22 



INTRODUCTION TO EVOLUTION 



FIG. 3.1. Comparison of vertebrate wing structures. (By 

 permission from The Dinosaur Book, by Colbert, p. 

 100. Copyright, 1951. McGraw-Hill Book Company, 

 Inc.) 



case of the bat. The similar segments found in arm and wings may be 

 listed as follows, starting at the shoulder (Fig. 3.2): (1) humerus, 

 (2) radius and ulna, (3) carpals, (4) metacarpals, (5) phalanges. Here 

 is similarity of structure not readily explained as connected with similar 

 function. 



Fig. 3.2 presents, along with the forelimb of man, the limbs of four 

 mammals adapted for more or less rapid movement over the surface of 

 the earth. A glance at the figure suffices to reveal that dog, hog, sheep, and 

 horse all have their forelimb skeletons constructed of bones arranged ac- 



