PLANKTON OP THE GULF OF MAINE 
49 
The winter plankton of 1920-1921 differed from that of 1912-1913 in the rarity 
of the amphipod genus Euthemisto, both species of which not only occurred regularly 
during December, January, and February, 1912 and 1913, but usually in consider- 
able numbers. Sagitta elegans, though it occurred regularly, was also far less 
numerous in the midwinter of 1920-1921 than at that season in 1912-1913, when it 
was an important factor in the tows made in Massachusetts Bay from December 
until February. Whether these differences were actually the result of annual fluctua- 
tion in the stock of these two animals present or whether both are normally more 
abundant in Massachusetts Bay and its vicinity than in other parts of the gulf in 
winter remains to be learned. 
Other features of the winter plankton of the gulf worth mention are that the 
buoyant eggs of the American pollock ( Pollachius wrens) appear in great numbers from 
November until February over its restricted breeding grounds; that cod eggs are to 
be expected throughout the winter (Bigelow and Welsh, 1925, p. 424) if the nets be 
towed near where the fish are spawning — seldom otherwise or in large numbers; and 
that some few copepods (probably Calanus) continue to reproduce right through the 
cold season, for their nauplii were detected at most of our December-January 
stations of 1920 and 1921, most plentifully in Massachusetts Bay. Euthemisto, too, 
must breed then (though probably in small numbers) to account for very young 
specimens taken off Gloucester on December 29, 1920. In this connection I may 
also call attention to numbers of large Calanus hyperboreus (5 per cent of all the cope- 
pods) among a very rich catch of C. jinmarchicus in the western basin on December 
29, 1920 (station 10490, p. 304), and of Stephanomia bells in the eastern basin and 
in the shoal water off Yarmouth (Nova Scotia), which was nearly barren otherwise, 
on January 5. On the other hand, the arrow-worm Sagitta serratodentata vanishes 
from the gulf sometime during late winter, our latest seasonal record of it being for 
January 16, 1913 (off Gloucester). 
Judging from the tow-net hauls made during 1913, the zooplankton of the 
Massachusetts Bay region continues decidedly uniform in composition throughout 
January and February, when the successive hauls reproduced one another with 
monotonous regularity, until early in March, when the quantity of animal plankton 
present in the water decreased to its annual minimum (p. 39) coincident with the 
vernal augmentation of vegetable plankton described elsewhere (p. 3S5), a change 
soon followed by the wave of reproduction on the part of the copepods which I 
have just discussed. It may safely be assumed that this is equally true of the 
northeastern part of the gulf, for although, unfortunately, we have no plankton records 
from its outer waters during the period January 9 to February 22, Doctor McMurrich 
found Calanus jinmarchicus and Pseudocalanus, with Temoralongicornis and the neritic 
copepod genus Acartia, the chief animal constituents of tow-net catches during this 
season of the year at St. Andrews. 
The seasonal planktonic cycle in the deep waters of the gulf below 100 meters 
calls for separate discussion, because the Euchseta community is largely below 
the reach of the wide fluctuations of temperature to which the inhabitants of the 
shoaler strata of the gulf are subject. Data on this for the early winter consist of 
two tow-net hauls, one from 240 meters in the western basin, December 29, 1920 
