3164. They are tubular nerves surrounded by a tegument.
The cilia also are perfected and lengthen into filaments, which no longer perform simply vortical movements, but now actually seize and convey the food self-substantially into the mouth. Such animals are called Polyps. Their multiplication takes place no longer by division or fissure, but by ova and shoots, or ramification.
The oviducts or egg-tubes lie between the intestine and tegument, and open upon the margin of the mouth between the tentacula. In many instances the ovisacs, or cysts, hang also freely from other parts of the body, as in the Sertulariæ.
The sprouts or offshoots detach themselves from the parent and become independent animals; but they frequently continue to stand as ramules upon the maternal animal, though they nourish themselves independently of the latter.
3165. If the process of oxydation be augmented, then, the tube's external wall indurates, becomes coriaceous, and, lastly, ceratoid or horn-like in texture. The nerve-tubes or the animal proper can now swim no longer, since one kind only of motion is left it, namely, to protrude itself out of, and then retract itself within, the tube. It consequently falls to the ground, and while the external mucus hardens, it clings to the former; such are the Sessile or fixed Polyps.
3166. Sessile Polyps having coriaceous or horny tubes are called Plant-animals, Zoophyta, Phytozoa.
3167. The adherent, dried and dead external tegument of the Polyp is called stem. Such a ramified stem completely resembles a plant.
3168. These woody or herbaceous stems are not rooted in the earth, but have the power of adhering firmly to every substance, to stone, glass, shells, and such like bodies. They do not therefore draw in nourishment through any root.
3169. The ramification is often wholly plant-like in character, resembling that of a shrub with separate ramules, which even assume too the form of leaves, and the animal tubes that of flowers.
But frequently the ramules grow together also by their extremities, giving rise to a trellis-work, the production of which in plants is impossible. The soft animalcules, which come in contact, cleave unto each other, and grow together like wounded parts in the Sarcose animals.