The nature of life is generally regarded as affording a theme which possesses no more than an academic interest: but there is one aspect of this great subject which must attract us all, and that is its power of reproducing itself. Life begets5 Life, as Love is said to beget4 Love. The nature of this mysterious power we can only dimly realize, and the forces which underlie6 its manifestations7 few even suspect, save perhaps in a vague way. Yet the tree of Knowledge bears no fruit more vitally important to our well-being8, than that which will make us “as Gods, knowing good and evil” in all that concerns the processes of reproduction. But curiously9 enough, this is a forbidden fruit, and those who eat thereof are expected 2to maintain a discreet10 silence on the subject. These enlightened ones, however, cannot remain altogether dumb. But they speak, in the veiled language, of Art and Poetry, Literature and the Drama. They talk round the subject rather than of it. Love, Hate, Jealousy11, and Envy, are but attributes thereof. We profess12 to believe that “Knowledge is Power” and to desire to increase its force among us by raising the standard of our system of education. But education which does not, of set purpose, reveal the sources of our being and of our emotions, good and evil, is no more than a travesty13 of education; and they who seek to foist14 upon the community Knowledge thus emasculated, are unworthy to wield15 the power which has been placed in their hands. If social well-being be the aim of the high-priests of Education, then something more than copybook maxims16 like “Be good and you will be happy” must henceforth be preached. Of what avail is it to exalt18 the name of Knowledge, while the straightest road thereto is barred across and marked “No thoroughfare!” These blind leaders of the blind seem to imagine that the social well-being they profess to desire can only be attained19 by side roads, leading anywhere, save in the direction of this Pool of Siloam.
The stuff of which living things are made is called “Protoplasm.” Text-books of Physiology21 give its chemical constituents22 with fearsome accuracy, and each of these constituents can be isolated23 in the laboratory, but “all the king’s horses and all the king’s men” cannot build these up again into living matter. Its consistent inconsistency defies us; every statement we make of it has to be qualified24 by reservations and saving clauses. 3Its permanency is attested25 by the fact that it has endured through millions of years, yet we are daily reminded of its evanescent nature. Its power of reproducing itself according to type, none can doubt, yet no two individuals are exactly alike.
The purely27 physical phenomena28 of life, to be rightly appreciated, must always be considered in relation to the psychical29 phenomena which are the soul of life. These subtle and intangible forces cannot be experimented with in the laboratory, or expressed in formul?; we cannot denote their strength in horse-power. Just as the physical manifestations of life begin with lowly types, so the psychical begin, and they gather strength and complexity30 with the bodies they pervade31. These manifestations we call behaviour, and in their more intense developments, “emotions.”
These emotions present an infinite range of variety in the higher animals, and they attain20 their maximum of intensity32 wherever the reproductive activities are concerned. The part which these activities play in controlling behaviour is by no means always apparent, and is commonly not even suspected. Even man himself is subject to this control. And it is this fact which lifts the “Courtship” of the lower animals out of the category of merely curious phenomena. For the springs of his conduct, his behaviour and “emotions” under varying circumstances, can only be understood, and even then but imperfectly, by comparison with other creatures lower in the scale, so far, of course, as comparison is possible.
This line of inquiry34, then, takes one back to the simplest living things, among which there is neither marrying nor giving in marriage, neither birth nor death. Life is reduced to its simplest terms—a speck35 of animated36 jelly is all that confronts one, and this is only to be seen under a 4high power of the microscope. It has neither mouth nor organs of digestion37, no visible means of locomotion38 are traceable, and the special senses of sight and hearing are wanting; but taste and smell, of a nebulous kind, are there. Shape it cannot be said to have, for its bodily outline is constantly changing, thereby39 it moves. A long tongue of its jelly-like substance, or “protoplasm” as it is called, is thrust forwards, and the rest of the body is, as it were, dragged after it. Whatever animal, or vegetable, matter it passes over, in the course of its wanderings, is drawn40 up into the semi-fluid substance of this diaphanous41 body, and its juices extracted, the undigestible residue42 is left behind in the course of the morning’s walk! In due time it becomes adult; further growth is impossible. When this stage is attained a strange thing happens. A certain minute, more solid portion of this body, which lies in the very centre of the mass and is known as the “nucleus,” begins to assume an hour-glass shape. Speedily the constriction43 becomes apparent across the whole body and rapidly increasing, cuts it in two, as if by the tightening44 of some invisible thread. Here Death is cheated, and records of births are unknown! And just as there are no parents so there are no children. But a foreshadowing of what is to be occurs even here. For every now and then two individuals, to all appearances identical, meet and promptly45 begin to merge46 the one into the other till they twain become one flesh in very truth. Here is the most primitive47 form of marriage in Nature. And here, in this union, or fusion48, of separate entities49 of Germ-plasm, we have the beginning of sex. Such unions are common among these primeval forms of life. In many cases this “marriage” takes place 5between two particles of Protoplasm of which one is rather larger than the other. In such case the smaller is regarded as male, the larger as female. Here we have the first sign of “sexual differentiation” or the evolution of “male” and “female” individuals.
