Influence of Environment 239 



is probable that heredity, which is the constant factor in this 

 case, is also the determining factor for that character. On the 

 other hand if a character develops in response to peculiar stimuli 

 and does not appear in other individuals of the same biotype in 

 which such stimuli are lacking it is said to be an environmental 

 or acquired character. In fine, inherited characters are those 

 whose distinctive or differential causes are in the germ cells, 

 while acquired characters are those whose differential causes are 

 environmental. 



Statement of Problem. Briefly stated the question of the in- 

 heritance of acquired characters is this: Can the differential 

 cause of a character be shifted from the environment to the germ- 

 plasm? Can peculiarities of the environment which influence 

 the development of somatic characters so affect the germ cells 

 that they will produce these somatic characters in the absence of 

 the peculiar environment ? Can the characteristics of a developed 

 organism enter into its germ cells and be born again in the next 

 generation? Considering the fact that germ cells are cells and 

 contain no adult characteristics, it seems very improbable that any 

 peculiarity of environment whether of nutrition, use, disuse or 

 injury, which brings about certain peculiarities of developed char- 

 acters in the adult, could so change the structure of the germ cells 

 as to cause them to produce this same character in subsequent 

 generations in the absence of its extrinsic cause. How, for ex- 

 ample, could defective nutrition, which leads to the production 

 of rickets,* affect the germ cells, which contain no bones, so as to 

 produce rickets in subsequent generations, although well nour- 

 ished? Or how can over-exertion, leading to hypertrophy of the 

 heart, so affect the germ cells that they, in turn, would produce 

 hypertrophied hearts in the absence of over-exertion, seeing that 

 germ cells have no hearts? Or how could the loss or injury of 



* It has recently been shown that rickets may also be produced by ab- 

 sence of sunlight or other radiant energy. It may be prevented by ex- 

 posure to sunlight, if taken in time. 



