The Theory of Sexual Selection. 399 



difficulty of supposing so much similarity and con- 

 stancy of taste on the part of female animals as Mr. 

 Darwin's theory undoubtedly requires. Although we 

 know very little about the psychology of the lower 

 animals, we do observe in many cases that small 

 details of mental organization are often wonderfully 

 constant and uniform throughout all members of a 

 species, even where it is impossible to suggest any 

 utility as a cause. 



Again, as regards the objection that each bird finds 

 a mate under any circumstances, we have here an 

 obvious begging of the whole question. That every 

 feathered Jack should find a feathered Jill is perhaps 

 what we might have antecedently expected ; but when 

 we meet with innumerable instances of ornamental 

 plumes> melodious songs, and the rest, as so many 

 witnesses to a process of sexual selection having 

 always been in operation, it becomes irrational to ex- 

 clude such evidence on account of our antecedent 

 prepossessions. 



There remains the objection that the principles of 

 natural selection must necessarily swallow up those of 

 sexual selection. And this consideration, I doubt 

 not, lies at the root of all Mr. Wallace's opposition to 

 the supplementary theory of sexual selection. He is 

 self-consistent in refusing to entertain the evidence of 

 sexual selection, on the ground of his antecedent per- 

 suasion that in the great drama of evolution there is 

 no possible standing-ground for any other actor than 

 that which appears in the person of natural selection. 

 But here, again, we must refuse to allow any merely 

 antecedent presumption to blind our eyes to the 

 actual evidence of other agencies having co-operated 



