Chapter III: Part 3

A paper in the Philosophical Transactions for 1693, mentions the collection of pearls from this shell, in the river Omagh, County Tyrone, in Ireland. “The poor people,” he says, “in the Summer months, go into the water, and some with their toes, some with wooden tongs, and some by putting a sharpened stick into the opening of the shell, take them up; and, although, by a common estimate, not above one shell in a hundred may have a pearl, and of these pearls not above one in a hundred be tolerably clear, yet a vast number of fair merchantable pearls, and too good for the apothecary, are offered for sale by those people every Summer assizes. Some gentlemen of the country make good advantage thereof, and myself, whilst there, saw one pearl bought for 50_l._ that weighed thirty-six carats, and was valued at 40_l._ A miller took out a pearl, which he sold for 4_l._ 10_s._ to a man that sold it for 10_l._, who sold it to the late Lady Glenanly for 30_l._, with whom I saw it in a necklace; she refused 80_l._ for it from the late Dutchess of Ormond.”

THE HEART-SHAPED ISOCARDIA,

(_Isocardia cor_.)

This shell, which is very common in the Mediterranean, where it goes by the name of the _foolscap-shell_, and the _bullock’s heart shell_, is rare in the British seas, but it is sometimes found on the Irish coast; it is the largest British bivalve shell.

THE WEDGE-SHAPED DONAX, (_Donax cuneata_.)

There are nearly thirty species of Donax, all extremely beautiful; that represented in the engraving is of a whitish colour with red streaks: it is often met with in collections of Indian shells. One of these species is found on the English coasts, of a delicate white colour, and streaked with pink.

In following the system of Lamarck, we are gradually led through various genera to two species figured on the next page, namely, the Tellina, or _earth-shell_, and the Pandora, and, ultimately, to the Solen, or _razor-shell_.

THE SHEATH SOLEN, (_Solen vagina_.)

The Solens are singular from the power they possess of burying themselves in the sands on the coast, sometimes even to the depth of a couple of feet. The foot of the Solen, by means of which it is able to penetrate the sand, is equal to one-half of the length of the shell. Their movements are confined to rising to the surface of the sand in which they have formed their hole, and in again sinking to the bottom. This movement is, no doubt, produced by the action of the foot, which forms itself into a sharp point in its descent, and when it remounts is enlarged as much as possible, to form a resting-point, for the purpose of raising the shell to the surface. It is not supposed that the animal ever entirely leaves its hole of its own accord, although it may possess the power; but it is certain, according to the observations of Réaumur, that if forcibly removed it can re-enter it. The hole it forms for its retreat is always perpendicular.

One of these creatures, being taken out of its retreat, was laid on the sand; it first extended its foot in the form of a wedge, or rather cone, and, applying it to the surface of the sand, slightly raised the farthest end of its shell; at the next effort the projecting part of the foot was buried in the sand, and the shell became more elevated; after two or three more attempts the hole had attained a perpendicular direction, and the shell was partly buried in it; the shell then began to descend, and that with considerable quickness.

The Solens are used sometimes, but rarely, for food; but in places where they abound, they are sought after as bait for fishes: the method of taking them is very singular. Having discovered the place of retreat of the creature, by observing the hole in the sand which leads to its chamber, the fisherman throws into its entrance a small quantity of salt. Although an inhabitant of salt water, the pure salt produces so irritating an effect on the extremity of its body, that it quickly mounts to the surface; the fisherman, waiting for its appearance, snatches hastily at it, and if he succeeds in seizing it firmly, makes good his capture; but if not sufficiently active, and the animal escapes, the application of fresh salt produces no further effect; either it is not sensible to the additional infusion of salt, or, which is most likely, the instinct of self-preservation causes it to put up with the inconvenience rather than be taken. In this case, no other means are left of securing it, than using an iron instrument to dig it out with. The number of species is upwards of twenty.

THE DATE-SHAPED PHOLAS, (_Pholas dactyloides_.)

These creatures have much more powerful means of boring than the solens, for not only do they imbed themselves in hard clay, but even in stone and lava. In what manner this is effected has been the subject of much dispute; it is almost certain that the process is not mechanical, for their soft body, and the fragile nature of their shells, seem an insuperable bar to such a proceeding. Some authors have asserted that the hole is formed by means of an acid secreted by the animal, which acts chemically on the stone; but there are two reasons against this solution of the difficulty; first, no acid liquid has been discovered in the living animal, and, secondly, although acid would act upon stone, it would have no effect whatever on lava.

Another curious part of the history of these shell-fish is their phosphorescence, which is so bright, that it has been asserted, if eaten in the dark without their being cooked, it appears as if the person devouring them was swallowing phosphorus.

Although not used as food in this country, they are not uncommonly eaten on the shores of the Mediterranean, where some large species are found.

The species represented in the engraving is found on the British coasts, imbedded in clay; its shell is of a delicate white, beautifully carved. The projecting piece at the lower part of the shell in the engraving is the long foot of the animal; on the right hand, the hole from which a shell has been removed is shown.

THE SHIP-WORM, (_Teredo navalis_.)

