ILLUSTRATIONS 

 FIGURE Page 



Frontispiece: Towing a plankton net from the Hugh M. Smith. 



1. Variations in the volume of zooplankton among the Subtropic, Transition, and Subarctic 



Zones. 4 



2. Seasonal variation in the northern limits of the Subtropic Zone 5 



3. Seasonal variation in the northern limits of the Transition Zone. 8 



4. Diagrams representing temperature-salinity relations. 10 



5. Comparison of the distribution of chaetognaths along the 180* and 157°30'W. meridians. . 11 



6. Location of various isotherms in the summer, winter, and fall. 12 



