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divisions it is probable that many of the groups, if they do not form new
individuals, sooner or later become disintegrated, and the Eudorina thus
eventually perishes.
When, however, the process of impregnation takes place, the division
stops at the second stage, that is when the Eudorina consists of 32 ceils
of the largest kind, each of which is about l-18(!6th of an inch in diameter
within its capsule, which is therefore a little larger. The process
is as follows ;—
At a certain period after the second stage has become fully developed
the contents of the/our anterior cells respectively present lines of duplicative
subdivision, wliioh radiate from a point in the posterior part of the
cell (in the subdivision of other cells the lines of fissiparation tend
towards the centre of the cell). These lines, which ultimately divide
the green contents of the cell into 64 portions, where the division stops,
entail a pyriform shape on the segments, from whose extremities a mass
of cilia may be observed waving in the anterior part of the cell of the
parent, while yet her own pair of cilia are in active motion, and her eye-
spot still exists in situ on one side of her progeny, thus showing that the
latter may be almost fully formed before the parent perishes. At length,
however, this takes place, and the progeny (Spermatozoids) separate from
each other, and finding an exit, probably by rupture, through the effete
parent cell and her capsule, soon become dispersed throughout the space
between the two large ovoid cells mentioned, where they thus freely come
into contact with the capsules of the twenty-eight remaining, or female
cells.
The form of the spermatozoid now varies at every instant from the
activity of its movements, and the almost semifluid state of its plasma.
Its changes, however, are confined to elongation and contraction ; hence
it is sometimes linear-fusiform, or lunular, at others pyriform, short, or
elongate. The centre of the body is tinged green by the presence of a
little chlorophyll, while the extremities are colourless, the anterior one
bears a pair of cilia, and there is an eye-spot a little in front of the middle
of the body, also probably a nucleus. It is about l-2700th of an inch
long and about one-fifth as broad.
Once in the space mentioned, the spermatozoids soon find their way
among the female cells to the capsules, of which tliey apply themselves
most vigorously and pertinaciously, flattening, elongating, and changing
themselves into various forms as they glide over their surfaces, until they
find a point of ingress, when they appear to slip in, and, coming in contact
with the female cell, to sink into her substance as by amalgamation.
This author explains that there was some difiioulty in seeing the act of
union, but of the act itself he entertained no doubts. Eudorina in this
stage also may frequently be seen with all the four anterior cells absent,
and only a few spermatozoids left, most of which are motionless and
adherent to the capsules, indicating that the rest have disappeared in the
way mentioned. Lastly, many Eudorinai in this stage may be observed
with not only the four anterior cells absent, but with hardly a spermatozoid
left, indicating that the whole had passed into the female cells or
had become expended in the process of impregnation.
■VVhat changes take place in the Eudorina after this he had not been
able to discover. At the time the female cells appear to become more
opaque by the incorporation of the spermatozoids, and the crenulated
state of the posterior part of the envelope iu this stage seems also to indicate
an approach to disintegration.
While undergoing impregnation the female cells always contain from
2 to 4 nuclei, as if preparatory to the third stage of development into
which they are sometimes actually seen passing, with the spermatozoids
present and scattered among them ; but the effect of impregnation
generally seems to arrest this stage, and thus save the species from
that minute division which leads to destruction.
The author cited then goes on to explain how he conceives the other
stages of the Eudorina are passed, which he had not the opportunity
of observing. The whole memoir is one of great interest, and will
well repay perusal by those who are investigating this subject.
E u d o r in a e le g a n s . Ehrh. Monats. Berl., 1831, p. 78.
Coenobia oval, cells usually 32, globose, eitber scattered or
quaternate, eight at each pole, distributed in three parallel
circles, at equal distances from each other, around the periphery
of the cænobium.
S iz e . Cænobium 'Od-'IS mm. long. Cells •018-'022 mm.
diam.
Eabh. Alg. Eur. ill. 99. Ehrb. Infus. 63, t. iii. _ Pritchard
Infus. p. 520. Carter, in Aim. Nat. Hist., Oct., 1858.
Pandorina elegans, Dujard. Zoophy., p. 317.
In standing water.
Formerly found at Hackney and Hampstead, most abundant in the
spring of the year, but doubtless quite extinct at both places. “ Clusters
are often seen,” says Pritchard, “ in such amazing numbers along with
Volvox and Chlamydomonas pnlvisculus as to render the water of a
decided green colour, especially towards the edges.”
Plate X X V I . fig. 1. a, 16-celled family ; 2, sixteen-celled family
dividing into a 32-oelled family ; 3, part of a family, showing division in
pairs ; 4, 32-oelled family divided into daughter-families ; 5, one-oelled
danghter-family. All after Stein. 6, colony with three spermatic
cells, having burst ; 7, spermatic cells X 400 ; 8, spermatic cell X 800 ;
9, spermatozoids X 800. After Carter.
Genus 41. PANDORINA . Ehrh. (1830.)
Cænobium globose or subglobose, invested by a broad colourless
hyaline tegument ; cells green, granulose, globose (16, 32,
or 64), included within a single ra th e r thick membrane, bearing
two vibrating cilia, with or without a red spot, aggregated in a
botryoid manner.
Propagation the same as in Eudorina.
Henfrey’s emended character of this genus was in the following
terms :—“ Frond a microscopic, ellipsoidal, gelatinous mass, containing,
embedded near the periphery, sixteen or more biciliated, permanently
active gonidia, arranged in several circles perpendicular to the long axis
of the frond. The gonidia almost globose, with a short beak-like
process, a red spot, and a pair of cilia which project through the
substance of the frond to form locomotive organs upon its surface.
Keproduotion—I., by the conversion of each gonidium into a new frond
within the parent mass; II., by the conversion of the gonidia into
encysted resting spores, which are set free and (?) subsequently germinate
to produce new fronds.”—Quart. Micro. Journ. (1856), p. 49.
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