99
SOME NEW AFRICAN SPECIES OF
By
VOLVOX.
G. 8. West, M.A., D.Sc, F.L.S., Professor of Botany at the
University of Birmingham.
{Communicated by Mr. C. F. Rousselet, Octoher
The
present short paper
is
largely a report on a
of Volvox recently submitted to
me
for
2oth, 1910.)
number
of slides
examination by Mr.
C
F.
They embraced a series of specimens of Volvox
Volvox aureus, and several other forms of considerable
Rousselet.
globaior,
interest.
of the two European species, V. glohator and
aureus, are now very well known and their specific distinction
This was due in the first instance to the
clearly established.
The characters
V.
researches of Klein,* and his investigations have been repeatedly
Overton t has also pointed out further distinctions.
confirmed.
In this country Hick t was the
first to direct
attention to the
species were widely distributed.
The distinguishing features are for the most part in the sexual
organs and ripe oospores, although each species can be definitely
fact
that these two
distinct
recognised by the structure of the vegetative colony.
It is not at all uncommon to find the two species mixed in the
same pool or pond, and perhaps the appended synopsis
distinctive
characters
vegetative
(or
may
asexual)
of their
In both species the
globular and the male
prove useful.
colonies
are
colonies ovoid, but in V. glohator the female colonies are almost
invariably globose, while in V. aureus they may occasionally
be ovoid.
*
Klein in Pringsheim's Jahrh. flir ivissensch. Botan., xx., 1889.
f Uverton in Botan. Centralhl., xxix., 1889.
1891.
\ Hick in Trans. Manchester Microscojncal Society,
100
G.
S.
WEST ON SOME NEW AFRICAN SPECIES OF VOLVOX.
The contrasted characters
of these species are as follows
Volvox globator Ehrenb.
[r= V.
Volvox aureus Ehrenb.
monoicus Cohn.]
[= V. minor
V. dioicus
Diam.
of colonies, 420-800/x.
Number of cells,
1,000-15,000.
Cells small, angular in surface
view, and somewhat irregularly
:
Diam.
Stein
;
Cohn.]
of colonies, 200-680/x,,
of cells, 200-4,400.
Number
Cells larger, almost
round in
surface view.
produced at the angles.
Connecting strands of proto-
plasm
and
thick
continuous
vacuoles,
2-6
(commonly 4).
Daughter-colonies, regularly
plasm very delicate (as fine as
cilia) and sharply marked
off from the cells.
the
w^ith processes of cells.
Contractile
Connecting strands of proto-
Contractile vacuoles,
2.
Daughter-colonies, 4-14.
8.
Oospores, 12-40 (average 30);
outer wall of ripe oospore verrucose with conical warts.
Each
androgonidium
pro-
duces 64 or 128 (rarely 256)
Oospores 3-9
outer wall
of
(average
ripe
6)
;
oospore
smooth.
Each
androgonidium
pro-
duces 16 or 32 antherozoids.
antherozoids.
Antherozoids
slender,
with
elongated nucleus and laterally
attached cilia,
Antherozoids and oospheres
commonly produced
in different
sexual colonies.
Antherozoids
with
spherical
terminal
less
elongated,
nucleus
and
cilia.
Antherozoids and oospheres
in the same sexual
usually
colony.
Mr. Eousselet's slides contained both these species, a collection
in Baden-Baden in 1906, containing some very fine examples
of V. globator with 20-32 ripe oospores.
A collection made by
Mr. Bousselet at Totteridge contained fine male colonies of
made
V. aureus.
There
is
which
is less
also a third
well
European species V. tertius A. Meyer*
known, and can only be regarded as doubt-
A. Meyer in Botan. Zeitung,
xi.
and
xii.,
189G.
G.
S.
WEST OX SOME NEW AFRICAN SPECIES OF FOLVOX.
In this species there are no connecting strands
fully distinct.
between the
101
cells of
the adult colony.
Quite recently two papers on American species of Volvox have
appeared by J. H. Powers,* in which the author describes
several new forms under the names of V. spermatosphaera^
V. Weismannia, and V. jjerglobator.
The distinctions drawn up
by Powers are concerned principally with the development of the
He thinks it
reproductive colonies and the reproductive cells.
likely that the
European
species do not exist in America,
and
that the American species of Volvox are distinct races.
Volvox Rousseleti,
sp. nov.
(PI. 3, Figs. 1-7.)
In September 1905, at the time of the British Association's
visit to South Africa, Mr. Bousselet collected from a pool near
the station at Gwaai in Rhodesia a truly remarkable species of
All the specimens sent me for examination were purely
Volvox.
Yet, notwithstanding the entire lack of knowledge
vegetative.
of the sexual colonies, I have no hesitation in regarding these
specimens as vegetative (or asexual) colonies of a new species of
the genus.
The adult colonies are large and globose, measuring 1,1 25-1, 240/x
in diameter.
In appearance they are very robust, much more
so than those of any other species of Volvox, a feature which is
to the dense crowding of the constituent cells.
The number
due
of cells in the colony could be very easily estimated, and was
found to vary from about 25,000 to rather more than 50,000.
It
is this
enormous number
of cells constituting the colony,
the density of their arrangement, which form
features of this large African species.
The
cells
the
and
diagnostic
and are separated by
than their own breadth. In surface
are 4-6 '5/x in diameter,
intervening spaces of less
view (vide Fig.
all the
7) they are seen to be somewhat angular, and in
specimens they appeared to possess relatively stout proto-
I say " appeared to possess
plasmic connecting processes.
because it is unsafe to give a decided opinion on this point unless
the colonies have been fixed with the greatest care.
