CILIATE PROTOZOA (INFUSORIA) 



281 



87 (60) With a well-developed peristome 88 



88^(101) Mouth not posterior to the middle of the body 89 



89 (98) Not surrounded by a lorica or gelatinous sheath 90 



90 (91) Peristome oblique. Body elongated, slightly flattened, rounded at 



both ends or slightly truncated in front. Mouth followed 

 by a short pharynx; ciliation regular. . Paramoecium Stein. 

 Representative species. . . Paramoecium caudatum Ehrenberg 1838. 

 Perhaps the most familiar ciliated protozoon known. 

 Body with a large central macronucleus and a small 

 micronucleus, and a contractile vacuole in either 

 extremity. Abundantly supplied with trichocysts. 

 Length variable, average 250 n. Everywhere in in- 

 fusions. 

 FIG. 498. Paramoecium caudatum. X 170. (After Conn.) 



91 (90) Peristome not oblique 92 



92 (97) With one or more membranes well developed in the peristome. . 93 



93 (94) Peristome very broad and conspicuous, occupying the entire right 



side. Body oval, flattened ventrally, convex dorsally; an- 

 terior end oblique, posterior end acute. A tuft of long cilia 



extends from the posterior end Lembadion Perty. 



Representative species Lembadion bullinum Perty 1849. 



Nucleus elongated, curved in the posterior region on the left side; con- 

 tractile vacuole opposite the nucleus. When stimulated the animal swims 

 rapidly backward rotating on its long axis. Length 50 to 100 /*. Among 

 aquatic plants in pond water. 



Hymenostoma Stokes differs from Lembadion in the more posterior, ven- 

 tral position of the mouth, the greater length of the adoral cilia, the 

 abruptly narrowing membrane and the double contractile vacuole. 



FIG. 499. Lembadion bullinum. macn, macronucleus; mien, micronucleus. 

 (After Blochmann.) 



X 250. 



94 (93) Peristome not broad and conspicuous . . 95 



95 (96) Without a long, posterior bristle. Peristome parallel to the right 



side with a large projecting membrane. Body oval, flat- 

 tened dorso-ventrally. Cilia very long. 



Pleuronema Dujardin. 

 Representative species. . . . Pleuronema chrysalis Ehrenberg 1838. 



Cilia in length nearly one-half the diameter of the body, stiffened, 

 setae-like. Nucleus central; contractile vacuole anterior. Length 

 75 to 125 n. Fresh water. Stokes recognizes two separate gen- 

 era, Histriobalantidium, with long setose bristles among the cilia 

 over the whole body, and Bothrostoma, with a long terminal tuft 

 of cilia. Biitschli places them both under Pleuronema. 



FIG. 500. Pleuronema chrysalis, macn, macronucleus; mien, micronucleus. 

 X 225. (After Blochmann.) 



