PHYLUM PROTOZOA 



55 



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

 able modification of this condition of things obtains. The shell 



3 --. 



I 



Fia. 3S, — Dimorphism and alternation of generations in Polystomella crispa. The arrows 

 indicate the direction of the life-cycle. A, young niegaspherie individual ; S, full-grown 

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

 the- protoplasm leaving the shell in the form of fiagellulse ; D, flagellula 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 o"wn diameter, and so full of vacuoles as to present a bubbly or 



