cut being through the gastric ostium. The floor of the _stomach_ was now
cut off by cutting out the four interradial points of attachment. The
stomach and the proboscis gave vigorous contractions and tied themselves
all up so that I could not cut off the proboscis.
The four pieces of the floor of the stomach left on the interradii gave
contractions nicely. The phacelli continued their squirming movements.
25. Cutting off the whole aboral end of the animal excites to very rapid
pulsations of the remaining part. The stream, as shown by particles
in the water, is apparently stronger out the aboral end than past the
velarium.
It seems that I get no good evidence that the subumbrella is able to
contract of itself without connection with special nerve centers. In the
one case noted (Experiment 31) I could not be sure but that the part that
contracted was intimately associated with the suspensorium or frenulum.
26. A piece of the subumbrella cut off and having, so far as I could
determine, no connection with ganglia, frenula, or suspensoria, gave
contractions. Another piece was not seen to contract.
A small piece of the subumbrella connected with a club can contract. The
proboscis can give contractions of itself when cut off with the base of
the stomach. Even a cut-off lip can twitch by itself. A portion of the
subumbrella by itself also showed twitchings. (See also Experiments 18,
19, 25, 26, 29, 47, 49.)
_Pedalia, Velarium, Radial and Interradial Ganglia._--27. The pedalia
with their tentacles were cut off at their bases to insure cutting out
the interradial ganglia. The animal could pulsate well enough, but
intermittently and without much progress (the velarium, of course, being
injured). Cutting one pedalium caused the others to contract.
28. When the pedalia were cut off from one, the power of direct motion
was entirely gone. It swam in circles, turned summersaults, changed its
course continually, the oral end getting ahead of the aboral end, or
trying to do so. The whole power of balancing was gone. It seemed excited
by the operation and swam continually. [Repeated.]
29. The pedalia can be made to contract inwards by stroking their outer
edge with a needle. This was noted last year and has been seen several
times this year. Their inner edge is not so sensitive.
Touching a _sensory club_ caused the pedalia to contract inwards in two
cases.
The pedalia could be made to contract by giving the subumbrella a
prick,--generally a rather severe one was necessary. The upper part
of the subumbrella seems not so sensitive as the lower part and the
proboscis, and the base of the stomach did not give any reflex at all
(two specimens). One of the two could be made to give the reflex only
with much difficulty. This was a very lively one. It would even stand
severe pricks on the nerve, or even through the region of the sensory
clubs, without contracting the pedalia or stopping pulsations.
Cutting the frenula seemed not to affect the ability to swim well.
Cutting in this region brings about the reflex of the pedalia.
In the preceding fish the _velarium_ was cut away wholly in some places,
in other places it was left only as ragged strips. The pedalia became
very strongly contracted and the _tentacles_ were brought inside the
bell. Pulsations that seemed strong produced much less progress than with
the velarium intact. [Repeated.]
30. One with the whole _margin_ cut off still gave pulsations. Upon the
removal of the region of the _radial ganglia_, however, pulsations were
seen no more.
The _velarium_ in the above continued to give twitchings. The four
pedalia were cut off with plenty of the tissue at their bases to insure
the removal of _interradial ganglia_, and twitchings of the velarium
with irregular contractions continued. No full contraction all around
the velarium was noticed. When all the tissue was trimmed off as nearly
as possible down to the _velarium_, the latter still gave twitchings and
irregular contractions as before,--even more so as if excited by the
operation. The power of originating contractions evidently resides in the
velarium or in the ganglion cells of the frenula just as it does in the
proboscis and the floor of the stomach.
Small pieces cut from between the pedalium corners and the frenula, so as
to have tissue on them from neither, could contract by themselves. (See
also for Pedalia, Experiments 15, 23, 41b; Velarium 18, 41c.)
_Tentacles._--31. A cut-off tentacle can contract by itself, sometimes
with squirming contractions. A prick at either end can produce a forcible
contraction. A slight prick at the distal end may produce a local
contraction. The proximal end is more sensitive, but this difference
is not very marked. One with only the tentacles removed seemed to be a
little less able to guide itself well.
