CEPHALOPODA. 



527 



which can lend but a feeble assistance in main- 

 taining the shell in its natural position. 



The mantle of the Nautilus is very thin and 

 membranous, excepting at its free margin, 

 where it is provided with longitudinal mus- 

 cular fibres for its retraction, and a thin exter- 

 nal stratum of transverse fibres, for the closing 

 of its anterior aperture, during the expulsion 

 of the respiratory currents. 



The large mandibles (a, b, Jig. 217; e, f, 

 Jig. 219,) are supported upon a fleshy substance 

 (g, Jig. 217), and moved by appropriate mus- 

 cles. The fringed lip (c, Jig. 217) which sur- 

 rounds them is provided with a longitudinal 

 stratum of fibres for its retraction, and an exte- 

 rior orbicular sphincter at its anterior margin. 

 The whole buccal apparatus is attached to the 

 cartilaginous skeleton by four strong retractor 

 muscles, two above (h, h, Jig. 217, 219), and 

 two below (i, i, Jig. 217), and its base is sur- 

 rounded by a transverse stratum of muscular 

 fibres (i, Jig. 219) continued from the external 

 labial processes, across the upper or dorsal 

 aspect of the jaws, which, by the contraction 

 of these fibres, are protruded outwards. 



The tongue (Jig. 236) is a large complex 

 muscular organ, the extremity of which is 

 retracted by two pair of long slender muscles 

 (^) arising from the dense membrane closing 

 the lower part of the mouth ; a third pair of 

 muscles (6) given off from the posterior mar- 

 gins of the lower mandible are inserted into 

 the anterior extremity of the horny lingual 

 rasp hereafter to be described. Other internal 

 muscular parts will be mentioned in the de- 

 scription of the viscera to which they relate. 



The muscular system of the Dibranchiate 

 Cephalopods, like their internal skeleton, is 

 much more elaborately developed than in the 

 inferior order of which the Nautilus is the 

 type : but the same plan may be observed to go- 

 vern the disposition of all the principal masses. 



A hollow cone of muscular fibres is attached 

 by a truncated apex to the anterior margin of 

 the cephalic cartilage, or to processes deve- 

 loped therefrom, in order to afford these fibres 

 an increased surface of origin. The fibres are 

 interlaced, one with another, in a close and 

 compact manner as the cone expands to 

 form the cavity containing the fleshy mass 

 of mouth ; and at the anterior extremity of 

 the mouth they are continued forwards and 

 separate into eight distinct portions, which 

 form the arms. 



These organs are developed in a kind of 

 inverse proportion to the body, being generally, 

 as Aristotle* twice takes occasion to observe, 

 longest in the short round-bodied Octopi or 

 Poulps, and shortest in the long-bodied Cala- 

 maries, Sepiae, &c. in which the two elongated 

 retractile tentacles (d, Jig. 207, 208, 209) are 

 superadded, by way of compensation. These 

 latter organs are rarely continued from the 

 muscular cone inclosing the apparatus of the 

 mouth, but arise from the cephalic cartilage, 

 close together, internal to the origins of the 



* De Historia Aniiiiiilium, (Ed. Schneider, Lip- 

 siae,) lib. iv. c. 1. 8 & 9. 



ventral pair of brachia; tliey proceed at first 

 outwards to a large membranous cavity situated 

 anterior to the eyes, and thence emerge between 

 the third and fourth arms on either side. 



The acetabula or suckers are disposed along 

 the whole extent of the inner surface of the 

 ordinary arms, but are generally confined to 

 the extremities of the tentacles, where they are 

 closely aggregated on the inner aspect. 



Of the difference between the arms and 

 tentacles Aristotle was well aware, and ac- 

 cordingly, with his usual exactness, he applies 

 to them distinct epithets : no'Jn; /*fv oSv OXTOJ 



f^EI XO.I TCUTSUf JlXOTIjXou? TTaVTCt K^riV IVOf yiVOC 



7roAu7ro'J'a>. "ijia 5' I^ouc-iv al' TS cwriai xai ai aiufliJic 

 xa; ot Tivdoi tivo OTpo/Jocrxi'Sac juaxpa; ITT' axpaiv rpa- 

 XU'TOTO l^wVttt j.xrrtAov.* " All (mollia) have 

 eight feet, provided with a double series of 

 suckers, except in one genus of Polypi.f The 

 Sepiae, Teuthides, and Teuthi,J have, besides, 

 two long probuscides, the extremities of which 

 are beset with a double series of suckers." 

 Pliny gives, after the Stagyrite, the fol- 

 lowing notice of their functions, " Sepiae et 

 Loligini pedes duo ex his longissimi et asperi, 

 quibus ad ora admovent cibos, et in fluctibus 

 se, velut ancoris, stabiliunt." German authors 

 generally term the ordinary feet, 'arms,' (urme,) 

 and the tentacles ' seizers,' (fangarme.) 



In the Cephalopods which have only the 

 eight normal feet, these present many vari- 

 ations ; and, although they are generally re- 

 markable for their length, yet in some species, 

 as the Octopus brevipes, they are extremely 

 short, resembling the digital processes of the 

 Nautilus. In Octopus Eylais, the first or 

 dorsal pair is alone developed so as to serve 

 as a locomotive organ,and the animal mustcrawl 

 along the ground by means of this pair only. 



In most Octopods the first pair of feet is the 

 longest. In Octopus Aranea, in which the 

 feet apparently present the maximum of de- 

 velopment, the dorsal feet are ten times, and 

 the ventral ones five times, the length of the 

 body. Besides their superior length the dorsal 

 feet present other peculiarities in this family 

 of Cephalopods. In the genus Argonauta 

 (Jig. 206, c 1,) they are provided with expanded 

 membranes, the fabled use of which has af- 

 forded a beautiful subject for poetic imagery 

 in all ages ; but similar appendages occur in 

 Octopus violaceus, and in Octopus velij'er, in 

 which both the first and second pairs of feet 

 support broad and thin membranes at their 

 extremities. Now neither of these species in- 

 habit a shell, in which the expanded mem- 

 branes could be used to waft the animal along 

 the surface of the ocean, as has been said or 

 sung of the Argonaut from Aristotle to Cuvier, 

 from Callimachus to Byron. The physiologist, 

 in contemplating the structure of the velated 

 arms, is compelled to disallow them the power 

 of being maintained erect and expanded to 



Ibid. lib. iv. c. 1. 4. 



t The genus Eledune of Aristotle, the eight feet of 

 which have only a single series of suckers upon each. 



$ Species of Loliijo or Calamaries, supposed to 

 be the Loliyo viilt/aris aiid Loliyo media of modern 

 naturalists. 



