Second Province.
— FOURTH CIRCLE—SARCOZOA.
Pisces, Reptilia, Aves and Thricozoa.
3530. These animals necessarily pass through all 4 circles, and each class therefore divides into 4 orders, or into 5, if the senses be allowed to hold good as constituting a distinct order in themselves.
Two points of departure for classification here admit of being thought of, either wholly from below, or first of all from the commencement of the present circle. In order to be convinced of this, we need only make a slight attempt. The animal series is as follows:
| A. Splanchnozoa. | ||
|---|---|---|
| Circle I. | Intestinal animals | Protozoa. |
| Class | 1. Gastric animals | Infusoria. |
| 2. Intestinal " | Polypi. | |
| 3. Absorbent " | Acalephæ. | |
| Circle II. | Vascular animals | Conchozoa. |
| 4. Venous animals | Mussels. | |
| 5. Arteriose " | Snails. | |
| 6. Cardiac " | Kracken. | |
| Circle III. | Respiratory animals | Ancyliozoa. |
| 7. Reticular animals | Worms. | |
| 8. Branchial " | Crabs. | |
| 9. Tracheal " | Flies. | |
| B. Somatozoa. | ||
| Circle IV. | Sarcozoa. | |
| 10. Osseous animals | Fishes. | |
| 11. Muscular " | Reptiles. | |
| 12. Nervose " | Birds. | |
| Circle V. | Aistheseozoa. | |
| 13. Sense-animals | Thricozoa. | |
3531. Now it is here conceivable, either that the families of Fishes, Reptiles, Birds, and Thricozoa, pass parallel to all the preceding classes from the Infusoria upwards, or that they first commence with the class of Fishes.
In regard to this question the Birds and Thricozoa give the most clear and decisive answer. If we adopt the last proposition, then the Birds must follow each other thus:
| 1. Fish-like Birds | Palmipedes. |
| 2. Reptilian Birds | Grallæ. |
| 3. Typical Birds | Gallinæ. |
| 4. Thricozooid Birds | Struthionidæ. |
According to this, the Aquatic Birds would occupy the lowest rank, just as they have actually done hitherto in all other systems. The three other families too do not admit of any other position. But what is to be done meanwhile with the large majority of other Birds? They would extend or pass beyond the Thricozoa, and have thus no anatomical system whatever for their basis. Besides, Humming-birds, Sparrows and Linnets would in this way rank higher than the Gallinaceous and Struthious Birds, which some indeed believe to be the case, but without any proof, so that it is scarcely necessary to abide by such an opinion.