20, 5 Shaw: Janetosphaera and Volvox 497 
of the specimen compressed under the cover, based on an as- 
sumed optical density of the mounting medium of 1.4, is 518 p. 
The short and long diameters of the specimen measured about 
790 and 930 ». The number of cells in the specimen was esti- 
mated to be 31,500 by assuming a mean diameter of 737 » and 
counting 149 cells in an irregular space, taken near the equator, 
having an area of 8,100 sq. ». The distribution of the somatic 
cells is not so regular as might be expected, many of the cells 
standing closer to one neighbor than to the others. The aver- 
age distance between centers of somatic cells is about 8 » in 
the equatorial region, about 14 » around the anterior pole, and 
about 7 » near the posterior pole. 
The protoplasts vary from ovoid at the anterior pole to 
pear-shaped at the posterior pole. The surface view shows 
them roundish with one, two, or sometimes more angles, and 
about 8.5 in diameter. The hexagonal intercellular membranes 
can barely be made out. The one, two, or more angles of the 
protoplasts are the bases of more prominent filaments. Most of 
the intercellular filaments are hardly visible. Between any 
two neighboring protoplasts there is no indication of the occur- 
rence of more than one filament. In the median optical section 
of the coenobium there is to be seen a clearly defined inner mem- 
brane about 22 » within the outer membrane of the colony. The 
protoplasts occupy a portion of the outer third of the space be- 
tween these two membranes. 
The oospores in this specimen, numbering about 224, were, 
as nearly as practicable, all sketched with a camera lucida for 
counting. An obstacle that precludes absolute accuracy in this 
sketching is the overlapping of the oospores at the sides of the 
colony, which is greater than at the posterior pole. There are 
No oospores in the anterior quarter of the colony, and there 
is a scarcity of them about the posterior pole. They all lie near 
the periphery of the colony, within and close to the inner mem- 
brane which, as before stated, is about 22 » below the outer 
membrane. The wall of the spore (see Plate 4, fig. 14) is de- 
veloped into spines which are rather broadly conical in form. 
These spines do not stand go close together as those of the type 
specimen of V. merrilli, are not so long, do not have such atten- 
uate form as in that specimen, and are more finely or sharply 
pointed. The spines appear to be hollow, thin-walled, and com- 
paratively colorless, though the latter character may have re- 
sulted from action of the fixing agent. Their peripheral count 
is about fifteen. The diameter of the spore, including the 
