67 



HELICID-iE. 



HELICID^E. 



Circulating System. In the Shell-Snail (Helix) the heart is situated 

 on the right side of the posterior third of the pulmonary sac ; and in 

 the Slug (Limaj-) it is situated at nearly the middle of the posterior 

 surface of the pulmonary sac, and protected above by the rudimentary 

 shell, so that this part of the structure in these animals is, as in other 

 points, nearly allied. The preparation in the College Museum, No. 

 882 (Gallery), is a specimen of Helix Pomatia with the shell removed 

 in order to show the heart, which is situated on the left side of the 

 dorsal aspect of the body, near the posterior part of the branchial sac. 

 The pericardium is laid open, and the heart being injected, the 

 auricle, from its thinner parietes, is seen of a red colour ; a bristle is 

 passed behind the ventricle, and the aorta may be seen ramifying over 

 the liver. No. 883 is a specimen of Limax ater, Linn. (Slug), to show 

 the heart situated in the middle of the back. (' Catalogue ' Gallery, 

 vol. ii.) 



Respiratory System. In the same series the soft parts of Helix 

 Pomatia are prepared (No. 1081), to show the pulmonary sac, which 

 receives the air by an anterior orifice on the right side of the neck. 

 The sac is laid open from that orifice to the opposite extremity ; and 

 the roof of the cavity, upon which the pulmonary artery or continua- 

 tion of the veins of the body ramifies, is turned back to exhibit the 

 reticulation of the vascular and respiratory surface. The parts are 

 injected with size and vermilion. No. 1082 is a similar specimen, 

 with the left parietes of the pulmonary sac removed, and the orifice 

 by which the air ig admitted and expelled left entire. No.- 1083 is 

 the portion of the vascular parietes of the pulmonary sac removed 

 from the preceding preparation, and inverted to show the ramifications 

 of the pulmonary vessels. These are continued from the veins of the 

 body without the interposition of the propelling ventricle. No. 1084 

 is a similar preparation. No. 1085 shows the roof of the pulmonary 

 oc of another Helix Pomatia, with the vessel injected ; and in No. 

 1086 there is, in a similar specimen, a bristle inserted into the 

 rectum, which terminates close to the orifice of the pulmonary sac. 

 (' Catalogue'- Gallery, vol. ii.) 



Brain, Nervous System, and Senses. In the same series of the same 

 collection is a preparation of a Slug (Limaj- rufia, Linn.) No. 1304 - 

 laid open longitudinally along the back to show the nervous system. 

 The viscera are removed. " In this," says Professor Owen, " as in 

 other Eucephalous Mollusks, a well-developed ganglion is situated 

 above the cesophagus ; it is of a transverse shape, slightly enlarged at 

 its extremities, and supplies the antenna;, or horns, and the eyes. The 

 cesophageal nervous ring is completed by a larger ganglion below the 

 tube, from which numerous nerves radiate to supply the body. The 

 principal nerves are the two inferior ones, which extend on either side 

 the mesial line of the ventral surface straight to the opposite end of 

 the body, giving off nerves to the muscular disc, or foot, from their 

 outer sides. A small unsymmetrical ganglion is formed on the nerve, 

 which supplies the heart and respiratory apparatus." No. 1305 is 

 the same species of slug laid open along the ventral aspect, and the 

 viscera removed, to show more especially the subccsophageal ganglion 

 and its nerves. A bristle' occupies the place of the oesophagus. No. 

 1306 exhibits the nervous system of a Black Slug removed from the 

 body. ('Catalogue' Gallery, vol. ii.) 



Touch. In the Shell-Snails the sense of touch will be readily sup- 

 posed, by any one who has observed the motions of a common garden- 

 snail, to reside especially in the ventral disc, or foot, and the lower 

 tentacles. In the museum of the College we find, No. 1391, a speci- 

 men of Helix Pomatia prepared to show the different character of 

 the surface of the skin in the exposed and protected parts of the 

 body : in the latter it is thin anil smooth ; in the former, thick, vascu- 

 lar, and rugose. No. 1392 is a snail injected, slit down the back and 

 eviscerated, to show the vascularity of the foot. No. 1393 is a snail 

 injected, with one pair of tentacles, which serve as special instruments 

 of touch, extended. Here too the pulmonary cavity is laid open. 

 (' Catalogue' Galltry, voL ii.) 



Sight In the gallery (Physiological Series) of the same rich 

 museum is a preparation of a ltdix Pomatia (No. 1756), with the 

 posterior tentacles or horns extended, showirig the eye-specks, or ocelli, 

 situated at the side of the extremity of each horn. " In this position, 

 although destitute of appropriate muscles, the eyes have the advantage 

 of all the mobility with which the tentacle itself is endowed ; and by 

 the admirable construction of the same part, they are defended from 

 external injury by being retracted and inverted, together with the 

 extremity on which they are supported within the cavity of the 

 tentacle, as in a sheath." (Professor Owen, ' Catalogue,' Gallery, 

 Tol. iii.) 



.Swammerdam describes the eyes in detail ; but some are of opinion 



that the organs above alluded to are not eyes. Sir Everard Home 



denied that they were visual organs; and so does M. Oaspard, who 



allows the snail no senses, save those of taste and touch, the latter of 



whii li lie- admit* it to possess in an extreme degree of delicacy. See 



M. 'iifpiird'H ' Memoir on the Physiology of Helix Pomatia.' (Majen- 



' foiinml de Physiol.,' torn. ii. p. 295, et seq. ; and an abstract of 



4>er, with notes, by T. Bell, Esq., ' Zool. Journ.,' vol. i.) See 



Ir. llrayley's paper ' On certain Organs of the Helicidae, usually 



regarded as their Eyes, Ac.' (' Zool. Journ.,' vol. ii.) 



