Smith. — Eyes of Pulmonate Gasteropods. 



PLATE 2. 



Fig. 13. Semi-diagrammatic section of a vom Rath preparation across the chief 

 axis of the eye at the level of the accessory retina. Ventral is toward 

 the bottom of the Figure. X 130. 



Fig. 14. Longitudinal section through large cells of a depigmented retina. The 

 sensory cell can be traced through the entire thickness of the retina. 



Figs. 15, 17. Methylen-blue preparations of sensory cells. 



Fig. 16. Fart of section through accessory retina, vom Rath preparation. Several 

 sensory cells cut at the level of their nuclei. Two rods are cut through. 



Fig. 18. Photomicrograph of portion of longitudinal, dorso-ventral median section 

 of tentacle, showing location of accessory retina at the right of chief 

 part of eye, i.e. ventral to it. Vom Rath preparation. X 190. 



Fig. 19. Semi-diagrammatic cross section of tentacle proximal to the eye, show- 

 ing the positions of the nerves, the bottom of the figure being ventral. 

 X 52. 



Fig. 20. Semi-diagrammatic representation of the retina of Planorbis trivohis, show- 

 ing the two classes of pigment cells. 



