INBREEDING EXPERIMENTS 139 



recessives or combinations of recessives which seldom are 

 seen under ordinary circumstances, because they are hid- 

 den by their dominant allelomorphs. These recessives 

 are the "corrupt fruit" which give the bad name to 

 inbreeding, for they are often very often undesir- 

 able characteristics. 



The homozygous inbred strains after stability has 

 been reached are quite comparable to naturally self -fer- 

 tilizing species provided they have passed as rigorous 

 selection as the latter have had to undergo by reason of 

 natural competition. And Darwin, as well as others, 

 found that artificial self-pollination causes no reduction in 

 such genera as Nicotiana, Pisum and Phaseolus where 

 self-fertilization is the general rule. 



Are then the immediate results of inbreeding some- 

 times injurious ? In naturally cross-fertilized organisms 

 they most emphatically are nay, more, even disastrous 

 when we recall the reduction to over half or one-third in 

 production in grain and a corresponding decrease in size 

 of plant and rate of growth in maize. But maize is prob- 

 ably an extreme case. With other organisms the results 

 are not so bad, and in some cases, especially when selec- 

 tion has been made, no evil effects are apparent. In fact, 

 there may be an actual improvement. But the truth is, we 

 did not set out to answer that question. It had already 

 received a correct answer. What we undertook to inquire 

 was whether inbreeding is injurious merely by reason of 

 the consanguinity. We answer, No! The only injury 

 proceeding from inbreeding comes from the inheritance 

 received. The constitution of the individuals resulting 

 from a process of inbreeding depends upon the chance 

 allotment of characters preexisting in the stock before in- 



