Thirteen Japanese species of Rotatoria belonging to the genera Ploesoma, Chromogaster, Asplanchna, Asplanchnopus and Pompholyx are described and figured. Of the thirteen species, Ploesoma lenticulare Herrick and Pompholyx sulcata Hudson are recorded for the first time from Japan.

View full abstract

Daphnia magna Straus, a representative species of the m-group of daphnids, which are distributed chiefly in arid regions, was found in 1949 in a pond on a hill north-west of Matsuyama City in Shikoku. The pond has an area of 27, 000 m² and a depth of 5 m. D. magna in this pond appeared most abundantly in March and entirely disappeared in August.

View full abstract

In the specimens over 5cm long of a cyprinid fish Zacco temminkii the scales on the median part of body side have always “apical circuli” or granules modified from them. This is an important feature to distinguish this species from Zacco platypus.

View full abstract

1.Owing to the introduction of the acid water of stream Tamagawa in the biginning of 1940 in Connection with the Construction of hydroelektric Works, the water of the oligotrophic Lake Tazawa (425m. in depth) has become remarkably acid, the pH values measuring as low as 4.3-5.3 at my visit in the summer of 1948.
2.The inflowing water from the acid stream. with temperatures of 15-20°C sinks to a dept of 10-20 m. and remains there up to the outlet. Therefore the pH value shows a V-shaped stratification.
3.The zooplankters in the lake are represented by Scapholeberis mucronata, Chydorus sphaericus, Cyclops strenuus and so forth, among which the first named water-flea is found in great abundance-4636 individuals per cubic metre of water. Oscillatoria sp.seems to be the only phytoplankter. Though the plankton organisms are collected even from layers deeper than over 200m., they are most abundant in the surface layer.
4.There are found three species of fishes, namely, Tribolodon sp., Pseudobagrus aurantiacus and Salvelinus kundscha, the first named species being Predominant.None of Oncorhynchus nerka which inhabited the lake before the acidification is collected.

View full abstract

The underground water of Takashigahara, a hill south of Toyohashi City, Aichi Prefecture, was studied according to the results of observations of 156 wells and of geoloy of the area. In the eastern half of the area the ground-water table is shallower and higher above sea level than in the western half. A discontinuous zone of water with the fall of 68.5 m was found. The pH value of water is 5.8 in the shallower eastern half and 6.06.2 in the deeper western half, the limit of its change appearing to agree rather well with the discontinuous zone. There is seen a close relationship between the geological structure of the area and the discontinuous water zone

View full abstract

On the eastern slope of Mt. Fuji there are rather rich in cold-springs and shallow underground water, each of which has hydrological characteristics. These springs are so-called “lava spring.” The underground water of this slope exists in volcanogenic soils (volcanic ash and detritus soils), and are considerably rich in quantity of water than those which are distributed on the other slopes of the mountain. The water is used for irrigation, and is noticed that they are in conditions to be polluted easily.

View full abstract

The underground waters of the Higashiyama area, a diluvial hill in Nagoya City, are found as flows in the direction of dip. In spite of the fact that there is a small area of only 0.25 km², the underground water character is best expressed in a rich variety such as shallow, deep and perched wells. The differences of temeratures of water, which are influenced rather strongly by soils, suggest pionts of contact between two different systems of under-ground waters. It is found that the impervious strata of deep and of water table wells become contact with each other on the marginal part of the hill.

View full abstract

The distribution of the chemical quality of water agrees well with the direction of flow of underground water. In passing along from upper to lower flows the temperatures of water become higher and the chlorine content increases markedly. Nitrite-nitrogen which seems to be derived from manure given on the surrounding farms is considerable, while phosphorus content is very scarce.

View full abstract

In the City of Pei-chin and its vicinity, the underground waters are found in the formations of sand and gravel carried by the River In-Tin-Ho. These ground waters seem to be supplied from either northern or north-western mountain land. Judging from the seasonal fluctuations of well-waters, the ground-water level fluctuates high and low alternately twice a year, showing the maximum hight in February and March.

View full abstract

The water temperatures of twenty selected rivers in Japan are discussed. The maxima are observed in August in the majority of the rivers, while the minima are in January in almost all rivers. From the relationship between the temperatures of water (tw) and of air (ta), tw=2.34-0.77ta (aver. deviation ±1.7°C) has been obtained in twenty rivers. The difference between tw and ta is shown as Δt=2.46-0.18 ta (av. dev. ±2.0°C). Such relations, according to the upper, middIe and lower stream types, are summarized in tables 4 and 5.

View full abstract

The oxygen dissolved in a mountain stream Misakagawa 7 km long in the northern part of Okayama Prefecture were studied during a year from August 1949 to September 1950. It is natural that the oxygen dissolved in the upper course of the stream is greater in quantity than in the lower, where the water is 5 °C warmer than in the upper. The oxygen content is the greatest in February and the smallest in July.

View full abstract

The chemical analyses of the water of ca. 300 Japanese rivers show that these rivers are characterized by the paucity of salts especially in calcium carbonate and by generally rather rich in silicate. The chemical constituents of the water of 27 selected rivers are shown in the accompanying diagram, in comparison with the average data of the world rivers adapted from Clark's Data of Geochemistry. The possible quantities of nutritive salts to be supplied by river waters for irrigation are calculated. It becomes evident that the quantities of potassium, silicate and calcium in river waters seem to be suficient to supply to rice-fields as the source of nutrients.

View full abstract