Before the anatomy of this destructive creature had been carefully examined, there was as much difficulty in guessing at the means it employed in penetrating the solid timbers in which it is found, as there is with regard to the operations of the Pholas; but subsequent observation shows that the hard parts, of which the mouth is formed, are fully equal to the task.

Perhaps we may say, with propriety, that this is the only species of the shell-bearing tribes that is decidedly injurious to mankind. The animal of the Teredo is a long worm-shaped creature, dwelling in a tube of a shelly substance, which it forms for itself in its progress through the wood; the small pointed shell-like pieces, to the right in the engraving, form the jaws of the animal. With the assistance of these it cuts its way into the timber, and, at the same time, lines the excavation it is making with a shelly substance, which is gradually formed into a tube, the animal occupying that part which is most deeply sunken in the timber; in directing its course it generally excavates in the direction of the grain of the wood, but in some instances it crosses this grain.

In Holland a great part of the country is below the level of high water, and, to prevent the irruption of the sea, immense dykes have been formed along the coast; these are framed, on the sea-side, of large masses of sand, while to the landward they are strengthened by means of strong piles driven into the ground and wattled together. These piles were once discovered pierced in all directions by this destructive worm, to such an extent as to endanger their safety, and had it not been for a timely discovery of the mischief, immense tracts of country would have been laid under water, and irretrievably lost.

CLASS CIRRHIPEDA.

The Cirrhipeds are well known under the names of _Barnacles_ and _Acorn-shells_, being found attached to rocks, ships’ bottoms, and pieces of timber which have been under the water for a length of time. They also at times fix themselves on the shells of the larger Mollusca, and on the backs of whales, tortoises, &c. These creatures, from their singular formation, have often proved a stumbling-block in the way of the systematic naturalist, who, from their anomalous characters, was unable to refer them to any part of his system; and although their true nature, which has more recently been discovered by a British naturalist, was partially suspected by Lamarck, (without, however, any definite idea on the subject,) we have still placed them immediately after the Conchifera, although, as we shall presently show, they ought more properly to be ranged with the Crustacea, that is, the crab and lobster tribes, and in future systems this no doubt will be the case.

After noticing their resemblance in many respects to the Crustacea, Lamarck thus expresses himself. “In fact, when I established the CLASS of Crustacea, I formed the _first order_ of this class, (the _Cirrhipeds_,) under the name of _sightless Crustacea_, but a few years afterwards I separated them and placed them at the end of the Mollusca, but this was no better. If, for example, we consider those characters which furnish their most important organs, we shall find that the Cirrhipeds, without any doubt, most nearly resemble the Crustacea, for they have the same system of nerves, they have jaws analogous to those of the Crustacea, and their tentacula resemble the antennæ of the shrimps.” To prove that they really were Crustacea, was a task that devolved upon a British naturalist, I. V. Thomson, Esq., a surgeon in his Majesty’s forces. The manner in which this discovery took place, we shall notice further on.

The Cirrhipeds have obtained their name from the hairy feelers, or tentacula, with which they are provided; the name Cirrhipeda being derived from two Latin words,—_cirrhus_, hair, and _pes_, the foot; these appendages, being figuratively called feet, although they have, in reality, but little relation to that organ of motion.

They have been separated into two orders; namely, _Cirrhipeda pedunculata_, which are attached to any object by a tube of a leathery nature, as, for instance, the Barnacle,—and _Cirrhipeda sedentaria_, which are fixed directly to the rock, like the Acorn-shell.

_ORDER CIRRHIPEDA PEDUNCULATA._

(_Cirrhipeda with a Footstalk._)

THE SMOOTH BARNACLE, (_Anatifa lævis_.)

The curious popular error, that the Barnacle contained the young of a species of goose, which was thence called the Barnacle Goose, has lasted for many ages, and still prevails among the uneducated, on the shores of many of the European seas. One reason of the continuance of this error in several Roman Catholic countries, is the permission granted by the priest to its members, to eat this goose on fish-days, because it is considered, on account of its supposed watery origin, to partake more of the character of a fish than a fowl. To show the extent to which an erroneous belief may be carried, we may quote the following notice sent by Sir Robert Moray to the Royal Society, and _printed_ by them in their _Transactions_. He says, “The pedicle seems to draw and convey the matter which serves for the growth and vegetation of the shell and the little bird within it.” “In every shell that I opened, I found a perfect _sea-fowl_; the little bill like that of a _goose_, the eyes marked; the head, neck, breast, wings, tail, and feet formed; the feathers everywhere perfectly shaped, and blackish-coloured; and the _feet_ like those of other water-fowl, to my best remembrance!” “Nor did I ever see any of the little birds alive, nor met with anybody that did; only some credible persons have assured me that they have seen some as big as their fist!!”

_ORDER CIRRHIPEDA SEDENTARIA_,

(_Sedentary Cirrhipeds_.)

THE ACORN-SHELL, (_Balanus_.)

Mr. Thomson describes his discovery of the real nature of the Cirrhipeds in these words. “On April 28, 1823, which the author had devoted to the investigation of some marine productions, he was returning home without any addition to his stock of knowledge, when, casually throwing out a small muslin towing-net, on crossing the ferry at Passage, such a capture of marine animals was made, as furnished a treat which few can ever expect to meet, and could hardly be excelled for the variety, rarity, and interesting nature of the animals taken.” After mentioning the names of several very rare species, he continues “and others perfectly nondescript, and incapable of being associated in any of our classifications of the Crustacea; of this description is the little animal about to be described.

