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TEE AMERICAN NATURALIST [Vol. XLVII 



Agouti Spotted with White by Tricolors 

 A spotted agouti $ mated to tricolor black, 414 J, gave 

 three tricolor blacks, 385, 499, 487, and two bicolor reds 

 with agouti spots (i. e., they had white spots, red spots 

 and agouti spots), viz., 486, 487 and one, viz., 500, spotted 

 agouti. It may seem that when agouti spots are present 

 they take the place of the black. Castle's (1905) records 

 support this suggestion. The agouti female seems to 

 have been heterozygous for the agouti factor. 10 



Discussion 



It has been stated by Castle that when guinea-pigs with 

 uniform coat are crossed to spotted guinea-pigs the off- 

 spring have uniform coats. 1 Our own limited experience 

 confirms this statement. In the F 2 generation a variable 

 offspring is obtained, ranging from uniform to much 

 spotted. This question will be considered later. 



A question of fundamental importance is whether the 

 uniform coat can be treated as allelomorphic to spotted 

 coat. This involves the question whether spotting is the 

 product of one factor or of more than one. 



In rats and in mice the same question has come up and 

 Cuenot has handled the problem on the basis of a pair of 

 allelomorphs. The main evidence on which the assump- 

 tion of a pair of allelomorphs rests, is derived from the 

 number of kinds of offspring in the F 2 generation. If 

 uniform coat is treated as allelomorphic to spotted coat, 

 the F 2 expectation is three uniform to one spotted, and 

 this condition is the reported result for this generation. 



On the other hand, if the spotted coat is due to more 

 than one factor the situation becomes complicated, and 

 the F 2 expectation is no longer three to one, unless we 



black, 423, calls fo/special attention/ This individual, TB 521, had among 



