  It is shown that the Lame's equation ${d^{2}\over d z^{2}}X+\kappa^{2}
cn^{2}(z, {1\over \sqrt 2})X=0$ can be reduced to the hyper-geometric equation.
The characteristic exponents of this equation are expressed in terms of
elementary functions of the parameter $\kappa$. An analytical condition for
parametric amplification is obtained.
