Typed letter from Ramsay Spillman to H.J. Muller regarding Muller's difficulty finding a job due to his connection with Russia, 1941.

Typed letter with handwritten postscript from John B. Penniston to H.J. Muller regarding chromosome number classification, 1957.

Handwritten letter from H.J. Muller to Irwin Oster Drosophila genetics, 1954.

Handwritten letter from H.J. Muller to Irwin Oster regarding an Atomic Energy Commission grant budget and Drosophila genetics, 1954.

Handwritten letter from H.J. Muller to Irwin Oster, 1954.

Handwritten note from H.J. Muller to Irwin Oster regarding the printing of a book, "The Muller Papers" on a copy of a letter of the same topic, 1961.

Handwritten letter from H.J. Muller to Irwin Oster regarding Drosophila genetics, 1954.

Typed letter with handwritten additions from Julian Huxley to H.J. Muller, 1940.

Typed letter with handwitten additions and postscript from H.J. Muller to Elof Carlson regarding who to consult about writing a biography of Muller, 1963.

Typed letter with handwritten corrections from H.J. Muller to Elof Carlson regarding Elof's book "The Gene", Muller's additions to "Out of the Night", and Elof's request to write a biography of Muller, 1966.