Chap. HI. STRUGGLE FOR EXISTENCE. 63 



plant which annually produces a thousand seeds, of 

 which on an average only one comes to maturity, may 

 be more truly said to struggle with the plants of the 

 same and other kinds which already clothe the ground. 

 The missletoe is dependent on the apple and a few other 

 trees, but can only in a far-fetched sense be said to 

 struggle with these trees, for if too many of these para- 

 sites grow on the same tree, it will languish and die. 

 But several seedling missletoes, growing close together 

 on the same branch, may more truly be said to struggle 

 with each other. As the missletoe is disseminated by 

 birds, its existence depends on birds ; and it may meta- 

 phorically be said to struggle with other fruit-bearing 

 plants, in order to tempt birds to devour and thus 

 disseminate its seeds rather than those of other plants. 

 In these several senses, which pass into each other, I 

 use for convenience sake the general term of struggle 

 for existence. 



A struggle for existence inevitably follows from the 

 high rate at which all organic beings tend to increase. 

 Every being, which during its natural lifetime produces 

 several eggs or seeds, must surfer destruction during some 

 period of its life, and during some season or occasional 

 year, otherwise, on the principle of geometrical increase, 

 its numbers would quickly become so inordinately great 

 that no country could support the product. Hence, as 

 more individuals are produced than can possibly sur- 

 vive, there must in every case be a struggle for exist- 

 ence, either one individual with another of the same 

 species, or with the individuals of distinct species, or 

 with the physical conditions of life. It is the doctrine 

 of Malthus applied with manifold force to the whole 

 animal and vegetable kingdoms ; for in this case there 

 can be no artificial increase of food, and no prudential 

 restraint from marriage. Although some species may 



