766 



EVOLUTION OF ANIMALS 



Part V 



Fig. 37.15. Upper, northern white-tailed deer {Odocoileus virginianus) (bore- 

 alis). Southern New England and New York through south-eastern Canada and 

 westward. Lower, Virginia whitetailed deer (Odocoileus virginianus virginianus) . 

 From southern New Jersey to east central Florida. These are members of the 

 Artiodactyla, the great order of even-toed hoofed mammals that includes such 

 extremes as the pig and hippopotamus, and all the cud chewers whether oxen or 

 gazelles. (Courtesy, Mochi and Carter: Hoofed Mammals of The World. New 

 York, Charles Scribner's Sons, 1953.) 



known as whale bone, that hang from the upper jaw like curtains, their fringed 

 edges sweeping down to the floor of the mouth (Fig. 37.18). When a whale is 

 feeding, it swims at the surface with its mouth open, collects a mouthful of the 

 plankton-filled water, expels the water between the close set plates, and keeps 

 the plankton. 



Whales may dive 3,600 feet or more when wounded and doubtless do so 

 at other times. When harpooned, a baleen whale can carry a line straight 

 down for a half a mile, a depth where the pressure is half a ton — on every 



