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.

Questions in connection with the preparation of a new edition of Pauli's encyclopedia article on relativity.

Pauli comments on J. Leite Lopes' letter of 12 August 1944, and in particular the integral operators used by Lopes.

Pauli writes about a remark by Dyson on Thellung's manuscript. He mentions administrative details of a lecture program in the summer term.

Permit delivered for W. Pauli to go to some European countries for Nobel prize lectures.

The Institute for Advanced Studies offers W. Pauli membership of the faculty of mathematics.

Letter from W. Pauli to M. Delbrück. Considerations on physics and biology.