_Proboscis, Stomach, Phacelli._--32. The lips of the proboscis are
highly contractile by themselves. The movement of the stomach and the
phacelli goes on, after the lips are cut off, with increased vigor, due
to the stimulus of shock. The vigor and frequency of their contractions,
however, diminish quicker than that of the cut-off lips. (See for
Proboscis, 12, 15, 18, 26, 29; Stomach, 18, 24, 29, 31; Phacelli, 18, 24,
31.)
_Temperature._--33. Temperature does not seem to have much effect. Some
placed in a tumbler half full of water, in the bright sunlight, swam
vigorously over three-fourths of an hour. The water was quite warm to the
hand.
34. The above experiment was repeated with the same results. A
thermometer placed in the water with them showed 92° F.; hung in the sun
near by, it showed 94° F.
Ice in the water did not stop their pulsating temporarily or permanently,
except that it did for a short time after being held against one. Even
then it took some time (fifteen to twenty pulsations) before it produced
any effect.
35. Ice placed in the water again showed no marked effect. They swam as
lively as ever. Some, after pulsating against the ice for a little while,
seemed to be less vigorous, but quickly recovered in another part of the
jar. Others did not seem to be the least bit affected by contact with the
ice.
_Food and Feeding._--36. I tried to feed one. A red and a white copepod
were put into the subumbrella cavity. No attempt to eat it was observed
in either case, though the copepods remained in the subumbrella cavity
for some time.
Animals found in the stomach of Charybdea: small fish were most
frequently seen; at another time a small stomatopod; again, a small
polychæte; small shrimps; amphipod.
Those taken on August 16th (3 to 4 P. M.) seemed to have, for the most
part, food in the stomach, and this more so than those taken in the
morning.
_Occurrence of Charybdea._--37. In the first tow on the bottom (with a
net made of mosquito-netting and weighted with rocks in order to sink it)
the haul was forty. I do not think that we could have been towing more
than four or five minutes. The time was about seven A. M. A light breeze
was blowing and there had been a heavy shower a half-hour previous.
38. The usual time of towing was about 6.30 to 7.30 A. M. The water was
four to five feet (1.2 to 1.5 m.) nearest shore but deeper farther out.
At this time of day one could count on getting plenty of the larger sized
(15 to 20 mm.), many small ones, but very few of the smallest. This was
the experience of several mornings.
On August 12th I towed about nine A. M., and got but few of the larger
sized, many small ones, and very many of the smallest.
The next day (7.00 to 7.45 A. M.) those obtained were mostly of the
larger size. On the same day (3 P. M.) others of the party towed at the
same place and obtained but few.
On another day I towed in the afternoon (3 to 4 P. M.) and obtained great
numbers as I usually did in the morning.
39. We towed about 7.30 to 8.30 at night. Very few Charybdeæ were taken.
On this evening we towed five times in the same locality, and obtained
but seven or eight specimens. Towing with the same net on our way home,
it was filled with Aureliæ and five or six Charybdeæ. It seems as if
Charybdea came to the surface at night. Those towed in the evening were
dead the next morning.
The next morning Richard, our colored attendant, towed from 5.30 to 6.30.
There were heavy showers. The usual find of large and medium ones was
obtained. There were only two with planulae.
40. The material of September 2nd was obtained about six A. M. They were
mostly of large size. In all only fifteen or twenty were taken. Richard
explained the small number by saying that the bottom had changed in the
locality where we usually towed and that he got no weeds in his net, but
mud.
The next day more were brought in by Richard (6.30 A. M.) There were
rather more than yesterday but the quality was the same. There were three
with planulae.
On another morning Richard brought in a great many, about a hundred.
Among these there were three with planulae (light-colored and budding);
on a previous day there was one with the reddish-brown kind and with a
mouth.
_Activity of Charybdea._--41. a. About five o’clock in the morning
a Charybdea was taken in the tow. It was in good condition swimming
incessantly round and round without change of direction, in a jar of
about twenty centimeters in diameter. It came to the surface every now
and then, after eight to fifteen pulsations. The tentacles and the
phacelli were of a lilac shade. If a pencil was placed in its way it
would pulsate against it repeatedly without any effort to dodge around it.
