314 AIR. A. HANCOCK ON THE ANATOMY 



mosing tubes spread over the intestine, the tubes being divided 

 into systems by the interruption of the anastomoses along certain 

 lines where the twigs end in blind sacs, which are occasionally a 

 little enlarged and rounded. The main branches leading from 

 the network exhibit a tendency to divide dichotomously, and 

 unite to form two slender ducts, which pass at once from the 

 intestine to the left side and close to the posterior margin of the 

 stomach, into which they pour the biliary secretion a little in 

 advance of the pylorus. 



In Pelonaia there is only one hepatic duct, which is very 

 slender, and passes in a fold of the lining membrane or " inner 

 tunic " of Husley, that extends from the intestine to the right 

 side of the stomach, a little way in advance of the pylorus. 

 Before terminating, it receives a twig or two from the surface of 

 the stomach ; so that in this genus the liver is apparently not 

 confined to the intestine, but is also spread over a portion of the 

 stomach. The ultimate twigs divide dichotomously with consi- 

 derable regularity, and terminate in round or ovate vesicles, which 

 are very numerous and form a distinct, opaque, yellowish layer. 



The liver in Stycla is not more conspicuous than it is in 

 ^Ascid^a. It is well developed nevertheless, and is provided with 

 its secreting vesicles and ducts. In 8. iuherosa, and, indeed, in 

 all the members of this genus that have come under my observa- 

 tion, there is a fold of the lining membrane within the loop of 

 the alimentary tube, which passes between the stomach and intes- 

 tine. This fold is united to the pyloric end of the stomach, 

 where there is a csecal prolongation of that organ. The hepatic 

 ducts lie within this fold ; and before they reach the stomach, in 

 this species, they unite to form a simple, slender duct, which 

 opens into the left side of the caecum. The branches of the 

 ducts ramify dichotomously over the lower portion of the intes- 

 tine, and communicate with comparatively large rounded vesicles, 

 arranged like those in Pelonaia. 



In Clavelina there is only one hepatic duct, which passes from 

 the middle portion of the intestine, and opens into the alimentary 

 tube immediately below the rounded stomach. The branches of 

 the duct ramify over the intestine, dividing dichotomously, and 

 ending in comparatively large, oval vesicles. Exactly the same 

 form of organ is observed in Perophora ; but in this genus the 

 duct opens through the right wall of the stomach, near the 

 pylorus. The hepatic organ in this interesting form was undoubt- 

 jejily noticed by Dr. Lister ; for he figures and describes, in his 



