Notes on the lngestii ri of I'uod-material by the Swarm-cells
of Mycetozoa. By AwrHua LISTER,
F.L.S.
[Read 4th April, 1889.1
BEFORE
proceeding to describe the manner in which the Bwarmcells of Mycetozoa take in and digest their food-material, it may
not be out of p1:rce t o refer to some experiments bearing on the
mode of feeding of the plasmodium of Badhamia utricztlaris, the
account of which appeared in the 'Annals of Botany' for J u n e
1888. In that paper 1 described the action of the plasmodium on
starch, as well as on thin slices of Agarieus campestris and other
fungi ; I especially drew attention t o its feeding onliving Sterezcn,
hirsutunz, the favourite pabulum of this species of Badhamin.
I n following those experiments I observed that when the
plasmodium had become loaded with the food-material with
which i t had been supplied, many of the large vacuoles became
charged with undigested matter, which collected as a dark ball in
the centre of the hynline contents of the vacuole. I repeatedly
saw these vacuoles push out as bubbles on the surface of the
plasmodium and burst, discharging a cloud of refuse, consisting
of fragments of starch and broken fungus-hyphae, into the
water.
When the plusiiiodiuni creeps over a glass plate aiid is not
immersed in water, the rtjected matter is left with a certain
amount of plasmodiuni substance on each side of the retreating
veins, leaving a map of the network after the plasmodium has
withdrawn.
This appears to be of soiiie interest in its relation t o the
behaviour of swarm-cells described in the sequel.
The following account of a cultivation of plasmodium from the
spores of Chondrioderma dafoorme has also a bearing 011 the
same :These spores germinated in water under u coverslip in about
twelve hours. On the 11th day after sowing, many of the
swarm-cells had assumed the character of microcysts, and a large
proportion had withdrawn their cilia aud were moving slowly as
amcebs, with a tendency to adhere when they came together.
O n the 13th day several young plasmodia were seen with
rhythmic streaming of their granular contents, the current continuiug for about a niinute in each directiou.
When in their wandwings the young plasmodia met, or came in
LINN. JOURN.--POTANr,
VOL. XSV.
2 H
486
XR. 4. LlSl’Lll ON THE INaESTION O P FOOD-BfATEBIAL
contact with :imceboid swarm-cells, they coalesced ; the investing
hyaloplasmic substance offered for a time a resistaiice to uuioii,
this a t length gave way, and the contents of one gushed into the
other. When a microcyst was met with iu the line of march, it
was taken in as foreign matter and enclosed in a vacuole ; it was
dowly absorbed in the course of three or four hours.
Active swarm-cell*, which had probably hatched out later
than the others, though often seen t o approach the plasmodia,
and even t o lie for sonic minutes enfolded by their pseudopodia,
never coalesced, and in time wandered away again. The plasmodia
did not all unite, but continued t o crawl over the glass for four
days longer, when the conditions became unfavourable, aud they
dwindled away without developing into sporangiu *.
Eeferring to tho process of nutrition in the Mycetozoa,
De Bury states t ‘‘ that the food is talcen in during the swarmcell condition only in a fluid state or state of solution, and this
is also the case, a t least in most instaiices, with the plasmodium .’I
This is a poiiit o n which there has been some controversy.
Mr. Saville Kent, in the appendix to his ‘ Manual of the Inf’usoria,’ described in 1881 the appearance of swarm-cells of Physicrum tussilayinis, which contained vacuoles filled with bacteria
of the same kind as abounded in the surrounding medium. He
also relates how, on adding pulverized carmine to the water, the
granules were freely ingested, and, as in the case of the bacteria,
were collected within “ crphseroidal vacuoles.”
Although this experiment clearly sliows that the mwm-cells
of I’hysm-um tirssilnginis take in food-material in other than iii
the fluid stntc, yet as De Bary’s high authority, published so
* I n sowings of LhoizJ) zodi) BLQ d ~ f i r m csporcq on blotting-paper u i t h cress
seedq, I have a l ~ a y sfoiind the sporangia begin to form in eleven to fourteen
clays from the date of sowing, and mag continue to make thew appearance for
four nwn ths
I have had tht- plasinotliiiir~of Uitdha,nici ~ ~ t r z c z 1 2111
~ i constant
r~~
btreannng
movement for more than a j e u , though many cultlvations from the original
stock of plasinodiulu have chonged to sporangia at different interlals during
that time. Sclerotium of the last numed specics, after two >ears’ preswvat~on,
lias clianged to spormgia within a foi tnight of being revived , while other
coiitinued to stteaut wltllplasniodi~uii,revived froni tho w ~ i Sed C I Y J t i l l l l l , 11~1s
out olmnge for 1i)e nionths, althougli both uero l e d nith bteiewt hzrsutuni, tmck
n c r e qip.ticiitIj unilw 11 srly [lie s ~ i i ~cuiitlitioiis
c
1 l l e Bwy, ~ I ~ W I ~Oxlord
J L Ucditiui~,
A
11. 152.
