116 SEA-SIDE STUDIES. 



tails ; lie simply asserts the fact, that no distinct organs 

 exist. Siebold follows Kolliker, who establishes the 

 order Apneusta, " in opposition to the other Gastero- 

 poda, which have distinct respiratory organs." But 

 the only reason adduced by him seems to me far from 

 cogent ; and I can understand how Alder and Han- 

 cock, who must have been perfectly aware of the posi- 

 tion taken by Kolliker and Siebold, might altogether 

 disregard it. Siebold says that the opinion respecting 

 the branchial nature of the papillae " is untenable, since 

 it has been shown that they contain prolongations of 

 the digestive canal."'' I believe it to be untenable, 

 simply because the papillae contain none of the dis- 

 tinctive characters of gills ; did they possess these, the 

 fact of their also containing digestive prolongations 

 would not deprive them of their rank as gills ; any 

 more than the fact of the heart, in some Molluscs, 

 allowing the intestine to pass through it, deprives it 

 of cardiac dignity. 



Quitting this discussion for topics more surprising, 

 let us fix our attention on one fact, cursorily indicated 

 on a preceding page, namely, the existence, in the foot 

 of the Doris, of a system of pores through which the 

 water enters into the general cavity of the body. It is 

 a fact w^hich has not excited sufficient notice. Con- 

 sider it, for a moment, and you will remark that water 

 entering the general cavity must mingle with the 

 blood, and that largely. But if it mingles thus freely 

 with the blood, on its entrance, will it not also on its 



* Siebold— Comp. Anat, English Trans., p. 249. 



