THE PLAY OF ANIMALS. 237 



the ancestors of the peacocks, from the time when they 

 attained a certain assurance of existence, were constant- 

 ly in possession of surplus energy that favoured the 

 production of strong (and useless) feathers, it is yet in- 

 explicable how a still further development was attained, 

 such as Wallace indicates. That such hindrances should 

 arise before adaptation is out of the question, and it 

 seems hardly possible after it, without the aid of sexual 

 selection, for we see that success attained in the strug- 

 gle for life prevents Nature from further directing 

 the growing energies. The contest of males in which 

 the strongest have the advantage would then come 

 prominent forward as the only possible explanation. 

 Wallace, however, has but cursorily referred to this 

 principle and rightly, as I believe, for it is diffi- 

 cult to see how selection acting through the contests 

 of courtship could directly favor the development 

 of such peculiarities, since we can hardly suppose 

 that surplus energy would find its only expression in 

 them. 



Perhaps Wallace recognised this difficulty when he 

 wTote, " As all the evidence goes to show that, so far 

 as female birds exercise any choice, it is of the ^ most 

 vigorous, defiant, and mettlesome ' males, this form of 

 sexual selection will act in the same direction (as natu- 

 ral selection), and help to carry on the process of plume 

 development to its culmination." * 



With these words, however hypothetical their form, 

 Wallace overturns his whole argument, for if it is once 

 admitted that the female chooses the strongest male, 

 the chief point of the Darwinian theory is conceded. 

 Whether her preference is for strength and courage 



* Ibid., p. 293. 



