THE EYES OF RHINEURA FLORIDANA 539 



cells of this layer around the distal margin of the eye are free from 

 pigment. Over the anterior face of the eye this layer is usually com- 

 posed of a regular layer of cells whether these are free from pigment 

 or not (PI. XXXIII, figs, i and 3). On the posterior face the series of 

 cells is not nearly so regular. The pigmented epithelium is here in- 

 vaginated and folded upon itself in various ways. The infoldings are 

 sometimes solid masses of pigment cells, but sometimes they form 

 hollow spheres which contain a mass of concentrically arranged un- 

 pigmented material, probably of choroidal origin (PI. xxxii, fig. 6c and 

 PI. xxxiii, fig. 3). What the significance of these cysts may be I 

 cannot conjecture. Indications of similar structures were in these ne 

 eyes of Amblyopsis. 



The narrow stalk of the pear-shaped eye is usually filled with an 

 irregular jumble of pigment cells. In favorable sections it is seen that 

 these are also the result of an invagination of the pigment epithelium 

 from the pointed end of the eye (PI. xxxiii, fig. 2). The pigment 

 epithelium has not been reduced at the same rate as the rest of the 

 retina ; as a consequence it is infolded in various ways. Small pig- 

 ment cells are sometimes found in the inner layers of the retina among 

 the ganglionic cells and along the optic nerve within the eye. Pigment 

 cells were also found in the eyes of Typhlotnolge (Eigenmann, 1900, 

 figs. 2 and 6, z'). There are rarely any pigment cells over the distal 

 face of the eye. 



\a. A', nuclei. In the eyes of Typhlichthys (Eigenmann, 1899, 

 fig. 44, A', and Troglichthys^ figs. 52 and 56, «/) I described a 

 few cells with elongated tangentially placed nuclei between the pig- 

 mented epithelium and the outer nuclear layer. I was unable to account 

 for these in the eyes of the two fishes mentioned. Similar cells, 

 similarly located, are present in this eye. They are distinctly outside 

 of the outer limiting membrane (PI. xxxii, fig. 5 ; PL xxxiii, figs. 

 I, 2). I am at as great a loss to explain the origin of these nuclei 

 as I was those found in Typhlichthys. Possibly they are derived from 

 the pigment epithelium which in some of the unpigmented regions 

 (PI. xxxiii, fig. 2, x^ are more than one layer deep. If the outer 

 layer should become pigmented the inner nuclei if they remained unpig- 

 mented might give rise to these longitudinal cells. 



2. Rods and cones are not present. There is in some cases a distinct 

 space between the pigment epithelium and the outer nuclear layer. 

 This space when present is partially filled with filmy, hazy structures, 

 but nothing suggesting definitely either a rod or cone was detected 

 (PI. xxxii, fig. 5 ; PI. XXXIII, fig. i). 