Some such union, some such process of “rejuvenation” by the importation of “fresh blood” seems to be imperative50 for the continuance of existence throughout the whole animal world, even though it may take place at rare intervals51 of time. Why should this be? Is this strange meeting and commingling52 a matter of chance, or is the one seeking the other possessed53 by a ravenous54 mate-hunger?
As we ascend55 higher in the scale it becomes apparent that life has gathered force. That primitive speck of jelly, the Am?ba, with which we started, gave but two signs of animation56—the power of movement, and hunger. Whether these responses to internal stimuli57 can be called instinctive58 is open to argument. But there can be no question about the instinctive nature of the behaviour of these higher animals. After the instinct to feed the two most powerful are the desire for self-preservation—the avoidance of danger—and the desire to mate. These two are the dominating instincts throughout the rest of the animal world, not even excepting man himself.
The tremendous power of “mate-hunger” has been overlooked by a strange confusion between cause and effect. Almost universally its sequel, the production of offspring, has been regarded as the dominant59 instinct in the higher animals. This view has no foundation in fact. “Desire” for the sake of the pleasure it affords, and not its consequences, is the only hold on life which any race possesses. And this is true both in the case of man 6himself and of the beasts that perish. Wherever this instinct becomes weak, or defective60, extinction61 speedily and inevitably62 follows. This “Amorousness” is the motive63 power of “Courtship” wherever it is met with; manifesting itself in the eccentric, and often grotesque64 posturings, or in the loud and often musical cries which constitute the study of courtship. Intensity of desire is indispensable to survival.
Only the lowly and sedentary types, of which the Oyster may be taken as an example, lack this fire; and here because it is unnecessary. For the reproductive germs of this animal are discharged into the water, to take their chance of attaining65 their object. They are liberated66 unconsciously, discharged like the undigested residue of the food, without effort, and without cognizance of the act. This must be so, for the Oyster merely lives—vegetates. Sightless, and without power of movement, after its larval wanderings are over, it lives merely to eat. And even in this, choice is denied it. The currents of water mechanically brought to afford the necessary oxygen for the maintenance of life, bring with them the food which is to restore the slowly wasting tissues. To such a creature there can be no “outer-world,” no consciousness of the existence of individuality other than its own.
The desire for sexual intercourse67 is met with only where the co-operation of two individuals is necessary to ensure the production of offspring. Such individuals being free to roam, must have some incentive68 to seek one another at the time when their germ-cells have attained maturity69. And this incentive is furnished by the glands70 in which these elements are produced: supplemented by the secretions71 of certain ancillary72 glands. These stimulating73 juices, 7known as the “Hormones,” will be presently described.
But if we owe our existence to the gratification of what may be called our lower instincts, it is no less certain that all that is best in us we owe to our offspring. We meet with the beginnings of altruism74, which the begetting75 of offspring entails76, far down in the animal kingdom, and it attains77 to its full perfection in the human race. Here only, in its best and truest sense, Love begins: though affection may be found, and in a high degree, in many of the lower animals.
Living things are as clay in the hands of the potter. But it is as if they made themselves, for the designer and the guiding hand are alike invisible. No vessel78 is exactly like its neighbour, either in the quality of its substance or in the details of its construction. And this because the clay of which it is made possesses that mysterious property we call life. A property which endows each new feature as it appears, with an individuality of its own, whose survival, or suppression, depends entirely79 on its relationship to surrounding parts; on its harmony with its environment, in short. Colour, size, shape, temperament80, behaviour, may each be regarded as so many entities depending for survival on whether or not they can exist in harmony with their environment—the several parts which make up what we call the individual.
In like manner the individual—the complex bundle of parts and qualities—must attain, and maintain, a certain harmony with its environment—the outer world. The process of change, both in quality and quantity, which is for ever going on among the several parts of every separate individual, brings about the elimination81 of unfavourable variations; and “selects” those which 8vary in the right direction: that is to say, which serve to maintain a place in the sun for the individual in which these momentous82 changes are going on. But it is not enough that the individual should be in “working order”; it must be in harmony with all the conditions on which existence depends. And the standard of this harmony is set by that very exacting83 arbiter84 of life and death, “Natural Selection.” It is not enough that the instincts in regard to this or that habit should be keen, or that this or that particular organ of the body should be efficient—a certain minimum, all-round, standard of efficiency is demanded, or elimination follows. It is through this instability of “temperament,” this tendency to vary in infinite directions, that the balance between the individual and the environment is maintained. Evolution follows the line of least resistance.
The little boy who remarked that it must be “fiddling work, making flies,” was more sage85 than he knew. The complex web of factors which even a fly represents are beyond the grasp of human understanding. But it is clear that the reproductive instincts, and the emotions they beget, have played, and play, a tremendous part in the evolution of the higher animals.
