Variations in oceanographic conditions of the Kuroshio (a warm ocean current) observed in Zunan sea region have an important bearing upon the oceanographical conditions and fisheries off the coast of Sanriku as well as in Zunan sea region. For this reason, the oceanographical observations in this region have been held from time to time by the Section of Oceanography, the Tokai Regional Fisheries Research Laboratory since January 1950, During four cruises in March, April, May and July 1950, the sectional observations were carried out in an area off Nojima-Zaki, extending from Sunosaki to Hachijo Island. Vertical distributions of water temperatures determined by the observa-tions reveal that a boundary area between the warm-water mass ot the Kuroshio and the cold-water mass of the Oyashio (a cold ocean current) is always outstanding and relatively stationary. It is supposed that stationariness of the boundary area is mainly caused by infusion of the Oyashio system which flows down southward along the Pacific coast of Japan.
With this view in mind the author reduced the equation of diffusion:
∂T/∂t=∂/∂χ(Aχ∂T/∂χ)+∂/∂y(Ay∂T/∂y)+∂/∂z(Az∂T/∂z)-u∂T/∂χ-υ∂T/∂y-ω∂T/∂z
to the following approximate simplified equation
l/tn+1-tn[T2, n+1+T1, n+1/2-T2, n+T1, n/2-(ΔT)S.V.]=-(A/l)[T2, n+1+T2, n/2-T1, n+1+T1, n/2].
In addition to this equation some assumptions have been introduced into consideration so as to estimate the horizontal diffusivity, A, in the boundary area and the flowing velocity of the Oyashio system. The present study is intended to provide an approach towards enlightening the variations in oceanographic conditions of the Kuroshio in Zunan sea region.

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In waters adjacent to the south-western coasts of Japan, especially on the coast banks off Kyushu, it has long been recognized that the dark green or gray, large, formless suspended organic matter appears from late autumn to early summer in every year. According to reports from pelagic fishing boats of the Japanese bonito and tuna fishery, we can know on naturally occurring of the larger suspended organic matter in oceanic water of the Warm Current of Kuroshio.
Although the people of the Japanese bonito fishery and tuna fishery had for a long time known about occurring seasons and areas of the matter, and any investigation on the mechanism and place of generation of such suspended organic matter has never been researched scientifically. In offshore waters of the Goto Islands of the western Kyushu and in almost every year, the larger organic matter can be seen intermittently in the surface-layer or at the surface of the waters near by the Goto Islands. The people in this district call the appearance of the larger organic matter “Shiogusare has come” when this appears.
Fishermen of the Pelagic fishery of bonito and tuna find often this kind of suspended organic matters much in offshore waters of the western part of the North Pacific Ocean, several hundreds miles far off the coast and in the Eastern Sea. It is called “Yogore” as its another name, and the people of the sett net fishery of the coastal regions and sailors of the coastal lines call it “Nuta”. It is popularly known that there is some relationship between the app6arance of “Nuta i. e. Shiogusare” and the fishing conditions, while not only as the nature or constituent of itself but also about the mechanism of appearance is not known clearly.
Some people say the appearance of the matter is bad for the fishery, but others say it is good. The author can consider that the suspended organic matter has at least some relations to fishing conditions, for instance, it seems that the season of its appearance relates closely to oceanographic conditions and meteorological conditions.
On the other hand, when the matter appears the anchor rope of vessels and fishing nets are stickled with them and are hastened to decay. In this point of view, fishermen and sailors think them unprofittable. The author had the wish to make a through investigation of nature of the matter and mechanism of the appearance, and then got a chance when he could find a generating state of the matter during the oceanographic research on the Goto Nada area held in April 1948.
Since that time, he has biologically studied about the naturally suspended organic matter, and as he got some of knowledge, he will report on the matter. Owing to some conclusions drawn by him, it became clear that they belong to a kind of materials of plankton origin, as some results of microscopic examination on the structure of the materials collected. And at first he tried to research the biological construction and the origin of the matter. The larger suspended organic matter found in waters adjacent to Kyushu is formed after explosive multiplication of plankton, and then in the view of the biotic structure the matter consists of two constituents, the one is matrix, the other plankton community. These constituents are represented in Figures and Plate 1. As mentioned above, it follows that the larger suspended organic matter is formed out of plankton in the water mass in which plankton population grows explosively.

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1. A new form of pearl oysters has been found at Shimizu, Suruga Bay.
2. When sperm of this form were used to fertilize the eggs of P. martensii. a very marked difference (over 70%) was observed between the rate of develop-ment of these hybrids and that of P. martensii eggs fertilized with self sperm. Fertilization was accomplished in ammoniacal sea water (0.5-1.0^-3 × N NH₄OH).
3. The rate of development in cross-fertilization increases markedly when sperm are employed in a high concentration.
4. In the breeding season, it is supposed that the ovarian eggs of P.martensii are in a more advanced stage of cytoplasmic maturation than those of the new species.
5. The new pearl oyster, being 8-9 cm in diameter, attains a larger size than P. martensii, and differs conchologically from the latter in various other respects : especially, longer hinge line, presence of a prominent posterior indenta-tion, flatter shell valves, coloration of the prismatic layer, etc.
6. It is concluded that newly found mollusc belongs to a new species, and it is denominated Pinctada shimizuensis n. sp. A description is given.The writers wish to express their indebtedness to the director of the Misaki Marine Biological Station for the use of laboratory facilities. Their thanks are also due to Dr. Jean C. Dan for her kind guidance in the preparation of the manuscript.

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The larvae of four important barnacles in Japan, that is, Balanus amphitrite communis; Balanus trigonus, Balanus tintinnabulum rosa and Tetraclita sqamosa were reared in the laboratory. As their foods the artificially cultured marine plankton diatom, Skeletonema costatum, were given. Barnacles passed through seven nauplius stages in their development from the egg to the cypris stage. The number of spines of the 1st appendage can be used as the standard in discriminating each naupius stage, because the increase of number occurs regularly during development. As the key to classify the species of these nauplii, the structural variations in their caudal horns and basipodites of the 2nd appendages are distinguishable.

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