414 
BULLETIN OF THE BUREAU OF FISHERIES 
The hauls listed above are further interesting as showing that C. arcticum, so 
widely distributed in spring (p. 407) but not detected in the gulf in late summer or 
autumn, reappears there in small numbers in midwinter, but curiously enough along 
its northern and western shores and not in the eastern side. 
There is no reason to suppose that any notable alteration takes place in the 
relative numbers of the several species of Ceratium during the months of January and 
February; certainly not off Gloucester during the winter of 1913, where C. tripos 
Fig. Ill— Proportionate numbers of C. longipes (solid curve) and C. tripos (broken curve) in samples of 100 Ceratium of 
all species in the Massachusetts Bay region at different seasons, 1913 to 1922 
continued predominant until the diatom flowerings commenced in March. Doctor 
McMurrich’s plankton lists also show this to have been the case at St. Andrews during 
1916. 
The mutual fluctuations of C. tripos and C. longipes in the northern part of 
Massachusetts Bay are represented in the accompanying diagram (fig. Ill) based on 
the combined data for the years 1912, 1913, 1915, 1916, and 1920, which will serve 
equally for the offshore parts of the gulf if the reversal of dominance be imagined as 
