262 A COURSE ON ZOOLOGY. 



have no teeth, those organs being replaced by fibrous 

 plates, with which each side of the mouth is provided, 

 and formed of the blackish elastic substance commonly 

 called whalebone. These plates, from eight to ten inches 

 wide and as much as ten feet long, are rooted in the 

 upper jaw, and have together the appearance of an 

 enormous comb. Whales have two anterior limbs, com- 

 posed of the same bones that form the corresponding 

 limbs of large terrestrial animals, but only the hand is 

 outside of the body, and the phalanges, instead of being 

 free, are blended into a fin. There are no posterior limbs, 

 and the body terminates in a crescent-shaped tail, which 

 is horizontal, instead of being vertical, like a fish's tail. 



The respiration of whales is aerial; they have lungs, 

 and respire the air itself, so that although they live en- 

 tirely in the water, they are obliged to come frequently 

 to the surface to breathe. Like other mammals, they 

 are warm-blooded. They bring their young into the 

 world alive, not by eggs, like fish, and they suckle 

 their young. Their skin is not scaly, but a hard hide, 

 more than an inch thick, under which is a layer of fatty 

 tissue. This skin is black on the back, and grayish or 

 silver below. Whales feed on crustaceans, mollusks, and 

 small fish ; when they open their enormous mouths, the 

 mass of water that enters necessarily contains myriads 

 of small creatures ; in order to collect them and get rid 

 of the water, this latter is filtered out through the comb 

 formed by the whalebones. 



Whales do not leave the water, and only rarely the 

 deep sea ; their organization does not allow them to 

 come on land, and their weight and size prevent them 

 from approaching the shores. When they are driven on 

 shore by storm, they are stranded just like ships, and 



