No. 572] MULTIPLE ALLELOMORPHS 453 



to take G (gray), as the common letter, the series would 

 be g h , g w , G, g r . On the whole the first series seems to 

 me somewhat preferable. 



The factor for cinnamon is entirely independent in 

 heredity of the preceding series of allelomorphs. This 

 factor may be represented by ci and its normal allelo- 

 morph by Ci. The formula for the wild gray would then 

 be Ci Ci, and that for cinnamon would be ci ci. Black 

 would be b b, and the double recessive cinnamon black 

 (or chocolate) would be bb ci ci. Chocolate is one of the 

 commonest types of domesticated mice and since I have 

 used it very extensively in my matings, its relation to the 

 other types may be further stated. It is known that if 

 chocolate is bred to wild gray, and if the gray offspring 

 that are obtained are then inbred, they give, in F 2 , the 

 following classes: 9 wild gray, 3 cinnamon, 3 black, 1 

 chocolate. 



It is clear that chocolate is the double recessive type. 

 Of the two genes, that differentiate chocolate from wild 

 gray, chocolate has one in common with cinnamon and 

 the other with black. In other words, chocolate is cin- 

 namon black, and technically should receive this name. 



The Experimental Evidence 

 Is There a Separate Factor for White-belly? 

 The first series of experiments was made in order to 

 determine whether the peculiarity of white-belly, shown 

 by the wild race of white-bellied grays, is due to a factor 

 that may be separated from the gray white-bellied mice, 

 or whether it is completely linked to gray (or allelo- 

 morphic to it). As wild gray house mice offer some 

 drawbacks in breeding work, I used cinnamon blacks 

 (chocolates). Gray white-bellied mice were bred to 



