HAECKEL, ERNST HEINRICH. - Biologist, b. at Potsdam on 16 Feb. 1834, d. at Jena on 9 Aug. 1919. He studied medicine at Würzburg and natural sciences at Vienna and at Berlin. After numerous journeys for scientific purposes, he spent 1859 and 1860 at Naples and at Messina to study the fauna of the Mediterranean.
He wrote during this time Die Radiolaria, eine Monographie (Berlin 1862), which earned him the chair of zoology at Jena. In the following years he published numerous scientific works, among them Beiträge zur Naturgeschichte der Hydromedusen (Leipzig 1865); Zur Entwicklungsgeschichte der Syphonophoren (Utrecht 1869); Das System der Medusen (Jena 1879), etc.; and furthermore works of a general character, which, translated into many languages, had a wide diffusion: Generelle Morphologie der Organismen (Berlin 1866); Natürliche Schöpfungsgeschichte (ibid. 1868), translated into Italian by D. Rosa (Turin 1892), etc. In 1877 his Studien zur Gastrea-Theorie were published at Leipzig, a compendium and complement of his scientific-philosophical doctrine.
H. was one of the most eminent representatives of scientific materialism. A convinced Darwinian, he saw in embryology the clarification of evolution. From the moneron, a formless mass of living matter, up to man there is an uninterrupted chain (monism), through stages that are temporarily represented in the embryological development of each individual being. "Ontogeny is a recapitulation of phylogeny," this is the "fundamental biogenetic law" already expressed by Serres and by Müller and glimpsed by the Italian Tommasi in the first period of his scientific activity (S. Tommasi, Istituzioni di fisiologia, Turin 1852).
Apart from the falsifications of which he was accused, the necessity of pre-established schemas and dogmatic rigor led H. to imagine and invent forms and types of animals that never existed, so that, after the first enthusiasms, his doctrine ended by appearing devoid of any critical spirit. He affirms a priori that the second law of thermodynamics must be sacrificed because the constant increase of entropy would lead to the creation of the world, and therefore contradicts the first. His "phylogenetic trees," intended to show the historical connections between the classes and the animal types, according to a rigid monophyletism, were such that even Darwin, less imprudent, after having admired their originality, added: "your audacity sometimes makes me tremble." At the Cambridge Congress (1898), in order to speak on the origin of man, he arranged on the platform the skeletons of anthropomorphic apes in an upright position, an artifice he needed to insinuate their quasi-bipedalism, whereas it is known that the higher primates, being arboreal, are quadrupedal on the ground. Similar artifices served H. to insinuate the resemblance of human embryos to mammals, by retouching and schematizing the figures. In this way H. forced the hand of the facts, thus entering into polemic with expert embryologists; among them W. His in the early period, F. Keibel in the last.
Present-day biology has by now recognized that the problem of the beginning of evolution is just as insoluble as that of the origin of life and that it is not possible to consider life as a simple consequence of random atomic aggregations and thought as a secretion of the brain, as the materialism of H. claimed.