178 THE MENDEL JOURNAL 



colour determiners and a colour producer. Let D^ 

 d^, D^ d^ and C c stand for the presence and 

 absence of these bodies respectively. Now if the pig- 

 mentary factors (determiners and producers) of the 

 European are allelomorphic with those of the negro, so 

 that C and c, or D^ and d^ cannot occur in the same 

 gamete, then the expectations attributed to the 

 " theorists " by Professor Pearson are rational enough, 

 however numerous these allelomorphic pairs may be. 

 But if they are not, then that expectation is wholly 

 irrational. 



This consideration brings us to the question whether 

 we are justified in believing that the pigmentary factors 

 of the negro are genetically of the same nature as those of 

 the European ? Ought we to regard the one series as 

 allelomorphic to the other ? Let us take an extreme 

 case. Should we expect the absence of blue pigment 

 = b in a sAveet pea to be allelomorphic to the presence of 

 black = B in a mouse ? Of course, we cannot make such 

 a mating, but we desire to illustrate by an extreme case 

 the point which seems to us to be one of the possible pivots 

 round which the problem of human hybrids may turn. 

 To take then the actual case, can we expect the absence 

 of the colour producer = c of the European to be allelo- 

 morphic to its presence C of the negro ? In other words, 

 is C of the European and C of the negro genetically the 

 same thing ? And is c of the European genetically the 

 same as, or is it different from, c of the negro ? This last 

 question compels us to consider what we mean by the 

 " absence " of a thing. Must we regard c as a mere 

 symbolical negation, or rather should it not be regarded 

 as a negative quality associated with a positive base ? That 

 is, to take an illustration, the positive base may be regarded 

 as an ultra-microscopic chloroplastid, and the negative 

 quality as the absence of chlorophyll from the positive 

 base or plastid. In a generalised way we may state it 

 thus : the hereditary characters of organisms are carried 

 in a physical base. When a character, let us say C, is 

 present, it is carried by this base. When it is absent 

 = c, then the base is present, but its associated character 

 is not. The base, however, when without its character, 

 behaves as an allelomorph to the base which- is carrying 



