The production of the adrenalin and the chromreaction in the suprarenal glands of the chick-embryo was studied. Adrenalin as determined by intestinal strip assay appeared on the 8th day of incubation. The chromreaction became apparent almost at the same time. With the progress of the development, the quantity of the adrenalin gradually increased, remarkable increments being observed after the 14-15th day and between the 20th and 21st days of incubation.