THE APPLICATION TO MAN 243 



mask recessive characters and render them inefTec- 

 tive. 



Cousin-marriages, although producing a high per- 

 centage of defects, do not necessarily reproduce un- 

 desirable traits. They simply bring out latent or 

 recessive characters for the reason that under these 

 conditions defect meets defect instead of the opposite 

 normal condition which would dominate the defect 

 and cause it not to appear. 



Since a recessive trait is properly regarded as the 

 absence of a positive dominant character, it more 

 frequently stands for an undesirable feature than 

 otherwise. Thus it comes about that inbreeding, 

 by combining negative features, may "produce" a 

 defective strain. 



Outcrossing always increases heterozygous com- 

 binations in the germplasm and covers up undesirable 

 recessive traits through the introduction of addi- 

 tional dominant traits. Inbreeding, on the contrary, 

 tends to simplify the germplasm, that is, to make it 

 more homozygous, and so to bring recessive defects 

 to the surface. 



