Origin of Species Variorum

→ of the same species; 1869 1872

but will have supplanted each other; 1859 1860 1861 1866

→ the same variety will be 1869

each variety will have 1859 1860 1861 1866

the same form will be 1872

→ OMIT 1869 1872

I believe that during the slow process of modification 1859 1860 1861 1866

→ same species inhabiting the same area will be 1869 1872

species will have been 1859 1860 1861 1866

→ OMIT 1869 1872

will not have been due, 1859 1860 1861 1866

→ will not be due to 1869 1872

to 1859 1860 1861 1866

→ facts. 1859 1860 1861 1866 1869

facts. Change of climate must have had a powerful influence on migration. 1872

→ Change of climate must have had a powerful influence on migration; an impassable region when 1869

Change of climate must have had a powerful influence on migration: a region when 1859 1860 1861 1866

A region now impassable to certain organisms from the nature of 1872

→ was different from what it now is, may 1869

was different may 1859 1860 1861 1866

might 1872

→ OMIT 1869

but now be impassable; 1859 1860 1861 1866

when the climate was different. 1872

varieties,

varie- ties,

varieties

→of the same species; so that, at each successive stage of

modification,

modification

~~and improvement,~~

and improvement,

all the individuals of →the same variety will be descended from a single parent. But in the

majority

great majority

of cases, namely, with all organisms which habitually unite for each birth, or which

often

occasionally

intercross, →OMIT the individuals of the →same species inhabiting the same area will be kept nearly uniform by intercrossing; so that many individuals will

have gone

on simultaneously changing, and the whole amount of modification →OMIT at each

stage,

stage

→will not be due to descent from a single parent. To illustrate what I mean: our English

racehorses

race-horses

differ

slightly

....

from the horses of every other breed; but they do not

own

owe

their

superiority

difference

and

difference

superiority

to descent from any single pair, but to continued care in

selecting

the selecting

and training

many

of many

individuals during

many

each

generations.

generation.

Before discussing the three classes of facts, which I have selected as presenting the greatest amount of difficulty on the theory of

"single

centres of

creation,"

I must say a few words on the means of dispersal.

Means

Dispersal .—

Dispersal. —

Dispersal .

Sir C. Lyell and other authors have ably treated this subject. I can give here only the briefest abstract of the more important →facts. →Change of climate must have had a powerful influence on migration; an impassable region when its

climate,

climate

→was different from what it now is, may have been a high road for

migration,

migration;

→OMIT I shall, however, presently have to discuss this branch of the subject in some detail. Changes of level in the land must also have been highly influential: a narrow isthmus now separates two marine faunas; submerge it, or let it formerly have been submerged, and the two