ENTAMOEBA HISTOLYTICA 209 



species it is difficult to form an opinion, as the encysted stages were not 

 seen. In any case there seems to be little ground for the creation of a 

 new genus. It has to be remembered, however, that undoubted E. histo- 

 lytica often move in a slug-like manner, as noted by Dobell and O'Connor 

 (1921), and that many free-living amoebae, as well as E. histolytica, may 

 develop the slug-like form with tapering posterior end to which debris 

 adheres, while other amoebae in the same pure culture move in the more 

 normal amoeboid manner. Whether Candamoeha sinensis is actually 

 distinct from E. histolytica future investigations alone will show, but it 

 seems to the writer that sufficient evidence to justify the distinction has not 

 yet been produced. Eecently the writer has had an opportunity of observing 

 E. histolytica in cultures. The assumption of a slug-like form with tapering 

 posterior end to which debris adheres is quite common. The fact that bacteria 

 as well as red blood-corpuscles occurred in vacuoles is a feature which may 

 be met with in undoubted E. histolytica. Schubotz (1905) has figured an 

 elongated form of E. hlattcB of the cockroach which bears some resemblance 

 to C. sinensis, while Jepps (1923) has described a somewhat similar form 

 of E. gingivalis, and Keilin (1917) one in E. mesnili (Fig. 109). 



Chaterjee (1920) gave the name Entamoeba jmradysenterica to amoebae 

 which he found post-mortem in dysenteric lesions, and which he regarded 

 as a distinct species on account of certain peculiarities of nuclear structure. 

 The writer has seen preparations of this amoeba, which is unquestionably 

 a degenerate E. histolytica. 



Kofoid and Swezy (19246) gave the name Karyamceha falcata to 

 an amoeba of the human intestine. As the generic name was preoccupied, 

 they (1925a) changed it to Karyamoebina (Fig. 98). The amoeba was 

 first described from three cases. The first harboured, in addition, E. 

 histolytica, E. coli, Endolimax nana, Dientamceba fragilis, as well as the 

 form described as CounciUnania lafieuri ; the second E. histolytica ; and 

 the third E. histolytica, E. coli, and C. lafieuri. Three further cases were 

 reported in their second paper. The chief distinguishing feature is the 

 nucleus and the method of nuclear division. The nucleus has a definite 

 membrane, upon which the chromatin is massed in one or two, rarely more, 

 crescentic clumps. There is an excentric karyosome round which is a halo. 

 In division the nucleus elongates, and there is formed at each end a deeply 

 staining pole cap. On this account the amoeba is supposed to be allied to 

 members of the genus Vahlkampfia (see p. 177). In Vahlkampfia, however, 

 the pole caps are formed from the divided karyosome, and it is definitely 

 stated that in K. falcata the karyosome does not divide. In this form the 

 pole caps are merely terminal aggregations of the large chromatin masses on 

 the nuclear membrane. On this account the amoeba cannot be allied with 

 Vahlkampfia. It is said that in K. falcata about twenty chromosomes occur 

 at the equator of the elongating nucleus. Cysts have not been observed. 

 I. ' 14 



