THE CARRIERS OF THE HERITAGE 23 



geometric progression throughout subsequent genera- 

 tions. In 1883, too late for Darwin to learn of it, 

 van Beneden discovered the important fact that the 



FIG. 14. Scheme to illustrate maturation of germ-cells. 



mature germ-cells, as expected, actually contain only 

 half the normal number of chromosomes. 



The mature egg- or sperm-cell, with half its normal 

 number of chromosomes, is termed a gamete (marry- 



