PLATE XVII. 



THE EDIBLE SNAIL. 



EXTERNAL CHARACTERS 



FIG. 1. THE SNAIL protruded from its shell 



HEAD b ' I ^ a * r ^ tentacles or eye-stalks with eyes. 



I Pair of tentacles without eyes. 



Foot flattened out ventrally, hence the name Gasteropod (Gr. gaster, the belly ; pous, a 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). 

 GENERAL STRUCTURE OF BODY 



FIG. 3. SECTION OF BODY, shell and viscera removed 



Parts of body foot, mantle, visceral sac, pulmonary chamber. 



BUCCAL CAVITY I Roof with horny J aw- 



I Floor with odontophore (Gr. odous, odontos, a tooth ; phoree, I bear). 



(Esophagus. 



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 pulmonary chamber turned back 



Heart consisting of auricle and ventricle. 



Blood-vessels ramifying 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 anu 



beside it. 

 ALIMENTARY SYSTEM 



FIG. 5 a. BUCCAL MASS removed from body 



Protractor and retractor muscles. 



(Esophagus and duct of salivary gland leading from it. 

 FIG. 5 b, and DIAG. 1. ODON'TOPHORE 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 teeth (red). 

 FIG. C 



a. Horny upper jaw detached. 



b. Teeth of radula arranged in transverse rows. 



FIG. 7. DISSECTION FROM DORSAL SURFACE, with organs gently separated and laid out 



iBuccal mass. 

 Gullet dilating into crop. 

 Salivary gland embracing crop. 

 ) Stomach, with a pyloric caecum near liver. 

 [ Liver, with coiled intestine embedded in it. 



CIRCULATORY SYSTEM / y entricle ( 1 * not shown). 

 ( Aorta. 



RESPIRATORY SYSTEM . Pulmonary chamber, with blood-vessels on wall. 

 RENAL ORGAN . . . Nephridium (Gr. nephroi, kidneys) or kidney for getting ri4 of 



nitrogenous waste. 



