Origin of Species Variorum

→ the 1859 1860 1861 1866

of our imaginary Glacial period, the 1869 1872

→ the foregoing remarks on distribution apply not only to strictly arctic forms, but also to 1859 1860 1861 1866

it is necessary also to 1869

it is also necessary to assume that 1872

→ for some of these are 1859 1860 1861 1866 1869

were 1872

→ lower mountain-slopes and 1866 1869

lower mountains and 1859 1860 1861

world, for some of the species which now exist 1872

→ plains 1859 1860 1861 1866 1869

lower mountain-slopes and on the plains 1872

→ and 1859 1860 1861 1866 1869

are the same; and 1872

→ they do at 1866 1869 1872

at 1859 1860 1861

→ from each other by 1866 1869 1872

by 1859 1860 1861

→ ocean; so that it may well be asked how the same species could have entered two regions then so widely separated. 1866

ocean. 1859 1860 1861

ocean; so that it may well be asked how the same species could have entered the two continents then so widely separated. 1869

ocean; so that it may well be asked how the same species could then or previously have entered the two continents. 1872

↑ 2 blocks not present in 1866 1869 1872; present in 1859 1860 1861

I believe the above difficulty may be surmounted by looking to still earlier changes of climate of an opposite nature. We have good reason to believe that during the newer Pliocene period, before the Glacial epoch, and whilst the majority of the inhabitants of the world were specifically the same as now, the climate was warmer than at the present day.

→ which now live under latitude 60°, 1866

now living under the climate of latitude 60°, 1859 1860 1861

which now live under latitude 60°, lived 1869

which now live under latitude 60°, 1872

→ during the Pliocene period lived 1859 1860 1861 1866

during the Pliocene period 1869

lived during the Pliocene period 1872

→ terrestrial globe, we see that 1866

globe, we shall see that 1859 1860 1861

terrestrial globe, we see 1869 1872

→the arctic productions were as uniform round the polar regions as they are at the present day. But →the foregoing remarks on distribution apply not only to strictly arctic forms, but also to

include many

many

sub-arctic and

some few

~~northern~~

northern

temperate

forms

forms,

→for some of these are the same

round

the →lower mountain-slopes and on the →plains of North America and

Europe

Europe;

→and it may be

reasonably

....

asked how I account for

the necessary

this

degree of uniformity

the sub-arctic and

northern

....

temperate forms round the world, at the commencement of the

real Glacial

Glacial

period. At the present day, the sub-arctic and northern temperate productions of the Old and New Worlds are separated from each other by the

Atlantic

whole Atlantic

Ocean and by the

extreme

....

northern part of the Pacific. During the Glacial period, when the

in-

....

habitants

inhabitants

of the Old and New Worlds lived

further

farther

southwards than →they do at present, they must have been still more completely separated →from each other by wider spaces of →ocean; so that it may well be asked how the same species could have entered two regions then so widely separated. The explanation, I believe, lies in the nature of the climate before the commencement of the Glacial period.

During

this, the newer Pliocene period,

~~when~~

when

the majority of the inhabitants of the world were specifically the same as now,

and we

have good reason to believe that the climate was warmer than at the present day. ↑ Hence we may suppose that the organisms →which now live under latitude 60°, →during the Pliocene period lived

further

farther

father

north under the Polar Circle, in latitude

66°-67°;

and that the

strictly

present

arctic productions then lived on the broken land still nearer to the pole.

Now

Now,

if we look at a →terrestrial globe, we see that under the Polar Circle

that there

there

is almost continuous land from western Europe, through Siberia, to eastern America. And

this continuity of the circumpolar land,

with

and to

the consequent