PLANKTON OF THE GULF OF MAINE 
173 
and 1,600 in deep). There are no vertical-net collections for July, 1915, and the 
normal summer status of A. clausi in the Gulf of Maine can not be stated from the 
other data at hand. In 1915 it varied in abundance from about 500 to upwards of 
Fig. 58. — Occurrence of the copepod Acartia clausi during the spring of 1920. X, locality records for February and March; 
®, locality records for April and May. The hatched curve incloses the area where it occurred in March 
10,000 per square meter at three stations in August, but was not detected at all at 
sea during this month in the three previous years, which I take to mean that it 
passes through a summer minimum succeeding the late spring maximum. In Sep- 
