NATURAL SELECTION. 391 



his notions. The available growth-energy of the male 

 being superior to that of the female in most animals, 

 his structure is more liable to excess of development 

 in useless directions. In many of the Arthropoda, 

 especially the Insecta, the males possess processes of 

 the head and thorax besides the especially useful pre- 

 hensile peculiarities of the limbs. Among Vertebrata 

 the male generally possesses the more brilliant colors. 

 This is especially noteworthy in fishes and birds. It 

 is also frequently the case in lizards, although in one 

 genus (Liocephalus) the female has the brighter hues. 

 The selection (taking no account of the origin of these 

 characters) acts in the probable preference by the 

 females for the most brilliant colors and most impres- 

 sive forms, thus propagating both, and in the neglect 

 of those males in which these characters are not so well 

 developed. The plainness of the females aids in their 

 concealment and enables them to perform their ma- 

 ternal functions in safety. 



The desire of the males to attract the favor of the 

 females leads to many peculiar performances among 

 birds. The males display their plumage by spreading 

 their wings, tail, tail-coverts, etc., and strut and go 

 through many antics in the presence of the females. 

 Familiar examples are seen in our barnyards in the 

 turkeys, peafowls, and pigeons. In the paradise-bird 

 the most remarkable exhibitions occur, according to 

 Wallace. In song-birds thfe male is freque,ntly the only 

 or the best songster, and the development of the vocal 

 powers resulting from the sexual impulse is most re- 

 markable. Among Mammalia the female selection is 

 less common than male selection. In the case of 

 some of the old world monkeys (Macacus, e. g.) the 

 female presents the greater physical indication of ex- 



