544 BIOLOGY FOR BEGINNERS 



However if these xy hybrids are crossed together, four possible 

 combinations may occur, thus: 



Joining x with x producing xx offspring. 

 " x " y " xy 



" y " x " yx " 



" y " y " yy " 



Of course the xy and yx individuals are of the same kind and 

 are also like their xy hybrid parents, but the xx and yy offspring 

 have those characteristics only and are pure bred: their off- 

 spring with either x or y respectively would produce pure x or 

 pure y characteristics, despite their mixed ancestry. 



Of course breeding is not so simple as this, because it cannot be 

 limited to one characteristic at a time, and some characteristics 

 do blend or average in the hybrids, but the law of inheritance, 

 known as Mendel's Law, has been proven true and is of great 

 value in plant and animal breeding. 



Though Mendel published his conclusions in 1865 and 1869 

 little notice was taken of them and he died in 1884 without recog- 

 nition. Later the same conclusions were independently reached 

 by three other scientists who would have been credited with an 

 important discovery, but in 1900 Mendel's papers were found and 

 his long delayed appreciation arrived, sixteen years after his 

 death. 



Briefly stated, his law comprises three facts: 



1. Pure bred mated with pure bred of same kind give offspring 

 pure bred. 



2. Pure bred mated with pure bred of different kind, hybrid 

 offspring. 



3. Hybrid mated with hybrid the offspring will be one-half 

 hybrid, one-quarter pure bred like grandfather, one -quarter pure 

 bred like grandmother. 



Law I. Pure bred with pure bred of same kind, x plus x makes 

 xx. 



Law II. Pure bred with pure bred of different kind, x plus y 

 makes xy. 



