Cellar Slug. 191 



oesophagus through the nerve collar^ being separated from 

 the aorta by the parieto-splanchnic portion of the suboeso- 

 phageal mass. They have been cut away in this Prepar- 

 ation. 



For the anatomy of the Pulmonate Gasteropoda generally, see 



Semj)er^ in Zeitschrift fiir Wiss. Zoologie, Bd. viii., 1857. 

 For figures of the anatomy of Limax, see Leidy, in vol. i. of 



"Binney^s Terrestrial Molluscs of the United States^ pi. i. 

 For the reproductive system, see Baudelot, Ann. Sci. Nat., 



tom. xix., pi. 3, fig. 17, 1863. 

 For the essential connection of the acoustic nerve with the supra- 

 oesophageal ganglia, which has been overlooked on account of 

 the close apposition to the pedal ganglia of the vesicles ap- 

 pended to those nerves, see Lacaze Duthiers, L^'Institut, No. 

 1 82 1, translated in Monthly Microscopical Journal, Feb. i, 

 1869; and for instances of the otic vesicle and its nerve 

 maintaining in actuality those morphological relations undis- 

 guised by approximation to the pedal ganglia, see Gegenbaur's 

 and Souleyet's figures of the Heteropodous Carinaria and Pte- 

 rotrachea in V. Carus^ Icones Zootomicae, tab. xx., fig. 13; 

 Gegenbaur, Untersuchungen iiber Pteropoden, und Hcteropo- 

 den, 1855, tab. vii., fig. i; Vergleichende Anatomic, p. 325, 

 fig. 83. 

 The two sets of organs of special sense, the auditory and the 

 ophthalmic, are thus seen in Gasteropoda to be both in connection 

 with the same nerve-centres. The attachment, however, of the otic 

 vesicle and nerve can scarcely be different in reality from what it 

 is in appearance in the Lamellibranchiata (for which see pi. y.J') ; 

 and the multiplicity of the ' eyes' in Pecten and Spondylus set 

 along the border of the mantle, to the nervous supply of which 

 both cephalic and parieto-splanchnic ganglia contribute, would lead 

 us to expect variability rather than fixity in the connections of the 

 organs of special sense in Mollusca. The varying allocation of the 

 organs of special sense in the two sub-kingdoms, Arthropoda and 

 Vernus^ would appear to pomt in the same direction. 



