animal of Baker, I think the reader will be better pleased to see his
description of it introduced in this place, than to have it raised into
a new and distinct species.
This little animal is extremely slender, and not uncommonly one-hundred
and fifty times longer than broad. Its resemblance to an hair induced
Baker to call it the hair-like insect. The body or middle part, which is
nearly straight, appears in some composed of such parallel rings as the
windpipe of land animals consists of, but seems in others scaled, or
rather made up of rings that obliquely cross each other. Its two ends
are bent or hooked, pretty nearly in the same degree, but in a direction
contrary each to the other; and as no eyes can be discerned, it is
difficult to judge which is the head or tail. Its progressive motion
differs from that of all animals hitherto described; for,
notwithstanding the body is composed of many rings and joints, it seems
unable to bend them, or move directly forwards; but when it is
inclinable to change its quarters, it can move from right to left, or
left to right, and proceed at the same time backwards or forwards
obliquely; and this it performs by turning upon one end as a center, and
describing with the other the quarter of a circle; then it does the same
with the other end, and so alternately; whereby its progression is in a
diagonal line, or from corner to corner. Of this any one may immediately
be satisfied, who will take the trouble of shifting the points of a
pair of compasses in that manner. All its motions are extremely slow,
and require much patience and attention in the observer. It has neither
feet, fins, nor hairs, but appears perfectly smooth and transparent,
with the head bending one way, and the tail another, so as to be like a
long Italic S; nor is any internal motion, or particularly opake part,
to be perceived, which may determine one to suppose it either the
stomach, or the intestines.
These creatures are so small, that millions of millions might be
contained in an inch square. When viewed singly, or separated from one
another, they are exceedingly transparent, and of a lovely green; but,
like all other transparent bodies, when numbers of them are brought
together they become opake, and lose their green colour in proportion as
the quantity increases, till at last they appear entirely black.
Notwithstanding the extreme minuteness of these animalcula, they seem to
be fond of society; for, on viewing for some time a parcel of them taken
up at random, they will be seen to disperse themselves in a kind of
regular order. If a multitude of them be put into a jar of water, they
will form themselves into a regular body, and ascend slowly to the top,
where, after they have remained some time exposed to the air, their
green colour changes to a beautiful sky-blue. When they are weary of
this situation, they form themselves into a kind of rope, which slowly
descends as low as they intend.
A small quantity of the substance containing these creatures having been
put into a jar of water, it so happened, that one part descended
immediately to the bottom, the other continuing to float on the surface.
After some time, each of these swarms of animalcula exhibited a
disposition to change its quarters. Both armies, therefore, set out at
the same time, the one proceeding upwards, and the other downwards; so
that after some hours journey they met in the middle. A desire of
knowing how they would conduct themselves on this occasion, engaged the
observer to watch them carefully; and to his surprize, he saw the army
that was marching upwards open to the right and left, to make room for
those that were descending. Thus without confusion or intermixture each
held on its way, the ascending army marching in two columns to the top,
and the other proceeding in one column to the bottom, as if each had
been under the direction of wise leaders.
63. VIBRIO LUNULA. V. arcuatus, utraque extremitate æquali. Plate XXV.
Fig. 16. Bow-shaped vibrio, both ends of an equal size.
The body resembles much the shape of the moon at the first quarter; it
is of a green colour, and has generally from seven to ten globules
disposed lengthwise; the smaller ones are of a very pale colour, a pale
green vacuity may sometimes be seen in the middle: some little varieties
may be observed amongst them, which are not easily to be described; it
will be enough to have given the reader their general and distinguishing
characteristics.
64. VIBRIO VERMINUS. V. linearis compressus, antice quam postice
angustior. Linear compressed vibrio, the fore-part narrower than the
hind-part.
A round transparent animalculum, or rather a long crystalline membrane,
the hind-part broader than the fore-part, the apex subtruncated, the
base obtuse, no perceptible intestines; in the middle are two spherical
vesicules, and a third towards the lower edge. It moves quickly
backwards and forwards with an undulatory motion; they seem to be
joined in a very singular manner, and were found in great plenty in salt
water that had been kept several days, till it became fetid.
65. VIBRIO MALLÆUS. V. linearis basi globuli, apice linea transversa. A
linear vibrio, with a globule at the base, and transverse line at the
apex.
