The Making of Species 
we can see how it is that we get unilateral in- 
heritance in the case of across. Where, however, 
the units from the two parents intermingle, 
although only one set is active in development, 
the result will be blended inheritance. Thus, we 
may regard the fertilised egg as made up of two 
sets of characters—a dominant set, which is active 
in the production of the resulting organism, and 
a recessive set, which appears to take little or no 
part in the production of the organism. 
This is quite in accordance with Mendelian 
conceptions. 
Let X be an organism having the unit char- 
acters ABCDEFG, and let Y be another 
organism having the unit characters abcde /fg. 
Now suppose that these behave as opposed 
Mendelian units, and that the unit characters 
in italics are dominant ones. Then the resulting 
individual will resemble each parent in certain 
unit characters. It may be represented by the 
formula aBcdEfG, but it will contain the 
characters AbC DeFg in a recessive form, 
so that its complete formula may be written 
aBcdEfG 
AbCDeFg 
When these hybrids are paired together it will 
. ABCDEFG 
be Zosszble to get such forms as ABCDEFG 
and cba a which exactly resemble the 
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