258 A. B. MACALLUM. 
The most readily accessible form was Beggiatoa alba. This 
organism, as is well known, manifests itself in five different 
conditions: long threads composed of cells of varying lengths, 
shorter filaments also formed of cells usually free and motile, 
spirillum-like elements, comma-shaped, two-celled, swarming 
bodies, and simple “cocci.” Cover-glass preparations of all 
these forms, fixed first with heat and subsequently with 
alcohol, were subjected for about two weeks to the action of 
the glycerine and sulphide mixture at 60°C., while like prepa- 
rations were treated with sulphuric acid alcohol for about two 
hours at a temperature of 30°C. The results of both methods 
agreed. In the long threads the abundance of sulphur granules 
causes the cytoplasm to have a reticular, or more properly 
speaking, a vesicular appearance, brought out very prominently 
when the glycerine and sulphide mixture has dissolved out the 
sulphur and at the same time given the cytoplasm a greenish 
colour, developing into a faint blue on treatment with an acid 
ferrocyanide mixture. At times the greenish or the blue re- 
action appears most prominently in some of the nodal points 
of the “network,” but this is doubtless due to the fact that 
more of the cytoplasm is condensed at such points. The 
shorter free, motile filaments, which contain, as a rule, very 
many fewer sulphur granules, have a more homogeneous cyto- 
plasm, and in these the reaction for “ masked” iron obtained 
was a diffuse one. A similar result was obtained in the 
examples of the spirillum form. In the comma-shaped forms 
the reaction obtained was, as a rule, slightly deeper, and 
it frequently appeared most markedly in the central portions 
of each of the two cells. In some examples a granule in this 
central mass gave a marked reaction for iron. I did not suc- 
ceed in determining the relations of the iron in the “ cocci.” 
So far as these results go they correspond with those ob- 
tained when cover-glass preparations of Beggiatoa alba are 
stained with hematoxylin, which colours diffusely the cytoplasm 
in all the forms, but rarely reveals the existence of special 
chromatin elements. I have been unable to determine, except 
in a few comma-shaped elements, the occurrence of the denser 
