Chap. VI II. Sexual Selection. 217 



poljgamoTis, but with animals belonging to the lower classes 1 

 have found no evidence of this habit. The intellectual powers 

 of such animals are, perhaps, not sufBoient to lead them to 

 collect and guard a harem of females. That some relation exists 

 between polygamy and the development of secondary sexual 

 characters, 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, which are strictly monogamous, especially birds, display 

 strongly-marked secondary sexual characters ; whilst some few 

 animals, which are polygamous, do not have such characters. 



We will first briefly run through the mammals, and then turn 

 to birds. The gorilla seems to be polygamous, 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 airaya 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 Cebus capucinus differs somewhat from the female, and 

 appears to be polygamous.^" Little is known on this head with 

 respect to most other monkeys, but some species are strictly 

 monogamous. The ruminants are eminently polygamous, and 

 tb^y present sexual differences more frequently than almost any 

 other group of mammals; this holds good, especially in their 

 weapons, but also in other characters. Most deer, cattle, and 

 sheep are polygamous ; as are most antelopes, though some are 

 monogamous. Sir Andrew Smith, in speaking of the antelopes 

 of South Africa, says that in herds of about a dozen there was 

 rarely more than one mature male. The Asiatic Amilope saiga 

 appears to be the most inordinate polygamist in the world ; for 

 Pallas" states that the male drives away all rivals, and collects a 

 herd of about a hundred females and kids together ; the female 

 is hornless and has softer hair, but does not otherwise differ 

 much from the male. The wild horse of the Falkland Islands and 

 of the Western States of N. America is polygamous, but, except 

 in his greater size and in the proportions of his body, differs but 

 little from the mare. The wild boar presents well-marked sexual 



>" On the Gorilla, Savage and Fasc. xii. 1777, p. 29. Sir Andrew 



Wyman. ' Boston Journal of Nat. Smitli, ' Illustrations of tlie Zoology 



Hist.' vol. V. 1845-47, p. 423. On of S. Africa,' 1849, pi. 29, on the 



Ilynooephalus, Brehm, 'Illust.Thier- Kobus. Owen, in his ' Anatomy of 



leben,' B. i. 1864, s. 77. On Mv- Vertebrates ' (vol. iii. 1868, p. 633) 



cetes, Rengger, 'Naturgesoh.; Sauge- gives a table shewing incidentally 



[hiere von Paraguay,' 1830, s. 14, which species of antelopes are gre- 



20. Cebus, Brehm, ibid. ». 108. garious. 



" Pallas, 'Spicilegia Zoolog.,' 