“There is a small translucent animal one-tenth of an inch long, of a somewhat elliptic form, moderately compressed, and of a brownish hue. When in a state of perfect repose, it resembles a very minute mussel, and lies upon one of its sides at the bottom of the vessel of sea-water in which it is placed. At this time all the members of the animal are withdrawn within the shell, which appears to be composed of two valves, united by a hinge along the upper part of the back, and capable of opening from one end to the other along the front, to give occasional exit to the legs. The limbs are of two descriptions; namely, in front a large and very strong pair, provided with a cup-like sucker and hooks, &c., and at the hinder part of the body, six pair of swimming-members, so articulated as to act in concert, and to give a very forcible stroke to the water, so as to cause the animal, when swimming, to advance by a succession of bounds, after the manner of the water flea.

Fig. 1. Larva of Barnacle, natural size.
2. " " " magnified, seen from above.
3. " " " highly magnified, seen from side;
_a_, swimming-members;
_b_, front limb, with sucker.
4. Eye, much magnified.
5. Perfect Young Barnacle, natural size.
6. " " " full grown.

]

“The greatest peculiarity, however, in the structure of this animal, is the eyes; which, although constantly shielded by the valves of the shell, are placed on footstalks, as in the crab and lobster, in front, at the sides of the body.

“Some of these curious creatures were collected in the Spring of 1826; and, in order to see what changes they might undergo, were kept in a glass vessel, covered by such a depth of sea-water, that they could be examined at any time by means of a common magnifying glass; they were taken on May the 1st, and on the night of the 8th, the author had the satisfaction to find that two of them had thrown off their _exuviæ_[4], and, wonderful to say, were firmly adhering to the bottom of the vessel, and changed into young Barnacles! such as are usually seen intermixed with grown specimens, on rocks and stones, at this season of the year. The eyes were still perceptible, although the principal part of the black colouring-matter appeared to have been thrown off with the _exuviæ_. On the 10th, another individual was seen _in the act of throwing off its shell_, and attaching itself, like the others, to the bottom of the glass.”

CLASS ANNULATA.

We cannot better describe the Annulose animals than in the words of Lamarck; he calls them,

“Animals with soft bodies, lengthened, worm-shaped, naked, or inhabiting tubes, with the body divided into segments, or at least transverse wrinkles, often without head, without eyes, and without antennæ, unfurnished with articulated limbs, but the greater number having, instead, small protuberances, bearing spines, and capable of being retracted at pleasure, disposed in rows along the sides, though not continued quite to the extremity of the body, and assuming various forms. They have also red blood circulating by veins and arteries; this separates them from the Worms, properly so called, which have white blood. This colour of the blood is a singular fact, since the animals are much less complex in their organization than the Mollusca, which have colourless blood. The Class of Annulose animals has been separated into three Orders, namely, _Annulata sedentaria_, which are fixed to other substances; _Annulata antennata_, possessing antennæ, or feelers; and _Annulata apoda_, without projecting members answering as feet, serving solely to attach the animal to rocks, stones, &c.”

_ORDER ANNULATA SEDENTARIA_,

(_Sedentary Annulose Animals_.)

The creatures which form this order are generally found attached to rocks, shells, &c. and are usually of small size. The engraving represents a variety of species of these animals. Of the genus Serpula there are many species, but as it is in general merely the shell that is found in collections, they are but ill defined; some of the species are found in almost all climates. The animal of the Serpula has great power of contracting its body, but it never leaves its shell or tube; this tube is gradually lengthened by the inhabitant, who always occupies the most recently-formed portion of it; its _operculum_, the lid with which it closes the opening of its tube, is very prettily formed; it is something like the mouth-piece of a trumpet, but of course not perforated, and it closes the opening with great accuracy.

THE MAGNIFICENT AMPHITRITE,

(_Amphitrite magnifica_.)

This beautiful species is perhaps the largest of the whole tribe as yet discovered. It is found in various parts of the coast of Jamaica, adhering to, or rather embedded in, the rocks. Its irritability is exceedingly great, and on being approached it instantly retreats into its elastic tube; this tube is of a leathery consistence, unlike that of the Serpula. Specimens of this elegant species can only be obtained by breaking off such parts of the stone as contain them. These, being put into tubs of sea-water, may be kept for months in perfect health. That part of the body which is so beautifully spread out like an umbrella, consists of the _branchiæ_ or organs of breathing; these are of a yellowish colour, beautifully marked with pink. The Amphitrite, although perhaps it never entirely leaves its tube, is not attached to it, and frequently draws out nearly the whole of its body.

_ORDER ANNULATA ANTENNATA_,

(_Annulose Animals possessing Antennæ_.)

THE SAND-WORM OF THE FISHERMEN,

(_Arenicola piscatorium_.)

This Worm forms its nest in the sand on the sea-shore, and is much sought after by fishermen as bait for fishes. It is found in all the European seas. There appears to be but one species, but that is met with in great abundance.

