Pauli questions and comments on the theory of holes.

Pauli writes about the difficulties of the theory of holes, as far as physical interpretation is concerned.

Pauli gives further critical comments on Heisenberg's formalism. He writes of Bloch's report on a theory of Beta-desintegration by Fermi.

Pauli talks about the solution he found for the matrix problem.

In connection with a note by De Broglie, published in: comptes rendus: (1934) Bd. 198, Heft Nr. 2, S. 135, Pauliremarks that the main problem is the correct formulation of the interaction terms of neutrino and electrons.

Appendix to the letter of the same date, entitled: "Ueber die quanten-elektrodynamische Formulierung der Löcher-theorie".

Addition to the letter of the 27 January 1934.

Pauli expresses scepticism about the theory of holes, especially in view of a certain arbitrariness in Dirac's derivations.

Pauli makes some remarks on Dirac's theory, on the mass of the neutron and on the negative protons.

Pauli replies to Heisenberg's letter concerning e$^{2}$. He gives an outline of how far a future theory will have to differ from the present one in order to avoid infinities.