PLANKTON OF THE GULF OF MAINE 155 



to the former suggests that Meganyctiphanes spawns in summer, which fits in with 

 the season of abundance of euphausiid larva? (p. 134) and points to the noitheaatern 

 part of the gulf, where this shrimp is so abundant, as its chief spawning ground. 



Nothing is yet known of the seasonal occurrence or distribution of the larvse 

 of Meganyctiphanes in the Gulf of Maine except that juveniles of the species were 

 taken in some numbers off Cape Cod on July 19, 1914, in a haul from 70 meters 

 (Bigelow, 1917, p. 282, station 10213). Very likely this genus was represented 

 among the larval euphausiids taken on the surface off Cape Elizabeth on August 14, 

 1913 (station 10103); in Massachusetts Bay and off Cape Cod in July, 1916 (Bige- 

 low, 1922, p. 133, and station 10343); and off the cape in August, 1914 (Bigelow, 

 1917, p. 2S3). These, however, have not been studied. 84 McMurrich, too, found 

 young (unnamed) euphausiids common at St. Andrews from April until August, 

 probably the offspring of the two pelagic shrimps Meganyctiphanes and Th. inermis, 

 which are so plentiful in that region. However, larval euphausiids of any sort 

 have always been very rare in our offshore catches in the northeastern part of the 

 gulf, notwithstanding the constant presence of the adults there. 



Hansen (1915, p. 6S), I may add, records "immense numbers of older 

 larva?" of Meganyctiphanes taken on May 25, 1891, over the 50-meter contour 

 south of Shinnecock Light, Long Island, which is more than 2° of longitude farther 

 west than the adults of this euphausiid have ever been found in any number. The 

 possibility that adult Meganyctiphanes, in company with the general Calanus com- 

 munity, may spread farther west and south over the shelf during the cold season 

 than it does in summer makes it unsafe to assume that the larva? in question had 

 drifted to the locality of capture from a more easterly birthplace. (Compare, in 

 this connection, the status of Thysanoessa inermis west of Cape Cod, p. 138.) 



Although the evidence that the Gulf of Maine is a successful breeding ground 

 for Meganyctiphanes still lacks something of proof positive, it is probable that this 

 shrimp is not only regularly endemic there but that the northeastern part of the 

 gulf is one of the most important centers of production for it off the American coast, 

 and one, too, which receives few accessions from the north but forms a distinct and 

 practically isolated colony. The relative distribution of euphausiid eggs and larvae, 

 like that of pelagic fish eggs and larvse, is consonant with a general drift around the 

 shore of the gulf with the dominant anticlockwise eddy, from the Bay of Fimdy to- 

 ward Cape Cod, on the part of the developmental stages. 



Thysanopoda acutifrons, Holt and Tattersall 



The claim of this species to mention here rests on a single record — five specimens 

 from the southeast corner of the gulf, July 23, 1914 (station 10225), identified by 

 Dr. W. M. Tattersall (Bigelow, 1917, p. 282). 



Other euphausiids 



The species discussed above are the only euphausiids actually identified from 

 within the Gulf of Maine or from the shoal waters over its southern rim up to the 

 present time. Sundry other members of this group have been taken at one time or 



81 According to Lebour (1924a) the larval stages or Meganyctiphanes and Thysanoessa are easily recognized. 



