Michel comments on Pauli's manuscript on time-reversal.

Lüders writes about Pauli's manuscript on time-reversal. He makes a comparison with Lüders work, in particular the identity of Pauli's "Wigner-transformation" and Lüders "formal time-mirroring".

Landé sends a reprint on electron theory with remarks on further work with Thomas.

Kröner writes about the relation between physics and biology. He believes in an intermediary region between both sciences. He says that quantum physics is perhaps the first glimpse of this region.

Møller and Kristensen thank Pauli for his instructive letter. They answer the question he asked and give some details of their form factor theory.

Klein wants Pauli to render his encyclopedia article consistent with Kottler's.

Källén thanks Pauli for an offprint of a paper by Pauli that is helpful for his calculations on the Lee model. He writes on the question of the unitary of the S-matrix in this model.

Jordan replies to a letter by Pauli. He discusses the problem of probability of mutations and of the statistical independence of successive mutations and the necessity for distinguishing between micro- and macro-evolution. He agrees with Pauli that nothing can be said at present about the time scale of evolutionary processes.