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 obscure colours, or a
greater number of males by being brightly-coloured and thus finding
partners, succeeded in leaving more numerous offspring.
In order to account for the frequent transmission of characters to one
sex alone, Mr. Wallace expresses his belief that the more common form
of equal inheritance by both sexes can be changed through natural
selection into inheritance by one sex alone, but in favour of this view
I can discover no evidence. We know from what occurs under
domestication that new characters often appear, which from the first
are transmitted to one sex alone; and by the selection of such
variations there would not be the slightest difficulty in giving bright
colours to the males alone, and at the same time or subsequently, dull
colours to the females alone. In this manner the females of some
butterflies and moths have, it is probable, been rendered inconspicuous
for the sake of protection, and widely different from their males.
I am, however, unwilling without distinct evidence to admit that two
complex processes of selection, each requiring the transference of new
characters to one sex alone, have been carried on with a multitude of
species, that the males have been rendered more brilliant by beating
their rivals, and the females more dull-coloured by having escaped from
their enemies. The male, for instance, of the common brimstone
butterfly (Gonepteryx), is of a far more intense yellow than the
female, though she is equally conspicuous; and it does not seem
probable that she specially acquired her pale tints as a protection,
though it is probable that the male acquired his bright colours as a
sexual attraction. The female of Anthocharis cardamines does not
possess the beautiful orange wing-tips of the male; consequently she
closely resembles the white butterflies (Pieris) so common in our
gardens; but we have no evidence that this resemblance is beneficial to
her. As, on the other hand, she resembles both sexes of several other
species of the genus inhabiting various quarters of the world, it is
probable that she has simply retained to a large extent her primordial
colours.
Finally, as we have seen, various considerations lead to the conclusion
that with the greater number of brilliantly-coloured Lepidoptera it is
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