CILIATE PROTOZOA (INFUSORIA) 



291 



167 (168) No caudal setae. Body rounded or oval, dorsal surface usually 

 furrowed. Peristome in the posterior region in the left- 

 lateral border, its right border prolonged into a triangular, 

 lip-like extension. Usually three frontal styles, four or five 

 ventral setae, and five or more anal styles. 



Aspidisca Ehrenberg. 

 Representative species Aspidisca costata Dujardin 1841. 



Dorsal surface with five or six furrows. 

 Length 35 /*. Common in infusions. 



Nucleus band-like. 



FIG. 533. Aspidisca costata. X 500. (After Conn.) 



1 68 (167) Caudal setae usually four in number. Body oval, with dorsal 

 convex surface furrowed. Peristome broad, on the left 

 side, extending backward to or beyond the middle of the 

 body. Frontal styles six or eight, a few scattered ventral 



setae, and five anal styles Euplotes Stein. 



Representative species Euplotes char on Miiller 1786. 



Frontal styles seven; ventral setae three. Nu- 

 cleus band-like. Length 80 /* Pond water. Dif- 

 fering from Euplotes patella Ehrenberg by its smaller 

 size and greater number of frontal styles. 



FIG. 534- Euplotes charon. Ventral view and individual 

 in process of division, cv, contractile vacuole; macn, 

 macro nucleus. X 300. (After Kent.) 



169 (128) Cilia usually limited to the adoral zone, sometimes with additional 

 rings of cilia. Body cup-like or cylindrical. 



Order Peritricha . . 170 



170(193) No lorica present. 171 



171 (180) Without a stalk. 172 



172 (175) With a permanent secondary ring of cilia at the posterior end 



enclosing an adhesive disk 173 



173 (174) Body short, barrel-shaped, with the posterior end discoidal, the 



inner border of which is supported by a horny ring, the 

 peripheral zone of which is radially striated and denticu- 

 late; the outer border surrounded by a wreath of cilia. 

 Adoral zone extends spirally around the flattened end. 

 Mouth eccentric. Parasitic forms. . . Trichodina Stein. 

 Representative species. . . Trichodina pediculus Ehrenberg 1830. 



Commonly observed gliding up and down on the tentacles 

 of fresh-water Hydra. Height of body 70 n. 



FIG. 535- Trichodina pediculus. Individuals adherent to tentacle of 

 Hydra. X 50. (After Kent.) 



