186 ANATOMY AND LIFE HISTORY OF MOLLUSCA. 



Plate vii., fig. 10. — Pair of dorsal eyes Onchidium damelii : 

 a a pigment-cells, b refractive, hyaline bodies on rods, c rods, d 

 optic nerve on the inner ends of rods, e probably pigment membrane 

 of third eye removed in making section. 



Plate viii., fig. 11. — Small double eye from dorsal eyes of 

 Onchidium damelii, a pigment coat, b rods, c optic nerve, d 

 pigment-coat with entrance of optic nerve, e passage of a branch 

 of the optic nerve into larger eye apparently connected with the 

 smaller eye, but this is probably due to the way in which the 

 section is cut. 



Plate viii., fig. 12. — Dorsal eye of Onchidium damelii highly 

 magnified, showing structure of rods, p c pigment-coat, r rods, g c 

 ganglion cell with refractive bodies, o n optic nerve, x 200 diam. 



Plate ix., fig. 13. — Dorsal eye of Onchidium damelii, showing 

 optic nerve, a optic nerve, passing through rods, b abrupt terminal 

 endings of nerve fibres on inner surface of rods, c foramina in 

 basilar membrane and pigment-cells, d cells at base of rods, e 

 basilar membrane. 



Plate ix., fig. 14. — Basilar membrane of dorsal eye Onchidium 

 damelii, a foramen for passage of nerve branches, b probably 

 foramina for vessels of circulation, x 400 diam. 



Plate x., fig. 15. — Section of an eye of embryo Octopus in egg; 

 a cornea or integument, b iris, c ciliary body, d aqueous chamber, 

 e internal rods of the retina, /pigment-layer, g external layer of 

 rods, h body of optic ganglion, i i white bodies, jj lens. 



Plate x., fig. 16. — Section of three ribs of Trigonia lamarckii, 

 Gray, a tegmentum showing pavement of eye-capsules, b stratum 

 of sheaths or tubes leading up to capsule, c strands of nerve fibre 

 between capsules and ganglion, d ganglion supplying capsules of 

 ribs, e ganglion or mass of nerve-sheaths in nacreous layer, in 

 which the nerves terminate. 



Plate xi., fig. 17. — -Nerve ganglion or mass of nervous matter 

 in nacreous layer of Trigonia lamarckii, Gray, a plate of 

 membranous tubes, b nerve ganglion in nacreous layer. 



Plate xi., fig. 18. — Trigonia margaritacea, Lam., a tegmentum 

 eye-capsules, b ganglionic mass with fibres and cells, c nerve-fibres 

 in nacreous layer. 



Plate xii., fig. 19. — Trochus (Uvanilla) tentoriiformis, a nerve 

 ganglia, two in number cut at different parts of the spire of 

 columella, b nerve-sheaths. 



Plate xiii., figs. 20, 21. — Exterior of right and left valve Trigonia 

 lamarckii. 



Plate xiii., fig. 22. — Interior of valve of Trigonia lamarckii. 



Plate xiii., fig. 23. — Interior of valve of Trigonia margaritacea. 



