12 INTERNAL ANATOMY OF INSECTS. 
guous as to resemble the rattle of the rattle-snake?. In 
others the internodes are longer, and the ganglions occur 
at nearly equal intervals, as in the larva of the Ephe- 
mere»; but in the majority they are unequal in length : 
thus in the scorpion the three first ganglions are the most 
distant®; in the hive-bee the third and fourth’; and in 
the spider the last ¢. 
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‘; in the water scorpion 
there are ¢wo&; in the louse there are three"; in the rhi- 
noceros-beetle there are four'; jive in the stag-beetle* ; 
seven in the hive-bee and some Lepidoptera!; eight in the 
grub of the stag-beetle™; nine in the great Hydrophilus? ; 
ten in Dytiscus°; eleven in the grub of the great Hydro- 
philus? ; twelve in the grub of Dytiscus and the caterpil- 
lars of Lepidoptera; thirteen in the larva of Ashna' ; 
and twenty-four in Scolopendra morsitans*. You must 
observe that, generally speaking, the number of ganglions 
@ Cuv. ubi supr, 325. » Swamm. Bibl. Nat. t. xv. f 6. 
¢ Treviran. Arachnid. t. 1. f. 13. 1—4. 
¢ Swamm. wbi supr. t. xxii. f. 7. 
© Treviran. whi supr. t. v. f. 45. {PLATE XX. Pigs 7. 
§ Cuy. Anat. Comp. ii. 346. * Pirate XXI. Fic. 8. 
Cuv. ubi supr. 337. © [bid. 335—. 1 Ibid. 348. 
m Ibid. 320—. " Ibid. 340—. ° Ibid. 338 —. 
P Gaede ubi supr. 
1 Cuv. ubi supr. 323—. 327—. Mr. Bauer (Phil. Trans. 1824. t. ii. 
J. 1.) has figured only seven, excluding the brain, in that of the silk- 
worm, and Malpighi (De Bombyc. t. vi. f. 2.) ten, —Swammerdam 
( Bibl. Nat. t. xxviii. f. 3.) however has twelve. 
" Ibid. 326. © Ibid. 352. 
