306 The Unity of the Organism 



ity and scope of these discoveries, and it is not surprising 

 that many of the leading investigators in the field have been 

 swept off their feet with enthusiasm for the rehabilitated 

 germ-plasm theor}^ Thus we hear one prominent student 

 declare that individual traits are a "veneer," and another 

 that "analysis of the constitution of the germ-plasm is ad- 

 mittedly the fundamental problem in the study of heredity." 

 In other words, the interpretations placed upon the indubi- 

 table results of the new researches have effected a rejuvena- 

 tion of the germ-plasm theory of Weismann. Rejuvenation, 

 I say, because that theory was approaching death and decay 

 when the rediscovery of the Mendelian mode of inheritance 

 occurred. It seems as though some students have lived so 

 exclusively and intensely in the invisible world of "deter- 

 miners," "factors," "bearers," etc., that for them the or- 

 dinary world of plants and animals has lost most of its in- 

 terest if not its reality. 



•J 



This Dae Particularly to the Discovery of the Interdepend- 

 ence Between Adult Characters and Chromosomes 



of Germ-Cells 



In what immediately follows I want to fix attention on the 

 remarkable way in which a long series of discoveries highly 

 interesting in themselves, and pertaining to fields quite re- 

 mote from each other have conspired to increase the plausi- 

 bility of the old theory that organic beings are caused by 

 the activities of pre-existent, simple representative units or 

 elements of some sort. 



On the face of the matter two fields of biology could hard- 

 ly be more sharply separated than that in which falls the 

 study of the nuclei of cells, and that which occupies itself 

 with the way color, size, and similar attributes appear in 

 successive generations of plants and animals. Yet the first, 

 or cytology, on the one hand, and breeding experiments 



