1941] Thoracic Ganglia of Ephestia kuehniella 125 
The lowest bundle of fibers (a) is the ventral counterpart 
of the uppermost group. These fibres originate in the pro- 
thoracic ganglion and end in the posterior lobe of the fused 
ganglia. Like the other bundles this one has side branches 
which ramify among the fibers of the neuropile in both lobes. 
The association fibers (j') which come from the abdominal 
region ramify among the fibers of the neuropile of the 
posterior lobe, but do not extend to the anterior lobe. There 
are association fibers, located on either side of the dividing 
line described above. 
By examining the association fiber tracts (dorso-ventral, 
and dextro-sinistral) it is easy to differentiate the larval 
components which have contributed to the formation of the 
fused adult ganglia. There are well defined fiber tracts 
which extend from dorsal to ventral (n), and dextral to 
sinistral (e, j, k) areas (in both directions) in each section. 
Each group of fibers, on the whole, is confined to that por- 
tion of the ganglion which originally constituted a larval 
ganglion. In sagittal sections the dextro-sinistral fibers 
(o, o') appear as well defined bundles and in frontal sections 
the dorso-ventral fibers have a like appearance. There are 
two main regions of dextro-sinistral association fibers as 
seen in sagittal view. The dorsal region (o) contains the 
motor association fibers, and the ventral region (o') the 
sensory association fibers. Furthermore, each group of 
fibers gives off connectives to the adjacent groups; this 
assures communications between all sections. 
The commissures to the mesothoracic legs (L 2 c) pass 
out of the ganglonic mass from the posterior lateral ventral 
portion of the anterior lobe; the motor cells (d) are located 
on the lateral anterior portion of the anterior lobe, e.g. that 
portion derived from the larval mesothoracic ganglion. 
Each of these cells gives off a large axon which in turn gives 
off a number of small branches to the neuropile before pass- 
ing ventrally to the leg. There are a number of sensory fibers 
from the leg (f) which ramify among the various fibers of 
the neuropile of the anterior lobe. 
Surprisingly enough the commissures to the metathoracic 
legs (L 3 c) leave the ganglionic mass at the posterior la- 
teral point of the posterior lobe. The motor cells (h), how- 
ever, which supply the neurones for these legs are located 
