much difficulty in ascertaining how
much modification much modification 1859 1860 1861 1866 | largely 1869 1872 |
our domestic productions have
undergone; undergone; 1859 1860 1861 1866 | been modified; 1869 1872 |
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 1859 1860 1861 | hand, 1866 1869 1872 |
we have evidence that
variability, variability, 1859 1860 1861 1866 1869 | variability 1872 |
when it has once come into play, does not
wholly wholly 1859 1860 1861 1866 | wholly 1869 1872 |
cease; cease; 1859 1860 1861 1866 | cease 1869 1872 |
for 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 |
new varieties are still occasionally produced by our
most anciently most anciently 1859 1860 1861 1866 | oldest 1869 1872 |
domesticated productions. |
|
Man does Man does 1859 1860 1861 1866 1869 | Variability is 1872 |
not actually
produce variability; produce variability; 1859 1860 1861 1866 1869 |
caused by man; 1872 |
he only unintentionally exposes organic beings to new conditions of life, and then nature acts on the
organisation, organisation, 1859 1860 1861 1866 1869 | organisation 1872 |
and causes
variability. variability. 1859 1860 1861 1866 1869 |
it to vary. 1872 |
But man can and does select the variations given to him by nature, and thus
accumulate accumulate 1859 1860 1861 1866 1869 | accumulates 1872 |
them in any desired manner. He thus adapts animals and plants for his own benefit or pleasure. He may do this methodically, or he may do it unconsciously by preserving the individuals most useful
to him at the time to him at the time 1861 |
to him at the time, 1859 1860 |
to him 1866 |
or pleasing to him 1869 1872 |
without any
thought thought 1859 1860 1861 1866 | intention 1869 1872 |
of altering the breed. It is certain that he can largely influence the character of a breed by selecting, in each successive generation, individual differences so slight as to be
....... 1861 1866 1869 1872 | quite 1859 1860 |
inappreciable
by an by an 1859 1860 1861 1866 | except 1869 1872 |
uneducated uneducated 1859 1860 1861 1866 |
by an educated 1869 1872 |
eye. This
process process 1859 1860 1861 1866 1869 | unconscious process 1872 |
of selection has been the great agency in the
production production 1859 1860 1861 1866 | formation 1869 1872 |
of the most distinct and useful domestic breeds. That many
of the of the 1859 1860 1861 1866 | of the 1869 1872 |
breeds produced by man have to a large extent the character of natural species, is shown by the inextricable doubts whether
very very 1859 1860 1861 1866 | very 1869 1872 |
many of them are varieties or
aboriginally aboriginally 1861 1866 1869 1872 | aboriginal 1859 1860 |
distinct species. distinct species. 1861 1866 1869 1872 | species. 1859 1860 |
|
|
There is no
obvious obvious 1859 1860 1861 1866 1869 | obvious 1872 |
reason why the principles which have acted so efficiently under domestication should not
have acted have acted 1859 1860 1861 1866 1872 | act 1869 |
under nature. In the
preservation preservation 1859 1860 1861 1866 | survival 1869 1872 |
of favoured
|