ON THE TIGRIDIA 



the structure of the plant body must have an effect 

 in modifying also the germ plasm in a way to 

 influence the character of the future plant that 

 develops from that germ plasm. 



And as much as this, it should be added, is 

 admitted by all experimenters, even by those who 

 deny the possibility of the transmission of acquired 

 traits in the older interpretation of that phrase. 

 That altered conditions of nutrition may modify 

 the condition of the germ plasm in such a way as 

 to modify the state of the offspring has been shown 

 by experiments in many fields, both with animals 

 and vegetables. Such being the case, the question 

 of the transmissibility of acquired traits is reduced, 

 as I have elsewhere quoted an authority as saying, 

 to a matter of definition. 



Nevertheless, for practical purposes, it is 

 unquestionably true that the germ plasm is enor- 

 mously difficult to influence, and that under all 

 ordinary circumstances it will convey its heredi- 

 tary factors unchanged, or not appreciably 

 changed, from one generation to another. In 

 attempting to modify the forms of successive 

 generations, the method that has hitherto proved 

 successful, has been, not the modification of the 

 individual germ plasm, but the bringing together 

 of different germ plasms trom diverse organisms 

 through hybridization. 



[101] 



