82 Colours of Mice [cii. 



the chocolate (more strictly, with the ''absence of the black 

 determiner"). So long as the same factors are introduced, 

 the consequences in F^ and the results of re-comxbination in 

 /% are the same. But when the dilution is introduced from 

 each side, F^ is of course the usual 3 dominants : i recessive, 

 thus : 



Blue X Silver-fawn 

 {Bd) I {bd) 



F, Blue 



{Bbdd) 



F^...B\ue'{Bd) Silver-f^wn {bd) 



Observed 46 17 



Calculated 47 -2^ 15 75 



It is evident that an extracted albino cannot be carrying 

 a determiner for a colour higher in the scale than that of 

 its coloured parents. Moreover if the parents from which 

 an albino is extracted are alike, and if they throw no 

 offspring with colours other than their own (besides the 

 albinos), then the albinos so extracted must be all bearers 

 of the determiner for their parental colour. If such albinos 

 are crossed with forms of a colour lower in the scale than 

 that borne by the albinos, F^ must be of the colour deter- 

 mined by the albinos. For example, Miss Durham obtained 

 the following : 



Silver-fawn x Albino (extracted from chocolates) 

 {Cbd) I {cbD) 



Fi Chocolate 



{CcbbDd) 



r -^ n . 



i^2 • • • Chocolate Silver-fawn Albino 



{CbD) {Cbd) (various) 



Observed 19 4 6 



Calculated 16-3 34 7' 2 



Black X Albino (extracted from chocolates) 



{CBD) I {cbD) 



F^ Black 



{CcBbDD) 



r ^ 1 . 



F2... Black Chocolate Albino 



Observed 76 24 27 



Calculated yi'4 23-8 3i'7 



