Pauli sends a few informal lines in answer to Bohr's letter of the 3rd March. Meanwhile he has seen Delbrück and received from him a report about his meeting with Bohr in Copenhagen. He said that Bohr changed his mind on these biological questions soon after he had sent his letter to Pauli. This seems to Pauli quite satisfactory as he is now rather convinced that there is no causal connection between the happenings in a gene and the environment (milieu) of the organism. Now Pauli has spoken with Delbrück and also with other biologists he sees much better where the real problems are. Meanwhile another of their common friends, Otto Stern, passed through New York on his trip from California to Europe. Bohr will soon see him in Copenhagen.

Pauli was glad to get Bohr's message that he will make a short stop in Zürich. Pauli gives some organisational information.

Pauli comments on Bohr's lecture on "Unity of knowledge". He differs from Bohr in his view on the degree of detachment in science. He explains his opinion with reference in physics, psychology and biology. He speaks about a remark made by Bohr on psychoanalytical treatment on the role of the unconscious and Jung's school.

Full text: "mein kommen moeglich brief folgt = pauli" (my coming possible letter arrives = pauli)

These three letters are about progress in Pauli's work on the He-model and some technical questions concerning his coming to Copenhagen.

Pauli complains to Bohr for taking Kramers with him to England at a time when himself is so much in need of Kramers' company.

Pauli asks about the possibility of visiting Copenhagen during his vacation. He says that he met Heisenberg in Copenhagen. He talks about his own work on heat conduction in solids.

Pauli talks about a formula made by Kramers and about his doubts about Goudsmith's idea on the spin of the electron.

Pauli writes about the little progress he made in his work on supra-conductivity.

Pauli talks about the offers made to Felix Bloch for a post in Göttingen. He urges Bohr to publish his considerations on the spin of the electron.