of instruments, which in figure and motion resemble wheels. It appears
only as a living creature when immersed in water; notwithstanding which,
it may be kept for many months out of water, and in a state of perfect
dryness, without losing the principle of life. When dry, it is of a
globular form, about the size of a grain of sand, and without any
apparent signs of life. If it be put into water, in the space of half
an hour a languid motion begins, the globule turns itself about,
lengthens itself by slow degrees, and becomes very lively; in a short
time it protrudes its wheels, and swims about in search of food; or
else, fixing itself by its tail, brings the food to it by its rotatory
organs, which throw the whole circumjacent fluid into a violent
commotion; when its hunger is satisfied, it generally becomes quiescent,
and sometimes resumes its globular form.
If the water that is found standing in gutters of lead, or the sediment
it has left behind, has any appearance of a red or a dark brown colour,
little doubt need be entertained of its containing these animalcula. In
the summer season, if a small quantity of this dust be put into water,
and placed under a microscope, it seldom fails of discovering a great
number of minute reddish globules, which are, in fact, the animals
themselves. It will be best to view them first with the third or fourth
magnifiers, and afterward apply those possessing greater powers.
The motions of this little creature somewhat resemble those of a
caterpillar; like many of those insects, removing itself from place to
place by first fixing the tail to some substance, then extending the
whole body, fixing the head, and afterward drawing the tail to it; by
these alternate actions it moves with some degree of swiftness.
This animal frequently changes its appearance, and assumes a very
different form; for, the snout being drawn inwards, the fore-part
becomes clubbed, and immediately dividing, exhibits to our view two
circular instruments set with minute hairs, that move very briskly,
sometimes in a rotatory, at other times in a kind of trembling or
vibratory manner. An aperture or mouth is also perceived between the
two semicircles; whilst in this state, the animal may often be perceived
swimming about in pursuit of food.
The most distinguishing parts of this animalculum are, the head, the
thorax, and the abdomen. It differs from any other creature hitherto
described in the wonderful form and structure of its head; the sudden
changes of which from one form to another are equally surprizing and
singular; from being of a very taper form, it becomes almost
instantaneously as broad as any part of its body, and protrudes an
amazingly curious machinery formed to procure its food.
The circular bodies which project from the animal have much the
resemblance of wheels, appearing to turn round with considerable
velocity, by which means a very rapid current of water is brought from a
great distance to its mouth. As these wheels are very transparent, the
edges excepted, which are set with fibrillæ, as cogs to a wheel, it is
difficult to determine how the rotatory motions are performed, or
whether their figure be flat, concave, or conical; be this as it may,
they are protruded from a couple of tubular cases, into which they can
be again withdrawn, at the will and pleasure of the animal. They do not
always turn the same way, nor with the same degree of velocity,
sometimes moving in opposite directions, at other times both one way.
The figure varies according to the degree of their protrusion, as well
as from other circumstances. They appear occasionally like minute oblong
squares, rising from the periphery of a circle; at other times they
terminate in sharp points, and sometimes they are curved, bending the
same way like so many hooks; now and then the ends appear clubbed, or in
resemblance like a number of small mallets.
When the fore-part of this creature is first seen to open or divide, the
parts, which when fully protruded resemble wheels, seem only like a
couple of semicircles, the edges of which are set with little spiculæ,
having a nimble, and continually vibrating motion upwards and downwards,
for the purpose of agitating the water, each wheel being in this case
doubled, or like a round piece of paper folded in the middle.
When the wheels are in motion, the head appears very large in proportion
to the size of the animal; and though it is then everywhere transparent,
yet a ring or circle, more particularly distinguished by its brightness,
may be perceived about the middle of the forehead, from whence many
vessels are seen to originate.
The thorax or breast is united to the head by a short annular circle or
neck; the size of the thorax is nearly one-sixth part of the whole
animalculum. In it the heart is distinctly seen; being placed nearly in
the center, the diastole and systole cannot fail to attract the eye of
every attentive observer; the alternate dilatation and contraction is
very perceptible through the back of the animal, being performed with
great strength and vigour. It appears to be composed of two semilunar
parts, which in the time of contraction approach each other laterally,
and form between them a figure somewhat like a horse-shoe, whose upper
side is flat, the under one convex. In the diastole, these two parts
separate; the separation begins exactly in the middle of the lower part
next the tail. In each of the semilunar parts there is a cavity, which
closes when they come together; and opens when they separate.
