54 TEXT-BOOK OF ZOOLOGY 



Baltic. Its real home is the sea, and it only leaves the water for the 

 shore in order to sleep or bask in the sun. Large companies of seals 

 may be seen under these conditions on the sands or the cliffs by the 

 shore, or on floating ice-floes. Here, too, may be heard their hoarse 

 barking, resembling somewhat that of the dog (whence the German name 

 of this animal, see-liund = sea-dog). 



The seal accordingly combines the habits of a land and water animal, 

 and its structure and anatomy also correspond with this double nature. 



B. The Seal regarded as an Aquatic Animal. 



i. Protection against Loss of Heat. 



As the seal passes two-thirds of its life in the water, no fur, 

 however thick or dense, would be able to maintain the heat of 

 its body (as, for instance, in the case of the otter) ; for after a day 



SEAL. (One-twenty-fourth natural size. 



passed in the water, so much air would gradually escape from 

 the fur that the water would penetrate to the skin, and produce a 

 great cooling of the body. Accordingly other means are provided for 

 preventing an excessive loss of heat, in the shape of a thick layer of fat or 

 blubber which envelops the whole body. 



ii. The Seal as a Diver and Swimmer. 



The sea supplies this animal with an abundance of food, chiefly 

 consisting of fish and the larger kinds of Crustacea. In winter, when 

 wide stretches of the surface are frozen, it keeps holes open in the ice 

 by repeatedly diving in and out. The seal is a rapid swimmer and 

 skilful diver, these capacities being essential to it both in the pursuit of 

 the fishes and crustaceans which form its prey, and also to enable it to 

 escape from its chief enemies, the greedy shark and the rapacious 

 dolphin (which see). In swimming it moves through the water with the 



