BRIEF [O.A.] Freyer, Clemens Author: Freyer, Clemens Recipient: Haeckel, Ernst Corporation: Berliner Literarisches Auskunfts-Bureau Dating: 29.10.1893
BRIEF [O.A.] Edwards, Arthur M... Author: Edwards, Arthur M... Recipient: Haeckel, Ernst Dating: 20.06.1893
BRIEF [O.A.] Reinicke, Emanuel Author: Reinicke, Emanuel Recipient: Haeckel, Ernst Corporation: Wilhelm Engelmann Verlagsbuchhandlung Dating: 22.04.1893
BRIEF [O.A.] Ernst [Prinz von Sachsen-Altenburg] Author: Ernst [Prinz von Sachsen-Altenburg] Recipient: Haeckel, Ernst Dating: 19.11.1893