310 
SEXUAL SELECTION : MAMMALS. 
Part II. 
until the animal is nearly matiire.^^ 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 w^hich 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 Khesus, in which the face and the posterior 
parts of the body are brilliantly coloured in one sex 
alone. In these latter cases we have every 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. 
Although, according to our taste, many kinds of 
monkeys are far from beautiful, other species are uni- 
versally admired for their elegant appearance and 
bright colours. The Semnopitheeus nemmus, though 
peculiarly coloured, is described as extremely pretty ; 
the orange-tinted face is surrounded by long whiskers 
of glossy whiteness, with a line of chesnut-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 
all of a pure white ; a gorget of chesnut surmounts the 
chest ; the hind thighs are black, with the legs chesnut- 
red. I will mention only two other monkeys on account 
of their beauty ; and I have selected these as they pre- 
sent slight sexual differences in colour, which renders it 
Bates, ‘ The Naturalist on the Amazons/ 1863, vol. ii. p. 310. 
