ZOOLOGICAL PROVINCES. 161 



tinguished six regions, the limits of which agreed fairly well 

 with the distribution of Mammalia and Reptilia. These regions 

 are 



(1) The Palaictrctic Region Europe, the temperate part of Asia, 

 and North Africa as far as Mount Atlas. 



(2) Nearctic Region Greenland and North America as far as 

 North Mexico. 



(3) The Ethiopian Reyion Africa, south of Atlas, Madagascar, 

 and the Mascarenes with South Arabia. 



(4) The Indian Region India south of the Himalayas, to South 

 China, Borneo and Java. 



(5) The Australian Region Celebes and Lonibok eastward to 

 Australia, and the South Sea Islands. 



(6) The Neotropical Reyion South America, the Antilles, and 

 South Mexico. 



Other naturalists (Huxley) have since shown that the four first 

 of these regions have a much greater resemblance to one another 

 than any one of them has to the Australian or South American 

 regions; that New Zealand is entitled by the peculiarities of its 

 fauna to be considered as forming a region by itself ; finally, that a 

 eircuni polar * province should be formed equal in value to the Palte- 

 arctic and Nearctic. 



Wallace objects to the establishment either of a New Zealand or of 

 a circumpolar region, and advocates the adoption of the six regions 

 of Sclater on practical grounds, but suggests the modification that 

 since the South American and Australian are much more isolated,, 

 the regions should not be of equal value. 



These regions are bounded by extended seas, lofty mountain ranges,. 

 or vast sandy deserts, and obviously such boundaries do not constitute 

 effective barriers to the migration of all animals, but allow certain 

 groups to pass from one region to another. 



The obstacles to immigration and emigration appear in certain. 

 places, at all events in the present time, to be insurmountable ; 



* Andrew Murray, on the contrary, in his work on the geographical dis- 

 tribution of Mammalia in 1866, distinguishes only four divisions the Palajarctic, 

 Indo-African, the Australian, and the American. Rutimeyer recognises in addi- 

 tion to the six provinces of Sclater a Mediterranean and Circumpolar province. 

 J. A. Allen ("Bulletin of the Museum of Comparative Zoology, Cambridge," 

 vol. ii.) proposes to distinguish eight regions, in connection with " the law of 

 circumpolar distribution of life in zones : " (1 ) Arctic realm ; (2) North Temper- 

 ate realm ; (3) Tropical American realm ; (4) Indo-African Tropical realm ; 

 (5) Tropical South American realm ; (6) Temperate African realm ; (7) Aut- 

 arctic realm ; (8) Australian realm. 



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