Origin of Species Variorum

→ natural 1859 1860 1861 1866 1869

species through natural 1872

→ almost 1869 1872

in a great degree 1859 1860 1861 1866

→ varying individuals of the same species 1869 1872

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

→ surrounding 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

→ also, be 1869

be 1859 1860 1861 1866

also, be thus 1872

→ for 1869

to be filled up by the modification of 1872

↑ 1 blocks not present in 1869 1872; present in 1859 1860 1861 1866

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, and become adapted to, through modifica- tions in their structure and constitution.

→ OMIT 1869 1872

by checking immigration and consequently competition, 1859 1860 1861 1866

→ and 1859 1860 1861 1866 1869

at a slow rate; and 1872

→ importance in the production of new species. 1859 1860 1861 1866 1869

much importance. 1872

→ inhabitants will be 1869 1872

individuals supported on it will necessarily be very 1859 1860 1861 1866

→ this will 1869 1872

fewness of individuals will greatly 1859 1860 1861 1866

→ the appearance of 1859 1860 1861 1866 1869

OMIT 1872

→ OMIT 1869

species 1861 1866

the forms of life 1872

→natural selection. In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be →almost uniform; so that natural selection will tend to modify all the →varying individuals of the same species in the same

manner

relation

the

same

conditions.

Intercrosses,

also,

with the

individuals

inhabitants

of the →surrounding

districts,

districts

will

will,

→also, be prevented. 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-

newly

formed varieties is probably greater even than I

~~have~~

have

supposed. But from reasons already assigned I can by no means agree with this naturalist, that migration and isolation are necessary

elements for

for

the formation of new species. The importance of isolation is likewise great in preventing, after any physical change in the

conditions

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

will be

are

left open →for the old

inhabitants.

~~struggle~~

~~for~~

~~and~~

~~become~~

~~adapted~~

~~to.~~

↑ Lastly,

isolation,

isolation

→OMIT will give time for

any

new variety to be

~~slowly~~

slowly

improved

improved;

→and this may sometimes be of →importance in the production of new species. If, however, an isolated area be very small, either from being surrounded by barriers, or from having very peculiar physical conditions, the total number of the →inhabitants will be small; and →this will retard the production of new species through natural selection, by decreasing the

chance

chances

of →the appearance of favourable

variations.

variations arising.

individual differences.

The mere lapse of time by itself does

nothing,

nothing

either for or against natural selection. I state this because it has been erroneously asserted that the element of time

has been

assumed by me to play an all-important part in

natural selection,

modifying species,

as if all →OMIT were necessarily

undergoing

under- going