Lamarck, Jean Baptiste Pierre Antoine de Monet, chevalier de

Born Aug. 1, 1744, in Bazantin-le-Petit, Picardy; died Dec. 18, 1829, in Paris. French naturalist; creator of the first unified theory of evolution (Lamarckism). Member of the Paris Academy of Sciences (1783).

Lamarck studied botany at a medical school in Paris from 1772 to 1776. His work on the flora of France was published in three volumes in 1778; it was here that he first proposed the dichotomous principle of defining plants. Lamarck warmly welcomed the French Revolution; at his suggestion, the Royal Botanical Garden was reorganized in 1793 as the Museum of Natural History, where he became a professor in the department of the zoology of insects, worms, and microscopic animals (he was department head for 24 years). By 1820, Lamarck was totally blind and dictated his work to his daughters. He lived and died in poverty.

Lamarck was the first (in 1794) to divide the animal world into two basic groups—vertebrates and invertebrates (the term “Invertebrata” was created by him). He divided the invertebrates into ten classes—arranging them, in the order of his principle of improvement (gradation), in four increasingly complex levels of organization. Lamarck at first described gradation as a linear series of living things, from protozoans to the most developed organisms. Later, he developed the genealogical tree. The term “biology” was introduced in 1802 simultaneously and independently by Lamarck and the German scientist G. R. Treviranus.

Lamarck was a deist in his treatment of living phenomena. According to Lamarck, matter, the basis of all natural bodies and phenomena, is absolutely inert; in order to vivify matter, it is necessary to introduce movement from without. Hence, Lamarck turns to a “supreme creator” as the source of the “first thrust,” which sets the “universal machine” in motion. According to Lamarck, the living arose from the nonliving, developing further on the basis of strict, objective, and causal dependencies in which there is no room for chance (mechanistic determinism). The simplest organisms both first appeared and now arise from “unorganized” matter (self-generation) under the influence of “fluids” (for example, thermogen and electricity) penetrating it. Lamarck described many forms of fossil invertebrates and described their connections with the system of extant groups. He laid the basis for animal psychology.

Lamarck was the author not only of botanical and zoological works but also of publications on geology, hydrology, and meteorology. In his treatment of geological phenomena in Hy-drogeology (1802), he set forth the principle of historicism and actualism.