IN previous papers in this series [e.g. Lovern, 1937] the theory has been advanced that certain fish have the ability to hydrogenate or dehydrogenate their depot fats according to their specific requirements in relation to the type of fat infested. Similar metabolic processes have been suggested for various mammals Banks & Hilditch, 1931; 1932; Hilditch, 1937; Schoenheimer & Rittenberg, 1936; R...