326 Spotting in Mice and their Genetic Behaviour 



proportion. The totals obtained from such matings are represented in 

 the following table 



The expectation accords closely with the experimental data; the 

 ratio of the two forms being one to one. 



Mating : " Daruma " x " Daruma." 



Curiously enough the " Daruma " race almost always gives mixed 

 young when 'the animal is mated with the piebald. The results point 

 to the heterozygosity of each mouse of the "Daruma" race used in these 

 matings. If such heterozygous mice are mated between themselves we 

 should expect " Daruma " and piebald in a ratio of three to one. The 

 actual results, however, differed widely from this expectation, as will be 

 seen in the following : 



" Daruma " Piebald Totals 



The observed number comes strikingly close to the calculated one 

 based on a ratio 2:1, while the normal expectation deviates widely 

 from it. 



Studying the same subject, Little formerly experienced also such an 

 abnormal ratio from analogous matings. The interpretation of such a 

 result will be fully discussed in the next section. 



The Modified Ratio. 



The modified ratio 2 : 1, which resulted in the cross " Daruma " x 

 " Daruma," recalls instantly the similar result observed in yellow mice. 



In breeding experiments with the yellow mice, Cuenot (1905) first 

 reported the results in Mendelian terms. After him Castle and Little 

 (1910) repeated the experiment and obtained a ratio of almost 2 : 1 

 of yellow : non-yellow in the cross yellow x yellow when their data 

 are added to Cuenot's, and this was confirmed by work done by 

 Durham (1911), Little (1911), Hagedoom (1912) and Dun (1916). The 

 writers breeding this race on a small scale observed also the same 

 facts. The views of many of the authors cited above agree that the 

 modified ratio is due to the mortality of the homozygous yellows which 



