72 



and the nuchal roof removed. M.T. <= PalHal 

 tentacle. O.s. = Osphratliuni. x Ij. 



Fif^. 0. The animal seen from the left anterior point of view 

 (diagrammatic ai'd based upon published figures). 

 The nuchal roof has l)een removed, x 2|^. 



Fig. G. Diagrammatic sagittal section — most of tlie blood 

 sinuses, also the kidneys and nerves are omitted 

 for the sake of clearness. ll.C. = Buccal cavity. 

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

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

 N.B. = Nuchal roof. Oes.P, = Tissue of oeso- 

 phageal pouch. Pdj). = 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. = 

 Yeinlet from mantle edge. (t.V. = A'einlet from 

 pallial gill, x 10. 



Plate H. 



Fig. 8a. Diagrannnatic 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 civity, tlie structure of the mantle skirf, 

 X 35. D.Pal.GI. = Dorsal palhal gland-tissue. 

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

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

 Lateral (" Epipodial ") streak. Lat.St. = Lateral 

 ("Epipodial") streak. Pal. Gl. = Fullinl gland- 

 tissue. Pa'.M. — Pallial muscle. Pal.X. = Nerve 

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

 Fjp.X.L. = Sub-epithelial nervous plexus. S.Z.= 

 Sensory zone of mantle epithelium. Vac.E. = 

 Vacuolated epithelium beneath the latei'al streak. 



Fig. Hb. Epithelium of one of the folds of a pallial tentacle in 

 cross-section (after Haller). Highly magnified. 



