TELEGRAMM Recipient: Haeckel, Ernst Corporation: Senckenbergische Naturforschende Gesellschaft Dating: 04.05.1915
BRIEF [O.A.] Gruyter, Walter de Author: Gruyter, Walter de Recipient: Haeckel, Ernst Dating: 16.10.1915
BRIEF OHNE UMSCHLAG Friederici, Erna Author: Friederici, Erna Recipient: Haeckel, Ernst Dating: 23.12.1915
BRIEF [O.A.] Frantzius, Fritz von Author: Frantzius, Fritz von Recipient: Haeckel, Ernst Dating: 15.03.1915
