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 larvoe 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. 2S3). 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 larvce 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 medusas spawn during the late summer or 

 early autumn (pp. 358, 364). We may also point out, what is discussed at some 

 length below, that larva? 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 medusa? (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. 



