Chapter V: Vibrio

Vermis inconspicuus, simplicissimus, teres, elongatus. An invisible worm, very simple, round, and rather long.

52. VIBRIO LINEOLA. V. linearis minutissimus. Very small linear vibrio.

This is one of the most minute animalcula, surpassing in slenderness the monas termo, No. 1. The greatest magnifier exhibits little more than a tremulous motion of myriads of little oblong obscure points. In a few days it almost fills the whole substance of the water in vegetable infusions.

53. VIBRIO RUGULA. V. linearis flexuosus. Vibrio like a bent line.

Myriads of this species may be found; it is between the vibrio lineola, just described, and the vibrio undula, No. 55. It appears as a little line, which is sometimes drawn up in an undulated shape, and moves backwards and forwards in a straight line, often without bending the body at all.

54. VIBRIO BACILLUS. V. linearis, æqualis utrinque truncata. Linear vibrio, equally truncated at both ends.

This is an exceeding small creature, but visible with the third lens; in a certain position of the light, transparent. It is gelatinous, and not half so large as the monas lens, No. 5, though six, and sometimes ten times longer; it is everywhere of an equal size, and has no visible intestines; its action is languid, the serpentine flexures of the body are with great difficulty perceived. Müller made two infusions of hay in the same water, and at the same time, in the one he put the hay whole, in the other it was cut in small pieces; in the first there were none of the vibrio bacillus, but many of the monas lens and kolpoda cucullus, No. 108; in the latter, many of the vibrio bacillus, and few of the monæ.

55. VIBRIO UNDULA. V. filiformis flexuosus. A filiform flexuous vibrio.

A perfect undulating little line, round, gelatinous, without any visible intestines. It is never straight; when at rest it resembles the letter V, when in motion the letter M, or a bending line like that which geese form in their flight through the air; its motions are so rapid, that the eye can scarce follow them. It generally rests upon the top of the water, sometimes it fixes itself obliquely by one extremity, and whirls itself round. This is the little creature that Leeuwenhoeck says exceeds in slenderness the tail of the animalculum seminale, which he has described in Fig. 5, Epis. Phys. 41, being an hundred times less than a mustard-seed, and on which he makes the following very just observation: That as these very small animalcula can contract and variously fold their little tails, we must conclude that tendons and muscles are as necessary to them as to other animals; if to these we add the organs of sensation, and those of the intestines, the mind is lost in the astonishment which arises from the impression of infinite, in the indefinitely small.

56. VIBRIO SERPENS. V. filiformis, ambagibus in angulum obtusum productis. A filiform vibrio, the windings or flexures obtuse.

A slender gelatinous little animal, in the form of a long serpentine line, all the bendings being nearly equal in size, and at equal distances; it generally moves in a straight line; an intestine may be discovered down the middle. It is to be found in river water, but is not commonly to be met with.

57. VIBRIO SPIRILLUM. V. filiformis, ambagibus in angulum acutum tornatis. Filiform vibrio, twisted something like a spiral wire or cork-screw, the bending acute.

It is an exceeding minute, singular creature, twisted in a spiral form; the shape of these bendings remains the same even when the animal is in motion, not occasioned by any internal force, but are its natural shape. It moves generally in a straight line, vibrating the hind and fore-parts. It was found in 1782, in an infusion of the sonchus arvensis, or corn sow-thistle.

58. VIBRIO VERMICULUS. V. tortuosus gelatinus. This little vibrio is twisted and gelatinous.

The body is white, or rather of a milky appearance, cylindric, long, the apex obtuse, rather growing smaller, and twisted towards the hind-part. Its motion is languid and undulatory, like that of the common worm; it sometimes moves quicker, but with seeming labour. When it bends itself alternately from one side to the other, a black long line may be discovered, sometimes whole, sometimes broken: when at rest, it occasionally twists into various folds. It may be observed easily with the first lens of the single microscope, and is probably the same animalculum mentioned by Leeuwenhoeck in all his works, as found in the dung of frogs, and in the spawn of the male libellula. It is to be found in marshy water in November, though but seldom.

59. VIBRIO INTESTINUM. V. gelatinosus, teres, antice angustatus. This vibrio is gelatinous, round, the fore-part small.

It is cylindric, milk-coloured, and slender towards the top, both ends obtuse; no traces of intestines to be discovered, though four or five spherical eggs are perceived at the extremity of the hind-part. It can draw the fore-part so much inwards as to give it a truncated and dilated appearance, something like a spatula. Its motion is slow and progressive. It is found in marshy waters.

60. VIBRIO BIPUNCTATUS. V. linearis, æqualis, utraque extremitate truncata, globulis binis mediis. Linear vibrio, of an equal size throughout, both ends truncated, and two small globules in the middle of the body.

