  A recent analytic test of the instanton method performed by comparing the
exact spectrum of the Lam${\acute e}$ potential (derived from representations
of a finite dimensional matrix expressed in terms of $su(2)$ generators) with
the results of the tight--binding and instanton approximations as well as the
standard WKB approximation is commented upon. It is pointed out that in the
case of the Lam${\acute e}$ potential as well as others the WKB--related method
of matched asymptotic expansions yields the exact instanton result as a result
of boundary conditions imposed on wave functions which are matched in domains
of overlap.
