n between Scandinavia, Greenland, and North America (Fig.
13). One of the highest authorities on the geographical distribution of
plants, Professor Engler, maintains that the arguments in favour of this
Arctic connection of America with Europe are more weighty than those for
a land-bridge between Greenland, Iceland, the Faroes, and Great Britain.
Moreover, he is of opinion that a certain number of species of plants
belonging to the Alpine flora of Arctic Siberia have travelled from
Scandinavia _via_ Greenland and North America to Eastern Asia, and not
direct from Scandinavia to Siberia (p. 143).

[Illustration: Fig. 13.--Map of Europe, indicating approximately the
distribution of land and water during the earlier stages of the Glacial
period--shortly after the period represented in Fig. 12, p. 156. The
darkly shaded parts indicate the areas covered by water, and the white
portions what was land at the time.]

That this ancient Arctic land-connection existed almost throughout the
Glacial period appears to me probable. It has often been suggested that
such a land-barrier was one of the principal causes of the production of
the glacial phenomena in Europe, and as such it must have existed intact
certainly during the earlier stages of the Glacial period. The barrier
must then have gradually subsided in one or two places; and once a
breach was formed, the complete union between the Atlantic and the
Arctic Oceans could not have been long delayed.

The terrestrial fauna and flora, as we have seen, lend strong support to
the view of the former connection between Scandinavia and Greenland, but
many other facts point in the same direction. It was Edward Forbes who
first drew attention to the presence of a number of species of littoral
molluscs on the coast of Finmark which also occur on the coast of
Greenland, and he expressed the firm conviction that they indicated by
their existence on both sides of the Atlantic some ancient continuity of
the coast-line. He held that the line of migration of these mollusca was
probably from west to east, and that it must have taken place during
physical conditions entirely different from those prevailing at present.
If Forbes's view is correct, a current must have existed from the north
coast of North America along the northern shore of the ancient land
which stretched east as far as Europe. We have also some palaeontological
evidence bearing on the existence of such a current (p. 173).

As