THE EVIDENCE OF THE ORGANS OF VISION 79 
above its optic ganglion, and presented an appearance remarkably like 
Fig. 32, which represents one of the simple eyes and optic ganglia 
of a larva of Acilius as described by Patten; then, with the fae 
growth of the upper lip, 
the right pineal eye was 
dragg ged forward and its 
nerve pulled horizon- 
tally over the ganglion 
habenule. Yor this 
reason the eye, nerve, 
and ganglion are better 
shown in a nearly hori- 
zontal than in a trans- 
verse section. 
The optic nerve be- 
longing to this eye is 
most evident and clearly 
shown in Fig. 31, and in 
the series of consecutive 
sections which follow 
upon this section; no 
doubt can arise as to 
the structure in ques- 
tion having been the 
nerve of the eye, even 
though, as is possible, it 
does not contain any 
functional nerve-fibres. 
The second, ventral 
or left, eye, belonging 
to the left ganglion 
habenule is very dif- 
ferent in appearance, 
being much less evi- 
dently an eye. Fig. 34 
is one of the same 
Fic. 34.—HorizontaL SECTION THROUGH BRAIN OF 
AMMOCCETES, TO SHOW THE LEFT, OR VENTRAL 
Pineau Eye, 
‘pn.o, left or ventral pineal eye; pn.,, last remnant of 
right, or dorsal pineal eye; g.h.r., right ganglion 
habenul@ ; g.hul.y, g.ll.g, parts of left ganglion 
habenule ; pi., fold of pia mater which separates 
the left ganglion habenul@ from the left pineal 
eye; f., strands of nerve-fibres connecting. the 
left eye with its ganglion, g.h.J.,; V,, third 
ventricle; V.aq., ventricle of aqueduct. 
series of horizontal sections as Fig. 31, pn., being the last remnant 
of the right, or dorsal, eye, while pn. shows the left, or ventral, eye 
with its connection with the left ganglion habenule. 
