NERVOUS SYSTEM OF GRASSHOPPER — SCHMITT 



311 



sosteira. This is especially obvious with respect to the spinae and 

 the muscles attached to these structures, and it seems to be clear 

 that possible future evolution of the ventral nerve cord toward con- 

 solidation of the thoracic ganglia will require drastic skeletal and 

 muscle system changes. 



II. THE DORSAL NERVE 



The mesothoracic nerve system is, in several respects, the most gen- 

 eralized of the three thoracic segments, and is accordingly described 

 first. Three pairs of lateral nerve roots extend from the mesothoracic 

 ganglion. The anterior root, here called the dorsal nerve (figs, i, 2, 



2CvN 



Gng3*lA*2A*3A 



HdN 



iCvN 



Pig. 2. — Diagram of cervicothoracic median nerves, dorsal nerves, and cervical 

 nerves of the right side, and the innervation of the ventral longitudinal muscles 

 of Dissosteira. 



2DN), passes under the second and third ventral longitudinal muscles 

 (60, 87), then passes dorsally along the tergosternal muscles (83, 84). 

 An anterior ganglionic connective extends anteriorly from the dorsal 

 nerve to the prothoracic ganglion (figs, i, 2, 2ACn), as described by 

 Nesbitt (1941). Near the dorsal nerve junction of this anterior 

 ganglionic connective, a short branch passes to the integument. Just 

 beyond the junction of the dorsal nerve and its connective, a large 

 branch passes anteriorly and provides innervation of the sternopleural 

 intersegmental muscle (59) and the spiracle muscles (79, 80). The 

 transverse nerve of the median system (fig. 2, 2TN) joins this an- 

 terior branch just proximal of the sternopleural muscle innervation. 

 After providing a second long anterior connection to the prothorax, 



