140 NATURAL SELECTION ^ vi 



this subject, I would again respectfully urge that they must 

 grapple with the whole of the facts, not one or two of them 

 only. It will be admitted 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 

 harmony with any other theory, we can hardly be expected 

 to abandon that which has already done such good service, 

 and which has led to the discovery of so many interesting 

 and unexpected harmonies among the most common (but 

 hitherto most neglected and least understood) of the phe- 

 nomena presented by organised beings. 



