negress. Dr. Scuddcr, ' Notes on Stri- " Welcker confirms this statement Julation,' in ' Proc. Boston Soc. of '' of Huschke from his measure- Nat. Hist.' vol. xi. April, 1868. " ments of regro and German Chap. XIX, Man— Musical Powers, 56/ air-breatMng Vertebrata necessarily possess an apparatus for inhaling and expelling air, with a pipe capable of being closed at one end. Hence when the primeval members of this class were strongly excited and their muscles violently contracted, purposeless sounds would almost certainly have been produced ; and these, if they proved in any way serviceable, might readily have been modified or intensified by the preservation of properly adapted variations. The lowest Vertebrates which breathe air are Amphibians; and of these, frogs and toads possess vocal organs, which are incessantly used during the breeding-season, and which are often more highly developed in the male than iu the female. The male alone of the tortoise utters a noise, and this only dui-ing the season of love. Male alligators roar or bellow during the same season. Every one knows how much birds use their vocal organs as a means of courtship ; and some species likewise perform what may be called instrumental music. In the class of Mammals, with which we are here more par- ticularly concerned, the males of almost all the species use their voices during the breeding-season much more than at any other time; and some are absolutely mute excepting at this season. "With other species both sexes, or only the females, use their voices as a love-call. Considering these facts, and that the vocal organs of some quadrupeds are much more largely developed in the male than in the female, either permanently or temporarily during the breeding-season ; and considering that in most of the lower classes the sounds produced by the males, serve not only to call but to excite or allure the female, it is a sui'prising fact that we have not as yet any good evidence that these organs are used by male mammals to charm the females. The American Mycetes caraya perhaps forms an exception, as does the Bylohates u(jilis, an ape allied to man. This gibbon has an extremely loud but musical voice. Mr. Waterhouse states,^ " It appeared to " me that in ascending and descending the scale, the intervals " were always exactly half-tones ; and I am sure that the highest " note was the exact octave to the lowest. The quality of the " notes is very musical ; and I do not doubt that a good violinist " would be able to give a correct idea of the gibbon's compo- " sition, excepting as regards its loudness." Mr, Waterhouse then gives the notes. Professor Owen, who is a musician, con- firms the foregoing statement, and remarks, though erroneously, that this gibbon "alone of brute mammals may be said to " sing." It appears to be much excited after its performance. *> Given in W. C. L. Martin's Owen, ' Anatomy of Vertebrates, ' General Introduct. to Nat. Hist, of vol. iii. p. *?00. Maram. Animal.o,' 1841, p. 432 ; 568 The Descent of Man. Part III. Unfortunately, its habits have never been closely observed in a state of nature ; but from the analogy of other animals, it is probable that it uses its musical powers more especially during the season of courtship. This gibbon is not the only species in the genus which sings, for my son, Francis Darwin, attentively listened in the Zoo- logical Gardens to H. leuciscus whilst singing a cadence of three notes, in true musical intervals and with a clear musical tone. It is a more surprising fact that certain rodents utter musical sounds. Singing mice have often been mentioned and exhibited, but imposture has commonly been suspected. We have, how- ever, at last a clear account by a well-known observer, the Eev. S. Lockwood,^^ of the musical powers of an American species, the Hesperomys cognatus, belonging to a genus distinct from that of the English mouse. This little animal was kept in confine- ment, and the performance was repeatedly heard. In one of the two chief songs, " the last bar would frequently be prolonged to " two or three ; and she would sometimes change from C sharp " and D, to 0 natural and D, then warble on these two notes " awhile, and wind up with a quick chirp on C sharp and D. " The distinctness between the semitones was very marked, and " easily appreciable to a good ear." Mr. Lockwood gives both songs in musical notation; and adds that though this little mouse " had no ear for time, yet she would keep to the key of B " (two flats) and strictly in a major key." ..." Her soft clear " voice falls an octave with all the precision possible ; then at the ' wind up, it rises again into a very quick trill on C sharp " and D." A critic has asked how the ears of man, and he ought to have added of