SEX-LINKED INHERITANCE IN DROSOPHILA 



99 



The expectation is as follows: 



There were 5 SWN 9's, all from one bottle; which can not be 

 explained by crossing-over. They are either mutations or due 

 to error. 



Concerning wing-characters, SRB cf = 146, while LRB d' = 

 78; SRN d = 282, while LRN d = 312. On the other hand, 

 LWN d = 616, while SWN d = 244; LWB d = 184, while SWB 

 cf = 89. The sum of the 'straight' males is 1228, while that 

 of the cross-overs is 721. The 'straights' are less than twice the 

 cross-overs, due largely to the SRN's being actually less than 

 the LRN's. 



CONCLUSION 



The principal object of the preceding experiments was to study 

 the phenomenon of linkage on a relatively large scale. The 

 results show that whatever sex-linked factors enter into combina- 

 tion, those factors come out together in the grandchildren. More- 

 over, it makes no difference from the point of view of linkage whether 

 a 'present' factor is linked to another 'present' factor or to an 

 'absence,' or even whether two absences are linked together in one 

 of the parents. The phenomenon is the same, as both Bateson 

 and I have pointed out.^ The results are the more striking when 



^ This statement is too sweeping in so far as based on the evidence given in 

 the text. 



