440 Acton. — Observations on the Cytology of the Chroococcaceae . 
Similar results were given with Loeffler’s methylene blue. Granules 
in the central region stained dark blue, and in some cases there were 
apparently large irregular granules with a reddish tinge. The larger the 
granules, the redder they appear. Delicate threads could be seen here and 
there joining the granules. The groundwork and granules in the peripheral 
region were stained a very greenish blue. 
With the iodine-green-fuchsin combination the cells appeared to stain 
uniformly red, with reddish granules distributed throughout the cell. 
These were not quite so conspicuous in the central region, but could be seen 
in sections. In certain parts of the cell, however, not isolated threads, but 
a definite reticulum of fine threads could be seen joining the granules, giving 
the appearance of a nuclear network. Finally, it was seen that the reticulum 
extended throughout the whole cell (PI. XXXIII, Fig. 6). This necessitated 
the revision of the whole work and preparation of new slides. The following 
conclusions were only arrived at as a result of careful examination of 
hundreds of specimens. 
The protoplast undoubtedly consists of a ground substance traversed 
by a very regular reticulum of delicate threads. This reticulum extends 
throughout the whole cell right up to the cell-wall (Fig. 6). At the junctions 
of the meshes of the reticulum, granules occur of fairly uniform size. These 
appear to correspond to Nadson’s ‘ plasmatic microsomes ’, although he only 
described them for Merismopedia and Aphanocapsa. They are a constant 
feature of every species examined by the author, and the name ‘ plasmatic 
microsomes ’ will be used for the sake of convenience in the remainder of 
the paper in describing these granular thickenings of the reticulum. 
The reticulum, with its granular thickenings at the nodal points, is 
seen most clearly in slides stained with iodine-green-fuchsin. With this 
stain, the ground substance, reticulum, and plasmatic microsomes stain red. 
In the central region, however, the microsomes are not so clearly marked, 
sometimes appearing to take on a bluish tinge. In good preparations the 
reticulum can be seen with other stains, but more often portions of it only 
can be seen in different parts of the cell. This reticulum has a very small 
mesh and can only be seen with a high magnification (Fig. 2 ). 
The granules in the central region, which stained deeply with Delafields 
haematoxylin, were found to be situated at the junctions of the meshes, the 
fact that the reticulum was imperfectly observed giving rise to the idea that 
these granules are sometimes joined by V-shaped threads. It is interesting 
to note in this connexion that Gardner (’06), in speaking of the a (central) 
granules, says : ‘ There often appears to be a connexion between two granules, 
but I presume that this is simply the deeply stained protoplasm, the colour 
of which is not washed out.’ Since they occupy the same position, i. e. at 
the junctions of the network, the metachromatin granules must be identical 
with the plasmatic microsomes in the centre of the cell, or, in other words, 
