Review. 
107 
the cell has a distinct nucleus. There are still others who take 
somewhat intermediate or conservative views, and find in the 
Cyanophyceae-cell a rudimentary or undifferentiated nucleus or a 
nucleus-like structure phylogenetically connected with the nucleus 
of the higher plants. Professor Kohl, of the University of Marburg, 
has just published the result of his extensive studies on this subject. 
The work comprises 240 pages and ten coloured plates. Tolypothrix, 
Nostoc and Anabaena are the principal forms studied and special 
attention seems to have been paid to the investigation of Tolypothrix 
\ 
lanatn. The results of these studies are given in great detail 
together with a critical discussion of those of previous investi¬ 
gators, under the following heads: 1. Central granules; 2. 
Cyanophycin granules; 3. Oil; 4. Chromatophores; 5. Gly¬ 
cogen; 6. Membrane and Sheath ; 7. Protoplasmic Connections ; 
8. *• Verschlusskorper ” ; 9. Vacuoles; 10. Chromatic Substance ; 
11. Heterocysts; 12. Concave Cells; 13. Central Body. 
According to Kohl the so-called central body (Zentralkorper) 
of the Cyanophyceae-cell is a genuine nucleus, and consists of a 
ground mass which stains relatively faintly, and in which is 
embedded a certain amount of chromatic substance. It also con¬ 
tains a larger or smaller number of the central granules 
(Zentralkorner) which have never been found outside the nucleus. 
The nucleus differs from that of the higher plants in the absence of 
a nuclear membrane and of nucleoli, and in its peculiar form. It is 
characterized by numerous pseudopodium-like radiations of various 
sizes which often reach the cell-wall. The radiating branches are 
often seen to be drawn into the nucleus after treatment with 
various fixing re-agents. This is the principal reason that this 
structure has been overlooked by most previous observers. The 
chromatophore is not a large hollow cylinder surrounding the 
central body as Fischer and others maintain, but a very small 
granule which is found in abundance all through the cytoplasm. 
The cytoplasm contains, besides chromatophores, cyanophycin 
granules, oil-drops, glycogen and vacuoles. The chromatophores 
contain chlorophyll, carotin and phycocyanin. Starch has not 
been found in any part of the cell, and Kohl takes glycogen for the 
product of carbon-assimilation since it is formed in the presence of 
carbonic acid and light, and disappears by darkening. The 
cyanophycin granules, which are found only in the cytoplasm, 
represent reserve-albumen, and disappear gradually in the dark. 
They are found abundantly in the spore and are used up during its 
germination. The oil-drops are only found in the cytoplasm, being 
