this fact in the Zoological Gardens; and many cases may be seen in the
coloured plates in Geoffroy St.-Hilaire and F. Cuvier, Histoire Nat.
des Mammiferes, tom. i. 1824.), being often pure white, sometimes
bright yellow, or reddish. The whole face of the South American
Brachyurus calvus is of a glowing scarlet hue ; but this colour does
not appear until the animal is nearly mature. (46. Bates, The
Naturalist on the Amazons, 1863, vol. ii. p. 310.) The naked skin of
the face differs wonderfully in colour in the various species. It is
often brown or flesh-colour, with parts perfectly white, and often as
black as that of the most sooty negro. In the Brachyurus the scarlet
tint is brighter than that of the most blushing Caucasian damsel. It is
sometimes more distinctly orange than in any Mongolian, and in several
species it is blue, passing into violet or grey. In all the species
known to Mr. Bartlett, in which the adults of both sexes have
strongly-coloured faces, the colours are dull or absent during early
youth. This likewise holds good with the mandrill and Rhesus, in which
the face and the posterior parts of the body are brilliantly coloured
in one sex alone. In these latter cases we have reason to believe that
the colours were acquired through sexual selection; and we are
naturally led to extend the same view to the foregoing species, though
both sexes when adult have their faces coloured in the same manner.
[Fig. 78. Cercopithecus diana (from Brehm).]
Although many kinds of monkeys are far from beautiful according to our
taste, other species are universally admired for their elegant
appearance and bright colours. The Semnopithecus nemaeus, though
peculiarly coloured, is described as extremely pretty; the
orange-tinted face is surrounded by long whiskers of glossy whiteness,
with a line of chestnut-red over the eyebrows; the fur on the back is
of a delicate grey, with a square patch on the loins, the tail and the
fore-arms being of a pure white; a gorget of chestnut surmounts the
chest; the thighs are black, with the legs chestnut-red. I will mention
only two other monkeys for their beauty; and I have selected these as
presenting slight sexual differences in colour, which renders it in
some degree probable that both sexes owe their elegant appearance to
sexual selection. In the moustache-monkey (Cercopithecus cephus) the
general colour of the fur is mottled-greenish with the throat white; in
the male the end of the tail is chestnut, but the face is the most
ornamented part, the skin being chiefly bluish-grey, shading into a
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