92 Trans. Acad. Sci. of St. Louis. 



have found it in cross sections only — near where the 

 optic disc should be. It seems to be venous in character. 



As I have never been able to see a nerve fibre layer in 

 the retina, I have, also, been unable to see exactly how 

 the nerve fibres pass out of the eye. In some sections 

 a line passes through the posterior pole of the retina to 

 the nerve. (See Figs. 9 and 10.) The latter simply 

 forms a process which is very darkly pigmented and 

 which beginning at the outer surface of the retina passes 

 through choroid and sclerotic and into the tissue cen- 

 trally from the eyeball in a direction toward the cranial 

 cavity and brain. I have no transverse sections which 

 allow of a better understanding very close to the eye, 

 but I have numerous transverse sections of the nerve 

 farther away centrally. Here the nerve in most speci- 

 mens is seen to be accompanied or surrounded by darkly 

 pigmented cells — in one no such pigment cells are found. 

 The optic nerve itself is small and consists of very few 

 fibres only. (See Fig. 18.) From their nuclei I can 

 only count about from 6 to 12. It appears from a num- 

 ber of sections that each optic nerve separately enters 

 the cerebral hemisphere on its side, at least in a number 

 of sections this seems to be the only explanation. In 

 these I find a strand of fibres with spindle shaped nuclei 

 going from the back of the eye towards the brain and 

 entering it through an opening in the cranial bones. The 

 only link wanting is the direct connection of this strand 

 of fibres with the retina, probably due to a curve which 

 the nerve makes just behind the eyeball. 



Eigenmann says : "In both adult and young the optic 

 nerve enters as a single strand and passes entirely 

 through the layers. A heavy mass of pigment is found 

 following the optic nerve to within a short distance of 

 the brain." 



The crystalline lens is very large and in most sections, 

 as far as I can see, it is perfectly spherical, although 

 Puetter (Graefe-Saemisch. 2 1 :192. [2nd ed.]) says: 

 "The lens of amphibia is not really spherical, as this 



