PLATE IX. 



Structure of the Eye. 



Fig. 1. Surface view of membrane limiting the " ommateum " loelow ; a, perforations for 

 the nerve fibres arranged in groups of four, corresponding to each retinula ; 

 n, nuclei. 



Fig. 2. Semidiagrammatic section through the eye of Serolis schythei ; c, corneal lenses ; 

 n, nuclei of Semper ; v, vitreous body ; r, retinula cells ; p, pigmentiferous 

 connective tissue corpuscles ; h, hyaline cells ; s, rhabdom. 



Fig. 3. Single element of the eye of Serolis cormita, depigmented and isolated by 

 teasing ; r, rhalidom ; r', its posterior filiform prolongation ; h, hyaline cells ; 

 n, their nuclei. 



Fig. 4. Single element of the eye of Serolis cormita to show the pigment sheath sur- 

 rounding the rhabdom (r). 



Fig. 5. Single element of the eye of Serolis schythei ; r, rhabdom ; h, hyaline cell. 



Fig. 6. One of the hyaline cells ; n, its nucleus. 



Figs. 7, 8. Transverse section through the upper part of the retinula of Serolis schythei; 

 r, rhabdom ; j:>, pigment. 



Figs. 9-15. A series of figures to show the varj-ing form of the rhabdom in Serolis 

 cormita. 



Figs. 16, 17. Transverse section through the upper part of the retinula of Serolis 

 cormita; r, rhabdom ; j^, its pigment sheath. 



Figs. 18, 19. Two isolated retinula cells oi Serolis schythei; r, rhabdomere. 



Fig. 20. Series of transverse sections through retinula of Serolis schythei; a, nervous 

 rods below membrane ; h, lower end of retinula cell just above the pigmented 

 membrane ; c, retinula cells at the level of the nucleus (n) ; d, four retinula 

 cells surrounding the hyaline cell (h) ; e, upper extremity of the retinula cells ; 

 (y), rhabdomere. 



