1.16 CONDITIONS AFFECTING TIIE 



means — given the climate, the particular kind of 

 place in which an animal or a plant lives or grows ; for 

 example, the station of a fish is in the water, of a fresh 

 water fish in fresh water ; the station of a marine fish 

 is in the sea, and a marine animal may have a station 

 higher or deeper. So again with land animals : the 

 differences in their stations are those of diiferent soils 

 and neighbourhoods ; some being best adapted to a 

 calcareous, and others to an arenaceous soil. The 

 third condition of existence is Food, by which I mean 

 food in the broadest sence, the supply of the materials 

 necessary to the existence of an organic being ; in the 

 case of a plant the inorganic matters, such as carbonic 

 acid, water, ammonia, and the earthy salts or salines ; 

 in the case of the animal the inorganic and organic 

 matters, which we have seen they require ; then these 

 are all, at least the two first, what we may call the 

 inorganic or physical conditions of existence. Food 

 takes a mid-place, and then come the organic condi- 

 tions ; by which I mean the conditions which depend 

 upon the state of the rest of the organic creation, upon 

 the number and kind of living beings, with which an 

 animal is surrounded. You may class these under two 

 heads : there are organic beings, which operate as 

 opponents, and there are organic beings which operate 

 as helpers to any given organic creature. The oppo- 

 nents may be of two kinds : there are the indirect op- 

 ponents, 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 