"
The number
of daughter-colonies produced
* J. H.
Powers in Trans.
Amev.
Jlicroscojj.
by one individual
Soc, xxvii., 1905; xxviii., 1906.
102
G.
S.
WEST ON SOME NEW AFRICAN SPECIES OF VOLVOX.
was regularly
and when
eight,
set free each
had a diameter of
In
this stage the cells apparently touch one another,
370/x.
a condition whicli exists almost np to the time the young colonies
about
have attained a diameter of 800-850//. It is at this period that
first formation of daughter-colonies can be observed in the
the
young colony {vide Fig. 5).
In size this species is similar
to the
American
V.
perglohator
Powers, but the cells in the latter species are so far removed
from one another that " the appearance under a moderate
magnification is that of a sponge-like reticulum," whereas the
attainment of a large size by the colonies of V. Rousseleti has been
accompanied by such an increase in the number of cells that the
colony has a much more solid and robust appearance than is
exhibited by any other species of Volvox.
Volvox africanus
(PL
A curious
by Mr. K.
to
form
of Volvox
T. Leiper,
3,
sp. nov.
Figs. 8-10.)
wns obtained from the Albert Nyanza.
who accompanied the
expedition dispatched
the Egyptian Survey Department in July 1907.
both in a sample of plankton and in material
Uganda by
occurred
It
collected in thirty feeb of water.
The material was sent
to
me
by Dr. W. A. Cunnington, and, in addition, to
I
in this material, Mr.
observed
F. Kousselet also
specimens
for examination
C
forwarded
me some
carefully mounted
slides of selected specimens.
this Volvox as " Volvox aureus Ehrenb.
* but since that time I have examined
(a form),"
many more
I
have already recorded
specimens and find constant characters scarcely in keeping with
those of V. aureus.
The
colonies are of approximately the
same
size as
those of
aureus^ but differ in being constantly ovoid or egg-shaped, and
in the nature of the daughter-colonies.
From one to four daughter-colonies arise in the adult asexual
V.
coenobium, and they soon attain a large
size, growing until they
become flattened by compression. They almost entirely fill up
the internal cavity of the parent, and they themselves show well-
developed daughter-colonies long before their escape from the
*
G.
S.
West
in .Town. Bot.,
Jaly 1909.
G.
S.
WEST ON SOME NEW AFRICAN SPECIES OF VOLVOX.
In
mother-colony.
common
marked
colony
fact,
a fourth generation
and
is
not at
103
all
un-
the specimens seen exhibited to a
{vide Fig. 10),
three
The ovoid form of the
the
generations.
degree
all
not entirely due to compression within the confined
examples were observed in which
is
space or the mother-colony, as
only one parthenogonidium had developed into a daughter-colony,
and this was of the typical ovoid form although there was ample
room for its development.
The cells of the adult colony are similar to those of F. airj-eus
in relative number and spacing, but no protoplasmic connections
could be observed.
Length
of
colony,
345-610/x;
breadth,
295-480/a.
One male colony was
colonies,
associated
with the purely asexual
and perhaps represents the male colony
of the
same
This colony exhibited a distinct polarity in
species of Volvox.
the development of the androgonidia, and differed in no essential
particular from
regretted that a
the male colony of V. aureus. It is to be
of sexual colonies in various stages could
number
not be found, as one might then have been much more certain of
the true relationships of this species of Volvox.
From available material, I can only suggest that it is a Volvox
V. aureus, but differing in the form of its vegetative (or
asexual) colonies, in the great development and compression of
the daughter-colonies before they are set free, and in the fact
near to
that three (and often four) generations of colonies always appear
to be well marked.
These characters appear to be sufficient for
its identification,
new
or
race of
and
it
seems proper to regard
it
as a
new
Volvox for which I would suggest the
species
name
V. africanus.
As
yet no trace of this Volvox has been seen from the other
large lakes of Central Africa, and it should be remarked that
they have been
Albert Nyanza.
A
much more thoroughly
investigated
than the
Species of Volvox from Australia.
One of Mr. Rousselet's slides contained two species of Volvox
from Heidelberg, near Melbourne, Australia.* One of these is
*
These were collected by Mr.
W.
J.
Hocking and sent
to
Mr. D. J
Scourfield.
JouRN. Q. M. C, Series
II.
No.
67.
8
104
G.^S.
WEST ON SOME NEW AFRICAN SPECIES OF VOLVOX.
-typical r. aureus, but the other
is
a
The adult
much
larger species closely
measure 700-1,1 10/x
are decidedly crowded.
The colonies
exhibit a slight polarity owing to a more or less distinct
concentration of the cells towards one pole.
The material was,
however, insutficient to be certain of the identity of this species.
V. Rousseleti.
approaching
in diameter and the
colonies
cells
Description of Plate
^igs. 1-7.
3.
Volvox Rousseleti sp. nov., from Rhodesia.
Figs. 1-6,
X 38 Fig. 7, surface view of part of colony,
;
X
84.
8-10. Volvox africcmus sp. nov., from the Albert Nyanza.
Figs. 8 and 9, x 70
Fig. 10, x 84.
;
9,
Three generations are clearly seen in Figs. 8 and
and in Fig. 10 four generations may be seen.
JovA'n. Quekett Microscopical Club, Ser. 2, Vol. A7., No.
<.".7,
Nocember 1910
JOURN. Q.M.C.
Ser. 2, Vol. XI. PI.
^
10.
'*...<
Q
S- West, photomicrogr.
AFRICAN
SPECIES OF VQLVOX.
5.
3.