The Descent of Man

and iridescent. (24. 'The American Agriculturalist,'
1868, p. 100.) Another striking instance out
of many is afforded by the male stickleback
(Gasterosteus leiurus), which is described by
Mr. Warington (25. 'Annals and Mag. of Nat.
Hist.' Oct. 1852.), as being then "beautiful beyond
description." The back and eyes of the
female are simply brown, and the belly white.
The eyes of the male, on the other hand, are "of
the most splendid green, having a metallic lustre
like the green feathers of some hummingbirds.
The throat and belly are of a bright crimson,
the back of an ashy-green, and the whole
fish appears as though it were somewhat translucent
and glowed with an internal incandescence."
After the breeding season these colours
all change, the throat and belly become of a
paler red, the back more green, and the glowing
tints subside.
With respect to the courtship of fishes, other
cases have been observed since the first edition