354 JouURNAL OF ComPARATIVE NEUROLOGY. 
I have been able to trace a single fiber from the nerve to the 
collar of the same side. 
Optico-arch Tract (fig. 3, 5, O.A.7.) This is a small tract 
which passes from the medial portion of the optic nerve, in a 
convex curve (convexity mesad) to the fibrillar arch. Near the 
optic nerve this tract is intimately associated with the anterior 
optic tract, but, at the optico-olfactory commissure, this enters 
the arch, turns outwards (laterad) and passes along towards the 
mushroom bodies, while the anterior optic tract crosses the 
arch and passes on to the ventral nidus of the same side. 
Anterior Optic Tract (fig. 5, A.O.7.). This is a small tract 
which passes from the optic nerve to near the root of the 
oesophageal collar and near the base of the antennary nerve. 
Where this tract apparently terminates there is a nidus of 
cells, but whether or not there is a direct union of those cells 
with the fibers of this tract could not be demonstrated. Be- 
tween the optic nerve and the fibrillar arch this tract is inti- 
mately associated with the fibrillar arch tract ; but near the arch 
they part company, this tract crossing the arch, the other curv- 
ing into it. 
I take this tract to be the homologue of what Kenyon (’96) 
in the bee brain calls the anterior optic tract. 
Oculomotor Commissure. Although there isa distinct oculo- - 
motor nerve yet, in sections, it is almost impossible to distin- 
guish it from the optic nerve proper. In addition to the com- 
missure described above, there is connected with the eye-nerves 
another commissure which in form resembles very much the 
lower optic commissure. Between it and the lower optic com- 
missure are located the central body, the optic chiasm with its 
associated tracts, etc. Whether it belongs to the optic nerve 
proper or to the oculomotor nerve cannot be decided positively 
on account of the intimate relation to the two nerves. Iam 
inclined to believe it related to the oculomotor nerve. 
Oculomotor Tract. This fiber tract arises near the tegumen- 
tary lobe and passes to the oculomotor nerve on the same side. 
When we consider the fact that in the Hexapoda the optic 
lobes are fused with the protocerebron, while in the crayfish 
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