CHAPTER I 



INTRODUCTION 



DURING the whole history of scientific enquiry, 

 one of the most fascinating and at the same time one 

 of the most baffling of the problems which confront 

 mankind has been the cause of the resemblances and 

 differences between parents and children. In general, 

 the facts are common knowledge; the essence of 

 Heredity and Variation is expressed in the proverbs 

 ' Like begets like ' and ( Nature never uses the same 

 mould twice.' Yet clearly the two proverbs are con- 

 tradictory, for if like really begets like Nature must 

 use the same mould for all the members of a family. 

 Our object therefore is to investigate, first, how 

 the characters of a parent actually are distributed 

 among the children, and how the offspring of the same 

 parentage may differ among themselves ; and secondly, 

 if possible, what is the mechanism by which the re- 

 semblances and diversities are brought about. 



These problems are interesting from various points 

 of view. They attract us for their own sake, as does 



D. 1 



