EXTENSION OF EVOLUTIONARY THEORIES 339 



must decrease in size, though not to such an extent as 

 to cause injury to the organism. But there is no trace 

 to be found in reality of either process. Therefore, the 

 hypothesis of a germinal selection cannot be sound. 



A number of experts have raised objections to this 

 hypothesis of germinal selection. 1 It has been pointed 

 out that we must assume that a determinant which 

 has increased in size owing to an accidental addition 

 to its food-supply will sink to its old level as soon as 

 this addition ceases. It is quite arbitrary to ascribe to 

 a living force such as the determinant is the power to 

 retain the increased size it has obtained from a better 

 food-supply when this supply has diminished. If a 

 gymnast strengthens his arm by exercise, it will not 

 remain at its full strength if he afterwards abandons 

 daily practice. If such complex structures as the 

 muscles of the arm are not able to maintain the force 

 they have acquired in this way when the exercise is 

 abandoned, how much less will this be possible for a 

 minute particle of living matter, which is so much 

 exposed to vacillations in its supply of food? 



It is just as arbitrary to identify size and force. A 

 determinant that has increased in size owing to better 

 nourishment has not necessarily acquired a greater 

 power of obtaining food than the neighbouring deter- 

 minants that have remained small. We should be 

 equally justified in assuming that the shrinking deter- 

 minants are so much the " hungrier." There is no 

 direct physiological relation between force and size. 



1 Professor Emery of Bologna and Professor Thomson of Aberdeen 

 are the only two distinguished authorities who have fully subscribed to 

 the theory. 



