Dissected so as to show its digestive, circulatory, respiratory, nervous, and reproductive systems.

Cellar Slug, Limax flavus.

Plate V. Cellar Slug, Limax flavus.

The muscular envelope has been separated from the foot along the left side, and turned over to the right, together with the shield-shaped mantle and the organs it overlies. The buccal mass and nerve collar, together with the salivary glands, have been displaced a little to the left, on which side of the animal's body the stomach and bilobed liver have been fastened out. Some of the nerves, muscles, and arteries have been cut away. The oesophagus and buccal mass have been pulled a little forward through the nerve-collar, and occupy much the same position relative to it that they do when in life the buccal mass and head are thrust forward. The two first convolutions of the intestine have been uncoiled, and it has thus been drawn as taking a much less sinuous course than it does in nature from its commencement at the pylorus to the point where it comes into relation with the dorsal integument and shield, and hooks round the muscle which retracts the buccal mass and tentacles. The generative organs have been detached from their normal connections, and are arranged on the right side of the animal's head. Their volume, as drawn here, is small in comparison with that which they attain in the breeding season.

The upper tentacles, the nerves which supply and the muscles which retract them, have been cut through, and turned forward so as to lie between the generative apparatus on the right hand and one of the salivary glands on the left. The right lower tentacle is seen between the right upper tentacle and the vestibulum of the reproductive system. a. Locomotive disk or 'foot' passing upwards at the sides into the general muscular envelope of the various organs of the animal's body, from which it is limited off by a furrow. Its internal circular coat is raised into two corrugated ridges along the greater part of the middle line of the body by the underlying supra-pedal gland. This gland is found in many Gastropoda, and is of very large size in this Slug. Its aperture lies above the foot and below the head, its duct is long, and lined by ciliated epithelium of two kinds, of which one is perhaps sensory (? olfactory). The gland cells are aggregated on either side of and below the duct. The supra-pedal gland must be carefully distinguished from the pedal which secretes the mucous thread by which certain Prosobranchiata suspend themselves to the surface of the water, and which opens on the sole of the foot anteriorly.

See p. no, and lit. p. 112.

b. Shield and organs in connection with it.

c. Stomach and bilobed liver, arranged upon the animal's left.

d. Generative apparatus arranged upon the animal's right.

e. Nerve-collar, consisting of two cerebral ganglia placed above, or rather at the sides of, the oesophagus, and two pairs of ganglia placed below it, and united with the upper pair by connectives. The two cerebral ganglia are connected by a flat commissure, and with the infra-oesophageal ganglia by a double connective, the posterior cord of which joins the posterior part of the mass or visceral ganglia, whilst the anterior cord joins the anterior or pedal ganglia from which nerves pass off to the foot.

f. Stomatogastric ganglion of right side placed below the oesophagus, where it enters the buccal mass together with the duct of the salivary gland. The ganglion is connected by a long and delicate commissural cord with the supra-oesophageal ganglion of its own side, and it gives off nerves to the buccal mass, to the oesophagus, and to the duct of the salivary gland.

g. Salivary gland.

h. Buccal mass containing the 'tongue' or 'odontophore.' i. Semper's organ. It is of very large size in this Slug, small in Helix, Arion, Lymnaeus, and has only been detected in Pulmonata. It consists of four to five lobes composed of cells, resembling those in the salivary or supra-pedal glands, held together by a network of connective tissue and a membrane. According to Sochaczewer (Z. W. Z. xxxv. 1881, p. 35), it receives two nerve twigs from the labial nerves, and is not, as Semper supposed, richly supplied with nerves. A ganglion has been detected by Sarasin (Arb. zool. zoot. Inst. Wurzburg, vi. 1883, p. 95) lying in the oral lobes and sending processes into this gland. It occurs also in Pulmonata Basommato-phora, in which Semper's organ is absent.

j. Coecal projection at pyloric end of stomach.

k. Liver consisting of two lobes opening each by a single duct close to the pylorus.

l. Intestine passing from the pylorus to end a little in front of and above the respiratory inlet. Its two first convolutions have been separated from the liver and reproductive apparatus. As it approaches the dorsal integument and shield it describes a curve like an Italic S. In the first loop of this S is seen the origin of the retractor muscles of the buccal mass and labial tentacles; at its opposite extremity arises a straight coecum, y.

m. Respiratory orifice, with the 'rectum' curving round to open a little above and anteriorly to it. To the right of the rectum is seen the duct of the renal organ.

n. Portion of dorsal integument, an incision immediately to the right of which would disclose the shell. Internally to it is the respiratory sac, with the ramifications of the pulmonary veins.

0. Renal organ, placed to the right of the heart in the natural position , of the parts, and giving off a duct which passes backwards, to run in company with the rectum and open near the anus. See enlarged figure by Professor Leidy in Binney's Terrestrial Molluscs of the United States, vol. i. Pl. I. Fig. iv.

p. Ventricle of bilocular heart.

q. Hermaphrodite gland.

r. Hermaphrodite duct.

s. Albuminiparous gland.

t. Vas deferens becoming distinct from oviduct v sooner than in Helix or Arion, and richly beset with prostatic glandules.

u. Penis, with part of its retractor muscle left attached to it; the muscle originates at a spot on the under surface of the muscular envelope of the viscera, close to the arterial outlet of the heart.

v. Oviduct, like the vas deferens, glandular above, and membranous below; and opening into a dilated vagina.

w. Receptaculum seminis, opening in this species, though not in the closely allied Limax cinereus into the vagina.

x. Pedal portion of the suboesophageal nerve mass, enclosing, together with the visceral, an orifice through which the anterior aorta passes. The line is drawn to a spot where in Helicidae the otic vesicle is readily found, but where in Limax it is not easy to convince oneself that it exists, even as a rudimentary organ, without the use of reagents, such as the oxalic acid recommended by de Lacaze Duthiers.

y. Coecum passing off from intestine just before it comes into relation with the pulmonary cavity, and extending back nearly to the termination of the body cavity.

z. Retractor muscle of the buccal mass and tentacles. Its fascicles pass with the oesophagus through the nerve-collar. They have been cut away in this Preparation.

Anatomical and general account of Limacidae, Simroth, Nacktschnecken, etc. Z. W. Z. xlii. Figures of the anatomy of Limax, Leidy, Binney's Terrestrial Molluscs of the United States, i. Pl. I.

Reproductive system, Baudelot, A. Sc. N. (4), tom, xix., 1863, Pl. III. Fig. 17.