Alt — Histology of the Eye of Typhlotriton Spelaeus. 89 



which I can 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 Eigenmann 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 Eigen- 

 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 lies 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- 

 lionic cells. The ganglionic cell layer, according to 

 Eigenmann, 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- 



