Origin of Species Variorum

→ first migration when 1866 1869 1872

migration as 1859 1860 1861

→ formerly permitted their 1866 1869 1872

permitted their former 1859 1860 1861

↑ 1 blocks not present in 1866 1869 1872; present in 1859 1860 1861

If the climate, since the Glacial period, has ever been in any degree warmer than at present (as some geologists in the United States believe to have been the case, chiefly from the distribution of the fossil Gnathodon), then the arctic and temperate productions will at a very late period have marched a little further north, and subsequently have retreated to their present homes; but I have met with no satisfactory evidence with respect to this intercalated slightly warmer period, since the Glacial period.

→ moved first southward and afterwards backwards to the north, in unison with the changing climate, they will not 1866 1869 1872

during their long southern migration and re-migration northward, will 1859 1860 1861

→ during their long migrations to any great diversity of temperature; 1869 1872

to nearly the same climate, 1859 1860 1861

during their long migrations to any great diversity of temperature, 1866

→ they all migrated 1869 1872

is especially to be noticed, they will have kept 1859 1860 1861

they will all have migrated 1866

at points so immensely remote as

the mountains of the United States and

those of

Europe. We can thus also understand the fact that the Alpine plants of each mountain-range are more especially related to the arctic forms living due north or nearly due north of them: for the →first migration when the cold came on, and the

remigration

re-migration

on the returning warmth,

will

would

generally have been due south and north. The Alpine plants, for example, of Scotland, as remarked by Mr. H. C. Watson, and those of the Pyrenees, as remarked by Ramond, are more especially allied to the plants of northern Scandinavia; those of the United States to Labrador; those of the mountains of Siberia to the arctic regions of that country. These views, grounded as they are on the perfectly well-ascertained occurrence of a former Glacial period, seem to me to explain in so satisfactory a manner the present distribution of the Alpine and Arctic productions of Europe and America, that when in other regions we find the same species on distant mountain-summits, we may almost

conclude

conclude,

without other evidence, that a colder climate →formerly permitted their migration across the

low

....

intervening

tracts, since

lowlands, now

become too warm for their existence. ↑

The

As the

arctic

forms,

forms

→moved first southward and afterwards backwards to the north, in unison with the changing climate, they will not have been exposed →during their long migrations to any great diversity of temperature;

and,

and

as →they all migrated in a body

together;

together,

consequently

....

their mutual relations will not have been much

disturbed,

disturbed.

and,

Hence,

in accordance with the principles inculcated in this volume,

they

these forms

will not have been liable to much modification. But with

our

the

Alpine productions, left isolated from the moment of the returning warmth, first at the bases and ultimately on the summits of the mountains, the case will have been