INTRODUCTION 13 



is the source, or point of departure, in the formation 

 of each new individual, rather than the somatoplasm, 

 which represents the end stages of the hereditary 

 processes. 



This has not been the method of the past. The 

 resemblances of the visible father and son have 

 usually been traced instead of the character of their 

 unseen germplasms. By following this old method, 

 investigators have often been misled because the 

 visible or apparent is not always the true index of 

 what lies behind it. A gray and a white rabbit, for 

 example, may produce some offspring that are 

 entirely black just as two white-flowering sweet peas 

 when crossed may sometimes produce purple blos- 

 soms. Consequently it is a great fallacy to affirm 

 that in heredity "like produces like," since the op- 

 posite is quite often the case. 



The new heredity, embodied in the science of 

 genetics, attempts to go deeper than the surface 

 appearance of the somatoplasm. It aims to get at 

 the source or origin of organisms, that is, the germ- 

 plasm which is the only connecting thread between 

 succeeding generations of living forms. It is con- 

 cerned not so much with somatoplasm, which repre- 

 sents what the germplasm has done in the past, as 

 with the germplasm and what it can do in the future. 



