Origin of Species Variorum

→ occurred within the same period; 1859 1860 1861 1866

probably occurred,— 1869 1872

→ transport,— a subject which has hardly ever been properly experimentised on; 1859 1860

transport,— a subject which has hardly ever been properly experimented on; 1861 1866

trans- port,— 1869

transport,— 1872

→ how 1859 1860 1861 1866 1869

and this is a very important consideration, how 1872

→ tracts, I think 1859 1860

tracts, 1861 1866

tracts,— 1869 1872

→ in 1859 1860 1861 1866

is not insuperable in 1869 1872

→ the same parents, are not insuperable. 1859 1860 1861 1866

common parents. 1869 1872

→ and 1859 1860 1861 1866

of all kinds, and 1869 1872

→ change most 1859 1860 1861 1866

have changed very 1869 1872

→ I do not think that 1859 1860 1861 1866

OMIT 1869 1872

→ insuperable; though they often are 1859 1860 1861 1866

far from insuperable; though 1869 1872

→ extremely grave. 1859

extremely great. 1860 1861 1866

they are often great. 1869 1872

→ has been the influence of the modern 1859 1860 1861 1866

a part the 1869

a part the last 1872

→ which I am fully convinced simultaneously affected the whole world, or at least great meridional belts. 1859 1860

which I am fully convinced simultaneously affected the whole world, or at least great longitudinal belts. 1861 1866

has played, which affected even the equatorial regions, and which, during the alternations of the cold in the north and south, allowed the productions of opposite hemispheres to mingle, and left some of them stranded in all parts of the world on the mountain-summits. 1869

has played, which affected even the equatorial regions, and which, during the alternations of the cold in the north and south, allowed the productions of opposite hemispheres to mingle, and left some of them stranded on the mountain-summits in all parts of the world. 1872

changes of climate and of the level of the land, which have certainly occurred within the recent period, and of other

~~similar~~

similar

changes which

~~may~~

may

have →occurred within the same period; if we remember how

~~profoundly~~

profoundly

ignorant we are with respect to the many

~~and~~

and

curious means of occasional →transport,— a subject which has hardly ever been properly experimentised on; if we bear in

mind,

mind

→how often a species may have ranged continuously over a wide area, and then have become extinct in the intermediate →tracts, I think the

difficulty

difficulties

→in believing that all the individuals of the same species, wherever

found, are

located, have

descended from →the same parents, are not insuperable. And we are led to this conclusion, which has been arrived at by many naturalists under the designation of single centres of creation, by

various

some

general considerations, more especially from the importance of barriers →and from the analogical distribution of sub-genera, genera, and families.

With respect to

~~the~~

the

distinct species

belonging to

the same genus, which on

our

theory

~~must~~

must

have spread from one parent-source; if we make the same

allowance

allowances

as before for our ignorance, and remember that some forms of life →change most slowly, enormous periods of time

having been

being

thus granted for their migration, →I do not think that the difficulties are →insuperable; though they often are in this case,

and

in that of the individuals of the same species, →extremely grave.

As exemplifying the effects of climatal changes on distribution, I have attempted to show how important →has been the influence of the modern Glacial

period

period,

→which I am fully convinced simultaneously affected the whole world, or at least great meridional belts. As showing how diversified are the means of occasional transport, I have discussed at some little length the means of dispersal of fresh-water productions.