This note is concerned with
analytic perturbations of spectral operators. It is shown that under small
perturbations simple isolated eigenvalues remain simple and isolated and depend
holomorphically upon the perturbation parameter. As one would expect
the bounds are rather complicated in the case of a spectral operator with
general quasinilpotent part. For scalar operators, however, these bounds
become simple and reproduce in the selfadjoint case those given by F. W.
Schäfke.