Thus, the Acalephæ first appear under the form of Infusoria; next change into Polyps, and then obtain for the first time the form of the perfect Acalephæ. The same phenomenon occurs in the naked snails or Slugs. They have, when freshly hatched from the egg, a small mussel-like shell, which they lose at a later period.
The Echini or Sea-urchins, which I believe ought to be ranged with the Kracken, also pass through a metamorphosis.
Finally, it is well known that the Crabs also are subjected to a metamorphosis. Their first condition must be regarded as that of the Worm.
The law is thus universal. The second and third class of every circle traverse after birth the classes, to whose series they belong.
It would even appear that the classes, also of a lower circle, are subject to similar changes; at least many Entozoa, and thus the first class of the third circle, appear to undergo such a metamorphosis, since they first of all resemble an Infusory animal, next change as pupæ into Molluscs, and are then manifested for the first time as Worms.
3299. The Dermatozoa or Sensitive animals range in the following manner, according to the anatomical systems:
| A. Intestinal animals. | B. Vascular animals. | C. Respiratory animals. |
|---|---|---|
| 1. Gastric animals. | 4. Venous animals. | 7. Reticular animals. |
| Infusoria. | Mussels. | Worms. |
| 2. Intestinal animals. | 5. Arterial animals. | 8. Branchial animals. |
| Polyps. | Snails. | Crustacea. |
| 3. Absorbent animals. | 6. Cardiac animals. | 9. Tracheal animals. |
| Acalephæ. | Kracken. | Insects. |
3300. According to the developments of the feeling-sense they stand thus:
| A. Ovum-animals. | B. Sexual animals. | C. Cutaneous animals. |
|---|---|---|
| 1. Vitelline animals. | 4. Ovarial animals. | 7. Papillary animals. |
| Infusoria. | Mussels. | Worms. |
| 2. Albuminose animals. | 5. Orchitic animals. | 8. Pedal animals. |
| Polyps. | Snails. | Crustacea. |
| 3. Involucral animals. | 6. Renal animals. | 9. Alary animals. |
| Acalephæ. | Kracken. | Flies. |
3301. From these tables the number and kind of relationships or affinities is readily deduced. There is a Relationship of Proximity, as that between Infusoria, Polyps, and Acalephæ.