No. 588] INHERIT ANCE OF SPOTTING IN MICE 



735 



appear to have slightly more irregular and less clearly 

 defined outlines than do those of the ordinary piebald 

 mice and many of the spots are distinctly smaller in size 

 (compare Figs. 3, 4 and 5). Just how much of this ap- 



pearance is due to true genetic difference between the two 

 types of spotting is of course problematical and must 

 remain so until a larger mass of data is available. 



Concerning class "B" (Fig. 6) little need be said save 

 that they appear in every way identical with heterozy- 

 gotes ordinarily obtained in a cross between * 1 self" and 

 1 1 piebald ' ' animals. They vary from entirely solid colored 

 animals to those having approximately 20 per cent, of the 

 ventral surface white. They may be tabulated as follows : 



2. Type "A" Animals Crossed Inter Se 

 Type "A" animals obtained in F x are distinctly "spot- 

 ted." They have a clearly discernible amount of white 



