24 ALBERT M. REESE. 



way, to form the iris. It is more or less closely filled with the 

 irregular, black pigment cells that were mentioned in connection 

 with the sclerotic. These cells are seen along the tract of the 

 optic nerve as it passes through the cartilaginous sclerotic. No 

 distinction of layers can be made out in the choroid, nor can a 

 true ciliary process be determined, though a thickening and fold- 

 ing in the region ordinarily occupied by that structure might be 

 interpreted as a ciliary process ; no connection of this thicken- 

 ing with the lens can be determined, however, and the appear- 

 ance of a ciliary process seems to be largely caused by a curious 

 folding of the retina, to be presently described. The reference 

 line CJi ends in the thickening just described. In that portion 

 of the choroid that extends in front of the lens to form the iris 

 (/) the pigment cells increase to such an extent that the iris is 

 almost or quite black, though this dark color is not so evident in 

 the living eye. 



The pupil (P) is, as has been said, small and irregular in out- 

 line. The retina, though not particularly well fixed in the ma- 

 terial studied, shows at least six layers, which may be given the 

 names usually applied to the corresponding structures in other 

 eyes. The outermost (Pg) is the pigmented layer ; it is com- 

 paratively thin, but shows an inner pigmented and an outer 

 nuclear portion. Close to the inner surface of the pigmented 

 layer, though often torn from it, is the layer of rods and cones 

 (K) ; it has been called the layer of rods and cones, though, ow- 

 ing to imperfect fixation, the two structures are indistinguishable. 

 Next to the layer of rods and cones lies a deeply-staining layer 

 (A 7 ") that, in favorable sections, shows an indistinct division into 

 an outer and an inner zone, which might be called the outer and 

 inner nuclear layers, respectively. The two nuclear layers are 

 composed of similar round, granular elements. Inside of the 

 inner nuclear layer is a finely- granular, nonstaining layer which 

 probably corresponds to the inner molecular layer (Mo*). The 

 outer molecular layer is not distinguishable in the material at 

 hand. The innermost layer of the retina (), which seems to cor- 

 respond to the ganglion-cell layer, is composed of a single row of 

 large, rounded or oval elements that stain deeply like the ele- 

 ments of the two nuclear layers. No layer of nerve fibers can 



