54 
BULLETIN OP THE BUREAU OF FISHERIES 
Ever since the early eighties it has been known (from many collecting trips 
carried on by the vessels of the United States Bureau of Fisheries from the laboratory 
at Woods Hole) that the inner edge of the tropical water, carrying with it an extra- 
ordinarily rich and diversified tropical plankton, lies only a few miles south of the 
100-fathom contour off Marthas Vineyard in summer, just as is the case farther west 
and south. Hence, although actual records of the pelagic fauna and flora at this 
same relative position farther east have been very scanty up to within the last few 
years, there was no reason to doubt that a tropical community occupied the same 
relative position along the slope off Georges Bank: while the deep-sea explorations of 
the National and Michael Sars, of the Canadian fisheries expedition of 1915, and of 
the international ice patrol (Fries, 1922), have shown that the same assemblage of 
warm-water planktonic animals and plants characterizes the inner (northern) edge 
of the Gulf Stream to and beyond the southern corner of the Grand Banks of New- 
foundland. It was therefore to be expected that any lines we might run seaward 
as far, say, as the 1,000-meter contour, would bring us into warm water, where our 
tow nets would yield a tropical plankton instead of the boreal community charac- 
teristic of the Gulf of Maine to the north. And so it has proved, as the follow- 
ing brief notes on our offshore hauls will illustrate. 
On July 10, 1913, for instance, we saw fragments of gulfweed on the surface 
near Nantucket Lightship, and the neighborhood of the stream was made evident 
over the 150-meter contour to the south (station 10061) by “the presence of Salpse, 
Phronima, and the amphipod genus Vibilia, though the bulk of the plankton still con- 
sisted of Calanus jinmarchicus, with such other boreal forms as Euchseta norvegica, 
Euthemisto, and Sagitta elegans ” (Bigelow, 1915, p. 268) . We had a similar experience 
over the 1,000-meter contour, some 70 miles farther east, about a week later in the 
season the following year (station 10218), when we found the water of the high tem- 
perature 27 characteristic of the inner edge of the Gulf Stream, more properly the 
tropical water (p. 52), with a typically tropical plankton including Salpa fusiformis 
and its relative genus, Doliolum; the tropical amphipod genera, Phronima, Vibilia, 
and Oxycephalus; the copepods Phincalanus and Sapphirina; the chfetognaths Sagitta 
enflata, S. hexaptera, and Pterosagitta draco; with the 11 species of tropical pteropods 
and 19 species of tropical medusas and siphonophores fisted below, and gulfweed 
(Sargassum) floating on the surface, as I have elsewhere noted (Bigelow, 1917, 
p. 245). 
Tropical pteropods and ccelenterates taken over the continental slope off Georges Bank, July 21, 1914, 
station 10218 
Species 
60-0 
meters 
300-0 
meters 
400-0 
meters 
Species 
60-0 
meters 
300-0 
meters 
400-0 
meters 
Mollusks: 
Medusae — Continued. 
1 
Rhopalonema funerarium 
X 
1 
Rhopalonema velatum 
X 
X 
1 
X 
1 
x 
Cuvierina columneila, Rang 
2 
Aglaura hemistoma 
X 
X 
Diacria trispinosa, Lesueur-. 
Cavolina longirostris, Lesueur 
1 
1 
Nausithoe punctata 
Siphonophores : 
X 
1 
Hippopodius hippopus 
X 
i 
Diphyes spiral is ______ 
X 
1 
i 
X 
1 
X 
2 
Diphyopsis dispar 
X 
X 
x 
x 
x 
x 
x 
x 
x 
x 
X 
X 
X 
X 
87 Temperature 17.7° and salinity 36.04 per mille at 40 meters; 20.48° at the surface. 
