. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. NUTRITION IN THE ACTINIA. 15 particles brought within reach of the mouth by means of currents excited by the motions of the cilia. Such are the simple forms assumed by the organs of as- similation among the lowest orders of the animal creation; namely, digesting cavities, whence proceed various canals, which form a system for the transmission of the prepared nourishment to different parts; but all these cavities and ca- nals being simply hollowed out of the
. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. NUTRITION IN THE ACTINIA. 15 particles brought within reach of the mouth by means of currents excited by the motions of the cilia. Such are the simple forms assumed by the organs of as- similation among the lowest orders of the animal creation; namely, digesting cavities, whence proceed various canals, which form a system for the transmission of the prepared nourishment to different parts; but all these cavities and ca- nals being simply hollowed out of the solid substance of the body. As we ascend a step higher in the scale, we find that the stomach and intestinal tube, together with tlieir appendages, are distinct organs, formed by membranes and coats proper to each, and that they are themselves contained in an outer cavity, which surrounds them, and which re- ceives and collects the nutritious juices after their elabora- tion in these organs. The t^ctinia, or Sea Jlnemone, for example, resembles a polypus in its general form, having a mouth, which is surrounded with tentacula, and which leads into a capacious stomach, or sac, open below, and occupying the greater part of the bulk of the animal; but while, in the polypus, the sides of the sto- mach constitute also those of the body, the whole being one simple sac; in the actinia, spaces intervene between the coats of the stomach, and the skin of the animal. As the stomach is not a closed sac, but is open below, these cavities are, in fact, continuous with that of the sto- mach: they are divided by numerous membranous parti- tions passing vertically between the skin, and the membrane of the stomach, and giving support to that organ. Fig. 257, representing a vertical section of the Jictinia coriaccd, dis- plays this internal structure, b is tlie base, or disk, by which the animal adheres to rocks: i is the section of the coriaceous integument, showing its thickness: m is the cen-
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Keywords: ., bookcentury18, booksubjectnaturaltheology, booksubjectphysiology
