BRITISH WARBLERS 



the antics take in closely-related species, and the fact that 

 they may be scarcely perceptible in one variety, whereas in 

 another closely akin their very frequency and intensity compels 

 our attention, we find little enough support for the first 

 proposition in the lives of these particular species. This 

 view, however, has in a great measure been discarded, opinion 

 generally favouring the second proposition as being a more 

 reasonable interpretation, since conscious display is discarded 

 and replaced by a more mechanical process, which readily 

 comes under the sway of natural selection. Thus Professor 

 Groos in his "Play of Animals" develops a theory which is 

 accepted by many as a provisional hypothesis. I quote it as 

 summarised in his preface to the above work. " The disciple 

 of Weismann who cannot accept Spencer's explanation of 

 such phenomena must either cleave to Darwin's sexual 

 selection, as Weismann himself does, or seek a new principle. 

 Such a principle I believe I have found. It depends on two 

 closely related facts. As sexual impulse must have tremendous 

 power, it is for the interest of the preservation of the species 

 that its discharge should be rendered difficult. This result is 

 partly accomplished in the animal world by the necessity for 

 great and often long continued excitement as a prelude to the 

 act of pairing. This thought at once throws light on the 

 peculiar hereditary arts of courtship, especially on the indul- 

 gence in flying, dancing, or singing by a whole flock at once. 

 But the hindrance to the sexual function that is most effica- 

 cious, though hitherto unappreciated, is the instinctive coyness 

 of the female. This it is that necessitates all the arts of 

 courtship, and the probability is that seldom or never does 

 the female exert any choice. She is not awarder of the 

 prize, but rather a hunted creature. So, just as the beast of 

 prey has special instincts for finding his prey, the ardent male 

 must have special instincts for subduing feminine reluctance ; 

 and just as in the beast of prey the instinct of ravenous 

 pursuit is refined into the various arts of the chase, so from 

 such crude efforts at wooing that courtship has finally developed 



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