Origin of Species Variorum

→ 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

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.

~~relation~~

~~the~~

~~same~~

~~conditions.~~

Intercrossing

~~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