6.58 A. M., 124 pulsations were counted to the minute.
8.00 “ 124 “ “ “ “ “
9.25 “ 136 “ “ “ “ “
10.15 “ 131 “ “ “ “ “
11.00 “ 146 “ “ “ “ “
At 10.15 it went around the dish in eight seconds, taking eighteen or
nineteen pulsations. If a bright platinum spatula or a black pencil was
placed in its circuit it would repeatedly butt against it each time it
came around. After the second or third pulsation against it, however, it
seemed to have some sense to change its direction.
b. The _pedalia_ have no perceptible action of their own. They move
inwards slightly toward the axis at each pulsation, but scarcely as much
as one would suppose from their attachment to the pulsating margin. It
seems as if they were for “winging” the moving animal more than for
anything else.
c. The _velarium_ is loose and it flaps. It seems to take part in
swimming something more than the passive diaphragm function,--i. e., it
straightens out during the recovery after each contraction of the bell.
AURELIA AND POLYCLONIA.
[The following experiments were performed at Port Henderson, Jamaica, in
1896.]
42. May 12th. An _Aurelia_ was pulsating normally at the rate of
twenty-five or twenty-six pulsations to the half-minute. One lithocyst
was cut out, when a few contractions, evidently caused by the stimulus
of cutting, followed; then, rest. In the first minute there were only
about five pulsations. In two or three minutes rhythmic pulsations were
resumed. Four minutes after the cutting there were nineteen pulsations
to the half-minute. About twenty minutes after there were nine to the
half-minute, in groups of six and three.
A _Polyclonia_, about four and one-half inches (115 mm.) in diameter,
gave twenty-six or twenty-seven regular pulsations to the half-minute.
After one otocyst was removed, pulsations continued, but in groups with
intervals of pause: _e. g._, thirteen, pause; ten, pause; six. Three
minutes after the removal of the lithocyst there were 5, 3, 1, 3, 5,
or seventeen pulsations to the half-minute. Eleven minutes after the
operation there were fifteen to the half-minute. The removed lithocyst
and surrounding tissue gave contractions.
43. May 13th. The _Aurelia_ was in rather poor condition but would
pulsate upon being stirred. The other seven lithocysts were removed when
only a few contractions originated thereafter.
The _Polyclonia_ was in good condition, but was pulsating only
intermittently when first seen in the morning. When the remaining seven
lithocysts were cut out and no more pulsations were observed, the oral
arms could still move.
May 14th. Both were found dead upon returning in the evening.
44. May 15th. An Aurelia and a Polyclonia were taken in the morning. The
_Aurelia_ was two and one-half to three inches (62.5-75 mm.) in diameter,
with three tufts of phacelli, three oral arms and seven lithocysts.
The _Polyclonia_ was normal and seven or eight inches (175-200 mm.) in
diameter.
In the _Aurelia_ all the lithocysts were removed. Spontaneous and
coördinated contractions could still occur after time had been allowed
for the shock from the operation to pass away. The next day the animal
was still alive and pulsating, but ragged, and the next day following was
quite dead.
In the _Polyclonia_ the normal rhythm was fourteen pulsations to the
minute. Some pulsations were apparently quicker than others and the
intervals were not the same. Thirteen, ten, and twelve pulsations were
also counted. After putting the animal into fresh sea-water, it pulsated
thirty-three to the minute. Six minutes later it was still pulsating
at the same rate, while in four minutes more eleven pulsations, many
of which were in groups of two, were noted. In five minutes more it
pulsated eleven times to the minute with only one double pulsation. One
_oral arm_ was then cut off and the rhythm counted about one minute
afterward--fourteen pulsations, then a pause of fifteen seconds, then two
pulsations, in all sixteen to the minute were counted. About ten minutes
later there were eight pulsations, two or three minutes later only three,
while in two or three minutes more only three. There was a long latent
period--two or three seconds--before the stimulation of cutting off the
arm made itself evident in the rhythm.
A second oral lobe was removed. Then there followed twenty-four
pulsations, a pause of two seconds, and two pulsations, in all twenty-six
pulsations to a minute. The rate of pulsation soon fell to the previously
abnormal low rate.
Third lobe removed: 21 pulsations in first half minute and then 16, or 37
per minute.
Fourth lobe removed: 17 pulsations in first half-minute plus 13 gives 30
for the minute.
No difference in the coördination of the animal was shown as a result of
the removal of one-half the number of oral arms.
