PLANKTON OP THE GULP OP MAINE 
407 
How closely the foregoing data, obtained in European waters, would apply to 
the Gulf of Maine is yet to be determined, but judging from Peck’s results and from 
the large volumes of phytoplankton which we have ourselves obtained, there is 
no reason to suppose that its fecundity is lower than that of the North Sea or even 
than the still more prolific waters of the West Baltic. When such numbers as I have 
listed as examples are expanded from the trifling hulk of a cubic meter of water to 
cover the 36,000 square-mile area of the Gulf of Maine north of its offshore hanks, 
and to a stratum at least 20 meters thick, they become too vast for the human mind 
to envisage. Peridinians never approach the diatoms in actual numbers so far as is 
known. For example, the largest count recorded by Gran (1915) in the North Sea 
(May 9, 1912) was 3,740 per liter for Ceratium longipes, a species with an April to 
June maximum, and hence to be expected in relatively large numbers at that par- 
ticular season. 
PERIDINIANS 
The peridinian communities of the Gulf of Maine, like those of the North Sea, 
consist chiefly of one or other of two species ( longipes and tripos) of the genus 
Ceratium, 37 with smaller numbers of C. fusus and at times C. arctica The two 
predominant species alternate in dominance with the season of the year. 
Ceratium 
Judging from winter data for Massachusetts Bay (Bigelow, 1914a) and from 
our December and January stations of 1920-1921, C. tripos predominates every- 
where in the gulf throughout the winter, though C. longipes likewise occurs in small 
numbers in most of the winter catches. Tripos was still the predominant member 
of the pair at every station in the western, central, and northern parts of the gulf 
and on Georges Bank as a whole during early March, 1920, except in the flowering 
centers for diatoms (p. 383 ; fig. 104), where so few Ceratium occurred that the relative 
numbers of the two species are not significant. C. longipes or intermediates between 
it and C. arctica, such as are reported by Paulsen (1908), occurred side by side with 
C. tripos at most of the March stations. Off the southeastern slope of Georges 
Bank longipes was at least as numerous as tripos, outnumbered it in the Eastern 
Channel, on Browns Bank, and over the slope farther east, and was the only member 
of the pair detected in tows made in the Northern Channel and over the shelf abreast 
of southern Nova Scotia, from March 17 to 20 (stations 20073 to 20076 and 20078). 
Ceratium arctica, interesting because its occurrence is associated with low tem- 
peratures (J0rgensen, 1911), was likewise very generally distributed over the gulf 
in March, 1920, occurring only in very small numbers in the western half, but rela- 
tively more abundant in the Eastern Basin (though subordinate to tripos there) ; 
predominant, or at least as numerous as either C. longipes or C. tripos, at our 
several stations from Browns Bank to Cape Sable and off Shelburne; and more 
abundant, absolutely as well as relatively, in the eastern side of the gulf than in the 
western. The distribution of C. arctica at this season suggests an intrusion on its 
37 Identifications of peridinians follow Paulsen (1908) strictly. Being concerned here only with questions of distribution and 
relative abundance, not with systematics or genetic relationships, Paulsen’s view that C. longipes and C. arctica are distinct (not 
varieties of one species as Meunier (1910) maintains) is accepted without comment. 