BLOOD-COLOURED LEODICE, (_Leodice sanguinea_.)

The antennated Annulata differ materially from those which are enclosed in a case; they possess, in addition to their antennæ, organs of motion, like the false legs of a caterpillar, and two or four well-formed eyes; they are all marine animals, and altogether they bear a strong resemblance to the _scolopendra_, or centipede.

The species represented above was taken on the southern coast of Devonshire; it is the largest English species, extending sometimes to the length of fourteen or fifteen inches.

When the animal was in a glass of sea-water, the circulation of the blood through the bristle-like appendages on each side of the body was a curious object, and appeared to be effected at the will of the animal, but when it became sickly, the circulation was slower, and as soon as it expired all the colour from those parts vanished.

The mouth is large, and placed beneath, concealing most formidable jaws, or complicated fangs, which were put forward occasionally as the animal became sickly, or in the agonies of death. The figure beneath the worm shows the shape of this singular apparatus.

THE SPINOUS SEA-MOUSE, OR SEA-CATERPILLAR,

(_Halithæa aculeata_.)

The Sea-Mouse is found in the European seas, and when in its native element is singularly beautiful, the hair with which it is partially covered being equal in splendour to the colours on the tail of a peacock.

_ORDER ANNULATA APODA_,

(_Footless Annulose Animals_.)

The greater portion of the Annulose animals, namely those already described, are furnished with small projecting points on the sides of their body, which assist them in their motions, and which may, consequently, be considered as supplying the place of feet; but those we have yet to notice have no similar appendages, and, therefore, they are called footless. They are all very lively in their movements, and live either in moist earth, or the mud at the bottom of ponds. We find among the footless Annulata two well-known genera, namely, the Earth-worm and the Leech.

THE COMMON EARTH-WORM,

(_Lumbricus terrestris_.)

The body of the Earth-worm is composed of a great number of narrow rings, and along each side are four rows of very small, short, silk-like bristles, of a substance partly horny and partly shell-like. These bristles are placed on the edges of the rings, and it is by the alternate contraction and expansion of these rings that the worm is enabled to move along, the little bristles acting like hooks, and so forming various fixed points of resistance or _fulcra_, upon which the animal can rest at each movement forwards. The organization of the Earth-worm is very simple, the intestinal canal for the food being a simple straight tube, except in one part of its length, where a kind of gizzard is found, which answers the purpose of a stomach. It is supposed to feed upon the vegetable substances it finds in the earth.

The hole, or burrow, formed in the earth by the worm, always has two openings, one by which it enters, and by which it throws out the dirt which is removed during the progress of its excavation, and the other by which it sometimes leaves its burrow, so that the hole made by the animal would be much in this form, descending at A, and reaching the surface by B. It has been said, that the Earth-worm, if divided by the spade or otherwise, will unite again and live; the foundation for this appears to be the more probable fact, that, when divided, that portion of the animal in which the head is placed may, perhaps, survive the mutilation, and ultimately again become a perfect creature.

Although worms, after wet weather, sadly disfigure our gravel walks, they are, at the same time, useful gardeners, loosening the earth round the roots of plants, and thus rendering it more capable of receiving the small fibres of the roots. During the Winter they penetrate very deeply into the ground, and remain, according to Latreille, rolled up in a kind of nest, protected from injury by the discharge of _mucus_, which is furnished by the pores of their body.

The Earth-worm appears to have been a considerable favourite with the author of the _Journal of a Naturalist_; among other remarks, he observes, “There is another creature, and that a very important one in the operations of nature, that is surrounded by dangers, harassed, pursued incessantly, and becomes the prey of all; the common Earth-worm. This animal, destined to be the natural manurer of the soil, and the ready indicator of an approved staple, consumes on the surface of the ground, where they soon would be injurious, the softer parts of decayed vegetable matter, and conveys into the soil the more woody fibres, where they moulder and become reduced to a simple nutriment, fitting for living vegetation. The parts consumed by them are soon returned to the surface, whence dissolved by frosts, and scattered by rains, they circulate again in the plants of the soil,

Death still producing life.

“Thus eminently serviceable as the Worm is, it yet becomes the prey of various orders of the animal creation, and perhaps is a solitary example of an individual race being subjected to universal destruction. The very emmet seizes it when disabled, and bears it away as its prize. It constitutes throughout the year the food of many birds; fishes devour it greedily; the hedgehog eats it; the mole pursues it unceasingly in the pastures, along the moist bottoms of ditches, and burrows after it through the banks of hedges, to which it retires in dry seasons. Secured as the Worm appears to be by its residence in the earth, from the capture of creatures inhabiting a different element, yet many aquatic animals seem well acquainted with it, and prey on it as a natural food, whenever it falls in their way: frogs eat it, and even the great water-beetle I have known to seize it, when the bait of the angler, and it has been drawn up by the hook. Yet notwithstanding this prodigious destruction of the animal, its increase is fully commensurate to its consumption, as if ordained the appointed food of all.

“Worms, generally speaking, are tender creatures, and water remaining over their haunts for a few days, drowns them. They easily become frozen, when a mortification commences at some part, which gradually consumes the whole substance, and we find them on the surface a mass of jelly. Their retiring deeper into the soil is no bad indication of approaching cold weather; but no sooner is the frost out of the ground, than they approach the surface.

