HTDROIDS FROM WOOD's HOLL, MASS. 343 



are not knobbed at the end. The pear-shaped nettling organs 

 are of only one kind, and they are evenly distributed, i. e, not 

 in groups. The longest tentacles are 8 mm. ; the endoderm of 

 the tentacles is a solid axis. From the paper I infer that the 

 foot end is in no way modified for fixation, but simply sticks 

 in the accumulated debris, hence its species name cumu- 

 lans. 



Schaudinn places Halermita between Hydridse and all 

 known hydroids, but this is only tentative, since he has not 

 been able to observe the sexual reproduction ; he admits that 

 it may also be the larval form of a more specialised hydroid. 



Up to the present time, then, all marine hydroids known to 

 be adults are ])ermanently fixed ; and even if we consider 

 Protohydra and Halermita to be mature forms, then the latter 

 would be the only one so far recorded which does not seem 

 to be specially modified at any point of its foot for fixation. 

 Naturally the case of Corymorpha suggests itself as a form 

 that might be an exception, but may be dismissed on account 

 of the processes at its foot end, which are undoubtedly rem- 

 nants of a Hydrorhiza.^ To the new polyp found at Wood's 

 HoU I have given the name Hypolytus peregrinus.^ 



General. 



The polyps of Hypolytus peregrinus are found tem- 

 porarily attached by the secretion of their ectoderm to some 

 foreign object several feet below the surface of the water, or 

 having become detached, probably by withdrawing from the 

 perisarcal tube (in which case a new one is quickly secreted), 

 they may be found floating at the surface of the water. This 

 no doubt accounts for their being occasionally taken with the 

 tow-net in clear water. Their temporary attachment is again 



* Korschelt and Heider (' Comp. Embryology') suj^gest that these may 

 indicate a previous colonial condition of Corymorpha. 



^ From iiTTo, under, below; and Xvw, loosen; peregrinus, travelling. 

 Should the name here proposed for this new genus be preoccupied, I propose 

 instead Gonohypolytus. 



