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1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1861
1866
1872

one with another, 1859 1860 1861 1866 1869
OMIT 1872

will produce perfection, or strength 1859 1860 1861 1866 1869
leads to success 1872

according to 1859 1860 1861 1866 1869
in accordance with 1872

OMIT 1866 1869 1872
as we see they do yield, 1859 1860 1861

whether known or not yet known, it must by my 1866 1869
it must by my 1859 1860 1861
whether known or unknown, it must on this 1872

use and disuse, being 1869
use and disuse, being slightly 1859 1860 1861 1866
the increased use or disuse of parts, being 1872

the
inhabitants,
inhabitants
one with another, and consequently will produce perfection, or strength in the battle for life, only according to the standard of that
particular country.
country.
Hence the inhabitants of one country, generally the smaller one,
will
will
often
yield,
yield
OMIT to the inhabitants of another and generally
the larger
larger
country. For in the larger country there will have existed more
individuals
individuals,
and more diversified forms, and the
com- petition
competition
will have been severer, and thus the standard of perfection will have been rendered higher. Natural selection will not necessarily
lead to
produce
absolute perfection; nor, as far as we can judge by our limited faculties, can absolute perfection be everywhere
predicated.
found.
On the theory of natural selection we can clearly understand the full meaning of that old canon in natural history, "Natura non facit saltum." This canon, if we look
only
only
to the present inhabitants
alone of
of
the world, is not strictly
correct,
correct;
but if we include all those of past times, whether known or not yet known, it must by my theory be strictly true.
It is generally acknowledged that all organic beings have been formed on two great
laws—
laws—Unity
Unity
....
of Type, and the Conditions of Existence. By unity of type is meant that fundamental agreement in
structure,
structure
which we see in organic beings of the same class, and which is quite independent of their habits of life. On my theory, unity of type is explained by unity of descent. The expression of conditions of existence, so often insisted on by the illustrious Cuvier, is fully embraced by the principle of natural selection. For natural selection acts by either now adapting the varying parts of each being to its organic and inorganic conditions of life; or by having adapted them during
the long-past
past
long-past
periods of time: the adaptations being aided in
many
some
cases by use and disuse, being