PLANKTON OF THE GULF OF MAINE 
353 
hydroid stage — and consequently that the medusa is independent of the coast line and 
of the bottom at all stages in development. Its distribution is therefore wholly 
independent of distance from land or from shoal water. 
Aglantha, like many other medusae, was first recorded from the Gulf of Maine by 
Alexander Agassiz (1865), who detected both large, sexually mature medusae and 
young ones at Nahant, Mass., during the summers of 1863 and 1864, since when 
it has been reported both by Hargitt (1905) and by Mayer (1910) as common in 
spring off the shores of southern New England. Consequently it was no surprise to 
find it in our plankton hauls at many stations in the Gulf of Maine. The localities of 
capture, as appears on the chart (fig. 99) , are concentrated in a peripheral zone 40 to 
60 miles broad, paralleling the coast from Cape Cod to Cape Sable and spreading 
thence southward and westward across Browns Bank, the Eastern Channel, and 
following the southern half of Georges Bank westward; but we have never taken 
a single specimen of Aglantha in the central waters of the Gulf or over the northern 
part of Georges Bank. 
The reader need but compare the chart of Aglantha with the corresponding chart 
for Beroe (fig. 102) or for Pseudocalanus elongatus (fig. 83), animals equally pelagic at 
all stages and of similar temperature affinity but regularly and constantly endemic in 
the Gulf of Maine, to note the sharp contrast between the definite localization of 
the records for Aglantha 93 and the universality of the others. 
Although we have never found Aglantha with sufficient regularity (and seldom in 
sufficient abundance) to regard it as a characteristic member of the plankton of the 
gulf, it has occurred often enough and at stations indifferently enough spaced to show 
that it may be expected anywhere and at any season in the area inclosed by the 
curve on the chart. Within this area the locality records show no definite concen- 
tration in one side of the gulf or the other, nor do they correspond to the depth of 
water, and our experience has been that the local presence or absence of Aglantha 
in the gulf at any particular time is as independent of precise temperature or salinity 
as it is of depth, the close neighborhood of land, or the contour of the bottom. Its 
distribution closely mirrors the anticlockwise circulation of the upper strata of 
water in the gulf. The natural inference from this is that the continued presence of 
Aglantha within the gulf depends more on immigration from the east and north than 
on local reproduction. Once such immigrants have passed Cape Sable they follow 
right around the gulf, first north then west, southwest, and south in their involuntary 
journey, with little more tendency to spread toward the center of this great eddy 
than have the various fish eggs or other animals of neritic nature that are set free 
near the coast line. In this its distribution in the gulf parallels (though it does not 
exactly reproduce) that of the elite tognath Eukrohnia hamata, another common visi- 
tor from colder seas to the east and north, which occurs far more regularly around 
the periphery of the deep basin than in its center and spreads southward along the 
slope of Georges Bank but at a deeper level than Aglantha. 
83 For locality records of Aglantha for the years 1913 to 1916, see Bigelow, 1915, p. 316; 1917, pp. 303 and 304; 1922, pp. 134 and 136. 
During the spring of 1920 it was taken at stations 20044, 20046, 20049, 20055, 20056, 20058, 20064, 20067, 20068, 20071, 20072, 20073, 20074, 
20075, 20076, 20077, 20079, 20081, 20087, 20096, 20105, 20107, 20111, 20115, 20116, 20118, 20122, 20128, and 20129, and at stations 10490, 10491, 
and 10499 during December-January, 1920-1921. 
