The Descent of Man

work; and from information kindly given me
by Mr. Hancock, it seems extremely doubtful
whether these colours usually serve as a protection.
With some species this may be the case, as
with one kind which lives on the green leaves
of algae, and is itself bright-green. But many
brightly-coloured, white, or otherwise conspicuous
species, do not seek concealment; whilst
again some equally conspicuous species, as
well as other dull-coloured kinds live under
stones and in dark recesses. So that with these
nudibranch molluscs, colour apparently does
not stand in any close relation to the nature of
the places which they inhabit.
These naked sea-slugs are hermaphrodites, yet
they pair together, as do land-snails, many of
which have extremely pretty shells. It is conceivable
that two hermaphrodites, attracted by
each other's greater beauty, might unite and
leave offspring which would inherit their parents'
greater beauty. But with such lowly-