48 



THE AMERICAN NATURALIST [Vol. XLIX 



Cross 1. Miniature $ by Eyeless <? 

 F„ Normal Long Normal Miniature Eyeless Long Eyeless Miniature 

 1142 1106 245 193 



Since the eyeless flies were females as well as males, the character 

 eyeless is shown not to be a sex-linked character ; for, if it were, 

 it would be inherited only by the grandsons of the eyeless male. 

 Since the eyeless flies are not nearly as viable as the wild stock, 

 the eyeless classes fall below the expectation. 



Cross 2. Black Vestigial 2 by Eyeless £ 

 F s . Normal Long Normal Vestigial Eyeless Long Eyeless Vestigial 

 1303 417 " 278 97 



The same count, when grouped according to the body color, was 



F 2 . Normal Gray Normal Black Eyeless Grey Eyeless Black 

 1289 431 293 82 



Cross 3. Spread $ by Eyeless <? 

 F 2 . Normal not Spread Normal Spread Eyeless not Spread Eyeless Spread 

 1349 373 300 76 



Allowing for the decreased viability of eyeless, both of the pre- 

 ceding crosses may be regarded as 9:3:3:1 ratios. Hence they 

 show that there is no linkage of eyeless with the characters whose 

 genes are in the second and third chromosomes. 



Eyeless females were then crossed to bent- winged males (Cross 

 4) . No bent eyeless flies were produced in the F 2 . As the count 

 was small, the F 2 bent flies were crossed to the F 2 eyeless, and 

 then the F 3 normal, which had the same germinal constitution as 

 the Fj, were inbred to give F 4 , which should give the same re- 

 sults as the F 2 . 



Cross 4. Bent <? by Eyeless $ 

 Normal not Bent Normal Bent Eyeless not Bent Eyeless Bent 

 F,. 596 193 195 



F<. 741 172 131 



Total 1337 "365 326 



Since an approximate 2:1:1:0 ratio, instead of a 9:3:3:1 

 ratio, was realized, the conclusion that eyeless and bent belong 



