DENDRONOTUS, 



the veil, for we have seen the blood passing to and fro in each of these organs so as to leave 

 little doubt of their branchial nature. The foot is linear and slender, formed as much for 

 clasping corallines and sea-weeds as for crawling on a flat surface, though from the thin and 

 pliant nature of its sides it may be used for either purpose. The sexual aperture is situated 

 on the right side below the first branchial tuft, and that of the anus further behind and a 

 little above, between the first and second branchiae. 



The digestive system varies in some respects from that of Uolis. The mouth and jaws 

 are the same, the latter varying only a little in form (f. 5). The tongue occupies in the 

 same manner the ridge of a wedge-shaped muscle that rises in the centre of the mouth, and 

 has a similar complicated muscular apparatus for its movement. In D. arborescens this 

 organ is composed of upwards of twenty transverse rows of curved, denticulated spines, with 

 a large central one, also denticulated. Each row contains twenty of the small spines, which 

 are brilliantly crystalline, the whole forming a very beautiful object for the microscope 

 (f. 6, 7, 8). On account of the smallness of our specimens we were not able to detect the 

 salivary glands, but as we did not find them outside the buccal mass, they are probably con- 

 cealed by the jaws, as in Bolls. The oesophagus is much larger than usual, and opens into 

 a well-defined stomachal pouch, which terminates in a short intestinal canal that opens on 

 the right side between the first and second branchial tufts. The hepatic organ, however, 

 shows the widest deviation from the structure of JEolis. The central vessel in Dendronotus 

 is not a mere canal passing from the stomach and receiving the branches from the glands of 

 the papillae or branchial tufts, but is a large folliculated mass (f. 2, 3) occupying the centre 

 of the body— occupying, in fact, the very position of the liver in the Doridida and 

 Tritoniadce, and communicating with the stomach by a constricted duct. From this mass 

 branches pass off into the branchiae and tentacular sheaths: these branches lose their 

 follicular structure and become mere tubes as they pass into the smaller ramifications of 

 these organs. They are lined, however, through their entire length, with the granular 

 substance observed in the other portions of the hepatic apparatus. The sides and upper 

 anterior portion of the stomach are covered with follicular masses, resembling in every 

 respect the great central trunk, which, as well as the stomach, is lined with vibratile cilia. 

 The central trunk of the digestive system lies above the ovarium, and not below it as in 

 Uolis. In this respect, as well as in the glandular structure of the central trunk or mass, 

 and in its separation from the stomach by a constricted duct, Dendronotus shows a deviation 

 from the type of the Uolidida, and an approximation to the Dorididce and Tritoniada, thus 

 supplying a connecting link between these two forms of gastric structure in the Nudi- 

 branchlata. 



The vascular system is furnished with a well-developed heart, consisting of a ventricle 

 and auricle, and in other respects does not appear to differ from the rest of the family. 



The nervous system is very similar to that of Eolis. The cerebral ganglions are four 

 in number (f. 9,) and are placed symmetrically, giving off nerves much in the order observed 

 in that genus. Of these we have been able to determine ten pairs. The ganglions of the 

 dorsal tentacles (the olfactory ganglions) are larger than usual (9 a, a,) and are placed at the 

 base of the laminated portion of these organs, consequently at a considerable distance from 

 the eerebral ganglions, to which they are united by large nerves : these form the first pair. 

 The eyes are very small. They are composed of a well-formed pigment cup, a lens, and a 



