Part 33

A new polype is formed out of small portions or fragments, in a very different manner, the operations in nature being always varied, according as the circumstances differ; each fragment is puffed up, the skin separated, and an empty space is formed within it; this part is to become the stomach of the rising polype, which soon sends forth arms, and is formed to the perfection proper to its kind. We learn from this instance that the skin of the polype is not so simple as was at first imagined; for we find it dividing itself into two membranes, and forming thereby a cavity fit to perform all the functions of a stomach; but why these membranes are separated in the small portions, and not in the larger, we cannot tell; but though we are ignorant of this, and many more circumstances relative to the re-production of these little animals, yet the foregoing facts enable us to understand better the nature of the existence of these polypes which have been turned inside out.

For as that part which formed the interior skin of the stomach in the little fragments before-mentioned, became the exterior part of the animal, the inside of the polype is consequently so similar to the exterior skin, that one may be substituted for the other, without injuring the vital functions; from hence we might, in some measure, have inferred the possibility of the polypes living, after they have been turned inside out, independent of the fact itself.

The viscera of the animal are situated in the thickness of the skin, and absorbing pores are placed both on the inside and outside, so that the animal can live whether the skin be turned one way or the other. The Author of nature did not create the polype to be turned as we turn a glove; but he formed an animal whose viscera were lodged in the thickness of the skin, and with powers to resist the various accidents to which it was unavoidably exposed by the nature of its life; and the organization necessary for this purpose was so constructed, that the skin might be turned without destroying life.

Every portion of a divided polype has, like the vegetable bud, all the viscera necessary to its existence; it can, therefore, live by itself, and push forth a head and tail, when placed end to end against another piece. The vegetation consists in uniting the portions, the vessels of each part increase in length, and a communication is soon formed between them, which unites the whole. The ease with which the parts unite, is as has been observed before, probably owing to their gelatinous nature; for we find many similar instances in tender substances. The solid parts of the embryo, as the fingers, unite in the womb; tender fruit and leaves may be also thus united.

A portion of these creatures is capable of devouring its prey almost as soon as it is divided from the rest. In the structure of those animals which are most familiar to us, a particular place is appropriated for the developement and passage of the embryo. But on the body of an animal, which, like a tree, is covered with prolific gems, it is not surprizing that the young ones should proceed from its sides, like branches from a tree. The mother and her young ones form but one whole; she nourishes them, and they contribute to her existence, as a tree supports, and is reciprocally supported by its branches and leaves.

OF THE HYDRA PALLENS.

The hydra pallens has been fully described only by M. Rösel;[113] it is very seldom to be met with, is of a pale yellow colour, and grows smaller gradually from the bottom, the tail is somewhat round or knobbed, the arms are about the length of the body, of a white colour, and generally seven in number, apparently composed of a chain of globules; it brings forth the young from all parts of its body. Linnæus defines it as, hydra pallens tentaculis subsenis mediocribus;[114] Pallas as, hydra attenuata corpore flavescente, sursum attenuato.[115]

[113] Insecten Belustigung, 3. Theil. pag. 465. Tab. LXXVI. LXXVII.

[114] System. Nat. p. 1320, No. 4.

[115] Zoophyt. 4.

OF THE HYDRA HYDATULA.

Plate XXI. Fig. 1, 2, 3, and 4.

The next in order is the hydra hydatula, which we have already defined from Linnæus as a hydra with four obsolete arms, and a vesicular body: it is spoken of by several medical writers, who are enumerated in the Systema Naturæ, p. 1321. It is described also by Hartman, Misc. Nat. Cur. Dec. I. An. 7, Obs. 206, Dec. II. An. 4, Obs. 73, as hydatis animata; also in the Dissert. de Inf. Viv. p. 50; n. 6, tænia hydatoidea. Pallas defines it as tænia hydatigena rugis imbricata corpore postice bulla lymphaticæ terminato. The following description is extracted from that in the Philosophical Transactions, No. 193, by Dr. Tyson, who names it lumbricus hydropicus.

