V. FI. Blackman. 
180 
considered to be of siliceous nature, and the genus was accordingly 
placed among the Diatoms, but later, in the “ Challenger ” narra¬ 
tive ( 7 ), the true nature of the wall was recognised. No projections 
were observed upon the wall, such as are shown in the “ Challenger ” 
figures. 
In the normal condition of the cell the main portion of the pro¬ 
toplasm is collected at one pole of the sphere, close against the 
wall (fig. 1) ; from this mass, which contains the nucleus, arise a 
number of radiating strands of protoplasm of varying thickness, the 
thicker ones appearing to run peripherally and the finer ones more 
centrally. The strands traverse a large central vacuole, and are 
connected with a thin layer of protoplasm which lines the wall. By 
far the the larger number of specimens, however, in a collection 
are in a more or less contracted condition, some of them only to a 
slight extent, as in fig. 2, but others show no radiating strands and 
have nearly all the protoplasm collected in a single more or less 
spherical clump. This contraction is, no doubt, artificially produced, 
and is probably brought about by the shaking and jostling to which 
the cells are subjected by the method of collection. The proto¬ 
plasm, however, does not separate itself completely from the wall, 
for in even the extreme state of contraction mentioned above, a thin 
layer of protoplasm is always to be found in close apposition to the 
membrane. The layer is easily over-looked, but it can always be 
made to separate itself from the wall by withdrawing water from 
the cell by means of dilute glycerine; it is clearly shown in 
fig. 2, where it has shrunk completely away from the wall and 
has become somewhat folded. 
The whole protoplasm, including the radiating strands, appears 
in the living state of a yellow-brown colour, of a tint like that of 
the colouring matter of diatoms, but when the cell is dying the colour 
becomes yellowish-green. The colouring matter is really confined 
to small homogeneous chromatophores which are usually oval in 
shape. John Murray ( 7 ) states that the nucleus, which lies in the 
polar mass of protoplasm and is completely obscured by it, is of 
large size, but he gives no indication of its shape. On making 
sections through the organisms it is seen, in the resting state, 
to be a narrow elongated body (fig. 3 ) somewhat sinuous in shape; 
it exhibits, not a network but a coarsely granular appearance. 1 Its 
behaviour during division has not hitherto been traced. 
’From one or two observations made it would appear that there 
exists, beside the nucleus, a body of au arclioplasinic (kino- 
plasmic) nature, but the material did not suffice to render this 
certain by following the details of division. 
