46 FOSSIL RADIOLARIA 



The protoplasm, or soft body of the tiny 

 organism, surrounds the framework inside and 

 outside. Some of the skeletons take the form 

 of a network with hexagonal apertures. 



A framework may be round for a time, and 

 then a second framework may be added below 

 the first with a wide opening at its base, the 

 whole having the outlines of a helmet orna- 

 mented at definite points. There is an extra- 

 ordinary variety of form in the skeletons of 

 Eadiolaria. In all cases the fossil forms, as 

 well as their existing representatives, are of 

 microscopic dimensions, and, taken individually, 

 they are scarcely, if at all, visible to unaided 

 sight. 



Eadiolaria are all marine ; most of them live 

 near the surface in tropical seas, and their 

 skeletons sink to the bottom of the ocean, 

 where they are now forming extensive deposits 

 of radiolarian ooze at depths of from 2,000 to 

 4,000 fathoms. 



Passing now to the fossil forms, the flinty 

 skeletons seem to retain most of their beauty, 

 even though embedded for untold centuries in 



