multiplication in a geometrical progression; the second, that the
offspring always vary slightly from the parents, though generally very
closely resembling them. From the first fact or law there follows,
necessarily, a constant struggle for existence; because, while the
offspring always exceed the parents in number, generally to an enormous
extent, yet the total number of living organisms in the world does not,
and cannot, increase year by year. Consequently every year, on the
average, as many die as are born, plants as well as animals; and the
majority die premature deaths. They kill each other in a thousand
different ways; they starve each other by some consuming the food that
others want; they are destroyed largely by the powers of nature--by cold
and heat, by rain and storm, by flood and fire. There is thus a
perpetual struggle among them which shall live and which shall die; and
this struggle is tremendously severe, because so few can possibly remain
alive--one in five, one in ten, often only one in a hundred or even one
in a thousand.

Then comes the question, Why do some live rather than others? If all the
individuals of each species were exactly alike in every respect, we
could only say it is a matter of chance. But they are not alike. We find
that they vary in many different ways. Some are stronger, some swifter,
some hardier in constitution, some more cunning. An obscure colour may
render concealment more easy for some, keener sight may enable others to
discover prey or escape from an enemy better than their fellows. Among
plants the smallest differences may be useful or the reverse. The
earliest and strongest shoots may escape the slug; their greater vigour
may enable them to flower and seed earlier in a wet autumn; plants best
armed with spines or hairs may escape being devoured; those whose
flowers are most conspicuous may be soonest fertilised by insects. We
cannot doubt that, on the whole, any beneficial variations will give the