A THEORY OF BIRDS' NESTS. 2(53 



that, on the theory of evolution and natural selection, a 

 wide range of facts with regard to colour in nature have 

 been co-ordinated and explained. Until at least an 

 equally wide range of facts can be shown to be in har- 

 mony with any other theory, we can hardly be expected 

 to abandon that which has already done such good ser- 

 vice, and which has led us to the discovery of so many 

 interesting and unexpected harmonies among the most 

 common (but hitherto most neglected and least un- 

 derstood), of the phenomena presented by organized 

 beings. 



