94 STRUGGLE FOE EXISTENCE. [Chap. III. 



One species of charlock has been known to supplant 

 another species ; and so in other cases. We can dimly 

 see why the competition should be most severe between 

 allied forms, which fill nearly the same place in the 

 economy of nature ; but probably in no one case could 

 we precisely say why one species has been victorious 

 over another in the great battle 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 dandelion, and in the flattened and fringed le^s 

 of the water-beetle, the relation seems at first confined 

 to the elements of air and water. Yet the advantage 

 of plumed seeds no doubt stands in the closest relation 

 to the land being already thickly clothed with other 

 plants ; so that the seeds may be widely distributed 

 and fall on unoccupied ground. In the water-beetle, 

 the structure of its legs, so well adapted for diving, 

 allows it to compete with other aquatic insects, to hunt 

 for its own prey, and to escape serving as prey to other 

 animals. 



The store of nutriment laid up within the seeds of 

 many plants seems at first sight to have no sort of 

 relation to other plants. But from the strong growth 

 of young plants produced from such seeds, as peas and 

 bians, when sown in the midst of long grass, it may be 



