VII 



MOLLUSCATHE ARMS OF THE CEPHALOPODA 



117 



which have a common sheath. The anterior portion of the left lobe also carries 

 eight tentacles, and the posterior portion forms the conical spadix, which, instead 



t s 



FIG. 104. Circumoral ring of tentacles in Nautilus pompilius (after Lankester and Bourne). 

 From the oral or ventral side. Upper figure male, lower female, a, Shell ; b, circular fold or hood 

 with its tentacles, g ; c, the two lateral inner lobes, in the male the left inner lobe forms the spadix 

 or hectocotylus p, and the right the antispadix q ; d, the posterior inner lobe, reduced in the male ; 

 n, lamellated organ (olfactory?) ; e, jaws in the buccal cone ; /, the tentacles of the outer muscular 

 circular fold ; I, eye ; m, paired lamellated organ ; o, siphon or funnel. 



of tentacles, carries imbricated lamellae. This spadix is looked upon as the hecto- 

 cotylised limb of the Nautilus, and probably takes some part in copulation (see 

 the Copulatory Apparatus, p. 242). 



2. The Arms of the Dibranchia. 



The Dibranchia have either eight or ten arms, which stand in a circle round the 

 mouth and carry two longitudinal rows of suckers (acetabula) ; rows of cirri may 

 accompany the suckers, and the cirri may here and there become transformed into 

 hooks or claws (e.g. Onychotcuthis). 



