48 Descriptions of Preparations. 



in it posteriorly to the peristome. In this point, as also in that 

 of jDossessing" a much smaller amount of organic matter, the Gaste- 

 ropodous contrasts with the Lamellibranchiate shell. 



For the structure and mode of development of the shell, see Huxley, 

 Cyclopaedia of Anatomy and Physiolog-y, Article 'Tegumentary 

 Organs,' pp. 489-492. For views somewhat different from 

 those put forth there, see Bronn und Keferstein, Klassen 

 und Ordnungen des Thierreichs, iii. 2, pp. 901, 902, 913, 

 920, 1 177, 1181, and Rose, Abhandlung, Berlin, Akad. 1858, 



PP- 94, 95- 

 For the terminology employed in describing shells, see English 

 Cyclopaedia, Article ^ Gasteropoda, '' p. 925. 



15. Edible Snail {Helix Pomatia). 



Dissected so as to show its digestive and reproductive, together with portions of its 

 circulatory and respiratory, organs. 



The shell has been detached from the body to which it adhered 

 mainly by means of the columellar muscles, and that part of the 

 general muscular envelope of the viscera, which was continuous 

 with their insertion. The greater part of this muscular envelope 

 and of the mantle has also been removed. The coils of the 

 liver, which were lodged in the uppermost whorls of the shell, 

 and which contain the hermaphrodite gland impacted in their 

 substance, have, together with the rest of the reproductive ap- 

 paratus, been arranged on the animaFs right side ; the larger part 

 of the liver with the intestine, heart, and respiratory sac, occupies 

 the left of the preparation ; the nerve collar and digestive ap- 

 paratus down to the pylorus, are seen in the middle line; and 

 between them and the parts to the left, lies at a lower level the 

 sole-shaped locomotor disc known as the 'foot.' A black bristle 

 has been passed between the cephalic ganglia, or supra-oesophageal 

 portion of the nerve-collar and the buccal mass, which, together 

 with the horny crescent-shaped jaw, has been retracted somewhat 

 from its natural position. From the lower part of the buccal mass, 

 a small conical body, in which the back part of the so-called 

 'tongue' is lodged, projects posteriorly. Along the upper and 



