BRIEF OHNE UMSCHLAG Weismann, August Author: Weismann, August Recipient: Haeckel, Ernst Dating: 28.11.1877
BRIEF [O.A.] Wiedersheim, Robert Author: Wiedersheim, Robert Recipient: Haeckel, Ernst Dating: 28.02.1877
BRIEF [O.A.] Wiedersheim, Robert Author: Wiedersheim, Robert Recipient: Haeckel, Ernst Dating: 18.05.1877