Philip Henry Gosse.

Evenings at the microscope (Volume 1) online

. (page 30 of 32)
Online LibraryPhilip Henry GosseEvenings at the microscope (Volume 1) → online text (page 30 of 32)
Font size
QR-code for this ebook


as difficult to assign to it a definite size as a definite
shape. It seems to be the E. sanguinea, so called because
it is said to occur sometimes of a deep red hue, and in such
vast profusion, as to give the waters the appearance of
blood. I have never seen it, however, other than as it
now appears, rich emerald green in the body, with the two
extremities perfectly clear and colorless. I might perhaps



INFUSORIA

describe its ordinary form as spindle-shaped, with a pointed
tail, and a blunt, rounded head; but it is remarkable for
the variableness of its shape. It is capable of assuming
an appearance very diverse from what it had half a minute
before, so that you would hardly identify it, if you were
not watching its evolutions. Whether this ability to prove
an alias be at all dependent on the remarkable clear-headed-
ness of the subject, I leave for you who are skilled in meta-
physics to determine. Away they go tumbling over and
over, revolving on the long axis as they proceed, which
they do not very rapidly, with the blunt extremity for-
ward.

Here is another form, a little larger than the former,
but much more slender; yet from the slowness and steadi-
ness of its movement more easy of observation. It is
named E. acus, or "the Needle Euglena." This is an
animalcule of great elegance and brilliance; its sparkling
green hue, with colorless extremities, and its rich pale
crimson eye, are very beautiful. It commonly swims ex-
tended, with a slow gliding motion, turning round on its
long axis as it proceeds, as may be distinctly seen by the
rotation of certain clear oblong substances in its body.
These then are seen not in the interior, but near the sur-
face, as they would appear if imbedded in the flesh around
a hollow centre. The interior is* probably not hollow, but
occupied with pellucid sarcode. These were assumed by
Bhrenberg, but on no adequate grounds, to be organs con-
nected with reproduction. They vary in number in differ-
ent individuals, and those which contain the greatest num-
ber are thereby more swollen. They appear to be separated
into two series, one anterior, the other posterior. The ani-
mal is capable of bending its head and body in various



438 EVENINGS AT THE MICROSCOPE

directions, but is most beautiful when straight. The front
is furnished with a slender thread-like proboscis. This
species affords us a good opportunity of observing the red
spot which, for convenience' sake, we may still term an
eye. It seems to be an irregular oblong vacuole, or ex-
cavation in the sarcode, filled with a clear ruby -red fluid.
The red spot in the ftotifera is connected with a well-
defined crystalline lens, whose definite form, and high re-
fractive power, may in many cases be distinctly marked;
but here nothing of the kind is seen; the spot itself has
no certain shape, and does not appear to be bounded by a
proper wall. Some forms, which are by general consent
admitted to be plants, have similar spots; and hence it
has been, rather too hastily, I venture to think, concluded
that they can have no connection with vision. I think, it
still possible that a sensibility to the difference between
light and darkness may be the function of the organ.

I have found that this animal, when allowed to dry on
a plate of glass, retains its form and color perfectly; but
in about two days the eye-spot, which at first becomes
much larger in the drying, gradually
loses all traces of its brilliant color,
probably by the evaporation of the
contained fluid.

Another pretty species you see
THREE-SIDED EUGLENA. gliding along among the rest, called
E. triquetra, or the Three-sided. It bears a resemblance
to a broad rounded leaf, with the foot- stalk forming a short
transparent point, and the mid-rib elevated into a sharp
ridge. The under side seems slightly concave. This is
equally attractive with the others. It is persistent in form,
and appears not to be even flexible. Its motion is slow,




INFUSORIA 439

and as it goes it rolls irregularly over and over in all
directions, not revolving on its long axis, and thus giving
you very satisfactory views though only momentary of
the keel with which the back is furnished. It is in the
turnings of such minute creatures that the microscopist
often gets a glimpse of peculiarities of form which a view
of the animal when in repose, however long continued,
fails to reveal. Longitudinal interrupted lines are seen
running down the body of this pretty leaf, which do not
appear to mark irregularities of the surface, and there-
fore are probably internal. Ehrenberg calls these and
similar collections of granules "ova," or eggs; but this
is to cut the knot, instead of untying it. There is
no sufficient reason to believe that these animals increase
by ova.

