LATENT CHARACTERS 193 



crosses were made with animals namely, mice. As 

 the result of his experiments Cuenot framed the hypo- 

 thesis that in mice the colours yellow (/), grey (G), 

 and black (N) can only make their appearance when 

 the zygote containing them contains also a perfectly 

 independent colour- producing factor (C), which is 

 allelomorphic to, and dominant over, the albino factor 

 (.4). (According to the notation which we have pre- 

 viously adopted, this last pair of factors would be more 

 properly written C and c.) 



According to Cuenot's scheme all albino mice (white 

 mice with pink eyes) contain some colour in a latent 

 condition. The different individuals with which ex- 

 periments were made were found to be capable of 

 representation by the following ' formulae ' of heredity : 



Homozygotes, AG ; AN ; AJ. 



Heterozygotes, AG . AN ; AG . AJ ; AN . AJ. 



In the visible expression of these colours when C is 

 present, yellow was found to be dominant over grey 

 and over black, and grey was dominant over black. 

 In the formation of the gametes the various factors 

 concerned follow Mendel's law precisely. There is, 

 however, one curious point to be noticed, if Cuenot's 

 interpretation is really correct. We have in this case 

 three alternative characters instead of a simple pair 

 of allelomorphs. On referring to the list of different 

 kinds of individuals given above, it will be seen that 

 homozygotes contain only one of these alternative 

 characters, whilst a heterozygote contains two. It is 

 not possible for a single individual to contain all three 



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