374 HANDBOOK OF PROTOZOOLOGY 



undulating membrane on the right. When contracted, the peri- 

 stome is much spirally coiled. The cytostome with a short cyto- 

 pharynx at the end of the peristome. Body ciliation uniform, 

 with longer cilia at the extremities. Contractile vacuole pos- 

 terior; macronucleus elongated. Fresh or salt water. Numerous 

 species. 



Metopus sigmoides Claparede and Lachmann (Fig. 160, i-k). 

 Fresh or rarely salt water. Body about 200 microns in length. 



Family 2 Bursariidae Kent 



Peristome is wide, more or less triangular, and of variable 

 length. The adoral zone is on the left margin of the peristome. 

 The right side ridge may or may not bear an undulating mem- 

 brane. Free-living or parasitic. 



Genus Bursaria Miiller. Body ovoid with the truncate an- 

 terior end. Dorsally convex, ventrally flattened. Deep peri- 

 stome begins at the anterior end, and forms on the ventral side 

 a slit reaching the middle where it passes into a long cyto- 

 pharynx. Adoral zone. No undulating membrane. Striation 

 and ciliation uniform. Macronucleus elongated band, often 

 curved. Micronucleus numerous. Contractile vacuole when 

 visible, numerous and scattered. Cysts are spherical with a 

 double thick membrane, the inner cover being connected at 

 places with the outer. Fresh water. 



Bursaria truncatella (Fig. 161, a). 500 to 600 microns long. 

 Pond or marshy water. 



Genus Balantidium Claparede and Lachmann. Body large, 

 oval to subcylindrical, slightly truncate anteriorly. Peristome 

 medium wide and slightly oblique in direction. At its posterior 

 end, is located a cytostome with a short cytopharynx. Ciliation 

 uniform. Macronucleus elongated. One or more contractile 

 vacuoles. A cytopyge. Several species. Parasitic in the intes- 

 tine of man, mammals and amphibians. 



Balantidium coli (Malmsten) (Fig. 161, b, c). In the intes- 

 tine of pigs and man. Body about 50 to 100 microns long by 

 30 to 70 microns broad. The infection in man is presumably 

 acquired from the cysts produced in pigs, and is responsible for 

 a serious intestinal disturbance in the unfortunate patient. 



Genus Balantidiopsis Blitschli. Body ovoid. Cytostome 



