BRIEF OHNE UMSCHLAG Dodel-Port, Arnold Author: Dodel-Port, Arnold Recipient: Haeckel, Ernst Dating: 24.02.1904
BILDPOSTKARTE Haeckel, Heinrich Author: Haeckel, Heinrich Recipient: Haeckel, Ernst Dating: 30.04.1914
BRIEF OHNE UMSCHLAG Dodel-Port, Arnold Author: Dodel-Port, Arnold Recipient: Haeckel, Ernst Dating: 20.06.1906
BRIEF OHNE UMSCHLAG Gegenbaur, Carl Author: Gegenbaur, Carl Recipient: Haeckel, Ernst Dating: 10.04.1889
