1. In October, 1938, we made the biological survey about fifteen simple springs and wie carbonic spring in Oita Prefecture. The temperature of the hot springs surveyed varies from 28° to 74°C, and the pH value ranges between 6.6 and 7.9.
2. 106 species of various groups of animals were collected in the simple springs, where the temperature of water varied from 28°to 56.5°C, and the pH value ranged between 6.6 and 7.9.
3. Thirteen species of various groups of animals were secured in the carbonic spring, where the temperature of water ranged from 32° to 50.2°C and the pH value was 7.0.
4. By adding the number of species collected in the simple springs and carbonic spring combined, we counted 108 species. Among these the following 22 species are newly recorded:Protozoa: Lesquereusia spiralis (EHRENBERG), Gromia ter-ricola LEIDY, Goniun pectorale O. F. MULLER, Synura uvella EHRENBERG, Chaenia teres DUJARDIN, Chaenia sp., Bryophyllum sp., Dileptus anser O. F. MULLER, Cychdium hepatrichium SCHWIAKOFF, Aspidisca Costata-(DUJARDIN).Mollusca : Gylanlus hiernantiurn (WESfERLUND), Segmentina nitidellus (VON MARTENS), Viviparus malleatus REEVE.Insecta : Orthetrum triangulare melania GELYS, Crocothemis servilia DRURY, Anax parthemope julins BRAUER, Ranatra chinensis MAYR, Coelostoma stultum WALKER, Palaplea japonica (HORVATH), Diplonychus japonicas (VUILLEFROY), Laccotrephes japonensis SCOTT, Cybister tripunctatus OLIVER.Pisces: Pseudogobio esocinus (TEMMINCK & SCHLEGEL) Amphibia : Rana limnocharis WIEGMANN.
5. CIOFALO (1927) recorded Lacrymaria coronata CLAP. & LACH., Halteria grandinella O. F. MULLER in saline springs of Sicily, and STROUHAL (1934) recorded Cyclogramma sp. and Urocentrum turbo O. F. MULLER in simple springs of Karnten, Austria. All these four protozoans were found to occur in our simple springs investigated, being the second discovery of such forms in hot springs.
6. Our record of collection. shows probably the highest temperature at which the following animals occur in natural spring-waters. The species and the temperature of water at the time of collectin for each species are as follow:Vahlkampfia limax (DUJARDIN), 56, 5°: Cyrtolophosis elongate SCHEWIAKOFF, 56, 5°: Oxytricha fallax Stein, 56, 5°:Stenothyra sp., 45°: Caridina denticulata DE HAAN, 38, 5°: Carassius auratus LINAEUS, 38, 5 Aplochelus latipes (TEMMINCK & SCHLEGEL), 38, 5°: Rana limnocharis WIEGMANN, 40°.

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Results of observations for surface air and water temperatures, as well as for pH, made at 29 points during about two hours in the afternoon on November 16th, 1939, show clearly the influences of the drainage into the lake from the hot spring of Yumoto, located immediately to the north of the lake.

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