DARWIN 



ganisms are accepted as facts, but they are, evidently, 

 not causes of variation until it can be shown what 

 forces within the organism act to modify it. 



The next step in the theory of evolution was taken 

 by Lamarck who proposed his famous doctrine of the 

 inheritance of acquired traits. As I have pointed out, 

 this method rests on the postulate that the use or dis- 

 use of any part of the organism during its life tends 

 to modify the part, and the variation is transmitted 

 to the next generation. The cause for increased use 

 or disuse is the desire of the organism to meet new 

 needs brought about by changes in the environment. 

 I have also pointed out that this is a true scientific 

 theory because future events are caused by past 

 actions and that, if the effects of use can be proved to 

 be inherited in all cases, we can predict what will be 

 the general trend of the variation in the offspring, be- 

 cause we may observe the changes which have oc- 

 curred in the parent. Darwin was reluctantly forced 

 to accept Lamarck's doctrine to a limited extent. At 

 the present time biologists are divided in opinion as to 

 the fact of the inheritance of acquired traits; some 

 hold that only changes in the genetic, or reproductive, 

 cells are transmitted and others that the variations 

 during life may react on the sperm and ovum and thus 

 be transmitted. If Lamarckism can be proved, it 

 would, in my opinion, have the inestimable advan- 

 tage of opposing the materialistic or mechanical theo- 



