Chap. XVI. THE YOUNG LIKE THE ADULT FEMALES. 197 
action would generally have been masked by the 
brilliant colours gained through sexual selection; but 
not so with the females. Each of the endless diver- 
sities in plumage, w^hich we see in our domesticated 
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 colour, thus induced, uniform in character. 
No one doubts that both sexes of many birds have 
had their colours adapted for the sake of protection; 
and it is possible that the females alone of some species 
may have been thus modified. Although it would be a 
difficult, perhaps an impossible process, as shewn in the 
last chapter, to convert through selection one form of 
transmission into another, there would not be the least 
difficulty in adapting the colours of the female, inde- 
pendently of those of the male, to surrounding objects, 
through the accumulation of variations 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 destroyed. 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 varia- 
tions which were of no service to the female as a protec- 
tion would be at once obliterated, instead of being lost 
simply by not being selected, or from free intercrossing, 
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 
