In Mr. Wallace’s Darwinism due attention has indeed been paid to pre-nuptial performances. But his explanation, viz. that the dancing and singing, etc., are only the effect of an inner impulse to movement and activity which accompanies sexual maturity,[270] can but incompletely unriddle the problem. For the purpose of affording an outflow to a surplus of vigour or of discharging a nervous tension, activities of a far simpler character would have been sufficient. As, however, amongst birds with gorgeous plumage every movement in the display tends towards exhibiting their splendour with the greatest possible éclat, an influence upon the hen cannot be argued away. It is, as Darwin remarks, impossible to believe that the Argus pheasant, for instance, should have developed precisely such a curious and peculiar sort of dance, through which his beautiful dress is so effectively shown forth, if this dance had been of no effect upon its spectators.[271] This effect cannot, as has been shown above, be considered an æsthetic one. It is also difficult to believe that the hen, as it has been suggested, should appreciate the secondary sexual characters as signs of greater or smaller vital force, and thus prefer not the most beautiful, but the most vigorous and ardent mate.[272] Whether it is founded on an æsthetic judgment or on an estimation of the force displayed, her conscious choosing seems to be alike improbable.
But if it is difficult to believe that the display of the males could call forth an intellectual activity in the hen, such as that of comparing and valuing the merits of the rival suitors,[273] one can safely assume that it might influence her emotional and instinctive life. And for the production of such an effect there is no need to suppose any intervening æsthetic activity. Considering the close parallelism which shows itself in the development of either sex, it would only be natural if a colour and voice alteration in the cock, which undeniably is dependent upon sexual ripening,[274] should directly and almost physiologically imply a reaction in the sexual life of the hen. The more energetically the male forces himself upon the attention of the female by the conspicuous visual and acoustic signs of his sex, the more powerful must necessarily be the emotional response in her.
If secondary sexual characters are interpreted in this way, as signs, by which the sex of the male is manifested in an unmistakable manner, then one can easily understand the influence of a prolonged display. When the cock is exhibiting his plumes or pouring forth his notes, and thereby impressing upon his female listener the notion of his malehood, he cannot but produce in her an enhanced inclination for pairing.[275] She needs no æsthetic appreciation or intellectual judgment in order to comprehend the simple text of all his utterances. With all her instincts and impulses she can at once grasp the only thing she wants to know—the thing that is brought home to her with a greater and greater clearness during the continuation of his performance, namely, that the passionate actor in front of her is a mature representative of the other sex. And besides this, the secondary sexual characters and activities tell another tale of no less importance. If the colours and the tones of the cock, as Westermarck has shown, are of great consequence for facilitating from a distance recognition between members of the same species,[276] their biological significance is perhaps yet greater when they, during the display before the hen, accentuate the community of species. By virtue of her inherited constitution, the instinctive life of the hen will be deeper stirred the more the male is able to show that he “wears the feathers of her tribe.”
It is evident that the effect upon the hen must be greater in proportion as the sex marks and species marks of the male are more clearly defined, and therefore easier to perceive. Not only as means of recognition, but also as instruments for sexual incitement, colour-patterns with lucent points must be more advantageous than any other system of decoration. It is easily understood that a design like that on the tails of pheasants and peacocks is eminently capable of attracting the female attention to the displaying cock. But it would be stretching the theory too far if the marvellous “balls on sockets” were explained as nothing but conspicuous signals, the meaning of which the hen is able to decipher by help of her inherited instincts. The influence of the display is amongst these species undoubtedly strengthened by an action which is quite independent of any sexual associations. Besides accentuating the sex and kind of the cock, these luminous spheres will, moreover, in virtue of their very smallness and brilliancy, provoke a stimulation in the mind of the hen before whom they are vibrated. To understand this effect, it is necessary to investigate the more general question of animal appreciation of brilliancy.
The powerful attraction exercised by lucent things can be sufficiently proved by numerous instances from the life of insects and fishes as well as of higher animals. It is needless to dwell upon the various means by which man has availed himself of this disastrous predilection in order to entice animals within reach of his weapons.[277] More important in this connection is the mania for collecting lustrous objects that has been noticed in the case of ravens, jays, magpies, jackdaws, goldfinches, chiff-chaffs, sea-pies, etc.[278] It has scarcely ever been suggested that the thievish jackdaw is prompted by any æsthetic liking for brilliant plate. But as it shows itself amongst the atlas birds and the bower birds, this exaggeration of the appropriative impulse has been regarded as an indication of artistic inclination. It has been contended that these birds not only appreciate shining and gorgeous objects, but even understand how to arrange them according to a decorative plan.[279]
No one will deny that structures, such as, for instance, the gardens of the atlas birds, which have been depicted by Beccari, are most wonderful specimens of animal industry.[280] But it is undoubtedly misleading to speak of them as artistic. As far as can be judged from the descriptions—which are seldom complete—the arrangement of the objects seems to be quite accidental. Darwin has indeed collected some most eulogistic accounts of the decorative taste of the Australian bower bird. But he has also, candidly enough, illustrated them with a picture, on which an irregular heap of shells and bones is to be seen in front of the bower. And the description he borrows from Mr. Strange is yet more significant. To judge from this account, which is further corroborated by the statement of Captain Stokes, the chief interest of the birds seems to be not the arranging of their treasures, but the playing with them. It has been noticed that the cock of the great bower bird amuses himself by flying to and fro in the bower carrying a shell in his bill, which he picks up on one side and carries to the other.[281] On an anthropomorphic interpretation such a behaviour would perhaps indicate a desire of trying some new decorative effect. But it seems more natural to assume that brilliant objects, even after they have been stored up in the nest, still exercise their irresistible attraction, and thereby tempt the birds to repeated trifling with them. If the supposed redecorations of the gardens be accounted for in this manner, then there is no reason for considering the collecting impulse in the Australian birds as anything more than a higher development of the same tendency which shows itself in our common magpies and jackdaws.
