§$ 322, 323. THE INSECTA. 401 



Siebold. Ueber die Fortpflanzung von Psyche : Ein Beitrag zur Natur- 

 geschichte der Schmetterliuge — in Siebold and Kclliker's Zeitsch. I. 

 1848, p. 93; see, also, for further researches on the subject, his Bericht iib. 

 die entomol. Arbeiten d. schles. Gesellsch. in J. 1850, or its transl. in the 

 Transact, of the Ent. Soc. I. 1851, p. 234. 



Leydig. Die Dotterfurchung nach ihrem Vorkommen in der Thierwelt 

 und nach ihrer Bedeutung, in the Isis, 1848, Hft. 3. 



Einige Beraerkungen iiber dei Entwickelung der Blattlause, 



in Siebold and K'dliker's Zeitsch. 1850, II. p. 62. 



Anatomisches und Histologisches iiber die Larve von Corethra 



plumicornis, in Ibid. III. 1852, p. 435. 



Zur Anatomic von Coccus hesperidum, in Ibid. V. 1853, p. 1. 



Meyer. Ueber die Entwickelung des Fettkorpers, der Tracheen und 

 der Keimbereitenden Geschlechtstheile bei den Lepidopteren, in Siebold 

 and Kclliker's Zeitsch. 1. 1849, p. 175 ; see also the Mitth. d. naturf. Ges. 

 in ZQrich, Hft. 2, p. 206. 



See, also, the various writings referred to in my notes. — Ed. 



CHAPTER I. 



EXTERNAL ENVELOPE AND CUTANEOUS SKELETON. 



§ 322. 



The cutaneous envelope of the multi-articulate body of the Insecta con- 

 sists, as with the other Arthropoda, of a kind of external skeleton, of a con- 

 sistence sometimes leathery and soft, sometimes horny and solid. Its 

 elasticity and flexibility is limited to the points of junction of the segments 

 of the body, and of the articles of the extremities. Its characteristic 

 chemical substance is likewise chitine, a peculiar azotic matter insoluble in 

 caustic potass, and with which highly-colored pigments are often chemically 

 combined.'^' Chitine enters also into the composition of the hairs and the 

 scales of the skin, and the internal processes which may be regarded as an 

 Internal Skeleton. 



§ 323. 



Histologically, the cutaneous envelope is so variously and often so ex- 



1 See Odier, Mem. de la Soc. d'Hist. Nat. de cutaneous skeleton is probably due to &n oil 



Paris, 1. loo. cit. ; Lassai^ne, Compt. rend. XVI. with which the chitine is impregnated, especially 



1843, p. 1087, or Froriep's neue Notiz. XXVIL p. with the Coleoptera. 



7, and Schmidt, Zur vergleich. Physiol. &c. p. See Bernard-Deschamps, Sur les Elytres des 



32. Lassaigne has proposed for this substance Coltopt^res, in the Ami. d. So. Nat. UI. 1845, p. 



the name Entomoderm. The coloration of the 354.* 



* [ § 322, note 1.] Recent researches have and fVieg-mann^s Arch. 18.50, p. 253 ; SchuUze, 



shown that the peculiar substance Chitine is not Beitr. zur Naturpesch. d. Turbellarien, p. 33 ; and 



limited in its distribution to the Ai-thropoda, for it Lettckart, Morphol. der wirbellosen Thiere, p. 49, 



has been found in nearly every class of the Inver- iu Siebold and Kol/ikeT\<i Zeitsch. 1851, p. 192, 



tebrata. See Grube, M-ulUr's Arch. 1848, p. 481, and in fViegmann's Arch. 1862, p. 22. — Ed. 

 34* 



