282 
The Ohio Naturalist. 
[Vol. VIII, No. 5, 
could not bg accurately represented by anything less than the 
heavy lines in the drawing. Since the rays are cylindrical rods 
rather than plates the membrane is not a first any membrane 
at all but a cage around the vacuole. The method bv which the 
interstices between the bars are filled up could not be followed 
satisfactorilv. But it mav be that the substance of the rays 
gradually spreads out around the vacuole till the membrane is 
completely formed. This process may be seen on the side of the 
nucleus towards the centrosome in those cases where the apex of 
the cone of rays is very acute. Here the rounded surface of the 
vacuole may be seen to acquire a membrane like that of the rest 
of the nucleus so gradually that it is often difficult to tell whether 
the membrane is present or absent (fig. 11). In these cases the 
cap of rays persists for a considerable time but graduallv fades 
when the membrane is complete (figs. 10,11). 
This method of the formation of the nuclear membrane by 
the ravs of the centrosome has been observed by the writer in 
very many cases; to the five figures given to illustrate the stages 
of the process could be added many more if it were deemed 
necessary. 
Aside from the' peculiar method of its formation, the nuclear 
membrane of Svnchytrium is a remarkable structure. In the 
primary nucleus it reaches a relatively enormous thickness (See 
Stevens ’03, fig. 5) and it is so stiff that it is often broken and 
carried away by the knife. In the succeeding mitoses it is not 
onlv thickened but sometimes presents some very peculiar aspects 
which we shall hope to deal with in .a later paper. One feature 
may be touched upon here. 
Those rays which form the membrane, like the others, fre¬ 
quently have granules strung a’ong them. In other ray s the 
granules are centrally placed on the ray but in these they are 
nearly always found on the inside of the nuclear cavity (figs. 4, 
7, 8). In older stages they may be found either within the 
nucleus, in the wall, or lying against its outer edge (fig. 12). Per¬ 
haps, correlated with these granules are others frequently seen 
loose in the cytoplasm, and surrounded each by a vacuole of its 
own (fig. 11). But consideration of these would carry us too 
far afield. We can not do more at this time than to suggest the 
possible analogy between the formation of these granules and 
the derivation cf the microsomes of the cytoplasm from the 
nucleus as described bv Lillie and others. 
Summary. The exact history of the structures touched inci¬ 
dentally, the asters and the chromatin content of the nucleus, is 
somewhat provisional, but the point of the present paper is the 
demonstration, confirming and amplifying Kusano’s announce¬ 
ment that the rays of the centrosome enclose the vacuole surround¬ 
ing the naked chromosomes, and form a very heavy deeply 
staining membrane around it, the nuclear membrane. 
