No. 1.] EVES OF ARTHROPODS. 125 
that it was of course impossible to reconcile with the great size 
of the cells to which they belonged, unless we assumed that 
each of these cells possessed many rods. 
In the smaller cells, the nerve fibres and pigment granules are 
also distributed in the manner just described, but their course 
ana arrangement is less easily followed. 
The small retinal cells contain an axial nerve which, between 
the two rods of each retinophora, breaks up into a fan-shaped 
bundle of fibres, that in cross sections appear like a row of dots 
midway between each pair of rods, and usually parallel with 
their broad surfaces (Fig. 55). 
In the gigantic retinophoree, the axial nerves are arranged ina 
sheet as broad as the ends of the cells. In longitudinal vertical 
sections, they are consequently seen as a row of dots between 
each pair of rods (Fig. 55). 
Most of the nerve fibres supplying the retinal cells come from 
two bundles that extend along the edges of the horizontal retina 
(Figs. 90 and 91). A third group extends along the middle of 
the under surface of the retina. From it arise two sheets of 
densely pigmented nerve fibres which extend upward into the 
Space between the two rows of gigantic cells (Pl. X., Fig. 56, v. 7.). 
These fibres are very straight and arranged with almost as 
much regularity as the large rods, with whose terminal edges 
they are parallel. I suspect that the number of these nerve fibres. 
bears a pretty constant relation to the number of large rods. In 
some of my preparations I could see that a single nerve fibre lay 
in or near a shallow furrow which marked the point of union of 
each pair. From this I judge that in the living, normal condi- 
tion, one of these vertical fibres extends along the terminal 
edge of each pair of large rods. But evidence of this condition 
is not often found in sections, owing to the action of the re- 
agents, which cause a contraction that draws the fibres away 
from the rods towards the middle of the furrow. Hence in hori- 
zontal sections, these nerve fibres are seen in cross sections as 
two rows of dots, a little distance from the terminal edges of the 
rods (PI. Xi, Figs 50, v7). 
From the vertical nerve fibres arise a great many fine fibrillze 
which extend at right angles to the main fibres towards the rods 
and apparently become continuous with the external nerve fibres. 
Others extend in an opposite direction where, detween the two 
