EDIBLE SNAIL. 



(2) i. 1 88 1, p. 435. Development, Rouzaud. C. R. 96, 1883 ; Jourdain, Revue 

 Sc. Nat. Paris and Montpellier, viii. Physiology, Dubrueil, Revue des Sci. Nat., 

 Paris and Montpellier, i. 1873; ii. 1874; cf. Jourdain in A. N. H. (4) viii. 1871. 

 Dart of British Heliddae, Ashford, Journal of Conchology, iv. 1883. 



Sperm. Ley dig, Untersuchungen zur Anat. und Histol. der Thiere, Bonn, x. 

 1883, p. 118; development of , Blomfield, Q. J. M. xxi. 1881 ; Nussbaum, A. M. A. 

 xxiii. 1884, p. 206; cf. Von Brunn, ibid. p. 459 ; Platner, A. M. A. xxv. 1885. 

 Ova and Development. Fol, A. Z. Expt. viii. 1880. 



23. EDIBLE SNAIL (Helix pomatia), 



Dissected so as to show its nervous system. 



THE collar has been divided to the right of the pulmonary aperture, to 

 the left of its columellar lobule, which is left in situ on the right side. The 

 attachment of the mantle below the collar to the integument of the body 

 has been divided from right to left, and again along the right margin of the 

 pulmonary chamber. The mantle-fold or roof of the pulmonary chamber 

 thus freed from its connections has been turned over to the left and displays 

 the terminal portion of the intestine at its edge, the pulmonary vessels, the 

 triangular kidney, and the pericardium, the latter opened to show the heart. 

 The integument covering the head and neck has been divided in the middle 

 line, and the floor of the pulmonary chamber continuous with it removed. 

 The whole of the viscera have also been removed, leaving only the buccal 

 mass, the nerve-collar and the columellar muscles cut short. The buccal 

 mass is much retracted, as it is when the animal's head is drawn in. At its 

 base are seen, the origins of the oesophagus and salivary ducts above, and 

 the sac of the radula below. A stout black bristle has been passed under 

 the right cerebral ganglion. From the anterior edge of this ganglion a 

 nerve passes to the right upper tentacle which bears the eye : a similar 

 nerve, not visible here, passes to the lower tentacle. From its posterior 

 edge a nerve passes along the buccal mass to a small stellate ganglion, the 

 buccal ganglion, which lies below the salivary duct and innervates the 

 buccal mass ; a fine black bristle has been placed beneath it. There are two 

 such ganglia, right and left, connected by a commissure below the oeso- 

 phagus. The right cerebral is united to the left by a commissure passing 

 across the buccal mass : it is united to the infra-oesophageal ganglion 

 below the buccal mass by a broad band. This band contains two nerve- 

 connectives (not visible here), one to the anterior or pedal portion, the other 

 to the posterior or visceral (parieto-splanchnic) portion of the infra-oeso- 

 phageal ganglion. From the posterior margin of this ganglion three nerves 

 pass backwards to the body walls ; a fourth, which accompanies the aorta 

 cephalica, has been removed together with that vessel. Bundles of nerves 

 may be seen passing down from the anterior or pedal portion of the 



