INFLUENCE OF ENVIRONMENT 351 



In conclusion: (1) Developed characters, 

 whether "acquired" or not, are never transmit- 

 ted by heredity, and the hereditary constitu- 

 tion of the germ is not changed by changes in 

 such characters. (2) Probably environmental 

 stimuli acting upon germ cells at an early 

 stage in their development may rarely cause 

 changes in their hereditary constitution, but 

 changes produced in somatic cells do not 

 cause corresponding changes in the hereditary 

 constitution of the germ cells. (3) Germ cells 

 like somatic cells may undergo modifiations 

 which are not hereditary ; they may be stained 

 with fat stains and the generation to which 

 they give rise be similarly stained; they may 

 be poisoned with alcohol or modified by tem- 

 perature and such influence be carried over to 

 the next generation without becoming heredi- 

 tary. All such cases are known as "induction" 

 and many instances of the supposed inheri- 

 tance of acquired characters come under this 

 category. 



