No.i99] A NEW MENDELIAN RATIO 445 



applies the terms "epistatic" and "hypostatic" to the 

 relative capacity of one unit to hide or to be hidden by 

 another, owing to what I call latency due to hypostasis. 

 As a simple illustration, a cross between a pea with 

 yellow cotyledons, Y, and one having green cotyledons, 

 G, shows Y dominant over its absence, y, and not over G. 

 This would become immediately obvious if we could cross 

 the yellow pea with still another type, say with one hav- 

 ing colorless cotyledons. The correct gametic formula 

 for the yellow pea is not Y but YG, in which the green is 

 latent owing to the fact that Y is epistatic to G. The 

 gametic formula of the green pea is yG. 



That this is a correct interpretation of the apparent 

 dominancy of one positive allelomorph over another is 

 shown by some of my bean crosses. Thus Ne Plus Ultra 

 (dark orange yellow) crossed with Long Yellow Six 

 Weeks (light yellow) produced in 14 F 2 families, 382 

 orange yellow: 130 light yellow, an apparent dominance 

 of orange over light yellow. That the light yellow is 

 latent in Ne Plus Ultra and is not the recessive condition 

 of the orange yellow allelomorph is proved by the fact 

 that in the F 2 families of the cross between White Flageo- 

 let and Ne Plus Ultra, light yellow beans appear. Let- 

 ting represent the orange allelomorph and Y the yellow 

 one, the gametic formula of Ne Plus Ultra with respect 

 to these two factors is OF, that of the yellow bean is oY, 

 and that of the white bean likewise oY. 



The ratio, 12 : 3 : 1, presented by the crosses of Prolific 

 Black Wax with Ne Plus Ultra and Long Yellow Six 

 Weeks, has been reported for but one other case so far 

 as I know, though it ought not to prove very uncommon. 

 It will appear in the F 2 of any cross which produces an 

 F! of the form AECab with B hypostatic to A, C hypos- 

 tatic to both A and B, and neither A, B, nor C latent from 

 any other cause. In these beans the crosses are of the 

 type ABC X dbC = ABCdb, i. e., both B and C are latent 

 in the one parent and no latent characters are demon- 

 strated in the other. The same ratio will result from a 



