BRIEF [O.A.] Kleinenberg, Nicolai Author: Kleinenberg, Nicolai Recipient: Haeckel, Ernst Dating: 20.09.1869
BRIEF OHNE UMSCHLAG Strasburger, Eduard Author: Strasburger, Eduard Recipient: Haeckel, Ernst Dating: 03.01.1869
BRIEF OHNE UMSCHLAG Strasburger, Eduard Author: Strasburger, Eduard Recipient: Haeckel, Ernst Dating: 09.01.1869
BRIEF [O.A.] Jeffreys, F... Gwynn Author: Jeffreys, F... Gwynn Recipient: Haeckel, Ernst Dating: 04.10.1869