PLANKTON OF THE GULF OF MAINE 



17 



Although copepods usually dominate, the other boreal animals just mentioned 

 are so nearly universal in the Gulf in summer that the planktonic community is then 

 surprisingly uniform qualitatively, with the list of prevalent species varying hardly 

 at all from station to station over its inner parts, as is illustrated by the two fol- 

 lowing tables of catches made north of the Cape Cod- Cape Sable line during the 

 summers of 1913 and 1914, seasons that may serve as representative because the 

 plankton of the upper water layers was of the same general type during the sum- 

 mers of 1912, 1915, and 1916, as I have pointed out eleswhere (Bigelow, 1917 

 and 1922). 



Occurrence of representative species in the Gulf of Maine, August, 1913 



Species 



Calanus fiDmarchicus 



Pseudocalanus elongatus 



Metridia lucens 



Anomalocera pattersoni 



Eucbjeta norvegica 



Meganyctiphanes norvegica.. 



Thysanoessa inerrais ' 



Euthemisto compressa 



Euthemisto bispinosa 



Hyperocne kroyeri 



Limacina retroversa 



Tomopteris catharina 



Sagitta elcgans _. 



Phialidium languidum 



Pleurobrachia pileus 



Stations 



X X 

 X X 



Per cent 

 lot* a 

 stations 

 for each 

 species 



100 

 80 

 80 

 80 

 70 

 40 



90 

 50 

 40 

 80 

 60 

 100 

 80 

 50 



' Data [or Th. inermis are not available for 1913; it can, however, be assumed to occur in at least 80 per cent of the cases, since 

 i t was taken at 14 of our 18 midsummer stations in 1914. 



Occurrence of representative species north of Georges and Browns Banks, July and August, 1914 



Notwithstanding the quahtative uniformity of the animal plankton of the 

 waters of the Gulf of Maine in summer, the actual aspect of the catches of the tow 

 nets often differs markedly from station to station, according to the relative abundance 

 of their several components and especially of the copepods. As a rule these (chiefly 

 Calanus, Pseudocalanus, and Metridia, with Euchseta in the deepest layers of 



