Part 2

It belongs by origin not to the earliest form of snail, but to the most highly organized group in the world, especially characteristic of the European region, and possessing in their superiority the power to colonize and dispossess the original native snails of other lands. The shell is globular in form with five whorls (the Greek word "helix" means a coil), each usually marked with five bands of pigment. It is mainly a vegetarian, and by habit a lover of the twilight and of moisture. With the exception of _H. pomatia_ it is the largest of our native shells, and is too common to satisfy gardeners. A powerful animal of its kind, it can travel a yard in twelve minutes, or at the rate of a mile in a fortnight, can bear or draw on level ground a weight fifty times its own. It breathes about four times a minute, and its heart-beat varies from sixty to eighty per minute according to temperature, or its activity. It takes its winter rest in clusters, closing its mouth with a membranous film, while if the cold increases it shrinks farther into its shell and makes more epiphragms or film curtains to keep out the cold. Not only on the Continent, but in several parts of England, notably about Bath and Bristol, it is sought, sold, and used for food, and in Belgium it is said to be preferred to the larger and more firm-fleshed _H. pomatia_. The eggs, from forty to a hundred, are laid in the earth and hatched in from a fortnight to a month, according to the weather. I had observed them as a boy, and used to call tapioca pudding "snail's egg pudding." In the year of their hatching they attain but half their proper size, but after hibernation they eat voraciously and grow rapidly, so as to attain full size in a little more than a year. Most die in their second hibernation (if not destroyed by their many enemies, gardeners, collectors, rats, rabbits, ducks, thrushes, and beetles); but when kept and protected for observation they have achieved the great age of even ten years.

They have a great power of "homing" like pigeons, however far (for them) is their journey after favourite food. The slime-marked journeys or feeding tracks of this species (and still more of slugs) afford matter of great interest. As to sight the two eyes are the dark specks on the tip of the upper pair of "horns," but the range of vision is very short indeed, and the difference between light and approaching darkness is all that some seem able to perceive. The organs of hearing are two small sacs filled with fluid in which are some calcareous grains. They hear little which is audible to human ears, and if not altogether deaf they are dumb as far as we can hear. The power of taste they possess, as is shown by the preference of some foods to others. The sense of touch is acute and resides in all parts of the soft and moist external skin, and especially in the upper tentacles or horns in the _Helicidæ_. Jaws they have with which to seize and to bite off food, and in _H. aspersa_ and others these bear teeth, but the chief work is done by a sort of toothed tongue, the radula, which rasps off particles of food with a side to side motion of the head as the animal advances. Our _aspersa_ has 12,615 teeth on this ribbon, contained in 145 transverse rows. The organs of digestion are complex and practically much the same as our own. Little vegetation would be left in nature had not, on the one hand, snails been kept down by many enemies as well as by their need of hibernation and their short life; while on the other by numerous devices in the course of ages many plants have protected themselves against the moving machine of a snail's mouth. Cultivated plants, which generally lose their natural protections, have to be guarded by human guards or gardeners. Some plants defend themselves by prickles or hairs, some by hardening themselves with lime or flint, some by bitter or acrid juices. A heart of two chambers, veins, arteries, and blood our snail possesses, and, like man, the old snail has a slower pulse than the young one, and in both exercise increases the pulse rate and also warmth. Breathing is accomplished by a single chamber or air-cell, but also through the skin. As in the case of plants, some kinds are male and female separately, and as some have both powers and products in the same plant, so also is it with mollusca. _H. aspersa_ and most Gasteropoda are of the latter kind.

Having now taken _H. aspersa_ as the representative of our univalves, let us take the "Pearl Mussel"--_Unio margaritifer_--as that of our bivalves, all of which live in the water, whereas of univalves some are "land snails" and some "water snails." It would say of itself, "I am a species of the genus Unio (_unio_, a pearl), which belongs to the family Unionidæ, which belongs to the sub-order Isomya (_i.e._ having muscles of equal power to close the two valves of the shell), which belongs to the order Lamellibranchiata (_i.e._ having gills arranged in leaf-like fashion), which belongs to the sub-class Pelecypoda (_i.e._ having a foot somewhat of an axe-shape), which belongs to the class Acephala (headless), which is the second of the two chief classes into which Mollusca are divided.

