BIRDS. 539 



have been masked by the brilliant colors gained through 

 sexual selection; but not so with the females. Each 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 difficult, 

 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 varia- 

 tions which were from the first limited in their transmission 

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

 the bright tints of the male would be deteriorated or de- 

 stroyed. Whether the females alone of many species have 

 been thus specially modified is at present very doubtful. 

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

 for the admission would remove some difficulties. Any 

 variations which were of no service to the female as a 

 protection would be at once obliterated, instead of being 

 lost simply by not being selected, or from free intercross- 

 ing, or from being eliminated when transferred to the male 

 and in any way injurious to him. Thus the plumage of the 

 female would be kept constant in character. It would also 

 be a relief if we could admit that the obscure tints of both 

 sexes of many birds had been acquired and preserved for the 

 sake of protection, for example, of the hedge- warbler or kitty- 

 wren (Accentor modular is and Troglodytes vulgaris), with 

 respect to which we have no sufficient evidence of the 

 action of sexual selection. We ought, however, to be cau- 

 tious in concluding that colors which appear to us dull 

 are not attractive to the females of certain species; we 

 should bear in mind such cases as that of the common 

 house-sparrow, in which the male differs much from the 

 female, but does not exhibit any bright tints. No one 



