No. 3.] EXPERIMENTS IN BREEDING MICE. 



Sixth Generation. 



Seventh Generation.- -The colors of only eight members of 



this generation were determined 



too few to be significant. 



General Res ~n Its. 



In the successive generations the percentage of walzing 

 individuals undergoes a steady decline from eighteen per cent 

 and nineteen per cent in the third and fourth generations to 

 eleven per cent in the fifth and four per cent in the sixth gen- 

 eration. Is this decline due to the elimination of an unstable 

 condition or to the circumstance that too little of the walzing 

 blood has been employed in the later crosses to keep up the 

 original proportion ? The question whether the normal law of 

 inheritance is followed here may, indeed, be asked of all the 

 colors. The normal law of inheritance, as defined by Galton, 

 is that one-half the heritage of any generation is derived from 

 the parents, one-fourth from the grandparents, one-eighth from 

 the great-grandparents, and so on, according to the formula : 



Inheritance --. ' k 1 + ' k 2 + i k 3 + T L k 4 + etc. 



