No. 598] 



INHERITANCE OF EYE PATTERN 



583 



the piebald pattern are always heterozygous. These re- 

 sults could be very simply interpreted on a single-factor 

 hypothesis, but the numerical results do not fit the 2 : 1 : 1 

 ratio demanded by that hypothesis. 



While the data at hand are not as extensive as one might 

 desire in order to build a complete theory, yet there is 

 much to be said in favor of the following provisional 

 hypothesis. Let 7 be a factor which in its homozygous 

 condition II produces the Improved Yellow Eye pattern. 

 Then Ii will be the zygotic constitution of the piebald 

 plants and ii that of the Old-Fashioned Yellow Eye pat- 

 tern. Assume further a lethal factor L independent in 

 its segregation and of such a nature that LL in the pres- 

 ence of II produces a non-viable zygote. The complete 

 F 2 segregation would then be as follows : 



1 II LL Non-viable 8 



2 I I L I 

 1 I I I I 



I. Y. E. 



L I 0. F. V. E. 



Such a segregation would result in the ratio 

 3 I. Y. E. : 4 0. F. Y. E. Testing this ratio i 

 total observed numbers in Table I we get 



It is seen that there is a very close agreement between 

 the observed and expected numbers; much closer, in fact, 

 than in the case of the 9 : 3 : 4 ratio previously used. 



