stomach, which, however, becomes quite black in the fourth or fifth
year. There is also a strongly-marked difference in colour between the
sexes of Mycetes seniculus and Cebus capucinus; the young of the
former, and I believe of the latter species, resembling the females.
With Pithecia leucocephala the young likewise resemble the females,
which are brownish-black above and light rusty-red beneath, the adult
males being black. The ruff of hair round the face of Ateles marginatus
is tinted yellow in the male and white in the female. Turning to the
Old World, the males of Hylobates hoolock are always black, with the
exception of a white band over the brows; the females vary from
whity-brown to a dark tint mixed with black, but are never wholly
black. (30. On Mycetes, Rengger, ibid. s. 14; and Brehm, Thierleben,
B. i. s. 96, 107. On Ateles Desmarest, Mammalogie, p. 75. On
Hylobates, Blyth, Land and Water, 1867, p. 135. On the Semnopithecus,
S. Muller, Zoog. Indischen Archipel. tab. x.) In the beautiful
Cercopithecus diana, the head of the adult male is of an intense black,
whilst that of the female is dark grey; in the former the fur between
the thighs is of an elegant fawn-colour, in the latter it is paler. In
the beautiful and curious moustache monkey (Cercopithecus cephus) the
only difference between the sexes is that the tail of the male is
chestnut and that of the female grey; but Mr. Bartlett informs me that
all the hues become more pronounced in the male when adult, whilst in
the female they remain as they were during youth. According to the
coloured figures given by Solomon Muller, the male of Semnopithecus
chrysomelas is nearly black, the female being pale brown. In the
Cercopithecus cynosurus and griseo-viridis one part of the body, which
is confined to the male sex, is of the most brilliant blue or green,
and contrasts strikingly with the naked skin on the hinder part of the
body, which is vivid red.
[Fig. 69. Head of male Mandrill (from Gervais, Hist. Nat. des
Mammiferes ).]
Lastly, in the baboon family, the adult male of Cynocephalus hamadryas
differs from the female not only by his immense mane, but slightly in
the colour of the hair and of the naked callosities. In the drill (C.
leucophaeus) the females and young are much paler-coloured, with less
green, than the adult males. No other member in the whole class of
mammals is coloured in so extraordinary a manner as the adult male
mandrill (C. mormon). The face at this age becomes of a fine blue, with
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