460 
BULLETIN OP THE BUREAU OF FISHERIES 
We have never found Halosphaera dominant in the plankton of the gulf. The 
richest catches have been over the outer part of the shelf off Nova Scotia (fig. 130; 
stations 10293 to 10295) and off Mount Desert Island (station 10284) in June, 1915. 
Most of our records are based on the vegetative stage and on stages in division of 
the protoplasm (Lemmermann, 1908, p. 21, figs. 71 and 72). Cells with aplanospores 
have been detected only once in our towings — that is, near Shelburne, Nova Scotia, 
June 23, 1915 (station 10293), and no attempt has been made to trace the life history 
of Halosphaera in American waters, as Gran (1902, p. 12) has done so carefully for 
the Norwegian Sea. 
The seasonal fluctuations of Halosphaera in the Gulf of Maine generally parallel 
its occurrence in the North Sea, where it is at its maximum in May and its minimum 
in August. But east of Cape Sable it evidently reaches its greatest abundance later 
in the season, for Wright (1907) describes it as an important factor in the plankton 
at Canso, eastern Nova Scotia, in June and July. 75 
It is now well established that Halosphsera is not endemic in the North Sea but 
occurs there only as an immigrant from the Atlantic via the northern route around 
Scotland; and it is primarily of southern — Atlantic — origin in the Norwegian Sea, 
though it may also be endemic there to some degree. Whether it is equally an 
immigrant in the Gulf of Maine is yet to be determined, but the facts that our largest 
catches of it have been made over the outer part of the continental shelf and that 
we have never found it in any great numbers in the inner part of the Gulf point 
in this direction. 
ACANTHARIAN RADIOLARIANS 76 
The swarming of radiolarians, represented by the genus Acanthometron, is 
a decidedly sporadic event in the Gulf of Maine, as it is in North European waters 
also (Mielk, 1913), but on such occasions they are extremely conspicuous among 
the plankton, thanks to their large size, distinctive appearance, and reddish color. 
Up to the present time we have only once found Acanthometron dominant — that 
is, on August 22, 1914 (station 10253, fig. 131), when it swarmed off Cape Ann and 
in the western basin. We have never found Acanthometron before or since in 
midsummer in the gulf. Apparently it occurs more regularly in early autumn and 
is more generally distributed then, for it was comparatively plentiful in the center 
of the gulf (station 10309), in the northeast corner (station 10316), off Penobscot 
Bay (station 10318), and off Shelburne, Nova Scotia (station 10313), during the 
first and second weeks of September in the year 1915. It was a conspicuous ele- 
ment in the plankton of Massachusetts Bay during the last week of that month 
(stations 10320 and 10321; fig. 132), but its presence there was short-lived, for none 
were found a month later (stations 10337, 10338, and 10339, October 26 and 27). 
Acanthometron has been detected in only one October tow elsewhere in the gulf 
(a few miles off Penobscot Bay, October 9, 1915, station 10329). It was not found 
at any of the stations in the western part of the gulf in the late autumn, winter, or 
spring, but a few specimens were noted on German Bank and in the North Channel 
on April 15, 1920 (stations 20103 and 20105). 
78 For notes on the temporal occurrence of Halosphsera in the open Atlantic, the Norwegian Sea, and in the Mediterranean 
see Cleve (1900), Gran (1902), Steuer (1910), and Ostenfeld (1910). 
78 For an excellent account of the northern acantharians see Popofsky, 1905. 
