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64
Popular Science Eeview, vol. v. p. 137. A. W. Wills in
Midland Naturalist, Sept.-Oct., 1880. A. Bennett in Popular
Sci. Eev. 1878, p. 225.
Sphoet'osira volvox, Elir. Infus. (maie). Pritch. Infus. p.
526. Williamson in Popular Soi. Eeview, vol. ix. p. 225.
Volvox stellatus, Ehr. Infus. (oospore).
In clear pools, ponds, &o.
The relationship of Spliærosira rolvcx to Volrom glolator has not been
satisfactorily determined (see Williamson), although there remains no
doubt of the existence of relationship. Some regard it as the male
form, but Professor Williamson considers it a peculiar condition of
Volvox.
For details of a successful experiment in keeping Volvox during the
winter see N. B. Brown in Gardener’s Chronicle (1879 p. 599) and
“ Ponds and Ditches,” by M. C. Cooke, p. 63.
Plate X X I I. figs. 1-3. Volvox glolator, after A. W. Wills; 4-5, after
Cohn. Explanation given above.
Plate X X I I I . figs. 1-5. A fte r, A. W. Wills; 6, ideal section after
Williamson ; 7, after Wills—also fully described above ; 8-9, X 800
after Stein; 10, complete antheridium; 11, stellate resting spore or
oosphere X 400 ( Volvox stellatus) ; 12, spermatozoids X 600.
Plate X X IV . Male plants of Volvox, known as Sphærosira volvox,
after Williamson, Fig. 1, cænobium; 2, protoplasmic mass from the
cænobium, containing grannies ; 3, mass divided in two ; 4, the same
divided into four ; 5, the same divided into sixteen ; 6, further division
into thirty-two, provided with movable cilia ; 7, discoid family revolving
within its mother-cell.
V o lv o x m in o r. Stein Infus. p. 47.
Coenobia and the number of cells smaller ; the number of
daughter-coenobia evolved without sexuality within the mother,
1-9 ; fructification sexual, monoecious ; many male cells
changing into bundles of spermatozoa; 5-10 female cells in
the same cænobium, after fecundation, evolved into as many
oospores, surrounded by a smooth epispore { ^V o lv o x aureus,
Ehr.).
S izB . Variable, but smaller than the preceding.
Eabh. Alg. Eur. iii. 98. Stein Infus. t.
Volvox glohator, of authors, in part.
Volvox aureus, Ehrb. Inf. 71, t. 4, f. 2 (oospore).
In similar places to the preceding.
Plate XXV. Volvox minor X 400 after Stein. Fig. 1, portion of
coenohium with two young daughter families ; 2, cænobium with two
young daughter families enclosed in mother-cell ; 3, cænobium with five
young fertile cells ; 4, cænobium with six young fertile cells ; 5, a fertile
cell enclosing nnmerous vacuoles indicating the commencement of
subdivision ; 6, isolated daughter-family still enclosed in the mother-
oell ; 7, encysted cell—the Volvox aureus of Ehrenberg; 8, isolated
ordinary individual enclosed in a flask-shaped cell.
G en u s 40. EVDORINA. Fhrb. (1831.)
Ooenobium oval, involved in a common tegument ; cells green,
globose (16-32), enclosed within a single membrane, bearing
vibratile cilia, often with a red spot (eye-spot), distributed
around the hyaline sphere at equal distances apart. Asexual
propagation in all the coenobia, the cells of which are divided
into 16-32 parts, and soon evolved into new coenobia. Sexual
propagation in all the coenobia, the cells being converted into
motionless oospores enclosed in a narrow epispore, afterwards
becoming red.
The most complete account we possess of the life-history of Eudorina
is that by H. J. Carter (Ann. Nat. Hist., Oct., 1858), of which the following
is a summary :—Unable to recognise this organism in its simplest
form as a solitary cell, nor any stage of segmentation prior to the third
degree of duplicative subdivision into 16 cells, he commences from this
period.
At this time, which we call the first stage, the Eudorina consists of an
o v o i d green body, partial]}' divided into the number of cells just mentioned,
each of which is provided with a pair of cilia, which project
through a thin gelatinous envelope that surrounds the whole mass. It
is now about 1-llOOths of an inch long, i.e., not more than the diameter
of the Chlamydococcus cell, and swims by means of its cilia, with the
small end foremost, and with a rotatory motion on its longitudinal axis,
as often from right to left as from left to right. An eye-spot is also
present in each of the four anterior cells, hut seldom visible in the rest
at this period.
As development pi-ogresses each cell is provided with a sphærioal,
translucent utricle, an eye-spot midway between the cilia and the opposite
end of the cell, a contractile vesicle at the base of the cilia, and the
pair of cilia themselves.
During the second stage each of the cells again undergoes duplicative
division, and the whole organism becoming larger, they are separated
from each other, and being no longer subject to compression, become-
sphæricai and enclosed respectively within distinct transparent capsules.
The Eudorina is now six times as long as in the first stage, and contains
32 green cells, which are evidently situated between two large ovoid,
colourless, transparent cells, one of which bounds a, similarly shaped
cavity in the centre of the Eudorma, and the other is the original cell
wall, round which again is the newly secreted envelope. Thus we see
that the Eudorina is derived from a simple (daughter) cell, and that its
green cells have resulted from a duplicative subdivision of the green
matter which lined the cavity of this cell. Arrived at this state, which
we shall see is th a t of maturity, we also observe that the posterior part
of the envelope becomes crenulated, apparently from fiacoidity.
After this, however, it again presents another phase, which may be
called the third, or last, stage of development. Here each cell again
undergoes a rapid duplicative subdivision into 16 or 32 cells, which, in
the group, assume a more or less oblong figure respectively, and thus the
Eudorina’s length is increased to 10 times that of its first stage. The internal
structure now gradually breaks down before the external envelope,
when for a short time the groups may be seen swimming about the cavity
thus formed, till at last the envelope bursts and they become liberated.
What becomes of them afterwards he couid not state from observation,
hut the green cells having been greatly reduced in size by the latter subi'.
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