40 JOTJENAL OF ENTOMOLOGY AND ZOOLOGY 



tions of this ganglion are closely applied to the region of the 

 eyes and the ocular lobes are evident as lateral extensions of 

 the brain some distance from the connection with the subeso- 

 phageal center. The nerve cells form a sheath over the central 

 mass of fibers in most parts of the brain, only a few ventral 

 and lateral areas are without them, with the exception of a 

 small dorsal region not far from the level of the eyes. The 

 length of the brain in a specimen of about 1 mm. in length was 

 found to be about 45 microns. In this part of the central 

 nervous system as in all other portions the nerve cells are very 

 small. 



The subesophageal ganglion although longer than the brain 

 is much less broad and deep. A considerable portion of its 

 dorsal surface is without nerve cells, as well as some lateral 

 portions. The center extends from near the forward region 

 of the brain to some distance back of it. In the same specimen 

 mentioned above, the length of the subesophageal in section 

 was found to be about 90 microns. 



The first thoracic ganglion is the shortest of all the chief 

 ganglia, being about 40 microns. Nearly all parts of the 

 central fibrous center are covered with nerve cells. The bi-lobed 

 nature of the ganglion is evident in this nerve center. 



The second thoracic ganglion is quite similar to the first. It 

 is about 50 microns long in this specimen. 



The last ganglion is evidently composed of a number of ele- 

 ments. In all specimens, both young and old, there is a clear 

 indication of a cephalic portion which seems but recently fused 

 with the more caudal mass. This is shown in the figures of 

 cross sections, but more especially in median longitudinal 

 views. Fig. 4 shows something of this, as does the drawing of 

 a more lateral median section shown in 5. These views of this 

 ganglion show also with great clearness a number of divisions 

 of fibers and cells which may indicate the fusion of a large 

 number of abdominal segments. 



From a study of the sections and the figures presented the 

 following points may be mentioned: 



