$^ 322, 323. THE INSECTA. 401 



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

 geschichte der Schmetterlinge — in Siebold and Killiker's Zeitsch. I. 

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

 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. 



ICinige Bemerkungen über dei Entwickelung der Blattläuse, 



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



Anatomisches und Histologisches über die Larve von Corethra 



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



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



Meyer. Ueber die Entwickelung des Fettkörpers, der Tracheen und 

 der Keimbereitenden Geschlechtstheile bei den Lepidopteren, in Siebold 

 and K Hiker's Zeitsch. 1. 1849, p. 175 ; see also the Mitth. d. jiaturf. Ges, 

 in Zürich, Hft. 2, p. 206. 



See, also, the various writings refei-red 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 

 corabined.^^' 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'llist. Nat. rie cutaneous skeleton is probably due to an oil 



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



1813, p. 10S7, or Froriep's neue Notiz. XXVII. p. with the Coleoptera. 



7, and Schmidt, Zur vergleich. Physiol. &c. p. See Bernard-Üeschomps, Sur les Elytres de» 



32. Lassaisne has proposed for this substance Col»opt<;res, in the Ann. d. So. Nat. III. 1845, p. 



the name Entonioderm. The coloration of the 354.* 



* [ § 322, note 1.] Recent researches have and JViesmann's Arch. 1850, p. 253 ; Schultze^ 



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



limited in its distribution to the Arthropoda, for it Leuckart, Morphol. der wirbellosen Thiere, p. 49, 



has been found in nearly every class of the Inver- in Siehold and Kölliker''s Zeitsch. 1851, p. 192, 



tebrata. See Grube, Müller\'t Arch. 1848, p. 461, and in JVieg?nann's Arch. 1852, p. 22. — Ed. 



34* 



