BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Schmidt, Reinhold Corporation: Zoologisches Institut der Universität Jena Dating: 30.05.1904
BRIEF [O.A.] Haeckel, Ernst Author: Haeckel, Ernst Recipient: May, Walther Corporation: Zoologisches Institut der Universität Jena Dating: 19.05.1904
PORTRÄTPOSTKARTE Haeckel, Ernst Author: Haeckel, Ernst Recipient: Friederici, Erna Dating: 23.12.1904
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Whitelock, William Wallace Dating: 26.08.1904
BRIEF OHNE UMSCHLAG Haeckel, Ernst Author: Haeckel, Ernst Recipient: Rottenburg, Paul von Dating: 30.04.1904