TOO 



THE AMERICAN NATURALIST [Vol. XLVIII 



These errors were corrected in an "errata" in Band VI, heft 5, 

 which Dr. Little unhappily did not find. The sentences should 



Without exception they have given agouti, or equal numbers of agouti 

 and albino young-, depending upon the purity of the black used. But 

 never has one of these albinos produced a single black young in a mating 

 with black. Counting together the colored young of such families I 

 get 89 agouti young. 



Professor Punnett was so kind as to draw my attention to 

 these mistakes. They were corrected in the reprints sent out. 



The facts were simply these : Albinos were bred of two sorts, 

 with and without G (the gene which agoutis have more than 

 blacks) . These albinos can only be distinguished by test-mating 

 them to blacks. The albinos with G (aG) give agouti young, if 

 mated to black (Ag), the ag albinos give black young from such 

 a mating. In one series, some agoutis were produced, which 

 were heterozygous for A as well as for G(AaGg). Ordinarily, 

 such agoutis, when mated inter se, produce 9 agouti (1 AAGG, 

 2 AAGg, 2 AaGG, 4 AaGg), 3 black (1 aaGG, 2 aaGg) and 4 

 albinos ( 1 aaGG, 2 aaGg, 1 aagg) in every sixteen. Mated to 

 albinos without G(ag) the ordinary AaGg animals give four 

 kinds of young, agoutis (AaGg), blacks (Aagg) and two kinds 

 of albinos (aaGg) and (aagg) in equal numbers. 



Now these particular AaGg animals did not produce four 

 kinds of gametes, as expected, namely, AG, Ag, aG and ag, but 

 only two kinds, Ag and aG. Thirty one agoutis were test-mated 

 to aagg albinos. -These test matings gave 181 young, of which 94 

 were black (Aagg) and 87 albino (aaGg). No agoutis were 

 produced. 



As a further proof, the result of breeding these agoutis inter se 

 can be adduced. These matings gave 73 agouti (AaGg) , 37 black 

 (AAgg) and 32 albinos (aaGG). Of these 32 albinos, thirteen 

 were tested by mating them to blacks. If one of them should 

 have lacked G, it would have given black young. But no black 

 young were produced. Some young were albino (when the black 

 parent was heterozygous for A), but all the colored young were 

 agouti (89 in all). 



This, I hope, will make it perfectly clear, that in this series 

 we have been dealing with a case of repulsion between the genes 

 A and G. A. L. Hagedoorn 