; -native Functions. In the common Shell-Snails (Helix), the 

 male and female sexual organs are complete in one individual, but it 



requires a reciprocal junction of two individuals to produce a fruitful 

 impregnation. The situation of these organs is at the anterior orifice 

 of the neck ; and at the time of congress a sharp horny or glass-like 

 excitatory appendage is protruded, apparently for the purpose of 

 stimulus. Some assert that these appendages are absolutely shot 

 out from the body of one snail into the body of another, and engrav- 

 ings even exist where two snails are represented at a distance from 

 each other reciprocally darting these spicula amoris, some of which are 

 seen actually in the intervening space, and others on the ground. 

 There is reason to doubt whether the spiculum amoris is ever thrown : 

 we have had opportunities of examining the common garden shell- 

 snails frequently when engaged in the reproduction of the species, 

 and have never seen the hard excitatory appendage thrown from the 

 body of the snail. Colonel Montagu, it appears, is of the same opinion. 

 He admits the existence of the spicula in the. animal of Helix aspcrsa, 

 as well as II. nemoralia (or at least some of them) ; but " that they 

 are missile darts," he continues, " we have much reason to doubt, 

 though it is natural to suppose the animals are furnished with them 

 for the purpose of stimulating each other to love, because it is only 

 at that season they are found to possess them. If such are ever dis- 

 charged at each other, we have been extremely unfortunate in our 

 observations, for in no one instance could we ever find the dart pene- 

 trated, though at the time the animals are close'the point may irritate ; 

 but it is neither sufficiently strong nor sharp-pointed to penetrate the 

 tough skin with which these animals are furnished ; and indeed the 

 extremely viscid secretion with which they are so copiously provided 

 adheres so strongly to the spiculi (spicula), when wholly projected 

 from the body, that they are for a time held by it. Perhaps we may 

 be told hereafter that this tough excretory fluid is used as a cord to 

 regain these darta after they have been discharged ; but such we 

 should hold equally fabulous with much of the accounts related by 

 various authors. These celebrated love-darts are sub-pellucid, white, 

 and very brittle, about one-fourth or three-eighths of an inch in 

 length, and somewhat triangular like the blade of a small sword." 

 ('Testacea Britannica.') Dr. Maton often observed these spicula, but 

 never saw them actually projected from one to the other. 



Where the reproduction is by means of eggs, as it is in the great 

 majority of Helicida, these are either enveloped in a skin, and round, 

 as in the common garden-snail, or provided with a hard calcareous 

 shell, generally of a white or of a dirty-white colour, as in Acltatina 

 and Bidimia. [BuLiMCS.] These hard-shelled eggs are generally 

 oval ; in other instances they are round. Specimens of these eggs, 

 some whole, some showing the young shell included, and others show- 

 ing it breaking out of the egg-shell, are now in the British Museum 

 (from Mr. Broderip's collection). In the museum of the College of 

 Surgeons are several preparations, showing the organs of generation in 

 the shell-snail. 



Power of repairing Injuries. The power which snails, in common 

 with other Testaceous Mollusks, possess of repairing their shells, is 

 known to most observers, and requires no comment ; but the extent 

 to which these animals will repair lesions of the soft parts, and even 

 reproduce some of the principal ones after they have been deprived 

 of them, is deserving of notice. The works of Schoeffer, Spallauzani, 

 Bonnet, and others bear testimony to the wonderful vis vittc in these 

 animals, and its energy in replacing parts, the deprivation of some of. 

 which must, it might have been previously thought, have been fol- 

 lowed by immediate death. Spallauzani cut off one of a snail's horus : 

 it began to bud again in about 25 days, and continued to grow till it 

 was equal in length to the other. He removed part of the head : in 

 course of time the part was renewed. Not that this was always the 

 case in those instances where the entire head had been taken off ; but 

 even in these instances the snail often recovered, and at the end of a 

 few months appeared with a new head in all respects equal to the old 

 one. The snails so treated retired into their shells the moment the 

 operation was over, and there they concealed themselves for weeks 

 and even months, covering the aperture with the parchment-like 

 secretion so well known to those who have seen this temporary sort 

 of operculum. When forced out for examination at the end of 30 or 

 40 days, some appeared without any marks of renewal ; but in others, 

 especially in those cases which had the advantage of warm weather, 

 there was a fleshy globule towards the middle of the trunk, soft, and 

 whitish-ash in colour. At this period no organisation was detected in 

 the globule ; but in 8 or 10 days the globule became larger, rudi- 

 ments of lips were seen, and of the smaller horns, mouth, and tongue. 

 A membranaceous substance was observed fixed in the upper jaw : 

 this proved to be the new tooth. The parts then became further 

 developed and more conspicuous, occupying a greater space, and in 

 two or three mouths the injury was so completely repaired that the 

 lighter colour only of the new head served to distinguish it from the 

 old one. These experiments were confirmed by others, by Gerardi 

 among the rest. 



Hyberuation. M. Gaspard remarks that in our temperate climate, 

 as soon as the first autumnal chills are felt, about the commencement 

 of October, generally, HclLc Pomatia becomes indolent, loses its 

 appetite, and associates in considerable numbers on hillocks, the banks 

 of ditches, in thickets, hedges, and such pluces. In a day or two the 

 animals cease feeding, expel the last contents of the intestines, and 

 then hide themselves under moss, grass, dead leaves, or the lika 



