160 PATTEN. [VoL. II. 
cells with double horizontal rods, and the so-called hairs are the 
external nerves of these rods. In sections parallel with the broad 
surface of the rods of Acilius, the external nerves are conspic- 
uous, and in alcoholic material they appear like hairs, or at any 
rate might give rise to the impression that each cell was provided 
with a number of slender rods. That these external nerves are 
probably present in Myriapods is shown by the fact that Gren- 
acher, p. 456, has himself described in the large flat rods of 
Scrutigera a set of cross striations which he says recall the 
“ Plaittchenstructur’”’ so frequently described in the rods of 
Arthropods, and he even hints that there may be some connec- 
tion between this fact and the hair-like rods in the eyes of 
Myriapods. 
Finally, in his Fig. 14, is shown a semi-transverse section of the 
retina of Glomeris, where the hair-like rods are united in groups 
that would correspond very closely to the flattened rods of 
Acilius, and even in his vertical sections we see indications of 
the same thing. 
The bodies projecting beyond the pigment layer in his Fig. 
1, look more like a layer of short rods than the ends of cells, 
as he calls them. There is no other instance to my knowl- 
edge where only the outer ends of retinal cells are free from 
pigment. I regard them as rods, and support this interpreta- 
tion mainly on the fact that Grenacher represents them as 
extending into the notch at the bettom of the eye. 
But what shall be done with the layer of rods in his first 
figure? I should regard it as a corneagen, which like that in 
Acilius had lost its nuclei, if in Fig. 2 both a corneagen and 
this striated layer were not present. If we do not accept 
Grenacher’s interpretation, no course appears to be open except 
to consider the outer layer of Fig. 2 as a corneagen, and the 
middle one, if it is really a separate layer, as the outer wall of 
an optic vesicle, which forms in this case a vitreous, striated 
body comparable to that in Chauliodes (Fig. 3) or with that in 
the cavity of the optic vesicle of Peripatus. 
That there is a tendency to form two kinds of rods in Myria- 
pods is clearly shown in Grenacher’s drawing of the eye of 
Heterostoma (Fig. 4). We might expect to find the outer rods 
short and upright as in the eyes II. and IV. of Acilius, although 
