610 THE DESCENT OF MAN 



early youth, would generally have been transmitted to 

 both sexes. 



In addition to the effects of the partial transference of 

 characters from the males to the females, some of the differ- 

 ences between the females of closely allied species may be 

 attributed to the direct or definite action of the conditions 

 of life." With the males any such action would generally 

 have been masked by the brilliant colors gained through 

 sexual selection; but not so with the females. Bach of the 

 endless diversities in plumage which we see in our domes- 

 ticated birds is, of course, the result of some definite cause ; 

 and under natural and more uniform conditions some one 

 tint, assuming that it was in no way injurious, would almost 

 certainly sooner or later prevail. The free intercrossing of 

 the many individuals belonging to the same species would 

 ultimately tend to make any change of color, thus induced, 

 uniform in character. 



No one doubts that both sexes of many birds have had 

 their colors adapted for the sake of protection; and it is 

 possible that the females alone of some species may have 

 been modified for this end. Although it would be a diffi- 

 cult, perhaps an impossible process, as shown in the last 

 chapter, to convert one form of transmission into another 

 through selection, there would not be the least difficulty in 

 adapting the colors of the female, independently of those of 

 the male, to surrounding objects, through the accumulation 

 of variations which were from the first limited in their trans- 

 mission to the female sex. If the variations were not thus 

 limited, the bright tints of the male would be deteriorated 

 or destroyed. Whether the females alone of many species 

 have been thus specially modified is at present very doubt- 

 ful. I wish I could follow Mr. Wallace to the full extent; 

 for the admission would remove some difficulties. Any vari- 

 ations which were of no service to the female as a protection 

 would be at once obliterated, instead of being lost simply 



" See, on this subject, chap, xxiii. in the "Tariation of Animals and Plants 

 under Domestication. " 



