Now let us turn to the other side of the argument. Under domestication we see much
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. 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 |
variability. 1859 1860 1861 1866 |
variability, caused, or at least excited, by changed conditions of life. 1869 |
↑1 blocks not present in 1869 1872; present in 1859 1860 1861 1866 | This seems to be 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.
|
Variability
is governed by many complex laws,— by
correlated correlated 1872 | correlation 1859 1860 1861 1866 | correlation, 1869 |
growth, growth, 1872 | of growth, 1859 1860 1861 1866 | growth, 1869 |
compensation, the increased compensation, the increased 1872 |
by 1859 1860 1861 1866 1869 |
use and
disuse disuse 1872 | disuse, 1859 1860 1861 1866 1869 |
of parts, and the definite of parts, and the definite 1872 |
and by the direct 1859 1860 1861 1866 |
and by the definite 1869 |
action of the
surrounding surrounding 1869 1872 | physical 1859 1860 1861 1866 |
conditions. conditions. 1869 1872 | conditions 1859 1860 1861 1866 |
....... 1869 1872 | of 1859 1860 1861 1866 |
....... 1869 1872 | life. 1859 1860 1861 1866 |
There is much difficulty in ascertaining how
largely largely 1869 1872 | much modification 1859 1860 1861 1866 |
our domestic productions have
been modified; been modified; 1869 1872 | undergone; 1859 1860 1861 1866 |
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, 1866 1869 1872 | hand 1859 1860 1861 |
we have evidence that
variability variability 1872 | variability, 1859 1860 1861 1866 1869 |
when it has once come into play, does not
....... 1869 1872 | wholly 1859 1860 1861 1866 |
cease cease 1869 1872 | cease; 1859 1860 1861 1866 |
under domestication for a very long period; nor do we know that it ever ceases, for under domestication for a very long period; nor do we know that it ever ceases, for 1872 |
for 1859 1860 1861 1866 |
under domestication for a very long period; for 1869 |
new varieties are still occasionally produced by our
oldest oldest 1869 1872 | most anciently 1859 1860 1861 1866 |
domesticated productions. |