342 JouRNAL OF COMPARATIVE NEUROLOGY. 
cepting in Notodromas, a median unpaired structure. Where 
it leaves the brain there is a cluster of cells. Whether or no 
these cells are the homologue of the optic ganglion of the higher 
forms is an unseitled point. If not, then the optic ganglion is 
absent. In my paper on the nervous system of Cypms (96) I 
unfortunately called that the optic ganglion and described the 
optic nerve as arising from it. But in so doing it was not in- 
tended to predicate the homology of that group of cells with 
the optic ganglion of insects. The nomenclature was unhappy. 
Optic nidus would have been a better expression. 
Oculomotor nerves. Near the latero-ventral edge of the 
brain of Cambarus arises a nerve which passes to the eye mus- 
cles (fig. 1, O.Z.V.). This nerve is not found in the Hexa- 
poda. There sessile eyes render it unnecessary. 
In Branchipus, froma theoretical standpoint, I expected 
to find this nerve, but if it exists, I have not been able to dif- 
ferentiate it from the optic nerve. 
Antennulary nerves. From near the middle of the cephalic 
- surface of the brain arise the antennulary nerves. They pass 
forward (cephalad) to the antennules (fig. 1, A. /.). 
This nerve is also found in the Cladocera (SAMASSA, ’91), 
the Ostracoda, and the Hexapoda (VIALLANES, ’93 etc.). 
Tegumentary nerves. This nerve arises from the caudal 
surface of the brain, near the origin of the oesophageal collar 
and passes latero-cephalad to the skin of the head (fig. 1, Z./V.).. 
It has not been possible to determine whether this nerve 
is found in the insects or not, but I feel quite sure that it is not 
homologous with the tegumentary nerve of the Ostracoda. 
Antennary nerves. This is a large pair of nerves which 
arise from each ventro-lateral edge of the brain and pass out- 
wards (laterad) to the antenna (fig. 1, Avz.). Immediately 
after leaving the brain, a small nerve arises from the Sue 
nerve and passes downwards (ventrad). 
This nerve (the antennary) seems to be universally present 
throughout the Crustacea; but according to VIALLANES (’93) 
and other students of insect neurology it is found neither in the 
Hexapoda, nor the Avachnida, nor the Myrzapoda, nor Limulus. 