BT TIIF, S\VARM-CRLTS OF MYC'R'l'O%Ok.
437
lately as 1887, still stands in support of his view, and IS it
appears t o be a matter of considerable physiological interest, I
venture to offer the following observations on the swarni-cells of
Stemonitis ficscn and some other species which hare come under
my notice.
On October 9, 1688, I gathered ripe sporangia of Stemonitzs
fusca, the spores of which were unusually rapid in developing.
Within an hour and a quarter after placing the spores in water
under a thin coverslip they began to hatch, and in a couple of
hours the water teemed with swarm-cells ; they emerged in four
t o ten minutes after the rupture of the spore, and in about a
quarter of ail hour the ciliuiii was protruded. Almost immediately behind the cilium, and occupyiiig the greater portion of
the conical anterior part of the cell, lies the nucleus, and behind
this again extends the main protoplastnic substance containing
minute granules and often several vacuoles. Sometimes only one
contracting vacuolc is observed, but frequently six or seven
others may be seen, appearing and disappearing a t irregular
intervals. There is continued change of position of the vacuoles
and the contents of the body of the organism ; the nucleus,
however, always retains its place in the conical end.
This change of position of the contents varies in character in
different species ; in the large swarm-cells of Amnurochate ntva
there is a remarkable flow suggesting an appyoach t o streaming
movement, more than the mere mixing together occasioned by
the spasmodic jogging of those of St~inoizitis.
The rounded posterior end of the swarm-cell is frequently
seen to broaden out and t o extend pseudopodia, either as irregular projections or as extremely delicate threads.
On one occasion I had under a square coverslip many hundreds
of swarm-cells of Sfemoibitis, which had been hatched two days
previously, and were in rather a flagging condition. I happened
to have in a wine-glass of water some pieces of Stereurn hirsutum
which had been soaking for some days, and the water was turbid
with large bacilli, measuring 3 to 6 p in length. I admitted
a drop of this water under the coverslip. The bacilli rapidly
spread among the swarm-cells, which soon appeared t o revive
from their sluggish condition, the jogging movement and the
lashing of the cilia becoming much more active; at the sanie
time I noticed that inany had bacilli, in some cases as inany
438
MR. A. LISTER ON T l I E INGESTION O F FOOD-MATEIlIAL
as six or seven, attached to the pseudopodia produced from the
posterior extremity. Shortly after, many vacuoles were seen to
contain foreign matter.
I dried several drops of the preparation and stained with
magenta, and mounted in balsam ; the mountings showed deeplystained bacilli, principally in a large vscuolo near the nucleus.
Next day I wetted another dusting of spores, and in a couple of
hours, when the pure water wm thickIy peopled with &warm-cells,
I added a drop of the water crowded with bacilli; as on the
previous occasion, bacilli were aoon observed attached to the
rugged posterior region, and others were seen enclosed in
vacuoles. I watched one swarm-cell with a wriggling bacillus
adhering to a delicate pseudopodium ; it was gradually drawn
inwards as the pseudopodium contracted. I then saw an extension of protoplasmic matter fold over the bacillus, and absorb it
into the interior substance ; shortly after I saw it conveyed into
a large vacuole near the nucleus, which already contained three
bacilli. I watchcd these for an hour; they gradually became
more and more indistinct, until nothing vas visible b u t a faint
indefinite residuum. N o fresh bacilli Mere taken in during this
time.
I n the next observation a bacillus 5 p in length was attached
to a pseudopodium so extremely fine, that its continuity could
only be determined by the violently moving captive indicating
the distance t o nhich the thread extended. In the course
of a few minutes the bacillus was drawn inwards, and, as in the
former case, an extension ma8 folded over it, and it was taken
into the interior, where it was soon surrounded with a vacuole ;
another large vacuole containing two other bacilli was stationed
near the nucleus, but during the twenty minutes it was under
observation the two vacuoles remained distinct. In another
instance, when a large bacillus was caught by a pseudopodium
and drawn up to the main body, a tube-like process was extended,
investing it almost to its extremity ; the bacillus was then sucked
in, and as i t lay athwart the swarm-cell in a large vacuole, i t was
of so great a length that the ovoid cell was bulged out on each
side by the stiff rod ; a violent jerking movement followed, such
as I have repeatedly noticed after the ingestion of food, and in a
few minutes the bacillus was bent double, the vacuole decreased
in size, and in a quarter of an hour its contents had become less
distinct by the process of absorption. (See figs. 1-6, p. 440.)
B Y TIIF, SWARM-CELJJS OF M Y C E T O Z O t .
