The anatomy of Lucapina crenulata. 471 



circum-pallial chord which will be spoken of later. These branches 

 of the anterior mantle nerves lie in that part of the mantle lining the 

 anterior part of the shell, that is the dorsal wall of the mantle cavity. 

 A well prepared nitric acid specimen shows these nerves with very- 

 little dissecting, but I have not been able to trace them by any other 

 method. 



The intestinal ganglia. The subintestinal ganglion gives 

 off three nerves, first, that to the visceral ganglion (Vis.g), second, 

 a large nerve (5) running into the body wall to the gill ganglion (G-.g) 

 and third, a small nerve {R.i.p) that springs from between these last 

 two, and runs back just with in the wall. Haller ('94) discribed 

 this latter nerve in Fissurella costaria, as the genital nerve, but if 

 we follow it in L. crenulata we find that all of its branches go into 

 the mantle, some of them reaching almost to the posterior end of the 

 animal. Where these nerves come in contact with those going to the 

 mantle from the pleural chords, they fuse (2), and are thus connected 

 to the circum-pallial chord. The supraintestinal ganglion also gives off 

 three similar nerves. Here the small central one {L. i.p) has a some- 

 what ditierent course, running back and down along the wall. One 

 of its fibres, as on the right side, fuses with a pleuro-pallial connective 

 (2)] while another branch passes backward and unites directly with 

 the circum-palHal cord. Lacaze-Duthieks has described nerves 

 similar to these in Halioiis, naming them internal palliai nerves. This 

 name seems to describe these nerves very well so I have used it here. 

 In Fissurella costaria, Haller ('94) describes a nerve which seems 

 to be homologous with the left internal palliai of Lucapina, and calls 

 it the intestinal nerve. Though I made a careful dissection of this 

 part I could trace no connection with the alimentary canal. 



The visceral ganglion is simply a thickening of the posterior part 

 of the visceral loop. This ganglionic enlargement extends further for- 

 ward on the right side than on the left. I have found great variation 

 in difi'erent specimens as to the nerves given off from this thickened 

 chord. Usually there are two nerves coming from the right side of 

 the ganglion (K.-K) going to the right kidney. A large one (Pig. Ba) 

 from the median line the reno-anal nerve, proceeds at once upward 

 after leaving the ganglion, passing along in ihe posterior wall of the 

 basibranchial sinus. A small branch is given to the external papilla 

 of the right nephridium (5), and a little further along nerves are given 

 off to the walls of the ventricle (4). On the under side of the rectum 

 the reno-anal bifurcates, one part going up on each side of the rectum. 



Zool. Jahrb. XVI. Abth. f. Morph. gj^ 



