﻿EYES or CHOLOGASTER COENUTUS. 119 



nuclear layer has been reduced one-third and more from the lowest point in papilli- 

 ferus. There is no longer any definite difference between the inner spongiose and 

 outer bipolar cells of this layer, a difference that is usually well marked and is still 

 evident in paplllifcrus. An equally marked change has unquestionably occurred 

 in the ganglionic layer where a layer of cells, continuous but for the strands of the 

 n. opticus passing between them, has dwindled to irregularly scattered cells. 



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Fig. 40. (a) Section Tangential to Ganglionic Layer, showing Distribution of Ganglionic Nuclei, 9. 

 On Left, 4-7, Row of Nuclei of Inner Nuclear Layer, 2 mm. and 4. 

 ib) Section of Retina through Old Individual (47 mm. long). Pigmented Layer left 

 Blank. All Nuclei as seen in one Focus except Vertical Miillerian Nucleus, which 

 is from Another Section. 2 mm. and 4. 

 (c) Fragment of Same Retina at Another Point. 

 {d) Cells of Lens Epithelium, Surface and Tangential, 2 ram. and 4. 

 (e) Cells and Blood Cells from Hyaloid Membrane. 



The position of the Miillerian fiber nuclei is also unique in this retina. 



The eye is in some respects more degenerate than that of Typhlichthys sub- 

 terraneus. The dioptric arrangements in this eye and the cones are better developed 

 and the layers in general are better differentiated than in T. subterraneus, 

 but the nuclear layers are in the latter species composed of more series of cells. 

 A section of the iris is much longer than in either of the other species of this genus. 

 Since the differences in the eye and retina of the species of Chologaster are largely 

 a matter of measurements, the following tables are added : 



