viii PREFACE 



part, they have only expanded, rather than altered in any 

 essential respect, the subjects discussed in the Theory of 

 the Gene. In a few instances, however, I have added a brief 

 account of the discoveries made since the earlier date, 

 especially in those cases where the new results confirmed, 

 expanded, or made less probable statements in the origi- 

 nal text. 



T. H. M. 

 Woods Hole, Mass. 

 August, 1928. 



