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. 
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