312 H. S. AVILLIAMS PERSISTENCE OF FLUCTUATING VARIATIONS 



elbow is as essential a part of the specific structure in making up the 

 mechanism of a limb as are the rigid bones of the arm. The range and 

 direction of movement provided by the flexibility of a joint is as much 

 a specific character as is the shape of the rigid bones. 



So we may generalize these facts and say that the range and direction 

 of the fluctuating characters constitute an essential part of the specific 

 constitution of an organism, and according to the statistics here presented 

 appear to be transmitted with the same persistence from generation to 

 generation as are the non-fluctuating characters which we are accustomed 

 to regard as indicating their specific rank by ceasing to fluctuate. 



