20 THE TREND OF THE RACE 
But while it is futile to argue over this question in the abstract, 
it may become a very practical problem if it is narrowed down to 
particular characteristics of a given breed under a specified range 
of conditions. We may illustrate this by considering the effects 
of heredity and environment in raising corn. Everyone knows 
that corn grown on rich fertile soil produces a much greater yield 
than corn grown on poor soil. Everyone knows also that, in a 
given soil, the yield depends largely on the variety of corn that 
is used for seed. There are varieties which in fair soil will yield 
over 100 bushels per acre; others under the same condition which 
produce only miserable nubbins yielding less than five bushels 
per acre; and some, to take an extreme case, which would produce 
no seed at all. We get a variation due to heredity between say 
150 bushels per acre and o. If we take extreme environmental 
conditions we get a variation in a given strain between the 
maximum yield (say 200 bushels per acre) and 0, for it is obvious 
that if we planted our corn in an environment sufficiently unfa- 
vorable it would not grow at all. There is no use arguing which is 
the more important in raising corn, good seed or good soil and 
climate. If, however, we ask whether it is more important to 
make the best choice of seed between variety A and variety B 
or to make the best choice of one or the other of two pieces of 
ground, our question is a sensible one and capable of fairly easy 
solution. We may test our varieties under given conditions and 
compare our yield. We could then obtain a measure of their 
hereditary difference under a given constant environment, and 
express it in a ratio such as A:B: :3:4. Similarly we might test 
out the yield of each variety in our two fields and we might find 
that one field C is so much better than the other that both vari- 
eties produce twice as much in the first as they did in the second. 
If they continue to do so over a period of years varying with 
temperature, rainfall, etc., we might say that for these particular 
varieties of corn the relative influence of fields C and D is as 2:1. 
Therefore we might conclude that the choice of a proper field is 
more important than the choice of the best seed. If, however, it 
was a question of the seed of variety B and the seed of variety C 
