NERVOUS SYSTEM OF GRASSHOPPER — SCHMITT 327 



tinues along the large tergal remotors of the coxa and forks just 

 below the tympanum, the anterior fork passing anterior to the first 

 abdominal spiracle to innervate the lateral oblique intersegmental 

 muscle (140), the longitudinal dorsal muscles (141), and the lateral 

 oblique dorsal muscles (142). The posterior fork next provides a fine 

 branch which is joined by the metathoracic transverse nerve and then 

 innervates the spiracle muscles (147, 148). The posterior fork con- 

 tinues as the tympanal nerve to enter Miiller's organ. 



The ventral nerve leaves the ganglion medially and proceeds ven- 

 trally below the main nerve cord. As in other pregenital abdominal 

 segments, it passes beneath the median internal ventral muscles, 

 innervates the external ventral muscle (145)) the lateral muscle (146) 

 which is specialized as the tensor of the tympanum, and provides a 

 branch which joins the dorsal nerve of the next posterior segment. 



The dorsal nerves of the second and third abdominal segments 

 leave the ganglion side by side and proceed posteriorly together, pass- 

 ing beneath the transverse nerve of the first abdominal segment. 

 Rather strangely, a short connection extends between the third ab- 

 dominal dorsal nerve and this transverse nerve as the dorsal nerve 

 passes beneath the transverse nerve. A second connection leaves the 

 second abdominal dorsal nerve posterior to this point and provides 

 two branches. The anterior branch connects with the first abdominal 

 transverse nerve ; the posterior branch innervates the ventral internal 

 muscles (154, 155) and also marks the anterior end of the paramedian 

 nerve in the female. 



A group of lateral muscles, numbered 157 to 164, are described 

 by Snodgrass as differing in many respects from those of the seg- 

 ments following. Three of these muscles, 157, 158, and 160, are in- 

 nervated by the anterior branch of the dorsal nerve which connects 

 with the ventral nerve of the first segment. In this respect these 

 muscles correspond with the first external lateral muscle, the first 

 internal lateral muscle, and the second internal lateral muscle of the 

 preceding segment. The remaining muscles of the lateral series are 

 innervated by a branch of the ventral nerve, as are the second and 

 third external lateral muscles of the segments following. In most 

 respects, therefore, the innervation of the second abdominal segment 

 presents no unusual aspects. 



The median or unpaired systems of the first and second abdominal 

 segments consist of median nerves which terminate in the usual trans- 

 verse nerves. Only the median nerve of the third segment extends to 

 the following ganglion. 



