A BLIND SNAKE FROM CUBA. 



269 



One young specimen, 10 cm. in length, was examined. The 

 eye as a whole, as well as the lens, is nearly spherical. The eye 

 measures in width .290 mm. and .322 mm. in depth. All parts are 

 so developed that the vitreous cavity is relatively much smaller 

 than that of the adult. The coats are thicker, the ciliary processes 

 better developed, the lens capsule thicker, and the retina at the 

 back actually measures one and two thirds the depth of the adult 

 retina. The elements of each layer are much more numerous 

 than in the adult, and they are packed much more closely to- 

 gether (Fig. 6). The ganglion nuclei are apparently arranged 

 one against the other. In the inner reticular layer occur the 

 " interpolated cells." These were not found in the sections of 

 the adult eye that were examined. The cells of the inner nuclear 

 layer are smaller and arranged in five or six rows. There is a 

 well-developed outer reticular layer similar in its make-up to the 

 inner reticular. Instead of a single row of cone nuclei with its 

 surrounding homogeneous mass, as in the adult, this layer in the 

 young consists of five or six rows of small, closely arranged cells. 

 The cones likewise are smaller and more numerous (Fig. 6). 



COMPARATIVE MEASUREMENT' OF RETINAL LAYERS IN MM. 



RELATIVE PROPORTION* OF EYE PARTS. 



