Influence of Environment 227 



Opinions of Lamarck and Darwin. It is well known that La- 

 narck taught that characters due to desire or need, use or disuse, 

 md to changed environment or conditions of life were inherited 

 ind thus brought about progressive evolution. Long ago desire 

 >r need was repudiated as a factor of evolution. Lowell satir- 

 zed it in his Biglow Papers in these words: 



"Some filosifers think that a fakkilty's granted 



The minnit it's felt to be thoroughly wanted, 



* * * * * 



That the fears of a monkey whose holt chanced to fail 

 Drawed the vertibry out to a prehensile tail." 



Darwin wrote to Hooker, "Heaven forfend me from Lamarck's 

 lonsense of adaptation from the slow willing of animals" ; 

 )Ut although he repudiated this feature of Lamarckism he held 

 hat characters due to use or disuse and to changed conditions of 

 ife might be inherited and he proposed his hypothesis of pan- 

 genesis in order to explain the process of the transmission of 

 iuch characters to the germ cells. 



Weismann's Theories. Weismann introduced a new era in 

 iology by denying the inheritance of all kinds of acquired char- 

 terers, and by challenging the world to. produce evidence that 

 vould stand a rigorous analysis. But Weismann's greatest ser- 

 vice lay in his constructive theories rather than in destructive 

 :riticism ; he forever disposed of theories of pangenesis and the 

 ike by showing that the germ cells are not built up by contribu- 

 ions from the body and that characters are not transmitted from 

 generation to generation ; but on the other hand that there is 

 ransmitted a germ plasm which is relatively independent of the 

 )ody and which is relatively very stable in organization. This 

 ipoch-making theory of Weismann's has naturally undergone 

 ;ome changes, as the result of new discoveries. It is no longer 

 )elieved that the germ plasm is really independent of the body, 

 lor that it is absolutely stable, as Weismann at one time held. 

 There is no doubt that the germ cells and the germ plasm are 



