244 THE MEANING OF EVOLUTION 



a time the variations which have not yet become use- 

 ful to the animal. It has always been difficult on 

 Darwinian principles to understand how the begin- 

 nings of the useful variations could be selected before 

 they were strong enough to be of actual value to the 

 animal. This tendency to variations in certain di- 

 rections instead of at random would account for such 

 early development. This theory of Orthogenesis has 

 not figured very strongly in the history of the move- 

 ment, but it recurs at intervals. 



Both in America and France there is a constant 

 tendency on the part of zoologists to return to the 

 Lamarckian idea that it is the use of an organ that 

 develops it, its disuse that makes it fade away. This 

 is undoubtedly true of the individual, and although 

 Weissman insists that it is useless to the species as a 

 whole, many zoologists are slow to relinquish entirely 

 the idea that somehow these favorable developments 

 become reproduced in the offspring. 



Professor Cope, the American paleontologist, was 

 a strong believer in the effect of activity, both upon 

 the individual and upon his descendants. He believed 

 that the insistent beating of the foot of an animal 

 upon the hard soil of the drying Tertiary plateau, 

 had influenced the production of a firmer nail, which 

 spread around the entire end of the toe and made 

 the hoof of the ungulate. He believed that the use 