Those whose business it is, for one reason or another, to study these emotions know well that “mate-hunger” may be as ravenous as food-hunger, and that, exceptions apart, it is immensely more insistent86 in the males than in the females. But for this, reproduction in many species could not take place: for the sexes often live far apart, and mates are only to be won after desperate conflict with powerful rivals no less inflamed87. Thus it is idle to speak of an equality between the sexes in this matter, in regard to the human race. Dogmatism, and the frequent 9repetition of pretty platitudes88, will not alter what Nature has ordained89. The failure to realize this is painfully obvious in the utterances90 of many who speak in the name of the newly-founded “Eugenics” society, which seeks the means to ensure the well-being of the race by the spread of a more intimate knowledge of this all-important subject. The existence of what Mr. Heape has recently called a “sex-antagonism” is beyond dispute, for the instincts of the male and female are fundamentally different. The male is dominated by the desire to gratify the sexual appetite; in the female this is counteracted91 by the stimulation92 of other instincts concerned with the cares of offspring.
Amorousness, then, is the dominant feature of the males among all animals: and this sex presents yet another characteristic which is to be borne in mind. In all that concerns the evolution of ornamental94 characters the male leads. In him we can trace the trend which evolution is taking; the female and young afford us the measure of the advance along the new line which has been taken. Why this should be is inexplicable95. But sooner or later the females assume, or will assume, all the features originally possessed by their lords; and finally the young also follow suit. That is to say, the females and young tend to retain the ancestral characters. In the course of time the ability to develop new features by the male loses its impetus96, and not till then, apparently97, do the females, and still later, the young, begin to share his glory. These remarkable98 features are strikingly illustrated99 among the birds, as these pages will show.
Nature is nothing, if not perverse100. And hence it happens that there are many exceptions to every rule which one formulates101. Among the birds, for example, 10there are species wherein the rule that the female follows her mate in the acquisition of new characters is, so to speak, set aside. She follows a line of her own. This is true, at any rate, of superficial characters, such as coloration. By some curious change in her “metabolism,” as the conversion102 into living tissue of the substances taken as food is called, this coloration may attain a brilliance103 in no way inferior to that of the male, but strikingly different. The beautiful Orange Fruit-pigeon (Chrysoenas victor) furnishes a case in point, the male being of a gorgeous orange-yellow, the female of a no less vivid green. But the differences are not so great as they appear at first sight. For the male was originally green, and the female has thus but intensified104 the ancestral livery. Green, it should be remarked, of a more or less olive shade, always precedes yellow in development; and yellow may yield to red, but this order is never reversed. A no less striking case is that of the Upland Goose (Cloephaga magellanica), the male of which is pure white, while the female wears a livery of chestnut105 and brown. But so sharply are the colours defined that it would be difficult to say that one was of a higher order of coloration than the other. To what causes or factors are these departures due?
Reproduction in the simplest living things takes place by a simple division of the body into two as soon as its maximum size or adult condition has been attained. In such simple types the body consists only of a single “blob,” or particle, of jelly. But a new era began when large numbers of such particles, or “cells,” began to form coherent masses, different parts of the mass performing different work for the mutual106 benefit of the community. Some have come to form what we call the 11body, which is born, and in due course dies. Others are alone concerned with the task of reproduction. They are nourished by the body, and on attaining maturity, give rise to new bodies. These reproductive cells are excessively small. The male, or “sperm” cell, can only be distinguished107 under the highest powers of the microscope. The female cell, or “Ovum,” is always larger than the male, because, in addition to the germinal matter which it contains, it is furnished with a store of food in the shape of yolk108. This accounts for the relatively109 enormous size of the egg of the hen. Within the hardened shell the germ develops into the chick, deriving110 food for its growth from this generous store. Where this yolk is limited in quantity the growing body is hastily fashioned, and launched forth17 into the world in the form of a “larva,” when it must forage111 for itself till it has attained its adult form. Or it is retained within the body of the mother until development is complete.
The reproductive cells are the bearers of the Germ-plasm, the stuff of which man and the beasts of the field alike are fashioned. Only a portion of this germ-plasm gives rise to a new body; the rest is, as it were, held over and stored within the new body to give rise to another in due course. That which produces the body we call the “Somatoplasm,” because it is the “plasm” or stuff of which the “Soma,” or body, is made. As to the nature of this Germ-plasm and its mysterious properties, a wide divergency of opinion exists among savants. But the views which find most favour to-day are those of the veteran Professor August Weissmann, as set forth in his work on the “Germ-Plasm, a Theory of Heredity.”
The excessively minute quantity of this germ-plasm 12which suffices to form a new body is incredible. By what miracle of miracles is the essence of a man distilled112? His body arises from the union or commingling of two particles of living matter so minute as to be invisible to the naked eye. One of these particles is the “sperm”—cell furnished by the male parent; the other, the “ovum,” furnished by the mother. True the ovum may measure as much as the one-hundred and fiftieth part of an inch, but the bulk of this is yolk-food necessary to furnish the tender germ with life and energy till it shall have attached itself to the walls of the womb, whence all its future nourishment113 is derived114.
