GENERAL CONCLUSIONS 321 



hope at present of settling the question. A few years ago 

 I attempted to make a calculation as to the size of the 

 gene in the hope that it might throw a little light on the 

 problem, but at present we lack sufficiently exact meas- 

 urements to make such a calculation more than a specula- 

 tion. It seemed to show that the order of magnitude of 

 the gene is near that of the larger-sized organic mole- 

 cules. If any weight can be attached to the result it indi- 

 cates, perhaps, that the gene is not too large for it to be 

 considered as a chemical molecule, but further than this 

 we are not justified in going. The gene might even then 

 not be a molecule but only a collection of organic matter 

 not held together in chemical combination. 



When all this is given due weight it nevertheless is 

 difficult to resist the fascinating assumption that the gene 

 is constant because it represents an organic chemical 

 entity. This is the simplest assumption that one can make 

 at present, and since this view is consistent with all that 

 is known about the stability of the gene it seems, at least, 

 a good working hypothesis. 



