C. Matsudaira (1950) Tohoku Journal of Agricultural Research Vol.I, No.2, P. 177. (1950) æ16 Å245 On the Vertical Distribution of Catalytic ActiVity in Tohoku Sea-Area with the Consideration of Water Mass. By C. Matsudaira Synoopsis In present paper, the vertical distribution of catalytic artivitroff Cape Erimo in August 1948 and Kinkazan Island in July-1949 was dealt with. The water samples with the observation data made on board the research ship gsopmaru h and gno. 4 Kaiyo-maru h were given for the determination of catalytic activity from the Fisheries Experimental Station and Maritime Safety Agency. As shown in Fig. 3 and Fig. 5, many layers of water mass were found in Oyashio h and gkuroshio h current from the distribution of activity. gfrom the strength of activity, Oyashio current was divided into two groups, ceastal and off-shore. The activity of dicotherm layer in coastal Oyaahio current wastel- low 50, while in off-shore Oyashio current it was above 1600.