The motion of the heart is communicated to all the other parts of the
thorax, and indeed through the whole animal. It is necessary however to
remark, that this motion is sometimes suspended, or at least quite
imperceptible, for two or three minutes, after which it re-commences,
and goes on with the same vigour and regularity as before. From the
under part of the thorax a small transparent horn proceeds, which cannot
be seen unless the insect turns on its back or side.
Below the thorax there is an annular circle that joins the thorax to the
abdomen; this is considerably the largest part of the animal, and
contains the stomach and viscera. When full of food, the intestines are
opake, and of a crimson colour, extending from the thorax quite through
the abdomen and a great part of the tail, exhibiting a fine view of the
peristaltic motion, or those gradual contractions and dilatations of the
intestines, which propel their contents downwards. Numerous
ramifications of vessels, both longitudinal and transverse, surround the
intestines. The abdomen is not only capable of contraction, but also
admits of such a degree of extension, as to form a case for all the
other parts of the body. The tail extends from a joint at the lower part
of the belly to the posterior extremity; it is of a tapering form, and
consists generally of three joints; when the animal is inclined to fix
itself to any thing by the tail, it thrusts out four, sometimes six,
little hooks from the extreme part; these are placed in pairs, one at
the very extremity itself, the other two a little way up the sides; the
three pair are seldom seen at the same time. The wheels appear to be the
organs used by the animal to assist it in swimming.
All the actions of this creature seem to imply sagacity and quickness of
sensation; at the least touch or motion in the water, they instantly
draw in their wheels. Baker conjectures that they have eyes lodged near
the wheels, because while they are in the globular or maggot state,
their motions are slow and stumbling; but after the wheels are
protruded, they are performed with great regularity, swiftness, and
steadiness. Can we sufficiently admire the wonderful contrivance in the
apparatus of this animal? a being so diminutive, as not to exceed in
size a grain of sand!
Plate XXVI. Fig. 17, represents the wheel animal in what Baker calls the
maggot state; while in this form small spiculæ are seen to dart out near
the anterior part; the snout is sometimes more, at other times less
acute than in this delineation. _a_, a small horn near the thorax.
Fig. 15 represents its manner of moving from place to place, while in
the maggot state. _a_, the projecting horn.
Fig. 12 exhibits it with the two semicircular parts, _a a_, protruded,
and in the posture in which it places itself, when preparing to swim
about, or going to set its wheels in motion.
Fig. 1 shews the head at its full extent, and a couple of small bodies,
_a a_, on the top of it, armed with small teeth, _b_, like those of the
balance-wheel of a watch.
At Fig. 18 the interior parts are more particularly exhibited. _a_, the
circle from which many vessels originate; _b_, the thorax or breast,
joined to the head by the neck, _c_; the part which is supposed to be
the heart is plainly seen at _d_; the abdomen, _f_, is separated from
the breast by a ring, _e_; _g_, the tail.
Fig. 19 exhibits the animal not fully extended, though with its wheels
in motion.
Fig. 20 shews it with its side towards the eye; in this position one of
the wheels, _a_, appears to lie considerably below the other.
Fig. 6 and 16 represent two of these creatures in the postures in which
they are frequently seen when the wheels are not protruded, but with the
fibrillæ, _a b_, vibrating quickly.
Fig. 2 exhibits the animal with the body nearly drawn into the abdomen;
at Fig. 21, the body still further drawn in; at Fig. 22, as it appears
with the tail partly drawn in; at Fig. 23, in a globular form, but still
adhering by the tail.
Sometimes, when in the maggot form, it rolls its head and tail together,
without drawing them into the body; as represented at Fig. 14.
Baker has also described three other species, one of which, differing
only from the preceding in having a very long tail, is represented at
Fig. 7.
Fig. 11 is another kind, with crustaceous spiculæ, _b_, at the
fore-part; within this, at _c_, an opake oval body may be seen, which
has been taken for an egg.
Fig. 3 is another kind; it has two projecting points, _a a_, from the
tail, and the head furnished with a number of fibrillæ, _b b_.
Fig. 13 represents another species, described by Spallanzani.
Plate XXVII. Fig. 46, 47, 48, 49, represent the wheel animals seen and
delineated by Müller. _a_, the head; _b_, the eyes; _c_, a small horn;
_d_, the rotatory organ; _e_, the tail; _f_, the points of the tail.
