742 PROTOZOOLOGY 



contractile vacuole occurs (Kahl); with or without a striped band; 

 trichocysts slanting posteriorly; in salt or brackish water. Kirby 

 (1934) showed that several species of the genus are common in the 

 pools and ditches in salt marshes of California, salinities of which 

 range 3.5-10 per cent or even up to 15-20 per cent. 



S. pharyngea Kirby (Fig. 315, d). Ovoid to ellipsoid; flattened; 84- 

 110/x by 48-65/x; gelatinous layer about 2/* thick, with bacteria; 

 about 60 longitudinal ciliary rows, each with 2 borders; peristome 

 about 35/x long, at anterior end, oblique; with closely set cilia from 

 the opposite inner surfaces; cytopharynx conspicuous; spherical 

 macro nucleus anterior, with a micro nucleus; trichocysts (7-9m long) 

 distributed sparsely and unevenly, oblique to body surface; a group 

 of bristle-like cilia at posterior end; often brightly colored because of 

 food material; in salt marsh, California. 



S. vorax Kahl (Fig. 315, e). Broadly ellipsoid; size variable, 70- 

 180/n long; ventral surface flattened; posterior border of peristomal 

 cavity extending anteriorly; in salt marsh; California (Kirby, 1934). 



Family 7 Clathrostomidae Kahl 



Genus Clathrostoma Penard. Ellipsoid ; with an oval pit in anterior 

 half of the flattened ventral surface, in which occur 3-5 concentric 

 rows of shorter cilia; cytostome a long slit located at the bottom of 

 this pit; with a basket composed of long fibrils on the outer edge of 

 the pit ; in fresh water. 



C. viminale P. (Fig. 315, /). Resembles a small Frontonia leucas; 

 macronucleus short sausage-form; 4 micronuclei in a compact group; 

 endoplasm with excretion crystals; 5 preoral ciliary rows; 130-180/x 

 long; in fresh water. 



Family 8 Parameciidae Grobben 



Genus Paramecium Hill (Paramaecium M tiller). Cigar- or foot- 

 shaped; circular or ellipsoid in cross section; with a single macronu- 

 cleus and 1 to several vesicular or compact micronuclei; peristome 

 long, broad, and slightly oblique; in fresh or brackish water. Several 

 species. Comparative morphology (Wenrich, 1928a; Wichterman, 

 1953); ciliary arrangement (Lieberman, 1928); pellicular structure 

 (Gelei, 1939); excretory system (Gelei, 1939a); spiral movement 

 (Bullington, 1930); cultivation (Wichterman, 1949). 



P. caudatum Ehrenberg (Figs. 21, a, b; 43, a-e; 52; 83; 316, a). 

 180-300ju long; with a compact micronucleus, a massive macronu- 

 cleus; 2 contractile vacuoles on aboral surface; posterior end bluntly 

 pointed; in fresh water. The most widely distributed species. Cytol- 



