336 HEREDITY AND ENVIRONMENT 



as Weismann at one time held. There is no 

 doubt that the germ cells and the germ plasm 

 are physiologically related to other cells and 

 to other plasms, and similarly there is no doubt 

 that the germ plasm although very stable can 

 and does change its constitution under some 

 rare conditions. But in the main the germ 

 plasm theory is accepted by the great majority 

 of biologists to-day, and recent work in gen- 

 etics and cytology has brought many confir- 

 mations of this theory. 



As long as it was believed that the developed 

 characters of an organism could be transmit- 

 ted as such to its descendents it was customary 

 to speak of developed characters as heredi- 

 tary or acquired and to talk of the inheritance 

 or non-inheritance of acquired characters. 

 This distinction is not a logical one for all 

 developed characters are invariably the result 

 of the responses of the germinal organi- 

 zation to environmental stimuli; and of course 

 no developed character can be purely heredi- 

 tary or purely environmental. But when a 

 given character arises in many individuals of 

 the same genotype under different environ- 



