BIGELOW: EXPL.OR.\TIONS OF THE COAST WATERS. 243 



possibly other definite intrusions of the sort may occur later in the 

 season. 



In the deeper layers, particularly near the bottom, this process 

 probably takes place more or less at all seasons. But although the 

 salinity of the western side of the Gulf rises during the winter (p. 206; 

 1914b), the fact that the mean salinity is no higher off Cape Ann, or 

 on the northwest part of Georges Bank in early spring, than off Mt. 

 Desert in August, is good evidence that no general flooding of the 

 Gulf by offshore, or Gulf Stream water, takes place during the winter. 

 The hydrographic history^of that season is, rather, one of general 

 equalization, horizontal as well as vertical (1914b), the eddy-like 

 circulation of the Gulf gradually bringing Salter and salter water 

 to its western side, as the land water gradually mixes with the higher 

 salinities in its center. In short the Gulf is probably more nearly 

 stagnant, if that term can fairly be applied to the open sea, in the 

 winter than at any other time. 



The comparative constancy of salinity, temperature, and character 

 of plankton in the Gulf, since 1912 (p. 231), is good evidence that there 

 has been no general alteration of the circulatory scheme here outlined, 

 i. e., no important sporadic floodings by either Gulf Stream or by 

 Cabot Current water during the four year period. But the annual 

 hydrographic variations described above (p. 231) show that there have 

 been small fluctuations in the relative importance of these waters in 

 the Gulf from year to year. Thus only a relatively lesser amount 

 of offshore water can account for the low salinity of the eastern part 

 of the Gulf in 1913 as compared with 1912, 1915. And offshore 

 water was relatively less important in the western part in 1914 than 

 in 1912; though it is not clear whether this was due to an increased 

 amount of land water, to St. Lawrence water, or to an actual dimin- 

 ution in the inflow via the Eastern Channel. By 1915 we once 

 more found the conditions of 1912 reestablished there. 



Pl.\nkton. 



General Character of the Macro plankton. — The summer plankton 

 of the Gulf of Maine was of the same general type in 1914 as in pre- 

 vious years (1914a, 1915), Copepods, chiefly Calanus and Pseudo- 

 calanus, predominating, with smaller numbers of hyperiid amphipods 

 (Euthemisto, p. 286), euphausiids (Meganyctiphanes and Thysanoessa, 

 p. 281), pteropods (Limacina, p. 298), Sagittae (p. 294), and other 



