Interaction between Elementary Particles. Part II.

A particle described by an exact $\delta$-function with shift of origin, rather than by a structural smoothed-out $\delta$-function, has equations of motion derivable from Fokker's least action principle, in analogy to Feynman's work. The two objections of arbitrariness of the structure function, and of violation of the linear field equations within the particle radius, are thereby avoided. The relation to Born's new theory of elementary particles is discussed.