26O HISTORY OF THE EUROPEAN FAUNA. 



Bedriaga, docs 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 Bom- 

 binator 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 //. 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 



