160 Inheritance of Coat Colour in Mice 



of dark-eyed mice and carry the conditions of concentration and dilu- 

 tion just as they do, and in their colourings the effects of these 

 are shown. The paleness of colour therefore which accompanies the 

 pink eye must be due to some other cause. Tiiis statement however 

 applies only to those mice in which yellow pigment is absent. For 

 it is possible to produce pink-eyed yellow mice with hair as deeply pig- 

 mented as that of dark-eyed yellow mice. These will be dealt with later 

 on. Also in the case of the pink-eyed agouti mice, while the black and 

 chocolate pigments are there in very much diminished quantities the 

 yellow banding may be as deeply coloured as in the hair of the ordinary 

 agouti. It is possible to arrange the pink-eyed mice in classes cor- 

 responding to those which have been distinguished among the dark- 

 eyed mice. 



Pink-eyed mice which behave genetically like black mice are of a 

 pale greyish colour and were named lilacs by Mr Darbishire(6) who 

 was the first to breed them and kindly gave me two living specimens. 



In order to distinguish them from other lilac mice, on account of 

 their colour, I have called them " blue lilacs." They breed perfectly 

 true mated inter se. Mated with chocolate mice, they never throw any 

 other colour but black in F^. 



In the F.2 generation from this mating two new varieties appear 

 which I have named "chocolate-lilac" and "champagne" {"cafe au lait" 

 of Cu^not) respectively. 



The chocolate-lilacs vary very much in appearance in depth of 

 colouring, but the colour is always browner than that of the blue lilac 

 more resembling that of the silver fawn. For this reason I called them 

 chocolate-lilacs, and I thought at first they were a chocolate variety of 

 the pink-eyed mouse. But when mated with chocolate mice they throw 

 a mixture of blacks and chocolates. 



Chocolate-lilacs mated together throw blue lilacs, chocolate-lilacs 

 and champagnes. 



The champagne mice, mated with chocolates, throw only chocolates 

 and are I believe the pink-eyed variety of chocolate. Mated inter se, 

 they breed perfectly true, I therefore regard the blue lilacs as the 

 homozygous pink-eyed variety of the dark-eyed black mouse, the 

 chocolate-lilac mouse as the heterozygous variety of dark-eyed black 

 (throwing chocolate) and the champagne as the homoz^'gous chocolate 

 pink-eyed form. 



When the various forms are mated with the dilute forms of dark- 

 eyed mice, blues or silver fawns, then in the F., generation pink-eyed 



