II. THE PHENOMENA EXPLAINED BY THE 



THEORY 



WE have reversed the natural order in our treatment 

 of the theory of evolution. It was the phenomena, to which 

 we wish now to direct our attention, which first suggested 

 the theory, and it was only by prolonged study of these 

 phenomena that the theory was tested and established. 

 For the sake of brevity in the presentation of the subject, 

 we have chosen first to develop the theory and then to 

 apply it to the phenomena upon which it bears. 



For the purposes of our treatment the phenomena to 

 which we wish to direct attention may be classified as 

 follows : the phenomena of comparative anatomy ; the phe- 

 nomena of comparative embryology; the phenomena of 

 paleontology; the phenomena of geographical distribution; 

 and the phenomena of color in animals and in the blos- 

 soms of plants. A complete discussion of these subjects 

 would still be but a partial treatment of the phenomena 

 which have a bearing upon the theory. Many points of 

 physiology, the phenomena of sterility, hybridization, in- 

 stinct, habit, etc., etc., would still be omitted. We shall 

 attempt but a very brief treatment of some of the phe- 

 nomena of the several types mentioned in the classification 

 given above. Do not, then, be under the impression that 

 we shall have reviewed, even in outline, the whole subject. 



87 



