GENETICS AND EUGENICS 



843 



that in this group the number of births occurring in completed families 

 averaged 7.9 and the average number of children born to mothers of all 

 ages was 5.7. The average number of surviving children of the two 

 groups was 6.1 and 4.6 respectively. The significance of these data in 

 comparison with those concerned with the size of the families from 



III 



• i i 



I£CSND 



Bale without trait 



Female without trait 



IT 



klale and female with trait 



Sax unknown; 7 inheritance unknown 



Fig'. 439. — Standard pedigree chart. Charts such as this can be used in tracing 

 a trait tlirough several generations of a family. This particular chart shows the 

 inheritance of a dominant trait starting with a cross between a male who was 

 heterozygous for the trait and a female in whom it was homozygously recessive. 



which college students come can be realized from the fact that if the 

 reproductive rates in these two groups continue for ten generations, 

 the descendants of one hundred families of the dysgenic group will 

 number more than twenty-eight thousand, while in the same genera- 

 tion, one hundred families of the present-day college-student group 

 will be represented by eleven persons. 



