CHAPTER XI 



THE PAL^ARCTIC AND NE ARCTIC REGIONS COMPARED AS 

 REGARDS THE FAMILIES AND GENERA OF THEIR MAM- 

 MALIA AND BIRDS 



In a paper read before the Cambridge Natural Science 

 Club on March 12 (and printed in Nature of April 26, 

 1894), I discussed the question of the nature and uses of 

 Zoological Regions, and arrived at the conclusion that, in 

 order to secure the maximum of utility, it is essential to 

 have only one set of regions for all groups of land animals ; 

 and, further, that the six regions established by Dr. P. L. 

 Sclater are the most natural and convenient, and are best 

 adapted to facilitate the comparative study of distribution, 

 which is the main purpose for which Zoological Regions, 

 as distinct from the ordinary geographical divisions of the 

 globe, have been established. 



These regions were at first generally adopted ; but of 

 late years many eminent naturalists, both in America and 

 Europe, have proposed other divisions, though hardly any 

 two of these agree with each other. The most important 

 modification, and that which has been adopted by several 

 zoologists both as regards mammals and birds, is to unite 

 the Palsearctic and Nearctic Regions so as to form one 

 new region, coextensive with the extratropical Northern 

 Hemisphere. This new region, which has been termed 

 the Holarctic, is said to be more nearly equal to the other 

 regions as regards peculiar genera and families, and, 

 therefore, to form part of a more natural and harmonious 

 series than if we treat the two component parts as 



