No. 598] 



INHERITANCE OF EYE PATTERN 



581 



relative quantity of pigment these beans agree very well. 



Von Tschermak assumed a unifactorial difference be- 

 tween the large and small-eyed beans, with the spotted 

 pattern as the heterozygote. In the F. generation lie ob- 

 tained a 1:2:1 ratio. 



Returning now to our own data as given in Table I it is 

 clear that if the difference between the Improved and < >]<1- 

 Fashioned patterns is due to a single factor we should 

 expect in the segregating generations 2 piebald :1 I. Y. E. 

 : 1 0. F. Y. E. The numbers obtained in Table I will 

 hardly support this view. 146:53:70 can hardly be 

 looked upon as a 2:1:1 ratio. It is true that the devia- 

 tion is not so great, but that these observed numbers might 

 be chance fluctuations from a 2:1:1 ratio. On the theory 

 of probability the odds against the occurrence 1 of such a 

 deviation are about 5 to 1. 



Of the more common Mendelian ratios the observed 

 figures are much more closely fitted by 9:3:4. The ob- 

 served and expected numbers in this case are 



It is clear that there is a very reasonable agreement. 



Further evidence in support of the view that the segre- 

 gation is not 2 : 1 : 1 is found by examining Table I in more 

 detail. Thus the totals for each of the five pedigrees show 

 an excess of Old-Fashioned Yellow Eyes over the Im- 

 proved type. In three of these pedigrees the number of 

 plants is relativelv small. However, the cumulative evi- 

 dence makes it almost certain that the deviations are not 

 due to chance. 



It was stated above that only a portion of these plants 

 belonged to the F 2 generation. In a bifactorial character 

 considerable difference might be introduced by the com- 

 bination of data from different generations. From the 

 records it is known that all the plants in pedigree NToe. 

 153 X, 1318 and 1321, together with two rows, 104 and 292, 



