20 HEREDITY IN RELATION TO EUGENICS 



4. Inheritance of Multiple Characters 

 In the foregoing section we considered the simplest case, 

 namely that in which a single character is taken at a time — 

 I. e., one parent has some character that the other lacks. 

 We have now to consider the cases which are still commoner 

 in nature where the parents differ in respect to two independ- 

 ent characters. Let, for example, the two characters be 

 eye-pigment and hair curliness. Then each one of the six 

 matings given in Table I for eye-color may occur com- 

 bined with any one of the six matings for hair form; so that 

 there would be a total of 6 times 6 or 36 possible combina- 

 tions of matings. Similarly Table II would be replaced 

 by one of 9 entries as follows. 



Table III 



LAW OF COMBINED INHERITANCE OP EYE-COLOR AND HAIR FORM 



One parent 

 Brown eye, curly hair 



Other parent 

 Brown eye, curly hair 



Brown eye, curly hair 



OffspriTig 



Either all browTi-eyed and 

 curly-haired ; or one- 

 fourth blue-eyed and also 

 one-fourth of all straight- 

 haired (with or without 

 blue eyes) 

 Brown eye, straight hair All (or all but one-fourth) 



brown-eyed, and either all 



or one-half straight-haired 



Brown eye, straight hair Brown eye, straight hair All (or all but one-fourth) 



brown-eyed; all straight- 

 haired 



All (or one-half) brown-eyed; 

 all (or three-fourths) curly- 

 haired 



All (or one-half) brown- 

 eyed; all (or one-half) 

 curly-haired 



All (or one-half) brown- 

 eyed; all straight-haired 



All blue-eyed; all (or three- 

 fourths) cm-ly-haired 



All blue-eyed; all (or one- 

 half) curly-haired 



All blue-eyed; all straight- 

 haired 



Brown eye, curly hair Blue eye, curly hair 



Brown eye, curly hair Blue eye, straight hair 



Brown eye, straight hair Blue eye, straight hair 

 Blue eye, curly hair Blue eye, curly hair 

 Blue eye, curly hair Blue eye, straight hair 

 Blue eye, straight hair Blue eye, straight hair 



