82 STRUGGLE FOR EXISTENCE. Cuap. III. 



see why the competition should be most severe between allied 

 forms, which fill nearly the same place in the economy of Na- 

 ture ; but probably in no one case could "vve precisely say why 

 one species has been victorious over another in the great bat- 

 tle of life. 



A corollary of the highest importance may be deduced 

 from the foregoing remarks, namely, that the structure of 

 every organic being is related, in the most essential yet often 

 hidden manner, to that of all the other organic beings, with 

 "which it comes into competition for food or residence, or from 

 which it has to escape, or on which it preys. This is obvious 

 in the structure of the teeth and talons of the tiger ; and in 

 that of the legs and claws of the parasite which clings to the 

 hair on the tiger's body. But in the beautifully-plumed seed 

 of the dandehon, and in the flattened and fringed legs of the 

 water-beetle, the relation seems at first confined to the ele- 

 ments of air and Avater. Yet the advantage of plumed seeds 

 no doubt stands in the closest relation to the land being 

 already thickly clothed Avith other plants ; so that the seeds 

 may be widely distributed and fall on iinoccupied ground. In 

 the water-beetle, the structm-e of its legs, so well adapted for 

 diving, allows it to compete with other a'quatic insects, to 

 hunt for its own prey, and to escape ser\dng as prey to other 

 animals. 



The store of nutriment laid up witliin the seeds of many 

 plants seems at first sight to have no sort of relation to other 

 jilants. But from the strong growth of young plants produced 

 from such seeds (as peas and beans), when sown in the midst 

 of long grass, it may be suspected that the chief use of the 

 luitriment in the seed is to favor the growth of the young seed- 

 ling, while struggling with other plants growing vigorously 

 all around. 



Look at a plant in the midst of its range, why does it not 

 double or qviadruplc its nimibers ? We know that it can per- 

 fectly well withstand a little more heat or cold, dampness or 

 dryness, for elsewhere it ranges into slightly hotter or colder, 

 damper or drier districts. In this case we can clearly sec that 

 if we wished in imagination to give the plant the power of in- 

 creasing in number, we should have to give it some advantage 

 over its competitors, or over the aTiimals which jireyed on it. 

 ( )n the confines of its geographical range, a change of consti- 

 tution Avith respect to climate would clearly be an advan- 

 tage to our plant ; but we have reason to believe that only a 