other animals, could have been adapted by selection so as to distinguish musical notes. But this question shews some confusion on the subject ; a noise is the sensation resulting from the co-existence of several aerial "simple vibrations" of various periods, each of which intermits so frequently that its separate existence cannot be perceived. It is only in the want of con- tinuity of such vibrations, and in their want of harmony inter se, that a noise differs from a musical note. Thus an ear to be capable of discriminating noises— and the high importance ot this power to all animals is admitted by every one— must be sen- sitive to musical notes. We have evidence of this capacity even low down in the animal scale: thus Crustaceans are provided with auditory hairs of different lengths, which have been seen to vibrate when the proper musical notes are struck.''^ As stated " The 'American Naturalist,' " Helmholtz, 'Thiwrie Fhys. de 1871, p. 761. la Musique,' 1868, p. 187. Ohap. XIX. Man — Musical Powers. 569 in a previous chapter, similiar observations have been mado on the hairs of the antennae of gnats. It has been positively- asserted by good observers that spiders are attracted by music. It is also well known that some dogs howl when hearing par- ticular tones.^^ Seals apparently appreciate music, and their fondness for it " was well known to the ancients, and is often " taken advantage of by the hunters at the present day." Therefore, as far as the mere perception of musical notes is concerned, there seems no special difficulty in the case of man or of any other animal. Hehnholtz has explained on physio- logical principles why concords are agreeable, and discords dis- agreeable to the human ear ; but we are httie concerned with these, as music in harmony is a late invention. We are more con- cerned with melody, and here again, according to Hehnholtz, it is intelhgible why the notes of our musical scale are used. The ear analyses aU sounds into their component " simple vibrations," although we are not conscious of this analysis. In a musical note the lowest in pitch of these is generally predominant, and the others which are less marked are the octave, the twelfth, the second octave, &c., aU harmonies of the fundamental pre- dominant note ; any two notes of our scale have many of these harmonic over-tones in common. It seems pretty clear then, that if an animal always wished to sing precisely the same song, he would guide himself by sounding those notes in succession, which possess many over-tones in common — that is, he would choose for his song, notes which belong to our musical scale. But if it be further asked why musical tones in a certain order and rhythm give man and other animals pleasure, we can no more give the reason than for the pleasantness of certain tastes and smells That they do give pleasure of some kind to animals, we may infer from their being produced during the season of coui'tship by many insects, spiders, fishes, amphibians, and birds ; for unless the females were able to appreciate such sounds and were excited or charmed by them, the persevering efforts of the males, and the complex structures often possessed by them alone, would be useless ; and this it is impossible to believe. Human song is generally admitted to be the basis or origin of instrumental music. As neither the enjoyment nor the capacity of producing musical notes are faculties of the least ^' Several accounts have been another instance of a dog alvvavs published to this effect. Mr. Peach whining, when one note on a coiii- vvrites to me that he has repeatedly ccrtina, which was out of tune, w excited often bursts forth in song ; " another will reply in song, " while the company, as if touched by a musical wave, murmur 3° Since this chapter was printed, I have seen a valuable article by- Mr. Chauncey Wright (' North Amer. Review,' Oct.* 1870, page 293), who, in discussing the above subject, remarks, " There are many ''consequences of the ultimate laws " or uniformities of nature, thi-ough " which the acquisition of one use- ** ftil power will bring with it many " resulting advantages as well as- "limiting disadvantages, actual or " possible, which the principle of " utility may not have comprehended' " in its action." As I have attempted- to shew in an early chapter of this- work, this principle has an impor- tant bearing on the acquisition by man of some of his mental charac- teristics. 5/2 The Descent of Man. Paet IIT, " a chorus in perfect unison."*^ Even monkeys express strong feelings in different tones— anger and impatience by low, — fear and pain by high notes.'