Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

SNAIL

Online Encyclopedia
Originally appearing in Volume V25, Page 285 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

SNAIL . In See also:

England the word " snail " in popular See also:language is associated with Gasteropods which inhabit See also:land or fresh See also:water, and which possess large conspicuous See also:spiral shells; terrestrial Gasteropods, in which the See also:shell is rudimentary and concealed, are distinguished as " slugs." In See also:Scotland the word " slug " is absent from the See also:vernacular vocabulary, both shell-bearing and shell-less inland molluscs being known as snails. Marine Gasteropods are occasionally termed " See also:sea-snails," and the compounds " See also:pond-snails," " See also:river-snails," " water-snails " are in See also:common use. The commonest land-snails are those See also:species which constitute the See also:family Helicidae, See also:order Pulmonalaf ii;iib order Stylommatophora. The families Limacidae, Arionidae and Oncidiidae of the same sub-order, include nearly all the slugs. The Oncidiidae are entitled to the name " sea-slugs," as they are shell-less Pulmonates living on the seashore, though not actually in the sea. The See also:term " water-snails " includes the whole of the remaining sub-order of the Pulmonata, namely, the Basommatophora, in which the eyes are sessile, with the exception of the Auriculidae. The latter are terrestrial and occur mostly near the seashore. Thus the whole of the Pulmonata (which breathe See also:air, are destitute of gill-plumes and operculum and have a complicated hermaphrodite reproductive See also:system) are either snails or slugs. But there are a considerable number of snails, both terrestrial and aquatic, which are not Pulmonates. The land-snails which have no gill-plume in the See also:mantle-chamber and breathe air, but have the sexes separated, and possess an operculum, belong to the orders Aspidobranchia and Pectinibranchia, and constitute the families Helicinidae, Proserpinidae, Hydrocenidae, Cyclophoridae, Cyclostomatidae and Aciculidae. The fresh-water snails which are not Pulmonates are the Paludinidae, Valvatidae and Ampullaridae, together with Neritina, a genus of the Neritidae.

These all possess a fully See also:

developed gill-plume and are typical Pectinibranchs of the sub-order Taenioglossa, most of the members of which are marine. The family Helicidae has a See also:world-wide See also:distribution. In See also:Helix the See also:spire forms a more or less obtuse-angled See also:cone; there are above 1200 species, of which 24 are See also:British. Helix nemoralis, L., of which H. hortensis is a variety, is one of the commonest forms. Helix pomatia, L., is the largest species, and is known as the edible snail "; it is commonly eaten in See also:France and See also:Italy, together with other species. It was formerly believed to have been introduced into See also:Britain by the See also:Romans, but there is no doubt that it is a native. In Succinea the cone of the spite is acute-angled; three species are British. In See also:Farina the spire is very See also:flat and the See also:surface glassy. In Bulimus the spire is elongated with a pointed See also:apex. Pupa is named from its resemblance to a chrysalis, the apex being rounded. The shell of Clausilia is sinistral and its See also:aperture is provided with a hinged See also:plate. The commoner See also:European slugs of small See also:size all belong to the genus Limax, in which the opening of the mantle-chamber is posterior.

L. flavus is the cellar slug. L. agrestis, L. arborum, L. See also:

maximus occur in gardens and See also:fields. The larger See also:black slugs are species of See also:Arion, of which two are British, A. ater and A. hortensis. Testacella haliotidea is common in See also:Great Britain and throughout See also:Europe. The species of Helix are all herbivorous, like the Pulmonata generally; snails and slugs are well-known enemies to the gardener. The animals being hermaphrodite copulate reciprocally, The eggs of Helix are laid separately in the See also:earth, each contained in a calcified shell; those of Limax are also See also:separate, but the shell is gelatinous. Helix hibernates in a torpid See also:condition for about four months, and during this See also:period the aperture of the shell is closed by a calcareous membrane secreted by the See also:foot. The Limnaeidae occur in all parts of the world. Limnaeus contains the largest species. L. pereger, See also:Muller, is ubiquitous in Great Britain and common all over Europe. All the species are usually infested with Cercariae and Rediae, the larval forms of Trematode parasites of vertebrates. L. truncatulus harbours the Cercaria of Fasciola hepatica, the See also:liver-See also:fluke, which causes, rot in See also:sheep.

Ancylus, which occurs in See also:

rivers, has a See also:minute limpet-like shell. Planorbis has the spire of the shell in one See also:plane. Physa is smaller than Limnaeus and has the upper See also:part of the spire much shorter. In the Auriculidae the aperture is denticulated. See also:Auricula is confined to the See also:East Indies and See also:Peru. Carychium minimum is British. Of the Cyclostomidae only one species, Cyclostoma elegans, Muller, is British; it hides under stones and roots. The Helicinidae are See also:exotic, ranging from the See also:West ladies to the Philippines: Of the Aciculidae, which are all minute, Acicula lineata is British. The Ampullaridae are confined to the tropics. Ampullariahas very See also:long tentacles and a long See also:siphon formed by the mantle. Valvata is common in fresh See also:waters throughout Britain; the gill when the See also:animal is See also:expanded is protruded beyond the mantle-chamber. The Paludinidae are common in the N. hemisphere.

