LUTHER BURBANK 
itance as just noted in the following formula: 
Parent “D” being mated with parent “d,” the 
offspring, whether few or many, bear in each in- 
dividual case in their germ plasm the factors “D” 
and “d” in combination. But if two of these off- 
spring are interbred, there will be a splitting up 
of the factors and re-combination in such wise that 
in any average group of four of their progeny the 
result will be this: One member that is pure dom- 
inant (DD), two members that are mixed dom- 
inants (Dd), and one member that is pure re- 
cessive (dd). The DD individual is “homozygous” 
for dominant factors and will breed true to black- 
ness. The dd individual is homozygous for the 
recessive factors and will breed true to whiteness. 
The two Dd individuals are heterozygous for the 
color factors, and whereas they are individually 
black their offspring will repeat the formala 1 DD 
+ 2 Dd + 1 dd; they will reproduce, in other 
words, the conditions of the second filial genera- 
tion itself as just analyzed. 
Let me re-state all this, using only the letters, 
to show the convenience of the formula and at the 
same time to fix it in memory: D mated with d 
in the first generation gives us Dd + Dd + Dd, 
etc., in the second generation. Dd mated with Dd 
gives us in the third generation 1DD + 2Dd + 
1dd. 
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