158 PATTEN. [Vot. II. 
lens something like that in Peripatus. On the inner surface of 
the lens, we can still see some of the inverted rods that have 
not quite lost their identity. The outer surface of the lens is 
surrounded by a membrane, between which and the lens area 
few scattered nuclei. The latter are continuous with those of 
the retina. In vertical sections, the rods appear to be upright, 
but cross sections show that they are horizontal and arranged 
in a double row in a nearly circular space surrounded by the 
pigmented ends of the retinal cells. 
The optic vesicle is covered by a corneagen composed of a 
thick layer of colorless, columnar cells with distinctly stained 
nuclei. On the periphery of the corneagen is a thin layer of 
pigment. 
Myrtapops. — There are many important points in which the 
larval ocelli of Insects resemble those of Myriapods, and I ven- 
ture to assert we shall find a still greater resemblance when a 
better knowledge of the structure and arrangement of the rods 
in the latter group has been obtained. 
The material upon which Grenacher made his observations 
had been hardened in alcohol only, and as he himself had occa- 
sion to repeat, there was much to be desired, especially in the 
preservation of the rods. In only two instances was a clear 
picture of the rod mosaic obtained: in Cormocephalus, where 
they were cylindrical tubes; and in Scutigera, where they were 
flattened much like those of Acilius. If, after re-examination 
of properly prepared material, the first case should still stand, it 
would offset the significance that I attached to the flattened 
rods in Acilius. But there are not inconsiderable reasons for 
doubting that it will stand, for in Acilius the flattened rods 
when hardened in alcohol sometimes appear like cylindrical 
tubes. In other cases the rods were so poorly outlined that 
Grenacher was always in doubt as to their structure; indeed, in 
some instances he could go no farther than to assert that they 
were rods. 
Besides the similarity in the possession of horizontal rods, one 
that is all the more striking since these remarkable structures 
are at present only known in the two groups we are discussing, 
there are many minor points in which the ocelli of Insects re- 
semble those of Myriapods. The resemblance is striking when 