In the dissection of a gazella or antelope, Dr. Tyson observed several hydatides or films filled with water, about the size of a pigeon’s egg, and of an oval form, fastened to the omentum, and some in the pelvis, between the bladder of urine and the rectum; and he then suspected them to be a particular sort of insect, bred in animal bodies, or at least the embryos or eggs of them: 1. Because he observed them included in a membrane, like a matrix, so loosely, that by opening it with a finger or knife, the internal bladder, containing the serum or lympha, seemed no where to have any connection with it, but would very readily drop out, still retaining its liquor, without spilling any of it. 2. He observed that this internal bladder had a neck or white body, more opake than the rest of the bladder, and protuberant from it, with an orifice at its extremity, by which, as with a mouth, it exhausted the serum from the external membrane, and so supplied its bladder or stomach. 3. Upon bringing this neck near the candle, it moved and shortened itself. Fig. 1, represents one of these watery bladders inclosed in its external membrane, its shape was nearly round, being only a little depressed or flatted, as a drop of quicksilver will be by lying on a plane. In Fig. 2, the neck is better seen; the external membrane being taken off, an open orifice is found at its extremity; it consists of circular rings or incisures, which are more visible when magnified, as in Fig. 3; it then appears granulated with a number of little eminences all over the surface; the orifice at the extremity seems to be formed by retracting itself inwards, and upon trial it was found to be so; for in Fig. 4, the neck of this polype is represented magnified and drawn out its whole length; on opening it there were found within the two strings a, a, which probably convey into the stomach the moisture and nourishment, which the animal, by protruding its neck, extracts from the external membrane.[116]

[116] Hydra hydatula habitat in abdomine mammalium, ovium, suum, murium, &c. inter peritoneum et intestina. Vesica lymphatica, pellucida, magnitudine pruni, petiolata corpore cylindrico, in cujus apice os, quod, corpore compresso, movet tentacula vix manifesta. Linn. Syst. Nat. p. 1321, No.5.

OF THE HYDRA STENTOREA.

Plate XXII. Fig. 27 and 28.

Hydra tentaculis ciliaribus corpore infundibuliformi.

The arms of this hydra are rows of short hairs, the body trumpet-shaped.

This species of hydra is very common, and has been described by almost every writer on these subjects; it is placed by Müller among the vorticellæ.

Vorticella stentorea caudata, elongata, tubæformis limbo ciliato. Müller animalcula infusoria.

Mr. Baker originally named it the funnel-like polype, which Messrs. Trembley and Reaumur changed to the tunnel-like polype, under which name it appears in the Philosophical Transactions, No. 474.

There are three kinds of them, which are of different colours, green, blue, and white. The white ones are the most common. It is necessary to observe them often, and in various attitudes, in order to obtain a tolerable idea of their structure. They do not form clusters, but adhere singly by their tail to whatever comes in their way; their anterior end is wider than the posterior, and being round, gives the animal somewhat of a funnel form, though it is not completely circular, having a sort of slit or gap that interrupts the circle. The edge of this opening is furnished with a great number of fibrillæ, which by their brisk and continual motions excite a current of water; the small bodies that float or swim near this current, are forced by it into the mouth of the little animal. Trembley says, that he has often seen a number of very small animalcula fall one after another into the mouth, some of which were afterwards let out again at another opening, which he was not able to describe.

They can fashion their mouths into several different forms. If any thing touch them, they shrink back and contract themselves. They live independent of each other, swimming freely through the water in search of their prey, and fix to any thing they meet with.

These animals multiply by dividing themselves, not longitudinally, nor transversely, but sloping and diagonal wise; the proceedings in nature continually varying in every new form of life. Of the two polypes produced by the division of one, the first has the old head and a new tail; the other, the old tail and a new head.

