10 INTERNAL ANATOMY OF INSECTS. 
are distinguished only by a longitudinal furrow, and even 
where they are really distinct and separable, in the body 
of the insect they lie close together. In Oryctes nasi- 
cornis and Acrida viridissima &c. all the internodes con- 
sist of a double chord >; but in many other insects nume- 
rous variations in this respect occur.— Thus in the stag-— 
beetle the dast internode is single*; in the caterpillar of 
the cabbage butterfly (Pieris Brassica) the five first are 
double, and the séx Jast single‘ ; in that of the great goat- 
moth (Cossus ligniperda) the three first only are double, 
but the others terminate in a fork®; in the cock-roaches 
(Blatta) the four first, in Hydrophilus piceus the three 
first, and in Llophilus tenax the two first only are double, 
the rest being all single*. A singular variation takes 
place in Hypogymna dispar ; ail the internodes are single, 
except the second, the chords of which at first are sepa- 
rate, and afterwards united’; and, to name no more, in 
Clubiona atrox there is only one internode, which is sin- 
gle, with a longitudinal furrow’. In some, as in the louse, 
the grub of Oryctes nasicornis, and the cheese-maggot, 
there are no internodes, the spinal marrow being formed 
of knots separated only by slight or deep constrictions. 
I must next say something of the ganglions*. Lyon- 
net has observed that, in the caterpillar of the great goat- 
* Swamm. wb supr. 112. a. 
> Cuv. Anat. Comp. ii. 337. 343--. 
© Tbid. 336. 4 Herold Schmetterl. t. ii. f. 1. 
© Lyonnet Anat. 98. 
‘ Cuv. ubi supr. 342, Gaede N. Act. Acad. Cas. XL. ii. 323. Cuv. 
Thid. 351. & Ibid. 348. 
h Treviranus Arachnid. t. v. f. 45. 
' Prats XXI. Fic. 7. 8. Swamm. Bibl. Nat. t. xliii. Sea: 
* Prare XXI. Fic. 1. 7. 8. ¢. 
