ISOLATION BY DISTANCE

important S line of attack on the evolutionary problem. While such differences can only rarely represent first steps toward speciation in the sense of the splitting of the species, they are important for the evolution of the species as a whole. They provide a possible basis for intergroup selection of genetic systems, a process that provides a more effective mechanism for adaptive advance of the species as a whole than does the mass selection which is all that can occur under panmixia. TUDY of statistical differences among local populations is RANDOM DIPPERENTIATION UNDER THE ISLAND MODEL * A portion of the cost of composing the mathematical formulae is borne by the Galton and Acknowledgment is made to the DR.