Karl Gegenbaur

Born Aug. 21, 1826, in Würzberg; died June 14, 1903, in Heidelberg. German biologist and one of the initiators of the phylogenetic trend in comparative anatomy.

Gegenbaur was a professor at the universities of Jena (from 1855) and Heidelberg (from 1872). In his work on the embryology of invertebrate animals (1853) he was one of the first to describe the formation of a two-layered embryo (later known as the gastrula), and he contributed a great deal of new information on the reproduction and development of jellyfish. Gegenbaur definitely proved that the ova of vertebrate animals consist of single cells (1861). Basing his work on phylogenic examples such as the skeleton, skull, and extremities, he worked out the principles of the homology of organs. Gegenbaur developed a theory of “paired archipterygiums” in 1864 to explain the development of paired extremities, and he proposed the theory that bony skulls had evolved from the cartilaginous skulls of the shark family (1872). These theories were important at the time as examples of analytic comparative anatomy. He took a critical view of the biogenetic law and confined research in comparative anatomy to presently existing, growing forms belonging to one type. In his research on the “archetypes” of organs Gegenbaur gave due regard to the natural philosophical traditions of the pre-Darwinian period.