"I differ from the Gasteropoda (whether they be terrestrial or aquatic) in that I and my near relations are exclusively aquatic and of a sedentary life, which makes the protection of two encompassing shells necessary. These shells are secreted by my mantle lobes, and are united by a ligament which tends to make the valves 'gape' for water and food and by two contracting muscles which close them in danger. I have a degenerate brain and no eyes. My mouth has neither jaw nor teeth, but possesses nervous lips covered with cilia, the vibration of which carries food-laden water to my mouth. My foot, when protruded, is seen as a large muscular appendage, and, by alternately expanding and contracting, it enables me to burrow or plough through mud or even sand, and so disturb the minute organisms on which I feed. I can thus travel fifteen feet a day, or about a mile in a year.

"I have no eyes, but distinguish well between light and shade by means of the surface of my body when exposed. I breathe, that is, get oxygen from the water, by means of gill-plates. As regards other internal organs, I differ not much from _H. aspersa_, but I am either male or female. Outside I am black and uncomely; but within I am pearly-white, and but for my power of forming pearls round an irritating grain of sand the civilization of England would have come to pass later than it did, for it was the report of my pearls which brought Cæsar to Britain."

* * * * *

Now let us enumerate the species of land and freshwater shells to be found, (all but two) in England, and most of them in Ireland or Scotland.

_Arion ater_ is a large (3 to 5 inches) and common slug, usually black (whence its name _ater_), but also red, brown, or white. In some varieties the foot-fringe is orange. When irritated it contracts into a hemispherical lump. A few chalky granules under the mantle are the representatives of a shell. See the illustration of three specimens on p. 31. That hole in the mantle is the breathing orifice, and its forward position is a characteristic of the group _Arion_. The body of slugs is kept moist by a constant exuding of slime from a gland in the tail.

_Arion subfuscus_ (_i.e._ somewhat tawny). Smaller (2 to 3 inches) than _A. ater_, grey or yellowish, with usually a dark stripe on each side. Foot-sole white, and its fringe white with dark cross streaks. Never very abundant.

_Arion minimus._--The smallest Arion: not an inch long. Grey or yellowish. Feeds on fungi. Body wrinkled with microscopic spikes. Common. The _young_ of _A. ater_ might be mistaken for it.

_Arion hortensis._--Grey with purple side bands. Foot-sole yellow. 1 to 1-1/2 inch in length. Generally found in gardens, as its name indicates.

_Arion circumscriptus._--Very common in fields. A dark band down the back, foot-sole white. Very "sluggish."

_Geomalacus maculosus_ (_i.e._ the spotted earth-mollusc).--Only found in south-west Ireland. Probably a relic of the prehistoric time when Ireland was joined to Portugal and Spain. Has a solid chalky shell beneath the shield. Blackish with oval yellow spots. Feeds on lichens.

_Amalia gagates_ (_gagates_ is Greek for "jet").--Dark lead colour. Foot-sole white. Length 2-1/2 inches. Local, and mainly near sea.

_Amalia Sowerbyi._--Brown, speckled with black. Foot-sole yellowish. Length 2-1/2 inches. Local. Shell often very thick.

_Limax maximus._--Length 4 to 6 inches. Grey with two dark lateral bands. Often found in cellars.

_Limax cinereo-niger._--Ashy-black. Very like _L. maximus_, but with a sharp keel, and the sole paler in the middle than at the sides. Less nocturnal and less fond of houses; chiefly found in forests on hills. Local, and not common.

_Limax flavus._--Yellow, with a faint dark network of markings. Tentacles blue. Sole cream. Length 4 inches. Only found in cellars and near houses.

_Limax marginatus._--Semi-transparent. Grey, with two dark bands on each side. Foot-sole with a dark line down the middle. Shell solid, often a cube. Length 3 inches. Fond of tree climbing.

_Limax tenellus._--Yellow. Tentacles black. Mucus yellow. Found in woods. Lives on fungi. Rare.

_Agriolimax agrestis._--The common field slug. Swarms everywhere. Its milk-white slime is characteristic. Very variable in colour and markings.

_Agriolimax lævis._--Slender. All chocolate brown. Length 3/4 inch. Shell may be seen through the mantle. Active. Our smallest slug. Usually found near ditches.

