BRIEF OHNE UMSCHLAG Fürbringer, Max Author: Fürbringer, Max Recipient: Haeckel, Ernst Dating: 26.03.1895
BRIEF OHNE UMSCHLAG Dohrn, Familie Author: Dohrn, Familie Recipient: Haeckel, Ernst Dating: 28.09.1909
BRIEF [O.A.] Eisig, Hugo Author: Eisig, Hugo Recipient: Haeckel, Ernst Corporation: Stazione Zoologica Napoli Dating: 12.05.1903
BRIEF [O.A.] Donvito, Eduardo Author: Donvito, Eduardo Recipient: Haeckel, Ernst Corporation: il Mattiono - La Libre Pensée - il Pubblicista - La Gioventù Dating: 26.09.1909
BRIEF [O.A.] Donvito, Eduardo Author: Donvito, Eduardo Recipient: Haeckel, Ernst Corporation: Il Pubblicista - La Gioventù Dating: 25.04.1911