xxii INTR OD UCTION 



fact of evolution. Biologists do not doubt that evolution has 

 occurred and is continuing. 



It has seemed best to develop some one subdivision of the 

 subject a little more fully than the rest. The author has 

 chosen the phenomena of color in animals for this fuller 

 treatment, being led to this choice chiefly by the fact that 

 these phenomena may readily be observed by any reader in 

 any locality. 



We will speak first of the theory, then of some of the phe- 

 nomena which find their explanation in the theory ; we will 

 consider the relation of man to evolution, and finally will 

 refer to a few of the corollaries of the theory which are of 

 general interest. 



