576 PROTOZOOLOGY 



cleus more elongate and narrow; in pigs, apparently not infectious 

 to man. 



Other domestic and wild animals harbor various species of 

 Balantidium. 



B. duodeni Stein (Fig. 261,/). 70-80m by 55-60^; in intestine of 

 the frog. 



B. praenucleatum Kudo et Meglitsch (Fig. 261, g). 42-127/i 

 long, 32-102/x thick, 25-80At wide; macronucleus close to anterior 

 end; in colon of Blatta orientalis. 



Family 2 Metopidae Kahl 



Genus Metopus Claparede et Lachmann. Body form change- 

 able because of soft ectoplasm ; when extended oblong or fusiform ; 

 peristome conspicuous, slightly spirally diagonal, beginning at 

 anterior end and reaching middle of body; when contracted, peri- 

 stome much spirally coiled; cytopharynx short; body ciliation 

 uniform, longitudinal or in some, spiral; longer cilia at ends; con- 

 spicuous contractile vacuole terminal; macronucleus ovoid to 

 elongate; fresh or salt water, some parasitic. Numerous species. 



M. es (Miiller) (Figs. 76; 262, a). 120-200^ long; sapropehc. 

 Noland's (1927) study on its conjugation has been described (p. 

 152). 



M. striatus McMurrich (Fig. 262, h). 80-120^ long; fresh water. 



M. fuscus Kahl (Fig. 262, c). 180-300)U long by 60/i wide and 

 40/i thick; fresh water. 



M. circumlahens Biggar (Fig. 262, d). 70-1 65m by 50-7 5^; in 

 digestive tract of sea urchins, Diadema setosum and Echinometris 

 suhangularis ; Bermuda (Biggar). Powers observed it in Centre- 

 chinus antillarum, etc., at Tortugas. 



Genus Spirorhynchus da Cunha. Fusiform; somewhat flat- 

 tened; anterior end drawn out and curved toward left; posterior 

 end also drawn out; spiral peristome; cytopharynx small with an 

 undulating membrane; cilia uniformly long; contractile vacuole 

 posterior; longitudinally striated; body surface mth closely ad- 

 hering bacteria (Kirby); 3 spherical macronuclei; micronucleus 

 (?); in brackish water. 



S. verrucosus d. C. (Fig. 262, e). 122-140/i by 20-22^; Kirby 

 observed it in salt marsh with 3 per cent salinity; California. 



Genus Caenomorpha Perty (Gyrocoris Stein). Bell-shaped; car- 

 apaced ectoplasm in some species bears protrichocysts; strong 



