. Animal studies. 158 ANIMAL STUDIES the power of locomotion. In some of the sea-cucumbers five equidistant rows of tube-feet extend from one end of the body to the other, and the animal crawls worm-like upon any side that happens to be down; but certain spe- cies living in the sand, where tube - feet will not work satisfactorily, have lost all traces of them, and creep like an earthworm from place to place. In all the sea-cucumbers the feet, situated nearthe mouth, have been curiously modified to form a cir-. Fig. 97.— An unattached crinoid (Antedori). - half natural size. clet of tentacles,
. Animal studies. 158 ANIMAL STUDIES the power of locomotion. In some of the sea-cucumbers five equidistant rows of tube-feet extend from one end of the body to the other, and the animal crawls worm-like upon any side that happens to be down; but certain spe- cies living in the sand, where tube - feet will not work satisfactorily, have lost all traces of them, and creep like an earthworm from place to place. In all the sea-cucumbers the feet, situated nearthe mouth, have been curiously modified to form a cir-. Fig. 97.— An unattached crinoid (Antedori). - half natural size. clet of tentacles, which range in form from highly branched to short and thick structures, and in func- tion from respiratory organs and those of touch to con- trivances for scooping up sand and conveying it to the mouth. 147. Food and digestive system.—In the echinoderms the body-wall is comparatively thin (Fig. 98), and encloses a great space, the body-cavity, in which the digestive and re- productive organs are contained. As the former in various species is adapted for acting upon very different kinds of food, it shows many modifications; but there are a few prin- cipal types which may be briefly considered. In the starfishes the mouth enters almost directly into the cardiac division of the stomach, a capacious, thin-walled sac, much folded and packed away in the disk and bases of the arms (Fig. 98, Z>). This in turn leads into the second pyloric portion (a), with thicker walls and dorsal, to the first, from which a short intestine leads to the exterior, near the center of the disk. Another conspicuous and im- portant feature is the so-called liver, consisting of a pair. 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 Jordan, David Starr, 1851-1931; Kellogg, Vernon L. [from old catalog].
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Keywords: ., bookauthorjordanda, bookcentury1900, bookdecade1900, bookyear1903
