PLANKTON OP THE GULP OP MAINE 395 
tows on a line across the mouth of the bay (stations 10337 to 10339), where it had 
dominated the phytoplankton a month earlier. 
Bailey (1917, p. 101) also records an abundance of diatoms (Skeletonema) near 
Grand Manan Island in the Bay of Fundy in early September, and Dr. McMur- 
rich’s lists show a rather pronounced maximum of diatoms (chiefly Thalassiothrix) 
at St. Andrews in September and October, 1916. But during the season of 1917, 
when Fritz’s (1921) counts located the vernal maximum in late April and early 
May at St. Andrews, with a period of scarcity for diatoms in June, the second 
maximum fell in July, followed by a sudden diminution in the number of diatoms in 
August, with much smaller numbers in September. The wide fluctuations in her 
counts at the same locality on different dates in July and August is an instructive 
illustration of the streaky way in which shoals of diatoms often occur. Note 
especially an increase from 632,000 on July 23 to 7,186,000 on August 2, falling to 
14,900 on the 8th. It is more likely that the net chanced to hit a streak of diatoms 
on the occasion of the rich catch, which a haul made shortly previous or later might 
have missed, than that an active flowering culminated during the two-weeks interval. 
It is dangerous to generalize from a small number of hauls, especially for a 
tide-swept locality, but it seems that a secondary maximum of diatoms is to be 
expected sometime during the late summer or early autumn both in Massachusetts 
Bay and in Passamaquody Bay, and therefore probably all along the coast line in 
estuarine situations; one, however, which is less abundant than the vernal flowering 
and likewise less regular in the date of its occurrence. 
Little change has been noted in the general composition of the phytoplankton 
of the Massachusetts Bay region during the period November-January, Ceratium 
dominating. Hauls off Gloucester on November 20, December 4, and December 23, 
1912, yielded a scanty plankton, chiefly Ceratium, with few diatoms (Bigelow, 
1914a, p. 404). In 1920 the several species of diatoms that are most abundant from 
spring to early autumn had practically vanished from the whole coastal belt between 
Cape Cod and the mouth of the Bay of Fundy by December and January; but by 
contrast the diatom genus Coscinodiscus apparently has a flowering period in mid- 
winter, for it rivalled Ceratium at all the stations occupied by the Halcyon off the 
western and northern shores of the gulf from December 28, 1920, to January 9, 
1921, dominated locally off the Merrimac Biver (station 10442), and was the 
most numerous diatom genus (though dominated by the peridianians) in the eastern 
side of the basin, in the Fundy deep, and off western Nova Scotia at this time (stations 
10499 to 10502). 
Judging from the midwinter data just outlined and from our experience during 
the first days of March in 1920 and 1921, peridinians are predominant and diatoms — 
except for Coscinodiscus — fall to a very low ebb out at sea in the Gulf of Maine dur- 
ing the later winter. Fritz (1921) found only very small numbers at St. Andrews 
from November until the middle of March, compared with the tremendous flower- 
ings of spring. But diatoms may be a considerable element, quantitatively, in the 
plankton here and there along the open coast even in midwinter, as was the case off 
Gloucester on January 16 and in Ipswich Bay, a few miles north of Cape Ann, on 
January 30 in 1913, on which occasions our towings yielded about as great a bulk 
