No. 466.] STUDIES ON,PLANT CELL. VIII. 701 
Indeed the entire subject is so confused that it does not seem 
desirable for us to take it up in detail at this time, especially 
since these inclusions are apparently all secretions or excretions 
and not morphological features of the cell. The most compre- 
hensive discussions of the subject will be found in the papers of 
Hegler (: 01), Kohl (: 03), and Zacharias (: 03).! 
Schizomycetes (Bacteria) —The history of research upon the 
cell structure of the Schizomycetes has run in large part parallel 
with that on the Cyanophycez. The clearest results have come 
from. studies upon the larger forms of the sulphur bacteria, 
especially certain species of. Beggiatoa, and on certain forms of 
Spirillum. The more minute types and pathogenic forms in par- 
ticular have proved very baffling because of their small size and 
it can scarcely be said that we fully understand their cell struc- 
ture. As in the Cyanophycez, investigators of the bacteria fall 
into two groups: one holding that the Schizomycetes entirely 
lack a nucleus and the other that there is present a structure, 
often termed a central body, which is the equivalent of a nucleus. 
Bütschli ('96, : 02) has been the most conspicuous advocate 
of the latter view.. He described and figured clearly a central 
body in the cells of Beggiatoa, Chromatium, and Spirillum with 
the same organization as given in his account of that body in the 
Cyanophyceze. The central body contains granular material 
which Bütschli regards as chromatin and the structure is shown 
in stages of division. Bütschli has no hesitation in giving the 
central body the value of a nucleus. It lies within a peripheral 
1Since the above was written a lengthy paper by Fischer, “Die Zelle der 
Cyanophyceen " has appeared (Bot. Zeit., vol. 63, p. 51, 1905), too late to be 
included in these reviews. Fischer has not changed his conclusions on the chief 
points as discussed in his earlier papers. ‘The chromatophore is a closed cylin- 
drical structure; the cyanophycin granules are proteid in character ; vil cogen and 
another hoic des , anabzenin, are conspicuous substances in t cell; the 
central body is not a nucleus but the seat of important metabolic processes con- 
cerned with WR ra rates, and its contents and behavior in cell division 
holo must clearly establish the proteid nature of the central body and 
its contents para the“ so called” chromatin granules) before they can 
expect the acceptance of their conclusions as to its nuclear character. 
