  Castillejo-Dalitz-Dyson (CDD) poles are known to be connected with bound
states and resonances. We discuss a new type of CDD pole associated with
primitives i.e., poles of the P matrix that correspond to zeros of the D
function on the unitary cut. Low's scattering equation is generalized for
amplitudes with primitives. The relationship between the CDD poles and the
primitives is illustrated by a description of the S-wave nucleon-nucleon phase
shifts.
