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 
Pic. 58.—a, Rhabdosphere; b, Coccosphere highly magnified. (After J. 
ray.) 
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 
