No. 499] A NEW MENDELIAN RATIO 439 



spect to M, it would be impossible to have any of them 

 breed true, i. e., the mottled bean is in the same category 

 in this respect as the famous Blue Andalusian fowl. This 

 conclusion is supported by 48 families of the third and 

 fourth generations reported by Tschermak and by over 

 sixty families of the F 3 from my own mottled hybrids 

 which have been already examined. Not one instance 

 has been found in which the offspring of a mottled hybrid 

 were even approximately all mottled. 



The existence of pure-bred mottled races raises the in- 

 teresting question as to what relation exists between these 

 mottled hybrids which are heterozygous and can not 

 breed true and the true-breeding mottled varieties. 

 Tschermak 3 shows that in crosses between constant 

 mottled races and self-colored races, the mottled pattern 

 acts as a typical Mendelian dominant, the hybrids split- 

 ting in F 2 and subsequent generations in the ratio, 3 

 mottled : 1 self-colored. 



LATENCY DUE TO SEPARATION 



With respect to the question of latency since the 

 purple mottling may not be a latent character of the 

 White Flageolet, the type of latency discussed in my 

 previous papers was only certainly exemplified by the 

 pigment-changer, B, carried by the white bean. This 

 type of latency is discovered by the production of a 

 novelty when two allelomorphs are brought together, one 

 or each of which, when acting alone, produces no visible 

 character. Thus the black or purple color of these 

 hybrids is due to the combination of the yellow or brown 

 pigment of the pigmented parent and the colorless pig- 

 ment-changer borne by the white parent. It may be called 

 latency due to separation since patency is brought about 

 by recombination. In my first paper on latency, 4 issue 



3 Loc. cit. 



4 Shull, G. H. Some Latent Characters of a White Bean. Science, 

 N. S., 25, pp. 828-832, May 24, 1907. 



