In the present paper, physical and biological properties of the environment relating to the ecology of the saucy have been examined in connection with the characteristics of the boundary zone chiefly between Oyashio and Kuroshio.
The physical environment at the beginning of the fishing season was analysed by using the data from the observations made in the Tohoku sea-area off Hokkaido by Tohoku Regional Fish-eries Research Laboratory in September, 1951 (Fig. 1, 2). The environmental data on the fish-ing season were obtained from the oceanographic observations made by Hakodate Marine Meteoro-logical Laboratory in October, 1951. The plankton population war estimated from the oxygen supersaturation by the method described in the preceding paper. The distribution of the plankton population, water temperature and the catches of sauries is shown in Fig. 3. The appearance of sauries coincides with high plankton populations in the region. This fact shows that the quantitative distribution of plankton populations-a scalar field of the plankton is one of the most important environmental factors for the ecology of the aury.
Fig. 4 shows the seasonal trends of the distribution of plankton populations and sauries in the sea surrounding Japan, where the former is estimated by using the correlation between the oxygen supersaturation and the water temperature (see preceding paper) and the latter is based on the data of H. K_ASAHARA and N. O_TSURU (1952).
The seasonal trartsition of highly productive zone with high plankton populations which is mainly formed in the boundary zone is fairly in accord with the seasonal migration of the saury. As the result, such productive zone is considered as the habitat of saurie and their seasonal mig-ration is explained by the transition of the field of plankton population wnich is a biologic environment. At last, a discussion is made on the area of the productive zones and their seasonal trends (Table 1, 2).

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土壌微粒子を添加した培養液中では藻の増殖が促進される。これは微粒子が呈する吸着, 触媒, イオン交換等の作用によって生育が助長されたためと考えられる。実測の結果, 水深20m程度の浅海では底層においてこれと同様な藻類増殖助長作用の起り得ることがわかった。鳥取県下の浅海では, 海底堆積物の半径と有機物含有量が反比例しており, その相関度は高い。これらの事実から浅海の堆積物に含有される有機物は, 土壌粒子の呈する増殖助長作用にささえられて生産された藻類が主体をなすものと推論した。
これらの生物有機体は, 底層における生物生産において, 基礎生産物に相当するものであるから堆積物粒径の小さな砂浜ほど底層における生物生産が大であるということができる。

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P ysiological and ecological studies on red tide have been made in laboratory as well as in field.
In this paper the vertical migration of the plankton producing red tide has bean investigated. The plankton organism Sennia sp. collected from the red tide in Maizuru Bay (November, 1956) has mainly been used as the material in laboratory and following results have been obtained.
1) When a part of the water mass of red tide was brought in laboratory, the plankton organisms found within it usually sank to the bottom of a vessel and then came mostly to death. However, these sinking and death were kept in check by putting a proper number of pearl oys-ters Pteria martensii (D_UNKER) in the material, adding the ordinary sea water of bottom layer in it, and so on.
2) Strong light, high salinity, oxygen unsaturation, and low pH seem to increase a buoyancy of the plankton; and, the inverse states of them, fall of temperature and strong shock seem to increase the tendency of sinking of it.
3) The vertical migration of the plankton might be caused mainly by decrease of dissolved oxygen and increase of light in the morning, and by the inverse states of both in the evening.
4) It has often been observed that the plankton producing red tide were extraordinarily concentrated in the surface layer (Table) and formed the mass of discolored water along the coast or at the corners of a bay. These phenomena seem to be mainly based on that the plankton increases its buoyancy according to increase of light and recovery of salinity after much rain, and that the plankton which has come together to the water surface by such a buoyancy is further concentrated, wafted on the skin current caused by wind.
As for the mechanism of vertical migration, few studies have been done. It will be discussed in the future papers.

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The relation between the chemical constituents of Porphyra yezoensis and environmental factors was examined by dipping frozen laver nets every month and harvesting the fronds after one month at many culture grounds in the Kuwana district for two successive seasons, from December 1967 to March 1968 and from November 1968 to March 1969. The results are summarized as follows;
1) The total nitrogen and phosphorus contents of the laver reached its maxima in February 1968 and January 1969, when laver of superior quality was obtained. Both these chemical constituents decreased remarkably in March for both seasons and laver of an inferior quality was harvested.
2) The tendency for carbohydrate contents to become higher in the laver of the inferior quality was also recognized in the present study. The contents increased markedly at the end of both seasons.
3) A linear relationship was found between zinc and the protein contents. In laver fronds showing low values for protein nitrogen and phosphor elements such as manganese, copper, aluminium, calcium and sulfate were found to be rich.

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The dried laver Porphyra yezoensis was analyzed for its inorganic constituents, by using the specimens previously reported. The results obtained are summarized as follows.
1) Inferior samples contained more Ca, Fe, Mn, Cu, and Al than the superior ones.
2) A high concentration of Zn in the superior samples was noticeable.
3) The concentration rates of these elements were in the following order: P>Zn>Mn, Fe >Cu.>Si>Ca>Mg.
4) In the culture period between December and February, concentrations of P, Zn and Mg reduced gradually while those of Ca, Fe, Si, Mn and Cu increased gradually.

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If there are the data on the distribution of temperature, salinity, dissolved oxygen and phos phate in a given region, it is possible to estimate the standing crop of plankton population from the oxygen supersaturation by using the method described in the preceding paper. Unfortunately, however, we have little such complete data on the oxygen distribution covering different seasons and places for the practical calculation of the standing crop in the sea area surrounding the Japan. Therefore, in this paper, a statistical method is developed for the evaluation of the oxygen supersaturation.
The method has been based on the relationship between the oxygen supersaturation and the water temperature, and their statistical treatments have been made by using the data described in a series of publications of the Central Meteorological Observatory and the Imperial Fisheries Experimental Station in Japan respectively on temperature, salinity and oxygen distributions in the eastern sea of Japan (see references). The frequency distribution of the oxygen supersaturation against the different grades of water temperature in the eastern sea of Japan is given in Table 1. The values of the oxygen supersaturation in each water temperature are averaged respectively and plotted into Fig. 1 in the range of water temperatures from 11°C to 25°C together with the actual determinations for micro-plankton organisms obtained by T. S_HIMOMURA, 1953. As shown in Fig. 1, the maximum oxygen supersaturation which should be corresponded to the maximum standing crop of the plankton is found in the range of temperature from 14°C to 17°C and fairly agrees with the actual maximum amounts of mieroplankton organisms. However, the actual determination shows the another mode of plankton population at the range of temperature from 8°C to 9°C. For the lower range of temperature than 11°C in this area, the available data on the oxygen distribution have been very scant, so that the data on the Japan Sea have been refered, even if they might be unadequate (Fig. 2). According to Fig. 2, the mode of the oxygen supersaturation is found at the range of temperature between 4°C and 9°C. Therefore, from these facts it is assumed that there would exist a fertile zone also in colder sea areas than 11°C.

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