Herring fat has an abnormally high content of C22 acids, unusual unsatd. C16 and C18 acids and unusual satd. C20 and C22 acids. Progressive seasonal variations occur in the unsatn. of the various acids; these are ascribed to the sudden and intensive ingestion of highly unsatd. fat in June, thus causing a temporary unbalancing of the fat hydrogenation processes which is soon offset by adaptation of metabolism to the situation. Fasting herring appear preferentially to utilize the more unsatd. constituents of the fat. Immature herring contained a more unsatd. fat than adult herring caught in the same season.