NERVOUS SYSTEM OF GRASSHOPPER — SCHMITT 32I 



In the prothorax of Dissosteira, the dorsal nerve of that segment 

 passes mesad of the first ventral longitudinal muscle (55) and also 

 provides innervation to it, precisely as in the case of the dorsal nerve 

 and the internal ventral muscles in the abdomen. The cervical nerves 

 also pass mesad of the first longitudinal muscle. In the thorax of 

 Chaidiodcs, according to Maki, the prothoracic dorsal nerve passes 

 laterad of the ventral longitudinal muscle, but the two nerves from 

 the suboesophageal ganglion entering the cervix pass mesad as in 

 Dissosteira. 



In the pterothorax of Chauliodes, according to Maki, the dorsal 

 nerves pass laterad of longitudinal ventral muscles and also provide 

 innervation of them, as in the prothorax. In Dissosteira, the dorsal 

 nerves of the pterothorax pass laterad of the ventral longitudinal 

 muscles, as in Chauliodes, but the innervation of the muscles is at least 

 definitively quite different, both from Chauliodes and from the pro- 

 thoracic and the pregenital abdominal segments of Dissosteira. 



The second ventral longitudinal muscle (60) extends from the pro- 

 sternal apophysis to the mesosternal apophysis and is listed by Snod- 

 grass as a prothoracic muscle. The innervation of the second muscle 

 is provided by a branch from the anterior connection of the meso- 

 thoracic dorsal nerve (fig. 2), suggesting that this muscle should be 

 considered mesothoracic rather than prothoracic. 



The pr asternal muscle of the first cervical sclerite (54) and the 

 stcrnospinal muscle (61) are innervated by a fine nerve w^hich arises 

 from the dorsal surface of the prothoracic ganglion near its posterior 

 end. The stcrnospinal muscle receives a fine branch from this nerve, 

 which then passes along the anterior surface of the pleural apophysis 

 to enter the prosternal muscle. The prothoracic dorsal nerve passes 

 under the prosternal muscle and is joined with its anterior connection 

 to the suboesophageal ganglion just laterad of the point of crossing of 

 the prosternal muscles. The prothoracic dorsal nerve thus may be 

 said to pass dorsally through a triangle of which the first ventral 

 longitudinal muscle forms one side and the crossed prosternal muscles 

 form the other two sides. 



The third ventral longitudinal muscle (87) extends from the pro- 

 sternal spina to the mesosternal apophysis. It is innervated by a small 

 nerve which appears to arise from the intersegmental connective be- 

 tween the prothoracic and mesothoracic ganglia. This nerve pre- 

 sumably arises in the mesothoracic ganglion and has become incorpo- 

 rated in the connective simply by being in juxtaposition ; attempts to 

 "peel" it away from the connective failed. 



