152 ON THE RESTING-SPORES OF HDOGONIUM. 
each with its crown of cilia, and emerge from the extremely 
thin membrane. ‘Thus, the sac which surrounds the four 
Bulbocheete-zoospores is the original spore-membrane. Ac- 
cording to what I believe to have found, the covering which 
in C&dogonium surrounds the four cells is not the original 
spore-membrane. In Bulbochete the four masses originating 
from the division of the cell-contents directly form the zoo- 
spores; in Gidogonium, on the other hand, they are surrounded 
by a distinct cell-membrane, within which the formation of 
the zoospores takes place. The metamorphoses in the ger- 
mination of the spores in Gidogonium are thus greater than 
in the spores of Bulbochete. 