By no process of analysis known to us could the germ-plasm of man be distinguished from that of, say, a jelly-fish; and in the matter of quantity there is no more difference. Yet, identical to our senses, in potentiality how amazingly different are these two particles of jelly! In the lowliest animals, such as jelly-fish, one cannot distinguish male and female at sight. The appearance of separate male and female individuals begins somewhat high in the scale marking an epoch115 in the history of animal life. For the birth of sex inaugurated not merely individuals producing distinctive116 “male” and “female” germs, but individuals which, by virtue117 of their sex, developed differences of behaviour and mentality118 which were to be followed by tremendous consequences. Certain aspects of this behaviour are to furnish the theme of these pages; others, and no less important, those who will may discover in Professor Arthur Thomson’s “Evolution of Sex.”
We are far, indeed, from being able to explain the attributes of sex. At most, we can but endeavour to interpret the behaviour associated therewith. This was 13the task which Darwin set himself to achieve in his theory of sexual selection. He was influenced in the train of thought which he followed up with such brilliant success by what he had observed in the behaviour of highly-ornamented species, such as the Peacock and the Birds of Paradise. The strange antics of these birds when under the influence of sexual excitement persuaded him that they were at least dimly conscious of their splendour, and of its power to fascinate. The female, on the other hand, was supposed to be coy, and to bestow119 her person on the finest performer. In this way the dullest birds and the poorest performers were gradually eliminated. Here, indeed, was sexual selection. The frills thus begotten120 he called “Secondary Sexual Characters,” a term which is also used, and was used, by him, to include any feature whereby the sexes can be distinguished apart from the character of the genital organs.
Horns, tusks121, and spurs are other forms of secondary sexual characters. And these stand for another form of sexual selection—that of selection by battle. Herein victory falls to the strongest and most pugnacious122 male who, as the spoils of victory, annexes123 the females which formed the subject of the duel124. This theory, which must be discussed at greater length in the course of these pages, has had many critics, and among them men of mark. But whatever modifications125 may be deemed necessary, they will be such as are demanded by the results of later discoveries rather than to the force and subtlety126 of the arguments of his opponents.
One of the most formidable of the opponents of the Sexual Selection theory was Wallace. But his arguments were far from convincing, and often inconsistent. He attributed the more frequent occurrence in male animals 14of brilliant coloration and exaggerations of growth such as give rise to manes, beards, long plumes127, and so on, to a “surplus of strength, vitality128 and growth-power which is able to expend129 itself in this way without injury,” or, as he sometimes expresses it, to superabundant vitality. He was evidently striving to find words for the faith that was in him, and he was nearer the truth than he knew or than his critics supposed. He was seeking facts which only the physiologist130 could furnish. And these made their appearance long years after with Professor Starling’s discovery of Hormones. We are far from understanding the origin of these mysterious juices which must be so frequently alluded131 to in these pages, but they are evidently intimately associated with the expenditure132 of energy. This may sometimes find an outlet133 in increased stature134, sometimes in pure luxuries of growth. The force of Wallace’s arguments was crushed out by the weight of detail they were made to bear.
Mr. J. T. Cunningham a few years ago entered the lists and failed to achieve his purpose no less completely. His was a theory which assumed too much. In the first place it was based on the transmissibility of acquired characters, of the truth of which there is at present no evidence.
He contends, for example, that the vivid hues135 of scarlet136, blue, yellow and violet which colour the naked skin of the neck of the cassowaries and of both sexes, and the curious horny casque which surmounts137 the head, are the outcome of the constant laceration of the skin inflicted139 by the males during their conflicts for the possession of the females. He assumes that such conflicts take place, and he assumes that such “acquired characters” are transmitted. Now, as a matter of fact, these birds do 15not fight with their beaks141, but with their feet. And to this end the claw of the inner toe is enlarged to form a great spur. But there is no evidence that the skin of the neck is ever damaged in such conflicts as they may engage in. No scars are ever found, at any rate, to lend support to this theory. The casque, which is similarly supposed to be a mark of honourable142 conflict, is an “ornament93” of great frailty143, for it is composed of a delicate filigree-work of bone covered with a thin sheath of horn. In like manner, the long plumes which surmount138 the heads of birds like the Peacock, and many Birds of Paradise, and the wattle which surmounts the beak140 of the Turkey, are supposed to have had their origin in similar pugilistic encounters in the past. Mr. Cunningham is surely pushing the theory of the transmission of acquired characters a little far. For what has been transmitted in these cases is not a number of scarred surfaces, but a series of hypertrophied structures. An amazing array of ornamental characters, symmetrically disposed, and often vividly144 coloured, in short, has been produced from lacerated tissues which in kind and extent can have varied145 but little.
