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1859
1860
1861
1866
1869
1872

Compare with:
1860
1861
1866
1869
1872

do not 1859 1860 1861 1866
are not 1869
are by no means sufficient to 1872

overthrow 1859 1860 1861 1866 1872
sufficient to overthrow 1869

with 1859 1869 1872
from a few created forms with subsequent 1860
from a few primordial forms with subsequent 1861 1866

variability. 1859 1860 1861 1866
variability, caused, or at least excited, by changed conditions of life. 1869
variability, caused, or at least excited, by changed conditions of life; but often in so obscure a manner, that we are tempted to consider the variations as spontaneous. 1872

by 1859 1860 1861 1866 1869
compensation, the increased 1872

and by the direct 1859 1860 1861 1866
and by the definite 1869
of parts, and the definite 1872

for 1859 1860 1861 1866
under domestication for a very long period; for 1869
under domestication for a very long period; nor do we know that it ever ceases, for 1872

produce variability; 1859 1860 1861 1866 1869
caused by man; 1872

doubt their weight. But it deserves especial notice that the more important objections relate to questions on which we are confessedly ignorant; nor do we know how ignorant we are. We do not know all the possible transitional gradations between the simplest and the most perfect organs; it cannot be pretended that we know all the varied means of Distribution during the long lapse of years, or that we know how imperfect
is the
the
Geological
Record.
Record
is.
is.
Serious
Grave
as these several
objections
difficulties
are, in my judgment they do not overthrow the theory of descent with
subsequent modification.
modification.
Now let us turn to the other side of the argument. Under domestication we see much variability. This seems to be
in part
mainly
due to the reproductive system being eminently susceptible to changes in the conditions of life; so that this system, when not rendered impotent, fails to reproduce offspring exactly like the parent-form.
This variability
Variability
is governed by many complex laws,— by
correlation,
correlated
correlation
growth,
of growth,
of growth,
by use and
disuse
disuse,
and by the direct action of the
surrounding
physical
conditions.
conditions
of
of
life.
life.
There is much difficulty in ascertaining how
largely
much modification
our domestic productions have
been modified;
undergone;
but we may safely infer that the amount has been large, and that modifications can be inherited for long periods. As long as the conditions of life remain the same, we have reason to believe that a modification, which has already been inherited for many generations, may continue to be inherited for an almost infinite number of generations. On the other
hand,
hand
we have evidence that
variability
variability,
when it has once come into play, does not
wholly
wholly
cease
cease;
for new varieties are still occasionally produced by our
oldest
most anciently
domesticated productions.
Variability is
Man does
not actually produce variability; he only