264 PROTOZOOLOGY 



groove to posterior end; cytopharynx temporary and length 

 variable; 20-30/x long (Entz); 15-19// long (Kirby). Kirby ob- 

 served it in a pool with salinity of about 15 per cent at Marina, 

 California. 



Genus Collodictyon Carter. Body highly plastic; with longi- 

 tudinal furrows; posterior end bluntly narrowed or lobed; no 

 apparent cytostome; 4 flagella; a contractile vacuole anterior; 

 fresh water. 



C. triciliatum C. (Fig. 123, d). Spherical, ovoid or heart-shaped; 

 27-60/1 long; flagella as long as the body; pond water. Rhodes 

 (1919) made a comprehensive cytological study of the organism. 



Genus Costia Leclerque. Ovoid in front view; pyriform in pro- 

 file; toward right side, a funnel-like depression, at the posterior 

 end of which are located cytostome (?) and 2 long and 2 short 

 flagella; contractile vacuole in posterior half; longitudinal divi- 

 sion; encystment; ectoparasitic in various freshwater fishes. 



C. necatrix (Henneguy) (Fig. 123, e-j). 10-20^ by 5-10//; 

 compact nucleus central; a contractile vacuole; cyst uninucleate, 

 spherical, 7-10/z in diameter; when present in large numbers, the 

 epidermis of fish appears to be covered by a whitish coat. 



Genus Tricercomonas Wenyon et O'Connor. Body similar to 

 that of Cercomonas (p. 259), but with 3 anterior flagella and a 

 posterior flagellum; oblong cyst with 4 nuclei when mature; 

 parasitic. 



T. intestinalis W. et O'C. (Fig. 123, k). 4-8/1 long; in human 

 intestine. 



Genus Copromastix Aragao. 4 anterior flagella equally long; 

 body triangular or pyramidal; coprozoic. 



C. prowazeki A. (Fig. 123, /). About I6-I8/1 long; in human and 

 rate faeces. 



Family 3 Chilomastigidae Wenyon 



4 flagella, one of which undulates on body surface. 



Genus Chilomastix Alexeieff . Pyriform ; with a large cytostomal 

 cleft at anterior end; nucleus anterior; 3 anteriorly directed 

 flagella; short fourth flagellum undulates within cleft; cysts 

 common; in intestine of vertebrates. Several species. 



C. mesnili (Wenyon) (Fig. 124, a-c). 10-15/t long; cyst 5-10/t 

 long; in human intestine; commensal, although often found in 

 diarrhoeic stools. 



C. intestinalis Kuczynski. In guinea pigs. 



