many of the carnivorous Cyprinidae in India are ornamented with bright
longitudinal lines of various tints. (31. Indian Cyprinidae, by Mr.
M Clelland, Asiatic Researches, vol. xix. part ii. 1839, p. 230.) Mr.
M Clelland, in describing these fishes, goes so far as to suppose that
the peculiar brilliancy of their colours serves as a better mark for
king-fishers, terns, and other birds which are destined to keep the
number of these fishes in check ; but at the present day few
naturalists will admit that any animal has been made conspicuous as an
aid to its own destruction. It is possible that certain fishes may have
been rendered conspicuous in order to warn birds and beasts of prey
that they were unpalatable, as explained when treating of caterpillars;
but it is not, I believe, known that any fish, at least any fresh-water
fish, is rejected from being distasteful to fish-devouring animals. On
the whole, the most probable view in regard to the fishes, of which
both sexes are brilliantly coloured, is that their colours were
acquired by the males as a sexual ornament, and were transferred
equally, or nearly so, to the other sex.
We have now to consider whether, when the male differs in a marked
manner from the female in colour or in other ornaments, he alone has
been modified, the variations being inherited by his male offspring
alone; or whether the female has been specially modified and rendered
inconspicuous for the sake of protection, such modifications being
inherited only by the females. It is impossible to doubt that colour
has been gained by many fishes as a protection: no one can examine the
speckled upper surface of a flounder, and overlook its resemblance to
the sandy bed of the sea on which it lives. Certain fishes, moreover,
can through the action of the nervous system change their colours in
adaptation to surrounding objects, and that within a short time. (32.
G. Pouchet, L Institut. Nov. 1, 1871, p. 134.) One of the most
striking instances ever recorded of an animal being protected by its
colour (as far as it can be judged of in preserved specimens), as well
as by its form, is that given by Dr. Gunther (33. Proc. Zoolog. Soc.
1865, p. 327, pl. xiv. and xv.) of a pipe-fish, which, with its reddish
streaming filaments, is hardly distinguishable from the sea-weed to
which it clings with its prehensile tail. But the question now under
consideration is whether the females alone have been modified for this
object. We can see that one sex will not be modified through natural
selection for the sake of protection more than the other, supposing
both to vary, unless one sex is exposed for a longer period to danger,
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