Jean-Baptiste Lamarck was an exceedingly observant and creative thinker of vast learning but today he is remembered only for his pre-Darwinian theory of inheritance of acquired characters. That theory for a long time was held in poor repute. However, now days, with a fuller understanding of epigenetics, it is realized that his theory was not entirely wrong; it was just not the primary activator of easily observable change. For a modern treatment of the subject see: Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life by Jablonka and Lamb. In Robert Chambers 1844 book, the Vestiges of the Natural History of Creation, in the last chapter we find how some biological thinkers were still revering Lamarck, “The book, as far as I am aware, is the first attempt to connect the natural sciences in a history of creation.”
Darwin himself expanded on Lamarck’s idea in his 1868 book, The Variation of Animals and Plants Under Domenstication,
From Wikipedia, “Lamarck’s contribution to evolutionary theory consisted of the first truly cohesive theory of evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through “use and disuse” of characteristics, differentiating them from other organisms.”
Lamarck’s error was in proposing that the use and disuse of an inborn quality affected the transmission of that quality to the creature’s offspring. It isn’t so much that it is absolutely wrong; it is just a poor way to explain what were the operative factors.
Lamarck was a great scientist and he followed the rules of proposing ideas clearly enough that natural tests could be performed. Later scientists came along and built upon his knowledge and it is probable that without his observations and theories the whole field we now call Darwinism would not exist.
Science is the art of standing on the shoulders of giants.