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THE AMERICAN NATURALIST 



[Vol. XLV 



on the assumption that the ratio between these various 

 types is 9:3:1:2:1. The reason for assuming this ratio 

 will be given later. 



In the 5 families in which the large and small eyes 

 were not separated, and in which the corresponding ex- 

 pectation is the ratio 9:3:3:1, the results were : 



Number of individuals in 5 families 



taken together 100 30 34 16 



Highest expectation 101 34 34 11 



In both these groups the actual numbers are in close 

 accord with the theoretical numbers called for by the 

 assumed ratios. 



Cross: Holstein X Solid Color 

 Six crosses were made between various types of the 

 Holstein pattern and solid-colored races. The F x plants 

 all produced seeds that were fully pigmented. In F 2 , 

 taking the six families together, there were 75 individ- 

 uals bearing fully pigmented seeds and 25 with Hol- 

 stein seeds, or exactly the ratio 3 : 1. 



Cross: Watson Eye X Solid Color 

 Two of the 4 Watson parents used in these matings 

 proved to be heterozygous. The other two, taken to- 

 gether, gave 56 solid color and 13 Watson individuals in 

 F 2 . F, in all these cases was fully pigmented. The 3 : 1 

 ratio for the number of individuals in F 2 is 52 : 17, which 

 agrees fairly well with the experimental results. 



Cross: Small Eye X Holstein 

 Only one cross of this character was made. It gave 

 F t with large eye; in F 2 there were 3 Holstein, 4 Large 

 Eye and 1 Small Eye individuals, which is near the ratio 

 1:2:1 for these three types of color pattern. 



Mendelian Factors involved 

 We may bring together here the various ratios found 

 in the above classes of matings. For convenience let us 

 designate the various color patterns as follows: 



