354 Dientamoeba fragilis 
they are proportionate in size to the size of the whole organism, and 
range in diameter from about 2-3/x in very large to 0-8 ju in very small 
individuals (cf. Figs. 5 and 13). 
Although most individuals are binucleate, some can always be found 
which are uninucleate. Such individuals occur among amoebae of every 
size, but are commonest among those of small and intermediate dimen¬ 
sions (see Figs. 9, 12, 14). We have endeavoured to determine the 
proportions of binucleate and uninucleate amoebae in the species by 
counting the number of individuals of each category in preparations of 
the stools of the same person on different days, and in preparations 
made from different cases. The proportions found on different occasions 
are given below in tabular form: 
No. of amoebae with 
Case No. 
Date 
2 nuclei 
1 nucleus 
Total No. 
counted 
Percentage oj 
uninucleates 
D. 1 
27. i. 17 
235 
70 
305 
22-9 
5? 
20. iv. 17 
151 
49 
200 
24-5 
D. 2 
24. ii. 17 
162 
38 
200 
190 
D. 4 
9. vii. 17 
162 
38 
200 
19-0 
9f 
11. vii. 17 
170 
30 
200 
15-0 
Totals: 
880 
225 
1105 
20-3 
It will be seen that there is a good deal of difference in the percentages 
found; and it is possible that the greater number of uninucleates observed 
in case D. 1 on both occasions has some significance. However, the 
number of individuals counted at any single time is not great. Never¬ 
theless, we think that the aggregate result justifies us in concluding 
that, on the average, about 80 per cent, of the individual amoebae in 
the whole population are binucleate and 20 per cent, uninucleate. The 
interpretation of this conclusion will be discussed below. 
Although, as already noted, the structure of all nuclei appears to be 
the same, the appearances which they present may differ according to 
the way in which they have been stained. Each nucleus contains a 
large central karyosome whose diameter is about three-fifths of that of 
the entire nucleus. The nuclear membrane is extremely delicate, and 
separated from the karyosome by a clear zone traversed by a few very 
fine radiating linin threads (see Figs. 4, 9, etc.). There appears to be 
no chromatin on the nuclear membrane or in the clear zone, but some¬ 
times excessively minute and faintly stained granules can be made out 
at the points where the radiating threads join the nuclear membrane. 
The karyosome, when deeply stained with iron-haematoxylin, appears 
