ASSOCIATION OF CHARACTERS. 



45 



On an hypothesis of association we should expect types (1) and (8) to be 

 in excess of the numbers called for by random segregation. The experimental 

 results are: 



Observed . 



Expected on a basis of 

 random segregation. 



The sum of classes (1) and (8) on a basis of random segregation is 24. The 

 observed number is less by 2, showing no signs of association of the characters 

 A, B, and D. 



II. Cross 10. Pink-Eyed Black Agouti Crossed with Dilute Brown Agouti. 



The pink-eyed black agouti parent possesses B (black), D (density), and 

 lacks P (fullness of black and brown pigmentation, dark eye). The dilute 

 brown agouti parent is of the formula dP, lacking the factor for density but 

 possessing that for dark eye. Fi is indistinguishable from the wild black agouti 



{Mus musculus). 



Pink-eyed black agouti BrpBD x dilute-brown agouti BrPd. 



Fi Black agouti, BBr^PpOd 

 Fi {I) Black agouti, BrBPDA 



(2) Brown agouti, BrPDA 



(3) Pink-eyed black agouti, BBrpDA 



(4) Dilute black agouti, BrBPdA 



Fi (5) Pink-eyed brown agouti, BrpDA 



(6) Pink-eyed dilute-black agouti, BrBpdA 



(7) Dilute-brown agouti, BrPdA 



(8) Pink-eyed dilute-brown agouti, BrpdA 



Classes (3) and (7) should be in excess if there is anj^ association. The 

 experimental results follow: 



The sum of classes (3) and (7) on a basis of random segregation is 18, the 

 observed number in the classes is 17; again no evidence of association. 



III. Cross 66. Pink-eyed Black Crossed with Brown. 



The pink-eyed black parent possesses the factor B but lacks P and is there- 

 fore Bp; the brown parent lacks B but possesses P. 



Parents black Bp x brown P. 



Fi Black BPp. Fi (1) Black BP, 

 (2) Pink-eyed black Bp, (3) Brown P, (4) Pink-eyed brown p. 



