or 



54 SEA-SIDE STUDIES. 



Polype, in aspect closely resembling Tuhularia indivisa, 

 growing parasitically on the Sertularia. Proceeding to 

 identify it, I found the species to be one hitherto nnde- 

 scribed ; and I propose to name it Tuhularia parasi- 

 tica, if no one has been before me. On another occa- 

 sion I saw, with the naked eye, a polype-like creature 

 attached to the side of the glass, with its tentacles ex- 

 panded ; the lens showed it to be a Polyzoon, much re- 

 sembling the Alcyonidiuin hirsutum. It was single, 

 however ; and on other parts of the glass were eight 

 other specimens, all solitary. This was in itself no- 

 ticeable, because, as the name Polyzoon imports, these 

 animals live in colonies. Under the microscope, a new 

 fact presented itself : the animal was enclosed in an 

 oblong bivalve-shell, which seemed permanently open on 

 one side, and open at the summit to give passage to 

 the crown of tentacles. Imaoine a shell like that of a 

 mussel gaping open, within which is a quinine bottle, 

 the broad neck protruding, and you will form a toler- 

 able idea of the general aspect of this animal when the 

 tentacles are withdrawn. I believe this to be a new 

 genus, and also to have an interest beyond novelty, 

 because furnishing another decisive argument in favour 

 of the moUuscan nature of the Polyzoa — a point still dis- 

 puted among naturalists.* The existence of a bivalve- 

 shell is very important ; and I took pains to con- 

 vince myself that it was really a shell, and not a 

 membranous envelope having the aspect of a shell : 



* The recent publication, by the Ray Society, of Professor Allman's 

 monograph on Freslaoater Polyzoa, must for ever settle this dispixte. 



