Pleodorina illinoiensis Kofoid in Britain. i 77 
each cell, the two old flagella being attached on the outer side to 
one of the cells and the large eye-spot being in the other (Fig. 8). 
Other similar cases were seen in a fresh outburst of antheridia 
which occurred in the field at the beginning of May. 
The antherozoid-groups escape whole from the softening mucus 
of the mother-colony ; while trying to free themselves, they have a 
different motion from that of the daughter-ccenobia. They rotate 
and oscillate slowly, first in one direction, then in the opposite ; 
during this time their flagella frequently look knobbed and have been 
so described, but more careful observation shows that this appearance 
is due to a rhythmical undulation passing along them, from base to 
apex, in the line of sight. When swimming free the groups are 
not surrounded by a mucous envelope (Fig. 10). After buzzing 
around some of the other colonies for a considerable time, presum¬ 
ably in search of a colony containing megagametes, they become 
dissociated into their constituents. 
A small number of colonies showed a slight modification of the 
ordinary form of cell, which seemed to indicate them as female 
colonies. The presumed megagametes (never in the anterior zone) 
were slightly larger and darker in colour and, though no fertilisation 
was detected, some of them were seen surrounded by a thicker 
smooth wall and containing a quantity of oil which was expelled 
from them by pressure (Fig. 11). These were most probably the 
young oospores ; the colonies in which they occurred had the mucus 
much swollen, just as in the mature antheridial colonies. 
In considering what rank shall be assigned to these organisms, 
we meet with a very curious and involved state of things. The form 
of Eudorina elegans with which British microscopists are familiar 
is invariably described as globular, and the 32 cells are all alike in 
size, but in the mature colonies the eye-spots are largest in the 
foremost cells and become minute or non-existent in the posterior 
row, though the descriptions in British works do not mention this 
fact. Moreover manielons at the posterior end seem not to have 
been observed. Nevertheless ellipsoidal colonies of Eudorina do 
occur in Britain, though the cells remain all alike in size ; most 
of the mature ellipsoidal colonies which I saw were smaller than 
those of the Pleodorina. 
On the Continent, Eudorina is described as being ellipsoidal or 
sub-globular, never really spherical, and posterior mamelons are found 
in many cases. Conrad (6) describes the cells as alike in size in 
the same colony, ranging from 4/a when young to 25/a when adult. 
