404 The Inward Urge to Change 



Among the paleontologists the evidence is equally con- 

 vincing. The progressive change in successive periods re- 

 corded in the fossils is, for the layman, particularly impressive 

 among the horses, the camels and the elephants (see Figs. 8, 

 9 and 10) . Professor Osborn states very definitely that after 

 a line of mammals starts to become specialized in a given 

 direction, acquiring more and more distinct structures, and 



r 



Fig, 100. Variation in Wing Pattern 

 OF THE California Flower Beetle 



DiABROTICA SOROR 



There are commonly six distinct spots on the 

 wing case, A. The dots may run together cross- 

 wise, B, C, D, E, or lengthwise, F, G. After 

 Kellogg and Bell; from Jordan and Kellogg, Evo- 

 lution and Animal Life, published by D. 

 Appleton & Company. 



presumably corresponding habits, it tends to continue in the 

 same direction until it has gone beyond the point where the 

 " improvement " is of value. As a result of such overspecial- 

 ization, many lines of mammals (and of other vertebrates 

 also) have died out. 



Incidentally it is of interest to note the difficulty of 

 adhering consistently to a single theory as an adequate " ex- 

 planation " of the very complex facts of evolution. Professor 



