12 INTERNAL ANATOMY OF INSECTS. 



by numerous radiating nerves a ; in others again, as in 

 the scorpion, they are all abdominal. The ganglions 

 vary also in their situation with respect to each other. 

 Thus in some, as in the larva of the Chamaeleon-fly 

 (Stratyomis Chamaeleon)^ they are so near as to appear 

 like a string of beads b ; in that of the ant-lion (Myrme- 

 Icori) the two ganglions cff the trunk are separated by an 

 interval from those of the abdomen, which are so conti- 

 guous as to resemble the rattle of the rattle-snake c . In 

 others the internodes are longer, and the ganglions occur 

 at nearly equal intervals, as in the larva of the Ephe- 

 merae* ; but in the majority they are unequal in length : 

 thus in the scorpion the three first ganglions are the most 

 distant e ; in the hive-bee the third and fourth f ; and in 

 the spider the last g . 



2. The ganglions also in different species, and often 

 in the same insect in its different states, vary in their 

 number. Thus in the grub of the rhinoceros-beetle the 

 whole spinal marrow appears like a single ganglion di- 

 vided only by transverse furrows h ; in the water-scorpion 

 there are two l ; in the louse there are three k ; in the rhi- 

 noceros-beetle there arejfowr l : five in the stag-beetle m ; 



a PLATE XXI. FIG. 7- 



b Swamm. .ubi supr. t. xl./. 5. Cuvier (ii. 33.2.) accuses Swam- 

 merdam of representing the spinal marrow in this grub as producing 

 nerves only on one side ; whereas he expressly states (ii. 50. b.) that 

 a considerable number spring on each side from the eleven ganglions, 

 but that to avoid confusion he had omitted some. 



c Cuv. ubi supr. 325. d Swamm. Bibl. Nat. t. xv./. 6. 



e Treviran. Arachnid, t. I./. 13. 14. 



f Swamm. ubi supr. t. xxii.jf. 7. 



E Treviran. ubi supr. L v. /. 45. h PLATE XXI. FIG. 7. 



1 Cuv. Anal. Comp. ii, 346. k PLATE XXI. FIG. 8. 



1 Cuv. ubi supr. 337. m Ibid. 335. 



