696 THE AMERICAN NATURALIST. (VoL. XXXIX. 
try to give the present status of investigations in these most 
difficult subjects. 
Cyanophycee (Blue-green Algg).— The most recent and com- 
prehensive papers on the cell structure of the Cyanophycez are 
by Fischer ('97) Macallum ('99), Hegler (: o1), Bütschli (: 02), 
Kohl (: 03), Zacharias (:00, :03), and Olive (:04). Olive gives 
an especial clear analysis of the situation in this field of 
investigation at the present time and an excellent historical 
review of earlier literature may be found in Hegler (:01). The 
discussions center chiefly around (1) the presence or absence of 
a nuclear structure and its behavior in cell division, (2) the dis- 
tribution of the blue-green pigment (phycocyan) and the struc- 
ture of a possible chromatophore, and: (3) the nature of certain 
conspicuous inclusions within the cell, called cyanophycin gran- 
ules and slime globules. An outline in tabular form of the 
views of some thirty investigators on these subjects is given by 
Olive (:04, p. 10). 
Writers from the earliest periods of cell Wades on the Cyan- 
ophyceæ have recognized the presence of a central body in the 
interior of the cell more or less sharply differentiated from the 
peripheral region, which holds the coloring matter and certain 
inclusions. The central body contains granular material which 
stains and behaves in other particulars like chromatin. But as 
a rule this granular material is.not confined within a membrane 
or vacuolar cavity which has proved the most serious difficulty 
to its acceptance as chromatin and the central body as a nucleus. 
Then many investigators have not been able to satisfy them- 
selves that the central body exhibits the phenomena character- 
istic of nuclear division even in a simple form. Consequently 
much doubt has been expressed as to its morphology and pos- 
sible relation to a nucleus. 
The most recent and detailed investigations have, however, 
brought forward much evidence to the effect that the granular 
material in the central body is chromatin which becomes organ- 
ized into chromosomes that are distributed by a form of mitotic 
division. In the vegetative cells, which generally divide rapidly, 
the chromatin is never held within a nuclear membrane but in 
young heterocysts and spores such inclosing membranes have 
been found (Olive, : 04). 
