502 



iSGIENCE. 



[N. S. Vol. XI. No. 274. 



1. Part of the section of tbe head of Chologasler 

 papilliferus at the optic nerve ; sabo. -suborbital. 



2. Part of the section of the head of Ukologasier 

 agassizii. 



3. Part of the section of the head of an Amblyopsis 

 showing the location of the eye ; subo. -suborbital, 

 scl., scleral-cartilage. 



4. Part of the section of the head of Troglicldhys 



passing through the eye ; al. ep., alimentary epithe- 

 lium. 



5. The most degenerate vertebrate eye known, that 

 of TroglicMhys in vertical section. 1, pigment layer of 

 the retina ; 3-7, retina from the pigmented layer to the 

 inner reticular layer; 8, inner reticular layer; 9, gang- 

 lionic layer; n. op., optic nerve; nl. 1., nuclei of the hy- 

 aloid; chr. choroid pigment; scl. c, scleral cartilages. 



