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