112 SEA-SIDE STUDIES. 



kind. The blood they receive, which is not more than 

 other parts, is received into sinuses, as it is in the 

 cavities of the body ; and it is not more aerated there 

 than it is in every other part of the mantle from which 

 the papillse rise. If, therefore, w^e can detect in these 

 papillse neither the ordinary structure of gills, nor the 

 vessels which carry blood to and from gills, it is emin- 

 ently unphilosophic to call them gills, and to class the 

 Eolids among Nudibranchiates. 



Do but examine one of the other Nudibranchiates — 

 say a Doris — and you will there find the very charac- 

 teristics wantino- in the Eolis. It has a gill, distinct, 

 unmistakable ; although even here the gill performs 

 but a small part in the aeration of the whole blood. 

 According to Alder and Hancock, only that portion of 

 the blood which supplies the liver-mass goes to the 

 gill ; but small as the part may be, the organ is dis- 

 tinctly recognisable, and to compare it with the dorsal 

 papillae of the Eolis is to demonstrate that two such 

 dissimilar organs cannot play the same part. Indeed, 

 the Doris seems to me higher in the scale of orga- 

 nisation than the Eolis, although less active in its 

 movements. It has a sj)ecialised liver, a more perfect 

 vascular system, the commencement of a respiratory 

 system ; and it has not the arborescent intestines which 

 the Eolis has in common with the Planarice and 

 Pycnogonidce. I should propose, therefore, to remove 

 the Eolis from the Nudibranchiates, and call it Abran- 

 chiate. 



How, then, does the Eolis breathe? He does not 