* The sensations and ideas thus excited in us by music, or expressed by the cadences of oratory, appear from their vagueness, yet depth, like mental reversions to the emotions and thoughts of a long-past age. All these facts with respect to music and impassioned speech become intelligible to a certain extent, if we may assume that musical tones and rhythm were used by our half-human an- cestors, during the season of courtship, when animals of all kinds are excited not only by love, but by the strong passions of jealousy, rivalry, and triumph. From the deeply-laid principle of inherited associations, musical tones in this case would be hkely to call up vaguely and indefinitely the strong emotions of a long- past age. As we have every reason to suppose that articulate speech is one of the latest, as it certainly is the highest, of the sxrts acquired by man, and as the instinctive power of producing musical notes and rhythms is developed low down in the animal series, it would be altogether opposed t o the principle of evolution, if we were to admit that man's musical capacity has been deve- loped from the tones used in impassioned speech. We must suppose that the rhythms and cadences of oratory are derived from previously developed musical powers.^^ We can thus imderstand how it is that music, dancing, song, and poetry are such very ancient arts. We may go even further than this, and, as remarked in a former chapter, believe that musical sounds afforded one of the bases for the development of language.'*" *' Winwood Eeade, 'The Martyr- dom of Man,' 1872, p. 441, and ' African Sketch Book,' 1873, vol. ii. p. 313. " Rengger, ' Saugethiere von Paraguay,' s. 49. *' See the very interesting dis- cussion on the ' Origin and Function of Music,' by Mr. Herbert Spencer, in his collected 'Essays,' 1858, p. 359. Mr. Spencer comes to an ex- actly opposite conclusion to that at which I have arrived. He con- cludes, as did Diderot formerly, that the cadences used in emotional speech afford the foundation from which music has been developed ; whilst I conclude that musical notes and rhythm were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex. Thus musical tones became firmly associated with some of the strongest Tiassions an animal is capable of feeling, and are consequently used instinctively, or through association, when strong emotions are expressed in speech. Mr. Spencer does not offer any satisfactory explanation, nor can I, why high or deep notes should be expressive, both with man and the lower animals, of certain emotions. Mr. Spencer gives also an in- teresting discussion on the relations between poetry, recitative, and song. I find in Lord Monboddo's 'Origin of Language,' vol.i. (1774), p. 469, that Dr. Blacklock likewise thought "that the first language " among men was music, and that " before ovv ideas were expressed by Oh/j". XIX. Man — Love of Ornament. 573 As the males of several quadrumanous animals have their vocal organs much more developed than ia the females, and as a gibbon, one of the anthropomorphous apes, pours forth a wholo octave of musical notes and may be said to sing, it appears pro- bable that the progenitors of man, either the males or females or both sexes, before acqumng the power of expressing their mutual love in articulate language, endeavoured to charm each other with musical notes and rhythm. So httle is known about the use of the voice by the Quadrumana during the season of love, that we have no means of judging whether the habit of singing was first acquired by our male or female ancestors. "Womeu are generally thought to possess sweeter voices than men, and as far as this serves as any guide, we may infer that they first acquired musical powers in order to attract the other sex.*^ But if so, this must have occmTed long ago, before our ancestors had become sufficiently human to treat and value their women merely as useful slaves. The impassioned orator, bard, or musician, when with his varied tones and cadences he excites the strongest emotions in his hearers, little suspects that he uses the same means by which his half-human ancestors long ago aroused each other's ardent passions, dui'ing their courtship and rivalry. Tlie Influence of Bemdy in determining the Marriages of Man- land. — In civilised life man is largely, but by no means exclu- sively, influenced in the choice of his wife by external appearance ; but we are chiefly concerned with primeval times, and oui' only means of forming a judgment on this subject is to study tho habits of existing semi-civilised and savage nations. If it can be shewn that the men of different races prefer women having various characteristics, or conversely with the women, we have then to enquire whether such choice, continued during many generations, would produce any sensible effect on the race, either on one sex or both according to the form of inheritance which has prevailed. It will be well first to shew in some detail that savages pay the- greatest attention to then- personal appearance.