Chap. XVL] THE YOUNG LIKE THE ADULT FEMALES. 185 



the females differ much. In the Bourbon species the 

 female appears to have partially retained an immature 

 condition of plumage, for at first sight she " might be 

 taken for the young of the Mauritian species." These 

 differences majP be compared with those which occur, 

 independently of selection by man, and which we cannot 

 explain, in certain sub-breeds of the game-fowl, in which 

 the females are very different, while the males can hardly 

 be distinguished. 9 



As I account so largely by sexual selection for the dif 

 ferences between the males of allied species, how can the 

 differences between the females be accounted for in all 

 ordinary cases ? We need not here consider the species 

 which belong to distinct genera ; for, with these, adapta- 

 tion to different habits of life, and other agencies, will 

 have come into play. In regard to the differences be- 

 tween the females within the same genus, it appears to 

 me almost certain, after looking through various large 

 groups, that the chief agent has been the transference, in 

 a greater or less degree, to the female of the characters 

 acquired by the males through sexual selection. In the 

 several British finches, the two sexes differ either very 

 slightly or considerably ; and if we compare the females 

 of the greenfinch, chaffinch, goldfinch, bullfinch, crossbill, 

 sparrow, etc., we shall see that they differ from each othei 

 chiefly in the points in which they partially resemble t^eii 

 respective males ; and the colors of the males may safely 

 be attributed to sexual selection. With many gallina- 

 ceous species the sexes differ to an extreme degree, as 

 with the peacock, pheasant, and fowl, while with other 

 species there has been a partial or even complete transfer- 

 ence of character from the male to the female. The fe- 

 males of the several species of Polyplectron exhibit in a 

 dim condition, and chiefly on the tail, the splendid ocelli 



9 'Variation of Animals, etc., under Domestication,' vol. i. p. 251. 