324. VORTICELLA FURCATA. V. cylindrica, apertura integra, cauda
longiuscula bifida. Cylindrical vorticella, the aperture undivided, the
tail rather long, and divided into two parts.
A cylindric body with a rotatory organ, consisting of a row of hairs at
the apex; the tail is divided into two parts turning a little inwards.
When at rest, it joins the segments of the tail; but opens them when in
motion. It is generally found in common water.
325. VORTICELLA CATULUS. V. cylindracea, apertura mutica, cauda
perbrevi, reflexa, bicuspi. Plate XXVII. Fig. 50. Cylindrical
vorticella, the aperture plain, the tail short, bent back, and divided
into two points.
It is a little thick muscular animalculum, folding itself up; of an
equal breadth throughout, the body disfigured by longitudinal folds
winding in various directions; the anterior part or head is connected to
the body by a little neck, and it occasionally exhibits a very minute
rotatory organ. The tail, _e_, is short, terminating in two very small
bristles, _d_, which are exposed or concealed at pleasure; the
intestines ill-defined. Its motion is rotatory, but in different
directions. It is commonly found in marshy waters.
326. VORTICELLA CANICULA. V. cylindracea, apertura mutica, cauda brevi,
articulata, bicuspi. Cylindrical vorticella, the aperture plain, with a
short articulated tail divided into two pointed parts.
327. VORTICELLA FELIS. V. caudata, cylindracea, mutica, cauda spinis
duabus longis terminata. With a tail, cylindrical, beardless, the tail
terminating in two long spines.
The body is large, the apex of an equal thickness, obtuse, with rotatory
filaments; the tail acute, with two pellucid spines, in length about
one-third part of the body, alternately separating from and approaching
each other.
328. VORTICELLA STENTOREA. V. caudata, elongata, tubæformis limbo
ciliato. Long-tailed vorticella, trumpet-shaped, the arms furnished with
rows of short hairs. See this fully described by the name of hydra
stentorea, in page 392.
329. VORTICELLA SOCIALIS. V. caudata, aggregata, clavata; disco obliquo.
A description of this vorticella has also been given, as hydra socialis,
in page 395.
330. VORTICELLA FLOSCULOSA. V. caudata, aggregata, oblongo-ovata, disco
dilatato pellucido. Plate XXVII. Fig. 51 and 52. With a tail aggregated,
of an oblong oval shape, with a dilated pellucid disc.
To the naked eye it appears as a yellow globule, adhering to the
ceratophyllum, or common horn-wort, Fig. 52, _a_, like a little flower;
or a heap of yellow eggs, _b_. With the assistance of the microscope
they are discovered to be a congeries of vorticellæ, constituting a
sphere from a mouldy center. They contract or extend their bodies either
when alone or associated, and excite a vortex in the water by means of
the disc. When they quit the society, and act singly, their parts may be
more readily distinguished, and will be found to consist of a head,
abdomen, and tail. The head is often drawn back so far into the abdomen,
that it cannot be seen, exhibiting only a projecting, broad
kidney-shaped disc. The abdomen, Fig. 51, _d_, is oblong, oval, and
pellucid, replete with obscure intestines, amongst which are one or two
remarkable black oval spots, _e_; the tail, _f_, is sharp, twice as
long as the abdomen, either rough and annulated, or altogether smooth.
331. VORTICELLA CITRINA. V. simplex, multiformis, orificio contractili,
pedunculo æquali. Plate XXVII. Fig. 53. Simple, many-shaped, with an
orifice admitting of contraction, and equal-sized foot-stalk.
The head is full of molecules, round, everywhere of an equal size, and
very pellucid; both sides of the orifice are ciliated, and each has a
rotatory motion, appearing sometimes without the edge of the mouth, as
at _a a_; at other times within it. No distinct intestines or internal
motion are perceivable. Its motion is different from most of this genus,
but not easily described; at _c c_ are small feet. It is found in
stagnant water.
332. VORTICELLA PIRIFORMIS. V. simplex, obovata, pedicello minimo
retractili. Simple, somewhat oval, with a very small retractile foot,
which it can draw within itself.
333. VORTICELLA TUBEROSA. V. simplex, turbinata, apice bituberculata.
Simple vorticella, the upper part broad, the under part small, with two
projections at the anterior end, furnished with a number of fibrillæ,
which produce a current of water by their vibration, and thus collect
food for the animal. Baker has delineated it in Plate XIII. No. 10, 11,
12, of his Employment for the Microscope.
