458 



present time upwards of 50 species are known chiefly from the waters 

 north and south of Europe and the East Indian Archipelago. These 

 species constitute two families, the Chaetodermatidae and the Neo- 

 menidae. The members of the last group are, in some respects at least, 

 the more primitive and are readily recognized by the ventral furrow 

 extending the length of the body and containing the rudimentary foot. 

 Unlike the Chaetodermatidae they rarely burrow in the mud but crawl 

 about on hydroid colonies or alcyonarian corals and occasionally on 

 plants and some species of actinians. 



The presence of these molluscs under such circumstances has been 

 variously explained. Some consider that as a general thing it is a case 

 of commensalism ; others that the mollusc is a parasite and support 

 their belief by those cases that are known to exist where the alimen- 

 tary canal contained nettle cells and in one case [Proneomenia Sluiteri) 

 a bit 0Î Alcyonium. On the other hand the presence of diatoms in some 

 of these same species indicates that they are not strictly parasitic. 

 Furthermore those forms living on the eel grass [Zostera) are probably 

 not commensals nor parasites, the presence here, and in several other 

 cases, of a well developed radula indicating predatory habits. As the 

 matter now stands these forms are very difficult to observe and our 

 knowledge of their mode of life is still in such an imperfect state that 

 one is not justified in making sweeping statements. 



The U. S. Fish Commission steamer Albatross in her explorations 

 about the Hawaiian Islands during 1902 brought up several species of 

 solenogastres attached to hydroids or corals but in these cases there 

 was nothing whatever to show that they were parasitic in their habits. 

 The coelenterate host had in every case been preserved with great 

 care and the most attentive examination failed to show any signs of 

 mutilation. The finely granular contents of the alimentary canal of 

 the mollusc also gave no definite evidence. However in one specimen 

 belonging to the genus Neomenia definite proof is at hand to show that 

 this species at least is parasitic. It was closely wrapped about a polyp 

 oi Epizoanthus or some closely related genus and subsequent exami- 

 nation showed that its proboscis had penetrated the body wall of its 

 host and had removed some of the internal structures whose remains 

 were present in abundance in the stomach. In this species well devel- 

 oped ventral salivary glands are present and in this particular specimen 

 they opened at the free end of the fully extended proboscis and, in the 

 absence of a radula, probably produced some secretion that exercised a 

 solvent action on its prey. 



As an aside it is interesting to note that some have considered the 

 finger-shaped processes or cirri on the inner buccal wall to be not only 