^^ That they have " articulate sounds, they were com- " mumcated by tones, varied accord- " ing to different degrees of gravity "and acuteness." ■»' See an interesting discussion on this subject by Hiickel, ' Gene- relle Morph,' B. ii. 1866, s. 246. A mil and excellent account of tfie manner in which savages in all p«rt8 of the world ornament them- selves, is given by the Italian tra- veller, Prof. Mantegazza, ' Rio de la Plata, Viaggi e Studi,' 1867, pp. 525-545; all the following state- ments, when other references are not given, are taken from this work. See, also, Waitz, ♦ Introduct. to Anthropolog.' Eng. transl. vol. i. 1863, p. 275, et passim. Lawrence also gives very full details in his 574 The Descent of Man. Part Ui. a passion for ornament is notorious ; and an English philosopher goes so far as to maintain, that clothes were first made for . XXI. General Summary. 609 to modifications acquired independently of selection, and due to variations arising from the nature cf the organism and the action of the surrounding conditions, or from changed habits of life, no single pair will have been modified much more than the other pairs inhabiting the same country, for all will have been continually blended through free intercrossing. By considering the embryological structure of man, — the homologies which ho presents with the lower animals, — the rudiments which he retains,— and the reversions to which he is liable, we can partly recall in imagination the former condition of our early progenitors ; and can approximately place them in their proper place in the zoological series. "We thus learn that man is descended from a hairy, tailed quadruped, probably arboreal in its habits, and an inhabitant of the Old World. This creature, if its whole structure had been examined by a naturalist, would have been classed amongst the Quadrumana, as surelv as the still more ancient progenitor of the Old and New World monkeys. The Quadrumana and all the higher mammals are probably derived fi'om an ancient marsupial animal, and this through a long line of diversified forms, from some amphibian-like creature, and this again from some fish-like animal. In the dim obscurity of the past we can see that the early progenitor of all the Yertebrata must have been an aquatic animal, provided with branchiae, with the two sexes united in the same individual, and with the most important organs of the body (such as the brain and heart) imperfectly or not at all developed. This animal seems to have been more like the larvae of the existing marine Ascidians than any other known form. The high standard of our intellectual powers and moral dis- position is the gi-eatest difficulty which presents itself, after we have been driven to this conclusion on the origin of man. But every one who admits the principle of evolution, must see that the mental powers of the higher animals, which are the same in kind with those of man, though so different in degree, are capable of advancement. Thus the interval between the mental powers of one of the higher apes and of a fish, or between those of an ant and scale-insect, is immense ; yet their development does not offer any special difficulty ; for with our domesticated animals, the mental faculties are certainly variable, and the variations are inherited. No one doubts that they are of the utmost importance to animals in a state of nature. Therefore the conditions are favourable for their development through natural selection. The same conclusion may be extended to man ; the intellect must have been all-important to him, even at a very 2 K 6io The Descent of Man. Past HI. remote period, as enabling him to invent and use language, to make weapons, tools, traps, &c., whereby with the aid of his ■iocial habits, he long ago became the most dominant of all living creatures. A great stride in the development of the intellect will have followed, as soon as the half-art and half-instinct of language came into use ; for the continued use of language will have reacted on the brain and produced an inherited eifect ; and this again will have reacted on the improvement of language. As Mi*. Chauncey Wright^ has well remarked, the largeness of the brain in man relatively to his body, compared with the lower animals, may be attributed in chief part to the early use of some simple form of language, — that wonderful engine which affixes signs t, 375 ; swelling of the wattles of th ; male, 383 ; variety of, with a top-knot, 384-; recognition of a dog by a, 412 ; male, wild, acceptable to domesti- cated females, 418 ; wild, first ad- vances'iiade by older females, 419 ; wild, breast-tuft of bristles