PROTOZOA 



surface, is only unlike that below it in not containing granules; in 

 various planktonic protozoa (Figs. 32, 33) a highly vacuolated layer 

 whose low specific gravity confers buoyancy; in the Ciliophora and 



Fig. 6. Shells of foraminifera. A, Rhabdammina abyssorum, X 4-5. B, Nodo- 

 saria hispida, x 18. C, Globigerina bidloides, x 55. After various authors. 



many flagellates and sporozoa a stout pellicle with an underlying layer, 

 the cortex, which is said to be stiflPer than the endoplasm and may 

 exhibit differentiations of various kinds. 

 Occasionally the protoplasm contains structures (trichocysts of 



