MENDELISM 



113 



each of these two hair characters. When any two 

 individuals having this particular genotypic composi- 

 tion mate, therefore, they may produce any one of four 

 possible phenotypes dark curly, dark straight, light 

 curly or light straight 

 haired individuals. 

 These four phenotypes 

 in turn will present nine 

 different genotypic 

 combinations out of 

 sixteen possible cases, 

 as shown in Figure 20. 



Figure 19 further- 

 more serves to make 

 clear, first, the distinc- 

 tion between somato- 

 jplasm and germplasm ; 

 second, the maturation 

 of germ-cells ; third, 

 the segregation of 

 gametes ; and fourth, 

 jthe formation of zy- 

 gotes in sexual repro- 

 duction. 



The cells of the so- 



FIG. 20. Diagrams showing the 

 possible genotypic and pheno- 

 typic combinations resulting 

 when two heterozygous individu- 

 als with dark curly hair mate. 

 Symbols are the same as in 

 Figure 19. 



matoplasm are represented as making up the arcs within 

 which are inclosed the germ-cells after their reduction 

 through maturation, which results in giving to each 

 germ-cell half the number of determiners that are 

 present in the somatic cells. 



It will be remembered that when two gametes, or 



