The Visible Basis of Heredity 83 



It is very evident in the foregoing diagram 

 that any two chromosomes other than b and 

 might have found their way to the individual 

 from the grandparents. What combination 

 of chromosomes will finally arrive in any 

 individual is a matter of chance. Remember 

 that there are forty-eight chromosomes in the 

 human cells of the white woman (forty-seven 

 in the man), and it is apparent that almost an 

 endless number of combinations are possible. 

 Half of them in any child come from the mother, 

 half from the father, but which ones of the 

 forty-eight of the mother will make up the 

 twenty-four that go to the child, or which of 

 the father's wiU be contributed as his share, 

 chance only determines; so the probability is 

 that no two children of a family have the same 

 combination of parental chromosomes, unless it 

 be identical twins, which come from the separa- 

 tion of the fertilized egg at the two-cell stage, 

 each cell producing one child. This very pro- 

 cess of sexual reproduction seems to be an excel- 

 lent means of producing endless variations in 

 the offspring. If one had forty-eight dice in a 



