CILIATE PROTOZOA (INFUSORIA) 



289 



154 (iSS) Body elongate-oval, with five to eight frontal styles; ventral setae 



usually arranged in two or more rows, the inner rows having 

 but few setae. Anal styles five or six, two of which are near 



the posterior border . Pleurotricha Stein. 



Representative species. Pleurotricha lanceolata Ehrenberg 1838. 



Somewhat resembling Stylonychia but without caudal setae and 

 with anal styles arranged in two groups. Nuclei two in number, 

 one in front of the apex of the peristome. Length 250 fi. Among 

 algae. 



Fig. 525. Pl&urotricJta lanceolata. X 112. (After Edmondson.) 



155 (1S4) Body somewhat rectangular in outUne with slightly rounded ends. 



Three or four oblique rows of ventral setae running from 

 left to right, and three rows parallel to the peristome border. 

 Anal styles five or six. Border ciha uninterrupted. 



Onychodromus Stein. 

 Representative species Onychodromus grandis Stein 1859. 



Body not flexible. Frontal styles from sixteen to 

 twenty-eight, in three rows. Anal styles from five to 

 seven. Nuclei usually four. Length 100 to 300 it. 

 Onychodromopsis flexUis Stokes differs from Stein's form 

 in having a soft, flexible body. 



Fig. 526. Onychodromus grandis. X 125. (After Conn.) 



iS6 (153) Ventral setae in one obHque row. Body elongate-oval. Five or 

 six frontal styles and as many anal. Peristome triangular, 

 curved, with an undulating membrane. 



Gastrostyla Engelmann. 

 Representative species. Gastrostyla steinii Engelmann 1862. 



Body evenly rounded at each extremity. Three very 

 large frontal styles near the border. Anal styles five, 

 in an oblique row, not projecting beyond the border. 

 Nuclei four. Contractile vacuole near the middle of the 

 body on the left side. Length 250 n. Fresh water. 



Fig. 527. Gastrostyla steinii. X 125. (After Edmondson.) 



IS7 (132) Ventral cilia few, not in rows. . 



IS8 



158(165) Not produced posteriorly into a tail-hke process 159 



159 (162) Body flexible 160 



160 (161) Border ciha uninterrupted. Narrow, elliptical, rounded at both 



ends. Five ventral setae and five anal styles. No caudal 

 bristles. Inner right wall of peristome bent toward outer 



left wall. Oxytricha Ehrenberg. 



Representative species. . . Oxytricha pellionella Miiller 1786. 



Marginal setae set well in on the ventral surface. 

 Anal styles arising near the posterior border and ex- 

 tending nearly their entire length beyond it. Nuclei 

 two. Contractile vacuole on the left side. Length 80 

 to 100 ft. Common in infusions and fresh water. 

 Fig. 528. Oxytricha pellionella. X 335- Opisthotricha Kent resembles Oxytricha in general 

 (After Conn.) characteristics but has three caudal setae. 



