BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 20.10.1866
BRIEF OHNE UMSCHLAG Greeff, Richard Author: Greeff, Richard Recipient: Haeckel, Ernst Dating: 24.10.1866
BRIEF [O.A.] Gildemeister, E... Author: Gildemeister, E... Recipient: Haeckel, Ernst Dating: 02.04.1866
BRIEF OHNE UMSCHLAG Schleicher, August Author: Schleicher, August Recipient: Haeckel, Ernst Dating: 08.12.1866
BRIEF OHNE UMSCHLAG Gegenbaur, Carl Author: Gegenbaur, Carl Recipient: Haeckel, Ernst Dating: 18.04.1866