616 HOWARD. [VoL. XIX. 
two bodies, in several ways quite dissimilar, to a like function. 
Contrasting them we find in the paraboloid little affinity for 
stains, comparative stability after death, persistent clearness 
and lower index of refraction, while the ellipsoid has a strong 
chromophilic character, marked instability, rapid clouding at 
death, and a higher index of refraction. Both are more 
refractive than the surrounding media and have such geomet- 
rical forms as to exert a marked effect on the light rays which 
traverse them. 
The fibrils within the sheath of the paraboloid are probably 
what Hensen (’67) first described in the frog as the longi- 
tudinal striation of the inner segment. Schultze spoke of 
these as separate fibrils, saying that such were not demon- 
strable in the outer segment. If his observations were correct 
for internal and external fibrils in inner segments of the rods 
in man (Schultze, ’72b; p. 824, top), then it would seem 
probable that the fibrils I have described as surrounding the 
paraboloid of Necturus would be the homologues of the inter- 
nal fibrils. 
The enveloping membrane reported by Merkel (’70) and 
Landolt (’71), I have not been able to find in Necturus; 
1. e., there seems to be no conspicuous membrane distinct from 
the substance of the inner segment in which the longitudinal 
fibrils are embedded. 
Observations upon the farther course of the stained fibrils 
over the proximal part of the visual cell are not numerous. 
Schneider ( :02) describes these fibrils as passing over the 
nucleus. Hesse (:04) gives figures for the cones of Thalas- 
sochelys in which he shows spiral fibers proximal to the 
nuclei. I believe Bernard (:01) would have difficulty in 
upholding his contention that neurofibrils enter the nucleus. 
The fibrils which Schultze describes as forming the “fiber 
basket” (also Landolt, ’71) surrounding the rods in the 
human retina, can hardly be identified with those I have 
described. The latter converge proximally in the rod foot (PI. 
2, Fig. 8) after leaving the nucleus. From the concentration in ~ 
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