The opening of Preface
The first principles of the present work I laid down in my small pamphlet entitled Grundriss der Naturphilosophie, der Theorie der Sinne und der darauf gegrundeten Classification der Thiere; Frankfurt bey Eichenberg, 1802, 8vo (out of print). I still abide by the position there taken, namely, 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. Thus, strictly speaking, there are only 5 Animal Classes: Dermatozoa, or the Invertebrata; Glossozoa, or the Fishes, as being those animals in whom a true tongue makes for the first time its appearance; Rhinozoa, or the Reptiles, wherein the nose opens for the first time into the mouth and inhales air; Otozoa, or the Birds, in which the ear for the first time opens externally; Ophthalmozoa, or the Thricozoa, in whom all the organs of sense are present and complete, the eyes being moveable and covered with two palpebræ or lids.