The Descent of Man

tain 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, or has less power of escaping
from such danger than the other; and it does
not appear that with fishes the sexes differ in