GASTEROPODES. 299 



SECTION III. EOLIS. In the dismemberment of the genus Doris by 

 recent naturalists, they have left a place for a very large section, under 

 the name of Eolis. 



But, 'so many novelties, varieties, and difficulties, continually occur 

 to the practical naturalist attempting a systematic arrangement of such a 

 numerous tribe as the Doris, as taken in its original signification and 

 more comprehensive sense, that he will even find himself compelled to 

 modify his general plans on a retrospect. He cannot discover such spe- 

 cific, exclusive, and permanent characteristics, as enable him to assume 

 with confidence the exact principles laid down for his guidance, and, in 

 general, he will find that instead of including the great field of Nature, 

 they embrace but the narrowest portions of it. ' 



Thus, we cannot yet admit the detail proposed by some systematic 

 authors to be irrevocably settled. It is still open to alteration. 



Though having had a multitude of specimens of the different families 

 in my possession, as many, perhaps, as would have induced more skilful 

 observers to frame several genera from them, I can never take a retro- 

 spect of the subject without distrust, so much had to be seen amidst the 

 little that was disclosed. Therefore, instead of classing certain members 

 in determinate series, I shall do no more than give a general description, 

 and suggest how they may be united, from some of their most prominent 

 features. The accompanying figures may contribute assistance. 



The preceding sections comprehend such animals as may be gene- 

 rally discriminated with tolerable facility. Perhaps the whole to be in- 

 cluded here are not alike definite. 



EOLIS. Tentacula two, prolonged from the head. Cornicula two, 

 rising from the neck, without sockets. Back partly bare. Branchiae 

 commonly formed as elongated papillae, tapering or enlarging from their 

 origin on the upper surface, single or disposed in groups or clusters. 



