Handwritten letter from Jessie Jacobs Muller Offermann to H.J. Muller with typed letter from Carlos Offermann to H.J. Muller on back with cactus needle taped to the letter.

Typed list of materials to be brought to the Russian Institute of Genetics by H.J. Muller and C.A. Offermann with handwritten notes and additions, c.1932.

Original typed letter with signature from Carlos Offermann to Elof Carlson regarding Offermann's relationship with Hermann J. Muller.

Photograph of Carlos Offermann posing with two men and two women outside. Part of a series of photographs in the same folder.

Photograph of Carlos Offermann posing with another man outside. Part of a series of photographs in the same folder.

Photograph of Carlos Offermann holding a cigarette and posing with his arm around another man. Part of a series of photographs in the same folder.

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.