Haeckel, Ernst Heinrich, << HEHK uhl, ehrnst HYN rihk >> (1834-1919), a German zoologist, became known for his theory of recapitulation. This theory, no longer held by most zoologists, states that each animal during its growth as an embryo repeats the changes its ancestors underwent. For example, if a land animal had ancestors that lived in water and used gills, then each embryo of that animal continues to develop gills as did its ancestors, even though the gills may be lost during later embryonic development.
Haeckel studied and made drawings of the embryos of many animals. He also used his findings to support Charles Darwin’s theory of evolution (see Darwin, Charles R. ). Haeckel was the first to draw a “family tree” of animal life, showing the supposed relationships of animal groups. His widely read book, The Riddle of the Universe (1899), explained many of his theories. His early work included a study of marine organisms, chiefly radiolarians, coelenterates, and echinoderms.
Haeckel was born in Potsdam, Germany, on Feb. 16, 1834. He liked botany but studied medicine at his father’s insistence. He was educated at Wurzburg, Vienna, and Berlin universities. He served as a professor of zoology at the University of Jena from 1862 to 1909. He died in Jena on Aug. 9, 1919.
