VEGETABLE FEEDERS, (Phytophagi.)
VEGETABLE FEEDERS, (Phytophagi.)
Those genera of the Trachelipods which live on vegetable substances have no projecting siphon, but possess a mouth furnished with jaws; they are in general land-shells, and consequently, the air which they breathe is conveyed directly to their branchiæ. Some of their tribes however, live in fresh water, either in running streams or in stagnant pools: among these, some breathe water and others air. These last are obliged frequently to come to the surface for the purpose of breathing,—others again inhabit salt water, and are unable to exist out of that element.
There are as many as thirty or forty species of the Turban-shell. The Marble Turban,Turbo marmoratus, is the largest, being as much as four inches across; it is found in the Indian Ocean. The colour of this shell is of a brownish green, of greater or less intensity. It is ornamented by eight or ten narrow transverse belts, consisting of a series of white or brownish spots. This is one of those shells whose substance, after the outer coat is removed, is of the nature of mother-of-pearl.
TheTurbo littoreus(the Shore Turban), is the well-known periwinkle, with which our rocky coasts abound.
These shells have received their name from their resemblance in form to a boy’s top. They are all marine shells, and the apex of their spire isalways very sharp-pointed. In some places they are calledflat-mouthed snails. The greater number of these shells, (and the species are very numerous,) are of a beautiful pearly substance, and many of them are also elegantly marked with longitudinal ribs; there are as many as seventy species,—the larger and more elegant are only found in the seas of hot climates.
Haliotis iris.Scalaria pretiosa.Neritina pulligera.
Haliotis iris.Scalaria pretiosa.Neritina pulligera.
This shell is noted for its rarity, and for the singular arrangement of its whorls, which do not touch each other, and appear as if they were only connected by the ribs with which the shell is adorned. Like the turbans, the inhabitants of the Scalariæ are found on the sea-coast, on rocks and large stones, between high and low water mark. The native place of the Scalaria pretiosa seems to be uncertain; Lamarck, and several others, believe it comes from the East Indies, while others consider it an inhabitant of the Mediterranean. So great was the rage some years back, to possess a perfect specimen of this shell, that asmuch as twenty or thirty pounds, and even more, has been given for a well-preserved specimen. Travellers relate that the Scalariæ are much sought after and highly prized by the women on the coast of Amboyna, and at Batavia, where they are used as earrings, and in forming necklaces. They are, although rarely, as much as four inches in length. It is said, that there was a specimen in the cabinet of the empress Catherine of Russia, still larger; but the most usual size is from one to two inches in length. A fine specimen of this shell ought to be semi-transparent like porcelain, of a light brown, tinged with rose-colour, and the ribs of a beautiful opaque white.
TheHaliotides, or sea-ears, are very splendid shells; the species are numerous, and some of them are extremely common. The place in the system which this shell ought to occupy, appears to have caused many doubts in the minds of modern naturalists, and consequently, we find it continually shifted from one part to another in the different works of Lamarck and Cuvier. When moving from place to place in search of food, the animal and its shell present a very pleasing sight, the slender tentacula which appear through the different holes which ornament the margin of the shell, gracefully waving in all directions; these tentacula are supposed to be breathing-tubes. In the young shell, the number of perforations is not so great as in an adult, one being formed at each progressive stage of the creature’s growth. Sometimes the holes which were first formed become, by age, filled up. The proportions of the shell, also, vary materially, so as to render the separation of species very difficult and uncertain.
This shell is found in the rivers of India, and is about an inch and a quarter in length. All the species of this genus are supposed to inhabit fresh water only. There is a curious fact attached to the history of the Neritina, and of a neighbouring genus, Nerita,—namely, that when found in a fossil state, their colours are always in good preservation. The species, which are tolerably numerous, are in general natives of hot climates.
The animal of the genus Paludina is an inhabitant of fresh waters: it takes its specific name from the fact of the young being hatched within the parent shell, and deposited in the waters perfectly formed. In nearly the whole of this class the eggs are laid either in water or in the earth, and afterwards hatched after a longer or shorter period.
Planorbis corneus.Paludina vivipara.Lymnæa stagnalis.
