* v * De Leon: Balantidium Haughwouti 391 



small and spherical. This is the only species so far proved to 

 be pathogenic to its host. 



Balantidium duodeni Stein. 



This species has been found in the duodenum of the edible 

 frog Rana esculenta. It differs from Balantidium entozoon, a 

 parasite of the same host, in that the cuticular cilia of B. duo- 

 deni are longer and finer and are "mostly directed forwards and 

 have a tendency to group themselves into even, longitudinally 

 disposed, pencil-like tufts." It has a length of 85 M to 132 p, 

 barely exceeding its breadth. It has a short, oval, flattened 

 body with a short, narrow, slitlike peristome. There is no dis- 

 tinct cytopharynx. The meganucleus is oval. There is only 

 one contractile vacuole, and this lies at one side of the body 

 posteriorly. 



Balantidium medusarum Mereschowsky. 



Parasitic in the alimentary and radial canals of the medusae 

 of the coelenterate forms Eucope and Bougainvillea. Brada, as 

 quoted" by Saville-Kent(9) has also reported it as occurring in 

 certain marine worms. The body is soft, flexible, and some- 

 what oval ; it measures 42 n in length, this being about twice the 

 width of the body. The peristome is prolonged backward and is 

 supplied on the left border with an even row of powerful adoral 

 membranelles. The surface of the body is distinctly marked 

 with numerous longitudinal strise that are interlaced by finer, 

 less conspicuous transverse striations. The body is supplied 

 with long, slender, fine cilia that are well scattered. There are 

 one or two contractile vacuoles. The meganucleus is slightly 

 oval and may be rounded ; it is usually central in position. 



Balantidium minutum Schaudinn. 



This is a parasite of the human intestinal tract, its local hab- 

 itat being the small intestine, particularly the duodenum. It 

 appears only in the stools during active diarrhoea. The body 

 is oval, pointed anteriorly and more rounded at the posterior 

 end. It ranges in length from 20 p. to 32 n with a width of from 

 14 /x to 20 p. The peristome is fissurelike and ends at the center 

 of the body. The right lateral border of this peristome is sup- 

 plied with a row of cilia of the same size as those appearing on 

 the general surface of the body. The left side expands laterally 

 into a "thin hyaline membrane that extends towards the back 

 and can pass over to the right side." There is a single con- 

 tractile vacuole situated posterodorsally. The meganucleus is 



