Acton. — Observations on the Cytology of the Chroococcaceae. 435 
differing from the majority of authors, who believe that the central granules, 
with which he identifies anabaenin, are of a proteid nature. He has 
observed cyanophycin granules in the central body as well as in the 
chromatophore. 
Gardner (’06) finds that there is a small refractive structure in the 
centre of the cell with a definite outline for each species, and regards this as 
a true nucleus. It does not, however, divide mitotically. He describes 
nuclei of three types. ‘ The diffuse type is characterized by having the 
chromatin distributed throughout the nucleus in the form of thin, plate-like 
or small angular pieces, or more or less branched and knotty thread-like 
masses, according to the species and to the shape and size of the cell 
in which it is located ; or even a combination of these may be found in the 
same species. In whatever shape the chromatin is found, the essential 
characteristic is its quite equal distribution throughout the nucleus. . . . 
Within this type may be found quite a continuous series, showing how 
a very primitive nucleus becomes modified by gradual steps in the direction 
of the nuclear structure found in higher plants. . . . The differentiation seems 
to be proceeding towards the spireme formation found in the dividing 
of the nucleus of the higher plants.’ 
The second type he finds only in the genus Dermocarpa. c The type 
is characterized by having the chromatin united into a very definite fine 
network, on which, particularly at the junction of the threads, are small 
granules or knots, presumably of chromatin, since they stain like the 
remainder of the thread. This whole network occupies a very large part of 
the cell, leaving only a very narrow zone outside, next to the cell-wall. 
‘ Only a slight modification of the first type is necessary to produce 
the third or primitive mitosis type, which has been found in a single species 
only ( Synechocystis ) . In this type the chromatin unites into a single 
contorted thread, quite irregular and indefinite in shape. This thread 
breaks into a definite number of pieces preparatory to cell division. 
4 In all the species studied, with the possible exception of Synechocystis, 
the nucleus divides amitotically.’ 
He describes granules of two kinds, which for convenience he terms 
a and /3 granules. These presumably correspond to central granules and 
cyanophycin granules respectively. There is no definitely organized 
chromatophore. 
It will be seen that Gardner strikes out quite a new line with regard to 
the form and arrangement of the chromatin. At the same time, judging 
from his figures, the amount of chromatin present in proportion to the size 
of the cell is very great, and it is difficult to believe that so much chromatin 
is really present in the cells of such a primitive group as the Cyanophyceae. 
Guilliermond (’06) states that the central body consists of a hyaloplasm 
with a deeply staining reticulum. The arrangement of this reticulum 
G g 3 
