  We derive the Weyl anomaly in two dimensional space-time by considering the
Dirac sea regularized some negatively counted formally bosonic extra species.In
fact we calculate the trace of the energy-momentum tensor of the Dirac sea in a
background gravitational field. It has to be regularized, since otherwise the
Dirac sea is bottomless and thus causes divergence. The new regularization
method consists in adding various massive species some of which are to be
counted negative in the Dirac sea.The mass term in the Lagrangian of the
regularization fields have a dependence on the background gravitational field.
