  The problem of temperature in nonextensive statistical mechanics is studied.
Considering the first law of thermodynamics and a "quasi-reversible process",
it is shown that the Tsallis entropy becomes the Clausius entropy if the
inverse of the Lagrange multiplier, $beta$, associated with the constraint on
the internal energy is regarded as the temperature. This temperature is
different from the previously proposed "physical temperature" defined through
the assumption of divisibility of the total system into independent subsystems.
A general discussion is also made about the role of Boltzmann's constant in
generalized statistical mechanics based on an entropy, which, under the
assumption of independence, is nonadditive.
