Philosophie zoologique ou exposition des considérations relatives à l'histoire naturelle des animaux (meaning "Zoological Philosophy: Exposition with Regard to the Natural History of Animals") is an 1809 book by Jean-Baptiste Lamarck in which he outlines his theory of evolution now known as Lamarckism.
Lamarck proposed that species could acquire new characteristics from influences in their environment:
- "as new modifications will necessarily continue to operate, however slowly, not only will there continually be found new species, new genera, and new orders, but each species will vary in some part of its structure and form ... individuals which from special causes are transported into very different situations from those where the others occur, and then constantly submitted to other influences - the former, I say, assume new forms, and then they constitute a new species."
He argued that gaps between differing kinds resulted from the extinction of intermediate forms:
- Species form "a branching series, irregularly graduated which has no discontinuity in its parts, or which, at least, if its true that there are some because of lost species, has not always had such. It follows that the species that terminate each branch of the general series are related, at least on one side, to the other neighboring species that shade into them".
- Lamarck: Contents
- 1809, vol. I: (Oxford)
- 1830, vol. I: (Harvard)
- 1830, vol. I: (Michigan)
- 1830, vol. II: (Michigan)
- "Lamarck, the Founder of Evolution" by Alpheus Spring Packard, page 240
- "Outlines of evolutionary biology", by Arthur Dendy and Maurice Burton on page 387