336 MOLLUSCS. 



DIAGRAM XVII. 

 Cephalopoda. 



The figure Sepia (from Vogt and Yung) shows the posterior aspect of 

 the body, the funnel (/), the entrance to the mantle-cavity (?«. c). 



The diagrammatic section {Sect.) beneath shows the flexure of the 

 gut, the ganglia {ga. ) around the gullet, the stomach {st. ), the dorsal and 

 posterior reproductive organs {rep.), the ink-bag (;. b.), the gills (g.), the 

 mantle-cavity (ni. c). 



The section of the eye (from Gegenbaur, after Hensen) shows the two 

 layers of the retina {re.), the lens (/.), the ciliary process {ci.), the iris- 

 cartilage {i. c), the silvery membrane {arg.), the cornea {c.), the white 

 body {w. ), the optic ganglion {o. g.), the optic nerve {o. n. ), the cartilage 

 of the optic capsule {c. and k. ), the cephalic cartilages {c. c. ). 



Diagram Circ. (after Nuhn) suggests the course of the blood ; — A. the 

 auricles, V. the ventricle, ao. the aorta, then the distribution in the 

 body and collection in veins {v. ), then the passage through the kidney 

 {k.), and through the gills {br.) to the auricles again. 



The series of hearts (after Gegenbaur) shows the specialisation of 

 auricles. A shows the dorsal vessel and entrant transverse vessels in a 

 worm, B the ventricle and so-called auricles of Nautilus, C the heart 

 of a bivalve or of Loligo, D of Octopus, E of the Snail. 



