74 



crop folds. Soc.F.Cr. = Eadial secondary folds 



on the transverse crop folds, x 15. 

 Fig. 19. The bend of the stomach (Fin fig. 10a) showing the 



opening of the dnct of the hepato-pancreas 



{D.II.P.). St.Gr. = Groove in stomach wall. 



V.St. = Valve hindering back flow of the secretion 



of the hepato-pancreas. x 3. 

 Fig. 20. Transverse section of ridges and groove in stomach 



wall of a young specimen (after Haller). Highly 



magnified. 



Plate III. 



Fig. 21. Transverse section across the rectal papilla, x 20. 



Fig. 22a — f. A series of transverse sections of gullet and crop 

 (the posterior faces of the sections are drawn) 

 showing the migration of the points of attach- 

 ment of the longitudinal folds {D.F.G. and 

 V.F.G.) through an angular distance of over 270°. 

 D.F.G. = Dorsalfold of gullet. V.F.G. = Ventral 

 fold of gullet. X 10. 



Fig. 23. Nervous system of Patella vitlgata ; — Biic. = Buccal 

 commissure. Buc.G. = Buccal ganglion. Ccr.= 

 Cerebral ganglion. Cer.C. = Cerebral commis- 

 sure. C.-Pccl. — Cerebro-pedal connective. C.-PI. 

 = Cerebro-pleural connective. Lab. = Labial 

 commissure. L. Osph. G. = Left osphradial 

 ganglion. Op.N. = Optic nerve. Ot.N. = Otocyst 

 nerve. Ot. = Otocyst. Peel. = Pedal nerve-cord. 

 PI = Pleural ganglion. P/.-PerZ. = Pleuro-pedal 

 connective. Peel. Anas. = Pedal anastomoses. 

 There are two such anastomoses. Pi.Ospk.G. = 

 Eight osphradial ganglion. Subces.C. = Sub- 

 cesophageal connective of the visceral loop. 

 Supint. — Supra-intestinal ganglion of the 

 visceral loop. T.N. = Tentacular nerve. V. = 

 Visceral loop. V.G. = Visceral ganglion. x 2. 



