384 Davis.— On Euglenopsis : a New 
Let us now consider what takes place when a filament 
branches. The first step in this process is a division of the 
mass of protoplasm, which, of course, is morphologically the 
cell. The plane of division is usually oblique and in the general 
direction of the length of the cell (see Figs. 9 and 11), but 
sometimes the division is across the cell at right angles to 
the axis of the filament (see Fig. 10 and portions of Fig. 1). 
When the division is oblique, the filament branches, because 
the two masses of protoplasm move upwards at slightly dif- 
ferent angles. In Fig. 11 we have an excellent illustration of 
the oblique division of a cell, and we can readily see that the 
lower cell in Fig. it, in trying to move upward, would be 
pushed to one side and the direction of its movement altered 
by the cell above. It is evident that, if the lower cell in 
Fig. 11 pushed out at one side and the upper cell continued 
to move upward, there would soon result a condition similar 
to Fig. 12 . 
When the division of a cell is transverse, that is at right 
angles to the long axis of the cell, the filament does not 
branch. Apparently the lower cell has no opportunity to 
move forward, and consequently remains enclosed in a com- 
partment of the filament. The upper cell may and does 
continue to move upward, thus increasing the length of the 
filament, and one not unfrequently finds a green cell separated 
from the end of a filament by two or three empty cell-cavities. 
On the right hand side of Fig. 1 may be seen such a cell left 
behind by the forward growth of the filament. These cells 
may develope into zoospores which escape by rupturing the 
wall of the filament. 
Occasionally after a cell-division the two daughter-cells 
will immediately divide again, so that as a result one finds 
four cells surrounded by a common cell-wall. A very usual 
arrangement for such a group of cells is shown in Fig. 3. In 
this case the plane of the first cell-division was oblique, and 
the plane of division of the two daughter-cells at right angles 
to the first. Four branches might result from such a division, 
if the planes of division were sufficiently oblique, so that 