About the front of all these EuglencB, you may discern
now and then a slight flickering or quivering in the water.
The power we are using, though best for the general dis-
play of the form, is insufficient to resolve this appearance:
I will put on a higher objective. You now see that there
proceeds from the frontal part of the body a long and
very slender filament, which is whisked about in the man-
ner of a whiplash. This is considered to be the organ of
locomotion; but I rather doubt that such is the function;
the smooth and even gliding, often rotating, of the creat-
ure, seems more like that produced by minute and gener-
ally distributed cilise than that caused by the lashings of
a single long thread.

Yet two more species of this extensive genus we dis-
cern in this well-stocked drop of water. They have re-
ceived the appellations of the Pear (E. pyrum), and the
Sloth (E. deses). The former is the most minute we have



440 EVENINGS AT THE MICROSCOPE

yet seen, and seems to be scarce; but it is highly curious
and interesting in appearance. It much resembles, in out-
line, a fish of the genus Batistes; the muzzle being some-
what protruded and truncate, and the form rhomboidal; it
terminates in a slender pointed tail. The body is obliquely
fluted, which gives a very singular effect; for from the
transparency of the tissues the lines of the opposite side
can be discerned crossing those next the eye, and dividing
the animal into lozenge-shaped areas. The color is spark-
ling green, but the tail and the edges of the body are clear
and colorless: and there is a bright red eye. At other
times this Euglena takes the form of a claret- bottle, or
an oil-flask; the muzzle being broadly truncate, or even
indented.

Its motion is rapid; a swift gliding in the direction of
its long axis; it turns continually on the same axis, which
gives a waving irregularity to its course; and has a pretty
effect from the continual crossing of the flutings in the
revolving. This specimen is about T^h of an inch in
length, including the tail.

EugUna deses is much larger, being about 8 forth of an
inch in length, though the tail is very short. It has a
thick body; with a round blunt head; it tapers suddenly
to the tail. Its color is bright green with a red eye; but
the presence of an infinite number of irregular oblong
granules and lines, with several globular vesicles, gives
an opacity and a blackness to its appearance. In manner
it is sluggish; it never swims or glides gracefully and
swiftly among its playful congeners, but contents itself
with twining slowly among the floccose stems and filaments
of the water-plants, or crawls upon the surface of the live-
box. It does not appear to change its form, otherwise



INFUSORIA 441

than its soft and flexible body necessitates, as it twines
about.

But enough of the Euglenas. For I have just caught
sight of a still more curious creature, the Swan Animal-
cule (Trachelocerca olor). It is reposing on one of the
leaves of the Myriophyllum, its long and flexible neck
lengthening and contracting at pleasure, the tip thrown
about in quick jerks, in every direction, somewhat like a
caterpillar when it touches several points impatiently with
its head.

If we admire the graceful sailing of a swan upon a
lake, the swelling of its rounded bosom, the elegant curves
of its long neck, we shall be struck with the form and
motion of this animal. The form has much resemblance
to that of a swan, or still more to that of a snake-bird
(Plotus); the body, swelling in the middle, tapers grad-
ually into a slender pointed tail at one extremity, and at
the other into a very long and equally slender neck, which
is terminated by a slight dilatation. The whole is perfectly
transparent, but the body is filled with numerous minute
globular vessels, or temporary stomachs. The grace of its
motion as it glides along with a free and moderately swift
progression through the clear water, or winds through the
intricate passages of the green conferva, throwing its long
neck into elegant curves, is very remarkable. There are,
I see, two of them, which, however, take no notice of each
other, even when passing close to each other; the neck of
one is much longer than that of the other. Now and then,
when gliding along, the neck is suddenly contracted, but
not wholly, as if something had alarmed or displeased the
animal: the body also can be swollen or lengthened at
pleasure; it can move in either direction, but the neck



442 EVENINGS AT THE MICROSCOPE

usually goes foremost, extended in the direction of the
motion, and seems to be used to explore the way.

