14 ee OLE DIO GON A CHE AE 
is apparently uncommon. The cap (or successive caps) may 
remain at the top of the terminal cell (Pl. LXIII, figs. 616 and 
617 and 621; Pl. LXI, fig. 602) or be pushed aside, adhering 
to the side of the filament (Ml. LXII, fic. 611; PL LXIM, 
nia 622), 
The nuclear phenomena accompanying cell division were 
early investigated by Strasburger (1880) and Klebahn (1892). 
More recently Tuttle (1910) has compared mitosis in Oedogon- 
ium with that seen in higher plants. 
A single multiciliate zoospore is formed from the entire 
contents of a vegetative cell. Rarely a small amount of 
protoplasm is visible in the old cell after the emergence of the 
zoospore. The formation and liberation of the zoospore can 
readily be followed if the plants are brought into a warm room 
and observed under the microscope. The protoplast of the 
cell contracts slightly, and near one side appears a colorless 
area. A circular rent soon appears near the upper extremity 
of the cell in the vicinity of the apical cap. The mass then 
passes with a slow steady movement through the opening in 
the wall, being considerably constricted at the place of exit. 
Zoospores are formed from any cell of the filament except the 
holdfast. 
Upon release from the cell, the zoospore assumes a spherical 
or ovoid shape. It is at first surrounded by a thin gelatinous 
envelope which rather rapidly increases in volume and trans- 
parency and finally disappears. At the anterior end of the 
forming zoospore appears a colorless area, around the base of 
which occurs the crown of cilia. The zoospore is active for a 
short time, its movements becoming progressively less and less 
until it comes to rest. The cilia are absorbed and the clear 
anterior end becomes the attached part of the holdfast cell 
(Cf. Pl. X, figs. 84-92). Sometimes growth of the zoospore 
begins before movement has ceased. Upon germination, re- 
peated cell division occurs in the manner described above, 
except in those species where the first division does not result 
in the formation of a ring. In Oedogonium the sporeling thus 
formed develops into a filament by intercalary growth. 
The development of the germinated zoospore in Bulbochaete 
involves variations that deserve separate mention. The basal 
cell formed from the germinated zoospore is usually the only 
one capable of division, as far as the main axis is concerned. 
In some of the forms with ellipsoid oospores, however, inter- 
