The Descent of Man

History of Mamm. Animals,' 1841, p. 431.),
which we may reasonably suspect serves as a
sexual charm; but I shall have to recur to this
subject in the next chapter. The vocal organs of
the American Mycetes caraya are one-third
larger in the male than in the female, and are
wonderfully powerful. These monkeys in
warm weather make the forests resound at
morning and evening with their overwhelming
voices. The males begin the dreadful concert,
and often continue it during many hours, the
females sometimes joining in with their less
powerful voices. An excellent observer, Rengger
(7. 'Naturgeschichte der Saugethiere von
Paraguay,' 1830, ss. 15, 21.), could not perceive
that they were excited to begin by any special
cause; he thinks that, like many birds, they delight
in their own music, and try to excel each
other. Whether most of the foregoing monkeys
have acquired their powerful voices in order to
beat their rivals and charm the females—or
whether the vocal organs have been strengt-