STATURE AND WEIGHT 511 



by two chief pairs of factors or genes neither of which is 

 fully dominant. If the reader will work out such a 

 cross by means of the Punnett square he will find that 

 this will account for nine different genotypes or shades 

 of color that might be expected in the second generation. 

 If the dominant color factors present in the Negro be 

 represented by A and B, of which A produces more color 

 than B, and their recessive genes in the Caucasian 

 by a and b, then the mulatto of intermediate color would 

 be AaBh. Genotypes of this constitution, when inter- 

 bred, would be expected to produce an Fa generation 

 consisting of 1 AABB (like the original Negro parent), 

 2 AABb (a shade lighter), 2 AaBB (slightly lighter still), 

 1 AAbb (still lighter), 4 AaBb (intermediate or mulatto), 

 1 aaBB, 2 Aabb, 2 aaBb (of decreasing color grades), and 

 1 aabb (like original Caucasian parent), out of sixteen. 

 When it is remembered that color is not uniform in either 

 parent race owing to modifying factors, it appears prob- 

 able that this hypothesis is sufficient to explain all the 

 diversity of color actually found in these interracial 

 hybrids. 



Stature and Weight are very evidently hereditary 

 (Fig. 148) but owing to the great influence of the environ- 

 ment, it has not been possible so far- to determine with 

 satisfactory accuracy the number of factors concerned. 

 Certain famihes and races are unusually tall, as for ex- 

 ample the natives of Patagonia and Scotland, while 

 others, for example, Welsh or Eskimos, are unusually 

 short. Since these races maintain their characteristic stat- 

 ure, even when living in other countries, it is obvious that 

 the causes controlling height are chiefly hereditary. In 

 families where tall has mated with tall the children are 

 mostly tall. Some, however, are short, as would be ex- 

 pected from the fact that both parents would rarely be 

 pure for all the factors for tallness. Human families are, 

 however, too small to enable one to determine the num- 

 ber of factors concerned. What has been said for stature 



