228 Annals Entomological Society of America [Vol. IV, 



in the centers of bundles of fibers and most easily seen in these 

 traced from the connectives. The exact place and method of 

 termination was not determined. Injections of fluids into the 

 ganglia by way of trachea failed to penetrate any of the finer 

 branches. 



All of the abdominal ganglia seem to be of practically the 

 same type, but individual variations occur. 



In all of the nerve centers the cells are grouped for the most 

 part on ventral and lateral portions of the ganglion and towards 

 the caudal end, a few cells occur on the dorsal side especially 

 near the middle line and these are often quite large. 



Description of 4th abdominal ganglion traced by sections 

 beginning at the caudal end: 



The connectives entering from the ventral side are easily 

 followed as distinct longitudinal masses of fibers well up into 

 the ganglion, these connectives as well as others in other parts 

 of the nervous system are composed of numerous closely 

 packed longitudinal fibers, scattered between these are the 

 openings of trachea, when the ganglion is reached the chitin 

 for each of the connectives becomes fused into one mass and 

 farther in the central portion of chitin between them disap- 

 pears and the two bundles of fibers are more or less crowded 

 against each other. Farther up into the ganglion the fiber 

 bundles do not occupy all of the area under the chitin because 

 large spaces on all sides occur and then soon cells in a single 

 layer are found close to the wall of the ventral side, and then on 

 the dorsal side a very large cell is found wedged in between the 

 two bundles of fibers. Some of the cells of the ventral side 

 may be seen at this level sending fibers into the two longitudi- 

 nal bundles. The single layer of cells on the ventral side 

 becomes a double row of medium and small, and the large cell 

 of the dorsal side gives way to a group of small ones and there 

 comes to be on the ventral side two groups of fibers running 

 more transversely, probably made up in part from fibers con- 

 nected with the cells appearing on the ventral side. 



Farther up these ventral nerve cells extend out laterally so 

 that numbers of them might be seen from the dorsal side. No 

 cells are left for a distance on the mid-ventral line, and they 

 disappear from the mid-dorsal line also to some extent, but 

 before they are gone fibers can be traced about the connective 

 bundles and to the cell region of the ventral side. At this 



