The Descent of Man

sometimes differ considerably in colour, and
they present, as we have already seen, other
remarkable sexual differences. Thus the male of
the Otaria nigrescens of the southern hemisphere
is of a rich brown shade above; whilst the
female, who acquires her adult tints earlier in
life than the male, is dark-grey above, the
young of both sexes being of a deep chocolate
colour. The male of the northern Phoca groenlandica
is tawny grey, with a curious saddleshaped
dark mark on the back; the female is
much smaller, and has a very different appearance,
being "dull white or yellowish strawcolour,
with a tawny hue on the back"; the
young at first are pure white, and can "hardly
be distinguished among the icy hummocks and
snow, their colour thus acting as a protection."
(23. Dr. Murie on the Otaria, 'Proceedings Zoological
Society,' 1869, p. 108. Mr. R. Brown on
the P. groenlandica, ibid. 1868, p. 417. See also
on the colours of seals, Desmarest, ibid. pp. 243,
249.)