GENETICS 135 



expressed the view that Mendelian ratios of inheritance have 

 reference to extrusion of impure strains, i.e., their separation 

 from pure strains, or, at any rate, a separation of strains 

 according to compatibilities. This would seem to be in 

 harmony with the fact that alternate (Mendelian) inheritance 

 is the rule in the case of artificial varieties (which lack the 

 bio-economic raison d'etre), whilst in the case of natural 

 varieties blended inheritance seems to predominate. 



Mendelian ratios, as is well known, refer to cases where 

 there occurs a pair of differentiated "characters" ("allelo- 

 morphs"), of which one (as is established by crossing) is 

 generally "dominant " to the other. What is the meaning of 

 this? Why are certain characteristics "dominant" and 

 others " recessive " ? 



In Mendelian parlance these terms do not possess a 

 qualitative connotation, but merely refer to the numerical 

 part (the ratios) of segregation on the part of Mendelian unit 

 " characters." They merely tell us in what ratios two 

 " allelomorphs " (two somewhat allied but yet opposite 

 "characters," which will not on crossing form a permanent 

 blend) split up again on subsequent in-breeding on the part of 

 the hybrids first formed. The " character " that comes out 

 numerically strongest from the splitting-up process (segrega- 

 tion) is denoted the " dominant," and the numerically weaker 

 the "recessive" character. 



It may turn out, however, that in reality the (less 

 conspicuous) numerically weaker " recessives " represent the 

 superior value so far as viability and genuine survival- 

 capacity are concerned. I hold that this is frequently the 

 case, and I hold, further, that we are with these phenomena 

 of mutual infertility primarily dealing with a biological 

 antagonism which prevents the blending of "characters" 

 under certain circumstances. This biological antagonism, I 

 believe, is founded on values, i.e., once biological values 

 became established, and mutually related, the preservation and 

 further enhancement of all that was (symbiogenetically 



