XV, 6 
Shaw: Campbellosphaera 
505 
side view, with the gonidia too closely packed to be counted. 
The two other asexual embryos are still less advanced, but with 
the entry of the gonidia accomplished. The sexual embryo, the 
presence of which is the reason for the description of its sisters 
and mother, is nearer the posterior pole and more advanced 
in development than any of its sisters. It retains the bullet 
form, with a sharper and blunter end, and measures 60 by 82 y. 
The average cell diameter is about 3.6 y, and the estimated 
number of cells is 1,250. The reproductive cells are sixteen in 
number and about 12 and 14 y in diameter. They are arranged 
in four alternating and intermeshing quartets, distributed in 
about three-fourths of the length of the coenobial cavity, the 
anterior quartet being more separated from its neighbors than 
are the others. 
Another sexual coenobium (specimen 24) with a small number 
of reproductive cells is shown in Plate II, fig. 12. It is on 
another slide (No. 12) of the same lot as the type slide. It 
measures 160 by 170 y. The somatic protoplasts are about 5 
y wide, and the somatic cells about 8.3. The number of cells is 
estimated at 1,400. The reproductive cells are fifteen in num- 
ber. Thirteen of them are oogonia of about 28 y, and two, near 
the posterior pole, are oospores of about 32 y, with the walls 
as yet only slightly developed. There is an absence of repro- 
ductive cells in the anterior quarter of the coenobium. 
Material containing a larger proportion of sexual coenobia was 
collected in a shallower neighboring pond, F, within a stone’s 
throw of pond J. A lot collected about 4 o’clock in the afternoon, 
September 22, 1915, was fixed in the laboratory at 8 in the 
morning on the following day. A batch of these, stained with 
Bismarck brown, saturated with Venetian turpentine, was 
mounted in abundance on four slides and sparingly on three 
others. In June, 1919, I looked at all of the specimens on slide 
1 of this lot, and at about 4 per cent of the area of each of the 
other mounts. These slides show not only a greater abundance 
of sexual coenobia of Campbellosphaera obversa, but also a 
larger proportion of other Volvocaceae, including Volvox afri- 
canus West, the latter being represented by sexual as well as by 
asexual specimens. The asexual specimens of these two species 
are readily distinguishable, but the free female coenobia of V. 
africanus are very similar to the sexual coenobia of C. obversa 
in these preparations. 
In this material many asexual coenobia were found containing 
asexual and sexual daughters in different numerical combina- 
