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from the ungainly turtle and alligator to the quick- 

 footed lizard among reptiles. The running birds have 

 powerful legs, and wings too short for flight; even 

 the ground birds have comparatively small wings and 

 feet adapted for the ground. They walk or run, in 

 contrast with the perching birds that hop along on 

 the ground. The mammals vary in running ability 

 up to or beyond the deer shown. Notice that, as 

 shown, the swift forms run on the toes, while others, 

 like the bear, put the whole foot down. The leaping 

 forms from the grasshopper to the kangaroo agree in 

 the unusual development of the hind legs. In the 

 climbing forms that follow, the adaptation is most 

 noticeable in the character of the hand or foot, as in 

 the sloth; the woodpecker has two toes pointed for- 

 ward and two pointed backward, to give him a hold. 

 The monkey can not only grasp with his hands and 

 feet but with his tail as well. The cat and squirrel 

 have the claws adapted for clinging to the rough bark 

 of trees. Lastly come the flying forms, of which the 

 buzzard with its long wings and its power of sustained 

 flight is one of the best examples. Notice the adap- 

 tations of animals of other classes, all agreeing in 

 having the bones very light, usually hollow. The 

 flying birds have the keeled breast-bo ue for the at- 

 tachment of the powerful muscles needed for flight. 

 The bat spreads a skin between his fingers, a method 



