88 THE FAUNA OF THE DEEP SEA 



bygone times, left to struggle for existence with 

 the more recent immigrants from shallow waters. 

 But after all the proportion of ancient forms to 

 modern ones in the fauna of the abyss is not larger 

 than it is in the fauna of fresh-water lakes and 

 streams or even of the dry land. Nor is there any 

 reason why it should be. The land and the fresh 

 water have been peopled by migrations from the 

 shallow water of the sea from generation to gener- 

 ation in precisely the same way, and they each can 

 show a certain number of archaic forms. 



We must now consider briefly some of the most 

 interesting deep-sea representatives of the various 

 classes of the animal kingdom, referring as we pass 

 on to the extent to which these classes contribute 

 to the fauna of the abyss. 



We find a great difficulty in determining with 

 any degree of certainty the actual depths at which 

 the supposed abysmal forms of Protozoa actually 

 live. All the Radiolaria and Forammifera the only 

 Protozoa that are largely represented in the fauna of 

 the open seas are planktonic in habit ; that is to say, 

 they float or drift about in the water without ever 

 becoming attached to the sea bottom; and when the 

 contents of a dredge, that has been hauled up from a 



