The Descent of Man

forwards, with its end rounded and covered
with sharp spines; in the female "this crown is
altogether absent," but what its use may be to
the male is utterly unknown. (19. F. Buckland,
in 'Land and Water,' July 1868, p. 377, with a
figure. Many other cases could be added of
structures peculiar to the male, of which the
uses are not known.)
The structures as yet referred to are permanent
in the male after he has arrived at maturity; but
with some Blennies, and in another allied genus
(20. Dr. Gunther, 'Catalogue of Fishes,' vol.
iii. pp. 221 and 240.), a crest is developed on the
head of the male only during the breedingseason,
and the body at the same time becomes
more brightly-coloured. There can be little
doubt that this crest serves as a temporary
sexual ornament, for the female does not exhibit
a trace of it. In other species of the same
genus both sexes possess a crest, and in at least
one species neither sex is thus provided. In ma-