PLANKTON OF THE GULF OF MAINE 149 



reflects the number of tow nettings that have been carried out along that part of the 

 slope rather than any general abundance of Meganyctiphanes there, corresponding to 

 which we have found it at only one of our stations off the slope of Georges Bank. 



The scarcity of Meganyctiphanes over Georges Bank and in the southeastern 

 deeps of the gulf generally, in spring as well as in summer, suggests that the few 

 specimens that drift westward beyond Nantucket Shoals along the continental slope 

 are migrants, either from along the Nova Scotian coast to the eastward (and possibly 

 even from as far away as the Gulf of St. Lawrence) or from the western side of I ho 

 Gulf of Maine, not from the eastern or central parts of the latter. 



The alternation of the seasons sees a corresponding expansion and contraction in 

 the area of distribution of Meganyctiphanes in the inner part of the Gulf of Maine. 

 Probably this is at its narrowest late in the winter and early in the spring, for from 

 February to April, 1920, we had only two records of it anywhere inside the 100-meter 

 contour in the whole coastal zone on both sides of the gulf — one for half a dozen 

 specimens near Mount Desert Island on March 3 (station 20056), and the other for 

 a single specimen off Yarmouth, Nova Scotia, on April 9 (station 20102) — although 

 we took it at many stations marked on the chart (fig. 54) in the central and northeast 

 deeps of the gulf during that period. Nor did we find it anywhere on Georges or 

 Browns Banks during these months. In fact, it is seldom that the local presence or 

 absence of any one of the larger members of the zooplankton can be defined so sharply 

 as in this instance. Thus it is evident that Meganyctiphanes withdraws altogether 

 from the shallows of the gulf within the 100-meter contour during the coldest season, 

 unless, perhaps, it persists locally around the shores of the Bay of Fundy; and our 

 failure to find it at any of our February-May stations over the continental slope 

 abreast of the gulf suggests that it vanishes similarly from this portion of its range in 

 late winter and spring. Thus its area of distribution in the Gulf of Maine is then 

 cut off from its more northerly centers of occurrence by an extensive zone off southern 

 Nova Scotia and extending around Cape Sable, where there are no Meganyctiphanes 

 at that season, which is not the case for Thysanoessa inermis (p. 135) or for Th. 

 longicaudata (p. 139). 



During the later spring and early summer Meganyctiphanes disperses in all 

 directions in the Gulf of Maine, to occupy the much more extensive range over which 

 we have found it occurring in midsummer, and reappears over the slope off Marthas 

 Vineyard. 



The contraction of the range of Meganyctiphanes, from its maximum in summer 

 and early autumn to the spring state just outlined, may commence as early as October 

 in the western side of the gulf, for we have not taken it anywhere in the Massachusetts 

 Bay region in October, November, December, or during the winter of 1912-1913. 

 It persists until later in the coastal belt north of Cape Ann, where we towed it near 

 the Isles of Shoals and off Monhegan Island on November 1 and 2, 1916 (stations 

 10400 and 10402) ; off Cape Elizabeth, near Mount Desert Island, in the northeastern 

 part of the basin, in the Fundy Deep, and off Lurcher Shoal during the last days of 

 December and first week of January of the winter of 1920-1921 (stations 10494, 

 10497, 10499, 10500, and 10502). 



