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yond the stage of the development; but specimens have
been taken by Professor Miiller swimming in the sea in
which scarcely a rudiment of the larva remained. They
had the form of round flattened disks, which freely moved
their spines and crawled about the sides of the vessel in
which they were kept, by means of their suckers, exactly
in the manner of the adult Urchin.

Thus "ends this strange, eventful history"; and in re-
viewing it, one can scarcely avoid being impressed with
a sense of the majesty of (rod in these His humble works.
By what wonderful, what unexpected roads does He ar-
rive at the completion of His designs! and if such things
as these are only now bursting upon our knowledge, after
six thousand years of man's familiar contact with the in-
ferior creatures, how many more wonders may yet remain
to be unfolded, as science pursues her investigations into
the Divine handiwork! And yet, how does this and all
similar manifestations of power and wisdom sink into in-
significance before the grand marvel, the wonder of won-
ders, the great mystery of godliness that GOD WAS MANI-
FEST IN THE FLESH! We are surprised and delighted
when we see one creature change, as it were, into an



SEA-URCHINS AND SEA-CUCUMBERS 347

other, but too often the story of that greater wonder, that
God should have become man, falls upon listless ears and
cold hearts; and yet the former, which we scarcely weary
of tracing, concerns only the well-being of a poor dull
creature scarcely raised above the life of a plant, whereas
the latter had for its object the lifting of creatures from a
state of ruin and wrath to immortal life and everlasting
glory; and the creatures are ourselves!



348 EVENINGS AT THE MICROSCOPE



CHAPTER XYII

JELLY-FISHES

AS this afternoon was delightfully calm and warm
the very model of an autumnal day I took my
muslin ring-net and walked down to the rocks at
the margin of the quiet sea. Nor was I disappointed ; for
the still water, scarcely disturbed by an undulation, and
clear as crystal, was alive with those brilliant little globes
of animated jelly, the Ciliograde and Naked-eyed Medusae,
apparently little more substantial than the clear water it-
self. Multitudes of them were floating on the surface, and
others were discerned by the practiced eye, at various
depths, shooting hither and thither, now ascending, now
descending, now hanging lightly on their oars, and now,
as if to make up for sloth, darting along obliquely with
quickly-repeated vigorous strokes, or rolling and revolv-
ing along, in the very wantonness of humble happiness.
After gazing a while with admiration at the undis-
turbed jollity of the hosts, I made a dip with my net, the
interior of which, on lifting it from the water, was lined
with sparkling balls of translucent jelly. They were far
too numerous to allow me to transfer them all to captiv-
ity; they would soon have choked up and destroyed one
another; I therefore selected the finest and most interest-
ing, shaking an example or two of each kind into my
glass jar of sea-water, where they immediately began to



JELLY-FISHES 349

frolic and revel as if still in the enjoyment of unrestricted
liberty. And here they are.

Among these bright and agile beings which are shoot-
ing their wayward traverses across each other, and inter-
twining their long thread-like tentacles, we will select one
or two for examination, as samples of their kindred. And
first let me isolate this active little Beroe (Gydippe pomi-
formis), which I dip out with a tea-spoon and transfer to
this other glass jar, that we may watch its form and move-
ments unaffected by the presence of its companions.

We see, then, a little ball, almost perfectly globular,
except that a tiny wart marks one pole, of the size of a
small marble, and apparently turned out of pure glass, or
ice, or jelly according to your fancy perfect transpar-
ency and colorlessness being its characteristics, so much
that it is not always easy to catch sight of the little creat-
ure, except we allow the light to fall on the jar in a par-
ticular direction. From two opposite sides of the globe
proceed two threads of great length and extreme tenuity,
which display the most lively and varied movements.

These filaments shall occupy us for a few moments.
We trace them to their origin, and find that they proceed
each from the interior of a lengthened chamber, on each
of two opposite sides of the animal. Suddenly, on the
slightest touch of some foreign object, one of the threads
is contracted to a point and concealed within its chamber,
but is presently darted forth again. When the lovely
globe chooses to remain still, the threads hang downward,
gradually lengthening more and more, till their extremities
lie along the bottom of the jar, extended to a length of
six inches from the chamber. Then we see that this deli-
cate thread is not simple, but is furnished along one side,



350 EVENINGS AT THE MICROSCOPE

throughout its length, at regular distances, with a row of
secondary filaments, which project at right angles from the
main thread.

