. Animal physiology. Physiology, Comparative; Physiology, Comparative. 108 STRUCTURE OF THE ECHINODERMATA. part of the body. These are seen in rows on the under side of each arm of the Star-fish; they are put forth through rows of very minute apertures in the shell of the Sea-Urchin (commonly termed the sea- egg) ; and they are also arranged in rows on the surface of the body of the Holothuria, as seen in Fig. Fig. 70.—Shell of Sea-urchin ; on the right side, covered with spines ; on the left, the spines removed. 129. The radiated arrangement is very evident in the whole bodies of the Sta
. Animal physiology. Physiology, Comparative; Physiology, Comparative. 108 STRUCTURE OF THE ECHINODERMATA. part of the body. These are seen in rows on the under side of each arm of the Star-fish; they are put forth through rows of very minute apertures in the shell of the Sea-Urchin (commonly termed the sea- egg) ; and they are also arranged in rows on the surface of the body of the Holothuria, as seen in Fig. Fig. 70.—Shell of Sea-urchin ; on the right side, covered with spines ; on the left, the spines removed. 129. The radiated arrangement is very evident in the whole bodies of the Star-Jish (Fig. 16), and Sea-Urchin; but in the Holothuria it is nearly confined to the parts about the mouth ; which, however, exhibit it so completely, that such an animal cannot be mistaken for one of the Articulated series, even though, as sometimes happens, the body is prolonged into a worm-like form. The digestive apparatus in this class has usually a high degree of complexity. In the Sea-Urchin and Holothuria, there is a regular stomach and intestinal tube ; and the latter terminates by a distinct orifice, at a distance from the mouth. The circu- lating apparatus, however, is imperfect, the blood not being impelled by a distinct heart; still, however, it moves through proper vessels, and not through mere channels in the tissue. There is also a regular provision for respiration; the water being admitted to the interior of the shell, in order to convey air to the fluids of the body. In the Star-fish, however, the body is very much flattened; and the stomach, instead of having a separate intestinal tube with a distinct orifice, is a mere bag with. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carpenter, William Benjamin, 1813-1885. London : Wm. S. Orr and Co.
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