iv] Colours of Mice 81 



periments of Miss Durham (116) have shown that not 

 only the particular pigment is thus constituted, but also 

 that the intensity or degree of saturation in which it is 

 formed can be represented as determined by similar factors. 



For example the black colour may exist in the saturated 

 condition, when the mouse is called black, or in a more 

 dilute form, when it gives the "blue" appearance. Similarly 

 the chocolate colour when diluted gives what fanciers call 

 "silver-fawn." Experiment shows that the cross black x 

 silver fawn gives exactly the same result (in F^ and /%) as 

 blue x chocolate. (See Plate II.) 



The following are experimental results illustrating these 

 points. 



The allelomorphs concerned may be represented as B, 

 the black determiner, b the absence of B, leaving the 

 colour chocolate. D the dense or saturated condition of 

 the colour, d, the absence of D, leaving the colour dilute. 

 (In the case of the introduction of the albino we should 

 have also to take cognizance of C, the presence of colour, c, 

 its absence.) 



The actual results may then be expressed in a tabular 

 form. 



Blue x Chocolate 

 (Bd) \ (bD) 



A Black 



(BbDd) 



r - J l 



F 2 ... Black Blue Chocolate Silver-fawn 



(BD) (Bd) (bD) (bd) 



Observed 42 16 14 8 



Calculated 45 15 15 5 



Black x Silver-fawn 

 (BD) \ (bd) 



FI Black 



(BbDd) 



It is thus immaterial whether the factor for saturation 

 is brought in together with the black determiner or with 

 B. H. 6 



