58 PHYSICAL BASIS OF HEEEDITY 



somes come together at this time in pairs, and subse- 

 quently separate, so that each egg comes to contain 

 one or the other member of a pair. The same process 

 takes place in the formation of the sperm-cells. It is 

 obvious that if one member of any pair contains material 

 that produces an effect on some character as one of the 

 end results of its activity, and the other member of the 

 pair contains a different material, the behavior of the 

 chromosomes at the time of maturation supplies exactly 

 the mechanism that Mendel's law of segregation calls for. 



