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



hydrofluoric acid in the nascent state corroded them extensively, 

 leaving little doubt in oiu* minds that the spines are composed of 

 siliceous matter. 



It is difficult to understand how M. de Quatrefages could have 

 mistaken the buccal mass for the stomach, and yet there is no 

 doubt that he has done so in Eolidina. From his diagram it ap- 

 pears clear that he has not understood the parts, and his de- 

 scription sets the matter at rest. At page 284 of his memoir, 

 after describing as the oesophagus the channel that leads 

 through the lips to the buccal mass, that gentleman goes on to 

 say, " En arriere de I'cesophage, on aper9oit une masse oblongue, 

 formee par des fibres musculaires entrecroisees. La cavite oeso- 

 phagieune se continue dans son interieur en s'y retrecissant au 

 moins dans I'etat de vacuite oii etait cette portion de I'appareil 

 digestif chez les individus que j'ai examinees, Peut-etre est-ce la 

 le lieu oil se fait la digestion des substances avalees par Tanimal. 

 Du moins, dans im autre mollusque fort voisin de celui-ci, et que 

 j'ai rencontre egalement k Saint Vast, je trouvai dans un organe 

 entierement semblable un petit poisson, dont toutes les parties 

 molles avaient entierement disparu, et dont la colonne vertebrale 

 elle-meme commenyait a se dissoudi-e par Taction des forces di- 

 gestives.'' And in the next paragraph adds, "Au-dcla de ce 

 hulbe stomachale, si I'on pent s'exprimer ainsi, commence le veri- 

 table intestin." It appears to us that this naturalist has here 

 drawn a hasty conclusion from an imperfect observation. But 

 afterwards, in a paper on his proposed order Phlehenterata, he re- 

 cognises the tongue of Actceon elegans, which also at first sight 

 he mistook for the back-bone of a small fish. Now the tongue of 

 Actceon resembles closely that of several small species of Eolis, so 

 that we trust that by this time M. de Quatrefages has come to a 

 recognition of the true signification of the parts in Eolidina pa- 

 radoxmn. 



The account however of the anatomy of this latter animal in 

 the 'Annales des Sciences' for May and June 1843, shows at 

 once that M. de Quatrefages has mistaken the outer lip for the 

 mouth, the channel of the mouth for the oesophagus, the mouth 

 itself for the stomach, and the stomach for the "veritable 

 intestin." 



In minute specimens of the Eolidina the microscope is neces- 

 sary for the detection of these parts, and the compressor must be 

 adjusted carefully with reference to them : great pressm'e is re- 

 quisite to show the tongue. In large specimens the same parts 

 can be dissected out either with or without a lens. 



[To be continued.] 



