or i zy i 5) ia Char a arte Toa in ‘1 es: tot nt Be i Aiea Nestea Raa OR Nua NR ICR foe a ait LG Ly hat ny nies ; Gents ted aeaneaetat ath sot eke pre?) Tay earls Au ey k Gory a ( A 0 v-l CORNELL UNIVERSITY LIBRARY i: = Gift’in memory of MARY STEPHENS SHERMAN, °13 from JOHN H. SHERMAN, ’11 | @QH3 | v.1 iE il el 2! | iii (seosean isin fecal THE DESCENT OF MAN AND SELECTION IN RELATION TO SEX BY CHARLES DARWIN, M.A., LL.D., F.R.S. PART ONE NEW YORK P. F. COLLIER & SON MCMII 2 \4 bos 1 36SVE SCIENCE PREFACE TO THE SECOND EDITION Durine the successive reprints of the first edition of this work, published in 1871, I was able to introduce several im- portant corrections; and now that more time has elapsed, 1 have endeavored 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 in- debted to a large number of correspondents for the commu- nication 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 Some new illustrations have been introduced, and four of the old drawings have been replaced by better ones, done from life by Mr.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 Profes- sor 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 observations, because during the last few years sev- eral memoirs on the subject have appeared on the Conti- nent, 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 se- lection of such variations as are often called spontaneous; whereas, even in the first edition of the ‘‘Origin of Species,”’ T distinctly stated that great weight must be attributed to the inherited effects of use and disuse, with respect both | (8) 4 PREFACE TO THE SECOND EDITION 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 structure; nor must we forget what I have called ‘‘correlated’’ growth, meaning thereby, that various parts of the organization are in some unknown man- ner so connected, that when one part varies, so do others; and if variations in the one are accumulated by selection, other parts will be modified. Again, it has 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 of 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-favorable criticisms on sexual selection with those which appeared at first on natu- ral selection; such as, that it would explain some few de- tails, but certainly was not applicable to the extent to which Ihave employed it. My conviction of the power of sexual selection remains unshaken; but it is probable, or almost certain, that several of my conclusions 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 be- lieve, be much more largely accepted; and it has already been fully and favorably received by several capable judges. Down, BECKENHAM, KENT, September, 1874 TABLE OF THE PRINCIPAL ADDITIONS AND CORRECTIONS TO THE PRESENT EDITION First Edition Present Edition Vou. I. Vol, I. Page Page 22 33-35 Discussion on the rudimentary points in the human ear re- vised. 26 38 Cases of men born with hairy bodies. 27, note. 39, note. |Mantegazza on the last molar. tooth in man. 29 42-43 |The rudiments of a tail in man. 32, note. 44, note. | Bianconi on homologous struct- ures, a8 explained by adapta- tion on mechanical principles. 40 101 Intelligence in a baboon. 42 102 Sense of humor in dogs. 44 104-105 | Further facts on imitation in man and animals. 47 106 Reasoning power in the lower animals. 50 113-114 ees of experience by ani- mals. 53 117 Power of abstraction in animals. 58 124-125 |Power of forming concepts in re- lation to language. 64 128 Pleasure from certain sounds, colors, and forms. 78 142 Fidelity in the elephant. 79 148 Galton on gregariousness of cattle. oS 144-145 | Parental affection. the ip, note. 158, note. |! Persistence of enmity and hatred. (@) 6 TABLE OF THE PRINCIPAL ADDITIONS AND First Edition Present Edition Vol. L Vol. L Page Page 91 155 Nature and strength of shame, regret, and remorse. 94 ° 159, note. {Suicide among savages. 97 163, note. |The motives of conduct. 112 49 Selection, as applied to primeval man. 122 58-59 Resemblances between idiots and animals. 124, note. 61, note. | Division of the malar bone. 125, note. | 59-60, note. |Supernumerary mamme and igits. 128-129 64-65 Further cases of muscles proper to animals appearing in man. 146 81, note. |Broca: average capacity of skull diminished by the preservation of the inferior members of society. 149 84 Belt on advantages to man from his hairlessness. 150 85-86 Disappearance of the tail in man and certain monkeys. 169 180-181 |Injurious forms of selection in civilized nations. 180 192 Indolence of man, when free from. a struggle for existence. 193 208 Gorilla protecting himself from rain with his hands, 208, note. | 216, note. | Hermaphroditism in fish. 209 218 Rudimentary mammeze in male mammals. 239 248-251 | Changed conditions lessen fertil- ; ity and cause ill-health among savages. 245 257-260 |Darkness of skin a protection against the sun. 250 263-273 | Note ay Professor Huxley on the development of the brain in man and apes. 256 276-278 |Special organs of male parasitic worms for holding the female, CORRECTIONS TO THE PRESENT EDITION 7 First Edition Present Edition Vol. I. Vol. 1. Page Page 275-276 295-297 |Greater variability of male than female; direct action of the en- vironment in causing differ- ences between the sexes. 290 “310 Period of development of pro- tuberances on birds’ heads de- termines their transmission to one or both sexes. 301 821-323 |Causes of excess of male births. 314 336 Proportion of the sexes in the bee family. 815 338-340 |Excess of males perhaps some- times ietenaadd by selection. 327 350 Bright colors of lowly organized animals. ' 838 859 Sexual] selection among spiders. 839 360 Cause of smallness of male spiders. 345 366 Use of phosphorescence of the glow-worm. 849 369 The humming noises of flies. 350 370 Use of bright colors to Hemip- tera ve. 851 370-871 |Musical apparatus of Homoptera. 854 374-875 |Development of stridulating ap- 359 379, note. paratus in Orthoptera. 366 884-385 |Herman Miiller on sexual differ- ences of bees. 387 402 Sounds produced by moths. 397 410 Display of beauty by butter- flies. 401 414 Female butterflies, taking the more active part in courtship, brighter than their males. 412 421-493 |Further cases of mimicry in but- terflies and moths. 417 424 Cause of bright and diversified Vol. IL Vol. I colors of caterpillars. 2 432 Brushlike scales of male Mallo- tus. 8 TABLE OF THE PRINCIPAL ADDITIONS AND First Edition Vol. IL Present Edition Vol. UL. Page Page 14 443-444 |Further facts on courtship of fishes, and the spawning of Macropus. 23 451 | Dufossé on the sounds made by fishes. 26 454 Belt on a frog protected by bright coloring. 30 458 Further facts on mental powers of snakes. 82 459 Sounds produced by snakes; the rattlesnake. 36 463 Combats of Chameleons. 72 496 Marshall on protuberances on birds’ heads. 91 518 Further facts on display by the Argus pheasant. 108 530 Attachment between paired birds. 118 5389 Female pigeon rejecting certain males, 120 541 Albino birds not finding partners, in a state of nature. 124 545-546 | Direct action of climate on birds’ colors. 147-150 560-569 | Further facts on the ocelli in the Argus pheasant. 152 571 Display by humming birds in courtship. 157 574-575 |Cases with pigeons of color trans- mitted to one sex alone. © 232 640-642 | Taste for the beautiful permanens. enough to allow of sexual selec- tion with the lower animals, 247 652 Horns of sheep originally a mas- culine character. 248 653 nese affecting horns of ani- mals. 256 662 Prong-horned variety of Cervus virginianus. 260 666 Relative sizes of male and female whales and seals. CORRECTIONS TO THE PRESENT EDITION 9 First Edition Present Edition Vol. I. Vol. II. Page Page 266 672 _| Absence of tusks in male miocene igs. 286 690 Debion on sexual differences of ats. 4 299 701 Reeks on advantage from pecul- jar coloring. 316 719 Difference of complexion in men and women of an African tribe. 337 736 Speech subsequent to singing. 356 154 Schopenhauer on importance of courtship to mankind. 859 et seg. | 756 et seg. | Revision of discussion on com- munal marriages and promis- cuity. 3738 769-770 |Power of choice of woman in marriage, among savages. 380 776 Long-continued habit of plucking out hairs may produce an in- inherited effect. CONTENTS INTRODUCTION . . ‘ a 5 . . . . e . PART I THE DESCENT OR ORIGIN OF MAN CHAPTER I THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM Nature of the evidence bearing on the origin of mari—Homologous struc- tures in man and the lower animals—Miscellaneous points of corre- spondence—Development—Rudimentary structures, muscles, sense- organs, hair, bones, reproductive organs, ete. —The bearing of these three great classes of facts on the origin of man _ . 5 7 CHAPTER II v 21 ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM Variability of body and mind in man—Inheritance—Causes of variability —tLaws of variation the same in man as in the lower animals—Direct action of the conditions of life—Effects of the increased use and dis- use 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 struc- ture—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 skuil—Nakedness—Absence of a tail —Defenceless condition of man 5 2 5 . . 2 7 CHAPTER IIt The difference in mental power between the highest ape and the lowest savage, immeénse—Certain instincts in common—The emotions— Curiosity—Imitation-— Attention — Memory—Imagination—Reason— Progressive Improvemetit—Tools and weapons used by animals— Abstraction, self-conscious#ess—Language—Sense of beauty—Beliet in God, spiritual agencies, superstitions. . . . . . (11) £6 COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS 94 12 CONTENTS CHAPTER IV ©OMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER 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 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 . : . 134 CHAPTER V ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FAOULTIES DURING PRIMEVAL AND CIVILIZED TIMES Advancement of the intellectual powers through natural selection—Impor- tance of imitation—Social and moral faculties—Their development within the limits of the same tribe—Natural selection as affecting civ- ilized nations—Evidence that civilized nations were once barbarous . 173 CHAPTER VI ON THE AFFINITIES AND GENEALOGY OF MAN Position of man in the animal series—The natural system genealogical— Adaptive characters of slight value—Various small points of resem- blance between man and the Quadrumana—Rank of man in the nat- ural system—Birthplace and antiquity of man—Absence of fossil con- necting-links—Lower stages in the genealogy of man, as inferred, first, from his affinities, and, secondly, from his structure—LHarly _ androgynous condition of the Vertebrata—Conclusion . ‘ - 196 CHAPTER VII ON THE RACES OF MAN The nature and value of specific characters—Application to the races of man—Arguments in favor of, and opposed to, ranking the so-called races of man as distinct species—Sub-species—Monogenists and polyg- enists—Convergence of character—Numerous points of resemblance in body and mind between the most distinct races of man—The state of man when he first spread over the earth—Each race ~~’ 7-7 * ' “+ from a single pair—The extinction of races—The f- The effects of crossing—Slight influence of * conditions of life—Slight or no influence of selection . . . : . -¥ CONTENTS PART II SEXUAL SELECTION CHAPTER VIII PRINOIPLES 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 selec- tion—Inheritance, at corresponding periods of life, at corresponding seasons of the year, and as limited by sex—Relations between the several forms of inheritance—Causes why one sex and the young are net modified through sexual selection—Supplement on the proportional numbers of the two sexes throughout the animal kingdom—tThe pro- portion of the sexes in relation to natural selection . . . CHAPTER IX 13 » a4 SECONDARY SEXUAL CHARACTERS IN THE LOWER OLASSES OF THE ANIMAL KINGDOM These characters absent in the lowest classes—Brilliant colors—Mollusca— Annelids—Crustacea, secondary sexual characters strongly developed; dimorphism; color; characters not acquired before maturity—Spiders, sexual colors of; stridulation by the males—Myriapoda_ . . % CHAPTER X SECONDARY SEXUAL OHARAOTERS OF INSEOTS Diversified structures possessed by the males for seizing the females—~ Differences between the sexes, of which the meaning is not under- stood—Difference in size between the sexes—Thysanura—Diptera— Hemiptera—Homoptera, musical powers possessed by tho males Ce “Savage, mmMeE musical instruments of the males, much diversi- Curiosity —Imitarion's0acity 5 colors—Neuroptera, sexual differences Progressive Improvemenusnacity and colors—Coleoptera, colors; Abstraction, self-conscious#? apparently as an ornament; battles; in God, spiritual agencies, sup@mon to both sexes. . : . 344 362 14 CONTENTS CHAPTER XI INSECTS, continued—ORDER LEPIDOPTERA (BUTTERFLIES AND MOTHS) Courtship of butterflies—Battles—Ticking noise—Colors common to both sexes, or more brilliant in the males—Examples—Not due to the direct action of the conditions of life—Colors adapted for protection—Colors of moths—Display—Perceptive powers of the Lepidoptera—Variability —Causes of the difference in color between the males and females— Mimicry, female butterflies more brilliantly colored than the males —Bright colors of caterpillars—Summary and concluding remarks on the secondary sexual characters of insects—Birds and insects compared 2 ‘ ‘ : : : ‘ c A : . 401 CHAPTER XII SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, AND REPTILES Fisuzs: Courtship and battles of the males—Larger size of the females —Males, bright colors and ornamental appendages; other strange characters—Colors and appendages acquired by the males during the breeding season alone—Fishes with both sexes brilliantly colored— Protective colors—The less conspicuous colors 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: Differ- ences in structure and color between the sexes—Vocal organs. REp- TILES: Chelonians—Crocodiles—Snakes, colors in some cases protec- tive—Lizards, battles of—Ornamental appendages—Strange differences in structure between the sexes—Colors—Sexual differences almost as great as with birds . : , ‘ 7 r : 3 . 431 CHAPTER XIII SECONDARY SEXUAL CHARACTERS OF BIRDS Sexual differences—Law of battle—Special weapons—Vocal organs— Instrumental music—Love-antics and dances—Decorations, perma- nent and seasonal—Double and single annual moults—Display of ornaments by the males ‘ : : - : ‘ ° . 466 CHAPTER XIV BIRDS—continued Choice exerted by the female—Length of courtship—Unpaired birds— Mental qualities and taste for the beautiful—Preference or antipathy shown by the female for particular males—Variability of birds— Variations sometimes abrupt—Laws of variation—Formation of ocelli —Gradations of character—Case of Peacock, Argus pheasant, and Urosticte ‘ ‘ a> fabs . : 5 : . é . 522 CONTENTS 15 CHAPTER XV BIRDS—continued Discussion as to why the males alone of some species, and both sexes of others, are brightly colored—On sexually limited inheritance, as ap- plied to various structures and to brightly colored plumage—Nidifica- tion in relation to color—Loss of nuptial plumage during the winter 5972 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 differences between the males of closely allied or representative species—The female as- suming the characters of the male—Plumage of the young in relation to the summer and winter plumage of the adulis—On the increase of beauty in the birds of the world—Protective coloring—Conspicu- ously colored birds—Novelty appreciated—Summary of the four chap- terson birds. 3 ef ‘i 5 5 5 = . . 598 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 shown by either sex in the pairing of quadrupeds 646 CHAPTER XVIII SECONDARY SEXUAL CHARACTERS OF MAMMALS—continued Voice—Remarkable sexual peculiarities in seals—Odor—Development of the hair—Color of the hair and skin—Anomalous case of the female being more ornamented than the male—Color and ornaments due to sexual selection—OColor acquired for the sake of protection—Color, though common to both sexes, often due to sexual selection—On the disappearance of spots and stripes in adult quadrupeds—On the colors and ornaments of the Quadrumana—Summary . . © . 699 16 CONTENTS PART III SEXUAL SELECTION IN RELATION TO UAN AND CONCLUSION CHAPTER XIX SECONDARY SEXUAL CHARACTERS 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 determin- ing the marriages of mankind—Attention paid by savages to ornaments —Their ideas of beauty in woman—The tendency to exaggerate each natural peculiarity - . : ‘ : . ° - . 716 CHAPTER XX SECONDARY SEXUAL OHARACTERS OF MAN—continued On the effects of the continued selection of women according to a different standard of beauty in each race—On the causes which interfere with sexual selection in civilized and savage nations—Conditions favorable to sexual selection during primeval times—On the manner of action of sexual selection with mankind—On the women in savage tribes having some power to choose their husbands—Absence of hair on the body, and development of the beard—Color of the skin—Summary . ° 153 CHAPTER XXI GENERAL SUMMARY AND CONOLUSION Main conclusion that man is descended from some lower form—Manner of development—Genealogy of man—Intellectual and moral faculties —Sexual selection—Concluding remarks é ‘i : 3 . 780 InDEx ‘ 2 ‘i . a é si ° ° . ° ® 799 THE DESCENT OF MAN AND SELECTION IN RELATION 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 thrown on the origin of man and his history’’; and this implies 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 ventures to say in his address as President of the National Institution of Geneva (1869), ‘‘personne, en Europe au moins, n’ose plus soutenir la création indépendante et de toutes piéces, des espéces,’’ it is manifest that at least a large number of naturalists must admit that species are the. modified descendants of other species; and this espe- cially 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 de- cide, that I have greatly overrated its importance. Of the older and honored chiefs in natural science, many unfortu- nately are still opposed to evolution in every form. (17) | 18 INTRODUCTION In consequence of the views now adopted by most natu- ralists, and which will ultimately, as in every other case, be followed by 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 applicable to man. This seemed all the more desirable, as I had never deliberately applied these views to a species taken singly. When we confine our attention to any one form, we are de- prived of the weighty arguments derived from the nature of the affinities which connect together whole groups of organisms—their geographical distribution in past and pres- ent times, and their geological succession. The homological structure, embryological development, and rudimentary or- gans 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 favor 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, first, whether man, like every other species, is descended from 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 necessary 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 labors of a host of eminent men, beginning with M. Boucher de Perthes; and this is the indispensable 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 anthropomorphous apes; for Prof. Huxley, in the opinion INTRODUCTION 18 of most competent judges, has conclusively shown 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 contains hardly any original facts in regard to man; but as the conclusions at which I arrived, after drawing up a rough draught, 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 little, 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 any degree new. Lamarck long ago came to this conclusion, which has lately been maintained by several eminent naturalists and philoso- phers; for instance, by Wallace, Huxley, Lyell, Vogt, Lub- bock, Biichner, Rolle, etc.,’ and especially by Hickel. This last naturalist, besides his great work, ‘‘Generelle Morpholo- gie’’ (1866), has recently (1868, with a second edit. in 1870) published his ‘‘Natiirliche Schdépfungsgeschichte,’’ in which he fully discusses the genealogy of man. If this work had appeared before my essay had been written, I should prob- ably never have completed it. Almost all the conclusions at which I have arrived I find confirmed by this naturalist, whose knowledge on many points is much fuller than mine. Wherever I have added any fact or view from Prof. Hickel’s 1 As the works of the first-named authors 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 iiber.die Darwin’sche Theorie’’: zweite Auflage, 1868, von Dr. L. Biichner; translated into French under the title “‘Confétences sur la Théorie Darwinienne,’’ 1869. ‘‘Der Mensch, im Lichte der Darwin’sche Lehre,’’ 1865, von Dr. F. Rolle. 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, 186%, p. 81) a very curious paper on rudimentary characters, as bearing on the origin of man. Another work has (1869) been published by Dr. Francesco Barrago, bearing in Italian the title of ‘‘Man, made in the image of God, was also made in-the image of the ape.” 20 INTRODUCTION writings, I give his authority in the text; other statements I leave as they originally stood in my manuscript, occasion- ally giving in the footnotes references to his works, as & confirmation of the more doubtful or interesting points. During many years it has seemed te me highly probable that sexual selection has played an important part in differ- entiating 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 full detail.* Consequently the second part of the present work, treating of sexual selection, has extended 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 illus- trious anatomist 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 de- scended 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 pres- ent work, I have thought it better to reserve my essay for separate publication. 2 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 ful importance, since the publication of the *‘Origin’’; and this he did in a very able manner in his various works, PART ONE THE DESCENT OR ORIGIN OF MAN i CHAPTER I THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM Nature of the evidence bearing on the origin of man—Homologous struc- tures in man and the lower animals—Miscellaneous points of corre- spondence—Development—Rudimentary structures, muscles, sense- organs, hair, bones, reproductive organs, ete.—The bearing of these three great classes of facts on the origin of man E who wishes to decide whether man is the modified H descendant of some pre-existing form would prob- ably first inquire whether man varies, however slightly, 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. Azain, 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 ease of other organisms; for wustance, by correlation, the inherited effects of use and disusé,ctc-? Is man subject to similar malconformations, the result dretitested develop- ment, of reduplication of parts, etce., and dow * he display in any of his anomalies reversion to some former a. 22ncient type of structure? It might also naturally be inquitea 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 distrib- uted over the world; and how, when crossed, do they react (21) 22 THE DESCENT OF MAN on each other in the first and succeeding generations? And so with many other points. The inquirer would 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 conse- quently to beneficial variations, whether in body or mind, being preserved, and injurious 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 an- swered in the affirmative, 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 suc- ceeding chapters, the mental powers of man, in comparison with those of the lower animals, will be considered. The Bodily Structure of Man.—lt is notorious that man is constructed on the same general type or model as other mammals. All the bones in his skeleton can be compared 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 importag¢ st-ait tie organs, follows the same law, as shown by Huxley and other anato- mists. Bischoff,’ who is a béstile witness, admits that every” chief fissure and fold. }7‘the brain of man has its analogy in that of the oren~phut he adds that at no period of deveiop- ment do the’ ¢orains perfectly agree; norcould perfect agree- eerts expected, for otherwise their mental powers would have been the same. Vulpian* remarks: ‘‘Les difiérences ass hirnwindungen des Menschen,” 1868, 8. 96. The conclusions of this ae as well as thoes of Gratiolet and Aeby, concerning the brain, will be diseussed by Prof, Huxley in the Appendix alluded to in the Preface to this mere sur la Physiologie,” 1866, p. 890, as quoted by M. Dally, “L’Ordre des Primates et le Transformisme,”’ 1868, p. 29. THE DESCENT OR ORIGIN OF MAN 23 ~ réelles qui existent entre l’encéphale de l’homme et celui des singes supérieurs, sont bien minimes. TI] ne faut pas se faire d’illusions 4 cet égard. L’homme est bien plus pras des singes anthropomorphes par les caractéres anatomiques de son cerveau que ceux-ci ne le sont non-seulement des autres mammiféres, mais méme de certains quadrumanes, des guenons et des macaques.’’ But it would be superflu- ous here to give further details on the correspondence be- tween 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 structure, by which this correspondence or relationship is well shown. Man is liable to receive from the lower animals, and to communicate to them, certain diseases, as hydrophobia, vari- ola, the glanders, syphilis, cholera, herpes, etc.;* and this fact proves the close similarity* of their tissues and blood, both in minute structure and composition, far more plainly than does their comparison under the best microscope, er by the aid of the best chemical analysis. Monkeys are lia- ble to many of the same non-contagious diseases as we are; thus Rengger,® who carefully observed for a long time the Cebus Azarce in its native land, found it liable to catarrh, with the usual symptoms, and which, when often recurrent, led to consumption. ‘These monkeys suffered also from apoplexy, inflammation of the bowels, and cataract in the eye. The younger ones when shedding their milk-teeth often died from fever. Medicines produced the same effect on them as on us. Many kinds of monkeys have a strong 8 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. : 4 A Reviewer has criticised (‘‘British Quarterly Review,’’ Oct. 1, 1871, 2) what I have here said with much severity and contempt; but, as I do ‘use the term identity, I cannot see that I am greatly in error. There rs to me a strong analogy between the same infection or contagion pro- morg the same result, or one closely similar, in two distinct animals, and the - of two distinet fluids by the same chemical reagent. *Naturgeschichte der Saugethiere von Paraguay,’’ 1830, s. 50. Del 24 THE DESCENT OF MAN 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 northeastern Africa catch the wild baboons by exposing vessels with strong beer, by which they are made drunk. He has seen some of these animals, which he kept in confinement, in this state; and he gives a laugh- able account of their behavior and strange grimaces. On the following morning 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 relished 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 caus- ing fatal effects; and is plagued by external parasites, all of which belong to the same genera or families as those infest- ing 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 matura- tion 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.” 6 The same tastes are common to some animals much lower in the scale, Mr. A. Nicols informs me that he kept in Queensland, in Australia, three indi- viduals of the Phaseolarctus cinereus; and that, without having been taught in any way, they acquired a strong taste for rum, and for smoking tobacco. 7 Brehm, ‘‘Thierleben,’’ B. i. 1864, 8. 75, 86. On the Ateles, s. 105. For other analogous siatements, see s. 25, 107. s, ‘8 Dr, W. Lauder Lindsay, ‘Edinburgh Vet. Review,’’ July, 1858, p, 3% ® With respect to insects see Dr. Laycock, ‘On a Ger-~al Law = Periodicity,” “British Association,” 1842. Dr, Maccullock = ~~ ,"or American Journal of Science,”’ vol. xvii. p. 305, has seen : an tertian ague. Hereafter I shall return to this subject. fag 10 J have given the evidence on this head in my ‘Var’ 3) Plants under Domestication,’’ vol. ii, p. 15, and more co i { | a THE DESCENT OR ORIGIN OF MAN 25 The whole process of that most important function, the reproduction of the species, is strikingly the same in all mammals, 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 full-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 tropi- cal 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, etc., as well as in mind, in the same manner as do the two sexes of many mammals. So that the corre- spondence in general structure, in the minute structure of the tissues, in chemical composition and in constitution, between man and the higher animals, especially the an- thropomorphous apes, is extremely 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 em- bryo itself at a very early period can hardly be distin- guished from that of other members of the vertebrate king- dom. At this period the arteries run in arch-like branches, N “Mares e diversis generibus Quadrumanorum sine dubio dignoscunt femi- nas humanes a maribus, Primum, credo, odoratu, postea aspectu. Mr. Youatt, qui diu in Hortis Zoologicis (Bestiariis) medicus animalium erat, vir in rebus observandis cautus et sagax, hoc mihi certissime probavit, et curatores ejusdem loci et alii e ministris confirmaverunt. Sir Andrew Smith et Brehm notabant idem in Cynocephalo. Mlustrissimus Cuvier etiam narrat multa de hae re, qué ut opinor, nihil turpius potest indicari inter omnia hominibus et Quadrumanis communia, Narrat enim Cynocephalum quendam in furorem incidere aspectu feminarum aliquarum, sed nequaquam accendi tanto furore ab omnibus. Sem- per eligebat juniores, et dignoscebat in turb4, et advocabat voce gestfique.”” #2 This remark is made with respect to Cynocephalus and the anthropo- morphous apes by Geoffroy Saint-Hilaire and F. Cuvier, ‘Hist. Nat. des Mammiféres,”? tom. {. 1824. 18 Huxley, ‘‘Man’s Place in Nature,” 1863, p. 84. Descent—Vot. L—2 26 THE DESCENT OF MAN as if to carry the blood to branchie which are not present in the higher vertebrata, though the slits on the sides of the neck still remain (f, g, Fig. 1), marking their former posi- tion. Ata somewhat later period, when the extremities are developed, ‘‘the feet of lizards and mammals,”’ as the illus- — trious 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 de- velopments 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 copied from two works of undoubted accuracy.’® After the foregoing statements made by such high au- thorities, it would be superfluous on my part to give a num- ber of borrowed details, showing 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 ves- sel; the excreta are voided through a cloacal passage; and the os coceyx projects like a true tail, ‘‘extending consider- ably beyond the rudimentary legs.’’'* In the embryos of all air-breathing vertebrates, certain glands, called the corpora 4 ‘“Man’s Place in Nature,’’ 1863, p. 67. 1% The human embryo (upper fig.) is from Ecker, ‘‘Icones Phys.,’? 1851< 1859, tab. xxx. fig. 2. This embryo was ten lines in length, so that the drawing is much magnified. The embryo of the dog is from Bischoff, ‘‘Ent- wicklungsgeschichte des Hunde-Hies,’’ 1845, tab. xi. fig. 42 B. This drawing is Sve times magnified, the embryo being twenty-five days old. The internal viscera have been omitted, and the uterine appendages in both drawings re- moved. I was directed to these figures by Prof. Huxley, from whose work, ‘‘Man’s Place in Nature,’’ the idea of giving them was taken. Hackel has also given analogous drawings in his ‘‘Sch6pfungsgeschichte.”’ 16 Prof. Wyman in “‘Proc. of American Acad. of Sciences,’? vol. iv., 1860, p. 1%. THE DESCENT OR ORIGIN OF MAN 27 Wolffiana, correspond with and act like the kidneys of ma- ture fishes." Hven at a later embryonic period, some strik- ing resemblances between man and the lower animals may Fia. 1.—Upper figure human embryo, from Ecker. Lower figure that of a dog, from Bischoff. a. Fore-brain, cerebral hemispheres, etc. 6. Mid-brain, corpora uadrigemina, c. Hind-brain, cerebellum, medulla oblongata. d. Bye. e. Ear. f. irst visceral arch. g. Second visceral arch. H. Vertebral columns and muscles in process of development. 7. Anterior extremities. K. Posterior extremities, L. Tad or oS Coccyx. 11 Owen, ‘‘Anatomy of Vertebrates,”’ vol. i. p. 533. ‘ 28 THE DESCENT OF MAN 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 fulerum 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 permanent condition of this part in the quadru- mana.’’ I will conclude with a quotation from Huxley,” who, after asking, does man originate in a different way from a dog, bird, 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 immediatély 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 rudi- mentary condition; and man forms no exception to the rule. Rudimentary organs must be distinguished from those that are nascent; though in some cases the distinction is not easy. The former are either absolutely useless, such as the mammz of male quadrupeds, or the incisor teeth of ruminants which never cut through the gums; or they are 18 “Die Grosshirnwindungen des Menschen,’’ 1868, s. 95, 19 ‘Anatomy of Vertebrates,’’ vol. i. p. 553. 20 ‘Proc, Soc. Nat. Hist.’? Boston, 1863, vol. ix. p. 185. 21 **Man’s Place in Nature,”’ p. 65. 22 T had written a rough copy of this chapter before reading a valuable paper, “‘Caratteri rudimentali in ordine all origine del uomo”’ (‘‘Annuario della Soc. d, Nat.,’? Modena, 1867, p. 81), by G. Canestrini, to which paper I am consid- erably indebted. Hackel has given admirable discussions on this whole subject, under the title of Dysteleology, in his ‘‘Generelle Morphologie,’’ and *“‘Schépfungsgeschichte.”” THE DESCENT OR ORIGIN OF MAN ap of such slight service to their present possessors that we can hardly suppose that they were developed under the 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. Rudimentary organs are 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 be- come wholly suppressed. When this occurs, they are never- theless liable to occasional reappearance through reversion —a circumstance well worthy of attention. The chief agents in causing organs to become rudimen- tary 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 corresponding period of life. 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, from being subjected to fewer alternations of press- ure, or from becoming in any way less habitually active. Rudiments, however, may occur in one sex of those parts which are normally present in the other sex; and such rudi- ments, as we shall hereafter see, have often originated in a way distinct from 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 life. The process of reduction is probably often aided through the two principles of compensation and econ- omy of growth; but the later stages of reduction, after dis- use has done all that can fairly be attributed to it, and when ‘tue coving to be effected by the economy of growth would be very smui:,” are difficult to understand. The final and complete suppres.‘on of a part, already useless and much reduced in size, in which case neither compensation nor 33 Some good criticisms on this subject have been given by Messrs. Murie and Mivart, in ‘“‘Transact. Zoolog. Soc, ’? 1869, vol. vii. p. 92. 30 THE DESCENT OF MAN economy can come into play, is perhaps intelligible by the aid of the hypothesis of pangenesis. But as the whole sub- ject of rudimentary organs has been discussed and illustrated in my former works,* I need here say no more on this head. Rudiments of various muscles have been observed in many parts of the human body, and not a few muscles which are 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 their skin; and this is effected by the pan- niculus carnosus. Remnants 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 Edin- burgh, has occasionally detected, as he informs me, muscu- lar fasciculi in five different situations, namely in the axille near the scapula, ete., all of which must be referred to the system of the panniculus. He has also shown” that the musculus sternalis or sternalis brutorum, which is not an ex- tension of the rectus abdominalis, but is closely allied to the panniculus, occurred in the proportion of about three per cent in upward of 600 bodies: he adds, that this muscle affords ‘‘an excellent illustration of the statement that oc- casional and rudimentary structures are especially liable to variation in arrangement.”’ Some few persons have the power of contracting the superficial muscles on their scalps; and these muscles are in a variable and partially rudimentary condition. M. A. de Candolle has communicated to me a curious instance of 4 “Variation of Animals and Plants under Domestication,’ vol. * and 397. See also ‘‘Origin of Species,”’ 5th edit. p. 535. 2 For instance M. Richard (‘Annales des Sciences Natading a valuable paper, 1852, tom. xviii. p. 13) describes and figures rudimer:(‘‘Annuario della Soc. d, “muscle pédieux de la main,’’ which he says is so» Which paper I am consid- Another muscle, called “‘le tibial postérieur,”’ ig-¢ discussions on this whole hand, but appears from time to time in a more “Generelle Morphologie,” and 36 Prof. W. Turner, ‘‘Proc. Royal Soc. Edi THE DESCENT OR ORIGIN OF MAN 31 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 per- forming this feat. His father, uncle, grandfather, 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 cousin in the seventh degree to the head of the 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 trans- mission 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 of the panniculus,; they are also variable in development, or at least in function. I have seen one man who could draw the whole ear forward; other men can draw it upward; another who could draw it backward; and, from what one of these persons told me, it is probable that most of us, by often touching our ears, and thus directing our attention toward them, could recover some power of movement by repeated trials. The power of erecting and directing the shell of the ears to the various points of the compass is no doubt of the highest service to many animals, -wné-ew thus perceive the direction of danger; but I have be very smaim sufficient evidence, of a man who possessed complete suppress». which might be of use to him. The reduced in size, in Emotions in Man and Animals,”’ 1872, p. 144, 38 Some good criticisms on Annuario della Soe, dei Naturalisti, 2 Modena, and Mivart, in ‘“‘Transact. Zoolog. 32 THE DESCENT OF MAN whole external shell may be considered a rudiment, together with the various folds and prominences (helix and anti- helix, tragus and anti-tragus, etc.) which in the lower ani- mals strengthen and support the ear when erect, without adding much to its weight. Some authors, however, sup- pose that the cartilage of the shell serves to transmit vibra- tions to the acoustic nerve; but Mr. Toynbee,” after collect- ing all the known evidence on this head, concludes that the external shell is of no distinct use. The ears of the chim- panzee and orang are curiously like those of man, and the proper muscles are likewise but very slightly developed.” Iam also assured by the keepers in the Zoological Gardens that these animals never move or erect their cars; 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 little, 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 compensated by the freedom with which they can move the head in 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 rudi- ment of it is found in the gorilla’’;* and, as I hear from Prof. Preyer, it is not rarely absent in the negro. 2% “The Diseases of the Ear,’’ by J. Toynbee, F.R.S., 1860, p. 12. A dis- tinguished physiologist, Prof. Preyer, informs me that he had lately been ex- perimenting on the function of the shell of the ear, and has come to nearly the same conclusion as that given here. 30 Prof. A. Macalister, ‘‘Annals and Mag. of Nat. History,”’ vol. vii., 1871, p. 342. 31 Mr, St. George Mivart, ‘‘Hlementary Anatomy,’ 1873, p. 396, THE DESCENT OR ORIGIN OF MAN 33 The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity in the external ear, which he has often ob- served both in men and women, and of which he perceived the full significance. His attention was first called to the subject while 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 subsequently 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 wo- man. Mr. Woolner made an exact model of one such case, and sent me the accompanying draw- ing (Fig. 2). These points not only project inward toward the centre of the ear, but often a little outward 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 con- fined to mankind, for I observed ae deawa ty We Woonee a. The projecting point case in one of the spider-monkeys (Ateles beelzebuth) in our Zoological Gardens; and Dr. HE. Ray Lankester informs me of another case in a chimpanzee in the gardens at Hamburg. The helix obviously consists of the extreme margin of the ear folded inward; and this folding appears to be in some manner connected with the whole ex- ternal ear being permanently pressed backward. 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 in- 32 See also some remarks, and the drawings of the ears of the Lemuroidea, = Messrs. Murie and Mivart’s excellent paper in ‘‘Transact. DOO Ee Soe.,’’ vol , 1869, pp. 6 and 90. 84 THE DESCENT OF MAN ward; but if the margin were to be thus folded, a slight . point would necessarily project inward toward the centre, and probably a little outward from the plane of the ear: and this I believe to be their origin in many cases. On the other hand, Prof. L. Meyer, in an able paper recently published,** maintains that the whole case is one of mere variability; and that the projections are not real ones, but are due to the in- ternal cartilage on each side of the points not having been fully developed. Iam 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 microcephalous 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 from the frequency of their occurrence, and from the general correspondence in position with that of the tip of a pointed ear. In one case, of 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 perfect 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 inward, but is pointed, so that it closely resem- bles 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 outlines are closely similar. If, in these two 33 Ueber das Darwin’sche Spitzohr, Archiv fir Path. Anat. und Phys., 1811, p. 486. % ‘The Expression of the Emotions,” p. 136. THE DESCENT OR ORIGIN OF MAN 35 eases, the margin had been folded inward in the normal manner, an inward projection must have been formed. I may add that in two other cases the outline still remains somewhat pointed, although the margin of the upper part of the ear is normally folded inward—in one of them, how- ever, very narrowly. The following woodcut (No. 8) is an accurate 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 outline of the ear is at this period from its adult condition, when it bears a close general re- Fie. 3.—Foetus of an Orang. Exact copy of a photograph, showing the form of the ear at this early age. semblance 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 inward. On the whole, it still seems to me prob- able that the points in question are in some cases, both in man and apes, vestiges of a former condition. The nictitating membrane, or third eyelid, with its ac- cessory 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 . 386 THE DESCENT OF MAN certain fishes, as in sharks. It is fairly well developed in the two lower divisions of the mammalian series, namely, in the monotremata and marsupials, and in some few of the higher mammals, as in the walrus. But in man, the quad- rumana, 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 find- . : ~~ . . . ing 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-colored races of men, in whom it is much more highly developed than in the white and civilized races.** Nevertheless it does not warn them of danger, nor guide them to their food; nor does it prevent the Eskimos from sleeping in the most fetid atmosphere, nor many savages from eating half-putrid meat. * In Euro- peans the power differs greatly in different individuals, as Iam assured by an eminent naturalist who possesses this sense highly developed, and who has attended to the sub- ject. Those who believe in the principle of gradual evolu- tion 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 85 Miiller’s ‘‘Hlements of Physiology,’’ Eng. translat., 1842, vol. ii. p. 1117. Owen, ‘‘Anatomy of Vertebrates,’’ vol. iii. p. 260; ibid. on the Walrus, ‘‘Proe. Zoolog. Soc.,’’ November 8, 1854. See also R. Knox, ‘‘Great Artists and Anatomists,’’ p. 106. This rudiment apparently is somewhat larger in Negroes aud Australians than in Europeans; see Carl Vogt, ‘‘Lectures on Man,’’ Eng. translat. p. 129. 86 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 Facultés Mentales,”’ ete., tom. i., 1872, p. 91) asserts that he repeatedly made experiments, and proved that Negroes and Indians could recognize persons in the dark by their odor. Dr. W. Ogle has made some curious observations on the connection between the power of smell and the coloring matter of 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-colored races having a finer sense of smell than the white races. See his paper, ‘‘Medico-Chirurgical Transactions,’’ London, vol. liii., 1870, p. 276. THE DESCENT OR ORIGIN OF MAN 37 rudimentary condition, from some early progenitor, to whom it was highly serviceable, and by whom it was continually used. In those animals which have this sense highly devel- oped, such as dogs and horses, the recollection of persons and of places is strongly associated with their odor; and we can thus perhaps understand how it is, as Dr. Maudsley has truly remarked, that the sense of smell in man ‘‘is singu- larly 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, while in others they bear thick tufts of hair.** There can be little doubt that the hairs thus scat- tered over the body are the rudiments of the uniform hairy coat of the lower animals. This view is rendered all the more probable, as it is known that fine, short, and pale- colored hairs on the limbs and other parts of the body occa- sionally become developed into ‘‘thick-set, long, and rather coarse, dark hairs,’’ when abnormally nourished near old- standing inflamed surfaces. * 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 slight pecu- liarity 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 consider- able length rising from the naked skin above the eyes, and corresponding to our eyebrows; similar long hairs project 31 ‘The Physiology and Pathology of Mind,”’ 2d edit., 1868, p. 134. 38 Eschricht, Ueber die Richtung der Haare am menschlichen Kérper, “Miller’s Archiv fir Anat. und Phys.,’? 1837, s. 47. I shall often have to refer to this very curious paper. 2 39 Paget, ‘‘Lectures on Surgical Pathology, 7? 1853, vol. i. p. 71. 38 THE DESCENT OF MAN from the hairy 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 curious 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 mustache of this kind was observed by Eschricht* on a female foetus; but this is not so surprising a circumstance as it may at first appear, for the two sexes generally resem- ble each other in all external characters during an early period 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 quite naked, like the in- ferior surfaces of all four extremities in most of the lower animals. As this can hardly be an accidental coincidence, the woolly covering 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 abnormal condition of the teeth." Prof. Alex. Brandt informs me that he has compared the hair from the face of a man thus characterized, aged thirty-five, with the lanugo of a fcetus, and finds it quite similar in texture; therefore, as he re- marks, the case may be attributed to an arrest of develop- ment in the hair, together with its continued growth. Many delicate children, as I have been assured by a surgeon to a hospital for children, have their backs covered by rather 40 Eschricht, ibid., s. 40, 47. 4 See my “Variation of Animals and Plants under Domestication,” vol. ii, p. 327. Prof. Alex. Brandt has recently sent me an additional case of a father and son, born in Russia, with these peculiarities. I have received drawings of both from Paris. THE DESCENT OR ORIGIN OF MAN 39 long silky hairs; and such cases probably come under the same head. It appears as if the posterior molar or wisdom teeth were tending to become rudimentary in the more civilized races of man. These teeth are rather smaller than the other molars, as is likewise the case with the corresponding teeth in the chimpanzee and orang; and they. have only two separate fangs. They do not cut through the gums 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 struc- ture 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 civilized,** and this shortening may, I presume, be attributed to civilized men habitually feeding on soft, cooked food, and thus using their jaws less. Iam 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 nor- mal number.** With respect to the alimentary canal, I have met with an account of only a single rudiment, namely, the vermi- form appendage of the cecum. The cecum is a branch or 4 Dr, Webb, ‘““Teeth in Man and the Anthropoid Apes,’’ as quoted by Dr. C. Carter Blake in *‘Anthropological Review,”’ July, 1867, p. 299. 4 Owen, ‘‘Anatomy of Vertebrates,’’ vol. iii. pp. 320, 321, 325, 4 “On the Primitive Form of the Skuli.’”? Eng. translat. in ‘‘Anthropologi- cal Review,’’ Oct., 1868, p. 426. 45 Prof. Mantegazza 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 civilized races they are on the road toward atrophy or elimination. 40 THE DESCENT OF MAN diverticulum of the intestine, ending in.a cul-de-sac, and is extremely long in many of the lower vegetable-feeding mam- mals. In the marsupial koala itis actually more than thrice as long as the whole body.** It is sometimes produced into a long, gradually tapering point, and is sometimes con- stricted in parts. It appears as if, in consequence of changed diet or habits, the cecum had become much shortened 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 from the evidence which Prof. Canestrini‘’ has collected of its vari- ability in 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 cecum, 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 some. times 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 inflammation.” In some of the lower Quadrumana, in the Lemuride and Carnivora, as well as in many marsupials, there is a passage near the lower end of the humerus, called the supra-condy- loid foramen, through which the great nerve of the forelimb and often the great artery pass. Now in the humerus of man there is generally a trace of this passage, which is some- times 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 46 Owen, ‘‘Anatomy of Vertebrates,’’ vol. iii. pp. 416, 434, 441. 47 *‘Annuario della Soc. d. Nat.,’? Modena, 1867, p. 94. 48 M. C. Martins (‘‘De l’Unité Organique,’’ in ‘‘Revue des Deux Mondes,”? sune 15, 1862, p. 16), and Hackel (‘‘Generelle Morphologie,”’ B. ii. s. 278), have both remarked on the singular fact of this rudiment sometimes causing death. 49 With respect to inheritance, see Dr. Struthers in the ‘‘Lancet,’’ Feb. 15, 1873, and another important paper, ibid., Jan. 24, 1863, p. 83. Dr. Knox, as I am informed, was the first anatomist who drew attention to this peculiar THE DESCENT OR ORIGIN OF MAN 41 now shown 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 present, 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. Turner estimates, as he informs me, that it occurs in about one per cent of recent skeletons. But if the occasional development of this structure in man is, as seems probable, due to reversion, it is a return to a very ancient state of things, because in the higher Quadru- mana it is absent. There is another foramen or perforation in the humerus, occasionally present in man, which may be called the inter- condyloid. This occurs, but not constantly, in various an- thropoid 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 ‘Cimetiére du Sud,’ at Paris; and in the Grotto of Orrony, the contents of which are referred to the Bronze period, as mary as eight humeri out of thirty- two were perforated; but this extraordinary 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 the Lesse, belonging to the Reindeer period; while M. Leguay, in a sort of dolmen at Argenteuil, observed twenty-five per cent to be perforated; and M. Pruner-Bey found twenty-six per structure in man; see his ‘‘Great Artists and Anatomists,’’ p. 63. See also an important memoir on this process by Dr. Gruber, in the ‘‘Bulletin de lAcad. Imp. de St. Petersburg,”’ tom. xii., 1867, p. 448. 50 Mr, St. George Mivart, ‘‘Transact. Phil. Soc.,’’ 1867, p. 310. 51 “On the Caves of Gibraltar,’’ ‘Transact. Internat. Congress of Prehist. Arch.’ Third Session, 1869, p. 159. Prof. Wyman has lately shown (Fourth Annual Report, Peabody Museum, 1871, p. 20) that this perforation is present in thirty-one per cent of some human remains from ancient mounds in the West- ern United States, and in Florida It frequently occurs in the negro. 42 THE DESCENT OF MAN cent in the same condition in bones from Vauréal. Nor should it be left unnoticed that M. Pruner-Bey states that this condition 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 nearer in the long line of descent to their remote animal- like progenitors. . In man, the os coccyx, together with certain other ver- tebre 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) ofa humanembryo. Hven after birth it has been known, in certain rare and anomalous cases, to form a small external rudiment ofa tail. The os coccyx is short, usually includ- ing only four vertebree, all anchylosed together: and these are in a rudimentary 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. Turner, 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 downward as the last dorsal or first lumbar vertebra; but a thread-like structure (the filum terminale) runs down the axis of the sacral part 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 homologous with 5 Quatrefages has lately collected the evidence on this subject. ‘‘Revue des Cours Scientifiques,’’ 1867-68, p. 625. In 1840 Fleischmann exhibited a human foetus bearing a free tail, which, as is not always the case, included vertebral bodies; and this tail was critically examined by the many anatomists present at the meeting of naturalists at Erlangen (see Marshall in Niederlind- ischen Archiv fiir Zoologie, December, 1871). 53 Owen ‘‘On the Nature of Limbs,’’ 1849, p. 114. THE DESCENT OR ORIGIN OF MAN 43 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 inclosed within a bony canal. The following fact, for which I am also indebted to Prof. Turner, shows how closely the os coccyx corresponds with the true tail in the lower ani- mals: Luschka has recently discovered at the extremity of the coccygeal bones a very peculiar convoluted body, which is continuous with the middle sacral artery; and this discov- ery led Krause and Meyer to examine the tail of a monkey (Macacus) and of a cat, in both of which they found a simi- larly convoluted body, though not at the extremity. The reproductive system offers various rudimentary structures; 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 in an efficient state, but with a part efficient in the one sex and represented in the other by a mere rudiment. Never- theless, the occurrence of such rudiments is as difficult to explain, on the belief of the separate creation of each spe- cies, as in the foregoing cases. Hereafter I shall have to recur to these rudiments, and shall show that their presence generally depends merely on inheritance, that is, on parts acquired by one sex having been partially transmitted to the other. I will in this place only give some instances of such rudiments. Itis well known, that in the males of all mam- mals, including man, rudimentary mammz 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 shown by their occasional sym- pathetic enlargement in both during an attack of the measles. The vesicula prostatica, which has been observed in many male mammals, is now universally acknowledged to be the homologue of the female uterus, together with the connected passage. It is impossible to read Leuckart’s able descrip- tion of this organ, and his reasoning, without admitting the 44 THE DESCENT OF MAN 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 structures belonging to the reproductive system might have been here adduced.” The bearing of the three great classes of facts now given is unmistakable. 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 of a horse, the flipper of a seal, the wing of a bat, etc., is utterly inexplicable.” It is no scientific explanation to assert that they have all been formed on the same ideal plan. With respect to de- velopment, we can clearly understand, on the principle of variations supervening at a rather late embryonic period, and being inherited at a corresponding period, how it is 54 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. 55 See, on this subject, Owen, ‘‘Anatomy of Vertebrates,”’ vol. ili, pp. 675, 676, 706. 56 Prof, Bianconi, in a recently published work, illustrated by admirable engravings (‘La Théorie Darwinienne et la Création dite indépendante,’’ 1874), endeavors to show that homological structures, in the above and other cases, can be fully explained on mechanical principles, in accordance with their uses, No one has shown so well how admirably such structures are adapted for their final purpose; and this adaptation can, as I believe, be explained through natu- ral selection. In considering the wing of a bat, he brings forward (p. 218) what appears to me (to use Auguste Comte’s words) a mere metaphysical principle, namely, the preservation ‘‘in its integrity of the mammalian nature of the ani- mal.’? 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 shows clearly to be of service to the animal. Itis unfortunate that he did not consider such cases as the minute teeth, which never cut through the jaw in the ox, or the mamme of male quad- rupeds, 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 naturalists seems to me left unshaken, that homological structures are inexplicable on the principle of mere adaptation. THE DESCENT OR ORIGIN OF MAN 45 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, etc., can at first hardly be distinguished from each other. In order to understand the existence of rudi- mentary 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 indicated. 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 of 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 ani- mals around us, is a mere snare laid to entrap our judg- ment. This conclusion is greatly strengthened if we look to the members of the whole animal series, and consider the evidence derived from their affinities or classification, their geographical distribution and geological 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 wonder- ful that naturalists, who were well acquainted with the com- parative structure and development of man and other mam- mals, should have believed that each was the work of a separate act of creation. 46 THE DESCENT OF MAN CHAPTER II ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM Variability of body and mind in man—Inheritance—Causes of variability —tLaws of variation the same in man as in the lower animals—Direct action of the conditions of life—Hffects of the increased use and dis- use 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 struc- ture—The causes which have led to his becoming erect—Consequent changes of structure—Decreuase in size of the canine teeth—Increased size and altered shape of the skull—Nakedness—Absence of a tail —Defenceless condition of man T IS manifest that man is now subject to much varia- bility. No two individuals of the same race are quite alike. Wemay compare millions of faces, and each will be distinct. There is an equally great amount of diversity in 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 elon- gated 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 Australia—the latter a race ‘‘probably as pure and homoge- neous in 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 1 “Investigations in Military and Anthropolog. Statistics of American Sol- diers,’’ by B. A. Gould, 1869, p. 256. 2 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. 8%. On the Sandwich Islanders, Prof. J. Wyman, ‘‘Observations on Crania,’’ Boston, 1868, p. 18. THE DESCENT OR ORIGIN OF MAN 47 there is nearly as much diversity in the teeth as in the fea- tures. The chief arteries so frequently run in abnormal courses that it has been found useful for surgical purposes to calculate from 1,040 corpses how often each course pre- vails.* 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. He adds, that the power of performing the appropriate movements must 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 want- ing in departures from the standard descriptions of the mus- cular 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 palmeris accessorius. The famous old anatomist, Wolff,’ insists that the inter- nal viscera are more variable than the external parts: Nulla particula est que non aliter et aliter in aliis se habeat homini- bus. 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, etc., 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 differences between the men of distinct races, is so notorious that not a word need here be said. So it is with the lower animals. 3 “Anatomy of the Arteries,’? by R. Quain. Preface, vol. i., 1844. 4 “Transact. Royal Soc. Edinburgh,’’ vol. xxiv. pp. 175, 189. 5 “Proc, Royal Soc.,’? 186%, p. 544; also 1868, pp. 483, 624. There is a » previcas paper, 1866, p. 229. 6 “*Proc. R. Irish Academy,”’ vol. x., 1868, p. 141. 7 “Act, Acad. St. Petersburg,’? 1778, part ii. p. 217. 48 THE DESCENT OF MAN 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 his own peculiar disposition and temper: he mentions one baboon remarkable for its high intelligence; and the keepers in the Zoological Gardens pointed out to me a monkey, belonging to the New World division, equally remarkable for intelligence. Reng- ger, also, insists on the diversity in the various mental char- acters 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. ° XI have elsewhere’ so fully discussed the subject of Inheri- tance, that I need here add hardly anything. A greater number of facts have been collected with respect to the transmission of the most trifling, as well as of the most important, characters in man than in any of the lower ani- mals; though the facts are copious enough with respect to the latter. So in regard to mental qualities, their transmis- sion is manifest in our dogs, horses, and other domestic ani- mals. Besides special tastes and habits, general intelligence, courage, bad and good temper, etc., are certainly transmitted. With man we see similar facts in almost every family; and we now know, through the admirable labors of Mr. Galton,* that genius, which implies a wonderfully complex combina- tion of high faculties, tends to be inherited; and on the other hand, it is too certain that insanity and deteriorated mental powers likewise run in families. X 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 gen- 8 Brehm, ‘‘Thierleben,’’ B. 1. 3. 58, 87. Rengger, ‘‘Sdugethiere von Para- guay,’’ s. 57. 