of the, 461. Turkey-cock, scraping of tho wings of, upon the ground, 375 ; wild, display of plumage by, 394; fight- ing habits of, 404. Turner, Prof. W., on muscular fasci- culi in man referable to the pan- niculus carnosus, 13 ; on the occur- rence of the supra-condy loid foramen in the human humerus, 21 ; on muscles attached to the coccyx in man, 22 ; on the filum terminale in man, 23 ; on the variability of the muscles, 26 ; on abnormal conditions of the human uterus, 39 ; on the development of the mammary glands, 162; on male fishes hatch- ing ova in their mouths, 163, 345; on the external perpendicular fissxire of the brain, 200 ; on the bridging convolutions in the brain of a chim- panzee, 201. Turnix, sexes of some species of, 475 ; 480. Turtle-dove, cooing of the, 374. Tuttle, H., on the aumber of species of man, 174. Tylor, E. B., on emotional cries, ges- tures, &n., of man, 85; on the origin of the belief in spiritual agencies, 94 ; remorse for violation of tribal usage in marrying, 115; on the primitive barbarism ot civilised nations, 143 ; on the origin of counting, 144 ; inventions of savages, 145 ; on resemblances, of the mental characters indifferent races of man, 178. Type of structure, prevalence of, 164. fyphmus, stridulatiug organs of, 301 ; stridulation of, 303. Tyranga cestiva, 462. Twins, tendency to produce, here- ditary, 45. Twite, proportion of the sexes in the, 248. Ugliness, said to consist in an approach to the lower animals, 534 Umbrella-bird, 373, Umbrina, sounds produced by, 347. United States, rate of increase in, 44 ; influence of natural selection on the progress of, 142 ; change under- gone by Europeans in the, 196. Upupa epops, sounds produced by the male, 376. UraniidjE, coloration of the, 314. Uria troile, variety of (= U. lacry- mans), 424. Urodela, 348. Urosticte Benjamini, sexual differences in, 442. Use and disuse of parts, effects of, 32 . influence of, on the races of man, 197. Uterus, reversion in the, 38 ; more or less divided, in the human subject, 38, 43 ; double, in the early pro- genitors of man, 161. V. Vaccination, influence of, 134. Vancouver Island, Mr. Sproat or. the savages of, 183 ; natives of, eradi- cation of facial hair by the, 580. Vanellus cristatus, wing tubercles cf the male, 366. VanesscB, 308 ; resemblance of lower surface of, lo baiic of trees, 311. Variability, causes of, 28 ; in man, analogous to that in the lower animals, 29 ; of the races of man, 174 ; greater in men than in women, 223 ; period of, relation of the, to sexual selection, 240 ; of birds, 422 ; of secondary sexual characters in man, 559. Variation, laws of, 29 ; correlated, 43; in man, 146; analogous, 152; analogous, in plumage of birds, 385. Variations, spontaneous, 44. Varieties, absence of, between two species, evidence of their distinct- ness, 167. Variety, an object in nature, 493. Variola, communicable between man and the lowfr animals, 7. .VAUUEAL. WALLACE. 689 VauT^al, human bones from, 22. Veddahs, monogamous habits of, 591. Veitch, Mr,, on the aversion of Japanese ladies to whiskers, 581. Vengeance, instinct of, 113. Venus Erycina, priestesses of, 587. Vermes, 264. Vermiform appendage, 21. Verreaux, M., on the attraction of numerous males by the female of an Australian Bombyx, 252. Vertebra:, caudal, number of, in macaques and baboons, 58 ; of monkeys, partly imbedded in the body, 59. Vertebrata, 330; common origin of the, 158 ; most ancient progenitors of, 161 ; origin of the voice in air- breathing, 567. Vesicula prostatica, the homologue of the uterus, 24, 161. Vibrissae, represented by long hairs in the eyebrows, 19. Vidua, 403, 462. axillaris, 219. Villerme, M., on the influence of plenty upon stature, 31. Vinson, Aug., courtship of male spider, 273 ; on the male of Epeira nigra, 273. Viper, difference of the sexes in the, 351. Virey, on the number of species of man, 174. Virtues, originally social only, 116 ; gradual appreciation of, 131. Viscera, variability of, in man, 27. Vlacovich, Prof., on the ischio-pubic muscle, 41. Vocal music of birds, 368. organs of man, 87 ; of birds, 90, 450 ; of frogs, 350 ; of the Inses- sores, 370; difference of, in the sexes of birds, 371 ; primarily used in relation to the propagation of the species, 566. Vogt, Karl, on the origin of species, 1 ; on the origin of man, 3 ; on the semilunar fold in man, 17 ; on mi- crocephalous idiots, 35 ; on the imi- tative faculties of microcephalous idiots, 87 ; on skulls from Brazilian caves, 168 ; on the evolution of the races of man, 177 ; on the formation of the skull in women, 557 ; on the Ainos and negroes, 560 ; on the in- creased cranial difference of the sexes in man with race development, 566 ; on the obliquity of the eye iu the Chinese and Japanese, 578. Voice in mammals, 