THE TIGRIDIA 159 



ing influences that affect the body of the plant. 

 And from this it would follow, at least as a 

 reasonable inference, that environing influences 

 that modify 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 off- 

 spring has been shown by experiments in 

 many fields, both with animals and vegetables. 

 Such being the case, the question of the trans- 

 missibility of acquired traits is reduced, as I 

 have elsewhere stated, to a matter of definition. 



Nevertheless, for practical purposes, it is un- 

 questionably 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 