It is of a small size, and rather less than the following animalculum; the body is of a pellucid talc-like appearance, the fore and hind-part truncated; in the middle are two (sometimes there is only one) pellucid globules, placed lengthwise. It most commonly moves forward in a straight line; its movements are slow. It was found in fetid salt water.

61. VIBRIO TRIPUNCTATUS. V. linearis, utrinque attenuatus, globulis tribus, extremis minoribus. Linear vibrio, both the ends smaller than the middle, furnished with three globular points, the two which are at the extremities being smaller than that at the middle.

The body is pellucid, talky, each of the ends rather tapering, furnished with three pellucid globules, the middle one is the largest; the space between these globules is generally filled with a green matter; in some there is nothing of the green substance near the extremities, but only about the middle. It seldom moves far, and then its motion is rectilinear, backwards and forwards.

62. VIBRIO PAXILIFER. V. flavescens paleis gregariis multifariam ordinatis. Plate XXV. Fig. 13, 14, 15. Yellow, gregarious, straw-like vibrio.

This is a wonderful animalculum, or rather a congeries of animalcula. It is invisible to the naked eye, and consists of a transparent membrane, with yellow intestines, and two or three visible points; they are generally found collected together in different parcels, from seven to forty in number, and ranged in a variety of forms, sometimes in a straight line, as in Fig. 14, then forming the concave Figure 13, at others, moving in a zig-zag direction, as in Fig. 15; when at rest they are generally in a quadrangular form, and found in great plenty with the ulva latissima, or brown laver.

As this animalculum seems to have some affinity with the hair-like 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.

These eels are in general of a large size, and may be seen with a common magnifying glass, being about one-thirtieth of an inch in length, and one-hundred and fortieth broad. Fig. 5 represents one of them magnified about one-hundred and twenty times; they are in general of a bright chesnut colour, the extremity _a b_ is whiter and more transparent than the rest of the body. The end _a_ is rather round, the end _c_ is pointed. A distinguishing mark of these little creatures is a row of transparent globules, which are placed at intervals through the whole length of the body, beginning at _b_, where the transparency of the fore-part ceases, and going on towards the extremity _c_. They are in diameter rather less than one-third of the body. Another peculiar mark is a small lunular space _d_, near the middle of the body. This part is transparent, and is free from the coloured matter of the intestines; there is a neck in the intestines near this space, which confines them to one part of the body.

Great care should be taken by the observer, not to burst the skin of the eels in disengaging them from the grain, for they never break or burst of themselves; but if broke, visible intestines, filled with a black matter, rush out of the body, from which little black globules are disengaged; if the observation be made immediately after these globules proceed from the eel, they swim slowly about the water, though divested of any principle of internal motion; but if the eels that are broke be left long in the water, the same phænomena will take place, as in other animal and vegetable infusions. The want of due attention to these circumstances has been productive of many of the fanciful positions of Needham, which were deduced from ill-conducted experiments; and, consequently, when properly examined, are found to be in a great measure false.

M. Roffredi sowed some of the grains of this wheat, which sprang up; but the ear was either wholly or in a great measure spoiled, being filled with these eels. He also found them in other parts of the plant; in order to disengage them, the plant must be soaked in water, and then compressed a little. At first sight these eels seem to resemble the foregoing, but a more accurate inspection shews that they have neither the same curious disposition of the internal globules, nor the transparent place in the middle of the body. The intestinal bag leaves indeed in these an empty space, but it is of an undetermined form. The animalcula from the plant are much more lively than those which are procured from the dried grains.

The principal phænomena in this kind of blighted wheat is probably owing to these animalcula, who prevent the regular circulation of the sap. They increase in size in a certain proportion to the plant, so that at last they may be observed with great ease by the naked eye, being two-tenths of an inch long, and nearly one-tenth in diameter. Fig. 4 represents one of these magnified nearly in the same proportion as Fig. 5; _a a a a_, the ovary, which may be traced almost from the lower extremity to the middle of the body, where the body becomes so opake as to prevent its being seen any further. The eggs, when arrived at their full growth, are nearly of a cylindric shape, both ends rounded; towards the extremity _b_ there are two little protuberances _d d_, through which the eggs are most probably extruded; these protuberances are not always visible. The eggs are formed of a fine transparent membrane; it covers the young eel, which is folded curiously therein; these eggs may be frequently found in the plant.

A most satisfactory view of these eels is obtained by examining them with the solar microscope; it affords one of the most surprizing and magnificent spectacles; two generations may be often seen, one, which draws near the allotted period of its existence, and another which only begins to enjoy the blessings of life: some arrived at their full growth, and others quite small. In some we may perceive the young animalcula in motion in the eggs, in others, no such motion can be observed; with a variety of other circumstances too tedious to enumerate, though they afford great pleasure to the spectator.

