SUPPLEMENTAL NOTE.
ON SEXUAL SELECTION IN RELATION TO MONKEYS.
Reprinted from NATURE, November 2, 1876, p. 18.
In the discussion on Sexual Selection in my Descent of Man, no case
interested and perplexed me so much as the brightly-coloured hinder
ends and adjoining parts of certain monkeys. As these parts are more
brightly coloured in one sex than the other, and as they become more
brilliant during the season of love, I concluded that the colours had
been gained as a sexual attraction. I was well aware that I thus laid
myself open to ridicule; though in fact it is not more surprising that
a monkey should display his bright-red hinder end than that a peacock
should display his magnificent tail. I had, however, at that time no
evidence of monkeys exhibiting this part of their bodies during their
courtship; and such display in the case of birds affords the best
evidence that the ornaments of the males are of service to them by
attracting or exciting the females. I have lately read an article by
Joh. von Fischer, of Gotha, published in Der Zoologische Garten,
April 1876, on the expression of monkeys under various emotions, which
is well worthy of study by any one interested in the subject, and which
shews that the author is a careful and acute observer. In this article
there is an account of the behaviour of a young male mandrill when he
first beheld himself in a looking-glass, and it is added, that after a
time he turned round and presented his red hinder end to the glass.
Accordingly I wrote to Herr J. von Fischer to ask what he supposed was
the meaning of this strange action, and he has sent me two long letters
full of new and curious details, which will, I hope, be hereafter
published. He says that he was himself at first perplexed by the above
action, and was thus led carefully to observe several individuals of
various other species of monkeys, which he has long kept in his house.
He finds that not only the mandrill (Cynocephalus mormon) but the drill
(C. leucophaeus) and three other kinds of baboons (C. hamadryas,
sphinx, and babouin), also Cynopithecus niger, and Macacus rhesus and
nemestrinus, turn this part of their bodies, which in all these species
is more or less brightly coloured, to him when they are pleased, and to
other persons as a sort of greeting. He took pains to cure a Macacus
rhesus, which he had kept for five years, of this indecorous habit, and
at last succeeded. These monkeys are particularly apt to act in this
manner, grinning at the same time, when first introduced to a new
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