1. Distances have been calculated between thirty natural populations of Vicia faba. 2. The results strongly suggest the existence of a Central Nucleus from which different trends of evolution have arisen. 3. The Central Nucleus represents the equilibrium between different genetic tendencies; this equilibrium is postulated for the primitive populations of this species. 4. Disturbance of this balanced system can be produced by cycles of cross and self-fertilization; recombinations following these cycles are the origin of new genetic combinations so that a new equilibrium is reached with a new cycle of disturbance. 5. The Muratova classification is discussed. It is not possible to give a new classification based on these concepts, because of the great number of possible lines of evolution. The species must be considered as a whole, because there are no genetic barriers of isolation, only geographical ones and no sterility barriers have been produced between the subspecies. 6. A description of the Central Nucleus of Evolution is given.