I. Undor Calculus and Charge-Conjugation -- Zusammenfassung. Resumo -- ยง 1. Introduction -- ยง 2. The Dirac wave-function (undor of the first rank) -- ยง 3. Charge-conjugation of four-spinors -- ยง 4. Neutrettors of the first rank -- ยง 5. Undors of the second rank -- ยง 6. Covariant undor calculus -- References -- II. The Undor Equation of the Meson Field -- Zusammenfassung. Resumo -- ยง 1. The Proca-Kemmer meson equation in undor notation -- ยง 2. The generalized meson equation and the neutretto equation -- ยง 3. The charge-conjugated meson equation -- ยง 4. The charge current-density and the magnetic moment of mesons -- ยง 5. Charge-invariance and statistics -- References -- III. The Heavy Quanta Theory of Nuclear and Cosmic Ray Phenomena -- ยง 1. Introduction -- ยง 2. The four types of meson fields proposed by Kemmer and the simplified deuteron problem -- ยง 3. The charge-dependence of nuclear forces -- ยง 4. Quantization and relativistic invariance of the theory -- ยง 5. Elimination of the longitudinal electromagnetic field -- ยง 6. Discussion of the Hamiltonian -- ยง 7. The heavy quanta interaction between nuclons -- ยง 8. The deuteron problem -- ยง 9. The neutron-proton scattering -- ยง 10. The spontaneous disintegration of heavy quanta. -- ยง 11. The ?-disintegration of instable nuclei -- ยง 12. Scattering and absorption of mesons by nuclei -- ยง 13. Discussion of the limits and the value of the theory -- References -- Samenvatting