334. VORTICELLA RINGENS. V. simplex, obovata, pedunculo minimo, orificio
contractili. Simple, somewhat of an oval shape, with a small pedicle,
and an orifice which it contracts or dilates.
The small head, or rather body of this little creature is pear-shaped,
pellucid, the middle of the aperture convex, both sides ciliated, the
pedicle four times shorter than the body; it can contract the orifice to
an obtuse point.
335. VORTICELLA INCLINANS. V. simplex, deflexa, pedunculo brevi,
capitulo retractili. Simple, bent, with a short pedicle, and small
retractile head.
This has a pellucid pendulous little head; the anterior part truncated,
occasionally contracting itself twice as short as the pedicle; its shape
resembles that of a tobacco-pipe.
336. VORTICELLA VAGINATA. V. simplex, erecta, ovato-truncata, pedunculo
vaginato. Simple vorticella, erect, of the shape of a truncated egg; the
pedicle is contained in a sheath.
For the 337th, 338th, and 339th, the author refers to the Zool. Dan. he
terms them, vorticella cyathina, vorticella putrina, vorticella
patellina.
340. VORTICELLA GLOBULARIA. V. simplex, sphærica, pedunculo retortili.
Simple, spherical, with a twisted pedicle.
This animalculum has a small spherical head, the aperture of the mouth
ciliated; the pedicle four times longer than the body, which it
contracts into a spiral form. It is frequent among the cyclopa
quadricorni.
341. VORTICELLA LUNARIS. V. simplex, hemisphærica, pedunculo retortili.
Plate XXVII. Fig. 54. Simple, hemispherical, with a twisted pedicle.
The small head of this animalculum is goblet-shaped, the margin of the
orifice protuberant, ciliated on both sides, with undulating hairs; the
pedicle eight or ten times the length of the body. The pedicle extends
itself as often as the mouth is opened, but is twisted up spirally when
it is shut; and these motions are frequently repeated in a short space
of time, _a a_, the head when expanded; _b_, when shut; _c_, the
undulated edge; _d d_, the cilia erect; _e_, when horizontal; _f_, the
pedicle when straight; _g_, when bent in a spiral form.
342. VORTICELLA CONVALLARIA. V. simplex, campanulata, pedunculo
retortili. This animalculum, the bell-animal of Baker, has been fully
described in page 407.
343. VORTICELLA NUTANS. V. simplex, turbinata, pedunculo retortili.
Simple, with a twisted turbinated pedicle.
The pedicle is simple, and twists itself spirally; is extremely slender,
with a kind of cap on its head; the margin white and round, and
appearing as if encompassed with a lucid ring; the head diminishes
towards the base. It is transparent.
344. VORTICELLA NEBULIFERA. V. simplex, ovata, pedunculo reflexili.
Plate XXVII. Fig. 66. Simple, egg-shaped, the pedicle bent back.
The body is narrow at the base, open and truncated at the top; the
margin apparently surrounded with a ring; but, when the aperture is
shut, the animalculum is egg-shaped, with a simple setaceous pedicle,
considerably longer than the body, and generally much bent back. _a a
a_, the head open; _b_, partly closed; _c_, quite shut; _d_, the stalk
when straight; and at _e_, when bent.
345. VORTICELLA ANNULARIS. V. simplex, truncata, pedunculo apice
retortili. Simple, truncated, with a pedicle twisted at the end.
This is visible to the naked eye; when contracted, it appears to be
annulated; the head is an inverted cone, convex when the mouth is shut,
but truncated when it is open, and with a protuberant edge; the pedicle
is simple, very long and thick, whiter at the top than any other part,
and formed into a little head; the apex is twisted spirally.
346. VORTICELLA ACINOSA. An ample description of this animalculum, under
the title of vorticella umbellaria, has been given in page 402.
347. VORTICELLA FASCICULATA. V. simplex, viridis, campanulata, margine
reflexo, pedunculo retortili. Simple, green, bell-shaped, the margin or
edge turned back, the pedicle twisted.
The head is bell-shaped, green, opake, narrow at bottom, pellucid. It
has a rotatory organ, which may sometimes be seen projecting beyond the
aperture; there is a little head at the apex, and the pedicle is twisted
and very slender. A congealed green mass, which is often swimming about
in ditches, is composed of myriads of these animalcula, which are
invisible to the eye, but when magnified, appear like a bundle of green
flowers.
