PLANKTON OF THE GULF OF MAINE 
327 
Inasmuch as the planktonic communities of the deeper levels of the Atlantic 
never penetrate the gulf in toto ( p. 67) , it can hardly be questioned that such examples 
of S. maxima as appear there come via the northeastern route in the band of cold 
mixed water along the edge of the continent, not from the much greater depths which 
they inhabit off the slope. Very likely the chief source of supply for this species in 
the Gulf of Maine is the deep oceanic triangle between the Nova Scotian and New- 
foundland Banks, where the Canadian fisheries expedition found S. maxima in great 
abundance in a haul from 200 meters on the 1st of June, 1915 (Huntsman, 1919, 
p. 429). In short, it is as a distinctively northern visitor and as such alone that 
S. maxima reaches the Gulf of Maine, but our experience so far has been that but few 
individuals find their way in through the eastern channel, which is the only line of 
ingress sufficiently deep to be normally open to it. 
S. maxima is an extraordinarily voracious animal and as such must occupy an 
important position in the natural economy of the plankton of the deepest waters of 
the gulf if it ever enters the latter in any abundance. 
Sagitta lyra Krohn 
This chsetognath is as distinctly a summer visitor as is its larger relative, 
S. maxima, a winter one to the inner parts of the Gulf of Maine, where it has been 
detected on six occasions in three distinct years — all in July and August. These 
records are as strictly confined to the deep trough as are those of S. maxima (p. 325), 
and whether within or without the gulf the depths of capture are about the same as 
for that species. 
Station 
Depth 
in meters 
Speci- 
mens 
Station 
Depth 
in meters 
Speci- 
mens 
10031.. 
100-0 
2 
10227 
180-0 
1 
10093 
155-0 
2 
10246 . 
150-0 
2 
10225 
225-0 
2 
10254 
225-0 
1 
S. lyra occurs side by side with S. maxima over the continental slope in late winter 
and early spring as well as in summer. 
Station 
Date 
Depth in 
meters 
Speci- 
mens of 
S. lyre 
20129 
May 17,1920 
June 24, 1915 
July 22,1914 
July 10, 1913 
50-0 
2 
10295 
750-0 
10 
10220 
400-0 
5 
10061 
73-0 
1 
Being a summer visitor to the gulf, S. lyra occurs there in rather higher tem- 
peratures than does S. maxima. About 6° is the lowest in which our records estab- 
lish its presence, and the upper temperature limit for the captures so far made 
within the gulf is at least as warm as 8.17° (station 10031). Our records for it over 