Planorbis corneus.Paludina vivipara.Lymnæa stagnalis.
These shells are found generally in running streams of fresh water; sometimes, however, they are met with in brackish water, at the mouths of rivers. The operculum of the Paludina is of a strong horny substance. The young, immediately they are hatched, attach themselves to the outside of the shell of the mother, where they remain until they are sufficiently strong to trust themselves in the water.
TheLymnæa stagnalisis found in stagnant waters, particularly narrow ditches, in great abundance. As it breathes air, it is necessary for its existence that it should frequently resort to the surface of the water; and consequently, we find these shells floating about in great numbers, with the body partly out of the shell. The least appearance of danger causes a Lymnæa to withdraw the whole of its body into its shelly covering; and as this increases its specific gravity, it instantly sinks to the bottom, where it remains in safety. In order to reach the surface again, it is obliged to crawl to the side of the ditch, and when it has reached the level of the water, it again trusts its little bark to the mercy of the winds and stream, for it has very little power to direct its own course.
During the Winter, these creatures remain at the bottom, buried in the mud, and in a state of torpor. Although apparently useless to mankind, they form part of the subsistence of many water-birds, and of fishes, which are extremely fond of them. The species of this shell are not easily decided, since they bear so great a resemblance to each other.
ThePlanorbis, although differing in form from the Lymnæa, possesses the same habits, and is found in the same localities. The jelly-like substance which is frequently found, in the Spring of the year, attached to water-cresses and other aquatic plants, and which is considered by many to be of a poisonous nature, and looked on as the spawn of toads, is merely the covering of the ova of this and other inhabitants of fresh-water shells; and, although very disagreeable, certainly not poisonous.
TheBulimus hæmastomusis a most beautiful shell; it is a native of Guiana, and is frequently as much as four inches in length. The most singular part of its natural history is the large size of the egg of the animal in comparison with its magnitude; it is said to equal that of a moderate-sized pigeon.
Bulimus hæmastomus.Pupa mummia.
Bulimus hæmastomus.Pupa mummia.
ThePupa mummiais found in the Antilles; it takes its name from the singularity of its form, which very much resembles that of a mummy.
The Pupa is essentially a land-shell, living among grass, on stones, and sometimes in places much exposed to the heat of the sun. The greater number of the species, which are very numerous, are natives of tropical countries; there are, however, several found in Germany, and other parts of the Continent, but they are extremely small.
The Snail (Helix) is an animal well-known in every part of the globe, and its species are still extremely numerous, although many shells which belonged to this tribe, under the Linnæan arrangement, have been placed in other divisions. The head of the Snail is furnished with two pair of tentacula, or feelers; these, unlike similar appendices in other Mollusca, are retractile; that is, they can be withdrawn into the body at the will of the animal. The use of these tentacula is uncertain. At the top of each of the longest pair we find a black spot; these spots have been supposed to be the eyes of the animal, and a celebrated anatomist says, that he has discovered in them all the component parts of perfect eyes. However this may be, the animal appears to use them rather as organs of touch than of sight. Some writers suspect that the sense of smell resides in one or both pairs of these appendages.
The uses to which Snails are applied are not many; some of the larger kinds, however, are, in some countries, employed as food. The Romans, according to Pliny, consumed large quantities, and considered them in the light of delicacies, and considerable pains were taken in fattening them for the table. Those from Sicily and the Balearic Islands were in great request, and attained a very large size. Some authors say they are still used as food in several parts of the Continent.
Helix nemoralis.
Helix nemoralis.
In Paris, London, and many large towns, great numbers of Snails are frequently brought to market; but these are not employed as food, but used medicinally by persons suffering under consumption, and other diseases of the chest.
It was already known that polypi, and some species of worms, could have portions of their body cut off, and that the parts removed would be afterwards reproduced; and as these animals had no well distinguished extremities, such as heads or limbs, the fact, although singular, was not disputed; but, when it was asserted by Spallanzani, that Snails,which have a very well defined series of parts, could, after the head was removed, reproduce that portion of the body, the scientific world became naturally incredulous, and numerous experiments were made, and thousands of Snails slaughtered, to ascertain the fact. No one, however, for a length of time, could succeed;—it was then suspected that Spallanzani had only removed a portion of the head. At length, it would appear, from the experiments of M. G. Tarenne (an account of which appeared in 1808), that these creatures could actually reproduce a complete head. He gives as a reason of the want of success of others, the little precaution taken to provide the mutilated Snails with proper nourishment. The new head, according to him, is perfect in about two years after the old head has been removed.
