Abstract
1. This paper deals with the results of the quantitative and qualitative investigations, of potamoplankton of the Yosino-gawa which is the longest river (236 km long) in Sikoku. Its general route is shown in fig. 1.
2. Plankton samples were obtained at three stations, i.e. TUZI, KAWASIMA and NADA (fig. 1), on 28/VIII '36, 7/I '36, and 7IV '36 respectively. The physical and chemical conditions of river water at each station are shown in Table 1.
3. The plankton organisms observed are listed in Tab. 2 and 3. The chief component of the plankton is Bacillariaceae, zooplankters rarely appearing. No fundamental differences of plankton are found not only quantitatively but also qualitatively at these stations, though they are far apart from one another. It suggests, therefore, that in a small river like the Yosino-gawa, the potamoplankton is furnished chiefly from ponds or lakes connected with river or from river bottom.
