PLANKTON OF THE GULF OF MAINE 241 



No seasonal localization of the species in one region or another is demonstrated 

 within the gulf. In other seas H. croni has usually been taken at or near the surface, 

 and the Grampus specimens of 1894, just mentioned, were likewise from hauls at or 

 near the surface. Similarly, this copepod occurred in about 25 per cent of the 

 surface hauls during the spring of 1920, but only in about 12 per cent of the verticals. 

 Evidently it lives chiefly close to the top of water, but the fact that seven verticals 

 took it at April and May stations when the surface net missed it, although the latter 

 filtered much the larger volume of water, is evidence that its vertical range extends 

 down at least for some few meters and possibly to a considerable depth. No infor- 

 mation is available as to its presence or absence on the surface in the gulf during the 

 remainder of the year. 



H. croni has never been more than a very minor factor in the copepod fauna of 

 the gulf, as revealed by the tow net. At the stations where it has been recognized 

 it has averaged only about 1 per cent of the copepods; at the most 5 per cent. The 

 numbers per square meter at the stations of record for the species have varied from 

 a mere trace to a maximum of about 2,300 (station 10304, August 6, 1915). Although 

 H. croni was taken at more stations during the spring months than in summer, the 

 numbers per haul were less (average less than 150 per square meter for March, 

 April, and May; maximum about 277) than in August, when there were 1,700 and 

 2,300 per square meter at the two stations (stations 10304 and 10309; table, p. 298); 

 but it is not safe to draw conclusions as to the numerical fluctuations of the species 

 from so few hauls. 



Dr. C. B. Wilson, in a letter, speaks of the egg sacs of the females; therefore 

 it is to be presumed that this copepod is endemic in the gulf, but no observations have 

 yet been made on its season of reproduction there. 



Harpacticus littoralis G. O. Sars 



This is a littoral species, known from the south and west coasts of Norway, 

 where it is usually found in very shallow water, especially at the heads of flat, sandy 

 creeks, and about Great Britain. 35 H. littoralis has not been reported previously 

 from the American coast under its own name, but it is possible that it was included 

 among the H. chelifer recorded by Sharpe (1911) from Woods Hole and from the 

 vicinity of New York. 



At St. Andrews Doctor McMurrich lists H. littoralis occasionally between Decem- 

 ber 12 and March 28, rather more frequently but always in small numbers during 

 April and May (about 45 per cent of the stations), and not at all during the other 

 months. 



Judging from its littoral nature on the other side of the Atlantic there is no reason 

 to suppose that it ever becomes planktonic outside the outer islands in the Gulf of 

 Maine; but probably tow nets would take it in most of the harbors north of Cape 

 Cod at some stage of the tide. 



" See Sars (1903-1911) (or the history of this species, previously contused with H. chelifer Muller. 



