Ernst Haeckel: Phylogeny as the
Mechanical Cause of Ontogeny

Es ist ein ewiges Leben, Warden und Bewegen in ihr. Sie verwandelt sich ewig, und ist kein Moment Stillstehen in ihr. Fur's Bleiben hat sie keinen Begriff, und ihren Fluch hat sie an's Stillstehen gehangt. Sie ist fest: ihr Tritt ist gemessen, ihre Gesetze unwandelbar.

Goethe on Nature, quoted by Haeckel
on title page of Generelle Morphologic, 1866

The law of recapitulation was "discovered" many times in the decade following 1859. Fritz Mtiller applied it in his masterful Für Darwin (1864), a short treatise on Darwinian explanations for crustacean morphology. He did not grant to recapitulation the universal status afforded it by his successors. Cope and Hyatt, the intellectual descendants of Agassiz in America, published their first works on recapitulation independently in 1866. In that same year, Haeckel's Generelle Morphologie der Organismen made its appearance; Huxley called it "one of the greatest scientific works ever published" (quoted in McCabe's footnotes to Haeckel, 1905).

Ernst Haeckel, son of a government lawyer, was born in Potsdam in 1834. He took a medical degree in 1858 and, after a short practice, moved to Jena to study zoology under the great anatomist Carl Gegenbaur. He became professor of zoology and comparative anatomy in Jena in 1862 and remained there until his death in 1919.

Haeckel published major treatises on three protist and invertebrate groups: Radiolaria (Die Radiolarien, 1862-1868), calcareous sponges (Die Kalkschwdmme, 1872), and medusae (Das System der Medusen, 1879). But his dominating influence grew from two articles on the "gastraea theory" (1874 and 1875, though the idea was first promulgated in 1872, p. 467), and especially from three books: Generelle Morphologie (lSQ6),NatürlicheSchöpfungsgeschichte (1868), andAnthropogenie (1874). Haeckel conceived the books as popular works, but they contain a great amount of complex detail amidst speculation both bold and absurd. All deal heavily in phyletic reconstruction. His famous evolutionary trees first appear as plates in the second volume of Generelle Morphologie; Haeckel's trees have their roots (and most of their branches) in the principle of recapitulation—the "biogenetic law."* "Ontogeny is the short and rapid recapitulation of phylogeny . . .

Haeckel was an inveterate coiner of terms; many words, common to scientists and laymen alike, were his invention: ecology, ontogeny, phylogeny. But most died with him, among them "biogeny"—the genesis of the history of organic evolution. Thus his phrase "biogenetic law" is often misunderstood, or at least not granted the force that Haeckel intended; for, under his definition, it is the law of the history of evolution.