This is a white pellucid animalculum, resembling the letter T, with a
globule affixed to the base. It is in motion and at rest every moment
alternately; in the former case, it resembles the letter V; in the
latter, the letter T. They are found plentifully in spring water.
66. VIBRIO ACUS. V. linearis, colli, apice obtuso, cauda setacea. Linear
vibrio, with a neck, the upper extremity obtuse, the lower one
terminating in a setaceous tail.
This vibrio is of the shape of a sewing needle; the neck round, partly
transparent, and marked in the middle with a red point; the trunk
cylindrical, the edges obscure, the middle bright, and nearly of a
triangular appearance, the tail resembling a fine bristle. A motion may
be observed in the inside of this little creature. It does not bend the
body when in motion.
67. VIBRIO SAGITTA. V. sublinearis, colli, apice truncato atro, cauda
setacea. Somewhat linear in its appearance, a well-marked neck, the apex
truncated and open, the tail setaceous.
The body is very long and flexible, broadest towards the middle, which
is also filled with grey molecules; the fore-part is drawn out into a
straight transparent neck, the upper end of it thick and black. The
motion of this animalculum seems to be produced by the contraction and
extension of the neck. It is found in salt water.
68. VIBRIO GORDIUS. V. æqualis, caudæ apice tuberculato. Vibrio of an
equal size throughout, the tail terminated by a little tubercle.
A round animalculum; the fore-part for about one-sixth of the whole
length is transparent, and furnished with a sky-coloured alimentary
tube; the lower part is bright and pointed, the middle full of small
globules; a small knob terminates the tail. Found in an infusion made
with salt water.
69. VIBRIO SERPENTULUS. V. æqualis utrinque subacuminatus. This vibrio
is of an equal size, rather pointed at both ends.
It is very similar to the vibrio anguillula, No. 71, differing
principally in the shape of the ends, which in this are furnished with a
long row of the most minute points. It does not adhere to objects by the
pointed tail. The body is of a whitish colour, frequently convoluted,
and drawn into different figures. Its motion is serpentine, sometimes to
be met with perfectly straight and still, and is found in infusions of
vegetables after some weeks standing.
70. VIBRIO COLUBER. V. filiformis, seta caudali geneculata. Filiform
vibrio, the tail setaceous, and bending up nearly to form a right angle
with the body.
In this vibrio, the mouth, the oesophagus, the molecules in the
intestines, and the twisting of them, are very conspicuous. The tail is
exceeding small, and bent so as to form a considerable angle with the
body. It is found in river water.
71. VIBRIO ANGUILLULA. V. æqualis, subrigidus. Vibrio of an equal size
throughout, and somewhat hard.
This animalculum may be divided into four varieties, if not distinct
species: namely, 1. Anguillula aceti. 2. Anguillula glutinis farinosi.
3. Anguillula aquæ dulcis; and 4. Anguillula aquæ marinæ. These
varieties I shall first describe, together with the eels in blighted
wheat, and then proceed with the rest of the vibrio.
1. ANGUILLULA ACETI, OR VINEGAR EEL.
Plate XI. Fig. 7.
Chaos redivivum, Linn. Syst. Nat. 1326.[124] Leeuwenhoeck Opera Omn. p.
3, n. 1, f, l, o. Joblot Observ. Micros. 1, p. 2, pl. 2. Hooke’s
Micrograph, p. 216, pl. 25, fig. 3. Borelli Observ. Micros. 1, p. 7.
Power’s Micros. Observ. p. 32. Adams Micrograph. Illustr. 4th edition,
p. 125, pl. 38, fig. 197, A, B, C, D. Rozier Journal Physique, Mars
1775, Janv. & Mars 1776. Spallanzani Opusc. Phys. part 1, p. 83.
[124] Linnæus includes this and the paste eel under the same
title:--Habitat in aceto et glutine bibliopegorum. He
adds,--Reviviscit ex aqua per annos exsiccatum. EDIT.
