y, either dead or alive; some inhabiting new stations,
climbing trees, frequenting water, and some perhaps becoming less
carnivorous. The more diversified in habits and structure the
descendants of our carnivorous animal became, the more places they would
be enabled to occupy. What applies to one animal will apply throughout
all time to all animals--that is, if they vary--for otherwise natural
selection can do nothing. So it will be with plants. It has been
experimentally proved, that if a plot of ground be sown with one species
of grass, and a similar plot be sown with several distinct genera of
grasses, a greater number of plants and a greater weight of dry herbage
can thus be raised. The same has been found to hold good when first
one variety and then several mixed varieties of wheat have been sown on
equal spaces of ground. Hence, if any one species of grass were to go
on varying, and those varieties were continually selected which differed
from each other in at all the same manner as distinct species and genera
of grasses differ from each other, a greater number of individual plants
of this species of grass, including its modified descendants, would
succeed in living on the same piece of ground. And we well know that
each species and each variety of grass is annually sowing almost
countless seeds; and thus, as it may be said, is striving its utmost to
increase its numbers. Consequently, I cannot doubt that in the course
of many thousands of generations, the most distinct varieties of any one
species of grass would always have the best chance of succeeding and
of increasing in numbers, and thus of supplanting the less distinct
varieties; and varieties, when rendered very distinct from each other,
take the rank of species.

The truth of the principle, that the greatest amount of life can be
supported by great diversification of structure, is seen under many
natural circumstances. In an extremely small area, especially if freely
open to immigration, and where the contest between individual and
individual must be severe, we always find great diversity in its
inhabitants. For instance, I found that a piece of turf, three feet by
four in size, which had been exposed for many years to exactly the same
conditions, supported twenty species of plants, and these belonged to
eighteen genera and to eight orders, which shows how much these plants
differed from each other. So it is with the plants and insects on small
and uniform