270 THE CEPHALOPODA. ^§ 231, 232. 



ADDITIONAL BIBLIOGRAPHY. 



Reivhnrdt and Prasrh. Oin Sciadephorus Bliilleri en Nudersogelse. 

 Kjobciihavn, 18-4G, niit 5 Tat'cln. 



Prasch. Nogle uye Cephalopoder, beskrevne og anatomisk undersogte. 

 (From the Mer.i. of the Danish Academy 5th ser. I.) Kjobenhavn, 1847. 



Milne Edwards. Regne animal, ed. illustr. MoUusques, PI. 1'. V. V. 

 Y. V. V. (Octopus). — Ed. 



CHAPTER I. 



INTERNAL SKELETON. 



§ 231. 



The Cephalopoda have many cartilages, which, serving as points of inser- 

 tion for muscles, and surrounding the nervous centres, may therefore 

 be reo'arded as the rudiments of an internal skeleton. 



Their texture is essentially the same as that of the true cartilages of the 

 vertebrata. There is a homogeneous, usually yellowish base, having the 

 aspect of ground glass, in which are scattered numerous dark-colored mole- 

 cules. This base contains, moreover, the proper cartilage cavities, which 

 enclose a mass of granules, and each a more or less distinct nucleus. These 

 cavities are more or less numerous, and are often partitioned each into two 

 by a thin septum. 



§ 232. 



These rudiments of an internal skeleton may be divided into the 

 cephalic, dorsal, articular, branchial, and pinnate cartilages. ^^* 



1. The Cephalic cartilage is concave in front and convex behind. It 

 is perforated in the centre by the oesophagus and by two lateral conchoidal 

 prolongations. At its upper part there is a deep excavation for the 

 reception of the brain ; and, at the inferior part, an enlargement containing 

 the auditive organs. It is, moreover, traversed by canals of different sizes 

 for the passage of nerves. The two lateral prolongations cover, by their 

 anterior and concave surface, the ocular bulbs, and are thus the analogues 

 of a kind of orbits. With Loligo, and Sepia, there are, beside, two lanceo- 

 late, cartilaginous lamellae, which join with the anterior and inferior parts 

 of the cartilage, covering the ocular bulb in front, and thus completing the 

 orbit. Nautilus differs very much from the other Cephalopoda in this 

 respect. The lateral prolongations are wanting, and the body, which is 

 incomi)lete above, is much developed below, and has two prolongations 

 extending in front in a forked manner and concealing the auditory 

 organs. ^^' 



1 For the different cartilages, see Scliultze, in XXIX.; and Van Beneden, loc. cit. PI. l.{Argo- 



Meckefs deutsch. Arch. IV. n. 334, Taf. IV. (vi. nautd). 



1, A-G ; Sjiix, Cephalogenesis, p. 3:i, Taf. V. fig. i! See Owen, On the Nautilus, p. 16, 1'l. VIII. flg. 



15-17 ; Mickcl, Syst. d. vergleich. Aiiat. II. Aluh. 1, or Isis. lS:i5, p. 14, or Ami. A. Sc. Nat. XXVIII. 



1. p. 125 ; Hrandt, Medi/.in Zoul. II. p. 303, Tab. p, 102, PI. IV. tig. 1, and yalencienne.t, loc. cit. 



XXXII.; Oii-in, Cyclo]). Aiiat. and Pliys. I. p. p. 271, PI. IX. fig. 4t-6. 

 524, lig. 212, A-D ; IVagner, Icon. zoot. Tab. 



