al 
21,1 Shaw: Merrillosphaera ° 103 
that all form flattened surfaces of contact. There is little if 
any trace of a central core of the anterior part of the coenobium. 
If present, it is reduced to a bit about 15 » thick and 50 » wide. 
The somatic layer of cells has membranes so proportioned as to 
form a thin layer over each gonidium and a thick layer in other 
‘parts of the coenobium wall. 
Specimen 42.—An asexual coenobium with ten daughters, 
shown in Plate 4, fig. 26, presents a side view with the charac- 
teristic arrangement of two groups of four and a hinder pair 
of smaller daughters. The central core of the anterior part 
of the coenobium seems to be present. 
Specimen 43.—An asexual coenobium with twelve daughters 
is shown in Plate 4, fig. 25. In this the four hindmost daughters 
are smaller than the others. 
CELL MEMBRANES 
In some Venetian turpentine preparations of material stained 
with Bismarck brown the cell membranes are rendered visible, 
partly by the stain and sometimes, apparently, partly by the 
absorption of water by the membranes. One specimen from 
Pond E, November 1, 1914, was selected to illustrate the cell 
membranes. Particulars in regard to this specimen follow. 
Specimen 44.—An asexual coenobium with eight daughters was 
photographed as shown in Plate 4, fig. 31, on May 15, 1916. On 
the following day it presented a different appearance and was 
again photographed as shown in Plate 4, fig. 30, and Plate 6, 
fig. 40. It was believed to have rotated with a slipping move- 
ment of the cover as a result of the slide having been left in 
a vertical position. The first picture seems to be a side view 
of a coenobium that has had the poles flattened by pressure,‘ 
and the others appear to be anterior polar views in which the 
flattened condition of the poles does not show. It is evident 
from all of these figures that the somatic cells form a layer, which 
is thin over the daughters and thick between them and over 
the poles. The membranes of the somatic cells form prisms 
with the protoplast in the outer end of each. In the thicker 
parts of the coenobium wall these prisms are about 18 » high; 
over the daughters they grade down to only a small fraction of 
that height. The outer ends of the prisms are slightly convex 
in the photographs. By further shrinkage they have become, 
“This flattening of the poles may have been due to great shrinkage 
of the parts of the coenobial core that filled the front and back of the 
coenobial cavity. 
