Masao So and Yoshitaka Iiviai 331 



equal numbers. From eight matings of this sort eighteen self and 

 twenty-two piebald were counted. But if the extracted piebalds are 

 mated between themselves or crossed to piebald of the pure race, they 

 always breed true to the type. By twenty-eight matings one hundred 

 and sixty animals were born and they were all characterized with 

 spotted coat. 



Thus the extracted mice of these races having non-contamination of 

 the D factor always transmitted their characteristics in the proper manner. 



Summary. 



1. The results reported in this paper agree in the main with 

 those of Little and Detlefsen. More experimental evidence, however, 

 is supplied by the present investigation. 



2. In the present studies, however, the dominant spotting of the 

 " Kasuri " i-ace was distinguished and separately recorded from the 

 recessive ordinary spotting, so the comparison between observation and 

 expectation was more closely dealt with. 



3. The D factor acting upon S, the factor for self, in somewhat 

 restricted fashion on the development of the coat-colour results in the 

 " Kasuri " pattern, and the same factor working upon S', a factor for the 

 spotting, results in a dark-eyed white of the " Daruma " type. 



4. On the one hand the D factor acts as dominant upon the pattern 

 development as was stated above, and on the other hand it works reces- 

 sively in regard to the lethal effect. Mice homozygous for this factor 

 perish in the early ontogeny whether they have S or S' as the hypostatic 

 factors. 



5. The " Kasuri " race often become sterile, especially on the female 

 side. This condition was also found to occur in the " Daruma " race in 

 a few instances. 



Agricultural College, 



Tokyo Imperial University, 

 November^ 1918. 



P.S. This paper had been written some time ago but not published 

 when, quite recently. Little's paper on " The Fate of Individuals Homo- 

 zygous for Certain Color Factors in Mice " appeared in The American 

 Naturalist, Vol. 53, No. 625, 1919. 



