H and W became tenants by the entirety in certain lands in 1917. H died in 1925. A federal estate tax was collected under section 302 of the Revenue Act of 1924, 43 Stat. 253, 304, which provides that the gross value of the decedent's estate subject to tax shall include all property "to the extent of the interest therein held . . . as tenants by the entirety by the decedent and spouse," with certain exceptions. The same provision appeared in the 1916 and successive revenue acts without material change. W protested the levy on the ground that Congress had no power to impose a retroactive tax of this nature. Held, the case falls under the rule enunciated in Milliken v. United States, 283 U. S. 15, 51 Sup. Ct. 324, 75 L. ed. 809 ( 1931) : "The knowledge available before the creation of the estate that it was embraced within an established taxing system and that its taxation, on the same basis and in the same manner as decedents' estates, was an essential part of the system to prevent evasions, relieves the present tax of the objection that it is arbitrarily retroactive." The tax was valid, Phillips v. Dime Trust & Safe Deposit Co. (U.S. 1931) 52 Sup. Ct. 46, 76 L. ed. 68.