GENETIC SYSTEM: RELATION TO CHARACTERISTICS 1 27 



The spot Is not inherited through the females of the spotted 

 race. 



Next mate the female of the non-spotted race, xx, with 

 a male from the spotted race, XY, as follows: 



Females Males 



Parents xx XY 



Spotted 



Fi xX xY 



Spotted 



This yields In Fi females Xx and males xY. These males 

 carry the Y from the spotted race, and they are spotted. 

 Thus far the spot goes with the Y from the spotted race. 



This Y may be traced further, for example, by breeding 

 together the non-spotted females xx with the Fi males xY, 

 from the preceding cross, thus: 



Females Males 



Parents xx xY 



Spotted 



F2 XX xY 



Spotted 



This gives in the F2 females xx and males xY. These 

 males are again spotted; they carry the Y from the spotted 

 race. Wherever this Y from the spotted race Is found, the 

 black spot appears; wherever the Y Is from the non-spotted 

 race It does not appear. It appears clear therefore that 

 whether the black spot appears In the male depends upon 

 the type of Y-chromosome that It carries. There are two 

 types of Y-chromosome In the species, one producing the 

 black spot, the other not producing it. 



It has been shown by Winge ^ that there are many other 

 color markings in this fish that depend for their occurrence 



