. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 162 COMPARATIVE ZOOLOGY. the contraction of longitudinal muscles. The Earth-worm lengthens and shortens itself in the same way as the Leech, but instead of suckers for holding its position, it has nu- merous minute spines pointing backward; while the Cat- erpillar has short legs for the same purpose. The legless Serpent moves by means of the scutes, or large scales, on the under side of the body, acted upon by the ribs. In a straight line, locomotion is sl
. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 162 COMPARATIVE ZOOLOGY. the contraction of longitudinal muscles. The Earth-worm lengthens and shortens itself in the same way as the Leech, but instead of suckers for holding its position, it has nu- merous minute spines pointing backward; while the Cat- erpillar has short legs for the same purpose. The legless Serpent moves by means of the scutes, or large scales, on the under side of the body, acted upon by the ribs. In a straight line, locomotion is slow; but by curving the body, laterally or vertically, it can glide or leap with great rapidity. Most animals have movable jointed limbs, acted upon as levers by numerous muscles. The Centipede has forty- two legs, each with five joints and a claw. The Crab has five pairs of six-jointed legs; but the front pair is modified into pincers for prehen- sion. With the rest, which end in a sharp claw, the Crab moves backward, forward, or sideways. The Spider has eight legs, usually seven- joint- ed, and terminating Fig. 127. —Feet of Insects: A, Bibio febrilis; B, \n ^WO claWS toothed House-fly (Musca domestica); C, Water - beetle (Dytiscus). like n comb, and a third which acts like a thumb. In running, it moves the first right leg, then the fourth left; next, the first left, and then the fourth right; then the third right and sec- ond left together; and lastly, the third left and second right together. The front and hind pairs are, therefore, moved like those of a quadruped. The Insect has six. 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 Orton, James, 1830-1877; Birge, E. A. (Edward Asahel), 1851-1950. New York : Harper & Bros.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1883
