PHYLUM PROTOZOA IN GENERAL 



71 



sitic genus which inhabits the large intestine of the frog, (b) Hetero- 

 trichida possess a well-developed undulating membrane in the cyto- 

 pharynx. The body cilia are small or partially absent, 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 Balantidnim (Fig. 389) is a parasite in the 

 intestine of man and some other mammals, (c) Tlypotrichida possess 

 cirri or structures formed by fusion of cilia ; these are found prin- 

 cipally on the ventral side. The cell is flattened dorsoventrally and 



Prorodon 



From ton I a 



iupiom 



StyhnyoMa 



Laorymaria 



i^m 



lionotw 



Fig. 28. — Representatives from class Infusoria. (Reprinted by permission from 

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

 (Figure of Frontonia modified.) 



most of the genera use creeping as their means of locomotion. 

 Stylony cilia, Oxytricha and Euplotes are common fresh-water genera. 

 Kerona is a parasitic form and is often found creeping over the ex- 

 ternal surface of fresh-water Hydra, (d) Peritrichida is an order 

 composed of sedentary 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. Vor'ticeJla is probably 



