Based on the accurate records reported from the fishing-boats, about fifty in number, distributed on our Pacific side from 1936 to 1938, N-θ. curves of “Katuo” (or the curves of the frequency of the catch of “katuo” as ordinate against the surface water temperature as abscissa) were plotted and examined (Fig. 1). (1) N-θ curve referred to the sea-district off North-eastern Japan shows asymmetrical form, with a clear maximum lying on it, which can be considered as the result of deformation of a normal curve having equal area, as plotted by a dotted line in Fig. 1. On the higher temperature side of N-θ curve, another small and some-what vague maximum is seen, which also corresponds to a smaller probability curve. The asymmetrical deviation of the curve to the lower temperature is explained by the accumulation of shoals of “Katuo” on the line of convergence (Cold Wall) corresponding to the polar front which is especially distinguished in summer. (2) In the southern, Dunan and Satunan, seadistricts, of Japan, N-θ curves are represented by the combination of two or three probability curves approximately.

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Sources of errors attached to the pycnometry of sea water such as the variation of surface tension aroused by the varied condition of the glass surface of the hydrometer, by the contamination of water surface due to dust, oil etc. or by the convection in the water specimen, also with personal error, which are superposed in complexed manner, were investigated carefully. As the result of statistics and the experiments on the effects of the contamination of water surface etc. it was shown that the accuracy of the density measurement by means of the Akanuma's Hydrometer is usually of the order of 0.1‰ S.

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This report embodies the results of salmon tagging experiments made by three guard ships of Bureau of Fisheries, Kaihô-maru, Syunkotu-maru and Syôhô-maru and by a training ship belonging to Hakodate Colledge of Fisheries, Osyoro-maru in the east and west. sides of Camehatska in 1937 and 1938.

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Seven specimens of the yellow-fin, Thunnus macropterust (T. & S.), caught in the South-Sea in November to December, 1937 (Table 1) were promptly eviscerated and preserved in a frozen state at about -7°C for 3-4 months. They were then melted, and 500-800g. of each of such five bodily parts as shown in Fig. 1 and also of gonad were canned at 6 lbs. for 1•5 hours. The material from each can underwent ether extraction which yielded respective fats ranging on the average from 145•7 to 191•8 in iodine value and from 1•4727 to 1•4758 in refractive index (Tables 2 & 3). remarkably enough, the fat from the dark muscle was found to have the highest iodine value in spite of low refractive index.

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In order to study the physiological property of the sea-water, especially its effect on the the growth of diatoms, the present experiment was carried out. Sea-water samples were collected at different depths and on different dates off Sinmaiko, west coast of Tita Peninsula. The sample were enriched with nitrate, phosphate, silicate and iron, and used for culture media of diatoms, artificial light being employed for the illumination. Media prepared with different sea-water samples gave different effect upon the growth of diatoms as shown in Tables 1 and 2, and Fig. 1. The growth of diatoms in media of both the surface and the bottom water was better than in that of the water taken from middle layer (Table. I). The media prepared with water samples taken on different dates at the same place show different grades of effect upon the growth. As the sea-water moves in the sea the water at a certain place changes its property occasionally and it becomes sometimes coastal and others oceanic in its nature. Culture media prepared with coastal water gave better growth than those with oceanic water collected thus at the same place but on different dates (Table 2, Fig. 1). The miqueld sea-water enhances the growth of diatoms in the present experiment as in the case of A_LLEN and N_ELSON (1910), yet the culture with the miquelded sea-water show similarly as in the non-miqueled that the sea-water at different vertical layers has different effect upon the growth of diatoms (Table. 1). This points to the conclusion that the sea-water contains some substance which enhances the growth of diatoms. As both the coastal and the bottom sea-water are alike rich in the organic matter, this substance may enhance the growth of diatoms in the culture media.

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