I 



FURTHER EXPERIMENTS ON THE INHERITANCE 

 OF COAT COLOUR IN MICE. 



By FLORENCE M. DURHAM. 



In Report IV of the Evolution Committee of the Royal Society, I 

 published a preliminary account of the results of my breeding experi- 

 ments to determine the inheritance of coat colour in mice. I now 

 propose to complete that account by giving the results of my investiga- 

 tions into the genetic behaviour of pink-eyed mice with coloured coats 

 and also of yellow mice. 



I propose to begin with an account of the pink-eyed mice with 

 coloured coats, but at the same time to leave the question of the 

 behaviour of pink-eyed mice with yellow coats until I deal with dark- 

 eyed yellow mice, and to confine myself at first to pink-eyed mice of 

 any coat colour except yellow. 



The albinos have been dealt with in Report IV. The pink-eyed 

 mice with coloured coats as stated in Report IV have only apparently 

 unpigmented eyes. Examination of sections of the eyes microscopically 

 reveals the presence of pigment both in the retina and iris. The 

 amount of pigment present is however so little, that it is extremely 

 difficult to say of what colour it is. 



There is a correlated absence of pigment in the hairs of these mice, 

 so that they are much paler in colour than any of the corresponding 

 varieties of dark-eyed mice. But this absence of pigment in the eyes 

 and hair of the pink-eyed mice has a genetic significance different 

 from that of the dilution of coat colour in the dark-eyed mice. For 

 in the case of the dark-eyed mice, the absence of a factor which effects 

 the den.se deposition of pigment in the hairs gives rise to what are 

 known as the dilute forms, and for each coloured type there is a dilute 

 variety. The pale colours of the pink-eyed mice are not due to the 

 same cause, and cannot be explained in the same way. For pink- 

 eyed mice behave genetically like the concentrated and diluted varieties 



