1909] ATKINSON—FUNGUS PARASITES OF ALGAE 333 
moist chamber. While these two developing groups of zoospores 
were under observation, the water, which had not been changed 
for some time, slowly evaporated, so that a portion of it was removed 
from under the cover. At this time it was noted that the dividing 
protoplasmic mass, where there were two forming zoospores, was 
fusing again, and soon the mass was spherical, with no sign of the 
division which up to this time was quite marked, and showed all the 
phenomena of movement and formation of cilia which accompany the 
normal development of the zoospores, except that the movements 
were not so active. Very soon also the four forming zoospores in the 
other group were fusing and the movements had likewise ceased. 
The fusion in this case also continued until there was no trace of the 
forming zoospores, the mass was again spherical, and movement 
had ceased. 
Thinking this might be due to the want of fresh water, some was 
quickly run under the cover glass, and the observation was renewed. 
The smaller protoplasmic mass burst on the absorption of the water, 
So great was the tension, but the larger one soon began slow rotary 
movement again and the constrictions appeared a second time, indi- 
cating the formation of four zoospores. This time the division pro- 
ceeded, accompanied by all the phenomena of the formation of the 
zoospores noted in the normal cases, until the zoospores were com- 
plete and whirled away. 
This would suggest that there were two opposing tensions in the 
formation of the zoospores, one individual and under normal condi- 
tions the stronger, and the other belonging to the mass and the weaker. 
When the conditions favorable for the formation of the zoospores 
ceased, the individual tension lessened to such a degree that it was 
lower than that of the mass, and the separating smaller portions were 
drawn together again in the common larger mass. These two 
pposing tensions might possibly explain the peculiar behavior of 
the zoospores when they still remain closely associated in the group, 
how partially separating and again coming close together, continu- 
ing this process of coquetting until the individual tension is strong 
fnough to free them, in the case of those where there does not seem 
to be any inclosing membrane. The tension of the entire mass 
May possibly be somewhat similar to the force called adelphotaxy 
