26 K. S. LASHLEY 



amount to less than one one-hundredth of the total variation. 

 The difficulty of accounting physiologically for such a condition, 

 upon other than the mutation theory, and the lack of any posi- 

 tive evidence of such heredity suggest that the most tenable 

 position is one which assumes that the continuous variations of 

 Hydra are not inherited in asexual reproduction but are wholly 

 the result of the interaction of the constant reaction-norm of 

 the clone with a fluctuating environment. 