Paludirtii 'and See also:

Bithynia are both British genera. In Paludinathe whorls of the spiral are very prominent ; the genus is viviparous. Bithynia is smaller and the shell smoother. Neritina has a very small spire, the terminal portion of the shell containing nearly the whole animal. For the See also:morphology and See also:classification of snails, see See also:GASTROPODA. A See also:history of the British forms is given in See also:Gwyn See also:Jeffreys's British Conchology (1862), and by See also:Forbes and See also:Hanley in British See also:Mollusca. For speciegraphical details, see See also:Woodward's See also:Manual of the Mollusca (1875), and See also:Bronn's Tierreich (Weichtiere). For Fasciola hepatica, see See also:Thomas, Quart. Journ. Mic. Sci. (1802).

SNAKE-See also:

BIRD (the " darter " of many authors, and the Plolus anhinga 1 of See also:ornithology), the type of a small but very well-marked genus of birds, Plotus, belonging to the family Phalacrocoraeidae which contains the 'cormorants and shags. The name commonly given to it by the See also:English in N. See also:America was derived from its "long slender See also:head and See also:neck," which, its See also:body being submerged as it swims, " appears like a snake rising erect out of the water " (J. Bartram's MS., quoted by G. F. Ord in A. See also:Wilson's Am. Ornithology, ix. 81). Snake-birds See also:bear a See also:general resemblance both outwardly and in habits to Cormorants (q.v.), but are much more slender in See also:form and have both neck and tail much elongated. The See also:bill also; instead of being tipped with a maxillary See also:hook, has its edges beset with serratures directed backwards, and is sharply pointed—in this respect, as well as in the attenuated neck, likening the Snake-birds to the Herons; but the latter do not generally. transfix their See also:prey as do the former. The male of the See also:American species, which ranges from See also:Illinois to the S. of See also:Brazil, is in full breeding-plumage a very beautiful bird, with See also:crimson irides, the See also:bare skin See also:round the eyes See also:apple-See also:green and that of the See also:chin See also:orange, the head, neck and most part of the body See also:Indian Snake-Bird (from S.

R. See also:

Tickell's See also:Drawing in the Library of the Zoological Society). clothed in black glossed with green; but down each See also:side of the neck runs a See also:row of long See also:hair-like See also:white feathers, tinged with See also:pale See also:lilac. The much elongated scapulars, and the small upper wing-coverts bear each a median white See also:mark, which on the former is a stripe pointed at either end, and on the latter a broad ovate patch.' The larger wing-coverts are dull white, but the See also:quill-feathers of the wings and tail are black, the last broadly tipped with brownish-red, passing into greyish-white, and forming a conspicuous See also:band when the tail is spread in form of a See also:fan, as it often is under water.' The See also:ben differs much in See also:appearance from the See also:cock, having the head, neck and See also:breast of a more or less deep See also:buff, bounded beneath by a narrow See also:chestnut band; but otherwise her plumage is like that of her See also:mate, only not so See also:bright in See also:colour. The Snake-bird frequents the larger rivers or back-waters connected with them, where it may be seen resting motionless on some neighbouring See also:tree, generally choosing a dead See also:branch, or on a " snag " projecting from the bottom, whence it plunges beneath the surface, in pursuit of its prey, to emerge, in the manner before related, showing little more than its slender head and neck. Its See also:speed and skill under water are almost beyond exaggeration, and it exhibits these qualities even in captivity, taking—apparently without effort—See also:fish after fish, however rapidly they may swim and twist, and only returning to its See also:perch when its appetite is appeased or its See also:supply of See also:food exhausted. At See also:liberty it will indulge in long flights, and those of the male at the breeding- " Anhinga," according to Marcgrav, who first described this bird (Hist. rer. nat. Brasiliae, p. 218), was the name it See also:bore among the natives. 2 These feathers are very characteristic of each species of the genus, and in See also:India, says Jerdon,are among the Khasias a badge of See also:royalty. 3 This peculiarity, first pointed out to the writer by A. D.

