_Natural host._--_Periplaneta americana_, India (Ghosh, 1922a; Bhatia and Gulati, 1927); Indochina, Saigon (Weill, 1929): Intestinal tract. =Balantidium praenucleatum= Kudo and Meglitsch _Natural host._--_Blatta orientalis_, U.S.A., Illinois (Kudo and Meglitsch, 1938; Meglitsch, 1940): This protozoan is found in the lumen of the anterior region of the colon in association with several other species of protozoa. Only 7.6 percent of 500 cockroaches examined contained _B. praenucleatum_. The largest number encountered in a single host was 59, but as a rule each host harbored a smaller number. =Balantidium= sp.? _Natural host._--_Periplaneta americana_, Brazil (Magalhães, 1900): These organisms were numerous in the intestine. Family SPIROSTOMIDAE =Nyctotherus buissoni= Pinto _Natural host._--"Barata sylvestre," Brazil (Pinto, 1926): Organism found in the cockroach's intestine. =Nyctotherus ovalis= Leidy _Synonymy._--_Bursaria blattarum_; _Plagiotoma blattarum_. _Natural hosts._--_Blatta orientalis_, U.S.A. (Leidy, 1850, 1853, 1853b, 1879a; Kudo, 1922, 1926, 1936; McAdow, 1931; Kudo and Meglitsch, 1938; Meglitsch, 1940); Germany (Stein, 1860; Schubotz, 1905; Chen, 1933); England (Lankester, 1865; Schuster, 1898; Lucas, 1927a, 1928); Spain (Zulueta, 1916); U.S.S.R. (Yakimov and Miller, 1922; Zasukhin, 1928, 1930; Ostroumov, 1929); Portugal (Lima Ribiero, 1924); Brazil (Pinto, 1926); Venezuela (Tejera, 1926). _Blattella germanica_, South Africa (Porter, 1930); U.S.A. (Balch, 1932; McAdow, 1931). _Parcoblatta pensylvanica_, U.S.A. (Semans, 1939, 1941). _Periplaneta americana_, India (Bhatia and Gulati, 1927); Indochina (Weill, 1929); Philippine Islands (Hegner and Chu, 1930); South Africa (Porter, 1930); U.S.A. (McAdow, 1931; Hatcher, 1939; Meglitsch, 1940; Armer, 1944); Goa (Mello et al., 1934); China (Pai and Wang, 1947); Czechoslovakia (Low, 1956). "Barata sylvestre," Brazil (Pinto, 1926). "Küchenschaben," Austria (Bělǎr, 1916). _Nyctotherus ovalis_ (fig. 2, G) inhabits the hind gut of cockroaches, where it occurs almost always in the anterior half of the colon in association with other species of Protozoa (Kudo, 1936). Ninety percent of 500 _B. orientalis_ contained _N. ovalis_ (Kudo and Meglitsch, 1938). Yakimov and Miller (1922) found _N. ovalis_ in 68 percent of 124 _B. orientalis_. Zasukhin (1930) found this organism in 63 percent of over 3,000 _B. orientalis_. Zasukhin (1928, 1934) found a fungus and possibly a bacterium hyperparasitic in the cytoplasm of _N. ovalis_. _N. ovalis_ has been cultured outside the cockroach in several media (Lucas, 1928; Balch, 1932; Chen, 1933; Low, 1956). =Nyctotherus uichancoi= Kidder _Natural hosts._--_Panesthia angustipennis_, Philippine Islands, and _Panesthia spadica_, Japan (Kidder, 1937): About 90 percent of all _P. angustipennis_ harbored this ciliate in their hindguts. =Nyctotherus viannai= Pinto