380 Davis. — On Euglenopsis : a Neiv 
partition across the filament, that separates the green cell from 
the empty cavity below it (see Figs. 2, 8, 12, &c.). These 
characters are associated with its peculiarities of growth, and 
will be considered after the motile condition of the plant is 
described. 
The green cells at certain times pass into motile conditions 
that, from analogy to the motile stages of other Algae, may 
be called zoospores. Each zoospore consists of the entire 
mass of protoplasm of one of the green cells and is provided 
with four cilia. In these respects they resemble the macro- 
zoospores of many Algae. The change from a vegetative cell 
to a zoospore takes place during the night, and the latter 
escape from the ends of the filaments the following forenoon. 
They appear to be strictly non-sexual. 
Some of the plants were kept for many days in aquaria, and 
every morning a swarm of the zoospores made their appear- 
ance at the sides of the aquaria nearest the light, thus 
exhibiting the phenomena of heliotropism so characteristic of 
zoospores of Algae. The zoospores were found early in the 
morning before their escape enclosed in their parent cells. 
Such a specimen is shown in Fig. 4. The cilia of this speci- 
men waved slowly from side to side long before it escaped 
from the cell into the water. 
The zoospores (see Fig. 5) are about the same size and 
shape as the vegetative cells, being 12-18 /x long and 6-8 fi 
wide, and the nucleus, chromatophore, and pigment-spot main- 
tain the same relative positions in the former that they held 
in the latter. This agreement in cell-structure would be 
expected from the manner in which the vegetative cells change 
into zoospores. The pigment-spot, however, is usually larger 
in the zoospore than the vegetative cell, sometimes, as has 
been before noted, being as much as ii /jl wide. The four 
cilia, each one of which is about as long as the zoospore, 
are attached to the centre of that end which was inferior 
when the zoospore was contained in the filament. Therefore 
the pigment-spot is situated about one-third the length of the 
zoospore from the ciliated end. The non-ciliated end of the 
