constitutionality of the act.

At the outset it is essential to determine the exact nature of the tax.
Obviously it is not a tax upon income _as income_. If it were, it would
be obnoxious to the decision in the Pollock case as imposing a direct
tax without apportionment among the states. The language of the act, as
well as the declarations of its sponsors, clearly indicate that it is
intended, not as a direct tax on property, but as an excise tax on
privilege. The phraseology of the act itself is--"A special excise tax
with respect to the carrying on or doing business by such corporation,"
etc. Undoubtedly Congress has power to impose an excise tax upon
occupation or business. This was expressly decided, in the case of the
businesses of refining petroleum and refining sugar, by the Spreckels
case,[1] referred to in President Taft's message. The message says:

The decision of the Supreme Court in the case of Spreckels
Sugar Refining Company against McClain (192 U.S., 397) seems
clearly to establish the principle that such a tax as this is
an excise tax upon privilege and not a direct tax on property,
and is within the federal power without apportionment
according to population.

[Footnote 1: _Spreckels Sugar Refining Co. vs. McClain_, 192 U.S., 397.]

What, then, is the privilege with respect to which the tax is imposed?
Is it, like the tax involved in the Spreckels case, the privilege of
doing the various kinds of business (manufacturing, mercantile, and the
rest) in which the corporations subject to the operation of the law are
engaged? Obviously not. No kind or kinds of business are specified in
the act. The tax falls not only on corporations doing every conceivable