“Earth-worms do considerable mischief to the floriculturist by drawing the young plants, immediately after they are transplanted, into the earth. In the drainage of lands they are of essential service, penetrating the clay that lies beneath the vegetable mould in every direction, and thus forming numerous small canals to carry off the water into the deep trenches dug by the agriculturist.” The author we have already quoted, after concluding this account of the Worm, says, “I would advocate the cause of all creatures, had I the privilege of knowing the excellency of them; not willingly assigning vague and fanciful claims to excite wonder, or manifesting a base pride by any vaunt of superior observation; but when we see, blind as we are, that all things are formed in justice, mercy, truth, I would tell my tale as a man, glory as a Christian, and bless the gracious Power that permitted me to obtain this knowledge.”

THE MEDICINAL LEECH, (_Hirudo medicinalis_.)

The medicinal utility of the Leech seems, even in very remote times, to have been acknowledged by mankind, and accordingly we find it noticed in the writings of many ancient physicians. It was not simply applied to the cases in which it is at present employed, but was recommended to be used in many singular ways: a paste made of the ashes of a burnt leech was said to have the property of removing the hair from any part of the body. It was also employed to suck the blood from a wound occasioned by a mad dog, or any other rabid animal.

At present the employment of this useful creature is confined to the operation of drawing blood from inflamed parts of the surface of the body, for which use it is eminently adapted.

There are as many as twelve or fifteen species of these creatures, but only two have been employed in medicine, namely, the _Hirudo medicinalis_, which may be known by having six yellowish lines, or striæ, on its back, while the under part is of a grayish hue spotted with black, but, as we shall presently see, these markings are not uniformly found; and the _Hirudo troctina_, of a brownish colour, the upper part of the body marked with black spots, each of which is surrounded with a golden-coloured ring, the sides of a dingy yellow, and the under part of a yellowish green with black spots.

The first of these species, the medicinal leech, is common throughout the whole of Europe, but is much more abundant in the Southern parts; it is generally about three inches in length. Formerly it was very abundant in Great Britain, but the improvements in agriculture, and the consequent drainage of the land, together with the great use made of it in medicine, have of late years rendered it of less frequent occurrence. On this account great quantities of leeches are imported; these chiefly come from Bourdeaux and Lisbon. On a moderate calculation, it appears that, in England, on an average, out of every hundred leeches employed, ninety-nine may be considered of foreign production; these differ from the English leech in being somewhat larger, and having the under part of a uniform colour, without spots. Some idea may be formed of the number of leeches used in medicine by the statement, that in the hospitals of Paris alone, 300,000 were employed in one year. The prevailing colour of the medicinal leech appears to vary according to the nature of the soil on which it is found. In Winter the leech retires to waters of considerable depth, and seeks shelter in the mud at the bottom; but in the Summer it appears to delight in shallow pools, basking, as it were, in the warmth of the sun: but if the water it frequents is in danger of being dried up by the Summer-heat, the leech buries itself in the mud at a considerable depth. Just before a thunder-storm, leeches appear much agitated, and rise frequently to the surface of the water; this, therefore, is considered by the _leech-gatherers_ as a favourable time for collecting them.

The property by which a leech anticipates thunder, has induced some persons to employ it as a species of barometer; for this purpose a leech is enclosed in a glass vessel half-filled with water, and the following is supposed to be the result. When the weather is about to be serene and pleasant, the leech will remain at the bottom of the vessel without the least movement; secondly, if it is about to rain, the animal will rise to the surface, and there remain until the approach of fine weather; thirdly, before boisterous weather, it will appear in a state of great agitation; fourthly, on the approach of thunder, it will remain out of water for several days, appearing agitated and restless, and so on.

This natural barometer _appears_ to answer tolerably well, if there is sufficient belief in its virtues on the part of the possessor, and if one leech only is employed; but when several of these creatures are enclosed in the same vessel, they do not appear to obey the same laws, and, consequently, their movements do not correspond with sufficient accuracy to render their indications of the weather of much use.

The medicinal leech appears during its whole life to exist on the blood or other juices of the creatures on whose body it fixes itself; this is not the case with the horse-leech, which lives entirely on the _larvæ_ of aquatic insects, worms, &c., so that the common idea of the danger of the bite of the horse-leech is without foundation.

The horse-leech is exceedingly voracious, not only swallowing worms, tadpoles, &c., but even preying upon its own species. Sixty-five horse-leeches were placed in a glass vessel, and in five days the number was reduced to fifty-two, and not a vestige of those that were missing was to be discovered.

The usual slowness of action of the digestive powers in all animals of cold blood, was curiously illustrated in the case of a horse-leech, which, after swallowing two small leeches of a different species, disgorged one of the two at the end of three days, in a living state, and apparently not much injured from its sojourn in so unusual a lodging; but it enjoyed its liberty only for a few hours, its more powerful companion swallowing it a second time at the end of that period.

