ON THE QUICK GROWING WALNUT 
Alfred Russell Wallace conceived the same idea 
independently, and must always be credited with 
a share in the discovery. 
But of course it was Darwin’s exposition that 
gave the subject general vogue, and the scheme of 
heredity that it connotes is with full propriety 
spoken of as Darwinian evolution. 
The essentials of this scheme of heredity may 
be stated in a few words, as follows: Animals and 
plants tend to increase in geometrical ratio. If 
unopposed, the progeny of a single pair of animals 
or an individual plant would soon populate and 
over-populate the entire earth. Opposition to such 
over-population comes from the rivalry of other 
animals and plants. The struggle for existence 
thus induced puts a premium on the individual 
animal or plant that is better able than its fellows 
to seek means of sustenance. Such an individual 
will, on the average, live longer and produce more 
offspring than an individual less well adapted to 
its surroundings. 
The preservation of these favored individuals 
and their progeny may be described in a phrase 
as “the survival of the fittest.” 
The natural processes that determine such sur- 
vival on one hand, and the destruction of the less 
fit on the other, may be spoken of as constituting 
“natural selection.” 
[207] 
