The Thricozoa must stand thus:

1. IcthyoidCetacea.
2. HerpetoidPachydermata.
3. OrnithoidRuminantia.
4. TypicalAll the remaining Thricozoa.

In the systems now in vogue the Thricozoa certainly follow in this manner, and no scruple whatever is made of placing the Mice, Ant-eaters, Shrews, and Bats above Elephants, Horses, and Deer. Yet apart from all this, the former must pass beyond the Thricozoa, and would thus likewise have no other organ as a foundation than perhaps the organs of sense, of which there are but five, while the families of Thricozoa not yet provided for are much more numerous, namely, besides those named, the Seals, Dogs, Bears, and Apes.

The above methods of arrangement must be consequently cast aside without limitation or reserve, although they may have held good for hundreds of years. But what does or will not hold good in an age that is devoid of principles?

It is thus evident that the smaller Birds stand below the Aquatics, just as the smaller Thricozoa do beneath the Whales, quite apart from organic structure, which in every respect is imperfect. They must correspond, consequently, to the Asarcous animals, wherewith also their great number agrees.

If this holds good of the two highest classes, so also must it hold good of the two lower, namely, Fishes and Reptiles, and we shall thus have:

I.Protozooid Fishes, Reptiles, Birds, and Thricozoa.
II.Conchozooid Fishes,&c.
III.Ancyliozooid "&c.
IV.Icthyoid "&c.
V.Herpetoid "&c.
VI.Thricozooid "&c.
VII.Ornithoid "&c.

3532. But this parallelism depends essentially upon the organs, and they are called, in the language of Physio-philosophy, more correctly:

I. Intestinal Fishes, Reptiles, Birds, and Thricozoa.
II. Vascular Fishes,&c.
III. Pulmonary "&c.
IV. Osseous "&c.
V. Muscular "&c.
VI. Nervose "&c.
VII. Sensorial "&c.

But as these names are unused, and give or convey only the anatomical idea, but no external image, the first appellations are to be preferred.