SEXUAL SELECTION 419 



posed to the same conditions. Mr. Wallace believes that 

 the difference between the sexes is due not so much to the 

 males having been modified, as to the females having, in 

 all or almost all cases, acquired dull colors for the sake 

 of protection. It seems to me, on the contrary, far more 

 probable that it is the males which have been chiefly modi- 

 fied through sexual selection, the females having been com- 

 paratively little changed. "We can thus understand how it 

 is that the females of allied species generally resemble 

 one another so much more closely than do the males. They 

 thus show us approximately the primordial coloring of the 

 parent-species of the group to which they belong. They 

 have, however, almost always been somewhat modified by 

 the transfer to them of some of the successive variations, 

 through the accumulation of which the males were rendered 

 beautiful. But I do not wish to deny that the females alone 

 of some species may have been specially modified for pro- 

 tection. In most cases the males and females of distinct 

 species will have been exposed during their prolonged larval 

 state to different conditions, and may have been thus 

 affected; though with the males any slight change of color 

 thus caused will generally have been masked by the brilliant 

 tints gained through sexual selection. When we treat of 

 Birds, I shall have to discuss the whole question, as to how 

 far the differences in color between the sexes are due to the 

 males having been modified through sexual selection for 

 ornamental purposes, or to the females having been modi- 

 fied through natural selection for the sake of protection; 

 so that I will here say but little on the subject. 



In all the cases in which the more common form of equal 

 inheritance by both sexes has prevailed, the selection of 

 bright-colored males would tend to make the females bright- 

 colored, and the selection of dull -colored females would 

 tend to make the males dull. If both processes were carried 

 on simultaneously, they would tend to counteract each 

 other; and the final result would depend on whether a 

 greater number of females from being well protected by 



