I do not mean that existing animals form a very simple series, regularly graded throughout; but I do mean that they form a branching series, irregularly graded and free from discontinuity, or at least once free from it. For it is alleged that there is now occasional discontinuity, owing to some species having been lost. It follows that the species terminating each branch of the general series are connected on one side at least with other neighboring species which merge into them. This I am now able to prove by means of well-known facts. (Philosophie Zoologique)
Lamarck remains the best known figure of the pre-Darwinian era of evolutionism. Regrettably, he is usually viewed as a mere caricature of his ideas, namely as the person who got it “wrong” for insisting on the inheritance of acquired features as the central mechanism of transmutation. Lamarck’s career and scholarly interests were both eclectic and diverse – and his ideas about evolutionary transformation were critical to the overall development of the discipline. Lamarck published the first dichotomous key of plants in 1778, went on to oppose the new chemistry of Lavoisier and others in the 1780s and 1790s, published annual meteorological predictions (not particularly accurate), and survived the purges of the French Revolution.
Although originally a botanist, Lamarck’s appointment in 1793 to the Museum d’Histoire Naturelle in Paris resulted in assigned responsibilities for invertebrates and microscopic organisms. In 1800, Lamarck gave a lecture in which he espoused the idea of evolution (published in 1801). In 1809, Philosophie Zoologique (Zoological Philosophy) the first book-length treatment of evolution was published. Remarkably, a full English translation did not appear until 1914 (pdf Part I, pdf Part II, pdf Part III). Lamarck embraced invertebrate zoology for much of the remainder of his career and ultimately wrote an important set of volumes on invertebrates between 1815 and 1822, which also contain his final views on evolution. For the last several years of his life, Lamarck was blind and impoverished.
The definitive (English language) treatment of Lamarck’s scholarship can be found in The Spirit of System: Lamarck and Evolutionary Biology by Richard W. Burkhardt, Jr. (1977 and 1995).
An extensive website for information on the works and heritage of Lamarck can be found by clicking here.