294 Mr. A. Hancock on the Anatomy of Oithona. 



The hepatic apparatus is very peculiar in this animal. The 

 pyloric extremity of the stomach receives two biliary ducts, one 

 on each side of the intestine. These ducts or hepatic canals 

 (PL X. fig. 1 e> e) are nearly as wide as the intestine, and, diver- 

 ging as they leave the stomach, very shortly pass into the skin at 

 the sides of the back, where each opens into a wide channel that 

 extends nearly the whole length of the body. The channels 

 receive numerous branches (/), which communicate with the 

 glands of the papillse, and as they approach the lateral expansion 

 at the side of the body, they appear to be subdivided several 

 times. The exact order of their subdivisions, however, was not 

 determined ; but as the papilla? have no definite arrangement, it 

 is probable that these branches also are irregularly disposed. 

 The anterior portions of the great hepatic channels are appa- 

 rently connected with two folliculated glandular bodies {g, g) 9 

 much and irregularly sacculated. These bodies are united to 

 the skin, one on each side near the region of the stomach, and 

 probably form the inner walls of those portions of the channels. 

 Amidst the cellular tissue at the extremity of the body, behind 

 the ovary, there is likewise a glandular substance (A), of a reddish 

 colour, folliculated and apparently branched, in connexion with 

 the branches of the hepatic canals (i) within the skin. These 

 branches at the posterior portion of the body probably form a 

 sort of network of tubes across the dorsal aspect. Such perhaps 

 may be inferred from the appearance the branches present when 

 the skin of the back is divided down the median line. 



The arrangement of the hepatic canals differs from that which 

 prevails in the Eolidida. In Eolis, Embletonia, Doto, Dendro- 

 notus, Lomonotus, and Antiopa f the principal canals lie free in 

 the visceral cavity, and in all of them there is a median posterior 

 trunk. In this genus there is no such trunk, and the canals 

 are almost entirely within the skin. In these respects Oithona 

 would appear to resemble Hermaa, in which the whole of the 

 hepatic ramifications are apparently connected with the skin, 

 and there are only two principal trunks, which pass down the 

 sides of the back. It is evident, however, that the digestive 

 system alone sufficiently distinguishes Oithona from all the above 

 genera, not even excepting Hermaa. 



The hepatic glands are large, nearly filling the papillse ; they 

 are slightly and irregularly sacculated, with the inner surface of 

 the investing membrane lined with a dark granular substance ; 

 above, this substance is very abundant, forming a dense mass; 

 below, the membrane in some of the papillse is entirely devoid of 

 it. We failed to detect any ovate vesicle like that of Eolis in 

 the apex of the papillse, neither have we been able to determine 

 whether or not the apex is perforated. 



