166 EVOLUTION 



the Blue Gums and Black Wattles, quickly 

 growing, with soft wood, and with abundant 

 foliage that caught the snow. On the other 

 hand, the deodars from the Himalaya moun- 

 tains, constitutionally adapted to let the 

 snow slide from their pendulous branches 

 and acicular leaves, had hardly a twig broken. 



Implications of the Concept of Nat- 

 ural Selection. — As a naturalist of very 

 rich experience Darwin realized the complex- 

 ity of the evolution problem more than most 

 naturalists have done, and a careful study of 

 his sentences makes it quite clear that when 

 he used phrases like "struggle for existence" 

 and "natural selection," which have acquired 

 by familiarity a somewhat hard and mechani- 

 cal sound in our ears, he had a singularly rich 

 concrete content in his mind. 



"Nothing is easier," he said, "than to 

 admit in words the truth of the universal 

 struggle for life, or more difficult — at least 

 I have found it so — than constantly to bear 

 this conclusion in mind." . . . "I use this 

 term ['struggle for existence'] in a large and 

 metaphorical sense, including dependence of 

 one being on another, and including (which 

 is more important) not only the life of the 

 individual, but success in leaving progeny." 

 . . . "Nature may be compared to a surface 

 on which rest ten thousand sharp wedges 



