VOLVOCINEA, 73 
coloured contents of the individual portions become drawn back towards 
the periphery in centrifugal direction, a colourless plasma remaining 
about the central point ; this disappears at first in the centre, a cavity is 
formed in the middle of the disc, and as this enlarges the eight portions 
assume the form of a wreath, consisting of eight globular or ellipsoid 
-bodies in close contact, usually not exactly in one plane, owing to the 
outer membrane not having expanded in proportion to the enlargement of 
the plasma. The original cilia continue active, causing the motion of 
the whole organism, until the eight portions are completely individualized, 
and then their motion ceases. The separate parts of the plasma now form 
eight independent but closely packed membraneless primordial cells. 
thortly afterwards a delicate membrane common to them all is secreted 
beneath the mother-cell membrane round the disc formed by the primordial 
cells. This membrane is at first in contact, but afterwards becomes further 
and further removed as it swells and tends to assume a globular form. By 
the motion of the cilia the mother-cell membrane is thrown off, and the 
young family escapes into the water. When the Chlamydococcus-like 
unicellular Stephanosphera 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 investing membrane grow until the latter attains « diameter 
of ‘04 to 048 mm. During this growth the shape of the primordial 
cells is changed by the formation of various prolongations, but in the 
course of the afternoon they again become round, and during the even- 
ing division commences in them precisely similar to the process in the 
unicellular Stephanosphera. On the following morning we find eight 
young families. It is calculated that in eight days, under favourable 
circumstances, 16,777,216 families may be formed from one resting cell 
of Stephanosphera. 
We have given but a barren outline of the history of this little plant, 
but for further information must refer the student to Cohn’s Original 
Memoir in Siebold and Kolliker’s Zeitschrift fur Zoologie, 1852, p. 
77. Translated in the “ Annals of Natural History,” 2nd series, Vol. X., 
pp. 321 and 401. Also Cohn and Wichura’s subsequent memoir “ Ueber 
Stephanosphera’’ in Nova Acta Acad. Leop. Car., 1857, part I., Vol. 
XXVI. Of which an abstract is given by Currey in “ Quarterly Journal 
of Microscopical Science,” Vol. VI. (1858), p. 131. Also an admirable 
summary by Archer in the ‘ Quart. Journ. of Microscopical Science” 
for 1865, p. 117, with additional observations by himself. 
Plate XXVII1. fig. 1. Polar view of family with globose primordial 
cells; 2, equatorial view, with fusiform primordial cells ending in 
mucous filaments; 3, the same, with primordial cells collected on one 
side; 4, commencement of formation of macrogonidia; 5, all eight pri- 
mordial cells divided in fours; 6, division advancing so that each 
primordial cell consists of eight cuneate segments; 7, further advanced 
in division, movement in the mother-cell having commenced; 8, 
division completed, eight young individuals revolving in the mother- 
cell; 9, the eight original primordial cells broken up into microgonidia ; 
10, young Stephanosphera, (figs. 1 to 10 X 300); 11, microgonidia after 
exit from mother-cell X 500; 12, full-grown resting cells ; 13, commence- 
ment of division in resting cell; 14 to 19, successive stages in division 
of resting cell; 20 to 22, naked zoospores; 23, 24, encysted zoospores ; 
25 to 27, division of encysted zoospores; 28, young eight-celled family 
resulting from division of encysted zoospore; 29, 30, young families, 
all after Cohn X 400; 31, ameboid condition of primordial cells, after 
Archer. 
