_Natural vectors._--_Blaberus atropos_, Venezuela (Tejera, 1926): In a lot of 60 cockroaches captured in latrines, two were found that carried apparently live cysts similar to cysts of _E. coli_. _Blattella germanica_ or _Periplaneta americana_, Egypt (DeCoursey and Otto, 1956, 1957): One out of 44 cockroaches collected in a village harbored _E. coli_. _Experimental vector._--_Periplaneta americana_, Gold Coast Colony (Macfie, 1922): In nine experiments cysts of _E. coli_ were fed to the cockroaches. In seven of the experiments cysts of _E. coli_ were found in the feces. Cysts were observed in the feces for only one to three days, and eventually disappeared completely. The cysts appeared to be unharmed. No amoebae were found. * =Entamoeba histolytica= Schaudinn _Natural vectors._--_Blatta orientalis_, _Blattella germanica_, _Periplaneta americana_, _Periplaneta australasiae_, and/or _Supella supellectilium_, Peru (Schneider and Shields, 1947). _Blattella germanica_ and/or _Periplaneta americana_, Egypt (DeCoursey and Otto, 1956, 1957). Cockroaches, Venezuela (Tejera, 1926). _Experimental vectors._--_Blatta orientalis_, Italian Somaliland (Mariani and Besta, 1936). _Periplaneta americana_, Gold Coast Colony (Macfie, 1922); U.S.A. (Frye and Meleney, 1936). Cockroaches, Venezuela (Tejera, 1926). =Entamoeba pitheci= Prowazek? _Experimental vector._--_Periplaneta americana_, Formosa (Morischita and Tsuchimochi, 1926): Eleven of 15 cockroaches fed feces of a monkey [_Macaca cyclopis_ (Swinhoe)] containing cysts of the amoeba voided live cysts in their own feces. =Entamoeba thomsoni= Lucas _Synonymy._--_Endamoeba thomsoni_ [Kudo, personal communication, 1957]. _Natural hosts._--_Blatta orientalis_, England (Lucas, 1927a, 1928); U.S.A. (Taliaferro, 1928; McAdow, 1931); U.S.S.R. (Zasukhin, 1930); Germany (Chen, 1933). _Blattella germanica_, U.S.A. (McAdow, 1931). _Periplaneta americana_, England (Lucas, 1927a); U.S.A. (Smith and Barret, 1928; McAdow, 1931); Philippine Islands (Hegner and Chu, 1930). The organism is found in the hind intestine and rectum of the cockroach. Smith and Barret (1928) developed a synthetic medium in which cultures of _E. thomsoni_ were carried through successive transfers for 24 months. =Entamoeba= sp. _Natural vector._--_Periplaneta americana_, Gold Coast Colony (Macfie, 1922): Under the heading "_Entamoeba histolytica_ and _E. coli_" Macfie (p. 445) stated, "The cockroaches used in these experiments had previously been carefully examined for amoebic infections a precaution which was doubly necessary, because some of these insects at Accra had been found naturally infected." _Experimental vectors._--_Periplaneta americana_, Gold Coast Colony (Macfie, 1922): _Entamoeba_, resembling _E. coli_, from feces of the monkey [_Erythrocebus patas patas_ (Schreber)] were fed to cockroaches, and on the second to fourth days thereafter apparently healthy cysts were recovered in the cockroach feces.