HOLOTRICHA 603 



the cytostome with posteriorly directed membrane; macro nucleus 

 oval or spherical; micro nuclei; in fresh water. 



B. havariensis K. (Fig. 285, h). 50-120m long. 



Genus WoodruflBa Kahl. Form similar to Chilodonella (p. 588); 

 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 (?) 

 micro nuclei; contractile vacuole flattened, terminal; in salt water. 



W. rostrata K. (Fig. 285, i). 120-180ai long; salt water culture with 

 Oscillatoria. 



W. nictabolica Johnson and Larson. 85-400iu long; division cysts 

 85-1 55/i in diameter; resting cysts 40-62/x 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 innermost endocyst, a rigid mesocyst and a gela- 

 tinous 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-ions, and low oxygen 

 tensions, 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. 



Family 10 Entorhipidiidae Madsen 



Genus Entorhipidium Lynch. Triangular in general outline; color- 

 less; large, 155-350^ 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; trichc cysts; macro- 

 nucleus oval to sausage-form; one to several micro nuclei; several (ex- 

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

 locentrotus purpuratus. Four species. 



E. echini L. (Fig. 286, a). About 253iu by 125m; California. 



Genus Entodiscus Madsen. Broadly or narrowly lancet-like, with- 

 out narrowed posterior portion; cytostome small on left narrow side, 



