The Days of a Man X^'^l^ 



ward joined the ranks of the evolutionists. For he 



taught us to think for ourselves, not merely to 



follow him. Thus, though I accepted his philosophy 



regarding the origin and permanence of species 



when I began serious studies in Zoology, as my work 



went on their impermanence impressed me more and 



more strongly. Gradually I found it impossible to 



believe that the ditferent kinds of animals and 



plants had been separately created in their present 



My forms. Nevertheless, while I paid tribute to Darwin's 



accept- marvelous insight, I was finally converted to the 



"^Darwin- ^hcory of divergence through Natural Selection and 



ism other factors not by his arguments, but rather by 



the special facts unrolling themselves before my 



own eyes, the rational meaning of which he had 



plainly indicated. I sometimes said that I went 



over to the evolutionists with the grace of a cat 



the boy "leads" by its tail across the carpet! 



All of Agassiz's students passed through a similar 

 experience, and most of them came to recognize 

 that in the production of every species at least four 

 elements were involved — these being the resident 

 or internal factors of heredity and variation, and 

 the external or environmental ones of selection and 

 segregation. 



In the original Penikese group, the man who most 

 interested me was William Keith Brooks, then 

 occupying a precarious professorship in a little 

 college at Niagara Falls. Very wise and self-con- 

 tained, he was especially sparing of words and keen 

 in all his conclusions. Later, as professor in Johns 

 Hopkins University, he came to be the most dis- 

 tinguished American biologist of his time, a true 



n 114 ^ 



