How Lamarck Divided the Species

Here is a fact worthy of readers attention. From Jean-Baptiste Lamarck:

In order to avoid ambiguity and hypothesis, I divide the entire known animal world in my first course of lectures at the Museum in the spring of 1794 (the year II of the republic) into two perfectly distinct groups, viz: Animals that have vertebrae; Animals without vertebrae.

J. B. Lamarck, Zoological Philosophy. Translated by Hugh Elliot (New York and London: Hafner Publishing Co, 1963), p. 62.