These secondary filaments constitute an important ele-
ment in the charm which invests this brilliant little creat-
ure. They are about fifty in number on each thread, and
some of them are half an inch long, when fully extended,
but it is seldom that we see them thus straightened; for
they are ever assuming the most elegant spiral coils, which
open and close, extend and contract, with an ever-chang-
ing vivacity. The animal has a very perfect control over
the threads, as well as over the secondary filaments in
their individuality. One, or both, are frequently projected
from their chambers to their full extent by one impulse;
sometimes the extension is arrested at any stage, and then
proceeded with, or the thread is partially or entirely re-
tracted. Sometimes the secondary filaments are coiled up
into minute balls scarcely perceptible, or only so as to
give to the main thread the appearance of small beads re-
motely strung on a fine hair; then a few uncoil and spread
divergently; contract again, and again unfold; or many,
or all, interchange these actions together, with beautiful
regularity and rhythmical uniformity, repeating the alter-
nation for many times in rapid succession.

The beauty and diversity of the forms assumed by
these elegant organs beguile us to watch them with un-
wearied interest, and we wonder what is their function.
For, with all our watching, this is by no means clear.
They are certainly not organs of motion. At times it
seems as if they were cables intended to moor the animal,
while it floats at a given depth ; or we see them with their
extremities spread upon the bottom, to which they appear



JELLY-FISHES 351 -

to have a power of adhering, thus forming fixed points,
from which the little globe rises and falls at pleasure,
shortening or lengthening its delicate and novel cables,
maintaining all the while its erect position.

When the Cydippe swims, however, which it does with
great energy, the threads seem unemployed, streaming
loosely behind, and evidently taking no part in the pro-
gression, though still adding beauty and grace to the tout
ensemble. The organs by which the sprightly motions of
the whole animal are effected are of quite another char-
acter, and shall now engage our attention.

You have doubtless observed, while gazing on the ani-
mal, a peculiar glittering appearance along its sides, min-
gled in certain lights with brilliant rainbow-reflections.
Now let us take an opportunity, when it approaches the
side of the glass, to examine this appearance with a lens.
The globe, you see, is marked by longitudinal bands,
eight in number, set at equal distances, and ranging like
meridians, except that they do not quite reach to either
pole. These bands are the seats of the motile organs,
which are highly curious, and in some sort peculiar.

Each band is of considerable width in the middle, but
becomes narrower toward the extremities. It carries a
number usually from twenty to thirty of flat thin mem-
branous fins, set at regular distances, one above the other,
which may be considered as single horizontal rows of cilia,
agglutinated together into flat plates. Each plate has a
rapid movement up and down, from the line of its inser-
tion into the band, as from a hinge, and thus striking the
water downward, like a paddle. The whole band may be
likened to the paddle-wheel of a steamer, except that the
paddles are set in a fixed line of curvature instead of a



352



EVENINGS AT THE MICROSCOPE



revolving circle. The effect, however, is exactly the
same: that of paddling the beautiful little globe vigor-
ously through the water. The prismatic colors are pro-
duced by the play of light on their glittering surfaces,
which are ever presented to the eye of the beholder at
changing angles.

We rarely see these rows of paddle-fins wholly at rest,
but occasionally one or two bands will be alone in a state




CYDIPPE.



of vibration; or one or more will suspend their action
while the rest are paddling. Sometimes in a band that is
at rest, a minute and momentary wave will be seen to run
rapidly along its length. All these circumstances show
that the ciliary motion is perfectly under the control of
the animal's will, not only in the aggregate, but in every
part.

In an excellent memoir on this animal by Mr. K. Pat-
terson of Belfast, 1 there are some interesting observations
on the power of its tissues to become tinged with extra-

1 "Trans. Roy. Irish. Academy," vol. xix. pt. 1.



JELLY-FISHES 353

neous colors, a fact which may be useful to you in your
researches, as enabling you with more ease and precision
to demonstrate the internal structure.