This eel is both oviparous and viviparous; it is filiform, but in other
respects differs considerably from the paste eel. It is longer, not near
so large, the tail is smaller and more tapering; it moves with much
greater ease, and is more lively. In the tail of this eel we may observe
in miniature, what may be seen on a much larger scale in that of the
viper, viz. a small projection somewhat resembling a tongue, which
occasionally appears as delineated in the figure at _a b_, and at other
times adheres close to the body. An alimentary duct may be easily
discovered, but no other intestines can be discerned, without deranging
altogether the organization of the animalculum. The pungent taste of
vinegar was formerly attributed to these animalcula, an opinion which
was soon exploded.
2. ANGUILLULA GLUTINIS FARINOSI, OR PASTE EEL.
Plate XI. Fig. 6, 8, 9, and 10.
Chaos redivivum, Linn. Syst. Nat. 1326. Ledermüller Micros. Ergötzungen,
p. 33, tab. 17. Baker Micros. made easy, p. 81. Ibid. Empl. for the
Micros. p. 244, pl. 10, no. 8 and 9. Rozier Journal Physique, Mars 1775,
Mars 1776. Adams Micrograph. Illustr. 4th edition, p. 125, pl. 38, fig.
179.
The eels in paste have been more distinguished than most other
animalcula, as well on account of their many curious properties, as the
various speculations and theories to which they have given rise. Four
different species of eels may be found in paste; of the first, I shall
now give a particular description. The body is filiform or like a
thread, round, pellucid, replete with little grains in the middle, both
extremities very pellucid and empty, the fore-part a little truncated,
the hind-part terminating in a very short bristly point. It is the same
of every age and size. To be certain of procuring this species of eels,
boil some flower in water, to which you have added a few drops of
vinegar; provide an earthen pot which has an hole at the bottom, and
fill it with earth; then put the paste in a piece of coarse cloth, and
bury it in this earth; the pot is to be exposed to the sun in the
summer, or kept in a warm place in the winter; by these means in ten or
twelve days you will very seldom fail of finding a large quantity of
eels in the paste.
This eel, when at its full growth, is about one-tenth of an inch long,
and rather less than one-hundredth of an inch in diameter. Fig. 6
represents one of these eels magnified about one-hundred and twenty
times, only compressed so much between two plates, by means of an
adjusting screw, as not only to prevent it from moving, but to lengthen
and flatten it in a small degree. At the upper part there are two little
moveable pieces or nipples, _a a_, between which an empty space _b_ is
formed, that terminates in the mouth; the hinder-part is round, but
there projects from it a short setaceous tail _w_; in the young eels the
termination of the tail is not so abrupt as in the present specimen, but
it finishes by a gradual diminution. There is probably a vent near _z_,
for the passage of the excrements; because when that part has been
gently pressed, two or three jets of a very subtile substance have been
observed to issue from it. If the pressure be increased, a small bladder
will be forced out, a further compression bursts the bladder, and the
intestines are forced through the opening.
A greater degree of magnifying power is necessary to obtain an exact
idea of the viscera of these eels. Fig. 10 represents the alimentary
duct further magnified, from its origin to the belly. It is shewn here
as separated from the animal, which is easily effected; for nature,
assisted by very little art, performs the operation. The oesophagus, _b
c_; Fig. 6 and 10, at its origin _a a_, is very small, but soon grows
larger, as at _c_, and forms a kind of oblong bag, _c d_; the diameter
of this increases till it comes to _d_, where it swells out as at _d e
f_; it then grows smaller till it comes to _g_, when it again swells out
at _g k l_. The part _k l_ is the stomach. M. Becli has shewn, that the
alimentary duct of many species of worms is formed of two bags, one of
which is inclosed within the other. It is the same with this
animalculum; the little vessel _b c_, that we have called the
oesophagus, which is the origin of the bag _c d_, enters into the same
bag, and preserves its form within it till it comes to _m_, from whence
it is prolonged in the form of a black line _m n_, which passes by the
axis of the duct _e_, and apparently terminates itself at the beginning
of the abdomen _l_. To this tube, near the center of the swelling _g k
l_, are fixed two small transparent bodies; that end of these which is
connected with the tube is round, the other end is pointed; these small
pieces cannot be discerned in every position of the eel.
