Microbiological estimation (TEPLY, L. J. and ELVEHJEM, C. A., 1945) of the amounts of folic acid (FA) has been carried out by the use of Streptococcus faecalis as the test microbe. The specimens of fish used in the present study were almost the same that were delt with in the preceding work for the pantothenic acid content. From the results shown in the tables it has been revealed that:
1. This member of vitamin is abundantly held in visceral tissues of fish, especially in the liver, kidney, and spleen, but low in the meat (Table 1).
2. In the common mackerel, Scomber japonicus, the quantitative ratios of FA in the liver and the meat to the total in all tissues are about 30 and 20%, respectively (Table 2).
3. Among the same species, the individual difference of the FA content is not appreciable in the ordinary meat, but occasionaly large in the liver. A group of fish with large locomo-tive power generally stores more FA in the liver than the other less locomotive or living on the bottom (Table 3).
4. Apparently there are two groups of fish showing parallelism between the FA content and the pantothenic acid content in the body. One group when they hold a larger amount of pantothenic acid in the meat than the other, they also show a higher level of FA in the liver and/or in the meat than the other (Table 4).
5. The level of FA in the soft parts of bivalves is generally between those in the liver and the ordinary meat of fish with a moderate FA potency. The liver of top shell, Turbo cornutus, contains FA at an extremely high level (Table 5).