230 Annals Entomological Society of America [Vol. IV,. 



Beyond this something of the central commissure remains, many 

 of the other crossed fibers in the central part of the ganglion 

 have disappeared. A bundle of fibers partly transverse and 

 partly fused with the central longitudinal bands begins to be 

 seen on either side of the ganglion ventrally, these are partly 

 mixed with the main longitudinal tracts. They are endings of 

 the bundles of the lateral nerves to be followed later and might 

 be called lateral nerve tracts. At this level a few scattering 

 cells on the ventral side and two small dorso-lateral groups, one 

 on each side of the ganglion indicate about all of the cell masses 

 seen lower down, while in the mid-dorsal line a new group of 

 dorsal cells makes its appearance and sends fibers through the 

 central part of the ganglion as a central tract which breaks up 

 laterally and can be traced to various parts of the central fiber 

 mass of the ganglion. For several sections these fibers become 

 quite prominent and the central commissure seems to be lack- 

 ing, then as this central tract disappears higher up, another and 

 a better marked commissure comes to view running trans- 

 versely through the center of the ganglion from side to side. 

 At this level cells again come into view laterally. The ventral 

 tracts of the lateral nerves become more prominent and there 

 is a dorsal band of fibers close to the edge of the "punktsub- 

 stanz " on the dorsal side. This last is parallel with the median. 



Slightly beyond this a few cells are seen on the ventral side 

 laterally, two of the same commissures, a dorsal and a median 

 may be seen, but the lateral cells have disappeared to give place 

 to the entrance of the fibers of the large lateral nerves. These 

 fibers for the most part run directly into the lateral nerve tract 

 noted above when it was seen more caudally. Beyond this and 

 beyond the entrance of the lateral nerve, a few cells are seen 

 laterally, one or so in the mid-dorsal line, and the dorsal and 

 median connectives disappear and only a few tangled fibers 

 replace them, although for a few sections the great sweep of 

 transverse fibers is continued from side to side, from the lateral 

 nerve tract. 



Above this no commissure or cross fiber of any sort connects 

 the lateral halves of the ganglion and a small group of nerve 

 cells comes to lie on the middle line and dorsal and ventral to it. 

 At the line of separation of the lateral halves, the tracts of the 

 lateral nerves can be distinguished as a dense mass on either 