525 ; in monkeys and man, 558 ; in man, 566 ; origin of, in air-breathing vertebrates, 567 Von Baer, definition of advancement in the organic scale, 164. Vulpian, Prof., on the resemblance between the brains of man and of the higher apes, 6. Vultures, selection of a mate by the female, 416 ; colours of, 493. V. Waders, young of, 486. Wagner, R., on the occurrence of tha diastema in a Kaffir skull, 40 ; on the bronchi of the black stork, 374. Wagtail, Ray's, aiTival of the male before the female, 212. Wagtails, Indian, young of, 468. Waist, proportions of, in soldiers and sailors, 32. Waitz, Pi-of., on the number of spe- cies of man, 174; on the liability of negroes to tropical fevers after residence in a cold climate, 194; on the colour of Australian infants, 558 ; on the beardlessness of negroes, 560 ; on the fondness of mankind for ornaments, 573; on negro ideas of female beauty, 579 ; on Javan and Cochin Chinese ideas of beauty, 580. Walckenaer and Giervais, spider at- tracted by music, 273 ; on the Myri- apoda, 274. Waldeyer,M., on the hermaphroditism of the vertebrate embryo, 161. Wales, North, numerical proportion ot male and female births in, 242. Walker, Alex., on the large size of the hands of labourers' children, 33. , F., on sexual differences in the diptera, 280. Wallace, Dr. A., on the prehensile use of the tarsi in male moths, 209 ; on the rearing of the Ailanthus silkmoth, 251 ; on breeding Lepi- doptera, 251 ; proportion of sexes of Bombyx cyntkia, B. yamamai, and 2 y WALLACE. INDEX. WATERII0D8E. B. Pernyi reared by, 253 ; on the development of Bomhyx cynthia and B. yamamai, 278 ; on the pair- ing of Bombyx cynthia, 318. WdlJace, A. R., on the origin of man, 3 ; on the power of imitation in man, 68 ; on the use of missiles by the orang, 82 ; on the varying appreciation of truth among differ- «nt tribes, 122 ; on the limits of natural selection in man, 49, 127 ; on the occurrence of remorse among savages, 131 ; on the effects of natural selection on civilised na- tions, 133 ; on the use of the con- vergence of the hair at the elbow in the orang, 151 ; on the contrast in the characters of the Malays and Papuans, 168 ; on the line of sepa- ration between the Papuans and Malays, 169 ; on the birds of para- dise, 219 ; on the sexes of Omithop- tera Croesus, 250 ; on protective re- semblances, 261 ; on the relative sizes of the sexes of insects, 278 ; on Ela- phomyia, 280 ; on the pugnacity of the males of Leptorhynchus angus- tatus, 299 ; on sounds produced by Uachirus longimanus, 304 ; on the colours of Diadema, 309 ; on Kal- liina, 311 ; on the protective colour- ing of moths, 313 ; on bright colora- ration as protective in butterflies, 314; on variability in the Papi- lionidee, 320 ; on male and female butterflies inhabiting different sta- tions, 321 ; on the protective nature of the dull colouring of female but- terflies, 321, 322, 325 ; on mimicry in butterflies, 324 ; on the bright colours of caterpillars, 325 ; on brightly-coloured fishes frequenting reefs, 343; on the coral snakes, 353 ; on Paradisea apoda, 385 ; on the display of plumage by male birds of paradise, 395 ; on assemblies of birds of paradise, 405 on the in- stability of the ocellated spots in Hipparchia Janira, 428 ; on sexually limited inheritance, 444; on the •exual colwation of birds, 452,472, 473, 475, 480; on the relation be- tween the colours and nidification of birds, 452, 455 ; on the colora- tion of the Cotingidse, 460 ; on the females of Paradisea apoda and papuana, 470 ; on the incubatiun of the ciissowary, 478 ; on protective coloration in birds, 489 ; on the Babirusa, 519 ; on the markings of the tiger, 545 ; on the beards of the Papuans, 560 ; on the hair of the Papuans, 575 ; on the distribution of hair on the human body, 600. Walrus, development of the nicti- tating membrane in the, 17 ; tusks of the, 502, 507 ; use of the tusks by the, 513. Walsh, B. D., on the proportion of the sexes in Papilio Tumvs, 250* on the Cynipidae and Cecidomyidae, 254 ; on the jaws of Ammophila, 275 ; on Corydalis comutus, 275 ; on the prehensile organs of male insects, 275; on the antennae of Penthe, 275 ; on the caudal appen- dages of dragon-flies, 276 ; on Platy- phyllum concavum, 286 ; on the sexes of the Ephemeridae, 289 ; on the difference of colour in the sexes of Spectrum femoratum, 289 ; on sexes of dragon-flies, 290 ; on the differ- ence of the sexes in the Ichneu- monidoB, 292 ; on the sexes of Orso- dacna atra, 294; on the variation of the horns of the male PLancsvs camifex, 297 ; on the coloration of the species of Anthocliaris, 312. Wapiti, battles of, 501 ; traces of horns in the female, 504 ; attacking a man, 511 ; crest of the male, 531 ; sexual difference in the colour of the, 536. Warbler, hedge-, 473 ; young of the, 481. Warblers, superb, nidification of, 454. Wariness, acquired by animals, SO. Wai-ington, R., on the habits of the stickle-backs, 331, 345; on the brilliant colours of the male stickle-back during the breeding season, 340. Wart-hog, tusks and pads of the, 519. Watchmakers, short-sighted, 33. Waterhen, 360. Waterhouse, C. 0., on blind beetles. 