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). 
Metridia lucens Boeck 
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, 1908). 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 (Flerdman, Thompson, and Scott, 1898), 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 
39 For a summary of what is known of its distribution see Sars (1903) and Farran (1910). 
8951— 2S 17 
