VARIATION 31 



of the alcoholized animals are injured. This case is considered further 

 in Chapter XXX. 



On the whole it must be admitted that the experimental induction 

 of heritable variations is still largely an un worked field. The complex 

 conditions to be considered and consequent obstacles to be overcome 

 are appreciated by no one more fully than by those who have attempted 

 such investigations. For, as Tower has said: "It is evident that the 

 problem of germinal change is one of difficulty, and involves more of 

 indirect than of direct methods of investigation. There is little reason to 

 expect that present biochemical methods can give a solution, but they 

 may give valuable suggestions for further indirect investigation. It 

 seems not improbable, however, that this problem like so many others 

 in biology, must await the solution of the larger question of what life is 

 before it will be possible to express in exact terms the nature of germinal 

 changes. Our present status, with several methods of production and 

 much knowledge of the behavior of induced germinal changes available, 

 is a basis from which great advances in knowledge and in operation may 

 reasonably be expected." 



