PROTOZOA IN GENERAL 



273 



but the cilia of the oral region are well developed. In some forms this 

 oral region possesses membranelles. Stentor, Halteria, and Bursaria 

 are common fresh-water genera while Balantidium is a parasite in 

 the intestine of man and some other mammals. This order is often 

 divided into two orders, forming a second by the name of Oligo- 

 trichida, of which Halteria is typical, (c) Hypotrichida possess cirri 

 or structures formed by fusion of cilia ; these are found principally on 

 the ventral side. The cell is flattened dorsovent rally and most of the 

 genera use creeping as their means of locomotion. Stylonychia, 



Prorodoti 



Fronton I a 



I 



'5 



:i 



BiplGtes 



Stylonyohk 



I- -f / ,'.•/• 



lacrymaiia 



Fig. 90. — Representatives from class Infusoria. (Reprinted by permission from 

 Curtis and Guthrie, Textbook of General Zoology, John Wiley and Sons, Inc.) 

 (Figure of Frontonia modified.) 



Oxytricha and Euplotes are common fresh-water genera. Kerona is 

 parasitic and is often found creeping over the external surface of 

 fresh-water Hydra, (d) Peritrichida is an order composed of seden- 

 tary ciliates with a whorl of oral cilia continued into a depression in 

 which are located the oral spot and aperture of the contractile 

 vacuole. At the base of this depression is located the mouth. There 

 are no body cilia in certain phases of the life history. These forms 

 are typically attached by stalks. Vorticella is probably the most 

 common living genus. Epistylis and Carchesium are well-known 



