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XI PHENOMENA OF ORGANIC NATURE 435 
The opponents may be of two kinds: there are 
the indirect opponents, which are what we may 
call rivals; and there are the direct opponents, 
those which strive to destroy the creature; and 
these we call enemies. By rivals I mean, of course, 
in the case of plants, those which require for their 
support the same kind of soil and station, and, 
among animals, those which require the same kind 
of station, or food, or climate; those are the in- 
direct opponents; the direct opponents are, of 
course, those which prey upon an animal or 
vegetable. The helpers may also be regarded as 
direct and indirect : in the case of a carnivorous 
animal, for example, a particular herbaceous plant 
may, in multiplying, be an indirect helper, by en- 
abling the herbivora on which the carnivore preys 
to get more food, and thus to nourish the carnivore 
more abundantly ; the direct helper may be best 
illustrated by reference to some parasitic creature, 
such as the tape-worm. The tape-worm exists in 
the human intestines, so that the fewer there are 
of men the fewer there will be of tape-worms, 
other things being alike. It is a humiliating re- 
flection, perhaps, that we may be classed as direct 
helpers to the tape-worm, but the fact is so: we 
can all see that if there were no men there would 
be no tape-worms. 
It is extremely difficult to estimate, in a proper 
way, the importance and the working of the Con- 
ditions of Existence. Ido not think there were 
any of us who had the remotest notion of properly 
FF 2. 
