36 
Olive. Mitotic division of tlie iiuclei of tlie Cvanoplivceae. 
/ t/ -Le/ 
4. Centers of division activity occnr with rliytlunic regular- 
ity in tlie tilamentous fornis, a plienomenon already noted in 
Spirogyra (p. 24). 
5. Tlie division of tlie central body is mitotic, since we can 
find in tlie clianges wfiicli it undergoes tlie usual plienomena 
which accompany mitosis in tlie liiglier organisms (pp. 20—24). 
6. The krnoplasmic, acliromatic portion of the central body 
constitutes a „spindle“, which has the shape of a fiattened disc 
in the narroAv celled species; and in the longer celled fornis, of 
a broad-poled, somewhat cylindrical figure; or, in still others, 
narrow-poled and spindle-fonned. The aclironiatin consists of 
a central spindle, which is offen verv denselv fibrous, between 
the drviding clironiosomes; and a portion leading from the 
cliromosonies to the cross walls, which corresponds to the mantle 
fibers in position and apparently in function (pp. 19—20). 
OAving to the peculiar plane of location of the nuclear 
figure in Gloeocapsa , there is little appreciable development of an 
achromatic spindle (p. 29). 
7. A spireme arrangenient of the chromatin granules is also 
evident in the preliminary nuclear clianges. The „ segment ed 
spireme“ in Gloeocapsa appears to consist of a simple, more or 
less spiral thread, haA r ing about 8 chromatin granules held by 
the Imin, and situated in the middle of the cell, with its long 
axis corresponding to the long axis of tlie cell (p. 29). 
In the filamentous species, the spireme apparently consists 
of a much convoluted thread, and it is further probable that it 
also is made up of a definite number of distinct chromatin 
granules, arranged along a linin thread (pp. 22, 31). 
8. Finally, the rnost necessary requirement of mitosis is 
fulfihed in tliat a longitudinal fission of the clironiosomes occurs.^ 
Tliis is plainly eAudent in the case of Gloeocapsa, in which the 
simple spireme thread d hü des lengthwise, beginning at the tivo 
ends and Splitting thence progressrvely to the middle of the 
thread. It is liighiy probable, further, that the Splitting of the 
coiwoluted spireme of the filamentous species takes place in 
a somewhlt similar manner, since the fission plane begins at 
the edge of the disc-sliaped figure and travels progressively in¬ 
ward to the middle (pp. 22, 23, 31). 
9. The number of clironiosomes in the cells of the same 
species is constant. There are 8 clironiosomes in Gloeocapsa 
polydermatica and Nostoc commune ; 16 in Oscillatoria tenuis , in 
an undet. sp. of Oscillatoria , Calothrix thermalis, Phormidium sp.; 
and probably 32 in Oscillatoria princeps and 0. Froeldichia (p. 19). 
Eacli chromosome apparently corresponds to a single cliro- 
matin granule of the spireme thread. Sliould tliis proA'e true, 
then tliis presents the liitherto unrecorded plienomenon of 
a chromosome which consists of a single chromomere. 
10. The division of the cell is usually accomplished by the 
groAving in of a ring-formed wall, Avliicli appears to groAv inde- 
pendently of and simultaneously Avitli nuclear diAusion (p. 24). 
