EVOLUTION 107 



to induce a shorter tail in the descendants. 

 All such experiments yielded absolutely nega- 

 tive results and fell in line "with what was 

 known of the oft-repeated mutilations of the 

 human body as, for instance, in the Jewish 

 practice of circumcision. From observations of 

 this kind it was soon concluded that such ac- 

 quired characters as mutilations were not in- 

 herited. 



The effects of changes of temperature on 

 one generation and their inheritance by the 

 next were likewise tested. Certain butterflies, 

 when in the pupal stage, were subjected to ab- 

 normal temperatures and in consequence the 

 wing-markings were much modified. These 

 changes were shown to be inherited by their 

 descendants. But it was pointed out with cor- 

 rectness that the pupal insects on which the 

 abnormal temperatures acted carried in their 

 bodies, almost fully formed, the germ cells for 

 the next generation, and that these germ cells 

 were just as much open to the effects of the 

 change in temperature as the somatic cells of 

 the parent were. Hence such instances were 

 set aside as not crucial. 



The same is true of the effect of liofht in 

 producing pigmented individuals of the sala- 



