156 PATLIEN: [VoL. II. 
upright ones, except that in the first case between each pair 
would be the cut ends of a row of axial nerves, and in the sec- 
ond, a bundle of vertical nerve fibres (Fig. 5, C. and D.). 
Some observations have been made upon the eyes of other 
insect larvz. With one or two exceptions, nothing was found 
that I care to speak of here. When enough material has been 
obtained, it is possible that I may be able to give a more ex- 
tended comparative account of the larval ocelli of insects than 
I desire, or am able, to do now. 
Figure 3.— Vertical (4) and horizontal (2) section of a Hydrophilus larva about 
7mm.long. cg. corneagen; o. w. outer wall of the optic vesicle; 7d. rods. 
The eyes in the young larvze of both Hydrophilus and Dytiscus 
are much alike. In the woodcut (Fig. 3) is represented a sec- 
tion of the eye of a Hydrophilus larva about 8 mm. long. We 
perceive at once the fundamental differences in the construction 
of this eye and that shown in Grenacher’s well-known figure of 
the young larval ocellus of Dytiscus. First, there are three 
distinct layers in my figure produced by the invagination of an 
optic vesicle. The outer wall of the vesicle is represented by a 
cluster of small, deeply stained nuclei over the centre of the 
retina. The latter is composed, not of upright cells, as Gren- 
acher has it, but of horizontal ones, bearing short horizontal rods. 
The latter form a thin oblong and vertical plate in the middle 
