Chap. III. 
STKUGGLE FOR EXISTENCE. 
63 
for life against tlie drouglit^ though more properly it 
should be said to be dependent on the moisture. A 
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, vdiich pass into each other, I 
use for convenience’ sake the general term of struggle 
for existence. 
A struggle for existence inevitably follows from the 
liigh 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 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 
