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THE AMERICAN NATURALIST [Vol. XLVIII 



gray female with a not-pure-white belly. She was not 

 used in the main lines of the experiments described above. 

 But she was kept in stock and bred with chocolates. 

 About a year later I noticed in the offspring of a pair of 

 cinnamon white-bellied mice a few mice that looked like 

 chocolates, but which showed, on closer inspection, dis- 

 tinctly ticked hair. One of these new grays bred to 

 black (heterozygous) gave some chocolates, blacks, new 

 grays, and one very dark, almost black, mouse with 

 ticked hair. 5 The female was bred next time to a house 

 mouse (gray gray-belly) and produced all gray gray- 

 bellied offspring that had a dark coat, but not nearly so 

 dark as that present when the new gray is heterozygous 

 for black. Until further tests have been made it can not 

 be stated whether or not the new factor belongs to the 

 yellow-black system of quadruple allelomorphs. 



s The resemblance of this mouse to the rabbit "agouti-black" homozygous 

 for black is very striking (Punnett, Jour, of Genetics, II, 1912). 



