434 University of California Publications in Zoology [Vol. 20 



figs. 20, 33, 34) are of Councilniania decmnani. These have coarse 

 blobs of peripheral chromatin on the nuclear membrane, and the 

 nuclei are somewhat smaller than the general run in C. muris. It 

 appears from this that Wenyon (1907) found in mice the two species 

 which we have found, but recognized only one of them, C. muris. 



Brug (1919), working on the amoebic infections of the wild Mus 

 rattus of Java, encountered two amoebae (possibly three). To one 

 of these he gave the name Entamoeba muris, the other he called 

 Entamoeba tetragena. This last he found in a natural infection in 

 a wild rat and succeeded in one instance in inducing an infection 

 in the rat by feeding cysts from human stools. His figures and dis- 

 cussion convince us that he was dealing in these instances with an 

 infection by Endamoeba dysenteriae (Councilman and Lafleur). 



His figures (his pi. 1) of the amoeba called by him Entamoeba 

 miiris clearly portray an amoeba with a few coarse blobs of peripheral 

 chromatin on the nuclear membrane in the encysted stages in stained 

 material. Two of his figures (17 and 18) are indeterminate and one 

 only (fig. 15) may possibly belong to Councilmania muris. The others 

 are clearly referable, not to C. muris, but to C. decumani Rudovsky 

 (1921). 



In 1921 Rudovsky failed to find Endamoeba nmris (Grassi) Wen- 

 yon in mice but described an amoeba which he found in 139 wild rats 

 as Entamoeba muris decumani. This amoeba is correctly character- 

 ized as having thin nuclear membrane, small karyosome, and a small 

 amount of chromatin. He noted the difficulty in getting a typical 

 glycogen reaction of the contents of the vacuole in the binucleate 

 stage when the glycogen vacuole has its greatest volume. He figures 

 2-, 4-, 8-nucleate cysts, not very clearly, but with sufficient detail to 

 be recognizably distinct from Wenj'on's (1907) main type which he 

 (Rudovsky) cites as E. muris. He does not figure, and apparentlj' 

 did not find the species muris. We conclude that this species of 

 Rudovsky (1921) is identical with one we find in both rats and 

 mice and that it is different from the one which Wenyon regarded 

 as Grassi 's Amoeba muris. 



Wenyon (1907) seemingly found both species (but recognized 

 only one) in the mouse. Brug (1919) seemingly found both in the 

 rat (but recognized only one) and applied Grassi 's name to it 

 although it differed from the species to which Wenyon applied the 

 name. Rudovsky (1921) found only one species in the rat but recog- 

 nized its differences from the species muris. 



