PLANKTON OF THE GULF OF MAINE 253 



found in the stomach of the Arctic cod (Boreogadus saida) in the Greenland Sea 

 (Damas and Koefoed, 1907, p. 566). 



Metridla lucens Bosck 



This species has a more southern range than M. Tonga, being widely distributed 

 over the temperate and boreal parts of the North Atlantic but hardly entering the 

 Arctic zone. On the European side it occurs regularly west of France, at the mouth 

 of the English Channel, south and west of Ireland, between the Faroes and Iceland, 

 in the northern part of the North Sea to the Skager-Rak, and northward along 

 the west coast of Norway to the Lofoten Islands. There are a few records of it 

 north of the Murman coast and in the Greenland Sea 39 . To the southward it occurs 

 in the Mediterranean, and it has also been recorded from the Gulf of Suez (van 

 Breemen, 190S). Presumably M. lucens ranges right across the North Atlantic, 

 though Herdman did not find it on his passages between England and the Gulf of 

 St. Lawrence (Herdman, Thompson, and Scott, 1S98), for the Canadian fisheries 

 expedition had it generally in and off the mouth of the Laurentian channel, along 

 Nova Scotia, and occasionally in the Gulf of St. Lawrence (Willey, 1919, p. 202, 

 fig. 27). 



M. lucens is a common species in the Gulf of Maine. Wheeler (1901) reports it 

 from Woods Hole (as " M. hibernica Brady and Robertson") and Fish (1925) found 

 it there in winter. During the summers of 1913, 1914, and 1916 the Grampus towed 

 it at about a dozen stations on the outer part of the shelf and outside the continental 

 edge southward from off Cape Cod to abreast of Chesapeake Bay (Bigelow, 1915, p. 

 295; 1917, p. 290; 1922, p. 147), as well as at two localities near land — off Long 

 Island (station 10083, August 1, 1913) and off Delaware Bay (station 10375, August 

 4, 1916). West of Cape Cod it seems to keep offshore, for Williams (1906 and 1907) 

 does not list it from Narragansett Bay nor does Fowler (1912) from New Jersey. 

 The latitude of Chesapeake Bay, in the one direction, and the deep water between 

 the Scotian and Newfoundland Banks and the Gulf of St. Lawrence, in the other, 

 are, respectively, the southern and northern limits to its known range along eastern 

 North America. 



M. lucens is also known from the Pacific, being described by Esterly (1905) as 

 one of the most abundant copepods in the plankton at San Diego, Calif., both in 

 summer and winter. 



As van Breemen (1908) has pointed out, this is one of the few copepods which 

 is luminescent, and as it is chiefly responsible for the phosphorescence on the Irish 

 coast in spring (Farran, 1903, p. 12), no doubt it is partly responsible for the 

 brilliant phosphorescence so often seen in the Gulf of Maine. 



Distribution in the Gulf of Maine. — Next to Calanus finmarchicus and Pseudocala- 

 nus elongatus, M. lucens has appeared most frequently in the towings in the gulf, but 

 with considerable fluctuation in the regularity of its distribution and in the numerical 

 strength of the local stock from year to year. In the summer of 1912 it was recog- 

 nized at 26 per cent of the offshore stations and at 30 per cent during the ensuing 

 winter; but this was the poorest period for it in our experience, for Doctor Esterly 



" For a summary of what is known of its distribution see Sars (1903) and Farran (1910). 



