ON THE QUICK GROWING WALNUT 



In the same way we conceive of the evolutionary 

 changes through which new species were evolved 

 in the past as having been relatively sudden. I 

 have already referred to the difficulty with which 

 the average mind can grasp the idea that precisely 

 the same sort of change in animal and vegetable 

 forms is taking place to-day that has taken place 

 in all other stages of evolution. 



It was one of the great merits of Darwin's expo- 

 sition of the "Origin of Species", that he gave de- 

 tailed illustrations of the struggle for existence, 

 and brought tangibly before the minds of thought- 

 ful people the conception that each race of beings 

 is more or less in competition with every other 

 race, and that the race that is adaptable enough to 

 adjust itself to new conditions is the only one that 

 stands any prospect of survival. 



The idea of the progression of the normal 

 increase of living creatures in geometrical ratio 

 and of the resulting over-population of any terri- 

 tory by the progeny even of a single pair, if there 

 were no counteracting factors, was of course re- 

 ceived by Darwin from Malthus. But the applica- 

 tion of that idea to all races of animals and plants, 

 and the logical deduction from its application 

 which first made possible anything like a clear 

 understanding of the reason why vegetable and 

 animal races have evolved, was due to Darwin. 



[205] 



