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BULLETIN OF THE BUREAU OF FISHERIES 



our surface net took great numbers of them over the northwest part of the bank 

 (station 10059). These were submitted to Dr. C. McLean Fraser for study, and 

 the reader is referred to his report (in Bigelow, 1915, pp. 268 and 306) for details. 

 It will suffice to say here that the catch of hydroids was not only considerable in 

 amount but included no less than 13 species, belonging to 4 families. Most of these 

 were represented by broken fragments only, or by colonies attached to bits of eel- 

 grass (Zostera) ; but the hundreds of colonies of Clytia cylindrica (the predominant 

 species) were floating free of any support, and not only in a perfectly healthy state 

 as far as appearances go, but so completely regenerated that there were few or no 

 broken ends visible. 



As it can hardly be supposed that these colonies had passed through their 

 whole development, from the planula stage onward, at the surface of the sea, the most 

 reasonable explanation for their presence afloat is that they had been torn from 

 their attachments on the bottom by the strong tidal currents and kept suspended 

 in the water by this agency. Finding a rich food supply in their pelagic surround- 

 ings, with nothing fatal in such an environment, they regenerate, grow, and even 

 propagate their land, as appears from their development of gonophores. After all, 

 there is nothing surprising in such a phenomenon, for it is "not unusual to find 

 fragments of hydroid colonies torn from their support or from the rest of the colonies, 

 living for a considerable time as they float on the surface" (Fraser, 1915, p. 307). 

 Similar congregations of floating hydroids have been encountered thrice since 1913, 

 always on Georges Bank — viz., July 23, 1914 (station 10224), July 23, 1916 (stations 

 10347 and 10348), and February 23, 1920 (station 20047). Judging from the geo- 

 graphical grouping of these stations (fig. 98) their place of origin is probably on the 

 shallows known as "Georges" and the " Cultivator" Shoals. 



