. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CILIA. 615 within the tentacula, were moved in two diffe- rent directions, namely, from the base to the point, and from the point to the base ; and (supposing the arm spread out horizontally,) the outward current was along the under part of the tube, and the returning one along the upper: (see A.) I also observed these internal currents of the tentacula in a young specimen of Actinia senilis, which seemed to have been very recently discharged from the parent; in it also there were radiating currents on the disc, but they
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CILIA. 615 within the tentacula, were moved in two diffe- rent directions, namely, from the base to the point, and from the point to the base ; and (supposing the arm spread out horizontally,) the outward current was along the under part of the tube, and the returning one along the upper: (see A.) I also observed these internal currents of the tentacula in a young specimen of Actinia senilis, which seemed to have been very recently discharged from the parent; in it also there were radiating currents on the disc, but they stopped at the base of the tentacula. Thus the external currents on the disc and ten- tacula were found in one species, and they occur on the disc in some other species in the young state, but their occurrence in this situa- tion is by no means general in adult Actiniae. The phenomena described are in all proba- bility connected with the processes of nutri- tion and respiration. They bear a striking analogy to those I have observed in the Echino- dermata. The ova of the Actiniae were observed by Rathke to revolve round their axis, and occa- sionally to move straightforwards in the water. He could detect no cilia or other moving organs.* 6. Echinodermata.—The animals of this class in which I have observed the ciliary motion, are different species of the Sea-star (Asterias), and the Sea-urchin (Echinus). In proceeding to describe the phenomena in the Asterias, I must first take the liberty of ex- plaining some points in the anatomy of that animal, referring the reader for other details to the proper sources, especially the monograph of On the under surface of the Asterias, (I speak of the Asterias rubens in particular, Jig. 298, A, B, C, as it is a large species and common on our shores,) we observe the mouth in the centre, and the tubular feet (I, Jig. B) projecting in rows along the under part of the rays. Nearly the whole surface of the animal is beset with th
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