162 



Biology in America 



zoogeographer divides the earth into five great realms, which 

 are more or less overlapping but which show in a broad way 

 the arrangement of animal life upon our globe. These realms 

 are the Holoarctic, including North America to Mexico, Eu- 

 rope, northern Africa, and most of Asia; the Neotropical, 

 comprising South and Central America and Mexico; the 



Arctic-Alpine [ 1 



HiKlsonian 



Canadian 



Transition 



Upper Sonoran 



Lower Sonoran 



Tropical 



AFTER U. S. BIOLOGICAL SURVEY 



Ethiopian, Africa, south of the Sahara ; the Oriental, India and 

 most of the Malay Archipelago ; and the Australian, Australia, 

 New Zealand, the southeastern portion of the Malay Archi- 

 pelago and the South Sea Islands. 



In the study of the geographical distribution of animals 

 (especially birds and mammals) in the United States and 

 in the correlation of their distribution with that of plants, 

 the principal agency has been the United States Biological 



