232 Annals Entomological Society of America [Vol. IV, 



branches also send fibers to the central mass, some of these run 

 straight through, while others seem to cross in commissures 

 or end. 



In general then, there are in each abdominal ganglion, cells 

 on the ventral caudal region, on the lateral sides, and a few on 

 the median dorsal side. These cells surround a central fibrous 

 mass made up of strands running longitudinally through the 

 ganglion from the connectives and best marked in the cephalic 

 and caudal parts; fibers running across from side to side, these 

 run in about three commissures, a dorsal, a ventral and a 

 median and at various cephalic and caudal levels these com- 

 missures are interrupted. The lateral nerve trunks may be 

 seen to contribute largely to the formation of the large ventral 

 commissure. The other cross connections seem to be more 

 exclusively from cells on the sides of the ganglia and from these 

 cells also other cross or diagonal fibers may be followed. 



The dorsal group of cells which seems to be to a large 

 degree for association, sends fibers through the ganglion to the 

 cells of the lateral and ventral groups, so that these fiber tracts 

 may be found above or below the commissures penetrating to 

 the opposite side, or part way through when the median com- 

 missure is present. 



THORACIC GANGLIA. 



Methylene blue method. (Fig. 3). 



The three thoracic ganglia are quite a little larger than the 

 abdominal and the branches come off differently. 



There are on each side three main trunks the most cephalic 

 of these has its most cephalic branches pure sensory, but No. 2 

 was not determined, also No. 1 of trunk B or the middle trunk 

 seems sensory while other branches of the middle trunk are 

 more or less mixed and the last which goes into the leg is also 

 mixed. So then the more cephalic nerves are sensory while the 

 rest seem to be mixed. The exact nature of the two parts of 

 the last or leg branch was not determined, but there was no 

 reason from the staining reactions to indicate that they were 

 of greatly different composition. 



In the thoracic region as in the abdominal, the main trunks 

 easily took up the stain, but here greater difficulty was encoun- 

 tered in surface studies because of the larger opaque mass of the 

 ganglion. Cells and fibers were however made out and found 



