250 bulletin: museum of comparative zoology. 



brachia abundant, though less dominant, in other years (1914a, 

 1915). 



Similarly the much more diversified plankton of the Eastern Basin, 

 varied little throughout the season, September, like May hauls, 

 consisting chiefly of Calanus finviarchicus, and Pseudocalanus, with 

 smaller numbers of such other boreal forms, as Euchaeta norve- ^ 

 gica (p. 292), Sagittae, Euthemisto (p. 286), Limacina balea (p. 298), 

 and Thysanoessa (p. 283). In the northeast corner of the Gulf the 

 deep hauls yielded large numbers of Mcganyctiphanes norvegica and 

 Euchaeta norvegica, besides the typical Calanus plankton, both in 

 May (Station 10273) and in June (Station 10283), while they were 

 similarly abundant at this locality, below about 100 meters, in the 

 summers of 1914 (Station 10246), and 1913, 1915 (Station 10097). 



In the coastal belt from Cape Elizabeth to Mount Desert a decided 

 increase took place during the summer (p. 314) in the amount of 

 macroplankton present in the water, coincident with the shrinkage of 

 the diatom swarm (p. 325). But the only important change in its 

 composition, either off Mt. Desert (Stations 10275, 10285, 10329) or 

 off Cape Elizabeth (Stations 10277, 10326), was that the nearly pure 

 copepod plankton (chiefly Calanus) of May grew more varied, as the 

 season advanced, by an increase in the relative abundance of such 

 other typical boreal organisms as Euthemisto, Sagitta elegans, Mcga- 

 nyctiphanes, Thysanoessa, and Limacma balea. 



A similar change took place both in the Western Basin (Stations 

 10267, 10299, 10307) and off Cape Ann, (Stations 10266, 10306, 10324), 

 where great numbers of young Euthemisto appeared in the August- 

 October hauls, besides a general increase in the, other boreal forms 

 typical of the general Gulf of Maine plankton (p. 243, 1915) ; and off 

 Cape Cod, where swarms of Pleurobrachia appeared in October 

 (Station 10323). 



Station 10282 in the Bay of Fundy deserves brief mention, as no 

 deep tows had previously been made in this region. The bulk of the 

 hauls consisted of Calanus fi^imarchicus and small copepods, with 

 occasional Clione, Euthemisto, Sagitta elegans, i. e., they were of the 

 usual Gulf of Maine type. But there were no Euchaeta, even in the 

 haul from 175 meters. 



Our records all go to show that regional, like seasonal differences in 

 the plankton are slight in the Gulf. In fact the only important 

 variations from the general type so far detected are a prevalence of 

 neritic organisms, larvae etc., close to land; a greater proportional 

 importance of animals of oceanic, and of northern origin in the eastern 



