HOW ANIMALS MOVE 3/1 



The starfish creeps by the working of hundreds of 

 tubular suckers, which are extended by being filled with 

 fluid forced into them by little sacs. The clam moves 

 by fixing and contracting a muscular appendage, called 

 a "foot." The snail has innumerable short muscles on 

 the under side of its body, which, by successive contrac- 

 tions, resembling minute undulations, enable the animal 

 to glide forward apparently without effort. The leech 

 has a sucker at each end ; fixing itself by the one on 

 its tail, and then stretching the body, by contracting the 

 muscular fibers which run around it, the creature fastens 

 its mouth by suction, and draws forward the hinder 

 parts by the contraction of longitudinal muscles. The 

 earthworm lengthens and shortens itself in the same 

 way as the leech, but instead of suckers for holding its 

 position, it has numerous minute spines which may be 

 pointed backward or forward ; while the caterpillar 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 Jeap 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 prehension. With the 

 rest, which end in a sharp claw, the crab moves back- 

 ward, forward, or sideways. The spider has eight legs, 

 usually seven-jointed, and terminating in two claws 

 toothed like a 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 second left together; 