Fifth lobe removed: 17 pulsations plus 15 equals 32 to the minute.
Sixth lobe removed: 17 in first half-minute plus 4 in the second
half-minute gives 21 pulsations for the minute.
Seventh lobe removed: 17 plus 9, or 26 per minute.
In all these instances the rhythm in the second half of the first minute
was irregular and intermittent.
Seventeen and then seven pulsations were provoked after the animal had
become quiescent, or nearly so, by merely handling it.
45. Eighth oral lobe was removed and pulsations stopped. The next day
the animal was in good condition. The pulsations counted in the evening
were 12, 14, 14, 11, per minute. The rhythm was not regular; there was a
tendency to groups of twos, threes, or more, but no prolonged intervals
of rest were observed. When placed into fresh sea-water, the pulsations
were fourteen to the half-minute or twenty-six to the minute; seventeen
to the half-minute, and thirty-three to the minute were also counted.
This specimen gave spontaneous contractions during two weeks, after which
it was thrown out, the aboral end being eaten through and little or no
regeneration having taken place.
46. Two more were operated upon: A. Its rhythm was 18, 14, 17. Its entire
margin was cut off. The separate pieces of the margin pulsated, 6, 7,
4, 6, 7, 9. The animal seemed paralyzed by the operation; it responded
by a contraction now and then to stimulation but gave no spontaneous
pulsations. B. Its rhythm was 17, 15, 12, 12. All its _oral arms_ were
removed. Its rhythm was only raised to seventeen and not perfect. In
twenty-five minutes it had fallen to eleven, in four hours to ten
pulsations [per minute].
May 22nd. A and B are living as also the pieces of the _margin_ of A;
all are giving spontaneous pulsations now and then at comparatively long
intervals--even A, with its margin removed.
May 26th. Everything is still living. The one with the margin cut (A)
counted sixteen and nineteen pulsations per minute, though this was not
kept up all the time.
June 2nd. A and B and pieces are still living and contracting
spontaneously. It is now two weeks, and they were thrown out eaten
through at the aboral end with little or no regeneration.
47. The margin was cut off another one (C) and it was then paralyzed. The
margin contracted vigorously by itself. The margin was next split, but a
connection of about one-half an inch wide was left between the two rings.
Over this bridge the contractions passed from the outer and inner ring.
The inner ring did not originate any contractions. Both rings were then
cut near their connecting bridge of tissue and the larger ring with the
marginal bodies was split longitudinally so as to separate the exumbral
from the subumbral portion. It was found that the contractions started
only from the subumbral portion while the exumbral portion did not
contract at all.
June 5th. Five of the eight small pieces of C were not seen to contract
either to-day or yesterday. A slow rotary motion was observed in
some of the pieces suggesting ciliation, but no cilia or currents
pointing to ciliation were seen with a low power. C was seen to pulsate
spontaneously. Possibly it did yesterday but it was not watched closely.
A piece of the subumbral surface of C broken off (not from the margin)
was found to contract spontaneously.
48. June 6th. In a fresh one (D) from Port Royal, the eight lithocysts of
one side were removed in order to compare its movements with an intact
one. Coördination was apparently unaffected.
June 9th. The margin of C is still pulsating vigorously. Parts of the
subumbrella broken loose from the strip pulsated by themselves now and
then. Fifteen lithocysts were removed, leaving only one at the end of the
strip. It was found that with this single ganglion (lithocyst) left, and
originating most of the contractions, now and then a contraction would
originate at another part of the strip where there was no ganglion. Three
days later contractions originated as often from other parts as from the
ganglion.
CASSIOPŒA.
[The remaining experiments were all performed in 1897, at Port Antonio.]
49. Removal of the sixteen marginal bodies caused paralysis for a time;
then recovery followed.
Contraction was limited to the subumbrella.
A portion of the _subumbrella_ not from the margin can contract by itself
as well as a portion of the margin with the marginal bodies (lithocysts).
In the _margin_ cut off as a strip with only one marginal body attached
at one end, contractions sometimes started from the opposite end.
AURELIA.