I shall now shew how this duct is to be forced out of the eel. The body,
when compressed, generally bursts either at the head or tail, and always
at that part which is least pressed; hence when the mass of fluids
contained in the body is forced towards the anterior part, they meet
with a resistance in passing from the abdomen to the duct already
described; the abdomen, being forced by the fluids which are made to act
against it, bursts at the upper end, and the fluids, striking against
the neck, force it, with all its contents, out of the body, through an
opening at the anterior part; on lessening the pressure, the intestine
thus discharged will float in the water between the two plates of glass.
Not to enter into a detail of those parts which have been supposed by
some writers to constitute the heart, &c. of these minute animalcula, it
will be sufficient here to describe those in which motion may be
discovered, and to leave the rest to future observations on the subject.
The parts which may be seen in motion within these minute creatures are,
1. the small tube or duct, from its origin at _m_, to the two
appendages; 2. these appendages themselves, _h_; 3. the remainder of the
tube, from the appendages to the insertion at the ventricle _k_; 4. in
the swelling _g k l_. The rest of this duct, from the beginning by the
oesophagus _b c_, to the second swelling, has no motion. There is a
variety in the motions of the first part of this duct, sometimes it
dilates and contracts, at other times it has an oscillatory motion. It
is difficult to gain a good view of the appendages; but when the
position of the little creature is favourable, they seem to have a
two-fold motion, by which the pointed ends approach to, and then
separate from, each other, and another by which they move up and down.
The part _g k l_ moves backwards and forwards alternately; the motion of
each of these parts is independent of the rest. These are the principal
parts, whose motion is connected with the life of the animal.
The other viscera that are contained in the body of the eel, and which
may be observed by the aid of the microscope, are, the vessels which
contain the food, those which are filled with a transparent substance,
and the womb or ovary. The first form the abdomen and intestines; these
are filled with a black substance, which prevents their being properly
and clearly distinguished; these vessels, in their passage through the
posterior part of the body, form an empty space, in which we may
perceive that one side of the animalculum is occupied by the ovary _q q
q_, which runs from _j_ to _u x_; it is at these two extremities of the
ovaries that the eggs begin to be formed, for the largest eggs are
always to be found in the middle, and the smallest at the ends, as may
be seen at _j f_ and _u x_.
All the eels which bear eggs have two protuberances, _y y_, formed on
the exterior part near the center of the ovary; it appears like a
transparent semicircular membrane, but is really a kind of hernia or
bag, in which one or two eggs may be sometimes seen; all the larger eels
have this appendage, which also bears the marks of having been burst.
Now, as the younger eels have not this appendage, nor any marks of a
rupture, we may reasonably conclude that it is from hence that the
little eels issue from the parent.
In the latter part of the year, and during the winter, these eels are
oviparous, and the young eels may be seen to proceed from the egg; at
other times they are viviparous; six live eels have been seen at one
time in the belly of the parent, twenty-two eggs have been counted in
the ovary. Müller suspected that there was a difference of sex in some
of these animalcula, but it was left to M. Roffredi to afford the proof,
and it was only from a variety of repeated observations that he could
allow himself to be convinced of this truth. He continued his researches
upon the same subject on other microscopic eels, and has since been able
to distinguish the sexual parts of the vinegar eels.
The second species of paste eel is oviparous. It is easily distinguished
from the first kind by being much smaller; in Fig. 8, is exhibited a
magnified view of this eel. The conformation of the alimentary duct and
the intestines are in general nearly the same, though an intelligent
observer will find out some specific differences. By the flexion of the
intestines _c c c_, a void space is left a little beyond the middle of
the body, where the ovary, _d d_, is situated. There is no exterior
protuberance near this ovary, as in the preceding one.
We meet with another eel in paste, which may with propriety be called
the common eel. It is often to be found in grains placed in the earth,
in which the germ is destroyed, in the roots and stems of farinaceous
plants, in the tremella of Adanson, and in several species of conferva,
as well as in several infusions. This eel, when at its full growth is
rather longer than the common eel of blighted wheat; one of them is
represented at Fig. 11. They are easily distinguished from the eels of
blighted wheat, because they have no ranges of globules like it, by the
two little protuberances which are near the middle of the body, and by
the regular diminution of the tail. It is oviparous.
A very small species, represented at Fig. 9, may also be found in paste;
they may be distinguished from the young eels of the larger sort by
their vivacity and slenderness.