A number of this species of leech, inhabiting the water that supplied a trough in which a tench had been placed, fixed themselves to different parts of the body of the fish, and so effectually was the poor tench annoyed, that it was soon deprived of life. “The leeches then tore it (previously breaking the line of connexion between the various parts of the body, by inflicting a vast number of bites or wounds,) into such pieces as they could readily receive into the stomach, and so diligent were they, that in a few days nothing remained of the fish but the mere skeleton.”

From these habits it would appear, that the name of Hirudo _sanguisuga_, (the blood-sucking leech,) has been improperly applied to the horse-leech; on this account a recent author has suggested the name of Hirudo _vorax_, (the voracious leech,) as being more suitable to its nature.

Leeches are supposed to be very long-lived; two were preserved in confinement for eight years before they died, and the well-ascertained slowness of their growth seems to place their length of life beyond a doubt.

On the head of the medicinal leech ten points are arranged in the form of a horse-shoe, thus—

These are considered, by some authors, to be organs of sight, or eyes, while, on the other hand, it is stated by others, that they are merely tubercles. Lamarck was of this opinion, and, consequently, in describing their character, says they are without eyes.

The teeth, or rather piercers, with which the leech is furnished, are three in number, of a hard gristly substance, and so placed, with regard to each other, as to meet in the centre at equal angles; these piercers are thrust into the skin when the animal attaches itself; not by one plunging effort, but by constantly scratching or sawing upon the surface (assisted at the same time by the sucking action of the lips); in this manner they gradually become buried in the skin, and there remain as long as the creature retains its hold; this movement of the piercers occasions the gnawing pain felt for the first two or three minutes after the leech has commenced operation.

Leeches are at times so scarce and valuable, that great care has been taken in preserving them in a healthy state and fit for use. The principal art in managing them consists in placing them in vessels sufficiently large, keeping the water clear, and in removing those which are unhealthy as soon as they are discovered.

Leeches, when applied to the skin, frequently show little inclination to bite, and many plans have been resorted to, to induce them to commence operations, such as bathing the part with milk, &c.; but these methods may be considered useless, and the best plan appears to be, to wash the part clean, and this is the more necessary when any embrocation has been previously applied; but the surest way is to puncture the place slightly, so as to cause the blood to appear. If the little surgeon, before it is fully gorged, appears lazy and unwilling to proceed, it can be usually roused by being sprinkled with a little cold water.

After a leech has fallen off, it is usual to sprinkle salt on it to induce it to disgorge the blood it has swallowed; but as the salt frequently blisters its body, it has been recommended by Dr. Johnson of Edinburgh, from whose work on the Leech, we have obtained most of the preceding information, to apply a small portion of vinegar to the head of the leech instead of salt.

The necessity for obliging the leech to dislodge the blood it has swallowed, arises from the fact that it would remain in the body of the animal for some months before it could be all digested; but the most singular thing is, that, during the whole of this time, the blood remains in nearly as fluid a state as when it was newly swallowed[5]. The stomach of this creature is very curiously formed, being composed of a number of chambers, each chamber having a separate connexion with the intestinal canal, in such a manner that, at the will of the animal, the contents of each chamber can be emptied singly into that canal, through a distinct opening.

It was long a matter of dispute as to whether leeches were produced from eggs or born alive, but it is now ascertained that the ova are developed in a singular case, having some resemblance to the cocoon of a silkworm. The following engraving represents this case, of its natural size: fig. 1, shows the perfect case or cocoon, and fig. 2, the same opened, with the young leeches contained within it; it is said that, at times, there are as many as thirteen or fourteen in one case. This cocoon is formed by the parent animal, and by it deposited in the mud or clay, which composes the bed of the pool it inhabits.

The fact of the young leech being produced from these cocoons, although only latterly ascertained by naturalists, was long since well-known to the dealers in leeches on the French coast, who avail themselves of this knowledge of their habits, to multiply them for the purpose of sale.

“It was by these means the leech-dealers of Bretagne, and particularly in Finisterre, replenished the ponds in which they preserved those leeches which were intended for the Paris market.

“About the month of April or May, according to the nature of the season, they send out labourers, provided with spades and baskets, to the little muddy marshes, where they are known to exist in abundance. These workmen then set about removing those portions of mud that are known to contain cocoons, which are afterwards deposited in sheets of water previously prepared for their reception; here the young leeches quit the cocoons, and are allowed to remain for six months, when they are removed to larger ponds.” While they remain in these ponds, the cattle and other animals are driven to the water, for the purpose of allowing the young to feed upon them, as it is supposed that they grow much more rapidly after having partaken of blood.

There is a small species of leech in the island of Ceylon, which is more dreaded, and, from its great numbers, produces more evil, than even the venomous reptiles which are found in the island, including the terrible hooded snake itself.

The largest of these leeches are seldom more than half an inch in length, and the smallest are minute indeed. This leech is a very active animal; it moves with great rapidity, and is even said occasionally to spring. It is supposed to have an acute sense of smelling, for no sooner does a person stop where leeches abound, that they appear to crowd eagerly to the spot from all quarters. In rainy weather, it is shocking to see the legs of men on a long march thickly beset with these creatures, gorged with blood, and the blood itself trickling down in streams. It might be supposed there be little difficulty in keeping them off; but they crowd to the attack, and fasten on more quickly than they can be removed. Their bites are much more troublesome than would be imagined, being very apt to fester and become sores, and, in persons of a bad habit of body, to degenerate into extensive ulcers, and ultimately cause the loss of a limb, if not that of life itself.

