See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1861
1866
1869
1872

at 1859 1860 1861
they do at 1866 1869 1872

by 1859 1860 1861
from each other by 1866 1869 1872

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 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 1859 1860 1861; present in 1866 1869 1872
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, we have good reason to believe that the climate was warmer than at the present day.

now living under the climate of latitude 60°, 1859 1860 1861
which now live under latitude 60°, 1866
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

globe, we shall see that 1859 1860 1861
terrestrial globe, we see that 1866
terrestrial globe, we see 1869 1872

for intermigration under a more favourable climate, 1859 1860 1861
under a more favourable climate for intermigration, 1866
under a more favourable climate 1869 1872

I attribute the necessary amount of uniformity in 1859 1860 1861
I attribute a considerable degree of uniformity in 1866
for intermigration, will account for the supposed uniformity of 1869 1872

large, but partial 1859 1860 1861 1866 1869
great 1872

whole Atlantic
Atlantic
Ocean and by the
extreme
extreme
northern part of the Pacific. During the Glacial period, when the
in-
....
habitants
inhabitants
of the Old and New Worlds lived
farther
further
southwards than at present, they must have been still more completely separated by wider spaces of ocean. 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. Hence we may suppose that the organisms now living under the climate of latitude 60°, during the Pliocene period lived
farther
father
further
north under the Polar Circle, in latitude
66°-67°;
66°-67°;
and that the
present
strictly
arctic productions then lived on the broken land still nearer to the pole.
Now,
Now
if we look at a globe, we shall see that under the Polar Circle
that there
there
is almost continuous land from western Europe, through Siberia, to eastern America. And
to
to
this continuity of the circumpolar land,
with
and to
the consequent freedom for intermigration under a more favourable climate, I attribute the necessary amount of uniformity in the sub-arctic and
northern
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
still earlier
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