Since April 1931, the collection of plankton samples has been carried out by the staff of the Meteorological Station at Tomizaki, Bôsô Peninsula. Using Nansens's quantitative closing net, 19cm. in diameter, plankton hauls were made from the following layers; 0-10m., 10-20m., 20-30m., 30-50m. and 50-80m. depth. Hensen's method was adopted for counting the plankton. Phytoplanktonic association represented by Chaetoceras, Rhizosolenia and Thalassiothrix was most abundant at all seasons of the year and indeed, at the end of July over 98% of the total number of plankton individuals was phytoplankton. And in addition to the above mentioned species in summer Bacteriastrum and Nitzschia seriata appeared in a large quantity. As far as the present observations in the daytime were concerned, the layer between the 0-20m. depth was most densely populated by diatoms, and they suddenly decreased in the 50-80m. layer to as much as below 20% in quantity of these in the surface layer. Dinoflagellata showed maximum abundance in the layer between the 0-10m. depth and almost disappeared in the layer below 50m.. The most common species found among the zooplankton were Oithona spp., Paracalanus parvus etc.. Although phytoplankton was generally prevailing, Copepods were found crowded in the layer between 20-30m. depth while Noctiluca, Tintinnoidea, nauplius juv. of Copepod as well as pelagic fish eggs mainly existed in the uppermost layer.
The late Dr. H. Nakano(1) studied the propagation of seismic waves in a semi-infinite solid when the three surface stress cmponents are given, and showed that at the surface the amplitude of the wave transmitted with the velocity of longitudinal wave is proportional to the inverse square of the distance from the origin when the surface stress is confined on the parts near the origin. This is due to the fact that the force is applied on a plane surface. It is, therefore, desirable to solve the problem of the propagation of seismic waves when the surface stress components or the components of the surface displacement on a sphere in the semi-infinite solid are given. In this preliminary report the author obtained the solutiong satisfying the boundary conditions, and the analysis of the result will be given in the next paper.