20 
BULLETIN OF THE BUREAU OF FISHERIES 
were so abundant on these occasions that every haul yielded quarts of them, and that 
they fish through the water so thoroughly with their trailing tentacles that a great 
scarcity of all smaller pelagic animals regularly characterizes this part of the gulf 
in summer. In fact, a more striking contrast would be far to seek than between the 
masses of these glassy sea marbles, which have filled our nets there, and the abundant 
crustacean plankton of the deeper basin a few miles to the westward. 
Although spring, not midsummer, is the chief season of reproduction in the 
Gulf of Maine (p. 41), certain of the planktonic groups of animals breed in sufficient 
numbers there in July or August for their larvae to loom large in the summer plankton. 
This is true of the euphausiids, for we have found their larval stages common in 
Provincetown Harbor on July 20, 1916 (station 10343); on the surface off northern 
Cape Cod, August 28, 1914, in company with large Calanus (station 10264; Bigelow, 
1917, p. 283). Young euphausiids were also abundantly represented in the hori- 
zontal haul at 40-0 meters on August 31, 1915 (station 10306), but so closely re- 
stricted to the upper stratum that a haul from 110-0 meters brought back very few 
among a half liter or so of calanoid copepods. Euthemisto is likewise produced in 
great numbers well within the gulf in August — witness rich hauls of the newly- 
hatched larvae off Penobscot Bay on August 11, 1913 (station 10092), and in the 
western basin two summers later (p. 160). Copepods, too, breed throughout the sum- 
mer, as noted below (p. 46) , and in sufficient numbers for their young stages to char- 
acterize the plankton locally. Most of the medusae spawn during the late summer or 
early autumn (pp. 358, 364). We may also point out, what is discussed at some 
length below, that larvae of coastwise origin and of the most diverse natures are 
likewise produced during the warm season, though few of them color the aspect of 
the plankton more than a few miles out from the land (p. 32). 
In a later section the seasonal plankton cycle is discussed in some detail (p. 37) ; 
however, it may clarify the account to note here that very little change takes place 
in the general composition of the Calanus community during the period (July to 
August) covered by our midsummer cruises, except for the disappearance of the 
earlier and the appearance of the later maturing species of medusae (p. 46). For 
example, the only notable change during the interval between hauls made at the same 
location off Cape Cod on July 8 (station 10057) and again on August 5 (station 10086) 
in 1913 was that Staurophora, Stephanomia, and Beroe, which were prominent in 
the tow on the first occasion, were no longer to be found on the second., the lists be- 
ing practically identical otherwise. 8 Three years later we found Calanus and its 
companion copepods as overwhelmingly predominant in the upper 40 meters or so 
off Cape Cod on August 29 (station 10398), among such boreal animals as Pleuro- 
brachia, Aglantha, Sagitta elegans, Euthemisto compressa, and larval euphausiids, as 
we had five weeks previous (station 10344, July 22) in the corresponding stratum of 
water a few miles to the south. One very notable event does take place during the 
summer, however; that is, the entrance of Sagitta serratodentata into the gulf and 
its westward dispersal there, which are described in a later chapter (p. 322). 
The foregoing remarks have reference chiefly to the inner waters of the gulf — 
that is, north of the offshore banks that form its southern rim — but the same ele- 
ments unite to form the general planktonic assemblage over all but the outermost 
8 A typical Calanus community with Sagitta elegans, Euthemisto, a few euphausiids, and Limacina. 