* * * * *

It may be useful here to give the chief differences between the genera Arion, Amalia, Limax, and Agriolimax. The shield in the first two is granulated, in the other concentrically striated. The breathing orifice in Arion is in front of the centre of the mantle margin; in the others behind. The shell is distinctly formed in all but Arion, in which it is absent or represented by a few granules. Arion has no dorsal keel. Amalia has one all down the back. In Limax and Agriolimax it is confined to the caudal part. Other differences are only discovered by dissection.

One may also here note that to preserve slugs is difficult, and the best plan is to have a coloured drawing made of them when extended. Otherwise they may be drowned in cold water, cleaned of slime with a soft brush, and then preserved in glass tubes with diluted formalin or alcohol. Or, after drowning, they may be skinned and the skins dried on a card and varnished. Note also that most slugs have many variations in colour and markings.

_Testacella haliotidea._--This genus of slugs forms a link between the naked slugs with rudimentary shells within, and the snails which live within their shells. The name _Testacella_, or little shell, was given by Cuvier in 1800, because this slug has a small shell at the end of the tail. Haliotidea means having a shell in the form of the marine shell _Haliotis_, the meaning of which again is the ear-shaped seashell, often called "Venus' Ear." It is subterranean in habit, and lives on worms. It should be looked for on the surface on damp nights, or is found when digging. Its length is 3 inches at most. Pale yellow in colour. See the illustration on page 35.

_Testacella scutulum_ (a little shield).--Not so common as the former species, and differing chiefly in anatomy.

_Testacella Maugei._--First found at Tenerife by M. Mauge. Reaches 4 inches in length. Deep brown in colour. Shell larger. Rarer and more western in habitat than the other species.

_Vitrina pellucida._--The Vitrinas in several ways afford a connecting link between the slugs and snails, having the same tooth-formation and mantle as the former, while the shell cannot contain the whole body. As the name indicates, the shell is like a bubble of clear greenish glass and very delicate. It is small, and found in damp places, coming out mostly at night. Omnivorous, it is often found feeding on dead worms, and, unlike nearly all our earth molluscs, can be found abroad in winter.

_Vitrea (Polita) lucida._--This is the largest of our British Hyaliniæ, which are difficult to distinguish. The body of this species is cobalt blue, the apex of the shell is flat, its colour opaque, and the last whorl more expanded than in others. All belong to the sub-genus _Polita_, and have polished or glossy shells. All love shade and moisture, and should be sought under stones or wood or in moss. They only come out by day when it is wet, a habit they may have acquired from their being a favourite food of birds, 416 having been found in the crop of one nestling Stockdove; while various flies are very destructive to them. This species prefers animal food, and is more gregarious than others. Not common.

_Vitrea (Polita) cellaria._--The next largest species is the most common of all. It is fond of cellars (whence its name), and I found it under the stone lid of a manhole in the drain of S. Peter's Rectory, Walworth--the only shell left in that part of London. It resembles the previous species, but is smaller and has a broader and deeper suture between the whorls, while the foot-sole is paler than the body.

_Vitrea (Polita) Rogersi._--Local. Found in dense woods. It is much like both _H. cellaria_ and _H. alliaria_, and all three smell of garlic, but the last is much smaller than the others. The tentacles in the first are long, and in the third short; while in _Rogersi_ the upper pair are long and the lower very short. It is also the most glossy of all. If put in a box with other small shells it will clean them by cannibalism.

_Vitrea (Polita) alliaria_, _i.e._ smelling of garlic.--Often confused by quite good conchologists with the preceding species, but the body is much darker, and the shell smaller and less white below than either _cellaria_ or _helvetica_. The always present smell is said to protect it from ants. Common, but local, and often a pest in greenhouses and ferneries.

_Vitrea (Polita) nitidula._--Common. Less glossy. Marked expansion of the last whorl as it nears the mouth.

_Vitrea (Polita) pura._--Like _nitidula_ but smaller, and edge of mantle white instead of dark. More common in the north. Shell thin and dull white.

_Vitrea (Polita) radiatula._--Never abundant. Striations on shell give it a radiated appearance when magnified. Animal nearly black.

_Vitrea crystallina._--The smallest of the genus. Shell transparent, pearly white. Umbilicus (_i.e._ the opening in the centre of the underside showing the whorls) very narrow. Subterranean in habit. Whorls, four; whereas _H. pura_ has five; also more compressed.

