There are many bored hot springs showing a geyser-like phenomenon in Japan, and their temperatures do not attain to the boiling point of water. Its mechanism is not explained by the boiling of deep water in a vertical pipe as usual, but they contain much gases, such as methane or carbon dioxide, which are said to be the main role in geyser like mechanism. The present authors tried to explain it with the aid of a model. When there is supplied with some gases at the bottom of water column, the water dissolve it upward from the bottom. Through the water column saturated with gas, the following gas bubbles pass up freely and cause the water level to rise in the pipe. When the water flows over the pipe head, the dissolved gas will be free from the water and expand, and will rush out of the pipe. The rising height of water level and the time interval of the rest relate to the amount of gas supply and to the difference between the pipe head and water level. Some mathematical treatment is procedured.

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The river water flowing into a lake is considered to mix gradually with the lake water and may diffuse in that lake. The mechanism of mixing and diffusion in such cases are so complicated that any definite theoretical investigation has not yet appeared.
In any flood, when the river water is turbid owing to much suspension and solvents in the water, its density will be higher than that either of the river water in an ordinary state or of the lake water. After the flood, if we can detect the density distribution of the lake water near the mouth of the river, the diffusion process of the inlet water in the lake will be found.
On such assumption we tried to measure the density distribution of the water of Lake Biwa off the mouth of the River Ado ; the results obtained are shown in Table 2 and are graphically represented in Figs. 2, 3, 4 and 5.
The density measurements were carried on in the laboratory of the Geophysical Institute, Kyoto University, by using a specially designed equipment for density measurement. Its accuracy is±2×10^-6 gr/cm³. Δρ, the tabulated values (Table 2) indicate the density difference between the sampling water and the distilled water at 0°C ; i.e., Δρ_s0-Δρ_d0.
It is very interesting that there likely exists a water mass of high density,
Δρ=70, floating in the surface layer at about 1500m off the mouth of the river.Another water mass, Δρ=5060, sinks to the bottom at about the same position. Moreover, a small water mass occurs in the layer of 1020 m in depth 500 m off the mouth. These water masses of high density are certainly brought into from the river at any previous flood, because the proper density of the lake water seems to be about Δρ=3040.
We attempted to analyse the water masses as in the case of the sea water, in taking the density and B. C. P. alkalinity, instead of the water temperature and salinity for the sea water. It is easily seen in Fig. 7 that the river water in the ordinary stage is in the lower left corner, the lake water proper nearly in the central region, and the inlet water at flood is scattered in the upper region. Such a configuration may prove to hold the key to solve the mechanism in mixing and diffusion of the inlet river water in the lake water. We intend to discuss this problem in the future when additional data are obtained.
In conclusion, it is worthy of notice that the inlet river water and the lake water cannot easily mix, because the water masses of high density maintain their properties in the lake for such a long time.

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Kellicottia longispina (KELLICOTT) is a Brachionid rotifer, which is widely distributed throughout the Northern Hemisphere. In our country, however, the localities, where the present species occurs, are not recorded plenty enough, as shown in Table 1. The quantitative samplings of it were carried out only in four lakes, i. e., Lakes Aoki-ko, Kizaki-ko, Nojiri-ko and Shikaribetsu-ko. So far as these four examples are concerned, the following characteristics may be given in regard to the distributing conditions of Kellicottia longispina.
1. When the lakes show the direct stratification of temperatures, the mode of its vertical distribution exists in the hypolimnion ; more exactly saying, it is in the clinolimnion.
2. Sometimes, the present species occurs either in the metalimnion or in the epilimnion, though very poor in quantity.
3. The median value of water temperature observed at the depth where the mode appears is 7.7°C (±0.7°). Were the depths insufficient, higher tempertures would be observed as in the case of the St. II of Kizaki-ko.
More additional peculiarities of conditions may be summarized from the examples given in Table 1.
4. Lakes and ponds of our country, where Kellicottia longispina occurs, are located in the districts north of 35°N.
5. It shows an inclination that the higher the latitude becomes, the lower the altitude of lake surface will do.
6. Most of lakes where the present species is distributed have either considerable dimension or pretty large depth, but there are several exceptions, such as Hyotannuma of the Akan lake group, and Nakatsuna-ko, one of the Nishina three lakes. In both cases, however, there are some lakes that stand close to them and seem to be suitable for the occurrence of Kellicottia longispina.
7. The pH values of lakes (Table 1) range between 6.3 and 7.8. The results of quantitative samplings obtained vertically show that the most suitable values of pH for it are observed between 6.8 and 7.0.

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(1) The seasonal changes in the contents of dissolved inorganic salts, organic substances and the number of bacteria were measured in three pools of Tokyo in 1952 and 1953. The interrelation between these three were also investigated.
(2) The amounts of NH₄-N of the surface layer was 0.010.042 mg/l in pool A, 0.030.83 mg/l in pool B, and 0.010.64 mg/l in pool C. In all the pools the maximum concentrations were seen in spring and autumn, and the minimum onesin winter and summer. The amount was always larger at the bottom layer than at the surface layer.
The difference of the amounts of NO₂-N and NO₃-N between the surface and the bottom layers was very small, the former being 00.007 mg/l and the latter 00.08 mg/l, both of which decreased to zero in spring and autumn. The concentration in pool A was lower than in any other pools in general.
(3) The content of organic-N showed two maxima every year. It was high in spring and in autumn, and low in winter and in summer in all the pools. At the surface layer it was about 0.530.76 mg/l, being lower than in the bottom layer. The content in pool A was lower than those in any other pools.
(4) Among the phosphorus compounds, the amount of PO₄-P was 00.008 mg/l in pool A and B, 00.003 mg/l in pool C. It became zero in the surface layer in spring and summer, and in every layer in autumn. The content of total P was 0.010.19 mg/l, which was 24 times as much in pool C as in the other pools.
(5) The concentrations of the above minerals in each pool was nearly agreeable with those which were seen in neutral dystrophic lakes.
(6) The reciprocal relations were seen among the amount of dissolved salts and the amount of albuminoid-N, organic-N or chlophyll content. The relationship was especially marked in the case of chlorophyll content.
(7) The measurement of bacterial number was made monthly by the method of plate culture. The bacterial numbers were between ×10²-10³ per cc water of the pools and were fewer than those of eutrophic lakes. Two maxima and two minima occurred during 1952. The maxima were seen in spring and autumn, and the minima in winter and summer. In 1953 no tremendous abundance occurred, and a minimum was seen during the summer stagnation.
(8) It was recognized that bacteria increased in general during the time of optimum temperature (1025°C). However, even in that time they decreased in accordance with the increase of Protozoa and Protophyta or with the shortage of dissolved oxygen.
(9) The maximum size of bacterial population appeared at the same time with the maximum of chlorophyll content ; or, the latter followed immediately the former. The increase in the dissolved salts was seen at the same time with or immediately after the increase in bacterial population. The increase of chlorophyll followed the increase of salts.
(10) The amount of inorganic salts was 40400 times as much in the living body as in the pool water.
(11) According to physiological analyses, the minimum element in the water of pools for biological production seemed to be P rather than N. This shortage of phosphorus was considered to be caused by the abundance of humic substances.

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