GEOGRAPHICAL DISTRIBUTION. 607 



2. Indian region, with two provinces, viz. : 



a. Continental. 



b. Insular. 



V. South American Temperate realm, with two provinces, viz. : 



a. Andean. 



b, Pampeau. 



VI. Australian realm, with three regions, viz. : 



1. Australian, with two provinces, viz. : 



a. Australian. 



b. Papuan. 



2. Polynesian. 



3. New Zealand. 



VII. Lemurian realm, undivided. 

 VIII. Antarctic or South Circumpolar, undivided. 



Migrations of Animals. Intimately connected with zoogeog- 

 raphy are the migrations of animals, especially birds. Nearly all the 

 birds of the United States which breed in the central and northern 

 portions pass southward in the autumn, and winter in the Southern 

 States or in Central America and the West Indies. Most of the birds 

 which breed in Northern and Central Europe fly at the approach of 

 cold weather into Southern Europe or across the Mediterranean into 

 Northern Africa. The causes of this regular periodical migration are 

 probably due, primarily, to the changes of the seasons and to the want 

 of food in the colder portion of the year, and, secondarily, to the 

 breeding habits of birds. 



The periodical migrations of fishes from deep to shoal water are 

 connected with their breeding habits, the marine fish being in most 

 cases compelled to spawn in rivers or in shoal- water. The migratory 

 movements of fishes along the coast n.re probably connected with the 

 presence or absence of their accustomed food. 



The partial, occasional migrations of locusts depend on the undue 

 increase in the numbers of the insects, and the consequent lack of 

 food, while the direction of the swarms is largely dependent on the 

 general course and force of the winds. 



