By extending the Sakata model, a unified model for elementary particles is proposed, the basic particles in the Sakata model are assumed to be constructed of the lepton and B+, which is regarded as a new kind of matter. The full symmetry among three basic particles and the symmetrical property of the weak interactions which was recently pointed out by Gamba, Marshak and Okubo come automatically of this model. The nature of B+ and the new mechanics which accounts for the binding of B+ to the lepton will be the central problem to be studied in the future. § L Introdud:i.on A few years ago, one of the present authors (S. S.)l) proposed the composite model for elementary particles, in which all particles belonging to the boson-baryon family were considered to be constructed of protons, neutrons, A-particles and their anti-particles. On the basis of this model, many works 2 ) have so far been carried out; especially, postulating the full sym_metry among the three basic particles,3),4) Ikeda, Ogawa and Ohnuki,5) and Savvada and Yonezawa 6 ),7) have recently obtained very interesting results which are in good agreement with experimental data.In spite of these successes, the Sakata model has been concerned only with the strongly interacting particles, and nothing has been done with the lepton. TvIoreover, even in the case of strong interactions, the charge independence or the full symmetry (which -we shall call the 1.0.0. symmetry) among the three basic particles was introduced in a formal \vay, and it has not yet been clear why the strong interaction should have such invariance properties. In order to describe both baryon and lepton in a unified way, and to find out a profound meaning hidden behind the charge independence or the 1.0.0. symmetry, we must go further from the Sakata model.For this purpose let us turn our attention to the weak interaction. The theory of yveak interaction has now come to a very definite point after the great success of the current-current interaction theory proposed by· Feynman and Cell-Mann. 8 ) Furthermore, it has recently become clear that the Feynman-Gell-Mann current derived from the Sakata model is quite suf--ficient to account for the experimental facts concerning the weak processes. 9 ),10) Especially, it should be noted that the terms which obeyed the conditions J S/ LiQ = -1 and I LlS/ LlO I > 1 automatically dropped out of the current. Thus, by adopting the Feynman and Cell-Mann theory and at
