BRIEF [O.A.] Dallmann, Friedr... Author: Dallmann, Friedr... Recipient: Haeckel, Ernst Dating: 15.02.1904
BRIEF [O.A.] Vorpahl, Katharina Author: Vorpahl, Katharina Recipient: Haeckel, Ernst Dating: 15.02.1904
BRIEF [O.A.] Hoeniger, K... Th... Author: Hoeniger, K... Th... Recipient: Haeckel, Ernst Dating: 17.09.1904