The physical dimensions and biological meaning of the coefficients in the Volterra competition equations and their consequences for the possibility of coexistence.

Exact definitions in physical and biological terms of the coefficients in Volterra's (1926, 1931) original competition equations are indispensable for the understanding of the system. In agreement with Volterra's own, but not quite sufficient specifications, it is tried in this paper to give more precise definitions of the parameters used by Volterra. This leads to some consequences; i.a. that there does not exist a "principle of competitive exclusion". In order to allow for competitive exclusion - or for stabilization - the Volterra equations need additional biophysical specifications and mathematical modifications. Some such modifications are proposed, for instance for aggressive interference as a function of population numbers.