IjO Hagedoorn. 



In mice I never found any "dominant" silvers, all my silvered mice 

 were so because of a lack of E. 



This factor f, as its presence or absence does not interfere with 

 the activity of the other colour-modifying factors, is one of the most 

 easily studied. In the plate are figured black-silvered, ABCDEfgH 

 (No 17) agouti-silvered, abcde£GH (N^ 20) and blue-silvered, ABCdEfgH 

 (No 7) animals. My first ff mice were black, the others were produced 

 by mating one of these blacks, which was heterozygous for B, to 

 cinnamon, abcCDEFGH, in the F2 of which mating I obtained the 

 three other kinds of silvered mice. Silvered cinnamon, silvered dilute 

 cinnamon, or silvered plumsilver (.\BcDEfGH), (ABcdEfCH) and (ABcdEfgH) 

 were not produced in this Fg, which consisted of a few animals only. 

 Matings of Ff and ft animals were very few. In all I obtained 31 

 young from such matings, 18 of which remained fully coloured, being 

 Ff, whereas the remaining 13 turned silver after moult. The expected 

 ratio was 15.5 : 15.5. 



From the tables can be seen the independance of the factor F 

 from factors: C D and G. 



Factor G. 



This factor is again one which has been extensively studied. Its 

 presence has been demonstrated in the mouse, rabbit, cav}', in the 

 brown rat, and without any doubt it exists also in the hamster, the 

 squirrel, in the hare and the fieldvole, as black individuals of all 

 those animals are occasionally met with. When this factor G is absent 

 from a germ, which contains all the other factors, a. b, c, d. e, f and H, 

 but not I, the animal resulting from it is black. Thus differ black 

 and agouti cavies, mice, rats and rabbits only in the presence and 

 absence of this factor. Black and agouti individuals of Mus ratlus 

 do not differ in this way, it seems from the experiments of Morgan 

 that in black Mus rattus G is present, and that here the agouti colour 

 is modified by the action of an additional factor, not present in the 

 agouti animals. Some black rabbits seem to possess this same factor. 



Wliereas the factors A, b. c, d. e, f and H all tend by their 

 cooperation to the development to make the colour darker, this 

 factor, when present, tends to produce a lighter tint than would 

 result in its absence. 



Its action seems to be a modification of the activity of the factors 

 A, b and c, so that part of the developing hair only becomes black 

 (brown if c be absent), other parts being brown and yellow. The 