One of the most remarkable circumstances in these animalcula is the faculty they have of receiving again the powers of life, after having lost them for a considerable time; for instance, when some of these blighted grains, that have been preserved for many years, have been soaked in water for ten or twelve hours, living eels of this species have been found in it; if the water evaporate, or begin to fail, they cease to move, but, on a fresh application, will be again revived.[125]

[125] The property of revivification is not confined to this species,
being common to other kinds of worms, and it is not improbable that
the hydræ may possess the same faculty. EDIT.

It may be proper to notice here, that according to the observations of Roffredi, those eels which have done laying of eggs are incapable of being resuscitated upon being moistened; the same seems to be also the case with those that are very young; it is probable they must attain a certain age and degree of strength before they are endowed with this wonderful faculty.

In the month of August, 1743, a small parcel of blighted wheat was sent by Mr. Needham to Martin Folkes, Esq. President of the Royal Society, with an account of his then new discovery; which parcel the president was pleased to give to Mr. Baker, desiring him to examine it carefully. In order so to do, he cut open some of the grains that were become dry, took out the fibrous matter, and applied water to it on a slip of glass, but could discern no other motion than a separation of the fibres or threads, which separation he imputed wholly to an elasticity in the fibres; and perceiving no token of life, after watching them with due care, and repeating the experiment till he was weary, an account thereof was written to Needham, who, having by trials of his own, found out the cause of this bad success, advised him to steep the grains before he attempted to open them; on doing which he was very soon convinced of his veracity, and entertained with the pleasing sight of this wonderful phænomenon. At different times after this, Baker made experiments with grains of the same parcel, without being once disappointed. He soaked a couple of grains in water for the space of thirty-six hours, when, believing them sufficiently moistened, he cut one open, and applying some of the fibrous substance to the microscope in a drop of water, it separated immediately, and presented multitudes of the anguillulæ without the least motion or sign of life; but being taught by experience that they might notwithstanding possibly revive, he left them for about four hours, and then examining them again, found much the greatest number moving their extremities pretty briskly, and in an hour or two after they appeared as lively as these creatures usually are. Mr. Folkes and some other friends were witnesses of this experiment. We find an instance here that life may be suspended and seemingly destroyed; that by an exhalation of the fluids necessary to a living animal, the circulations may cease, all the organs and vessels of the body may be shrunk up, dried, and hardened; and yet, after a long while, life may begin anew to actuate the same body, and all the animal motions and faculties may be restored, merely by replenishing the organs and vessels with a fresh supply of fluid. Here is a proof that the animalcula in the grains of blighted wheat can endure having their bodies quite dried up for the space of four years together, without being thereby deprived of the property of resuscitation.

It appears plainly from the foregoing experiments, that when the blighted grains of wheat have been kept a long time, and the bodies of these animalcula are consequently become extremely dry, the rigidity of their minute vessels requires to be relaxed very gently, and by exceeding slow degrees; for we find that, on the application of water immediately to the bodies of these animalcula, when taken from the dry grains, they do not so certainly revive, as they do if the grains themselves be either buried in earth, or steeped in water for some time before they are taken out: the reason of which most probably is, that too sudden a relaxation bursts their delicate and tender organs, and thereby renders them incapable of being any more employed to perform the actions of life; and, indeed, there are always some dead ones amongst the living, whose bodies appear bursten, or lacerated, as well as others that lie extended and never come to life.

Some discretion is needful to adapt the time of continuing the grains in water or earth to the age and dryness of them; for if they be not opened before they have been too much or too long softened, the animalculum will not only seem dead, but will really be so. Of the two grains mentioned to have been four years old when put to soak, one was opened after it had lain thirty-six hours, and the event proved as already related; the other was suffered to lie for above a week, on opening which, all the anguillulæ near the husk were found dead, and seemingly in a decayed condition; but great numbers issued alive from the middle, and moved themselves briskly. Unless the husks be opened to let these creatures out after being steeped, they all inevitably perish; and when taken out and preserved in water, if the husks be left with them, they will die in a few days; but otherwise, continue alive in water for several months together; and, should the water evaporate, may be revived again by giving them a fresh supply.

72. VIBRIO LINTER. V. ventricoso-ovatus, collo brevissimo. Ventricose oval vibrio, with a short neck.

This is one of the larger animalcula, of an egg-shape, pellucid, inflated, somewhat depressed at top; the apex is prolonged into a moveable crystalline neck, the belly is replete with pellucid molecules. It is not very common, though occasionally to be found among the lemnæ.

73. VIBRIO UTRICULUS. V. teres, antice angustatus truncatus, postice ventricosus. Round vibrio, the fore-part narrow and truncated, the lower ventricose.

It does not ill resemble a bottle in shape; the belly is replete with molecular intestines, the neck bright and clear, the top truncated; in some a pellucid point is visible at the bottom of the belly. It is in an unceasing, vehement, and vacillatory motion, the neck moving from one side to the other as fast as possible.

