5 2 4 



TRANSMISSION 



Both the second and third, especially the former, suggest a 

 blend, and there is much in the experience of breeders to indi- 

 cate that certain characters do blend, making a successful union, 

 entirely against Mendel's law, whose operations indicate the 

 non-formation of stable hybrids. 



The writer ventures to urge, therefore, not the attempt to 

 prove or disprove this great principle, but the endeavor to learn 

 and define the limits of its action. That it applies to crosses 

 generally there is the greatest reason to believe, and to its gen- 

 eral truth many a breeder can testify, when he has seen some of 

 his favorite productions revert to their original forms before his 

 very eyes. 



Experiments in crossing Japanese waltzing mice with albinos. 1 

 Darbishire conducted extensive experiments with this cross, 

 producing thousands of individuals, which are fully classified in 

 the original, to which reference is here made. It is more work 

 of this kind that is needed. Space forbids giving more than a 

 brief outline of some of the more characteristic conclusions of 

 the experimenter : 



1. When the race of waltzing mice is crossed with albino mice which do 

 not waltz, the waltzing habit disappears in the resulting young, so that 

 waltzing is completely recessive in Mendel's sense ; the eye color of the 

 hybrids is always dark, the coat color is variable, generally a mixture of 

 wild gray and white, the character of the coat being distinctly correlated 

 with characters transmitted both by the albino and by the colored parent. 

 There is thus no proper dominance in Mendel's sense, so far as eye color 

 and coat color are concerned, the hybrids differing always in age, color, and 

 generally in coat color, from both parents. 



2. When the hybrids produced from the cross described are paired 

 together, the resultant young exhibit a segregation into three groups so far 

 as eye color and coat color are concerned, into two so far as regards the 

 waltzing habit. The phenomenon of segregation is closely similar to that 

 described by Mendel ; and in color, whether of eyes or of fur, the propor- 

 tions are closely identical with those observed by him, a quarter of the 

 young resembling their albino grandparents, half representing their hybrid 

 parents, and a quarter resembling their waltzing grandparents in so far that 

 they have pink eyes and the same-colored fur, but differing from any of 

 their immediate ancestors in the range of coat color exhibited. The pro- 

 portion of individuals which exhibit the waltzing habit is less than one fifth 

 of the whole number of young, and is not a Mendelian proportion, 



1 Biometrika, Vol. Ill, Part I, pp. 1-51. 



