PLANKTON OP THE GULF OF MAINE 



251 



year to suggest that any unusual influx of northern water or immigration of Arctic 

 animals had entered the gulf during that summer. The large catch of M. Tonga on 

 October 21, 1915, near Marthas Vineyard (station 10331, about 9,000 per square 



Fig. 76.— Localities where the vertical hauls have yielded more MHridia longa per square meter of sea area than the average 

 for the respective month. • March to June: X, August to October. The arrows indicate tho chief migration routes; 

 the hatched curve incloses the area where reproduction probably takes place within the Oulf 



meter), at a location much farther west and south than the species had ever been 

 taken before, is especially instructive in this connection, for in this case there is no 

 possibility that any direct influx had taken place from Nova Scotian waters for 



