248 A. B. MACATLLUM. 
those represented in fig. 5. The differences observed appear 
to depend on the cytoplasmic structure in the specimen ex- 
amined. When there are a few large vesicles in the cell, the 
iron-holding substance seems to be, in great part, at their peri- 
pheries. This disposition also obtains in the buds. The 
remaining portion of the cytoplasm in each element is very 
slightly coloured greenish, but whether that is due to ferrous 
sulphide is uncertain. When, on the other hand, the cells are 
markedly vesiculated, the glycerine and sulphide mixture gives 
the cytoplasm between the vesicles a distinct reaction for iron, 
In the majority of such cells there are one or more large 
spherical elements, which, in the glycerine and sulphide mix- 
ture, after the third or fourth day appear dark green, much 
more so than does the surrounding cytoplasm. They are 
homogeneous, manifesting a uniform reaction throughout their 
substance, and their position is, if not in the centre of the 
cell, at least in that neighbourhood ; but smaller granules of 
the same character may be more remotely situated. From 
their position, size, and shape, they would appear to be the 
bodies which, in preparations made with corrosive sublimate, 
hematoxylin, and eosin, stain exclusively with the latter 
reagent. In cells which are treated with acid alcohol, then 
with an acid ferrocyanide solution, and finally, after being 
stained with eosin, mounted in balsam, similar bodies are 
given a violet tint, while the cytoplasm is coloured bluish, the 
violet being undoubtedly due to a combination of the Prussian 
blue colour with the eosin stain. As the granules of Raum 
are not specially selected by eosin, it would appear that the 
iron-containing body observed does not belong to that class. 
It is thus seen that in 8S. cerevisiz the assimilated iron is, 
like the substance which absorbs hematoxylin, distributed 
through the cytoplasm and sometimes also in the latter in the 
form of granules, but in S. Ludwigii it may be chiefly found 
at the periphery of each large vesicle when only a few vesicles 
are present, while in those cells in which the whole of the 
cytoplasm is vesiculated, the latter gives a uniform reaction 
for iron corresponding in its depth with that given by hema- 
