The Descent of Man 2 i 



the head and tail, either single or double, pointed or clubbed.' 

 Mr. Wallace adds, 'Now, if all these beautiful and varied 

 ornaments can be produced and rendered constant in each 

 species by some unknown cause quite independent of sexual 

 selection, why cannot the same cause produce the colours 

 and many of the ornaments of perfect insects ? ' — we may 

 also add, the colours and ornaments of all other animals, 

 including birds ? 



There is, however, another reason which induces Mr. 

 Darwin to accept sexual selection; and it is probably this 

 which, in his mind, mainly gives importance to the facts 

 mentioned as to the plumage and motions of birds. He says 

 of 'display': 'It is incredible that all this display should be pur- 

 poseless ' (vol. ii. p. 399) ; and again (vol. ii. p. 93), he declares 

 that any one who denies that the female Argus pheasant can 

 appreciate the refined beauty of the plumage of her mate ' will 

 be compelled to admit that the extraordinary attitudes as- 

 sumed by the male during the act of courtship, by which the 

 wonderful beauty of his plumage is fully displayed, are pur- 

 poseless ; and this is a conclusion which I for one will never 

 admit.' It seems then that it is this imaginary necessity of 

 attributing purposelessness to acts, which determines Mr. 

 Darwin to attribute that peculiar and special purpose to 

 birds' actions which he does attribute to them. But surely 

 this difficulty is a mere chimsera. Let it be granted that the 

 female does not select ; yet the display of the male may be 

 useful in supplying the necessary degree of stimulation to 

 her nervous system, and to that of the male. Pleasurable 

 sensation, perhaps very keen in intensity, may thence result 

 to both. There would be no difficulty in suggesting yet 

 other purposes if we were to ascend into higher speculative 

 regions. Mr. Darwin has given us in one place a very 

 remarkable passage ; he says : — 



' With respect to female birds feeling a preference for particular 