As the eels in paste are objects which are so often exhibited in the
microscope, it will be proper, before we leave this subject, to inform
the reader how he may procure the young eels from the parent animalcula;
a discovery which was originally made by Mr. Sherwood, but more
particularly pursued and described by Baker. Take up a very small
quantity of paste where these eels abound on the point of a pin, or with
a sharpened quill; lay it on a slip of glass, and dilute it well with
water; by these means, many of them will become visible to the naked
eye; then with the nib of a pen cut to a very fine point, and shaved so
thin as to be extremely pliable, single out one of the largest eels, and
insinuate the point of the pen underneath it; remove it into a very
small drop of water, which you must have ready prepared on another slip
of glass. When thus confined, it may easily be cut asunder transversely,
by the help of a good eye and steady hand, with a lancet or sharp
penknife; or if the eye be deficient, a hand-magnifier will enable
almost any person to perform the operation. As soon as the parts are
separated, apply your object to the microscope, and if the division has
been made about the middle of the animal, several oval bodies of
different sizes will be seen to issue forth. These are young anguillulæ
of different degrees of maturity, each of which is coiled up, and
included in its proper membrane, of so exquisite a fineness, as to be
scarce discernible by the greatest magnifier while it incloses the
embryo animal. The largest and most forward break immediately through
this delicate integument, unfold themselves, and wriggle about nimbly in
the water; others get out, uncoil, and move about more slowly; and the
least mature continue entirely without motion. The uterus or vessel that
contains all these oval bodies is composed of many annula or ringlets,
not unlike the aspera arteria of land animals, and it seems to be
considerably elastic; for as soon as the operation is performed, the
oval bodies are thrust out with some degree of violence by the spring or
action of this bowel. An hundred or upwards of young ones have been seen
to issue from one single eel, whereby the prodigious increase of them
may be accounted for, as probably several such numerous generations are
produced in a short time. Hereby we also learn that these creatures are
not only like eels in shape, but are likewise viviparous, as eels are
generally supposed to be.
Few experiments are to be found more entertaining, or in which there is
so little risk of being disappointed; for they seem, like earth-worms,
to be all prolific, and you may be sure of success, unless by accident
you cut one that has already brought forth all its young, or make your
trials when the paste has been kept a very long time, in which cases
they have been found unfruitful.
3. ANGUILLULA AQUÆ DULCIS, OR FRESH WATER EEL.
Corculum vermiculo simile, Linn. Amæn. (Mund. Invis.) Anguille Vulgaire,
Rozier Journal Physique, 1775. Mars, Nov. 1776. Ibid. Anguille du Bled
Rachitique. Ibid. Anguille du Faux Ergot. Spallanz. Opusc. Phys. part 2,
p. 354, pl. 5, fig. 10.
The body of this is exceedingly transparent, with no visible entrails,
though a few transverse lines may be discovered on the body. It is
sometimes, though rarely, furnished with a long row of little globules,
and often with two small oval ones; the tail terminates in a point.
Müller says he found these eels in the sediment which is formed by
vegetables on the sides of vessels in which water had been kept for some
time.
4. ANGUILLULA AQUÆ MARINÆ, OR SALT WATER EEL.
This, when pressed between two plates of glass, appears to be little
more than a crystalline skin, with a kind of clay-coloured intestines.
The fore-part of the body is truncated, the lower part drawn out to a
fine point, the rest of the body is of an equal size throughout. The
younger ones are filled with pellucid molecular intestines.
OF THE EELS IN BLIGHTED WHEAT.
Plate XI. Fig. 4 and 5.
These animalcula were discovered by Needham, and described by him in a
work entitled, New Microscopical Discoveries, and afterwards more fully
treated upon by Baker. They are not lodged in those blighted, grains
which are covered externally with a soot-like dust, whose inside is
often also little more than a black powder; but abundance of ears may be
observed in some fields of corn, which have grains that appear blackish,
as if scorched: these, when opened, are found to contain a soft white
substance, that when attentively examined looks like a congeries of
threads or fibres lying as close as possible to each other in a parallel
direction, and much resembling the unripe down of some thistles. This
fibrous matter does not discover any signs of life or motion, unless
water be applied to it; the fibres then separate, and prove themselves
to be living creatures.