I had once an opportunity of seeing the process of in-
crease by spontaneous self-division in this creature. It
was an unusually large specimen, found in an old infu-
sion of sage leaves. When I discovered it, it was darting
about its long neck in the most beautiful contortions. As
it was partly hidden by the vegetable fibres present, I
partly turned the glass cover to alter the position of the
contents. On again looking, the Swan was in a clear part
of the field, but in the form of a dark globose mass, the
neck being entirely contracted. It was quite still, except




SWAN-NECK AND ITS DIVISIONS.



a continual slight alteration of the form by the protrusion
or contraction of parts of the outline. The body seemed
full of minute globules, set in a granular mass of a black-
ish hue, and the outline was not a continuous line, but
formed a multitude of rounded elevations. Presently it
protruded the clear neck, but only for a short distance,
and then retracted it as before; when the only indication
of the presence of this organ was a depression in one part
of the surface, somewhat like the mouth of a closed Ac-
tinia, where there was a slight but incessant working, very
much like the irregular motion on the surface of boiling
water, in miniature; there was also an indistinct ciliary



INFUSORIA

action at this part, not of rotation, nor of vibration, but a
sort of waving. At this point I had occasion to get up
from the table, and though I was not away more than a
minute, on my return I observed a strong constriction
around the middle of the body. It was transverse, for
the depressed and ciliated mouth was at a point exactly at
right angles to the constriction. From the depth to which
this latter extended in so few minutes, I supposed the
process of separation would be very rapid; for I could
very soon see a line of light all across at intervals, and
the two halves seemed to slide freely on each other. Yet
they remained long without much apparent progress, or
even change, except that the anterior half at one time
threw forth its neck a short distance; at this time it
looked extremely like a bird, bridling up its lithe neck
and swelling bosom; while, to make the resemblance per-
fect, it began to imitate the action of a fowl picking up
grain, bobbing its head hither and thither; so curious are
the analogies of nature! Along the dividing line there
had appeared, very early in the posterior half, a distinct
ciliary action ; after a while (how, I do not exactly know),
without the general relation of position being ehanged, the
mouth of the anterior (which must now be called the old)
animal appeared on the side, and at the point correspond-
ent in the other a similar ciliary wreath appeared, while
the action along the dividing line was no longer seen. So
that the division which was at first transverse now ap-
peared longitudinal. I believe, however, the animals were
really separated before this, though they remained in con-
tact; for as they slid over each other it was manifest that
each had an independent action.

At length, about an hour and a half after the first



444 EVENINGS AT THE MICROSCOPE

appearance of the constriction, the new animal threw out
its clear neck to a great length, writhing it about with
rapid agility, and forming the most elegant curves, like
those of a serpent, often completely encircling its own
body with it. It still remained, however, in contact
with its parent, which, after a time, also protruded its
neck in the same manner. Both then retracted and re-
mained still for a while; and again, almost simultane-
ously, threw out their long necks, and again retired to
sluggish repose.

Among the sediment, the grains of which are driven
hither and thither by their spasmodic jerking movements,
you see several individuals of another sort of creatures
the Chrysalis Animalcule (Paramoecium aurelia). This
is a "whale among minnows"; for it is greatly larger than
any of those we have yet observed; and is just visible to
the naked eye, when we hold up the live -box obliquely
against the light; for then the animals appear as the small-
est possible white specks.

Bringing them again under the microscope, each pre-
sents a pellucid appearance, and an oblong figure, of which
the fore part is somewhat narrowed. The back rises in a
rounded elevation; and the mouth is situated as far back
as the middle of the body upon the under surface, where
its position is marked by a sort of long fold, the sides of
which are fringed with long cilia, whose vibrations are
very marked. The whole surface, on both sides, is cov-
ered with minute cilia, arranged in longitudinal rows, of
which, according to the great Prussian professor, there are
from thirty to sixty on each surface, each row bearing
sixty or seventy cilia. This must be considered as an
approximation ; for we may well doubt the accuracy of the



INFUSORIA -M5

counting, when the objects are so very evanescent as these
vibrating cilia.

