(1834—1919) German biologist and philosopher
German biologist, who became professor of zoology and comparative anatomy at the University of Jena in 1862. An ardent follower of Darwin, Haeckel was the first to divide animals in protozoan (unicellular) and metazoan (multicellular) forms. However, he had a mistaken belief in the spontaneous combination of the elements to produce elementary life forms. His recapitulation theory, that the stages of embryological development of an individual organism recapitulate the evolution of its species, is no longer accepted.