BRIEF [O.A.] Chamberlain, H... R... Author: Chamberlain, H... R... Recipient: Haeckel, Ernst Corporation: The New-York Sun, London Office Dating: 16.03.1899
BRIEF [O.A.] Rücker, Arthur W... Author: Rücker, Arthur W... Recipient: Haeckel, Ernst Corporation: Royal Society of London Dating: 23.09.1899