186 WILLEY. 



Mctridia loncja. They are all more or less common constituents of 

 the plankton in the xVtlantic water where it mixes with the Labrador 

 and Cabot currents to the southeast of Nova Scotia. Here the 

 material obtained by the Canadian Fisheries Expedition under the 

 direction of Dr. Johan Hjort (1914-15) contained many young and a 

 fair admixture of adult females, both of Euchacta norvegica and of 

 C. hypcrboreus, but xevy few adult males of Euchacta and none of 

 C. hypcrboreus. Their zoogeographical character has been defined 

 by C. W. S. Aurivillius (1898), C. finmarchicus being arctic and antarc- 

 tic in the wide sense with far reaching adaptability to thermal changes, 

 while the other three are arctic in the strict sense. Only the first- 

 named (C. finmarchicus) figures in the hst from \Yoods Hole. In the 

 winter plankton of Passamaquoddy Bay (191-1-15), ]Mc^Iurrich 



•< observed C. hypcrboreus only in one gathering and then only as a single 

 individual. 



Passamaquoddy Bay is a branch of the Bay of Fundy which in its 

 turn may be regarded, in its present configuration, as an arm of the 

 Gulf of ISIaine. It is therefore necessary to refer briefly to the occiu-- 

 rence of the above-named species in the Gulf of ]Maine as determined 



. by the explorations of the U. S. F. S. "Grampus" under the direction 

 of Dr. Henry B. Bigelow. In the 1912 cruise of the "Grampus," 

 Mctrklia longa did not appear in any gathering. Of 50 stations where 

 C. finmarchicus occurred, C. hypcrboreus was present twice only, one 

 indiAidual at station 40 and six examples amongst thousands of 

 C. finmarchicus at station 23 (20-0 m.; Bigelow, 1914, p. 102). 

 Euchacta norvegica, a typical constituent of the deep water plankton 

 of the Gulf of INIaine, occurred in greatest abundance at station 43, 

 where it formed the bulk of the haul in the closing net at 85 to 60 

 fathoms, its numbers equalling those of C. finmarchicus. At this 

 depth (85-60 fathoms) the temperature was 42° F., and the salinity 

 about 33.5%o- 



In the 1913 cruise of the "Grampus," Metridia longa was recorded 

 from several stations in the Gulf of Maine in small numbers. At 

 station 10100, between Penobscot Bay and Cape Sable (i. e. opposite 

 to the mouth of the Bay of Fundy), the quantitative haul (90-0 

 fathoms) registered 270 C. hypcrboreus to 5400 C. finmarchicus. At 

 this station Euchacta norvegica was likewise abundant (Bigelow, 1915, 

 p. 292). 



In order to appreciate the contrast between the seasons 1916-17 

 and 1919-20, in Passamaquoddy Bay, it will be enough to consider 

 two typical hauls at "Prince" station 6 in 1920, and then to present 



