Comparison with 1860 |
|
occasional intercross with a
distinct individual
is a law
of nature. I am well aware that there are, on this view, many cases of difficulty, some of which I am trying to investigate. Finally then, we may conclude that in many organic beings, a cross between two individuals is an obvious necessity for each birth; in many others it occurs perhaps only at long intervals; but in none, as I suspect, can self-fertilisation go on for perpetuity. |
Circumstances
Circumstances
1859 1860 1861 |
Circumstances
1866 1869 1872 |
favourable
favourable
1859 1860 1861 |
favourable
1866 1869 1872 |
to Natural Selection.
—
to Natural Selection.
—
1860 1861 |
to Natural Selection
.—
1859 |
to Natural Selection. 1866 |
for the production of new forms through Natural Selection.
1869 |
for the production of new forms through Natural Selection. 1872 |
|
This is an extremely intricate subject. A
large large 1859 1860 1861 1866 | great 1869 1872 |
amount of
inheritable and diversified variability is favourable, but I believe mere inheritable and diversified variability is favourable, but I believe mere 1859 1860 |
variability will evidently be favourable for the work of natural selection, but mere 1861 1866 |
variability, under which term 1869 1872 |
individual differences
suffice for the work. suffice for the work. 1859 1860 |
probably suffice. 1861 1866 |
are always included, will evidently be favourable. 1869 1872 |
A large number of individuals, by giving a better chance
for the appearance within any given period of profitable variations, for the appearance within any given period of profitable variations, 1859 1860 1861 1866 |
for the appearance of profitable variations within any given period, 1869 |
within any given period for the appearance of profitable variations, 1872 |
will compensate for a lesser amount of variability in each individual, and is, I believe, an extremely
important element of success. Though
nature nature 1859 1860 | Nature 1861 1866 1869 1872 |
grants
vast vast 1859 1860 1861 1866 | long 1869 1872 |
periods of time for the work of natural selection, she does not grant an indefinite period; for as all organic beings are
striving, striving, 1859 1860 | striving 1861 1866 1869 1872 |
it may be said, it may be said, 1859 1860 |
OMIT 1861 1866 1869 1872 |
to seize on each place in the economy of nature, if any one species does not become modified and improved in a corresponding degree with its competitors, it will
soon soon 1859 1860 1861 1866 | soon 1869 1872 |
be exterminated. ↑1 blocks not present in 1859 1860; present in 1861 1866 1869 1872 | Unless favourable variations be inherited by some at least of the offspring, nothing can be effected by natural selection.
|
|
|
In
man's man's 1859 1860 1861 1866 |
the case of 1869 1872 |
methodical selection, a breeder selects for some definite object, and free intercrossing will wholly stop
|
occasional intercross
with a with a 1859 1860 1861 1866 1869 | between 1872 |
distinct
individual individual 1859 1860 1861 1866 1869 | individuals 1872 |
is a
law law 1859 1860 1861 1866 1869 |
very general, if not universal, law 1872 |
of nature. I am well aware that there are, on this view, many cases of difficulty, some of which I am trying to investigate. Finally then, we may conclude that in many organic beings, a cross between two individuals is an obvious necessity for each birth; in many others it occurs perhaps only at long intervals; but in none, as I suspect, can self-fertilisation go on for perpetuity. |
Circumstances
Circumstances
1866 1869 1872 |
Circumstances
1859 1860 1861 |
favourable
favourable
1866 1869 1872 |
favourable
1859 1860 1861 |
for the production of new forms through Natural Selection.
for the production of new forms through Natural Selection.
1869 |
to Natural Selection
.—
1859 |
to Natural Selection.
—
1860 1861 |
to Natural Selection. 1866 |
for the production of new forms through Natural Selection. 1872 |
|
This is an extremely intricate subject. A
great great 1869 1872 | large 1859 1860 1861 1866 |
amount of
variability, under which term variability, under which term 1869 1872 |
inheritable and diversified variability is favourable, but I believe mere 1859 1860 |
variability will evidently be favourable for the work of natural selection, but mere 1861 1866 |
individual differences
are always included, will evidently be favourable. are always included, will evidently be favourable. 1869 1872 |
suffice for the work. 1859 1860 |
probably suffice. 1861 1866 |
A large number of individuals, by giving a better chance
for the appearance of profitable variations within any given period, for the appearance of profitable variations within any given period, 1869 |
for the appearance within any given period of profitable variations, 1859 1860 1861 1866 |
within any given period for the appearance of profitable variations, 1872 |
will compensate for a lesser amount of variability in each individual, and is, I believe,
an extremely an extremely 1859 1860 1861 1866 1869 | a highly 1872 |
important element of success. Though
Nature Nature 1861 1866 1869 1872 | nature 1859 1860 |
grants
long long 1869 1872 | vast 1859 1860 1861 1866 |
periods of time for the work of natural selection, she does not grant an indefinite period; for as all organic beings are
striving striving 1861 1866 1869 1872 | striving, 1859 1860 |
...OMIT 1861 1866 1869 1872 |
it may be said, 1859 1860 |
to seize on each place in the economy of nature, if any one species does not become modified and improved in a corresponding degree with its competitors, it will
....... 1869 1872 | soon 1859 1860 1861 1866 |
be exterminated. Unless favourable variations be inherited by some at least of the offspring, nothing can be effected by natural
selection. selection. 1861 1866 1869 |
selection. The tendency to reversion may often check or prevent the work; but as this tendency has not prevented man from forming by selection numerous domestic races, why should it prevail against natural selection? 1872 |
↑1 blocks not present in 1859 1860 1869 1872; present in 1861 1866 | Non-inheritance of any new character is, in fact, the same thing as reversion to the character of the grandparents or more remote ancestors; and no doubt the tendency to reversion may often have checked or prevented the action of natural selection; but its importance has been greatly exaggerated by some writers.
|
The
tendency to reversion
may often check or prevent the work; but as this tendency has may often check or prevent the work; but as this tendency has 1869 |
has 1861 1866 |
not prevented man from
forming by selection numerous domestic races, forming by selection numerous domestic races, 1869 |
creating innumerable hereditary races in the animal and vegetable kingdoms, 1861 1866 |
why should it
prevail against prevail against 1869 |
have stopped the process of 1861 1866 |
natural selection? |
|
In
the case of the case of 1869 1872 |
man's 1859 1860 1861 1866 |
methodical selection, a breeder selects for some definite object, and
free intercrossing will wholly stop free intercrossing will wholly stop 1859 1860 1861 1866 1869 |
if the individuals be allowed freely to intercross, 1872 |
|