The vacuoles, and the temporary stomachs, more or
less completely filled with the brown and green food, which
the animals are collecting from the decayed vegetable
matters, are sufficiently numerous and conspicuous; but
they may be rendered still more so by the device of mix-
ing a little carmine with the water. The ciliary currents
are thus instantaneously rendered strikingly visible. The
crimson atoms are attracted from all quarters toward the
tail of the animal, whence they are urged in a rapicj. stream
along one side toward the head, around which they are
hurled, and then down the other side to the tail, pouring
off in a dense cloud in a direction contrary to that in which
they originally approached.

But now the gathered currents have produced their
expected result; for many of the globular vacuoles are
already become of a beautiful rosy hue, from the minute
particles of the pigment which have been whirled to the
mouth, and swallowed.

The feature of greatest interest, however, in this animal
is the contractile bladder. Two of these organs are usually
seen co-existent in each individual; placed, the one on the
front, the other in the rear of the mouth, but near the
opposite i.e., the dorsal surface of the body; for as
the creature slowly revolves on its longitudinal axis, the
3ine of the vesicles alternately approaches and recedes
from that of the mouth. They are remarkable for their
structure. Far from the simplicity in which the organ
is usually presented to us in the animals of this class, the
contractile bladders are here very complex. Each when
distended is globular; and it is surrounded by a number



446 EVENINGS AT THE MICROSCOPE

of others of much smaller dimensions, and of a drop-like
form, so set as to radiate round the principal vesicle as a
centre, the rounded portion of each in apparent contact
with the vesicle; and the slender extremity running off
as an attenuated point till lost to sight in the sarcode.
The main vesicles alternately become distended, and sud-
denly contract to a point; while the radiating cells are
continually varying in size, though in a less degree. It
is customary to describe the secondary vesicles as coming
into view at the instant of the contraction of the primary
one, and to suppose that the emptying of the one is the
filling of the other; but I have not been able to observe




PARAMCECIUM.



this mutual relation satisfactorily made out. The smaller
as well as the larger vesicles are conspicuous from their
colorless transparency; for the general sarcode of the body,
though pellucid, is only so in the same degree as glass,
slightly smoked; besides that its clearness is often im-
paired by crowds of granules and minute globules.

You ask what is that comparatively large oval body
attached by its side to one of the leaves of the plant. It
is the egg of some considerable Kotifer, probably Euchla-
nis, which is always glued to some filament or stem of
a water-plant. It may interest you to watch the progress
of the contained embryo, which you can readily do, since
the egg-shell is as transparent as glass, and the infant ani-
mal already displays the movements of independent life.



INFUSORIA 437

Meanwhile I will tell you the tragical and lamentable his-
tory of just such an embryo as this, that was eaten up
before it was born, under my own eye. One of the depre-
dators was a very amusing animalcule, which is sufficiently
scarce to make its occurrence a thing of interest, especially
to a young microscopist, as I was at the time.

A large egg of (as I believe) Euchlanis dilatata had
been laid during the night on a leaf of Nitella, in the live-
box. When I observed it, the transparency of the shell
allowed the enclosed animal to be seen with its viscera;
which occasionally contracted and expanded; the place
of the mastax I could distinctly make out. The cilia were
vibrating, not very rapidly, but constantly, on the front,
where there was a vacant space between the animal and
the shell. From 7 A.M., when I first saw it, I watched
it for about eight hours, without perceiving any change;
but at that hour, having with-
drawn for a short time, I per-
ceived on my return that a
portion of the animal was out-
side the shell. The appear-
ance was that of a small col-
orless bladder oozing out at
an imperceptible aperture; and
this oval vesicle quickly but
gradually increased, until it COLEPS AND CHILOMONAS -

was half as large as the egg itself. A little earlier than
this point, the cilia were seen on the front or lower side
of the excluded portion, and these began to wave lan-
guidly in a hooked form. They thus seemed much longer
and more substantial than when rotating in the perfect
animal. When excluded to the extent just named, some




