ANCULA. 



cipal branches of the leaflet, appearing in these parts as a double row of white dots. The 

 walls of the vesicles are firm, and undoubtedly possess some degree of resiliency. 



The oesophageal ganglia are not so much concentrated as in Idalia, in this respect 

 agreeing with Polycera. In Jncula there are six principal ganglia, in three pairs. The 

 cerebroids are placed above the alimentary tube, and are broadly fusiform, with their apices 

 united across the median line. These supply nerves to the channel of the mouth, the lips, and 

 dorsal tentacles ; the channel and labial nerves are three in number ; the olfactory or tentacu- 

 lar have each a small round ganglion at the origin, and from the root of these latter nerves 

 there is also a minute twig given off, which goes apparently to the tentacular filaments at the 

 base of the dorsal tentacles. The branchial ganglia are spherical, and are cemented to the 

 under side of the cerebroids ; they are placed at the sides of the oesophagus, and give off each a 

 large nerve from behind, which supplies the dorsal skin. The right branchial also supplies, from 

 the anterior margin, a nerve which goes to the root of the penis, and there joins a minute ganglion 

 from which three or four small twigs are given to the intromittent organ. The pedial ganglia 

 are situated below the alimentary tube, and are of the size and form of the branchial ; they 

 are closely united to the other two pairs above, and to each other below ; thus completing 

 a constricted collar of ganglia round that tube ; they send three or four nerves to the foot. 

 A small visceral ganglion is attached to the right branchial, at its junction with the pedial. 

 Two or three nerves issue from it, which will, there can be no doubt, go to the viscera ; but, 

 from the minuteness of the species, we have failed to trace them. A delicate cord likewise 

 passes from this ganglion, and, going to the branchial of the opposite side, forms the 

 branchial collar. 



There is nothing peculiar in the buccal ganglia, except that the commissure which unites 

 them across the median line is rather long. The gastro-cesophageal ganglia have not been 

 observed. 



The eyes have the usual development ; they are seated each on a minute round ganglion, 

 which is sessile on the outer margin of the cerebroids. The auditory capsules contain numerous 

 otolithes, but we have not succeeded in determining to which ganglia they belong. 



Vibratile cilia appear to clothe the whole surface of the animal ; they have been detected 

 along the margin of the foot, and ridge of the back, on the gills and lateral papilla?, on the 

 dorsal and oral tentacles, and on the tentacular processes. 



The skin is smooth, soft, and delicate, with scattered imbedded spicula of a cylindrical 

 form, bent in the centre and a little enlarged at the ends. 



