A New Family with a Fourth Lepton Flavour

We present here arguments in favor of the existence of the most lightest lepton and its neutrino. This new family with a fourth lepton flavour in the first turn must uncover so far unobserved universal properties of matter. The unity of their laws predicts the flavour symmetrical schemes for the decays of the electron and the proton. Thereby, it admits the new modes in the decays of the muon, tau lepton and the neutron. At the same time, in all these transitions no conservation laws are violated.