448 EVENINGS AT THE MICROSCOPE

little creatures that were flitting about found it, and began
to assemble round it. These were far too rapid in their
movements to allow me to identify them before, or to per-
ceive anything else than their swift motion and oval form;
but this attraction causing them to become still, allowed
me to perceive their singular and beautiful structure. Each
consists of an oval vase open at the top, the margin of
which is cut into a number of little points; the sides are
marked by a series of ribs, which run down longitudinally,
and are crossed by other transverse ones; the rounded
bottom is furnished with three short points; so that the
whole reminded me of a barrel with its staves and hoops,
set on a three-legged stool. Within the body, which is
colorless, are seen small dark spots, which are probably
the stomach- vacuoles. Thus I identified these little bar-
rels with Coleps hirtus of Ehrenberg, but I found no record
of their carnivorous propensities. One after another
whirled into the field, and after a few gyrations became
stationary at the head of the half -born Euchlanis, just as
I have seen vultures gather one by one to a carcass. Yery
soon there were a dozen or fifteen of them, some of which
were ever shifting their places, and some were playing
around, or revolving on their longitudinal axis. I found
that their object really was to prey on the soft parts of
the creature just excluded from the egg; for by carefully
watching one, I distinctly perceived particles of the flesh
fly off, as it were, and disappear in the body of the Coleps.
The appearance was that of steel-filings drawn to a magnet,
for the mouth of the Coleps was not in actual contact with
the flesh; and therefore, I suppose, the surface having
been in some way ruptured (which I could see it was),
the loose gelatinous atoms were sucked off by a strong



INFUSORIA 449

ciliary current. They did not attack any other part, and
*fter having continued their murderous occupation about
ten minutes, they one by one departed. The ciliary mo-
tion of the Euchlanis ceased immediately after it was first
attacked, and I suppose it was soon killed, for it did not
increase in size in the least afterward. When the Colepes
left it, a great portion, perhaps a third, of the excluded
parts was devoured.

As soon as the depredators were gone, or even before,
others more diminutive, but more numerous, were ready
to take their place. The drop of water under review had
been found amazingly full of a small Monas, perfectly
transparent, of an oval form, with some granules visible
in the interior. They were about srJWth of an inch in
length. They filled the whole field, gliding about very
nimbly, but so close as but just to allow space for motion,
and that in several strata. By the morning these were
collected in masses, which, to the naked eye, looked like
little undefined white clouds, but which under the micro-
scope showed the Monads in incalculable multitudes, but
for the most part in still repose. Some were still moving
to and fro, however, and, in the course of the day, most of
them became again active. As soon as the Colepes had
forsaken their prey, the Monads began to gather around
it, cleaving to the same parts, and apparently imbibing the
juices; for the extruded parts still slowly decreased, until
at length these were reduced to about one-third of their
original dimensions.

A close examination of these latter, when they had set-
tled to rest, showed me that they were of the species Chilo-
monas paramcecium. There is an indentation on one side
of the front, where the mouth is situated; here there is a



450 EVENINGS AT THE MICROSCOPE

ciliary action; the projecting part, called the lip, is said
to be furnished with two -slender flexible proboscides; but
my power was not sufficient to discern any trace of these.
A sort of a ridge, or keel, runs down the length of the
body, perceptible by a slight line; numbers of stomach
cells also are perceptible. The motion of these lip -monads
was not very rapid when unexcited; it is performed by
a sort of lateral half-roll, the two sides alternately being
turned up, like a boat broadside to a swell, and the line
of progression is undulating.

And now having pretty well exhausted the contents of
this live-box, let us try a dip from this other phial from
another locality, equally productive, if I am not mistaken.
Yes; for, to begin, the stalks of Nitella here are fringed
with populous colonies of the most attractive of all the
Infusoria, the beautiful Vorticellce. The species is not
the common bell-shaped one, but the smaller with pursed
mouth, the little V. microstoma.

Look at this active group, consisting of a dozen or so
of glassy vases, shaped something like pears, or elegant
antique urns, elevated on the extremities of long and very
slender stalks, as slender as threads, and about six times
as long as the vases. The stalks grow from the midst of
the floccose rubbish attached to the plant, and diverge as
they ascend, thus carrying their lovely bells clear of one
another.

Each vase is elegantly ventricose in the middle, termi-
nating below in a kind of nipple to which the stalk is
attached, and above in a short wide neck with a thickened
rim. This last is highly sensitive and contractile ; its inner
edge is set round with a circle of vi bra tile cilia, which,
when in full play, produce a pair of small circular vortices



Online LibraryPhilip Henry GosseEvenings at the microscope (Volume 1) → online text (page 30 of 32)