THE SNAIL. 59 



PLATE XIV. 



THE SNAIL. THE NERVOUS SYSTEM AND SENSE OIIGANS. THE REPRODUCTIVE ORGANS 



AND THE GASTEBOPOD LARVA. 



FIG. I. Dissection to show the leading ganglia and nerves, from the right side. 



The lung-sac was opened up, cutting along the edge of the rectum, the rectum itself 

 being next severed and reflected, as drawn. The hody-wall was then removed on the right 

 side from the head to the albumen gland, and along with it the tentacles, a good portion 

 of the foot and the greater part of the genital apparatus, x 2. 



PIG. II. Dissection from above, to show some of the important nerves, and incidentally 

 the tentacular and other retractor muscles. 



The pulmonary sac and body cavity were opened up from above by a clean cut, 

 passing to the right side of the excretory organ, and the two halves were reflected. 



The tentacles of the left side were cut open. The crop, retractor muscle of the buccal 

 mass, and the genital apparatus, were all for the most part removed, their cut ends being 

 drawn, x 2. 



In both the above figures the whole nervous system is drawn in deep black. The 

 sheath of the nerve-collar, having been for the most part removed, is not indicated. 



FIG. III. The circumcesophageal nerve-collar, after removal from the body, seen from 

 behind, x 3. 



The dotted lines indicate the limits of its sheath. 



The so-called parieto-splanclmic ganglia, ^.,9., represent those known as visceral, 

 pleural, and abdominal, in allied forms. Spengel (81) has recently instituted an elaborate 

 inquiry into the whole question of their morphology. 



FIG. IV. An enlarged view of the tentacles of Fig. II., to show their nerves, 

 ganglia, and the visual organ, in situ.f x 6. 



FIG. V. The otocyst, seen in situ. D. 3. 



FIG. VI. The generative apparatus, after removal from the body. 



The vestibule, cl., and adjacent parts have been opened up, at * is exposed the fold 

 which incompletely subdivides the lower part of the hermaphrodite duct. x 2. 



The ovotestis is best got at by removing it together with the right lobe of the liver, 

 and then dissecting it out carefully. (Compare Figs. V. and XV., Plate XIII.) 



t The condition of the nervous structures lodged within the optic tentacle clearly points to the conclusion that it 

 performs a double function. See W. Flemming, " Untersuchungen uber Sinnerepithelien der Mollusken," Archr. Mk. 

 Anat., vol. vi., 187''. 



