144 THE OCEAN 



ruses and similar animals do the same and 

 yet no one would think of calling a seal a 

 fish. 



Whales, porpoises, narwhals and several 

 other species of large marine animals are very 

 nearly related and if the skeletons of some of 

 these are examined we will find that beneath 

 the flesh and skin the bones of diminutive hind 

 legs may still be seen. Once upon a time all 

 such creatures had well-developed legs and 

 lived, at least part of the time, on land, but ow- 

 ing to various circumstances they spent more 

 and more time in the water until at last they 

 abandoned the land entirely and took up their 

 life in the sea, and their legs, for want of use, 

 gradually disappeared, while their fore feet 

 developed into flippers. Because they forsook 

 the land and dwelt in the sea they were free 

 from the attacks of other creatures, and no 

 doubt this very fact was a most important 

 cause of their having survived through all the 

 countless ages to the present time. 



Although whales are found in all oceans 

 the largest species dwell in the Arctic and 

 Antarctic seas, and strangely enough these 



