s. The most recent addition which our continent has received from
Siberia is, according to Mr. Petersen, the present Scandinavian fauna.
Scandinavia has obtained a larger number of species than the European
plain, because to this last migration were added such as prefer a
northern or Alpine climate.

As a contribution to the history and composition of the European fauna,
by far the most important work ever published is that of Dr. Kobelt, the
eminent German conchologist. Whilst the researches into the origin of
the Lepidoptera, above described, have been marred by the prevalent
prejudice as to the deleterious effects of a glacial climate on the
butterflies, the present author boldly works out the problem on
independent lines. He shuns theories and speculations almost altogether.
His great work, as yet practically unknown, the result of a lifetime of
the most painstaking labour, ranks among the most important
contributions to zoogeography. I shall have frequent occasion to refer
to it throughout these pages. Meanwhile some of his more remarkable
conclusions may be mentioned. "Comparing all classes of animals as to
their zoogeographical importance, the highest rank must undoubtedly be
accorded to the land-snails" (i., p. 7). "The Pleistocene, and with it
the land and fresh-water molluscan fauna of the present day has been
gradually evolved from the Tertiary one, and its roots can be traced
through the Cretaceous to the Jurassic epoch. During the whole of that
time no sudden appearance of a new fauna can be demonstrated. Quite
slowly, step by step, the Cretaceous is succeeded by the Tertiary fauna,
and one after the other of the characteristic palaearctic genera
appear--first the fresh-water, then the land forms" (p. 141). "The
division of the North Alpine from the South Alpine fauna must be older
than the Glacial period; and the present Central European fauna had
already become developed from the Pliocene _in all its details of form
and distribution_ before the commencement of the Ice Age" (p. 162). "We
must draw the conclusion from the preceding remarks, that the present
(palaearctic) molluscan fauna in its distribution is older than the
Glacial period, and that the latter produced merely a retreat of the
fauna from the most inhospitable regions of Europe with a subsequent
re-immigration, but did not cause its destruction" (i., p. 169).

A few attempts have also been made by naturalists to trace the origin of
the fauna