  We embed the Seiberg-Witten solution for the low energy dynamics of N=2 super
Yang-Mills theory with an even number of massive hypermultiplets into the
Whitham hierarchy. Expressions for the first and second derivatives of the
prepotential in terms of the Riemann theta function are provided which extend
previous results obtained by Gorsky, Marshakov, Mironov and Morozov. Checks in
favour of the new equations involve both their behaviour under duality
transformations and the consistency of their semiclassical expansions.
