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THE AMERICAN NATURALIST [Vol. XLVII 



cY= cinnamon-yellow (giving also cinnamon offspring). 



bcy = black-cinnamon-yellow (giving also black-cin- 

 namon offspring). 



To express the modification which this series under- 

 goes if the d mutation is added to it, we need only pre- 

 fix the symbol d to each of the formulae given and omit 

 the term ivild as no longer applicable. The series then 

 becomes 



d = dilute gray. 



db~ dilute black. 



dc = dilute cinnamon. 



etc. 



Similarly an added p factor gives us the series 



p = pink-eyed gray. 



pb = pink-eyed black. 



pc = pink-eyed cinnamon. 



etc. 



Also an added s gives us the series 



s = spotted gray. 



sb = spotted black. 



sc = spotted cinnamon. 



etc. 



Adding both d and p gives us the series 

 dp = dilute pink-eyed gray. 

 dpb = dilute pink-eyed black. 

 dpc = dilute pink-eyed cinnamon. 

 etc. 



Adding d and 5 gives us the series 

 ds = dilute spotted gray. 

 dsb = dilute spotted black. 

 dsc = dilute spotted cinnamon. 

 etc. 



Adding p and s gives us the series 

 ps = pink-eyed spotted gray. 

 psb = pink- eyed spotted black. 

 psc = pink-eyed spotted cinnamon. 

 etc. 



Adding simultaneously d, p and s, gives us the series 



