The Making of Species 
fitable to itself, under the complex and some- 
times varying conditions of life, will have a 
better chance of surviving, and thus be naturally 
selected. From the strong principle of inherit- 
ance, any selected variety will tend to propagate 
its new and modified form.” 
In other words, the struggle for existence 
amongst all organic beings throughout the world, 
which inevitably follows from the high geometri- 
cal ratio of their increase, results in the survival 
of the fittest, that is to say, of those best adapted 
to cope with their enemies and to secure their 
food. Since organisms are thus naturally selected 
in nature, we may speak of a natural selection 
which acts in much the same way as the human 
breeder does. Darwin’s theory, then, is that all 
the variety of organisms which now exist have 
been evolved from one or more forms by this 
process of natural selection. 
The objections which have been urged against 
the theory of natural selection fall into two 
classes. 
I. Those which strike at its root, which either 
deny that there is any natural selection, or 
declare that it is not capable of producing a 
new species. 
II. Those which are directed against the all- 
sufficiency of natural selection to account for 
organic evolution. 
Those of the first class need not detain us 
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