CURREY, ON STEPHANOSPH ERA PLUVIALIS. 135 
organism, until the eight portions are completely individual- 
ised, and then their motion ceases. But at this period each 
of the eight parts may be seen to be provided with two cilia, 
which are in motion so far as their limited space allows. 
(Compare fig. 21, which represents an instance in which the 
division has only extended to four portions.) The separate 
parts of the plasma now form eight independent but closely 
packed membraneless primordial cells. Shortly afterwards 
it is seen that a delicate membrane, common to them all, has 
been secreted beneath the mother-cell-membrane, round the 
disc formed by the primordial cells; this membrane at first 
lies in close contact with the latter cells, following the con- 
strictions of the disc, but afterwards becomes further and 
further removed as it swells and tends to assume a globular 
form (figs. 22, 23). By the motion of the cilia the mother- 
cell-membrane is gradually thrown off, and the young family 
escapes into the water (fig. 24). Its eight green primordial 
cells still enclose the last traces of the red substance, which 
gradually disappears, and instead of which are seen two 
granules (fig. 25); the primordial cells are in immediate con- 
tact at the sides, and are of an oval or globular shape; their 
common enveloping membrane is at first constricted at the 
border following the outline of the primordial cells; it even- 
tually becomes globular, although continuing for a long time 
much flattened at the poles, in the form of a disc-shaped 
spheroid (fig. 24). When the Chlamydococcus-like unicel- 
lular Stephanosphzera has commenced its division early in the 
evening, the division into eight is perfected during the night, 
and early in the morning the young family quits its cast-off 
mother-cell-membrane. 
In the course of the day the individual primordial cells, 
and their common enveloping membrane, grow until the latter 
attains a diameter of 0:°040—O0:048 m.m. During this growth 
the shape of the primordial cells is changed by the formation 
of various prolongations in the manner above described (fig. 
1); but in the course of the afternoon the primordial cells 
again become round, and during the evening division com- 
mences in them precisely similar to the process in the uni- 
cellular Stephanosphera; on the following morning we find 
eight young families, with the common enveloping membrane, 
which soon escape and go through the same process. It is 
calculated that in eight days, under favorable circumstances, 
16,777,216 families may be formed from one resting-cell of 
Stephanosphera. It is remarkable that the division of the 
primordial cells in Stephanosphera is confined to a certain 
time of day ; it begins towards evening, and is completed the 
