1898-99. | ON THE CYTOLOGY OF NON-NUCLEATED ORGANISMS. 477 
GENERAL CELL STRUCTURE. 
In fresh actively growing specimens of 4. alba the cytoplasm of the 
filaments is crowded with minute sulphur droplets, and it is difficult to 
determine the presence of any other structures. One can, with very high 
powers and good illumination of the microscopic field, see the transverse 
septa marking the thread off into cells, and at the same time find the 
cytoplasm next these septa free from granules. 
In the fixed preparations which have been passed through alcohol and 
stained the result is different. In Fig. 60 are represented three cells ofa 
thread of B. ala. The sulphur has been removed by the alcohol and 
the places occupied by the sulphur are shown as clean vacuoles. The 
protoplasm near the transverse septa appears denser than elsewhere, 
although because of the aggregation of the vacuoles around the centre 
sometimes the cytoplasm at the latter point gives an appearance of con- 
densation. The stain taken by the cytoplasm is uniform throughout the 
cell, but fine granules may not unfrequently be observed. I am, how- 
ever, unable to corrobrate Mitrophanow regarding such large granules 
as he illustrates. When the threads become less rich in sulphur and 
therefore, ill nourished, large granules may be found, not quite so 
often indeed, as he observed, but still much more frequently than 
in the preparations from actively growing cultures. I am inclined to 
believe that Mitrophanow’s preparations were made from ill-nourished 
cultures, and an examination of his illustrations (Figs. 28 and 30) 
convinces one of this, for in them is an utter absence of such vesiculation 
as would be present, had the cells, when prepared, contained sulphur 
droplets. 
There is no evidence whatever of the presence of any nuclear struc- 
ture. The cells of well-nourished threads in no case show a differ- 
entiation of their cytoplasm into central and peripheral parts according 
to the views of Biitschli. It is rare even to get, as Fischer did with 
hematoxylin and safranin, a slightly deeper stain in the central part, and 
when this does appear it is due to the fact that the central part of the 
cell is seen through a greater quantity of cytoplasm than is the periphery 
of the cell. 
In &. mirabilis hardened in alcohol the cell frequently contains a 
slightly denser portion of cytoplasm placed adjacent to one of the 
transverse septa, but an examination of this mass shows that it is really 
a shrunken portion of the cytoplasm which filled the whole cell. When 
