CONSTITUTION OF THE CHROMOSOMES 



157 



Figure 36. Diagram to illustrate the arrangement of the genes in 

 the genetic sj^stem. The genes, represented by the circles, arranged 

 in consecutive order in long paired strings which are the chromo- 

 somes. One series (P) is derived from the father, the other (M) 

 from the mother. Thus the genes are in pairs, one member of each 

 pair from each parent, the two members of each pair having anal- 

 ogous functions, though one may be dominant, the other recessive. 



show that these relations do hold, and they agree with and 

 confirm this consecutive arrangement of the genes. Fur- 

 thermore, the chromosome is seen under the microscope to 

 be, at the time when crossing-over occurs, a linear struc- 