To make the description more clear, Trembley called that with the old head the superior polype, that with the new head the inferior one. The first particular that is observable in these polypes, when they are going to divide, is the lips of the inferior one; a transverse and oblique stripe indicates the part where it is going to divide; the new lips are formed at about two-thirds of the length of the polype, reckoning from the head; the division is made in a sloping line, that goes about half way round the parent animal; these lips are at first discerned by a slow motion, which engages the attention of the observer. They then insensibly approach each other and close, whereby a swelling is formed on the side of the polype, which is soon found to be a new head. When the swelling is considerably increased, the two polypes may be plainly distinguished. The superior one being now connected with the inferior one only by its lower extremity, is soon detached from it, and swims away to fix itself on some convenient substance; the inferior one remains fastened to the place where the original polype was fixed before the division.

From the various modes by which different species of polypes are multiplied, we are led to form more exalted ideas of nature, and to see that the little we discover is but an exceeding small part of her contents; we learn also to be more cautious in reasoning from analogy, and laying down the known for a model to the unknown, because we find that the operations in nature are varied ad infinitum.

The growth of the hydra fusca is very quick, but that of the hydra stentorea is much more so. The progress of the fœtus is always more rapid than that of the infant and adult animal; but in these organized atoms the evolution is so rapid, as to appear almost like an immediate creation.

Fig. 28 represents the hydræ stentoreæ, or funnel-polypes, fixed to the under side of a piece of some vegetable substance; they are in this figure of their natural size.

Fig. 27, the same polypes magnified; the different forms they assume are also seen here, sometimes short and thick, as at m m; long, as at n; nearly globular, as at o; extended to the full size, as at k; seen as contracted at i. The fibrillæ or little hairs may be seen in most of the attitudes except those of l.

OF THE HYDRA SOCIALIS.

Plate XXI. Fig. 11.

Hydra socialis mutica torosa rugosa.[117]

[117] Linn. Syst. Nat. p. 1321. No. 7.

Social hydra, bearded thick and wrinkled.

This species of hydra has been described by many writers. It is the vorticella socialis of Müller, who defines it as vort cella caudata, aggregata, clavata; disco obliquo. Müller Animalcula Infusoria, p. 304. Pallas makes it a brachionus, Pall. Zooph. 53.

In Fig. 11, these animals are represented as considerably magnified; they appear like a circle, surrounded with crowns, or ciliated heads, tied by small thin tails to a common center, from whence they advance towards the circumference, where they turn like a wheel, with a great deal of vivacity and swiftness, till they occasion a kind of whirlpool, which brings into its sphere the proper food for the polype. When one of them has been in motion for a time, it stops, and another begins; sometimes two or three may be perceived in motion together. They are often to be found separate, with the tail sticking in the mud. The body contracts and dilates very much, so as sometimes to have the appearance of a cudgel; at others, to assume almost a globular form. The young polypes of this species have been sometimes taken for the hydra stentorea.

OF THE VORTICELLÆ.

We now come to another division of these animals, to which later writers have given the name of vorticellæ; this term I shall therefore adopt, being of opinion that it behoves every man to maintain that order in scientific arrangement which is not inconsistent with truth, except he can produce another arrangement more expressive of the nature of the objects it is designed to discriminate; a process requiring no small degree of attention.

The variety that may be observed in these minute animals confirms a principle, which, the more it is inquired into, the more it will be found to accord with the general operations in nature, namely, that there is always a pre-existent principle of life necessary to the organization both of animals and vegetables; that the alimentary and other particles which are added to, or apparently belong to them, produce nothing of themselves; they are incapable of forming the least fibre, but they are able to become constituent parts of one organical whole, together with the instruments whereby the forming principle is manifested, and rendered capable of acting upon certain orders of creatures.

VORTICELLA.

Animal calyce vasculoso; ore contractili ciliato, terminali. Stirps fixa.

A small animal, with a vascular cup; the mouth is at one end ciliated, and capable of being contracted, the stem fixed.

VORTICELLA ANASTATICA.

Plate XXI. Fig. 13, 14, 15, and 16*.

