38 INDIVIDUALITY IN ORGANISMS 



less rapid and less intense than that of a, and, as 

 indicated in Fig. 2^ the transmitted change will be 

 weaker, perhaps less rapid, and its limit of effectiveness 

 less than that arising from a. The influence of the 

 region b must then be less than that of a in determining 

 the metabolic rate in other regions and a remains the 

 dominant region. 



Fig. 2, — Diagram illustrating origin of major and minor gradients in 

 a simple case: a, apical region of major gradient; h, apical region of 

 minor gradient. 



If, however, the region h or any other region is suffi- 

 ciently intensely or sufficiently often locally excited 

 independently of a, a persistent gradient may arise with 

 relation to h without destroying that related to a. In 

 such a case two dominant regions, a and h, exist, but a 

 may still dominate h to a greater or less extent unless 

 the reactive capacity or irritability of h becomes equal 



