Chap. VI.] BEAUTY, HOW ACQUIRED. 253 



beautiful for beauty's sake; but this has been effected 

 through sexual selection, that is, by the more beautiful 

 males having been continually preferred by the females, 

 and not for the delight of man. So it is with the music 

 of birds. We may infer from aU this that a nearly 

 similar taste for beautifid colours and for musical sounds 

 runs through a large part of the animal kingdom. 

 When the female is as beautifully coloured as the male, 

 which is not rarely the case with birds and butterflies, 

 the cause apparently lies in the colours acquired 

 through sexual selection having been trasmitted to 

 both sexes, instead of to the males alone. How the 

 sense of beauty in its simplest form — ^that is, the re- 

 ception of a peculiar kind of pleasure from certain col- 

 ours, forms, and sounds — ^was first developed in the 

 mind of man and of the lower animals, is a very ob- 

 scure subject. The same sort of difficulty is presented, 

 if we enquire how it is that certain flavours and odours 

 give pleasure, and others displeasure. Habit in all 

 these cases appears to have come to a certain extent 

 into play; but there must be some fundamental cause 

 in the constitution of the nervous system in each 

 species. 



Natural selection cannot possibly produce any modi- 

 fication in a species exclusively for the good of another 

 species; though throughout nature one species inces- 

 santly takes advantage of, and profits by, the structures 

 of others. But natural selection can and does often 

 produce structures for the direct injury of other ani- 

 mals, as we see in the fang of the adder, and in the ovi- 

 positor of the ichneumon, by which its eggs are de- 

 posited in the living bodies of other insects. If it 



