n 



PHYLUM PROTOZOA 



57 



flagellum or a pair of flagella. In some cases the flagellulae have been 

 observed to copulate in pairs. The young may develop shells while 



J) 





J* 







-i- 



. 



" , '-'*''M.fi h J 



''*iO-,''>-^f! ' 



' - ',;*~^-* 



"/ 



% 



FIG 39 Dimorphism and alternation of generations in Polystomella crispa. The arrows 

 indicate the direction of the life-cycle. A, young megasphenc individual ; B. full-grown 



Lang, alter Schandinn.) 



still within the shell of the parent or only after becoming free. In 

 the dimorphic Foraminifera there is evidence of the occurrence of an 



