8i 



the lateral (6) of wliich innervates the dorsal buccal cone, while the median (7) supplies 

 the middle cone, and moreover sends off a slender thread to the false "lips". 



According to Pelseneer, the dorsal and middle cone are supplied by two nerves, 

 arising from a common median trunk. He speaks of a lateral trunk, innervating the anterior 

 tentacle and the ventral cone ; besides there is an anastomosis between the nerves to the 

 ventral and to the middle cone. I could not discover this anastomosis. Finally Pelseneer 

 mentions a lateral slender nerve, rising independently, to the false "lips". In the main 

 points agreeing with him, I cannot, however, entirely share his opinion, as I have explained 

 above (as regards the anastomosis, and the innervation of the "lips"). 



II. The pedal ganglia have a triangular shape (fig. 146) and present a long and rather thin 



commissure [peed) between them. In one specimen, however, the ganglia were close 

 together, and so the commissure was short. The very long anterior pedal commissure {apeic) 

 issues from the base of the median nerve (8), which proceed from the pedal ganglion, as 

 Pelseneer already remarked. From the proximal surface of each ganglion one nerve (9) 

 arises, supplying the fins, and another nerve (10) innervating the lobes of the foot, as the 

 median nerve (8) does too. 



From the lateral part a cervical nerve (11) forms a plexus with another nerve (12) 

 from the pleural ganglion (fig. 144) I have already told that I could not observe this 

 cervical plexus in P neumonoderma in which it is said to exist as well. 



Finally, from the ventral surface of the ganglion and thus on dorsal view concealed 

 for the greater part, a strong nerve issues (fig. 146, 13). I could not clearly make out 

 its destination, but as this nerve passes ventrally to the visceral ganglion, it seems as if 

 it proceeds from this ganglion. Probably it is this nerve which Wagner ') took for a 

 visceral one, when he says, that the lateral nerve of the left visceral ganglion in some cases 

 arises from the pedal ganglion. 



The otocysts are placed in the usual manner. 



III. The pleural ganglia are in apparent juxtaposition to the pedal ganglia, but a connective 

 between these ganglia really exists. The only nerve passing from the pleural ganglion 

 (fig. 144, 12) anastomoses with a pedal nerve and has been mentioned already. 



III. The pleuro-visceral connective (fig. 144, pkf) is shorter than in Pneumonodertna. The 

 visceral ganglia show a scarcely indicated asymmetry, which is distinctly pronounced in 

 the nerves. From each ganglion a strong nerve (14) arises; besides there are two visceral 

 nerves from the left ganglion (15, 16). The lateral of these nerves (16) is stronger than 

 the median (15), w^hose origin is so close to the separation between the ganglia, that a 

 slight mistake as Wagner has committed '), who figured this nerve as having its origin 

 between the two ganglia, may be readily for given. 



i) Die Wirbellosen des Weissen Meeres, Bd. I, p. loo, pL XI, figs. 4, 11 

 2) Op. s. cit., pL XII, figs. I, 12. 



SIBOGA-EXPEDITIE LII. 



