See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1860
1861
1866
1869
1872

I have already attempted to show that 1859 1860 1861 1866
as already stated 1869
as already stated, 1872

I am convinced that 1859 1860
of time, 1869 1872
OMIT 1861 1866

If there exist 1859 1860 1861 1866 1869
With respect to 1872

which never 1859 1860 1861 1866 1869
extremely low in the scale, which do not propagate sexually, nor conjugate, and which cannot possibly 1872

as long as their 1859 1860 1861 1866 1869
under the same 1872

remain the same, 1859 1860 1861 1866 1869
OMIT 1872

destroying any which depart 1859 1860 1861 1866 1869
which will destroy any individuals departing 1872

but if their 1859 1860 1861 1866 1869
If the 1872

process of 1859 1860 1861 1866
changes effected through 1869
modification of 1872

natural 1859 1860 1861 1866 1869
species through natural 1872

in a great degree 1859 1860 1861 1866
almost 1869 1872

individuals of a varying species throughout the area 1859 1860 1861 1866
varying individuals of the same species 1869 1872

same species, which otherwise would have inhabited the surrounding and differently circumstanced 1859 1860 1861
same species, which othewise would have inhabited the surrounding and differently circumstanced 1866
surrounding 1869 1872

be 1859 1860 1861 1866
also, be 1869
also, be thus 1872

3 blocks not present in 1859 1860 1861 1866; present in 1869 1872
Moritz Wagner has lately published an interesting essay on this subject, and has shown that the service rendered by isolation in preventing crosses between newly formed varieties is probably greater even than I have supposed. But from reasons already assigned I can by no means agree with this naturalist, that migration and isolation are necessary for the formation of new species. The importance of isolation is likewise great in preventing, after any physical change in the conditions, such as of climate, elevation of the land, &c., the immigration of better adapted organisms; and thus new places in the natural economy of the district are left open for the old inhabitants to struggle for and become adapted to.

which unite for each birth;
but,
but
I have already attempted to show that we have reason to believe that occasional intercrosses take place with all animals and
with all
with all
plants. Even if these take place only at long
intervals
intervals,
I am convinced that the young thus produced will gain so much in vigour and fertility over the offspring from long-continued self-fertilisation, that they will have a better chance of surviving and propagating their kind; and thus, in the long run, the influence of
crosses,
intercrosses,
even at rare intervals, will be great. If there exist organic beings which never intercross, uniformity of character can be retained
by
amongst
them
them,
as long as their conditions of
life,
life
remain the same, only through the principle of
inheritance
inheritance,
and through natural selection destroying any which depart from the proper
type.
type;
but if their conditions of life change and
the
they
form undergoes
undergo
modification, uniformity of character can be given to
the
their
modified offspring, solely by natural selection preserving
similar
the same
favourable variations.
Isolation, also, is an important element in the process of natural selection. In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be in a great degree uniform; so that natural selection will tend to modify all the individuals of a varying species throughout the area in the same
manner.
manner
in
in
relation
relation
to
to
the
the
same
same
conditions.
conditions.
Intercrossing
Intercrosses,
also,
also,
with the
inhabitants
individuals
of the same species, which otherwise would have inhabited the surrounding and differently circumstanced
districts
districts,
will,
will
be prevented. But isolation probably acts more efficiently in checking the immigration of better adapted organisms, after any physical change, such as of climate or elevation of the land, &c.; and thus new places in the natural economy of the country are left open for the old inhabitants to struggle
for
for,
and become adapted to, through
modifications
modifica- tions