DIGESTIVE SYSTEM. 121 



The dissection is greatly facilitated by freqiicnt washing 

 under the tap. 



A. The Alimentary Canal. 



The alimentary canal is a convoluted tube, of nearly uni- 

 form size along the greater part of its length, but presenting 

 special features in its anterior portion. 



1. The buccal mass or pharynx is the enlarged anterior end 



of the canal, into which the mouth opens. It forms 

 a prominent rounded mass in the head, with stout 

 muscular walls, and will be more fully examined 

 at a later stage of the dissection (p. 128). It 

 contains the odontophore. 



Insert a seeker into the mouth, and note that it passes 

 upivards and backwards into the buccal mass. 



2. The oesophagus is a narrow thin-walled tube, which 



arises from the dorsal surface of the buccal mass 

 and runs backwards, passing into the crop. 



8. The crop is a large fusiform thin-walled dilatation of 

 the alimentary canal, lying partly in front of the 

 visceral hump, partly in the first turn of the spire. 

 It is widest about the middle of its length, and 

 gradually narrows behind. 



4. The ' stomacli ' is a slightly dilated loop of the alimentary 

 canal, between the crop and the intestine. It lies 

 close to the surface of the visceral hump, near the 

 commencement of the second turn of the spire, 

 and between the right and left lobes of the liver. 



Fig. 30.— Helix pomatia. Dissection from the right side to show the 

 digestive and reproductive systems, (a. m. m.) 



A, anus. AG-, albumen gland. B, buccal mass. C, sac ot radnla. CG-, 

 cerebral ganglion. J), jaw. E, mouth. F, flagellum. Gr, genital aperture. 

 H, crop. HD, hermaphrodite duct. HG-, hermaphrodite gland. I, intes- 

 tine. K, dart sac. L, mucous glands. LD, left bile-duct. LL, left lobes of 

 liver. M, female portion of the common duct. M", male portion of the common 

 duct. O, receptaculum seminis. O', dilatert end of receptaculum seminis. P, 

 penis, retracted. PG-, pedal ganglion. R, rectum. ED, right bile-duct. 

 -EL, right lobe of liver. S, 'stomach.' SD, salivary duct. SG, salivary 

 gland. T, tentacle. VD, vas deferens. VG, visoero-pleural ganglion. Y, eye. 

 Z, posterior end of foot. 



