148 THE OCEAN 



weeds, marine-grass and other forms of vege- 

 tation. 



Beyond a doubt the ancestors of these "sea 

 cows" were slow-moving, browsing beasts 

 which dwelt upon the land, just as the pre- 

 historic ancestors of the seals and whales were 

 savage, meat-eating creatures which roamed 

 among the swamps and rushes of the coasts in 

 those far-off times. While so very different 

 in habits these several forms of ancient animal 

 life saved their descendants from total de- 

 struction by taking refuge in the sea. 



All this we know, just as we know that every 

 form of marine life, from the smallest micro- 

 scopic diatom to the giant whales, has its 

 place and its importance in the ocean world, 

 but just how such things came about and just 

 what took place in those dim ages of the past 

 is another unsolved mystery of the sea. 



