358 HANDBOOK OF PROTOZOOLOGY 



caudal style. Cytostome antero-ventral. Pharyngeal basket 

 short. Salt or fresh water. Rare. 



Aegyria oliva Claparede and Lachmann (Fig. 153, n). About 

 100 microns long. Marine. 



Suborder 3 Trichostomina Butschli 



The cytostome is a permanent opening and is located at the 

 posterior end of the peristome (oral groove). There is one 

 (or more) undulating membrane which runs into the cyto- 

 pharynx or borders the cytostome. The membrane is inconspicu- 

 ous in many, but in others it is a large sail-like expansion 

 apparently used for capturing the food. The cilia are usually 

 uniformly developed and distributed, although in some they 

 may be much reduced. The group contains both free-living and 

 parasitic forms. 



The suborder is divided into six families: 



Cilia on two broad zones and on the posterior tip Family 1 Urocentridae 



Cilia not arranged in zones 



With small circular or ellipsoidal peristome 



Cystotome in the anterior half of body Family 2 Ophryoglenidae 



Cytostome in the posterior half of body Family 3 Microthoracidae 



With large peristome 



Undulating membrane in the cytopharynx Family 4 Parameciidae 



Huge undulating membrane in peristome Family 5 Pleuronematidae 



Parasitic in the digestive tract of mammals. .. .Family 6 Isotrichidae 



Family 1 Urocentridae Schouteden 



Genus Urocentrum Nitzsch. Somewhat short cocoon-shaped, 

 with a constriction slightly behind the middle. Two broad 

 zones of cilia and a conspicuous tuft of fused cilia at the pos- 

 terior end. Large and oval cytostome posterior; with a distinct 

 cytopharynx. Macron ucleus horseshoe-shaped and a micro- 

 nucleus. A contractile vacuole at the posterior end with four 

 radiating canals. Movement rapid. Fresh water. 



Urocentrum turbo Mliller (Fig. 154, a). About 100 microns 

 long. Fresh water. 



Family 2 Ophryoglenidae Kent 



The body uniformly ciliated, with or without peristome. 

 Cytostome is at the anterior half of the body. 



