al fauna and flora are supposed to
have been absolutely destroyed by the glacial climate, or whether part
of them have been able to take refuge somewhere in the south; but the
great mass of our Alpine plants and animals are believed to have been
derived from the Siberian invasion, which I have fully described in the
fifth chapter. This invasion spread over the European plain, and when
the climate ameliorated, both animals and plants migrated north and
south to the mountains. This view agrees with the earlier theory, except
that the adaptation to Alpine conditions would, according to the former,
have taken place since the close of the Glacial period, during which
time no such modification or change of species seems to have been
produced in other parts of the world. The characteristic fauna of the
Alps, as has been gathered from the preceding pages, is mainly of
Central Asiatic rather than of Siberian origin. Migration to the Alps
took place by the Oriental route long before the Siberian invasion. Some
of the species of the latter have penetrated to the Alps, but these
Siberian species have not given to the fauna of the highest European
mountain range the striking character with which we all associate it.

Before concluding this chapter, a few remarks on the botanical aspect
of the Alpine problem might not be out of place. It will enable us to
judge which of the views indicated is the more probable, and will add to
the interest which may have been aroused by the perusal of this sketch
of the fauna of the Alps. Very much the same train of argument was
applied as to the course of events in the formation of the Alpine flora
as in the case of the fauna. The plants were all supposed to have been
killed or driven away by the arctic temperature of the Glacial period,
and their place taken by new migrants from the north or east when the
climate ameliorated.

Professor Engler, one of the highest living authorities on the
geographical distribution of plants, is of opinion (p. 102) that a large
number of the indigenous Alpine species did not originate till after the
close of the Glacial period, because so many of them are absent from the
Sierra Nevada in Spain, where the condition for their well-being exists,
while many have evidently spread from the Alps to the Carpathian
Mountains and to the Pyrenees. He does not believe that a glacial flora
could have existed in the plain between the Sierra Nevada and the
Pyrenees during the Gla