164 GENETICS 



albino guinea-pig having no pigment, some of the 

 offspring "reverted" to the ancestral agouti, or 

 "pattern" type, thus proving that the pattern must 

 be carried in this case by the white or albino guinea- 

 pig as a factor independent of the color which is 

 necessary for its expression. 



c. Cuenofs Spotted Mice 



Another instance of the interaction of supple- 

 mentary factors is seen in the spotting of piebald 

 mice. Cuenot discovered that such spotting is due 

 to the absence of a uniformity factor which if present 

 causes color to be uniformly distributed over the 

 entire coat. 



Both of these independent factors, spotting and 

 uniformity, are real and not imaginary, since they may 

 be separately transmitted through albino animals in 

 the same way as the pattern factor mentioned above, 

 notwithstanding that in albinos both are hidden 

 through the absence of pigment, upon the presence of 

 which their visibility depends. 



Whenever piebald or spotted animals appear in a 

 progeny derived originally from self-colored stock, 

 it is evidently due to the absence of such a "uni- 

 formity" factor as has just been described. 



Gal ton's theory of "particulate inheritance" 

 (page 121) is now satisfactorily explained as true al- 

 ternative inheritance in which the mosaic appearance 

 is caused by a Mendelian determiner, in this instance 

 a spotting factor or, in other words, the absence of 

 a factor for uniformity. 



