PLANKTON OF 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. longa on 
October 21, 1915, near Marthas Vineyard (station 10331, about 9,000 per square 
Pig. 76. — Localities where the vertical hauls have yielded more Metridia longa per square meter of sea area than the average 
for the respective month. ©, March to June; X, August to October. The arrows indicate the.chief migration routes; 
the hatched curve incloses the area where reproduction probably takes place within the gulf 
meter), at a location much farther west and south than the speciesjhad^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 
