12 



tions that can not be determined. He would 

 then have had no latent character in any 

 other sense than that it was invisible owing 

 to the absence of pigment. 



The explanation here offered is essentially 

 that presented by Cuenot for mouse hybrids, 

 in which one unit is assumed to give pig- 

 mentation and another to determine the color 

 which this pigment will exhibit. Cuenot con- 

 siders the various colors to be latent in the 

 albino and he is supported in this respect by 

 my hybrids, but I prefer not to call this char- 

 acter a latent pigment but an active pigment- 

 changer. 



This reference of various colors to the ac- 

 tion of a pigment-changer requires that the 

 pigments upon which the various colors de- 

 pend shall bear some simple relation to each 

 other. I have made some preliminary studies 

 on the pigments of these beans and have 

 partially demonstrated this simple relation by 

 converting the yellow and brown pigments to 

 black by the use of alkalies but I have not yet 

 been able to reverse the process. It is easily 

 demonstrable that the black (dark purple) 

 bean contains anthocyan, and this gives a 

 simple explanation of the correlation between 

 black seed-coats and red flowers, observed by 

 Mendel and all other students who have 

 chanced to use black-seeded peas or beans. 



That the yellow, red, and black pigments of 

 animals are closely related is also well known, 

 and there can be no doubt that the l latent 

 black' which Castle 18 reported in certain 

 albino guinea-pigs is to be interpreted exactly 

 as Cuenot's mice, the black being due to the 

 presence of a melanizer which is a unit char- 

 acter wholly independent of the pigment-pro- 

 ducing unit. The fact that half the gametes 

 of this individual carried the so-called 'latent 

 black' simply showed the animal to be heter- 

 ozygous with respect to this allelomorph, and 



u Castle, W. E., loc. tit. 



