SEXUAL SELECTION 607 



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 may be 

 compared with those inexplicable ones which occur inde- 

 pendently of man's selection in certain sub-breeds of the 

 game fowl, in which the females are very different, while 

 the males can hardly be distinguished.' 



As I account so largely by sexual selection for the differ- 

 ences between the males of allied species, how can the dif- 

 ferences 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, adaptation to different 

 habits of life, and other agencies, will have come into play. 

 In regard to the differences between 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 greater or less transference to the female of the charac- 

 ters 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, chaf&nch, goldfinch, bullfinch, crossbill, 

 sparrow, etc., we shall see that they differ from one another 

 chiefly in the points in which they partially resemble their 

 respective males; and the colors of the males may safely 

 be attributed to sexual selection. With many gallinaceous 

 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 transference of charac- 

 ter from the male to the female. The females of the several 

 species of Polyplectron exhibit in a dim condition, and 

 chiefly on the tail, the splendid ocelli of their males. The 

 female partridge differs from the male only in the red mark 

 on her breast being smaller; and the female wild turkey 

 only in her colors being much duller. In the guinea-fowl 



' "Variation of Animals," etc., i. p. 251. 



