288 



THE CEPHALOPODA 



structure being largely composed of an extension of the sheaths 

 of the tentacles in question. On the ventral side an extensive 

 part of the internal surface of the muscular ring is laminated, 



Fio. 255. 



Male (upper) and female (lower) specimens of Nautilus pompiltus, as seen in the expanded 

 condition ; oral view, showing the disposition of the tentaculifcrous lobes and the differences 

 between the two sexes, a. the shell ; b, the outer ring-like expansion or annular lobe of the 

 circumoral mass of the foot, dorsally forming the hood ; c, the right ami left inner lobes of the 

 foot, each carrying twelve tentacles in the female, in the male divided into p, the " spadix " 

 (hectocotylus) on the left side, and q, the "anti-spadix," a group of four tentacles, on the right 

 side ; d, the inner inferior lobe of the foot (reduced in the male to a paired group of lamellae) ; 

 , the buccal cone, fringing the jaws with a series of minute papillae ; /, the tentacles of the 

 outer lobe, projecting from their sheaths ; g, the two most posterior tentacles, belonging to the 

 hood ; t, superior ophthalmic tentacle ; k, inferior ophthalmic tentacle ; I, eye ; w, paired 

 laminated organ on each side of the base of the inner inferior lobe of the female ; n, olfactory 

 lamellae upon the inner inferior lobe, in the female ; o, the funnel ; p, the sjuidix (in the male) 

 or hectocotylised portion of the left inner lobe of the foot, representing four modified tentacles : 

 g, theantispadix (in the male), being four of the twelve tentacles of the right inner lobe, isolated 

 from the remaining eight. (After Lankester.) 