Vorticella anastatica, composita, floribus campanulatis, stirpe multiflora rigescente.

Vorticella anastatica, compound, with bell-shaped flowers, and a rigid stem.

Cluster polype, second species. Trembley, Philos. Trans. vol. xliv. part. 2. p. 643.

These polypes form a group resembling a cluster, or more properly an open flower; this flower or cluster is supported by a stem, which is fixed by its lower extremity to some of the aquatic plants or extraneous bodies that are found in the water; the upper extremity forms itself into eight or nine lateral branches, perfectly similar to each other; these have also subordinate branches, whose collective form much resembles that of a leaf. Every one of these assemblages is composed of one principal branch or nerve, which makes with the main stem of the cluster an angle somewhat greater than a right one; from both sides of this nerve the smaller lateral branches proceed; these are shorter the nearer their origin is to the principal branch.

At the extremity of the principal branch, and also of all the lateral ones, there is a polype or vorticella. There are others on both sides of the lateral twigs, but at different distances from their extremity. These polypes are all exceeding small, and of a bell-like figure; near their mouth a quick motion may be discerned, though not with sufficient distinctness to convey an adequate idea of its cause; upon the branches of these clusters are round bodies, which will be more particularly described presently.

Every cluster has eight or nine of these branches or leaves; they do not all proceed from the same point, but the points from whence they set out are not far asunder; each of these branches is bent a little inwards, so that all of them taken together form a kind of shallow cup. If the eye be placed right over the base of this cup, the appearance of the whole eight or nine branches is like unto that of a star, with so many rays proceeding from the center. If the cluster be slightly touched, all the branches instantly fold up, and form a small round mass. The stem which supports the cluster contracts also at the same time, folding up like a workman’s measuring rule, that consists of three or four joints. This extraordinary assemblage constitutes one organized whole, formed of a multitude of similar and particular ones. A new species of society, in which all the individuals are members of each other in the strictest sense, and all participate of the same life.

A few days after one of these clusters is formed, small round bodies or bulbs may be perceived to protrude in several places from the body of the branch; these grow very fast, and arrive at their greatest growth in two or three days. The bulbs detach themselves from the branches out of which they spring, and go away, swimming till they can settle upon some substance which they meet with in the water, and to which they fix themselves by a short pedicle; the bulbs are then round, only a little flatted on the under side, the pedicle continues to lengthen gradually for about twenty-four hours, during the same time the bulbs also change their figure, and become nearly oval. There are in a cluster but few of these bulbs, compared with the number of the vorticellæ, neither do all the bulbs come out at the same time. The bulb then divides lengthways into two smaller ones, but which are still much larger than the vorticellæ themselves. It is not long before these are separated like the first, and thus form four bulbs on the same stalk; these again divide themselves, and form eight; which again subdivide, and consequently make sixteen. They are all connected with the stalk by a proper pedicle, but they are not all of an equal size; the largest continue to divide, and the smallest begin to open, and take the bell-formed shape. Trembley observed from one round bulb, in about twenty-four hours, by repeated divisions, one-hundred and ten vorticellæ to be formed.

It has been asked with propriety, what plant or what animal could have led us to expect an existence and mode of propagation similar to that of the vorticella anastatica?

Fig. 13 represents one branch of the vorticella anastatica; on this branch, besides the vorticellæ which are of a bell-like form, some of those round bodies from which they first spring, and by which they are so remarkably distinguished from any other species, may be seen.

Fig. 14 represents one of the globular bodies after it has parted from the cluster, and has fixed itself to some other body, and after the globule itself and its pedicle have begun to lengthen.

Fig. 15 represents the two bodies that were formed by the parting of that which is shewn at Fig. 14.

Fig. 16* represents four that were formed by the separation of the two bulbs, exhibited in the foregoing figure.

VORTICELLA PYRARIA.

Plate XXII. Fig. 25, 26.

