360 
Dientamoeba fragilis 
DISCUSSION OP THE NUCLEAP. SYSTEM OF DIENTAMOEBA. 
NOMENCLATURE, 
Before we discuss the nomenclature of the organism here described, 
it is necessary to consider its nuclear system, and to compare it with 
certain other amoebae: since our interpretation of the nuclei, when 
contrasted with the nuclear structures of related forms, constitutes the 
chief justification for oixr regarding the organism as new, and conse¬ 
quently for proposing for it a new name. 
We have already pointed out that most individuals of Dientamoeha 
are binucleate, though in a certain number (about 20 per cent.) only 
one nucleus is present. It might be suggested that this is due to the fact 
that, in the samples of infected faeces studied, the individuals—which 
are, in the resting stage, normally really uninucleate—happened to be 
encountered at a moment when rapid multiplication was taking place. 
We cannot accept this interpretation for the following reasons. First, 
although binucleate individuals are always in the majority, stages of 
nuclear division are either excessively rare or absent. That rapid division 
was occurring when the specimens were obtained appears therefore to 
be excluded. Secondly, binucleate individuals are always present in 
large numbers, Mo matter when the specimens are obtained. Whenever 
Dientamoeha is present in the stools, whether passed normally at any 
time or after the administration of a saline purgative, there is always 
the same preponderance of binucleate individuals. When the difficulty of 
obtaining dividing forms of any of the other intestinal amoebae by random 
sampling of the stools is remembered, it seems incredible that dividing 
forms of Dientamoeha should be present always. Thirdly, the binucleate 
individuals of Dientamoeha are actively motile (cf. Fig. 5); whereas most 
amoebae, when undergoing division, are rounded and at rest (cf. Dobell, 
1914). Fourthly, it is to be noted that the binucleate or uninucleate 
condition is not peculiar to individuals of any particular size. If a 
uninucleate species is examined at the moment when an epidemic of 
division into two is occurring, the large dividing forms alone are binucleate, 
whilst the young forms resulting from the division are uninucleate. 
Here again, therefore, the hypothesis that Dientamoeha is an amoeba in 
process of division appears inadequate. 
If the foregoing considerations appear unconvincing, and it be still 
urged that the organism is really only a division form of one of the 
amoebae of the human gut, then we woxxld ask: To which species of 
human intestinal amoeba does it belong? Clearly not to E. coli or 
