244 THE ROYAL SOCIETY OF CANADA 



lion and are connected with it by a plexus of nerve fibres which arise 

 from its anterior end. In one specimen stained with methylen blue 

 these fibres were highly differentiated and could be traced down the 

 middle of the dorsal side of the ganglion, continuing as the median 

 nerve of the next segment 



From the point where the median nerve unites with the trans- 

 verse nerve of the mesothorax two minute branches are given off and 

 run to the ventral intergument. 



The transverse nerves run laterally above the recti muscles near 

 their point of insertion. Their connection with the nerves of the 

 connectives in the thorax and with the nerves A in the abdomen have 

 been described above and may be readily seen from the figures. 



In the thorax these nerves give off several branches which go 

 chiefly to the trachea but some minute branches have been found 

 going to the muscles. After crossing the tracheal trunk, the nerve 

 continues into the dorsum in close connection with a branch of the 

 tracheal system which goes to the dorsal muscles. 



In the abdominal segments near the insertion of the recti muscles 

 the transverse nerve is very closely connected with a branch of the 

 trachea. Not far from the ganglion it receives a nerve from branch 

 c of nerve B. Before crossing the tracheal trunk, the nerve some- 

 times sends a branch to the transversi latérales muscles, and after 

 crossing the trachea another branch is sent to the same muscles. 

 In the dorsum the nerve ramifies through the dorsal diaphragm 

 closely united with a tracheal branch. It is thus evident that the 

 function of this nerve is to supply the respiratory system. 

 gjH There are two transverse nerves given off from the last abdominal 

 ganglion. The first one belongs to the seventh segment and is united 

 with nerve A for a short distance, often appearing to be a branch of 

 this nerve. Its distribution is similar to that of the other transverse 

 nerves of the abdomen. The origin of the second pair of transverse 

 nerves of the terminal ganglion may sometimes be traced to the dorso- 

 median point of the posterior end of the ganglion. There is no median 

 nerve. The transverse nerve is fused with nerve C from the origin 

 of the latter until it enters the eighth segment. It then separates 

 from nerve C and projects outward. As in the case of the other 

 abdominal transverse nerves, this one receives a branch from nerve 

 A of the anterior segment. This nerve appears to be rudimentary, 

 as it has been traced only a short distance from the point where it 

 leaves nerve C. 1 



