22 



THE STORY OF LIFE IN THE SEAS. 



shells that can survive this long journey are the 

 siliceous shells of the Diatoms and Radiolarians, 

 and in those parts of the ocean where these 

 organisms live in abundance their empty shells 

 form an important percentage of the composition 

 of the Eed clay. Over a very considerable area 

 of the Pacific Ocean, however, the Eed clay con^ 

 tains only a minute proportion of these shells, 



FIG. 2. 

 Radiolarian Shells from a deep-sea deposit. 



and its composition has given rise to a good deal 

 of discussion among the authorities. It may be 

 considered to be a conglomerate of the horny 

 fragments of dead surface-living animals, of 

 volcanic and meteoric dust, and of small pieces 

 of water-logged pumice-stone. 



In some of the very deep holes of the Pacific 