"From the inconsiderable quantity of solid material/ 7
remarks this observer, "which enters into the body of the
Beroes, and the rapid circulation of water which is appar-
ent throughout their frame, we would naturally suppose
that any tinge which the body might accidentally acquire
would be extremely fugitive. It was found, however, to
be much less so than d priori would have been expected.
My attention was drawn to this peculiarity by the circum-
stance of all my glass vessels being one evening occupied
by Beroes and Crustacea, so as to compel me to place a
small Medusa in a tin vessel, which chanced to be rusted
at the seams. Next morning the colorless appearance of
the animal was changed into a bright yellow, which ap-
peared to pervade every part, and doubtless arose from
the oxide of iron diffused through the sea- water. This
tint remained during the entire day, although the animal
was transferred to pure sea-water. Wishing to try if the
vessels of the Beroe would become distinct, if filled with
some colored fluid from which the animal could suddenly
be withdrawn, and viewed through the usual transparent
medium of sea-water, I placed a Beroe in a weak infusion
of saffron. At the end of twenty minutes its color had
undergone a perceptible change. I allowed it, however,
to remain immersed for about six or seven hours, when
it had assumed a bright yellow hue. It was then placed
in pure sea-water, but retained its yellow color for twenty-
four hours afterward; and though it gradually became
fainter, it was very perceptible even at the expiration of
forty-eight hours."



354 EVENINGS AT THE MICROSCOPE

I am sure you will pardon my interrupting your micro-
scopic gazings for a moment by quoting the following
charming lines by the Kev. Dr. Drummond, which were
elicited by his having watched with pleasure the elegant
form and motions of this little creature.

"Now o'er the stern the fine-meshed net-bag fling,
And from the deep the little Beroe bring:
Beneath the sunlit wave she swims concealed
By her own brightness; only now revealed
To sage's eye, that gazes with delight
On things invisible to vulgar sight.
When first extracted from her native brine,
Behold a small round mass of gelatine,
Or frozen dew-drop, void of life or limb:
But round the crystal goblet let her swim
'Midst her own element and lo! a sphere
Banded from pole to pole a diamond clear,
Shaped as bard's fancy shapes the small balloon
To bear some sylph or fay beyond the moon.
From all her bands see lucid fringes play,
That glance and sparkle in the solar ray
With iridescent hues. Now round and round
She wheels and twirls now mounts then sinks profound,
Now see her, like the belted star of Jove,
Spin on her axis smooth as if she strove
To win applause a thing of conscious sense,
Quivering and thrilling with delight intense.
Long silvery cords she treasures in her sides,
By which, uncoiled at times, she moors and rides;
From these, as hook-hairs on a fisher's line,
See feathery fibrils hang, in graceful twine,
Graceful as tendrils of the mantling vine;
These, swift as angler, by the fishy lake,
Projects his fly, the keen -eyed trout to take,
She shoots with rapid jerk to seize her food,
The small green creatures of crustaceous brood:



JELLY-FISHES . 355

Soon doomed herself a ruthless foe to find,
"When in th' Actinia's arms she lies entwin'd.
Here prison 'd by the vase's crystal bound,
Impassable as Styx's ninefold round,
Quick she projects, as quick retracts again,
Her flexile toils, and tries her arts in vainer
Till languid grown, her fine machinery worn
By rapid friction, and her fringes torn,
Her full round orb wanes lank, and swift decay
Pervades her frame till all dissolves away.
So wanes the dew, conglobed on rose's bud,
So melts the ice-drop in the tepid flood:
Thus too shall many a shining orb on high
That studs the broad pavilion of the sky,
Suns and their systems fade, dissolve, and die."

While we have been admiring our lovely little Cydippe,
and comparing notes with other observers and admirers,
other species as small, as transparent, as sprightly, and
scarcely less elegant, have been impatiently waiting for
their share of admiration; shooting to and fro, tossing
their little bells of ductile glass about, and alternately
lengthening and snatching in their sensitive tentacles, in
astonishment at our stoical indifference to their charms,
and saying, s uo more, with the little urchin whose feelings
were hurt by the neglect of his papa's visitor "You don't
notice how beautiful I be?"

A thousand pardons, sweet little Sarsia! We will now
give you our undivided attention; and for this end we
must take the liberty of catching you and of transferring
your translucency to isolated grandeur in this other glass.
Ha! but you don't want to be caught, eh? And so you
pump and shoot round and round the jar as the spoon
approaches! Truly you are a supple little subject, diffi-
- cult to catch as a flea, and difficult to hold (in a spoon)



356 EVENINGS AT THE MICROSCOPE

as an eel. But here you are at last, lying as motionless
and as helpless in the silver as a half-melted atom of calf's-
foot jelly, to which, indeed, you possess no small resem-
blance.

