The limnological studies of the six pools located on the dried riverbed near the estuary of the Goto river were made from February to April, 1938. The distribution of algae in these pools seems to depend upon the difference of the chlorine content of their water. After a flooding, freshwater forms, such as, Fragilaria capucina DESMAZ., Cymbella turgida (GREG.) CLEVE, Nitzsrehia sigmoidea (NITZSCH.) W. SM., invaded into the pool nearest to the estuary. But, with the restoration of chlorine content to the original state, these fresh-water forms have been replaced by the brackish-water forms, such as, Diploneis interrupta (KÜTZ.) CL., Dip. elliptica KÜTZ., Melosira Borreri GREV.