ASSOCIATION OF CHARACTERS. 



45 



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

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

 results are: 



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. /'\ is indistinguishable from the wild black agouti 

 (Mus musculus). 



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



F x Black agouti, BBr.PpDd 

 F-, (1) Black agouti, BrBPDA 



(2) Brown agouti, BrPDA 



(3) Pink-eved black agouti, BBrpDA 



(4) Dilute' black agouti, BrBPdA 



Ft (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 any association. The 

 experimental results follow: 



(1) 

 BAg. 



( Hbserved. 



in 



Expected on a basis of 



random segregation. 10.5 



The sum of classes (3) and (7) on a basis of random segregation is IS, 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 t here- 

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



Parents black Bp x brown P. 



F, Black BPp. F 2 (1) Black BP, 

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



