|Birth||23 August 1855, Clenze, Lüchow-Dannenberg, Lower Saxony, Germany|
|Death||6 December 1912, Lüneburg, Lüneburg, Lower Saxony, Germany (aged 57 years)|
Johann Wilhelm Haacke (August 23, 1855 – December 6, 1912) was a German zoologist born in Clenze, Lower Saxony.
He studied zoology at the University of Jena, earning his doctorate in 1878. Afterwards he worked as an assistant at the Universities of Jena and Kiel. In 1881 he emigrated to New Zealand, and during the following year moved to Australia, where he was director of the Natural History Museum in Adelaide (1882–84).
From 1888 to 1893 he was director of the zoo in Frankfurt-am-Main, and afterwards was a lecturer at Darmstadt University of Technology (until 1897). Later, he worked as a private scholar and grammar school teacher. He died in Lüneburg on December 6, 1912.
Haacke is remembered for research of oviparity in monotremes, and studies involving the morphology of jellyfish and corals. In 1893 he coined the evolutionary term "orthogenesis". He also conducted investigations in the field of animal husbandry.
Haacke studied under Ernst Haeckel. He later turned against Haeckel for holding Darwinist views. He was also a critic of August Weismann. He experimented with mice and proposed a system of heredity similar to Gregor Mendel but differed in results. Haacke was a neo-Lamarckian and proponent of the inheritance of acquired characters.
Haacke believed that cells consist of individuals called gemmaria that operate as hereditary units. These consist of even smaller units known as gemmae. He believed these units to explain neo-Lamarckian inheritance. He was a proponent of orthogenesis. He held that from his theory of epimorphism evolution is a directed process tending towards perfection.
He made contributions towards Brehms Tierleben, and with illustrator Wilhelm Kuhnert, published Das Tierleben der Erde. Other noteworthy written efforts include:
- Die Schöpfung der Tierwelt, (1893)
- Gestaltung und Vererbung. Eine Entwickelungsmechanik der Organismen, (1893)
- Die Schöpfung of Menschen und seiner Ideal. Ein Versuch zur Versöhnung zwischen Religion und Wissenschaft, (1895)
- Aus der Schöpfungswerkstatt, (1897)
- Grundriss der Entwickelungsmechanik, (1897)