Zao volcanic group is well known for its activity which has often taken place in the historic time. In the surrounding area, poisonous acid waters are found here and there. They are represented by Zao and Kamoshika hot-springs, the Su-kawa River and the Zao River. The studies on these have been made already by the author from the geochemical point of view. Meanwhile, the literature on the springs flowing out at the foot of this volcanic group has never been published. In such a circumstance, he has made the geochemical survey of these springs since 1963. In this paper, the chemical quality of the waters and the regional features of these are presented in detail. The Su-kawa mud flow formed by the ancient eruption of Ryu-zan volcano is subjected to the solfataric action even at the present time. Therefore, the waters of the springs there are characterized by high contents of calcium and sulfate ions. The same is the case with the total evaporation residue. In addition, among the springs in question, only this group belongs to sulfate type spring while the others are of bicarbonate type.
Regarding the quality-of-water, the springs in the Kanno mud flow area are compared stochastically with those in Mt. Yokokura-yama area. As for the chloride, bicarbonate, calcium and sodium ions, the mean concentration of the former group is always higher than that of of the latter. Different from this, in the case of sulfate ion the latter has a larger mean content. Moreover, the seasonal difference of dissolved ingredients is examined stochasticaly with the springs of the two areas mentioned above. Common to the two areas, the concentrations of calcium and chloride ions are higher in August than in November. Reverse is the case with sulfate and bibarbonate ions.

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1. The collecting methods of zooplanton which have been used in many countries are summarised in this report.
2. They are roughly classified into three types, net method, trap or sampler method, and pump and hose method. Their merits and demerits are pointed out by comparison.
3. The development of the apparatus is indicated by a schema. It explains the processes of the modification of the apparatus.
4. There are many reports of limnological studies in Japan, but from the quantitative view point they are rather few. Also, there are few comparative studies regarding the efficiency of different mesh nets and apparatus in the same waters.
5. There are many quantitative studies of zooplankton in foreign countries. Net, trap and sampler are used for collection, especially those with Muller gause No. 20, mesh 173/inch net.
6. A few examples of the comparative studies regarding the efficiency of plankton net and collecting methods are introduced (Rawson, 1956; Ishida, 1965).
7. The collecting methods of zooplankton are important, but the methods of estimating secondary production must be decided as soon as we can. Therefore, not only the collecting methods, but the work of revealing the life cycle, reproduction, mortality, excretion, respiration, etcf of zooplankton must be performed side by side.

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1. Decrease of oxygen dissolved in water close, to the bottom with the lapse of time was studied experimentally.
2. Mud or sand was put into cylindrical glass vessels with adequate depths and water was poured upon them. These vessels were placed quietly in a room with slight temperature change.
3. Using a special water sampling apparatus, a small amount of water was sampled from 0 cm, 1. 5 cm, 3 cm above the bottom and from the surface respectively, at some time intervals up to 30 days. The oxygen content was measured by the poralograph-method.
4. Vertical gradient in oxygen content appeared near the bottem owing to oxygen consumption by the soil and became remarkable with progress of time. This gradient was observed as high as about 2 cc/L/cm.
5. Extent of the gradient was approximately proportional to the quantity of the soil used. This may indicate that, besides the soil that is in direct touch with upper water, even the soil in deeper place actively consumes the oxygen.

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