The Descent of Man

manently in colour from the females, often become
more brilliant during the breedingseason.
This is likewise the case with a multitude
of fishes, the sexes of which are identical in
colour at all other seasons of the year. The
tench, roach, and perch may be given as instances.
The male salmon at this season is "marked
on the cheeks with orange-coloured stripes,
which give it the appearance of a Labrus, and
the body partakes of a golden orange tinge. The
females are dark in colour, and are commonly
called black-fish." (22. Yarrell, 'History of British
Fishes,' vol. ii. 1836, pp. 10, 12, 35.) An analogous
and even greater change takes place
with the Salmo eriox or bull trout; the males of
the char (S. umbla) are likewise at this season
rather brighter in colour than the females. (23.
W. Thompson, in 'Annals and Magazine of Natural
History,' vol. vi. 1841, p. 440.) The colours
of the pike (Esox reticulatus) of the United States,
especially of the male, become, during the
breeding-season, exceedingly intense, brilliant,