THE EYES OF MOLLUSCS 



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Fig. 107. — Section through one of the Eyes on the Outer Margin of the 

 Pallium of a Scallop (Pecten). (After Patten.) 



The optic nerve divides into two branches, one of these passes to the inner, or 

 posterior, pole of the eyeball, where it divides into fibres which spread out 

 on the inner surface of the optic plate, and radiating in all directions pass 

 to the peripheral margin of the plate. Here they turn round its edge and 

 form a nerve-fibre layer containing ganglion cells, in front of the retinal 

 cells, which they enter on their superficial surface. The other branch 

 passes directly to the edge of the plate, having reached the margin it bends 

 round this and breaks up into branches which form a superficial nerve-fibre 

 layer containing ganglion cells in front of the retinal cells. 



bl. s. : blood sinus. 

 c. : cornea. 

 ep. : epithelium. 

 g.c. : ganglion cells. 

 /. : lens of cellular type. 

 n. 1 , n.- : branches and nerve fibres of 

 optic nerve. 



op. n. : optic nerve. 



pig. I. : pigment layer. 



ret. : retinulas. 



rh. : rhabdomes. 



scl. sclera. 



tap. : tapetum. 



