274 THE FACTORIAL HYPOTHESIS 



It is a matter of little theoretical importance what 

 system of symbols is adopted, unless that system 

 proves to be impracticable, or unless it implies re- 

 lations that are unnecessary or unjustifiable. (See 

 Appendix.) 



We do not wish to appear to base our objection to 

 the presence and absence hypothesis on the im- 

 practicability of its nomenclature in a new field, 

 but rather on the grounds that the conception of 

 presence and absence assumes that we do know 

 something about the relation between character 

 and factor that we can not possibly know. To as- 

 sume the absence of a factor from the absence of a 

 character is, in a sense, as naive as it was to assume 

 that an animal moved toward light because it liked 

 the light. 



It need not be denied that losses of factors may 

 occur, and it may even be probable that a loss in the 

 germ plasm might lead to a loss in some part or parts 

 of the body, but there still remains no justification 

 for the assumption in any given case that we can 

 infer from the lack of a character in an animal or 

 plant a loss of factors. Such an assumption is en- 

 tirely gratuitous; and gives a totally false impression 

 concerning the factorial hypothesis of Mendelian 

 heredity. Moreover, if taken literally it may lead 

 to unwarranted conclusions in other fields. 



It is similarly naive to assume the absence of a 

 factor from the recessiveness of the character, yet 

 the literature abounds with instances where the re- 

 cessiveness of the character is taken as a criterion for 