9 “Variation of Animals and Plants under Domestication,”’ vol. ii. chap. xii. 10 ‘‘Hereditary Genius: an Inquiry into its Laws and Consequences,’’ 1869, THE DESCENT OR ORIGIN OF MAN 49 erations. Domesticated animals vary more than those ina state of nature; and this is apparently due to the diversified and changing nature 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 area, like that of America. We see the influence of diversified conditions in the more civilized 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 uniformity of savages has often been exaggerated, and in some cases can hardly 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 ex- posed, 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 completely subjugated by other men, as that certain individuals should be preserved, and thus unconsciously selected, from somehow excelling in utility to their masters. Nor have certain male and female individuals been intentionally picked out and matched, ex- cept in the well-known case of the Prussian grenadiers; and in this case man obeyed, as might have been expected, the law of methodical selection; for it is asserted that many tall men were reared in the villages inhabited by the grenadiers and their tall wives. In Sparta, also, a form of selection was followed, for it was enacted that all children should be 11 Mr, Bates remarks ia Naturalist on the Amazons,’’ 1863, vol. ii. p. 159), with respect to the Indians of the same South American tribe, ‘‘no two of them were at all similar in the shape of the head; one man had an oval vis- age with fine features, and another was quite Mongolian in breadth and promi- nence of cheek, spread of nostrils, and obliquity of eyes.”” 12 Blumenbach, ‘‘Treatises on Anthropolog.,”’ Eng, translat., 1865, p. 205. Descent—Vo.t. L—3 50 THE DESCENT OF MAN examined shortly after birth; the well-formed and vigorous being preserved, the others left to perish.” If we consider all the races of man as forming a single species, his range is enormous; but some separate races, as the Americans 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 domesti- cated animals. Not only does variability appear to be 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 such full de- tail by Godron and Quatrefages that I need here only refer to their works.“ ¥Monstrosities, which graduate into slight variations, are likewise so similar in man and the lower ani- mals, that the same classification and the same terms can 18 Mitford’s “‘History of Greece,’’ vol. i. p. 282. It appears also from a passage in Xenophon’s ‘‘Memorabilia,’’ B. ii. 4 (to which my attention has been called by the Rev. J. N. Hoare), that it was a well recognized principle with the Greeks, that men ought to select their wives with a view to the health and vigor of their children. The Grecian 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! the cause is plaix, And to lament the consequence is vain.”’ —The Works of J. Hookham Frere, vol. ii., 1872, p. 334. 14 Godron, ‘‘De l’Espéce,’’ 1859, tom. ii. livre 3. Quatrefages, ‘Unité de l’Espéce Humaine,’’ 1861. Also Lectures on Anthropology, given in the “Revue des Cours Scientifiques,’’? 1866-68. THE DESCENT OR ORIGIN OF MAN 51 be used for both, as has been shown 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 under the following heads: The di- rect 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 considerable length. The direct and definite action of changed conditions. -This is a most perplexing subject. It cannot be denied that changed conditions produce some, and occasionally a con- siderable 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 obtain clear evidence in favor of this conclusion, 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, 15 ‘Hist. Gén. et Part, des Anomalies de l’Organisation,’’ in three volumes, tom. i. 1832. : 16 T have fully discussed these laws in my ‘‘Variation of Animals and Plants under Domestication,’’ vol. ii. chaps. xxii, and xxiii. M. J. P. Durand has lately (1868) published a valuable essay, ‘‘De 1’Influence des Milieux,” ete, He lays much stress, in the case of plants, on the nature of the soil. 52 THE DESCENT OF MAN by which the whole organization is rendered in some degree plastic. In the United States, above one million soldiers, who served in the late war, were measured, and the States in which they were born and reared were recorded.” From this astonishing number of observations it is proved that local influences 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 influ- ence on the stature.’’ For instance, it is established ‘‘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 shown ‘‘by the great difference between the statures of soldiers and sailors at the ages of seventeen and eighteen years.’’¥ Mr. B. A. Gould endeavored 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 ‘Gn 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 Villermé, 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 within 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 subsistence are very different, it is scarcely possible to avoid the conclusion that 1 Investigations in Military and Anthrop. Statistics,’ etc., 1869, by B. A, Gould, pp. 93, 107, 126, 131, 134. 18 For the Polynesians, see Prichard’s ‘‘Physical Hist. of Mankind,” vol, v., 18417, pp. 145, 283. Also Godron, ‘“De lEspéce,’’ tom. ii. p. 289. There is also a remarkable difference in appearance between the closely allied Hindus inhabiting the Upper Ganges and Bengal; see Elphinstone’s ‘‘History of India,” vol. i, p. 324. THE DESCENT OR ORIGIN OF MAN BB better food and greater comfort do intluence stature. But the preceding statements show 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 cer- tain occupations 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 maximum of physical development, it rises highest in energy and moral vigor.’ ’° Whether external conditions produce any other direct effect on man is not known. It might have been expected that differences of climate would have had a marked influ- ence, inasmuch as the lungs and kidneys are brought into activity under a low temperature, and the liver and skin under a high one.” It was formerly thought that the color 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 dur- ing many ages. But this subject will be more properly dis- cussed when we treat of the different races of mankind. With our domestic animals there are grounds for believ- ing 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. Liffects of the increased Use and Disuse of Parts.—It is well known that use strengthens the muscles in the individ- ual, 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 19 “Memoirs, Authropolog. Soc.,’’ vol. iii., 1867-69, pp. 561, 565, 567. ® Dr. Brakenridge, ‘‘Theory of Diathesis,”’ ‘‘Medical Times,’’ June 19, and July 17, 1869. 54 THE DESCENT OF MAN 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 propor- tions in various parts of the body. Thus it was ascertained by the United States Commission” that the legs of the sail- ors 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; while their arms were shorter by 1.09 of an inch, and therefore, out of proportion, shorter in rela- tion to their Jesser height. This shortness of the arms is apparently due to their greater use, and is an unexpected result: but sailors chiefly use their arms in pulling, and not in supporting weights. With sailors, the girth of the neck and the depth of the instep are greater, while the circum- ference of the chest, waist and hips is less, than in soldiers, Whether the several foregoing modifications would be- come hereditary, if the same habits of life were followed during many generations, is not known, but it is probable. Rengger™® attributes the thin legs and thick arms of the Payaguas Indians to successive generations having passed nearly their whole lives in canoes, with their lower extremi- ties motionless. Other writers have come to a similar con- clusion in analogous cases. XAccording to Cranz,™ who lived for a long time with the Eskimos, ‘‘the natives believe that ingenuity and dexterity in seal-catching (their highest art and virtue) is hereditary; there is really something in it, for the son of a celebrated seal-cateher 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 laborers are at birth larger than 21 T have given authorities for these several statements in my ‘‘Variation of Animals under Domestication,” vol. ii. pp. 297-300. Dr. Jaeger, ‘“‘Ueber das Langenwachsthum der Knochen,”’ ‘‘Jenaischen Zeitschrift,’ B. v. Heft i, 22 ‘Investigations,’ ete. By B. A. Gould, 1869, p. 288. % “‘Saugethiere von Paraguay,’’ 1830, s. 4. % “History of Greenland,’’ Eng. translat., 1767, vol. i. p. 230. THE DESCENT OR ORIGIN OF MAN 55 those of the gentry.* From the correlation which exists, at least in some cases,” between the development of the ex- tremities and of the jaws, it is possible that in those classes which do not labor much with their hands and feet, the jaws would be reduced in size from this cause. That they are generally smaller in refined and civilized 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 muscles, 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. Tt is familiar to every one that watchmakers and engravers are liable to be short-sighted, while 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 eyesight and in the other senses, is no doubt the accumu- lated and transmitted effect of lessened use during many generations; for Rengger® states that he has repeatedly observed Europeans, who had been brought up and spent their whole lives with the wild Indians, who nevertheless 35 “‘Tntermarriage.’? By Alex. Walker, 1838, p. 377. 86 “The Variation of Animals under Domestication,” vol. i. p. 173. %1 ‘*Principles of Biology,’ vol. i. p. 455. 3% Paget, ‘‘Lectures on Surgical Pathology,”’ vol. ii., 1853, p. 209. 29 It is a singular and unexpected fact that sailors are inferior to lands- men in their mean distance 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 “restricted to the length of the vessel and the height of the masts.”’ 30 “The Variation of Anim&ls under Domestication,”’ vol. i. p. 8. 31 “Saéugethiere von Paraguay,’’ s. 8,10. I have had good opportunities for observing the extraordinary power of eyesight in the Fuegians. See also Lawrence (‘‘Lectures on Physiology,”’ etc., 1822, p. 404) on this same subject. M. Giraud-Teulon has recently collected (‘Revue des Cours Scientifiques,”’ 1870, p. 625) a large and valuable body of evidence proving that the cause of short-sight ‘‘c’est le travail assidu, de pres.” 56 THE DESCENT OF MAN did not equal them in the sharpness 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 dimensions 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 per- fect 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 plateaus of Peru; and Alcide d’Orbigny states® that, from continually breath- ing 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 observations have been doubted; but Mr. D. Forbes carefully measured many Aymaras, an allied race, living at the height of between ten thousand and fifteen thousand feet; and he informs me™ that they differ conspicuously from the men of all other races seen by him in the circum- ference and length of their bodies. In his table of measure- ments the stature of each man is taken at one thousand, 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; 8 Prichard, ‘‘Phys. Hist. of Mankind,”’ on the authority of Blumenbach, , vol. i., 1851, p. 311; for the statement by Pallas, vol. iv., 1844, p. 407. 28 Quoted by Prichard, ‘‘Researches into the Phys. History of Mankind,’ vol. v. p. 463. 34 Mr. Forbes’s valuable paper is now published in the ‘‘Journal of the Ethnolog. Soc. of London,’’ new series, vol. ii., 1870, p. 193. THE DESCENT OR ORIGIN OF MAN 57 while in two Europeans, measured at the same time, the femora to the tibize were as 244 to 230; and in three Negroes as 258 to 241. The humerus is likewise shorter relatively to the forearm. This shortening of that part of the limb which is nearest to the body appears to be, as suggested to me by Mr. Forbes, a case of compensation in 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 acclimatized 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 mortality. Nevertheless Mr. Forbes found a few pure families which had survived during two genera- tions, and he observed that they still inherited their charac- teristic peculiarities. But it was manifest, even without measurement, that these peculiarities had all decreased; and on measurement, their bodies were found not to be so much elongated as those of the men on the high plateau; while their femora had become somewhat lengthened, as had their tibie, although in a less degree. The actual measurements .mmay be seen by consulting Mr. Forbes’s memoir. From these observations, there can, I think, be no doubt that residence during many generations at a great elevation tends, both directly and indirectly, to induce inherited modifications in the proportions of the body.* Although man may not have been much modified during the latter stages of his existence through the increased or decreased use of parts, the facts now given show that his liability in this respect 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 8 Dr. Wilckens (“‘Landwirthschaft. Wochenblatt,’? No. 10, 1869) has lately published an interesting essay showing how domestic animals which live in mountainous regions have their frames modified. 58 THE DESCENT OF MAN changing from quadrupeds into bipeds, natural selection would probably have been greatly aided by the inherited effects of the increased or diminished use of the different parts of the body. Arrests of Development.—There is a difference between arrested development and arrested growth, for parts in the former state continue to grow while still retaining their early condition. Various monstrosities come under this head; and some, as a cleft-palate, are known to be occa- sionally 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 projection over the eyebrows, is largely developed, and the jaws are prognathous to an ‘‘effrayant’’ degree; so that these idiots somewhat re- semble the lower types of mankind. Their intelligence and most of their mental faculties are extremely feeble. KX They cannot acquire the power of speech, and are wholly incapa- ble of prolonged attention, but are much given to imitation. They are strong and remarkably active, continually gambol- ling and jumping about, and making grimaces. They often ascend stairs on all-fours, and are curiously fond of climbing up furniture or trees. We are thus reminded of the delight shown by almost all boys in climbing trees; and this again reminds us how lambs and kids, originally alpine animals, delight to frisk on any hillock, however small. x 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 using his mouth in aid of his hands while hunting 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 remarkably hairy.” 36 “Mémoire sur les Microcéphales,’’ 1867, pp. 50, 125, 169, 171, 184-198. 31 Prof. Laycock sums up the character of brute-like idiots by calling them theroid; ‘Journal of Mental Science,” July, 1863. Dr, Scott (‘‘The Deaf and THE DESCENT OR ORIGIN OF MAN 59 Reversion.—Many of the cases to be here given might have been introduced under the last heading. When a structure is arrested in its development, but still continues growing, until it closely resembles a corresponding structure 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 pro- genitor 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 ultimately to per- form its proper function, unless it had acquired such power during some earlier state of existence, when the present exceptional or arrested structure 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 more strictly Dumb,”’ 2d edit., 1870, p. 10) has often observed the imbecile smelling their food. See, on this same subject, and on the hairiness of idiots, Dr. Maudsley, “Body and Mind,’’ 1870, pp. 46-51. Pinel has also given a striking case of hairiness in an idiot. 38 In my “Variation of Animals under Domestication’’ (vol. ii. p. 57) I attributed the not very rare cases of supernumerary mammee in women to rever- sion. I was led to this as a probable conclusion, by the additional mamme being generally placed symmetrically 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 with supernumerary mamme. But I now find (see, for instance, Prof. Preyer, ‘‘Der Kampf um das Dasein,’’ 1859, s. 45) that mamme erratice occur in other situations, as on the back, in the armpit, and on the thigh; the mamme in this latter instance having given so much milk that the child was thus nourished. The probability that the addi- tional mammz are due to reversion is thus much weakened; nevertheless it still seems 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 mammez on the breast. Five cases have been recorded of the presence of more than a pair of mamme (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, in which two brothers exhibited this peculiarity; see also a paper by Dr. Bartels in ‘‘Reich- ert’s and du Bois-Reymond’s Archiv.,’’ 1872, p. 304, In one of the cases al- luded to by Dr. Bartels, a man bore five mammz, 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 mammz would ever have been developed in both sexes of mankind, had not his early progenitors been provided with more than a single pair. In the above work (vol. ii. p. 12), I also attributed, though with much hesita- 60 THE D&SCENT OF MAN under our present head of reversion. Certain structures, regularly occurring in the lower members of the group 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 nor- mal, 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 gra- dations 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 of body exists the cornua remain un-united. As the tion, the frequent cases of polydactylism in men and various animals to rever- sion. I was partly led to this through Prof. Owen’s statement, that some of the Ichthyopterygia possess more than five digits, and therefore, as I supposed, had retained a primordial condition; but Prof. Gegenbaur (‘‘Jenaischen Zeit- schrift,’? 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 cen- tral 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. I am 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 supernumerary digits might be due to reversion from the fact that such digits not only are strongly inherited, but, as I then believed, had the power of regrowth after amputation, like the normal digits of the lower vertebrata. But I have explained 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, inasmuch as arrested develop- ment and reversion are intimately related processes; that various structures in an embryonic or arrested condition, such as a cleft palate, bifid uterus, ete., are frequently accompanied 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 supernumerary digits and reversion to some lowly organized progenitor of man. THE DESCENT OR ORIGIN OF MAN 61 development of the uterus proceeds, the two cornua become gradually 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 ag 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 in- stance 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 per- forming’ 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 impossible, that the two simple, minute, primitive tubes should know how (if such an expression may be used) to grow into two distinct uteri, each with a well-constructed orifice and pas- sage, and each furnished 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 the principle of reversion, by which a long-lost structure is called back into existence, might serve as the guide for its full development, even after the. lapse of an enormous interval of time. Prof. Canestrini, after discussing the foregoing and vari- ous 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 39 See Dr. A. Farre’s well-known article in the ‘‘Cyclopzdia of Anatomy and Physiology,’ vol. v., 1859, p. 642. Owen, ‘‘Anatomy of Vertebrates,” vol, jii., 1868, p. 68%. Prof. Turner in “‘Mdinburgh Med. Journal,’’ February, 1865. 40 *Annuario della Soc. dei Naturalisti in Modena,” 1867, p. 83. Prof, 62 THE DESCENT OF MAN mammals, normally consists of two portions. This is its condition in the human foetus when two months old; and, through arrested development, it sometimes remains thus in man when adult, more especially in the lower prognathous races. Hence Canestrini concludes that some ancient pro- genitor of man must have had this bone normally divided into two portions, which afterward became fused together. In man the frontal bone consists of a single piece, but in the embryo, and in children, and in almost all the lower mam- mals, it consists of two pieces separated by a distinct suture. 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 brachy- cephalic 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 greater distance in the long line of descent from their early semi-human progenitors. Various other anomalies in man, more or less analogous to the foregoing, have been advanced by different authors, as cases of reversion; but these seem not a little doubtful, for we have to descend extremely low in the mammalian series before we find such structures normally present.” Canestrini gives extracts on this 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 aceidental. An- other paper on this same anomaly has been published by Dr. Saviotti in the “Gazzetta delle Cliniche,’’ Turin, 1871, where he says that traces of the division may be detected in about two per cent of adult skulls; he also remarks that it more frequently occurs in prognathous skulls, not of the Aryan race, than in others. See also G. Delorenzi on the same subject, ‘‘Tre nuovi casi d’anomalia dell’ osso, malare,’’ Torino, 1872, Also, E. Morselli, ‘‘Sopra una rara anomalia dell’ osso malare,’’ Modena, 1872. Still more recently Gruber has written a pamphlet on the division of this bone. I give these references because a re- viewer, without «ny grounds or scruples, has thrown doubts on my statements, 41 A whole series of cases is given by Isid. Geoffroy St.-Hilaire, ‘“Hist. deg Anomalies,’’ tom. iii. p. 437, A reviewer (‘Journal of Anat, and Physiology,” THE DESCENT OR ORIGIN OF MAN 63 In man, the canine teeth are perfectly efficient instru- fnents for mastication. But their true canine character, as Owen" remarks, ‘‘is indicated by the conical form of the crown, which terminates in an obtuse point, is convex out- ward 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 Aus- tralian. 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 func- tion is concerned, be considered as rudimentary. In every large collection of human skulls some may be found, as Hickel** observes, with the canine teeth projecting con- siderably 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 skull, figured by Wagner, is surprisingly 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 Naulette jaw they are spoken of as enormous.‘ Of the anthropomorphous apes the males alone have their 1871, p. 366) blames me much for not having discussed the numerous cases, which have been recorded, of various parts arrested in their development. He says that, according to my theory, ‘‘every transient condition of an. organ, dur- ing its development, is not only a means to an end, but once was an end in it- self.” This does not seem to me necessarily to hold good. Why should not variations occur during an early period of development, having no relation to reversion; yet such variations might be preserved and accumulated, if in any way serviceable, for instance, in shortening and simplifying the course of development? And again, why should not injurious abnormalities, such as atrophied or hypertrophied parts, which have no relation to a former state of existence, occur at an early period, as well as during maturity? 42 “Anatomy of Vertebrates,’ vol. ili., 1868, p. 323. 43 “‘Generelle Morphologie,’’ 1866, B. ii. s. elv. 4 Carl Vogt’s ‘‘Lectures on Man,?’ Eng. translat., 1864, p. 151. . 45 C, Carter Blake, on a jaw from La Naulette, ‘‘Anthropolog. Review,” 1867, p. 295. Schaaffhausen, ibid., 1868, p. 426. o4 THE DESVUENT OF MAN canines fully developed; but in the female gorilla, and ina less degree in the female orang, these teeth project consid- erably beyond the others; therefore the fact, of which I have been assured, that women sometimes have considerably pro- jecting canines, is no serious objection to the belief that their occasional great development in man is a case of reversion to an apelike prcegenitor. XHe 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 fore- fathers having been provided with these formidable weapons, will probably reveal, by sneering, the line of his descent. For though he no longer intends, nor has the power, to use these teeth as weapons, he will unconsciously retract his ‘snarling muscles’’ (thus named by Sir C. 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. Prof. Vlacovich*? examined forty male subjects, and found a mus- cle, 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 muscle de- veloped 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 intelligfble; 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 4 *‘The Anatomy of Expression,’ 1844, pp. 110, 181. 41 Quoted by Prof. Canestrini in the ‘‘Annuario,”’ etc., 1867, p. 90. 48 These papers deserve careful study by any one who desires to learn how frequently our muscles vary, and in varying come to resemble those of the Quadrumana. The following references relate to the few points touched on jn my text: ‘Proc. Royal Soc., vol. xiv., 1865, pp. 379-384; vol. xv., 1866, pp. 241, 242; vol. xv., 186%, p. 544; vol. xvi., 1868, p. 524. I may here add that Dr. Murie and Mr. St. George Mivart have shown in their Memoir on the Lemuroidea (‘‘Transact. Zoolog. Soc.,”’ vol. vii., 1869, p. 96) how extraordinarily THE DESCENT OR ORIGIN OF MAN 65 minutely described a vast number of muscular variations in man, which resemble normal structures in the lower animals. The muscles which closely resemble those regu- larly present in our nearest allies, the Quadrumana, are’ too numerous to be here even specified. In a single male sub- ject, having a strong bodily frame, and well-formed skull, no less than seven muscular variations 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 clavicule,’’ such as is found in all kinds of apes, and which is said to occur in about one out of sixty human subjects.“® Again, this man had ‘‘a special abductor of the metatarsal bone of the fifth digit, such as Prof. Huxley and Mr. Flower have shown ’ to exist uniformly in the higher and lower apes.’’ I will give only two additional cases; the acromio-basilar muscle is found in all mammals below man, and seems to be correlated with a quadrupedal gait, and it occurs in about one out of sixty human subjects. In the lower extremities Mr. Brad- ley® 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 resemblances are either perfect or imperfect; yet in the latter case they are manifestly of a transitional nature. Certain variations are more common in man, and others in woman, without our being able to 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 ani- mals still lower in the scale, are numerous in the Lemuroidea, 49 See also Prof. Macalister in ‘‘Proc. R. Irish Academy,”’ vol. x., 1868, . 124, 50 Mr. Champneys in ‘‘Journal of Anat. and Phys.,’’ Nov., 1871, p. 178. 51 ‘Journal of Anat. and Phys.,’’ May, 1872, p. 421. . 82 Prof, Macalister (ibid., p. 121) has tabulated his observations, and finds that muscular abnormalities are most frequent in the forearms, secondly, in the face, thirdly, in the foot, ete. 66 THE DESCENT OF MAN 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 comprehen- sive knowledge of general and scientific anatomy.” © That this unknown factor is reversion to a former state of existence may be admitted as in the highest degree prob- able. It is quite incredible that a man should through mere accident abnormally resemble certain apes in no less than seven of his muscles, if there had been no genetic con- nection between them. On the other hand, if man is de- scended from some apelike creature, no valid reason can be assigned why certain muscles should not suddenly reap- pear after an interval of many thousand generations; in the same manner as, with horses, asses and mules, dark-colored stripes suddenly reappear on the 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 53 The Rev. Dr. Haughton, after giving (‘‘Proc. R. Irish Academy,’’ June 27, 1864, p. 715) a remarkable case of variation in the human flexor pollicis longus, adds: ‘“‘This remarkable example shows 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 upward into a man, or a man passing downward into a macaque, or as a con- genital freak of nature, I cannot undertake to say.’? It is satisfactory to hear so capable an anatomist, and so imbittered an opponent of evolutionism, admit- ting even the possibility of either of his first propositions. 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. 54 Since the first edition of this book appeared, Mr. Wood has published another memoir in the ‘‘Phil. Transactions,’’ 1870, p. 83, on the varieties of the muscles of the human neck, shoulder and chest, He here shows how ex- tremely variable these muscles are, and how often and how closely the varia- tions resemble the normal muscles of the lower animals, He sums up by re- murking: ‘‘It will be enough for my purpose if I have succeeded in showing the more important forms which, when occurring as varieties in the human sub- ject, tend to exhibit in a sufficiently marked manner what may be considered as proofs and examples of the Darwinian principle of reversion, or law of aghiehie tance, in this department of anatomical science.’ THE DESCENT OR ORIGIN OF MAN 67 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 condi- tion, the same organ in its normal state in certain mammals. Some parts which are rudimentary in man, as the os coceyx in both sexes, and the mamme in the male sex, are always present; while others, such as the supra-condyloid foramen, only occasionally appear, and therefore might have been in- troduced under the head of reversion. These several rever- sionary structures, as well as the strictly rudimentary ones, reveal the descent of man from some lower form in an un- mistakable 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 part. Various monstrosities, as I. Geof- froy repeatedly insists, are thus intimately connected. Homologous structures are particularly liable to change together, as we see on the opposite sides of the body, and in the upper and lower extremities. Meckel long ago re- marked, 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 leg. The organs of sight and hearing, the teeth and hair; the color of the skin and of the hair, color and constitution, are more or less cor- related.** Prof. 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 probability under the foregoing heads, there is a large class of variations which may be provisionally called spon- 55 The authorities for these several statements are given in my ‘‘Variation of Animals under Domestication,’’ vol. ii. pp. 320-335, 68 THE DESCENT OF MAN taneous, for to our ignorance they appear to arise without any exciting cause. It can, however, be shown that such variations, whether consisting of slight individual differ- ences, or of strongly marked and abrupt deviations of structure, depend much more on the constitution of the organism than on the nature of the conditions to which it has been subjected.* Rate of Increase.—Civilized populations have been known under favorable conditions, as in the United States, to double their numbers in twenty-five years; and, according to a cal- culation by Euler, this might occur in a little over twelve years.*’ At the former rate the present population 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 difficulty 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 civilized 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 greater mortality, from various diseases, of the inhabitants of crowded and miserable houses, at all ages. The effects of severe epidemics and wars are soon counter- balanced, and more than counterbalanced, in nations placed under favorable conditions. Emigration also comes in aid as a temporary check, but, with the extremely poor classes, not to any great extent. There is reason to suspect, as Malthus has remarked, that 56 This whole subject has been discussed in chap. xxiii. vol. ii. of my *‘Variation of Animals and Plants under Domestication.’’ 57 See the ever-memorable ‘‘Essay on the Principle of Population,’’ by the Rey, T, Malthus, vol, i,, 1826, pp. 6, 517, THE DESCENT OR ORIGIN OF MAN 69 the reproductive power is actually less in barbarous than in civilized 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 believed, 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 much nutritious food as civilized men, would be actually less prolific. I have shown in a former work, that all our domesticated quadrupeds and birds, and all our cultivated plants, are more fertile than the corre- sponding species in a state of nature. It is no valid objec- tion 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, ex- pect that civilized men, who in one sense are highly domes- ticated, would be more prolific than wild men. It is also probable that the increased fertility of civilized nations would become, as with our domestic animals, an inherited charac- ter: 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 civilized people, they would no doubt rapidly increase if their numbers were not by some means rigidly kept down. The Santali, or hill-tribes of India, have recently afforded a good illustration of this fact; for, as shown by Mr. Hunter,” they have increased at an extraordinary rate since vaccina- tion 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 58 ‘Variation of Animals and Plants under Domestication,”’ vol. ii. pp. 111- 113, 163, . 89 Mr. Sedgwick, ‘British and Foreign Medico-Chirurg. Review,”’ July, 1863, p. 170. 60 “The Annals of Rural Bengal,” by W. W. Hunter, 1868, p. 259, 70 : THE. DESCENT OF MAN the adjoining districts, and worked for hire. Savages almost always marry; yet there is some prudential restraint, for they ‘do not commonly marry at the earliest possible age. The young men are often required to show 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 civilized 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 be injured. 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 periodical, depending chiefly on extreme seasons, all tribes must fluctuate in number. They cannot steadily and regularly increase, as there is no arti- ficial increase in 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 neighbors. They are liable to many accidents on land and water in their search for food; and in some countries they suffer much from the larger beasts of prey. Even in India, districts have been depopulated by the ravages of tigers. Malthus has discussed these several checks, but he does not lay stress enough on what is probably the most impor- tant 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 Mr. M‘Lennan” has shown, on a still more extensive scale. These practices appear to have originated in savages recognizing the diffi- culty, or rather the impossibility, of supporting all the in- fants that are born. Licentiousness may also be added to the foregoing checks; but this does not follow from failing 61 ‘‘Primitive Marriage,’’ 1865. THE DESCENT OR ORIGIN OF MAN 71 means of subsistence; though there is reason to believe that in some cases (as in Japan) it has been intentionally encour- aged 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 practiced infanticide or polyandry; for the instincts of the lower animals are never so perverted” as to lead them regularly to destroy their own offspring, or to be quite devoid of jealousy. There would have been no prudential restraint from marriage, and the sexes would have freely united at an early age. Hence the progenitors of man would have tended to increase rap- idly; 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 ele- phant, 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 district became fully stocked, this same power was diminished. No doubt 8 A writer in the “‘Spectator’’ (March 12, 1871, p. 320) comments as fol- lows on this passage: ‘‘Mr. Darwin finds himself compelled to reintroduce a new doctrine of the fall of man. He shows that the instincts of the higher animals are far nobler than the habits of savage races of men, and he finds him- self, therefore, compelled to reintroduce—in a form of the substantial orthodoxy of which he appears to be quite unconscious—and to introduce as a scientific hypothesis the doctrine that man’s gain of knowledge was the cause of a tem- porary but long-enduring moral deterioration, as indicated by the many foul customs, especially as to marriage, of savage tribes. What does the Jewish tradition of the moral degeneration of man through his snatching at a knowl- edge forbidden him by his highest instinct assert beyond this?”’ 72 THE DESCENT OF MAN in this case, and in all others, many checks concur, and different checks under different circumstances; periodical dearths, depending on unfavorable seasons, being probably the most important of all. So it will have been with the early progenitors of man. Natural Selection.—We have now seen that man is vari- able 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 loweranimals. Man has spread widely over the face of the earth, and must have been exposed, during his incessant migrations,” to the most diversified conditions. The inhabitants of Tierra del Fuego, the Cape of Good Hope, and Tasmania in the one hemi- sphere, and of the Arctic regions in the other, must have passed through many climates, 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 the rigid law of natural selection. Beneficial variations of all kinds will thus, either occasionally or habitually, have been preserved, and injurious ones eliminated. I do not refer to strongly marked deviations of structure, which occur only at long intervals of time, but to mere individ- ual differences. We know, for instance, that the muscles of our hands and feet, which determine our powers of move- ment, are liable, like those of the lower animals,® to inces- sant variability. If then the progenitors of man inhabiting any district, especially one undergoing some change in its conditions, were divided into two equal bodies, the one-half 63 See some good remarks to this effect by W. Stanley Jevons, ‘‘A Deduc- tion from Darwin’s Theory,”’ ‘‘Nature,’’ 1869, p. 231. 64 Latham, ‘‘Man and his Migrations,’’ 1851, p. 135, 65 Messrs. Murie and Mivart in their ‘‘Anatomy of the Lemuroidea’’ (‘‘Trans- act. Zoolog. Soc.,’’ vol. vii. 1869, pp. 96-98) say: ‘“Some muscles are so irregular in their distribution that they cannot be well classed in any of the above groups.’? These muscles differ even on the opposite sides of the same individual. THE DESCENT OR ORIGIN OF MAN 73 which included all the individuals best adapted by their powers of movement for gaining subsistence, or for defend- ing 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 than any other highly organized form, and all others have yielded before him. He mani- festly owes this immense superiority to his intellectual facul- ties, 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 shows that even the smallest pro- ficiency in it might require more brain DNS than the great- est proficiency in any other direction.’’ He has invented and is able to use various weapons, tools, traps, etc., with which he defends himself, kills or catches prey, and other- wise obtains food. He has made rafts or canoes for fishing or crossing over to neighboring fertile islands. He has dis- covered the art of making fire, by which hard and stringy roots can be rendered digestible, and poisonous roots or “herbs innocuous. This discovery of fire, probably the great- est ever made by man, excepting language, dates from be- fore 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 Mr. Wallace” 66 Limits of Natural Selection, ‘‘North American Review,’’ October, 1870, p. 295, “Quarterly Review,” April, 1869, p. 392. This subject is more fully dis- cussed in Mr. Wallace’s ‘Contributions to the Theory of Natural Selection,’ 1870, in which all the essays referred to in this work are republished. The Descent—Vou. I.—4 TE ; THE DESCENT OF MAN maintains 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 remainder of this chapter will be devoted; the development of the intellectual and social or moral faculties being dis- cussed in a later chapter. Even to hammer with precision 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 de- fending himself, or in killing birds, requires the most con- summate perfection in the correlated action of the muscles of the hand, arm, and shoulder, and, further, a fine sense of touch. In throwing a stone or spear, and in many other actions, a man must 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,” re- marks, the shaping fragments of stone into knives, lances, or arrow-heads shows ‘‘extraordinary ability and long prac- tice.”” This is to a great extent proved by the fact that primeval men practiced a division of labor; each man did not manufacture his own flint tools or rude pottery, but cer- tain individuals appear to have devoted themselves to such work, no doubt receiving in exchange the produce of the ‘‘Bssay on Man’? has been ably criticised by Prof. Claparéde, one of the most distinguished zoologists in Europe, in an article published in the ‘‘Bibliothéque Universelle,’’? June, 1870. The remark quoted in my text will surprise every one who has read Mr. Wallace’s celebrated paper on ‘“‘The Origin of Human Races deduced from the Theory of Natural Selection,”’ originally published in the ‘‘Anthropological Review,’’ May, 1864, p. elviii. I cannot here resist quot- ing a most just remark by Sir J. Lubbock (‘‘Prehistoric Times,’ 1865, p. 479) in reference to this paper, namely, that Mr. Wallace, ‘‘with characteristic un- selfishness, ascribes it (¢.e., the idea of natural selection) unreservedly to Mr. Darwin, although, as is well known, he struck out the, idea independently, and published it, though not with the same elaboration, at the same time.’’ 6 Quoted by Mr. Lawson Tait in his ‘‘Law of Natural Selection,” ‘‘Duvlin Quarterly Journal of Medical Science,’’ Feb., 1869. Dr. Keller is likewise quoted to the same effect. THE DESCENT OR ORIGIN OF MAN 75 chase. Archeologists are convinced that an enormous in- terval of time elapsed before our ancestors thought of grind- ing chipped flints into smooth tools. One can hardly doubt that a manlike animal who possessed a hand and arm suffi- ciently perfect to throw a stone with precision, or to form a flint into a rude tool, could, with sufficient practice, as far as mechanical skill alone is concerned, make almost anything which a civilized mancan make. The structure of the hand in this respect may be compared with that of the vocal or- gans, which in the apes are used for uttering various signal- cries, or, aS in one genus, musical cadences; but in man the closely similar vocal organs have become adapted through the inherited effects of use for the utterance of articulate language. Turning now to the nearest allies of men, and therefore to the best representatives of our early progenitors, we find that the hands of the Quadrumana are constructed on the same general pattern as our own, but are far less perfectly adapted for diversified uses. Their hands do notserve for locomotion so well as the feet of a dog; as may be seen in such monkeys as the chimpanzee and orang, which walk on the outer margins of the palms, or on the knuckles.” Their hands, however, are admirably adapted for climbing trees. Monkeys seize thin branches or ropes, with the thumb on one side and the fingers and palm on the other, in the same manner as we do. They can thus also lift rather large ob- jects, such as the neck of a bottle, to their mouths. Ba- boons turn over stones and scratch up roots with their hands. They seize nuts, insects, or other small objects with the thumb in opposition to the fingers, and no doubt they thus extract eggs and the young from the nests of birds. Ameri- can monkeys beat the wild oranges on the branches until the rind is cracked, and then tear it off with the fingers of the two hands. In a wild state they break open hard fruits with stones. Other monkeys open mussel-shells with the two thumbs. With their fingers they pull out thorns and 69 Owen, ‘‘Anat, of Vertebrates,”’ iii. p 71. 76 THE DESCENT OF MAN burs, and hunt for each other’s parasites. They roll down stones, or throw them at their enemies: nevertheless, they are clumsy in these various actions, and, as I have myself seen, are quite unable to throw a stone with precision. It seems to me far from true that because ‘‘objects are grasped clumsily’? by monkeys, ‘‘a much less specialized organ of prehension’’ would have served them” equally well with their present hands. On the contrary, I see no reason to doubt that more perfectly constructed hands would have been an advantage to them, provided that they were not thus rendered less fitted for climbing trees. We may suspect that a hand as perfect as that of man would have been disadvantageous for climbing, for the most arboreal monkeys in the world, namely, Ateles in America, Colobus in Africa, and Hylobates in Asia, are either thumbless, or their toes partially cohere, so that their limbs are converted into mere grasping hooks.” As soon as some ancient member in the great series of the Primates :came to be less arboreal, owing to a change in its manner of procuring subsistence, or to some change in the surrounding conditions, its habitual manner of progression would have been modified; and thus it would have been rendered more strictly quadrupedal or bipedal. Baboons frequent hilly and rocky districts, and only from necessity climb high trees;” and they have acquired almost the gait of a dog. Man alone has become a biped; and we can, I think, partly see how he has come to assume his erect atti- tude, "which forms one of his most conspicuous characters. Man could not have attained-his present dominant position in the world without the use of his hands, which are so ad- 7 “Quarterly Review,” April, 1869, p. 392. 1 In Hylobates syndactylus, as the name expresses, two of the toes regu- larly cohere; and this, as Mr. Blyth informs me, is occasionally the case with the toes of A agilis, lar, and leuciscus. Colobus is strictly arboreal and extraordinarily active (Brehm, “Thierlehen,’’? B, i. s. 50), but whether a better climber than the species of the allied genera, I do not know. It deserves notice that the feet of the sloths, the most arboreal animals in the world, are wonderfully hooklike. 82 Brehm, ‘‘Thierleben,” B, i. s, 80. THE DESCENT OR ORIGIN OF MAN T7 mirably adapted to act in obedience to his will. SirC. Bell” insists that ‘‘the hand supplies all instruments, and by its correspondence with the intellect gives him universal domin- ion.” But the hands and arms could hardly have become perfect enough to have manufactured weapons, or to have hurled stones and spears with a true aim, as long as they were habitually used for locomotion and for supporting the whole weight of the body, or, as before remarked, so long as they were especially fitted for climbing trees. Such rough treatment would also have blunted the sense of touch, on which their delicate use largely depends. From these causes alone it would have been an advantage to man to become a biped; but for many actions it is indispensable that the arms and whole upper part of the body should be free; and he must for this end stand firmly on his feet. To gain this great advantage, the feet have been rendered flat; and the great toe has been peculiarly modified, though this has entailed the almost complete loss of its power of prehen- sion. It accords with the principle of the division of physi- ological labor prevailing throughout the animal kingdom, that as the hands became perfected for prehension, the feet should have become perfected for support and locomotion. With some savages, however, the foot has not altogether lost its prehensile power, as shown by their manner of climb- ing trees, and of using them in other ways.” If it be an advantage to man to stand firmly on his feet and to have his hands and arms free, of which, from his pre- eminent success in the battle of life, there can be no doubt, then I can see no reason why it should not have been ad- vantageous to the progenitors of man to have become more and more erect or bipedal. They would thus have been 7 *‘The Hand,”’ etc., ‘‘Bridgewater Treatise,’’? 1833, p. 38. ™ Hackel has an excellent discussion on the steps by which man became a biped; ‘‘Natirliche Schépfungsgeschichte,’’ 1868, s. 507%. Dr. Buchner (‘‘Conférences sur la Théorie Darwinienne,’’ 1869, p. 135) has given good eases of the use of the foot as a prehensile organ by man; and has also written on the manner of progression of the higher apes, to which I allude in the fol- lowing paragraph; see also Owen (‘‘Anatomy of Vertebrates,”’ vol. iii. p. 71) on this latter subject. 78 THE DESCENT OF MAN better able to defend themselves with stones or clubs, to attack their prey, or otherwise to obtain food. The best built individuals would in the long run have succeeded best, and have survived in larger numbers. If the gorilla and a few allied forms had become extinct, it might have been argued, with great force and apparent truth, that an animal could not have been gradually converted from a quad- ruped into a biped, as all the individuals in an intermediate condition would have been miserably ill-fitted for progres- sion. But we know (and this is well worthy of reflection) that the anthropomorphous apes are now actually in an intermediate condition; and no one doubts that they are on the whole well adapted for their conditions of life. Thus the gorilla runs with a sidelong shambling gait, but more commonly progresses by resting on its bent hands. The long-armed apes occasionally use their arms like crutches, swinging their bodies forward between them, and some kinds of Hylobates, without having been taught, can walk or run upright with tolerable quickness; yet they move awkwardly and much less securely than man. We see, in short, in ex- isting monkeys a manner of progression intermediate between that of a quadruped and a biped; but, as an unprejudiced judge” insists, the anthropomorphous apes approach in structure more nearly to the bipedal than to the quadru- pedal type. As the progenitors of man became more and more erect, with their hands and arms more and more modified for pre- hension and other purposes, with their feet and legs at the same time transformed for firm support and progression, endless other changes of structure would have become nec- essary. The pelvis would have.to be broadened, the spine peculiarly curved, and the head fixed in an altered position, all which changes have been attained by man. Prof. Schaaft- hausen” maintains that ‘‘the powerful mastoid processes of 7 Prof. Broca, La Constitution des Vertébres caudales: ‘‘La Revue d’An- thropologie,”’ 1872, p. 26 (separate copy). 76 “Qn the Primitive Form of the Skull,” translated in “Anthropological THE DESCENT OR ORIGIN OF MAN 79 the human skull are the result of his erect position’; and these processes are absent in the orang, chimpanzee, etc., and are smaller in the gorilla than in man. Various other structures, which appear connected with man’s erect posi- tion, might here have been added. It is very difficult to decide how far these correlated modifications are the result of natural selection, and how far of the inherited effects of the increased use of certain parts, or of the action of one part on another. No doubt these means of change often co-operate; thus when certain muscles, and the crests of bone to which they are attached, become enlarged by habit- ual use, this shows that certain actions are habitually per- formed and must be serviceable. Hence the individuals which performed them best would tend to survive in greater numbers. The free use of the arms and hands, partly the cause and partly the result of man’s erect position, appears to have led in an indirect manner to other modifications of structure. The early male forefathers of man were, as previously stated, probably furnished with great canine teeth; but as they gradually acquired the habit of using stones, clubs, or other weapons, for fighting with their enemies or rivals, they would use their jaws and teeth less and less. In this case, the jaws, together with the teeth, would become reduced in size, as we may feel almost sure from innumerable analogous cases. In a future chapter we shall meet with a closely parallel case, in the reduction or complete disappearance of the canine teeth in male ruminants, apparently in relation with the development of their horns; and in horses, in rela- tion to their habit of fighting with ‘their incisor teeth and hoofs. In the adult male anthropomorphous apes, as Riitimeyer™ and others have insisted, it is the effect on the skull of the Review,’? Oct., 1868, p. 428. Owen (‘‘Anatomy of Vertebrates,” vol. ii., 1866, Pp. 651) on the mastoid processes in the higher apes. ‘Die Grenzen der Thierwelt, eine Betrachtung zu Darwin’s Lehre,’ 1888, 8. 51. 80 THE DESCENT OF MAN great development of the jaw-muscles that causes it to differ so greatly in many respects from that of man, and has given to these animals ‘‘a truly frightful physiognomy.’’ There- fore, as the jaws and teeth in man’s progenitors gradually became reduced in size, the adult skull would have come to resemble more and more that of existing man. As we shall hereafter see, a great reduction of the canine teeth in the males would almost certainly affect the teeth of the females through inheritance. _ As the various mental faculties gradually developed themselves the brain would almost certainly become larger. No one, I presume, doubts that the large proportion which the size of man’s brain bears to his body, compared to the same proportion in the gorilla or orang, is closely connected with his higher mental powers. We meet with closely analo- gous facts with insects, for in ants the cerebral ganglia are of extraordinary dimensions, and in all the Hymenoptera these ganglia are many times larger than in the less intelli- gent orders, such as beetles.”* On the other hand, no one supposes that the intellect of any two animals or of any two men can be accurately gauged by the cubic contents of their skulls. It is certain that there may be extraordinary mental activity with an extremely small absolute mass of nervous matter: thus the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cere- bral ganglia are not so large as the quarter of a small pin’s head. Under this point of view, the brain of an ant is one of the most marvellous atoms of matter in he world, perhaps more so than the brain of a man. The belief that there exists in man some close relation between the size of the brain and the development of the intellectual faculties is supported by the comparison of the skulls of savage and civilized races, of ancient and modern people, and by the analogy of the whole vertebrate series. 8 Dujardin, ‘‘Annales des Sc. Nat.,’’ 3d series, Zoolog., tom. xiv., 1850, p. 203. See also Mr. Lowne, “Anatomy and Phys. of the Musca vomitoria, % 1870, p. 14. My son, Mr. F. Darwin, dissected igs me the cerebral ganglia ‘of the Formica rufa, J THE DESCENT OR ORIGIN OF MAN 81 Dr. J. Barnard Davis has proved,” by many careful meas- urements, that the mean internal capacity of the skull in Europeans is 92.3 cubic inches; in Americans 87.5; in Asi- atics 87.1; and in Australians only 81.9 cubic inches. Prof. Broca® found that the nineteenth century skulls from graves in Paris were larger than those from vaults of the twelfth century, in the proportion of 1484 to 1426; and that the increased size, as ascertained by measurements, was exclu- sively in the frontal part of the skull—the seat of the intel- lectual faculties. Prichard is persuaded that the present inhabitants of Britain have ‘‘much more capacious brain- cases’’ than the ancient inhabitants. Nevertheless, it must be admitted that some skulls of very high antiquity, such as the famous one of Neanderthal, are well developed and capa- cious.“ With respect to the lower animals, M. E. Lartet,” by comparing the crania of tertiary and recent mammals belonging to the same groups, has come to the remarkable conclusion that the brain is generally larger and the convo- lutions are more complex in the more recent forms. On.the other hand, I have shown™ that the brains of domestic rab- bits are considerably reduced in bulk, in comparison with those of the wild rabbit or hare; and this may be attributed to their having been closely confined during many genera- tions, so that they have exerted their intellect, instincts, senses, and voluntary movements but little. 79 ‘*Philosophical Transactions,’’ 1869, p. 513. 8 “Tes Sélections,’? M. P. Broca, ‘‘Revue d’Anthropologie,’’ 1873; see also, as quoted in C. Vogt’s “‘Lectures on Man,’’ Eng. translat., 1864, pp. 88, 90. Prichard, ‘‘Phys. Hist. of Mankind,”’ vol. i., 1838, p. 305. 81 In the interesting article just referred to, Prof. Broca has well remarked, that in civilized nations the average capacity of the skull must be lowered by the preservation of a considerable number of individuals, weak in mind and body, who would have been promptly eliminated in the savage state. On the other hand, with savages, the average includes only the more capable individ- uals, who have been able to survive under extremely hard conditions of life. Broca thus explains the otherwise inexplicable fact, that the mean capacity of the skull of the ancient Troglodytes of Lozére is greater than that of modern Frenchmen. 82 “Comptes rendus des Sciences,”’ etc., June 1, 1868. 8 “The Variation of Animals and Plants under Domestication, pp. 124-129. : ” vol. i. 82 THE DESCENT OF MAN The gradually increasing weight of the brain and skull in man must have influenced the development of the sup- porting spinal column, more especially while he was becom- ing erect. As this change of position was being brought about, the internal pressure of the brain will also have in- | fluenced the form of the skull; for many facts show how easily the skull is thus affected. Hthnologists believe that it is modified by the kind of cradle in which infants sleep. Habitual spasms of the muscles, and a cicatrix from a severe burn, have permanently modified the facial bones. In young persons whose heads have become fixed either sidewise or backward, owing to disease, one of the two eyes has changed its position, and the shape of the skull has been altered ap- parently by the pressure of the brain in a new direction.“ I have shown that with long-eared rabbits even so trifling a cause as the lopping forward of one ear drags forward almost every bone of the skull on that side; so that the bones on the opposite side no longer strictly correspond. Lastly, if any animal were to increase or diminish much in general size, without any change in its mental powers, or if the mental powers were to be much increased or diminished, without any great change in the size of the body, the shape of the skull would almost certainly be altered. I infer this from my observations on domestic rabbits, some kinds of which have become very much larger than the wild animal, while others have retained nearly the same size, but in both cases the brain has been much reduced relatively to the size of the body. Now I was at first much surprised on finding that in all these rabbits the skull had become elongated or dolichocephalic; for instance, of two skulls of nearly equal breadth, the one from a wild rabbit and the other from a 84 Schaaffhausen gives from Blumenbach and Busch the cases of the spasms and cicatrix, in ‘‘Anthropol. Review,’’ Oct., 1868, p. 420. Dr. Jarrold (‘‘Anthropologia,’? 1808, pp. 115, 116) adduces from Camper and from his own observations, cases of the modification of the skull from the head being fixed in an unnatural position. He believes that in certain trades, such as that of a shoemaker, where the head is habitually held forward, the forehead becomes more rounded and prominent. THE DESCENT OR ORIGIN OF MAN 83 large domestic kind, the former was 8.15 and the latter 4.3 inches in length.** One of the most marked distinctions in different races of men is that the skull in some is elongated, and in others rounded; and here the explanation suggested by the case of the rabbits may hold good; for Welcker finds that ‘‘short men incline more to brachycephaly, and tall men to dolichocephaly’’ ;** and tall men may be compared with the larger and longer- bodied rabbits, all of which have elongated skulls, or are dolichocephalic. From these several facts we can understand, to a certain extent, the means by which the great size and more or less rounded form of the skull have been acquired by man; and these are characters eminently distinctive of him in compari- son with the lower animals. Another most conspicuous difference between man and the lower animals is the nakedness of his skin. Whales and porpoises (Cetacea), dugongs (Sirenia), and the hippo- potamus are naked; and this may be advantageous to them for gliding through the water; nor would it be injurious to them from the loss of warmth, as the species which inhabit the colder regions are protected by a thick layer of blubber, serving the same purpose as the fur of seals and otters. Elephants and rhinoceroses are almost hairless; and as cer- tain extinct species, which formerly lived under an Arctic climate, were covered with long wool or hair, it would al- most appear as if the existing species of both genera had lost their hairy covering from exposure to heat. This appears the more probable, as the elephants in India which live on elevated and cool districts are more hairy” than those on the lowlands. May we then infer that man became divested of hair from having aboriginally inhabited some tropical land ? That the hair is chiefly retained in the male sex on the chest and face, and in both sexes at the junction of all four limbs 8 ‘Variation of Animals,’’ ete., vol. i. p. 117, on the elongation of the skull; p. 119, on the effect of the lopping of one ear. %© Quoted by Schaaffhausen, in *Anthropolog. Review,’’ Oita 1868, p. 419, 81 Owen, ‘‘Anatomy of Vertebrates,’ vol. ili. p. 619. : * 84 THE DESCENT OF MAN with the trunk, favors the inference—on the assumption that the hair was lost before man became erect; for the parts which now retain most hair would then have been most protected from the heat of the sun. The crown of the head, however, offers a curious exception, for at all times it must have been one of the most exposed parts, yet it is thickly clothed with hair. The fact, however, that the other members of the order of Primates, to which man belongs, although inhabiting various hot regions, are well clothed with hair, generally thickest on the upper surface," is op- posed to the supposition that man became naked through the action of the sun. Mr. Belt believes® that within the tropics it is an advantage to man to be destitute of hair, as he is thus enabled ‘to free himself of the multitude of ticks (acari) and other parasites, with which he is often infested, and which sometimes cause ulceration. But whether this evil is of sufficient magnitude to have led to the denudation of his body through natural selection, may be doubted, since none of the many quadrupeds inhabiting the tropics has, as far as I know, acquired any specialized means of relief. The view which seems to me the most probable is that man, or rather primarily woman, became divested of hair for orna- mental purposes, as we shall see under Sexual Selection; and, according to this belief, it is not surprising that man should differ so greatly in hairiness from all other Primates, for characters, gained through sexual selection, often differ to an extraordinary degree in closely related forms. According to a popular impression, the absence of a tail 88 Isidore Geoffroy St.-Hilaire remarks (“‘Hist. Nat. Générale,’ tom. ii., 1859, pp. 215-217) on the head of man being covered with long hair; also on the upper surfaces of monkeys and of other mammals being more thickly clothed than the lower surfaces. ~ This has likewise been observed by various authors, Prof. P. Gervais (‘‘Hist. Nat. des Mammiféres,’’ tom. i,, 1854, p. 28), however, states that in the Gorilla the hair is thinner on the back, ‘where it is partly rubbed off, than on the lower surface. 89 “The Naturalist in Nicaragua,’? 1874, p. 209. As some confirmation of Mr. Belt’s view, I may quote the following passage from Sir W. Denison (‘Varieties of Vice-Regal Infe,”? vol. i, 1870, p. 440): ‘It is said to be a practice with the Australians, when the vermin get troublesome, to singe themselves.”’ THE DESCENT OR ORIGIN OF MAN 85 is eminently distinctive of man; but as those apes which come nearest to him are destitute of this organ, its disap- pearance does not relate exclusively to man. The tail often differs remarkably in length within the same genus; thus in some species of Macacus it is longer than the whole body, and is formed of twenty-four vertebra; in others it consists of a scarcely visible stump, containing only three or four vertebrz. In some kinds of baboons there are twenty-five, while in the mandrill there are ten very small stunted caudal vertebrz, or, according to Cuvier, sometimes only five. The tail, whether it be long or short, almost always tapers toward the end; and this, I presume, results from the atro- phy of the terminal muscles, together with their arteries and nerves, through disuse, leading to the atrophy of the termi- nal bones. But no explanation can at present be given of the great diversity which often occurs in its length. Here, however, we are more specially concerned with the complete external disappearance of the tail. Prof. Broca has recently shown” that the tail in all quadrupeds consists of two por- tions, generally separated abruptly from each other; the basal portion consists of vertebre, more or less perfectly channelled and furnished with apophyses like ordinary ver- tebre; whereas those of the terminal portion are not chan- nelled, are almost smooth, and scarcely resemble true verte- bre. A tail, though not externally visible, is really present in man and the anthropomorphous apes, and is constructed on exactly the same pattern in both. In the terminal por- tion the vertebre, constituting the os coccyx, are quite rudi- mentary, being much reduced in size and number. In the basal portion the vertebre are likewise few, are united firmly together, and are arrested in development; but they have been rendered much broader and flatter than the corre- sponding ‘vertebre in the tails of other animals; they consti- 9 Mr. St, George Mivart, ‘‘Proe. Zoolog. Soc.,”’ 1865, pp. 562, 583. Dr. J. E. Gray, ‘‘Cat. Brit. Mus.: Skeletons.’? Owen, ‘Anatomy of Vertebrates,” vol. ii. p. 517. Isidore Geoffroy, ‘“‘Hist. Nat. Gén.,”’ tom. ii. p, 244, 1 “Revue d’Anthropologie,”? 1872; ‘“‘La Constitution des Vertébres cau- dales,’’ 86 THE DESCENT Of MAN tute what Broca calls the accessory sacral vertebra. These are of functional importance by supporting certain internal parts and in other ways; and their modification is directly connected with the erect or semi-erect attitude of man and the anthropomorphous apes. This conclusion is the more trustworthy, as Broca formerly held a different view, which he has now abandoned. ‘The modification, therefore, of the basal caudal vertebree in man and the higher apes may have been effected, directly or indirectly, through natural selection. But what are we to say about the rudimentary and vari- able vertebrae of the terminal portion of the tail, forming the os coccyz? A notion which has often been, and will no doubt again be, ridiculed, namely, that friction has had something to do with the disappearance of the external portion of the tail, is not so ridiculous as it at first ap- pears. Dr. Anderson™ states that the extremely short tail of Macacus brunneus is formed of eleven vertebra, including the imbedded basal ones. The extremity is tendinous and contains no vertebre; this is succeeded by five rudimentary ones, so minute that together they are only one line and a half in length, and these are permanently bent to one side in the shape of a hook. The free part of the tail, only a little above an inch in length, includes only four more small vertebrae. This short tail is carried erect; but about a quar- ter of its total length is doubled on to itself to the left; and this terminal part, which includes the hooklike portion, serves ‘‘to fill up the interspace between the upper diver- gent portion of the callosities’’; so that the animal sits on it, and thus renders it rough and callous. Dr. Anderson thus sums up his observations: ‘“‘These facts seem to me to have only one explanation: this tail, from its short size, is in the monkey’s way when it sits down, and frequently becomes placed under the animal while it is in this attitude; and from the circumstance that it does not exterd beyond the extremity of the ischial tuberosities it seems as if the # “Prog. Zoolog. Soc.,’? 1872, p. 310. THE DESCENT OR ORIGIN OF MAN 87 tail originally had been bent round, by the will of the ani- mal, into the interspace between the callosities, to escape being pressed between them and the ground, and that in time the curvature became permanent, fitting in of itself when the organ happens to be sat upon.’’ Under these circumstances it is not surprising that the surface of the tail should have been roughened and rendered callous; and Dr. Murie,* who carefully observed this species in the Zoological Gardens, as well as three other closely allied forms with slightly longer tails, says that when the animal sits down, the tail ‘tis necessarily thrust to one side of the buttocks; and whetlier long or short its root is consequently liable to be rubbed or chafed.’’ As we now have evidence that mutilations occasionally produce an inherited effect, it is not very improbable that in short-tailed monkeys the projecting part of the tail, being functionally useless, e:cuid after many generations have become rudimentary and dis- torted, from being continually rubbed and chafed. We see the projecting part in this condition in the Macacus brunneus, and absolutely aborted in the M. ecaudatus and in several of the higher apes. Finally, then, as far as we can judge, the tail has disappeared in man and the anthropomorphous apes, owing to the terminal portion having been injured by friction during a long lapse of time; the basal and imbedded portion having been reduced and modified, so as to become suitable to the erect or semi-erect position. I have now endeavored to show that some of the most distinctive characters of man have in all probability been acquired, either directly, or, more commonly, indirectly, through natural selection. We should bear in mind that %8 **Proc, Zoolog. Soc.,’? 1872, p. 786. % T allude to Dr. Brown-Séquard’s observations on the transmitted effect of an opera.ion causing epilepsy in guinea-pigs, and likewise more recently on the analogous effects of cutting the sympathetic nerve in the neck. I shall here- after have d2casion to refer to Mr. Salvin’s interesting case of the apparently inherited efiects of mot-mots biting off the barbs of their own tail-feathers, See also, on the general subject, ‘‘Variation of Animals and Plants under Domesticati«n,’’ vol. ii. pp. 22-24. 88 THE DESCENT OF MAN modifications in structure or constitution which do not serve to adapt an organism to its habits of life, to the food which it consumes, or passively to the surrounding conditions, cannot have been thus acquired. We must not, however, be too confident in deciding what modifications are of service to each being: we should remember how little we know about the use of many parts, or what changes in the blood or tissues may serve to fit an organism for a new climate or new kinds of food. Nor must we forget the principle of correlation, by which, as Isidore Geoffroy has shown in the case of man, many strange deviations of structure are tied together. Independently of correlation, a change in one part often leads, through the increased or decreased use of other parts, to other changes of a quite unexpected nature. It is also well to reflect on such facts as the won- deriu! growth of galls on plants caused by the poison of an insect, and on the remarkable changes of color in the plumage of parrots when fed on certain fishes, or inocu- lated with the poison of toads;°* for we can thus see that the fluids of the system, if altered for some special purpose, might induce other changes. We should especially bear in mind that modifications acquired and continually used during past ages for some useful purpose would probably become firmly fixed, and might be long inherited. Thus a large yet undefined extension may safely be given to the direct and indirect results of natural selection; but I now admit, after reading the essay of Nageli on plants, and the remarks by various authors with respect to animals, more especially those recently made by Prof. Broca, that in the earlier editions of my ‘‘Origin of Species’’ I perhaps attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the ‘Origin’? so as to confine my remarks to adaptive changes of structure; but’ I am convinced, from the light gained during even ‘the last few years, that very many % ‘The Variation of Animals and Plants under Domestication,‘’ vol. ii. pp. 280, 282. é THE DESCENT OR ORIGIN OF MAN 89 structures which now appear to us useless will hereafter be proved to be useful, and will therefore come within the range of natural selection. Nevertheless, I did not formerly consider sufficiently the existence of structures which, as far as we can at present judge, are neither beneficial nor injurious;*and this I believe to be one of the greatest oversights as yet detected in my work. I may be permitted to say, as some excuse, that I had two distinct objects in view: first, to show that species had not been separately created, and, secondly, that natural selection had been the chief agent of change, though largely aided by the inherited effects of habit, and slightly by the direct action of the surrounding conditions. I was not, however, able to annul the influence of my former belief, then almost universal, that each species had been purposely created; and this led to my tacit assumption that every detail of structure, excepting rudiments, was of some special, though unrecog- nized, service. Any one with this assumption in his mind would naturally extend too far the action of natural selec- tion, either during past or present times. Some of those who admit the principle of evolution, but reject natural selection, seem to forget, when criticising my book, that I had the. above two objects in view; hence if I have erred in giving to natural selection great power, which I am very far from admitting, or in having exaggerated its power, which is in itself probable, I have at least, as I hope, done good service in aiding to overthrow the dogma of separate creations. X It is, as I can now see, probable that all organic beings, including man, possess peculiarities of structure which neither are now nor were formerly of any service to them, and which, therefore, are of no physiological importance. We know not what produces the numberless slight differences between the individuals of each species, for reversion only carries the problem a few steps backward; but each peculiarity must have had its efficient cause. If these causes, whatever they may be, were to act more uniformly and energetically dur- ing a lengthened period (and against this no reason can be 90 THE DESCENT OF MAN assigned), the result would probably be not a mere slight in- dividual difference, but a well-marked and constant modifi- cation, though one of no physiological importance. Changed structures, which are in no way beneficial, cannot be kept uniform through natural selection, though the injurious will be thus eliminated. Uniformity of character would, how- ever, naturally follow from the assumed uniformity of the exciting causes, and likewise from the free intercrossing of many individuals. During successive periods the same organism might, in this manner, acquire successive modifi- cations, which would be transmitted in a nearly uniform state as long as the exciting causes remained the same and there was free intercrossing. With respect to the exciting causes we can only say, as when speaking of so-called spontaneous variations, that they relate much more closely to the constitution of the varying organism than to the nature of the conditions to which it has been subjected. Conclusion.—In this chapter we have seen that as man at the present day is liable, like every other animal, to multi- form individual differences or slight variations, so no doubt were the early progenitors of man; the variations being for- merly induced by the same general causes, and governed by the same general and complex laws as at present. As all animals tend to multiply beyond their means of subsistence, so it must have been with the progenitors of man; and this would inevitably lead to a struggle for existence and to nat- uralselection. The latter process would be greatly aided by the inherited effects of the increased use of parts, and these two processes would incessantly react on each other. It ap- pears, also, as we shall hereafter see, that various unimpor- tant characters have been acquired by man through sexual selection. An unexplained residuum of change must be left to the assumed uniform action of those unknown agencies which occasionally induce strongly marked and abrupt devi- ations of structure in our domestic productions. Judging from the habits of savages and of the greater THE DESCENT OR ORIGIN OF MAN 91 number of the Quadrumana, primeval meh, and even their apelike progenitors, probably lived in society. With strictly social animals, natural selection sometimes acts on the individual, through the preservation of variations which are beneficial to the community. A community which in- cludes a large number of well-endowed individuals increases in number, and is victorious over other less favored ones, even although each separate member gains no advantage over the others of the same community. Associated insects have thus acquired many remarkable structures, which are of little or no service to the individual, such as the pollen- collecting apparatus, or the sting of the worker-bee, or the great jaws of soldier-ants.. With the higher social animals I am not aware that any structure has been modified solely for the good of the community, though some are of second- ary service to it. For instance, the horns of ruminants and the great canine teeth of baboons appear to have been ac- quired by the males as weapons for sexual strife, but they | are used in defence of the herd or troop. In regard to cer- tain mental powers the case, as we shall see in the fifth chap- ter, is wholly different; for these faculties have been chiefly, or even exclusively, gained for the benefit of the commu- nity, and the individuals thereof have at the same time gained an advantage indirectly. It has often been objected to such views as the foregoing, that man is one of the most helpless and defenceless crea- tures in the world; and that during his early and less well- developed condition he would have been still more helpless. The Duke of Argyll, for instance, insists that ‘‘the human . frame has diverged from the structure of brutes, in the direc- tion of greater physical helplessness and weakness. That is to say, it is a divergence which of all others it is most im- possible to ascribe to mere natural selection.”” He adduces the naked and unprotected state of the body, the absence of great teeth or claws for defence, the small strength and 96 ‘*Primeval Man,’’ 1869, p. 66. _ 92 THE DESCENT OF MAN speed of man, and his slight power of discovering food or of avoiding danger by smell. To these deficiencies there might be added one still more serious, namely, that he can- not climb quickly, and so escape from enemies. The loss of hair would not have been a great injury to the inhabi- tants of a warm country, for we know that the unclothed Fuegians can exist under a wretched climate. When we compare the defenceless state of man with that of apes, we must remember that the great canine teeth with which the latter are provided are possessed in their full develop- ment by the males alone, and are chiefly used by them for fighting with their rivals; yet the females, which are not thus provided, manage to survive. In regard to bodily size or strength, we do not know whether man is descended from some small species, like the chimpanzee, or from one as powerful as the gorilla; and, therefore, we cannot say whether man has become larger and stronger, or smaller and weaker, than his ances- tors. We should, however, bear in mind that an animal possessing great size, strength, and ferocity, and which, like the gorilla, could defend itself from all enemies, would not perhaps have become social; and this would most effect- ually have checked the acquirement of the higher mental qualities, such as sympathy and the love of his fellows. Hence it might have been an immense advantage to man to have sprung from some comparatively weak creature. The small strength and speed of man, his want of natural weapons, etc., are more than counterbalanced: first, by his intellectual powers, through which he has formed for him- self weapons, tools, ete., though still remaining in a barba- rous state; and, secondly, by his social qualities, which lead him to give and receive aid from his fellow-men. No coun- try in the world abounds in a greater degree with dangerous beasts than Southern Africa; no country presents more fear- ful physical hardships than the Arctic regions; yet one of the puniest of races, that of the Bushmen, maintains itself in Southern Africa, as do the dwarfed Eskimos in the THE DESCENT OR ORIGIN OF MAN 93 Arctic regions. The ancestors of man were, no doubt, in- ferior in intellect, and probably in social disposition, to the lowest existing savages; but it is quite conceivable that they might have existed, or even flourished, if they had advanced in intellect, while gradually ‘losing their brutelike powers, such as that of climbing trees, etc. But these ancestors would not have been exposed to any special danger, even if far more helpless and defenceless than any existing sav- ages, had they inhabited some warm continent or large isl- and, such as Australia, New Guinea, or Borneo, which is now the home of the orang. And natural selection arising from the competition of tribe with tribe, in some such large area as one of these, together with the inherited effects of habit, would, under favorable conditions, have sufficed to raise man to his present high position in the organic scale. 94 THE DESCENT OF MAN CHAPTER IIT 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—The emotions— Curiosity—Imitation—A ttention — Memory — Imagination—Reason— Progressive improvement—Tools and weapons used by animals— Abstraction, self-consciousness—Language—Sense of beauty—Belief in God, spiritual agencies, superstitions E have seen in the last two chapters that man bears \/ \ / inhis bodily structure clear traces of his descent from some lower form; but it may be urged that, as man differs so greatly in his mental power from all other animals, there must be some error in this conclusion. No doubt the difference in this respect is enormous, even if we compare the mind of one of the lowest savages, who has no words to express any number higher than four, and who uses hardly any abstract terms for common objects or for the affections,’ with that of the most highly organized ape. The difference would, no doubt, still remain immense, even if one of the higher apes had been improved or civilized as much as a dog has been in comparison with its parent-form, the wolf or jackal. The Fuegians rank among the lowest barbarians; but I was continually struck with surprise how closely the three natives on board H.M.S. ‘‘Beagle,’’ who had lived some years in England, and could talk a little English, resembled us in disposition and in most of our mental faculties. If no organic being excepting man had possessed any mental power, or if his powers had been of 1 See the evidence on those points, as given by Lubbock, ‘‘Prehistoric Times,’’ p. 354, ete. THE DESCENT OR ORIGIN OF MAN 95 & wholly different nature from those of the lower animals, then we should never have been able to convince ourselves that our high faculties had been gradually developed. But it can be shown that there is no fundamental difference of this kind. We must also admit that there is a much wider interval in mental power between one of the lowest fishes, as a lamprey or lancelet, and one of the higher apes, than between an ape and man; yet this interval is filled up by numberless gradations. Nor is the difference slight in moral disposition between a barbarian, such as the man described by the old navigator Byron, who dashed his child on the rocks for dropping a basket of sea-urchins, and a Howard or Clarkson; and in intellect, between a savage who uses hardly any abstract terms and a Newton or Shakespeare. Differences of this kind between the highest men of the highest races and the lowest savages are connected by the finest gradations. Therefore it is possible that they might pass and be developed into each other. My object in this chapter is to show that there is no fundamental difference between man and the higher mam- mals in their mental faculties. Hach division of the subject might have been extended into a separate essay, but must here be treated briefly. As no classification of the mental powers has been universally acceptedXI shall arrange my remarks in the order most convenient for my purpose; and will select those facts which have struck me most, with the hope that they may produce some effect on the reader. x With respect to animals very low in the scale, I shall give some additional facts under Sexual Selection, showing that their mental powers are much higher than might have been expected. The variability of the faculties in the indi- viduals of the same species is an important point for us, and some few illustrations will here be given. But it would be superfluous to enter into many details on this head, for I _ have found, on frequent inquiry, that it is the unanimous opinion of all those who have long attended to animals of 96 THE DESCENT OF MAN many kinds, including birds, that the individuals differ greatly in every mental characteristic. In what manner the mental powers were first developed in the lowest organisms is as hopeless an inquiry as how life itself first originated. These are problems for the distant future, if they are ever to be solved by man. XAs man possesses the same senses as the lower animals, his fundamental intuitions must be the same“ Man has also some few instincts in common, as that of self-preservation, sexual love, the love of the mother for her new-born off- spring, the desire possessed by the latter to suck, and so forth. But man, perhaps, has somewhat fewer instincts than those possessed by the animals which come next to him in the series. The orang in the Hastern islands, and the chimpanzee in “Africa, build platforms on which they sleep; and, as both species follow the same habit, it might be argued that this was due to instinct, but we cannot fee] sure that it is not the result of both animals having similar wants, and possessing similar powers of reasoning. These apes, aS we may assume, avoid the many poisonous fruits of the tropics, and man has no such knowledge; but as our domestic animals, when taken to foreign lands, and when first turned out in the spring, often eat poisonous herbs, which they afterward avoid, we cannot feel sure that the apes do not learn from their own experience or from that of their parents what fruits to select. It is, however, cer- tain, as we shall presently see, that apes have an instinctive dread of serpents, and probably of other dangerous animals. The fewness and the comparative simplicity of the in- stincts in the higher animals are remarkable in contrast with those of the lower animals. Cuvier maintained that instinct and intelligence stand in an inverse ratio to each other; and some have thought that the intellectual faculties of the higher animals have been gradually developed from their instincts. But Pouchet, in an interesting essay,’ has 2 “T/Instinct chez Jes Insectes,”’ ‘‘Revue des Deux Mondes,’’ Feb., 1870, p. 690. THE DESCENT OR ORIGIN OF MAN 97 shown that no such inverse ratio really exists. Those in- sects which possess the most wonderful instincts are cer- tainly the most intelligent. In the vertebrate series, the least intelligent members, namely fishes and amphibians, do not possess complex instincts; and among mammals the animal most remarkable for its instincts, namely, the beaver, is highly intelligent, as will be admitted by every one who has read Mr. Morgan’s excellent work.® Although the first dawnings of intelligence, according to Mr. Herbert Spencer,* have been developed through the multiplication and co-ordination of reflex actions, and al- though many of the simpler instincts graduate into reflex actions, and can hardly be distinguished from them, as in the case of young animals sucking, yet the more complex instincts seem to have originated independently of intelli- gence. Iam, however, very far from wishing to deny that instinctive actions may lose their fixed and untaught charac- ter, and be replaced by others performed by the aid of the. free will. On the other hand, some intelligent actions, after being performed during several generations, become con- verted into instincts and are inherited, as when birds on oceanic islands learn to avoid man. These actions may then be said to be degraded in character, for they are no longer performed through reason or from experience. But the greater number of the more complex instincts appear to have been gained in a wholly different manner, through the natural selection of variations of simpler instinctive actions. Such variations appear to arise from the same unknown causes acting on the cerebral organization which induce slight variations or individual differences in other parts of the body; and these variations, owing to our igno- rance, are often said to arise spontaneously. We can, I think, come to no other conclusion with respect to the ori- gin of the more complex instincts, when we reflect on the marvellous instincts of sterile worker-ants and bees, which 3 “The American Beaver and his Works,”’ 1868. . 4°-“*"Tne Principles of Psychology,’’ 2d edit., 1870, pp, 418-443, Descent—Vot. I.—5 98 THE DESCENT OF MAN leave no offspring to inherit the effects of experience and of modified habits. Although, as we learn from the above-mentioned insects and the beaver, a high degree of intelligence is certainly compatible with complex instincts, and although actions, at first learned voluntarily, can soon through habit be per- formed with the quickness and certainty of a reflex action, yet it is not improbable that there is a certain amount of interference between the development of free intelligence and of instinct—which latter implies some inherited modi- fication of the brain. Little is known about the functions of the brain, but we can perceive that as the intellectual powers become highly developed, the various parts of the brain must be connected by very intricate channels of the freest intercommunication; and as a consequence, each sepa- rate part would perhaps tend to be less well fitted to answer to particular sensations or associations in a definite and in- herited—that is instinctive—manner. There seems even to exist some relation between a low degree of intelligence and a strong tendency to the formation of fixed, though not in- herited habits; for, as a sagacious physician remarked to me, persons who are slightly imbecile tend to act in every- thing by routine or habit, and they are rendered much happier if this is encouraged. I have thought this digression worth giving, because we may easily underrate the mental powers of the higher animals, and especially of man, when we compare their actions founded on the memory of past events, on fore- sight, reason, and imagination, with exactly similar actions instinctively performed by the lower animals; in this latter case the capacity of performing such actions has been gained, step by step, through the variability of the mental organs and natural selection, without any conscious intel- ligence on the part of the animal during each successive generation. No doubt, as Mr. Wallace has argued,* much 5 “Contributions to the Theory of Natural Selection,’? 1870, p. £12. THE DESCENT OR ORIGIN OF MAN 99° of the intelligent work done by man is due to imitation and not to reason; but there is this great difference between his actions and many of those performed by the lower animals, namely, that man cannot, on his first trial, make, for in- stance, a stone hatchet or a canoe, through his power of imitation. He has to learn his work by practice; a beaver, on the other hand, can make its dam or canal, and a bird its nest, as well, or nearly as well, anda spider its wonderful web quite as well,* the first time it tries, as when old and experienced. To return to our immediate subject: the lower animals, like man, manifestly feel pleasure and pain, happiness and misery. Happiness is never better exhibited than by young animals, such as puppies, kittens, lambs, etc., when playing together, like our own children. Even insects play together, as has been described by that excellent observer, P. Huber,’ who saw ants chasing and pretending to bite each other, like so many puppies. The fact that the lower animals are excited by the same emotions as ourselves is so well established that it will not be necessary to weary the reader by many details. Terror acts in the same manner on them as on us, causing the mus- cles to tremble, the heart to palpitate, the sphincters to be relaxed, and the hair to stand on end. Suspicion, the off- spring of fear, is eminently characteristic of most wild ani- mals. It is, I think, impossible to read the account given by Sir E. Tennent, of the behavior of the female elephants, used as decoys, without admitting that they intentionally practice deceit, and well know what they are about. Cour- age and timidity are extremely variable qualities in the individuals of the same species, as is plainly seen in our dogs. Some dogs and horses are ill-tempered, and easily turn sulky; others are good-tempered; and these qualities are certainly inherited. Every one knows how liable ani- 6 For the evidence on this head, see Mr. J. Traherne Moggridge’s most interesting work, ‘‘Harvesting Ants and Trap-door Spiders,’’ 1873, pp. 126, 128, 1 “Recherches sur les Mceurs des Fourmis,”” 1810, p. 173. 1v0 THE DESCENT OF MAN mals are to furious rage, and how plainly they show it. Many, and probably true, anecdotes have been published on the long-delayed and artful revenge of various animals. The accurate Rengger, and Brehm? state that the American and African monkeys which they kept tame certainly re- venged themselves. Sir Andrew Smith, a zoologist whose scrupulous accuracy was known to many persons, told me the following story of which he was himself an eye-witness: At the Cape of Good Hope an officer had often plagued a certain baboon, and the animal, seeing him approaching one Sunday for parade, poured water into a hole and hastily made some thick mud, which he skilfully dashed over the officer as he passed ae to the amusement of many bystand- ers. For long afterward the baboon rejoiced and ae whenever he saw his victim. The love of a dog for his master is notorious; as an old writer quaintly says,° ‘‘A dog is the only thing on this earth that luvs you more than he luvs himself.’’ y' In the agony of death a dog has been known to caress his ~ master, and every one has heard of the dog suffering under vivisection, who licked the hand of the operator; this man, unless the operation was fully justified by an increase of our knowledge, or unless he had a heart of stone, must have felt remorse to the last hour of his life.% As Whewell” has well asked, ‘‘who that reads the touch- ing instances of maternal affection, related so often of the women of all nations, and.of the females of all animals, can doubt that the principle of action is the same in the two cases?’’ We see maternal affection exhibited in the most trifling details; thus Rengger observed an American monkey (a Cebus) carefully driving away the flies which plagued her infant; and Duvaucel saw a Hylobates washing the faces 8 All the following statements, given on the authority of these two natural- ists, are taken from Rengger’s “‘Naturgesch. der Séugethiere von Paraguay,’ 1830, s. 41-57, and from Brehm’s “‘Thierleben,’’ B. i. 8, 10-87. ® Quoted by Dr, Lauder Lindsay, in his “Physiology of Mind in the Lower Auimals’’; ‘‘Journal of Mental Science,”’ April, 1871, p. 38. 10 “Bridgewater Treatise,’? p. 263. THE DESCENT OR ORIGIN OF MAN : 101 of her young ones inastream. So intense is the grief of female monkeys for the loss of their young, that it invari- ably caused the death of certain kinds kept under confine- ment by Brehm in North Africa. Orphan monkeys were always adopted and carefully guarded by the other monkeys, both males and females. One female baboon had so capa- cious a heart that she not only adopted young monkeys of other species, but stole young dogs and cats, which she con- tinually carried about. Her kindness, however, did not go so far as to share her food with her adopted offspring, at which Brehm was surprised, as his monkeys always divided everything quite fairly with their own young ones. An adopted kitten scratched this affectionate baboon, who cer- tainly had a fine intellect, for she was much astonished at being scratched, and immediately examined the kitten’s feet, and without more ado bit off the claws." In the Zoological Gardens, I heard from the keeper that an old baboon (C., Chacma) had adopted a Rhesus monkey; but when a young drill and, mandrill were placed in the cage, she seemed to perceive that these monkeys, though distinct species, were her near relatives, for she at once rejected the Rhesus and adopted both of them. The young Rhesus, as I saw, was greatly discontented at being thus rejected, and it would, like a naughty child, annoy and attack the young drill and mandrill whenever it could do so with safety; this conduct exciting great indignation in the old baboon. Monkeys will also, according to Brehm, defend their master when attacked by any one, as well as dogs to whom they are attached, from the attacks of other dogs. But we here trench on the subjects of sympathy and fidelity, to which I shall recur. Some of Brehm’s monkeys took much delight in teasing a certain old dog whom they dis- liked, as well as other animals, in various ingenious ways. n A critic, without any grounds (‘‘Quarterly Review,”’ July, 1871, p. 72), disputes the possibility of this act as described by Brehm, for the sake of dis- crediting my work. Therefore I tried, and found that I could readily seize with nly own teeth the sharp little claws of a kitten nearly five weeks old. \ | 1020 THE DESCENT OF MAN Most of the more complex emotions are common to the higher animals and ourselves. Every one has seen how jeal- ous a dog is of his master’s affection, if lavished on any other creature; and I have observed the same fact with monkeys. This shows that animals not only love, but have desire to be loved. Animals manifestly feel emulation. They love approbation or praise; and a dog carrying a basket for his master exhibits in a high degree self-complacency or pride. There can, I think, be no doubt that a dog feels shame, as distinct from fear, and something very like modesty when begging too often for food. A great dog scorns the snarling of a little dog, and this may be called magnanimity. Sev- eral observers have stated that monkeys certainly dislike being laughed at; and they sometimes invent imaginary offences. In the Zoological Gardens I saw 4 baboon who always got into a furious rage when his keeper took out a letter or book and read it aloud to him; and his rage was so violent that, as I witnessed on one occasion, he bit his own leg till the blood flowed. Dogs show what may be fairly called a sense of humor, as distinct from mere play; if a bit of stick or other such object be thrown to one, he will often carry it away for a short distance; and then, squatting down with it on the ground close before him, will wait until his master comes quite close to take it away. The dog will then seize it and rush away in tri- umph, repeating the same manceuvre, and evidently enjoy- ing the practical joke. We will now turn to the more intellectual emotions and faculties, which are very important, as forming the basis for the development of the higher mental powers. Animals manifestly enjoy excitement, and suffer from ennui, as may be seen with dogs, and, according to Rengger, with monkeys, All animals feel Wonder, and many exhibit Curiosity. They sometimes suffer from this latter quality, as when the hunter plays antics and thus attracts them; I have witnessed this with deer, and so it is with the wary chamois, and with some kinds of wild ducks. Brehm gives a curious account c” * «the ei, With THE DESCENT OR ORIGIN OF MAN 1093 instinctive dread which his monkeys exhibited for snakes; but their curiosity was so great that they could not desist from occasionally satiating their horror in a most human fashion, by lifting up the lid of the box in which the snakes were kept. I was so much surprised at his account, that I took a stuffed and coiled-up snake into the monkey-house at the Zoological Gardens, and the excitement thus caused was one of the most curious spectacles which I ever beheld. Three species of Cercopithecus were the most alarmed; they dashed about their cages and uttered sharp signal cries of danger, which were understood by the other monkeys. A few young monkeys and one old Anubis baboon alone took no notice of the snake. I then placed the stuffed specimen on the ground in one of the larger compartments. After a time all the monkeys collected round it in a large circle, and, staring intently, presented a most ludicrous appearance. ‘They became extremely nervous; so that when a wooden ball, with which they were familiar as a plaything, was ac- cidentally moved in the straw, under which it was partly hidden, they all instantly started away. These monkeys behaved very differently when a dead fish, a mouse,” a liv- ing turtle, and other new objects were placed in their cages; for, though at first frightened, they soon approached, han- dled, and examined them. I then placed a live snake in a paper bag, with the mouth loosely closed, in one of the larger compartments. One of the monkeys immediately ap- proached, cautiously opened the bag a little, peeped in, and instantly dashed away. Then I witnessed what Brehm has described, for monkey after monkey, with head raised high and turned on one side, could not resist taking a momentary peep into the upright bag, at the dreadful object lying quietly at the bottom. It would almost appear as if mon- keys had some notion of zoological affinities, for those kept by Brehm exhibited a strange, though mistaken, instinctive dread of innocent lizards and frogs. An orang, also, has 2 T have given a short account of their behavior on this occasion in my **Rixpression of the Emotions,’ p. 43. 104 THE DESCENT OF MAN been known to be much alarmed at the first sight of a turtle. ** The principle of Jmitation is strong in man, and espe- cially, as I have myself observed, with savages. In certain morbid states of the brain this tendency is exaggerated to an extraordinary degree; some hemiplegic patients and oth- ers, at the commencement of inflammatory softening of the brain, unconsciously imitate every word which is uttered, whether in their own or in a foreign language, and every gesture or action which is performed near them.’* Desor’® has remarked that no animal voluntarily imitates an action performed by man, until in the ascending scale we come to monkeys, which are well known to be ridiculous mockers, Animals, however, sometimes imitate each other’s actions; _ thus two species of wolves, which had been reared by dogs, learned to bark, as does sometimes the jackal,'* but whether this can be called voluntary imitation is another question. Birds imitate the songs of their parents, and sometimes of other birds; and parrots are notorious imitators of any sound which they often hear. Dureau de la Malle gives an account’ of a dog reared by a cat, who learned to imi- tate the well-known action of a cat licking her paws, and thus washing her ears and face; this was also witnessed by the celebrated naturalist, Audouin. I have received several confirmatory accounts; in one of these, a dog had not been suckled by a cat, but had been brought up with one, together with kittens, and had thus acquired the above habit, which he ever afterward practiced during his life of thirteen years. Dureau de la Malle’s dog likewise learned from the kittens to play with a ball by rolling it about with his forepaws, and springing on it. A correspondent assures me that a cat in his house used to put her paws into jugs of milk having too narrow a mouth for her head. A kitten of this cat soon 18 W, CO. L. Martin, “‘Nat. Hist. of Mammalia,’’ 1841, p. 405. 144 Dr, Bateman ‘‘On Aphasia,’’ 1870, p. 110. 18 Quoted by Vogt, ‘‘Mémoire sur les Microcéphales,’’ 1867, p. 168. 16 “The Variation of Animals and Plants under Domestication,’’ vol. i. p. 27. “Annales des Sc. Nat.’’ (1st Series), tom. xxii, p. 397, THE DESCENT OR ORIGIN OF MAN 105 learned the same trick, and practiced it ever afterward whenever there was an opportunity., The parents of many animals, trusting to the principle of imitation in their young, and more especially to their instinctive or inherited tendencies, may be said to educate them. We see this when a cat brings a live mouse to her kittens; and Dureau de la Malle has given a curious account (in the paper above quoted) of his observations on hawks which taught their young dexterity, as well as judgment of distances, by first dropping through the air dead mice and sparrows, which the young generally failed to catch, and then bringing them live birds and letting them loose. Hardly any faculty is more important for the intellectual progress of man than Aétention. Animals clearly manifest this power, as when a cat watches by a hole and prepares to spring on its prey. Wild animals sometimes become so absorbed when thus engaged that they may be easily ap- proached. Mr. Bartlett has given me a curious proof how variable this faculty is in monkeys. A man who trains monkeys to act in plays used to purchase common kinds from the Zoological Society at the price of five pounds for each; but he offered to give double the price, if he might” keep three or four of them for a few days, in order to select one. When asked how he could possibly learn so soon whether a particular monkey would turn out a good actor, he answered that it all depended on their power of atten- tion. If, when he was talking and explaining anything to a monkey, its attention was easily distracted, as by a fly on the wall or other trifling object, the case was hopeless. If he tried by punishment to make an inattentive monkey act, it turned sulky. On the other hand, a monkey which carefully attended to him could always be trained. lt is almost superfluous to state that animals have excel- lent Memories for persons and places. A baboon at the Cape of Gocd Hope, as I have been informed by Sir Andrew Smith, recognized him with joy after an absence of nine months. I had a dog who was savage and averse to all 106 THE DESCENT OF MAN strangers, and I purposely tried his memory after an ab- sence of five years and two days. I went near the stable where he lived, and shouted to him in my old manner; he showed no joy, but instantly followed me out walking, and obeyed me, exactly as if I had parted with him only half an hour before. A train of old associations, dormant during five years, had thus been instantaneously awakened in his mind. Even ants, as P. Huber’ has clearly shown, recog-. nized their fellow-ants belonging to the same community after a separation of four months. Animals can certainly by some means judge of the intervals of time between recur- rent events. The Imagination is one of the highest prerogatives of man. By this faculty he unites former images and ideas, independently of the will, and thus creates brilliant and novel results. A poet, as Jean Paul Richter remarks,” ‘“‘who must reflect whether he shall make a character say yes or no—to the devil with him; he is only a stupid corpse.’? Dreaming gives us the best notion of this power; as Jean Paul again says, ‘‘The dream is an involuntary art of poetry.”’ The value of the products of our imagination depends of course on the number, accuracy, and clearness of our impressions, on our judgment and taste in selecting or rejecting the involuntary combinations, and to a certain extent on our power of voluntarily combining them. vertébré par la seule condition vitale de l’adaptation, et cette simple possibilité du passage supprime l’abime- entre les deux sous-régnes, encore bien qu’on ignore par ob le passage s’est fait en réalité.”” THE DESCENT OR ORIGIN OF MAN 215 probably pointed, and capable of movement; and their bodies were provided with a tail, having the proper mus- cles. Their limbs and bodies were also acted on by many muscles which now only occasionally reappear, but are normally present in the Quadrumana. At this or some earlier period, the great artery and nerve of the humerus ran through a supra-condyloid foramen. The intestine gave forth a much larger diverticulum or cecum than that now existing. The foot was then prehensile, judging from the condition of the great toe in the foetus; and our progenitors, no doubt, were arboreal in their habits, and frequented some warm, forest-clad land. The males had great canine teeth, which served them as formidable weapons. At a much earlier period the uterus was double; the excreta were voided through a cloaca; and the eye was protected by a third eyelid or nictitating membrane. At a still earlier period the progenitors of man must have been aquatic in their habits; for morphology plainly tells us that our lungs consist of a modified swim-bladder, which once served as a float. The clefts on the neck in the embryo of man show where the branchiz once existed. In the lunar or weekly recurrent periods of some of our functions we apparently still retain traces of our primordial birthplace, a shore washed by the tides. At about this same early period the true kidneys were replaced by the corpora wolffiana. The heart existed as a simple pulsating vessel; and the chorda dorsalis took the place of a vertebral colunin. These early ancestors of man, thus seen in the dim recesses of time, must have been as singly: or even still more simply, organized than the lancelet or amphioxus. There is one other point deserving a fuller notice. It has long been known that in the vertebrate kingdom one sex bears rudiments of various accessory parts, appertaining to the reproductive system, which properly belong to the oppo- site sex; and it has now been ascertained that at a very early embryonic period both sexes possess true male and female glands. Hence some remote progenitor of the whole verte- 216 THE DESCENT OF MAN brate kingdom appears to have been hermaphrodite or an- drogynous.”* But here we encounter a singular difficulty. In the mammalian class the males possess rudiments of a uterus with the adjacent passage, in their vesicule prostatics; they bear also rudiments of mammz, and some male Marsupials have traces of a marsupial sac.*” Other analo- gous facts could be added. Are we, then, to suppose that some extremely ancient mammal continued androgynous, after it had acquired the chief distinctions of its class, and therefore after it had diverged from the lower classes of the vertebrate kingdom? This seems very improbable, for we have to look to fishes, the lowest of all the classes, to find any still existent androgynous forms.” That various, acces- sory parts, proper to each sex, are found in a rudimentary condition in the opposite sex, may be explained by such organs having been gradually acquired by the one sex, and then transmitted in a more or less imperfect state to the other. When we treat of sexual selection we shall meet with innumerable instances of this form of transmission— as in the case of the spurs, plumes, and brilliant colors acquired for battle or ornament by male birds, and in- herited by the females in an imperfect or rudimentary condition. 26 This is the conclusion of Prof. Gegenbaur, one of the highest authorities in comparative anatomy; see ‘‘Grundziige der vergleich. Anat.,’? 1870, s. 876, The result has been arrived at chiefly from the study of the Amphibia; but it appears from the researches of Waldeyer (as quoted in ‘‘Journal of Anat. and Phys.,’’ 1869, p. 161), that the sexual organs of even ‘‘the higher vertebrata are, in their early condition, hermaphrodite.’’ Similar views have long been held by some authors, though until recently without a firm basis. 1 The male Thylacinus offers the best instance. Owen, ‘‘Anatomy of Vertebrates,’’ vol. iii. p. 771. 28 Hermaphroditism has been observed in several species of Serranus, as well as in some other fishes, where it is either normal and symmetrical or ab- normal and unilateral. Dr. Zouteveen has given me references on this subject, more especially to a paper by Prof. Halbertsma, in the ‘‘Transact. of the Dutch Acad. of Sciences,’’ vol. xvi. Dr. Ginther doubts the fact, but it has now been recorded by too many good observers to be any longer disputed. Dr. M. Lessona writes to me that he has verified the observations made by Cavolini on Serranus. Prof. Ercolani has recently shown (‘‘Accad. delle Scienze,”’ Bologna, Dec, 28, 1871) that eels are androgynous. THE DESCENT OR ORIGIN OF MAN 217 The possession by male mammals of functionally imper- fect mammary organs is, in some respects, especially curi- ous. The Monotremata have the proper milk-secreting glands with orifices, but no nipples; and as these animals stand at the very base of the mammalian series, it is prob- able that the progenitors ot the class also had milk- secreting glands, but no nipples. This conclusion is sup- ported by what is known of their manner of develop- ment; for Professor Turner informs me, on the authority of Kélliker and Langer, that in the embryo the mammary glands can be distinctly traced before the nipples are in the least visible; and the development of successive parts in the individual generally represents and accords with the development of successive beings in the same line of descent. The Marsupials differ from the Monotremata by possessing nipples; so that probably these organs were first acquired by the Marsupials, after they had diverged from, and risen above, the Monotremata, and were then trans- mitted to the placental mammals.” No one will suppose that the Marsupials still remained androgynous after they had approximately acquired their present structure. How then are we to account for male mammais possessing mammz? It is possible that they were first developed in the females and then transferred to the males; but from what follows this is hardly probable. It may be suggested, as another view, that long after the progenitors of the whole mammalian class had ceased to be androgynous, both sexes yielded milk, and thus nour- ished their young; and in the case of the Marsupials, that both sexes carried their young in marsupial sacs. This will not appear altogether improbable, if we reflect that the males of existing syngnathous fishes receive the eggs of the females ' 99 Prof, Gegenbaur has shown (‘‘Jenaische Zeitschrift,’ B. vii. p. 212) that two distinct types of nipples prevail throughout the several mammalian orders, but that it is quite intelligible how both could have been derived from the nipples of the Marsupials, and the latter from those of the Monotremata. See, also, a memoir by Dr. Max Huss, on the mammary glands, ibid., B. viii. p. 176. = ; Descent—VoL. f.—10 218 : THE DESCENT OF MAN in their abdominal pouches, hatch them, and afterward, as some believe, nourish the young; that certain other male fishes hatch the eggs within their mouths or branchial cavi- ties; that certain male toads take the chaplets of eggs from the females, and wind them round their own thighs, keeping them there until the tadpoles are born; that certain male birds undertake the whole duty of incubation, and that male pigeons, as well as the females, feed their nestlings with a secretion from their crops. But the above sugges- tion first occurred to me from the mammary glands of male mammals being so much more perfectly developed than the rudiments of the other accessory reproductive parts, which are found in the one sex though proper to the other. The mammary glands and nipples, as they exist in male mam- mals, can indeed hardly be called rudimentary; they are merely not fully developed, and not functionally active. They are sympathetically affected under the influence of certain diseases, like the same organs in the female. They often secrete a few drops of milk at birth and at puberty; this latter fact occurred in the curious case, before referred to, where a young man possessed two pairs of mamme. In man and some other male mammals these organs have been known occasionally to become so well developed during maturity as to yield a fair supply of milk. Now if we suppose that during a former prolonged period male mam- mals aided the females in nursing their offspring,” and that afterward from some cause (as from the production of a smaller number of young) the males ceased to give this aid, disuse of the organs during maturity would lead to their becoming inactive; and from two well-known princi- 30 Mr. Lockwood believes (as quoted in ‘‘Quart. Journal of Science,’’ April, 1868, p. 269), from what he has observed of the development of Hippocampus, that the walls of the abdominal pouch of the male in some way afford nourish- ment. On male fishes hatching the ova in their mouths, see a very interesting paper by Prof. Wyman, in “Proc, Boston Soc. of Nat. Hist., ”? Sept. 15, 1857; also Prof. Turner, in “Journal of Anat, and Phys.,”’ Nov. 1, 1866, p. 78. Dr. Giinther has likewise described similar cases. 31 Mdlle. C. Royer has suggested a similar view in her ‘‘Origine de YHomme,”’ ete, 1870. THE DESCENT OR ORIGIN OF MAN 219 ples of inheritance this state of inactivity would probably be transmitted to the males at the corresponding age of maturity. But at an earlier age these organs would be left unaffected, so that they would be almost equally well devel- oped in the young of both sexes, Conclusion.—Von Baer has defined advancement or prog- ress in the organic scale better than any one else, as resting on the amount of differentiation and specialization of the several parts of a being—when arrived at maturity, as I should be inclined to add. Now as organisms have become slowly adapted to diversified lines of life by means of natu- ral selection, their parts will have become more and more differentiated and specialized for various functions, from the advantage gained by the division of physiological labor. — The same part appears often to have been modified first for one purpose, and then long afterward for some other and quite distinct purpose; and thus all the parts are ren- dered more and more complex. But each organism still retains the general type of structure of the progenitor from which it was aboriginally derived. In accordance with this view it seems, if we turn to geological evidence, that organi- zation on the whole has advanced throughout the world by slow and interrupted steps. In the great kingdom of the Vertebrata it has culminated in man. It must not, however, be supposed that groups of organic beings are always sup- planted, and disappear as soon as they have given birth to other and more perfect groups. The latter, though victori- ous over their predecessors, may not have become better adapted for all places in the economy of nature. Some old forms appear to have survived from inhabiting protected sites, where they have not been exposed to very severe competition; and these often aid us in constructing our gene- alogies, by giving us a fair idea of former and lost popula- tions. But we must not fall into the error of looking at the existing members of any lowly organized group as perfect representatives of their ancient predecessors. 220 THE DESCENT OF MAN The most ancient progenitors in the kingdom of the Ver- tebrata, at which we are able to obtain an obscure glance, apparently consisted of a group of marine animals,” resem- bling the larvee of existing Ascidians. These animals proba- bly gave rise to a group of fishes, as lowly organized as the lancelet; and from these the Ganoids, and other fishes like the Lepidosiren, must have been developed. From such fish a very small advance would carry us on to the Am- phibians. We have seen that birds and reptiles were once intimately connected together; and the Monotremata now connect mammals with reptiles in a slight degree. But no one can at present say by what line of descent the three higher and related classes, namely, mammals, birds, and reptiles, were derived from the two lower vertebrate classes, namely, amphibians and fishes. In the class of mammals the steps are not difficult to conceive which led from the ancient Monotremata to the ancient Marsupials; and from these to the early progenitors of the placental mammals. We may thus ascend to the Lemuride; and the interval is not very wide from these to the Simiade. The Simiade 8 The inhabitants of the sea-shore must be greatly affected by the tides; animals living either about the mean high-water mark, or about the mean low- water mark, pass through a complete cycle of tidal changes in a fortnight. Consequently, their food supply will undergo marked changes week by week. The vital functions of such animals, living under these conditions for many generations, can hardly fail to run their course in regular weekly periods. Now it isa mysterious fact that in the higher and now terrestrial Vertebrata, as well as in other classes, many normal and abnormal processes have one or more whole weeks as their periods; this would be rendered intelligible if the Vertebrata are descended from an animal allied to the existing tidal Ascidians, Many instances of such periodic processes might be given, as the gestation of mammals, the duration of fevers, ete. The hatching of eggs affords also a good example, for, according to Mr. Bartlett (‘‘Land and Water,’’ Jan. 7, 1871), the eggs of the pigeon are hatched in two weeks; those of the fowl in three; those of the duck in four; those of the goose in five; and those of the ostrich in seven weeks. As far as we can judge, a recurrent period, if approximately of the right duration for any process or function, would not, when once gained, be liable to change; consequently it might be thus transmitted through almost any number of generations. But if the function changed, the period would have to change, and would be apt to change almost abruptly by a whole week, This conclusion, if sound, is highly remarkable; for the period of gestation in each mammal, and the hatching of each bird’s eggs, and many other vital processes, thus betray to us the primordial birthplace of these animals. THE DESCENT OR ORIGIN OF MAN 221 then branched off into two great stems, the New World and Old World monkeys; and from the latter, at a re- mote period, Man, the wonder and glory of the Universe, proceeded. Thus we have given to man a pedigree of prodigious length, but not, it may be said, of noble quality. The world, it has often been remarked, appears as if it had long been preparing for the advent of man; and this, in one sense, is strictly true, for he owes his birth to a long © line of progenitors. If any single link in this chain had never existed, man would not have been exactly what he now is. Unless we wilfully close our eyes, we may, with our present knowledge, approximately recognize our parent- age; vor need we feel ashamed of it. The most humble organism is something much higher than the inorganic dust under our feet; and no ene with an unbiased mind can study any living creature, however humble, without being struck with enthusiasm at its marvellous structure and properties. 222 THE DESCENT OF MAN CHAPTER VII ON THE RACES OF MAN The nature and value of specific characters—Application to the races of man—Arguments in favor of, and opposed to, ranking the so-called races of man as distinct species—Sub-species—Monogenists and polyg- enists—Convergence of character—Numerous points of resemblance in body and mind between the most distinct races of man—The state of man when he first spread over the earth—Each race not descended from a single pair—The extinction of races—The formation of races— The effects of crossing—Slight influence of the direct action of the conditions of life—Slight or no influence of natural selection—Sexual selection called races of men; but 1 am about to inquire what is the value of the differences between them under a classificatory point of view, and how they have originated. In determining whether two or more allied forms ought to be ranked as species or varieties, naturalists are practically guided by the following considerations; namely, the amount of difference between them, and whether such differences relate to few or many points of structure, and whether they are of physiological importance; but more especially | whether they are constant. Constancy of character is what is chiefly valued and sought for by naturalists. When- ever it can be shown, or rendered probable, that the forms in question have remained distinct for a long period, this becomes an argument of much weight in favor of treat- ing them as species. Even a slight degree of sterility be- tween any two forms when first crossed, or in their offspring, is generally considered as a decisive test of their specific dis- tinctness; and their continued persistence without blending within the same area is usually accepted as sufficient evi- |" IS not my intention here to describe the several so- THE DESCENT OR ORIGIN OF MAN 223 dence, either of some degree of mutual sterility, or, in the case of animals, of some mutual repugnance to pairing. Independently of fusion from intercrossing, the complete absence, in a well-investigated region, of varieties linking together any two closely allied forms, is probably the most important of all the criterions of their specific distinctness; and this is a somewhat different consideration from mere constancy of character, for two forms may be highly vari- able and yet not yield intermediate varieties. Geographical distribution is often brought into play unconsciously and sometimes consciously; so that forms living in two widely separated areas, in which most of the other inhabitants are specifically distinct, are themselves usually looked at as distinct; but in truth this affords no aid in distinguishing geographical races from so-called good or true species. Now let us apply these generally admitted principles to the races of man, viewing him in the same spirit as a natu- ralist would any other animal. In regard to the amount of difference between the races, we must make some allowance for our nice powers of discrimination gained by the long habit of observing ourselves. In India, as Elphinstone re- marks, although a newly arrived European cannot at first distinguish the various native races, yet they soon appear to him extremely dissimilar;' and the Hindu cannot at first perceive any difference between the several Huropean nations. Even the most distinct races of man are much more like each other in form than would at first be sup- posed; certain negro tribes must be excepted, while others, as Dr. Rohlfs writes to me, and as I have myself seen, have Caucasian features. This general similarity is well shown by ~ the-French_photographs | in the Collection Anthropologique du Muséum de Paris of the men belonging to various races, the greater number of which might pass for Huropeans, as many persons to whom | have shown them have remarked. Nevertheless, these men, if seen alive, would undoubtedly 1 «History of India,” 1841, vol. i. p. 323, Father Ripa makes exactly the epme remark with respect to the Chinese. 224 THE DESCENT OF MAN appear very distinct, so that we are clearly much influenced in our judgment by the mere color of the skin and hair, by slight differences in the features, and by expression. There is, however, no doubt that the various races, when carefully compared and measured, differ much from each other—as in the texture of the hair, the relative proportions of all parts of the body,’ the capacity of the lungs, the form and capacity of the skull, and even in the convolutions of: the brain.