SEX-LINKED INHERITANCE IN DROSOPHILA 



41 



and SR formed one pair and SW and LR another pair, because 

 the results, as far as they go at present, do not seem to give very 

 significant difference in relation to which way the original couple 

 was made, but here again a more critical examination may be 

 called for. In these latter figures we have omitted the 'small 

 classes' containing the cross-overs of YW and RG. Their omis- 

 sion does not affect materially the sum total although they 

 should be included, with certain corrections that can not now 

 be made. 



Finally, these same data give the linkage ratio of S and L to 

 B (black and normal) and b (yellow and brown). This is the 

 linkage between the factor in question for wings and that for 

 body color. We should expect that this ratio would closely 

 approximate to the last since the first calculation showed that 

 crossing-over between eye color and body color occurred only 

 once in 88.3 cases. 



In the paper of 1911, there were 1713 cross-overs to 3175 

 coupled cases, a ratio of 1:2.4 In the 1912 paper (Morgan- 

 Cattell) there were 2921 cross-overs to 5383 coupled cases, a 

 ratio of 1:1.8. In the present paper there are 527 cross-overs 

 to 1155 coupled cases, a ratio of 1:2.2. The sum of all these 

 cross-overs is 5161 and of the coupled cases, 9713, a ratio of 

 about 1:1.98. 



In these counts the 'small classes' are not included. The ratio 

 of the total count is 1: 1.88, which is almost identical with the 

 ratio 1: 1.94 for wings and eye color. 



The difference to be expected between the gametic ratios of 

 the last two cases (wings and eye color and wings and body color) 

 would, on the basis of the first case considered (eye color and 



