FERTILITY AND iSTERILITY IN DROSOPHILA 



201 





Diagram F Summary of tables 18, 19 and 20, showing the effect on fertil- 

 ity of back-crossing the hybrids into the recessive low-producing truncates. 



T/ fiV 



&- Calculated 



Diagram G Expresses the essential relations of the behavior of fertility in 

 heredity a^ based on the foregoing experiments. The numbers in the circle 

 express the calculated percentage. The other numbers express the observed 

 percentage of fertility. 



In diagram G a composite picture is given of all the experiments 

 that bear on fertility in these crosses where an accurate method of 

 measurement has been employed. 



If 24, 75, 55, and 80 express the actual fertilizing powers of the 

 gametes of the different combinations then the percentages as 

 given in the hybrid back crosses can be explained on the following 

 assumption. 



