PLANKTON OF THE GULF OF MAINE 21 



slope of the latter. Thus, a typical Oalanus community, with Clione, Limacina, 

 and the other boreal forms characteristic of the inner parts of the Gulf, occupied the 

 waters over Nantucket Shoals on July 14, 190S (Bigelow, 1909, p. 201), and at the 

 same time of year in 1913, when we found no decided change in the boreal character 

 of the plankton (Calanus predominating) until we had sailed westward nearly to 

 New York (Bigelow, 1915, p. 269). During the summer of 1914 we again found Cal- 

 anus, with its usual companions, predominant over the greater part of Georges Bank 

 in July, and across the mid-zone of the continental shelf abreast of Marthas Vine- 

 yard in August; also in August, 1915; and from Cape Cod out to the continental 

 slope in July, 1916. But although Calanus is as universal over the offshore banks as 

 within the gulf, it does not dominate the plankton so constantly there. Thus we 

 found Sagitta elegans as important, faunally, as were the copepods over the central 

 part of Georges Bank during our summer cruise of 1914, and swarming both over the 

 northeast corner of the bank on July 23 (station 10224 9 ) and in the Northern Chan- 

 nel on July 25 (station 10229), practically to the exclusion of everything else, except 

 for an abundance of adult Euthemisto, which (we may suppose) are sufficiently large 

 and active to protect themselves from the glassworms, voracious though the latter 

 are (p. 107). 



Even when copepods, as a group, are the chief factor in the summer plankton over 

 Georges Bank, it is sometimes the little brown Temora longicornis (fig. 20), not 

 Calanus, that is the dominant species there. This was the case at a station on the 

 northwestern part of the bank in July, 1913 (station 10059), while the frequency 

 with which Kendall, in his field notes for August, 1896, describes "small brown 

 copepods" (which could only be Temora) as abundant, side by side with "red 

 feed" (Calanus) and "green copepods" (Anomalocera), or even as constituting the 

 bulk of the surface tow, suggests that such dominance on its part is a common event 

 on the northern part of the bank (lat. 41° 45' to 42°, long. 66° 30' to 68° 30'). His 

 records suggest that Temora increases in number there with the advance of the 

 summer, 10 which parallels its seasonal history in the Massachusetts Bay region (p. 289) . 



Hyperiid amphipods (two species of the genus Euthemisto, p. 156) have often 

 been reported as plentiful over the outer part of the continental shelf off Marthas 

 Vineyard. We found them in abundance over the corresponding zone off Nantucket 

 Shoals and over the western end of Georges Bank, side by side with the copepods, 

 in July of 1913 and 1916 and August of 1913 and 1914. They are equally charac- 

 teristic of the outer parts of the banks eastward across the mouth of the Gulf of 

 Maine and off the Nova Scotian coast, where they breed in abundance (p. 160) and 

 grow larger than within the gulf to the north. 



The outer part of the continental shelf is the offshore limit to the occurrence of 

 copepods in abundance abreast of the Gulf of Maine; but the pelagic amphipod genus 

 just mentioned is perhaps most plentiful along the upper part of the continental slope, 

 where it mingles with the oceanic planktonic community of the warmer waters of the 

 Atlantic basin. It has likewise been our experience (though fresh observations may 

 give cause to alter conclusions drawn from a single summer's cruise) that in mid- 



• The catch o( one-half hour's haul of the Helgoland net at 40-0 meters was about 5 liters of Sagitta cltgam, and very little 

 else except a few Calanus, Temora, Pseudocalanus, 3 or 4 Euthemisto, 2 Limacina, young crabs and other decapods, and some 

 floating hydroid fragments described below (p. 380). 



10 Kendall's tows were taken during the last week in August. 



