No. 499] A NEW MENDELIAN RATIO 443 



lieterozygotes. There are many other cases in which the 

 homozygote and heterozygote show marked and often un- 

 expected differences, the case of the Blue Andalusian fowl 

 being one of the best known of these, but the heterozygous 

 type of the Blue Andalusian fowl or other similar forms 

 is not a case of latency at all, since no hidden allelomorph 

 is brought to light as a result of heterozygosis, but only an 

 unexpected external manifestation. 



LATENCY DUE TO HYPOSTASIS 



A third type of latency has also appeared in these bean 

 hybrids, as best exemplified by a cross between the Prolific 

 Black Wax and the Ne Plus Ultra, and between Prolific 

 Black Wax and Long Yellow Six Weeks. In both of these 

 crosses, besides the black and orange or black and yellow 

 which were expected in the ratio 3 : 1, there have appeared 

 a considerable number of beans of a dark seal brown or 

 a dark greenish brown color. It is certain that these 

 dark brown beans owe their color to the latency of a dark 

 brown factor in the black bean. It has not been an in- 

 frequent occurrence to find black beans, not quite perfectly 

 matured or which have been more or less weathered, that 

 show this brown color apparently underlying the black. 

 In this case the appearance of the. novelty is due to the 

 presence of a characteristic which can not be seen (i. e., 

 which is latent), for the simple reason that the black pig- 

 ment possessed by the same bean is so intense as to 

 cover over and hide the brown pigment. The independ- 

 ence of the brown and black pigments allows them to be 

 separated into different individuals upon crossing the 

 black with some other color. 



Letting D represent this dark brown factor, the gametic 

 formula for the black bean is BD, and for the orange 

 brown and yellow beans, bd. This assumption leads to 

 another rather unfamiliar modification of the Mendelian 

 ratio, since the F 2 should consist of black, brown and 

 orange or yellow in the ratio 12:3:1. The actual ratios 

 are in essential accord with this expectation though there 



