Griffiths.—On Glaucocystis Nostochinearum , Itzigsohn. 425 
regular monthly collections of Glaucocystis from the pool throughout 1913, 
and at frequent intervals between 1910 and 1913, but almost all the speci¬ 
mens found were in the division stage of the chromatophores. In only 
a few cases were the radiating bands seen. The unusual situation in which 
the organisms were found may be correlated with this. The usual habit is 
in Sphagnum- bogs, and in such places the chromatophores frequently show 
the structure described by Hieronymus. The colouring matter in the 
chromatophores consists largely of phycocyamn. In one case some speci¬ 
mens had been allowed to become unhealthy through long keeping in 
a tube. The phycocyanin came out of the plastids and filled the cell-sap 
with the characteristic blue colour. 
The Cytoplasm. 
This consists of a reticulum with granular threads. The size of the 
alveoli varies from 1 to 2 ju. The cytoplasm fills the cell completely and 
does not contain a central vacuole. On division of the cell, the cytoplasm 
constricts slightly in the equatorial plane, but the complete division takes 
place by a rectilinear fission transverse to the axis of the cell. In this respect 
Glaucocystis resembles many other Cyanophyceae, more especially the 
Chroococcaceae. The preliminary slight constriction of the cytoplasm does 
not seem to be correlated directly with the phases of nuclear division, but 
may occur either before or after. The final transverse fission takes place 
after nuclear division and is very rapid. The two parts of the cytoplasm 
round off into oval masses and daughter cell-walls are formed. 
The Nucleus and Nuclear Division. 
The nucleus, both in structure and in its division stages, shows many 
features of a remarkable kind. At one stage it bears a striking resemblance 
to the nucleus of higher plants. In another stage it appears to be little 
more than a vacuole. The following phases may be observed : 
(a) A large round space 11 /x in diameter lies in the equatorial portion 
of the cytoplasm, but close to the cell-wall. It stains very feebly indeed 
(PI. XIX, Fig. 1). The surrounding cytoplasm also stains feebly, but it is full 
of small oval and round bodies which stain deeply. None of these deeply 
staining bodies are to be found immediately between the clear space and the 
wall of the cell. The clear space does not possess a membrane, but is 
simply a space free from staining bodies. It appears to be continuous with 
the cytoplasm, and is not a vacuole. Under moderately great magnification 
it certainly does look like a vacuole, but under high magnification it is seen 
to consist of the same extremely delicate reticulum as the cytoplasm. The 
boundary of the clear space is not perfectly regular, but only approximately 
spherical owing to the slight intrusion of the staining bodies on its extreme 
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