  Starting from the 1-dimensional complex-valued Ornstein-Uhlenbeck process, we
present two natural ways to imply the associated eigenfunctions of the
2-dimensional normal Ornstein-Uhlenbeck operators in the complex Hilbert space
$L_{\Cnum}^2(\mu)$. We call the eigenfunctions Hermite-Laguerre-Ito
polynomials. In addition, the Mehler summation formula for the complex process
are shown.
