The results of the first paper of this series, a study of the plankton in a tropical shallow water region in the Gulf of Mexico, suggested the desirability of extending the observations to more typically oceanic areas in order to analyze productivity factors in relation to the depth of water and to attempt to estimate the relative productivity of northern and southern seas. Opportunity for such an investigation was obtained during a cruise of the "Atlantis" from the northern coast of Cuba to Woods Hole. Eighteen stations were established during the cruise, and measurements were made at each station of temperature, oxygen, phosphate, nitrate, and total plant pigments from the surface to the approximate limit of the occurrence of phytoplankton. In the surface waters of all stations the chlorophyll content was also determined, and experimental measurements were made of the oxygen and nitrate production and consumption in light and dark bottles. Finally, at five of the stations, quantitative collections of zooplankton were made with Clarke plankton samplers....