CETACEA. 



483 



structed entirely fur swimming, the Cetacea are 

 strictly confined to the watery element ; neverthe- 



FlG. 4U9.— TKOOP OF DULl'IIlNb, MAiJATEK IN TilE DIbTAKCE. 



less, they breathe air by means of lungs, and are 

 thus perpetually obliged to come to the surface for 

 the purpose of respiration. Their blood is hot ; they 

 bring forth living young, which they feed with their 

 own milk, precisely in the same way as the terres- 

 trial quadrupeds, and thus in all the details of their 



Fig. 410.— bones of the fin of a dolphin. 



structure they differ widely from the cold-blooded, gill- 

 breathing and oviparous fishes. Diving, as the Whales 



Y 2 



