Alt—Histology oj the Eye of Typhlotriton Spelaeus. 89 
which I ean find no trace of any muscular fibers. It is, 
also, impossible to demonstrate any muscular tissue in 
the iris. 
The cells of the pigment epithelium are comparatively 
well preserved in a good many of my sections, although 
their continuity is frequently interrupted. They are 
large flat cuboid cells, the protoplasma of which is filled 
with fuscin needles. Their nucleus is quite large. In 
most sections they adhere to the outer surface of the 
retina, which must be distinctly stated as it is of impor- 
tance for the understanding of the outer structures of 
the retina. 
According to Kigenmann there is a very marked differ- 
ence between the retina in the larval state and that in the 
adult. : 
My specimens show no such marked difference, in fact 
they appear very much the same in both states. It may, 
of course, be possible that at an earlier age than that 
which my larval specimens had attained, the retina of 
the larva is really as nearly perfectly developed as Higen- 
mann states. 
In all the sections next to the crystalline lens the retina 
is really the most conspicuous part of the eye. Even 
where it is well preserved and hes approximately in its 
normal position its great thickness is obvious. When 
viewed from within outward under a higher power the 
first striking fact is an absence of a plainly visible nerve 
fibre layer. Eigenmann does not mention this layer at 
all. I have not been able to see any nerve fibres no mat- 
ter what stain I used. Possibly they had become dis- 
integrated. Surely their absence would seem particu- 
larly strange with such a well developed layer of gang- 
honie cells. The ganglionic cell layer, according to 
Kigenmann, is composed of five or six rows of cells in 
the larva, and of two to five rows of cells in the adult. 
The thickness of this, as of all the layers of the retina 
depends, of course, on the part of the retina from which 
the section is taken and on the plane in which the sec- 