_Euconulus fulvus._--Distinctively pyramidal in shape. Small. Brown. Common under rotten branches and moss in woods. Hardly hibernates.

_Zonitoides nitidus._--Chocolate-brown, with no white round the umbilicus (as has _H. nitudula_). Larger than, but not unlike, _H. radiatula_. Gregarious. Chiefly found by water; also in damp hothouses. Amphibious.

_Zonitoides excavatus._--Its broad and deep umbilicus is quite distinctive. Mainly British. Dislikes lime, and is most plentiful on the coal measures.

We come now to the Helicidæ family and its genus Helix, in which there are various sub-genera of which the name is given in brackets. The shell in this genus can wholly contain the body; the tentacles are always four; the shell conical, and rarely with a depressed spire. The word "helix" is Greek, and means a coil.

_Helix (Gonyodiscus) rotundata._--Very common under stones, moss, etc. Circular, flat, with a large open umbilicus. Horn colour with brown markings.

_H. (Pyramidula) rupestris_, _i.e._ inhabiting rocks.--Small. Gregarious. Dark brown. Mainly on exposed dry walls and cliffs.

_H. (Punctum) pygmæum._--Very small. Yellowish brown and glossy shell. Mainly on moist dead leaves. Not unlike _H. rupestris_ except as to habitat.

_H. (Acanthinula) lamellata._--Small. Horn-colour. Epidermis raised into lamellæ or ridges in the line of growth. Mainly northern. Frequents dead leaves, especially beech and holly.

_H. (Acanthinula) aculeata._--More common than the former; which it resembles in habitat. Differs chiefly by the ridges being produced into spines.

_H. (Vallonia) pulchella._--Tiny. White. Mouth trumpet-shaped. Umbilicus wide. Under stones and at the roots of grass. Its variety _costata_ (which some make a separate species) is strongly ribbed.

_H. (Helicigona) lapicida._--Circular, flattened, dark brown, strong white reflected rim to mouth. Large umbilicus. Marked keel, which distinguishes it from all other British land shells. Chiefly on chalk soils. Often on beech tree trunks.

_H. (Gonostoma) obvoluta._--Common abroad, but confined in England to a few spots in Sussex and Hants. Circular, flat above, mouth triangular, with a strong pinkish-white rim with three denticles.

_H. (Pomatia) pomatia._--Described earlier. Found in Hants, Sussex, Kent, Surrey, Oxford, Gloucester, and Bedfordshire; but very local. Elsewhere it may well be an escape from captivity, or the remains of an attempt (always unsuccessful) to establish a colony. Box Hill and Caterham are two good localities for Londoners. In Kent it has two centres, Charing and Shoreham with their contiguous parishes, but there is a great gap between them, and it is absent from places on the same chalk ridge which are identical in soil and vegetation.

_H. (Cryptomphalus) aspersa._--The sub-generic name means that the umbilicus is hidden in adult shells by a fold of the pillar lip; the specific name means sprinkled (with brown blotches); but it may be a slip of the pen, for _aspera_, or rough, from the rough shagreening of its surface. Five banded, like so many of the Helicidæ, but usually the second and third band unite. No umbilicus. The variety _exalbida_ (chiefly found in Kent and the West) is straw colour and somewhat transparent. Commonly sold for food on the Continent as well as _pomatia_, which is cultivated in "snail-farms," but not native in Germany or Switzerland, and in France chiefly found in the coast departments. Insipid; but as nourishing as calf's-foot jelly. Fond of gardens (whence its common name), but not of gardeners. As most animals are marvellously gifted with a knowledge of what food to eat and what to avoid, it is curious that _aspersa_ will eat voraciously the leaves of the spindle-tree, though this soon poisons them. It is said also that they share with cows and horses the ignorance that the leaves of the yew should be avoided on pain of sickness or even of death.

