or has less power of escaping from such danger than the other; and it
does not appear that with fishes the sexes differ in these respects. As
far as there is any difference, the males, from being generally smaller
and from wandering more about, are exposed to greater danger than the
females; and yet, when the sexes differ, the males are almost always
the more conspicuously coloured. The ova are fertilised immediately
after being deposited; and when this process lasts for several days, as
in the case of the salmon (34. Yarrell, British Fishes, vol. ii. p.
11.), the female, during the whole time, is attended by the male. After
the ova are fertilised they are, in most cases, left unprotected by
both parents, so that the males and females, as far as oviposition is
concerned, are equally exposed to danger, and both are equally
important for the production of fertile ova; consequently the more or
less brightly-coloured individuals of either sex would be equally
liable to be destroyed or preserved, and both would have an equal
influence on the colours of their offspring.
Certain fishes, belonging to several families, make nests, and some of
them take care of their young when hatched. Both sexes of the bright
coloured Crenilabrus massa and melops work together in building their
nests with sea-weed, shells, etc. (35. According to the observations of
M. Gerbe; see Gunther s Record of Zoolog. Literature, 1865, p. 194.)
But the males of certain fishes do all the work, and afterwards take
exclusive charge of the young. This is the case with the dull-coloured
gobies (36. Cuvier, Regne Animal, vol. ii. 1829, p. 242.), in which
the sexes are not known to differ in colour, and likewise with the
sticklebacks (Gasterosteus), in which the males become brilliantly
coloured during the spawning season. The male of the smooth-tailed
stickleback (G. leiurus) performs the duties of a nurse with exemplary
care and vigilance during a long time, and is continually employed in
gently leading back the young to the nest, when they stray too far. He
courageously drives away all enemies including the females of his own
species. It would indeed be no small relief to the male, if the female,
after depositing her eggs, were immediately devoured by some enemy, for
he is forced incessantly to drive her from the nest. (37. See Mr.
Warington s most interesting description of the habits of the
Gasterosteus leiurus in Annals and Magazine of Nat. History, November
1855.)
The males of certain other fishes inhabiting South America and Ceylon,
373