98 THE CELL IN RELATION TO 



the cell true to its specific type and builds the 

 incoming food-stuffs into the characteristic fabric 

 of the species, I need not dwell on a conception 

 with which we are all so familiar. Some of the 

 specific applications of the doctrine may have 

 proved unacceptable, but the advances in our 

 knowledge of the cell are ever adding weight to 

 the fundamental principle of germinal continuity 

 for which so many eminent investigators, from 

 Remak and Virchow to Nussbaum and Weis- 

 mann, have contended. And this principle ob- 

 viously affords the true standpoint from which 

 the phenomena of heredity and development 

 must be viewed. 



From this standpoint we are confronted with 

 four principal questions, which I shall in the 

 briefest possible way attempt to consider. (1) 

 What is the physical basis of heredity? (2) How 

 is it transmitted from cell to cell? ' (3) In what 

 way does it play its part in the determination of 

 the hereditary characters? (4) How may it be 

 so modified as to give rise to new heritable char- 

 acters? 



THE PHYSICAL BASIS OF HEREDITY 



It is now universally admitted that the physical 

 basis of heredity is contained in the germ-cell. 

 Is this basis formed by the entire living energid, 

 or may we distinguish in the cell a particular 

 species-substance or idioplasm, that is at least 

 theoretically separable from the other cell-con- 



