50 GEOMETRICAL RATIO OF INCREASE. [Chap. IIL 



TJie Term, Struggle for Existence, used in a large sense. 

 I should premise that I use this term in a large and metaphorical 

 sense including dependence of one being on another, and including 

 (which is more important) not only the life of the individual, but 

 success in leaving progeny. Two canine animals, in a time of 

 dearth, may be truly said to struggle with each other which shall 

 get food and live. But a plant on the edge of a desert is said to 

 struggle for life against the drought, though more properly it should 

 be said to be dependent on the moisture. A plant which annually 

 produces a thousand seeds, of which only one on an average 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 

 misletoe 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 parasites grow on the same tree, it languishes- 

 and dies. But several seedling misletoes, growing close together on 

 the same branch, may more truly be said to struggle with each 

 other. As the misletoe is disseminated by birds, its existence 

 depends on them ; and it may metaphorically be said to struggle 

 with other fruit-bearing plants, in tempting the birds to devour and 

 thus disseminate its seeds. In these several senses, which pass into 

 each other, I use for convenience' sake the general term of Struggle 

 for Existence. 



Geometrical Ratio of Increase. 



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 suffer 

 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 survive, there must in every case 

 be a struggle for existence, either one individual with another of 

 the same species, or with the individuals of' distinct species, or 

 \rith 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 be now increasing, more or less rapidly, in numbers, all cannot 

 do so, for the world would not hold them. 



There is no exception to the rule that every organic being 