294; on difference of colour in the sexes of beetles, 294. , G. R., on the voice of Hylobatet agilis, 567 WATER-OUZEL. INDEX. WESTWOOD. 691 ♦^ater-ouzel, 455; autumn song of the, 370. Waterton, C, on the Bell-bird, 389 ; on the pairing of a Canada goose with a Bernicle gander, 414; on hares fighting, 500. Wattles, disadvantageous to male birds in fighting, 404. Weale, J. Mansel, on a South African caterpillar, 325. Wealth, influence of, 134. Weapons, used by man, 48 ; employed by monkeys, 81 ; offensive, of males, 210; of mammals, 501 et seq. Weaver-bird, 370. Weaver-birds, rattling of the wings of, 375; assemblies of, 405. Webb, Dr., on the wisdom teeth, 20. Wedderburn, Mr., assembly of black game, 407. Wedgwood, Hensleigh, on the origin of language, 87. Weevils, sexual difference in length of snout in some, 208. Weir, Harrison, on the numerical proportion of the sexes in pigs and rabbits, 247 ; on the sexes of young pigeons, 247 ; on the songs of birds, 368 ; on pigeons, 411 ; on the dis- like of blue pigeons to other co- loured varieties, 417 ; on the de- sertion of their mates by female pigeons, 418. ■ , J. Jenner, on the nightingale and blackcap, 212 ; on the relative sexual maturity of male birds, 213 ; on female pigeons deserting a feeble mate, 214; on three starlings fre- quenting the same nest, 219 ; on the proportion of the sexes in Ma- chetes puynax and other birds, 247, 248 ; on the coloration of the Tri- phcenas, 313; on the rejection of certain caterpillars by birds, 326 ; on sexual, differences of the beak in the goldfinch, 360 ; on a piping bullfinch, 369 ; on the object of the nightingale's song, 368; on song- birds, 369 ; on the pugnacity of male fine-plumaged birds, 400 ; on the courtship of birds, 401 ; on the finding of new mates by Peregrine- falcons and Kestrels, 408 ; on the DoUfinch and starling, 408 ; on the cause of birds remaining unpaired, 409 ; on starlings and parrots living in triplets, 409 ; on recognition of colour by birds, 411 ; on hybrid birds, 414; on the selection of a greenfinch by a female canary, 415 ; on a case of rivalry of female bull- finches, 420 ; on the maturity of the golden-pheasant, 483. Weisbach, Dr., measurement of men of different races, 167 ; on tke greater variability of men than of women, 223 ; on the relative pro- portions of the body in the sexes of different races of man, 559. Weismann, Prof., colours of Lyccence, 312. Welcker, M., on brachyceplialy and dolichocephaly, 56 ; on sexual dif- ferences in the skull in man, 557. Wells, Dr., on the immunity of co- loured races from certain poisons, 193. Westring, on the stridulation of males of Theridion, 273 ; on the stridu- lation of Reduvius personatus, 281 ; on the stridulation of beetles, 302 ; on the stridulation of OmalopUa hrunnea, 303 ; on the stridulatiEg organs of the Coieoptera, 304 ; on sounds produced b/ Cychrus, 304. Westropp, H. M., on reason in a bear, 76 ; on the prevalence of certain forms of ornamentation, 179. Westwood, J. O., on the classification of the Hymenoptera, 148 ; on the Culicidse and Tabanidas, 208 ; on a Hymenopterous parasite with a sedentary male, 221 ; on the pro- portions of the sexes in Lucanus cervus and Siagonium, 253 ; on the absence of ocelli in female mii- tillidae, 274 ; on the jaws of Am- mophila, 275; on the copulation of insects of distinct species, 275 ; on the male of Crabro cribrarius, 276; on the pugnacity of male Tipulx^ 280 ; on the stridulatiou of Pirates stridulus, 281 ; on the Cicadce, 281 ; on the stridulating organs of the crickets, 284 ; on Ephippiger vitiutn, 284, 288; on Pneumora, 287 ; the pugnacity of the Mantides, 289 ; on Platyblemnus, 289 ; on diKereaoe in the sexes of the Agrionidae, 290 , 692 WHALE. INDEX. WOODPECKEHS. on the pugnacity of the mules of a species of Tenthredinaj, 291 ; on the pugnacity of tlie male stag- beetle, 299 ; on Bledius taunts and Siagonium, 299 ; on lamellicorn beetles, 301 ; on the coloration of Lithosia, 314. Whale, Sperm-, battles of male, 500. Whales, nakedness of, 56. Whately, Archb., language not pe- culiar to man, 84 ; on the primitive civilisation of man, 143. Whewell, Prof., on maternal affection, 70. Whiskers, in monkeys, 150. White, F. B., noise produced by ZTi/fo' phila, 308. , Gilbert, on the proportion of the sexes in the partridge, 248 ; on the house-cricket, 283 ; on the ob- jsct of the song of birds, 369 ; on the finding of new