HYDROIDS PROM WOOD's HOLL, MASS. 341 



Hydroids from Wood's HoU, Mass. 



Hypolytus peregrinus, a New Unattached Marine Hydroid 

 Corynitis Agassizii and its Medusa. 



By 

 L.. Miirbacli. 



With Plate 34. 



Hypolytus peregrinus, a New Marine Hydroid. 



Introductory. 



During the last part of the summer of 1895, while searching 

 for the larvae of Goniouemus ^ in tow and dredgings from 

 the eel pond at Wood's Holl, a curious little hydroid polyp 

 was found. At the time it was sketched, and a few notes 

 made on the supposition that it was the larval form of some 

 other hydroid, perhaps a Tubularian. In the following 

 summer forms of the same kind with gonophores were found. 

 This left no doubt that it was after all a mature form, but the 

 limited number of specimens warranted no further conclusion 

 than that the animal would probably prove interesting on 

 account of its unattached condition, a character which would 

 not have been remarkable in a larval form. Nothing like a 

 perisarc was at first thought to be present, for, as was after- 



1 Although this medusa breeds regularly every summer in the eel pond, yet 

 after three summers of careful searching I have found only few metamor- 

 phosing larval stages, but have not been able to get the stages intermediate ; 

 nor have I been able to raise any beyond the stage of the polyp with four 

 tentacles. 



VOL. 42, PART S.^NEW SERIES. Z 



