4.02 CG. O. WHITMAN. 
which appears to me to reconcile Leydig’s fig. 2! (pl. i) 
with an actual longitudinal section of the eye. 
Ranke’s fig. 82 (pl. x.) presented one feature that should 
be noticed here, namely, a ganglion opticum, placed not at 
the base of the eye, but near its external end. 
Between the so-called ganglion and the epidermal cap of 
the eye only two layers of the large clear cells (P. in my fig.) 
intervene, while as many as eight lie between it and the base 
of the eye. The large clear cells in front of the ganglion are 
supposed to function as a cornea and lens, and to throw images 
of external objects on the retinal area (‘ ganglion opticum ”’). 
I find nothing in my sections at all comparable with Ranke’s 
optic ganglion, unless it be the axial fibres seen in section. 
With the ganglion placed near the peripheral end of the eye, 
as in Ranke’s figure, and on the supposition that the large 
clear cells which lie in front of it serve the purpose of a 
cornea and lens, the great mass of these clear cells lying 
behind the ganglion would appear to be useless. This fact 
alone invalidates Ranke’s interpretation and lends some weight 
to the suggestion that his ganglion opticum was only a sec- 
tional view of the axial fibres. 
The point on which I differ most widely from Leydig and 
Ranke lies in the interpretation of the axial fibres of the eye. 
I regard these fibres as very much elongated sense-cells, derived 
primarily from the epidermis, and in no sense of the word re- 
presenting nerve-fibres. My reasons for this view are briefly 
the following: 1. The optic nerve is at least three times as 
thick as the widest place in the axial cord of fibres. 2. Ina 
preparation treated with chromic acid twelve hours, washed in 
water twelve hours, gold chloride one hour, formic acid forty 
hours, I find that the optic nerve has a decided pinkish colour, 
while the axial fibres of the eye are stained blue, like the large 
clear cells and the epidermal cells. These two facts show quite 
conclusively that the axial fibres are not a direct continuation 
of the optic nerve. 
1 *Tafeln zur Vergl. Anat.,’ Tibingen, 1864. 
2 ¢ Zeitschr. f. wiss. Zool.,’ xxv, 1875. 
