( Title in Polish - 'Jean-Baptiste de Lamarck. Spór wokól mechanizmu ewolucji. W dwusetna rocznice ogloszenia dziela 'Philosophie zoologique' (1809)'). The author of the paper has made an attempt to prove that a teleological interpretation of Lamarck's theory is false. It is unwarranted to attribute to Lamarck the idea that a living organism has an internal tendency to complicate its organization and to improve its mode of functioning; such a concept is not confirmed by existing textual evidence, and it is also in direct conflict with Lamarck's undisputed mechanicism. The proof presented in the paper begins with an outline of the history of this false interpretation, including the opinions of Charles Lyell and Charles Darwin. As the tendency is ascribed also to nature itself, the next phase of the proof has involved reconstructing the fully ateleological notion of nature to which Lamarck subscribed. Supposed evidence for the tendency is said to be provided by the existence of a series in which the organization of a living body grows from the simplest to the most complex. That is why the author of the current paper has analysed the concept of 'série animale' used by Lamarck in some detail, in order to demonstrate that it is typological in character, and has nothing to do with the tendency that is allegedly inherent in the nature of an organism. Also presented in the paper, in connection with the construction of the series, is the problem of spontaneous generation, which was made complicated by Lamarck. Finally, the very notion of tendency is analysed and confronted with Lamarck's text; the latter in fact does not contain any explanations that would be teleological in the strict sense of the word. The analysis has enabled the author of the current paper to conduct an exegesis of the fragment of Lamarck's text which might give grounds to it being construed in terms of an explanation resorting to the notion of tendency, and possible interpretations of that fragment have been presented. The paper ends with a description of the mechanism which, according to Lamarck, is responsible for the rise in complexity of an organism that has the nature of a machine; such a mechanism leaves no place for any tendency to be in operation.