II 



PHYLUM PROTOZOA 



55 



perforated spiral shell, called Hastiyerina (Fig. 37), a very remark- 

 able modification of this condition of things obtains. The shell 



' 







J 



- - 2 





FIG. 3s. Dimorphism and alternation of generations in Polystomella crispa. The arrows 

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

 megaspheric individual, decalcified ; C, megaspheric individual in the act of spore-formation, 

 the protoplasm leaving the shell in the form of flagellulae ; D, fiagellula more highly 

 magnified ; E, microspheric individual developed from a flagellula ; F, microspheric individual 

 in the act of producing amoeboid embryos. (From Lang, after Schaudinn.) 



(sh.) is surrounded with a mass of protoplasm (plsm.) many times 

 its own diameter, and so full of vacuoles as to present a bubbly or 



