Moreover, fossil animals were, according to his views, practically extinct species, and stood in the light of being the ancestors of the members of our existing fauna.

In fact, his views, notwithstanding shortcomings and errors in classification naturally due to the limited knowledge of anatomy and development of his time, have been at the end of a century entirely confirmed--a striking testimony to his profound insight, sound judgment, and philosophic breadth.
The reforms that he brought about in the classification of the invertebrate animals were direct and positive improvements, were adopted by Cuvier in his _Regne animal_, and have never been set aside.

We owe to him the foundation and definition of the classes of Infusoria, Annelida, Arachnida, and Crustacea, the two latter groups being separated from the insects.

He also showed the distinctness of echinoderms from polyps, thus anticipating Leuckart, who established the phylum of Coelenterata nearly half a century later.

His special work was the classification of the great group of Mollusca, which he regarded as a class.