The Descent of Man

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. Cer-