186 SEAWEEDS 



Their broken-down parts, called Rhabdoliths and 

 Coccoliths, occur in the globigerina oozes, and they 

 form a not inconsiderable part of deep-sea deposits, 

 except those laid down in polar and subpolar seas. 

 The Rhabdoliths and Coccoliths are known from the 

 deposits of the ancient cretaceous seas. Their minute 

 investigation in the living state is one of the most 



FIG. 58. a, Rhalxlosphere ; b, Coccosphere highly magnified. (After J. 

 Murray.) 



important researches yet to be undertaken in marine 

 botany. (See p. 28.) " There is considerable 

 variety both in the form and size of Coccospheres 

 and Rhabdospheres, some varieties having the com- 

 ponent parts (Coccoliths and Rhabdoliths) much 

 more compactly united into a sphere than others. 

 The interior of the spheres is perfectly clear when 



