218 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
may occupy the whole interior of the zoosporangium cell. For 
example, there are no evidences of a vacuole in figure 6 (plate 11), 
which represents a zoosporangium cut in cross section. On the 
other hand, there are in many of the larger ones, conspicuous 
central vacuoles (pi. 11, fig. 5). As the zoosporangium increases in 
size, the nuclei arrange themselves in a single row midway between 
the wall and the central vacuole when the latter is present. 
There is great variation in the number of nuclei in the different 
zoosporangia. The size of the latter, however, varies directly with 
this number since each nucleus is the center of a zoospore and these 
vary little in size. The zoosporangium is now cut off from the 
parent hypha by a cell wall laid down in the distal end of the con¬ 
striction. As the zoosporangium develops, certain portions of the 
cytoplasm take the stain less deeply. This is due to two causes: 
first, there are fewer granules in this region; second, the strands 
themselves become thinner until they are finally severed. During 
the further development of the zoospore this process continues until 
the strands are severed and the zoospores separated. Figures 4, 
5, and 6 (plate 11) represent stages in this process. It will be 
observed that this is not a progressive cleavage from the vacuolar 
membrane out to the plasma membrane or in the opposite direction. 
The cleavage takes place almost simultaneously around the surface 
of each zoospore by the separation of the connecting meshes. 
Usually, particularly when there is a vacuole present, more advanced 
stages of separation can be seen nearer the vacuolar surface (pi. 
11, fig. 5). This would suggest that in such cases the plasma mem¬ 
brane itself is the last cytoplasm to be severed. If this be true, the 
entire contents of the zoosporangium should function as a cell and 
remain turgid until this membrane is ruptured at one point when it 
would, of course, collapse. 
In a great many cases zoospores escape from the zoosporangium 
as individuals; in other instances they emerge as a mass and sepa¬ 
rate as individuals during the exit or later as the case may be. The 
writer has seen no indications of a second wall about the zoospore 
mass and from the manner in which the zoospores are formed it seems 
reasonable to conclude that they are bound together by the original 
plasma membrane which may not rupture until the mass is making 
its exit. If this conclusion be correct, we may have here an addi¬ 
tional factor in zoospore expulsion. As long as the entire zoospore 
