Is that true? I thought he did.
Nope. He speculated that through spontaneous generation new life forms were being produced all the time. These organisms would then evolve according to the environmental pressures.
"In the late 18th century, Cuvier in France had described extinct mammals and Blumenbach in Germany had described fossil shellfish that were now extinct. In 1800, Lamarck adopted and modified the Aristotelian view of Bonnet of a gradual transition from inanimate matter to the most perfect being, and added a principle of transition over time. Moreover, Lamarck added that the transition was not a ladder, but a branching tree, with new forms created. However, Lamarck asserted the existence of a number of qualitatively separate trees for different lineages - several for animals and several for plants and other forms of life - rather than a common tree for all life. Lamarck accepted the then widely-held view of the possibility of the spontaneous generation of new living forms from inanimate matter, which was disproven by Pasteur in the late nineteenth century."
http://www.biologie.uni-hamburg.de/b-online/e36_talk/precursors/precurs4.html