DEVELOPMENT OF THE EYE OF AMBLVOPSIS. 



153 



optic cavity, led to the mass of ganglionic cells (fig. 62 c). This condition of the 

 choroid fissure and its relation to the interior of the eye leads me at this point to say 

 a few words concerning the general structure of the eye. In the description of the 

 eye of the adult I considered that the central ganglionic mass was the result of the 

 collapsing of the eye with the disappearance of the vitreous body and cavity. I 

 was justified in this conclusion by the process of degeneration going on in the eye 

 of Typhiomolge, Typhlichthys, and Typhlogobius. Whatever may have been the 



_st.nlex. in. 



(<i) Anterior Face of Transverse Section of Left Eye of Larva 5 mm. long. Sections run obliquely 

 in such "a way that Right Eye is cut first, series beginning in front. Divergence from Spherical 

 Outline is due to Pressure of Brain on Proximal Face and Epidermis on Distal Face. 



(/>) Anterior Face of Transverse Section of Left Eye of Larva 6 mm. long. No Lens in connection 

 with this Retina. 



(c) Parasagittal Section of Eye of Larva 6 mm. long, showing Ventrally Choroid Fissure represented 

 by space between Pigmented Layers and Vitreous Cavity represented by Shallow Depression on 

 Ventral Face. Retina differentiated into Ganglionic, Inner Reticular, and Nuclear Layers. 



(d) Anterior Face of Transverse Section through Right Eye of Larva, 7.5 mm. long. 



(<0 Horizontal Section through Middle of Eye of Larva, 7 mm. long, showing Choroid Groove. 



phylogenetic process in Amblyopsis, it is evident that ontogenetically the mass of 

 cells does not arise as imagined. It appears from the embryos that the condition of 

 the adults arises more as the result of a contracting of the retinal area without a cor- 

 responding decrease in the size of the eye as a whole than as the result of the col- 

 lapsing of a vesicle followed by the coalescence of the walls brought together by the 

 collapse. Sagittal sections of the eye (fig. 62 c) show the lips of the choroid fissure 

 drawn apart with the contraction of the retina, only the dorsal two thirds of the 

 eye reaching full development. From a study of the embryos of this size the point 



