The number of chaetognaths and pteropods 

 per cubic meter of water varied greatly among 

 samples. The highest number of chaetognaths 

 per unit of water strained was found in the Sub- 

 arctic Zone and the highest number of pteropods 

 per unit of water strained was found in the 

 Transition Zone. The chaetognaths composed 

 on the average 14 percent of the total number of 

 net macroplankton taken in the Subtropic Zone, 

 8 percent in the Transition Zone, and 6 percent 

 in the Subarctic Zone. The pteropods composed 

 on the average 3 percent of the total nunnber of 



organisnns in the Subtropic Zone, 9 percent in 

 the Transition Zone, and 1 percent in the 

 Subarctic Zone. 



Subtropic Zone 



The area immediately north of the Hawaiian 

 Islands, which we have designated the Subtropic 

 Zone, was characterized by a great diversity of 

 species and relatively low biomass (fig, I). As 

 shown in tables 1 and 2, at least 9 species of 

 chaetognaths and 17 species of pteropods were 



300 



200 



100 



SUBTROPIC ZONE 



I I TRANSITION ZONE 



KJ';;^ SUBARCTIC ZONE 



200 



100 



180° 



TZ'SO'W 



I65°W 



IST'SO'W 



25° 



30° 



35° 40 



NORTH LATITUDE 



Figure 1 . --Variations in the volume (cc./ 1000 m.3) of zooplankton among the Subtropic, Transition, 

 and Subarctic Zones as found on Hugh M. Smith cruise 30, in July - August 1955. 



