386 W.-R. THOMPSON 



accompanics the pair of nerves supplying the seventh segment. 

 The second (d. a."), which is an unpaired nerve, bifurcates in 

 the seventh segment, and the resnlting nerves proceed to the 

 body-wall in association with the nerves supplying the rigth 

 segment. The third and posterior dorsal accessory nerve 

 {(/, a'") bifurcates in the seventh segment. Fach of the resulting 

 nerves undergoes a second bifurcation ; the dextral nerve, 

 bifurcating in the eigth segment, accompanies the nerves sup- 

 plying the ninth segment ; the sinistral nerve bifurcates bet- 

 ween segments eight and nine,andthe resulting nerves proceed 

 to the tenth segment. None of the reniai ning latéral nerves 

 appear to be accompanied by an accessory nerve, of which there 

 are four pairs only. The ganglionic sheath is penetrated by tra- 

 chea", some of which arise from the ganglion in association 

 with the nerves which theaccompany to the body-wall. Two of 

 thèse tracheae are shown (tîg. 53). Similar fine tracheae arise 

 with the three posterior pairs of latéral nerves, and on 

 account of their siifiilarity to accessory nerves I at first mistook 

 them for such, even when dissecting with a magnifîcation of 

 sixty-five diameters, uiitil my sériai sections showed their real 

 nature... » 



« The viscéral ou stomatogastric nervous si/s/em (fig. 54) con- 

 sists of a small central ganglion [c. g.) lying on the dorsal side 

 of the œsophagus, immecliately hehind the transverse commis- 

 sure of the cercbi'al lo])es from the bases of which two ihie ner- 

 ves are given olf to join a tine nerve from the ganglion, wliich 

 runs dorsally toward the anterior end of the dorsal nessel. A 

 fine nerve from the ganglion runs forward on the dorsal side 

 of the œsophagus toward the pharynx. A posterior nerve 

 (fig. 53, V. 11.) runs from the ganglion along the dorsal side of 

 the œsophagus to the neck of theproventriculus, where it forms 

 a small posterior ganglion (fig. 54, pv. g.), from which fine 

 nerve-fîbres arise and run ovor the anterior end of the jiroven- 

 triculus ». 



J'ai cru devoir faire cette longue citation du travail de; 

 Hewitt, non seulement parce que celui-ci ne se trouve pas dans 

 toutes les bibliothèques, mais aussi parce qu'elle donne une idée 

 assez nette de la topographie générale du système nerveux qui 



