Messrs. Hancock and Embleton on the Anatomy of Eolis. 3 



and taper to a point ; they arc arranged down the sides of the 

 back in about twenty transverse series of from twelve to eighteen 

 papillae each ; the foot is broad, and slightly produced at the sides 

 in front. 



We have not however confined ourselves to this species, but 

 have extended our inquiries to several others, for the purpose of 

 showing how far the internal organization varies in the group. 



E. olivacea, PI. I. fig. 3, is thus frequently alluded to. It 

 closely resembles the species described by M. de Quatrefages, 

 and is in fact, according to the generic characters given by him, 

 with the exception of a posterior dorsal anus, an Eolidina. It 

 is generally about half an inch long, has four simple, slightly 

 conical tentacles ; the anterior part of the foot is rounded at the 

 sides, or only slightly angulated ; the branchial papillae are cylin- 

 drical, and arranged down the sides in about seven transverse 

 rows of four or five papillse each. 



E. coronata, Forbes, PI. I. fig. 2, has also been examined with 

 the same view. This species differs from the two former as much 

 perhaps as any of the genus, and is therefore well calculated for 

 our purpose. It is sometimes one inch and a half long, the body 

 is almost cylindrical, and terminates in a fine point behind ; the 

 anterior lateral angles of the foot are somewhat produced; the 

 oral tentacles are long and simple, the dorsal annularly laminated ; 

 the branchial papillse are cylindrical, and arranged down the sides 

 in six or seven clumps. 



Besides these three, we have had upwards of twenty other spe- 

 cies, to some of which we shall occasionally refer. A few of these 

 have the anterior angles of the foot produced into tentacular 

 points, as described by Cuvier ; and others have the large vase- 

 shaped branchial papillse resembling those of the genus Ampho- 

 rina of M. de Quatrefages. 



During our investigations, we have used in the dissection of 

 the organs the simple lens, and for the examination of the mi- 

 nuter parts of the organs, the tissues and fluids, one of Powell and 

 Lealand's best compound microscopes. We have avoided using 

 the compressor as much as possible, being aware that it is a great 

 cause of error in studying the structure of animals so complicated 

 and delicate as the Eolidina. These mollusks invariably contract 

 themselves greatly when subjected to pressure, and the various 

 organs are confusedly crushed together, so that it is quite impos- 

 sible to distinguish any of them with precision. We have never 

 succeeded in tracing in this manner the whole of any of the vis- 

 cera, though we have several times made the attempt, and we can 

 easily conceive that the compressor has led to many of the errors 

 which we believe M. de Quatrefages has committed, though we 

 give him full credit for the amount of information that he has 



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