See also:

Bartlett, who observed it in birds in the Zoological Society's See also:possession, doubtless suggested the name of " Water-See also:Turkey " by which in some places Rotas anhinga is said to be known. See also:season are ostentatiously performed in the. presence of his mate, vast See also:majority of See also:snakes are further characterized by having the right and See also:left halves of the under-jaws connected by an elastic band; a median, See also:longitudinal furrow in the skin below and behind the chin; the. whole palatal apparatus is but loosely connected with the See also:skull, nowhere articulating with it. The quadrate is indirectly articulated with the skull, first by the See also:horizontal, movable squamosal, secondly by the See also:columella auris. The quadrato-mandibular See also:joint is placed in a level far behind the occiput: around whom he plays in irregular zigzag courses. The See also:nest is almost always in trees or bushes overhanging the water's edge, and is a large structure of sticks, roots and See also:moss, in which are laid four eggs with the white chalky shell that is so characteristic of most Steganopodous birds. Not infrequently several or even many nests are built See also:close together, and the locality that suits the Snake-bird suits also many of the herons.' The See also:African snake-bird, P. congensis (or levaillanti of some authors), inhabits the greater part of that See also:continent N. from See also:Natal; but, though met with on the White See also:Nile, it is not known to have occurred in See also:Egypt; a fact the more remarkable seeing that See also:Canon Tristram found it breeding in considerable See also:numbers on the See also:Lake of See also:Antioch, to which it is a summer visitor, and it can hardly reach its See also:home without passing over the intervening See also:country. The male bird is easily distinguishable from the American species by its rufous coronal patch, its buff See also:throat and its chestnut greater wing-coverts. A third species, P. inelanogaster, ranges from See also:Madagascar to India, See also:Ceylon, See also:Borneo, See also:Java and See also:China. This so closely resembles the last-mentioned that the See also:differences between them cannot be briefly expressed. The Australian region also has its snake-bird, which is by some regarded as forming a See also:fourth species, P. novae-hollandiae; but others unite it to that last mentioned, which is perhaps somewhat variable, and it would seem (P.Z.S.; 1877, p. 349) that examples from New See also:Guinea differ somewhat from those inhabiting See also:Australia itself. The See also:anatomy of the genus Flatus has been dealt with more fully than that of most forms.

Beside the excellent description of the American bird's alimentary See also:

canal furnished to See also:Audubon by See also:Macgillivray, other important points in its structure have been well set forth by A. H. Garrod and W. A. Forbes in the Zoological Proceedings (1876, pp. 335-345, pls. See also:xxvi.-See also:xxviii.: 1878, pp. 679-681; and 1.882, pp. 208-212), showing among other things that there is an appreciable anatomical difference between the species of the New World and of the Old; while the See also:osteology of P. melanogaster has been admirably described and illustrated by A. Milne-See also:Edwards in A. Grandidier's great Oiseaux de Madagascar (pp. 691-695, pls. 284, 285).

In all the species the neck affords a feature which seems to be unique. The first seven of the cervical vertebrae form a continuous See also:

curve with its concavity forward, but the eighth articulates with the seventh nearly at a right See also:angle, and, when the bird is at See also:rest, lies horizontally. The ninth is directed downwards almost as abruptly, and those which succeed See also:present a See also:gentle forward convexity. The muscles moving this curious framework are as curiously specialized, and the result of the whole piece of mechanism is to enable the bird to See also:spear with facility its fishy prey. . (A. N.) SNAKE-See also:FLY, the name given to neuropterous See also:insects of the genus Raphidia, closely allied to the See also:alder-flies, remarkable for the See also:elongation of the head and prothorax to form a neck and for the presence in the See also:female of a long ovipositor. The larva, which is active and carnivorous, is terrestrial, and lives in rotten See also:timber. SNAKE-See also:ROOT. In most countries where snakes abound some root or See also:herb is used by the natives as an antidote for the bitesof venomous species, and many herbs have consequently received the name of snake-root. Botanically speaking, the name properly belongs to Ophiorrhiza Mungos, the Mungoose plant, a plant of the natural order See also:Rubiaceae, used in the E. Indies loathe purpose above indicated. In See also:medicine, however, the roots of See also:Aristolochia Serpenlaria, Polygala See also:Senega and See also:Cimicifuga racemosa were understood by this name, being distinguished as the Virginian, See also:seneca and black snake-roots.

The root of Aristolochia reticulates is known in the See also:

United States as Red river or Texan snake-root. The roots or rhizome of Liatris spicata, Eryngium aquaticum and Eupatoriurn altissimum have all been used in N. America for snake-bites, the first two being known as See also:button snake-root and the last as white snake-root. The rhizome of Asarum canadense passes under the name of See also:Canadian snake-root. All of these contain acrid or aromatic principles which, when a warm decoction of the See also:drug is taken, exercise a powerfully diaphoretic or, in some cases, diuretic See also:action, to which any benefit that may be derived from their use must be attributed.

End of Article: SNAIL

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
SMYTH, SIR WARINGTON WILKINSON (1817-1890) 		[next]
SNAKES

Site © 2006 - Net Industries