No. 499] A NEW MENDELIAN RATIO 451 



which hides the presence of a wholly distinct brown allel- 

 omorph, and a dark orange bean which carries invisibly 

 a light yellow allelomorph. This condition gives rise 

 in one series of crosses to the ratio, 12 : 3 : 1. Properly 

 the term "dominance" should be limited to the relation 

 between any positive characteristic and its own absence. 

 Whenever one positive character seems to dominate 

 another positive character, the latter is latent by hypo- 

 stasis in the individual possessing the former. 



(d) Latency due to fluctuation, a very frequent phe- 

 nomenon in which characteristics disappear under con- 

 ditions of poor nutrition, etc. Cultivation under favor- 

 able conditions makes such characteristics patent and this 

 fact may account in part for the general impression that 

 cultivation induces variation. Cases of "double adapta- 

 tion" are examples of this type of latency. 



Many discrepancies between theoretical and empirical 

 inheritance-ratios are due to latency, and care should be 

 taken to investigate the possible latencies which may be 

 present before declaring that a character is non-Men- 

 delian, because of a discrepant ratio. "Variable 

 potency," "contamination" or "impurity" of the 

 gametes, and "alternating dominance" which have been 

 proposed to account for the appearance of various novel- 

 ties, or of deviations from expected ratios, can have no 

 secure standing until the question of latency in the sense 

 of invisibility has been taken into account. 



A modification of expected ratios may rarely result 

 also from the failure of certain allelomorphs to make 

 vigorous zygotes when joined together in certain com- 

 binations. 



