72 



aiid the nuchal roof removed. M.T. = PalHal 

 tentacle. Os. = Osphradium. x Ij. 



Fig. 5. Tlie animal seen from the left anterior point of view 

 (diagrammatic and based upon published figures). 

 The niTchal roof has been removed. x 2^. 



Fig. 6, Diagrammatic sagittal section — most of the blood 

 sinuses, also the kidneys and nerves are omitted 

 for the sake of clearness. ]l.C. = Buccal cavity. 

 D.P. = Dorsal palatal plate. I.L. = Inner lip 

 (not in median section). O.L. = Outer lip. 

 N.R. = Nuchal roof. Ocs.r. = Tissue of oeso- 

 phageal pouch. Pap. = Ridged papilla. S.L.P. 

 = Sublingual pouch, x 2^. 



Fig. 7. A small portion of the ventral surface of the mantle 

 showing the circulatory arrangements. VI. = 

 Veinlet from mantle edge. (i.V. = Yeinlet from 

 pallial gill, x 10. 



Plate IF. 



Fig. Sa. Diagrammatic transverse section of a very young 

 specimen to show the lateral streak, the arrange- 

 ment of fibres in the foot, the relations of the 

 kidney cavity, tlie structure of the mantle skirf, 

 X 35. D.Pal.dl. = Dorsal pallial gland-tissue. 

 Ep.F. = Epithelial fold. Fl. = Flap of Lateral 

 (" Epipodial ") streak. GL = Gland tubules of 

 Lateral (" Epipodial '') sti'eak. Lett. St. = Lateral 

 ("Epipodial") streak. /'r(/.Cr/. = Palhal gland- 

 tissue. Pai.M. = Pallial muscle. Pal.N. = Nerve 

 in mantle tissue. Pcd.S. = Pedal sinus. Stib- 

 Ep.N.L. = Sub-epithelial nervous plexus. S.Z. = 

 Sensory zone of mantle epithelium. Vac.E. = 

 Vacuolated epithelium beneath the lateral streak. 



Fig. 8h. Epithelium of one of the folds of a pallial tentacle in 

 cross-section (after Haller). Higlily magnified. 



