seeds may be widely distributed and fall on unoccupied ground. In the
water-beetle, the structure of its legs, so well adapted for diving,
allows it to compete with other aquatic insects, to hunt for its own
prey, and to escape serving as prey to other animals.

The store of nutriment laid up within the seeds of many plants seems at
first sight to have no sort of relation to other plants. But from the
strong growth of young plants produced from such seeds, as peas and
beans, when sown in the midst of long grass, it may be suspected that
the chief use of the nutriment in the seed is to favour the growth of
the seedlings, whilst struggling with other plants growing vigorously
all around.

Look at a plant in the midst of its range! Why does it not double or
quadruple its numbers? We know that it can perfectly well withstand a
little more heat or cold, dampness or dryness, for elsewhere it ranges
into slightly hotter or colder, damper or drier districts. In this case
we can clearly see that if we wish in imagination to give the plant the
power of increasing in numbers, we should have to give it some advantage
over its competitors, or over the animals which prey on it. On the
confines of its geographical range, a change of constitution with
respect to climate would clearly be an advantage to our plant; but we
have reason to believe that only a few plants or animals range so far,
that they are destroyed exclusively by the rigour of the climate. Not
until we reach the extreme confines of life, in the Arctic regions or on
the borders of an utter desert, will competition cease. The land may be
extremely cold or dry, yet there will be competition between some few
species, or between the individuals of the same species, for the warmest
or dampest spots.

Hence we can see that when a plant or animal is placed in a new country,
among new competitors, the conditions of its life will generally be
changed in an essential manner, although the climate may be exactly the
same as in its former home. If its average numbers are to increase in
its new home, we should have to modify it in a different way to what we
should have had to do in its native country; for we should have to give
it some advantage over a different set of competitors or enemies.

It is good thus to try in imagination to give any one species an
advantage over another. Probably in no single instance should we know
what to do. This ought to convince us of our ignorance o