Evidence has been accumulating during the last few years which would have rejoiced the heart of Darwin. Had he known that birds of sober hues “display” with the same animation and with as much elaboration of posture146 as the Peacock and the Pheasant, his theory of “Sexual Selection “would probably have left little for those who came after him to criticize. Since his time it has been discovered that both permanent and recurrent secondary sexual characters, such as the antlers of deer and the temporary nuptial147 plumage of birds, such as the Ruff for example, are controlled as to their growth by 16the stimulating action of the “secretions or juices formed by certain of the ductless glands “; that is to say, of glands having no apparent connection with their surrounding tissues. We owe much of our knowledge of this subject to Professor Starling, who has called these secretions “Hormones.”
Darwin knew that the essential sexual glands, the testes and the ovaries, in some mysterious way controlled, in a large degree, the development of these “hall-marks” of sex, for it was known in his time that castrated stags failed to produce antlers, and that hen pheasants, for example, in extreme old age, or when the ovaries were damaged by disease or injury, at once assumed the plumage of the cock; but the part played by these ductless glands was quite unsuspected. They are the Thyroid, and the Thymus glands, which are attached to the outer walls of the trachea or windpipe. The Pituitary body, which forms part of the brain, and the Suprarenal bodies, attached to the kidneys. It would be foreign to the purpose of these pages to enter into the functions of these glands; suffice it to say, that the juices formed therein are taken up by the blood, and distributed over the system. Their action is only very imperfectly understood. We know that any derangement148 in their efficiency results in disease, and that they play a very important part in the reproductive system, as will become abundantly evident in the course of these pages. Much hitherto attributed to the action of “Sexual Selection” alone, it is now evident is largely due to their action.
The all-sufficiency of the “Sexual Selection” theory to account for the development of armature, such as horns, antlers, and the huge spine-like outgrowths 17which form so conspicuous149 a feature of many of the extinct Land-dragons, or Dinosaurs150, has been by no means universally accepted. Some authorities like Dr. A. Smith Woodward and Professor Osborne interpret these after another fashion. They hold that these are the “expression points” of inherent growth forces, a process of concentration marking the final stages of evolution prior to extinction. From which it may be inferred that there is a term to the life of a species as there is to the life of the individual. In many cases it is suggested the very exuberance151 of growth has been the exterminating152 factor, as in the case of the huge antlers of the Irish “elk,” whose enormous weapons hampered153 his endeavours to escape his enemies. This is the theory of “Orthogenesis,” or direct development. According to this, new structures, arising in the germ-plasm as “variations,” will of their own inherent vitality go on increasing in each generation unless, and until, checked by “Natural Selection.” Changes in the character of the “Hormones” might very well bring about these excesses of growth. It is well known that the exuberance of growth which produces giants among the human race is due to a derangement of the secretions or hormones of the pituitary body which largely control growth.
Another factor of Sexual Selection which is commonly ignored, but which is of profound importance, is to be found in the part played by the emotions in regard to sexual relationships; the part which the “mind” has played, and plays, in the mating of animals, at any rate of the higher types.
Darwin touched but lightly on this theme. Later writers have almost entirely ignored it. Almost all that is worth knowing on the subject we owe to Professor 18Lloyd Morgan, who was one of the first to take up this difficult line of investigation154, and to Professor Groos. Their researches have shown that there can be no doubt but that the emotions have played and are playing an important part in the phenomena we are striving to analyse. Sexual selection, in short, is concerned not merely with the evolution of the physical characters of the body, but also, and no less, with the psychological attributes thereof. Many new and extremely valuable facts in this regard have been brought to light by Mr. H. Eliot Howard in the course of his remarkable studies on our native warblers. Not until the psychology155 of sex in the lower orders of creation has been further investigated shall we have a properly balanced account of the part played by sexual selection in the scheme of evolution.
By now it will have become apparent that the study of the “Courtship” of animals is one of alluring156 interest and full of pitfalls157 for the unwary. And this because of the apparent difficulty in drawing any hard-and-fast line between the part played by “Natural” and the part played by “Sexual” Selection, at any rate in some cases.
To this aspect of the theme Professor Lloyd Morgan has drawn particular attention. “It is difficult,” he remarks, to accept the view that individual choice has played no part where the sexual instincts are concerned. But supposing that it has played its part ... the effects will be wrought158 into the congenital tissue of the race if, and only if, there are certain individuals which, through failure to elicit159 the pairing response, die unmated. Is preferential mating, supposing it to occur, carried to such a degree that some individuals 19fail to secure a mate? That is the question. If so, sexual selection is a factor in race progress; if not, though it may occur in nature, it is inoperative as a means of evolutionary160 development. The whole question, in itself a difficult one, is further complicated by the fact that the males which are possessed of the most exuberant161 vitality, and are therefore by hypothesis rendered the most acceptable through emotional suggestion, are likely to compete with other males of less exuberant vitality by direct combat. Such competition, by which the weakest are excluded from mating through no choice on the part of the female, falls under the head of natural selection, and not of sexual selection, if by that term we understand preferential mating.
