218 TROPICAL NATUEE, AND OTHER ESSAYS. 



forms, or on geographical or climatic changes. In so 

 complex a subject, for wliicli experiment and systematic 

 inquiry lias done so little, we cannot expect to explain 

 every individual case, or solve every difficulty ; but it 

 is believed that all the great features of animal colora- 

 tion and many of the details become explicable on the 

 principles we have endeavoured to lay down. 



It will perhaps be considered presumptuous to put 

 forth this sketch of the subject of colour in animals, as 

 a substitute for one of Mr. Darwin's most highly elabo- 

 rated theories — that of voluntary or perceptive sexual 

 selection ; yet I venture to think that it is more in ac- 

 cordance with the whole of the facts, and with the theory 

 of natural selection itself ; and I would ask such of my 

 readers as may be sufficiently interested in the sub- 

 ject, to read again Chapters XI. to XVL of the Descent of 

 Man, and consider the whole subject from the point of 

 view here laid down. The explanation of almost all 

 the ornaments and colours of birds and insects as having 

 been produced by the perceptions and choice of the 

 females, has, I believe, staggered many evolutionists, but 

 has been provisionally accepted because it was the only 

 theory that even attempted to explain the facts. It 

 may perhaps be a relief to some of them, as it has been 

 to myself, to find that the phenomena can be shown to 

 depend on the general laws of development, and on the 

 action of natural selection," which theory will, I 

 venture to think, be relieved from an abnormal excres- 

 cence and gain additional vitality, by the adoption of 

 the views here imperfectly set forth. 



Although we have arrived at the conclusion that 



