EVES OF BLIND VERTEBRATES OF NORTH AMERICA. 65 



difference in the thickness of this layer in the two eyes, as it 

 measures 6 IJL in Ainphisbicna and 7 // in Anolis. 



The Inner Nuclear Layer. The inner nuclear layer is a com- 

 pact mass of somewhat irregular spherical nuclei and is 24 <>. in 

 thickness (6, Fig. 3). The corresponding layer in Anolis \s 59^. 

 Spongioblast and bipolar cells cannot be differentiated from each 

 other. All the nuclei appear to be very much alike, except the 

 nucleated enlargements of the fibers of Muller, which have no 

 definite shape and which stain very densely. However, some 

 nuclei, more especially those of the inner stratum, stain a very 

 deep black color, and show no structure whatever. Parts of cer- 

 tain other nuclei stain densely, while the rest retains its original 

 identity. Some of the nuclei have from four to six nucleoli. In 

 Anolis two other kinds of nuclei appear. A few flattened hori- 

 zontal nuclei can be seen near the middle of the layer and in the 

 inner stratum are a number of large spherical nuclei. Penetrat- 

 ing this layer are many fibers of JYIuller. Each fiber as it passes 

 through is characterized by a nucleated enlargement. 



The Inner Rcticnlar Layer.- -The inner reticular layer meas- 

 ures 20 // in thickness as against 45 p in Anolis (8, Figs. 3 and 4). 

 The method of staining brought out no definite structures. The 

 fibers of Muller pass through it as fine vertical filaments. Occa- 

 sionally there is a nucleus from the nuclear layer or from the 

 ganglionic layer which lies imbedded in the edge of this layer. 



Tlie Ganglionic Layer. - -The ganglionic layer (9, Fig. 3) con- 

 sists of a single layer of nuclei 6 u in diameter, with now and 

 then another nucleus above or below the single layer. From the 

 outer side of these nuclei fibers which run out and penetrate the 

 inner reticuiar layer, can be traced for a short distance. On 

 the opposite side are also fibers which continue as fibers of the 

 nerve fiber layer. In Anolis this layer measures 23 it. and is 

 made up of loosely connected nuclei, some of which are large 

 and spherical, others are smaller and irregular, while still others 

 stain very densely. 



T/ie Nerve Fiber Layer. The nerve fiber layer is 6 IJL in depth 

 while in Anolis it is 26 IJL. 



The Fibers of Muller. The Miillerian fibers can be traced 

 from the membrana limitans interna to the outer nuclear layer. 