* But it would be an endless task to specify the’ numerous points of difference. ‘The races differ also in constitution, in acclimatization, and in liability to certain diseases. Their mental characteristics are likewise very distinct; chiefly as it would appear in their emotional, but partly in their intellectual faculties. Every one who has had the opportunity of comparison must have been struck‘ with the contrast between the taciturn, even morose, abo- rigines of South America and the light-hearted, talkative negroes. There is a nearly similar contrast between the” Malays and the Papuans,* who live under the same physi- cal conditions, and are separated from each other only by a narrow space of sea. We will first consider the arguments which may be advanced in favor of classing the races of man as distinct species, and then the arguments on the other side. If a naturalist, who had never before seen a Negro, Hottentot, Australian, or Mongolian, were to compare them, he woul at once perceive that they differed in a multitude of char ters, some of slight and some of considerable importance. On inquiry he would find that they were adapted to live under widely different climates, and that they differed some- ? A vast number of measurements of Whites, Blacks, and Indians are given in the ‘‘Investigations in “the Military and Anthropolog. Statistics of American Soldiers,’’ by B. A. Gould, 1869, pp. 298-358; ‘“On the capacity of the lungs,’® p. 471. See also the numerous and valuable tables, by Dr. Weisbach, from the observations of Dr. Scherzer and Dr. Schwarz in the ‘Reise der Novara; Anthropolog. Theil,”? 1867. 3 See, for instance, Mr. Marshall’s account of the brain of a Bushwoman, in ‘Phil. Transact.,”? 1864, p. 519. 4 Wallace, “The Malay “Archipelago,” vol. ii,, 1869, p. 178. THE DESCENT OR ORIGIN OF MAN 225 what in bodily constitution and mental disposition. If he were then told that hundreds of similar specimens could be brought from the same countries, he would assuredly declare that they were as good species as many to which he had been in the habit of affixing specific names. This conclusion would be greatly strengthened as soon as he had ascertained that these forms had all retained the same char- acter for many centuries; and that negroes, apparently iden- tical with existing negroes, had lived at least 4,000 years ago.* He would also hear, on the authority of an excellent observer, Dr. Lund,® that the human skulls found in the caves of Brazil, intombed with many extinct mammals, be- longed to the same type as that now prevailing throughout the American Continent. Our naturalist would then perhaps turn to geographical distribution, and he would probably declare joe ae. must be distinct species which differ not only in appear- ance, but are fitted for hot as well as damp or dry countries, and for the Arctic regions. He might appeal to the fact that no species in the group next to man, namely the Quadrumana, can resist a low temperature, or any consid- erable change of climate; and that the species which come nearest to man have never been reared to maturity, even 7 5 With respect to the figures in the famous Egyptian caves of Abou-Simbel, M. Pouchet says (‘‘The Plurality of the Human Races,”’ Eng. translat., 1864, p. 50) that he was far from finding recognizable representations of the dozen or more nations which some authors believe that they can recognize. Even some of the most strongly marked races cannot be identified with that degree of unanimity which might have been expected from what has been written on the subject. Thus Messrs, Nott and Gliddon (“‘Types of Mankind,” p. 148) state that Rameses II., or the Great, has features superbly European; whereas Knox, another firm believer in the specific distinctness of the races of man Robe of Man,”’ 1850, p. 201), speaking of young Memnon (the same as meses II., as I am informed by Mr. Birch), insists in the strongest manner that he is identical in character with the Jews of Antwerp. Again, when ¥ looked at the statue of Amunoph IIL., I agreed with two officers of the estab- lishment, both competent judges, that he had a strongly marked negro type of features; but Messrs. Nott and Gliddon (ibid., p. 146, fig. 53) describe him 6s a hybrid, but not of ‘‘negro intermixture.”’ 6 As quoted by Nott and Gliddon, ‘‘Types of Mankind,” 1854, p. 439. They give also corroborative evidence; but C. Vogt thinks that the subject requires further investigation. 226 THE DESCENT OF MAN under the temperate climate of Europe. He would be deeply impressed with the fact, first noticed by Agassiz," that the different races of man are distributed over the world in the same zoological provinces as those inhab- ited by undoubtedly distinct species and genera of mam- mals, This is manifestly the case with the Australian, Mongolian, and Negro races of man; in a less well-marked manner with the Hottentots; but plainly with the Papuans and Malays, who are separated, as Mr. Wallace has shown, by nearly the same line which divides the great Malayan and Australian zoological provinces. The Aborigines of America range throughout the Continent; and this at first appears opposed to the above rule, for most of the produc- tions of the Southern and Northern halves differ widely: yet some few living forms, as the opossum, range from the one into the other, as did formerly some of the gigantic Edentata. The Eskimos, like other Arctic animals, extend round the whole polar regions. It should be observed that the amount of difference between the mammals of the sev- eral zoological provinces does not correspond with the de- gree of separation between the latter; so that it can hardly be considered as an anomaly that the Negro differs more, and the American much less, from the other races of man than do the mammals of the African and American conti- nents from the mammals of the other provinces. Man, it may be added, does not appear to have aboriginally inhab- ited any oceanic island; and in this respect he resembles the other members of his class. In determining whether the supposed varieties of the game kind of domestic animal should be ranked as such, or as specifically distinct, that is, whether any of them are descended from distinct wild species, every naturalist would tay much stress on the fact of their external parasites being specifically distinct. All the more stress would be laid on this fact, as it would be an exceptional one; for | am in- 7 “Diversity of Origin of the Human Races,”’ in the ‘*Christian Examiner, * July, 1850. THE DESCENT OR ORIGIN OF MAN 227 formed by Mr. Denny that the most different kinds of dogs, fowls, and pigeons, in England, are infested by the same species of Pediculi or lice. Now Mr. A. Murray has care- fully examined the Pediculi collected in different countries from the different races of man;° and he finds that they differ not only in color, but in the structure of their claws and limbs. In every case in which many specimens were obtained the differences were constant. The surgeon of a whaling ‘ship in the Pacific assured me that when the Pedi- euli with which some Sandwich Islanders on board swarmed, strayed on to the bodies of the English sailors, they died in the course of three or four days. These Pediculi were darker colored, and appeared different from those proper to the natives of Chiloe, in South America, of which he gave me specimens. These, again, appeared larger and much softer than European lice. Mr. Murray procured four kinds from Africa, namely, from the Negroes of the Hastern and Western coasts, from the Hottentots and Kaffirs; two kinds from the natives of Australia; two from North and two from South America. In these latter cases it may be presumed that the Pediculi came from natives inhabiting different dis- tricts. With insects slight structural differences, if constant, are generally esteemed of specific value; and the fact of the races of man being infested by parasites which appear to be specifically distinct might fairly be urged as an argument that the races themselves ought to be classed as distinct species. ; Our supposed naturalist, having proceeded thus far in his investigation, would next inquire whether the races of men, when crossed, were in any degree sterile. He might consult the work® of Prof. Broca, a cautious and philosophi- al observer, and in this he would find good evidence that some races were quite fertile together, but evidence of an opposite nature in regard to other races. Thus it has been 8 “Transact. R. Soc. of Edinburgh,” vol. xxii., 1861, p. 567. ® “On the Phenomena of Hybridity in the Geaus Homo,” Eng. translat., 1864. 228 THE DESCENT OF MAN asserted that the native women of Australia and Tasmania rarely produce children to European men; the evidence, however, on this head has now been shown to be almost valueless. The half-castes are killed by the pure blacks: and an account has lately been published of eleven half- caste youths murdered and burned at the same time, whose remains were found by the police.” Again, it has often been said that when mulattoes intermarry they produce few children; on the other hand, Dr. Bachman, of Charleston," positively asserts that he has known mulatto families which have intermarried for several generations, and have contin- ued on an average as fertile as either pure whites or pure blacks. Inquiries formerly made by Sir C. Lyell on this’ subject led him, as he informs me, to the same conclusion.” In the United States the census for the year 1854 included, according to Dr. Bachman, 405,751 mulattoes; and this number, considering all the circumstances of the case, seems small; but it may partly be accounted for by the degraded | and anomalous position of the class, and by the-profligacy of the women. A certain amount of absorption of mulattoes into negroes must always be in progress; and this would lead to an apparent diminution of the former. The inferior vitality of mulattoes is spoken of in a trustworthy work” as a well-known phenomenon; and this, although a different 10 See the interesting letter by Mr. T. A. Murray, in the ‘‘Anthropolog. Review,’’ April, 1868, p. lili, In this letter Count Strzelecki’s statement, that Australian women who have borne children to a white man are afterward sterile with their own race, is disproved. M. A. de Quatrefages has also collected (‘Revue des Cours Scientifiques,’’? March, 1869, p. 239) much evi- dence that Australians and Europeans are not sterile when crossed. 11 “An Examination of Prof. Agassiz’s Sketch of the Nat. Provinces of the Animal World,’’ Charleston, 1855, p. 44. 12 Dr, Rohlifs writes to me that be found the mixed races in the Great Sahara, derived from Arabs, Berbers, and Negroes of three tribes, extraordi- narily fertile. On the other hand, Mr. Winwood Reade informs me that the negroes on the Gold Coast, though admiring white men and mulattoes, have a maxim that mulattoes should not intermarry, as the children are few and sickly. This belief, as Mr. Reade remarks, deserves attention, as white men have visited and resided on the Gold Coast for four hundred years, so that the natives have had ample time to gain knowledge through experience. 13 **Military and Anthropolog. Statistics of American Soldiers,’? by B. A. Gould, 1869, p. 319. THE DESCENT OR ORIGIN OF MAN 229 consideration from their lessened fertility, may perhaps be advanced as a proof of the specific distinctness of the parent races. No doubt both animal and vegetable hybrids, when produced from extremely distinct species, are liable to pre- mature death; but the parents of mulattoes cannot be put under the category of extremely distinct species. The com- mon Mule, so notorious for long life and vigor, and yet so sterile, shows how little necessary connection there is in hybrids between lessened fertility and vitality; other analo- gous cases could be cited. Even if it should hereafter be proved that all the races of men were perfectly fertile together, he who was inclined from other reasons to rank them as distinct species might with justice argue that fertility_and_sterility are notsafe— criterions of specific distinctness. We know that these qualities are easily affected by changed conditions of life, or by close interbreeding, and that they are governed by highly complex laws; for instance, that of the unequal fertility of converse crosses between the same two species. With forms which must be ranked as undoubted species, a perfect series exists from those which are absolutely sterile when crossed, to those which are almost or completely fer- tile. The degrees of sterility do not coincide strictly with the degrees of difference betwéen the parents in external structure or habits of life. Man in many respects may be compared with those animals which have long been domesti- cated, and a large body of evidence can be advanced in favor of the Pallasian doctrine," that domestication tends to elimi- 4% “Phe Variation of Animals and Plants under Domestication,’’ vol. ii. p. 109. I may here remind the reader that the sterility of species when crossed is not a specially acquired quality, but, like the incapacity of certain trees to be grafted together, is incidental on other acquired differences, The nature of these differences is unknown, but they relate more especially to the repro- ductive system, and much less so to external structure or to ordinary differences in constitution. One important element in the sterility of crossed species ap- parently lies in one or both having been long habituated to fixed conditions; for we know that changed conditions have a special influence on the reprodue- tive system, and we have good reason to believe (as before remarked) that the fluctuating conditions of domestication tend to eliminate that sterility which is so general with species, in a natural state, when crossed. It has elsewhere 230 THE DESCENT OF MAN nate the sterility which is so general a result of the crossing of species in a state of nature. From these several con- siderations it may be justly urged that the perfect fertility of the intercrossed races of man, if established, would not absolutely preclude us from ranking them as distinct species. Independently of fertility, the characters presented by the offspring from a cross have been thought to indicate whether or not the parent-forms ought to be ranked as spe- cies or varieties; but, after carefully studying the evidence, I have come to the conclusion that no general rules of this kind can be trusted. The ordinary result of a cross is the production of a blended or intermediate form; but in certain cases some of the offspring take closely after one parent- form, and some after the other. This is especially apt to occur when the parents differ in characters which first appeared as sudden variations or monstrosities."* I refer to this point because Dr. Rohlfs informs me that he has frequently seen in Africa the offspring of negroes crossed with members of other races, either completely black or ‘completely white, or rarely piebald. On the other hand, it is notorious that in America mulattoes commonly present an intermediate appearance. We have now seen that a naturalist might feel himself been shown by me (ibid., vol. ii. p. 185, and ‘‘Origin of Species,’’ 5th edit, p. 317) that the sterility of crossed species has not been acquired through natural selection: we can see that when two forms have already been rendered very sterile, it is scarcely possible that their sterility should be augmented by the preservation or survival of the more and more sterile individuals; for as the sterility increases, fewer and fewer offspring will be produced from which to breed, and at last only single individuals will be produced, at the rarest inter- vals. But there is even a higher grade of sterility than this. Both Gartner and Kélreuter have proved that in genera of plants including many species, a series can be formed from species which when crossed yield fewer and fewer seeds, to species which never produce a single seed, but yet are affected by the pollen of the other species, as shown by the swelling of the germen. It is here manifestly impossible to select the more sterile individuals, which have already ceased to yield seeds; so that the acme of sterility, when the germen alone is affected, cannot have been gained through selection. This acme, ard no doubt the other grades of sterility, are the incidental results of certam unknown differences in the constitution of the reproductive system of the species which are crossed. % «The Variation of Animals,”’ etc., vol ii. p. 92. THE DESCENT OR ORIGIN OF MAN 2381 inlly justified in ranking the races of man as distinct species; for he has found that they are distinguished by many differ- ences in structure and constitution, some being of impor- tance. These differences have also remained nearly constant for very long periods of time. Our naturalist will have been in some degree influenced by the enormous range of man, which is a great anomaly in the class of mammals, if mankind be viewed as a single species. He will have been struck with the distribution of the several so-called races, which accords with that of other undoubtedly distinct species of mammals. Finally, he might urge that the mutual fertility of all the races has not as yet been fully proved, and even if proved would not be an absolute proof of their specific identity. On the other side of the question, if our supposed natur- alist were to inquire whether the forms of man keep distinct like ordinary species, when mingled together in large num- bers in the same country, he would immediately discover that this was by no means the case. In Brazil he would behold an immense mongrel population of Negroes and Portuguese; in Chiloe and other parts of South America he would behold the whole population consisting of Indians and Spaniards blended in various degrees.’* In many parts of the same continent he would meet with the most complex crosses between Negroes, Indians, and Europeans; and, judging from the vegetable kingdom, such triple crosses afford the severest test of the mutual fertility of the parent- forms. In one island of the Pacific he would find a small population of mingled Polynesian and English blood; and in the Fiji Archipelago a population of Polynesian and Negritos crossed in all degrees. Many analogous cases could be added; for instance, in Africa. Hence the races 38 M. de Quatrefages has given (“‘Anthropolog. Review,’’ January, 1869, p. 22) an interesting account of the success and energy of the Paulistas in Brazil, who are a much-crossed race of Portuguese and Indians, with a mixture of the blood of other races. Se 232 THE DESCENT OF MAN of man are not sufficiently distinct to inhabit the same-conn- try without fusion; and the absence of fusion affords the usual and best test of specific distinctness. Our naturalist would likewise be much disturbed as soon as he perceived that the distinctive characters of all the races were highly variable. This fact strikes every one on first beholding the negro slaves in Brazil, who. have been imported from all parts of Africa. The same remark holds good with the Polynesians, and with many other races. It may be doubted whether any character can be named which is distinctive of a race andis constant. Savages, even within the limits of the same tribe, are not nearly so uniform in character as has been often asserted. Hottentot women offer certain peculiarities, more strongly marked than those oc- curring in any other race, but these are known not to be of constant occurrence. In the several American tribes, color and hairiness differ considerably; as does color to a certain degree, and the shape of the features greatly, in the negroes of Africa. The shape of the skull varies much in some races;’7 and so it is with every other character. Now all naturalists have learned by dearly bought experience how rash it is to attempt to define species by the aid of inconstant characters. But the most weighty of all the arguments against treat- ing the races of man as distinct species is that they graduate into each other, independently in many cases, as far as we can judge, of their having intercrossed. Man has been studied more carefully than any other animal, and yet there is the greatest possible diversity among capable judges whether he should be classed as a single species or race, or as two (Virey), as three (Jacquinot), as four (Kant), five (Blumenbach), six (Buffon), seven (Hunter), eight (Agas- siz), eleven (Pickering), fifteen (Bory St. Vincent), sixteen. " For instance with the aborigines of America and Australia. Prof, Huxley says (‘‘Transact. Internat. Congress of Prehist. Arch.,’’ 1868, p. 105) that the skulls of many South Germans and Swiss are ‘‘as short and as broad as those of the Tartars,’’ etc. THE DESCENT OR ORIGIN OF MAN 233 (Desmoulins), twenty-two (Morton), sixty (Crawfurd), or as sixty-three, according to Burke."* This diversity of judg- ‘ment does not prove that the races ought not to be ranked as species, but it shows that they graduate into each other, and that it is hardly possible to discover clear distinctive characters between them. Every naturalist who has had the misfortune to under- take the description of a group of highly varying organisms has encountered cases (I speak after experience) precisely like that of man, and if of a cautious disposition, he will end by uniting all the forms which graduate into each other under a single species; for he will say to himself that he has no right to give names to objects which he cannot define. Cases of this kind occur in the Order which includes man, namely, in certain genera of monkeys; while in other genera, as in Cercopithecus, most of the species can be determined with certainty. In the American genus Cebus, the various forms are ranked by some naturalists as species, by others as mere geographical races. Now if numerous specimens of Cebus were collected from all parts of South America, and those forms which at present appear to be specifically dis- tinct were found to graduate into each other by close steps, they would usually be ranked as mere varieties or races; and this course has been followed by most naturalists with respect to the races of man. Nevertheless, it must be con- fessed that there are forms, at least in the vegetable king- dom,”® which we cannot avoid naming as species, but which are connected together by numberless gradations, indepen- dently of intercrossing. Some naturalists have lately employed the term ‘‘sub- species’’ to designate forms which possess many of the 18 See a good discussion on this subject in Waitz, ‘“Introduct. to Anthro- pology,’’ Eng. translat., 1863, pp. 198-208, 227. I have taken some of the above statements from H. Tuttle’s ‘‘Origin and Antiquity of Physical Man,” Boston, 1866, p. 35. ae : Y 19 Prof. Nageli has carefully described several striking cases in his “Botanische Mittheilungen,’’? B. ii., 1866, s. 294-369. Prof. Asa Gray has made analogous remarks on some intermediate forms in the Composite of North America. 234 THE DESCENT OF MAN characteristics of true species, but which hardly deserve so high arank. Now if we reflect on the weighty arguments above given, for raising the races of man to the dignity of | species, and the insuperable difficulties on the other side in defining them, it seems that the term ‘‘sub-species’’ might | here be used with propriety. But from long habit the term | ‘‘race’’ will perhaps always be employed. The choice of terms is only sb far important in that it is desirable to use, as far as‘ possible, the same terms for the same degrees of difference. Unfortunately this can rarely be done: for the larger genera generally include closely allied forms, which can be distinguished only with much difficulty, while the smaller genera within the same family include forms that are perfectly distinct; yet all must be ranked equally as species. So again, species within the same large genus by no means resemble each other to the same degree; on the contrary, some of them can generally be arranged in little groups round other species, like satellites:round planets.”° The question whether mankind consists of one or several species has of late years been much discussed by anthropolo- gists, who are divided into the two schools of monogenists and po lygenists. Those who do not admit the principle of evolution must look at species as separate creations, or as in some manner as distinct entities; and they must decide what forms of man they will consider as species by the analogy of the method commonly pursued in ranking other organic beings as species. But it is a hopeless endeavor to decide this point, until some definition of the term ‘‘species’’ is generally accepted; and the definition must not include an indeterminate element such as an act of creation. We might as well attempt without any definition to decide whether a certain number of houses should be called a village, town, or city. We have a practical illustration of the difficulty in the never-ending doubts whether many closely allied mammals, birds, insects, and plants, which 90 “Origin of Species,’’ 5th edit., p. 68. THE DESCENT OR ORIGIN OF MAN 235 represent each other respectively in North America and Hurope, should be ranked as species or geographical races; and the like holds true of the productions of many islands situated at some little distance from the nearest continent. Those naturalists, on the other hand, who admit the principle of evolution, and this is now admitted by the ma- jority of rising men, will feel no doubt that all the races of man are descended from a single primitive stock; whether or not they may think fit to designate the races as distinct species, for the sake of expressing their amount of differ- ence.” With our domestic animals the question whether the various races have arisen from one or more species is somewhat different. Although it may be admitted that all the races, as well as all the natural species within the same genus, have sprung from the same primitive stock, yet it is a fit subject for discussion, whether all the domestic races of the dog, for instance, have acquired their present amount of difference since some one species was first domesticated by man; or whether they owe some of their characters to inheritance from distinct species, which had already been differentiated in a state of nature. With man no such ques- tion can arise, for he cannot be said to have been domesti- cated at any particular period. During an early stage in the divergence of the races of man from a common stock, the differences between the races and their number must have been small; consequently, as far as their distinguishing characters are concerned, they then had less claim to rank as distinct species than the ex- isting so-called races. Nevertheless, so arbitrary is the term of species, that such early races would perhaps have been ranked by some naturalists as distinct species, if their dif- ferences, although extremely slight, had been more constant than they are at present, and had not graduated into each other. It is however possible, though far from probable, that 21 See Prof. Huxley to this effect in the ‘‘Fortnightly Review,’’ 1865, p. 275. 236 THE DESCENT OF MAN the early progenitors of man might formerly have diverged much in character, until they became more unlike each other than any now existing races; but that subsequently, as sug- gested by Vogt,” they converged in character. When man selects the offspring of two distinct species for the same ob- ject, he sometimes induces a considerable amount of conver- gence, as far as general appearance is concerned. This is the case, as shown by Von Nathusius,” with the improved breeds of the pig, which are descended from two distinct species; and in a less marked manner with the improved breeds of cattle. A great anatomist, Gratiolet, maintains that the anthropomorphous apes do not form a natural sub-group; but that the orang is a highly developed gib- bon or semnopithecus, the chimpanzee a highly developed macacus, and the gorilla a highly developed mandrill. If this conclusion, which rests almost exclusively on brain- characters, be admitted, we sbould have a case of conver- gence, at least in external characters, for the anthropo- morphous apes are certainly more like each other in many points than they are to other apes. All analogical resem- blances, as of a whale to a fish, may indeed be said to be cases of convergence; but this term has never been applied to superficial and adaptive resemblances. It would, how- ever, be extremely rash to attribute to convergence close similarity of character in many points of structure among the modified descendants of widely distinct beings. The form of a crystal is determined solely by the molecular forces, and it is not surprising that dissimilar substances should sometimes assume the same form; but with organic “beings we should bear in mind that the form of each de- pends on an infinity of complex relations, namely, on varia- tions due to causes far too intricate to be followed—on the nature of the variations preserved, these depending on the 2 “Tectures on Man,’’ Eng. translat., 1864, p. 468. 23 ‘Die Racen des Schweines,’’ 1860, s. 46. ‘‘Vorstudien fiir Geschichte, etc., Schweineschadel,’? 1864, s. 104. With respect to cattle, see M. de Quatrefages, ‘‘Unité de l’Espéce Humaine,’’ 1861, p. 119. THE DESCENT OR ORIGIN OF MAN 237 physical conditions, and still more on the surrounding or- ganisms which compete with each—and lastly, on inheri- tance (in itself a fluctuating element) from innumerable progenitors, all of which have had their forms determined through equally complex relations. It appears incredible that the modified descendants of two organisms, if these differed from each other in a marked manner, should ever afterward converge so closely as to lead to a near approach to identity throughout their whole organization. In the case of the convergent races of pigs above referred to, evi- dence of their descent from two primitive stocks is, accord- ing to Von Nathusius, still plainly retained in certain bones of their skulls. If the races of man had descended, as is supposed by some naturalists, from two or more species, which differed from each other as much, or nearly as much, as does the orang from the gorilla, it can hardly ibe doubted that marked differences in the structure of ‘certain bones would still be discoverable in man as he “now exists. Although the existing races of man differ in many re- spects, as in color, hair, shape of skull, proportions of the body, etc., yet, if their whole structure be taken into con- sideration, they are found to resemble each other closely in a multitude of points. Many of these are of so unimportant or of so singular a nature that it is extremely improbable that they should have been independently acquired by abo- riginally distinct species or races. The same remark holds good with equal or greater force with respect to the numer- ous points of mental similarity between the most distinct races of man. The American aborigines, Negroes, and Europeans are as different from each other in mind as any three races that can be named; yet I was incessantly struck, while living with the Fuegians on board the ‘‘Beagle,’’ with the many little traits of character showing how similar their minds were to ours; and so it was with a full-blooded negro with whom I happened once to be intimate. 238 THE DESCENT OF MAN He who will read Mr. Tylor’s and Sir J. Lubbock’s interesting works” can hardly fail to be deeply impressed with the close similarity between the men of all races in tastes, dispositions, and habits. This is shown by the pleasure which they all take in dancing, rude music, act- ing, painting, tattooing, and otherwise decorating them- selves; in their mutual comprehension of gesture-language, by the same expression in their features, and by the same inarticulate cries, when excited by the same emotions. This similarity, or rather identity, is striking, when contrasted with the different expressions and cries made by distinet species of monkeys. There is good evidence that the art of shooting with bows and arrows has not been handed down from any common progenitor of mankind; yet, as Westropp and Nilsson have remarked,* the stone arrow- heads, brought from the most distant parts of the world, and manufactured at the most remote periods, are almost | identical; and this fact can only be accounted for by the various races having similar inventive or mental powers. The same observation has been made by archeologists” with respect to certain widely prevalent ornaments, such as zigzags, etc.; and with respect to various simple beliefs and customs, such as the burying of the dead under mega- lithic structures. I remember observing in South America,” that there, as in so many other parts of the world, men have generally chosen the summits of lofty hills to throw up piles of stones, either as a record of some remarkable event, or for burying their dead. Now when naturalists observe a close agreement in numerous small details of habits, tastes, and dispositions between two or more domestic races, or between nearly 24 Tylor’s ‘‘Early History of Mankind,’’ 1865; with respect to gesture- language, see p. 54. Lubbock’s ‘‘Prehistoric Times,”’ 2d edit., 1869. 25 “On Analogous Forms of Implements,’’ in ‘‘Memoirs of Anthropolog, Soc.,”? by H. M. Westropp. ‘‘The Primitive Inhabitants of Scandinavia,” Eng. translat., edited by Sir J. Lubbock, 1868, p. 104. 26 Westropp, ‘‘On Cromlechs,”’ etc., “‘Journal of Ethnological Soc.,”’ as given in ‘‘Scientific Opinion,’’ June 2, 1869, p. 3. 21 “Journal of Researches: Voyage of the Beagle,”’ p. 46. THE DESCENT OR ORIGIN OF MAN 289 allied natural forms, they use this fact as an argument that they are descended from a common progenitor who was thus endowed; and consequently that all should be classed under the same species. ‘The same argument may be applied with much force to the races of man. As it is improbable that the numerous and unimportant points of resemblance between the several races of man in bodily structure and mental faculties (I do not here refer to similar customs) should all have been independently acquired, they must have been inherited from progenitors who had these same characters. We thus gain some insight into the early state of man, before he had spread step by step over the face of the earth. The spreading of man to regions widely separated by the sea, no doubt, preceded any great amount of divergence of character in the several races; for otherwise we should sometimes meet with the same race in distinct continents; and this is never the case. Sir J. Lub- bock, after comparing the arts now practiced by savages in all parts of the world, specifies those which man could not have known when he first wandered from his original birth- place; for if once learned they would never have been for- gotten.” He thus shows that ‘‘the spear, which is but a development of the knife-point, and the club, which is but along hammer, are the only things left.’” He admits, how- ever, that the art of making fire probably had been already discovered, for it is common to all the races now existing, and was known to the ancient cave inhabitants of Europe. Perhaps the art of making rude canoes or rafts was likewise | known; but as man existed at a remote epoch, when the ‘land in many places stood at a very different level to what it does now, he would have been able, without the aid of canoes, to have spread widely. Sir J. Lubbock further re- marks how improbable it is that our earliest ancestors could have ‘‘counted as high as ten, considering that so many races now in existence cannot get beyond four.’’ Neverthe- less, at this early period, the intellectual and social faculties % ‘Prehistoric Times,’’ 1869, p. 574. 240 THE DESCENT OF MAN of man could hardly have been inferior in any extreme degree to those possessed at present by the lowest savages; otherwise primeval man could not have been so eminently successful in the struggle for life, as proved by his early and wide diffusion. From the fundamental differences between certain lan- _guages, some philologists have inferred that when man first became widely diffused, he was not a speaking animal; but it may be suspected that languages, far less perfect than any now spoken, aided by gestures, might have been used, and yet have left no traces on subsequent and more highly developed tongues. Without the use of some language, however imperfect, it appears doubtful whether man’s in- tellect could have risen to the standard implied by his dominant position at an early period. Whether primeval man, when he possessed but few arts, and those of the rudest kind, and when his power of lan- guage was extremely imperfect, would have deserved to be called man, must depend on the definition which we employ. In a series of forms graduating insensibly from some ape-like creature to man as he now exists, it would be impossible to fix on any definite point when the term ‘‘man’’ ought to be used. But this is a matter of very little importance. So, again, it is almost a matter of indifference whether the so-called races of man are thus designated, or are ranked as species or sub-species; but the latter term appears the more appropriate. Finally, we may conclude that when the principle of evolution is generally accepted, as it surely will be before long, the dispute between the monogenists and polygenists will die a silent and unob- served death. One other question ought not to be passed over without notice, namely, whether, as is sometimes assumed, each sub- species or race of man has sprung from a single pair of pro- genitors. With our domestic animals a new race can readily be formed by carefully matching the varying offspring from % a THE DESCENT OR ORIGIN OF MAN 241 a single pair, or even from a single individual possessing some new character; but most of our races have been formed, not intentionally from a selected pair, but unconsciously by the preservation of many individuals which have varied, however slightly, in some useful or desired manner. If in one country stronger and heavier horses, and in another country lighter and fleeter ones, were habitually preferred, we may feel sure that two distinct sub-breeds would be pro- duced in the course of time, without any one pair having been separated and bred from, in either country. Many races have been thus formed, and their manner of formation is closely analogous to that of natural species. We know, also, that the horses taken to the Falkland Islands have, during successive generations, become smaller and weaker, while those which have run wild on the Pampas have ac- quired larger and coarser heads; and such changes are mani- festly due, not to any one pair, but to all the individuals having been subjected to the same conditions, aided, per- haps, by the principle of reversion. The new sub-breeds in such cases are not descended from any single pair, but from many individuals which have varied in different degrees, but in the same general manner; and we may conclude that the races of man have been similarly produced, the modifica- tions being either the direct result of exposure to different conditions, or the indirect result of some form of selection. But to this latter subject we shall presently return. On the Extinction of the Races of Man.—The partial or complete extinction of many races and sub-races of man is historically known. Humboldt saw in South America a parrot which was the sole living creature that could speak a word of the language of a lost tribe.“ Ancient monuments and stone implements found in all parts of the world, about which no tradition has been preserved by the present inhab- itants, indicate much extinction. Some small and broken tribes, remnants of former races, still survive in isolated and generally mountainous districts. In Europe the ancient Descent—Vo.. I.—11 | This race is | modern, that we have ever heard of.’’® It differed, there- 242 THE DESCENT OF MAN races were all, according to Schaaffhausen,” ‘‘lower in the scale than the rudest living savages’; they must therefore have differed, to a certain extent, from any existing race. The remains described by Prof. Broca from Les Eyzies, though they unfortunately appear to have belonged to a single family, indicate a race with a most singular com- bination of low or simious, and of high characteristics. “entirely different from any other, ancient or fore, from the quaternary race of the caverns of Belgium. Man can long resist conditions which appear extremely unfavorable for his existence. He has long lived in the extreme regions of the North, with no wood for his canoes or implements, and with only blubber as fuel and melted snow as drink. In the southern extremity of America the Fuegians survive without the protection of clothes, or of \ any building worthy to be called a hovel. In South Africa . the aborigines wander over arid plains, where dangerous beasts abound. Man can withstand the deadly influence of the Terai at the foot of the Himalaya, and the pestilential shores of tropical Africa. Extinction follows chiefly from the competition of tribe with tribe, and race with race. Various checks are always in action, serving to keep down the numbers of each sav- age tribe—such as periodical famines, nomadic habits, and the consequent deaths of infants, prolonged suckling, wars, accidents, sickness, licentiousness, the stealing of women, infanticide, and especially lessened fertility. If any one of these checks increases in power, even slightly, the tribe thus affected tends to decrease; and when of two adjoining tribes one becomes less numerous and less powerful than the other, the contest is soon settled by war, slaughter, cannibalism, slavery, and absorption. Even when a weaker tribe is not thus abruptly swept away, if it once begins to %9 Translation in ‘‘Anthropological Review,’’ October, 1868, p. 431. 2 ‘Transact. Internat. Congress of Prehistoric Arch.,’? 1868, pp. 172-15. See also Broca (translation) in ‘‘ Anthropological Review,’ October, 1868, p. 410. 81 Dr, Gerland ‘‘Ueber das Aussterben der Naturvélker,’’ 1868, s. 82. THE DESCENT OR ORIGIN OF MAN 243 decrease, it generally goes on decreasing until it becomes extinct.” When civilized nations come into contact with barbarians the struggle is short, except where a deadly climate gives its aid to the native race. Of the causes which lead to the vic- tory of civilized nations, some are plain and simple, others complex and obscure. We can see that the cultivation of the land will be fatal in many ways to savages, for they cannot, or will not, change their habits. New diseases and vices have in some cases proved highly destructive; and it appears that a new disease often causes much death, until those who are most susceptible to its destructive influence are gradually weeded out;* and so it may be with the evil effects from spirituous liquors, as well as with the uncon- querably strong taste for them shown by so many savages. It further appears, mysterious as is the fact, that the first Co. of distinct and separated peoples generates disease.™ Mr. Sproat, who in Vancouver Island closely attended to the subject of extinction, believed that changed habits of life, consequent on the advent of Europeans, induces much ill-health. He lays, also, great stress on the apparently trifling cause that the natives become ‘‘bewildered and dull by the new life around them; they lose the motives for exertion, and get no new ones in their place.’’ * The grade of their civilization seems to be a most impor- tant element in the success of competing nations. A few enturies ago Europe feared the inroads of Eastern barba- | rans now any such fear would be ridiculous. It is a more curious fact, as Mr. Bagehot has remarked, that savages did not formerly waste away before the classical nations, as they now do before modern civilized nations; had they done so, 32 Gerland (‘‘Ueber das Aussterben der Naturvélker,’’ 1868, s. 12) gives facts in support of this statement. 33 See remarks to this effect in Sir H. Holland’s ‘‘Medical Notes and Reflec- tions,’’ 1839, p. 390. 24 J have collected (‘‘Journal of Researches: Voyage of the Beagle,” p. 435) a good many cases bearing on this subject; see also Gerland (ibid., 8. 8). Poeppig speaks of the ‘‘breath of civilization as poisonous to savages.” Sproat, “Scenes and Studies of Savage Life,’’ 1868, p. 284. 244 THE DESCENT OF MAN Kp the old moralists would have mused over the event; but | there is no lament in any writer of that period over the perishing barbarians.*° The most potent of all the causes of extinction appears in many cases to be lessened fertility and ill-health, especially among the children, arising from changed conditions of life, notwithstanding that the new conditions may not be injurious in themselves. J am much indebted to Mr. H. H. Howorth for having called my atten- tion to this subject, and for having given me information respecting it. I have collected the following cases. When Tasmania was first colonized the natives were roughly estimated by some at 7,000, and by others at 20,000. Their number was soon greatly reduced, chiefly by fighting with the English and with each other. After the famous hunt by all the colonists, when the remaining natives delivered themselves up to the government, they consisted only of 120 individuals,*” who were in 1882 trans- ported to Flinders Island. This island, situated between Tasmania and Australia, is forty miles long, and from twelve to eighteen miles broad: it seems healthy, and the natives. were well treated. Nevertheless, they suffered greatly in health. In 1834 they consisted (Bonwick, p. 250) of forty-seven adult males, forty-eight adult females, and sixteen children, or in all of 111 souls. In 1835 only one hundred were left. As they continued rapidly to decrease, oy and as they themselves thought that they should not perish so quickly elsewhere, they were removed in 1847 to Oyster Cove, in the southern part of Tasmania. They then con- sisted (December 20, 1847) of fourteen men, twenty-two women, and ten children. But the change of site did no good. Disease and death still pursued them, and in 1864 one man (who died in 1869), and three elderly women alone 36 Bagehot, ‘‘Physics and Politics,’’ ‘‘Fortnightly Review,” April 1, 1868, p. 455. 31 All the statements here given are taken from ‘‘The Last of the Tas- manians,”’ by J. Bonwick, 1870. % This is the statement of the Governor of Tasmania, Sir. W. Denison, “Varieties of Vice-Regal Life,’? 1870, vol. i. p. 6%. THE DESCENT OR ORIGIN OF MAN 245 survived. The infertility of the women is even a more remarkable fact than the liability of all to ill-health and death. At the time when only nine women were left at Oyster Cove, they told Mr. Bonwick (p. 886) that only two had ever borne children: and these two had together pro- duced only three children! ~——~With respect to the cause of this extraordinary state of things, Dr. Story remarks that death followed the attempts to civilize the natives. ‘‘If left to themselves to roam as they were wont and undisturbed, they would have reared more children, and there would have been less mortality.” Another careful observer of the natives, Mr. Davis, remarks: ‘“The births have been few, and the deathsnumerous. This may have been in a great measure owing to their change of living and food; but more so to their banishment from the mainland of Van Diemen’s Land, and consequent depression of spirits’’ (Bonwick, pp. 888, 390). Similar facts have been observed in two widely different parts of Australia. The celebrated explorer, Mr. Gregory, told Mr. Bonwick that in Queensland ‘‘the want of repro- duction was being already felt with the blacks, even in the most recently settled parts, and that decay would set in.” Of thirteen aborigines from Shark’s Bay who visited Mur- chison River, twelve died of consumption within three months. * The decrease of the Maories of New Zealand has been carefully investigated by Mr. Fenton, in an admirable Re- port, from which all the following statements, with one exception, are taken.*® The decrease in number since 1830 is admitted by every one, including the natives themselves, and is still steadily progressing. Although it has hitherto been found impossible to take an actual census of the na- tives, their numbers were carefully estimated by residents - 39 For these cases, see Bonwick’s ‘‘Daily Life of the Tasmanians,” 1870, p. 90; and ‘The Last of the Tasmanians,’’ 1870, p. 386. ; 40 “Observations on the Aboriginal Inhabitants of New Zealand,” published by the Government, 1859, » 246 THE DESCENT OF MAN in many districts. The result seems trustworthy, and shows that during the fourteen years previous to 1858 the decrease was 19.42 per cent. Some of the tribes thus carefully ex- amined lived above a hundred miles apart, some on the coast, some inland; and their means of subsistence and habits differed to a certain extent (p. 28). The total num- ber in 1858 was believed to be 58,700, and in 1872, after a second interval of fourteen years, another census was taken, and the number is given as only 36,359, showing a decrease of 32.29 per cent!** Mr. Fenton, after showing in detail the insufficiency of the various causes usually assigned in expla- nation of this extraordinary decrease, such as new diseases, the profligacy of the women, drunkenness, wars, etc., con- cludes on weighty grounds that it depends chiefly on the unproductiveness of the women, and on the extraordinary mortality of the young children (pp. 31, 34). In proof of this he shows (p. 83) that in 1844 there was one non-adult for every 2.57 adults; whereas in 1858 there was only one non-adult for every 8.27 adults. The mortality of the adults is also great. He adduces as a further cause of the decrease . |fthe inequality of the sexes; for fewer females are born than males. To this latter point, depending perhaps on a widely ‘distinct cause, I shall return in a future chapter. Mr. Fen- ton contrasts with astonishment the decrease in New Zealand with the increase in Ireland—countries not very dissimilar in climate, and where the inhabitants now follow nearly similar habits. The Maories themselves (p. 35) ‘‘attribute their de- cadence, in some measure, to the introduction of new food and clothing, and the attendant change of habits’’; and it will be seen, when we consider the influence of changed conditions on fertility, that they are probably right. The diminution began between the years 1830 and 1840; and Mr. Fenton shows (p. 40) that about 1880 the art of manu- facturing putrid corn (maize), by long steeping in water, was discovered and largely practiced; and this proves that a change of habits was beginning among the natives even 4 ‘New Zealand,’’ by Alex. Kennedy, 1873, p. 47. THE DESCENT OR ORIGIN OF MAN 247 when New Zealand was only thinly inhabited by Europeans. When I visited the Bay of Islands in 1885, the dress and food of the inhabitants had already been much modified: they raised potatoes, maize, and other agricultural produce, and exchanged them for English manufactured goods and tobacco. It is evident, from many statements in the life of Bishop Patteson,*? that the Melanesians of the New Hebrides and neighboring archipelagoes suffered to an extraordinary de- gree in health, and perished in large numbers, when they . were removed to New Zealand, Norfolk Island, and other salubrious places, in order to be educated as missionaries. ‘~The decrease of the native population of the Sandwich Tslands is as notorious as that of New Zealand. It has been } roughly estimated, by those best capable of judging, that when Cook discovered the Islands in 1779, the population amounted to about 800,000. According to a loose census in 1823, the numbers then were 142,050. In 1832, and at sever- al subsequent periods, an accurate census was officially taken, \ but I have been able to obtain only the following returns: \ Native Porutation. {Annual rate of decrease per — cent, assuming it to have (Except during 1832 and] been uniform between the Year. 1836, when the few for-| successive censuses; these eigners in the islands} censuses being taken at ir- were included.) regular intervals. DOB Dias isccevei send scieeesodeaekae 130,313 ; 4.46 TRS Giccsiwesreacereataneacn sees 108,579 t 2.47 LEDS ricaesrinpdcnesenesidosscincaces 71,019 t 0.81 L860 wieawosedacds verses: sseneus 67,084 2.18 TSG6i cisedossacndonanecanciaesse 58,765 ; 2.17 DST Qi sseciedasganaicaendenceoubees 51,531 We here see that in the interval of forty years, between 1832 and 1872, the population has decreased no less than 2 “Tife of J. C. Patteson,’’? by C. M. Monge; 1874; see more especially - vol. i. p. 530. 248 THE DESCENT OF MAN sixty-eight per cent! This has been attributed by most writers to the profligacy of the women, to former bloody wars, and to the severe labor imposed on conquered tribes and to newly introduced diseases, which have been on sev- eral occasions extremely destructive. No doubt these and other such causes have been highly efficient, and may ae- count for the extraordinary rate of decrease between the years 1832 and 1836; but the most potent of all the causes + seems to be lessened fertility. According to Dr. Ruschen- berger of the U. S. Navy, who visited these islands between 1835 and 1837, in one district of Hawaii, only twenty-five men out 1,184, and in another district only ten out of 687, had a family with as many as three children. Of eighty married women, only thirty-nine had ever borne children; and ‘‘the official report gives an average of half a child to each married couple in the whole island.’’ This is almost exactly the same average as with the Tasmanians at Oyster Cove. Jarves, who published his History in 1848, says that ‘‘families who have three children are freed from all taxes; those having more, are rewarded by gifts of land and other encouragements.’’ This unparalleled enactment by the gov- ernment well shows how infertile the race had become. The Rev. A. Bishop stated in the Hawaiian ‘‘Spectator,’’ in 1839, that a large proportion of the children die at early ages, and Bishop Staley informs me that this is still the case, just as in New Zealand. This has been attributed to the neglect of the children by the women, but it is probably in large part due to innate weakness of constitution in the children, in relation to the lessened fertility of their parents. There is, moreover, a further resemblance to the case of New Zealand, in the fact that there is a large excess of- male over female births: the census of 1872 gives 31,650 males to 25,247 females of all ages, that is 125.386 males for every 100 fe- ;-mnales; whereas in all civilized countries the females exceed \ the males. No doubt the profligacy of the women may in part account for their small fertility; but their changed hab- its of life is a much more probable cause, and which will at THE DESCENT OR ORIGIN OF MAN 249 the same time account for the increased mortality, especially of the children. The islands were visited by Cook in 1779, by Vancouver in 1794, and often subsequently by whalers. In 1819 missionaries arrived, and found that idolatry had been already abolished, and other changes effected by the king. After this period there was a rapid change in almost all the habits of life of the natives, and they soon became “the most civilized of the Pacifie Islanders.’’ One of my informants, Mr. Coan, who was born on the islands, remarks that the natives have undergone a greater change in their habits of life in the course of fifty years than Englishmen during a thousand years. From information received from Bishop Staley, it does not appear that the poorer classes have ever much changed their diet, although many new kinds of fruit have been introduced, and the sugar-cane is in universal use. Owing, however, to their passion for imitating Europeans, they altered their manner of dressing at an early period, and the use of alcoholic drinks became very general. Although these changes appear inconsider- able, I can well believe, from what is known with respect to animals, that they might suffice to lessen the fertility of the natives.** Lastly, Mr. Macnamara states“ that the low and degraded inhabitants of the Andaman Islands, on the eastern side of the Gulf of Bengal, are ‘‘eminently susceptible to any change of climate; in fact, take them away from their island homes, and they are almost certain to die, and that independently of diet or extraneous influences.’’ He further states that the inhabitants of the Valley of Nepal, which is extremely hot 4 The foregoing statements are taken chiefly from the following works “Jarves’s History of the Hawaiian Islands,’’ 1843, pp. 400-407. Cheever, “Tife in the Sandwich Islands,’’ 1851, p, 277. Ruschenberger is quoted by Bonwick, ‘‘Last of the Tasmanians,’’ 1870, p. 378. Bishop is quoted by Sir E. Belcher, ‘‘Voyage Round the World,’’ 1843, vol. i. p. 272. I owe the census of the several years to the kindness of Mr. Coan, at the request of Dr. Youmans, of New York; and in most cases I have compared the Youmans figures with those given in several of the above-named works. I have omitted the census for 1850, as I have seen two widely different numbers given. #4 “The Indian Medica} Gezette,’’ November 1, 1871, p. 240. 250 THE DESCENT OF MAN in summer, and also the various hill-tribes of India, suffer from dysentery and fever when on the plains; and they die if they attempt to pass the whole year there. We thus see that many of the wilder races of man are apt to suffer much in health when subjected to changed condi- tions or habits of life, and not exclusively from being trans- ported to a new climate. Mere alterations in habits, which do not appear injurious in themselves, seem to have this same effect; and in several cases the children are particu- larly liable to suffer. It has often been said, as Mr. Mac- namara remarks, that man can resist with impunity the greatest diversities of climate and other changes; but this is true only of the civilized races. Man in his wild condi- tion seems to be in this respect almost as susceptible as his nearest allies, the anthropoid apes, which have never yet survived long, when removed from their native country. Lessened fertility from changed conditions, as in the case of the Tasmanians, Maories, Sandwich Islanders, and apparently the Australians, is still more interesting than their liability to ill-health and death; for even a slight de- gree of infertility, combined with those other causes which tend to check the increase of every population, would sooner or later lead to extinction. The diminution of fertility may be explained in some cases by the profligacy of the women ‘(as until lately with the Tahitians), but Mr. Fenton has shown that this explanation by no means suffices with the New Zealanders, nor does it with the Tasmanians. In the paper above quoted, Mr. Macnamara gives reasons for believing that the inhabitants of districts subject to malaria are apt to be sterile; but this cannot apply in several of the above cases. Some writers have suggested that the aborigines of islands have suffered in fertility and health from long-continued interbreeding; but in the above cases infertility has coincided too closely with the arrival of Euro- peans for us to admit this explanation. Nor have we ar present any reason to believe that man is highly sensitive to the evil effects of interbreeding, especially in areas so _ THE DESCENT OR ORIGIN OF MAN 251 large as New Zealand, and the Sandwich Archipelago with its diversified stations. On the contrary, it is known that the present inhabitants of Norfolk Island are nearly all cousins or near relations, as are the Todas in India, and the inhabitants of some of the Western Islands of Scotland; and yet they seem not to have suffered in fertility.** A much more probable view is suggested by the analogy of the lower animals. The reproductive system can be shown to be susceptible to an extraordinary degree (though why we know not) to changed conditions of. life; and this susceptibility leads both to beneficial and to evil results. A large collection of facts on this subject is given in chapter Xviii. of volume ii. of my ‘‘Variation of Animals and Plants under Domestication.’’ I can here give only the briefest abstract; and every one interested in the subject may consult the above work. Very slight changes increase the health, vigor, and fertility of most or all organic beings, while other changes are known to render a large number of ani- mals sterile. One of the most familiar cases is that of tamed elephants not breeding in India, though they often breed in Ava, where the females are allowed to roam about the forests to some extent, and are thus placed under more natural conditions. The case of various American monkeys, both sexes of which have been kept for many years together in their own countries, and yet have very rarely or never bred, is a more apposite instance, because of their relationship to man. It is remarkable how slight a change in the condi- tions often induces sterility 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 45 On the close relationship of the Norfolk Islanders, see Sir W. Denison, “Varieties of Vice-Regal Life,’? vol. i, 1870, p. 410. For the Todas, see Colonel Marshall’s work, 1873, p. 110. For the Western Islands of Scotland, Dr. Mitchell, ‘Edinburgh Medical Journal,’’ March to June, 1865. 4 For the evidence on this head, see ‘‘Variation of Animals,”’ etc., vol. ii, p. 111. 252 THE DESCENT OF MAN 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, while the others are not so; on the other hand, a single species may retain its fertility while 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 off- spring, 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 be 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 life, 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 inhabited 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. Civilized races can certainly resist changes of all kinds far better than savages; and in this respect they resemble do- mesticated animals, for though the latter sometimes suffer in health (for instance, Kuropean dogs in India), yet they are rarely rendered sterile, though a few such instances have been recorded.*” The immunity of civilized races and domesticated animals is probably due to their having been 47 “Variation of Animals,” ete., vol. ii, p. 16, o THE DESCENT OR ORIGIN OF MAN 258 subjected to a greater extent, and therefore having grown somewhat more accustomed, to diversified or varying con- ditions, than the majority of wild animals; and to their having formerly immigrated or been carried from country to country, and to different families or sub-races having intercrossed. It appeats that a cross with civilized 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 English, 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 134 children, making a total of 194. Here they likewise increased so rapidly that, although sixteen of them returned to Pitcairn Island in 1859, they numbered in January, 1868, 800 souls—the 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 800; 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 8,081, while the half-castes, who are believed to be healthier, increased 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 first generation. The cases which I have here given all relate to aborigines who have been subjected to new conditions as the result of the immigration of civilized men. But sterility and ill- health would probably follow, 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 in- teresting circumstance that the chief check to wild animals 4 These details are taken from ‘‘The Mutineers of the Bounty,’’ by Lady Belcher, 1870; and from ‘‘Pitcairn Island,’’ ordered to be printed by the House of Commons, May 29, 1863. The following statements about the Sandwich Islanders are from the ‘‘Honolulu Gazette,’’ and from Mr. Coan. 254 THE DESCENT OF MAN becoming domesticated, which implies the power of their breeding freely when first captured, and one chief check to wild men, when brought into contact with civilization, sur- viving to form a civilized race, is the same, namely, sterility from changed conditions of life. 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 pre- sented by the extinction of one of the higher animals—of the fossil horse, for instance, which disappeared from South America, soon afterward 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 later lead to extinction; the end, in most cases, being promptly determined by the inroads of con- quering tribes. On the Formation of the Races of Man.