38 JOURNAL OF ENTOMOLOGY AND ZOOLOGY 
of the ganglia. Another point which is equally interesting is 
the small size of the nerve cells. The small size of the animal 
and the consequent smaller number of nerve cells as compared 
with larger insects, is apparently not the only difference be- 
tween this insect and those of larger size. Most of the nerve 
cells of Aphorura are about two or two and a half microns in 
diameter. They are much smaller than other cells of the body, 
even smaller, in fact, than the nuclei of certain cells, such for 
example as the epithelial cells of the intestine. 
The details of structure of the nervous system will not be 
considered at this time, but a brief description will be given of 
the ganglia and the chief branches of the nerve centers of the 
head region. The larger ganglia of the animal are disposed 
much as shown in Fig. 37, pl. XII, of Philiptschenko’s work. 
Hlowever he shows no supraesophageal ganglion in this figure 
and the position of some of the caudal parts of the nervous 
system differs from the corresponding portions of Aphorura. 
In Aphorura the supra- and subesophageal ganglia are large 
and joined together by broad connectives in their forward por- 
tions. A section across these ganglia at such a level shows 
them as one mass with the small esophagus in a little opening 
in the center of this mass. The connections between the sub- 
esophageal ganglion and the first thoracic are not as close as 
between the two large head ganglia. 
There are three large thoracic gangha about opposite each 
pair of legs. These are jomed together by broad and short 
connectives. Beyond the third thoracic ganglion and broadly 
connected with it, is a thick mass which represents the fused 
abdominal ganglia. This extends into the abdominal region a 
short distance and ends in a nerve which probably supplies 
most of the abdominal organs. I found no gangha below this 
point but there were some indications of nerve cells where there 
were no distinct ganglia. 
The large abdominal mass broadly fused to the last thoracic 
center, was found on median sections, to show evidences of being 
composed of several fused ganglia. 
