those cases the gifts inter vivos were not “ in contemplation of death,” and the only relevant question was one of construction, whether some of them were of the class intended by Congress to be taxable under § 402 (c) as transfers “intended to take effect in possession or enjoyment at or after death.” It was held that they were not. But those gifts were not of the class now involved, gifts in contemplation of death, made before the passage of the .Act, which are expressly named by § 402 (c) as subject to its provisions.
This Court has not passed directly on the constitutionality of the federal taxation of gifts made in contemplation of death. But taxation of transfers at death has been upheld, Knowlton v. Moore, 178 U. S. 41, as has, more recently, the taxation of gifts inter vivos, Bromley v. McCaughn, 280 U. S. 124; and we hold, as this Court has several times intimated, that the inclusion of this type of gifts in a single class with decedents’ estates to secure equality of taxation, and prevent evasion of estate taxes, is a permissible classification of an appropriate subject of taxation. See Nichols v. Coolidge, 274 U. S. 531, 542; Tyler v. United States, 281 U. S. 497, 505; Corliss v. Bowers, 281 U. S. 376, 378; Taft v. Bowers, 278 U. S. 470, 482; cf. Schlesinger v. Wisconsin, 270 U. S. 230, 239.
The objection to the. tax chiefly urged in brief and argument, is that the taxing statute, as applied, is a denial of due process of law because retroactive. It is said that the statute is invalid not alone because it reaches a gift made before its enactment, but because it measures the tax by rates not in force when the gift was made, applied to the value of the property not when given, but at the uncertain later time of the death of the donor.
This Court has held the taxation of gifts made, and completely vested beyond recall, before the passage of any statute taxing them, to be so palpably arbitrary and un