404 
SEXUAL SELECTION. 
Part IX', 
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 haying 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 would 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 
