Lorenz Oken - New System of Animal Classification

New System of Animal Classification

In the Grundriss der Naturphilosophie of 1802 Oken sketched the outlines of the scheme he afterwards devoted himself to perfecting. The position advanced in that work, to which he continued to adhere, is that "the animal classes are virtually nothing else than a representation of the sense-organs, and that they must be arranged in accordance with them." Consequently, Oken contended that there are only five animal classes:

1. Dermatozoa, or invertebrates
2. Glossozoa, or fish, those animals in which a true tongue makes, for the first time, its appearance
3. Rhinozoa, or reptiles, in which the nose opens for the first time into the mouth and inhales air
4. Otozoa, or birds, in which the ear for the first time opens externally
5. Ophthalmozoa, or mammals, in which all the organs of sense are present and complete, the eyes being movable and covered with lids.

In 1805 Oken made a further advance in the application of the a priori principle, in a book on generation (Die Zeugung), in which he maintained that "all organic beings originate from and consist of vesicles or cells. These vesicles, when singly detached and regarded in their original process of production, are the infusorial mass or protoplasma (Urschleim) whence all larger organisms fashion themselves or are evolved. Their production is therefore nothing else than a regular agglomeration of Infusoria--not, of course, of species already elaborated or perfect, but of mucous vesicles or points in general, which first form themselves by their union or combination into particular species."

A year after the production of this treatise, Oken developed his system one stage further, and in a volume published in 1806, written with the assistance of Dietrich Georg von Kieser (1779–1862), entitled Beiträge zur vergleichenden Zoologie, Anatomie, und Physiologie, he demonstrated that the intestines originate from the umbilical vesicle, and that this corresponds to the vitelius or yolk-bag. Caspar Friedrich Wolff had previously claimed to demonstrate this fact in the chick (Theoria Generationis, 1774), but he did not see its application as evidence of a general law. Oken showed the importance of the discovery as an illustration of his system. In the same work Oken described and recalled attention to the corpora Wolffiana, or "primordial kidneys."