SEX-RATIO IN DROSOPHILA AMPELOPHILA. 



357 



SELECTION EXPERIMENT II. (Saratoga Stock.) 



In the first experiment, a much larger number of flies were 

 examined than were examined by Moenkhaus. But since oppo- 

 site results were obtained, a criticism might be offered that the 

 writer, by chance, selected a stock which was not affected by 

 selection. So the second experiment was made upon a new and 

 unrelated stock. This stock was collected at Saratoga, Indiana. 

 Fifty matings were made from among the offspring of a single 

 pair. The extremes of these fifty were used as parents of the 

 high and low strains. The counts of these fifty pairs are given 

 in Table V. There were 21,019 fli es examined before selection 

 began and the stock showed a ratio of i : 1.0512, or 10, 247 males 

 to 10,772 females. 



TABLE V. 



Showing the Origin of the "High" and "Low" Strains of the Saratoga Stock. 



Grand Total 10,247 cf's to 10,772 9 's 



The results of the selection in this experiment are given in 

 Tables VI. and VII. In this stock there were greater individual 

 variations from the normal sex-ratios in each direction but they 

 did not breed true. The totals show the high strain to have a 

 higher relative number of females than the low strain. They 

 are as follows: for the high strain, 7,377 males to 8,365 females, 

 or a ratio of i: 1.134; for the low strain, 10,923 males to 11,246 

 females or a ratio of 1 : 1.029. Considering these totals, it might 

 seem that something had been accomplished by selection but when 

 the totals are considered generation by generation the results do 

 not seem so conclusive. If selection has been the factor which 



1 From this mating originated the "low" strain. 



2 From this mating originated the "high" strain. 



