404 SEXUAL SELECTION. Part II. 



that the less brilliant colours of the female have been 

 specially gained in all or almost all cases for the sake 

 of protection. On the contrary it seems to me more 

 probable that the males alone, in the large majority of 

 cases, have acquired their bright colours through sexual 

 selection, the females having been but little modified. 

 Consequently the females of distinct but allied species 

 ought to resemble each other much more closely than 

 do the males of the same species ; and this is the general 

 rule. The females thus approximately show us the pri- 

 mordial colouring of the parent-species of the group to 

 which they belong. They have, however, almost always 

 been modified to a certain extent by some of the succes- 

 sive steps of variation, through the accumulation of 

 which the males were rendered beautiful, having been 

 transferred to them. The males and females of allied 

 though distinct species will also generally have been 

 exposed during their prolonged larval state to different 

 conditions, and may have been thus indirectly affected ; 

 though with the males any slight change of colour thus 

 caused will often have been completely masked by the 

 brilliant tints gained through sexual selection. When 

 we treat of Birds, I shall have to discuss the whole 

 question whether the differences in colour between the 

 males and females have been in part specially gained 

 by the latter as a protection ; so that I will here only 

 give unavoidable details. 



In all cases when the more common form of equal 

 inheritance by both sexes has prevailed, the selection of 

 bright-coloured males would tend to make the females 

 bright-coloured ; and the selection of dull-coloured fe- 

 males wmdd tend to make the males dull. If both pro- 

 cesses were carried on simultaneously, they would tend 

 to neutralise each other. As far as I can see, it would 

 be extremely difficult to change through selection the 



