570 
MARGARET ROBINSON. 
but I found some conjugations in which there was apparently 
a fusion of the cytoplasm of the gametes, as well as of their 
nuclei. 
In neither gamete nor zygote could I demonstrate a cell- 
wall by the use of Delafield’s hfematoxylin, but preparations 
stained with Licht-Griin and picric acid showed a delicate 
outline to the cells. This outline was more easily shown in 
sections than in whole cell preparations. 
The z}"gote is at first pyriform with very little in the way 
of a stalk, but with one end a good deal thicker and rounder 
than the other. The cell-wall is slightly more pronounced 
than it was in the conjugation stage. It is at the narrow, 
pointed end of the zygote that its nucleus lies. This nucleus 
is also pyriform and has its wide end directed towards the 
wide end of the zygote. Its chromatin is loosely arranged 
in large thick rods and lumps, and is not surrounded by a 
membrane. The absence of a nuclear membrane here is 
probably not merely a result of the fusion of the nuclei, but 
also a means of aiding the expulsion of a vacuole from the 
nucleus (fig 8, h). 
Brasil (1905) also notes the expulsion of a vacuole (sphere 
hyaline) from the nucleus of every zygote in a cyst; and, as 
well as the vacuole, he saw extruded a small globule of 
chromatin, which he conjectures may form part of that 
chromatin which is subsequently to be seen at both ends of 
the spores of Monocystis after the first nuclear division. 
I saw no such extrusion of a grain of chromatin here, but on 
the assumption that it is merely superfluous chromatin this 
is not to be wondered at, for a small globule of superfluous 
chromatin was ejected at an earlier stage (see above and 
fig. 8). 
The absence of a nuclear membrane may possibly facilitate 
the movements of the nucleus, for it certaiidy does move. 
One can see the vacuole forming, and after its extrusion the 
nucleus has not only acquired a membrane, but now lies at 
the wide end of the zygote. Nuclei can be seen in inter- 
mediate positions during' the formation of the vacnole. Its 
