204 HEREDITY AND SEX 



per bushel is much increased, as shown in the next 

 figure (Fig. 98). 



When the vigorous FI corn is self -fertilized, it produces 

 a very mixed progeny, more variable than itself. Some 

 of the F 2 offspring are like the original grandparental 

 strains, some like the corn of first generation, and 

 others are intermediate (Fig. 99). 



FIG. 99. No. 9 and No. 12, two inbred strains of Learning Dent corn 

 compared with F l and F 2 (to right). (After East.) 



It will not be possible for us to go into an analysis 

 of this case, but Shull and East have shown that the 

 results are in full harmony with Mendelian principles 

 of segregation. The vigor of the FI corn is explained 

 on the basis that it is a hybrid product. To the extent 

 to which the two parent strains differ from each other, 

 so much the greater will be the vigor of the offspring. 



This seems an extraordinary conclusion, yet when 

 tested it bears the analysis extremely well. 



Shull and apparently East also incline to adopt the 



