XV, 6 
Shaw: Campbellos'phaera 
501 
measures about 250 by 300 fi. In June, 1919, it measured 230 
by 285 The somatic protoplasts are about 5 ^ in diameter 
and the total cell width is about 10 The estimated number 
of somatic cells is 2,200. The general appearance of the somatic 
cells and their membranes resembles that of the asexual coenobia 
at about the time when the gonidia divide. At the present time 
the radial dimension of the somatic cells varies from about 20 ^ 
between the oospores to about 10 ^ over the spores, grading 
gradually from one size to the other. The protoplasts in all 
the cells lie close to the convex or rounded outer end of the 
somatic prisms. There are present twenty-three reproductive 
cells which are scattered throughout the coenobium just under 
the somatic layer except for a small vacant space about each 
pole and another on each side of the coenobium. Applying the 
simplest interpretation to them, I will call four dark ones, with 
thin walls and diameters of about 37 /*, oogonia; and nineteen 
paler ones, with thick walls and diameters of about 42 n, oospores. 
The protoplasm of both these kinds of cells is much denser than 
that of the gonidia in any stage of the latter that has been 
observed. Vacuoles are practically absent and the nucleus is 
not evident. The thickened wall of the oospores fits loosely 
and in optical section is wavy from reticulate wrinkles. The 
spore wall seems to hinder the penetration of stains and other 
reagents. An oogonium and two oospores from this coenobium 
were photographed with a magnification of 400 diameters and 
they are shown in Plate I, fig. 7. I have closely inspected this 
specimen, and the six other specimens on the same slide, for 
vacancies in the pattern of somatic cells and protoplasts which 
might represent the sites, either of cells that became oogonia, 
or of cells that had formed antheridia. I found only one vacancy. 
It appears to be a somatic cell membrane of about one and a 
half times the usual diameter, containing in place of a proto- 
plast a cavity of about one and a half times the diameter of the 
average protoplast. It lies beside (not directly over) one of the 
oospores on the upper face of the coenobium. I am unable to 
attach any particular significance to it. There is a number of 
endophytic algae present in the somatic layer. The layer is 
somewhat battered and broken, and one or more of the oospores 
seem to have been fixed when about to make their escape. Each 
of the neighboring coenobia in Plate I, fig. 6, contains seven 
gonidia. 
A younger sexual coenobium (specimen 14) on the type slide 
is shown in Plate I, fig. 8. It contains twenty-nine reproductive 
