I06 Hagedoorn. 



zygous for the factor B has been mated to a j'ellow one without B 

 (. .bb..) I get; 



ii6 other colour than yellow (. . Bb . .) and 107 yellow (. . bb . .), 

 the calculated ratio being 11 1.5 : 11 1.5. 



At the end of the paper I will give the experimental proof of 

 the independance of factor B from the factors A, c, D and G. 



On the coloured plate, Nos 6, 12, 18 and 24 are without B, the 

 others all have it. 



Factor C. 



This factor, like a has been extensively studied, in mice as well 

 as rabbits and cavies. Its action is chiefly to modify that of the 

 factor B on the colour. When a and B are both present, but G is 

 absent, the colour which would be chocolate without c (if def and h 

 are also present) becomes an intense black with it. Thus is ABcDEFgH 

 chocolate, ABCDEFgH = black. Addition of G to these two formulae 

 makes abcDEFGH, which is cinnamon (N" i), and abcdefgh, which 

 is agouti (No 13), the colour of most wild Miis musculus. 



ABcdEFgH is dilute chocolate, silverfawn (No 4), ABCdEFgH is blue 

 (dilute black. No 3). The difference between orange (AbcDEFgH) and 

 tortoise (AbCDEFgH) is also due to a cooperation or not of this factor. 

 In the absence of the factors D or E or both, it is very difficult to 

 tell by simply looking at a mouse, whether it contains the factor c 

 or not. Thus, the difference between an (.\BcdEFgH) suverfawn, and 

 an ABCdEFgH (blue) mouse or rabbit can well be seen, but that 

 between ABcdeFgH and dilute lilac, ABCdeFgH, I could hardly ever 

 detect. Such mice can only be distinguished by mating them to others 

 having D or E present. As illustration I will give the result of a testing 

 of three very light coloured mice born from lilac (ABCDeFgH) parents. 



The first, a male, was given three females, one silverfawn, dilute 

 chocolate (ABcdEFgH) the other two ABcDeFgH (champagne). 



ä No 4117 X Q ABcdEFgH, gave all young ABCdEFgH, that is blue, 

 thus proving to be homozygous for c. 



d No 4117 X 9 9 ABcDeFgH, gave all young ABCDeFgH, lilac which 

 again proved him to be homozygous cc. 



The sister of No 4117, No 4113, was mated to an ABcdEFgH 

 (silverfawn) male, she gave in two litters: 



Q No 4113 X <5 ABcdEFgH, 5 ABCdEFgH and 7 ABcdEFgH, blues and 



silverfawns, thus showing to be heterozygous for c, her formula being: 



AABBCcddeeFFggHH. 



