Darwin's Theory of Sexual Selection 209 
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. 
“Lastly, in the baboon family, the adult male of Cyno- 
cephalus hamadryas differs from the female not only by his 
immense mane, but slightly in the color of the hair and of 
the naked callosities. In the drill(C. leucopheus) the females 
and young are much paler-colored, with less green, than the 
adult males. No other member in the whole class of mam- 
mals is colored in so extraordinary a manner as the adult 
male mandrill (C. mormon). The face at this age becomes 
of a fine blue, with the ridge and tip of the nose of the most 
brilliant red. According to some authors, the face is also 
marked with whitish stripes, and is shaded in parts with 
black, but the colors appear to be variable. On the fore- 
head there is a crest of hair, and on the chin a yellow beard. 
‘Toutes les parties supérieures de leurs cuisses et le grand 
espace nu de leurs fesses sont également colorés du rouge le 
plus vif, avec un mélange de bleu qui ne manque réellement 
pas d’élégance.’ When the animal is excited all the naked 
parts become much more vividly tinted.” 
Darwin sums up the evidence in regard to the differences 
in color between the male and female in the following 
statement :— 
“T have now given all the cases known to me of a differ- 
ence in color between the sexes of mammals. Some of 
these may be the result of variations confined to one sex 
and transmitted to the same sex, without any good being 
gained, and therefore without the aid of selection. We 
have instances of this with our domesticated animals, as in 
the males of certain cats being rusty-red, whilst the females 
are tortoise-shell colored. Analogous cases occur in nature: 
Mr. Bartlett has seen many black varieties of the jaguar, 
leopard, vulpine phalanger, and wombat; and he is certain 
that all or nearly all these animals, were males. On the 
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