BRIEF [O.A.] Maschmeyer, Chas... Author: Maschmeyer, Chas... Recipient: Haeckel, Ernst Dating: 21.02.1903
BRIEF [O.A.] Molenaar, Heinrich Author: Molenaar, Heinrich Recipient: Haeckel, Ernst Corporation: Zeitschrift "Die Religion der Menschheit" Dating: 23.11.1903
BRIEF [O.A.] Mantero, Giovanni Author: Mantero, Giovanni Recipient: Haeckel, Ernst Dating: 06.11.1903
BRIEF [O.A.] Macdonell, Helen A. Author: Macdonell, Helen A. Recipient: Haeckel, Ernst Dating: 15.07.1903
