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 unworked 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.” 
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