GASTROPODA. 



35 



serving for the tactile sensation. The antenna? of the terrestrial 

 Gastropods possess on their end-plates a great number of fine sense- 

 cells (club-shaped cells with rods, Flernnring), which are placed between 

 specially-modified epithelial cells, and probably function as olfactory 

 organs. Recently an organ, which was supposed to be a rudi- 

 mentary gill and is innervated from the supraintestinal ganglion, 



*P 



\Ir 



n 



FIG. 511. Anatomy of Helix pomatia (after Cuvier). The mantle cavity is opened on the 

 left side, and the mantle is turned over to the right. The body cavity has been opened 

 and the viscera are unravelled. Cg, cerebral ganglion ; Sp, salivary gland ; .!/, stomach; 

 D, intestine ; L, liver ; A, anus ; N, kidney ; At, auricle ; C, ventricle ; PI, lung ; Zd, 

 hermaphrodite gland, invested by the lobes of the liver ; Ed, albumen gland ; P*-, 

 prostate ; Ut, uterus ; Us, receptaculum seminis ; Dr, finger-shaped glands ; Ps, dart 

 sac; P, penis ; Fl, flagellum; Mr, retractor muscle; Sp, spindle muscle. 



has been recognised as a sense organ and explained as an olfactory * 

 organ. 



In the Zeugobranchiata (Fissurella, Hatiotis), two such organs are 

 present, one on the right and the other 011 the left side, and are 

 indicated by a considerable ganglion. 



The digestive organs rarely have a straight course ; they are 



* J. \V. Spengrel, " Die Geruchsorgane und das Nervensystem der ilollusken." 

 Zeit. fur. miss. Zool., Torn. XXXV. 



