
57? IHE AMERICAN NATURALIST. [Vor. XXXVI. 
investigations will probably bring out more complex relations 
than here portrayed. 
On each side of the abdominal ganglia of Pieris there are two 
large branches or nerve trunks (Fig. 10). The more cephalic of 
C these comes from bipolar nerve cells at the 
bases of hairs, and the other more caudal 
branch goes to muscles; so, as nearly 
as could be determined, the cephalic 
trunks are sensory and the caudal ones 
motor. There may have been a few 
motor nerves in the cephalic trunk and 
M LLL ganglion Sensory nerves in the caudal one, but if 
from Pieris. Methylen blue. there were such, they were inconspicuous 
and not noted in the examination of numerous specimens; so 
for the present, at least, the more cephalic branch may be 
regarded as a sensory branch. 
This sensory branch upon entering 
the ganglion seems to run as a distinct 
tract cephalad without sending branches 
to the central cell area of the ganglion. 
This tract runs cephalad for some dis- 
tance along the outside of the connec- 
tive and is finally lost sight of. The iara pone 
course of the motor nerve is quite Io caterpillar (Automeris io). a 
different ; its fibers seem to come '?""* rok aem 
directly from the central cell area of either side of the ganglion. 
Aside from the fibers just described, there are nerve fibers 
which may be seen to run through 
the ganglion longitudinally ; these 
take a lighter stain. They run along 
the connectives and are just inside 
the sensory tracts. 
Variations in the number and posi- 
Fro. 12.—Small and large hairs from tion of the nerve trunks from the 
p DN ganglion occur in different species. 
In Io and in a tiger moth the same sensory tract may be noted, 
but part of the sensory trunk upon entering the ganglion leaves 
the sensory tract and enters the cell area (Fig. r1), but on 


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