222 



SAHRA COLBY TICK. 



F 2 generation (Table I.) with class ratios I : I : I : i is consistent 

 with this expectation. In the following analyses Br r is the factor 

 for the dominant barring and br' is its recessive normal allelo- 

 morph. 



TABLE I. 



Pi Normal 9 , X br' X br' . 

 Barred d" , X Br' - 



Gametes of Fi barred 9 , X br' X Br'. 

 Gametes of Fi normal cf, X br' 



1 Females. 



F Males. 



The barred females of the above F 2 generation were heterozy- 

 gous in barring, and, when mated to their barred brothers, gave 

 an equal number of barred and normal sons (Table II.). 



TABLE II. 



Gametes of F 2 barred 9 , X Br' X br' . 



Gametes of ~Fz barred d", X Br' . 

 Fa Females. Fa Males. 



'X Br' fX br' [X Br' fX br' 



^X Br' \X Br' \ - [ - 



Barred 9. barred c? 1 - Normal c 



236 106 123 



The original barred male was crossed to his daughters (Fi 9 9 , 

 Table I.) and as expected the results (Table III.) were similar 

 to those of Table II. 



