EPISTATIC CHARACTERS 207 



of more recent work by Miss Durham, and her 

 account of the facts runs as follows. For the sake of 

 simplicity we shall deal in the first instance with 

 only four types of colour [in mice] the 'agouti' or 

 wild grey colour, black, ' chocolate/ and albino. The 

 behaviour of these colours in heredity can be described 

 in terms of three pairs of allelomorphs : 



Gg : The presence and absence of the factor which 

 gives the ' agouti ' or grey pattern in the hairs. 



Bb : Presence and absence of the black determiner. 



Cc : Presence and absence of colour. 



Where C is present without G or B, the colour is 

 chocolate, the proper formula for such an animal 

 being CCggbb or Ccggbb. Black mice may be CCggBB, 

 etc., and grey mice CCGGBB, etc. 



All albino mice are to be represented as those from 

 which C i.e., the chocolate colour is absent ; but 

 either G or B, or both, may be present (but masked) 

 in an albino individual. 



When B and C are both present, the colour is black, 

 and not chocolate. We cannot, however, speak of 

 black as being dominant to chocolate, since these two 

 factors belong to independent allelomorphic pairs. A 

 new term is therefore required for this relationship, 

 and also for the relationship between grey and black. 

 Bateson's suggestion for the required terminology may 

 be given in his own words : ' We can, perhaps, best 

 express the relation between the grey and the black 

 by the use of the metaphor " higher and lower/' and 

 I therefore suggest the term epistatic as applicable to 

 characters which have to be, as it were, lifted off in 

 order to allow the lower or hypostatic character to 