“This serves to bring out the difference ... between natural selection through elimination and conscious selection through choice.... Sexual selection by preferential mating begins by selecting the most successful in stimulating the pairing instinct.... The process is determined162 by conscious choice. It is in and through such choice that consciousness has been a factor in evolution.”
Herein Lloyd Morgan, like Darwin, recognizes the existence of a dual26 machinery163 in determining survival, where this depends on the co-operation of two individuals leading separate existences—Natural, and Sexual, Selection—sometimes the one and sometimes the other prevailing164. In the former, the females are seized by force; in the latter, won by displays.
But is this really so? In these pages it is contended that a sharp line must be drawn between all those attributes and characters which are necessary to achieve individual survival, the survival of the Ego33, and all those which, 20on the other hand, are necessary to achieve reproduction and the survival of the race. The former are governed, or determined, by Natural, the latter by Sexual, Selection.
The sphere of influence of these two factors may be delimited, if we regard natural selection as the factor accountable only for the qualities necessary for the survival of the individual—necessary to ensure success in the struggle for existence. Then it will become apparent that the qualities and attributes necessary to achieve the survival of the race are of a different kind, and these are the factors which are embraced under the term “Sexual Selection.”
It is a mistake to regard animals in relation to the selection theory as if they were so many tailors’ “mannikins.” Yet a large number of the critics of the selection theory seem to fall into this error, ignoring all but the most superficial characters.
The peculiarities165 of colour, structure and behaviour, that is to say, the characters and qualities which distinguish the individuals of any given race, are due to inherent qualities of the germ-plasm. Each of such qualities, therefore, may be regarded as entities. Selection determines their survival. Intracellular selection is the first sieve166 through which they have to pass, natural and sexual selection are others, as circumstances may determine.
As a rule the sex of an individual is attested by more or less conspicuous external features. These are known as the “Secondary Sexual Characters.” But no hard-and-fast line can be established for these, at any rate, so far as colour and ornament are concerned, for such, as will become apparent in the course of these pages, tend to appear first in the male, and then, later, to be acquired by the female, until in many cases the two sexes become again indistinguishable.
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oyster
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| n.牡蛎；沉默寡言的人 | |
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amorousness
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hormones
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| n. 荷尔蒙，激素 名词hormone的复数形式 | |
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beget
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| v.引起；产生 | |
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begets
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| v.为…之生父( beget的第三人称单数 )；产生，引起 | |
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underlie
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| v.位于...之下，成为...的基础 | |
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manifestations
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| n.表示，显示（manifestation的复数形式） | |
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well-being
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| n.安康，安乐，幸福 | |
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curiously
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| adv.有求知欲地；好问地；奇特地 | |
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discreet
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| adj.(言行)谨慎的；慎重的；有判断力的 | |
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jealousy
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| n.妒忌，嫉妒，猜忌 | |
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profess
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| v.声称，冒称，以...为业，正式接受入教，表明信仰 | |
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travesty
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| n.歪曲，嘲弄，滑稽化 | |
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14
foist
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| vt.把…强塞给，骗卖给 | |
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15
wield
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| vt.行使，运用，支配；挥，使用(武器等) | |
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16
maxims
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| n.格言，座右铭( maxim的名词复数 ) | |
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17
forth
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| adv.向前；向外，往外 | |
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18
exalt
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| v.赞扬，歌颂，晋升，提升 | |
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19
attained
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| （通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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20
attain
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| vt.达到，获得，完成 | |
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21
physiology
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| n.生理学，生理机能 | |
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22
constituents
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| n.选民( constituent的名词复数 )；成分；构成部分；要素 | |
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23
isolated
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| adj.与世隔绝的 | |
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24
qualified
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| adj.合格的，有资格的，胜任的，有限制的 | |
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25
attested
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| adj.经检验证明无病的，经检验证明无菌的v.证明( attest的过去式和过去分词 )；证实；声称…属实；使宣誓 | |
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26
dual
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| adj.双的；二重的，二元的 | |
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27
purely
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| adv.纯粹地，完全地 | |
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28
phenomena
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| n.现象 | |
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29
psychical
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| adj.有关特异功能现象的；有关特异功能官能的；灵魂的；心灵的 | |
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30
complexity
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| n.复杂(性)，复杂的事物 | |
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31
pervade
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| v.弥漫，遍及，充满，渗透，漫延 | |
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32
intensity
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| n.强烈，剧烈；强度；烈度 | |
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33
ego
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| n.自我，自己，自尊 | |
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34
inquiry
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| n.打听，询问，调查，查问 | |
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35
speck
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| n.微粒，小污点，小斑点 | |
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36
animated
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| adj.生气勃勃的，活跃的，愉快的 | |
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37
digestion
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| n.消化，吸收 | |
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38
locomotion
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| n.运动，移动 | |
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39
thereby
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| adv.因此，从而 | |
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40
drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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41
diaphanous
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| adj.(布)精致的，半透明的 | |
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42
residue
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| n.残余，剩余，残渣 | |
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43
constriction
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| 压缩； 紧压的感觉； 束紧； 压缩物 | |
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44
tightening
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| 上紧，固定，紧密 | |
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45
promptly
