rmany, Switzerland,
Austria, Sicily, and Greece. _B. igneus_--the eastern race--is found in
Southern Sweden, Denmark, Germany, Austria, and Russia. The latter has
therefore a more northerly and easterly range. The species is not known
from Siberia, but makes its appearance again in China in a form which,
according to Dr. von Bedriaga, does not quite agree with either of the
two European races.

Now if we supposed _Bombinator_ to have originated in Europe, its
absence from the British Islands, most of the Mediterranean islands, and
the greater part of Scandinavia would not be easy of explanation, while
as an Asiatic migrant the European range is more readily understood. Its
apparent absence from Western Asia might quite likely be due to the fact
that the zoology of that part of the Continent is only now being
investigated. The latter has, moreover, undergone great physical changes
in recent geological times. The supposition that one migration of
_Bombinator_ from the south-east has taken place, and then another from
the east, seems to explain this case of distribution, as other similar
ones, in a most satisfactory manner.

The Tree-Frog (_Hyla arborea_) must be an ancient species, but it is not
of European origin. Few genera of Amphibia have a wider distribution
than _Hyla_. There are only three species in Asia, Europe, and Africa,
the remaining 129 being confined to America and Australia. Two of the
three Old World Tree-frogs are so closely allied that until recently
they were regarded as mere varieties of one another. These are _Hyla
arborea_ and _H. chinensis_. The former is found in Asia Minor, Persia,
China and Japan, and in most of the Mediterranean islands and Southern
Europe generally. It does not occur in the British Islands, Norway, or
North Russia, but in South Sweden, Germany, France, and Spain. It is
also known from North Africa and from Madeira, the Canaries, and the
Salvages. The occurrence of the Tree-Frog on so many of the
Mediterranean islands is of particular interest, especially as four
well-marked varieties have been distinguished by our leading
herpetologists, so that the more minute features of the various forms
can be traced from island to island, adding one more proof--if proof
were needed--of their former continuity. Of course, that _Hyla arborea_
must be considered an Oriental migrant seems so evident that it scarcely
needs further comment.

A number of mollusca might be mentioned whose rang