Vorticella composita, floribus muticis obovatis; tentaculis bigeminis, stirpe ramosa. Compound, with beardless oval florets, two double arms, the stem branched.

It is somewhat of a pear shape, the base is pellucid, the top truncated, the lateral arms, which are a pair on each side, cannot be distinguished without some attention; they are sometimes to be seen disengaged from the pedicle, and rolling swiftly in a kind of circle.

VORTICELLA CRATÆGARIA.

Plate XXII. Fig. 40.

Vorticella composita, floribus muticis globosis; tentaculis binis, stirpe ramosa. Compound, with globous naked florets, two tentacules, and a branched stem.

These vorticellæ are to be found in the month of April, both in the mud, and upon the tail of the monoculus quadricornis; they are generally heaped together in the manner in which they are represented in the figure; they are of a spherical form, and united to one common stalk. They are also often to be found without any pedicle. The body is rather contracted; the aperture is circular, and surrounded with a marked margin; it has two small arms. With a deep magnifier, a vehement rotatory motion may be seen. They sometimes separate from the community, and go forwards in a kind of spiral line, and then in a little time come back again to the rest.

The figure represents a parcel of these vorticellæ united together.

Among the other authorities for this animal, Linnæus refers to Baker’s description of the mulberry insect, “Employment for the Microscope,” p. 348, which, as it differs a little from the preceding account, we shall insert here. That from which his drawing was made, and which he has described, was found in a ditch near Norwich; he called it the mulberry insect, from the resemblance it bore to that fruit; though the protuberances that stand out round it are more globular than those of a mulberry. It is to be seen rolling about from one place to another, and is probably a congeries of animalcula; they are to be met with in different numbers of knobs or protuberances, some having fifty or sixty, others more or less, down to four or five. The manner of moving is the same in all. They are generally of a pale yellow.

VORTICELLA OPERCULARIA.

Plate XXII. Fig. 29.

Vorticella composita floribus muticis ovalibus, stirpe ramosa. Compound, with naked oval florets, and a branched stem.

These vorticellæ are of a lemon shape, and are generally found in clusters, branching out from a stem, which mostly adheres to some convenient substance.

That species of them which is described by Baker had a very short pedicle, and the animals were much longer than those which are represented at Fig. 29. There was no main stem, but all the pedicles were joined in one center, round which the animals extended themselves as so many radii, forming a very pleasing figure.

The mouths of these animalcula are not ciliated, but they are furnished with a round operculum or cover, connected by a long ligament or muscle, which extends downwards through the body, and is affixed withinside of it, near the tail. This ligament may be contracted or dilated, so that the cover can be removed to some distance from the mouth; in this situation several short hairs maybe found to radiate from it; these have a vibratory motion, by which they excite a current of water, most probably to draw in the proper nourishment, after which they shut or pull down the cover, which they again extend at pleasure: when the cover is pulled close down, the mouth contracts, and no hairs are to be seen.

Fig. 29 represents the vorticella opercularia; ſ, the operculum removed at some distance from the mouth, at t; it is nearly close at r, the mouth contracted, the cover drawn in, and no hairs to be seen; u, a part of the stalk, from which some of the animalcula are separated.

VORTICELLA UMBELLARIA.

Plate XXII. Fig. 30.

Vorticella composita, floribus ciliatis globosis muticis, stirpe umbellata. Compound, with ciliated globous naked florets and an umbellated stem.

Vorticella acinosa, simplex, globosa, granis nigricantibus, pedunculo rigido. Müller Animal. Infus. p. 319.

We frequently find in divers places, upon water-plants, and other bodies in the water, a whitish substance that looks like mould; plants, pieces of wood, snail shells, &c. are often entirely covered over with this substance. If we examine any of these minute bodies by the microscope, we shall find such motions as will induce us to think them an assemblage of living animals, severally fixed to the extremities of small stems or pedicles, many of which are often so united as to form together a sort of branches or clusters, from whence they have been termed clustering polypes, or des polypes en bouquet.