No. 3.] VISUAE / GELES~ INV VERTED RA TES: 607 
Schultze found no peripheral fibrils except those of the 
“fiber-basket,”” which he described as running over the inner 
end only of the rod and belonging to the system of retinal 
sustentative cells, ““Muller’s fibers.” I have not identified any 
such structure on the rods of Necturus, though some might 
claim that the peripheral ‘stained fibrils,” as I have termed 
them, are identical with the fibers of Schultze’s “‘fiber-basket.”’ 
The reasons against this view I will take up more in detail 
later, and I will merely add here that the intimate structural 
‘ 
connection of the “stained fibrils” with the outer segment and 
the fact of their extension over the whole length of the seg- 
ment argue against this opinion. 
The large single peripheral fibril figured by Kolmer (:04) 
in the frog, can hardly be identified with any structure that 
I have described, unless in Kolmer’s preparations only a single 
fibril was impregnated. Impregnation methods lke Golgi’s 
and Bielschowsky’s, which Kolmer used, act selectively, as 
all know who have worked with them. If there ts selection 
here in a single element, the fact would have considerable 
interest. ‘That only a single fibril might be present, as Retzius 
(:05) described for the dogfish, is conceivable, in which case 
this would be a simpler condition than exists 1n amphibians 
and teleosts; but he figures some single rods, in which 
two fibrils have been impregnated. This, it seems to me, 
favors my contention that there may be selection of a single 
fibril, or at least of a smaller number, in certain elements. The 
same comment would apply to the fibrils described by Held 
(:04). The “diplosomes’’ mentioned by these authors imply 
a connection between fibrils and a couple of spherules in the 
region of the ellipsoid. I have seen nothing of such relations 
myself, but Iam not prepared to deny their existence. 
So far, then, as I have been able to demonstrate, the 
cylindrical outer segments possess peripheral fibrils run- 
ning lengthwise and each fibril is raised slightly above the 
surface of the cylinder. 
Another character of the outer segments which has been 
described is the transverse striation. This is demonstrated in 