By the Australian instances, however, the general predilection for brilliant objects is brought into connection with the pairing dresses of pheasants, peacocks, and humming birds. The small and brilliant objects with which the bower birds play during their pairing season remind us irresistibly of the “balls on sockets” and of the ocelli designs of the colibri.[282] It is true that the pheasants carry on their tail what the Australian birds keep in their bill. But apart from this unimportant difference, the display seems to be the same in both cases. In Mr. Strange’s letter it is said that the cock, when performing the exalted antics that precede pairing, “runs to the bower, picks up a gaudy feather or a spotted leaf, pours forth some peculiar notes, and runs through the pavilion.” It is not quite clear from this wording whether the objects really are exhibited before the hen. But one may safely assume that she in any case has paid some attention to her consort’s performance. She has decidedly not, any more than the pea-hen, received any sort of æsthetic impression from the display. But the brilliancy has undoubtedly stimulated her, as it stimulates all the other birds quoted in this connection, in a purely physiological way. This action, on the other hand, is sufficiently explained by recent researches on the physiological effects which the contemplation of concentrated lustre produces on animal organisms. It is also well known that objects with exactly the same qualities as the ocelli on the peacock’s tail play an important part in hypnotic experiments. And the primitive shamans as well as the modern cultivators of “crystal-gazing” are acquainted with the peculiar effects of prolonged gazing on glass-balls or the shining surface of water. More familiar still is the fascinating influence exercised by that lustrous little globe, the human eye.
In all these various examples the smallness of the object fetters the attention, and thereby makes the mind a defenceless prey to the images, feelings, and impulses which for the moment invade it. The lustre, on the other hand, will, to use the language of M. Binet, strengthen the intensity of these mental images.[283] There is no reason why these effects, which presuppose no sort of intellectual activity, should not take place in animals as well as in man. In the case of the peacock, therefore, the idea “male” will imprint itself with greater and more efficacy upon the mind of the hen when she is exposed on every side to the twinkling eyes on the expanded tail of her mate.
Even in the very cases that have been regarded as the most incontestable proofs of a taste for the beautiful, the influence on the hen can thus be explained as one which directly, i.e. without any æsthetic mediation, has served the interests of pairing. But it may still be asked, Whence the need of strengthening and intensifying the emotions in the female, which must already have been awakened by the mere presence of the male? This objection, however, is easily met by a reference to the psychological aspects of pairing. Throughout the animal kingdom the males have to conquer a resistance from the side of the females. This instinctive coyness, the importance of which for the maintenance of the species is incalculable and self-evident, constitutes by itself a sufficient cause for the supposed æsthetic characters and activities of the males.[284] It has made it necessary for them to have a stately carriage, which makes them bigger and more pompous than ever, and to display their bodies in flying tricks, or dances and antics,—in a word, to emphasise their sex as energetically as possible by colours and tunes and movements. And this necessity has, by means of a natural selection, called forth a colouring which is not only easily recognisable from a distance, but which also forces itself on the senses when seen at close quarters.
The æsthetic judgment of the hen forms the pivot of the whole Darwinian theory. When it has been eliminated, it is therefore quite superfluous to controvert the assertion, which Darwin himself would not positively defend, that the performances of the males have originated in an artistic endeavour.[285] Once granted an instinctive coyness in the hen, which must be overcome by every possible means, one can easily understand that secondary sexual characters and activities would gradually appear in the males. The expressive movements in which they seek to relieve their nervous tension afford a material out of which natural selection will shape, as the most effective means of incitation, the various forms of display, or dance, or song. As is well known, Wallace,[286] Spencer,[287] and Hudson[288] have even contended that emotional pressure, or, as they put it, overflowing vitality, by itself constitutes a sufficient explanation of the “Balz.” In the above treatment of the question, which in its main points accords with the conclusive researches of Professor Groos, we have endeavoured to show that the various sorts of display never could have reached their special and differentiated forms if it had not been for the necessity of overcoming female coyness. But, on the other hand, this necessity could never have created out of nothing all these complicated activities. It is difficult—perhaps even impossible—to make any general assertions about the relative importance of these two explanations.[289] The only point which it is necessary to bring out in this connection is that a sort of nuptial performance would have appeared amongst the males even independently of its influence upon the hen. The hygienic need of an outburst is one reason, and a very strong one indeed, for such motor manifestations. But it seems also as if their purpose ought not to be restricted to this cathartic effect. The “lek” of the wood-birds tends no doubt to increase nervous force at the same time as it relieves the tension. M. Espinas thinks that the males, when collecting in great numbers during the pairing season, are led by an unconscious desire to stimulate their feelings by the view of other equally excited fellow-males.[290] Such an unconscious desire of enhancing nervous force probably lies also behind the inclination for brilliant objects and the trifling with them in the bowers.[291] That a sort of artificial stimulation really is necessary may perhaps be concluded from Brehm’s general remark about the sexual life of birds: “The pairing is often repeated, and still more often ineffectually attempted.”[292] In a private communication to Groos, Professor Ziegler, the eminent zoologist, also refers to the increased nervous activity which is necessary for pairing, and the passionate preludes which precede it in so many animals.[293]