After examination of the baroclinic structure below 3000 db, recent data were used to map the geopotential topography at 1000, 1500, and 2000 db (referred to 3000 db) in the Pacific Ocean. In the high-latitude regions and in the western boundary currents, considerable relief is present at 1000 and 1500 db, and the Circumpolar Current is still well-developed at 2000 db. The geostrophic circulation inferred is very similar to the surface circulation in these areas. Neglect of the structure below 1000 db results in appreciable errors in estimates of the transport of these currents ; direction of near-surface flow is properly shown, however, and computed speeds are not greatly in error. In the equatorial Pacific and central North Pacific, little relief is present, and the trends are generally unlike thesurface flow.

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Scaling of the equations of motion of the Antarctic Circumpolar Current indicates that the Rossby number and the Ekman number are 10^-4to 10^-5but the vertical Ekman number may reach unity in the bottom boundary layer. The equations of motion are integrated vertically from the surface to the bottom and averaged over a latitude circle. The resulting equation in the meridional direction is predominantly geostrophic, whereas the main terms of the equation in the zonal direction are the wind stress and the bottom stress. When the vertical eddy viscosity near the bottom is of the order of 10²cm², /sec, the total zonal transport through the Drake Passage computed from the balance of the wind stress and the bottom stress equals 260×10⁶m³/sec, the amount determined by REID and NOWLIN (1970) from observations.
The northward transport reduces the eastward transport corresponding to the wind stress of the westerlies in the A. C. C. through the Coriolis' term in the vertically integrated equation of motionof the zonal direction. South of the Drake Passage, such reduction reaches about ten percent of the wind-driven transport mainly due to the peripheral water discharge. North of the Drake Passage, the northward transport may be generated by the effect of the South American coast which prevents free eastward movement of the A. C. C., causing a wake to the east.This transport may contribute to a part of the northward transport of the bottom water postulated by MUNK (1966). The effect of the horizontal eddy viscosity in the zonal transportequation is negligible except near the Antarctic coast, if the eddy viscosity is less than10⁹cm²/sec.

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At each localized sphere for dynamics of organic matter in the sea, the total amount of nutrient substances is constant, and the total and inorganic substances must keep a steady state within a certain time.
Based on the simplified assumptions, the mechanism of this steady state in the sea was analyzed using the data of primary productivity, especialy nutrient absorption of diatom. When a certain amount of phosphate was supplied to different volume of a basic medium, the absorbed-phosphate per pigment unit (chlorophyll-αμg per liter) of diatom was constant. The absorbed-phosphate per pigment unit and initial concentration of phosphate in the medium had linear relationship within about 200μg phosphate per liter of the medium. The curves of experimental phosphate absorption and growth of diatom were found to be consistent with the theoretical one.

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The plate culture method using the two formulae for non-nitrogenous media was adopted in this investigation for the purpose of counting and isolating nitrogen-fixing bacteria distributed in the open sea.
Sea water samples were collected at eighteen different stationsin the region of Lat. 50°N-15°S along Long. 155°W and two other stations in the Pacific Ocean. In order to compare with those samples from the open sea, water samples were also obtained at four stations in Suruga and Sagami Bays.
Nitrogen-fixing bacteria appear to be widely but very unevenly distributed at all depths in sea water, in numbers approximately ranging from nil to 10⁴per 100 mlof sea water, and denser vertical populations have been found in the area of Lat. 40°N and 5°N along Long. 155°W, even at depths from 2, 000 to 3, 000m. A comparatively denser population of bacteriawas found in sea water from Suruga Bay and Sagami Bay.
The bacteria associated with plankton were abundantly demonstrated, in numbers ranging from 10⁶to 10⁸per 1 mlsettling volume of plankton, in many plankton samples collected at fourstations in the southern parts of the Pacific Ocean. Almost all the bacteria isolated fromthe samples of blue green algal colonies, Trichodesmiumsp., were able to grow on nonnitrogeneous media.

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