378 ELEMENTARY ZOOLOGY. 



flying forms, whereas a very narrow bit of sea- water would 

 be a complete barrier to fish or other animals living in a 

 river emptying into it. Some forms have a very narrow 

 range of temperature, as the polar bear; others may 

 range widely without feeling the limiting effects of tem- 

 perature, as man. 



In general, the barriers that count for most in determin- 

 ing the great world faunas are temperature as determined 

 by latitude ; the oceans to land forms ; and the continents 

 to ocean forms. The continents and oceans divide the 

 earth roughly from north to south; the temperature 

 zones divide it from east to west. 



374. The Principal World Areas of Animal Life. The 



result of these barriers has been to separate the earth 

 into realms which are usually indicated about as follows: 

 (i) the Near die, including temperate North America 

 and Greenland; (2) Neotropical, including Mexico, Central 

 America, and tropical South America; (3) the P alee- 

 arctic, including Europe and northern and central Asia; 



(4) the Indo- African, including tropical Asia and Africa; 



(5) Australian, including besides Australia the islands of 

 the south Pacific and Indian oceans. In addition to 

 these are certain oceanic islands, such as Madagascar, 

 which have been so long isolated as to have faunas very 

 different from the nearest continents. 



375. Practical Exercise for Library. The student should by refer- 

 ence to all sources find what are the most characteristic types of the 

 higher animals, at least, of these five geographical regions. What 

 are the conditions that are believed to have produced the peculiar 

 differences between them and those nearest them? Treat especially 

 the fauna of Madagascar and of Australia. 



376. Topics for Themes in Zoology and English. i. 



What is the original home and natural distribution of the 



