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



Sciences Naturelles' a very elaborate article by M. A. de Quatre- 

 fages on what that gentleman considers a new generic form, to 

 which he has given the name Eolidina paradoxum ; this he states 

 differs from the typical organization, not only in its digestive 

 apparatus, but also in many other respects, and in some instances 

 in the most extraordinary manner. 



The subject of M. de Quatref ages' memoir however does not 

 vary in any external characters from Eolis, to some of the British 

 species of which it is closely allied. We should therefore expect 

 the anatomy of Eolidina paradoocum to coincide pretty accurately 

 with that of Eolis, at least not to deviate from it to any extent 

 in the more important organs ; yet very considerable deviations 

 do exist, if the observations of M. de Quatrefages be correct. 

 Several of these observations however we are disposed to question. 



Previously to the publication of the memoir just named, we had 

 investigated the anatomy of Eolis in company with Mr. Joshua 

 Alder, and although many of our results were borne out by those 

 of the French naturalist, yet in several important particulars we 

 found that we entirely disagreed with him. We have therefore 

 reinvestigated the matter with much care, and particularly with 

 reference to the points in dispute, and have been able to corro- 

 borate our original views in the most satisfactory manner. 



The subject is of considerable interest, as it is principally on 

 his views of the anatomy of Eolidina and two other allied species 

 that M. de Quatrefages has proposed his order Phlebenterata. 



It is therefore desirable that the anatomy and physiology of 

 the Eolidina should be fully ascertained. 



With a view to this we now publish the results of our researches, 

 hoping that they may have the effect of fixing the attention of 

 others more able than ourselves to inquire into the matter. 



W^e would premise that, in the following paper, where no au- 

 thority is given after the name of any species mentioned, it must 

 be understood that that species has been described by Messrs. 

 Joshua Alder and Albany Hancock. 



We have chiefly turned our attention to Eolis papillosa, John- 

 ston, probably E. Cuvierii of French authors, PL I. fig. 1 ; not 

 more on account of its general resemblance in form to Eolidina 

 paradoxum than for the advantages presented by its great size, 

 which has enabled us to ascertain by actual dissection almost 

 every point of importance. 



Of this species we have had numerous specimens, both alive 

 and in spirits, and in all stages of growth, from two lines to two 

 inches in length. 



It is slightly depressed, tapering more abruptly than usual to 

 a point behind ; both the dorsal and oral tentacles are simple, 

 short and conical ; the branchial papillae are slightly compressed 



