CEPHALOPODA. 



531 



ascertaining if these muscles presented a corre- 

 sponding degree of development, but found 

 them proportionally smaller even than in the 

 naked Octopus. All trace of internal shell has 

 disappeared in the Ocythoc ; yet there is no 

 muscular connexion between the body and the 

 external shell which contains it. 



The fleshy fibres of the mantle being white 

 like the rest of the muscles, and very compact, 

 are extremely difficult to follow in dissection. 

 Cuvier* observes, that in the Octopus those 

 which are external are evidently longitudinal ; 

 those which are internal, transverse ; and that 

 there are short fibres which pass through their 

 thickness from one surface to another. 



In the Cuttle-fish the muscular fibres of the 

 posterior part of the mantle recede laterally to 

 leave a large space for the lodgement of the 

 sepium or cuttle-bone, which is covered exter- 

 nally by a thin and flaccid skin : the rest of the 

 mantle is formed by a thick muscular tissue, as 

 in the Poulp. The lateral fins are connected 

 not only by the skin, cellular tissue, and vessels, 

 as Cuvier describes, but by a distinct though 

 thin stratum of muscular fibres; these arise 

 from the lateral and dorsal aspects of the apo- 

 neurotic capsule of the rudimental shell, and 

 are inserted into the spinal ridge of the alar 

 cartilage (h, h, fg. 212); from this ridge pro- 

 ceed the fibro-cartilaginous laminae and inter- 

 mediate muscles, which are disposed perpen- 

 dicularly to the ridge, and extend to the mar- 

 gins of the fin. 



In the Calamaries the muscles which con- 

 nect the terminal fins to the body are still 

 more distinct. By means of these fins they 

 are enabled to propel themselves forward in 

 the sea ; and there is good reason for believing 

 that some of the small slender-bodied subu- 

 late species of this genus are enabled to strike 

 the water with such force as to raise them- 

 selves above the surface, and dart, like the 

 flying fish, for a short distance through the 

 air.f 



DIGESTIVE SYSTEM. The animals which we 

 have thus seen to be endowed with so various 

 and formidable means for seizing and over- 

 coming the struggles of a living prey are pro- 

 vided with adequate weapons for completing 

 its destruction, and preparing it for deglutition. 

 These consist of a pair of strong, sharp, hooked 

 mandibles, which are of a horny texture in the 

 Dibranchiate Cephalopod, (a, 6, Jig. 218,) 

 where they are fitted for cutting and tearing the 

 softer animals which they are enabled to catch ; 

 but are strengthened by a dense calcareous sub- 

 stance in the Nautilus, (a, 6, Jig. 217,) which, 

 from its more limited sphere of action, is pro- 



* Menaoire sur le Poulpe, p. 11. 



t See Proceedings of the Zool. Society, Pt. i, 

 1833, p. 90. The faculty possessed by the Cala- 

 marics of darting thiough the atmosphere was not 

 unknown to the ancients. Pliny (Hist. Nat. lib. 

 ix. torn. ii. p. 105, Cuvier's Ed.) says, " Loligo 

 etiam volitat, extra aquam se efferens, quod et 

 pectunculi faciunt sagittae modo ;" and so general 

 appears to have been this belief that Varro sup- 

 posed the name Loligo to be a corruption of Voligo. 

 " Loligo dicta, quod subvolat, littera commulata, 

 primo Voliyo."De Ling. Lut. lib. iv. p. 21. 



bably restricted in regard to food to such crus- 

 taceous and testaceous animals as it may sur- 

 prise by stealth, and whose defensive armour it 

 is thus enabled to break up.* 



The mandibles, which are hollow sheaths, 

 like the horny covering of the beak of a Bird 

 or Tortoise, are fixed upon a firm fleshy sub- 

 stance, (c, c, Jig. 217,) which resembles the 



Fig. 217. 



Mandibles of the Navtiliu. 



animal part of bone after the earth has been 

 removed by means of an acid. At the base of 

 the mandibles the fibrous structure of this part 

 becomes apparent, and a strong stratum, 

 (g, Jig. 217,) passing between the bases of the 

 mandibles, serves for their divarication ; their 

 closure is effected by fasciculi of muscular 

 fibres, which surround them externally near 

 the reflection of the circular lip. When the 

 mouth is closed, the lower mandible (6) over- 

 laps the upper (a). 



The oral aperture is in the centre of the 

 base of the feet, and appears in the form of a 

 small circular orifice, formed by the contracted 

 fleshy lip wjiich surrounds and more or less 

 conceals the mandibles. 



In the Nautilus the margin of the lip (c) is 

 beset with several rows of elongated papillae, 

 irregularly disposed ; external to which are 

 the labial processes with their tentacles : 

 these, in the specimen we dissected, com- 

 pletely overlapped and concealed the oral ap- 

 paratus. 



In the Calamaries the jaws are surrounded, 

 external to the fringed circular lip, by a thin 

 membrane, which is produced into short pyra- 

 midal processes, corresponding in number to 

 the eight feet, and supporting minute rudimen- 

 tal suckers ; thus imitating the external feet, 

 as the labial processes of the Nautilus repeat 

 the structure of the digital processes. In the 

 genus Sepioteuthis the circular lip immediately 

 surrounding the jaws is tumid and plicated, 

 but not papillose ; external to it are two cir- 

 cular ridges of membrane, then a thin mem- 

 brane with jagged margins, and lastly a mem- 

 brane with its margin produced into eight 

 angular processes, which are not, however, 

 free, as in Loligo, but are tied down in the 

 interspaces of the eight legs ; small rudimental 

 suckers may be observed on these processes. 



* The digestive canal of the Nautilus was found 

 filled exclusively with the remains of a species of 

 crab. 