Look at the pretty little Medusa in his new abode, at
once recovering all his jelly-hood as he feels the water
laving him, and dashing about his new domain with a
vigor which makes up for lost time.

It is a tall bell of glass, a little contracted at the mouth
its outline forming an ellipse, from which about a third
has been cut off. The margin of this bell carries four tiny
knobs, set at equal distances, and thus quartering the
periphery; and these are the more conspicuous because
each one is marked with a bright orange-colored speck.
Physiologists are pretty well agreed to consider such specks
as these, on the margins of the smaller Medusce, as eyes
rudimentary organs of vision, capable, probably, of ap-
preciating the presence and the stimulus of light, without
the power of forming any visual image of external objects.
You will not gain much information about their function
from microscopic examination; for all you can discern
is an aggregation of colored specks (pigment-granules)
in the midst of the common jelly.

The knobs, however, are connected with other organs;
for from each of them depends a highly sensitive and very
contractile tentacle. Sometimes one, or more, or all, of
these organs hang down in the water motionless, lengthen-
ing more and more, especially when the bell is still, until
they reach a length some twelve or fifteen times that of
the bell, or umbrella. Then suddenly one will be con-
tracted, and, as it were, shrivelled, to mere fragments of
a quarter of an inch long; then lengthened again to an



JELLY-FISHES 357

inch or two; then shortened again. Now the little bell
resumes its energetic pumping, and shoots round and
round in an oblique direction, the summit always going
foremost, and the tentacles streaming behind in long trail-
ing lines. Now it is again arrested; the bell turns over
on one side and remains motionless, and the tentacles, as
"fine as silkworms' threads," float loosely in the water,
become mutually intertangled, instantly free themselves,
pucker and shrivel up, slowly lengthen, and hang motion-
less again, or, as the bell allows itself to sink slowly, are
thrown into the most elegant curves and arches.

Though these tentacles look at first like simple threads
of extreme tenuity, yet when viewed closely they are seen
to be composed of a succession of minute knobs separated
by intervals like white beads strung on a thread; the
beads being more remote from each other in proportion as
the tentacle is lengthened.

This structure is worthy of a more minute investiga-
tion. We will, therefore, confine our little Sarsia in this
narrow glass trough, which is sufficiently deep to allow its
whole form to be immersed, though somewhat flattened;
which is an advantage, as its movements are thereby im-
peded. Now, with a power of 300 diameters you see that
each of the knobs of the tentacle is a thickening or swell-
ing of the common gelatinous flesh, in which are imbedded
a score or two of tiny oval vesicles, without any very ob- .
vious arrangement; but for the most part so placed that
the more pointed end of each is directed toward the cir-
cumference of the thickening. The intermediate slender
portions of the tentacle the thread on which the beads
are strung; is quite destitute of these vesicles.

These little bodies are called cnidce, and, in the whole



358 EVENINGS AT THE MICROSCOPE

of this class of animals, and also in that of Zoophytes,
they play an important part in the economy of the creat-
ure. I shall probably take occasion to exhibit them to
you under conditions more favorable than are presented
here; viz., in the Sea-anemones, where they attain far
greater dimensions; and therefore I will merely say here
that each one of these tiny vesicles carries a barbed and
poisoned arrow, which can be shot forth at the pleasure of
the animal with great force, and to an amazing length
that hundreds are usually shot together and that this is
the provision which the All- wise Glod has given to these
apparently helpless animals for securing and subduing
their prey.

There is, however, another organ still more conspicu-
ous in our little tiarsia, of which I have not yet spoken.
As the whole animal has the most absolute transparency,
we see that the roof of the bell is much thicker than the
sides, and that it gradually thins off to the edge. The in-
terior surface is called the sub-umbrella, and it carries
within its substance four slender tubes, which, radiating
from the centre of the roof, proceed to the margin, where
they communicate with another similar canal which runs
round the circumference, sending off branches into the
tentacles. This is the circulatory system; and you may
see, with the magnifying power which you are at present
using, that a clear fluid is moving rapidly within all these
canals, carrying minute granules; not with an even for-
ward current, but with an irregular jerking vacillating
movement, as if several conflicting eddies were in the
stream. Yet we discern that, on the whole, the granules
are moved forward; passing from the centre of radiation
toward the margin, when we see them slip into the mar-



JELLY-FISHES



359-



ginal canal from the several mouths of the radiating
canals.

