24 
Olive, Mitotic division of the nuclei of tlie Cyanophyceae. 
main axis of tlie cell; while tlie seconcl division is also trans- 
verse, and resnlts in twelve shorter daugliter cliromosomes. The 
two lowermost cells of Wäger*s hg. 1 show nuclear bodies wliicli 
are quite similar in many respects to some from which Kohl 
derived his diagrams to illustrate liis sclieme of mitosis; an Ob¬ 
servation particularly interesting from the fact that Wäger 
concluded from such appearances that the division of the nucleus 
is amitotic. It has already been pointed out in this paper that, 
in the opinion of the writer, such appearances as are figured by 
both Kohl and Wäger are misleading, and that they have 
probably resulted from too thick or from overstained prepara- 
tions. Such an opinion is based upon the fact that the writer 
has also often obtained many similar results in rnounts of Os- 
ciüatoria and other species, in which the cells were either poorly 
fixed or in which the stain was not weh differentiated, owino; 
to insufficient washing out, or to the section being too thick 
(figs. 2 and 3). 
Division of the cell. 
It is said that in Spirogyra tlie partition wall which grows 
across the ceh, thus cutting it in two, appears only after the 
nuclear division is accomplished. In the Cyanopliyceae, on the 
other hand, we apparently have the new ring-formed partitions be- 
ginning to grow in from the outer walls long before nuclear 
division is fully completed. The striking example has already 
been mentioned, how in Oscillatoria princeps and 0. Froelichia , 
division may take place with such wonderful rapidity that we 
may have, in one cell at the sarne time, as many as three ring- 
formed walls in different stages of growth (figs. 11, 13). In this 
instance, long before tlie two daugliter nuclei are completelv 
severed from each other, the daughters themselves have begun 
to divide mitoticahy. Wäger (03) also has noted tlie fact tliat 
several divisions may go on at tlie same time and he further 
points out that the division of the cell appears to go on inde- 
pendently of the nuclear division. Figs. 6—9, 14, 17, 34 show the 
usual condition, in wdiich the cells are completely cut in two 
before a second division wall begins. 
Close examination further reveals the liighly interesting fact 
that in the filamentous forms, the division of the cells takes 
place witli more or less rhytlimic regularity. According to Mac- 
farlane (01), a similar wave-like rhythm of division activity has 
been observed in Spirogyra. Fig. 9 is a camera drawing of Os¬ 
cillatoria Froelichia, showing clearly this plienomenon. In this 
figure, tliree niaxima are indicated, at a, d, and a third at br\ 
points at which division lias progressed the farthest. Two cells 
below a is a central body in which division is least advanced, 
and half way between c and d is another point of minimum 
advancement. At both b and c are cells which liave completed 
division, the two daugliter cells at b having apparently finislied 
this act sooner than the two at c. In the young- nuclei shown 
