SEXUAL COLORATION. 261 



colour of the scales which are not conspicuous ; convert every 

 scale into a feather, and the differences will be much more 

 striking, even without any complication of the pigment. In 

 fact, what seems to require an explanation is not so much the 

 diversity of coloration in the two sexes, but the occasional 

 similarity. 



Slight Development of Colour Dimorphism in Mammals. 



It is a remarkable fact that there is but little sexual diversity 

 among mammals, except such as is directly connected with 

 pairing and reproduction. It may be as well to explain here 

 that secondary sexual characters may be referred to two classes, 

 which are perhaps not very sharply marked off ; first, those 

 which have an obvious relation to the habits of the sex which 

 possesses them ; secondly, those characters which have not 

 such an obvious relation. To the first category I would refer 

 the antlers of deer and the spurs of gallinaceous birds ; the 

 males of these animals are pugnacious, and use the weapons 

 in question in their combats with each other ; the accessory 

 grasping organ possessed by the males of the Isopod genus, 

 Serolis, and the great development of olfactory hairs in the 

 genus Tanais * are of evident use to the crustacean in 

 seizing or finding the female. To the second category belong 

 colour differences, and perhaps such structural differences as 

 are exhibited in the male of the lemur, Hapalemur griseus. 

 In this animal I pointed out some years ago t the existence of 

 a peculiar patch of spine-like structures, upon the arm of the 

 male, which, as I was informed by Prof. Milne Edwards, are 

 not so highly developed in the female ; but this organ may 

 possibly be used by the male as a grasping organ at the time 



* Fritz Miiller, " Facts for Darwin." 

 f Proc. ZooL Soc., 1884. 