Many plans have, of course, been resorted to, to avoid this pest, such as anointing the legs with tobacco-water, grease, &c., but all to very little purpose, the only successful mode appearing to be, the enclosing the lower part of the legs in boots and pantaloons, fitting very closely to the limb, a very unpleasant dress in so sultry a climate.

CLASS CRUSTACEA.

The arrangement of the Crustacea in systems of natural history has undergone numerous changes; they were placed by Linnæus among the insects:—others considered them to have more analogy to the spiders. Lamarck was the first who made the Crustacea an independent CLASS forming two _orders_, which he has named after the arrangement of the branchiæ, or gills, by which they breathe, namely,—the _Crustacea homobranchiæ_, the distinguishing marks of which he describes in this manner: branchiæ hidden under the lateral margins of a kind of cuirass, covering the body of the animal, with the exception of the tail; the mandibles always furnished with feelers, the eyes placed on footstalks, the head not distinct from the trunk, and possessing ten feet to assist them in their movements. Secondly, the _Crustacea heterobranchiæ_, in which the branchiæ are external, in various situations, but never under the lateral margin of a cuirass; they are either under the belly or the tail, adhering to the feet, or confounded with them: the eyes are in general fixed, _sedentary, not on footstalks_.

_ORDER CRUSTACEA HOMOBRANCHIÆ_,

(_Shell-Fish with concealed gills._)

The first of these orders, the _homobranchial_ Crustacea, includes most of the larger kinds of shell-fish, as, for instance, crabs, lobsters, and cray-fish; shrimps and prawns are also in this division.

Their organization is much more perfect than that of the other order, and, according to Lamarck, it is among these animals that the last appearance of the organ of hearing is seen, in tracing the animal kingdom from the most perfect animals to those whose formation is apparently less complex.

The body of these creatures appears to be composed of only two principal parts, the body and the tail; for the head is so intimately united and confounded with the trunk, as to appear to be merely a portion of it. The two eyes are fixed at the top of two moveable supports, and are placed in a hollow prepared for their reception, on each side of a projecting portion of the shell that covers the head. The antennæ, which are usually four in number, are placed about this spot; they are inserted beneath the stems that support the eyes. The two outermost of these antennæ are generally the longest.

The branchiæ, or organs by which they breathe, assume a form somewhat pyramidical, arranged like a series of leaves, or the web of a feather; they are placed in the interior of the shell along each side, and are so arranged as to adhere to the roots of the feet, so that each of these feet has a hidden branchia attached to its base.

The mouth is composed of a fleshy lip, projecting between the mandibles; of two hard triangular mandibles, more or less notched at their extremity, and each having a kind of feeler inserted on the upper part; they also possess a little tongue between these mandibles, at the root of which is the opening to the stomach: they have besides two pair of jaws, like leaves, the borders of which are fringed, and six other members, which Lamarck calls _foot-jaws_, from their bearing some resemblance to legs, or feet. From this it appears that the parts of the mouth in the Crustacea form a complicated apparatus, and accordingly we find the whole tribe exceedingly voracious, the Crabs in particular, feeding upon any animal substance, putrid or not, that may come within their reach. Some of the species are well known as articles of food, but they are not equally wholesome at all seasons of the year.

_THE CRAB TRIBE._

The genera of the Crustacea are so extremely numerous, and the knowledge we possess of their natural history is so scanty, being generally confined to their form and colour, that we shall limit ourselves to a description of some of the best known and most useful species.

The Crabs are a very numerous tribe, and contain many singular species, as far as regards their form, which assumes an endless variety of curious shapes, sometimes elegantly decorated with the most brilliant colours; this more particularly applies to those which are found in the seas of hot climates.

The singular little animal represented in the preceding page, was placed by naturalists among the _Crustacea_, and considered a perfect animal of a distinct species; it was named Zoea. Mr. Thomson, the experienced naturalist we have already noticed, was the first to discover the real nature of this little creature. We cannot do better than to introduce the subject by the following observations of the author of this discovery, showing the reason so little is known respecting these inhabitants of the deep.

“The sea (which is the habitation of the greater part of the _Crustacea_) to the casual observer offers nothing but an immense body of water, here and there presenting a solitary whale, or a vagrant troop of some of the smaller cetaceous animals; the appearance of a fish of almost any other kind in the track of a vessel over a vast expanse of the open ocean, is regarded, even by the mariner, as a kind of phenomenon, and creates an interest not to be appreciated by those who have not engaged in distant voyages. The fathomless parts of the ocean certainly do not offer the same profusion of inhabitants with the shores of islands and continents, or those parts where the bottom is within reach of the sounding-line, or where the surface is interspersed with fields of Sargosa[6]. On due examination, however, we shall not fail to find it everywhere peopled by a considerable variety of animals, either of small size, or possessed of such a degree of translucency as to render them invisible, or scarcely perceptible, even when on or near to its surface; that it should possess its share of the organized beings which we see spread over every other part of the surface of our globe, is a conclusion we might arrive at indirectly, from the consideration of oceanic fishes and birds being observed in those parts of the ocean most distant from the land, and the provident care of the Deity, which we invariably witness throughout the domain of nature, to furnish food for all, even the meanest of his creatures; the more minute and invisible inmates of the sea, then, must constitute the food of oceanic fishes and birds.

