The Descent of Man

as the greater prominence of the superciliary
ridge, the males of certain monkeys differ from
the females (8. As in Macacus cynomolgus
(Desmarest, 'Mammalogie,' p. 65), and in Hylobates
agilis (Geoffroy St.-Hilaire and F. Cuvier,
'Histoire Nat. des Mammiferes,' 1824, tom. i. p.
2).), and agree in this respect with mankind. In
the gorilla and certain other monkeys, the cranium
of the adult male presents a stronglymarked
sagittal crest, which is absent in the
female; and Ecker found a trace of a similar
difference between the two sexes in the Australians.
(9. 'Anthropological Review,' Oct. 1868, p.
353.) With monkeys when there is any difference
in the voice, that of the male is the more powerful.
We have seen that certain male monkeys
have a well- developed beard, which is
quite deficient, or much less developed in the
female. No instance is known of the beard,
whiskers, or moustache being larger in the female
than in the male monkey. Even in the colour
of the beard there is a curious parallelism