100 THE MENDEL JOURNAL 



other a dominant. The former is a true recessive, and 

 is manifested as a white because no colour is present. 

 But the latter is, as it were, a false white. It is so, 

 not because colour is absent, but because another 

 factor is present which inhibits the manifestation of 

 the colour in the body tissues.* 



It is therefore conceivable that two sorts of bays 

 and browns among horses may exist. First, those 

 which are true recessives to greys because they 

 carry nothing but bayness or brownness. Second, 

 those which carry greyness in addition ; but in these 

 cases, to the greyness there is superadded a third factor, 

 which, meeting it in the body tissues, inhibits its 

 developement and allows the recessive or underlying 

 bayness to manifest itself. 



If we let B stand for the factor producing bay 

 colour, G for that producing greyness and g for its 

 absence, and B^ for that producing inhibition of G 

 and b' for its absence, then we can symbolically 

 represent the relationship of grey to the two postu- 

 lated types of bay horses as follows : — 



Bay colour - - = B g b^ 

 Grey colour - - = B G V 

 Bay colour following grey = B G B^ 



There is yet a third possible type of bay or 

 brown horse. Its early greyness may be simply due 

 to a late developement of its normal colour. 



The bay horse of the composition B g b^ may be 

 regarded as a true recessive bay and is bay because it 



* For fuller information about these and for a general discussion 

 of colour phenomena see " Mendel's Principles of Heredity," by 

 Prof. W. Bateson, p. 102, Cambridge University Press. 



