IN two important papers, Gordon A. Riley continues his investigations on the interaction of the plankton with its environment (“Plankton Studies. 3. Long Island Sound”, Bull. Bingham Oceanograph. Coll., Peabody Museum of Natural History, Yale University, 3, Jan., 1941. “Plankton Studies. 4. Georges Bank”, ibid., June, 1941). The preceding work (“Plankton Studies” 1 and 2, in the same periodical, 1938 and 1939) dealt with the Tortugas region and the western North Atlantic. Light and dark bottles filled with natural sea water and suspended near the surface were used to determine oxygen production and consumption, the utilization and regeneration of nutrients and the production and consumption of chlorophyll. Analyses were made of oxygen, chlorophyll and phosphates in the Long Island surface waters for a period of about a year. Counts were made of zooplankton and, during the last half of the investigation, nitrate determinations were made.