mates by white owls, 408 ; on spring coveys of male partridges, 409. Whiteness, a sexual ornament in some birds, 494 ; of mammals in- habiting snowy countries, 542. WTiite-throat, aerial love-dance of the male, 380, Whitney, Prof., on the development of language, 86 ; language not in- dispensable for thought, 88. Widow-bird, polygamous, 219 ; breed- ing plumage of the male, 392, 403 ; female, rejecting the un- adorned male, 419. Widows and widowers, mortality of, 140. Wigeon, pairing with a pintail duck, 414. Wilckens, Dr., on the modification of domestic animals in mountainous regions, 35 ; on a numerical re- lation between the hairs and excre- tory pores in sheep, 198. Wilder, Dr. Burt, on the greater fre- quency of supernumerary digits in men than in women, 223. Williams, on the marriage-customs 01 the Fijians, 599. Wilson, Dr., on the conical heads of the natives of North-Western Ame- rica, 583 ; on the Fijians, 583 ; on the persistence of the fashion of compressing the skull, 584. Wing-spurs, 449. Wings, differences of, in the two sexes of butterflies and Hyraenoptera, 277 ; play of, in the courtship of birds, 401. Winter, change of colour of mam- mals in, 542. Witchcraft, 96. Wives, traces of the forcible capture of, 144. Wolf, winter change of the. 542. Wolff, on the variability of the vis- cera in man, 27, Wollaston, T. V., on Eurygnathus, 277 ; on musical Curculionida:, 301 ; on the stridulation of Acallea, 306. Wolves learning to bark from dogs, 73 ; hunting in packs, 101. , black, 540. Wombat, black varieties of the, 539. Women distinguished from men bj- male monkeys, 8 ; preponderance of, in numbers, 244 ; selection of, for beauty, 397 ; effects of selection of, in accordance with different standards of beauty, 584; practice of capturing, 589, 592 ; early be- trothals and slavery of, 593 ; free- dom of selection by, in savage tribes, 598. Wonder, manifestations of, by ani- mals, 71. Wonfor, Mr., on sexual peculiarities in the wings of butterflies, 277. Wood, J., on muscular variations m man, 26, 41, 43 ; on the greater variability of the muscles in men than in women, 223. , T. W., on th« colouring of the orange-tip butterfly, 313 ; on the habits of the Saturniidae, 315; quarrels of chamseleons, 357 ; on the habits of Menura Alberti, 371 ; on Tetrao cupido, 371 ; on the dis- play of plumage by male pheasants, 396 ; on the ocellated spots of the Argus pheasant, 441 ; on the habits of the female cassowary, 478. Woodcock, coloration of the, 491. Woodpecker, selection of a mate by the female, 416. Woodpeckers, 371 ; tapping of, 376; colours and nidification of the, 455, 458, 489 ; characters of young, 465, 474, 481. WOOLNER, INDEX. Woolner, Mr., observations on the ear in man, 15. Wnrinald, Mr., on the coloratioia of Hypopyra, 315. Wounds, healing of, 8. Wren, 473 ; young of the, 481. Wright, C. A., on the young of Oro- cetes and Petrocincla, 487. , Chauncey, great brain-power requisite for language, 48 ; on cor- relative acquisition, 571 ; on the enlargement of the brain in man, 610, ■ ■■■ , Mr., on the Scotch deerhound, 517 ; on sexual preference in dogs, 524; on the rejection of a horse by a mare, 525. , W. von, on the protective plu- mage of the Ptarmigan, 391. Writing, 144. Wyman, Prof., on the prolongation of the coccyx in the human embryo, 11 ; on the condition of the great toe in the human embryo, 11 ; on the occurrence of the supra-condy- loid foramen in the humerus of man, 22 ; on variation in the skulls of the natives of the Sandwich Islands, 26 ; on the hatching of the eggs in the mouths and branchial cavities of male fishes, 163, 345. X. Xenarchns, on the Cicadse, 281. Xenophon, selection in mankind advo- cated by, 29. Xmorhynchus, sexual difference in the colour of the eyes in, 425. Xiphophorus Hellerii, peculiar anal fin of the male, 337, 338. Xylocopa, diffarence of thi> sexes in, 292. Y. Yarrell, W., on the habits of the Cyprinidse, 250 ; on Haia clavata, 331 ; on the ciharacters of the male salmon during the breeding season, 332, 342 ; on the characters of the rays, 334 ; on the gemmeous drago- net, 336 ; on tne spawning of the salmon, 344 ; on the incubation of the Lophobranchii, 346 ; on rivalry in song-birds, 369 ; on the trachea of tl.e swan, 374 ; on the moulting of the Anatidte, 393 ; on the young of the waders, 486. Yellow fever, immunity of negroes and mulattoes from, 193. Touatt, Mr., on the development of the horns in cattle, 235. Yura-caras, their notions of beauty, 580. Z. Zebra, rejection of an ass by a female, 540 ; stripes of the, 545 Zebus, humps of, 532. Zigzags, prevalence of, as ornaments. 179. Zincke, Mr., on European emigration to America, 142. Zootoca vivipara, sexual difference in the colour of, 357. 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