CHAPTER IX 



REPULSION AND COUPLING OF FACTORS 



ALTHOUGH different factors may act together to pro- 

 duce specific results in the zygote through their inter- 

 action, yet in all the cases we have hitherto considered 

 the heredity of each of the different factors is entirely 

 independent. The interaction of the factors affects the 

 characters of the zygote, but makes no difference to the 

 distribution of the separate factors, which is always in 

 strict accordance with the ordinary Mendelian scheme. 

 Each factor in this respect behaves as though the other 

 were not present. 



A few cases have been worked out in which the dis- 

 tribution of the different factors to the gametes is af- 

 fected by their simultaneous presence in -.the zygote. 

 And the influence which they are able to exert upon one 

 another in such cases is of two kinds. They may repel 

 one another, refusing, as it were, to enter into the same 

 zygote, or they may attract one another, and, becoming 

 linked together, pass into the same gamete, as it were 

 by preference. For the moment we may consider these 



two sets of phenomena apart. 



88 



