212 • PHOTOZOOLOCY 



indcr; flagellum as long as body; nuclous central or terminal; 15- 

 25m by 7-8m; in standing fresh water. Hall (1923) made a careful 

 cytological study of the organism. 



M. tortuosum Stokes. S-form; posterior end drawn out to a 

 sharp point; elongate paramylon bodies; 42-78^ long; in infusion. 



Genus Scytomonas Stein. Oval or pyriform, with a delicate pel- 

 licle; a single flagellum; a contractile vacuole with a reservoir; 

 holozoic on bacteria; longitudinal fission in motile stage; stag- 

 nant water and coprozoic. 



S. pusilla S. (Fig. 97, g). About 15m long. 



Genus Copromonas Dobell. Elongate ovoid; with a single fla- 

 gellum; a small cytostome at anterior end; holozoic on bacteria; 

 permanent fusion followed by encystment (p. 145); coprozoic in 

 faecal matters of frog, toad, and man; several authors hold that 

 this genus is probably identical with Scytomonas which was in- 

 completely described by Stein. 



C. siibtilis D. (Fig. 69). 7-20^ long. 



Family 3 Anisonemidae Schewiakofif 



Colorless body plastic or rigid with a variously marked pellicle; 

 2 flagella, one directed anteriorly and the other usually posteri- 

 orly; contractile vacuoles and reservoir; stigma absent; paramy- 

 lon bodies as a rule present; free-swimming or creeping. 



Genus Anisonema Dujardin. Generally ovoid; more or less 

 flattened; asymmetrical; plastic or rigid; a slit-like ventral fur- 

 row; flagella at anterior end; cytopharynx long; contractile vacu- 

 ole anterior; nucleus posterior; in fresh water. Several species. 



A. acinus D. (Fig. 97, h). Rigid; oval; somewhat flattened; pel- 

 licle slightly striated; 25-40/x by 16-22^. 



A. truncatum Stein (Fig. 97, i). Rigid; ovoid; 60/i by 20/^. 



A. emarginatum Stokes (Fig. 97, j). Rigid; 14/x long; flagella 

 long. 



Genus Heteronema Dujardin. Plastic; rounded or elongate; 

 flagella arise from anterior end, one directed forward and the 

 other trailing; cytostome near base of flagella; holozoic; fresh 

 water. Several species. 



H. acus (Ehrenberg) (Fig. 97, k). Extended body tapers to- 

 wards both ends ; anterior flagellum as long as body, trailing one 

 about 1/2; contractile vacuole anterior; nucleus central; 45-50^ 

 long; freshwater. 



