PLANKTON OF THE GULF OF MAINE 
397 
Diatoms may also be expeqted to flower on one part of Georges Bank or another 
at any season from late winter to midsummer, but nothing is known of their status 
there in autumn or early winter. 
Fish (1925) has pointed out that the waters just west of the barrier of Cape Cod 
show quite a different seasonal cycle — namely, rich diatom plankton throughout the 
winter, usually with a brief summer maximum, but with few diatoms in spring — this 
seasonal distribution corresponding to the Mediterranean, as that of Massachusetts 
Bay and of the Gulf of Maine generally does to the diatom cycle of the North Sea, 
Irish Sea, and Skager-Rak. Thus, as Fish (1925, p. Ill) emphasizes, the same 
relationship between the seasonal succession of diatom maxima and the latitude and 
temperature obtains in the western side of the North Atlantic as in the eastern. 
Peridinians dominate the phytoplankton of the open gulf throughout the summer 
and autumn, but they become very scarce, actually as well as by contrast, during the 
flowering period of the diatoms. The latter are much the more important group of 
the two in estuarine situations, where they occur in greater or less abundance through- 
out the year instead of dwindling almost to the vanishing point between their flower- 
ing periods. Peridinians, on the other hand, are seldom more than a very minor 
constituent of the plankton in estuarine situations. 
Finally, before turning to the quantitative records, I may point out that the 
Gulf of Maine diatoms are chiefly of local origin — that is, that they are produced 
in the gulf itself and are not immigrants thither from elsewhere. For the western 
center of dispersal this may be taken as proved; and while the chain of evidence 
favoring the endemic origin of the diatom plankton of the Nova Scotian side of the 
gulf is not so complete, there is nothing in our records to suggest that it receives any 
important accessions from the east around Cape Sable. On the contrary, none of the 
hauls made east of the cape during March, 1920, June, 1915, or July and August, 
1914, have yielded diatoms in any abundance; nor are the diatoms of the eastern 
side of the gulf more Arctic in their affinities than those of the western, as might be 
expected if the Nova Scotian current were responsible for their presence there, but 
rather the reverse. 
QUANTITATIVE DISTRIBUTION OF THE PHYTOPLANKTON 
When the study is undertaken of the plankton of an ocean area previously 
virgin ground in this respect, a general qualitative and seasonal survey is the first 
task. Until we know what groups of organisms are the chief constituents of the 
pelagic community, at what seasons they reach their maximum abundance, and 
have outlined their temporal and geographic fluctuations in general, it is difficult to 
plan counts of the actual numbers in which they occur, to yield results commen- 
surate with the vast amount of labor entailed. For this reason our hauls in the Gulf 
of Maine have so far been made with the ordinary horizontal nets of appropriate 
mesh, but I believe that with the information now at hand the time is ripe for more 
intensive quantitative studies of the phytoplankton of the offshore waters of the 
gulf, such as Fritz (1921) has undertaken for the St. Andrews region. 
In north European waters this stage has long been passed, and since the time 
when Henson (1887) first focused scientific attention on the productivity of the 
high seas, quantitative determinations innumerable of marine and fresh-water 
