  For stochastic evolution equations with fractional derivatives, classical
solutions exist when the order of the time derivative of the unknown function
is not too small compared to the order of the time derivative of the noise;
otherwise, there can be a generalized solution in suitable weighted chaos
spaces. Presence of fractional derivatives in time and space leads to various
modifications of the stochastic parabolicity condition. Interesting new effects
appear when the order of the time derivative in the noise term is less than or
equal to one-half.
