BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Ziegler, Heinrich Ernst Dating: 17.03.1907
BRIEFENTWURF Haeckel, Ernst; Schultze, Leonhard Author: Haeckel, Ernst; Schultze, Leonhard Dating: 13.11.1907
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Ziegler, Heinrich Ernst Dating: 05.10.1907
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Ziegler, Heinrich Ernst Dating: 28.02.1907
BRIEFENTWURF Haeckel, Ernst Author: Haeckel, Ernst Recipient: Eggeling, Heinrich von Dating: 06.06.1907