338 bulletin: museum of comparative zoology. 



Thus the only part of the Gulf where volume, or number of copepods, 

 or both, was greatest in 1912 was off Massachusetts Bay, and near 

 Cape Elizabeth and Piatt's Bank; a difference which may be seasonal. 

 Everywhere else both the volume of plankton and the number of 

 copepods was greater in 1913 than in 1912. It is possible that locations 

 close to shore might have proved an exception ; but judging from what 

 was found east of Mt. Desert and on German Bank, there is no rea- 

 son to suppose that shore stations would have altered the case materi- 

 ally. On the average, the hauls for the whole Gulf were nearly twice 

 as large in bulk, and 60% larger in number of copepods, in 1913; a 

 difference so great that it can hardly be accidental, especially as the 

 same net was used in both years. In short, there seems no escape 

 from the conclusion that both the plankton as a whole, and its copepod 

 constituent, were richer in August, 1913, than in the summer of 1912. 

 Very little can be said about the microplankton of the two years 

 until the microscopic examination of the hauls is completed. But 

 enough has been done to show that diatoms were far less numerous 

 in August, 1913, than in the corresponding month of 1912. And the 

 species which formed the bulk of the catch in that year, Asterionella 

 japonica, has not been detected at all in the 1913 hauls. Furthermore 

 the Ceratium plankton was nowhere so dense in 1913 as off Cape 

 Elizabeth in 1912. 



Macroplankton of the Gulf of Maine and of the northeastern 

 Atlantic. 



Our survey of the plankton of the Gulf of Maine in 1912 led to the 

 conclusion that it was characteristically boreal, in the sense in which 

 the term is used by Hjort (Murray and Hjort, 1912, p. 637), not Arctic, 

 though with Arctic and Gulf Stream components (1914a, p. 106). 

 And subsequent catches support this general thesis. The most im- 

 portant member of the plankton of the Gulf, Calanus finmarchicus, 

 it is true, is practically eurythermal, but it is only in boreal, and in 

 Arctic-boreal waters that it swarms (Farran, 1911) and it is not dis- 

 tinctive of polar water, although it is very numerous and very large 

 in the Labrador Current (Herdman, Thompson, and Scott, 1898). 

 On our coasts Calanus plankton apparently occupies an unbroken 

 belt from the Labrador Current to Cape Cod. The only copepod 

 which vies with it in abundance in the Gulf, Pseudocalanus elongatus, 

 is likewise chieflj boreal, not polar, and far more plentiful in coastal 



