I9I2] Wilder D. Bancroft 387 



is a good Instance of how unsafe it is to predict from negative re- 

 sults. There is a much more serious charge to be brought against 

 the biologist. He rules out all cases in which the acquired character 

 is not permanent for a number of generations.^ In this way he bars 

 out practically all the data which could be used against him. In 

 general we can say that inheritance is a hysteresis phenomenon and 

 that changes which take place readily disappear readily. It is safer 

 not to apply this to mutants for the present, though they can hardly 

 be classed as changes which take place readily because there is grave 

 doubt whether anybody has ever produced a mutant at will. They 

 have Seen mutants appear but that is a very different thing. 



If a plant adapts itself readily to new conditions, it will presum- 

 ably revert quickly when brought back to the old conditions and 

 consequently people say that there has been no inheritance of 

 acquired characters, whereas the whole thing may be merely a 

 matter of definition. On the other hand an organism which does 

 not react readily to the new conditions will require experiments 

 extending over many generations in order to show results. With 

 organisms of this class, there is practically no inherited adaptation 

 within the time usually covered by the experiments. We get admi- 

 rable illustrations of thisinthework of Naegeliand of Zederbauer.^* 

 Naegeli took plants up the mountains and found that they assumed 

 alpine characteristics which disappeared when seeds of the plants 

 were brought back again to Munich, wherefore he said that the 

 acquired characters were not inherited. There is a beautiful logical 

 dilemma here. Unless one knows where the plants originally came 

 from, one cannot teil whether it is the Munich characteristics er 

 the alpine characteristics which are inherited while the others are 

 not. In Zederbauer's experiments, " when seeds were taken from 

 plants on the elevated plateau where their ancestors may have been 

 for many years or many centuries (perhaps as long as 2,000 years) 

 and sowed at Vienna and at other places, it was found that in four 

 generations the leaves lost their xerophytic forms and structure, but 

 the other characters were retained within the limits of variability. 

 The stems showed an increase in average length of 1-2 cm., the 

 roots changed as much, but the reproductive branches and floral 



•Cf. MacDougal: Science, 33, 96 (191 1). 

 **Cf. MacDougal: Science, 33, 98 (1911). 



