ARCTIC COPEPODA IN PASSAMAQUODDY BAY. 187 



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the exhibits at the same station in 1916-17. On January 16, 1920 at 

 3.15 P.M., towing a net of No. 5 mesh at about 5 metres below the 

 surface yielded 4 cc. of a microcalanoid plankton consisting mostly 

 of young to submature copepods. So conspicuous was the paucity 

 in adult individuals and so predominant was the genus Acartia that 

 it might fittingly be designated a nepionic Acartia plankton. The 

 following percentages were obtained, only the submature and mature 

 Acartia being counted: — 



Acartia clausi 68 per cent. 



" longiremis 13 " 



Pseudocalanus elongatus 16 " 



Temora longicornis 3 " (juniors). 



About the same date (January 27) in 1915, Professor McMurrich 

 recorded a maximum of Temora at this station. Such fluctuations 

 in the plankton are possibly correlated to some extent with the weir- 

 catches of young herring, Temora being herring food par excellence, 

 but there are no data at hand for proving this to be the case. On 

 March 25, 1920, with the tow-net (No. 5) at about 7 metres, 6 cubic 

 centimeters of an Acartia-Balanus plankton were obtained, Balanus 

 larvae and Copepods occurring in subequal quantity. In addition 

 there were a few C fimnarchicus from stage IV to adults of both sexes, 

 two C. hyperhoreus of stage IV, some Pseudocalanus, and a single 

 example of Monsirilla canadensis McMurrich, dark brown in colour 

 after preservation. 



Turning to the winter of 1916-17, the catches are not strictly com- 

 parable with those of 1919-20, as they were taken at a different depth 

 with a closing net (mesh No. 0) towed at 18-23 metres. On November 

 2, 1916, 64 cc. of a red macrocalanoid plankton were obtained, several 

 Sagittae being present, but no fish eggs. One Calanus hyperhoreus, 

 stage V, was seen; one Eurytemora herdmani with ovisac, and one 

 male Metridia longa. The remaining percentage content indicated a 

 Calanus-Tortanus demonstration : — 



Calanus finmarchicus V 46 per cent. 



a a Q 9 u 



Pseudocalanus elongatus 5 " 



Temora longicornis 1 " 



Tortanus discaudatus (cf and 9 ) 46 " 



On December 8, 1916, the plankton had the same general appear- 

 ance and was still more copious, amounting to 87 cc, with Sagittae 



