268 THE TRIXCIPLES OF [Part II. 



selected the more attractive females, and the latter the 

 more attractive males. This process, however, though it- 

 might lead to the modification of both sexes, would not 

 make the one sex different from the other, unless indeed 

 their taste for the beautiful differed ; but this is a suppo- 

 sition 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 ornaments, which analogy 

 would lead us to attribute to the agency of sexual selec- 

 tion. In such cases it may be suggested with more 

 plausibility, that there has been a double or mutual pro- 

 cess 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 at- 

 tractive 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 trans- 

 mitted to the offspring 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 anothei 

 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 colored 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 colors, such as plain black or white. Obscure 



