112 MICROSCOPICAL STUDIES. 



optic nerve. In Fig. VII. the epidermis is sinking 

 downwards to meet this hollow outgrowth, while in 

 VIII. it has become pinched off and forms now the 

 basis of the future crystalline lens. e. epidermis. 



(Figs. II. to VIII. are after Carriere, "Die Sehorgane der Thiere," 

 Miinchen and Leipsig, 1885). 



Fig. IX. Diagram of the structure of the eye in Nautilus ; on. 

 branches of the optic nerve ; r. retina. 



Fig. X. Diagrammatic representation of the eye structure in Cepha- 

 lopods, to show the arrangement of the retinal elements 

 in relation to the optic nerves. (After Graber). 



Fig. XI. A similar representation of the retinal arrangement, &c.. 

 of the Vertebrate eye. (After Graber). 



September 10th, 1896. 



