856 
Dieiitamoeba fragilis 
the appearance of a vacnole in the protoplasm. This vacuole often 
becomes very large, and is generally lenticular or fusiform in outline 
(cf. Fig. 6). Some individuals develop numerous vacuoles, and thus 
appear to be full of bubbles. The vacuolate amoebae may continue to 
move for some time, but finally they all become rounded and die. By 
an increase in the size of the large vacuole or a fusion of smaller ones, 
the whole organism soon presents the appearances shown in Figs. 8 and 7. 
At this late stage in degeneration the whole amoeba has become one 
inflated vacuole surrounded by a thin covering of protoplasm, so that 
it appears annular in optical section (Fig. 7). Such ring-like individuals 
often measure 12p, to fS/r in diameter. The two nuclei can usually be 
seen in the unstained organism at this stage. In the faeces the degenerate 
ring-like individuals may remain almost unchanged for many hours, 
and sometimes some of them persist thus for even two or three days. 
At first sight they resemble dead Blastocystis, for which they can easily 
be mistaken. The large central vacuole of the degenerate Dientanioeba 
corresponds in position to the large central reserve body of Blastocystis, 
but has, of course, quite a different appearance. The resemblance, 
therefore, is most striking when the reserve body has disappeared from 
the dead Blastocystis, and its position is occupied by an apparently 
empty space. The nuclei sometimes break up before the Dientamoeha 
becomes ring-like, and may almost have disappeared before it ceases to 
move. In any case they undergo fragmentation sooner or later. 
On account of the rapidity with which it degenerates and dies the 
living amoeba can only be studied satisfactorily in very fresh stools, and 
preferably on a warm stage. For the same reason good stained prepara¬ 
tions can be made from such stools only; and even in the freshest 
specimens the amoebae are often very troublesome to stain, and many 
may appear degenerate. 
It has recently been stated by Swellengrebel (1917) that Blastocystis 
is merely a degenerate form of several different intestinal protozoa. 
From our own observations—more especially from those of one of us 
(C. D.) which extend over more than ten years, but which are still for 
the most part unpublished—we have no doubt that he is mistaken. 
We have convincing reasons for believing that Blastocystis is not a 
degenerate protozoon, but an independent organism belonging to the 
vegetable kingdom. When, therefore, we refer above to the resemblance 
of a degenerate Dientamoeba to a dead Blastocystis, we would not be 
understood to suggest that they are in any way connected. Although 
most of our cases infected with Dientamoeba are infected also vdth 
