Basic Structure of \ ertebrates 



Fig. 173. Sections of successive stages in the development of the lens of the eye 

 from the first thickening of the ectoderm (ec) to the complete separation of the 

 lens (/). (Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Phila- 

 delphia, The Blakiston Company.) 



WITREOUS BOW 



Fig. 174. Diagram illustrating the growth of optic nerve-fibers from the retina 

 along the optic stalk into the brain. Some of the fibers cross below the brain to 

 form the optic chiasma, while the remaining pass into the thalamus of the same 

 side. (Courtesy, Neal and Rand: "Chordate Anatomy," Philadelphia, The Blakis- 

 ton Company.) 



FOVEA CENTRALIS 



Fig. 175. Diagram of a median section of the eye. (After Sobotta. Courtesy 

 Neal and Rand: "Chordate Anatomy," Philadelphia, The Blakiston Company.) 



