THYLUM PROTOZOA 



ft 



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

 able modification of this condition of things obtains. The shell 





***** J? I 



^ 



Fio. 3R.— Dimorphism and alternation of generations in Poly stome 11a crispa. The arrows 

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

 mega8pheric 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 ; B, microspheric individual developed from a fiagellula ; 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 



