ON THE QUICK GROWING WALNUT 
still matter for change and adaptation; still in the 
experimental stage, as it were. And precisely be- 
cause such is their status, these are the things 
that aré subjected to the Mendelian test when they 
are brought in juxtaposition, through hybridizing, 
with forms that differ as to these details. 
And as only the relatively new structures 
Mendelize, so it is the newer member of any pair 
that assumes prepotency or dominance. Contrari- 
wise, the older member is recessive. 
Students of different examples of Mendelian 
heredity, as applied to animals and plants, have 
puzzled long to discover the underlying principle 
that determines which character shall be dominant 
and which recessive. But this simple principle 
appears to furnish the explanation. 
The new trait or characteristic is dominant over 
the older one precisely because it is new. 
By making it dominant, nature gives it the best 
possible chance. It will reproduce itself in all the 
immediate progeny of the individual that possesses 
it. Thus nature shows anew that she is progress- 
ing. She accepts the new characteristic and gives 
it more than an even chance. 
But at the same time she is not so foolish as to 
renounce the old character without full testing. 
She allows it to be subordinated for a generation, 
but in the next generation it reappears, isolated, to 
[223] 
