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 range indicates that they have migrated to Europe from Asia Minor. _Buliminus pupa_ is one of these. It is known from Asia Minor, Greece, South Italy, Sicily, and Algeria. _Buliminus detritus_ is perhaps better known, being common in some parts of Germany. From there its range spreads east as far as Asia Minor. Many closely allied species inhabit Western Asia, to which they are confined, while others enter on European territory in some of the Greek islands. _B. fasciolatus_ occurs on the islands of Crete, Rhodes, Cyprus, and in Greece and Syria. Most of the species of _Buliminus_ have a very restricted range, but _Buliminus obscurus_ is found almost all over Europe, from Ireland in the west to the Crimea and Transcaucasia in the east. Whether the sub-genus _Pomatia_ of the genus _Helix_--to which the so-called Roman Snail belongs--is of Asiatic origin, or whether some of the species have migrated from Europe to Asia, I am not prepared to say; but there can be no doubt that _Helix pomatia_ has reached Western Europe from the east.