1912] Anatomy of Tomato-worm Larva 259 
enlarged, oval knots, found in each segment of the body, are the 
ganglia. Only one ganglion exists in each body segment outside 
of the head and the seventh and eighth abdominal segments. 
The cords running between the ganglia, which in some cases are 
double or partially so, are the commissures. The nerves are 
the branches of various sizes extending from each ganglion and 
in some cases from the commissures. These fine threads 
permeate all parts of the body. The nervous system will be 
discussed under the following divisions: Abdominal Ganglia, 
Thoracic Ganglia, Head Ganglia, and Sympathetic Systems of 
the Head. 
ABDOMINAL GANGLIA (Fig. 14 and 15).—The abdominal gan- 
glia are the simplest in type. The distinct similarity between 
the first six abdominal ganglia makes it possible for one descrip- 
tion to answer for all. The seventh and eighth abdominal 
ganglia will be discussed under a separate heading. 
First Six Abdominal Ganglia (Fig. 15, A. 1g).—The first six 
abdominal ganglia are located in the middle or cephalic part of 
each abdominal segment and consist of the following parts :— 
Lateral Nerves —The lateral nerves (/) are the two branches, 
which arise from the cephalic part of the lateral margins of the 
ganglia and innervate the latero-dorsal portion of the body. 
Ventral Nerves——Directly caudad and slightly ventrad of 
the lateral nerves, the ventral nerves (v) arise and extend 
caudo-laterad to innervate the ventral area of the body segments 
Near the point of entrance of the ventral nerves, a pair of small 
nerve-like trachez enter the ganglia. These two trachez, one 
on each side, are derived from the transverse trachez located 
in each abdominal segment ventrad of the nerve cord. The 
trachez can be distinguished from the nerves by staining with 
Delafield’s hematoxylin as heretofore advocated. A stained 
trachea is more deeply colored than a nerve and also shows its 
distinct ringed nature on high magnification. 
Ventral Sympathetic System (Fig. 15, m. and ¢t. n.)—Extend- 
ing between the ganglia there is a single, large, white cord, the 
commissure. Just before.the commissure enters the cephalic 
end of a ganglion, it divides into two cords or is furrowed on the 
dorsal surface. The ventral sympathetic nerves arise from the 
cephalic end of this fork. With some of the ganglia, this 
forking or splitting of the commissure is not very great but can 
in each case be detected. 
