316 Darwin, and after Darwin. 
So much, then, by way of generalities. But perhaps 
the proof of natural selection as an agency of the first 
importance in the transmutation of species may be best 
brought home to us by considering a few of its 
applications in detail. I will therefore devote the rest 
of the present chapter to considering a few cases of this 
kind. 
There are so many large fields from which such 
special illustrations may be supplied, that it is difficult 
to decide which of them to draw upon. For instance, 
the innumerable, always interesting, and often aston- 
ishing adaptations on the part of flowers to the 
fertilising agency of insects, has alone given rise to an 
extensive literature since the time when Darwin him- 
self was led to investigate the subject by the guidance 
of his own theory. The same may be said of the 
structures and movements of climbing plants, and, in 
short, of all the other departments of natural history 
where the theory of natural selection has led to the 
study of the phenomena of adaptation. For in all these 
cases the theory of natural selection, which first led to 
their discovery, still remains the only scientific theory 
by which they can be explained. But among all the 
possible fields from which evidences of this kind may 
be drawn, I think the best is that which may be 
generically termed defensive colouring. To this field, 
therefore, I will restrict myself. But, even so, the 
cases to be mentioned are but mere samples taken 
from different divisions of this field; and therefore it 
must be understood at the outset ‘that they could 
easily be multiplied a hundred-iold. 
