Hachijô Island, one of the Zunan Group (or Izu Islands), is located at lat. 33° 02'-09' N and long. 139°43'-52' E, 157 miles south of Tôkyô, just exposed to the great warm current, “Kuroshiwo.”
The plankton materials dealt with here are those collected five times in the coastal waters beyond the breakwater, nine times at the beach, and twice in the tide pools of the island, covering the years 1950, 1951, and 1952. All were collected by means of plankton net of ordinary type, made of bolting cloth of 128 meshes a linear inch.