—In some cases the crossing of distinct races has led to the formation of anew race. The singular fact that Huropeans and Hindus, who belong to the same Aryan stock, and speak a language fundamentally the same, differ widely in appearance, while 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 49 “On Anthropology,” translation, ‘‘Anthropolog. Review,” Jan. 1868, p. 38. THE DESCENT OR ORIGIN OF MAN 255 having been largely crossed by indigenous tribes during their wide diffusion. When two races in close contact cross, the first result is a heterogeneous mixture: thus Mr. Hunter, in describing the Santali or hill-tribes of India, says that hundreds of imperceptible gradations may be traced ‘from the black, squat tribes of the mountains to the tall, olive- colored Brahmin, with his intellectual brow, calm eyes, and high but narrow head;’’ so that it is necessary in courts of justice to ask the witnesses whether they are Santalis or Hindus.” Whether a heterogeneous people, such as the inhabitants of some of the Polynesian islands, formed by the crossing of two distinct races, with few or no pure 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 genera- tions, we may infer that the free intercrossing of a hetero- geneous 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 homo- geneous, 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 color ’ of the skin is the most conspicuous and one of the best marked. It was formerly thought that differences of this kind could be accounted for by long exposure to different climates; but Pallas first showed that this is not tenable, and he has since been followed by almost all anthropolo- gists. This view has been rejected chiefly because the dis- tribution of the variously colored races, most of whom must have long inhabited their present homes, does not coincide 50 ‘‘Annals of Rural Bengal,’’ 1868, p. 134. 51 “The Variation of Animals and Plants under Domestication,”’ vol. ii. . 95, P 52 Pallas, ‘Act. Acad. St. Petersburg,’’ 1780, part ii. p. 69. He was fol- lowed by Rudolphi, in his ‘‘Beytrage zur Anthropologie,”’ 1812. An excellent summary of the evidence is given by Godron, ‘‘De l’Espéce,’’ 1859, vol. ii, p. 246, ete. 256 THE DESCENT OF MAN 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 authority,” have not undergone the least change of color after residing for three centuries in South Africa. An argument on the same side may likewise be drawn from the uniform appearance in various parts of the world of gypsies and Jews, though the uniformity 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 color 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 dryness, any con- clusion on this head must be considered as very doubtful.* Various facts, which I have given elsewhere, prove that the color of the skin and hair is sometimes correlated in a surprising 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 afterward found that this same idea had long ago occurred to Dr. Wells. It has long been known that ne- groes, and even mulattoes, are almost completely exempt from the yellow fever, so destructive in tropical America.” They likewise escape to a large extent the fatal intermittent 53 Sir Andrew Smith, as quoted by Knox, ‘‘Races of Man,’’ 1850, p. 473. 54 See De Quatrefages on this head, ‘‘Revue des Cours Scientifiques,’’ Oct. 17, 1868, p. 731. 55 Livingstone’s ‘‘Travels and Researches in 8. Africa,’’ 1857, pp. 338, 329. D’Orbigny, as quoted by Godron, ‘‘De l’Espéce,”’ vol. ii. p. 266. 58 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’s views in the Historical Sketch (p. xvi.) to my ‘‘Origin of Species.’? Various cases of color correlated with constitutional peculiarities are given in my ‘‘Variation of Animals ander Domestication,’ vol. ii. pp. 227, 335. 51 See, for instance, Nott and Gliddon, ‘‘Types of Mankind,’’ p. 68. THE DESCENT OR ORIGIN OF MAN 257 fevers that prevail along at least 2,600 miles of the shores of Africa, and which annually cause one-fifth of the white set- tlers 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 acclimatization. Pouchet® 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 originally brought from various parts of Africa and accus- tomed to the climate of the West Indies. That acclimatiza- tion plays a part is shown by the many cases in which ne- groes have become somewhat 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 dur- ing 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 acclimatization, implies exposure during a prodig- ious length of time; for the aborigines of tropical America who have resided there from time immemorial are not ex- empt from yellow fever; and the Rev. H. B. Tristram states that there are districts in Northern Africa which the native inhabitants are compelled annually to leave, though the negroes can remain with safety. That the immunity of the negro is in any degree corre- lated with the color of his skin is a mere conjecture: 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 88 Major Tulloch, in a paper read before the Statistical Society, April 20, 1840, and given in the ‘‘Athenzeum,”’ 1840, p. 353. 59 “The Plurality of the Human Race”? (translat.), 1864, p. 60. 6 Quatrefages, ‘‘Unité de l’Espéce Humaine,” 1861, p. 205. Waita, “Introduct. to Anthropology,’’ translat., vol. i., 1863, p. 124. Livingstone gives analogous cases in his ‘‘Travels.”’ 258 THE DESCENT OF MAN between complexion and a tendency to consumption, the conjecture seemed to me not improbable. Consequently I endeavored, with but little success,” to ascertain how far it holds good. The late Dr. Daniell, who had long lived on the West Coast of Africa, told me that he did not believe in any such relation. He was himself unusually fair, and had withstood the climate in a wonderful manner. When he first arrived as a boy on the coast, an old and experi- enced 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 dark-colored Europeans escape the yellow fever more than those that are light-colored. 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 selec- tion of men for service on the coast of Africa, to choose those with red hair.” As far, therefore, as these slight 61 In the spring of 1862 I obtained 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 table, with the following appended re- marks, but I have received no returns. ‘‘As several well-marked cases have been recorded with our domestic animals of a relation between the color of the dermal appendages and the constitution, and it being notorious that there is some limited degree of relation between the color of the races of man and the climate inhabited by them, the following investigation seems worth considera- tion: Namely, whether there is any relation in Europeans between the color of their hair and their liability to the diseases of tropical countries. If the surgeons of the several regiments, when stationed in unhealthy tropical dis- tricts, 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-colored hair, and hair of intermediate or doubtful tints; and if a similar account were kept by the same medical gentlemen, 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 color of the hair and constitutional liability to tropical diseases. Perhaps no such relation would be discovered, but the investigation is well worth making. In case any positive results were obtained, it might be of some prac- tical use in selecting men for any particular service. Theoretically the result would be of high interest, as indicating one means by which a race of men inhabiting from a remote period an unhealthy tropical climate, might have become dark-colored by the better preservation of dark-haired or dark-com- plexioned individuals during a long succession of generations.”’ 62 **Anthropological Review,’’ Jan. 1866, p. xxi. Dr. Sharpe also says, with respect to India (‘‘Man a Special Creation,’’ 1873, p. 118), that “it has THE DESCENT OR ORIGIN OF MAN 259 indications go, there seems no foundation for the hypothe- sis that blackness has resulted from the darker and darker individuals having survived better during long exposure to fever-generating miasma. Dr. Sharpe remarks,“ that a tropical sun, which burns and blisters a white skin, 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, although larger than freckles, and that these patches were never affected by sun-burning, while 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 burned is of sufficient importance 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-colored Hindus 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 color in the races of man, through any been noticed by some medical 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 appear 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. 6 “*Man a Special Creation,’’ 1873, p. 119. ‘Variation of Animals and Plants under Domestication,’’ vol. ii. pp. 836, 337. Ae 260 THE DESCENT OF MAN 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 frame in a direct manner, and that the effects are transmitted. Thus, as is generally admitted, the European settlers in the United States undergo a slight but extraordinarily rapid change of appearance. Their bodies and limbs become elongated; and I hear from Colonel 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 regi- ments, 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 considerable body of evidence showing that in the Southern States the house- slaves of the third generation present a markedly different _appearance from the field-slaves.” If, however, we look to the races of man as distributed over the world, we must infer that their characteristic dif- ferences cannot be accounted for by the direct action of different conditions of life, even after exposure to them for an enormous period of time. The Eskimos live exclusively on animal food; they are clothed in thick fur, and are ex- posed 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 productions of their 6 See, for instance, Quatrefages (“‘Revue des Cours Scientifiques,’’ Oct. 10, 1868, p. 724) on the effects of residence in Abyssinia and Arabia, and other analogous cases. Dr. Rolle (‘‘Der Mensch, seine Abstammung,”’ etc., 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 genera- tions dark hair and eyes. Mr. D. Forbes informs me that the Quichuas in the Andes vary greatly in color, according to the position of the valleys inhabited by them. = 66 Harlan, ‘‘Medical Researches,’’ p. 532. Quatrefages (‘‘Unité de l’Espéce Humaine,’’ 1861, p. 128) has collected much evidence on this head. . THE DESCENT OR ORIGIN OF MAN 261 mhospitabre 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 b 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, are 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 insignificant degree. Men who habitually 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 civilized nations, the reduced size of the jaws from lessened use—the habitual play of different muscles serving to express different emo- tions—and the increased size of the brain from greater intel- lectual activity, have together produced a considerable effect n their general appearance when compared with savages." ) Increased bodily stature, without any corresponding increase in the size of the brain, may (judging from the previously adduced case of rabbits) have given to some races an elon- gated skull of the dolichocephalic type. Lastly, the little-understood principle of correlated devel- opment has sometimes come into action, as in the case of great muscular development and strongly projecting supra- orbital ridges. The color of the skin and hair are plainly correlated, as is the texture of the hair with its color in the Mandans of North America. The color also of the skin, 81 See Prof. Schaaffhausen, translat. in ‘‘Anthropological Review,’’ Oct. 1868, p. 429. 68 Mr. Catlin states (‘‘N. American Indians,’’ 3d edit., 1842, vol. i. p. 49) that in the whole tribe of the Mandans, about one in ten or twelve of the members, of all ages and both sexes, have bright silvery gray hair, which ig , 262 THE DESCENT OF MAN and the odor) emitted by it, are likewise in some manner connected: “With the breeds of sheep the number of hairs within a given space and the number of the execretory pores are related. If we may judge from the analogy of our domesticated animals, many modifications of struct- ure in man probably come under this principle of correlated development. = We have now seen that the external characteristic differ- ences between the races of man cannot be accounted for in a satisfactory 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 eminently 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 are enabled to judge, although always liable to err on his head, none of the differences between the races of man [re of any direct or special service to him. The intellec- tual 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 such variations being of an indifferent nature, and to their hav- ing 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 hereditary. Now this hair is as coarse and harsh as that of a horse’s mane, while the hair of other colors is fine and soft. 69 On the odor of the skin, Godron, ‘‘Sur l’Espéce,”’ tom. ii. p. 217. On the pores in the skin, Dr. Wilckens, ‘‘Die Aufgaben der Landwirth. Zootechnik,’’ 1869, s. 7. . STRUCTURE OF THE BRAIN 263 there remains one important agency, namely Sexual Selec- tion, which appears to have acted powerfully on man, as on many other animals. Ido 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 individuals are con- tinually 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 uniform, if the unknown agencies which induced them were to act in a more constant manner, aided by long-continued intercrossing. Such varia- tions come under the provisional class alluded to in our sec- ond 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 shown that it would be an inexplicable fact if man had not been modified by this agency, which appears to have acted powerfully on innumerable animals. It can’ - further be shown that the differences between the races of man, as in color, hairiness, form of features, etc., are of a kind which might have been expected to come under the influence of sexual selection. But in order to treat this sub- ject 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 show how far he has been modified through sexual selection, will give a brief summary of the chapters in this First Part. Note ON THE RESEMBLANCES AND DIFFERENCES IN THE STRUCTURE AND THE DEVELOPMENT OF THE BRAIN IN MAN AND ApEs. By Pror. Huxusy, F.R.S. THE controversy respecting the nature and the extent of the differences 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 264 THE DESCENT OF MAN present, totally different from what it was formerly. It was originally asserted and reasserted, with singular perti- nacity, that the brain of all the apes, even the highest, dif- fers 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 ventricle 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 developed in apes’ as in human brains, or even better; and that it is characteristic of all the Primates (if we excludg the Lemurs) to have these parts well developed, stands at present on as secure a basis as any proposition in compara- tive anatomy. Moreover, it is admitted by every one of the long series of anatomists who, of late years, have paid spe- cial attention to the arrangement of the complicated sulci and gyri which appear upon the surface of the cerebral hemi- spheres in man and the higher ape that they are Sipe after the very same pattern in him, as in them. KHvery principal gyrus and sulcus of a chimpanzee’s brain is clearl represented in that of a man, so that the terminology whic applies to the one answers for the other. On this point there is no difference of opinion. Some ie be since, Prof. Bischoff published a memoir” on the cerebral convolutions of man and. apes; and as the purpose of my learned colleague was certainly not to diminish the value of the differences between apes and men in this respect, I am glad to make a citation from him: ‘That the apes, and especially the orang, chimpanzee, and gorilla, come very close to man in their organization, much nearer than to any other animal, is a well-known fact, disputed by nobody. Looking at the matter from the point of view of organization alone, no one probably would ever have disputed the view of Linnzus, that man should be placed, merely as a peculiar species, at the head of the mam- malia and of those apes. Both show, in all their organs, so close an affinity, that the most exact anatomical investiga- tion 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. ¢., p. 101). 7 “Die Grosshirn-Windungen des Menschen; ‘‘Abhandlungen der K. Bayerischen Akademie,’’ Bd. x., 1868. STRUCTURE OF THE BRAIN 265 There remains, then, no dispute as to the resemblance. in fundamental characters, between the ape’s brain an man’s; nor any as to the wonderfully close similarity be- tween the chimpanzee, orang, and man, in even the details of the arrangement of the gyri and sulci of the cerebral hemispheres. Nor, turning to the differences between the brains of the highest apes and that of man, is there any seri- ous question as to the nature and extent of these differences, It is admitted that the man’s cerebral hemispheres are abso- lutely and relatively larger than those of the orang and chim- panzee; that his frontal lobes are less excavated by the up- ward protrusion of the roof of the orbits; that his gyri and sulci are, as a rule, less symmetrically disposed, and present a greater number of secondary plications. And it is admitted that, as a rule, in man the temporo-occipital or ‘external per- endicular” fissure, which is usually so strongly marked a eature of the ape’s brain, is but faintly marked. But it is also clear that none of these differences constitute a sharp demarcation between the man’s and the ape’s brain. In respect to the external perpendicular fissure of Gratiolet, in the human brain, for instance, Prof. Turner remarks:” ‘In some brains it oe simply as an indentation of the margin of the hemisphere, but, in others, it extends for some distance more or less transversely outward. 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 outward, and then extended downward 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 distinctness in the brain of most Quadru- mana, is owing to the presence, in the former, of certain su-: erficial, well-marked, secondary convolutions which bridge it over and connect the parietal with the occipital lobe. The closer the first of these Brdgiig ri lies to the longitudinal flan ue shorter is the sliraal parieto-occipital fissure”’ « Gay Pe 12). The obliteration of the external perpendicular fissure of Gratiolet, therefore, is not a constant character of the human brain. On the other hand, its full development is not a con- stant character of the higher ape’s brain. For, in the chim- panzee, the more or less extensive obliteration of the exter- ~ 1 “Convolutions of the Human Cerebrum Topographically Considered,” 1866, p. 12. Descent—Vou. L—12 266 THE DESCENT OF MAN nal perpendicular suleus by ‘‘bridging convolutions,'’ on one side or the other, has been noted over and over again by Prof. Rolleston, Mr. Marshall, M. Broca, and Prof. Turner. 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 generalization which Gratiolet has attempted to draw of the complete absence of the first con- necting convolution and the concealment of the second, as essentially characteristic features in the brain of this animal, is by no means universally applicable. In only one speci- men did the brain, in these particulars, follow the law which Gratiolet has expressed. As regards the presence of the ee bridging convolution, I am inclined to think that it has existed in one hemisphere, 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 the second bridging convolution is evidently less frequent, and has as waat believe, only been seen in the brain (A) recorded in this communication. The asymmetrical arrangement in the convolutions of the two hemispheres, which previous ob- servers have referred to in their descriptions, is also well illustrated in these specimens’’ (pp. 8, 9). Even were the presence of ths temporo-occipital, or ex- ternal perpendicular, 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 tem- Poort! is one of the most constant of sulci in the atarrhine or Old World apes, it is never very strongly de- veloped in the New World apes; it is absent in the smaller Platyrhini; rudimentary in Pithecta ;"* and more or less obliterated by bridging convolutions in Afeles. A character which is thus variable within the limits of a single group can have no great taxonomic value. It is further established that the degree of asymmetry of the convolution of the two sides in the human brain is ubject to much individual variation; and that, in those individuals of the Bushman race who have been examined, the gyri and sulci of the two hemispheres are considerably 72 Notes more especially on the bridging convolutions in the Brain of the | Chimpanzee, ‘‘Proceedings of the Royal Society of Edinburgh,’’ 1865-66. % Flower ‘On the Anatomy of Pithecia Monachus,’’ ‘‘Proceedings of the Zoological Society,’’ 1862. STRUCTURE OF THE BRAIN 267 less complicated and more symmetrical than in the Euro- pean brain, while in some individuals of the chimpanzee their complexity and asymmetry become notable. This is particularly the case in the brain of a young male chim- Pe aes yy M. Broca. (‘‘L’Ordre des Primates,” i , 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 difference between the smallest healthy human brain and the largest chimpanzee’s or orang’s brain. oreover, there is one circumstance in which the orang’s and chimpanzee’s brains resemble man’s, but in which they differ from the lower apes, and that is the presence of two corpora candicantia—the Cynomorpha having but one. n view of these facts I do not hesitate in this year 1874 to repeat and insist upon the proposition which I enunciated in 1863:” ‘‘So far as cerebral structure goes, therefore, itis clear that man differs less from the chimpanzee or the orang than these do even from the monkeys, and that the difference between the brain of the chimpanzee and of man is almost insignifi- cant, when compared with that between the chimpanzee brain and that of a Lemur.” In the paper to which I have referred, Prof. Bischoff does not deny the 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 are very different; and sec- ondly, goes on to assert that, ‘‘If we successively 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 Hylobates, Semnopithecus, Cynocephalus, Cercopithecus, Macacus, Cebus, 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, first, that whether this assertion be true or false, it has nothing whatever to do with the proposi- tion 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 Prof. Bischoff had taken ™ “‘Man’s Place in Nature,’’ p. 102. 268 THE DESCENT OF MAN the trouble to refer to p. 96 of the work he criticises, in fact, he would have found the following passage: ‘‘And it isa remarkable circumstance that though, so far as our present knowledge extends, there és one true structural break in the series of forms of Simian brains, this biatus does not lie be- tween 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 cerebel- lum partially visible from above; and its posterior lobe, with the contained posterior cornu and hippocampus minor, more or less rudimentary. Every marmoset, American monkey, Old World monkey, baboon, or manlike ape, on the con- trary, has its cerebellum entirely hidden, posteriorly, by the cerebral lobes, and possesses a large posterior cornu with a well-developed hippocampus minor.’ This statement was a strictly accurate account of what was known when it was made; and‘it does not appear to me to be more than apparently weakened by the subsequent dis- covery of the relatively small development of the posterior lobes in the Siamang and in the Howling monkey. Not- withstanding the exceptional brevity of the 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 Hapale out of its natural place, as Prof. Bischoff most unaccountably does, we write the series of ani- mals he has chosen to mention as follows: Homo, Pithecus, Troglodytes, Hylobates, Semnopithecus, Cynocephalus, Cerco- ithecus, Macacus, Cebus, Callithrix, Hapale, Lemur, Stenops, f ventate to reaffirm that the great break in this series lies between Hapale and Lemur, and that this break is consider- ably greater than that between any other two terms of that series. Prof. Bischoff ignores the fact that long before he wrote, Gratiolet had suggested the separation cf the Lemurs from the other Primates on the very ground of the difference in their cerebral characters; and that Prof. Flower had made the following observations in the course of his description of the brain of the Javan Loris: ‘“‘And it is especially remarkable that, in the develop- ment of the posterior lobes, there is no approximation to the Lemurine, short-hemisphered brain, in those monkeys which are commonly supposed to approach this family in % ‘Transactions of the Zoological Society,’’ vol. v., 1862. STRUCTURE OF THE BRAIN 269 other respects; viz., the lower members of the Platyrhine group.” ; So far as the structure of the adult brain is concerned, then, the very considerable additions to our knowledge, which have been made by the researches of so many investi- gators, during the past ten years, fully justify the statement which [ made in 1868. 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 agreement in the development of the brain in men and apes. Gratiolet originated the statement that there is a funda- mental 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 hemispheres, 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 4 born, in which the osterior gyri were ‘‘well developed,’’ while those of the rontal lobes were ‘‘hardly indicated”’” (1. ¢., p. 39), and %8 ‘Chez tous les singes, les plis postérieurs se développent les premiers; les plis antérieurs se développent plus tard, aussi la vertébre occipitale et la pariétale sont-elles relativement trés-grandes chez le foetus. L’Homme pré- sente une exception remarquable quant & Vépoque de apparition des plis frontaux, qui sont Jes premiers indiqués; mais le développement général du lobe frontal, envisagé seulement par rapport a son volume, suit les mémes lois que dans les singes.*’ Gratiolet, ‘‘Mémoire sur les plis cérébraux de 1’Homme et des Primates,’’ p. 39, tab. iv. fig. 3. 7 Gratiolet’s words are (I. ¢., p. 39): ‘“‘Dans Je foetus dont il s’agit les plis eérébraux postérieurs sont bien développés, tandis que les plis du lobe frontal sont & peine indiqués.’’ The figure, however (PI. iv. fig. 3), shows the fissure of Rolando, and one of the frontal sulci, plainly enough. Nevertheless, M. Alix, in his ‘“‘Notice sur les travaux anthropologiques de Gratiolet’? ((‘Mém. de la Société d’Anthropologie de Paris,”? 1868, p. 32), writes thus: ‘Gratiolet a eu entre les mains le cerveau d@’un foetus de Gibbon, singe éminem- ment supérieur, et tellement rapproché de orang, que des naturalistes trés compétents l’ont rangé parmi les anthropoides. M. Huxley, par exemple, n’hésite pas sur ce point. Eh bien, c’est sur le cerveau d’un foetus de Gibbon que Gratiolet a vu les cérconvolutions du lobe temporo-sphénoidal déja développées dors-qu'il n’existe pas encore de plis sur le lobe frontal. Il était donc bien autorisé a dire que, chez ’homme les circonvolutions apparaissent d’e en @, tandis que chez les singes elles se développent d’« en a.”? 270 THE DESCENT OF MAN the other of a human foetus at the 22d or 23d week of utero- gestation, in which Gratiolet notes that the insula was un- covered, but that, nevertheless, ‘‘des incisures sément le lobe antérieur; une scissure peu profonde indique la sépa- ration du_lobe occipital, ee uit d’ailleurs dés cette époque. Le reste de la surface cérébrale est encore abso- lument lisse.”’ Three views of this brain are given in Plate II., Figs. 1, 2, 3 of the work cited, showing the upper, lateral, and inferior views of the hemispheres, but not the inner view. It is worthy of note that the figure by no means bears out . Gratiolet’s description, inasmuch as the fissure (antero- temporal) on the posterior half of the face of the hemi- sphere 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: ‘‘1l y a done entre ces cer- veaux [those of a Callithrix and of a Gibbon] et celui du foetus humain une différence fondamentale. Chez celui-ci, longtemps 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, Bischoff, 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 utero-gestation. In this and in the fourth month the cerebral hemispheres are smooth and rounded (with the exception of the Sylvian depression), and they project backward far beyond the cerebellum. 2. The sulci, properly so called, begin to uke in the interval between the end of the fourth 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 appear- ance is subject to considerable individual variation. In no case, however, are either the frontal or the temporal sulci the earliest. %8 “‘Yeber die typische Anordnung der Furchen und Windungen auf den Grosshirn-Hemispharen des Menschen und der Affen.”” ‘‘Archiv fir Anthro- pologie,’? iii., 1868. a ” “Yur Entwickelungs Geschichte der Furchen und Windungen der Grosshirn-Hemispharen im Foetus des Menschen.”” “‘Archiv fir Anthropolo- gie,”’ iii., 1868. STRUCTURE OF THE BRAIN 271 The first which appears, in fact, lies on the inner face of the hemisphere (whence doubtless Gratiolet, who does not seem to have examined that face in his foetus, overlooked it), and is either the internal perpendicular (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 ‘‘Fissure of Rolando,”’ 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 ae at the period described and figured by Hecker (1. ¢., pp. 212-18, Taf. II. Figs. 1, 2, 8, 4), -the antero-temporal sulcus (scissure paralléle), so character- istic of the ape’s brain, is as well if not better developed than the fissure of Rolando, and is much more marked than the proper frontal sulci. aking the facts as they now stand, it appears to me that the order of the appearance of the sulci and gyri in the foetal human brain is in perfect harmony with the general doctrine of evolution,’ and with the view that man has 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 their 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 characters of a fish, and, if it went no further, would have to be grouped among fishes. But it is equally true that the tadpole is very differ- ent from any known fish. : In like manner, the brain of a human fcetus, at the fifth month, may correctly be said to be not only the brain of an ape, but that of an Arctopithecine or marmoset-like ape; for its hemispheres, with their great posterior lobes, and with no sulci but the Sylvian and the calcarine, present the char- 272 THE DESCENT OF MAN acteristics found only in the group of the Arctopithecine Pri- mates. But it is equally true, as Gratiolet remarks, that, in its widely open Sylvian fissure, it differs 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 Apella, in addition to the Sylvian fissure and the deep calcarine fissure, only a very shallow antero-temporal fissure (scissure paralléle 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 ante- rior half of the exterior of the cerebral hemispheres, or none at all, undoubtedly, so far as it goes, affords fair evidence in favor of Gratiolet’s hypothesis, that the posterior sulci appear before the anterior, in the brains of the Platyrhint. But it by no means follows that the rule which may hold good for the Platyrhint extends to the Catarrhini. We have no information whatever respecting the development of the brain in the Cynomorpha;: and, as regards the An- thropomorpha, 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 show 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, ‘‘I] est dangereux dans les sciences de conclure trop vite.’’ I fear he must have forgotten this sound maxim by the time he had reached the discussion of the differences between men 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 een made, would have been the first to admit the insuffi- ciency of his data had he lived to profit by the advance of inquiry. The misfortune is- that his conclusions have been employed by persons incompetent to appreciate their foun- dation, as arguments in favor of obscurantism.” But it is important to remark that, whether Gratiolet was 80 For example, M. Abbé Lecomte in his terrible pamphlet, ‘“‘Le Darwinisme et lorigine de 1’Homme,”’’ 1873. STRUCTURE OF THE BRAIN 2738 right or wrong in 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 gradual modi- fication of the same form as that from which the other Pri- mates have sprung. — PART TWO SEXUAL SELECTION CHAPTER VIII PRINCIPLES 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 selec- tion—Inheritance, at corresponding periods of life, at corresponding seasons of the year, and as limited by sex—Relations between the several forms of inheritance—Causes why one sex and the young are not modified through sexual selection—Supplement on the proportional numbers of the two sexes throughout the animal kingdom—The pro- portion of the sexes in relation to natural selection ITH animals which have their sexes separated, 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 characters, which are not di- rectly connectedswith the act of reproduction; 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 hold- ing her securely. These latter organs, of infinitely diversi- fied kinds, graduate into 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 append- ages at the apex of the abdomen. in male insects. Unless indeed we confine the term ‘‘primary’’ to the reproductive (274) SEXUAL SELECTION 275 glands, it is scarcely possible to decide which ought to be called primary and which secondary. The female often differs from the male in having organs for the nourishment or protection of her young, such as the mammary glands of mammals, and the abdominal sacs 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 with a special apparatus for col- lecting and carrying pollen, and their ovipositor is modified into a sting for the defence of the larve and the community. Many similar cases could be given, but they do not here concern us. ‘here are, however, other sexual differences quite unconnected with the primary reproductive organs, - and it is with 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 coloring 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 ani- mals 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 (Culicids and Tabanide) are blood-suckers, while the males, living on flowers, have mouths destitute of mandibles.’. The males of certain moths and of some crustaceans (e.g., Tanais) have imperfect, closed mouths, and cannot feed. The complemental males of cer- tain Cirripeds live 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- 1 Westwood, *‘Modern Class. of Insects,’’ vol. ii., 1840, p. 541. For the gtatement about Tanais, mentioned below, I am indebted to Frits Miller. 276 THE DESCENT OF MAN 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 (Curculionide) there is a great difference between the male and female in the length of the rostrum or snout;? but the meaning of this and of many analogous differences is not at all understood. Differences of structure between the two sexes in relation to 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 won- derfully great, and we hear from Dr. Buller* that the male uses his strong beak in chiselling the larve of insects out of decayed wood, while 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, differ- ences of structure between the sexes are more or less directly connected with the propagation of the species: thus a female, which has to nourish a multitude 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 he 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. XK We are, however, here concerned only with sexual selec- tion. This depends on the advantage which certain_indi- viduals have over others of the same sex and species solely in respect of reproductionX When, as in the cases above mentioned, the two sexes differ in structure in relation to different habits of life, they have no doubt been modified through natural selection, and by inheritance limited to one 2 See Kirby and Spence’s work, ‘‘Introduction to Entomology,’’ volume iif,, 1826, page 309. 3 “Birds of New Zealand,’’ 1872, p. 66 SEXUAL SELECTION 277 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 gen- - erated or nourished their offspring best would leave, ceteris paribus, the greatest number to inherit their superiority, while those which generated or nourished their offspring badly would leave but few to inherit their weaker 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 requires 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 antennze modified in an extraordinary manner for the prehension of the female; hence we may suspect that it is because these animals are washed about by the waves of the open sea that they require 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 iow 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 like a rasp, and with 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 4M. Perrier advances this case (‘‘Revue Scientifique,’? Feb. 1, 1873, p. 865) as one fatal to the belief in sexual selection, inasmuch as he supposes that I attribute ell the differences between the sexes to sexual selection. This distinguished naturalist, therefore, like so many other Frenchmen, has not taken the trouble to understand even the first principles of sexual selection. An English naturalist insists that the claspers of certain male animals could not have been developed through the choice of the female! Had I not met with this remark, I should not have thought it possible for any one to have read this chapter and to have imagined that I maintain that the choice of the female had anything to do with the development of the prehensile organs in the male. 278 THE DESCENT OF MAN highly developed than those of the female, it may be that the perfection of these is indispensable to the male for find- ing 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 acquired their present structure not from being better fitted to survive in the struggle for exist- ence, 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 Selec- tion. 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 indi- viduals 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 sensory, locomotive, and prehensile organs. As, however, these structures are not more interesting than others adapted for the ordinary purposes 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 con- trivances for producing vocal or instrumental music—and their glands for emitting odors, most of these latter struct- ures serving only to allure or excite the female. It is clear that these characters are the result of sexual and not of SEXUAL SELECTION 279 ordinary selection, since unarmed, unornamented, or unat- tractive 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 performing strange antics before an assembled body of females, we cannot doubt that, though led by in- stinct, they know what they are about, and consciously exert their 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 cock-pit, so it appears that the strongest and most vigorous males, or those provided with the best weapons, have pre- vailed under nature, and have led to the improvement of the natural breed or species. A slight degree of variability leading to some advantage, however slight, in reiterated deadly contests would suffice for the work of sexual selec- tion; and it is certain that secondary sexual characters are eminently variable. Just as man can give beauty, accord- ing 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 ap- pears that female birds in a state of nature have, by a long selection of the more attractive males, added to their beauty or other attractive qualities. No doubt this implies pow- ers of discrimination and taste on the part of the female which will at first appear extremely improbable; but, by the facts to be adduced hereafter, I hope to be able to show that the females actually have these powers. When, however, 280 THE DESCENT OF MAN it is said that the lower animals 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 comparison 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 man- ner in which sexual selection acts is somewhat uncertain. Nevertheless, if those naturalists 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 among almost all animals there is a struggle 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 supposition that their mental capacity suffices for the exertion of a choice. In many cases special circumstances tend to make the strug- gle 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 nightingale 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 Ray’s wagtail (Budytes fait) before he saw a single female. Mr. Gould has ascer- tained, by the dissection of those snipes which arrive the first in this country, that the males come before the females. And the like holds good with most of the migratory birds SEXUAL SELECTION 281 of the United States.*° The majority of the male salmon in our rivers, on coming up from the sea, are ready to breed before the females. So it appears 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 ean 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 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, with- out at the same time interfering with the period of the pro- duction 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 under- standing how it is that the males which conquer other males, or those which prove the most attractive to the females, leave a greater number of offspring to inherit their superi- ority 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, 5 J, A, Allen, on the ‘‘Mammals and Winter Birds of Florida,’’ Bull. Comp. Zoology, Harvard College, p. 268. 6 Even with those plants in which the sexes are separate, the male flowers are generally mature before the female. As first shown by C. K. Sprengel, many hermaphrodite plants are dichogamous; that is, their male and female organs are not ready at the same time, so that they cannot be self-fertilized, Now in such flowers the pollen i is in general matured before the stigma, though there are exceptional cases in which the female organs are beforehand. 282 THE. DESCENT OF MAN and leave as many offspring, as well fitted for their general habits of life as the best-endowed males. From 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 even 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 inhabiting 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 earliest breeders would on an average succeed in rearing the largest number of fine offspring.” The males, as we have seen, are generally ready to breed before the 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, because they are the first to breed. Such vigorous pairs would surely rear 1 Here is excellent evidence on the character of the offspring from an ex- perienced ornithologist. Mr. J. A. Allen, in speaking (‘‘Mammals 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-colored than those hatched earlier in the season. 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 perfect and vigorous.”’ 8 Hermann Miller 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 SEXUAL SELECTION _ 288 a larger number of offspring than the retarded females, which would be compelled to unite with the conquered and less 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 weapons. But in very many cases the males which conquer their rivals 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 proba- ble that they would at the same time prefer the more vig- orous 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 attractive. Both sexes, therefore, of such early pairs would, as above explained, have an advantage over others in rear- ing offspring; and this apparently has sufficed during a long course of generations to add not only to the strength and fighting powers of the males, but likewise to their various ornaments or other attractions. In the converse and much rarer case of the males select- ing 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 advantage in rearing offspring, more especially if remarkable essay, “‘Anwendung den Darwin’schen Lehre auf Bienen,”’ ‘*Verh, a. V. Jabrg.,”? xxix. p. 45. ® With respect to poultry, I have received information, hereafter to be giver, to this effect. Even with birds, such as pigeons, which pair for life, the female, as I hear from Mr. Jenner Weir, will desert her mate if he is injured or grows weak. 284 THE DESCENT OF MAN 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 princi- ples would apply if each sex preferred and selected certain individuals of the opposite-sex; supposing that they selected not only the more attractive, but likewise the more vigorous individuals. Numerical Proportion of the Two Sexes.—I have remarked that sexual selection would be a simple affair if the males were considerably 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 will here give only a brief ab- stract of the results, retaining the details for a supplement- ary discussion, so as not to interfere with the course of my argument. Domesticated animals alone afford the means of ascertaining the proportional numbers at birth; but no rec- ords have been specially kept for this purpose. By indirect means, however, I have collected a considerable body of sta- tistics, from which it appears that with most of our domestic animals the sexes are nearly equal at birth. Thus 25,560 births of race-horses have been recorded during twenty-one years, and the male births were to the female births as 99.7 to 100. In greyhounds the inequality is greater than with any other animal, for out of 6,878 births during twelve years, the male births were to the female as 110.1 to 100. It is, however, in some degree doubtful whether it is safe to infer that the proportion would be the same under natural condi- tions as under domestication; for slight and unknown dif- — ferences in the conditions affect the proportion of the sexes. Thus with mankind, the male births in England are as 104.5, in Russia as 108.9, and with the Jews of Livonia as 120 to 100 female births. But I shall recur to this curious 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 SEXUAL SELECTION 285 several years in the proportion of between 90 and 99 to 100 female children. For our present purpose we are concerned with the pro- portion of the sexes not only at birth, but also at maturity, and this adds another element of doubt; for it is a well- 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 almost 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 until they become greatly emaciated. They must also be often exposed to various dangers, while wandering about in eager search for the females. In many kinds of fish the males are much smaller than the females, and they are believed often to be devoured by the latter, or by other fishes. The fe- males of some birds appear to die earlier than the males; they are also liable to be destroyed on their nests, or while in charge of their young. With insects the female larva are often larger than those of the males, and would conse- quently be more likely to be devoured. In some cases the mature females are less active and less rapid in their move- ments 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 little trustworthy, except when the inequality is strongly marked. Neverthe- less, 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 birds, of some fish and insects, are considerably more numerous than the females. The proportion between the sexes fluctuates slightly luring successive years: thus with race-horses, for every 100 mares born the stallions varied from 107.1 in one year to 92.6 in another year, and with greyhounds from 116.3 to 25.8. But had larger numbers been tabulated throughout an area more extensive than England, these fluctuations 286 THE DESCENT OF MAN would probably have disappeared; and, such as they are, would hardly suffice to lead to effective sexual selection in a state of nature. Nevertheless, in the cases of some few wild animals, as shown in the supplement, the proportions seem to fluctuate either during different seasons or in differ- ent localities 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 off- spring, and would not subsequently be eliminated. During the succeeding seasons, when, from the equality of the sexes, every male was able to procure a female, the stronger or more attractive males previously produced would still have at least as good a chance of leaving offspring as the weaker or less attractive. Polygamy.—The practice of polygamy leads to the same results as would follow from an actual inequality in the number of the sexes; for if each male secures 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 are polygamous, but with animals belonging to the lower classes I 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 would be eminently favorable to the action of sexual selection. Nevertheless, many animals which are strictly monogamous, especially birds, display strongly marked secondary sexual charac- ters; while 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 SEXUAL SELECTION i 287 male differs considerably from the female; so it is with some baboons, which live in herds containing twice as many adult females as males. In South America the Mycetes caraya presents well-marked sexual differences, in color, beard, and vocal organs; and the male generally lives with two or three wives: the male of the Cebus 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 sex- ual 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 ante- lopes 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 collecost+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 wild horse of the Falkland Islands and of the West- ern States of North 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 well- marked sexual characters, in his great tusks and some other points. In Europe and in India he leads a solitary life, except during the breeding season; but, as is believed by Sir W. Elliot, who has had many opportunities in India of observing this animal, he consorts at this season with 10 On the Gorilla, Savage and Wyman, ‘‘Boston Journal of Nat. Hist.,”’ vol. v., 1845-47, p. 423. On Cynocephalus, Brehm, ‘‘Illust. Thierleben,” B. i., 1864, 3. 77. On Mycetes, Kengger, ‘“‘Naturgesch.: Saugethiere von Paraguay, °? 1830, s. 14, 20. Cebus, Brehm, ibid., s. 108. 11 Pallas, “Spicilegia Zoolog.,’? Fase. xii., 1777, p. 29. Sir Andrew Smith, “Tllustrations of the Zoology of S. Africa,’’ 1849, pl. 29, on the Kobus, Owen, in his ‘‘Anatomy of Vertebrates” (vol. iii., 1868, p. 633) gives a table showing incidentally which species of antelopes are gregarious. 288 THE DESCENT OF MAN several females. Whether this holds good in Europe is doubtful, but it is supported by some evidence. The adult made 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 his immense tusks, greater size, strength, and endurance; so great is the difference in these respects that the males when caught are valued at one-fifth 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 Rodents being polygamous, ex- cepting that, among the Rodents, the common rat, according to some rat-catchers, lives with several females. Neverthe- less the two sexes of some sloths (Hdentata) differ in the character and color of certain patches of hair on their shoul- ders.** And many kinds of bats (Cheiroptera) present well- marked sexual differences, chieii™@™™®ihe males possessing odoriferous glands and pouches, and by their being of a lighter color.’* In the great order of Rodents, as far as I can learn, the sexes rarely differ, and when they do so, it is but slightly in the tint of the fur. As I hear from 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 among all the terres- trial Carnivora, and he alone presents well-marked sexual characters. If, however, we turn to the marine Carnivora, as we shall hereafter see, the case is widely different; for many species of seals offer extraordinary sexual differences, 12 Dr. Campbell, in ‘‘Proc. Zoolog. Soc.,’? 1869, p. 138. See also an interesting paper, by Lieut. Johnstone, in ‘‘Proc. Asiatic Soc. of Bengal,” May, 1868. 13 Dr, Gray, in ‘‘Annals and Mag. of Nat. Hist.,’’ 1871, p. 302. 144 See Dr. Dobson’s excellent paper, in ‘‘Proc, Zoolog. Soc.,’’ 1873, p. 241. SEXUAL SELECTION 289 and they are eminently polygamous. Thus, according to Péron, the male sea-elephant of the Southern Ocean always possesses several females, and the sea-lion of Forster 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 greater 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.’’ Among 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 bull-finch, which is said to pair for life. I am informed by Mr. Wallace that the like is true of the Chatterers or Cotingide of South America, and of many other birds. In several groups I have not been able to discover whether the species are polygamous or mo- nogamous. Lesson says that birds-of-paradise, so remark- able for their sexual differences, are polygamous, but Mr. Wallace doubts whether he had sufficient evidence. Mr. Sal- vin tells me he has been led to believe that humming- birds are polygamous. The male widow-bird, remarkable for his caudal plumes, certainly seems to be a polygamist.’ I have been assured by Mr. Jenner Weir, 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 Gallinacez exhibit almost as strongly marked sexual differences as birds-of-paradise or humming-birds, and many 18 The Eared Seals, ‘‘American Naturalist,’ vol. iv., Jan. 1871. 16 “The Ibis,’’ vol. iii., 1861, p. 133, on the Progne Widow-bird. See also ‘on the Vidua awillaris, ibid., vol. ii., 1860, p. 211. On the polygamy of the Capercailzie and Great Bustard, see L. Lloyd, ‘‘Game Birds of Sweden,’’ 1867, pp. 19 and 182. Montagu and Selby speak of the Black Grouse as polygamous, and of the Red Grouse as monogamous. Descent—Vou. I,.—13 290 THE DESCENT OF MAN 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 monogamous guinea-fowl or partridge! Many simi- lar cases could be given, as in the grouse tribe, in which the males of the polygamous capercailzie and black-cock differ greatly from the females; while the sexes of the monoga- mous red grouse and ptarmigan differ very little. In the Cursores, except among the bustards, few species offer strongly marked sexual differences, and the great bustard (Otis tarda) is said to be polygamous. With the Gralia- tores, extremely few species differ sexually, but the ruff (Machetes pugnax) affords a marked exception, and this species is believed by Montagu to be a polygamist. Hence it appears that among birds there often exists a close rela- tion between polygamy and the development of strongly marked sexual differences. I asked Mr. Bartlett of the Zoological Gardens, who has had very large experience with birds, whether the male tragopan (one of the Gal- linacesws) was polygamous, and I was struck by his an- swering, ‘‘I do not know, but should think so from his splendid colors.”’ It deserves notice that the instinct of pairing with a single female is easily lost under domestication. The wild-duck is strictly monogamous, the domestic duck highly polyga- mous. The Rev. W. D. Fox informs me that out of some half-tamed wild-ducks, on a large pond in his neighborhood, 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 mo- nogamous; but Mr. Fox finds that his birds succeed best when he keeps one cock to two or three hens. Oanary- birds pair in a state of nature, but the breeders in England successfully put one male to four or five females. J have noticed these cases, as rendering it probable that wild mo-, nogamous species might readily become either temporarily or permanently polygamous. SEXUAL SELECTION 291 Too little is known of the habits of reptiles and fishes to enable us to speak of their marriage arrangements. The stickleback (Gasterosteus), however, is said to be a polyga- mist;” 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 shown that the largest number of vigorous offspring will be reared from the pairing of the strongest and best-armed males, victorious in contests over other males, with the most vigorous and best-nourished 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 num- ber 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 advantage thus gained by the more vigorous pairs in rearing a larger number of offspring has apparently sufficed to render sexual selection efficient. Buta large numerical preponderance of males over females will be still more efficient; whether the preponderance is only occasional and local, or permanent; whether it occurs at birth, or afterward from the greater destruction 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 fe- male 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 u oer are “River Gardens,’’ 1854. 292 THE DESCENT OF MAN 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 su- periority to their male offspring. Why both sexes do not thus acquire the characters of their fathers will be consid- ered hereafter. That the males of all mammals eagerly pursue the females is notorious to every one. So it is with birds; 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 re- marks,’® ‘‘the law is that the male shall seek the female.”’ Two good authorities, Mr. Blackwall and Mr. C. Spence Bate, tell me that the males of spiders and crustaceans are more active and more erratic in their habits than the fe- males. 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 shows that the male is the more active member in the courtship of the sexes.’ The female, on the other hand, with the rarest ex- ceptions, 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 endeavoring 18 Kirby and Spence, ‘‘Introduction to Entomology,”’ vol. iii., 1826, p. 342. 19 One parasitic Hymenopterous insect (Westwood, ‘‘Modern Class. of Tnsects,’’ vol. ii. p. 160) forms an exception to the rule, as the male has rudi- mentary wings, and never quits the cell in which it is born, while the female has well-developed wings. Audouin believes that the females of this species are impregnated 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 inter- breeding 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, 30 “‘Hssays and Observations,’’ edited by Owen, vol. 1., 1861, p. 194, SEXUAL SELECTION 293 for a long time to escape from the male. Every observer of the habits of animals will be able to call to mind in- stances of this kind. It is shown by various facts, given hereafter, and by the results fairly attributable to sexual selection, that the female, though comparatively passive, generally exerts some choice and accepts one male in pref- erence 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 naturally led to inquire 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 ac- tive part in courtship. 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 fertilization have to be nourished for a time; hence the pollen is necessarily brought to the female organs —hbeing placed on the stigma, by means of insects or the wind, or by the spontaneous movements of the stamens; and in the Alge, etc., by the locomotive power of the anthero- zooids. With lowly organized aquatic animals, permanently affixed to the same spot and having their sexes separate, the male element is invariably brought to the female; and of this we can see the reason, for even if the ova were de- tached before fertilization, and did not require subsequent nourishment or protection, there would yet be greater diffi- culty 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 respect, analogous with plants.** The males of affixed and aquatic animals having been led to emit their fertilizing ele- ment in this way, it is natural that any of their descendants, 21 Prof. Sachs (‘‘Lehrbuch der Botanik,’’ 1870, s, 633), in speaking of the male and female reproductive cells, remarks, ‘“‘Verhalt sich die eine bei der Vereinig'ing activ, . . . die andere erscheint bei der Vereinigung passiv.”’ 294 THE DESCENT OF MAN which rose in the scale and became locomotive, should re- tain the same habit; and they would approach the female as closely as possible, in order not to risk the loss of the fertilizing element in a long passage of it through the water. With some few of the lower 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 progenitors 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 acquirement 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 favor of this conclusion can be produced by a comparison of the two sexes in man- kind. During the Novara Hxpedition® 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 recur to this subject in a future chapter. Mr. J. Wood,” who has carefully attended to the variation of the muscles in man, puts in italics the conclusion that % “*Vortrige iiber Viehzucht,’’ 1872, p. 63. 28 “Reise der Novara: Anthropolog. 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 males of domesti- cated animals, see my ‘‘Variation of Animals and Plants under Domestication,’’ vol. ii., 1868, p. 75. 24 ‘Proceedings Royal Soc.,”’ vol. xvi., July 1868, pp. 519 and 524. SEXUAL SELECTION ~ 295 “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.’’ Prof. Macalister likewise remarks” that variations in the muscles ‘‘are probably more common in males than females.’’ Certain muscles which are not nor- mally present in mankind are also more frequently devel- oped in the male than in the female sex, although exceptions to this rule are said to occur. Dr. Burt Wilder’ has tabu- lated the cases of 152 individuals with supernumerary digits, of which 86 were males, and 89, or less than half, females, the remaining 27 being of unknown sex. It should not, ‘however, be overlooked that women would more frequently endeavor 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 tem- perature 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 sexual and natural selection male animals have been rendered in very many instances widely different from their females; but independently of selection the two sexes, from differing constitutionally, 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 exert- 25 “*Proc, Royal Irish Academy,’’ vol. x., 1868, p. 123. %6 **Massachusetts Medical Soc.,’’ vol. ii. No. 3, 1868, p. 9. 2 “Archiv fir Path, Anat. und Phys.,’’ 1871, p. 488. 98 The conclusions recently arrived at by Dr. J. Stockton-Hough, on the temperature of man, are given in the ‘‘Pop. Sciente Review,’’ Jan. 1, 1874, p. 97. 296 THE DESCENT OF MAN ing his voice, pouring out odoriferous secretions, etc.; and this expenditure is generally concentrated within a short period. The great vigor of the male during the season of love seems often to intensify his colors, independently of any marked difference 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 ia 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. Nevertheless, they may become permanent if the exciting cause acts permanently; and, in accordance with a frequent form of inheritance, they may be transmitted to that sex alone in which they first appeared. In this case the two sexes will come to present permanent, yet unimportant, differences of character. For instance, Mr. Allen shows that with a large number of birds inhabiting the northern and southern United States, the specimens from the south are darker-colored than those from the north; and this seems to be the direct result of the difference in temperature, light, etce., between the two re- gions. Now, in some few cases, the two sexes of the same species appear to have been differently affected; in the 29 Prof. Mantegazza is inclined to believe (‘‘Lettera a Carlo Darwin,” ‘Archivio per l’ Anthropologia,’’ 1871, p. 306) that the bright colors common in so many male animals are due to the presence and retention by them of the spermatic fluid: but this can hardly be the case; for many male birds, for instance young pheasants, become brightly colored in the autumn of their first year. 80 For mankind, see Dr. J. Stockton-Hough, whose conclusions are given in the ‘‘Pop. Science Review,’’ 1874, p. 97. See Girard’s observations on the Lepidoptera, as given in the ‘‘Zoological Record,” 1869, p. 347, SEXUAL SELECTION 297 Ageleus pheniceus the males have had their colors greatly intensified in the south; whereas with Cardinalis virginianus it is the females which have been thus affected; with Quiscalus major the females have been rendered extremely variable in tint, while 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 secondary sexual characters, such as brighter colors, greater size, strength, or pugnacity. With birds there has sometimes been a complete transpo- sition of the ordinary characters proper to each sex; the females having become the more eager in courtship, 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 colored 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 attrac- tive 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 beautiful differed; but this is a supposition too improb- able to be worth considering in the case of any animal, ex- cepting 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 attrib- ute to the agency of sexual selection. In such cases it may be suggested with more plausibility, that there has been a double or mutual process of sexual selection; the more vigorous and precocious females selecting the more attrac- tive and vigorous males, the latter rejecting all except the more attractive females. But from what we know of the 31 **Mammals and Birds of E. Florida,’’ pp. 234, 280, 295. 