60 STRUGGLE FOR EXISTENCE. [Chap. 111. 



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 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 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 seedsj 

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

 suspected that the chief use of the nutriment in the seed is to favour 

 the growth of the seedlings, whilst struggling with other plants 

 growing vigorously all around. 



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

 or quadruple its numbers? We know that it can perfectly well 

 withstand a little more heat or cold, dampness or dryness, for else- 

 where it ranges into slightly hotter or colder, damper or drier dis- 

 tricts. In this case we can clearly see that if we wish in imagination 

 to give the plant the power of increasing in number, we should have 

 to give it some advantage over its competitors, or over the animals 

 which prey on it. On the confines of its geographical range, a change 

 of constitution with respect to climate would clearly be an advantage 

 to our plant ; but we have reason to believe that ooly a few plants 

 or animals range so far, that they are destroyed exclusively by the 

 rigour of the climate. Not until we reach the extreme confines of 

 life, in the Arctic regions or on the borders of an utter desert, will 

 competition cease. The land may be extremely cold or dry, yet 

 there will be competition between some few species, or between the 

 individuals of the same species, for the warmest or dampest spots. 



Hence we can see that when a plant or animal is placed in a new 

 country amongst new competitors, the conditions of its life will 

 generally be changed in an essential manner, although the climate 



