Abstract
The seasonal fluctuation of phytoplankton was observed quantitatively during Dec., 1932 and January, 1934 at St. Futakotamagawa. Diatom was the most predominant species in phytoplankton and appeared abundant'y in the both seasons of winter and spring. The maximum occurrence fell on 21, Dec., 1932, counting 3, 230 per litre and Melosira varians and Synedra spp. were representatives in the diatom. The vertical distribution of marine plankton was examined in the water of Rokugobasi with 7m. in depth.
