136 • BOOKS AND CURRENT LITERATURE 



The Algal and Bacterial Flora of Japanese Water Systems. — 

 Hattori's recently published investigations^ on the water systems of 

 Japan," although written largely from the standpoint of the sanitary 

 engineer, really constitutes a valuable contribution to ecology. The 

 writer had in view the influence of rainfall, temperature, soil and water 

 content on the nature of the flora of filter beds, as well as on the char- 

 acter of the water. An introductory chapter briefly outlines the der 

 velopment of the Japanese water systems. 



The first water system of Japan was planned about 1590 for the city 

 of Yedo, now Tokyo. This system was followed by six others of which 

 the Tamagawa alone finally remained. This consisted of an open canal 

 52 kilometers in length, reaching from a dam in the Tama River to the 

 city of Yedo where it discharged its flow without filtration into wooden 

 pipes. At present over 70 systems are in operation or building in Japan. 

 Most of these utilize rivers as the source and make use of the sand 

 filtration method. 



The efficiency of the sand filter is greatly increased by the slime 

 covering of the sand bed which is formed by a growth of bacteria, blue- 

 green algae, green algae and diatoms. Seasonal variations occur in 

 the flora of this slime coat. In Tokyo, Microneis and Navicula domin- 

 ated the algal flora in June, with Merismopedia, Ceratoneis, Fragilaria, 

 Melosira, Cosmarium, Pediastrum and Mougeotia abundant. Spirogyra 

 was dominant in the Nagasaki filter in August, and Coelosphaerium 

 in September and October. In Kobe, Anabcena, Conferva and Oedo- 

 gonium dominated in July, and Melosira in August and September. 

 In Yokohama, Melosira was apparently independent of climatic in- 

 fluence, being present throughout the year, but other species of diatoms 

 were seasonal. As a general thing diatoms were first and conjugates 

 second in dominance in the algal flora of the water systems investigated. 

 Fungi such as Penicillium, Aspergillus, Mucor and Verticillium were 

 also found, and numerous species of bacteria were identified. In general 

 bacteria were more numerous in summer than in winter, but in some 

 cases there was a tendency to increase in January and February at the 

 time of greatest cold, due to pollution of water sources by dry earth 

 particles rich in bacteria. Also in March and April an increased 

 bacterial count occurred in systems whose sources were subject to 

 washings from melted snow. 



1 Hattori, H., Mikrobiologische Untersuchiingen iibereinige japanische Wasser- 

 leitungen. Jour. Coll. of Sci., Imperial University of Tokyo. Vol. 40, Art. 4. 

 1917. 



