452 MR FRANK E. BEDDARD ON THE EYE IN CYMOTHOID^. 



hyaline cells do not end in a nervous filament, unless the axial cuticular rod, 

 which is hollow, encloses a nerve fibre. The specialisation of the retinula into 

 clear and pigmented cells recalls the eye of certain Annelids and Molluscs. 

 The eye is " diplostichous,'' the upper row of cells forming the vitrella, and the 

 lower row the retinula. To this extent, therefore, my results harmonise with 

 those of Grenacher rather than those of Patten. 



EXPLANATION OF PLATE XXX. 



Lettering. — v. Vitrella. 

 ret. Retinula. 

 r. Rhabdoni. 



/. Filiform extremity of the rhabdoni. 

 It. Hyaline cells. 

 n. Nuclei of the same. 



N.B. Cuticular structures, i.e., corneal lens, vitreous body, rhabdoni, are 

 coloured yellow. 



Fig. 1. Isolated ommatidium of Serolis schythei. 



Fig. 2. Hyaline cells and adjacent structures of the same more highly magnified. 



Fig. 3. Hyaline cells and rhabdom of S. comuta. 



Fig. 4. Transverse section through ommatidium of Cirolana at different levels. 



Fig. 5. A single ommatidium of same species. A, nucleus of hyaline cell highly magnified. 



Fig. 6. An isolated rhabdomere of same. 



Fig. 7. Transverse section through retinula of same. 



Figs. 8, 9. Isolated retinula of same ; all the pigmented retinula cells are not shown. 



Fig. 10. Nucleus of hyaline cell. 



Fig. 11. Two nerve rods, continuous anteriorly with pigmented retinula cells, showing their transverse 



striation. 

 Fig. 1 2. Transverse section of retinula of yEga, sp. 



Fig. 13. Transverse section of prolongations of retinula cells below ommateal membrane. 

 Fig. 1 i. Isolated retinula of same. 



Fig. 15. Transverse section of retinula of same at its upper extremity. 

 Pig. 16. Isolated retinula cell of same. 



Figs. 17, 18. Transverse section through retinula of young Serolis schytliei. 

 Fig. 19. Isolated ommatidia of same. 

 Fig. 20. Retinula cell of S. comuta, showing two nuclei. 



