It is pointed out that a model of dynamical balance discussed by Weenink and Groen (1953) appears to lead to a solution which involves a discontinuity in the vicinity of the equator. The origin of this unreasonable singularity is found to be in the assumed density model. A modification for density model near the equator which seems more realistic in view of recent observations is suggested to yield a reasonable solution.

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The meridional variation in the Coriolis parameter causes an intensification of the vertical upward current in the vicinity of the equator in a convective circulation induced by density differences between the equatorial and polar regions in a zonal basin comparable in size to the Pacific Ocean.

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The depth measured by the unprotected thermometer sometimes does not agree with the expected depth, owing to the inclination of the wire caused by current and wind. The author has tried to get an experimental formula which enables to estimate the depth of the sampling bottle by means of measuring the wire length and the angle between the wire and the vertical above thesea-surface, and he got the following formula;
D=l cosθ-Cθⁿ
where D, l, and θ are depth, wire length and angle respectively; C, n are constants which vary with the depth (600, 800, 1200, 1500 m).
As illustrated in the figure (Fig. 2), the results of estimation are very satisfactory for practical purpose.

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In temperate latitudes the oxygen content of sea water near the surface varies with seasons. This occurs since the solubillity of oxygen in sea water changes with water temperature and further since the production and utilization of oxygen by organisms are not equal in different seasons.
A. C. Redfield estimated the exchange of oxygen across the sea surface (ΔQ_E) and the net production of oxygen by organisms (ΔQ_X) during the period of observations. He concluded that ΔQ_X is equal to two fifths of ΔQ_E using the data of oxygen content in the waters of the Gulf of Maine.
In the present paper the anther has made an attempt to determine the magnitude of ΔQ_E and ΔQ_X- in Gotonada, pointing out the error of Redfield's estimation.

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Planktological and oceanographical observations were made every third day at a pier on the east side of Jogashima Island from March 1952 to May 1953. Every time, sea water of two hundred cc was collected by Kitahara's water bottle, and in general all the numbers of diatom cells in the water were counted after condensation by centrifugal method. At the same time oceanogrophical elements were also observed.
(1) Generally speaking, the variation of the number of diatom cells shows a periodicity, namely the burst of plankton diatoms occurs three times in a year, in March and April, in June and in October, with reference to the former investigations at the same pier from June 1951 to March 1952.
And there can be be seen a close relation between the number of diatom cells and rain-fall.
(2) The “Kyutio” which means the flowing of an oceanic water mass into the coastal area, appeared several times in the observation period. In this paper some discussion is made about two cases of this phenomenon, the one in July 1952 and the other in January 1953, when the south or southwest gale blew hardly and the number of diatom cells decreased extremely.

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