394 
BULLETIN OF THE BUREAU OF FISHERIES 
as was the case at our outermost stations in the summer of 1914 (stations 10218 
and 10220). July and August stations (10218 and 10261) in 1914 over the slope 
west of longitude 68° W. and south of latitude 42° 10' N. likewise yielded small 
amounts of the characteristically tropical alga Trichodesmium, together with 
Ceratium macroceras, which also occurred off the southeast face of Georges Bank 
in July (station 10220) and in the coastal waters off Martha Vineyard in August 
(stations 10258 to 10260) ; but we have never found C. macroceras along the conti- 
nental slope farther east than the Eastern Channel. 
Although tropical pelagic plants, both large and miscroscopic, as well as plank- 
tonic animals belonging to this same category in their relationship to temperature, 
may be expected to encroach on the western half of Georges Bank at some time during 
most summers, just as they do more regularly and abundantly farther west and 
south, the exact season when this happens varies considerably from year to year, as 
might be expected from the fluctuations in the location of the inner edge of the 
Gulf Stream, a fact illustrated by their failure to appear there by the third week of 
July in 1916. Probably they are hardly to be expected along Georges Bank earlier 
than the first of that month, even in warm years, and are locally more characteristic 
of the months of August and September. 
Autumnal data on the phytoplankton of the gulf outside the Bay of Fundy are 
limited to a series of stations covering its northern half for September, 1915, and to 
occasional October and November hauls between Cape Cod and the Grand Manan 
Channel during the years 1912, 1915, and 1916. Bailey (1910 and 1917) and Fritz 
(1921) have also published lists of diatoms from St. Andrews and neighboring parts 
of the Bay of Fundy, for the autumn as well as for other seasons of the year, and 
Doctor McMurrich’s plankton lists include the status of several genera of diatoms and 
of peridinians at St. Andrews in autumn. These records, united, show that diatoms 
practically disappear from the deeper parts of the gulf- — not, however, from the 
Bay of Fundy — after the last days of August, leaving almost its entire area outside 
the outer headlands occupied by a Ceratium community, with the Mount Desert 
and Massachusetts Bay regions and the Bay of Fundy alone supporting diatoms in 
appreciable number. In fact, we have never found abundant diatom plankton 
anywhere else in the open gulf, either in September or in October, though diatoms 
were present in some numbers, together with the peridinians, along shore from 
Penobscot Bay to the Bay of Fundy up until the 9th of October in 1915, and 
dominated the phytoplankton near Mount Desert Island on that day (station 10328). 
Considerable catches of diatoms at the mouth of Massachusetts Bay during 
the last week of September, 1915, resulted from a rich flowering of Skeletonema. 
This genus is comparatively rare there in spring (p. 448), but in the summer of 1922 
it had commenced flowering in the coastwise belt and among the islands along the 
northern shore of the bay by August, and the three successive states — spring, August, 
and September — though for different years, suggest that its normal cycle is to 
spread offshore as the season advances. Its flowering period was apparently brief 
in 1915, however, and probabfy is in most years, having come to an end before 
October 26 or 27, by which date its place had been taken once more by Ceratium, 
with only occasional diatoms (Coscinodiscus and Thalassiothrix longissima ) in the 
