EDIBLE SNAIL. 



columnar where the nerve is in contact with them than elsewhere. It bends 

 round the anterior edge of the pulmonary aperture, and at the spot where it bends 

 swells into a small ganglion with large ganglion-cells. A nerve extends from the 

 ganglion to the glandular cells of the epidermis (?) of the collar. The homologous 

 nerve, but devoid of a ganglion, is present in Sucdnea amphibia, Bulimus detritus, 

 B. decollatus and Limax cinereoniger. It is distributed to the glandular epithelium 

 as in H. per sonata. The corresponding nerve is apparently present in H.pomatia^. 

 The osphradial apparatus is well developed in the aquatic Pulmonates, Limnaeus, 

 Planorbis, and Physa. In the first of the three, which has a dextral shell, the nerve 

 is derived from the right visceral ganglion ; in the other two, which have sinistral 

 shells, from the corresponding left ganglion. The nerve ends in a ganglion with 

 large ganglion cells, in connection with a ciliated canal or depression in the 

 pulmonary chamber above and behind its orifice. In branchiate Gastropoda the 

 nerve is also derived from the visceral ganglion, and ends in a similar ganglion 

 lying immediately beneath the epidermis close to the ctenidium. The epidermic 

 cells above this ganglion are large and columnar. The apparatus is paired when the 

 ctenidia are paired. See general account of the Class. 



Nervous system : of Helix pomatia and Limnaeus, Bohmig, Inaugural Disserta- 

 tion, Leipzig, 1883 ; of terrestrial Pulmonata, Leydig, A. M. A. i. 1865 ; of aquatic 

 Pulmonata, De Lacaze Duthiers, A. Z. Expt. i. 1872; of Mollusca, von Ihering, 

 Vergleich. Anat. des Nervensystems, &c. der Mollusken, Leipzig, 1877. 



Homology of the ganglia. Spengel, Z. W. Z. xxxv. 1881. Cf. Ray Lankester, 

 ' Mollusca,' Encyclopaedia Brit. (ed. ix.) xvi. p. 636, and Fig. i D. 



Pedal nerves : of Zonites, Nalepa, SB. Akad. Wien. Ixxxvii. Abth. i. 1883, 

 p. 282; of Limax, Helix, Arion, Simroth, Z. W. Z. xxxii. 1879, pp. 304-318; of 

 Vaginulus, Semper, A. M. A. xiv. 1877, p. 123. 



Histology. See Bohmig, op. cit. supra \ Vignal, A. Z. Expt. (2) ii. 1883. Cf. 

 Haller, Marine Rhipidoglossa, ii. M. J. xi. 1886. 



Organs of special sense. Sensory epithelium. Flemming, A. M. A. v. 1869. 

 Tentacular ganglion, &c., Id. A. M. A. vi. 1870 ; Sarasin, Arb. Zool. Zoot. Inst. 

 Wurzburg, vi. 1883. Oral ganglion (=Semper's organ), Sarasin, op. cit. Eye, 

 Hilger, M. J. x. 1885. Carriere, Sehorgane der Thiere, Leipzig, 1885 ; Z. A. ix. 

 1886. Otocyst. Leydig, A. M. A. vii. 1871. Cf. Simroth, Z. W. Z. xxvi. 1876, pp. 

 278-281 ; De Lacaze Duthiers, A. Z. Expt. i. 1872. Osphradium (= olfactory 

 organ) : of Mollusca, Spengel, Z. W. Z. xxxv. 1881 ; of aquatic Pulmonata, 

 Simroth, Z. W. Z. xxvi. 1876, p. 308; De Lacaze Duthiers, A. Z. Expt. i. 1872 

 (=organe nouveau d'innervation) ; of terrestrial Pulmonata, Sarasin, op. cit. supra. 



Regeneration of eye, 6r. in Pulmonata. Carriere, Studien iiber die Regenerations- 

 erscheinungen bei den Wirbellosen, i. Wurzburg, 1 880. 



1 Simroth has described (Z. A. v. 1882, and with figures in J. B. Mai. Gesellsch. x. 1883), in the 

 slug Parmacella Olivieri, a groove with projecting edges extending from the pulmonary aperture 

 forwards to the left, and lying in the furrow between the edge of the mantle-fold and body. Ganglion 

 cells underlie the groove and its edges, which are supplied by the right pallial nerve, as well as by 

 a branch from the left pallial nerve. The position of the organ external to the pulmonary chamber 

 appears to render an homology with the osphradium impossible. Zonites has a sac opening close to 

 the pulmonary aperture and lying in the roof of the pulmonary chamber. It is beset with gland- 

 cells and supplied by the ' olfactory ' nerve, which is, however, devoid of a ganglion (see Nalepa, op. 

 cit. ante, p. 239). 



