TABLE 15. --Night (N) and day (D) collections of plankton volumes-'- on Grids I-V. 



5 -day ratio ml. per haul N/D: 2.38 



■"■ Small organisms only (see table 1) 



^ Stations omitted if taken at or one-half hour before or after sunset 



-^ Based on plankton volimie per haul 



volumes, and these were near the center of 

 the grid. 



Ratios of night and day hauls were deter- 

 mined for the plankton volumes by dividing 

 the grid stations in the same manner as was 

 done for the larvae of Leuroglossus stilbius 

 and Lampanyctus mexicanus . 



The 5-day ratios of volumes on the grids 

 showed 2.38 times as much plankton collected 



at night as in the day (table 15), while the same 

 ratios on the drogue and anchor stations 

 respectively showed 1.47 and 1.46 times as 

 much plankton collected at night as in the 

 day (table 16). 



The histograms for the drogue and anchor 

 stations (fig. 7) show the changes in volume 

 caused by diurnal migration; generally in- 

 creasing to a maximum at night and decreasing 

 to a minimum in the day. 



40 