M. Tarenne says, that after having cut off the heads of two hundred Snails, he threw them all into a moist spot at the end of his garden, that they might obtain the nourishment most fitted for them (how they could eat without their heads he does not say); at the end of the Summer he examined all the mutilated Snails he could find, and he discovered that they all had a new head, about the size of a grain of coffee; they had four small tentacula, a mouth, and lips; at the end of the following Summer, the heads were perfectly reproduced, and like the original head, with the exception of the skin, which was more delicate. “After this experiment,†says a French author, “we cannot doubt that the entire head of a Snail can be regenerated after it has been removed; however, I cannot disguise the fact, that I have a kind of repugnance at admitting the matter to be entirely beyond dispute.â€
If the advantages bestowed on man by Snails are not numerous, thedisadvantages, or rather inconveniences, produced by them are very considerable; they are particularly destructive in orchards and kitchen-gardens. On this account, many methods have been recommended for the purpose of destroying them. Although many of these are tolerably successful, there is no plan more likely to keep the breed of Snails under, particularly in enclosed gardens, than that of early rising and gathering them, if we may so express ourselves, while the dew is yet on the grass: if the shells are then broken, they become excellent food for poultry. Ducks may sometimes be allowed to wander in the garden, as they do but little damage to the vegetation, and are great destroyers both of Snails and slugs.
A singular account of the instinct of Snails is, perhaps, worth recording.
The garden of a small house, by the side of one of the roads leading into London, was much infested by a colony of Snails; the proprietor of this house, desirous of getting rid of the pest, and yet unwilling to kill the Snails, collected them, and threw them unharmed into the road; but still, he every morning discovered as many Snails among his pinks and tulips as he had removed the previous day; this somewhat puzzled him, until once, on leaving his house early, he perceived the Snails which he had but an hour before thrown into the dusty road, moving, not in a body, but each from the spot on which it was thrown, in a direct line from that spot to the low wall which encompassed the garden, as if they comprehended the mathematical fact that, “a straight line is the nearest way from one given point to another.†How were these Snails aware that by moving in that direction, they should arrive at a green spot? From the road nothing could be visible to them but dust,—from thepath, nothing but the wall in front,—but still, although the whole of their path was covered with dust, they proceeded steadily on, until they had surmounted the wall, and reached their old quarters. By what other faculty were they guided but that instinct which supplies the place of the higher powers of the mind, and which is imparted with so liberal a hand to the meanest creature in nature?
The Gasteropods are so called from two Greek words, meaning belly and foot, because the foot, or organ of motion of the animals of which this order consists, is attached to the whole of the under part of the creature, or rather, the belly or under part is itself the foot, and is for that purpose broad and flat. The Gasteropods are also distinguished from the last order by having a straight body, in no case spiral, and never possessing a shell capable of enclosing the whole body; in some cases, the body is completely naked, and without the protecting covering of any shell whatever.
The Common Slug is a good example of an individual of this order, entirely wanting a shell. The Slugs, like the snails, are found in all countries; they are equally destructive to vegetation, but as yet have never been used by man for any useful purpose, if we except the fact of their sometimes becoming the food of ducks and poultry. TheLimax rufus, Red, or more properly brown, Slug, for the colour is of areddish-brown, varying in intensity to such an extent as to render it impossible to find two specimens of the same colour, is more commonly found in fields than in gardens.
Limax rufus.
Limax rufus.
There are many species of the Slug; but they are not well defined, on account of the variable nature of their colour; the black and the brown kinds are, however, pretty well known: the black, in particular, is very destructive in kitchen-gardens, and commits great havoc in fields of cabbages and turnips.
In one or two species, the buckler, or smooth space near the head, contains a very small oval shell.
