92 Trans. Acad. Sci. of St. Louis. | 
have found it in cross sections only—near where the 
optic dise 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. 
Kigenmann 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 ean see, it is perfectly spherical, although 
Puetter (Graefe-Saemisch. 2':192. [2nd ed.]) says: 
‘‘The lens of amphibia is not really spherical, as this 
