CILIATE PROTOZOA (INFUSORIA) 281 



87 (60) With a well-developed peristome gg 



88 (loi) Mouth not posterior to the middle of the body gg 



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



go (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 1858. 



^^^^ Perhaps the most famihar cih'ated protozoon known. 



^^^^^^^^gj^*.|pj^^ Body with a large central macronucleus and a small 



^^t'^'^%/'^r ■' ' '■' ^^'"^0'^^^ micronucleus, and a contractile vacuole in either 



4^^^^^-!:. '^■■^^i^- *'*'^^ extremity. Abundantly supplied with trichocysts. 



^'^^^^^■^^^T^^^^'"''''^^'^ Length variable, average 250 ^l. Everywhere in in- 



-<»'*:'«aKSiift,Aaiii'.j - ;:-:- - fusions. 



Fig. 498. Paramoecium caudatum. X 170. (.^fter Conn.) 



91 (90) Peristome not oblique 02 



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 Lcmbadion 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 m- 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. x 250. 

 (.\fter Blochmann.) 



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, fat- 

 tened dorso-ventrally. Cilia very long. 



Plciironcma Dujardin. 

 Representative species. . . . Pleuroncma chrysalis Ehrenberg 1838. 



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

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

 75 to 125 fx. Fresh water. Stokes rccogni/.es two separate gen- 

 era, II istriohalantidium. 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 Phuroncma. 



Fig. 500. Pleuroncma chrysalis, wdcw, macronucleus; miV«, micronucleus. 

 X 225. (.^Ucr Blochmann.) 



