M. W. Jepps and C. Dobell 
363 
amoebae hitherto described differ conspicuously from the form which 
we have found in man. It seems to us clear, moreover, that our amoeba 
cannot be placed in the genus Entamoeba (= Endamoeba). The type 
species of this genus is E. blatfae (Biitschli) Leidy 1879, an organism 
very different from the one under consideration. And although the 
three known intestinal amoebae of man are now usually placed in the 
same genus, there is reason to suppose that they may ultimately have 
to be separated, as they all differ considerably—so far as can be judged 
at present—from the parasite of the cockroach. Whilst, however, 
“Entamoeba” histolytica and “E.” coli are undoubtedly co-generic^, it 
is not improbable that “Entamoeba” nana is generically distinct. But 
for our present purpose it does not matter how the genus Entamoeba 
may ultimately be revised or amended. It is sufficient to note that in 
any case it cannot properly be made to comprise the form which we have 
just described. The nuclear structure of the latter is alone sufficient to 
distinguish it sharply from any organism which can be regarded as the 
type of the genus Entamoeba. 
We therefore think it necessary to introduce a new generic name for 
the organism which we have described: and accordingly we propose the 
name Dientamoeba —a name suggested by the nuclear structure, which 
is duplicate in comparison with that of other parasitic amoebae of the 
genus Entamoeba. A diagnosis of the new genus and species may now 
be given: 
Dientamoeba nov. gen.—Small amoeba, with a diameter when rounded 
of ca. 3-5/r to 12p. (average ca. 9p.). Cytoplasm differentiated into 
ectoplasm and endoplasm. Pseudopodia flattened, hyaline, and leaf-like; 
usually few, with irregularly dentate margins. Progression snail-like. 
No contractile vacuole. Typically binucleate, both nuclei having the 
same size and structure. Size of nuclei ca. 0-8p—2-3/x (average ca. 2p). 
Each nucleus possesses a large central karyosome surrounded by a clear 
zone containing no peripheral chromatin and limited externally by a 
very delicate achromatic nuclear membrane. Details of nuclear division 
unknown; but organism probably divides when binucleate into two 
uninucleate daughter-individuals, which become binucleate by sub¬ 
sequent division of the nucleus during growth. Cysts unknown. Habitat: 
intestine (probably colon) of man. Food: small vegetable organisms in 
intestinal contents. 
Only known species D.frayilis nov. spec., with characters of genus. 
^ If these two species are ultimately placed in another genus, then it must be Loeschia 
(Chatton and Lalung-Bonnaire, 1912), not Proctamoeha (Alexeieff, 1912). 
