33 



PLATE XVII. 



THE EDIBLE SNAIL. 



External Chahactees — 



Fig. 1. The Snail protruded from its shell — 



„ V ■ f Pair of tentacles or eye-stalks with eyes. 



Head bearing < ^ . , , . / •' 



I rair of tentacles without eyes. 



Foot flattened out ventrally, hence the name Gastcropod (Gr. gaster, the belly ; j)ous, n. foot), 



Shell univalve and spiral. 



Fig. 2. Shell — 



Body-whorl, the last and largest whorl with the mouth. 



Spire, the rest of the whorls. 



Five brown bands running in the direction of the spire. 



Lines of growth running in a longitudinal direction from apex (shown in fig. 1 ). 



G KNERAL StRUCTDTIE OF BODY — 



Flu. 3. Section of Body, shell and viscera removed- 

 Parts of body — foot, mantle, visceral sac, pulmonary chamlicr. 



T, /-, f Roof with homy iaw. 



Buccal Cavity < _,, . -, , , ,r, -, , , , t , v 



( iloor with odontophore (Gr. oc/mia, oc/otifos, a tooth; jmoreo, I bear). 



CEsophagus. 



Piectum seen in section. 



Nervous ganglia seen in section above and below gullet. 



Columellar muscle attaching body to shell. 



FiG. 4. Common Snail with shell removed and covering of pulmonar)' chamber turned back — 



Heart consisting of auricle and ventricle. 



Blood-vessels raniifjdng in wall of pulmonary chamber. 



Renal organ or kidney for getting rid of nitrogenous waste. 



Pulmonary aperture leading into the modified mantle-cavity or pulmonary chamber, with aiiu« 



beside it. 



AUMENTAKY SYSTEM— 



Fio. 5 a. Buccal Mass removed from body — 



Protractor and retractor muscles. 



CEsophagus and duct of salivary gland leading from it. 

 Fig. 5 b, and Diag. 1. Odon'tophoee in Section — 



Skeleton formed of cartilage (blue). 



Sub-radular membrane with its muscles (yellow). 



Radula (L. a scraper), the surface of sub-radular membrane beset with cuticular leeth (red). 

 Fig. C— 



a. Horny upper jaw detached. 



h. Teeth of radula arranged in transverse rows. 

 Fig. 7. Dissection feom Doesal Sueface, with organs gently separated and laid out — 



! Buccal mass. 

 Gullet dilating into crop. 

 Salivary gland embracing crop. 

 ) Stomach, with a pyloric CKCum near liver. 

 ( Liver, with coiled intestine embedded in it. 



CiECULATOEY System . / Y^nt^^l^ (^uncls not shown). 



I Aorta. 

 Respieatory System . Pulmonary chamber, with blood-vessels on wall. 

 Renal Organ . . . Nephridium (Gr. nq,/n-oi, kidneys) or kidney for getting rid of 



nitrogenous waste. 



E 



