BRIEF [O.A.] Henning, Charles L... Author: Henning, Charles L... Recipient: Haeckel, Ernst Dating: 17.07.1912
BRIEF [O.A.] Solla, J... Mendes de Author: Solla, J... Mendes de Recipient: Haeckel, Ernst Dating: 07.05.1901
BRIEF [O.A.] Walther, Johannes Author: Walther, Johannes Recipient: Haeckel, Ernst Dating: 20.09.1891
BRIEF [O.A.] Salla, J... Mendes de Author: Salla, J... Mendes de Recipient: Haeckel, Ernst Dating: 17.06.1901
BRIEF [O.A.] Holdt, Friedrich von Author: Holdt, Friedrich von Recipient: Haeckel, Ernst Dating: 13.01.1916