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| adv.及时地，敏捷地 | |
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46
merge
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| v.(使)结合，(使)合并，(使)合为一体 | |
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47
primitive
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| adj.原始的；简单的；n.原(始)人，原始事物 | |
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48
fusion
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| n.溶化；熔解；熔化状态，熔和；熔接 | |
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49
entities
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| 实体对像； 实体，独立存在体，实际存在物( entity的名词复数 ) | |
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50
imperative
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| n.命令，需要；规则；祈使语气；adj.强制的；紧急的 | |
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51
intervals
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|
| n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息 | |
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52
commingling
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| v.混合，掺和，合并( commingle的现在分词 ) | |
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53
possessed
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| adj.疯狂的；拥有的，占有的 | |
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54
ravenous
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| adj.极饿的，贪婪的 | |
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55
ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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56
animation
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| n.活泼，兴奋，卡通片／动画片的制作 | |
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57
stimuli
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| n.刺激（物） | |
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58
instinctive
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| adj.(出于)本能的；直觉的；(出于)天性的 | |
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59
dominant
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|
| adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因 | |
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60
defective
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| adj.有毛病的，有问题的，有瑕疵的 | |
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61
extinction
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| n.熄灭，消亡，消灭，灭绝，绝种 | |
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62
inevitably
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| adv.不可避免地；必然发生地 | |
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63
motive
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| n.动机，目的；adv.发动的，运动的 | |
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64
grotesque
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| adj.怪诞的，丑陋的；n.怪诞的图案，怪人（物） | |
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65
attaining
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| （通常经过努力）实现( attain的现在分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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66
liberated
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| a.无拘束的，放纵的 | |
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67
intercourse
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| n.性交；交流，交往，交际 | |
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68
incentive
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| n.刺激；动力；鼓励；诱因；动机 | |
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69
maturity
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| n.成熟；完成；(支票、债券等)到期 | |
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70
glands
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| n.腺( gland的名词复数 ) | |
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71
secretions
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| n.分泌（物）( secretion的名词复数 ) | |
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72
ancillary
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|
| adj.附属的，从属的 | |
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73
stimulating
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|
| adj.有启发性的，能激发人思考的 | |
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74
altruism
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|
| n.利他主义，不自私 | |
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75
begetting
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|
| v.为…之生父( beget的现在分词 )；产生，引起 | |
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76
entails
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| 使…成为必要( entail的第三人称单数 )； 需要； 限定继承； 使必需 | |
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77
attains
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| （通常经过努力）实现( attain的第三人称单数 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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78
vessel
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|
| n.船舶；容器，器皿；管，导管，血管 | |
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79
entirely
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|
| ad.全部地，完整地；完全地，彻底地 | |
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80
temperament
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| n.气质，性格，性情 | |
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81
elimination
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|
| n.排除，消除，消灭 | |
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82
momentous
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|
| adj.重要的，重大的 | |
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83
exacting
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|
| adj.苛求的，要求严格的 | |
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84
arbiter
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| n.仲裁人，公断人 | |
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85
sage
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|
| n.圣人，哲人；adj.贤明的，明智的 | |
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86
insistent
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|
| adj.迫切的，坚持的 | |
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87
inflamed
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|
| adj.发炎的，红肿的v.（使）变红，发怒，过热( inflame的过去式和过去分词 ) | |
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88
platitudes
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|
| n.平常的话，老生常谈，陈词滥调( platitude的名词复数 )；滥套子 | |
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89
ordained
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|
| v.任命（某人）为牧师( ordain的过去式和过去分词 )；授予（某人）圣职；（上帝、法律等）命令；判定 | |
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90
utterances
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| n.发声( utterance的名词复数 )；说话方式；语调；言论 | |
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91
counteracted
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| 对抗，抵消( counteract的过去式 ) | |
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92
stimulation
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| n.刺激，激励，鼓舞 | |
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93
ornament
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| v.装饰，美化；n.装饰，装饰物 | |
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94
ornamental
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|
| adj.装饰的；作装饰用的；n.装饰品；观赏植物 | |
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95
inexplicable
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|
| adj.无法解释的，难理解的 | |
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96
impetus
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|
| n.推动，促进，刺激；推动力 | |
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97
apparently
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| adv.显然地；表面上，似乎 | |
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98
remarkable
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|
| adj.显著的，异常的，非凡的，值得注意的 | |
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99
illustrated
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|
| adj. 有插图的，列举的 动词illustrate的过去式和过去分词 | |
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100
perverse
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|
| adj.刚愎的；坚持错误的，行为反常的 | |
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101
formulates
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| v.构想出( formulate的第三人称单数 )；规划；确切地阐述；用公式表示 | |
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102
conversion
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| n.转化，转换，转变 | |
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103
brilliance
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|
| n.光辉，辉煌，壮丽，（卓越的）才华，才智 | |
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104
intensified
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| v.（使）增强， （使）加剧( intensify的过去式和过去分词 ) | |
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105
chestnut
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| n.栗树，栗子 | |
