OK THK ANATOMY OF NAUTILUS POMPILIUS. 197 



From this pass backwards two nerves into the sponge-work of 

 the pharyngeal wall {ph.n.). Whether they are continued back 

 in this along the sides of the crop to become connected with the 

 gastric ganglion, I was not able satisfactorily to determine. 

 From the aboral end of the buccal ganglion anteriorly a twig 

 passes to a large elevation of the buccal lining, within which it 

 divides up into numerous branches. At its oral end the 

 ganglion passes into the short convex-forwards commissure 

 which connects it with its fellow. From this two nerves pass 

 adorally on each side, the smaller more mesially situated 

 immediately underlying the radula. 



V. The Innervation of the "Inner Inferior Lobe." 



Posterior (ventral) to the buccal mass, well within the hood- 

 tentacle complex, is a flattened lobe, bearing on each side a 

 series of tentacles, separated by a peculiar lamellated organ 

 which has been supposed to be sensory. This lobe is called 

 the "inner inferior lobe" by Lankester. For its innervation 

 there is figured by Owen, and copied by Gegenbaur and others, 

 a small distinct ganglion on each side. In the specimens which 

 I have dissected, however, the conditions are as follows : — Upon 

 each side, somewhat external to the root of the funnel-nerve, 

 there arises from the anterior sub-oesophageal nerve-cord a 

 rather thinner nerve-trunk, which passes into the basal part of 

 the lobe mentioned. This bends towards the middle line, 

 pursues a curved course in the substance of the lobe, and meets 

 with its fellow of the opposite side. The two together form in 

 fact not two separate ganglia, but a continuous cord. The 

 median most strongly curved part of this cord gives off about 

 24 slender nerve-filaments, which radiate forwards to the 

 lamellae of the lamellated organ. The more lateral parts of the 

 cord, on the other hand, give off a stout unbranched nerve to 

 each of the tentacles of the lobe. These nerves, coursing as they 

 do through the fibro-muscular substance of the lobe, are very 

 hard to trace out in their entirety. 



