THE 



AMERICAN NATURALIST 



Vol. XLVIII August, 19 U No. 572 



MULTIPLE ALLELOMOBPHS IN MICE 



PROFESSOR T. H. MORGAN 

 Columbia University 



Some breeding experiments with mice that I have been 

 carrying on during the last two years have shown that 

 yellow, gray gray-belly, gray white-belly and black are 

 allelomorphs. To this series a fifth allelomorph may pos- 

 sibly be added which for the present may be called new 

 gray. This quadruple (or quintuple) system of allelo- 

 morphs fulfils the conditions of a multiple series in that 

 only two of the allelomorphs can exist at the same time 

 in any individual. In other words, a mouse may be pure 

 for any of these genes (except for yellow, in which the 

 pure form is not viable), or a mouse may be heterozygous 

 in any two of the genes, but never in more than two. 

 The evidence that establishes this series of allelomorphs 

 may be briefly stated as follows : 



In 1911, I pointed out that if yellow mice (producing 

 yellow and chocolates) are bred to agoutis (grays), and 

 their yellow offspring mated, they should produce not 

 only yellow and agoutis (as they did) but some choco- 

 lates (or blacks) also; but no chocolates appeared. I 

 stated that the results obtained were explicable if yellow 

 and agouti are allelomorphs. 1 



