148 MENDELISM chap, xii 



But the conception underlying the Presence and 

 Absence theory is not necessarily destroyed. It is 

 open to us to regard the segments of the chromosomes 

 as containers, differing in their content according as 

 they correspond to the factor for a recessive or for a 

 dominant character. The container of the factor 

 for grey body-colour may have all the constituents 

 to be found in the container of the factor for the 

 recessive black body-colour, and at the same time 

 may contain the additional constituent which decides 

 that the colour shall be grey. Were some such idea 

 adopted it would of course be necessary to distinguish 

 between the container, the constituents which the 

 dominant and recessive factors possess in common, 

 and the constituent which is found in the dominant 

 factor alone. Some revision of nomenclature would 

 be required, especially with regard to the precise 

 meaning to be attached to the term factor. While, 

 however, the nature of the machinery is so largely 

 a matter of speculation, it seems hardly necessary to 

 invent terms for its special parts. 



