xv, 4 De Leon: Balantidium Haughwouti 391 
small and spherical. This is the only species so far proved to 
be pathogenic to its host. 
Balantidium ducdeni 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 fx to 132 /*, 
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-KentO) has also reported it as occurring in 
certain marine worms. The body is soft, flexible, and some- 
what oval ; it measures 42 /x 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 striae 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 diarrhma. The body 
is oval, pointed anteriorly and more rounded at the posterior 
end. It ranges in length from 20 u to 32 u with a width of from 
14 fi to 20 /x. 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 
