Eyes of Molluscs and Arthropods. 747 



nuclei belonging to tlio iTtiuopIionie. At d, the hirge, circnlarly arranged 

 peripheral cells of the ganglionic layer, togcther with the circiilar fibre» 

 of the septum. 



Fig. 33. Two isolated cclls from the outer ganglionic layer. The end of one is 

 drawM out into niany nerve fibres er. which formed a part of the fibrous 

 layer of the retina; x is a ganglionic cell with two fibrous prolongations, 

 u, extending towards the rods ; the end, h, was connected with the gang- 

 lionic nerve brauch ; it gives off two lateral branches which divide into 

 minute fibrillae spread out over, and attaclied to, the wall of the neigh- 

 boring cell; n.f. is a single nerve fibre, extending from the ganglionic 

 nerve brauch to the rods. 



Fig. 34. An cntire retinophora, from the median part of the retina ofP. Jacobaeus, 

 with its two nuclei, a and h, and axial nerve fibres, ax.f. 



Fig. 3.5. A short and thin retinophora, from the periphery of the retina of P. Juco- 

 haeus- 



Fig. 36. Two retinophorac, with nerve fibres from the ganglionic layer, y. One of 

 the nerve fibres n.f. terminates on the wall of a largo retinophora in se- 

 veral fine branches surrounded by a circular one; b, is the secondnucleus 

 of avery slender retinophora from the median part of the retina. (Macerat- 

 ed in weak sulphuric acid.) 



Fig. 37. A detached flake of corneal cells seen from their inner ends, showing the 

 serrated walls, and the circular fibres undcrlying the cornea. T.Jucobaeuf!. 



Fig. 38. Section through the peripheral portion of the retina of F. Jacobaeus, show- 

 ing the continuation of the outer ganglionic layer , beneath the outer 

 edgc of the nucleated septum with its circular fibres, to the very edge of 

 the retina; one sees the continuation of the retinophorae with the fibres 

 of the axial nerve branch; the membrana circularis, cm., the ganglionic 

 cells «/./.' and r/./.2 with their fibrous Prolongation towards the rods, and 

 the rete vitrosum r.v. ; one also sees thc double layered sclerotica, con- 

 tinuous with the septum; and the tapetum and double argentea, con- 

 tinuous with the retina. (Through carelcssness, the two layers of the 

 sclerotica have been reversed ; see PI. 30, fig. 39.) 



external nerve fibres. 



invaginate eye. 



faceted eye. 



ganglionic cell. 



lens. 



nerve fibres. 



nucleus of retinophora. 



nucleolated nucleus of the retino- 

 phorae. 

 n.rf.- aborted nucleus of the retino- 

 phorae. 



Ophthalmie fold. 



ommatidium. 



ommateum. 



optic nerve. 



