io8 
Review . 
entirely absent from the nucleus or chromatophores. There are 
two kinds of vacuoles ; cell-sap vacuoles and gas vacuoles. The 
former are relatively rare in the normal vegetative cells, while the 
latter are found only in certain forms which float on the water 
surface. The central granules, which are found exclusively in the 
central body, consist chiefly of an albuminous substance agreeing 
nearly in its physico-chemical re-actions with the “ Voluntanskugel ” 
of A. Meyer. They also contain a substance which takes a blue- 
black colour when treated with chloriodide of zinc, and pectin 
substance. The membrane of the vegetative cells and the sheath 
are not cuticularized, but consist chiefly of chitin, with some 
cellulose and pectin, while the membrane of the heterocyst is 
mostly cellulose. All the cells of the Tolypothrix filament are 
found to be connected by protoplasmic threads (Plasmodesmen) 
through a central pit in the side-wall. 
As a strong proof of the nuclear nature of the central body the 
author describes the process of its division which he calls, without 
hesitation, mitosis. The description is illustrated by many figures. 
Before the divisiontheamountof the stainable substance (chromatin) 
in the central body is found to increase and soon a thick spirem 
thread is visible. The thread then divides into 4—8 rod-shaped 
chromosome which arrange themselves near the centre of the cell 
more or less parallel to the long axis of the filament. The chromo¬ 
somes divide transversely at the middle and each half passes to the 
opposite pole to form the daughter nuclei. 
At the close of the book some remarks are made on the 
relationship between the Cyanophyceae and Bacteria. The deeply- 
staining central part of the Bacteria is considered by Kohl to he 
homologous with the central body of the Cyanophyceae and 
represents a true nucleus. He believes, differing from Fischer, 
that these two groups are intimately related. As an appendix a 
valuable table containing the most important tests and staining 
re-actions for the study of the Cyanophyceae-cell is given. A 
considerable number of staining methods and physico-chemical 
tests are used in the course of the investigations, both with living 
and fixed material. But the author does not appear to have made 
use of microtome sections, a method which has been found very 
useful in the study of the fine structures of the cell. 
The work is indeed a very important contribution to the 
cytology of the lower organisms and deserves the attention of the 
zoologist as well as the botanist. K. MIYAKE (Bonnb 
R. MADLEY, PRINTER, WHITFIELD STREET, LONDON, W. 