50. Size, seventeen or eighteen millimeters. Pulsations, thirty-two.
Lithocysts, nine. The operation consisted in the removal of the
concretions with as little injury to the pigmented parts of the marginal
bodies as possible. One whole marginal body, however, was removed in the
operation. Soon after the operation the pulsations were 28, 26, 20, 20,
per minute.
Another one; size fifteen millimeters. Pulsations were forty per minute.
The operation consisted in the removal of the concretions and pigmented
parts of the marginal bodies with as little injury to the adjoining parts
as possible. After the operation it seemed as if the intervals between
the pulsations were irregular,--not a series at regular intervals. An
hour or so after the operation the pulsations were very intermittent.
During the afternoon it was not seen to pulsate except when it was
stirred up, when six or seven vigorous pulsations followed. These,
however, were rather aimless.
51. One sensory club (marginal body) was cut out, including its basal
part also. In one or two other cases more or less injury was done to
adjoining parts also. Pulsations ceased upon the removal of the last
club, but upon placing it in an aquarium and allowing it to come to rest
for two or three minutes, pulsations were now and then seen. In the
evening, this one and another did not pulsate except when stirred, when
they pulsated with good progress.
52. A circular cut, about two inches in diameter, was made through
the epithelium of the subumbrella around the base of the oral lobes.
The animal pulsated well enough, but the contractions seemed not so
simultaneous in all parts of the margin as normally. After a few days it
had partly regenerated but died. One of the oral lobes cut off had some
power of contraction, and this some time after the operation. A similar
cut, but semicircular, made no difference between the contractions of the
two halves.
53. The whole region of the sensory clubs was cut out when the animal was
not seen to pulsate again, except in the evening, when pulsations were
observed. The oral lobes also moved.
HISTOLOGICAL.
_Method._--The following results on the histology of the sensory clubs,
their eyes, and the tentacles, as already noted, were obtained from some
of Dr. Conant’s preserved material. These results relate almost wholly
to Charybdea, with only a few references to Tripedalia, noted in their
proper place.
A portion of this material was killed after keeping the animals in the
dark for some time, for the purpose of discovering any changes in the
pigment of the eyes. I believe that a retraction of the pigment of the
long pigment cells that project between the prisms and pyramids of the
vitreous body in the retina of the distal complex eye is very evident in
eyes killed in the dark. (But more on this below.)
I obtained my best results from the material preserved in saturated
corrosive sublimate, to which had been added (5 to 10 per cent.) acetic
acid. This also was Conant’s experience in his previous work on Charybdea
and Tripedalia.
My best sections were obtained by embedding the sensory clubs in
celoidin, passing the little blocks of celoidin with the sensory clubs
into chloroform until perfectly transparent, and then into paraffine. I
then cut sections as we ordinarily cut paraffine sections, mounted and
stained them on the slide. My purpose in using this method was to avoid
the displacement of the vitreous bodies of the eyes during embedding
and cutting. This object was fully realized and more besides. Since the
sections cut by the celoidin-paraffine method gave me so decidedly the
best differentiation of the axial fibers of the retinal cells, as also of
the cilia, basal bodies, etc., I am inclined to believe that the celoidin
was in part responsible for this differentiation.
Most of my series were cut 4 µ in thickness. All in all I cut sixty-five
clubs besides making some maceration preparations from material preserved
for that purpose. These sixty-five series represent material from
fourteen bottles. As a whole, my material was good, but the material from
one bottle was decidedly superior for showing the axial fibers of the
prisms and pyramids of the retinal cells. This shows the advantage of
plenty of material. It will be evident that I had plenty of material.
I found iron-hæmatoxylin the most satisfactory stain. I stained for a
shorter or a longer time--one-half to several hours and longer--and then
washed out the sections until under a low power of magnification they
appeared quite unstained, the nuclei and a few other parts only appearing
darkly stained.
Depigmentation I practiced but little. I obtained many of my series
almost wholly unpigmented, especially those I cut last. Others, of
course, were very heavily pigmented. I am not certain but that alcohol
slowly dissolves out the pigment after a long period of preservation.
Slight variations in the technique of killing and preserving may also,
perhaps, determine the stability or solubility of the pigment, as, of
course, also the condition of the pigment at the time of killing.
_Anatomy._--For a short epitome of the anatomy of a Cubomedusa and of a
Cubomedusan sensory club see p. 2 of the Introduction.