Class 8. Branchial, Pedal Animals.
3260. The representation of the Cutaneous animals is not yet the entire completion of the tegument. It attains a higher grade by separating in accordance with the visceral systems, and in the conversion of the branchiæ into sensorial organs or feet.
The branchiæ endeavour to separate self-substantially, and form a body of their own. The branchial body is the thorax.
By this attempt, the abdomen originates "per se" as the body of the intestinal and sexual system. The branchiæ upon it are arrested or stunted. In like manner the body of the nerves separates itself from the thorax and becomes head.
But meanwhile this separation is only imperfect; the head and thorax, if otherwise distinguished by their size and the feet, are for the most part connate; abdomen and tail are usually fused together, and only to be recognized as distinct by the limbs or members.
With this greater division of the body each division of it obtains its articulation into rings; but they will be hardened by virtue of the separation of the branchial network, or will become horny—Horny animals.
3261. With the conversion into horny texture of the body, its branchial filaments or tentacula must undergo a similar change, and divide likewise into rings like the general or bodily tegument.
Annulate, horny branchial filaments, are feet—Pedal animals.
A part of the branchiæ remains hanging to the feet, mostly to their basal joints, and is supported by animal motor members or limbs; the respiration becomes voluntary—Branchial animals.
The Annulate animals, having branchiæ and feet, are the Crustacea or Crabs.