See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1861
1869
1872

the course of ages chanced to arise, and which in 1859 1860 1861 1866
OMIT 1869 1872

by specially acting on the reproductive system, causes or 1859 1860 1861 1866
cause or 1869
give a tendency to 1872

increases variability; 1859 1860 1861 1866
excite a tendency to vary; 1869
increased variability; 1872

of life are supposed to have undergone a 1859 1860 1861 1866
are supposed to have 1869
have 1872

profitable variations occurring; and unless 1859 1860 1861 1866 1869
the occurrence of 1872

2 blocks not present in 1859 1860 1861 1866; present in 1869 1872
Under the term of "variations," it must never be forgotten that mere individual differences are always included. As man can certainly produce a great result with his domestic animals and plants by adding up in any given direction individual differences, so could natural selection, but far more easily, from having incomparably longer time for action.

OMIT 1861 1866
as I believe, 1859 1860

for action. 1861 1866
at her disposal. 1859 1860

to produce 1859 1860 1861 1866 1869
in order that 1872

for 1859 1860 1861 1866 1869
should be left, for 1872

influence of a single introduced tree or mammal has been shown to be. But in the case of an island, or of a country partly surrounded by barriers, into which new and better adapted forms could not freely enter, we should then have places in the economy of nature which would assuredly be better filled up, if some of the original inhabitants were in some manner modified; for, had the area been open to immigration, these same places would have been seized
on
on
by intruders. In such
cases,
case,
every
every
slight
modifications,
modification,
which in the course of ages chanced to arise, and which in any way favoured the individuals of any
of the
of the
species, by better adapting them to their altered conditions, would tend to be preserved; and natural selection would
thus
thus
have free scope for the work of improvement.
We have
good reason
reason
to believe, as
shown
stated
in the first chapter, that
a
a
changes
change
in the conditions of
life
life,
by specially acting on the reproductive system, causes or increases variability; and in the foregoing
cases
case
the conditions of life are supposed to have undergone a
changed,
change,
and this would manifestly be favourable to natural selection, by
affording
giving
a better chance of profitable variations occurring; and unless
such
profitable variations.
profitable variations
Unless such
do
occur, natural selection can do nothing. Not
that,
that
OMIT any extreme amount of variability is necessary; as man can certainly produce great results by adding up in any given direction mere individual differences, so could
Nature,
natural selection,
but far more easily, from having incomparably longer time for action. Nor do I believe that any great physical change, as of climate, or any unusual degree of isolation to check
immigra- tion,
immigration,
is
actually
actually
necessary to produce new and unoccupied places for natural selection to fill up by
modifying and
modifying and
improving some of the varying inhabitants. For as all the inhabitants of each country are struggling together