SKIN COLOUR 179 



its appropriate character. In other words, the base with 

 its character is allelomorphic to that without it. In mixed 

 races, such as the mulatto, we may be justified in beheving 

 that C introduced by the negro, and c introduced by 

 the European, may not be allelomorphic, and can there- 

 fore be carried in the same gamete. If we accept this 

 assumption, then the apparent breeding true of the 

 mulattoes receives an intelligible and consistent explana- 

 tion on purely Mendelian principles. And what is true of 

 C and c, will be so of D^ of the negro and of df^ of the 

 European. 



Let us work out a hypothetical case. We will sym- 

 boHse the presence and absence of a colour producer 

 ( = ferment ? ) in a negro by C and c respectively. Let 

 C and c stand for the presence and absence respectively 

 of a colour producer in an European. Let D^, D^, D^ 

 represent three grades of colour determiners in a negro, 

 and d^, d^, d^ their respective absences. In the Euro- 

 pean, let i)\ D^, D^ similarly represent the presence of 

 three grades of colour determiners, and d^, d'^, and d'^ 

 their absences respectively. 



Let us take the constitution of a particular negro to 

 be C D^ d- D^, and that of a particular European to be 

 C c D^ d^ d" D^. When such a negro is married to such 

 an European, the mulatto offspring will necessarily be 

 constituted as follows : C O c Qi i)i ^i d^ (Z^ Ds i)3 

 These mulattoes will then individually form the following 

 kinds of gametes : — 



Now, there are sixteen possible combinations between 

 these four gametes, and neither of them will produce 

 either a negro or an European. They will produce nothing 

 but mulattoes of varying tints. If we analyse the com- 

 position of the mulattoes produced by these sixteen 

 possible fertilisations, we shall find there are no less than 

 eight kinds of mulattoes. One of these will be identical 

 with the two parents, assuming them to be the same as 