298 THE DESCENT OF MAN habits of animals, this view is hardly probable, for the male is generally eager to pair with any female. It is more prob- able that the ornaments common to both sexes were acquired by one sex, generally the male, and then transmitted to the offspring of both sexes. If, indeed, during a lengthened period the males of any species were greatly to exceed the females in number, and then during 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 colored nor provided with special ornaments, and yet the members of both sexes or of one alone have probably acquired simple colors, 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 through sexual selection of conspicuous colors 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 will have been produced, unless a larger number of off- spring were left by the more successful males to inherit their superiority, than by the less successful: and this, as previously shown, depends on many complex contingencies. Sexual selection acts in a less rigorous manner than natu- _ ral 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 a retarded and less vigorous female later in the season, or, if polygamous, obtains fewer females; so that they leave fewer, less vigorous, or no off- SEXUAL SELECTION 299 spring. 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 pur- poses; but in regard to structures adapted to make one male victorious over another, either in fighting or in charming the female, there is no definite limit to the amount of advanta- geous modification; so that as long as the proper variations arise the work of sexual selection will go on. This circum- stance may partly account for the frequent and extraordi- nary amount of variability presented by secondary sexual characters. Nevertheless, natural selection will determine © that such characters shall not be acquired by the victorious males, if they would be highly injurious, either by expend- ing too much of their vital powers, or by exposing them to any great danger. The development, however, of certain structures—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 favored males derive from conquering other males in battle or courtship, and thus leaving a numerous progeny, are in the long run greater than those derived from rather more perfect adapta- tion 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 INHERITANCE 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 ‘‘inheri- tance’’—the transmission and the development of characters; 800 THE DESCENT OF MAN but, as these generally go together, the distinction is often overlooked. We see this distinction in those characters which are transmitted through the early years of life, but are de- veloped only at maturity or during old age. We see the same distinction more clearly with secondary sexual charac- ters, 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 transmits the char- acters proper to its own male and female sex to the hybrid offspring of either sex. ‘The same fact is likewise manifest when characters proper to the male are occasionally devel- oped 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 pug- nacity of the cock. Conversely, the same thing is evident, more or less plainly, with castrated males. Again, inde- pendently 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 simply developed in the female; for in every breed each detail in the structure of the spur is transmitted through the female to her male offspring. Many eases 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 development of characters in the female, and of transference to the male, is less frequent; it will therefore be well to give one striking instance. With bees the pollen- collecting apparatus is used by the female alone for gather- ing pollen for the larve, 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, 32 M. Miiller, ‘‘Anwendung der Darwin’schen Lehre,”’ ete., ‘Verh. d. n. V. Jabrg.’? xxix. p. 42. SEXUAL SELECTION 801 not even the wasp, which is closely allied to the bee, is pro- vided with a pollen-collecting apparatus, we have no grounds for supposing that male bees primordially collected pollen as well as the females; although we have some reason to sus- pect that male mammals primordially suckled their young as well as the females. Lastly, in all cases of reversion, characters are transmitted through two, three, or many more generations, and are then developed under certain unknown favorable 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 gem- mules or undeveloped atoms, which are transmitted to the offspring of both sexes, and are multiplied 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 units or cells previously developed in the due order of growth. Inheritance at Corresponding Periods of Life.—This ten- dency is well established. A new character appearing in a young animal, whether it lasts throughout 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 maturity, or even during old age, it tends to reappear in the offspring at the same advanced age. When deviations from this rule occur, the transmitted characters much oftener appear before than after the corre- sponding age. As I have dwelt on this subject sufficiently in another work,* I will here merely give two or three in- stances, for the sake of recalling the subject to the reader's mind. In several breeds of the Fowl, the down-covered chickens, the young birds in their first true plumage, and 33 ‘The Variation of Animals and Plants under Domestication,’’ vol. ii, 1868, p. 75. In the last chapter but one, the provisional hypothesis of pangenesis, above alluded to, is fully explained. 802 THE DESCENT.OF MAN the adults differ greatly from one another, as well as from their common parent-form, the Gallus bankiva; 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, while 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 first true plumage ‘‘they are beautifully pencilled,”’ that is, each feather is transversely marked by numerous dark bars; but in their second plumage the feathers all be- come spangled or tipped with a dark, round spot.** Hence in this breed variations have occurred at, and been trans- mitted 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 iridescent; yet there are breeds which do not acquire their characteristic colors until they have moulted two, three, or four times; and these modifications of plumage are regularly transmitted. Inheritance at Corresponding Seasons of the Year.—With animals in a state of nature, innumerable instances occur of characters appearing periodically at different seasons. We see this 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 colors and other decorations during the breeding-season alone. Pallas states,** that in Siberia domestic cattle and horses become lighter-colored during the winter; and I have myself observed and heard #4 These facts are given on the high authority of a great breeder, Mr. Teebay; see Tegetmeier’s ‘‘Poultry 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 Animals,’’ etc., vol. i. pp. 160, 249; vol. ii. p. 77. : 35 ‘Nove species Quadrupedum e Glirium ordine,’’? 1778, p. 7. On the transmission of color by the horse, see ‘‘Variation of Animals, etc., under Domestication,’’ vol. i. p. 51. Also vol. ii. p. 71, for a general discussion on ‘Inheritance as limited by Sex.”’ SEXUAL SELECTION 303 of similar strongly marked changes of color, that is, from brownish cream-color or reddish-brown to a perfect white, in several ponies in England. Although I do not know that this tendency to change the color of the coat during different seasons is transmitted, yet it probably is so, as all shades of color are strongly inherited by the horse. Nor is this form of inheritance, as limited by the seasons, more remarkable than its limitation by age or sex. Inheritance as Limited by Sex.—The equal transmission of characters to both sexes is the commonest form of inheri- tance, at least with those animals which do not present strongly marked sexual differences, and indeed with many of these. But characters are somewhat commonly trans- ferred 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 in- stances 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, ac- quired under domestication, are regularly transmitted to the same sex. Asarule, it is the females alone in cats which are tortoise-shell, the corresponding color 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, while the females differ considerably in color. The sexes of the pigeon in the parent-species do not differ in any external character; nevertheless, in certain domesticated breeds the male is colored differently from the female.* 36 Dr, Chapuis, ‘Le Pigeon Voyageur Belge,’’ 1865, p. 87. Boitard et Corbié, ‘‘Les Pigeons de Voliére,’’ etc., 1824, p. 173. See, also, on similar differences in certain breeds at Modena, ‘‘Le variazioni dei Colombi domestici,”’ del Paolo Bonizzi, 1873. 804 THE DESCENT OF MAN 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 are wholly due to the form of inheritance which has prevailed; for they have arisen, not from, but rather in opposition to, the wish of the breeder. Most of our domestic races have been formed by the ac- cumulation 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 sexual dis- similarity and complete similarity. Instances have already been given with the breeds of the fowl and pigeon, and under nature analogous cases are common. With animals under domestication, but whether in nature I will not ven- ture 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 be 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 spurs while young; or, as in certain Polish sub-breeds, in which the females, as there is reason to believe, originally acquired a crest, and subsequently transferred it to the males. All these cases are intelligible 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 in- stance, a breeder observed that some of his pigeons (of SEXUAL SELECTION 305 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, while the females remained un- changed? I will here only say that this, though perhaps not impossible, would be extremely difficult; 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 desired tint appeared, which were from the first limited in their development to the male sex, there would not be the least difficulty in making a breed with the two sexes of a different color, 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 sex- ually limited in its development to the females, it would be easy to make a breed with the females alone thus charac- terized; but if the variation was not thus originally limited, the process would be extremely difficult, perhaps impossible.” On the Relation between the Period of Development of a Character and its Transmission to One Sex or to Both Seaes.—. Why certain characters should be inherited by both sexes, and other characters 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 striz, though transmitted through the female, should be developed in the male alone, while every other character is equally transferred to both sexes. Why, again, with cats, the tortoise-shell color 37 Since the publication of the first edition of this work, it has been highly satisfactory to me to find the following remarks (‘‘The Field,’’ Sept. 1872) from go experienced a breeder as Mr. Tegetmeier. After describing some curious cases in pigeons, of the transmission of color by one sex alone, and the forma- tion of a sub-breed with this character, he says: ‘‘It is a singular circumstance that Mr. Darwin should have suggested the possibility of modifying the sexual colors of birds by a course of artificial selection. When he did so, he was in ignorance of these facts that I have related; but it is remarkable how very closely he suggested the right method of procedure.”’ 806 THE DESCENT OF MAN should, with rare exceptions, be developed in the female alone. The very same character, such as deficient or super- numerary digits, color-blindness, etc., 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 follow- ing rules seem often to hold good—that variations which first appear in either sex ata late period of life tend to be developed in the same sex alone, while 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 dis- cussed this subject, and as it has an important bearing on sexual selection, I must here enter into lengthy and some- what intricate details. It is in itself probable that any character appearing at an 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 side 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 gen- erality of this fact is quite remarkable: it holds good with almost all mammals, birds, amphibians, and fishes; also with many crustaceans, spiders, and some few insects, such as certain orthoptera and libellule. In all these cases the 38 References are given in my ‘Variation of Animals under Domestication,” vol. ii. p. 72. SEXUAL SELECTION 307 variations, through the accumulation of which the male acquired his proper masculine characters, must have oc- curred at a somewhat late period of life; otherwise the young males would have been similarly characterized; 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 ac- quired their present characters probably occurred, accord- ing to our rule, during youth. But there is here room for doubt, for characters are sometimes transferred to the off- spring at an earlier age than that at which they first ap- peared in the parents, so that the parents may have varied when adult, and have transferred their characters to their offspring while 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; neverthe- less, these characters, in apparent contradiction to our rule, are transferred to both sexes. We must not, however, overlook the possibility, or even probability, of successive variations 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 occurring 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 obvi- ously 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. 308 THE DESCENT OF MAN 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 life, 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 would lead to their development in that sex alone in which they first appeared in the pro- genitor of the whole Family. Now in seven species, belong: ing 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 varying 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 Professor Nilsson, who kindly made special inquiries 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 pro- vided with horns, while in the greater 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 horned, and also the young of a closely allied species, the eland (Ant. oreas), in which 89 Tt am much obliged to Mr. Cupples for having made inquiries for me in regard to the Roebuck and Red Deer of Scotland from Mr. Robertson, the experi- enced head forester to the Marquis of Breadalbane. In regard to Fallow-deer, I have to thank Mr. Eyton and others for information. For the Cervus alces of N. America, see ‘‘Land and Water,’’ 1868, pp. 221 and 254; and for the C. Virginianus and strongyloceros of the same continent, see J. D. Caton, in “Ottawa Acad. of Nat. Se.,”? 1868, p. 13. For Cervus Hidi of Pegu, see Lieut. Beavan, ‘‘Proc. Zoolog. Soc.,”’ 1867, p. 762. SEXUAL SELECTION 3809 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, considering the size ultimately attained by them; while 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 horns, 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 other antelopes, and from what we do know with respect to the horns of deer, cattle, etc., those of the prong-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 afterward.*? 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 inquiry* that the horns are developed later in life in this breed than in ordinary sheep in which both sexes are horned. But with domesticated 4 Antilocapra Americana. I have to thank Dr. Canfield for information with respect to the horns of the female: see also his paper in ‘Proc. Zoolog. Soc.,”? 1866, p. 109. Also Owen, ‘‘Anatomy of Vertebrates,’’ vol. iii. p. 627. 41 Thave been assured that the horns of the sheep in North Wales can always be felt, and are sometimes even an inch in length, 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, 42 JT am greatly indebted to Prof. Victor Carus for having made inquiries for me, from the highest authorities, with respect to the merino sheep of Saxony. On the Guinea coast of Africa there is, 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. 10, first showed horns on March 6, so that in this instance, in conformity with rule, the develop- ment of the horns occurred at a later period of life than in Welsh sheep, in which both sexes are horned. ; 310 THE DESCENT OF MAN sheep the presence or absence of horns is not a firmiy 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 protuberances 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 developed 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 auritum), however, offers 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 ap- pear 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 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 43 “‘TJeber die knéchernen Schadelhécker der Végel,’’ in the ‘‘Niederland- ischen Archiv fiir Zoologie,’’ Band I. Heft 2, 1872. 44 In the common peacock (Pavo cristatus) the male alone possesses spurs, while both sexes of the Java peacock (P. muticus) offer the unusual 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 previous year, of both species, compared on April 23, 1869, there was no difference in the development of the spurs, The spurs, however, were as yet represented merely by slight knobs or elevations. I presume that I should have been informed if any difference in the rate of development had been observed subsequently. SEXUAL SELECTION 811 developed very early in life, long before the other orna- ments, which are confined to the male. The wild-duck offers an analogous case, for the beautiful green speculum on the wings is common to both sexes, though duller and somewhat smallér in the female, and it is developed early in life, while 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 enes 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 colored scales, for instance, in two species of butterflies, in one of which the sexes differ in color, while 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 devel- oped on the wings of the same species of butterfly, in which certain colored marks are confined to one sex, while others are common to both sexes. A difference of this kind in the period of development is not so improbable as it may at first 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. 4 In some other species of the Duck family the speculum differs in a greater degree in the two sexes; but I have not been able to discover whether its full development 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 Mergus cucullatus we have, however, a case of this kind: the two sexes differ conspicuously in general plumage, and to a considerable degree in the speculum, which is pure white in the male and grayish white in the female. Now the young males at first entirely resemble the females, and have a grayish 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 differ- ences: see Audubon, ‘‘Ornithological Biography,”’ vol. iii., 1835, pp. 249-250. 312 THE DESCENT OF MAN We have as yet considered the transference of characters, relatively to their period of development, only in species in a natural state; we will now turn to domesticated animals, and-first touch on monstrosities and diseases. The presence of supernumerary digits, and the absence of certain pha- langes, must be determined at an early embryonic period— the tendency to profuse bleeding is at least congenital, as is probably color-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 transmitted to both sexes, here wholly fails. But 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 trans- mitted 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 draw any safe conclusion. Gout, however, seems to fall under our rule, for it is generally caused by intemperance during 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 their respective females in the shape or development of their horns, forehead, mane, dewlap, tail, and hump on the shoulders; and these pecu- liarities, 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 we 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 increased size being transmitted to his male offspring alone. On the SEXUAL SELECTION 313 other hand, the tortoise-shell color, which is confined to female cats, is quite distinct at birth, and this case violates the rule. There is a breed of pigeons in which the males alone are streaked with black, and the streaks can be de- tected even in the nestlings; but they become more con- spicuous 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, conform- ably 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 color 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- bird, namely, the London Prize, offers a nearly analogous case. With the breeds of the Fowl, the inheritance of vari- ous characters by one or both sexes seems generally deter- mined by the period at which such characters are developed. Thus in all the many breeds in which the adult male differs greatly in color from the female, as well as from the wild parent-species, he differs also from the young male, so that the newly acquired 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 colored in nearly the same manner as their parents, and this renders it probable that their colors first appeared early in life. We have instances of this fact in 48 “Das Ganze der Taubenzucht,’’ 1837, s. 21, 24. For the case of the , streaked pigeons, see Dr. Chapuis, ‘‘Le pigeon voyageur Belge,’’ 1865, p. 87, Descent—Vot. I.—14 314 THE DESCENT OF MAN 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 peculiar in a black or white 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 colored. With the so-called Cuckoo sub- breeds of the fowl, in which the feathers are transversely pencilled with dark stripes, both sexes and the chickens are colored in nearly the same manner. The laced plumage of the Sebright bantam is the same in both sexes, and in the young 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 do the sexes of the aboriginal parent-species; yet they acquire their char- acteristic plumage late in life, for the chickens are distinctly pencilled. With respect to other characters besides color, 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 theadult female. In the Game breeds pugnacity is developed at a wonderfully early age, of which curious proofs could be given; and this character is transmitted to both sexes, so that the hens, from their extreme pugnacity, are now generally exhibited in separate pens. With the Polish breeds the bony protuber- ance of the skull which supports the crest is partially developed even before the chickens are hatched, and the crest itself soon begins to grow, though at first feebly;* and in this breed the adults of both sexes are characterized by a great bony protuberance and an immense crest. Finally, from what we have now seen of the relation 4" For full particulars and references on all these points respecting the several breeds of the Fowl see ‘‘Variation of Animals and Plants under Domes- tication,’’ vol. i. pp. 250, 256. In regard to the higher animals, the sexual differences which have arisen under domestication are described in the same work under the head of each species. SEXUAL SELECTION 315 which exists in many natural species and domesticated races, between the period of the development of their char- acters and the manner of their transmission—for example, the striking fact of the early growth of the horns in the rein- deer, 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 charac- ters being inherited by both sexes is their development at an early age, while the sexes differ but little in constitution. It appears, however, that some difference must exist be- tween 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 discussion 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 atthe same age, and periodically at the same season of the year, in which they first appeared in the parents. But these rules, owing to unknown causes, are far from being fixed. Hence, 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 ardor 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 by natural selection tending toward the general welfare of the species. Hence the manner in which 816 THE DESCENT OF MAN 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 transmitted 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. Variations, however, may occur at any period of life 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 will be seen that all these cases frequently occur in nature. Sexual selection can never act on any animal before 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 dis- covering 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 modified 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 characters of the adult males; and differences of this kind between the old and young males may be observed in many species of animals. . Itis probable that young male animals have often tended to vary ina manner which would not only have been of no use to them at an early age, but would have been actu- ally injurious—as by acquiring bright colors, which would render them conspicuous to their enemies, or by acquiring structures, such as great horns, which would expend much vital force in their development. Variations of this kind SEXUAL SELECTION 317 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 de- rived 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 of conquering other males, or of finding, securing, or charming the 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 evi- dence with domesticated animals that variations of all kinds are, if not carefully selected, soon lost through intercrossing and accidental deaths. Consequently, 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 acquired char- acters 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 conse- quence be modified in the same manner, although such characters were of no use to the females; but I shall here- after have to recur to these more intricate 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 accumulated 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 frequently been accumulated through natural selec- tion, 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 818 THE DESCENT OF MAN classes. But this implies that the two sexes follow different habits in their struggles for existence, which is a rare cir- cumstance with the higher animals. The case, however, is widely different with the reproductive functions, in which respect the sexes necessarily differ. For variations in struc- ture which are related to these functions have often proved of value to one sex, and, from having arisen at a late period of life, have been 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 endeavor in each case to apply the principles 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 illus- trative instances of the innumerable structures by the aid of which the male 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 al- lures 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 to 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 first give them as a standard of comparison. Man.—In England during ten years (from 1857 to 1866) the average number of children born alive year.y was SEXUAL SELECTION 319 707,120, in the proportion of 104.5 males to 100 females. But in 1857 the male births throughout England were as 105.2, and in 1865 as 104.0 to 100. Looking to separate districts, in Buckinghamshire (where about 5,000 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; while in North Wales (where the average annual births are 12,878) it was as high as 106.2 to 100. Taking a still smaller district, viz., Rutlandshire (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 7,885 births; during the whole ten years, was as 104.5 to 100; that is, in the same ratio as throughout England.** The proportions are some- times slightly disturbed by unknown causes; thus Prof. Faye states ‘‘that in some districts of Norway there has been during a decennial period a steady deficiency of boys, while in others the opposite condition has existed.’’ In France 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 the female births 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 suc- cessive years between 90 and 99 males for every 100 females. It is a singular fact that with Jews the proportion of male 48 “Twenty-ninth Annual Report of the Registrar-General for 1866.’? In this report (p. xii.) a special decennial table is given. 49 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 ‘‘Annuaire pour ]’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 proportion of the sexes. 820 THE DESCENT OF MAN births is decidedly larger than with Christians: thus in Prussia the proportion is as 118, in Breslau as 114, and in Livonia as 120 to 100; the Christian births in these countries being the same as usual; for instance, in Livonia as 104 to 100.° 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 still-born females we have in several countries from 184.6 to 144.9 still-born males. During the first four or five years of life, also, 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 still more unfavorable.’’ * 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 variable in structure than the female; and variations in im- portant organs would generally be injurious. But the size of the body, and especially of the head, being greater in male than female infants is another cause; for the males are thus more liable to be injured during parturition. Con- sequently 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 children, both 50 In regard to the Jews, see M. Thury, ‘‘La Loi de Production des Sexes,”? 1863, p. 25. 51 ‘British and Foreign Medico-Chirurg. Review,’’ April, 1867, ‘p. 343, Dr. Stark also remaris (‘‘Tenth Annual Report of Births, Deaths, etc., in Scot- land,’’ 1867, p. xxviii.) that ‘‘These examples may suffice to show 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, however, of this pecu- larity 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 male death-rate 1s an impressed, natural, and constitutional peculiarity due to sex alone.”’ 52 “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 threv-eights of an inch in circumference, and by one-eighth in transverse diameter. Quetelet has shown that woman is born smaller than man; see Dr. Duncan, ‘‘Fecundity, Fertility, Sterility,’’ 1871, p. 382. SEXUAL SELECTION 321 at birth and for some time subsequently, and owing to the exposure of grown men to various dangers, and to their tendency to emigrate, the females in all old-settled coun- tries, 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 climates, in Naples, Prussia, Westphalia, Holland, France, Engiand, 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 dif- ferent ways, as from the mothers being generally young, from the large proportion of first pregnancies, etc. But we 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 labors, from vari- ous causes, such as attempts at concealment by tight lacing, hard work, distress of mind, etc., their male infants would proportionably suffer. And this probably is the most effi- cient of all the causes of the proportion of males to females born alive being less among illegitimate children than among 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 their struggles for the pos- session of the females, and no doubt it is owing to this fact that the two sexes of at least some animals differ in size at birth. Thus we have the curious fact that we may attrib- ute the more frequent deaths of male than female infants, especially among the illegitimate, at least in part to sexual selection. It has often been supposed that the relative age of the 53 With the savage Guaranys of Paraguay, according to the accurate Azara (“Voyages dans l’Amerique mérid.,”’ tom. ii., 1809, pp. 60, 179), the women are to the men in the proportion of 14 to 13. 54 Babbage, ‘‘Edinburgh Journal of Science,’’ 1829, vol. i. p. 88; also p. 90, on still-vborn children. On illegitimate children in England, see ‘‘Report of Registrar General for 1866 ” p. xv. 822 THE DESCENT OF MAN two parents determines the sex of the offspring; and Prof. Leuckart® has advanced what he considers sufficient evi- dence, with respect to man and certain domesticated animals, that this is one important 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 observations discountenance this belief. According to Dr. Stockton-Hough,® the season of the year, the poverty or wealth of the parents, residence in the country or in cities, the crossing of foreign immi- grants, etc., 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 En- glish race-horse, and we shall immediately see that his male and female offspring are 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- horses 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, consisting of 12,763 males and 12,797 females, or in the proportion of 99.7 55 Leuckart (in Wagner, ‘‘Handworterbuch der Phys.,’’ B, iv., 1853, s. 774), 56 Social Science Assoc, of Phila., 1874. 51 “Anthropological Review,’’ April, 1870, p. eviii. * ®8 During eleven years a record was kept of the number of mares which proved barren or prematurely slipped their foals; and it deserves notice, as showing how infertile these highly nurtured and rather closely interbred ani- mals have become, that not far from one-third of the mares failed to produce liv- ing foals. Thus during 1866, 809 male colts and 816 female colts were born, and 743 mares failed to produce offspring. During 1867, 836 males aad 902 females were born, and 794 mares failed. SEXUAL SELECTION 823 males to100 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, the two sexes are produced in almost equal numbers. The fluctuations in the proportions during successive years are closely ike those which occur with mankind, when a small and thinly populated area is considered; thus in 1856 the male horses were as 107.1, and in 1867 as only 92.6, to 100 females. In the tabulated returns the proportions vary in cycles, for the males exceeded the females during six successive years; and the females exceeded the males during © two periods each of four years: this, however, may be ac- cidental; at least I can detect nothing of the kind with man in the decennial table in the Registrar’s Report for 1866. Dogs.—During a period of twelve years, from 1857 to 1868, the births of a large number of greyhounds, through- out England, were sent to the ‘‘Field’’ newspaper; and I am again indebted to Mr. Tegetmeier for carefully tabulating the results. The recorded births were 6,878, consisting of 8,605 males and 3,273 females, that is, in the proportion of 110.1 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 is 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 inquired from several great breeders of dogs, and finds that all, without exception, believe that females are produced in excess; but he suggests that 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 agri- culturists 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 324 THE DESCENT OF MAN 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 the proportion of males would be somewhat larger at birth than at the age of castration. This is a remarkable coincidence with what, as we have seen, occurs with man- kind, 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 8,965 births, consisting of 4,407 males and 4,558 females; that is in the proportion of 96.7 males to 100 females. With respect to Cheviot and blackfaced sheep bred in Scotland, I have received returns from six breeders, two of them on a large scale, chiefly for the years 1867-69, 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 80,172 females, or as 97.7 to 100. So that with sheep at the 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 births, too few to be trusted; these consisted of 477 bull-calves and 505 cow-calves; i.e, in the proportion of 94.4 males to 100 females. The Rev. W. D. Fox informs me that in 1867, out of 84 calves born on a farm in Derby- shire, only one was a bull. Mr. Harrison Weir has inquired from several breeders of Pigs, and most of them estimate the male to the female births as about 7 to 6. This same gentleman has bred Rabbits for many years, and has noticed 59 T am much indebted to Mr. Cupples for having procured for me the above returns from Scotland, as well as some of the following returns on cattle. Mr. R. Elliot, of Laighwood, first called my attention 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 large returns as to sheep. SEXUAL SELECTION 825 that a far greater number of bucks are produced than does. But estimations are 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 re- ceived conflicting statements. Mr. R. Elliot, of Laighwood, informs me that a rat-catcher assured him that he had always found the males in great excess, even with the young in the nest. In consequence of this, Mr. Elliot himself subse- quently 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 males greatly exceed the females. In regard to Moles, it is said that ‘‘the males are much more numerous than the females;’’ ™ and as the catching of these animals is a special occupation the statement may perhaps be trusted. Sir A. Smith, in de- scribing an antelope of South Africa” (Kobus ellipsiprymnus), remarks that, in the herds of this and other species, the males are few in number 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 males alone, others affirm that this does occur. It appears probable that the young, when expelled from the herd, would often fall a prey fo the many beasts of prey of the country. Birds.—W ith respect to the Fowl, I have received only one account, namely, that out of 1,001 chickens of a highly bred stock of Cochins, reared during eight years by Mr. Stretch, 487 proved males, and 514 females; 7.¢., 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. Tegetmeier informs me, can always be pur- chased cheaper than females. Usually the two birds reared 60 Bell, “History of British Quadrupeds,’’ p. 100. *! “THustrations of the Zoology of 8. Africa,’’ 1849, pl. 29, 826 THE DESCENT OF MAN from the two eggs laid in the same nest are a male and a female; but Mr. Harrison Weir, who has been so large a 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. With 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 wild birds, and he informs Mr. Jenner Weir that four or five males to one female are generally produced. An experienced observer remarks® that in Scandinavia the broods of the capercailzie and biackcock contain more males than females; and that with the Dal-ripa (a kind of ptarmigan) more males than females attend the leks or places of courtship; but this lat- ter circumstance is accounted for by some observers by a greater number of hen birds being killed by vermin. From various facts given by White, of Selborne,“ it seems clear that the males of the partridge must be in considerable’ excess in the south of England; and I have been assured that this is the case in Scotland. Mr. Weir, on inquiring from the dealers, who receive at certain seasons large num- bers of ruffs (Machetes pugnax), was told that the males are much the more numerous. This same naturalist has also inquired for me from the bird-catchers, who annually catch an astonishing number of various small species alive for the London market, and he was unhesitatingly answered by an old and trustworthy man, that with the chaffinch the males are in large excess; he thought as high as 2 males to 1 female, or at least as high as 5 to 3. The males of 6? Brehm (“Tlust. Thierleben,”’ B. iv. s. 990) comes to the same conclusion, 63 On the authority of L. Lloyd, ‘‘Game Birds of Sweden,’’ 1867, pp. 12, 132. 64 “Nat. Hist. of Selborne,’’ letter xxix., edit. of 1825, vol. i. p. 139. 6 Mr, Jenner Weir received similar information, on making inquiries during the following year. To show the number of living chaffinches caught, I may SEXUAL SELECTION 3827 the blackbird, he likewise maintained, were by far the more numerous, whether caught by traps or by netting at night. These statements may apparently be trusted, because this same man said that the sexes are about equal with the lark, the twite (Linaria montana), and goldfinch. On the other hand, he is certain that with the common linnet the females preponderate greatly, but unequally during different years; during some years he 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 flocks at this period often consist of hens alone. Mr. Salvin paid particular attention to the sexes of the humming-birds in Central America, and he is convinced that with most of the 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 88 females. With two other species the females were in excess; but the proportions apparently vary either during different seasons or in different localities; for on one occasion the males of Campylopterus 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 chaffinch keeping apart, and ‘‘the females by far the most numerous’’; while in Palestine Mr. Tristram found ‘‘the male flocks appearing greatly to exceed the female in number.’’” So again with the Quiscalus major, Mr. G. Taylor® says that in Florida there were ‘‘very few females in proportion to the males,’’ while in Honduras the mention that in 1869 there was a match between two experts, and one man caught in a day 62, and another 40, male chaffinches. The greatest number ever caught by one man in a single day was 70. 86 ‘This,’ vol. ii. p. 260, as quoted in Gould’s ‘‘Trochilide,’’ 1861, p. 52, For the foregoing proportions I am indebted to Mr. Salvin for a table of hig results. 67 “*This,’? 1860, p. 187; and 1867, p. 369. 68 “This,’? 1862, p. 137. 828 THE DESCENT. OF MAN proportion was the other way, the species there having the character of a polygamist. Fish.—With Fish the proportional numbers of the sexes can be ascertained only by catching them in 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 regard to trout. Withsome species the males are believed to die soon after fertilizing the ova. With 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 the females were caught. M. Carbonnier,” who has especially attended to the natural history of the pike (Hsox luctus), 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 than the females. Nevertheless, in the few cases in which the proportional numbers have been actually observed, the males appear to be largely in excess. Thus Mr. R. Buist, the superintendent of the Stormontfield experiments, says that in 1865, out of 70 salmon first landed for the purpose of obtaining the ova, upward of 60 were males. In 1867 he again ‘‘calls attention to the vast dispro- portion of the males to the females. We had at the outset at least ten males to one female.’’ Afterward females suffi- cient for obtaining ova were procured. He adds, ‘‘from the great proportion of the males, they are constantly fighting and tearing each other on the spawning-beds.’’” This dis- proportion, no doubt, can be accounted for in part, but whether wholly is doubtful, by the males ascending the rivers before the females. Mr. F. Buckland remarks im regard to trout, that ‘‘it is a curious fact that the males 6° Leuckart quotes Bloch (Wagner, ‘‘Handwérterbuch der Phys.,’’ B. iv., 1853, s. 775), that with fish there are twice as many males as females. 7 Quoted in the ‘‘Farmer,’’ March 18, 1869, p. 369. 11 **The Stormontfield Piscicultural Experiments,’’ 1866, p. 23. The ‘‘Field”’ newspaper, June 29, 1867. : SEXUAL SELECTION 829 preponderate very largely in 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 suffi- cient 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 Cyprinide likewise seem to be in ex- cess; 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 while 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 that it is always recommended 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 spawning-beds the males are ten times as numerous as the females; when a female comes among the males, ‘‘she is immediately pressed closely by a male on each side; and when they have been in that situation for a time, are super- seded by two other males.’’ ” Insects. —In this great Class the Lepidoptera almost alone afford means for judging 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, 72 “Land and Water,’’ 1868, p. 41. 8 Yarrell, ‘‘Hist. British Fishes,’’ vol. i, 1826, p. 307; on the Cyprinus carpio, p. 331; on the inca vulgaris, p. 331; on the Abramis brama, p. 336, See, for the minnow (Leuciscus phoxinus), ‘‘Loudon’s Mag. of Nat. Hist. ,’’ vol. v., 1832, p. 682. 830 THE DESCENT OF MAN 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 Prof. 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 cynthia), the males greatly preponderate in the first, while in the second the two sexes are nearly equal, or the females rather in excess. : In regard to Butterflies in a state of nature, several ob- servers have been much struck by the apparently enormous preponderance of the males." Thus Mr. Bates,” in speak- ing 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 proportion of a hundred to one. In 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. turnus this is certainly the case. In South Africa, Mr. R. Trimen found the males in excess in 19 species;” and in one of these, which swarms in open 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.” Myr. 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 number; but three South African species per- haps offer an exception. Mr. Wallace” states that the ™ Leuckart quotes Meinecke (Wagner, ‘‘Handworterbuch der Phys.,’’ B. iv., 1853, s. 775) that the males of Butterflies are three or four times as numerous as the females. 7% ‘The Naturalist on the Amazons,”’ vol. ii., 1863, pp. 228, 3477. 76 Four of these cases are given by Mr. Trimen in his ‘‘Rhopalocera Africa Australis,’ ™ Quoted by Trimen, ‘Transact. Ent. Soc.,’”’ vol. v. part iv., 1866, p. 330. % “Transact, Linn. Soc.,’’ vol. xxv. p. 37. SEXUAL SELECTION 831 females of Ornithoptera cresus, in the Malay Archipelago, are more common and more easily caught than the males; but this is a rare butterfly. I may here add, that in Hyperythra, a genus of moths, Guenée says that from four to five females are sent in collections from India for one male. When this subject of the proportional numbers 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 attrib- uted by various observers to the more retiring habits of the females, and to the males emerging earlier from the cocoon. This latter circumstance 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 beginning of the sea- son, 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 butterflies 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 his view. Mr. Doubleday, however, and some others take an opposite view, and are convinced 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 places their fre- quenting more open stations, other causes may be assigned 7 “Proc, Entomolog. Soc.,’’ Feb. 17, 1868. , 89 Quoted by Dr, Wallace in ‘‘Proc, Ent. Soc.,’’ 3d series, vol. v., 1867, p. 487. 832 THE DESCENT OF MAN for an apparent or real difference in the proportional num- bers of the sexes of Lepidoptera, when captured in the imago state, and when reared from the egg or caterpillar state. I hear from Prof. 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 in rearing Lepidoptera more females die in the cocoon than males. With many species the female caterpillar is larger than the male, and a collector would naturally choose the finest specimens, and thus unintentionally collect a larger number of females. 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 worth the trouble of rearing. Birds when sur- rounded by caterpillars would probably devour the largest; and Prof. Canestrini informs me that in Italy some breed- ers 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 caterpil- lars. Dr. Wallace further remarks that female caterpillars, from being larger than the males, require more time for their development, and consume more food and moisture; and thus they would be exposed during a longer time to danger from ichneumons, birds, etc., and in times of scarcity would perish in greater numbers. Hence it appears quite possible that, in a state of nature, fewer female Lepidoptera may reach maturity than males; and for our special object we are concerned with their relative numbers at maturity, when the sexes are ready to propagate their kind. The manner in which the males of certain moths congre- gate in extraordinary numbers round a single female ap- parently indicates a great excess of males, though this fact may perhaps be accounted for by the earlier emergence of the males from their cocoons. Mr. Stainton informs me that from twelve to twenty males may often be seen con- gregated round a female Hlachista rufocinerea. It is well SEXUAL SELECTION iG 333 known that if a virgin Lastocampa quercus or Saturnia carpint 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 believes that he has seen from fifty to a hundred males of both these species attracted in the course of a single day by a female in con- finement. In the Isle of Wight Mr. Trimen exposed a box in which a female of the Lasiocampa had been confined on the previous day, and five males soon endeavored to gain admittance. In Australia, M. Verreaux, having placed the female of a small Bombyx in a box in his pocket, was followed by a crowd of males, so that about 200 entered the house with him.* Mr. Doubleday has called my attention to M. Stau- dinger’s” list of Lepidoptera, which gives the prices of the males and females of 800 species of well-marked varieties of butterflies (Rhopalocera). The prices for both sexes of the 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 2,000 species or varieties of moths (Heterocera) are cata- logued, those with wingless females being here excluded on account of the difference in habits between the two sexes: of these 2,000 species, 141 differ in price accord- ing 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 100 to 148. With respect to the butterflies in this price 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 difference in the prices of the two sexes, and that it can be accounted for only by an 81 Blanchard, ‘‘Metamorphoses, Mceurs des Insectes,’’ 1868, pp. 225-226, 82 “Tenidopteren-Doubletten Liste,’’ Berlin, No, x., 1866. 384 THE DESCENT OF MAN excess in the number of the males. But I am bound to add that Dr. Staudinger informs me that he is himself of a dif- ferent opinion. He thinks that the less active habits of the females and the earlier emergence 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 while 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 from eggs or caterpillars, I have received only the few following cases: Males | Females The Rev. J. Hellins,* of Exeter, reared, during 1868, imaEed of 73 species, which consisted of . . 153 137 Mr. Albert Jones, of Eltham, reared, pee 1868, imagos of 9 species, which consisted of . . . -| 159 126 During 1869 he reared imagos from 4 species, “consisting of .| 114 112 Mr. Buckler, of Emsworth, Hants, during 1869, reared imagos from 74 species, consisting of . 180 169 Dr. Wallace, of Colchester, reared from ‘one brood of Bombyx cynthia . . 52 48 Dr, Wallace raised, from cocoons of Bombyx Pernyi. sent from China, during 1869. . . 224 123 Dr. Wallace raised, during 1868 and 1869, from two lots off cocoons of Bombyx yamamai . . 2. 2 es 6 ew we 52 46 Totals . 2. 2 6 6 © © eo ee we we wt ff 984 161 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 83 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 found it impossible to tabulate them. SEXUAL SELECTION 835 of Lepidoptera, the mature males generally exceed the fe- males in number, whatever the proportions may be at their first emergence from the egg. With reference to the other orders of insects, I have been able to collect very little reliable information. With the stag-beetle (Lucanus cervus) ‘‘the males appear to be much 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 Elateride, the males are said to be much more numerous than the females, and ‘‘two or three are often found united with one female;* so that here polyandry seems to prevail.’’ With Siagonium (Staphylinide), in which the males are furnished with horns, ‘‘the females are far more numerous than the ‘opposite sex.’’ Mr. Janson stated at the Entomological Society that the females of the bark-feeding Tomicus villosus are so common as to bea plague, while the males are so rare as to be hardly known. It is hardly worth while saying anything about the pro- portion of the sexes in certain species and even groups of insects, for the males are unknown or very rare, and the females are parthenogenetic, that is, fertile without sexual union; examples of this are afforded by several of the Cynipide.** In all the gall-making Cynipide known to Mr. Walsh, the females are four or five times as numerous as the males; and so it is, as he informs me, with the gall- making Cecidomyiiz (Diptera). With some common species of Saw-flies (Tenthredine) Mr. F. Smith has reared hun- dreds of specimens from larve of all sizes, but has never reared a single male; on the other hand, Curtis says,** that 84 Ginther’s ‘‘Record of Zoological Literature,’’ 1867, p. 260. On the ex- cess of female Lucanus, ibid. p. 250. On the males of Lucanus in England, Westwood, ‘‘Modern Class. of Insects,’’ vol. i. p. 187. On the Siagonium, ibid. p. 172. 85 Walsh, in ‘“‘The American Entomologist,’ vol. i., 1869, p. 103. F. Smith, “Record of Zoological Literature,’’ 1867, p. 328. 86 ‘Farm Insects,’’ pp. 45-46. 836 THE DESCENT OF MAN with certain species (Athalia) bred by him, the males were to the females as six to one; while exactly the reverse oc- curred with the mature insects of the same species caught in the fields. In the family of Bees, Hermann Miiller® col- lected a large number of specimens of many species, 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 prac- tically in excess. Miiller also observed that the relative number of the two sexes in some species differed much in different localities. But as H. Miller has himself re- marked to me, these remarks must be received with some caution, as one sex might more easily escape observation than the other. Thus his brother, Fritz Miller, has noticed in Brazil that the two sexes of the same species of bee some- times frequent different kinds of flowers. With respect to the Orthoptera, I know hardly anything about the relative number of the sexes; Kérte,* 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 Odonatous group, there is a great overplus of males; in the genus Hetzrina, 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, while in two other species the females are twice or thrice as numerous as the males. In some European species of Psocus thousands of females may be collected without a single male, while with other species of the same genus both sexes are common.” In England, Mr. MacLachlan 81 “Anwendung der Darwin’schen Lehre,”’ ‘‘Verh, d. n. V. Jahrg.’’ xxiv. 8 “Die Strich, Zug oder Wanderheuschrecke,’’ 1828, p. 20. 89 “Observations on N. American Neuroptera,’? by H. Hagen and B. D. Walsh, ‘‘Proc. Ent Soc. Philadelphia,’’ Oct. 1863, pp. 168, 223, 239. SEXUAL SELECTION 838T has captured hundreds of the female Apatania muliebris, but has never seen the male; and of Boreus hyemalis only four or five males have been seen here.” With most of these species (excepting the Tenthredinz) 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 I have been able to collect still less information. With Spiders, Mr. Black- wall, who has carefully attended to this class during many years, writes to me that the males, from their more erratic habits, are more commonly seen, and therefore appear more numerous. This is actually the case with a few species; but he mentions several species in six genera, in which the females appear to be_much more numerous than the males." The small size of the males in comparison with the females (a peculiarity which is sometimes carried to an extreme degree), and their widely different appearance, may account in some instances for their rarity in collections.” Some of the lower Crustaceans are able to propagate their kind asexually, and this will account for the extreme rarity of the males; thus Von Siebold® carefully examined no less than 18,000 specimens of Apus from twenty-one localities, and among these he found only 319 males. With some other forms (as Tanais and Cypris), as Fritz Miller 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 Diastylide and of Cypridina on the shores of Brazil; thus with a species % ‘Proc, Ent. Soc. London,’? Feb, 17, 1868. *1 Another great authority with respect to this class, Prof. Thorell of Upsala (‘On European Spiders,’’ 1869-70, part i. p. 205) speaks as if female spiders were generally commoner than the males. ® See, on this subject, Mr. O. P. Cambridge, as quoted in ee Jour- nal of Science, »? 1868, p. 429. % “Reitrige zur Parthenogenesis, ” p. 174, Descent—Vox, i.—15 538 THE DESCENT OF MAN in the latter genus, 63 specimens caught the same day in- cluded 57 males; but he suggests that this preponderance may be due to some unknown difference in the habits of the two sexes. With one of the higher Brazilian crabs, namely, a Gelasimus, Fritz Miiller found the males to be more numerous than the females. According to the large experience of Mr. C. Spence Bate, the reverse seems to be the case with six common British crabs, the names of which he has given me. The Proportion of the Sexes in Relation to Natural 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 pro- ducing 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*t has recently found on careful examination that the Todas, a hill-tribe of India, consist of 112 males and 84 females of all ages—that is ina ratio of 183.8 males to 100 females. The Todas, who are polyandrous in their marriages, during former times invari- ably practiced female infanticide; but this practice has now been discontinued for a considerable period. Of the chil- dren born within late years, the males are more numerous than the females, in the proportion of 124 to 100. Col. Marshall accounts for this fact in the following ingenious % ‘The Todas,’”? 1873, pp. 100, 111, 194, 196, SEXUAL SELECTION 389 manner: ‘‘Let us for the purpose of illustration 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, while the third mother has three sons and three daughters. The first mother, fol- lowing the tribal custom, destroys four daughters and _pre- serves 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 while the males belong to families in which the tendency to produce sons is great, the females are of those of a converse inclina- tion. 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 extremely scanty, I have searched for ad- ditional evidence, but cannot decide whether what I have found is trustworthy; nevertheless the facts are, perhaps, worth giving. The Maories of New Zealand have long practiced infanticide; and Mr. Fenton’ states that he ‘‘has met with instances of women who have destroyed four, six, and even seven children, mostly females. However, the universal testimony of those best qualified to judge is con- clusive that this custom has for many years been almost ex- tinct. Probably the year 1835 may be named as the period of its ceasing to exist.’’ Now among the New Zealanders as with the Todas, male births are considerably in excess. Mr. Fenton remarks (p. 80): ‘‘One fact is certain, although the exact period of the commencement of this singular con- dition of the disproportion of the sexes cannot be demon- stratively fixed, it is quite clear that this course of decrease was in full operation during the years 1830 to 1844, when % ‘*Aborigina Inhabitants of New Zealand; Government Report,’’ 1859, p. 36. 840 THE DESCENT OF MAN 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 are 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 civilized countries, chiefly owing to the greater mortality 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 consisting of 31,667 males and 24,303 females of all ages, that is in the ratio 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 1844, at which period female infanticide had only lately ceased, the non-adult males in one district were 281, and the non-adult 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 practiced there to a frightful extent, but was by no means confined to female infants, as is shown by Mr. Ellis,** and as I have been in- formed by Bishop Staley and the Rev. Mr. Coan. Never- theless, 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 prob- 9 **Narrative of a Tour through Hawaii,’’ 1826, p. 298. * “History of the Sandwich Islands,’ 1843, p. 93. SEXUAL SELECTION 841 able, but must be received with much caution. The prac- tice of infanticide ceased about the year 1819, when idolatry was abolished and missionaries settled in the islands. A careful census in 1839, of the adult and taxable men and women in the island of Kauai and in one district of Oahu (Jarves, p. 404), gives 4,728 males and 8,776 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 in Oahu was 1,797, and of females of the same ages 1,429; 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 amounted to 36,272, and the females to 83,128, or as 109.49 to 100. The males under seventeen years amounted to 10,773, and the females under the same age to 9,598, 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 125.36 to 100. It must be borne in 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 civilized countries, the proportion of males would have been considerably higher if the numbers had referred to births.” % This is given in the Rev. H. T. Cheever’s ‘‘Life in the Sandwich Islands,” 1851, p. 277. 39 Dr. Coulter, in describing (‘‘Journal R. Geograph. Soc.,”’ vol. v., 1835, p. 67) the state of California about the year 1830, says that the natives, reclaimed by the Spanish missionaries, have nearly all perished, or are perishing, although well treated, not driven from their native land, and kept from the use of spirits. He attributes this, in great part, to the undoubted fact that the men greatly ex- ceed the women in number; but he does not know whether this is due to a fail- ure of female offspring, or to more females dying during early youth. The latter alternative, according to all analogy, is very improbable. -He adds that ‘‘infanti- cide, properly so called, is not common, though very frequent recourse is had to abortion.’’ If Dr. Coulter is correct about infanticide, this case cannot be advanced in support of Col. Marshall’s view. From the rapid decrease of the reclaimed natives, we may suspect that, as in the cases lately given, their fer- tility has been diminished from changed habits of life. I had hoped to gain some light on this subject from the breeding of dogs; fnasmuch 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. Unfortu- nately, I know nothing of 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 842 THE DESCENT OF MAN From the several foregoing cases we have some reason to believe that infanticide practiced in the manner above explained tends to make a male-producing race; but I am far from supposing that this practice in the case of man, or some analogous process with other species, has been the sole determining cause of an excess of males. There may be some unknown law leading to this result in decreasing races which have already become somewhat infertile. Be- sides the several causes previously alluded to, the greater facility of parturition among savages, and the less conse- quent 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 Tahitians now inhabiting Norfolk Island. As the males and females of many animals differ some- what in habits and are exposed in different degrees to dan- ger, 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 complication 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 para- mount importance, we can see that those communities would flourish best which contained females having a strong in- herited tendency to produce more and more females; and from inquiries 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, Therefore I 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, SEXUAL SELECTION 343 in such cases an unequal sex-producing tendency would be ultimately gained through natural selection. With ani- mals 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 preponderance of ren in the tribe is supposed to be one chief cause of t!:¢ practice of female infanticide. In no case, as far as we can see, would sa inherited tendency to produce both sexes in equal numbers, or to produce one sex in excess, be a direct advantage or dis- advantage to certain individuals more than {o others; for instance, an individual with a tendency to ‘produce more males than females would not succeed better in 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 certain animals (for instance, fishes and cirripeds) in which two or more males appear to be necessary for the fertilization 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 see that the whole prob- lem is so intricate that it is safer to leave its solution. for the future. 344 THE DESCENT OF MAN CHAPTER IX SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM These characters absent in the lowest classes—Brilliant colors—Mollusca— Annelids—Crustacea, secondary sexual characters strongly developed; dimorphism; color; characters not acquired before maturity—Spiders, sexual colors of; stridulation by the males—Myriapoda - ITH animals belonging to the lower classes, the \ \/ two sexes are not rarely united in the same individual, and therefore secondary sexual char- acters cannot be developed. In many cases where the sexes are separate, both are permanently attached to some support, and the one cannot search or struggle for the other. More- over, it is almost certain that these animals have too imper- fect 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 sub-kingdoms, such as the Pro- tozoa, Coelenterata, Echinodermata, Scolecida, secondary sexual characters, of the kind which we have to consider, do not occur; and this fact agrees with the belief that such characters in the higher classes have been acquired through sexual selection, which depends on the will, desire, and choice of either sex. Nevertheless some few apparent ex- ceptions occur; thus, as I hear from Dr. Baird, the males of certain Entozoa, or internal parasitic worms, differ slightly in color from the females; but we have no reason to suppose that such differences have been augmented through sexual selection. Contrivances by which the male holds the female, and which are indispensable for the propa- gation of the species, are independent of sexual selection, and have been acquired through ordinary selection. SEXUAL SELECTION 845 Many of the lower animals, whether 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 (Actiniz), some jelly-fish (Meduse, Porpita, etc.), some Planariz, many star-fishes, Hchini, Ascidians, etc.; but we may conclude from the reasons already indicated, namely, the union of the two sexes in some of these animals, the permanently affixed condition of others, and the low mental powers of all, that such colors do not serve as a sexual attraction, and have not been acquired through sexual selection. It should be borne in mind that in no case have we sufficient evidence that colors have been thus acquired, except where one sex is much more brilliantly or conspicuously colored than the other, and where there is no difference in habits between the sexes sufficient to account for their different colors. - But the evidence is rendered as complete as it can ever be, only when the more ornamented individuals, almost always the males, voluntarily display their attractions before the other sex; for we cannot believe that such display is use- less, and if it be advantageous, sexual selection will almost inevitably follow. We may, however, extend this conclu- sion to both sexes, when colored alike, if their colors are plainly analogous to those of one sex alone in certain other species of the same group. How, then, are we to account for the beautiful or even gorgeous colors of many animals in the lowest classes? It appears doubtful whether such colors often serve as a protection; 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 Medusa, or jelly-fishes, is of the highest service to them as a protection; but when we are reminded by Hickel that not only the medusz, but many floating mollusca, crustaceans, and even small oceanic fishes partake of this same glass-like appear- ance, often accompanied by prismatic colors, we can hardly 346 THE DESCENT OF MAN 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 colors are likewise beneficial to many animals as a warning to their would-be devourers that they are dis- tasteful, or that they possess some special means of defence; but this subject will be 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 of any benefit thus derived. Hardly any color is finer than that of arterial blood; but there is no reason to suppose that the color 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 ac- quired for this purpose. So again with many animals, especially the lower ones, the bile is richly colored; thus, as I am informed by Mr. Hancock, the extreme beauty of the Holide (naked sea-slugs) is chiefly due to the biliary glands being seen through the translucent integuments—this beauty being probably of no service to these animals. The tints of the decaying leaves in an American forest are de- scribed by every one as gorgeous; yet no one supposes that these tints are of the least advantage to the trees. Bearing in mind how many substances closely analogous to natural organic compounds have been recently formed by chemists, and which exhibit the most splendid colors, it would have been a strange fact if substances similarly colored had not often originated, independently of any useful end thus gained, in the complex laboratory of living organisms. The Sub-kingdom 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 consider- ing, never occur. Nor could they be expected in the three 1 “Archives de Zoolog Expér.,’’ Oct, 1872, p. 563, SEXUAL SELECTION 347 lowest classes, namely, in the Ascidians, Polyzoa, and Brachiopods (constituting the Molluscoida of some authors), for most of these animals are permanently affixed to a sup- port or have their sexes united in the same individual. In the Lamellibranchiata, 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 fight- ing with other males. As I am informed by Mr. Gary Jeffreys, the sole external difference between the sexes con- sists in the shell sometimes differing a little in form; for in- stance, 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 nature, it may be presumed, are directly connected with the act of reproduction, or with the development of the ova. The Gasteropoda, though capable of ideation 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 pul- moniferous gasteropods, or land-snails, the pairing is pre- ceded by courtship; for these animals, though hermaphro- dites, are compelled by their structure to pair together. Agassiz remarks,” ‘‘Quiconque a eu l’occasion d’observer les amours des limacons, ne saurait mettre en doute la séduction déployée dans les mouvements et les allures qui préparent et accomplissent le double embrassement de ces hermaphrodites.’’ These animals appear also susceptible of some degree of permanent attachment: an accurate ob- server, Mr. Lonsdale, informs me that he placed a pair of land-snails (Helix pomatia), one of which was weakly, in a small and ill-provided garden. After a short time the strong and healthy individual disappeared, and was 2 “De VEspéce et de la Class.,’’ etc., 1869, p. 106. 848 THE DESCENT OF MAN traced by its track of slime over a wall 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 wall. Even in the highest class of the Mollusca, the Cepha- lopoda, 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 circum- stance, 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 endeav- ors to escape from an enemy.® Certain Cephalopoda, how- ever, are characterized 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-disks to the female, lives for a time an inde- pendent life. So completely does the cast-off arm resemble a separate animal, that it was described by Cuvier as a para- sitic worm under the name of Hectocotyle. But this mar- vellous structure may be classed as a primary rather than as a secondary sexual character. Although with the Mollusca sexual selection does not seem to have come into play, yet many univalve and bivalve shells, such as volutes, cones, scallops, etc., are beautifully colored and shaped. The colors 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 growth. The amount of light seems to be influ- ential 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 colored, yet we generally see the lower surfaces, as well as the parts covered by the 3 See, for instance, the account a I have given in my ‘Journal of Researches, ’’ 1845, p. 7. SEXUAL SELECTION 849 mantle, less highly colored than the upper and , exposed surfaces.* In some cases, as with shells living among corals or brightly tinted sea-weeds, the bright colors may serve as a protection.* But that many of the nudibranch mollusca, or sea-slugs, are as beautifully colored as any shells, may be seen in Messrs. Alder and Hancock’s magnificent work; and, from information kindly given me by Mr. Hancock, it seems extremely doubtful whether these colors usually serve as a protection. With some species this may be the case, as with one kind which lives on the green leaves of alge, and is itself bright-green. But many brightly colored, white, or otherwise conspicuous species do not seek conceal- ment; while again some equally conspicuous species, as well as other dull-colored kinds, live under stones and in dark recesses. So that with these nudibranch mollusks, color apparent y does not stand in any close relation to the nature of the places which they inhabit. These naked sea-slugs are hermaphrodites, 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 deave offspring which would inherit their parents’ greater beauty. But with such lowly organized creatures this is extremely improbable. Nor is it at all obvious how the offspring from the more beautiful pairs of hermaphrodites would have any advantage over the offspring of the less beautiful, so as to increase in number, unless indeed vigor and beauty generally coincided. We have not here the case of a number of males becoming mature before the females, with the more beautiful males selected by the more vigor- ous females. If, indeed, brilliant colors were beneficial to 4 I have given (‘‘Geolog. Observations on Volcanic Islands,’’ 1844, p. 53) a curious instance of the influence of light on the colors of a frondescent incrustation, deposited by the surf, on the coast-rocks of Ascension, and formed by the solution of triturated sea-shells. 5 Dr. Morse has lately discussed this subject in his paper on the Adaptive Coloration of Mollusca. ‘‘Proceedings of the Boston Society of Natural His- tory,’’ vol. xiv., April, 1871. 350 THE DESCENT OF MAN a hermaphrodite animal in relation to its general habits of life, the more brightly tinted individuals would succeed best and would increase in number; but this would be a case of natural and not of sexual selection. Sub-kingdom 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 im- portance that they have been placed under distinct genera or even families, yet the differences do not seem of the kind which can be safely attributed to sexual selection. These animals are often beautifully colored, but as the sexes do not differ in this respect, we are but little concerned with them. Even the Nemertians, though so lowly organized, ‘‘vie in beauty and variety of coloring with any other group in the invertebrate series’’; yet Dr. McIntosh® cannot discover that these colors are of any service. The seden- tary annelids become duller-colored, according to M. Qua- trefages,’ after the period of reproduction; and this I pre- sume 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 individ- uals of the same sex to struggle together in rivalry. Sub-kingdom of the Anthropoda: Class, Crustacea.—In this great class we first meet with undoubted secondary sexual characters, often developed in a remarkable manner. Un- fortunately the habits of crustaceans are very imperfectly known, and we cannot explain the uses of many structures peculiar to one sex. With the lower parasitic species the males are of small size, and they alone are furnished with perfect swimming-leg’, antennas, and sense-organs; the fe- males being destitute of these organs, with their bodies 6 See his beautiful monograph on “‘British Annelids,”’ part i., 1873, p. 3. 1 See M. Perrier, ‘‘l’Origine de l’Homme d’aprés Darwin,’’ ‘“‘Revue Scien- tifique,”’ Feb. 1873, p. 866. SEXUAL SELECTION 851 often consisting of a mere distorted mass. But these ex- traordinary differences between the two sexes are, no doubt, related to their widely different habits of life, and, conse- quently, do not concern us. In various crustaceans, be- longing to distinct families, the anterior antennz are fur- nished with peculiar thread-like bodies, which are believed to act as smelling organs, and these are much more numer- ous 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 through sexual selection, by the better pro- vided males having been the more successful in finding partners and in producing offspring. Fritz Muller has de- scribed a remarkable dimorphic species of Tanais, in which the male is represented by two distinct forms, which never graduate into each other. In the one form the male is fur- nished with more numerous smelling-threads, and in the other form with more powerful and more elongated chele, or pincers, which serve to hold the female. Fritz Muller suggests that these differences between the two male forms of the same species may have originated in certain individ- uals having varied in the number of the smelling-threads, while other individuals varied in the shape and size of their chelz; so that of the former, those which were best able to find the female, and of the latter, those which 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 antenne of the female. In the male the modified antenna is either swollen in the middle or angularly bent, or con- 8 ‘Pacts and Arguments for Darwin,’’ Eng. translat., 1869, p. 20. See the previous discussion on the olfactory threads. Sars has described a somewhat analogous case (as quoted in ‘‘Nature.’’ 1870, p. 455) in a Norwegian crusta- cean, the Pontoporeia affinis, 852 THE DESCENT OF MAN verted (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 (2) on the same side of the body is converted into a forceps. In an-. other family the inferior or posterior antenne are ‘‘curiously zigzagged’’ in the males alone. In the higher crustaceans the an- terior legs are developed into chele, 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 pagurus), according to Mr. C. Spence Bate, is five times as great as that of the female. In many species the chelze are of unequal size on the opposite sides of the body, the right-hand one being, as I am informed by Mr. Bate, generally, though not invariably, the A larger. This inequality is also often Fig. 4.—Labidocera Dar- much greater in the male than in the winii (from Lubbock). a. Part of right anterior an- Fo ot eale terming 4 female. The two chele of the male ener ctkaracio lese ot Olten differ in structure (Figs. 5, 6, male. ¢. Ditto of female. 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 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 ‘often much larger in the male than in the female, is not known. AsI hear from Mr. Bate, the chele are sometimes of such length and size that they cannot possibly be used 9 See Sir J. Lubbock, in ‘‘Annals and Mag. of Nat. Hist.,’’ vol. xi., 1853, pl. i. and x.; and vol. xii., 1853, pl. vii. See also Lubbock in ‘‘Transact, Ent. Soc.,’’ vol. iv., new series, 1856-1858, p. 8. With respect to the zigzagged antenne mentioned below, see Fritz Miller, ‘‘Facts and Arguments for Darwin,” 1869, p. 40, footnote. SEXUAL SELECTION 853 for carrying food to the mouth. In the males of certain fresh-water prawns (Palemon) the right leg is avtually longer than the whole body.” The great size of the one leg with its cheles may aid the male in fighting with his rivals; but this will not account for their inequality in the R ' Fre. 5.—Anterior part of body of Calli: nassa (from Milne-Edwards), showing the unequal and differently constructed right- und left-hand chel of the male, N.B.—The artist by mistake has reversed the drawing, and made the left-hand chela the largest. Fig. 6.—Second leg of male Orchestia, Bia. 7.—Ditto of female. Tucuratinga (from Fritz Muller), female on the opposite sides of the body. In Gelasimus, according to a statement quoted by Milne-Edwards,'' the male and the female live in the same burrow, and this shows that they pair; the male closes the mouth of the 10 See a paper by Mr. C. Spence Bate, with figures, in ‘‘Proc. Zool. Soc.,” 1868, p. 363; and on the nomenclature of the genus, ibid., p. 585. I am greatly indebted to Mr. Spence Bate for nearly all the above statements with respect to the chele of the higher crustaceans. 1 “Hist, Nat. des Orust.,’’ tom. ii., 183%, p. 50. B54 THE DESCENT OF MAN burrow with one of its che », which is enormously devel- oped; so that here it indirectly serves as a means of de- fence. Their main use, however, is probably to seize and to secure the female, and this in some instances, as with Gammarus, is known to be the case. The male of the her- mit or soldier crab (Pagurus) for weeks together carries about the shell inhabited by the female."? The sexes, how- ever, of the common shcre-crab (Curcinus menas), as Mr. Bate informs me, unite directly after the female has moulted her hard shell, when she is so soft that she would be injured if seized by the strong pinccrs of the male; but as she is caught and carried sbout by the male before moulting, she could then be seized. with impunity. Fritz Miller sta‘es that certain species of Melita are dis- tinguished from all other amphipods by the females having ‘the coxal lamellz 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 fe- males which were the most securely held during the act of reproduction having left the largest number of offspring. Another Brazilian amphipod (Orchestia Darwinii, Fig. 8) presents a case of dimorphism, like that of Tanais; for there are two,male forms, which differ in the structure of their chelz.’* As either chela would certainly suffice to hold the female—for both are now used for this purpose— the two male forms probably originated by some having varied in one manner, and some in another; both forms havin;: derived certain special, but nearly equal, advan- tages 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 2 Mr. C. Spence Bate, Brit. Assoc., ‘‘Fourth Report on the Fauna of South Devon.” 18 Fritz Muller, ‘‘Facts and Arguments for Darwin,’’ 1869, pp. 25-28. SEXUAL SELECTION 355 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 ¥ie. 8.—Orchestia Darwinii (from Fritz Muller), showing the differently constructed : chele of the two male forms. of life, and most of the Entomostraca must be excepted. The chele of many crustaceans are weapons well adapted for fighting. Thus when a Devil-crab (Portunus puber) was seen by a son of Mr. Bate fighting with a Carcinus menas, the latter was soon thrown on its back, and had every limb 856 THE DESCENT OF MAN torn from its body. When several males of a Brazilian Gelasimus, a species furnished 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 menas into a pan of water, inhabited by a female which was paired with a smaller male; but the latter was soon dispossessed. Mr. Bate adds, ‘‘If they fought, the victory was a bloodless one, for I saw no wounds.’’ This same naturalist separated a male sand- skipper (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 time 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 away his wife. This fact shows that in the Amphipoda, an order low in the scale, the males and females recognize 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 cocoanut, 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 depres- sions are situated. It then breaks through one of these eyes by hammering with its heavy front pincers, and, turning round, extracts the albuminous 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 considered: A trustworthy naturalist, Mr. Gardner," 4 “Travels in the Interior of Brazil,’? 1846, p. 111. I have given, in my “Journal of Researches,’’ p. 463, an account of the habits of the Birgus. SEXUAL SELECTION 857 while watching a shore-crab (Gelasimus) making its burrow, threw some shells toward 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 diffi- cult to distinguish 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 color in the two sexes of our British crusta- ceans, 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 their different habits of life, such as by the male wandering more about, and being thus more exposed to the light. Dr. Power tried to distinguish by color the sexes of the several species which inhabit the Mauritius, but failed, except with one species of Squilla, probably S. stylifera, the male of which is described as being ‘‘of a beautiful bluish green,’’ with some of the appendages cherry-red, while the female is clouded with brown and gray, ‘‘with the red about her much less vivid than in the male.’’'* In this case we may suspect the agency of sexual selection. From 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 colors. With Saphirina (an oceanic genus of Entomostraca), the males are furnished with minute shields or cell-like bodies, which exhibit beautiful changing colors; 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 18 Mr, Ch. Fraser, in ‘‘Proc, Zoolog. Soc.,’’ 1869, p. 3. I am indebted to Mr. Bate for Dr. Power’s statement. 16 Claus, ‘‘Die freilebenden Copepoden,”’ 1863, s, 35. 358 THE DESCENT OF MAN by Fritz Muller that in the female of a Brazilian species of Gelasimus the whole body is of a nearly uniform grayish brown. Inthe 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 colors are liable to change in the course of a few minutes—the white becoming dirty gray or even black, the green ‘‘losing much of its brilliancy.’’ It deserves especial notice that the males do not acquire their bright colors until they become mature. They appear to be much more numerous than the females; they differ also in the larger size of their chele. 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 considera- tions it seems probable that the male in this species has become gayly ornamented in order to attract or excite the female. It has just been stated that the male Gelasimus does not acquire his conspicuous colors until mature and nearly ready to breed. This seems a general rule in the whole class in respect to the many remarkable structural differ- ences 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 Muller’ gives some striking instances of this law; thus the male sand-hopper (Orchestia) does not, until nearly full grown, acquire his large claspers, which are very differently constructed from those of the female; while young, his claspers resemble those of the female. Class, Arachnida (Spiders).—The sexes do not generally differ much in color, but the males are often darker than the females, as may be seen in Mr. Blackwall’s magnificent work.** In some species, however, the difference is con- 1 “Facts and Arguments,” ete., p. 79. 18 “A History of the Spiders of Great Britain,”? 1861-64, For the follow- ing facts, see pp. 77, 88, 102. SEXUAL SELECTION 859 spicuous; thus the female of Sparassus smaragdulus is dull- ish green, while the adult male has the abdomen of a fine yellow, with three longitudinal stripes of rich red. In cer- tain 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. Blackwall thinks that, as a general rule, it is the male; and Canestrini”® remarks that in certain genera the males can be specifically distinguished with ease, but the females with great diffi- culty. I am informed by Mr. Blackwall that the sexes while young usually resemble each other; and both often undergo great changes in color during their successive moults, before arriving at maturity. In other cases the male alone appears to change color. Thus the male of the above bright-colored Sparassus at first resembles the female, and acquires his peculiar tints only when nearly adult. Spiders are possessed of acute senses, and exhibit much intelligence; as is well known, the females often show 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, threatens 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 color 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 orna- ments. From the extreme variability of color in the male 1 This author has recently published a valuable essay on_ the “‘Caratteri gessuali secondarii degli Arachnidi,’’ in the ‘‘Atti della Soc. Veneto Trentina di Sc. Nat. Padova,’’ vol. i., Fasc. 3, 1873. . 360 THE DESCENT OF MAN of some species, for instance of Theridion lineatum, it would appear that these sexual characters of the males have not. as yet become well fixed. Canestrini draws the same con- clusion from 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 the 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 bim with horror and indignation.’ The Rev. O. P. Cambridge” accounts 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 favor 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, t.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 2 Aug. Vinson (‘‘Aranéides des Iles de la Réunion,” pl. vi. figs. 1 and 2) gives a good instance of the small size of the male in Zpetra 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 not seen the original accounts. "1 Kirby and Spence, ‘Introduction to Entomology,”’ vol, i, 1818, p. 280, 3% “Proce, Zoolog. Soc.,’? 1871, p. 621. SEXUAL SELECTION 861 males of several species of Theridion™ have the power of making a stridulating sound, while the females are mute. The apparatus 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. From the analogy of the Orthoptera and Homoptera, to be described in the next chapter, we may feel almost sure that the stridu- lation 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 millipeds and centipeds, can I find any well- marked instances of such sexual differences as more par- ticularly concern us. In Glomeris limbata, however, and perhaps in some few other species, the males differ slightly in color 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 prehensile hooks which serve to secure the female. In some species of Iulus the tarsi of the male are furnished with membranous suckers for the same purpose. As we shall see when we treat of Insects, it isa much more unusual circumstance that it is the female in Lithobius which is furnished with prehensile ap- pendages at the extremity of her body for holding the male.” % Theridion (Asagena, Sund.) serratipes, 4-punctatum et gutiatum; see Westring, in. Kroyer, ‘“‘Naturhist. Tidskrift,’’ vol. iv., 1842-43, p. 349; and vol. ii., 1846-49, p. 342. See also, for other species, ‘‘Araneze Suecicz,”’ . 184. : % Dr. H. H. van Zouteveen, in his Dutch translation of this work (vol. i. p. 444), has collected several cases. % Hilgendorf, however, has lately called attention to an analogous struc- ture 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. Descent—Vot. I.—16 562 THE DESCENT OF MAN CHAPTER X SECONDARY SEXUAL CHARACTERS OF INSECTS Diversified structures possessed by the males for seizing the females— Differences between the sexes, of which the meaning is not under- stood—Difference in size between the sexes—Thysanura—Diptera— Hemiptera—Homoptera, musical powers possessed by the males alone—Orthoptera, musical instruments of the males, much diversi- fied in structure; pugnacity; colors—Neuroptera, sexual differences in color—Hymenoptera, pugnacity and colors—Coleoptera, colors; furnished with great horns, apparently as an ornament; battles; stridulating organs generally common to both sexes ; N 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 plu- mose antennse of the males of many species. In Chloéon, one of the Ephemerz, the male has great pillared eyes, of which the famale is entirely destitute.* The ocelli are absent in the females of certain insects, as in the Mutillide; and here the females are likewise wingless. But we are chiefly concerned with structures by which one male is , enabled to conquer another, either in battle or courtship, through 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 1 Sir J. Lubbock, ‘Transact. Linnean Soc.,”’ vol. xxv., 1866, p. 484. With. respect to the Mutillide see Westwood, ‘‘Modern Class. of Insects,’ vol. ii., . 213, ? These organs in the male often differ in closely allied species, and afford excellent specific characters. But their importance, from a functional point of view, as Mr. R. MacLachlan has remarked to me, has probably been over- rated. It has been suggested that slight differences in these organs would suffice to prevent the intercrossing 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 instance, Bronn, “Geschichte der Natur,’? B. ii, 1843, s. 164; and Westwood, ‘*Transact, SEXUAL SELECTION 863 is astonishing,’’ as Mr. B. D. Walsh* has remarked, ‘‘how many different organs are worked in by nature for the seemingly insignificant object of enabling the male to grasp the female firmly.” The mandibles or jaws are sometimes used for this purpose; thus the male Corydalis cornutus (a neuropterous insect in some degree allied to the Dragon- flies, etc.) has immense curved jaws, many times longer than those of the female; and they are smooth instead of being footie’, so that he is thus enabled to seize her with- out 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 pur- pose, 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 Prof. Westwood observes, ‘‘are exceed- ingly ardent, seizing their partners round the neck with their sickle- shaped jaws;’’* while the females use their organs for burrowing in sand-banks and making their nests. ; The tarsi of the front legs are ye, 9,—Crabro cribrarius, Upper dilated in many male beetles, or *81" mele: lower figure, female, are furnished with broad cushions of hairs; and in many genera of water-beetles they are armed with a round, flat Ent. Soc.,”’ vol. 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 Phryganide, which present strongly pronounced differences of this kind, were confined together by Dr. Aug. Meyer, they emg, and one pair produced fertile ova, 8 «The Practical Entomologist,’ Philadelphia, vol. ii., May, 1867, p. 88. 4 Mr. Walsh, ibid., p. 107. 58 **Modern Classification of Insects,’ 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. 364 THE DESCENT OF MAN sucker, so that the male may adhere to the slippery body of the female. It is a much more unusual circumstance that the female of some water-beetles (Dytiscus) have their elytra deeply grooved, and in Acilius sulcatus thickly set with hairs, as an aid to the male. The females of some other water-beetles (Hydroporus) have their elytra punctured for the same purpose.® In the male of Crabro cribrarius (Fig. 9), it is the tibia which is- dilated into a broad horny plate, with minute membranous dots, giving to it a singular ap- pearance like that of a riddle.”_ In the male of Penthe (a genus of beetles) a few of the middle joints of the antenne are dilated and furnished on the inferior surface with cushions of hair, exactly like those on the tarsi of the Carabide, ‘tand obviously for the same end.’’ In male dragon-flies, ‘‘the appendages at the tip of the tail are modified in an almost infinite variety of curious patterns to enable them to embrace the neck of the female.’’ Lastly, in the males of many insects, 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 three pairs are elongated, sometimes Te. 10,— Taph- p roderes distortus to an extravagant length.° much enlarged). pper figure, ‘The sexes of many species in all the orders male; lower figure, . fs : : female. present differences of which the meaning is not understood. One curious case is that of a beetle (Fig. 10), ® We have here a curious and inexplicable case of dimorphism, for some of the females of four European species of Dytiscus, and of certain species of Hydroporus, have their elytra smooth; and no intermediate 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, 7 Westwood, ‘‘Modern Class.,’’ vol. ii. p. 193. The following statement about Penthe, and others in inverted commas, are taken from Mr. Walsh **Practical Entomologist,’’ Philadelphia, vol. ii. p. 88. ® Kirby and Spence, ‘‘Introduct.,”’ ete., vol. iii, pp. 332-336, SEXUAL SELECTION 365 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, unique 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 in the Lepidoptera: one of the most extraordinary is that certain male butterflies have their forelegs more or less atrophied, with the tibiz and tarsi reduced to mere rudimentary knobs. The wings, also, in the two sexes often differ in neuration,’? and sometimes considerably in outline, as in the Aricoris epitus, which was shown 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 disks of the posterior pair." In several British butterflies, as shown by Mr. Wonfor, the males alone are in parts clothed with peculiar scales. The use of the bright light of the female glow-worm has been subject to much discussion. The male is feebly luminous, as are the larve and even the eggs. It has been supposed 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’* appears to have solved the diffi- culty: he finds that all the Lampyride which he has tried are highly distasteful to insectivorous mammals and birds, Hence it is in accordance with Mr. Bates’s view, hereafter to be explained, that many insects mimic the Lampyride closely, in order to be mistaken for them, and thus to escape ® “Insecta Maderensia,’’ 1854, p. 20. 10 E, Doubleday, ‘tAnnals and Mag. of Nat. Hist.,”’ vol. i, 1848, p. 379. I may add that the wings in certain Hymenoptera (see Shuckard, ‘‘Fossorial Hymenop.,’’ 1837, pp. 39-43) differ in neuration according to sex. 1H, W, Bates, in ‘“‘Journal of Proce. Linn. Soc.,’’ vol. vi., 1862, p. 74. Mr, Wonfor’s observations are quoted in ‘‘Popular Science Review,”’ 1868, . B43, 2 “The Naturalist in Nicaragua,’? 1874, pp. 316-320, On the phos- phorescence of the eggs, see ‘‘Annals and Mag. of Nat. Hist.,’’ Nov. 1871, p. 372, 366 THE DESCENT OF MAN destruction. He further believes that the luminous species profit by being at once recognized as unpalatable. It is probable that the same explanation may be extended to the EHlaters, 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 larve 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 larve 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 maie and female cocoons of the silk-moth (Bombyx mori), thay in France they are separated by a particular mode of weigh- ing.** 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 acertain extent hold good with insects. But Dr. Wal- lace has suggested a much more probable explanation. He finds, after carefully attending to the development of the caterpillars of Bombyx cynthia and yamamat, and especially to that of some dwarfed caterpillars reared from a second brood on unnatural food, ‘‘that in proportion as the indi- vidual moth is finer, so is the time required for its meta-— morphosis longer; and for this reason the female, which is the larger and heavier insect, from having to carry her nu- merous 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 advantageous 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 13 Robinet, ‘‘Vers a Soie,’’ 1848, p. 207. 4 “Transact. Ent. Soc.,’’ 3d series, vol. v. p. 486. SEXUAL SELECTION 367 of the females; and this again would naturally follow, as Mr. A. R. Wallace has remarked, through natural selec- tion; for the smaller males would be first matured, and thus would procreate a large number of offspring which would inherit the reduced size of their male parents, while the larger males, from being matured 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 these cases, as with the stag-beetle (Lucanus), the males are larger than the females. There are, however, other beetles which are not known to fight together, of which the males exceed the females in size, and the mean- ing 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 (Libellulide) 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 assumed their proper masculine colors. But the most curious case, showing 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 gen- eral rule, are smaller than the females, and emerge about a week before them; but among the Bees, the males of Apis mellifica, Anthidium manicatum, and Anthophora acervorum, 18 **Journal of Proc. Ent. Soc.,’’ Feb. 4, 1867, p. lxxi. ; 16 For this and other statements on the size of the sexes, see Kirby and Spence, ibid., vol. iii. p. 300; on the duration of life in insects, see p. 344, 368 THE DESCENT OF MAN and among the Fossores, the males of the Methoca ichneu- monides are larger than the females. The explanation of this anomaly is that a marriage flight is absolutely necessary with these species, and the male requires great strength and size in order to carry the female through the air. Increased size has here been acquired in opposition to the usual rela- tion 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.—The members of this lowly organized order are wingless, dull-colored, minute insects, with ugly, almost misshapen heads and bodies. Their sexes do not differ; but they are interesting as showing 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 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 antennz; then for a bit they stand face to face, play with their antenne, and seem to be all in all to one another.” Order, Diptera (Flies).—The sexes differ little in color. The greatest difference, known to Mr. F. Walker, is in the genus Bibio, in which the males are blackish or quite black, and the females obscure brownish orange. The genus Ela- phomyia, discovered by Mr. Wallace’® in New Guinea, is 29 ” See “‘The Transactions of the Linnean Society,’’ volume xxvi., 1868, p. 296, 18 “The Malay Archipelago,” vol. ii., 1869, p. 313. SEXUAL SELECTION 369 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 palmated. 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 color, edged with black, with a pale central stripe, and as these imsects 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 Tipulz. ‘The males of other Diptera apparently try to win the females by their music: H. Miller” watched for some time two males of an Hristalis 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 (Culicidz) also seem to attract each other by humming; and Prof. Mayer has recently ascertained that the hairs on the antennz 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 sympa- thetically with the graver notes, and the shorter hairs with the higher ones. Landois also asserts that he has repeatedly drawn a whole swarm of gnats by uttering a particular note. It may be added that the mental faculties of the Diptera are probably higher than in most other insects, in accordance with their highly developed nervous system.” Order, Hemiptera (Field-Bugs).—Mr. J. W. Douglas, who has particularly attended to the British species, has kindly given me an account of their sexual differences. The males of some species are furnished with wings, while 19 ««Modern Classification of Insects,”’ vol. ii., 1840, p. 526. 20 Anwendung, etc., ‘‘Verh. d. n. V. Jahrg.,”? xxix. p. 80. Mayer, in ‘‘American Naturalist,’’ 1874, p. 236. é 21 See Mr. B. T. Lowne’s interesting work, ‘‘On the Anatomy of the Blow- fly, Musca vomitora,’’ 1870, p. 14. He remarks (p. 33) that “‘the captured flies utter a peculiar plaintive note, and that this sound causes other flies to disappear, ”’ 370 THE DESCENT OF MAN the females are wingless; the sexes differ in the form of their bodies, elytra, antenne, and tarsi; but, as the signifi- cation of these differences are unknown, they may be here passed over. The females are generally larger and more robust than the males. With British, and, as far as Mr. Douglas knows, with exotic species, the sexes do not com- monly differ much in color; 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 colored; and as these insects emit an extremely nauseous odor, their conspicuous colors may serve as a signal that they are un- palatable to insectivorous animals. In some few cases their colors appear td 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 Reduvide 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 pro- thoracic cavity. According to Westring, Reduvius person- atus also stridulates. But I have no reason to suppose that this is a sexual character, excepting that with non-social insects there seems to be no use for sound-producing organs, unless it be as a sexual call. Order, Homoptera.—Kivery one who has wandered in a tropical forest must have been astonished at the din made by the male Cicade. 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 #2 Westwood, ‘‘Modern Class. of Insects,”’ vol. ii. p. 473. SEXUAL SELECTION 371 pleasing to the ears of some men.” The Cicadid@ usually sing during the day, while the Fulgoride appear to be night-songsters. ‘The sound, according to Landois,” is pro- duced by the vibration of the lips of the spiracles, which are set into motion by a current of air emitted from the trachesz; but this view has lately been disputed. Dr. Powell appears to have proved” that it is produced by the vibration of a membrane, set into action by:a special muscle. In the living insect, while stridulating, this membrane can be seen to vibrate; and in the dead insect the proper sound is heard, if the muscle, when a little dried and hardened, is pulled with the point of a pin. In the female the whole complex musical apparatus is present, but is much less developed than in the male, and is never used for producing sound. With respect to the object of the music, Dr. Hartman, in speaking of the Cicada septemdecim of the United States, says,** “‘the drums are now (June 6 and 7, 1851) heard in all directions. This I believe to be the marital summons from the males. Standing in thick chestnut sprouts about as high as my head, where hundreds were around me, I ob- served the females coming around the drumming males.” He adds: ‘‘This season (August, 1868) a dwarf pear-tree in my garden produced about fifty larvae of Cic. pruinosa; and I several times noticed the females to alight near a male while he was uttering his ‘clanging notes.’ Fritz Miiller writes to me from South Brazil that he has often listened to a musical contest between two or three males of a species with a particularly loud voice, seated at a considerable dis- tance from each other: as soon as one had finished his song, another immediately began, and then another. As there is so much rivalry between the males, it is probable that the females not only find them by their sounds, but that, like 28 These particulars are taken from Westwood’s ‘*Modern Class. of Insects, ’? vol. ii., 1840, p. 422. See also, on the Fulgoride, Kirby and Spence, ‘‘Intro- duct.,”’ vol. ii. p. 401. *% “Zeitschrift far wissenschaft Zoolog.,’’ B. xvii:, 1867, 8. 152-158. 2% “Pransact. New Zealand Institute,’’ vol. v., 1873, p. 286. %6 T am indebted to Mr. Walsh for having sent me this extract from a “Journal of the Doings of Cicada septemdecim,”’ by Dr. Hartman. 372 THE DESCENT OF MAN female birds, they are excited or allured by the male with the most attractive voice. I have not heard of any well-marked cases of orna- mental differences between the sexes of the Homoptera. Mr. Douglas informs me that there are three British species in which the male is black or marked with black bands, while the females are pale-colored or obscure. Order, Orthoptera (Crickets and Grasshoppers).—The males in the three saltatorial families in this Order are remarkable for their musical powers, namely, the Achetida, or crickets, the Locustide, for which there is no equivalent English name, and the Acridiide, or grasshoppers. The stridulation produced by some of the Locustide is so loud that it can be heard during the night at the distance of a mile,” and that made by certain species is not unmusical even to the human ear, so that the Indians on the Amazons keep them in wicker cages. All observers agree that the sounds serve either to call or excite the mute females. With respect to the migratory locusts of Russia, Korte has given’ an interesting case of selection by the female of amale. The males of this species (Pachytylus migratorius) while coupled with the female stridulate from anger or jealousy if approached by other males. The house-cricket when surprised at night uses its voice to warn its fellows.” In North America the Katydid (Platyphyllum concavum, one of the Locustide) is described* as mounting on the upper branches of a tree, and in the evening beginning ‘“‘his noisy babble, while rival notes issue from the neighboring trees, and the groves resound with the call of Katy-did-she- did the livelong night.’’ Mr. Bates, in speaking of the European field-cricket (one of the Achetide), says, ‘‘The male has been observed to place himself in the evening % Guilding, ‘‘Trans. Linn. Soc.,’’ vol. xv. p. 154. 28 T state this on the authority of Képpen, “Ueber die Heuschrecken in Siidrussland,”’ 1866, p. 32, for I have in vain endeavored to procure Kérte’s work. 29 Gilbert White, ‘‘Nat. Hist. of Selborne,’’ vol. ii., 1825, p. 262. 20 Harris, ‘Insects of New England,’’ 1842, p. 128. SEXUAL SELECTION 373 at the entrance of his burrow, and stridulate until a female approaches, when the louder notes are succeeded by a more subdued tone, while the suc- cessful musician caresses with his antenne the mate he has won.’’* Dr. Scudder was able to excite one of these insects to answer him, by rubbing on a file with a quill. In both sexes a remarkable auditory ; apparatus has been discovered . st i ‘ 1 Fia. 11.—Gryllus campestris (from Lan- by Von Siebold, situated in dois). Bisbehend agus. under side of 33 part of a wing nervure, much magouified, the front legs. showing the teeth, st. Left-hand figure, In the three Families the wpperfuriace, of wiog-cover, with, thé sounds are differently pro- which the teeth (st) are scraped. duced. In the males of the Achetide both wing-covers have the same apparatus; and this in the field-cricket (Gryllus campestris, Fig. 11) consists, as de- % scribed by Landois,” of from 181 to 138 sharp, = transverse ridges or teeth (st) on the under side of one of the nervures of the wing-cover. This toothed nervure is rapidly scraped across a 2 projecting, smooth, hard nervure (r) on the upper surface of the opposite wing. First one wing is rubbed over the other, and then the y, 19 gecth of movement is reversed. Both wings are raised fervure of Grylius a little at the same time, so as to increase the Landois). resonance. In some species the wing-covers of the males are furnished at the base with a talc-like plate.** I here give a drawing (Fig. 12) of the teeth on the under side A nial va 31 “The Naturalist on the Amazons,’’ vol. i., 1863, p. 252. Mr. Bates gives a very interesting discussion on the gradations in the musical apparatus of the three families. See also Westwood, ‘‘Mod. Class.,’’ vol. ii. pp. 445, 453. 32 *“Proe, Boston Soc. of Nat. Hist.,’? vol. xi., April, 1868, 33 *‘Nouveau Manuel d’Anat. Comp.,’? French translat., tom. i, 1850, . 567, # * ‘Zeitschrift fir Wissenschaft. Zoolog.,’’ B. xvii., 1867, 3. 117. 35 Westwood, ‘“‘Modern Class. of Insects,”’ vol. i. p. 440. 574 THE DESCENT OF MAN of the nervure of another species of Gryllus, viz., G. domes- ticus. With respect to the formation of these teeth, Dr. Gruber has shown* that they have been developed 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 shows that their development is in part Fic. 13.—Chioroccelus Tanana (from Bates). a,6. Lobes of opposite wing-covers, directly due to the stimulus from the friction of one wing over the other. In the Locustide 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, lies over the right wing, which serves as the fiddle. One of the nervures (a) on the under surface of the former is finely serrated, and is scraped across the It % “*Yeber den Tonapparat der Locustiden, ein Beitrag zum Darwinismns,”? _ “Zeitsch. fiir Wissensch. Zoolog.,’’ B. xxii., 1872, p. 100. SEXUAL SELECTION 375 prominent nervures on the upper surface of the opposite or right wing. In our British Phasgonura 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, colored brown, and very sharp. 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 Ephippiger 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 of dome over the wing-covers, and which has probably the effect of increasing the sound.’’ * We thus see that the musical apparatus is more differen- tiated or specialized in the Locustide (which include, I believe, the most powerful eperformers in the Order), than in the Achetidz, in which both wing-covers have the same structure and the same function.** Landois, however, de- tected in one of the Locustide, namely, in Decticus, a short and narrow row of small teeth, mere rudiments, on 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 Phasgonura viridissima. Hence we may infer with confidence that the Locustide are descended from a form in which, as in the existing Achetide, both wing- covers had serrated nervures on the under surface, and could be indifferently used as the bow; but that in the Locustide the two wing-covers gradually became differen- tiated and perfected, on the principle of the division of labor, the one to act exclusively as the bow, and the other as the fiddle. Dr. Gruber takes the same view, and has shown that rudimentary teeth are commonly found on the inferior surface of the right wing. By what steps the more siniple apparatus in the Achetide originated, we do not 31 Westwood, ‘‘Modern Class, of Insects,” vol. i. p. 453. 38 Landois, ‘‘Zeitsch. f. Wiss. Zoolog.,’’ B, xvii., 1867, a, 121, 122, 376 THE DESCENT OF MAN know, but it is probable that the basal portions of 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 Acridiide, — 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 f/\ row of minute, elegant, lancet- .)\ shaped, elastic teeth, from 85 to 98 in number;** and these are ; scraped across the sharp, pro- Fie. 14.—Hind-leg of Stenobothrus . : Fi pe es ae ee eee eer anes oe ae. ine ridge, much magnified (from Landois), covers, which 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 alter- nately, 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 resounding board. In Pneumora (Fig. 15), a South African genus belonging 89 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 wing-covers together.’’ “0 Landois, ibid., s. 113. 41 “Insects of New England,’’ 1842, p. 133. SEXUAL SELECTION 877 to the same family, we meet with a new 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 remarkable that the thighs are not rubbed in the usual manner against the wing- Fie. 15.—Pneumora (from specimens in the British Museum), Upper figure, male; lower figure, female, 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 from analogy, would be finely serrated. The species of Pneumora have been more profoundly modified for the sake of stridulation than any other orthopterous insect; for in the 42 Westwood, ‘‘Modern Classification,’’ vol. i. p. 46°. 878 THE DESCENT OF MAN male the whole body has been converted into a musical instrument, being distended with air, like a great pellucid bladder, so as to increase the resonance. Mr. Trimen in- forms 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 shown that both sexes of Hphippiger vitiwm are thus provided, though the organs differ in the male and fe- male to a certain extent. Hence we 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 during the season of love. In most other Locustide (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 rudi- ments on the under surface of the wing-covers of the female Achetids, and on the femora of the female Acridiide. In the Homoptera, also, the femaies have the proper musical apparatus in a functionless state; aad we shall hereafter meet in other divisions of the animal kingdom with many instances of structures proper to the male being present in a rudimenta. y condition in the female. Landois has observed another important fact, namely, that in the females of the Acridiide, the stridulating teeth on the femora remain. throughout life in the same condition in which they first appear during the larval state in both sexes. In the males, on the other hand, they become fur- ther developed, and acquire their perfect structure at the jast moult, when the insect is mature 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 extremly diversified, and are altogether different from SEXUAL SELECTION 379 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 organization having undergone multifarious changes in the course of ages, and as part after part varied different varia- tions were taken advantage of for the same general purpose. The diversity of means for producing sound in the three families of the Orthoptera and in the 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 know, 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 stridulating apparatus of the male Locustide.”’ The insect, though in most respects related to the Neurop- tera, 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 the species are very pugnacious. When two male field- crickets (@ryllus 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 color, some exotic locusts are beautifully ornamented; the posterior wings being marked with red, blue, and black; but as throughout the Order the 43 Tandois has recently found in certain Orthoptera rudimentary structures closely similar to the sound-producing organs in the Homoptera; and this is a surprising fact. See “‘Zeitschr. fiir Wissensch. Zoolog.,’? B. xxii. Heft. 3, 3871, p. 348. - “4 “Transact. Ent. Soc.,’’? 3d series, vol. ii, (‘Journal of Proceedings,’ . 117). MS TY estwrood, ‘*Modern Class. of Insects,’’ vol. i. p. 427; for crickets, p. 446 380 THE DESCENT OF MAN sexes rarely differ much in color, it is not probable that they owe their bright tints to sexual selection. Conspicuous colors may be of use to these insects, by giving notice that they are unpalatable. Thus it has been observed* that a bright-colored Indian locust was invariably rejected when offered to birds and lizards. Some cases, however, are known of sexual differences of color in this Order. The male of an American cricket*’ is described as being as white as ivory, while 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 Phasmide) “is of a shining brownish-yellow color; 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. Order, Newroptera.—Little need here be said, except as to color. In the Ephemeride 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 Libellu- lidze, 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 Agrionide ‘‘are of a rich blue with black wings, while the females are fine green with colorless wings.”” But in Agrion Ramburii these colors are exactly reversed in the two sexes.’ In the extensive North Ameri- cans genus of Hetzrina, the males alone have a beautiful 46 Mr. Ch. Horne, in ‘‘Proc. Ent. Soc.,’? May 3, 1869, p. xii. “ The Geanthus nivalis. Harris, ‘‘Insects of New England,’’ 1842, p. 124. The two sexes of @. pellucidus of Europe differ, as I hear from Victor Carus, in nearly the same manner. 4 Platyblemnus: Westwood, ‘‘Modern Clas.,’’ vol. i. p. 447. #2 B. D. Walsh, the ‘‘Pseudo-neuroptera of Ilinois,”’ in ‘Proc. Ent. Soc., of Philadelphia,’’ 1862, p. 362. 50 **Modern Class.,”’ vol. ii. p. 37. 51 Walsh, ibid., p. 382. I a indebted to this naturalist for the following facts on Hetzerina, Anax, and Gomphus. SEXUAL SELECTION 381 carmine spot at the base of each wing. In Anaz 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 in some other genera, the sexes differ but little in color. In closely allied forms throughout 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 color between the sexes of many Libellulide, it is often difficult to say which is the more brilliant; and the ordinary colora- tion of the two sexes is reversed, as we have just seen, in one species of Agrion. It is not probable that their colors in any case have been gained as a protection. Mr. Mac- Lachlan, who has closely attended to this family, writes to me that dragon-flies—the tyrants of the insect-world— are the least liable of any insect to be attacked by birds or other * enemies, and he believes that their bright colors serve as a sexual attraction. Certain dragon-flies apparently are attracted by particular colors. Mr. Patterson observed™ that the Agrionids, of which the males are blue, settled in numbers on the blue float of a fishing line, while two other species were attracted by shining white colors. 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 colored exactly like the females; but that their bodies in a short time assume a conspicuous milky-blue tint, owing to the exuda- tion of a kind of oil, soluble in ether and alcohol. Mr. Mac- Lachlan believes that in the male of Lzbellula depressa this change of color does not occur until nearly a fortnight after the metamorphosis, when the sexes are ready to pair. Certain species of Neurothemis present, according to Brauer,” a curious case of dimorphism, some of the females having ordinary wings, while others have them “very richly netted, as in the males of the same species.’ 52 «Trans, Ent. Soc.,’? vol. i., 1836, p. Ixxxi. 8 See abstract in the “Zoological Record’? for 1867, p. 450. 882 THE DESCENT OF MAN Brauer ‘‘explains the phenomenon on Darwinian principles oy 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 the 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 color, and these are invariably females. This is probably a case of reversion; for in the true Libellule, when the sexes differ in color, the females are orange or yellow; so that, supposing Agrion to be descended from some primordial form which resembled the typical Libellule in its sexual characters, 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, powerful, and fierce insects, the males have not been observed by Mr. MacLachlan to fight together, excepting, as he believes, in some of the smaller species of Agrion. 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 fe- male, and contending with great eagerness who shall win the prize.’ The Atropos pulsatorius is said to make a noise with its jaws, which is answered by other individuals.* Order, Hymenoptera.—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” "4 Kirby and Spence, ‘‘Introduct. to Entomology,” oi ii., 1828, p. 35. 55 Houzeau, ‘‘Les Facultés Mentales,’’ ete., tom. i. . 104. 56 See an interesting article, ‘‘The Writings of Fabre,’ * in “Nat. Hist. Review,’’ April, 1862, p. 122. ™ See the “Journal of the Proceedings of the Entomological Society”? for September 7, 1863, p. 169. SEXUAL SELECTION 383 says that the males of one of the saw-flies (Tenthredinz) “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 recognizing each other after long intervals of time, and are deeply attached. For instance, Pierre Huber, whose accuracy no one doubts, separated some ants, and when, after.an interval of four months, they met others which had formerly belonged to the same community, they recognized and caressed one another with their antenna. Had they been strangers they would have fought together. Again, when two communities engage in a battle, 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 color, 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 colored—for instance in Chrysis, in which vermilion and metallic greens prevail—that we are tempted to attribute the result to sexual selection. In the Ichneu- monide, according to Mr. Walsh, the males are almost universally lighter-colored than the females. On the other hand, in the Tenthredinide the males are generally darker than the females. In the Siricide the sexes frequently differ; thus the male of Sirex juvencus is banded with orange, while the female is dark purple; but it is difficult to say which sex is the more ornamented. In Tremex columbe the female is much brighter-colored 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 color. The males are generally the brighter, and, in 58 DP Huber, ‘Recherches sur les Moeurs des Fourmis,’’ 1810, pp. 150, 166, 59 “Prog, Zatomolog. Soc. of Philadelphia,’? 1866, pp. 238-239. 384 THE DESCENT OF MAN Bombus as well as in Apathus, much more variable in color than the females. In Anthrophora retusa the male is of a rich fulvous-brown, while the 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 Andrena fulva, are much brighter-colored than the males. Such differences in color can hardly be accounted for by the males being defenceless and thus requiring protection, while the females are well defended by their stings. H. Miiller,° who has particularly attended to the habits of bees, attributes these differences in color in chief part to sexual selection. That bees have a keen per- ception of color is certain. He says that the males search eagerly and fight for the possession of the females; and he accounts through such contests for the mandibles of the males being in certain species larger than those of the fe- males. 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. Conse- quently, in certain genera (Miiller, p. 42), the males of the several species differ much in appearance, while the females are almost indistinguishable; in other genera the reverse occurs. H. Miiller believes (p. 82) that the colors gained by one sex through sexual selection have often been trans- ferred in a variable degree to the other sex, just as the pollen-collecting apparatus of the females has often been transferred to the male, to whom it is absolutely useless." . “Anwendung der Darwin’schen Lehre auf Bienen,’ ‘Verh. p. n. Jahrg.,”” xxix. 61 M. Perrier in his article, ‘‘La Sélection sexuelle d’aprés Darwin’’ (‘‘Revue 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 unfertilized ova, they could not transmit new characters to their male off- spring. This is an extraordinary objection. A female bee fertilized by a male, which presented some character facilitating the union of the sexes, or renderai him more attractive to the female, would lay eggs which would produce only SEXUAL SELECTION 385 Mutilla Furopea makes a stridulating noise; and accord- ing to Goureau both sexes have this power. He attributes the sound to the friction of the third and preceding abdomi- nal segments, and I find that these surfaces are marked with very fine concentric 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 wing- less. 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 while pursuing the females. Order, Coleoptera (Beetles).—Many beetles are colored go 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 colors, which are often arranged in stripes, spots, crosses, and other elegant patterns. Such colors can hardly serve directly as a protection, except in the case of certain ‘flower-feeding species; but they may serve as a warning or mears of recognition, on the same principle as the phos- phorescence of the glow-worm. As with beetles the colors 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 pos- sess other well-marked secondary sexual characters. Blind 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 grandfathers? To take a case with ordinary animals as nearly parallel as pos- sible; if a female of any white quadruped or bird were crossed by a male of a black breed, and the male and female offspring were paired together, will it be pretended that.the grandchildren would not inherit a tendency to blackness from their male grandfather? The acquirement of new characters by the sterile worker-bees is a much more difficult case, but I have endeavored to show in my ‘‘Origin of Species’? how these sterile beings are subjected to the power of natural selection. 