NOTE ON THE CYTOLOGY OP CALOTHEIX FUSCA. 625 
consist of real chromatiu. I also observed in the cells of 
Calothrix fusca the metachroinatic granules (volutine 
granules) ; they always were found iu the central body. 
The cells of Calothrix fusca do not possess a well de- 
veloped chromatophore, surrounding the central body, as is 
found in other members of the Cyanophycem. Often the 
cells are not at all green coloured, and when this is the case 
the green colour is diffusely spread thi’oughout the cell 
without a well-marked differentiation between coloured and 
non-coloured cytoplasma. This is perhaps the reason why 
the central body of Calothrix fusca is never so compactly 
built as in other Cyanophycem, and why it becomes so easily 
diffuse. 
The cytoplasma of the young cells (at the end of the fila- 
ments) contains few or no inclusions, and has an alveolar 
structure (PI. 32, figs. 1 — o) which is not always distinctly 
visible. The central body is generally of normal shape. It 
is formed of an achromatic sub.stratum (which, however, 
stains more deeply than the surrounding cytoplasma), in which 
are embedded the chromatic granules and filaments. The 
achromatic substratum determines the form of the central 
body ; this form is rather variable, often the central body is 
star-shaped, and resembles the same organ of Toly pot hr ix 
lanata described by Kohl (loc. cit.). The chromatin is 
not always distributed throughout the whole central body ; 
often several parts of it are free from chromatin (PI. 32, 
fig. 5). Such specimens are very favourable for the study of 
the relation between the achromatic substratum of the central 
body and the surrounding cytoplasma. Both have an alveolar 
structure, and by carefully examining the places where cyto- 
plasma and achi-omatic substratum come together, one can 
often observe that the septa of the cytoplasmic alveoli are 
continued without interruption into those of the achromatic 
substratum, the only difference consisting in the different 
avidity with which stains are absorbed (PI. 32, figs. 5, 6). 
Cell division is performed in the ordinary way ; in the 
middle of the cell an imperfect ring-shaped transverse mem- 
