The Theory of Natural Selection. 259 
before the publication of Darwin’s work ; and so much, 
likewise, for the only reasonable suggestions as to 
the causes of evolution which up to that time had 
been put forward, even by those few individuals who 
entertained any belief in evolution as a fact. It 
was the theory of natural sclection that changed all 
this, and created a revolution in the thought of our 
time, the magnitude of which in many of its far-reaching 
consequences we are not even yet in a position to 
appreciate; but the action of which has already 
wrought a transformation in general philosophy, as 
well as in the more special science of biology, that 
is without a parallel in the history of mankind. 
ad Although every one is now more or less well 
acquainted with the theory of natural selection, it is 
necessary, for the sake of completeness, that I should 
state the theory ; and I will do so in full detail. 
It is a matter of observable fact that all plants and 
animals are perpetually engaged in what Darwin calls 
a “struggle for existence.” That is to say, in every 
generation of every species a great many more in- 
dividuals are born than can possibly survive; so that 
there is in consequence a perpetual battle for life going 
on among all the constituent individuals of any given 
generation. Now, in this struggle for existence, which 
individuals will be victor‘ous and live? Assuredly 
those which are best fitted to live, in whatever respect, 
or respects, their superiority of fitness may consist. 
Hence it follows that Nature, so to speak, se/ec/s the 
best individuals out of each generation to live. And not 
only so; but as these favoured individuals transmit 
their favourable qualities to their offspring, according to 
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