would sooner or later be destroyed. But the tendency in the males to
continue for an indefinite period transmitting to their female
offspring their own brightness, would have to be eliminated by a change
in the form of inheritance; and this, as shewn by our previous
illustration, would be extremely difficult. The more probable result of
the long-continued destruction of the more brightly-coloured females,
supposing the equal form of transmission to prevail, would be the
lessening or annihilation of the bright colours of the males, owing to
their continual crossing with the duller females. It would be tedious
to follow out all the other possible results; but I may remind the
reader that if sexually-limited variations in brightness occurred in
the females, even if they were not in the least injurious to them and
consequently were not eliminated, yet they would not be favoured or
selected, for the male usually accepts any female, and does not select
the more attractive individuals; consequently these variations would be
liable to be lost, and would have little influence on the character of
the race; and this will aid in accounting for the females being
commonly duller-coloured than the males.
In the eighth chapter instances were given, to which many might here be
added, of variations occurring at various ages, and inherited at the
corresponding age. It was also shewn that variations which occur late
in life are commonly transmitted to the same sex in which they first
appear; whilst variations occurring early in life are apt to be
transmitted to both sexes; not that all the cases of sexually-limited
transmission can thus be accounted for. It was further shewn that if a
male bird varied by becoming brighter whilst young, such variations
would be of no service until the age for reproduction had arrived, and
there was competition between rival males. But in the case of birds
living on the ground and commonly in need of the protection of dull
colours, bright tints would be far more dangerous to the young and
inexperienced than to the adult males. Consequently the males which
varied in brightness whilst young would suffer much destruction and be
eliminated through natural selection; on the other hand, the males
which varied in this manner when nearly mature, notwithstanding that
they were exposed to some additional danger, might survive, and from
being favoured through sexual selection, would procreate their kind. As
a relation often exists between the period of variation and the form of
transmission, if the bright-coloured young males were destroyed and the
mature ones were successful in their courtship, the males alone would
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