no VERTEBRATES: MAMMALS. 



duce and nourish their young in the same manner as 

 other Mammals. They are destitute of hair, and cov- 

 ered with a smooth skin, under which is a thick layer 

 of fat called blubber. They propel themselves with ra- 

 pidity by the downward and upward movement of the 

 tail. In the most prominent members of the Cetacea 

 the breathing-hole, which corresponds to the nostrils of 

 other animals, is situated on the top of the head, and 

 through this the water which has been taken into the 

 mouth is spouted to a great height, and this spouting or 

 blowing may be seen at great distances, and often serves 

 to reveal these animals when they would otherwise be 

 unobserved. The species are numerous ; and there are 

 at least three families, Balaenidse or Right-Whale Fam- 

 ily, Physeteridas or Sperm-Whale Family, and Delphinidae 

 or Dolphin Family. The first two have the head exces- 

 sively large. 



BALyENiD^E, OR RIGHT- WHALE FAMILY. This Fam- 

 ily comprises Whales which have no real teeth, but the 

 two sides of their upper jaw, which is keel-shaped, are 

 furnished with rows of vertical horny plates, called whale- 

 bone, formed of a sort of fibrous horn, and which are 

 fringed on their inner edges. This arrangement is adapt- 

 ed to the nature of the food of these whales, which con- 

 sists of small marine zoophytes, mollusks, and crustaceans. 

 Fig. 81. Swimming through schools of 



these little animals, the Whale 

 engulfs myriads of them at 

 once in its enormous mouth ; 

 and the water taken with them 

 is strained off through the 

 fringes, and all the animals, 

 of Right""wfc[ir, showing the even tn e smallest, retained and 



whalebone. Swallowed. 



The Genus Balczna comprises the Right Whales proper. 



