94 STRUGGLE FOB EXISTENCE. [Chap. III. 



cies 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 pre- 

 cisely say why one species has been victorious over an- 

 other in the great battle of life. 



A corollary of the highest importance may be de- 

 duced 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 compe 

 tition for food or residence, or from which it has t^ 

 escape, or on which it preys. This is obvious in th? 

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

 that of the legs and claws of the parasite which clingb 

 to the hair on the tiger's body. But in the beautifully 

 plumed seed of the dandeliop, and in the flattened and 

 fringed legs 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 dis- 

 tributed and fall on unoccupied ground. In the water- 

 beetle, the structure of its legs, so well adapted for div- 

 ing, 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 re- 

 lation to other plants. But from the strong o-rowth 

 of young plants produced from such seeds, as peas and 

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



