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 caudaium Ehrenberg 1838. 



Perhaps the most familiar ciliated protozoon known. 

 Body with a large central macron iicleus and a small 

 micronucleus, and a contractile vacuole in either 

 extremity. Abundantly supplied with trichocysts. 

 Length variable, average 250 m- Everywhere in in- 

 fusions. 

 Fig. 498. Paramoecium caudaium. 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 Party. 

 Representative species Lembadion buUinum 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 m. Among 

 aquatic plants in pond water. 



Hymenosioma 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. 



'm, 



nilr 



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

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

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

 era, Hisiriobalantidium. with long setose bristles among the cilia 

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

 of cilia. Biitschli places them both under Pleuronema. 



Fig. SCO. Pleuronema chrysalis, macn, macronucleus; mien, micronucleus. 

 X 225. (After Blochmann.) 



