GASTROPODA HETEROPODA. 



49 



large auditory vesicles each receive a long auditory nerve from the 

 eerebral ganglion, and are characterised not only by the remarkable 

 vibrations of the long tufted cilia of their epithelium, but also by the 

 arrangement of the nerve cells (group of hair cells of the macula 

 acustica round a large central cell, fig. 83). In addition numerous 

 peculiar nerve-endings in the skin, which appear to serve the tactile 

 sensation, and the so-called ciliated organ on the anterior side of the 

 visceral sac, are present. The latter has the form of a ciliated pit, 

 under which is placed the ganglionic swelling of a nerye which 



Bm 



Fig. 521. Male of Carinaria mediterranea (after Gegenbaur). P, f oot ; S, sticker; O, mouth; 

 Bm, buccal mass ; M, stomach ; Sp, salivary gland ; L, liver ; A, anus ; CG-, cerebra 1 

 ganglion; Te, tentacles ; Oc, eye; Of, auditory vesicle ; B G, buccal ganglion; Pg, pedal 

 ganglion; My, mantle ganglion; N, kidney; Br, gills; At, auricle ; Ve, ventricle; Ar, 

 anterior aorta ; Z, posterior branch of same ; T, testis ; Vd, vas def erens ; Wp, ciliated 

 furrow ; Pe, penis ; F, flagellum with gland. 



arises in the visceral ganglion; it has the value of an olfactory 

 organ. 



The m^les are distinguished by the possession of a large copulatory 

 organ, which projects freely on the right side of the body ; the males 

 of Pterotrachea also possess a sucker on the foot. In Atlanta and 

 Carinaria the sucker is present in both sexes. The testes and 

 ovaries fill the posterior part of the visceral sac and are partially 

 imbedded in the liver. The ducts, viz., vas deferens and oviduct, 

 open on the right side of the body ; the former at some distance from 

 the organ of copulation, to which the sperm is conducted from the 

 sexual opening in a ciliated furrow. The copulatory organ consists 



VOL. IT. 4 



