No. 548] SHORTER ARTICLES AND DISCUSSION 491 



respect to all the 10 characters? "What proportion will be 

 homozygotic with respect to any given one character? To any 



Taking first the case for the entire 10 characters, by formula 

 (1) 



x - (^i ~ )° = ) 10 = log - 9 - 9830020 - - 961617 - 



Thus, out of 100 individuals, somewhat above 96 would be 

 pure homozygotes; or by formula (4), but one in 26 would be 

 heterozygotic in any respect (v = . 038383). 



With respect to any one character formula (1) gives 



so that all but 4 in 1,000 would be homozygotes with respect to 

 that character. 



In the same way we find that with respect to any two char- 

 acters the proportion of homozygotes would be .9922; with re- 

 spect to three, .9883; with respect to four, .9845, etc. 



(2) Suppose that there are 20 pairs of characters, and that 

 there have been 20 self-fertilizations. Then 



That is, of a million individuals, all but two would be pure 

 homozygotes. 



It thus appears that if the number of separably heritable 

 characters is not very great (say not above 100), while the or- 

 ganism has been self-fertilized for many generations, it is to be 

 expected that practically all of the organisms will be homozygotic 

 with respect to all their characters, they will be "pure homo- 

 zygotes." 



H. S. Jennings 



YELLOW AND AGOUTI FACTORS IN MICE NOT 

 " ASSOCIATED" 



In a recent number of the American Naturalist Mr. Sturte- 

 vant 1 suggests that these two color factors may bear to each other 

 the relation which Bateson has called "repulsion" or "spurious 

 allelomorphism" and which Morgan now includes with "coup- 

 ting" in a more general category, "association." The supposed 



