The Haeckel reception in Sweden.

The Haeckel reception in different European countries has received some attention from historians of biology, but the reception in Scandinavia remains relatively unknown. We have found letters to and from Haeckel to Swedish scientists and students in the Ernst Haeckel House in Jena and in the archives of the Royal Swedish Academy of Sciences (RSAS) in Stockholm. Here we present correspondence with Wilhelm Leche, Sven Lovén, and M. G. Retzius, all prominent scientists in Stockholm at the time and members of the RSAS. Most letters cover scientific matters such as the biogenetic law, or are concerned with practical matters such as loans of specimens. Sometimes also political issues are mentioned. In addition, we present a letter from Anton Nyström, the radical physician, in which he tells of his struggles with the church and the conservatives, and a letter from the explorer and geographer Sven Hedin, written in the midst of the First World War. Examples are also given of letters to Haeckel from students that were inspired by his world view as laid out in "Natural History of Creation". In conclusion, Haeckel's correspondence with his colleagues in Stockholm gives insights not only into how Haeckel's ideas were received at the time, but also into the relationships between the Swedish scientists, including their conflicting political views.