76 THE THEORY OF THE GENE 



rence of other dominant characters, the argument is not 

 one that makes a favorable appeal but seems rather a 

 forced attempt to save the theory at all costs. 



It must be remembered, too, that the distinction be- 

 tween recessive and dominant genes is largely arbitrary. 

 Experience has showTi that characters are by no means 

 always recessive or dominant. On the contrary, in a large 

 majority of cases, a character is not completely dominant 

 or completely recessive. In other words, the hybrid type, 

 containing a dominant and a recessive gene, lies some- 

 where between the parent types — both genes have some 

 effect on the character produced. When this relation is 

 realized, the theory that a recessive gene is an absence 

 does not appear in so favorable a light. It is true that it 

 might be claimed in such cases, with some grounds for 

 justification, perhaps, that the hybrid is intermediate 

 because one dominant gene produces less effect than two 

 dominant genes, but this introduces a new feature into 

 the situation. It does not necessarily mean that the effect 

 is really due to one absence. It can be brought into line 

 with this assumption perhaps, but is not a necessary in- 

 ference. 



If the preceding arguments are admitted as cogent we 

 might dismiss this interpretation of the meaning of the 

 recessive gene taken in a literal sense. But in recent years 

 another interpretation of the relation between the effect 

 of all the genes and the character has appeared that 

 makes the refutation of the presence and absence view 

 much more difficult. For example, suppose a gene were 

 actually lost from a chromosome and that when two such 

 chromosomes are brought together, some character of the 

 individual is modified or even absent. The modification or 

 absence might be said to be the effect produced by all 

 the rest of the genes. It is not the absence, as such, that 

 determines the result, but the effect produced, w^hen two 