439
Numbers of observations of a similar cliaracter were made,
which I need not describe in detail.
During one observation, a swarm-cell took in a t different
times two black particles of inorganic matter : one was enclosed
in a vacuole aud remained there as long as the observation was
continued; the other, after being sllifted into all parts of the
body-substance, was simply turned out a t the posterior end, not
apparently by the rupture of a vacuole.
Powdered carmine was readily seized upon. On one occasion
I watched for twenty minutes the efforts of a long irregular
pseudopodium t o embrace a large granule, but the finger-like
extensions seemed uuable t o grasp it ; at length they succeeded,
and the object was drawn in, when the postericr end of the
swarm-cell assumed, and retained until the close of the observation, the usual rounded form.
I have seen carmine discharged in the same manner a8 the
black particle above described. And here I would refer to what
suggests a power of discrimination in different species of swarmcells. While, as just stated, carmine was greedily incorporated by
swarm-cells of Stemonitis, I have supplied i t to those of Arnauroclmte, which I hadin full vigour and vast abundance ; but although
they spread out pseudopodia which occasionally caught hold of
carmine granule and retained it for some seconds, none were
taken in. I have tried the experiment two or three hours after
their issuhgfrom the spores, and also when they had been hatched
for more than 5 day, but in no instance have I seen a granule of
carmine within the substance of Antaurochate.
Although in Steinonitis fusca carmine was retained for many
hours, I was unable to detect any absorption, though I made
careful drawings from time to time of the size of the particles,
and no colour was communicated to the clear contents of the
vacuoles in which they were enclosed, such as is referred to by
De Bary (p. 452) in the plasmodium of Didymiunt SerpuEa. I
have watched the swarm-cells of Tr'richiafragilis, which hatched
three days after placing the spores in water, when the preparation abounded with bacilli; these behaved in the same way aa
those of Stemonitis, throwing out more or less delicate pseudopodia, to which bacilli adhered, and were then drawn in and
stored in vacuoles : many contained three vacuoles, each holding
four to five bacilli.
I have had the same results with the spores of Chondrioderma
I
/
i
?I.
3
x
4
1200
6
Fig. 1. Swarm-cell of Steitrowitiu,fima of the usual forin wheu swimming. g t ,
nucleus ; ti, vacuoles.
Fig. 2. Swarm-cell with three bacilli adhering to e\paudecl posterior extremity.
Fig. 3. A swarm-cell with delicate yseudopodiu, to one of which a bacillus is
attached.
Fig. 4. The same swarm-cell, the bacillus in the act of being drawn in, and
partly invested witli a tube-like extension of the body-substance.
Fig. 5. The mme bacillus, contained in a long vacuole, and bulging out the sides
of the swarm-cell.
Fig. G. The same bacillus, bent double after violent jerking iiloveinent of tlie
swarm-cell.
dz$bmze.
Here, a8 in other species, the Bpores of different
gatherings are uncertain in the time they take t o hatch, but the
swarm-cells usually appear in about ta elve hours after placing
tlie spores in water. They are protean in their forins, chaiigiiig from the ciliated and elongrtted shapc to stellate amcehp,
H Y T H E SWARM-CELLS 01' 31YCETOBOA.
441
which throw out pointed pseudopodia apparently from all parts
(though this is very probably deceptive). Then in a minute
or less they will resume the normal swarm-cell character, and
often show remarkable activity as they crawl over the surface of
the glass, the contents aitli the ingested matter and vacuoles
mixing together in a complete turmoil. They take in material
of various description, such as bacteria, alga-cells, and inorganic
matter, and may be seen discharging refuse together with a
portion of their own protoplasmic substance in the same way as
we observe rejected matter left behind by retreating plasmodium.
This throwing off of a part of the body-substance with refuse
matter I have repeatedly seen in the sKarm-cells of Trrichia
fallax in a very striking manner.
I n all these experiments I have invariably observed that foodmaterial was taken in only at the posterior end of the swarmcell ; and where I have seen refuse matter discharged, it has been
from the same region. I have rarely been able to observe the
discharge of any residuum of bacilli ; they appear to be almost
wholly assimilated.
LNom.-Since this paper was read, 1-have observed the swarmcells of C7Londriodermn d i f o m t e capture and a h o r b bacilli on
many occasions. I n one instance, after taking in two stout
bacilli tone measuring 8.8 p by 5' p), and enclosing their1 in separate
vacuoles, the swarm-ccll remained quiescent for a length of time.
1 watched the gradual proccss of digestion with a Beck's &
immersion-leus, and when, after remaining under observation for
nearly an hour and a half, the swarm-cell swam off with vigorous
lashing movement o f the cilium, every trace of the two bacilli and
their containing vacuoles had disappeared, and only the contracting vacuole remained i n the faintly turbid protoplasmic substance
of the creature.]