Smith. — Eyes of Pulmonate Gasteropoda. 



PLATE 3. 



Figures 22, 24, 26, 27, 29,33, and 34 are methylen-blue preparations of Helix pomatia. 



Fig. 21. Cross section of several rods. 



Fig. 22. Cross section of the optic nerve. 



Fig. 23. Cross section of three sensory cells at the distal limit of the pigment 



zone. 

 Fig. 24. Sensory cell with radicula and neurite. 

 Fig. 25. Methylen-blue preparation. One large cell in the accessory retina is 



sectioned and there are several pieces of neurites. 

 Fig. 26. Two sensory cells — the distal ends enveloped in pigment — and portion 



of optic capsule. 

 Fig. 27. One sensory cell, portions of others and of optic capsule. 

 Fig. 28. Methylen-blue preparation of a sensory cell of the accessory retina. 

 Fig. 29. Sensory cell with radicula and neurite. 

 Fig. 30. Methylen-blue preparation from the chief retina. 

 Fig. 31. Poorly stained methylen-blue preparation of rod from chief retina. The 



mantle has separated from the axis or core. 

 Fig. 32. Methylen-blue preparation, showing three sensory cells and the pale 



nucleus (?;/'.) of one pigment cell. 

 Fig. 33. One sensory cell and nucleus in its relation to the optic capsule. 

 Fig. 34. End view of a sensory cell cut cross-wise through the nucleus. 

 Fig. 35. Longitudinal section of the optic nerve where three strands of neurites 



pass out (downward in the Figure) from the retina through the capsule 



of the eye. Methylen-blue preparation. 

 Fig. 36. Basal view of a sensory cell from the accessory retina, showing one 



neurite and five radiculae. Methylen blue. 



