322 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



The fourth ventral longitudinal muscles (88) extend from the first 

 spina to the second spina, passing above the mesothoracic ganghon. A 

 pair of very fine nerves arise from the dorsal surface of the meso- 

 thoracic ganghon, each entering the fourth ventral longitudinal muscle 

 of its side. 



In its innervation, the fifth ventral longitudinal muscle (ii6) ap- 

 pears to be a homologue of the second ventral longitudinal muscle 

 (60). It receives its innervation at its anterior end, from the anterior 

 connection of the metathoracic dorsal nerve, in precisely the manner 

 of the second longitudinal muscle. 



The sixth ventral longitudinal muscle (117) resembles the third ven- 

 tral longitudinal muscle (87). The metathoracic dorsal nerve leaves 

 the ganglion approximately under the anterior end of the muscle, but 

 morphologically it may be said that the dorsal nerve passes ventrad of 

 the muscle. A pair of fine nerves arises from the dorsal surface of 

 the metathoracic ganglion, entering the sixth ventral muscles near 

 spina. 



VIII. THE ANTERIOR GANGLIONIC CONNECTIVES OF THE 

 DORSAL NERVES 



The anterior ganglionic connectives of the dorsal nerves have been 

 described in the Orthoptera by Nesbitt (1941). A comparative study 

 of these features of the nervous system indicates that they may have 

 a much vi^ider distribution than merely the Orthoptera but are not 

 recognizable in some cases because of juxtaposition with the connec- 

 tives of the ventral nerve cord. 



The anterior ganglionic connectives (ACn) in Dissosteira are il- 

 lustrated in figures i and 2. The connective of the mesothoracic dorsal 

 nerve passes under both the second posterior rotator of the coxa {6y) 

 and the sternospinal muscle (61) ; that of the metathorax passes under 

 the posterior rotator of the coxa (93). The route followed by these 

 connectives is thus such that no muscle intervenes between the dorsal 

 nerve connective and the ventral nerve cord, or passes between the 

 connective and the body wall. 



In Dissosteira, the dorsal nerve connectives leave the ganglia and 

 join the dorsal nerves as structures completely free of the nerve cord. 

 In Acheta (fig. 4 A) the prothoracic dorsal nerve connective exhibits 

 a similar condition, but the mesothoracic shows a marked adherence 

 of the connective to the nerve cord. Varying degrees of adherence 

 of both the dorsal nerve connectives and the dorsal nerve may be 

 seen in Periplaneta (fig. 4 B) and Orchelimum (fig. 4 C). The 



