POSTKARTE Daiber, Albert Ludwig Author: Daiber, Albert Ludwig Recipient: Haeckel, Ernst Dating: 29.11.1909
POSTKARTE Schuster, Adolf Niklaus Author: Schuster, Adolf Niklaus Recipient: Haeckel, Ernst Dating: 06.06.1909
BRIEF OHNE UMSCHLAG Porter, Carlos Emilio Author: Porter, Carlos Emilio Recipient: Haeckel, Ernst Corporation: Fauna de Chile Dating: 26.05.1909