“Few of these marine animals, except some of the larger and most conspicuous, have as yet been observed, so that the investigation of them holds out a promise of a rich harvest to the naturalist, and a vast field of exploration, replete with novelty and interest; to accomplish this, however, he must use the greatest diligence, seizing every opportunity, when the way of a ship does not exceed three or four miles per hour, to throw out astern a small towing-net of gauze, bunting, or other tolerably close material, occasionally drawing it up, and turning it inside out into a glass vessel of sea-water, to ascertain what captures have been made. When a ship goes at a greater rate, and in stormy weather, a net of this kind may be appended to the spout of one of the _sea-water_ pumps, and examined three or four times a day, or oftener, according to circumstances.”

Although naturalists were decided in calling the Zoea a crustaceous animal, they were still far from agreeing as to the place in the system it ought to occupy, for the different species were so unlike each other: but it will be no longer a matter of surprise, when it is known, that this singular creature is not a perfect animal, but merely the larva, or imperfect state of the Common Crab. This fact is perfectly new, and interesting in a double point of view, not only proving their real nature, but also that the Crustacea are not, as described in most systems, animals undergoing no metamorphosis, and on that account to be separated from the insects, but that they do undergo a metamorphosis, and that of a most wonderful nature.

It was in the Spring of 1822 that Mr. Thomson first met with Zoeæ, in the harbour of Cove, and that in considerable abundance; the year following, at the same season, one of considerable size occurred; this was considered a fit object for experiment, and was carefully supplied with fresh sea-water, from May 14th to June 15th, when it died in the act of changing its skin. That portion of its new form which it had been able to disengage was sufficient to show that it bore a great resemblance to the division of the Crustacea, in which the crabs and lobsters are placed. “This proof,” says the author, “might be considered incomplete, if I had not had the good fortune to succeed in hatching the _ova_ of the Common Crab, during the month of June, which presented exactly the appearance of the _Zoea taurus_.”

The Common Crab, _Cancer major_, is so well-known, that any description of its appearance would be useless.

One singular part of the history of these creatures is, the power that is possessed by them, of changing their shell once in every year; this power is providentially bestowed upon them, to enable them to increase in size, a thing that would otherwise be utterly impossible, from the peculiar nature of the hard coat in which they are enclosed.

The Crab, in order to prepare for the extraordinary change it is about to undergo, when shifting its shell, chooses a close and well-secured retreat, in the cavities of rocks, or under great stones, where it creeps in and remains during the operation. The time of the year when this occurs is about the beginning of the Summer, at which time their food is in plenty, and their strength and vigour in the highest perfection. But soon all their activity ceases; they are seen forsaking the open parts of the deep, and seeking some retired situation among the rocks, or some outlet where they may remain in safety from the attacks of their enemies. For some days before their change, the animal discontinues its usual voraciousness; it is no longer seen laboriously harrowing up the sand at the bottom, or fighting with others of its kind, or hunting its prey; it lies torpid and motionless, as if in anxious expectation of the approaching change. Just before casting its shell, it throws itself upon its back, strikes its claws against each other, and every limb seems to tremble; its feelers are agitated, and the whole body is in violent motion; it then swells itself in an unusual manner, and at last the shell is seen beginning to divide at its junctures, particularly at those of the belly, where it was before seemingly united. It also seems turned inside out; and its stomach comes away with its shell. After this, by the same operation, it disengages itself of its claws, which burst at the joints; the animal, with a tremulous motion, casting them off, as a man would kick off a boot that was too big for him.

Thus, in a short time, this wonderful creature finds itself at liberty; but in so weak and enfeebled a state that it continues for several hours motionless. Indeed, so violent and painful is the operation, that many of them die under it; and those which survive, are in such a weakly condition for some time, that they neither take food, nor venture from their retreats. Immediately after this change, they have not only the softness, but the timidity of a worm. Every animal of the deep is then a powerful enemy, which they can neither escape nor oppose; and this, in fact, is the time when the dog-fish, the cod, and the ray, devour them by thousands. But this state of weakness continues for a very short time; the animal, in less than two days, is seen to have the skin that covers its body almost as hard as before; its appetite appears to increase; and, strange to behold! the first object, it is said, that tempts its gluttony, is its own stomach, which it was lately disengaged from. This it devours with great eagerness. In about forty-eight hours, in proportion to the animal’s strength, the new shell is perfectly formed, and as hard as that which was but just thrown aside. Previous to the time of moulting or changing their skin, a flat chalky stone is found on each side of the stomach; this is believed to form a store of earthy matter for the renewal of the shell. These stones, popularly known as _crabs’ eyes_, were long highly esteemed for their medicinal properties, but in reality are not superior to so much chalk.

When completely equipped in its new dress, the dimensions of the old shell being compared with those of the new, it will be found the creature has increased in size nearly one-third, and it appears wonderful how the old shell could have contained it.