10 BIOLOGICAL SOCIETY OF WASHINGTON. 



the Arctic, the Indo-African, the Lemurian, the South American 

 Temperate, and the Antarctic. 



THE ARCTIC REALM. 



Mr. Allen gives the following reasons for retention of this realm : 



" Whether or not an Arctic Region should be recognized as a 

 division of the first rank is a question not easy to satisfactorily an- 

 swer. Naturalists who have made the distribution of animal life 

 in the boreal regions a subject of special study very generally agree 

 in the recognition of ahyperborealor circumpolar fauna, extending 

 in some cases far southward over the Temperate Zone. The Arctic 

 portion of this hyperborean region has been frequently set off as a 

 secondary division, or sub-region, and generally recognized as pos- 

 sessing many features not shared by the contiguous region to the 

 southward. For the present I prefer to still retain it as a division 

 of the first rank. It is characterized mainly by the paucity of its 

 life, as compared with every region except the Antarctic, and by 

 what it has not rather than by the possession of peculiar species or 

 groups. It wholly lacks both Amphibian and Reptilian life, is 

 almost exclusively the summer home of many birds, and forms the 

 habitat of the Esquimaux, the Arctic Fox, the Polar Bear, the 

 Musk Ox, the Polar Hare, the Lemmings, the Walruses, the Narwhal, 

 and the White Whale, which are confined within it. It has no 

 Chiroptcni nor Insecthwra, two or three species of Shrews, however, 

 barely reaching its southern border. It shares with the cold-temp- 

 erate belt the presence of the Moose and the Reindeer, several Pin- 

 nipeds, a number of boreal species of Glircs, several fur-bearing 

 Carnivora, and a considerable number of birds. Its southern bound- 

 ary may be considered as coinciding very nearly with the northern 

 limit of arboreal vegetation, and hence approximately with the iso- 

 therm of 32° F. Its more characteristic terrestrial forms range 

 throughout its extent, none being restricted to either the North 

 American or Europ^eo-Asiatic continent. Hence it is indivisible 

 into regions of the second and third grades (regions and provinces,) 

 and may be considered as embracing a single hyperborean assem- 

 blage of life." 



It cannot be overlooked that the reasons thus urged are very un- 

 satisfactory, and result in part from the confusion of inland and 

 marine faunae under the same category. The seals, walruses, and 