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106
mutual
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|
| adj.相互的，彼此的；共同的，共有的 | |
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107
distinguished
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| adj.卓越的，杰出的，著名的 | |
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108
yolk
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| n.蛋黄，卵黄 | |
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109
relatively
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| adv.比较...地，相对地 | |
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110
deriving
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| v.得到( derive的现在分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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111
forage
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| n.(牛马的)饲料，粮草；v.搜寻，翻寻 | |
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112
distilled
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|
| adj.由蒸馏得来的v.蒸馏( distil的过去式和过去分词 )；从…提取精华 | |
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113
nourishment
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| n.食物，营养品；营养情况 | |
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114
derived
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| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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115
epoch
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| n.(新)时代；历元 | |
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116
distinctive
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| adj.特别的，有特色的，与众不同的 | |
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117
virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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118
mentality
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| n.心理，思想，脑力 | |
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119
bestow
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| v.把…赠与，把…授予；花费 | |
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120
begotten
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| v.为…之生父( beget的过去分词 )；产生，引起 | |
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121
tusks
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| n.（象等动物的）长牙( tusk的名词复数 )；獠牙；尖形物；尖头 | |
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122
pugnacious
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| adj.好斗的 | |
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123
annexes
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| 并吞( annex的名词复数 )； 兼并； 强占； 并吞（国家、地区等）； 附加物，附属建筑( annexe的名词复数 ) | |
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124
duel
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| n./v.决斗；(双方的)斗争 | |
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125
modifications
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| n.缓和( modification的名词复数 )；限制；更改；改变 | |
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126
subtlety
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| n.微妙，敏锐，精巧；微妙之处，细微的区别 | |
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127
plumes
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| 羽毛( plume的名词复数 )； 羽毛饰； 羽毛状物； 升上空中的羽状物 | |
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128
vitality
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| n.活力，生命力，效力 | |
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129
expend
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| vt.花费，消费，消耗 | |
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130
physiologist
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| n.生理学家 | |
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131
alluded
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| 提及，暗指( allude的过去式和过去分词 ) | |
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132
expenditure
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| n.(时间、劳力、金钱等)支出；使用，消耗 | |
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133
outlet
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| n.出口/路；销路；批发商店；通风口；发泄 | |
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134
stature
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| n.（高度）水平，（高度）境界，身高，身材 | |
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135
hues
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| 色彩( hue的名词复数 )； 色调； 信仰； 观点 | |
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136
scarlet
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| n.深红色，绯红色，红衣；adj.绯红色的 | |
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137
surmounts
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|
| 战胜( surmount的第三人称单数 )； 克服（困难）； 居于…之上； 在…顶上 | |
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138
surmount
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| vt.克服；置于…顶上 | |
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139
inflicted
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| 把…强加给，使承受，遭受( inflict的过去式和过去分词 ) | |
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140
beak
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| n.鸟嘴，茶壶嘴，钩形鼻 | |
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141
beaks
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| n.鸟嘴( beak的名词复数 )；鹰钩嘴；尖鼻子；掌权者 | |
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142
honourable
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| adj.可敬的；荣誉的，光荣的 | |
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143
frailty
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| n.脆弱；意志薄弱 | |
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144
vividly
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| adv.清楚地，鲜明地，生动地 | |
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145
varied
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| adj.多样的，多变化的 | |
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146
posture
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| n.姿势，姿态，心态，态度；v.作出某种姿势 | |
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147
nuptial
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| adj.婚姻的，婚礼的 | |
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148
derangement
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| n.精神错乱 | |
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149
conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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150
dinosaurs
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| n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西 | |
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151
exuberance
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| n.丰富；繁荣 | |
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152
exterminating
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| v.消灭，根绝( exterminate的现在分词 ) | |
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153
hampered
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| 妨碍，束缚，限制( hamper的过去式和过去分词 ) | |
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154
investigation
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| n.调查，调查研究 | |
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155
psychology
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| n.心理，心理学，心理状态 | |
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156
alluring
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| adj.吸引人的，迷人的 | |
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157
pitfalls
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| （捕猎野兽用的）陷阱( pitfall的名词复数 )； 意想不到的困难，易犯的错误 | |
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158
wrought
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| v.引起；以…原料制作；运转；adj.制造的 | |
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159
elicit
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| v.引出,抽出,引起 | |
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160
evolutionary
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| adj.进化的；演化的，演变的；[生]进化论的 | |
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161
exuberant
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| adj.充满活力的；（植物）繁茂的 | |
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162
determined
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| adj.坚定的；有决心的 | |
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163
machinery
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| n.(总称)机械，机器；机构 | |
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164
prevailing
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| adj.盛行的；占优势的；主要的 | |
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165
peculiarities
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| n. 特质, 特性, 怪癖, 古怪 | |
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166
sieve
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| n.筛，滤器，漏勺 | |
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