HETEROTRICHIDA 375 



a narrow slit, opening at the anterior end. One contractile 

 vacuole at the posterior end. Macronucleus spherical and pos- 

 terior. Parasitic. 



Balantidiopsis duodeni (Stein) (Fig. 161, d). Body about 110 

 microns long. In the mid-gut of various frogs (Rana). 



Genus Condylostoma Dujardin. Body colorless and oval to 

 cylindrical or club-shaped. Contractile; flattened slightly dorso- 

 ventrally. Peristome short at the anterior region, the left mar- 

 gin bears the adoral zone and the right ridge an undulating 

 membrane. Macronucleus moniliform. One or several contrac- 

 tile vacuoles. If one is present, there is a long canal leading into 

 it. Cytopyge posterior. Fresh or salt water. 



Condylostoma patens Mliller (Fig. 161, e). Body large 350 to 

 550 microns long. Salt water. 



Condylostoma vorticella Ehrenberg (Fig. 161,/). 150 microns 

 long. Fresh water. 



Family 3 Stentoridae Claus 



The anterior end is broad and at about right angles to the 

 longitudinal axis of the body. Almost all of them free-living. 



Genus Stentor Oken. Attached or free-swimming. When ex- 

 tended, the body is cylindrical or trumpet-shaped. Occasion- 

 ally with a mucilaginous lorica. When free-swimming, the body 

 is oval to pyriform. The anterior end possesses a peristome 

 which is spiral in its course and at its end is located a cyto- 

 stome. A row of strong cilia marks the peristomal ridge. Cilia- 

 tion fine and regular. Macronucleus rounded to elongate or 

 moniliform. Several micronuclei indistinguishable in vivo. The 

 cytopyge is located near the left end of the adoral spiral. A 

 single contractile vacuole which is usually present near the 

 anterior end possesses a long canal which runs posteriorly in a 

 more or less straight course. Sometimes with chlorophyll. 

 Fresh or salt water. Johnson (1893) distinguishes the following 

 species. 



Stentor igneus Ehrenberg (Fig. 161, g). On plants in fresh- 

 water. When extended 350 microns long. 



Stentor pyriformis ]o\inson {Y'xg. \6\,h). Freshwater. When 

 extended 500 microns long, diameter of the anterior end 200 

 microns. 



