In this paper we have discussed certain ambiguities which arise in the description of the mass and charge distributions in heavy ion collisions. We have concentrated on two additional mechanisms, beyond the simple nucleon transfer with average relative momentum, required in the random walk formalism to obtain an agreement with the experimental data. We have shown that these two mechansims, Δ-process involving an additional "Fermi momentum" transfer and γ-process involving new non-transfer process for an energy dissipation, are formally interchangable as regards their effect on the total mass width. We have discussed the possible physical mechanisms responsible for these processes and their relationship to transport theories.