RULES AND RATIOS OF INHERITANCE 



221 



characters, and therefore manifest neither of the recessive 

 characters (figure 47). 



This is an extremely important relation. It holds both 

 when the two recessive characters affect the same structure 

 or function, and when they do not. Thus, if flies with eosin 

 eyes are mated with those having vermilion eyes, the off- 



FiGURE 47. Diagram to illustrate inheritance in cases in which the 

 parents are recessive for genes that are not alleles, but belong to 

 different pairs. The offspring (Fi) do not manifest either recessive 

 character. 



spring all have normal red eyes. Or again, if vermilion eyes 

 are mated with purple eyes, the offspring have normal red 

 eyes. In such a case the recessive characters of the two par- 

 ents may be indistinguishable, but if they are not alleles, the 

 offspring have the dominant character. Thus, as set forth on 

 page 187, the eye colors garnet (gene at I, 44.4) and purple 

 (at II, 54.5) are alike, but if garnet and purple parents are 

 mated, the offspring have normal red eyes. Similarly, if rudi- 

 mentary wings are mated with vestigial wings, the offspring 

 have normal wings. 



If the recessive characters of the two parents are quite di- 



