78 Messrs. Hancock and Embleton on the Anatomy of Eolis. 



the anus, appears to have been entirely overlooked by M. de Qua- 

 trefages in his Eolidina paradoxum, in which he says there is a 

 very small anus at the termination of the central channel. In all 

 the species we have examined we have not been able to detect 

 such an orifice, but have found the true anus and intestine as 

 above described in at least fifteen examples of the Eolidince. 



The stomach, PL III. fig. 7, is composed of three coats, a mu- 

 cous, a muscular, and an external one, which we suppose to be 

 serous. The inner surface of the bulb, of the great central 

 channel, and of the primary and secondary branches, is beset 

 with fine numerous longitudinal rugae or plicse, that appear to be 

 formed by projections of the muscular coat covered over by the 

 mucous membrane. In specimens that have been some time in 

 spirits, the mucous coat presents merely a minutely granular ap- 

 pearance ; but we have every reason to think that in the living 

 state it is lined with a layer of ciliated epithelium. The mus- 

 cular coat consists of minute flattened fibres, passing in nearly 

 all directions, the longitudinal and transverse fibres being most 

 distinct. The serous coat appears to be of more homogeneous 

 texture than the others, and much thinner. 



In E. papillostty PI. II. fig. 9, the branches forming the ante- 

 rior pair arise from about the middle of the dorsal surface of the 

 gastric pouch, and are the only ones which come off anterior to 

 the intestine ; they soon bifurcate, the anterior portion is subdi- 

 vided into four branches, the posterior is continued on without 

 further division ; the second pair have their origin in the upper 

 posterior surface of the stomach, and bifurcate like the first pair ; 

 the anterior portion remains undivided, the posterior bifurcates : 

 the two anterior pairs of branches however are not always sym- 

 metrical, as will be observed by referring to the diagram ; indeed 

 we have scarcely seen them alike in any two individuals. The 

 remaining four pairs of branches arise from the central canal, 

 and simply bifurcate. These branches at their origin are all 

 pointed more or less backward ; after their bifurcation they in- 

 cline obliquely forward along the side of the body, lying nearly 

 parallel to each other. From the whole of these branches con- 

 stricted ducts lead into the interior of the branchial papillae. In 

 this species there are from twelve to twenty of these ducts given 

 ofi^ from each row or branch. 



In E. coronata, PI. III. fig. 1, the ramifications of this curious 

 digestive apparatus are somewhat modified. The anterior pair 

 arise from the superior aspect of the lower extremity of the sto- 

 machal bulb, close in front of the origin of the intestine, and 

 each trunk passing forward gives ofi* seven branches, the poste- 

 rior of which is the largest and supplies about seven papillae. 

 There are five or six other pairs, all of which originate in the 



