266 
THE PRINCIPLES OF 
Part IL 
same results as would follow from an actual inequality 
in the number of the sexes ; for if each male secures 
two or more females, many males will not be able to 
pair; and the latter assuredly will be the weaker or 
less attractive individuals. Many mammals and some 
few birds are polygamous, but with animals belonging to 
the lower classes I have found no evidence of this habit. 
The intellectual powers of such animals are, perhaps, 
not sufficient to lead them to collect and guard a harem 
of females. That some relation exists between poly- 
gamy and the development of secondary sexual cha- 
racters, appears nearly certain; and this supports the 
view that a numerical preponderance of males would 
be eminently favourable to the action of sexual selection. 
Nevertheless many animals, especially birds, which are 
strictly monogamous, display strongly-marked secondary 
sexual characters ; whilst some few animals, which are 
polygamous, are not thus characterised. 
We will first briefly run through the class of mam- 
mals, and then turn to birds. The gorilla seems to be 
a polygamist, and the male differs considerably from 
the female ; so it is with some baboons which live in 
herds containing twice as many adult females as males. 
In South America the Mycetes caraya presents well- 
marked sexual differences in colour, beard, and vocal 
organs, and the male generally lives with two or three 
wives: the male of the Celus capucinus differs some- 
what from the female, and appears to be polygamous. 5 
Little is known on this head with respect to most other 
monkeys, but some species are strictly monogamous. 
The ruminants are eminently polygamous, and they 
5 On the Gorilla, Savage and Wyman, ‘ Boston Journal of Nat. Hist/ 
vol. v. 1845-4:7, p. 423. On Cynocephalus, Brehm, ‘Illust. Thierleben/ 
B. i. 1864, s. 77. On Mycetes, Rengger, ‘Naturgesch. : Saugethiere 
von Paraguay/ 1830, s. 14, 20. On Cebus, Brehm, ibid. s. 108. 