This is a very simple and rudimentary blood-system.
There is here no heart with its pulsations, no proper ar-
teries or veins, no lungs for oxygenation; but the prod-
ucts of digestion are themselves thus circulated through
the system. And this brings me back to the central
point, whence you see depending the curious organ I
spoke of. A long cylinder of highly
movable and evidently sensitive flesh,
hangs down from the middle of the
roof exactly like the clapper of a
bell; and % as if to add to the re-
semblance, this, same clapper is sus-
pended by a narrow cord, and is
terminated by a knob.

Sometimes this whole organ is
allowed to hang about as low as the
edge of the bell; then it gradually
lengthens to twice, thrice, nay to
five times that length; the tongue
lolling out of the mouth to a most
uncouth distance, and even the sus-
pending cord (as I presume to term
the attenuated basal portion) reach-
ing far beyond the margin; then, on
a sudden, like the tentacles, the
tongue is contracted, thrown into wrinkles, curle'd into
curves, and the whole is sheltered within the concavity;
presently, however, to loll out again.

This proboscis-like organ is called the peduncle, and
its office is that of a stomach, of which the knob at the




SARSIA.



360 EVENINGS AT THE MICROSCOPE

end is the mouth, having a terminal orifice with four mi-
nute lips. The flexible substance and rapid motions of
this peduncle are suited to enable it to seize small pass-
ing animals that constitute its prey; and I have seen the
Sarsia in confinement seize with the mouth, and swallow,
a newly-hatched fish, notwithstanding the activity of the
latter. For hours afterward, the little green-eyed fry was
visible, the engulf ment being a very slow process; but the
Medusa never let go its hold; and gradually the tiny fish
was sucked into the interior, and passed up the cavity of
the peduncle, becoming more and more cloudy and indis-
tinct as digestion in the stomach dissolved its tissues.

The greater portion of the food is by and by dis-
charged from the mouth, the fluids which have been ex-
tracted from it being on the other hand carried up through
the base of the peduncle, and distributed along the four
radiating vessels, conveying nutrition, supply of waste,
and growth to all parts of the system.

We may now liberate our little Sarsia, with thanks for
the gratification he has afforded us, to resume his active
play among his many companions. Meanwhile we will
look for one of another kind among the group.

Here is a pretty and interesting species. Active it is,
but less vigorously rapid in its movements than either the
Beroe or the Sarsia. It is, as you see, something less
than a hemisphere, or resembling a watch-glass in shape,
about three -fourths of an inch in diameter. In general
character it resembles the Sarsia, but the peduncle is
small, never reaching to the level of the margin, and its
mouth is terminated by four expanding fleshy lips, which
are extremely flexible and versatile.

The four radiating vessels here carry, just before they






JELLY-FISHES 361

merge into the marginal canal, a dilatation of the Common
flesh, which, as you see, bulges out the surface of the
umbrella. We will examine one of these dilatations with
the microscope.

It is, as you perceive, occupied by a number of clear
globes, each of which has another minute globose body in
its interior. They are very diverse in size, some being
very small, others comparatively large, and it is to the
dimensions of these latter that the swelling of the surface
of the umbrella is due. These vesicles are the eggs of
the animal considerably advanced toward maturity; and
the dilatations around the radiating vessels are the ovaries.

The margin, however, presents us with the most obvi-
ous, and perhaps the most interesting, points of diversity
from the little Sarsia. In the little beauty before us
whose name, by the way, Thaumanlias pilosella, I have
not yet told you the outline is fringed with about fifty
short and slender tentacles, each of which springs from a
fleshy bulb, in which, is set a speck of deep purple. These
collections of colored granules, which I have already ex-
plained to be rudimentary eyes, have a very charming
effect, and give a beautiful appearance to the little creat-
ure, as if its translucent crystalline head



Online LibraryPhilip Henry GosseEvenings at the microscope (Volume 1) → online text (page 24 of 32)