_H. (Cepæa) nemoralis._--As already stated, this is the most brilliantly and variously coloured and diversely banded of all our English land shells with the exception of its very close connection _H. (Tachea) hortensis_. It is happily very common, and so the attention of beginners should first be directed to this. Thrushes and mice are its great enemies, the former smashing it on some stone which may be found surrounded by the broken shells. The "mouth" or peristome is normally black, the shell larger and stouter than _hortensis_, in which the mouth is white. When a white-mouthed _nemoralis_ or dark-mouthed _hortensis_ (both rare) is found, the shape of the internal flinty dart at once distinguishes them. In some places both live together: in most one is found and not the other. _Nemoralis_ is fond of sand-hills by the coast, but is chiefly a hedge-snail, and the edges of main roads are preferred because of the greater variety of food, because the traffic scares away their bird enemies, and because the dust gives them abundance of already prepared material for their shells. When, however, the collector comes to a wayside cottage where fowls are kept he need not waste his time in looking for snails in the neighbouring hedge. The more the chicken industry extends and the more the Bird Protection Acts operates, the worse it is for collectors of snails. The banding is probably protective, as in the case of the tiger and the zebra, and renders the shell less visible.

_Helix (Cepæa) hortensis._--Rarely found in gardens in spite of its specific name. A hedge-snail. White forms not uncommon, though almost unknown in _nemoralis_. Though the weaker form, the coalescence of the five bands into one broad one is more common here than in _nemoralis_. Also the variety with only one band, and that on the periphery, is very common in _nemoralis_ and rare in _hortensis_. It is more dependent on shade and moisture than its congener. Smells of garlic when immersed in boiling water to be killed. _Hortensis_ is a more northern, and _nemoralis_ a more southern, shell by origin and distribution. There are 89 possible band variations in any normally five-banded shell, and all have been noted in the case of _nemoralis_, but in _hortensis_ only 61. They are distinguished, for purposes of record and exchange, by numbers. Thus the type is 12345, the usual one-banded variety 00300, the common coalescence of the second and third band is 1(23)45, and when all bands unite (12345). The unicolourous or bandless variations would be 00000.

_H. (Arianta) arbustorum._--Local. Usually found in hedges and by ditches on chalk and limestone. Shell globose, brown or yellow, with a check or willow leaf pattern, and a single dark band on the periphery. Lip strong and white. Animal usually nearly black. Very fond of moisture. Anatomically related to _A. lapicida_, but no external resemblance.

_Helix (Theba) cantiana._--First observed in Kent (where it is especially fine and abundant), whence its specific name, but generally dispersed in South and East England. A dull, creamy white shell with a pink tinge, sometimes becoming partially or wholly reddish.

_Helix (Theba) cartusiana_ (first noticed near a Carthusian monastery). Much resembles _cantiana_, but is much smaller and more smooth. Chiefly found on the downs of Kent and Sussex. Used to be common on Deal sand-hills--now devastated by golf! The tint in this is brown, in the former red.

_H. (Hygromia) rufescens._--A flattish, dark brown shell, abundant in the south of England, and not rare elsewhere. Has a semi-lunar mouth with a white internal rib. In gardens seems to prefer violet beds.

_H. (Hygromia) hispida_, _i.e._ hairy.--These hairs are deciduous, and the hairless variety used to be considered a separate species under the name of _concinna_ (_i.e._ neat), but would now be the variety _depilata_, or bald. Broad and deep umbilicus. Common, except in Ireland. Usually associates with _H. rufescens_ in moist places.

_H. (Hygromia) granulata_ is also hairy with white silky bristles. Yellowish in colour. Shell thin. Local, but abundant where found. Its umbilicus is very small. It falls from its food plants at the least shake.

_H. (Hygromia) revelata._--Scantily haired. Globular thin shell. Pale green. Mainly found in Cornwall and South Devon. In cold or dry weather it buries itself rather deeply.

_H. (Hygromia) fusca._--Very thin, glossy, brown shell. Local. Hardy, and even active in frost. Chiefly found on nettles, which many shells like as food, though avoiding the commonly associated horehound.

_H. (Euparypha) pisana._--First noticed at Pisa. Somewhat like _Helicella virgata_, but larger, sub-globular, and solid shell, yellowish-white with dark lines or bands. Aperture or mouth yellowish or rosy. Most common in Portugal and Morocco, and all round the Mediterranean, dry places, especially near the sea. In England chiefly confined to Tenby and other parts of Pembrokeshire; also in the Channel Islands. Varies much in tint and markings. Swarms where found; it loves sun and heat. Seems to lend itself better to colonization than most species.