172 PROTOZOAN PARASITISM 



liquid preparation, or in stained preparations. Aris- 

 ing also from the blepharoplast is a flagellum which 

 is directed backward in the cytostome and which 

 waves or undulates in sinuous movement, synchro- 

 nously with the three free flagella. The cytostome is 

 a distinct groove from the anterior extremity over 

 and into the surface of one side of the body for about 

 one half of its length. This groove is supported by 

 marginal fibers originating with the flagella. 



The nucleus, not distinct, is rounded or ovoid, 

 in the anterior end, just beneath the surface and back 

 of the cytostome. In iron-haematoxylon prepara- 

 tions it has a definite rim, on which is irregularly 

 distributed chromatin, and a central karyosome. 



The cytoplasm is variously vacuolated and con- 

 tains, usually, ingested bacteria. 



The cysts were first described by Prowazek and 

 Werner (1914), according to Wenyon (1926). The 

 writer mistook them for cysts of Trichomonas hominis 

 (1916). They are insignificant bodies, of ''ground 

 glass" appearance, apt to be taken for yeasts by the 

 inexperienced. They are pear or lemon shaped, the 

 anterior end being the narrower and often elevated 

 by a "shoulder" above the the adjacent convexity. 

 They are about 7 to 10 microns in length. In iodine 

 preparations the nucleus and cytostome may be seen 

 and sometimes they may be made out in the un- 

 stained specimen. 



Proper staining by the iron-haematoxylon method 

 is essential for studying the detail of these cysts. 



