40 



BULLETIN OF THE BUREAU OF FISHERIES 



Euchreta, Sagitta elegans, Eukrohnia, Euthemisto of both species, Clione, Limacina 

 retroversa, Tomopteris, Meganyctiphanes, Thysanoessa inermis, and Th. longicaudata. 

 This is a list that might be expected in summer or autumn, and the same was true of 

 the hauls made in Massachusetts Bay during the winter of 1912-1913, mentioned 

 above (p. 39). The plankton is as uniform, qualitatively, from season to season in 

 the deeper parts of the gulf as the following table shows for a location in the western 

 basin about 30 miles off Cape Ann. 



Zooplankton in the western basin, various months 

 [D, dominant; X, occurred] 



Broadly speaking, our March hauls have paralleled those made in midsummer 

 in the relative importance of the several groups of animals in different parts of the 

 gulf, as well as in the qualitative composition of the catches. Thus, Pleurobrachia 

 was dominant on German Bank both on March 23 and on April 16, 1920 (stations 

 20085 and 20103), just as it usually is in summer and autumn, and its area of abun- 

 dance extended from abreast of Yarmouth, on the north, to the shoals off Cape Sable, 

 to the south, on both these visits. On both these spring visits there was a second 

 center of abundance for Pleurobrachia on Browns Bank, where our June and July 

 tows have yielded only an occasional specimen; but although the area of abundance 

 for Pleurobrachia in this general region was more extensive in March and April, 

 1920, than we have found it in summer, these ctenophores were less plentiful in 

 actual number; nor had they so thoroughly exterminated the other smaller animals, 

 for we found the German Bank-Cape Sable swarm accompanied by copepods in 

 fair numbers on the April visit, besides barnacle (Balanus) nauplii (in abundance), 

 Sagitta elegans, euphausiids, Euthemisto, and Tomopteris. 



