SPREADING OF THE OTHER ANIMALS. 87 



rations, the region 10 degrees on the nether side of 

 the snow-line has been given as the limit of their 

 spreading. 



4. The family of Tortoises is peculiar to the 

 warm part of the Temperate Zone. The Marine 

 Tortoise does not extend beyond the 40th degree of 

 latitude in the Northern Hemisphere. Most of them, 

 and the largest, particularly the Green Turtle (Testudo 

 my das), are found in the seas between the Tropics 

 only. Those species which inhabit rivers and the main 

 land are removed somewhat further from the warm 

 countries ; yet, the region in the 50th degree of 

 latitude, on the Northern Hemisphere, may be re- 

 garded as the limit of their spreading. In Silesia 

 Mud Tortoises are met with in small numbers. 

 According to such observations, the line of the 

 spreading of the Marine Tortoise has been ex- 

 tended to the 40th degree : whilst the limits of the 

 species which inhabit rivers and the main land, 

 extend as far as the 50th degree. 



SPREADING OF THE OTHER ANIMALS. 



1. All Fish, inhabitants of the sea as well as 

 inhabitants of fresh water, gradually increase in 

 regard to number, size, appearance, and quickness, 

 from the cold to the Temperate Zones, and from 



