PLANKTON OF THE GULF OF MAINE 355 



Only eight hauls (whether with the open or closing nets) from deeper than 160 meters 

 have yielded Aglantha. Evidently, then, this medusa lives chiefly in the upper 

 strata of water in the Gulf of Maine, just as it does in the North Sea region (Kramp, 

 1913) and for that matter over the North Atlantic as a whole, though not on the 

 surface. The frequency of captures in haids made hetweon 50 and 150 meters (a depth 

 range which included about 40 per cent of all Gulf of Maine records for Aglantha) 

 points to this stratum as its chief center of abundance. The greatest depth from 

 which I can definitely establish the presence of Aglantha within the gulf is 180 to 

 140 meters (closing net, off Mount Desert Rock, March 3, 1920, station 20055J. The 

 only specimen we have taken in a tow from deeper than 200 meters (240-0 meters, 

 station 20049, western basin, February 23, 1920) may have been picked up by the open 

 net on its journey down or up; nor is it any more certain that the few Aglanthas 

 which we have collected along the continental slope ostensibly from 400-0 and 500-0 

 meters (e. g., station 20077, March 19, 1920), but in open nets, actually came from 

 so great a depth. 



Aglantha is seldom abundant in the Gulf of Maine; in fact, most of the records 

 obtained by the Grampus, Albatross, and Halcyon (now amounting to the respectable 

 total just mentioned) are for single or occasional specimens. Only five times have we 

 taken it in large numbers — that is, near Lurcher Shoal, May 10, 1915; near Glouces- 

 ter, July 19, 1916 (station 10340); in Provincetown Harbor the next day (station 

 10243); off Gloucester, October 31 of that same year (station 10399); and on the 

 southeast part of Georges Bank, March 12, 1920 (station 20069). 



Aglantha is present in the gulf throughout the year, taken there during every 

 month except October, when we have done little towing; nor is there anything in our 

 records to suggest that it is notably more abundant at one season than another, for 

 the rich hauls just mentioned were made in spring (March and May), summer 

 (July), and autumn (October). It is probable, however, that a more intensive 

 study of the local occurrence of this medusa in the gulf would show that its numbers 

 there do wax and wane with the succession of the seasons. At Woods Hole it occurs 

 most often in spring (March to May, according to Hargitt, 1905). 



Although the distribution of Aglantha in the Gidf of Maine is more consistent 

 with an extralimital source of supply than with widespread local production such as 

 maintains the stocks of Calanus, TJiysanoessa inermis, Sagitta elegans, or even Euchaeta 

 in the gulf, the fact that very young specimens as well as adults have repeatedly 

 been taken there not only during our recent cruises but half a century ago (A. Agas- 

 siz, 1865) is evidence enough that it reproduces itself to some extent. Occasionally 

 a local wave of production must take place to produce such an abundance of the 

 young medusEe as we found off Cape Ann on October 31, 1916 (Bigelow, 1922, 

 p. 136; station 10399). 



Aglantha, large or small, is usually so scarce anywhere in the gulf that such 

 events must be unusual. Additional information on this point would be very welcome, 

 for it is not possible to appraise the faunal significance of the occasional swarmings 

 of Aglantha as indices to influxes of northern water into the Gulf of Maine without 

 knowing how regularly the stock of this species existing there is replenished by local 

 breeding. 



