Pauli thanks Källén for his manuscript and letter. He makes a comparison of Källén's and Yang's results. He talks about results by Rohrlich for the case of charged scalar mesons in interaction with the quantized electromagnetic field. He also talks about results by Peasler and Kiroshita and about nu mber for charged vector mesons.

Pauli writes on the concept of chance in biology and on the lack of a quantitative definition of biological probabilities. He suspects that the present conception of evolution is still essentially incomplete. The two parameters of selection and mutation are logically independent of each other. It is not the gene that is thesmallest unit of life but the cell as Bohr has emphasized.

Pauli makes further critical remarks about Jordan's cosmology. He writes that some of his assumption should be derived mathematically from a new nuclear theory.

Pauli writes about Jordan's article in the Bohrfestchrift which deals with the role of chance in biology. Pauli criticizes the use of the concept of chance in biology and evolution in particular.

Pauli writes from Princeton to Jauch in Zürich about Jauch's calculations on electron scattering. He asks questions about life in the Institute.

Pauli expresses his satisfaction about Jauch's theoretical work on electron scattering, but he doubts the experimental results. He writes about the latest results of cosmic ray research.

Pauli thinks that he should remain in the U.S.A. until the end of the war. He asks Jauch to send him his lecture notes. He discusses the problems of electron scattering. He writes of theories about the meson in the U.S.A. and about experiments with proton-proton scattering.

Pauli discusses the treatment of interaction between heavy particles and electrons. He comments on Marshak and Weisskopf'calculations. The main problem is now the creation of mesons in explosions.

Pauli discusses a work by Wilson on the influence of damping on the brems-radiation of mesons with spin 1.

Pauli thanks Jauch for Jauch's and Rohrlich's book and says that he likes it. He gives some comments on a few passages. He writes about recent publications on field quantization.