No. 588] INHERITANCE OF SPOTTING IN MICE 737 



If now animals of Type A are bred inter se we should 

 expect 



S|WxS w 



1 SS = self 



2 SW =like Type "A" 



1 WW= (not formed because homozygous) 



The one WW individual could not be formed since by 

 experiment it has been shown that W can exist in only 

 one of the two gametes forming a zygote. When W meets 

 S, an animal like Class A is produced, when it meets sp 

 a black-eyed white results. 



The expectation therefore is that, if a system of triple 

 allelomorphs is operative here, we should have no black- 

 eyed whites formed from mating together class "A" 

 animals. 



The result of this mating quickly settles the above hy- 

 pothesis for 15 "self" colored, 31 spotted (like or nearly 

 like Type "A"), and 11 black-eyed whites have been 

 obtained. 



It is clear, therefore, that "black-eyed white" depends 

 upon a factor which is at least partly independent of that 

 producing "piebald" spotting. Let us suppose that this 

 is the case and that "black-eyed whites" always carry 

 piebald in all of their gametes and an epistatic inhibiting 

 or restrictive factor producing increased whiteness in one 

 half their gametes. If W equals restrictor and w its ab- 

 sence and sp equals the factor for piebald spotting, all 

 black-eyed whites will be Wwspsp, in zygotic formula and 

 will form two sorts of gametes, Wsp and wsp. 



This will account for the results in mating black-eyed 

 whites inter se due to the failure of the WWspsp zygote 

 to continue its development because of the double dose 

 of W. 



If now black-eyed whites Wwspsp are crossed with self s 

 wwSS, two classes of F t zygotes will result, WwSsp and 

 wwSsp. The former will produce a new zygotic combi- 



