No. 588] INHERITANCE OF SPOTTING IN MICE 



731 



the common range of variation within the black-eyed 

 white type and Figs. 3 and 4 the same for the ' 1 piebald" 

 type. 



2. Black-eyed White X Piebald 

 This mating brought out two interesting facts. First, 

 all black-eyed whites behaved in essentially the same way, 

 approximately an equal number of black-eyed white and 

 piebald young being produced. Second, the same dis- 

 tinctness between the two types held good, as will be seen 

 from the chart given below (solid line). 



3. Piebald X Piebald 

 Piebald animals from black-eyed white parents and 

 from the cross of piebald X black-eyed white were mated 

 inter se. They produced only piebald young, 93 in 

 number. 



The distribution of these young according to the degree 

 of dorsal pigmentation they possessed is shown by Chart 

 2 (dotted line). 



It will be noticed that there is no approach to the black- 

 eyed white condition (0-5 per cent.). There are also in- 

 dications of two main modal points, one at 41-50 per cent, 

 and one at 80-90 per cent. A complete curve formed from 

 the sum of all piebald animals included in Table I, is 

 given in Chart 2 (broken line). 



This further emphasizes the bi-modal nature of the 

 curve in the case of piebald mice and makes it seem likely 

 that there are two genetically distinct grades of this 

 variety. It is hoped that opportunity will arise in the 

 future to investigate this point more accurately. 



4. Discussion 



From the three types of matings given above the fol- 

 lowing facts may be deduced: (1) The inheritance of the 

 characters in question is alternative, not blending in 

 nature; (2) black-eyed white is epistatic to ordinary pie- 

 bald spotting. 



