PLANKTON OF THE GULF OF MAINE 
207 
of nauplii such as that just mentioned does actually presage the great augmentation 
of C. jinmarckicus that takes place in that side of the gulf during the late spring and 
early summer. In other words, the Massachusetts Bay region and neighboring 
waters are actually important centers of reproduction for the species, and of growth, 
leading to a dominance of adults in July. Willey (1921) has remarked that this 
part of the Gulf of Maine would seem to be the southern headquarters for the pro- 
duction of C. jinmarckicus in the northwestern Atlantic, and it is not unlikely that 
the Calanus population of the gulf as a whole originates chiefly in the area bounded 
by Cape Elizabeth on the north, Cape Cod on the south, and the western basin 
offshore. 
Judging from the data for 1915 and 1920, the production in this region must 
be very large to account for the local abundance of this copepod in May and July, 
but it is probably not to be compared with the tremendous production that takes 
place in the Norwegian sea, for Calanus eggs have not occurred in notable numbers 
in any of the samples in question , 7 8 whereas Damas (1905, p. 12) describes them as 
locally so abundant between Norway and Iceland that in certain regions they are 
one of the principal elements in the plankton, even to the exclusion of everything else. 
No attempt has yet been made to determine the presence or absence of the early 
stages of C. jinmarckicus in the samples from other parts of the gulf. Probably it 
breeds to some extent over the whole of it (Willey (1921) mentions juveniles in 
Passamaquoddy Bay in April), but the preliminary study of the tow nettings points 
to the region just outlined as by far the most productive center of local production. 
It is also safe to say that spring, from late April on, is the chief breeding season for 
Calanus in the gulf, and that breeding probably continues actively through June to 
account for the abundance of juveniles in various stages which we found off Cape Cod 
on July 9, 1913 (station 10057; Bigelow, 1915, p. 291), 8 and in Provincetown Harbor 
on July 20, 1916 (station 10343). It is certain that no production comparable with 
the vernal wave takes place later in the summer, though positive evidence (in the 
form of eggs and juveniles) as to whether Calanus spawns at all in the gulf during 
July, August, or September is yet to be sought among the masses of copepods collected 
on our cruises. Doctor Esterly’s 9 report of many juveniles at two stations off 
southern Nova Scotia on July 29 and August 6, 1914 (stations 10235 and 10237), 
shows that Calanus breeds well into the summer east of Cape Sable. 
In 1915 the increase in the numbers of C. jinmarckicus in the gulf during early 
autumn was preceded during the first half of September by an abundance of develop- 
ment stages of copepods in the tow. (See table, p. 298.) If these larval stages actually 
were C. jinmarckicus , as seems probable from the constant dominance of the copepod 
fauna by that species, this points to a second but less productive breeding season in 
autumn, an interpretation corroborated by the presence of a large proportion of 
juveniles of this species in the surface tows near the Isles of Shoals and in the western 
basin on November 1 , 1916 (stations 10400 and 10401). Development stages of 
some copepod were likewise recorded in comparative abundance for January, 1921, 
7 No special attention has yet been paid to the eggs in the Gulf of Maine tow nettings — a task for the future, 
8 These were identified by Dr. C. O. Esterly. 
8 In a letter. 