74. VIBRIO FASCIOLA. V. antice attenuatus, medio latiusculus, postice acutus. Vibrio with a small fore-part, the middle a little bigger, the hind-part acute.

This is a pellucid animalculum, in the middle are the intestines in the form of points; an alimentary pipe, which lessens gradually in size, is also perceptible. The motion of it is quick, darting itself up and down in the water with great velocity. It is found in water just loosened from the frost, and seldom elsewhere.

75. VIBRIO COLYMBUS. V. crassus, postice acuminatus, collo subfalcato. Thick vibrio, sharpened at the end, the neck a little bent.

It is larger than most of the vibrios, and not unlike a bird in shape. The neck is round, shorter than the trunk, of an equal size throughout, and of a bright appearance, the apex obtuse. The trunk is thick, somewhat triangular, full of yellow molecules; the fore-part broad, the hinder-part acute, the motion slow.

76. VIBRIO STRICTUS. V. elongatus linearis, anticem versus attenuatus, apice obtuso. Vibrio lengthened out almost to a line, small towards the fore-part, the apex obtuse.

The body linear, being a bright membranaceous thread, without any flexure; the hind-part somewhat thicker, round, and filled with molecules, excepting just at the end, where there is a small pellucid empty space. The apex is obtuse, and rather globose; it has a power of contracting and drawing in the filiform part.

77. VIBRIO ANAS. V. oblongus, utroque fine attenuatus, collo cauda longiore. Oblong vibrio, both ends attenuated, the neck longer than the tail.

The trunk is oblong, opake, and filled with molecules. Both the fore and the hind-part is prolonged into a pellucid talky membrane, which the animalculum has a power of retracting at pleasure. The tail is more acute than the neck. It is most generally found in salt water; a species of them have been found in river water, with a longer neck.

78. VIBRIO CYGNUS. V. ventricosus, collo adunco. Corpulent vibrio, with a crooked neck.

This animalculum is little more than a most pellucid line, crooked at top, prominent in the middle, and sharp at the end; the fore-part, or neck, is equal in length to the rest of the body, and three times longer than the hind-part or tail; the intermediate part swelling out, is full of dark-coloured molecules and pellucid intestines. It is very small, and the most slothful of all those which move and advance their necks.

79. VIBRIO ANSER. V. ellipticus, collo longo, tuberculo dorsali. Plate XXV. Fig. 27 and 29. Elliptical vibrio, with a long neck, and a little lump on the back.

It is between the vibrio proteus and vibrio falx, and is distinguished by the lump _b_, Fig. 29, on the back, placed behind the neck; from this an even long neck, _a_, proceeds. The trunk, _d_, is elliptic, round, and without any lateral inequality; full of molecules, the hind-part, _e_, sharp and bright, the fore-part produced into a bending neck that is longer than the body; the apex even and whole, with blue canals passing between the marginal edges, occupying the whole length of the neck; in one of them a vehement descent of water to the beginning of the trunk is perceivable. The motion of the body is slow, that of the neck is more lively and flexuous, sometimes spiral. It is found in water where duck-weed grows.

80. VIBRIO OLOR. V. ellipticus, collo longissimo, apice nodoso. Plate XXV. Fig. 28. Elliptical, with a very long neck, and a knob on the apex.

The form of the body is elliptical and ventricose, the hind-part somewhat sharp. It is membranaceous, dilatable, winding variously; the hind-part is sometimes replete with darkish molecules. The neck, _d_, is three or four times longer than the body, of an equal size throughout, except a small degree of thickness at the apex, _f_, very pellucid. The motion of its neck is very lively, that of the body slow. It is found in water that has been kept for a long time, and which has acquired a vegetable greenness.

81. VIBRIO FALX. V. gibbosus, postice obtusus, collo falcato. A gibbous vibrio, the hind-part obtuse, the neck crooked.

The body is pellucid, elliptical, the fore-part lessening into a little round bright neck, nearly of the same length as the trunk, the hind-part obtuse. The trunk itself is rather rounding or tending to the gibbous, and filled with very small molecules; there are also two bright globules, one within the hind extremity, the other in the middle of the body. The neck being immoveable, the motions of the animalculum somewhat resemble those of a scythe.

82. VIBRIO INTERMEDIUS. V. membranaceus, antice attenuatus, postice subacutus. Membranaceous vibrio, the fore-part small, the hinder part somewhat acute.

It seems to be an intermediate species between the preceding vibrio and the fasciola, No. 74; it is a thin membrane, constantly folded. The whole of it has a crystalline talky appearance, the middle replete with grey particles of different sizes; it has all round a distinct bright margin; the apex of the neck is truncated, the tail obtuse.