CILIATA 



109 



Suborder VESTIBULATA (HYMENOSTOMATA) 



Holotricha with a mouth and a gullet (vestibule) which is permanently 

 open and usually possesses an undulating membrane ; and with mega- 

 and micronuclei. 



Colpoda (Fig. 87 E). Kidney-shaped; with large vestibule on con- 

 cave side; but no undulating membrane; and no peristome. Fission, 

 binary or repeated, takes place in a cyst. Common in infusions, fresh- 

 water and marine. 



Colpidiiim. As Colpoda\ but with undulating membrane. Common 

 in infusions, freshwater and marine. 



Paramecium (Figs. 9, 15, 16, 17, 26, 85). Slipper- or pear-shaped 

 according to species; with undulating membranes^; and peristome. 

 Common in infusions, freshwater and marine. 



mrp 



Fig. 88. Ciliata from the rectum of the frog. From Borradaile. A, Balan- 

 tidium entozoon, x 65. B, Nyctotherus cordiformis, x 130. a«. anus ; cy. con- 

 tractile vacuole ; meg. meganucleus ; mi. micronucleus ; v. vestibule. 



Order HETEROTRICHA 



Ciliata which possess a gullet, permanently open and provided with 

 undulating membrane; an adoral wreath, curving clockwise; and 

 most often on the rest of the body a uniform covering of cilia ; and 

 whose body is not depressed. 



Suborder POLYTRICHA 



Heterotricha which retain the uniform ciliation of the general surface 

 of the body. 



Balantidium (Fig. 88 A). Egg-shaped; the peristome a deep groove 

 at the anterior end. Parasitic in the rectum of frogs, the intestine of 

 man (where it is occasionally harmful), etc. 



Nyctotherus (Fig. 88 B). Kidney-shaped; with permanent anus. 

 Parasitic in the rectum of frogs, the intestine of man, etc. 

 ^ There are three of these, each composed of four rows of cilia. See p. 104, 



