gle 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 of 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 mistletoe 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 mistletoes growing
close together on the same branch may more truly be said to struggle
with each other. As the mistletoe 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."

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 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 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 naturally
increases at so high a rate that, if not destroyed, the earth would soon
be covered by the progeny of a single pair. Even slow-breeding man has
doubled in twenty-five years, and at this rate in less than a thousand
years there would literally no