The Descent of Man

ightest, to conceive the admixture of brilliant
colours with which it, in other respects so illfavoured,
is at that time adorned." Both sexes of
the Labrus mixtus, although very different in
colour, are beautiful; the male being orange
with bright blue stripes, and the female bright
red with some black spots on the back.
[Fig. 30. Xiphophorus Hellerii. Upper figure,
male; lower figure, female.]
In the very distinct family of the Cyprinodontidae—inhabitants
of the fresh waters of foreign
lands—the sexes sometimes differ much in various
characters. In the male of the Mollienesia
petenensis (16. With respect to this and the following
species I am indebted to Dr. Gunther
for information: see also his paper on the 'Fishes
of Central America,' in 'Transact. Zoological
Soc.' vol. vi. 1868, p. 485.), the dorsal fin is greatly
developed and is marked with a row of large,
round, ocellated, bright-coloured spots;
whilst the same fin in the female is smaller, of a