ACQUIRED CHARACTERS 35 



then, are " acquired " as actually make their appear- 

 ance in the individual lifetime. 



Secondly, before we can describe anything as an 

 acquired character, we must be able to point to some- 

 thing more or less abnormal in the environment or 

 habits of the individual which has produced the 

 modification. Suppose, for example, that a person be- 

 comes grey-haired at an abnormally early age, and that 

 his children afterwards show the same tendency. This 

 in itself would be no evidence for the inheritance of 

 acquired characters, since the tendency to turn grey at 

 an early age might well have been an inborn variation. 

 But if we could point to a definite inducing cause for 

 the condition, such as a severe illness, its reappearance 

 in the next generation would be either a case of the 

 inheritance of acquired characters, or a very remarkable 

 coincidence. 



Thirdly, an acquired character is a change produced 

 on the body of an organism, and not directly on its germ 

 plasm. This is the most difficult point of all to grasp, 

 and it is extremely important. Tower has proved 

 that very considerable changes can be induced in a 

 race of beetles by subjecting them to unusual tem- 

 peratures, and that these changes are inherited. But 

 the changed temperature did not affect the body of 

 the adult beetle itself ; the action was directly on the 

 germ plasm. In this case we are dealing with an 

 induced inborn variation, and not with an acquired 

 character. 



It is readily conceivable, however, that certain causes, 

 acting on the body, may produce modifications, and 

 at the same time may produce variations in the germ 

 plasm. But in order to prove the inheritance of ac- 

 quired characters, we should require to show that the 

 change in the germ plasm actually specifically repre- 

 sents the body modification. If a man is a drunkard, 

 his germ cells may become poisoned and his children 

 be weaklings. But in order to prove the inheritance 

 of acquired characters, we should require to show a 

 reappearance in the offspring of the father's ruined 







