acent parts
of the continent and equally rich in species. The glaciation and
submergence destroyed much of this fauna; and the permanent change of
climate on the passing away of the glacial conditions appears to have led
to the extinction or migration of many species in the adjacent continental
areas, where they were succeeded by the assemblage of animals now occupying
Central Europe. When England became continental, these entered our country;
but sufficient time does not seem to have elapsed for the migration to have
been completed before subsidence again occurred, cutting off the further
influx of purely terrestrial animals, and leaving us without the number of
species which our favourable climate and varied surface entitle us to.
{339}

To this cause we must impute our comparative poverty in mammalia and
reptiles--more marked in the latter than the former, owing to their lower
vital activity and smaller powers of dispersal. Germany, for example,
possesses nearly ninety species of land mammalia, and even Scandinavia
about sixty, while Britain has only forty, and Ireland only twenty-two. The
depth of the Irish Sea being somewhat greater than that of the German
Ocean, the connecting land would there probably be of small extent and of
less duration, thus offering an additional barrier to migration, whence has
arisen the comparative zoological poverty of Ireland. This poverty attains
its maximum in the reptiles, as shown by the following figures:--

Belgium has 22 species of reptiles and amphibia.
Britain ,, 13 ,, ,, ,,
Ireland ,, 4 ,, ,, ,,

Where the power of flight existed, and thus the period of migration was
prolonged, the difference is less marked; so that Ireland has seven bats to
twelve in Britain, and about 110 as against 130 land-birds.

Plants, which have considerable facilities for passing over the sea, are
somewhat intermediate in proportionate numbers, there being about 970
flowering plants and ferns in Ireland to 1,425 in Great Britain,--or almost
exactly two-thirds, a proportion intermediate between that presented by the
birds and the mammalia.

_Peculiar British Birds._--Among our native mammalia, reptiles, and
amphibia, it is the opinion of the best authorities that we possess neither
a distinct species nor distinguishable variety. In birds, however, the case
is different, since some of our species, in particular our coal-tit and
long-tailed tit, pr