SEXUAL SELECTION. 201 



pairing must be left to mere chance, and this does not 

 appear probable " (1. c. p. 317). But he has just said 

 " The males sometimes fight together in rivalry, and many 

 may be seen pursuing or crowding round the same 

 female ;" while in the case of the silk-moths, " the 

 females appear not to evince the least choice in regard 

 to their partners." Surely the plain inference from all 

 this is, that males fight and struggle for the almost 

 passive female; and that the most vigorous and energetic, 

 the strongest- winged or the most persevering, wins her. 

 How can there be chance in this ? Natural selection 

 would here act, as in birds, in perpetuating the strongest 

 and most vigorous males ; and as these would usually be 

 the more highly coloured of their race, the same results 

 would be produced as regards the intensification and 

 variation of colour in the one case as in the other. 



Let us now see how these principles will apply to 

 some of the cases adduced by Mr. Darwin in support 

 of his theory of conscious sexual selection. 



In Descent of Man, 2nd ed., pp. 307-316, we find an 

 elaborate account of the various modes of colouring of 

 butterflies and moths, proving that the coloured parts 

 are always more or less displayed, and that they have 

 some evident relation to an observer. Mr. Darwin then 

 says : " From the several foregoing facts it is impos- 

 sible to admit that the brilliant colours of butterflies, 

 and of some few moths, have commonly been acquired 

 for the sake of protection. We have seen that their 

 colours and elegant patterns are arranged and exhibited 

 as if for display. Hence I am led to believe that the 

 females prefer or are most excited by the more brilliant 

 males ; for on any other supposition the males would, as 