7 62 Quoted by Westwood, ‘‘Modern Class. of Insects,’’ vol. ii, p. 214. Descent—Vou I.—17, 386 THE DESCENT OF MAN beetles, which cannot, of course, behold each other’s beauty, never, as I hear from Mr. Waterhouse, Jr., exhibit bright colors, though they often have polished coats; but the explanation of their obscurity may be that they generally inhabit caves and other obscure stations. Some Longicorns, especially certain Prionide, offer an exception to the rule that the sexes of beetles do not differ ia. 16.—Chalcosoma atlas. Upper figure, male (reduced); lower figure, female (natural size), . in color. Most of these insects are large and splendidly colored. The males in the genus Pyrodes,* which I saw in Mr. Bates’s collection, are generally redder but rather 8 Pyrodes pulcherrimus, in which the sexes differ conspicuously, has 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 color between the sexes of beetles, Kirby and Spence (‘‘Introduct. to Entomology,’’ vol. iii. p. 301) mention a Cantharis, Meloe, Rhagium, and the Leptura testacea; the male of the latter being testaceous, with a black thorax, and the female of a dull red all over. These two latter beetles belong to the family of Longicorns, Messrs, R. Trimen and Waterhouse, Jr., inform me of two Lamellicorns, viz., a Peri- trichia and Trichius, the male of the latter being more obscurely colored than the female. In Tillus elongatus the male is black, and the female always, as it is believed, of a dark-blue color, with a red thorax. The male, also, of Orso- dacna atra, a8 I hear from Mr. Walsh, is black, the female (the so-called O. rujicollis) having a rufous thorax. SEXUAL SELECTION 387 duller than the females, the latter being colored 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 purple. In the genus Esmeralda the sexes differ so greatly in color 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 Prio- nidee in which the sexes differ are colored more richly than the males, and this does not accord with the common rule in regard to color, 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, ete., and are wonderful both from their size and diversified shapes. Instead of describing them, I have given figures of the males and females of some of the more remarkable forms (Figs. 16 to 20). The females generally exhibit rudiments of the horns in the form of small knobs or ridges; but some are destitute of even the slightest rudi- ment. On the other hand, the horns are nearly as well developed in the female as in the male of Phaneus 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 in any manner corresponding with the more important characteristic differ- ences 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 which have two. In almost all cases the horns are remarkable from their excessive 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 588 THE DESCENT OF MAN Fic. 17.—Copris isidis, (Left-hand figures, males.) Fia. 20.—Onthophagus rangifer (enlarged), SEXUAL SELECTION 389 the females. Mr. Walsh" found that in Phaneus carnifex the horns were thrice as long in some males as in others. Mr. Bates, after examining above a hundred males of Onthophagus rangifer (Fig. 20), thought that he had at last discovered a species in which the horns did not vary; but further research proved the contrary. The extraordinary size of the horns, and their widely different structure in closely allied forms, indicate that they have been formed for some purpose; but their excessive variability in 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 suppose™ 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 examination of numerous species, find any sufficient evi- dence, in 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 Copride, did not find any marked difference in this respect among 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 ‘Prog, Entomolog. Soc. of Philadelphia,’ 1864, p. 228. 65 Kirby and Spence, ‘‘Introduct. Entomolog.,’’ vol. iii, p. 300. 590 THE DESCENT OF MAN shown by their extreme variability in the same species, and by their extreme diversity in closely allied species. This view will at first 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 kinds 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 species of the 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 Fg es fare may aid the male in clinging to the female. from beneath. Although the males have not even a trace of a horn on the upper surface of the body, yet the females plainly exhibit a rudiment of a single horn on the head (Fig. 22, a), and of a crest (0) on the thorax. That the slight thoracic crest in the female is a rudiment of a projee Fig. 22.—Left-hand figure, male of Onitis furcifer, viewed laterally. Right-hand figure, female. a. Rudiment of cephalic horn. 06. Trace of thoracic horn or crest. tion proper to the male, though entirely absent in the male of this particular species, is clear; for the female of Bubas bison (a genus which comes next to Onitis) has a similar slight crest on the thorax, and the male bears a great pro- jection in the same situation. So, again, there can hardly be a doubt that the little point (a) on the head of the female Onitis furcifer, as well as on“the head of the females of two or three allied species, is a rudimentary representative of the SEXUAL SELECTION 391 cephalic horn, which is common to the males of so many Lamellicorn beetles, as in Phanwus (Fig. 18). The old belief that rudiments have been created to com- plete 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 to 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 de- velopment of the large horns and projections on the lower surface; and as these are confined to the males, the rudi- ments of the upper horns on the females would not have been thus obliterated. The cases hitherto given refer to the Lamellicorns, but ad Fia. 3.—Bledius taurus (magnified), Left-hand figure, male; right-hand figure, female, the males of some few other beetles, belonging to two widely distinct groups, namely, the Curculionide and Staphylinids, are furnished 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 Staphylinide the horns of the males are extraordinarily variable in the same species, Just as we have 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 Staphylinide, Prof. West- wood ‘states that ‘‘male specimens can be found in the same locality in which the central horn of the thorax is very 6 Kirby and Spence, ‘‘Introduct, Entomolog.,’’ vol. iii. p. 329, 392 THE DESCENT OF MAN large, but the horns of the head quite rudimental; and others, in which the thoracic horn is much shorter, while the protuberances on the head are long.’’*’ Here we ap- parently 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 pos- session of the females. Mr. Wallace® saw two males of Leptorhynchus angustatus, a linear beetle with a much elon- gated 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, ac- knowledging 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 (Lucanus 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 engage in fierce conflicts. When Mr. A. H. Davis™ inclosed two males with one female in a box, the larger male severely pinched the smaller one, until he resigned his pretensions. A friend informs me 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 Lucanids, as well as of the above- 61 ‘*Modern Classification of Insects,’’ vol. i. p. 172: Siagonium, p. 172. in the British Museum I noticed one male specimen of Siagonium in an inter- mediate condition, so that the dimorphism is not st ‘ict. 88 “The Malay Archipelago,’”’ vol. ii., 1869, p. 276. Riley, Sixth ‘‘Report on Insects of Missouri,’’ 1874, p. 115. 6 “Entomological Magazine,”’ vol. i., 1833, p. 82. See also, on the conflicts of this species, Kirby and Spence, ibid., vol. iii. p. 314; and Westwood, ibid., vol. i. p. 18%. SEXUAL SELECTION 893 mentioned Leptorhynchus, are larger and more powerful insects than the females. The two sexes of Lethrus cepha- lotes (one of the Lamellicorns) inhabit the same burrow, and the male has larger mandibles than the female. If, during 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 encourages her mate by continually pushing him on from behind; and the battle lasts until the aggressor is killed or runs away.” The two sexes of another Lamellicorn 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 Luanide are extremely variable both in size and structure, and in this respect re- semble the horns on the head and thorax of many male Lamellicorns and Staphylinide. A perfect series can be formed from the best-provided to the worst-provided or degenerate males. Although 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 elaphus of North America for seizing the female. As they are so conspicuous and so elegantly branched, and as owing to their great 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 horns on the head and thorax of the various species above described. The male Chiasognathus grantit of South Chile—a splendid beetle belonging to the same family— has enormously developed mandibles (Fig. 24); he is bold Quoted from Fischer, in ‘‘Dict. Class. d’Hist. Nat.,’’ tom. x. p. 324. 1 “Ann, Soc, Entomolog. France,’’ 1866, as quoted in ‘‘Journal of Travel,” by A. Murray, 1868, p. 135. 394 THE DESCENT OF MAN . and pugnacious; when threatened he faces round, opens his great jaws, and at the same time stridulates loudly. But Fig. 24.—Chisognathus gran- tii (reduced). Upper figure, male; lower figure, female. 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 Lamellicorns 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 colored. Lastly, several of the largest beetles in the world belong to this family, which was placed by Linneus and Fabricius at the head of the Order.” Stridulating Organs.—Beetles be- longing to many and widely distinct families possess these organs. The sound thus produced can sometimes be heard at the distance of several feet, or even yards,” but it is not comparable with that made by the Orthoptera. The rasp generally con- sists of a narrow, slightly raised surface, crossed by very fine, parallel ribs, sometimes so fine as to cause iridescent 72 Westwood, ‘‘Modern Class.,”’ vol. i. p. 184. 73 Wollaston, ‘‘On Certain Musical Curculionide,” ‘‘Annals and Mag. of Nat. Hist.,’’ vol. vi., 1860, p. 14. SEXUAL SELECTION 395 colors, and having a very elegant appearance under the microscope. In some cases, as with Typhceus, minute, bristly, or scale-like prominences, with which the whole surrounding surface is covered in approximately parallel lines, could be traced passing into the ribs of the rasp. The 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 scraper 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. These organs are situated in widely different positions. Fig. 25.—Necrophorus (from Landois). +. The two rasps. Left-hand figure, part of the rasp highly magnified. In the carrion-beetles (Necrophorus) two parallel rasps (7, Fig. 25) stand on the dorsal surface of the fifth abdom- inal 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 Crioceridew, and in Clythra 4- punctata (one of the Chrysomelide), and in some Tene- brionide, etc.,”* the rasp is seated on the dorsal apex of the ™4 Landois, ‘‘Zeitschrift fiir Wiss. Zoolog.,’’ B. xvii., 1867, s, 221. 7% I am greatly indebted to Mr. G. R. Crotch for having sent me many pre- pared specimens of various beetles belonging to these three families and to others, as well as for valuable information. He believes that the power of stridulation in the Clythra has not been previously observed. Iam also much indebted to Mr. E. W. Janson, for information and specimens. I may add that my son, Mr. F. Darwin, finds that Dermestes murinus stridulates, but he searched in vain for the apparatus. Scolytus has lately been described by Dr. Chapman as a stridulator, in the ‘‘Entomologist’s Monthly Magazine,’’ vol. vi. p. 130. : 896 THE DESCENT OF MAN 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 Curculionid# and Cara- bide” the parts are completely reversed in position, for the rasps are seated on the inferior surface of the elytra, near their apices, or along their outer margins, and the edges of the abdominal segments serve as the scrapers. In Peélobius Hermanni (one of Dytiscide, 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 Cerambyx heros. Many Lamellicorns have the power of stridulating, and the organs differ greatly in position. Some species stridu- late very loudly, so that when Mr. F. Smith caught a Troa sabulosus, a gamekeeper, 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. stercorarius 84 ribs), which is scraped by a specially projecting part of one of the abdominal seg- ments. In the nearly allied Copris lunaris, an excessively 76 Schiddte, translated in ‘‘Annals and Mag. of Nat. Hist.,”’ vol. xx., 1867, . 37, Pn Westring has described (Kroyer, ‘‘Naturhist. Tidskrift,”’ B. ii., 1848-49, p. 334) the stridulating organs of these two, as well as in other families. In the Carabidz I have examined Hlaphrus uliginosus and Blethisa multipunctata, sent to me by Mr. Crotch. In Blethisa the transverse ridges on the furrowed border of the abdominal segment do not, as far as I could judge, come into play in scraping the rasps on the elytra. SEXUAL SELECTION 897 narrow fine rasp runs along the sutural margin of the elytra, with another sharp rasp near the basal outer margin; but in some other Coprini the rasp is seated, ‘according to Leconte,” on the dorsal surface 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 Omaloplia brunnea 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 in the Longicorns. : We thus see that in the different coleopter- 8=3= ous families the stridulating organs are won- derfully 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 vari- ous beetles made a shuffling or hissing noise by the rubbing together of any hard and rough parts of their bodies which happened to bein yg. 06. Hina. contact; and that, from the noise thus pro- les of Geotrupes stercorarius (from duced being in some way useful, the rough Lyuis)..7, Rasp. surfaces were gradually developed into regular * Tibia. tr. Tarsi. stridulating organs. Some beetles, as they move, now pro- duce, either intentionally or unintentionally, a shuffling noise, without possessing any proper organs for the purpose. Mr. Wallace informs me that the Huchirus longimanus (a Lamellicorn, with the anterior legs wonderfully elongated in the male) ‘‘makes, while moving, a low hissing sound by the protrusion and contraction of the abdomen; and when seized it produces a grating sound by rubbing 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 8 I am indebted to Mr. Walsh, of Illinois, for having sent me extracts from Leconte’s ‘Introduction to Entomology,’’ pp. 101, 143. 398 THE DESCENT OF MAN the grating sound by rubbing the shagreened surface of the femur against the granulated margin of the correspond- ing 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 doubt- ful 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. R. Crotch in preparing the many specimens which he had the kindness to send me. Any difference in these organs, if slight, would, however, be difficult to detect, on account of their great variability. Thus, in the first pair of specimens of Necrophorus humator and of Pelobiws which I examined, the rasp was consider- ably larger in the male than in the female; but not so with succeeding specimens. In Geotrupes stercorarius the rasp appeared to me thicker, opaquer, and more promjnent 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 proportion to the females in both the lots. Mr. F. Smith has kept alive numerous specimens of Monoynchus pseudacori (Curculionide) and is convinced that both sexes stridulate, and apparently in an equal degree. Nevertheless, the power of stridulating is certainly a sexual character in some few Coleoptera. Mr. Crotch dis- covered that the males alone of two species of Heliopathes (Tenebrionide) possess stridulating organs. I examined SEXUAL SELECTION 399 five males of H. gibbus, and in all these there was a well- developed rasp, partially divided into two, on the dorsal surface of the terminal abdominal segment; while 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 H. cribratostriatus the male has a similar rasp, excepting that it is not partially divided into two portions, and the female is completely desti- tute 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 ex- tremely fine ribs, parallel to and resembling those on the abdominal rasp; whether these ridges serve as an indepen- dent 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 Lamellicorn genus Oryctes we have a nearly parallel case. In the females of O. gryphus 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 seg- ment, when held in the proper light, is seen to be clothed with hairs, which are absent or are represented by exces- sively fine down in the males. It should be noticed that in all Coleoptera the effective part of the rasp is destitute of hairs. In O. 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 trans- parent object. In the female the whole surface is covered with little separate crests, bearing spines; while in the male these crests in proceeding toward 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 in the female. In the females, how- ever, of all three species of Oryctes, a slight grating or strid- ulating sound is produced when the abdomen of a softened specimen is pushed backward and forward. In the case of the Heliopathes and Oryctes there can 400 | THE DESCENT OF MAN hardly be a doubt that the males stridulate in order to call or to excite the females; but with most beetles the stridulation apparently serves both sexes as a mutual call. Beetles stridulate under various emotions, in the same man- ner as birds use their voices for many purposes besides sing- ing to their mates. The great Chiasognathus stridulates in anger or defiance; many species do the same from distress or fear, if held so that they cannot escape; by striking the hollow stems of trees in the Canary Islands, Messrs. Wol- laston and Crotch were able to discover the presence of beetles belonging to the genus Acalles by their stridula- tion. Lastly, the male Ateuchus stridulates to encourage the female in ber work, and from distress when she is re- moved.” 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 belief that the stridulation 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. Mr. Doubleday also in- forms me that he has sometimes observed a female ticking,® and in an hour or two afterward he has found her united with a male, and on one occasion surrounded by several males. Finally, 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 79 M. P. de la Brulerie, as quoted in ‘‘Journal of Travel,’’? A. Murray, vol. i., 1868, p. 135. 8 According to Mr. Doubleday, ‘‘the noise is produced by the insect raising ctself on its legs as high as it can, and then striking its thorax five or six times, in rapid succession, against the substance upon which it is sitting.’’? For refer- ences on this subject see Landois, ‘‘Zeitschrift fir Wissen. Zoolog.,”’ B. xvii. s, 131. Oliver says (as quoted by Kirby and Spence, ‘‘Introduct.,’’ vol. ii. p. 393) 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, soon attends her, and they pair.”’ SEXUAL SELECTION 401 best in finding partners, rugosities on various parts of their bodies were gradually developed by means of sexual selec- tion into true stridulating organs. CHAPTER XI INSECTS, continued—ORDER, LEPIDOPTERA (BUTTERFLIES AND MOTHS) Courtship of butterflies—Battles—Ticking noise—Colors common to both sexes, or more brilliant in the males—Examples—Not due to the direct action of the conditions of life—Colors adapted for protection—Colors of moths—Display—Perceptive powers of the Lepidoptera—Variability —Causes of the difference in color between the males and females— Mimicry, female butterflies more brilliantly colored than the males —Bright colors of caterpillars—Summary and concluding remarks on the secondary sexual characters of insects—Birds and insects compared : the differences in color between the sexes of the same species, and between the distinct species of the same genus. Nearly the whole of the following chapter will be devoted to this subject; but I will first make a few remarks on one or two other points. Several males may often be seen pursuing and crowding round the same female. Their courtship appears to be a prolonged affair, for I have fre- quently watched one or more males pirouetting 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 addresses. Although butterflies are weak and fragile creatures, they are pugnacious, and an Emperor butterfly’ has been cap- i this great Order the most interesting points for us are 1 Apatura Iris: ‘The Entomologist’s Weekly Intelligence,”? 1859, p. 139. For the Bornean Butterflies, see 0. Collingwood, ‘Rambles of a Naturalist,” 1868, p. 183. 402 THE DESCENT OF MAN tured with the tips of its wings broken from a conflict with another male. Mr. Collingwood, in spoaking of the fre- quent battles between the butterflies of Bornoo, says, ‘They whirl round each other with the yreatest rapidity, and appoar 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 sevoral yards: T noticod this sound at Rio de Janciro, only when two of those butterflios wero chasing each othor 4 in an, irregular courso, so that it is probably made. during the courtship of the sexes." Some moths also produce sounds; for instance, the males of Theophora fovea. On two occasions Mr. F. Buchanan White" heard a sharp, quick noise made by the male of MMylophila prasinana, and which he believes to be pro- duced, as in Cicada, by an elastic mombrane, furnished with a muscle. Ie quotes, also, Guonée, that Setinu pro- duces a sound like the ticking of a watch, apparently by the aid of ‘‘two large tympaniform vesicles, situated in the pectoral revion’’; and these ‘tare much moro 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. 1 have not alluded to the woll- known noise made by the Death’s Tead Sphinx, for it is generally heard soon after the moth has cimerged from. its cocoon. Girard has always observed that the musky odor which is emitted by two species of Sphinx moths is poculiar to the malos;* 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 2 Seo my ‘Journal of Resoarches,’’ 1846, p. 88. Mr. Doubleday jas do- tected (Proc, Mint. Soc.,’? Marchi 3, 1846, p. 128) » peculiar mombranous sac at the base of the front wings, which is probably connected with the produc. tion of the sound, Vor the ease of Nhecophorn, seo ‘*Zoologlenl Record,’? 1469, p. 401. For Mr, Buchanan White’s observations, “The Scottish Naturallnt, July, 1872, p. 214. “The Scottish Naturalist, ” July, 1892, p, 218. 4 “Zoological Record,’’ 1869, p. 347. SEXUAL SELECTION 408 many butterflies and of some moths; and it may be asked, aro their colors and diversified patterns the result of the direct action of the physical conditions to which these insvots have boon exposed, without any benofit being thus derived? Or have successive variations been accumulated and determined as a protection, or Lor some unknown pur- pose, or that one sox may be attractive to the other’ And, aguin, what is the moaning of the colors boing widely diflor- ent in the malos and females of cortain species, and alike in the two soxes of other species of the same genus? Bofore attempting to answer these questions a body of facts must be given. With our beautiful English butterflies, the admiral, pea- covk, and painted lady (Vaness:e), as well as many others, tho sexes are alike. This is also the caso with the magnill- cont Heliconide, and most of the Danaidee in the tropics. But in certain other tropical groups, and in some of our English butterflies, as the purple omporor, orange-tip, ete. (Apatura tris and Anthocharis cardamines), the sexes differ either greatly or slightly in color. No Isnguage suffices to describe the splendor of the males of somo tropical species. Evon within the same genus wo often find specios presenting extraordinary diferences between the sexes, while others have their sexes closely alike. Thus in the South Ameri- can genus Epicalia, 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 soxes of which haunt the same stations (and this is not al- ways the ease with butterflies), and which, therefore, cannot have been differently affected by external conditions.’ In nine of these twelve species the males rank among the most brilliant of all butterflies, and differ so greatly from the comparatively plain females that they wore formerly placed in distinct gonera. The females of these nine species re- 5 Seo also Mr. Bates's papor in ‘Proc. Nut. Soo. of Philadelphia’? 1865, P 206, Also Mr. Wallace on the samo subject, in regard to Diadema, in | ‘Transact, Entomolog. Soe. of London,’’ 1869, p, 378. 404 THE DESCENT OF MAN semble each other in their general type of coloration; and they likewise resemble both sexes of the species in several allied 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 colored in nearly the same manner. In the tenth species the female still retains the same general coloring, but the male resembles her, so that he is colored in a much less gaudy and contrasted manner than the males of the previous species. In the eleventh and twelfth species the females de- part from the usual type, for they are gayly decorated almost like the males, but in a somewhat less degree. Hence in these two latter species the bright colors of the males seem to have been transferred to the females; while in the tenth species the male has either retained or recovered the plain colors of the female, as well as of the parent-form of the genus. The sexes in these three cases have thus been ren- dered nearly alike, though in an opposite manner. In the allied genus Eubagis, both sexes of some of the species are plain-colored and nearly alike; while with the greater num- ber the males are decorated with beautiful metallic tints in a diversified manner, and differ much from their females. The females throughout the genus retain the same general style of coloring, so that they resemble one another much more closely than they resemble their own males. In the genus Papilio, all the species of the Auneas group are remarkable for their conspicuous and strongly contrasted colors, and they illustrate the frequent tendency to grada- tion in the amount of difference between the sexes. Ina few species, for instance in P. ascanius, the males and females are alike; in others the males are either a little brighter or very much more superb than the females. The genus Junonia, allied to our Vanesse, offers a nearly parallel case, for although the sexes of most of the species resemble each other, and are destitute of rich colors, yet in certain species, as in J. enone, the male is rather more bright- colored than the female, and in a few (for instance e/. an- SEXUAL SELECTION 405 dremiaja) the male is so different from the female that he might be mistaken for an entirely distinct species. Another striking case was pointed out to me in the Brit- ish Museum by Mr. A. Butler, namely, one of the tropical American Thecle, in which both sexes are nearly alike and wonderfully splendid; in another species the male is colored - in a similarly gorgeous manner, while the whole upper sur- face of the female is of a dull uniform brown. Our common little English blue butterflies of the genus Lycena illustrate the various differences in color between the sexes almost as well, though not in so striking a manner, as the above exotic genera. In Lycena agestis both sexes have wings of a brown color, bordered with small ocellated orange spots, and are thus alike. In Z. egon the wings of the male are of a fine blue, bordered with black; while those of the female are brown, with a similar border, closely resembling the wings of LZ. agestis. lastly, in Z. arion both sexes are of a blue color 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 first place, that when the sexes of butterflies differ the male, as a general rule, is the more beautiful, and departs _more from the usual type of coloring of the group to which the species 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 allude, the females are colored 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 gra- dation from no difference in color to so great a difference that it was long before the two were placed by entomologists in the same genus. In the third place, we have seen that when the sexes nearly resemble each other, this appears due either to the male having transferred his colors to the fe- 406- THE DESCENT OF MAN male, or to the male having retained, or perhaps recovered, the primordial colors 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 the males are beautiful to an extraordinary degree, the females ‘almost invariably exhibit some degree of beauty. From the many cases of gradation in the amount of difference be- tween the sexes, and from the prevalence of the same general type of coloration throughout the whole of the same group, we may conclude that the causes have generally been the same which have determined the brilliant coloring 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 colors to the great heat and moisture of these zones; but Mr. Bates* has shown, 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 con- clusive when brilliantly colored males and plain-colored 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 colors are the purposeless result of the nature of the tissues and of the action of the surrounding conditions. With animals of all kinds, whenever color has been modi- fied for some special purpose, this has been, as far as we can judge, either for direct or indirect protection, or as an attrac- tion 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 would be particularly liable to be attacked by their enemies when at rest; and most kinds while rest- ing raise their wings vertically over their backs, so that the & “The Naturalist on the Amazons,’’ vol. i., 1863, p. 19. SEXUAL SELECTION . 407 lower surface alone is exposed to view. Hence it is this side which is often colored so as to imitate the objects on which these insects commonly rest. Dr. Réssler, I believe, first noticed the similarity of the closed wings of certain Vanessa 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 antennz between its closed wings, which, in form, color, and veining, cannot be distinguished from a withered leaf with its foot- stalk. In some other cases the lower surfaces of the wings are brilliantly colored, and yet are protective; thus in Thecla vubi the wings when closed are of an emerald green, and re- semble the young leaves of the bramble, on which in spring this butterfly may often be seen seated. It is also remark- able that in very many species, in which the sexes differ greatly in color 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 upper and under sides of many butterflies no doubt serve to conceal them, yet we cannot extend this view to the brilliant and con- spicuous colors on the upper surface of such species as our admiral and peacock Vanessz, our white cabbage-butterflies (Pieris), or the greater 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 common brimstone butterfly (Gonepteryx rhamnt) the male is of an intense yellow, while 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, 1 See a very interesting article in the ‘‘Westminster Review”’ for July, 1867, p. 10. A woodcut of the Kallima is given by Mr. Wallace in ‘‘Hardwicke’s Science Gossip’’ for September, 1867, p. 196. 8 Mr. G. Fraser, in ‘‘Nature,’’ April, 1871, p. 489. 408 THE DESCENT OF MAN and it is not credible that their difference in color should stand in any relation to ordinary protection. Prof. Weis- mann remarks® that the female of one of the Lycene ex- pands 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 shows that the blue color cannot be in any way protective. Nevertheless, it is probable that conspicuous colors 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 spe- cies, which inhabit the same district and enjoy an immu- nity 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 show us the primordial. colors of the parent-species of the genus; for both sexes of four or five widely distributed species are colored 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 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 [phias 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- colored 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 9 ‘*Binfluss der Isolirung auf die Artbildung,’’ 1872, 10 See the interesting observations by Mr. T. W. Wood, “The Student,” Sept. 1868, p. 81. SEXUAL SELECTION 409 which compels us to believe that the lower surfaces have here been colored for the sake of protection, leads us to deny that the wings have been tipped with bright orange for the same purpose, especially when this character is con- fined to the males. Most Moths rest motionless during the whole or greater part of the day with their wings depressed, and the whole upper surface is often shaded and colored in an admirable manner, as Mr. Wallace has remarked, for escaping detec- tion. The front wings of the Bombycide and Noctuide," when at rest, generally overlap and conceal the hind-wings, so that the latter might be brightly colored without much risk; and they are in fact often thus colored. During flight, moths would often be able to escape from their enemies; nevertheless, as the hind-wings are then fully exposed to view, their bright colors must generally have been acquired at some little risk. But the following fact shows how cautious we ought to be in drawing conclusions on this head. The common Yellow Under-wings (Triphena) often fly about during the day or early evening, and are then conspicuous from the color of their hind-wings. It would naturally be thought that this would be a source of danger; but Mr. J. Jenner Weir believes that it actually serves them as a means of escape, for birds strike at these brightly colored and fragile surfaces, instead of at the body. For instance, Mr. Weir turned into his aviary a vigorous specimen of Triphena pronuba, which was instantly pursued by a robin; but the bird’s attention being caught by the colored wings, the moth was not captured until after about fifty attempts, and small portions ot the wings were repeat- edly broken off. He tried the same experiment in the open air, with a swallow and Z. fimbria; but the large size of this moth probably interfered with its capture.'* We are thus reminded of a statement made by Mr. Wallace,’* namely, il Mr. Wallace in ‘‘Hardwicke’s Science Gossip,” Sept. 1867, p. 193. 12 See also, on this subject, Mr. Weir’s paper in “Transact. Ent. Society,” 1869, P- 23, 13 **Westminster Rev.,’’ July, 1867, p. 16. Descent—Vou. I.—18 410 THE DESCENT OF MAN 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 ‘fare 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 indirectly beneficial.’’ Display.—The bright colors of many butterflies and of some moths are specially arranged for display, so that they may be readily seen. During the night colors are not visible, and there can be no doubt that the nocturnal moths, taken as a body, are much less gayly decorated than butterflies, all of which are diurnal in their habits. But the moths of certain families, such as the Zygeenidx, several Sphingide, Uraniide, some Arctiidae and Saturniide, fly about during the-day or early evening, and many of these are extremely beautiful, being far brighter colored than the strictly nocturnal kinds. A few exceptional cases, however, of bright-colored 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 while basking in the sunshine often alternately raise and depress them, thus exposing both surfaces to full view; and although the lower surface is often colored 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 colored than the upper.’® In the English fritillaries (Argynnis) the lower 14 For instance, Lithosia; but Prof. Westwood (‘‘Modern Class. of Insects,’? vol. ii. p. 390) seems surprised at this case. On the relative colors of diurnal and nocturnal Lepidoptera, see ibid., pp. 333 and 392; also Harris, ‘‘Treatise on the Insects of New England,’’ 1842, p. 315. 1’ Such differences between the upper and lower surfaces cf the wings of SEXUAL SELECTION 411 surface alone is ornamented with shining silver. Never- theless, as a general rule, the upper surface, which is prob- ably more fully exposed, is colored more brightly and diversely than the lower; hence the lower surface gener- ally affords to entomologists the more useful character for detecting the affinities of the various species. Fritz Muller informs me that three species of Castnia are found near his house in South 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 colored 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.’* Mr. Trimen informs me that in Guenée’s great work three moths are figured, in which the under sur- face is much the more brilliant. For instance, in the Aus- tralian Gastrophora the upper surface of the fore-wing is pale grayish-ochreous, while the lower surface is magnifi- cently ornamented by an ocellus 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 three moths are unknown, so that no explanation can be given of their unusual style of coloring. Mr. Trimen also informs me that the lower surface of the wings in certain other Geometre" and quadrifid Noctua are either more varie- gated or more brightly colored than the upper surface; but several species of Papilio may be seen in the beautiful plates to Mr. Wallace’s ‘“‘“Memoir on the Papilionide of the Malayan Region,’’ in ‘‘Transact. Linn. Soe.,’? vol. xxv. part i., 1865. 16 See Mr. Wormald on this moth: ‘‘Proc. Ent. Soc.,’? March 2, 1868. 11 See also an account of the S. American genus Erateina (one of the Geome- tree) in ‘‘Transact. Ent. Soc.,’’ new series, vol. v. pl. xv. and xvi, 412 THE DESCENT OF MAN some of these species have the habit of ‘‘holding their wings quite erect over their backs, retaining them in this position for a considerable time,’’ and thus exposing the under surface to view. Other species, when settled on the ground or herbage, 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 Saturniide 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 if for display, which is more characteristic of diurnal than of nocturnal Lepidoptera.’’ It is a singular fact that no British moths which are brilliantly colored, and, as far as I can discover, hardly any foreign species, differ much in color according to sex; though this is the case with many brilliant butterflies. The male, however, of one American moth, the Saturnia do, is described as having its fore-wings deep yellow, curi- ously marked with purplish red spots; while the wings of the female are purple-brown, marked with gray lines.’ The British moths which differ sexually in color 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 18 “*Prog, Ent. Soc. of London,”’ July 6, 1868, p. xxvii. 9 Harris, ‘‘Treatise,’’ etc., edited by Flint, 1862, p. 395. 20 For instance, I observe in my son’s cabinet that the males are darker than the females in the Lasiocampa quercus, Odonestis potatoria, Hypogymna dispar, Dasychira pudibunda, and Cycnia mendica. In this latter species the difference in color 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 explained. The white female of the Cyenia 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 eat- ing other moths; so that if the Cycnia was commonly mistaken by British birds for the Spilosoma, it would escape being devoured, and its white deceptive color would thus be highly beneficial. SEXUAL SELECTION 413 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 (Hepialus humuli) the 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 while flying about in the dusk. From the several foregoing facts it is impossible to admit that the brilliant colors of butterflies, and of some few moths, have commonly been acquired for the sake of pro- tection. We have seen that their colors and elegant patterns are arranged and exhibited as if for display. Hence I am led to believe that the females prefer or are most excited by the more brilliant males; for on any other supposition the 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 attachment for each other, and that ants recognize 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 colors. They certainly discover flowers by color. 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 assured, by two persons abroad, that these moths repeatedly visit flowers painted on the walls of a room, and vainly endeavor to insert their proboscis into them. Fritz Muller informs me that several kinds of butterflies in South Brazil show an unmistakable preference for certain colors over others: — 1 It is remarkable that in the Shetland Islands the male of this moth, instead of differing widely from the female, frequently resembles her closely in color (see Mr, MacLachlan, ‘‘Transact. Ent. Soc.,’’ vol. ii., 1866, p. 459), Mr. G. Fraser suggests (‘‘Nature,”’ April, 1871, p. 489) that at the season of the year when the ghost moth appears in these northern islands, the whiteness of the males would not be needed to render them visible to the females in the twilight night, 414 | THE DESCENT OF MAN he observed that they very often visited the brilliant 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 ac- counts 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. Collingwood,” in speaking of the difficulty in collecting certain butterflies in the Malay Archipelago, states that ‘ta dead specimen pinned 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 pursuing 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 colors of the latter will have been ren- dered brighter by degrees, and will have been transmitted to both sexes or to one sex, according to the law of inheri- tance 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 exceed the females in number. Some facts, however, are opposed to the belief that fe- male butterflies prefer the 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 % ‘*Rambles of a. Naturalist in the Chinese Seas,’’ 1868, p. 182. SEXUAL SELECTION 415 Bombycidew 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 ento- mologists 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.experi- ence in breeding Bombyx cynthia, is convinced that the females evince no choice or preference. He has kept above 800 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 vigor- ous males pass over the weakly females, and are attracted by those endowed with most vitality. Nevertheless, the Bombycide, though obscurely colored, are often beautiful to our eyes from their elegant and mottled shades. I have as yet only referred to the species in which the males are brighter colored 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 if, 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. But- ler showed me several species of Callidryas in the British Museum, in some of which the females equalled, and in others greatly surpassed, the maies in beauty; for the females alone have the borders of their wings suffused with crimson and orange, and spotted with black. The 416 THE DESCENT OF MAN 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. In England we have some analogous cases, though not so marked. The females alone of two species of Thecla have a bright-purple or orange patch on their fore-wings. In Hipparchia the sexes do not differ much; but it is the female of H. janira which has a conspicuous light-brown patch on her wings; and the females of some of the other species are brighter colored than their males. Again, the females of Colias deusa 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 in 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 com- monly 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 butterflies the females take the more active part in the final marriage ceremony, so that we may suppose that they like- wise do so in the wooing; and in this case we can under- stand how it is that they have been rendered the more _ beautiful. Mr. Meldola, from whom the foregoing state- ments have been taken, says in conclusion: ‘Though I am not convinced of the action of sexual selection in producing the colors of insects, it cannot be denied that these facts are strikingly corroborative of Mr. Darwin’s views.’’ ” 93 **Wature,’? April 27, 1871, p. 508. Mr. Meldola quotes Donzel, in ‘‘Soe. ; Ent. de France,’’ 1837, p. 77, on the flight of buttertiies while pairing. Sce also Mr. G. Fraser, in ‘‘Nature,’’ April 20, 1871, p. 489, on the sexual differences of several British butterflies. SEXUAL SELECTION 417 As sexual selection primarily depends on variability, a few words must be added on this subject. In respect to color there 1s no difficulty, for any number of highly vari- able Lepidoptera could be named. One good instance will suffice. Mr. Bates showed me a whole series of specimens of Papilio sesostris and P. childrene ; 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 among the males between the most and the least gaudy. The male of Papilio sesostris is much less beautiful than of P. childrene; and it like- wise varies a little in the size of the green patch on the fore-wings, and in the occasional appearance 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 Aineas group possess this crimson stripe. Hence, between the brightest specimens of Papilio sesostris and the dullest of P. childrene, there was but a small interval; and it was evident that, as far as mere variability is concerned, there would be no difficulty 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 shown” that the females of some species are extremely variable, the males being nearly constant. In a future chapter I shall _have occasion to show 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 inexplica- 24 Wallace on the Papilionide of the Malayan Region, in **Transact. Linn, S0c.,”” vol. xxv., 1865, pp. 8, 36. A striking case of a rare variety, strictly intermediate between two other well-marked female varieties, is given by Mr, Wallace. See also Mr. Bates, in ‘Proc. Entomolog. Soc.,’? Nov. 19, 1866, p. xl 25 Mr, Bates was so kind as to lay this subject before the Entomological Society, and I have received answers to this effect from several entomologists, 418 THE DESCENT OF MAN ble; but if it should hereafter be found that the formation of an ocellus is due to some change in the tissues of the wings, for instance, occurring at a very early period of 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 urged, it seems probable that most of the brilliantly colored species of Lepidoptera owe their colors to sexual selection, excepting in certain cases, presently to be mentioned, in which conspicuous colors have been gained through mimicry as a protection. From the ardor of the male throughout the animal kingdom, he is generally willing 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 colored, and this undoubtedly is the case. When both sexes are brilliantly colored and resemble each other, the characters acquired by the males appear to have been transmitted to both. We are led to this conclu- sion by cases, even within the same genus, of gradation from an extraordinary amount of difference to identity in color between the two sexes. But it may be asked whether the differences in color between the sexes may not be accounted for by other means besides sexual 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 adult state they are exposed to different conditions during a very short period; and the larve of both are ex- %¢ H. W. Bates, ‘‘The Naturalist in the Amazons,”’ vol. ii., 1863, p. 228, A. R. Wallace, in ‘‘Transact. Linn. Soc.,’’ vol. xxv., 1865, p. 10. 27 On this whole subject see ‘‘The Variation of Animals and Plants under Domestication,’ 1868, vol. ii. chap. xxiii, SEXUAL SELECTION 419 posed 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 colors for the sake of protection. It seems to me, on the contrary, far more probable that it is the males which have been chiefly modi- fied through sexual selection, the females having been com- paratively 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 show us approximately the primordial coloring of the parent-species of the group 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 pro- tection. In most cases the males and females of distinct species will have been exposed during their prolonged larval state tc different conditions, and may have been thus affeeted; though with the males any slight change of color thus caused will generally have been masked by the brilliant tints gained through sexual selection. When we treat of Birds, I shall have to discuss the whole question, as to how far the differences in color between the sexes are due to the males having been modified through sexual selection for ornamental purposes, or to the females having been modi- fied through natural selection for the sake of protection; so that I will here say but little on the subject. In all the cases in which the more common form of equal inheritance by both sexes has prevailed, the selection of bright-colored males would tend to make the females bright- colored, and the selection of dull-colored females would tend to make 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 wel] protected by 420 THE DESCENT OF MAN obscure colors, or a greater number of males by being brightly colored and thus finding partners, succeeded in leaving more numerous offspring. In order to account for the frequent transmission of characters to one sex alone, Mr. Wallace expresses his belief that the more common form of equal inheritance by both sexes can be changed through natural selection into inheritance by one sex alone, but in favor 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 colors to the males alone, and at the same time, or subsequently, dull colors to the females alone. In this manner the females of some butter- flies and moths have, it is probable, been rendered incon- spicuous 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 requir- ing 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-colored by having escaped from their enemies. The male, for instance, 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 protection, though it is probable that the male acquired his bright colors as a sexual attraction. The female of Anthocharis cardamines 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 resem- blance 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 SEXUAL SELECTION 421 she has simply retained to a large extent her primordial colors. Finally, as we have seen, various considerations lead to the conclusion that with the greater number of brilliantly colored Lepidoptera it is the male which has been chiefly modified through sexual selection; the amount of difference between the sexes mostly depending on the form of inheri- tance which has 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 iden- tical in color. As all the successive steps in the process of variation are necessarily transmitted through the female, a greater or less number of such steps might readily become developed in her; and thus we can understand the frequent gradations from an extreme difference to none at all between the sexes of allied species. These cases of gradation, it may be added, are much too common to favor the sup- position 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 South America, belong- ing to quite distinct families, resembled the Heliconide so closely in every stripe and shade of color that they could not be distinguished save by an experienced entomologist. As the Heliconide are colored in their usual manner, while the others depart from the usual coloring of the groups to which they belong, it is clear that the latter are the imi- %8 “The Variation of Animals and Plants under Domestication,” vol. a. ehap. xii. p. 17. ‘es 99 ‘Transact. Linn. Soc.,”’ vol. xxiii., 1862, p. 495. 422 THE DESCENT OF MAN tators, and the Heliconide the imitated. Mr. Bates fur- ther observed that the imitating species are comparatively rare, while the imitated abound, and that the two sets live mingled together. From the fact of the Heliconide being conspicuous and beautiful insects, yet so numerous in indi- viduals and species, he concluded that they must be pro- tected from the attacks of enemies by some secretion or odor; 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 va- riation 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 colors °° +he imitated, but only of the imitating butterflies. We mus account for the colors of the former in the same general manner as in the cases previously discussed in this chap- ter. Since the publication of Mr. Bates’s 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. Riley in the United States.™ As some writers have felt much difficulty in understand- ing 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 color. In this case even a slight variation would be beneficial, if it rendered the one species more like the other; and afterward the imitated species might be modified 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 an equally extreme de- 30 «Proc, Ent. Soc.,’’ Dec. 3, 1866, p. xlv. 21 Wallace, ‘‘Transact. Linn. Soc.,’’ vol. xxv., 1865, p. i.* also ‘Transact. Ent. Soc.,”’ vol. iv. (3d series), 1867, p. 301. Trimen, “‘Linn. Transact.,’’ vol. xxvi., 1869, p. 497. Riley, ‘‘Third Annual Report on the Noxious Insects of Missouri,’’ 1841, pp. 163-168. This latter essay is valuable, as Mr. Riley here discusses all objections which have keen raised against Mr. Bates’s theory. SEXUAL SELECTION 423 gree from their original condition; and they would thus ultimately assume an appearance or coloring wholly unlike that of the other members of the group to which they be- longed. It should also be remembered that many species of Lepidoptera are liable to considerable and abrupt variations in color. 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 Mr. Trimen gives, in the paper already referred to, three cases in which the sexes of the imitated form differ from each other in color, and the sexes of the imitating form differ in a like manner. Several cases have also been recorded where the females alone imi- tate brilliantly colored and protected species, the males re- taining ‘‘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 illustration of these re- marks in a statement by Mr. Belt,” that the males of some of the Leptalides, which imitate protected species, still re- tain in a concealed manner some of their original charac- ters. Thus in the males ‘‘the upper half of the lower wing is of a pure white, while 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 2 “The Naturalist in Nicaragua,’? 1874, p. 385. ~ 424 THE DESCENT OF MAN to the females, and thus gratify their deep-seated preference for the normal color of the Order to which the Leptalides belong.” Bright Colors of Caterpillars.—While reflecting on the beauty of many butterflies, it occurred to me that some caterpillars were splendidly colored; and as sexual selec- tion could not possibly have here acted, it appeared rash to attribute the beauty of the mature insect to this agency, unless the bright colors of their larve could be somehow explained. In the first place, it may be observed that the colors of caterpillars do not stand in any close correlation with those of the mature insect. Secondly, their bright colors do not serve in any ordinary manner as a protec- tion. 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 for solving difficulties. After some consideration he replied: ‘*Most caterpillars require protection, as may be inferred from some kinds being furnished with spines or irritating hairs, and from many being colored green like the leaves on which they feed, or being curiously like the twigs of the trees on which they live.”’ Another instance of pro- tection, 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 colored caterpillars were pro- tected by having a nauseous taste; but as their skin is ex- SEXUAL SELECTION 425 tremely tender, and as their intestines readily protrude from & wound, a slight peck from the beak of a bird would be as fatal to them as if they had been devoured. Hence, as Mr. Wallace remarks, ‘‘distastefulness alone would be insuffi- cient 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 instantane- ously and certainly recognized as unpalatable by all birds and other animals. Thus the most gaudy colors would be serviceable, and might have been gained by variation and the survival of the most easily recognized individuals. This hypothesis appears at first sight very bold, but when it was brought before the Entomological Society® it was sup- ported 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 skins, all of a green color, and all which imitate twigs, are greedily devoured by his birds. The hairy and spinose kinds are invariably rejected, as were four conspicu- ously colored species. When the birds rejected a caterpillar, they plainly showed, by shaking their heads and cleansing their beaks, that they were disgusted by the taste.“ Three conspicuous kinds of caterpillars and moths were also given to some lizards and frogs, by Mr. A. Butler, and were re- jected, 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 recognized by their enemies, on nearly the same principle that poisons are sold in colored 33 **Proe, Entomolog. Soc.,’? Dec. 3, 1866, p. xlv., and March 4, 1867, = mee 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 Annual Report on the N oxious Insects of Missouri,’’ 1871, p. 148. Some opposed cases are, however, given by Dr. Wallace and M. H. d’Orville; see ‘‘Zoological Record,’’ 1869, p. 349. 426 THE DESCENT OF MAN bottles by druggists for the good of man. We cannot, how- ever, at present thus explain the elegant diversity in the col- ors 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, etc., almost certainly would not be- come uniform in color, when its tints were rendered intense and bright; for in order to make a caterpillar merely con- spicuous, there would be no selection in any definite direction. Summary and Concluding Remarks on Insects.—Looking back to the several Orders, we see that the sexes often differ in various characters, the meaning of which is not in the least understood. The sexes, also, often differ in their or- gans 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 known to be highly pugna- cious; 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 smaller, so that they may be developed within a shorter time, to be ready in large numbers for the emergence of the females.’ In two families of the Homoptera and in three of the Qrthoptera, the males alone possess sound-producing organs i1an efficient state. These are used incessantly during the Lreeding-season, not only for calling the females, but appar- ently 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 SEXUAL SELECTION 427 these musical instruments have been acquired through sex- ual 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 be- fore those which were less noisy, so that their organs have probably been gained through sexual selection. It is in- structive 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 learn how effectual sexual selection has been in leading to modifica- tions which sometimes, as with the Homoptera, relate to important parts of the organization. From the reasons assigned in the last chapter, it is prob- able that the great horns possessed by the males of many Lamellicorn, and some other beetles, have been acquired as ornaments. From the small 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 complex horns, magnified to the size of a horse, or even of a dog, it would be one of the most imposing animals in the world. The coloring of insects is a complex and obscure subject. When the male differs slightly from the female, and neither is brilliantly colored, 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 colored and differs conspicuously from the female, as with some dragon-flies and many butterflies, it is probable that he owes his colors to sexual selection; while the female has retained a primordial or very ancient type of coloring, 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 428 THE DESCENT OF MAN 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 colored, there is no doubt that they have been in a multitude of cases so colored for the sake of protection. So it is in some instances when both are brightly colored, 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 cases in which the sexes resemble each other and are both brilliant, especially when the colors 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 color from the females, while others differ slightly or not at all, with intermediate gradations connect- ing these extreme states. In the same manner as bright colors 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 organs proper to the males of the Homoptera and Orthop- tera have generally been transferred in a rudimentary, or even in a nearly perfect condition, to the femaies; yet not sufficiently perfect to be of any use. It is also an interest- ing 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 colors 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. Sexual selection implies that the more attractive individ- uals are preferred by the opposite sex; and as with insects, when the sexes differ, it is the male which, with some rare exceptions, is the more ornamented, and departs more from SEXUAL SELECTION 429 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 beau- tiful 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 particular male, is probable from the many singular contrivances possessed by the males, such as great jaws, adhesive cushions, spines, elongated legs, etc., for seizing thc female; for these contrivances show that there is some difficulty in the aci, so that her concurrence would seem necessary. Judging from what we know of the perceptive powers and affections of vari- ous 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 pur- suing the same female, we can hardly believe that the pair- ing is left to blind chance—that the female exerts no choice, and is not influenced by the gorgeous colors or other orna- ments with which the male is decorated. If we admit that the females of the Homoptera and Orthoptera appreciate the musical tones of their male part- ners, and that the various instruments have been perfected through sexual selection, there is little improbability in the females of other insects appreciating beauty in form or color, and consequently in such characters having been thus gained by the males. But from the circumstance of color 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 pro- portion of cases sexual selection has played a part. This is more especially difficult in those Orders, such as Orthoptera, Hymenoptera, and Coleoptera, in which the two sexes rarely differ much in color; for we are then left to mere analogy. With the Coleoptera, however, as before remarked, it is in the great Lamellicorn group, placed 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 430 THE DESCENT OF MAN species possessing weapons for sexual strife, others furnished with wonderful horns, many with stridulating organs, and others ornamented with splendid metallic tints. Hence it seems probable that all these characters have been gained through the same means, namely, sexual selection. With butterflies we have the best evidence, as the males some- times take pains to display their beautiful colors; and we cannot believe that they would act thus, unless the display was of use to them in their courtship. When we treat of Birds, we shall see that they present in their secondary sexual characters the closest analogy with 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 during 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 colors, 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 pro- vided with ornaments which are usually confined to the male sex. In other groups both sexes are equally plain-colored 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 gradation 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 show in further detail, is sexual selection. END OF VOLUME ONE