542 
Entamoeba gingivalis 
within the endoplasm which we have taken for the nucleus has been 
that structure. When an amoeba shows numerous round inclusions, 
as is often the case, it is impossible to say that any particular round 
body in the endoplasm is the nucleus. 
(b) The stained organism. 
When stained with iron-haematoxylin the ectoplasm of the amoeba 
stains grey and appears finely granular in structure in protruding 
pseudopodia. The endoplasm is oftep sharply marked off from the 
ectoplasm and appears to be somewhat coarsely granular in structure 
and frequently shows an alveolar appearance. Usually one finds in¬ 
clusions of various shapes and sizes within the endoplasm and these 
are often present in sufficient numbers to obscure the structure of the 
endoplasm. 
The nucleus has been fully and accurately described by Craig who 
deals also with the differences and similarities between it and the 
nuclei of Entamoeba coli and Entamoeba histolytica. It consists essenti¬ 
ally of a circular or oval nuclear membrane separated by a clear zone 
from a small centrally situated karyosome. The membrane seems to 
be impregnated with a certain amount of chromatin for it stains deeply 
with iron-haematoxylin and also frequently bears granules or small 
thickenings of chromatin on its inner side. The karyosome may 
appear to consist of a single body homogeneous in structure and this 
is most commonly found, or it may very frequently appear to be made 
up of three or four distinct granules. In several of our preparations 
a karyosome appears to be absent and the space within the nuclear 
membrane is taken up with a net-work of linin fibres on which small 
granules of chromatin are irregularly disposed. It is possible that such 
appearances may represent stages in the break up of the chromatin 
prior to nuclear division, though none of the amoebae show anything 
which can be interpreted as mitotic division figures. 
The nucleus is extremely poor in chromatin, and only stains feebly 
with chromatin stains such as safranin, methyl-green, polychrome 
methylene-blue. There is thus a very marked contrast in appearance 
between it and the round or oval inclusions, many of which are coloured 
intensely with the stains just mentioned. PI. XX, fig. 2 is a photo¬ 
micrograph of an organism stained with safranin and shows how feeble 
is the contrast between the cytoplasm and the nucleus. 
Wenyon (1907) speaks of the paucity of chromatin in the nucleus 
of Entamoeba muris. and in this connection also w'e may note that a 
