268 bulletin: museum of comparative zoology. 



Over the southern part of the basin of the Gulf (Station 10058) 

 the plankton was qualitatively much the same — but quantitatively 

 very different, for Calanus was not nearly so abundant in the haul 

 from forty fathoms; the net, however, yielded many Euchaeta norve- 

 gica, with few Calanus hyperboreus; and fully one half the catch con- 

 sisted of Stephanomia bells and denuded stalks (p. 316); there were 

 also more fish fry than were found nearer shore. 



At the Station on the northwest side of George's Bank, a rather 

 surprising discovery was made, namely that the surface water was full 

 of campanularian hydroids (Obelia) broken from their attachments, 

 and many of them entirely regenerated. A similar phenomenon 

 was noted on George's Bank during the winter of 1912-1913 (1914b, 

 p. 414). It is interesting faunistically as showing how the strong 

 tides of the region, by keeping the detached hydroids afloat, mechani- 

 cally introduce an exotic element into the plankton. So far as I can 

 learn, nothing of the sort has been observed elsewhere, at least on so 

 large a scale. The place of Calanus was taken by another copepod, 

 Temora longicornis, while the bulk of the deep haul consisted of 

 Sagittae (S. elegans). The net also yielded many young Cyanea, and 

 several caprellids, no doubt shaken loose from the hydroids. 



In the waters over Nantucket Shoals (Station 10059) Calanus was 

 again the prevalent organism, with but few Sagittae; near the light- 

 ship, however, (Station 10060), Sagittae about equalled Calanus in 

 bulk; and this Station w^as also notable for swarms of young Euthe- 

 misto (p. 281), of pteropods {Limacina baica, p. 304), and of the free 

 medusae of Obelia. 



We saw fragments of Gulf weed on the surface south of Nantucket 

 light-ship, and at Station 10061, over the eighty fathom curve, the 

 influence of the Gulf Stream was made evident by the presence of 

 Salpae, Phroniraa, and the amphipod Vibilia, though the bulk of the 

 plankton still consisted of Calanus finmarchicus, with such other 

 boreal forms as Euchaeta norvegica, Euthemisto, Sagitta elegans, and 

 Limacina balea. The plankton over the shelf south of Marthas Vine- 

 yard and Block Island (Stations 10062 and 10063) consisted chiefly 

 of swarms of young and old Euthemisto (p. 281), with smaller numbers 

 of copepods (Calanus and Centropages, p. 287), Sagittae and an 

 occasional Pleurobrachia pileus. And here for the first time large 

 numbers of fish fry, a striking feature of the tows further south, were 

 encountered. When the deep water outside the shelf south of Long 

 Island (Station 10064) was reached the boreal plankton was replaced 

 by a warm water assemblage, for while the 175 fathom haul still 



