BRIEF OHNE UMSCHLAG Schatt, Karl Oswald [?] Author: Schatt, Karl Oswald [?] Recipient: Haeckel, Ernst Dating: 05.03.1912
BRIEF [O.A.] Kerschner, Ludwig Author: Kerschner, Ludwig Recipient: Haeckel, Ernst Dating: 02.10.1901
BRIEF [O.A.] Schollar, Franz von Author: Schollar, Franz von Recipient: Haeckel, Ernst Dating: 06.04.1908