publishing an account of this species in The Fishes of Zanzibar, by
Col. Playfair, 1866, p. 137, has re-examined the specimens, and has
given me the above information.), for the female is much more
vividly-coloured and spotted than the male, and she alone has a
marsupial sack and hatches the eggs; so that the female of Solenostoma
differs from all the other Lophobranchii in this latter respect, and
from almost all other fishes, in being more brightly-coloured than the
male. It is improbable that this remarkable double inversion of
character in the female should be an accidental coincidence. As the
males of several fishes, which take exclusive charge of the eggs and
young, are more brightly coloured than the females, and as here the
female Solenostoma takes the same charge and is brighter than the male,
it might be argued that the conspicuous colours of that sex which is
the more important of the two for the welfare of the offspring, must be
in some manner protective. But from the large number of fishes, of
which the males are either permanently or periodically brighter than
the females, but whose life is not at all more important for the
welfare of the species than that of the female, this view can hardly be
maintained. When we treat of birds we shall meet with analogous cases,
where there has been a complete inversion of the usual attributes of
the two sexes, and we shall then give what appears to be the probable
explanation, namely, that the males have selected the more attractive
females, instead of the latter having selected, in accordance with the
usual rule throughout the animal kingdom, the more attractive males.
On the whole we may conclude, that with most fishes, in which the sexes
differ in colour or in other ornamental characters, the males
originally varied, with their variations transmitted to the same sex,
and accumulated through sexual selection by attracting or exciting the
females. In many cases, however, such characters have been transferred,
either partially or completely, to the females. In other cases, again,
both sexes have been coloured alike for the sake of protection; but in
no instance does it appear that the female alone has had her colours or
other characters specially modified for this latter purpose.
The last point which need be noticed is that fishes are known to make
various noises, some of which are described as being musical. Dr.
Dufosse, who has especially attended to this subject, says that the
sounds are voluntarily produced in several ways by different fishes: by
the friction of the pharyngeal bones by the vibration of certain
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