Chap. VIII. SEXUAL SELECTION. 277 



would not make the one sex different from the other, 

 unless indeed their taste for the beautiful differed; but 

 this is a supposition too improbable in the case of any 

 animal, excepting man, to be worth considering. There 

 are, however, many animals, in which the sexes resemble 

 each other, both being furnished with the same orna- 

 ments, which analogy would lead us to attribute to the 

 agency of sexual selection. In such cases it may be 

 suggested with more plausibility, that there has been a 

 double or mutual process of sexual selection ; the more 

 vigorous and precocious females having selected the 

 more attractive and vigorous males, the latter having 

 rejected all except the more attractive females. But 

 from what we know of the habits of animals, this view 

 is hardly probable, the male being generally eager to 

 pair with any female. It is more probable that the 

 ornaments common to both sexes were acquired by one 

 sex, generally the male, and then transmitted to the off- 

 spring of both sexes. If, indeed, during a lengthened 

 period the males of any species were greatly to exceed 

 the females in number, and then during another 

 lengthened period under different conditions the reverse 

 were to occur, a double, but not simultaneous, process 

 of sexual selection might easily be carried on, by which 

 the two sexes might be rendered widely different. 



We shall hereafter see that many animals exist, of 

 which neither sex is brilliantly coloured or provided 

 with special ornaments, and yet the members of both 

 sexes or of one alone have probably been modified 

 through sexual selection. The absence of bright tints 

 or other ornaments may be the result of variations of 

 the right kind never having occurred, or of the animals 

 themselves preferring simple colours, such as plain black 

 or white. Obscure colours have often been acquired 

 through natural selection for the sake of protection, and 



