30 Mr. A. Hancock on the Anatomy of Antiopa Spinolse. 



of anastomosing tubes^ which form a network (PI. II. fig. 1 i & 

 PI. III. fig. 4 d) across the dorsal aspect in front of the anus. 

 This network inosculates with the minute twigs of the hepatic 

 oi'gan leading to the papillse^ and is apparently connected with 

 a dense gland-like body (PI. II. fig. 1 j & PI. III. fig. 4 c) 

 surrounding the termination of the intestine. There can be little 

 doubt that this network of tubes_, which is unnoticed by M. 

 Blanchard, is part of the hepatic apparatus ; and from its inter- 

 nal position points out Antiopa as one of the intermediate forms 

 connecting the Eolididse with the other families of the Nudi- 

 branchs. 



The digestive system of this animal thus becomes of great 

 interest, while it is evident that the hepatic canals are arranged 

 after the type of those of Eolis, in which the anterior ones always 

 enter the sides of the stomach from above, and the posterior or 

 central one from behind and below the pylorus : — the stomach 

 being, in fact, perforated by three hepatic ducts in the same 

 manner as it is in Antiojia. The chief differences being that in 

 this latter animal the anterior branches are excessively developed, 

 and the central one is below the ovary. 



Vascular Si/stem. — From deficiency of specimens, I have not 

 been able to investigate the circulatory ap})aratus to any great 

 extent. The heart is placed about the middle of the back im- 

 mediately below the skin, having the intestine in front, and the 

 ovai"y beneath exactly as in Eolis. The pericardium is of excessive 

 tenuity, and is of a pretty regular oval form. The ventricle 

 (PI. II. fig. 1 k) lies in front, and when contracted is irregularly 

 elliptical; it is rather large and muscular. The auricle (/) is 

 delicate, membranous, and is connected to the posterior margin 

 of the ventricle : at this point the two chambers of the heart 

 communicate. The aorta passes from the front of the ventricle, 

 and dipping almost directly beneath the intestine, gives off 

 branches to the generative organs, to the stomach and to the 

 buccal mass, in the same manner as in Eolis. I did not observe 

 the pedial artery, though there can be no doubt of its existence 

 as described by M. Blan chard. The auricle receives in front, 

 on either side, a large trunk vein which communicates with 

 numerous small branches from the skin, and is apparently joined 

 behind, on the median line, by two other large trunks, that on 

 the right side being considerably the smaller. There are several 

 other small vessels, but whether they entered the posterior margin 

 or belonged to the lateral trunks, I could not determine. This 

 is so different from what is observed in the other Eolididse, that 

 I should have doubted the accuracy of my observations, had not 

 M. Blanchard described numerous vessels entering the posterior 

 margin of the auricle. It would therefore appear that the 



