162 



ROSCOE R. HYDE 



eludes 15 sterile ones that occurred in one family and was probably 

 due to a chance combination. 



A glance at the sunmaary given in table 18 will show that the 

 sterility as it affected the female is practically the same whether 

 inherited through the male or female. I think that the 574 cases 

 of sterility recorded in this summary of 4042 pairs tested gives 

 a faithful picture of the actual facts in the case as seen on a minor 

 scale in each of the experiments and in the history of the inbred 

 stock. The evidence is conclusive that sterility as it affects the 

 female may be present in different intensities in the different 

 families and that female sterility is transmitted by the fertile 

 brothers and sisters of the affected females to the granddaughters 

 but not to the grandsons. This character behaves like a recessive 

 Mendelian character in that it disappears in Fi and reappears 

 in F2. 



CROSSES INVOLVING A SEX-LINKED FACTOR 



In this experiment, which unfortunately was not carried out on 

 a very extensive scale, the white-eyed stock was used. This 

 stock arose from a mutant of the inbred stock. Females were 



TABLE 19 



Behavior of sterility in F2 generation of No. 12 h; control of the supposed sterile 



male strain 



paired with the fertile males from No. 12 b, table 15. The recip- 

 rocal cross was not made. Family No. 12 b arose as a cross be- 

 tween the Woods Hole and truncate stocks. One-half of the males 

 from this particular combination were sterile. It was my hope 

 that this would develop into a male-producing strain; but the 

 sterility vanished suddenly. 



A number of flies from No. 12b were allowed to breed in order 

 to obtain the next generation. From this eighteen pairs were 



