Acton . — Observations on the Cytology of the Chroococcaceae . 439 
accumulate in the central region as a network, and confer on it the peculiari- 
ties which give it an appearance analogous to a nucleus. 
The present investigation extended over a period of three years, and 
comprised material collected from three different sources at different periods 
of the year. The variation in the distribution and staining capacity of the 
granules in the different collections, due probably to physical conditions, as 
suggested by Chodat, was well shown. 
As a result of these investigations, it has been found impossible to 
divide the work into descriptions of £ cytoplasm ’, ‘ nucleus *, and ‘ granules ’, 
in the usual way. The best plan seems to be to state first the actual 
results obtained by staining reactions, and to discuss these results afterwards. 
In the living cell one can only see that the protoplast is densely packed 
with rounded granules of a fairly uniform size. Some of these seem to be 
more refractive than others. Satisfactory results could not be obtained 
with living staining methods, on account of the tough thick membrane. In 
only one or two cases did there seem to be any indication of deeper staining 
in the central region. 
In considering the results obtained from fixed material, observations 
which were made early in the work, before the structure of the protoplast 
was fully understood, will be mentioned briefly, since they appear to coincide 
with results mentioned by other authors. But it will be shown later that 
these results, in my own case at any rate, were only due to imperfect 
observations. 
Staining with brilliant blue brought out deeply staining granules in the 
peripheral region of the cell, and with Bismarck brown granules in the 
central region. The number of granules reacting with Bismarck brown 
varied considerably. They were not confined entirely to the central region, 
but were chiefly concentrated there. These granules apparently correspond 
to the central granules of Kohl (’03), metachromatin granules of Guillier- 
mond (’05), and volutin of Wager and Peniston (TO). These will be called 
metachromatin granules in the remainder of the paper. The granules 
reacting with brilliant blue correspond to the cyanophycin granules of 
Kohl and others. 
Preparations stained with Delafield’s haematoxylin showed the meta- 
chromatin granules stained a dark red colour, sometimes appearing almost 
black. In most cases these granules were almost uniform in size, but some 
material showed, in addition to these metachromatin granules, larger 
irregular granules which were apparently hollow. In the peripheral region 
could be seen granules very faintly stained of the same colour as the rest of 
the groundwork. 
In addition to these granules, in several dividing cells, V-shaped threads, 
which might be compared to the spindle threads of a mitotic figure, were 
seen joining a few of the metachromatin granules. 
