THE INFUSORIA 



403 



end is drawn out into a conical papilla armed with long cilia. Biitschli 

 regards this end as posterior. 0'04. Freshwater. Tuamotu. Ptycho- 

 stomum, Stein. O'l. Occurs in the intestine of Oligochaeta. Ancystrum, 

 Maupas. Ovoid in form, with a series of long cilia on the ventral border. 

 0'07. In the pallial cavity of marine Pelecypoda. 



Family PARAMOECINA, Duj. Paramoecium, Stein. There is a 

 minute undulating membrane on the dorsal side of the pharynx. Tricho- 

 cysts tisually occur over the whole surface of the body. One or two con- 

 tractile vacuoles. One or two micronuclei. Up to 0'25 in length. Very 

 common. Freshwater and marine. (Fig. 46.) 



Family UROCENTRINA, Clap, and L. Urocentrum, Nitzsch. The 

 ciliation of the body reduced to two broad zones. The peristome extends 



from the posterior edge of 

 the anterior zone to the 

 hind end of the body. O'l. 

 Marine and freshwater. 



u.m. 



FIG. 52. 



Pleuronema chrysalis, O.F.M. M, meganucleus ; m, 

 micronucleus ; u.m, the large right undulating lip ; /, F, 

 food particles ; c.v, contractile vacuole. (After Schewia- 

 koff.) x 400. 



Fio. 53. 



Opalina ranarum, Purkinje. 

 a, a, the meganuclei. (From 

 Lankester, after Zeller.) x 100. 



Family PLEORONEMIXA, Biitschli. Lembadion, Perty. The peri- 

 stome is a deep groove extending from the anterior end of the body almost 

 to the posterior. It is covered by two large undulating lips. A small 

 undulating membrane also occurs on the right side of the peristomial 

 groove. Pleuronema, Duj. (Fig. 52). A very large peristome with a 

 large right undulating lip. Springing movement. 0'03. Marine and 

 freshwater. Lembiis, Cohn. An elongated form with two undulating lips. 

 O'l. Marine infusions. Cyclidium, Clap, and L. Very similar to Pleuro- 

 nema, but smaller. 0'03. Freshwater and marine. Cristigera, Roux. 

 Freshwater. Pleurocoptes, Wallengren, occurs on Hydractinia. 



Family ISOTRICHINA, Biitschli. Isotricha, Stein. Spherical forms 

 with a mouth situated at the posterior (1) end. A well-marked anus 

 situated anteriorly. Numerous minute contractile vacuoles scattered 

 through the protoplasm. O'l 6. Rumen of the Artiodactyla. Dasy- 

 tricha, 0. Schuberg. No anus. Lines of cilia rather more spirally 

 arranged than in Isotricha. O'l. Rumen of Artiodactyla. Paraisotricha, 

 Fiorent. Coecum of the horse. 



