Eyes of Molluscs and Arthropods. 



745 



ag. 



cells are separating themselves tu form ganglionic cells, g.c. The young 

 e5'e lies in a pigmented furrow at the base of the fold. Cam. H. obj. 7, 

 oc. IV. 



Fig. 17. Section through a nearly perfected eye of P. oj)crcu!aris. All the parts, 

 except the rete vitrosum, are formed; the scattered nerve fibres , which 

 had not united to form an optic nerve, are not represented ; at i/ are the 

 small dark bodies found in the fibrous layer at this period, and which 

 ,later' disappear. 



Fig. IS. Section through the Ophthalmie fold of a very young P./^«sto, 1 mm long, 

 showing the double-lobed fold, o.f., and the slight thickening, x, of the 

 hypodermis to form the first rudiment of the eye ; a ganglionic cell, g.c. 

 is already separating itself from the hypodermis. 



Piate 29. 



The Anatomy of the Eye of Pecten Jacobaeus and Pecten varius. 



l.h. lateral brauch of the optic nerve. 

 m.h. terminal membrane of the retino- 

 phorae 



median teeth of the corneal cells. 



nerve fibres. 

 H.;/. 'nuclei of the rod-beariug retino- 



phorae. 

 rt.?/.' nuclei of the short, pseudo-retin- 

 ophorae. 



optic nerve. 



pseudo-cornea. 



pseudo-retinophorae. 



septum. 



retinophorae. 



pseudo-retinophorae. 



radiating nerve fibrillae of the 

 rods. 



rods. 



rete vitrosum. 



sclerotica. 



outer layer of ganglionic cells. 



suspensory ligament of the lens. 



tapetum. 



ag^. 



ag^. 



ax.f. 



b.c. 



h.h. 



b.s. 



c. 



c.f.l. 



cl. 



argentea. 



» outer layer. 

 » inner » 



axial nerve fibre. 



blood corpuscles. 



basal brauch of optic nerve. 



blood sinus. 



cornea. 



circular fibres of the lens. 



ciliaris. 

 cm. circular membrane of the retina. 

 c.n.f. circular nerve fibres of the rods. 

 c.t.c. connective tissue capsule of the 



eye. 

 cu. cuticula. 



d.c.c. inner row of ganglionic cells. 

 ex.f. external nerve fibres of the rods. 

 f.rf. fibrous prolongatious of the reti- 

 nophorae. 

 g.c. ganglionic cells. 

 i. iris. 



i.t. inner teeth of the corneal cells. 

 l.ax.fK loop of the axial nerve. 

 ^.a.c./.'- nerve loop connecting two axial 

 neiTes. 



tn.t. 

 >'■/■ 



op.n. 



ps.c. 



ps.rf. 



S. 



rf. 



rf.' 



r.ß. 



rh. 

 r.v. 

 sc. 



S.C.C. 



s.l. 

 tu. 



Fig. 19. 

 Fig. 20. 



Section of a fully developed eye ofP. Jacobaeus, perpendicular to the 

 edge of the mantle. 



A constructed drawing of two rods , from the retina of P. Jacobaeus , to- 

 gether with the distal ends of the retinophorae, showing the two inner 

 ganglionic cells, d.c.c, and their fibrous prolongatious, ex./., to form the 

 external nerve fibres of the rods; ax.f. is the axial nerve fibre of the 

 retinophorae, giving rise, in the rods , to many cross fibrillae. Many of 

 the fibrillae unite to form, in the rod, circular fibrillae around the core; 

 from the circular fibrillae arise other minute fibres, continued outwards to 



