No. 635] WHITE SPOTTING IN MICE 469 



graded 0/1, or 0/3, etc. The results can be easily trans- 

 posed into Little's scale by simple subtraction of any 

 grade from 100, since his percentage expressed the 

 amount of color. For convenience, only the dorsal 

 grades have been used in the tabulation, since the results 



60 r''"\ 



obtained by using the ventral grades are in all respects 

 similar. 



Of 323 mice raised from crosses of black-eyed whites 

 by piebalds, approximately half (160) were 50 per cent, 

 white or more; the other half (163) were spotted mice 

 with less than 50 per cent, white ; expected 161.5 of each. 

 No mice were obtained early in the experiment which 

 were from 55 to 51 per cent, white and it was thought 

 that this zero class indicated a clear discontinuity be- 

 tween the types. With larger numbers, however, three 

 mice of this sort were born. That the division between 

 black-eyed white and piebald at 51 per cent, is, however, 