348. VORTICELLA HIANS. V. simplex, citriformis, pedunculo retortili.
This may be classed among the most minute. The head resembles a citron,
the apex is truncated, the base narrow; a gaping cleft is observable
descending from the apex, to one-third of the body.
349. VORTICELLA BELLIS. V. simplex, hemispherica, margine contractili.
Simple, hemispherical, with a margin which it can contract at pleasure.
The body is of a yellow colour, much resembling the flower of a daisy;
the head scarcely pellucid; the internal part quite filled; it is
abundantly ciliated round the margin, moving in a rotatory manner.
The foot or pedicle is long, slender, and pellucid; it is divided into
two parts, with small knobs on the top of each; the base adheres to a
bulb, the under-part is covered with small scales.
350. VORTICELLA GEMELLA. V. simplex, sphærica, capitulo gemino. Simple,
spherical, with a double head.
The pedicle is long, and constantly furnished with two small heads at
its apex; these are bright and clear.
351. VORTICELLA PYRARIA. The distinguishing characters of this
animalculum will be found at page 400.
352. VORTICELLA ANASTATICA. A full description of this vorticella has
also been given at page 397.
353. VORTICELLA DIGITALIS. At page 406 the reader will likewise meet
with an account of the v. digitalis.
354. VORTICELLA POLYPINA. V. composita, ovato-truncata, pedunculo
reflexili ramosissimo. Plate XXVII. Fig. 61. Compound vorticella, oval,
truncated, with a bending branching stalk.
When viewed with a small magnifier, they appear like so many little
trees; the upper part or heads are egg-shaped, the top truncated, the
lower part filled with intestines; the branches are thick set with
little knobs. _a_, the trunk; _b b b_, the branches; _c c_, the head
when extended; _d_, the small knobs on the branches.
355. VORTICELLA RACEMOSA. V. composita, pedunculo rigido, pedicellis
ramosissimis longis. Compound, rigid pedicle, with small branched long
feet.
To the naked eye it appears like the vorticella socialis, described in
page 395, but is distinguished from it by always adhering to the sides
of the vessel in which it is placed. With the microscope, a long very
slender pedicle is discovered sticking to the sides of the vessels, from
which proceed an innumerable quantity of crystalline pellucid pearls,
which, together with the stalk, are variously agitated in the water.
They sometimes move separately, at other times together, are sometimes
drawn down to the root, and in a moment expanded again.
XVII. BRACHIONUS.
Vermis contractilis, testa tectus, ciliis rotatoriis. A worm capable of
contracting, covered with a shell, and furnished with rotatory cilia.
356. BRACHIONUS STRIATUS. B. univalvis, testa ovata striata, apice
sexdentata, basi integra, cauda nulla. Plate XXVII. Fig. 64 and 65.
Univalved brachionus, the shell oval and striated, six notches or teeth
round the upper edge, the base whole or even, without a tail.
The shell is oblong, pellucid, and capable of altering its figure. The
apex, _a_, is truncated, with six small teeth on the edge of it, twelve
longitudinal streaks down the back, the base obtuse and smooth. The
teeth are occasionally either protruded or retracted; on the other side
of the shell, towards the tail, there are two little spines or horns,
_c_.
The animalculum itself is muscular, pellucid, and crystalline, often of
a yellow colour; from the apex it now and then puts forth three little
bundles of playing hairs, the two lateral ones shorter than the middle
one; a forked deglutatory muscle, _e_, is perceptible; and on the under
side, when the apex is drawn in, two rigid points may be discovered. It
is found in sea water.
357. BRACHIONUS SQUAMULA. B. univalvis, testa orbicularis, apice
truncata quadridentata, basi integra, cauda nulla. Univalved brachionus,
with an orbicular shell; the apex truncated, and having four teeth, the
base smooth, no tail.
358. BRACHIONUS PALA. B. univalvis, testa oblonga excavata, apice
quadridentata, basi integra, cauda nulla. Univalved brachionus, with an
oblong excavated shell, four long teeth at the apex, the base smooth, no
tail. It is of a yellow colour.
359. BRACHIONUS BIPALIUM. B. univalvis, testa oblonga inflexa, apice
decemdentata, basi integra, cauda spuria. Univalved brachionus, the
shell oblong and inflected, ten teeth at the apex, the base smooth, and
a spurious tail.
360. BRACHIONUS PATINA. B. univalvis, testa orbiculari integra, cauda
mutica. Univalved brachionus, with an orbicular shell, the edges
regular, and having a long beardless tail.