Origin of Species Variorum

→ 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 the two continents then so widely separated. 1869

ocean. 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; 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°, lived 1869

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

which now live under latitude 60°, 1866

which now live under latitude 60°, 1872

→ during the Pliocene period 1869

during the Pliocene period lived 1859 1860 1861 1866

lived during the Pliocene period 1872

→ terrestrial globe, we see 1869 1872

globe, we shall see that 1859 1860 1861

terrestrial globe, we see that 1866

→ under a more favourable climate 1869 1872

for intermigration under a more favourable climate, 1859 1860 1861

under a more favourable climate for intermigration, 1866

→ for intermigration, will account for the supposed uniformity of 1869 1872

I attribute the necessary amount of uniformity in 1859 1860 1861

I attribute a considerable degree of uniformity in 1866

→ large, but partial 1859 1860 1861 1866 1869

great 1872

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 the two continents 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

....

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°, lived →during the Pliocene period

further

father

farther

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 under the Polar Circle

there

that there

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

....

this continuity of the circumpolar land,

and to

with

the consequent freedom →under a more favourable climate →for intermigration, will account for the supposed uniformity of the sub-arctic and

northern

....

temperate productions of the Old and New Worlds, at a period anterior to the Glacial epoch.

Believing, from reasons before alluded to, that our continents have long remained in nearly the same relative position, though subjected to →large, but partial oscillations of level, I am strongly inclined to extend the above view, and to infer that during some

earlier

still earlier

and still warmer period, such as the older Pliocene period, a large number of the same plants and animals inhabited the almost continuous circumpolar land; and that these plants and animals, both in the Old and New Worlds, began slowly to migrate southwards as the climate became less warm, long before the

com-

....