PLANKTON OP THE GULF OF MAINE 
257 
rate of 16,500 per square meter (an unusually rich catch for it in the gulf), but a sec- 
ond vertical haul with the same net, hauled up at the same rate of speed and from a 
slightly greater depth (55 meters) at 10 p. m., gave a frequency of only 252 per 
square meter. Evidently the shoal encountered by the first haul had drifted past 
with the tide during the 7-hour interval before the second haul was made. Never- 
