748 PROTOZOOLOGY 



the cytostome with posteriorly directed membrane; macro nucleus 

 oval or spherical; micronuclei; in fresh water. 



B. bavariensis K. (Fig. 318, J*). 50-120ju long. 



Genus Woodruffia Kahl. Form similar to Chilodonella (p. 731); 

 highly flattened snout bent toward left; cytostome, a narrow diago- 

 nal slit, its left edge with a membranous structure and its right edge 

 with densely standing short cilia; macro nucleus spherical; several (?) 

 micronuclei; contractile vacuole flattened, terminal; in salt water. 



W. rostrata K. (Fig. 318, k). 120-180ju long; salt water culture with 

 Oscillatoria. 



W. metabolica Johnson and Larson (1938). Pyriform; 85-400^ 

 long; division cysts 85-155ju in diameter; resting cysts 40-62/i in 

 diameter; in freshwater ponds. Johnson and Evans (1939, 1940) 

 find two types of protective cysts in this ciliate: "stable" and 

 "unstable" cysts, formation of both of which depends upon the 

 absence of food. These cysts have three membranes: a thin inner- 

 most endocyst, a rigid mesocyst and a gelatinous outer ectocyst. 

 The protoplasmic mass of the stable cyst is smaller, and free from 

 vacuoles, and its ectocyst is thick, while that of the unstable 

 cyst is larger, contains at least one fluid vacuole and its ectocyst 

 is very thin. Crowding, feeding on starved Paramecium, increasing 

 the temperature, and increasing the salt concentration of the 

 medium, are said to influence the formation of unstable cysts. 

 The two authors (1941) further reported that when free-swimming 

 individuals were subjected, in the absence of food, to extremes of 

 temperature, high concentrations of hydrogen-ion, and low oxygen 

 tension, unstable cysts were formed; when the oxygen tension de- 

 creased, the tendency to encyst increased, even when ample food 

 was present. The unstable cysts are said to remain viable for six 

 months. Excystment is induced by changing the balanced salt solu- 

 tion, by replacing it with distilled water and by lowering tempera- 

 ture from 30° to 20°C. 



Family 10 Entorhipidiidae Madsen 



Genus Entorhipidium Lynch. Triangular in general outline; color- 

 less; large, 155-350/x long; flattened; posterior end drawn out, with 

 a bristle; anterior end bent to left; cytostome in depression close to 

 left anterior border, with long cilia; with or without a cross-groove 

 from preoral region; cytopharynx inconspicuous; trichocysts; macro- 

 nucleus oval to sausage-form; one to several micronuclei; several (ex- 

 cretory) vacuoles left-ventral; in intestine of the starfish, Strongy- 

 locentrotus -pur-pur atus. Four species. 



