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. I do not think there were 

 any of us who had the remotest notion of properly 



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