There is a very singular species of Slug found in Teneriffe, under stones in moist places, it is not more than an inch and a quarter in length; it is calledLimax noctiluca, the night-shining Slug. The buckler, in this species, is very narrow, and covered with pores, which exude a kind of viscous substance, which has the property of shining with a phosphorescent light, like that of the glow-worm.
We may have some idea of the rapid increase of Slugs, by a fact mentioned by Dr. Leech, that two individuals of a small species have laid as many as seven hundred and sixty-six eggs; and these eggs were dried in an oven without destroying their vital powers, since, on being placed in a damp situation, they were afterwards hatched.
The following plan of taking and destroying Slugs was resorted to by a gentleman near Ipswich. Having heard that turnips were employed to entice Slugs from wheat, he caused a sufficient quantity to dress eight acres to be got together, and then, the tops being divided and the apples sliced, he directed the pieces to be laid separately, dressing two rows with them, and omitting two, alternately, till the whole field of eight acres was gone over. On the following morning, he employed two women to examine the tops and slices, and free them from the Slugs, which they threw into a measure: and when cleared, they were laid on those rows that had been omitted the day before. It was observed invariably, that in the rows dressed with the turnips, no Slugs were to be found upon the wheat, or crawling upon the land, though they abounded upon the turnips; while, on the undressed rows, they were to be seen in great numbers, both 011 the wheat and on the ground. The quantity of Slugs thus collected was nearly a bushel.
The animal of theBullais singular, from possessing-within its stomach three pieces of a substance resembling bone; these give that organ the power of crushing or grinding the food, forming a kind of gizzard. The bony portion of this stomach is represented in the foreground in the engraving. The Bulla lignaria is about two inches anda half in length, and is found in the European seas; Lamarck mentions as many as eleven species.
Bulla lignaria.
Bulla lignaria.
The genusCrepidulatakes its name from its hearing some resemblance to a little shoe; none of the species are found in Europe. Of these there are about six, but they are all confined to the seas of warm climates.
TheUmbrella Mediterranea, as its name implies, is found in the Mediterranean, and in the Gulf of Tarento. The shell of the Umbrella is singular, from the lower part of its circumference being surrounded by a border of a substance much softer than the shell itself.
TheFissurella nimbosais found in various and distant parts of theworld,—in the north of Europe, the western coast of Africa, &c. It is rather a handsome shell, which seldom exceeds an inch and a half in length.
UmbrellaCrepidulaFissurellaMediterranea.unguiformis.nimbosa.
The Fissurella very much resembles our limpet, but differs from it by having a small, rather oval-formed hole in the summit of the shell, affording a passage to a small canal through which the water is discharged, after having passed over the branchiæ.
ThePileopsis Ungaricais extremely elegant both in its form andmarkings; it is of a delicate white, slightly tinged, internally, with rose-colour. The animal attaches itself to rocks, between high and low water mark, and very rarely, if ever, changes its situation, unless removed by accident, when it is driven about by the waves, until the creature, being thrown on a rock in a favourable situation, attaches itself firmly to the surface.
Pileopsis Ungarica.
Pileopsis Ungarica.
TheChitonsdiffer so much from all other shell-bearing animals in the arrangement of their shelly covering, that they have been placed by different naturalists in various parts of their system. Lamarck, in referring to these animals, has placed them near the end of the Mollusca.
Chiton squamosus.
Chiton squamosus.
“Although,†says Lamarck, “when we examine this creature, and observe the several pieces of which its shell is composed, attached to the marginal membrane of the mantle which surrounds them, it appears not a univalve, but a multivalve shell; yet these shelly pieces ought not to be regarded in any other light than as a lengthened shell of one piece,which Nature had originally broken transversely into several distinct moveable pieces, to give greater freedom to the animal in its movements.â€
The Chitons, like the neighbouring genera, frequent the rocks between high and low water mark, but are much more active in their movements. Poli, a learned Neapolitan, in describing the anatomy of a Chiton, says, that the interior of the mouth or throat of this animal is covered with a multitude of teeth,—some simple, and others with three points, and that these teeth are disposed in numerous longitudinal rows.