158 THE PROBLEMS OF EVOLUTION 



increasing the width as thus measured. He also 

 found that increase of temperature caused a lessen- 

 ing of length. When the animals were fed the ex- 

 perimental food for a single generation and then 

 returned to a normal medium their young showed 

 the acquired character strongly marked but in 

 later generations it returned rapidly to normal. 

 These results were based on about three thousand 

 parthenogenetic descendants of one female, hence 

 there can be no suggestion of Mendelian inheritance 

 in them. 



Finally, in plants, Bolley, working with wilt 

 resistance in flax, stated the following conclusions: 

 *'Our results indicate no other conclusion than that 

 wilt resistance may be accumulated rather rapidly 

 by a non-resistant strain or variety and that, 

 when it is thus accumulated, it is transmitted from 

 generation to generation through seed; and, fur- 

 ther, that when once obtained to a certain degree, 

 it can be fixed through artificial crossing." ^^ 



These experiments are not accepted generally as 

 proof of the inheritance of acquired characters. 

 The characters with which they deal were not 

 established permanently so that they would ap- 

 pear through an indefinite succession of generations 

 without the influence of the initial stimulus. Nev- 

 ertheless they have this significance, that the in- 

 dividuals of our hypothetical homogeneous stock 



" Science N. S.. Vol. LXVI, pp. 301-302, 1927. 



