Olive, Mitotic division of tlie nuclei of the Cyanophyceae. 
35 
boclies lying within a clelicate network. He employed this 
method, in fact, to assist in proving the nuclear natnre of the 
central bocly. Eis eh er, on the other hand, contends that such 
an appearance as that shown, e. g., in hg. 31, is due solely to 
„enzymatische Kontraktion“, and that no digestion whatever 
occurs. 
In my experiments, tilanients of Oscillatoria Froelichia and 
other forms were allowed to remain two or three days, at about 
33° — 36° Cent., in a preparation of Grrübler's pepsin: the 
masses were then washed in water, fixed, carried through the 
paraftine process, and sectioned. Fig. 20 illustrates a cross 
section of Oscillatoria thus treated, which is drawn to the same 
scale as the sections of the same species shown in figs. 24 and 
25. A comparison of the digested with the undigested sections 
will at once show that either considerable digestion has taken 
place, or eise a very large amount of „enzymatische Kontrak¬ 
tion“. Fig. 19 is a longitudinal view, also treated with pepsin. 
In both transverse and longitudinal sections, we can see all the 
parts of the protoplasm which we have previously noted in the 
untreated sections — chromatophore and chromatin, as well as the 
dimly defined achromatic portion of the nucleus. The assertions 
of He gier and Kohl that the cyanophycin granules are digested 
was conflrmed; and, further, the Statement, of Kohl that neither 
pepsin nor pancreatin will digest the slime globules, is also 
probably true. It is a much more difheult question as to whether 
any of the protoplasm itself is so affected. The writer, however, 
hrmly believes that some digestion of the protoplasm does occur, 
and he bases such a conclusion mainly on the fact, perhaps 
insufheient in itself, that there is not apparent in the normal 
cell of Oscillatoria enough vacuolar space to account for such 
an enormous shrinkage of volume, through simple plasmolysis 
alone. 
Summary of results and conclusions. 
1. The central body of the Cyanophyceae is a nucleus, not 
essentially different from the nucleus of tlie higher plants. It 
consists of a more or less dense, hbrous, achromatic portio, and, 
enclosed by this, a number of minute, globular, or somewhat 
irregularly shaped cliromatin granules. The chromatic and 
achromatic substances stain with the Standard nuclear stains, 
e. g., iron liaematoxylin and Flemming's triple stain, similarly 
to the corresponding elements of higher plants (pp. 17—24). 
2. In tlie opinion of the writer, thin, well stained sections, 
made in botli transverse and longitudinal planes, are necessary 
for the thorough study of the nuclear structure of these organ- 
isms. 
3. The nucleus of the Cyanophyceae usually appears to be 
in a state of mitotic division. Plants whicli were subjected to 
slow desiccation until tlioroughly dried showed no perceptible 
indication of entering a resting condition (p. 26.) 
3 * 
